Latest Articles Include:
- Animal models for nickel allergy
- Nat Nanotechnol 6(9):533 (2011)
Article preview View full access options Nature Nanotechnology | Correspondence Animal models for nickel allergy * Marc Schmidt1 * Stefan F. Martin2 * Marina A. Freudenberg3 * Matthias Goebeler1 * Affiliations * Corresponding authorJournal name:Nature NanotechnologyVolume: 6,Page:533Year published:(2011)DOI:doi:10.1038/nnano.2011.143Published online06 September 2011 To the Editor Vemula et al. report that calcium carbonate and calcium phosphate nanoparticles that are about 70 nm in diameter can capture nickel ions (Ni2+) from the surface of the skin1. They suggest that applying the nanoparticles to the skin may limit the exposure to — and thereby prevent allergy towards — Ni2+, which can cause skin irritation and inflammation or contact dermatitis. Although many individuals who are sensitive to Ni2+ will benefit from this innovative approach, the animal model used to study the clinical effectiveness of the nanoparticles is problematic. Subject terms: * Nanomedicine * Nanoparticles Article preview Read the full article * Instant access to this article: US$18 Buy now * Subscribe to Nature Nanotechnology for full access: Subscribe * Personal subscribers: Log in Additional access options: * Login via Athens * Login via your Institution * Purchase a site license * Use a document delivery service * British Library Document Supply Centre * Infotrieve * Thompson ISI Document Delivery * You can also request this document from your local library through inter-library loan services. Author information Article tools * Print * Email * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Affiliations * Department of Dermatology, University of Giessen, Giessen, Germany * Marc Schmidt & * Matthias Goebeler * Allergy Research Group, Department of Dermatology, University Medical Center Freiburg, Freiburg, Germany * Stefan F. Martin * Max-Planck-Institute for Immunobiology and Epigenetics, Freiburg, Germany * Marina A. Freudenberg Corresponding author Correspondence to: * Matthias Goebeler Author Details * Marc Schmidt Search for this author in: * NPG journals * PubMed * Google Scholar * Stefan F. Martin Search for this author in: * NPG journals * PubMed * Google Scholar * Marina A. Freudenberg Search for this author in: * NPG journals * PubMed * Google Scholar * Matthias Goebeler Contact Matthias Goebeler Search for this author in: * NPG journals * PubMed * Google Scholar Additional data - Animal models for nickel allergy
- Nat Nanotechnol 6(9):533 (2011)
Article preview View full access options Nature Nanotechnology | Correspondence Animal models for nickel allergy * Praveen Kumar Vemula1, 2, 3 * R. Rox Anderson4 * Jeffrey M. Karp1, 2, 3 * Affiliations * Corresponding authorJournal name:Nature NanotechnologyVolume: 6,Page:533Year published:(2011)DOI:doi:10.1038/nnano.2011.144Published online06 September 2011 Authors' reply The C3H/HeJ mouse model1 we used in our paper 'Nanoparticles reduce nickel allergy by capturing metal ions'2 is indeed one of many and is not a robust allergy model. Given that nickel-sensitized patients often endure a less heightened response when treated with lower doses of Ni2+ (refs 3, 4), the nickel-sensitized mouse model was used to demonstrate that nanoparticles could indeed reduce Ni2+ exposure. As suggested in the correspondence by Schmidt et al., regardless of the host and cutaneous-response pathways, nanoparticles that sequester nickel on the skin surface may offer protection against all such pathways. Our unpublished control experiments on mice ears showed that Ni2+ did not induce inflammation in non-sensitized healthy mice, which is in agreement with non-sensitized humans that typically do not experience a response to nickel ions5. It is also important to consider that we observed reactions to nickel only after, not during, nickel sensitization. In addition to s! howing that nanoparticles significantly reduced the inflammatory response induced by Ni2+in vivo, our in vitro experiments using inductively coupled plasma atomic emission spectrometry confirmed that the nanoparticles did efficiently capture Ni2+ in solution. Furthermore, energy-dispersive X-ray diffraction analysis of intact skin containing artificial sweat showed that the nanoparticles were able to prevent nickel from going through the skin. By performing inductively coupled plasma atomic emission on dissolved skin that had been treated with nickel, we verified that the nanoparticles can reduce the concentration of nickel in the skin from 400 to 2.5 ppm. Subject terms: * Nanomedicine * Nanoparticles Article preview Read the full article * Instant access to this article: US$18 Buy now * Subscribe to Nature Nanotechnology for full access: Subscribe * Personal subscribers: Log in Additional access options: * Login via Athens * Login via your Institution * Purchase a site license * Use a document delivery service * British Library Document Supply Centre * Infotrieve * Thompson ISI Document Delivery * You can also request this document from your local library through inter-library loan services. Author information Article tools * Print * Email * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Affiliations * Center for Regenerative Therapeutics and Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA * Praveen Kumar Vemula & * Jeffrey M. Karp * Harvard Stem Cell Institute, 1350 Massachusetts Avenue, Cambridge, Massachusetts 02138, USA * Praveen Kumar Vemula & * Jeffrey M. Karp * Harvard-MIT Division of Health Sciences and Technology, 65 Lansdowne Street, Cambridge, Massachusetts 02139, USA * Praveen Kumar Vemula & * Jeffrey M. Karp * Laser and Cosmetic Dermatology Center and Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA * R. Rox Anderson Corresponding author Correspondence to: * Jeffrey M. Karp Author Details * Praveen Kumar Vemula Search for this author in: * NPG journals * PubMed * Google Scholar * R. Rox Anderson Search for this author in: * NPG journals * PubMed * Google Scholar * Jeffrey M. Karp Contact Jeffrey M. Karp Search for this author in: * NPG journals * PubMed * Google Scholar Additional data - The Scherrer equation versus the 'Debye-Scherrer equation'
- Nat Nanotechnol 6(9):534 (2011)
Article preview View full access options Nature Nanotechnology | Correspondence The Scherrer equation versus the 'Debye-Scherrer equation' * Uwe Holzwarth1 * Neil Gibson1 * Affiliations * Corresponding authorsJournal name:Nature NanotechnologyVolume: 6,Page:534Year published:(2011)DOI:doi:10.1038/nnano.2011.145Published online28 August 2011 To the Editor X-ray diffraction is a convenient method for determining the mean size of single-crystal nanoparticles or crystallites in nanocrystalline bulk materials. The first scientist to investigate the effect of limited particle size on X-ray diffraction patterns was Paul Scherrer, who published his results in a paper that included what became known as the Scherrer equation1. However, it seems to us that this equation is often erroneously referred to as the 'Debye–Scherrer equation'. (Indeed, strictly speaking, there is no Debye-Scherrer equation.) We would, therefore, like to recall some relevant historical facts to illuminate the origins of the Scherrer equation, and to assist authors in citing the appropriate equations and references in future work. Subject terms: * Nanometrology and instrumentation * Structural properties Article preview Read the full article * Instant access to this article: US$18 Buy now * Subscribe to Nature Nanotechnology for full access: Subscribe * Personal subscribers: Log in Additional access options: * Login via Athens * Login via your Institution * Purchase a site license * Use a document delivery service * British Library Document Supply Centre * Infotrieve * Thompson ISI Document Delivery * You can also request this document from your local library through inter-library loan services. Author information Article tools * Print * Email * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Affiliations * European Commission, Joint Research Centre, Institute for Health and Consumer Protection, I-21027 Ispra (VA), Italy * Uwe Holzwarth & * Neil Gibson Corresponding authors Correspondence to: * Uwe Holzwarth or * Neil Gibson Author Details * Uwe Holzwarth Contact Uwe Holzwarth Search for this author in: * NPG journals * PubMed * Google Scholar * Neil Gibson Contact Neil Gibson Search for this author in: * NPG journals * PubMed * Google Scholar Additional data - Graphene: Show of adhesive strength
- Nat Nanotechnol 6(9):537-538 (2011)
Article preview View full access options Nature Nanotechnology | News and Views Graphene: Show of adhesive strength * Rui Huang1Journal name:Nature NanotechnologyVolume: 6,Pages:537–538Year published:(2011)DOI:doi:10.1038/nnano.2011.150Published online06 September 2011 The adhesion energies for atomically thin graphene membranes on silicon dioxide substrates have now been measured. Subject terms: * Nanomaterials * Structural properties Article preview Read the full article * Instant access to this article: US$18 Buy now * Subscribe to Nature Nanotechnology for full access: Subscribe * Personal subscribers: Log in Additional access options: * Login via Athens * Login via your Institution * Purchase a site license * Use a document delivery service * British Library Document Supply Centre * Infotrieve * Thompson ISI Document Delivery * You can also request this document from your local library through inter-library loan services. Author information Article tools * Print * Email * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Affiliations * Rui Huang is in the Department of Aerospace Engineering and Engineering Mechanics, University of Texas at Austin, Austin, Texas 78712, USA Corresponding author Correspondence to: * Rui Huang Author Details * Rui Huang Contact Rui Huang Search for this author in: * NPG journals * PubMed * Google Scholar Additional data - Biomaterials: A natural source of nanowires
- Nat Nanotechnol 6(9):538-539 (2011)
Article preview View full access options Nature Nanotechnology | News and Views Biomaterials: A natural source of nanowires * Fang Qian1 * Yat Li2 * Affiliations * Corresponding authorsJournal name:Nature NanotechnologyVolume: 6,Pages:538–539Year published:(2011)DOI:doi:10.1038/nnano.2011.148Published online06 September 2011 Fibrous proteins from bacteria can be used to make biofilms with electrical conductivities that are comparable to those measured in conducting polymers. Subject terms: * Electronic properties and devices * Nanobiotechnology Article preview Read the full article * Instant access to this article: US$18 Buy now * Subscribe to Nature Nanotechnology for full access: Subscribe * Personal subscribers: Log in Additional access options: * Login via Athens * Login via your Institution * Purchase a site license * Use a document delivery service * British Library Document Supply Centre * Infotrieve * Thompson ISI Document Delivery * You can also request this document from your local library through inter-library loan services. Author information Article tools * Print * Email * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Affiliations * Fang Qian is at the Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, California 94550, USA * Yat Li is in the Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, USA Corresponding authors Correspondence to: * Fang Qian or * Yat Li Author Details * Fang Qian Contact Fang Qian Search for this author in: * NPG journals * PubMed * Google Scholar * Yat Li Contact Yat Li Search for this author in: * NPG journals * PubMed * Google Scholar Additional data - Nanoparticles: Self-assembly finds its own limits
- Nat Nanotechnol 6(9):540-541 (2011)
Article preview View full access options Nature Nanotechnology | News and Views Nanoparticles: Self-assembly finds its own limits * Paulette Clancy1Journal name:Nature NanotechnologyVolume: 6,Pages:540–541Year published:(2011)DOI:doi:10.1038/nnano.2011.152Published online06 September 2011 Inorganic nanoparticles can self-assemble into uniformly sized supraparticles in a process governed by competition between electrostatic and van der Waals forces. Subject terms: * Nanoparticles * Structural properties Article preview Read the full article * Instant access to this article: US$18 Buy now * Subscribe to Nature Nanotechnology for full access: Subscribe * Personal subscribers: Log in Additional access options: * Login via Athens * Login via your Institution * Purchase a site license * Use a document delivery service * British Library Document Supply Centre * Infotrieve * Thompson ISI Document Delivery * You can also request this document from your local library through inter-library loan services. Author information Article tools * Print * Email * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Affiliations * Paulette Clancy is at the School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, USA Corresponding author Correspondence to: * Paulette Clancy Author Details * Paulette Clancy Contact Paulette Clancy Search for this author in: * NPG journals * PubMed * Google Scholar Additional data - Nanobiotechnology: Protein arrays made to order
- Nat Nanotechnol 6(9):541-542 (2011)
Article preview View full access options Nature Nanotechnology | News and Views Nanobiotechnology: Protein arrays made to order * Todd O. Yeates1Journal name:Nature NanotechnologyVolume: 6,Pages:541–542Year published:(2011)DOI:doi:10.1038/nnano.2011.127Published online31 July 2011 Symmetric protein molecules can be fused together with genetic techniques to produce molecular building blocks that self-assemble into specific ordered structures. Subject terms: * Molecular self-assembly * Nanobiotechnology * Nanomaterials Article preview Read the full article * Instant access to this article: US$18 Buy now * Subscribe to Nature Nanotechnology for full access: Subscribe * Personal subscribers: Log in Additional access options: * Login via Athens * Login via your Institution * Purchase a site license * Use a document delivery service * British Library Document Supply Centre * Infotrieve * Thompson ISI Document Delivery * You can also request this document from your local library through inter-library loan services. Author information Article tools * Print * Email * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Affiliations * Todd Yeates is in the Department of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095, USA * Todd O. Yeates Corresponding author Correspondence to: * Todd O. Yeates Author Details * Todd O. Yeates Contact Todd O. Yeates Search for this author in: * NPG journals * PubMed * Google Scholar Additional data - Ultrastrong adhesion of graphene membranes
- Nat Nanotechnol 6(9):543-546 (2011)
Nature Nanotechnology | Letter Ultrastrong adhesion of graphene membranes * Steven P. Koenig1 * Narasimha G. Boddeti1 * Martin L. Dunn1 * J. Scott Bunch1 * Affiliations * Contributions * Corresponding authorJournal name:Nature NanotechnologyVolume: 6,Pages:543–546Year published:(2011)DOI:doi:10.1038/nnano.2011.123Received13 May 2011Accepted30 June 2011Published online14 August 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg As mechanical structures enter the nanoscale regime, the influence of van der Waals forces increases. Graphene is attractive for nanomechanical systems1, 2 because its Young's modulus and strength are both intrinsically high, but the mechanical behaviour of graphene is also strongly influenced by the van der Waals force3, 4. For example, this force clamps graphene samples to substrates, and also holds together the individual graphene sheets in multilayer samples. Here we use a pressurized blister test to directly measure the adhesion energy of graphene sheets with a silicon oxide substrate. We find an adhesion energy of 0.45 ± 0.02 J m−2 for monolayer graphene and 0.31 ± 0.03 J m−2 for samples containing two to five graphene sheets. These values are larger than the adhesion energies measured in typical micromechanical structures and are comparable to solid–liquid adhesion energies5, 6, 7. We attribute this to the extreme flexibility of graphene, which allows it to co! nform to the topography of even the smoothest substrates, thus making its interaction with the substrate more liquid-like than solid-like. View full text Subject terms: * Nanomaterials * Structural properties Figures at a glance * Figure 1: Pressurizing graphene membranes. , Two optical images showing graphene flakes with regions of one to five suspended layers (top), and one and three suspended layers (bottom). The arrays of microcavities in the SiO2 substrate can also be seen. The number of graphene layers was verified with a combination of Raman spectroscopy, AFM and measurements of optical contrast and elastic constants measurements (see Supplementary Information). , Schematic of a graphene-sealed microcavity before it is placed in the pressure chamber. The pressure inside the microcavity, pint, is equal to the external pressure pext, so the membrane is flat. After four to six days inside the pressure chamber, pint increases to p0. , When the microcavity is removed from the pressure chamber, the pressure difference across the membrane causes it to bulge upward and eventually delaminate from the substrate, causing the radius a to increase. , Three-dimensional rendering of an AFM image showing the deformed shape of a monolayer graphene membr! ane with Δp = pint − pext = 1.25 MPa. , Deflection versus position for five different values of Δp between 0.145 MPa (black) and 1.25 MPa (cyan). The dashed black line is obtained from Hencky's solution for Δp = 0.41 MPa. The deflection is measured by AFM along a line that passes through the centre of the membrane. * Figure 2: Delaminating graphene membranes. –, Plots showing maximum deflection δ (), blister radius a () and internal pressure pint () versus input pressure p0 for all two-layer membranes studied. The solid black line is a theoretical curve assuming no delamination of the membrane. Dashed lines are theoretical curves for nEt = 694 N m−1, n = 2 and three different values of the graphene/SiO2 adhesion energy Γ. * Figure 3: Graphene/SiO2 adhesion energies. Measured adhesion energies Γ for membranes containing one layer of graphene (black circles), two layers (red squares), three layers (green triangles), four layers (blue triangles) and five layers (cyan diamonds). The upper solid line corresponds to Γ = 0.45 J m−2 and the lower dashed line corresponds to Γ = 0.31 J m−2. * Figure 4: Elastic constants and clamping of graphene membranes. –, K(υ)δ3/a4 versus pressure difference Δp for membranes containing one graphene sheet before delamination (black symbols) and after delamination (magenta). –, Same plot as for membranes containing two (red symbols, ), three (green, ), four (blue, ) or five (cyan, ) sheets of graphene before and after delamination (magenta symbols in all plots). The solid lines are linear fits to all the data with nEt = 347 (black), 694 (red), 1,041 (green), 1,388 (blue) and 1,735 N m−1 (cyan) (n, number of graphene sheets; E, Young's modulus; t, membrane thickness). Dashed lines show linear fits to the data for Δp < 0.50 MPa and have slopes corresponding to Et = 661 (red; two layers), 950 (green; three layers), 1,330 (red; four layers) and 1,690 N m−1 (cyan; five layers). Note that the vertical scales are different. , nEt versus number of layers. Solid symbols are fitted lines; open symbols indicate nE, with Et = 347. Author information * Abstract * Author information * Supplementary information Affiliations * Department of Mechanical Engineering, University of Colorado, Boulder, Colorado 80309, USA * Steven P. Koenig, * Narasimha G. Boddeti, * Martin L. Dunn & * J. Scott Bunch Contributions S.P.K. performed the experiments. S.P.K. and J.S.B. conceived and designed the experiments. N.G.B. and M.L.D. developed the theory and modelling. All authors interpreted the results and co-wrote the manuscript. Competing financial interests The authors declare no competing financial interests. Corresponding author Correspondence to: * J. Scott Bunch Author Details * Steven P. Koenig Search for this author in: * NPG journals * PubMed * Google Scholar * Narasimha G. Boddeti Search for this author in: * NPG journals * PubMed * Google Scholar * Martin L. Dunn Search for this author in: * NPG journals * PubMed * Google Scholar * J. Scott Bunch Contact J. Scott Bunch Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (996 KB) Supplementary information Additional data - Light–induced disassembly of self-assembled vesicle-capped nanotubes observed in real time
- Nat Nanotechnol 6(9):547-552 (2011)
Nature Nanotechnology | Letter Light–induced disassembly of self-assembled vesicle-capped nanotubes observed in real time * Anthony C. Coleman1, 2 * John M. Beierle1 * Marc C. A. Stuart1, 3 * Beatriz Maciá1 * Giuseppe Caroli1 * Jacek T. Mika2 * Derk Jan van Dijken1 * Jiawen Chen1 * Wesley R. Browne1, 2 * Ben L. Feringa1, 2 * Affiliations * Contributions * Corresponding authorJournal name:Nature NanotechnologyVolume: 6,Pages:547–552Year published:(2011)DOI:doi:10.1038/nnano.2011.120Received05 May 2011Accepted27 June 2011Published online14 August 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Molecular self-assembly is the basis for the formation of numerous artificial nanostructures1, 2. The self-organization of peptides3, 4, 5, 6, amphiphilic molecules composed of fused benzene rings7, 8, 9, 10 and other functional molecules11, 12, 13, 14, 15 into nanotubes is of particular interest. However, the design of dynamic, complex self-organized systems that are responsive to external stimuli remains a significant challenge16. Here, we report self-assembled, vesicle-capped nanotubes that can be selectively disassembled by irradiation. The walls of the nanotubes are 3-nm-thick bilayers and are made from amphiphilic molecules with two hydrophobic legs that interdigitate when the molecules self-assemble into bilayers. In the presence of phospholipids, a phase separation between the phospholipids and the amphiphilic molecules creates nanotubes, which are end-capped by vesicles that can be chemically altered or removed and reattached without affecting the nanotubes. The pre! sence of a photoswitchable and fluorescent core in the amphiphilic molecules allows fast and highly controlled disassembly of the nanotubes on irradiation, and distinct disassembly processes can be observed in real time using fluorescence microscopy. View full text Subject terms: * Molecular self-assembly * Nanomaterials Figures at a glance * Figure 1: Schematic representation of assembly and disassembly of vesicle-capped nanotubes. Self-assembly of a photochemically active amphiphile initially forms interdigitated bilayers followed by nanotube formation and capping of the nanotube with DOPC vesicles. Path 1: Treatment of vesicle-capped nanotubes with detergent (Triton X-100) dissolves the phospholipid capping vesicle without affecting the nanotube. Subsequent removal of detergent with Biobeads followed by freeze–thaw cycles regenerates the vesicle-capped nanotubes. Path 2: Irradiation leads to cyclization within the bilayer (signified here by a colour change from blue to green), eventually resulting in an intensity- and wavelength-dependent tube disassembly process. Real-time observation of the disassembly process shows distinct processes based on irradiation source or tube composition. * Figure 2: Structure and properties of amphiphilic switch 1 and self-assembled nanotube morphologies. , Molecular structure of anti-folded isomer (blue) and cyclized compound (green). ,, Change in absorption () and emission () spectra over time with irradiation of (λ = 365 nm) at room temperature in dichloromethane. , Amber forcefield26 calculated molecular model of the bilayer structure (PEG moieties are omitted from calculations). C, cyan; O, red; H, white; S, yellow. Interdigitated alkyl chains suggest an outer S–outer S distance of ~3 nm. Oligoethylene glycol units are omitted. , Summed cryo-TEM images of a cross-section of the amphiphile nanotubes. Dark regions are bilayer walls. Red bar indicates an approximate thickness of 3 nm. –, Cryo-TEM images of self-assembled nanotubes generated by amphiphile under aqueous conditions in the absence or presence of phospholipid. Scale bars, 100 nm. , Low-aspect-ratio nanotubes generated from pure amphiphile in the absence of DOPC. , Micrometre-long vesicle-capped nanotubes obtained from a 2:1 amphiphile /DOPC mixture. , Nanot! ubes capped with cardiolipin showing a change in phase behaviour of the appended cardiolipin vesicle (from lamellar to cubic/hexagonal phase) in the presence of CaCl2. , Expansion of amphiphile nanotubes capped with DOPC vesicles illustrating the two distinct bilayers of tube and vesicle. * Figure 3: Analysis of changes to morphology. –, Effect of addition of detergent Triton X-100 on DOPC-capped amphiphile nanotubes (1:1 amphiphile /DOPC). , 0 mg ml−1 of Triton X-100. , 1.6 mg ml−1 Triton X-100 – DOPC. Vesicles are completely solubilized, but nanotubes remain intact. , Triton X-100 is completely removed using Biobeads, and DOPC vesicles are concomitantly regenerated. , DOPC vesicles are reattached to the nanotubes after a freeze–thaw cycle. Scale bars, 100 nm. ,, Confocal fluorescence microscopy images of the self-assembled tubes () with emission profiles (, red line in ) as a function of time. Blue corresponds to emission intensity at an excitation wavelength of 406 nm, and green corresponds to emission intensity at an excitation wavelength of 494 nm. , Cryo-TEM images demonstrating structural changes observed within the amphiphile nanotubes under laser irradiation at a wavelength of 400.8 nm. Cryo-TEM images were taken at t = 0 min, 20 min and 120 min. Red arrows indicate the formation of kin! ks and loss of large sections of the nanotube bilayer. Scale bars, 100 nm. * Figure 4: Images of changes in tubular morphology as a function of time. –, Irradiation of tubes at 390 nm on an epifluorescence microscope. Tube composition, amphiphile :DOPC 2:1. Disassembly begins immediately and is complete after 25 s (), forming large aggregates. –, Tube composition as in –, with low-intensity ultraviolet light (λ = 365 nm) as the irradiation source. Tube degradation commences after 45 s of irradiation and continues for almost 2 min, leaving behind small vesicle-like morphologies. –, Tubes consisting of amphiphile :DOPC:DiO (2:1:0.05) are observed bending and coiling in response to light in a process that takes ~2.5 min under the same irradiation conditions as in –. See also corresponding Supplementary Movies S1–S3 and duplicate experiments (Movies S1b–S3b). Author information * Abstract * Author information * Supplementary information Affiliations * Center for Systems Chemistry, Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands * Anthony C. Coleman, * John M. Beierle, * Marc C. A. Stuart, * Beatriz Maciá, * Giuseppe Caroli, * Derk Jan van Dijken, * Jiawen Chen, * Wesley R. Browne & * Ben L. Feringa * Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands * Anthony C. Coleman, * Jacek T. Mika, * Wesley R. Browne & * Ben L. Feringa * Department of Electron Microscopy, Groningen Biomolecular Science and Biotechnology Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The Netherlands * Marc C. A. Stuart Contributions B.L.F. conceived the research. B.L.F., A.C.C., J.M.B., W.R.B. and B.M. designed the experiments. Synthesis of the amphiphile was carried out by B.M., D.J.v.D. and J.C. Solution photochemical studies, switching studies and tube generation were carried out by A.C.C. and B.M. Cryo-TEM was carried out by M.C.A.S. Molecular models were generated by G.C. Confocal microscope and epifluorescence studies were carried out by J.M.B. and J.T.M. A.C.C., J.M.B., W.R.B. and B.L.F. co-wrote the paper. All authors discussed the results and commented on the manuscript. Competing financial interests The authors declare no competing financial interests. Corresponding author Correspondence to: * Ben L. Feringa Author Details * Anthony C. Coleman Search for this author in: * NPG journals * PubMed * Google Scholar * John M. Beierle Search for this author in: * NPG journals * PubMed * Google Scholar * Marc C. A. Stuart Search for this author in: * NPG journals * PubMed * Google Scholar * Beatriz Maciá Search for this author in: * NPG journals * PubMed * Google Scholar * Giuseppe Caroli Search for this author in: * NPG journals * PubMed * Google Scholar * Jacek T. Mika Search for this author in: * NPG journals * PubMed * Google Scholar * Derk Jan van Dijken Search for this author in: * NPG journals * PubMed * Google Scholar * Jiawen Chen Search for this author in: * NPG journals * PubMed * Google Scholar * Wesley R. Browne Search for this author in: * NPG journals * PubMed * Google Scholar * Ben L. Feringa Contact Ben L. Feringa Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Author information * Supplementary information Movies * Supplementary information (2,765 KB) Supplementary movie 1 * Supplementary information (1,021 KB) Supplementary movie 2 * Supplementary information (2,818 KB) Supplementary movie 3 * Supplementary information (2,607 KB) Supplementary movie 4 * Supplementary information (7,583 KB) Supplementary movie 5 * Supplementary information (8,177 KB) Supplementary movie 6 PDF files * Supplementary information (4,285 KB) Supplementary information Additional data - A single synthetic small molecule that generates force against a load
- Nat Nanotechnol 6(9):553-557 (2011)
Nature Nanotechnology | Letter A single synthetic small molecule that generates force against a load * Perrine Lussis1 * Tiziana Svaldo-Lanero1 * Andrea Bertocco2 * Charles-André Fustin3 * David A. Leigh2 * Anne-Sophie Duwez1 * Affiliations * Contributions * Corresponding authorsJournal name:Nature NanotechnologyVolume: 6,Pages:553–557Year published:(2011)DOI:doi:10.1038/nnano.2011.132Received31 May 2011Accepted15 July 2011Published online21 August 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Some biomolecules are able to generate directional forces by rectifying random thermal motions. This allows these molecular machines to perform mechanical tasks such as intracellular cargo transport or muscle contraction1 in plants and animals. Although some artificial molecular machines have been synthesized2, 3, 4 and used collectively to perform mechanical tasks5, 6, 7, so far there have been no direct measurements of mechanical processes at the single-molecule level. Here we report measurements of the mechanical work performed by a synthetic molecule less than 5 nm long. We show that biased Brownian motion of the sub-molecular components in a hydrogen-bonded [2]rotaxane8—a molecular ring threaded onto a molecular axle—can be harnessed to generate significant directional forces. We used the cantilever of an atomic force microscope to apply a mechanical load to the ring during single-molecule pulling–relaxing cycles. The ring was pulled along the axle, away from the ! thermodynamically favoured binding site, and was then found to travel back to this site against an external load of 30 pN. Using fluctuation theorems, we were able to relate measurements of the work done at the level of individual rotaxane molecules to the free-energy change as previously determined from ensemble measurements. The results show that individual rotaxanes can generate directional forces of similar magnitude to those generated by natural molecular machines. View full text Subject terms: * Molecular machines and motors Figures at a glance * Figure 1: Chemical structure of the rotaxane-based molecule shuttle. The rotaxane consists of a benzylic amide molecular ring (blue) mechanically locked onto an axle (black) by bulky diphenylethyl ester groups situated at either end. The axle contains a fumaramide group (green) and a succinic amide-ester group (orange), and the ring can bind to either of these sites through up to four intercomponent hydrogen bonds. The affinity of the ring for the fumaramide site is much higher than for the succinic amide-ester site, so the fumaramide:succinic amide-ester occupancy ratio is ~95:5. Next to the fumaramide binding site, a disulphide group (red) was introduced to enable the grafting of the molecule onto gold substrates. A 4,600 Mn PEO tether (blue) is attached to the ring so that it can be linked to an AFM probe, which allows the motion of the ring along the axle to be tracked. * Figure 2: Single-molecule force spectroscopy of the rotaxane. , The rotaxane is grafted onto gold and the PEO tether is caught by the AFM tip and stretched by moving the tip away from the surface. The black arrow shows the direction of the cantilever displacement. , Force–extension curve (red trace, approach curve; blue trace, retraction curve) of an individual rotaxane–PEO molecule in TCE. The arrow indicates the peak characteristic of the rupture of the hydrogen bonds between the fumaramide site and the ring. , Force–extension curve of an individual PEO polymer chain in TCE for comparison. * Figure 3: Experimental AFM pulling curves. , High-resolution force–extension curve for the rotaxane–PEO molecule in TCE. , Histograms of the rupture forces for the hydrogen bonds in TCE (average ± s.d., n = 318) (left) and in DMF (average ± s.d., n = 249) (right) at a loading rate of 500 pN s−1. , Force–extension curve (data as in ) with worm-like chain model fits to the data (thin solid lines) with an increase in length (ΔLc) of the molecule after rupture of the hydrogen bonds of 3.9 nm. , Interpretation of the sequence of events taking place when pulling on the rotaxane–PEO. Black arrows show the direction of cantilever displacement. Blue arrows show the direction of the force exerted on the molecular ring. (I) Progressive stretching of the PEO tether. (II) Once the force exerted on the tether exceeds the force of the hydrogen bonds between the ring and the fumaramide site, the hydrogen bonds break. (III) After rupture, the ring is free to move along the thread, the tension in the PEO backbone is partl! y released, and the force decreases until the displacement of the cantilever increases again the tension in the PEO tether. (IV) Further cantilever displacement continues the stretching of PEO until the force exceeds the interaction strength of the chain with the tip, which leads to detachment. * Figure 4: Pulling–relaxing cycles for the rotaxane–PEO molecule. , Pulling (blue) and relaxing (red) curves for a single rotaxane–PEO molecule in TCE. The relaxing trace is offset vertically for clarity. , Schematic of the relaxing experiment showing our interpretation of events. Black arrows show the direction of cantilever displacement. Blue arrows show the direction of the force exerted on the ring. (I) Progressive release of the tension in the PEO tether. (II) The force suddenly increases as a result of the ring shuttling in the opposite direction (red arrow) to the force exerted on it (blue arrow). (III) The ring has rebound to the fumaramide site. , Relaxing curve (data as in ) with the area under the trace representing the work done by the molecule as the ring shuttles back to its preferred binding site. , Example of five successive pulling–relaxing curves. The stochastic nature of the rupture and rebinding process is characterized by a distribution of work trajectories. Author information * Abstract * Author information * Supplementary information Affiliations * Department of Chemistry, University of Liège, B6a Sart-Tilman, 4000 Liège, Belgium * Perrine Lussis, * Tiziana Svaldo-Lanero & * Anne-Sophie Duwez * School of Chemistry, University of Edinburgh, The King's Buildings, West Mains Road, Edinburgh EH9 3JJ, UK * Andrea Bertocco & * David A. Leigh * Institute of Condensed Matter and Nanosciences (IMCN), Place Louis Pasteur 1, Université catholique de Louvain, Belgium * Charles-André Fustin Contributions P.L. and T.S-L. performed the AFM experiments and analysed the data. A.B. carried out the rotaxane synthesis and characterization studies. C-A.F. participated in rotaxane synthesis. A-S.D., C-A.F. and D.A.L. designed the experiments and prepared the manuscript. Competing financial interests The authors declare no competing financial interests. Corresponding authors Correspondence to: * David A. Leigh or * Anne-Sophie Duwez Author Details * Perrine Lussis Search for this author in: * NPG journals * PubMed * Google Scholar * Tiziana Svaldo-Lanero Search for this author in: * NPG journals * PubMed * Google Scholar * Andrea Bertocco Search for this author in: * NPG journals * PubMed * Google Scholar * Charles-André Fustin Search for this author in: * NPG journals * PubMed * Google Scholar * David A. Leigh Contact David A. Leigh Search for this author in: * NPG journals * PubMed * Google Scholar * Anne-Sophie Duwez Contact Anne-Sophie Duwez Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (,179 KB) Supplementary information Additional data - Generation of protein lattices by fusing proteins with matching rotational symmetry
- Nat Nanotechnol 6(9):558-562 (2011)
Nature Nanotechnology | Letter Generation of protein lattices by fusing proteins with matching rotational symmetry * John C. Sinclair1 * Karen M. Davies1 * Catherine Vénien-Bryan2 * Martin E. M. Noble1 * Affiliations * Contributions * Corresponding authorsJournal name:Nature NanotechnologyVolume: 6,Pages:558–562Year published:(2011)DOI:doi:10.1038/nnano.2011.122Received09 February 2011Accepted29 June 2011Published online31 July 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg The self-assembly of supramolecular structures that are ordered on the nanometre scale is a key objective in nanotechnology. DNA1, 2, 3, 4 and peptide5, 6, 7 nanotechnologies have produced various two- and three-dimensional structures, but protein molecules have been underexploited in this area of research. Here we show that the genetic fusion of subunits from protein assemblies that have matching rotational symmetry generates species that can self-assemble into well-ordered, pre-determined one- and two-dimensional arrays that are stabilized by extensive intermolecular interactions. This new class of supramolecular structure provides a way to manufacture biomaterials with diverse structural and functional properties. View full text Subject terms: * Molecular self-assembly * Nanobiotechnology * Nanomaterials Figures at a glance * Figure 1: Design of representative classes of crysalins. N- and C-termini of fusion peptide chains are in blue and red cylinders, respectively. Lines and corresponding IUCr symbols in the original assemblies denote rotational two-, three- and fourfold symmetry axes. , A unary 1D crysalin formed by fusion along a twofold axis. Because the assemblies are homologous, there is one protomer and no discrete components. , A binary 2D crysalin formed by one fusion between homologous D4 and heterologous D2 assemblies. , A binary 3D crysalin constructed using homologous octahedral and D3 assemblies fused, respectively, to complementary chains of an heterologous C3 assembly. , Schematic showing how symmetry dictates the relative orientation and disposition of neighbouring components in a crysalin lattice. Linkers connecting protomer subunits (grey and black) are represented as springs to reflect a preferred conformation. Aligned symmetry axes (left) allow linkers to interact optimally whereas misaligned axes (right) do not. * Figure 2: Representative examples of 1D and 2D crysalins. , 1D crysalin 'strings' containing DsRed-Express and streptavidin/Streptag I assemblies. Two components (DsRed-Streptag I and streptavidin) produce a 2D binary crysalin through association along a twofold symmetry axis. Examples of ferritin molecules used as an internal sizing standard are ringed in the electron micrograph. , A 2D crysalin lattice containing ALAD and streptavidin/Streptag I assemblies. The two components (ALAD–Streptag I and streptavidin) produce a 2D binary crysalin through association along a twofold symmetry axis. AFM images of an equivalent grid are provided in Supplementary Fig. S3. , A 2D crysalin lattice containing ALAD and Lac21E/K assemblies. Two components (ALAD–Lac21E and ALAD–Lac21K) produce a 2D binary crysalin through association along a twofold symmetry axis. Larger examples of this crysalin lattice tend to be captured as aggregates on the TEM grid and stain poorly. Inset: a smaller example of the crysalin where the lattice is cleare! r. * Figure 3: Comparison of the observed and designed projection maps of a crysalin. , Fourier transform of a 1,980 × 1,980 pixel edge-tapered region of the electron micrograph presented in Fig. 2b. , P422-symmetrized back projection of the lattice after Fourier filtering, unbending, and contrast-transfer-function correction. Images were analysed at a resolution of 15 Å with the 2dx package, using programs from the MRC 2D crystallography suite as described in the Supplementary Information. , Close view of the lattice design shown in Fig. 2b, covering the 2D region for which projections are shown. , Calculated projection of the lattice design. The projection was made using programs from the CCP4 suite by calculating structure factors from the PDB file illustrated in , removing all but the L = 0 reflections, and back-transforming. Author information * Abstract * Author information * Supplementary information Affiliations * Laboratory of Molecular Biophysics, Department of Biochemistry, South Parks Road, Oxford OX1 3QU, UK * John C. Sinclair, * Karen M. Davies & * Martin E. M. Noble * Present address: IMPMC, CNRS-UMR 7590, Université P&M Curie, 4 place Jussieu, 75252 Paris, France * Catherine Vénien-Bryan Contributions J.C.S. proposed the original design principle and performed bioinformatics analysis, molecular modelling, cloning of expression constructs, protein production and biophysical characterization, as well as assisting in recording and analysing electron micrographs. K.M.D. recorded the presented electron micrographs and carried out initial image analysis. C.V-B. managed the EM facility and supervised K.M.D. in her contribution. M.E.M.N. worked with J.C.S. to develop the original design, advised on the direction of the research and performed the image analysis presented in Fig. 3. J.C.S. and M.E.M.N. prepared the manuscript with critical comment from all authors. Competing financial interests The authors declare no competing financial interests. Corresponding authors Correspondence to: * John C. Sinclair or * Martin E. M. Noble Author Details * John C. Sinclair Contact John C. Sinclair Search for this author in: * NPG journals * PubMed * Google Scholar * Karen M. Davies Search for this author in: * NPG journals * PubMed * Google Scholar * Catherine Vénien-Bryan Search for this author in: * NPG journals * PubMed * Google Scholar * Martin E. M. Noble Contact Martin E. M. Noble Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (1,549 KB) Supplementary information Additional data - Graphene nanoribbons with smooth edges behave as quantum wires
- Nat Nanotechnol 6(9):563-567 (2011)
Nature Nanotechnology | Letter Graphene nanoribbons with smooth edges behave as quantum wires * Xinran Wang1, 2, 4 * Yijian Ouyang3 * Liying Jiao1 * Hailiang Wang1 * Liming Xie1 * Justin Wu1 * Jing Guo3 * Hongjie Dai1 * Affiliations * Contributions * Corresponding authorJournal name:Nature NanotechnologyVolume: 6,Pages:563–567Year published:(2011)DOI:doi:10.1038/nnano.2011.138Received09 June 2011Accepted18 July 2011Published online28 August 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Graphene nanoribbons with perfect edges are predicted to exhibit interesting electronic and spintronic properties1, 2, 3, 4, notably quantum-confined bandgaps and magnetic edge states. However, so far, graphene nanoribbons produced by lithography have had rough edges, as well as low-temperature transport characteristics dominated by defects (mainly variable range hopping between localized states in a transport gap near the Dirac point5, 6, 7, 8, 9). Here, we report that one- and two-layer nanoribbon quantum dots made by unzipping carbon nanotubes10 exhibit well-defined quantum transport phenomena, including Coulomb blockade, the Kondo effect, clear excited states up to ~20 meV, and inelastic co-tunnelling. Together with the signatures of intrinsic quantum-confined bandgaps and high conductivities, our data indicate that the nanoribbons behave as clean quantum wires at low temperatures, and are not dominated by defects. View full text Subject terms: * Electronic properties and devices * Nanomaterials * Synthesis and processing Figures at a glance * Figure 1: High-quality unzipping-derived graphene nanoribbons. , AFM image of a typical high-quality as-made graphene nanoribbon (GNR, w ≈ 27 nm) next to a carbon nanotube (CNT) on the substrate. The obvious difference in height can be used to distinguish them. The nanoribbons are typically ~0.3–0.6 nm higher than those made from exfoliated graphene with the same number of layers as a result of the PmPV coatings introduced in the synthesis10, 13. h, height; w, width; d, diameter. It appears from the trace of the nanoribbon and nanotube that they have approximately equal widths. This is because (1) the trace is more parallel to the orientation of the nanotube and (2) the AFM tip-size effect15 depends on the height of the structure, with the higher nanotube therefore causing more widening due to the conical shape of the AFM tip. , AFM image of GNR1 (w ≈ 14 nm; discussed in the main text) before device fabrication. We carefully carried out AFM after device fabrication to ensure that only the nanoribbon was connected by the leads. , T! EM image of a w ≈ 17 nm graphene nanoribbon with subnanometre edge roughness. * Figure 2: Electron transport of GNR1 (L ≈ 86 nm). , Room-temperature low-bias (Vds = 1 mV) G–Vgs characteristics of GNR1. Lower inset: AFM image of the device. Upper inset: G versus T at Vgs = VDirac−35 V in the hole channel. The metallic behaviour, also observed in high-quality carbon-nanotube devices20, suggests that the palladium contact is ohmic to the valence band, and the lower resistances at lower temperatures are due to reduced scattering by thermal depopulation of acoustic phonons. , Low-bias (Vds = 1 mV) G–Vgs characteristics of GNR1 under various temperatures down to 60 K. Inset: zero-bias G–Vgs characteristics at 2 K. , Colour scale differential conductance versus Vds and Vgs near the bandgap, showing single electron charging behaviour. A gate switching was present near Vgs ≈ 1.5 V (indicated by the arrow). , Differential conductance in the electron branch near the bandgap, showing regular Coulomb diamonds with excited states. The number of electrons in the quantum dot is marked for each diamond. The e! xcited-state energies Δεn0 (for the nth excited state relative to the ground state in meV) are also marked. , Top panel: differential conductance in the hole branch near the bandgap. The number of holes in the quantum dot is marked for each diamond. Bottom panel: zero Vds line cut from the top panel, showing the peak pairing and enhanced conductance in the odd-numbered diamond valleys, a signature of the Kondo effect. Spin configurations are also marked for each valley. Inset: constant Vgs line cut in the middle of the third hole diamond in the top panel. The conductance is enhanced at zero bias, as expected for the Kondo effect28. * Figure 3: Electron transport of a high-quality quantum dot in GNR2 (L ≈ 140 nm). , Low-bias (Vds = 1 mV) G–Vgs characteristics under various temperatures down to 50 K. Inset: AFM image of the device. , Experimentally measured single electron addition energy Eadd as a function of number of holes in the quantum dot, with an even–odd pattern. A small gate-switching event occurred in diamond 6, and Eadd(6) was measured after correcting the switching. Single-particle level spacings could be extracted. For example, Δε10 = Eadd(2)−Eadd(1), Δε21 = Eadd(4)−Eadd(3). , Differential conductance as a function of Vgs and Vds at 3.3 K near the bandgap. The number of electrons and holes in the quantum dot are marked. , High-resolution differential conductance scan across diamond 0 and 1, clearly showing excited states. The excited states are marked and assigned to the corresponding single-particle level spacings. , Simulated differential conductance of the same area as in at T = 5 K. See Supplementary Information for details. , Differential conductance scan ! for six Coulomb diamonds on the hole branch. The number of holes and ground-state configuration for each diamond are illustrated. All the excited states are marked and assigned to the corresponding energy level spacings. See Supplementary Fig. S9 for the raw data without dashed lines drawn here to guide the eye. * Figure 4: Electron transport of GNR3 (L ≈ 60 nm). , Low-bias (Vds = 1 mV) G–Vgs characteristics under various temperatures down to 50 K. Inset shows the AFM image of the device. , Differential conductance as a function of Vgs and Vds near the bandgap, showing single electron charging behaviour. The central diamond (with size ~55 meV as marked by the solid blue lines) corresponds to the bandgap of the nanoribbon. There was a gate switching event near Vgs ≈ 8 V marked by the arrow. Author information * Abstract * Author information * Supplementary information Affiliations * Department of Chemistry, Stanford University, Stanford, California 94305, USA * Xinran Wang, * Liying Jiao, * Hailiang Wang, * Liming Xie, * Justin Wu & * Hongjie Dai * National Laboratory of Microstructures, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China * Xinran Wang * Department of Electrical and Computer Engineering, University of Florida, Gainesville, Florida, 32611, USA * Yijian Ouyang & * Jing Guo * Present address: Department of Material Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA * Xinran Wang Contributions X.W. and H.D. conceived and designed the experiments. X.W. and J.W. fabricated the devices, performed the experiments and analysed the data. Y.O. and J.G. performed simulations. L.J. provided graphene nanoribbon samples. H.W. and L.X. performed TEM characterizations. X.W., Y.O., J.G. and H.D. co-wrote the paper. All authors discussed the results and commented on the manuscript. Competing financial interests The authors declare no competing financial interests. Corresponding author Correspondence to: * Hongjie Dai Author Details * Xinran Wang Search for this author in: * NPG journals * PubMed * Google Scholar * Yijian Ouyang Search for this author in: * NPG journals * PubMed * Google Scholar * Liying Jiao Search for this author in: * NPG journals * PubMed * Google Scholar * Hailiang Wang Search for this author in: * NPG journals * PubMed * Google Scholar * Liming Xie Search for this author in: * NPG journals * PubMed * Google Scholar * Justin Wu Search for this author in: * NPG journals * PubMed * Google Scholar * Jing Guo Search for this author in: * NPG journals * PubMed * Google Scholar * Hongjie Dai Contact Hongjie Dai Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (1,464 KB) Supplementary information Additional data - Solution-processed core–shell nanowires for efficient photovoltaic cells
- Nat Nanotechnol 6(9):568-572 (2011)
Nature Nanotechnology | Letter Solution-processed core–shell nanowires for efficient photovoltaic cells * Jinyao Tang1, 3, 4 * Ziyang Huo1, 3, 4 * Sarah Brittman1, 3 * Hanwei Gao1, 3 * Peidong Yang1, 2, 3 * Affiliations * Contributions * Corresponding authorJournal name:Nature NanotechnologyVolume: 6,Pages:568–572Year published:(2011)DOI:doi:10.1038/nnano.2011.139Received22 June 2011Accepted18 July 2011Published online21 August 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Semiconductor nanowires are promising for photovoltaic applications1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, but, so far, nanowire-based solar cells have had lower efficiencies than planar cells made from the same materials6, 7, 8, 9, 10, 12, 13, even allowing for the generally lower light absorption of nanowires. It is not clear, therefore, if the benefits of the nanowire structure, including better charge collection and transport14 and the possibility of enhanced absorption through light trapping4, 15, can outweigh the reductions in performance caused by recombination at the surface of the nanowires and at p–n junctions. Here, we fabricate core–shell nanowire solar cells with open-circuit voltage and fill factor values superior to those reported for equivalent planar cells, and an energy conversion efficiency of ~5.4%, which is comparable to that of equivalent planar cells despite low light absorption levels16. The device is made using a low-temperature solution-based cation ! exchange reaction17, 18, 19, 20, 21 that creates a heteroepitaxial junction between a single-crystalline CdS core and single-crystalline Cu2S shell. We integrate multiple cells on single nanowires in both series and parallel configurations for high output voltages and currents, respectively. The ability to produce efficient nanowire-based solar cells with a solution-based process and Earth-abundant elements22, 23, 24 could significantly reduce fabrication costs relative to existing high-temperature bulk material approaches. View full text Subject terms: * Electronic properties and devices * Nanomaterials * Photonic structures and devices * Synthesis and processing Figures at a glance * Figure 1: Structural characterization of CdS and CdS–Cu2S core–shell nanowires. , Representative TEM image of an as-grown CdS nanowire with its tip capped by a gold nanoparticle. Inset: electron diffraction pattern taken on the single crystalline nanowire. , High-resolution TEM image of an individual CdS nanowire, showing the single crystalline structure. , High-resolution TEM image of a CdS–Cu2S nanowire at the heterojunction. , Constructed inverse FFT image along the growth direction for the area marked in . The green area shows the typical lattice fringe distortion at the core–shell interface (see Supplementary Information). –, EELS elemental mapping images for Cd () and Cu (), respectively. * Figure 2: Fabrication and characterization of CdS–Cu2S core–shell nanowire PV devices. , Schematic of the fabrication process. From left to right, a CdS (yellow) nanowire (NW) is partially converted in CuCl solution to form a layer of Cu2S (brown) shell, then metal contacts were deposited on the CdS core and Cu2S shell. The Al2O3 masking step is not shown. , SEM image of a PV unit; CdS and Cu2S are highlighted with yellow and brown false colours, respectively. , I–V characteristic of a core–shell nanowire under 1 sun (AM 1.5G) illumination. , Light intensity dependence of the photocurrent (ISC) and open-circuit voltage (VOC). , Wavelength dependence of the photocurrent compared with simulated nanowire absorption. Photocurrent (red curve) was normalized by the photon flux of the source and matches well the absorption spectrum of the simulated CdS–Cu2S core–shell nanowire with similar dimensions (blue curve). * Figure 3: SPCM of a core–shell nanowire. , SEM image of the PV device with metal contact shown in b. , SPCM image superimposed on the confocal reflection image collected simultaneously shows that only the core–shell portion of the nanowire is active for solar energy conversion. , Line profile of the photocurrent along the nanowire, revealing uniform photocurrent in the core–shell region. * Figure 4: Multiple PV units on a single nanowire, in series and in parallel. , SEM image of three PV units from a single nanowire in series with the core–shell regions marked by the brown rectangles. , SEM image of four PV units from a single nanowire in parallel with the core–shell regions marked by the brown rectangles. , I–V characteristic of the in series units under 1 sun illumination (AM 1.5G), showing that the voltages add and the current remains fixed. , I–V characteristic of the four units in parallel under 1 sun illumination (AM 1.5G), showing that the currents add and the voltage remains fixed. Author information * Abstract * Author information * Supplementary information Primary authors * These authors contributed equally to this work * Jinyao Tang & * Ziyang Huo Affiliations * Department of Chemistry, University of California, Berkeley, California 94720, USA * Jinyao Tang, * Ziyang Huo, * Sarah Brittman, * Hanwei Gao & * Peidong Yang * Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA * Peidong Yang * Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA * Jinyao Tang, * Ziyang Huo, * Sarah Brittman, * Hanwei Gao & * Peidong Yang Contributions J.T., Z.H. and P.Y. conceived and designed the experiments. J.T. fabricated the devices and performed the measurements. Z.H. collected and analysed the TEM images. S.B. was responsible for the scanning photocurrent mapping. H.G. provided the simulation results. J.T., Z.H. and P.Y. co-wrote the paper. All authors discussed the results and revised the manuscript. Competing financial interests The authors declare no competing financial interests. Corresponding author Correspondence to: * Peidong Yang Author Details * Jinyao Tang Search for this author in: * NPG journals * PubMed * Google Scholar * Ziyang Huo Search for this author in: * NPG journals * PubMed * Google Scholar * Sarah Brittman Search for this author in: * NPG journals * PubMed * Google Scholar * Hanwei Gao Search for this author in: * NPG journals * PubMed * Google Scholar * Peidong Yang Contact Peidong Yang Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (645 KB) Supplementary information Additional data - Tunable metallic-like conductivity in microbial nanowire networks
- Nat Nanotechnol 6(9):573-579 (2011)
Nature Nanotechnology | Letter Tunable metallic-like conductivity in microbial nanowire networks * Nikhil S. Malvankar1, 2 * Madeline Vargas2, 3 * Kelly P. Nevin2 * Ashley E. Franks2 * Ching Leang2 * Byoung-Chan Kim2, 5 * Kengo Inoue2, 5 * Tünde Mester2, 5 * Sean F. Covalla2, 5 * Jessica P. Johnson2, 5 * Vincent M. Rotello4 * Mark T. Tuominen1 * Derek R. Lovley2 * Affiliations * Contributions * Corresponding authorsJournal name:Nature NanotechnologyVolume: 6,Pages:573–579Year published:(2011)DOI:doi:10.1038/nnano.2011.119Received18 April 2011Accepted23 June 2011Published online07 August 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Electronic nanostructures made from natural amino acids are attractive because of their relatively low cost, facile processing and absence of toxicity1, 2, 3. However, most materials derived from natural amino acids are electronically insulating1, 2, 3, 4, 5, 6. Here, we report metallic-like conductivity in films of the bacterium Geobacter sulfurreducens7 and also in pilin nanofilaments (known as microbial nanowires8, 9) extracted from these bacteria. These materials have electronic conductivities of ~5 mS cm−1, which are comparable to those of synthetic metallic nanostructures2. They can also conduct over distances on the centimetre scale, which is thousands of times the size of a bacterium. Moreover, the conductivity of the biofilm can be tuned by regulating gene expression, and also by varying the gate voltage in a transistor configuration. The conductivity of the nanofilaments has a temperature dependence similar to that of a disordered metal, and the conductivity coul! d be increased by processing. View full text Subject terms: * Electronic properties and devices * Nanobiotechnology Figures at a glance * Figure 1: Strategy to measure in situ biofilm conductivity. , Schematic of microbial fuel cell with two gold electrodes serving as an anode, separated from the cathode by a proton exchange membrane (PEM). The biofilm grows over the electrodes and the non-conducting gap between the two electrodes. No biofilm forms on the control electrode pair. Gap width 2a = 50 µm, electrode width b ≈ 1.27 cm, electrode length L ≈ 2.54 cm, electrode thickness t ≈ 50 nm and biofilm height g. –, Representative fluorescent confocal scanning laser microscopy images of split electrodes. Images were taken when the microbial current was 0.25 mA and the biofilm height was 36 ± 1.4 µm. Gap is indicated by arrows. –, Top-down confocal image slices of biofilm spanning the non-conductive gap. X–Y image slices (parallel to the electrode surface). Scale bar, 100 µm. , Cross-sectional image of biofilm spanning the non-conductive gap. X–Z image slice through the biofilm, in a direction perpendicular to the surface of the gold anode and across the 5! 0 µm gap. Scale bar, 50 µm. * Figure 2: Measurement setup and conductance data. , Representative current produced by the DL-1 strain of G. sulfurreducens. , Schematic of conductivity measurements. , Conductance measured across the gap-spanning biofilm as well as measurements from controls in which a biofilm did not span the gap. Error bars indicate the standard deviation (s.d.) of individual measurements for several biofilms (n = 5 for the biofilm bridging the gap and control electrodes, n = 2 for the biofilm not bridging the gap). , Comparison of conductivity measured using two- and four-probe methods. Error bars show s.d. of individual measurements for four biofilms of KN400. AVG indicates the average of forward and reverse polarity conductivity. * Figure 3: Evidence for pili being associated with biofilm conductivity. , Comparison of conductivity of biofilms of various strains and corresponding structural pilin protein (PilA) in the biofilms. Error bars indicate s.d. PilA expression levels are normalized by PilA expression in DL-1. Correlation coefficient for conductivity and PilA abundance for all DL-1 strains is 0.94. Inset: Western blot analysis of PilA in electrode biofilms. Lane 1, KN400 strain; Lane 2, BEST strain; Lane 3, DL-1 strain; Lane 4, fumarate-grown DL-1 strain. , TEM image of sheared pili nanofilaments. Scale bar, 50 nm. , TEM image of biofilm of strain KN400 grown on split anode. Scale bar, 500 nm. , AFM image of interpenetrating pili filament network after placing pili on electrodes. Scale bar, 500 nm. , Conductivity measurements of filaments of wild-type and PilA mutant of KN400 strain in comparison with control buffer. Data represent mean ± s.d. of three biological replicates. * Figure 4: Observation of metallic-like nature of conductivity. , Temperature dependence of conductivity of free-standing biofilm formed by G. sulfurreducens strain CL-1 and pili filaments of strain KN400 measured with a four-probe method. Error bars represent s.d. Data are representative of several replicates (n = 4 for biofilm; n = 3 for biological replicates for pili). The difference in conductivity between pili and biofilm at 300 K is due to the lower pili concentration required on smaller electrodes for four-probe measurements (see Methods). Control experiments containing media buffer or with biofilm, but not bridging the gap, showed very low conductivity (<1 × 10−2 µS cm−1 at 300 K; see Fig. 3e) that did not change with temperature. Inset: Arrhenius fit for exponentially decreasing conductivity. , Conductivity of DL-1 biofilm and control measured by electrochemical gating. Error bars show s.d. of individual measurements for two biofilms of strain DL-1. There was no increase in conductivity in the absence of a biofilm. Inset: ! experimental setup for electrochemical gating: an electrolyte-gated field-effect transistor configuration. Vsd and Isd: voltage applied and current measured between source and drain electrodes, respectively. Vg and Ig: gate voltage applied between reference and source electrodes and gate current measured. Biofilm conductance is calculated as G = IsdVsd. Note that the lower scale refers to the voltage at the source electrode with respect to the Ag/AgCl gate electrode (electrochemical convention), whereas the upper scale refers to the voltage at the gate electrode with respect to the source electrode (solid-state transistor convention). Author information * Abstract * Author information * Supplementary information Affiliations * Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003, USA * Nikhil S. Malvankar & * Mark T. Tuominen * Department of Microbiology, University of Massachusetts, Amherst, Massachusetts 01003, USA * Nikhil S. Malvankar, * Madeline Vargas, * Kelly P. Nevin, * Ashley E. Franks, * Ching Leang, * Byoung-Chan Kim, * Kengo Inoue, * Tünde Mester, * Sean F. Covalla, * Jessica P. Johnson & * Derek R. Lovley * Department of Biology, College of the Holy Cross, Worcester, Massachusetts 01610, USA * Madeline Vargas * Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, USA * Vincent M. Rotello * Present address: Korea Research Institute of Bioscience and Biotechnology, Yusong-gu, Daejeon 305-806, South Korea (B.C.K.); Interdisciplinary Research Organization, University of Miyazaki, Kiyotake, Miyazaki 889-1692, Japan (K.I.); University of Michigan Medical School and Veterans Affairs Medical Research Centre, Ann Arbor, Michigan 48105, USA. (T.M.); Mascoma Corporation, Lebanon, New Hampshire 03766, USA (S.F.C. and J.P.J.) * Byoung-Chan Kim, * Kengo Inoue, * Tünde Mester, * Sean F. Covalla & * Jessica P. Johnson Contributions The experiments were designed by N.S.M., K.P.N. and M.T.T., with suggestions from A.E.F., S.F.C, V.M.T. and D.R.L. N.S.M. performed electrical measurements, X-ray studies and AFM imaging of pili preparations. M.V. prepared and TEM-imaged pilin filaments and performed haem staining. N.S.M., M.V., B.C.K., K.I. and T.M. performed protein measurements. B.C.K. generated the BEST strain. C.L. generated the CL-1 strain and performed the peeling and TEM-imaging of biofilms. A.E.F. and J.P.J. carried out the confocal imaging of biofilms. N.S.M., M.T.T. and D.R.L. analysed the data and wrote the manuscript. All authors discussed the results and commented on the manuscript. Competing financial interests The authors declare no competing financial interests. Corresponding authors Correspondence to: * Mark T. Tuominen or * Derek R. Lovley Author Details * Nikhil S. Malvankar Search for this author in: * NPG journals * PubMed * Google Scholar * Madeline Vargas Search for this author in: * NPG journals * PubMed * Google Scholar * Kelly P. Nevin Search for this author in: * NPG journals * PubMed * Google Scholar * Ashley E. Franks Search for this author in: * NPG journals * PubMed * Google Scholar * Ching Leang Search for this author in: * NPG journals * PubMed * Google Scholar * Byoung-Chan Kim Search for this author in: * NPG journals * PubMed * Google Scholar * Kengo Inoue Search for this author in: * NPG journals * PubMed * Google Scholar * Tünde Mester Search for this author in: * NPG journals * PubMed * Google Scholar * Sean F. Covalla Search for this author in: * NPG journals * PubMed * Google Scholar * Jessica P. Johnson Search for this author in: * NPG journals * PubMed * Google Scholar * Vincent M. Rotello Search for this author in: * NPG journals * PubMed * Google Scholar * Mark T. Tuominen Contact Mark T. Tuominen Search for this author in: * NPG journals * PubMed * Google Scholar * Derek R. Lovley Contact Derek R. Lovley Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (3,906 KB) Supplementary information Additional data - Self-assembly of self-limiting monodisperse supraparticles from polydisperse nanoparticles
- Nat Nanotechnol 6(9):580-587 (2011)
Nature Nanotechnology | Article Self-assembly of self-limiting monodisperse supraparticles from polydisperse nanoparticles * Yunsheng Xia1 * Trung Dac Nguyen2 * Ming Yang2 * Byeongdu Lee3 * Aaron Santos2 * Paul Podsiadlo4 * Zhiyong Tang1 * Sharon C. Glotzer2, 5 * Nicholas A. Kotov2, 5 * Affiliations * Contributions * Corresponding authorsJournal name:Nature NanotechnologyVolume: 6,Pages:580–587Year published:(2011)DOI:doi:10.1038/nnano.2011.121Received14 March 2011Accepted28 June 2011Published online21 August 2011Corrected online26 August 2011 Abstract * Abstract * Change history * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Nanoparticles are known to self-assemble into larger structures through growth processes that typically occur continuously and depend on the uniformity of the individual nanoparticles. Here, we show that inorganic nanoparticles with non-uniform size distributions can spontaneously assemble into uniformly sized supraparticles with core–shell morphologies. This self-limiting growth process is governed by a balance between electrostatic repulsion and van der Waals attraction, which is aided by the broad polydispersity of the nanoparticles. The generic nature of the interactions creates flexibility in the composition, size and shape of the constituent nanoparticles, and leads to a large family of self-assembled structures, including hierarchically organized colloidal crystals. View full text Subject terms: * Nanoparticles * Structural properties Figures at a glance * Figure 1: Electron microscopy and size distribution for supraparticles. –, EM (,,,), TEM (,,,) images and size distribution (,,,) of four CdSe supraparticle samples obtained at different reaction times: 20 min, CdSe-20 (–); 120 min, CdSe-30 (–); 1,080 min, CdSe-40 (–); 2,400 min, CdSe-50 (–). , SEM images of colloidal crystals made of CdSe supraparticles. * Figure 2: Intermediate stages of formation of supraparticle at 40 °C and detailed structural characterization of supraparticles. –, Stages of formation at 5 min (), 9 min (), 15 min () and 19 min (). , Experimental dependence of dSP/dNP and the electrokinetic ζ-potential on reaction times. dSP and dNP were measured by DLS and UV-vis spectroscopy, respectively, and electrokinetic ζ-potential was measured by DLS. , SAXS curves for CdSe-30 (1), CdSe-40 (2) and CdSe-50 (3) supraparticles. Red and blue lines represent solution and dried samples, respectively. Inflection points are marked by arrows. , Measured data for CdSe-50 in solution (magenta) and calculated curves from core–shell supraparticle model (blue). , Radial distribution of the number of subunits for the core–shell supraparticle model for CdSe-50. * Figure 3: Computer simulation results. , The four stages of supraparticle self-assembly as a function of time. The asphericity parameter of the simulated supraparticles in the final stage of assembly is 0.014 ± 0.006. , Size distribution of the simulated supraparticles assembled from nanoparticles with δNP = 20%, fitted by a 7% standard deviation Gaussian distribution (blue curve). VNP = πσ3/6 is the average nanoparticle volume. , Particle density versus distance r from supraparticle centre, scaled by nanoparticle average diameter σ. , Computer simulation of core–shell supraparticles self-assembled from CdSe nanoparticles (blue) and preformed gold nanospheres (orange). , Computer simulation of core–shell supraparticles self-assembled from CdSe nanoparticles (blue) and pre-formed gold nanorods (orange). * Figure 4: Analogous supraparticle assemblies from different materials. –, TEM and SEM images from CdS (), ZnSe () and PbS () supraparticles, and Au-sphere/CdS (), Au-sphere/CdSe (,), Au-rod/CdS (,) and Au-rod/CdSe () core–shell supraparticles. ,, Images of high-angle annular dark-field scanning TEM and energy-dispersive X-ray elemental mapping from Au-sphere/CdSe () and Au-rod/CdSe () core–shell supraparticles. , SEM image of colloidal crystals from Au-sphere/CdSe supraparticles. Change history * Abstract * Change history * Author information * Supplementary informationCorrected online 26 August 2011In the version of this Article originally published online, the full list of corresponding authors should have been Zhiyong Tang, Sharon C. Glotzer and Nicholas A. Kotov. This has been corrected in all versions of the Article. Author information * Abstract * Change history * Author information * Supplementary information Affiliations * National Center for Nanoscience and Technology, 11 Beiyitiao, Zhongguancun, Beijing, 100190, China * Yunsheng Xia & * Zhiyong Tang * Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA * Trung Dac Nguyen, * Ming Yang, * Aaron Santos, * Sharon C. Glotzer & * Nicholas A. Kotov * Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, Illinois 60439, USA * Byeongdu Lee * Center for Nanoscale Materials, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, Illinois 60439, USA * Paul Podsiadlo * Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA * Sharon C. Glotzer & * Nicholas A. Kotov Contributions Y.S.X., Z.Y.T., and N.A.K. conceived and designed the experiments. Y.S.X. performed the experiments. T.D.N., A.S. and S.C.G. designed and performed the computer simulations. B.L. and P.P. carried out SAXS measurements and corresponding data analysis. M.Y. contributed to the nanoparticle synthesis. Y.S.X., T.D.N., B.L., Z.Y.T., S.C.G. and N.A.K. analysed the data. Y.S.X., T.D.N., B.L., Z.Y.T., S.C.G. and N.A.K. co-wrote the paper. All authors discussed the results and commented on the manuscript. Competing financial interests The authors declare no competing financial interests. Corresponding authors Correspondence to: * Zhiyong Tang or * Sharon C. Glotzer or * Nicholas A. Kotov Author Details * Yunsheng Xia Search for this author in: * NPG journals * PubMed * Google Scholar * Trung Dac Nguyen Search for this author in: * NPG journals * PubMed * Google Scholar * Ming Yang Search for this author in: * NPG journals * PubMed * Google Scholar * Byeongdu Lee Search for this author in: * NPG journals * PubMed * Google Scholar * Aaron Santos Search for this author in: * NPG journals * PubMed * Google Scholar * Paul Podsiadlo Search for this author in: * NPG journals * PubMed * Google Scholar * Zhiyong Tang Contact Zhiyong Tang Search for this author in: * NPG journals * PubMed * Google Scholar * Sharon C. Glotzer Contact Sharon C. Glotzer Search for this author in: * NPG journals * PubMed * Google Scholar * Nicholas A. Kotov Contact Nicholas A. Kotov Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Change history * Author information * Supplementary information PDF files * Supplementary information (3,191 KB) Supplementary information Additional data - Photocurrent mapping of near-field optical antenna resonances
- Nat Nanotechnol 6(9):588-593 (2011)
Nature Nanotechnology | Article Photocurrent mapping of near-field optical antenna resonances * Edward S. Barnard1 * Ragip A. Pala1 * Mark L. Brongersma1 * Affiliations * Contributions * Corresponding authorJournal name:Nature NanotechnologyVolume: 6,Pages:588–593Year published:(2011)DOI:doi:10.1038/nnano.2011.131Received09 May 2011Accepted14 July 2011Published online21 August 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg An increasing number of photonics applications make use of nanoscale optical antennas that exhibit a strong, resonant interaction with photons of a specific frequency. The resonant properties of such antennas are conventionally characterized by far-field light-scattering techniques. However, many applications require quantitative knowledge of the near-field behaviour, and existing local field measurement techniques provide only relative, rather than absolute, data. Here, we demonstrate a photodetector platform that uses a silicon-on-insulator substrate to spectrally and spatially map the absolute values of enhanced fields near any type of optical antenna by transducing local electric fields into photocurrent. We are able to quantify the resonant optical and materials properties of nanoscale (~50 nm) and wavelength-scale (~1 µm) metallic antennas as well as high-refractive-index semiconductor antennas. The data agree well with light-scattering measurements, full-field simula! tions and intuitive resonator models. View full text Subject terms: * Nanometrology and instrumentation * Photonic structures and devices Figures at a glance * Figure 1: Near-field SOI detector platform architecture. , Schematic of the SOI photodetector platform developed to explore near-field resonances of optical antennas. The platform was first evaluated by analysing the ability of a plasmonic wedge antenna to concentrate light into the ultrathin (40 nm) silicon layer. At various resonant widths of the wedge, the near-field of the antenna produces an enhanced photocurrent that is laterally collected by the electrical contacts. , Top-view scanning electron microscopy image of a silver wedge antenna placed onto the SOI detector platform. , Dark-field optical image of the wedge in . Scale bars, 10 µm. * Figure 2: Spatial and spectral photocurrent mapping of a wedge antenna. , Spatial map of the photocurrent enhancement ratio (Ja/Jo) measured for the wedge antenna shown in Fig. 1b,c using an illumination wavelength of λo = 700 nm. Red regions indicate photocurrent enhancements, and blue regions show photocurrent suppression. Scale bar, 5 µm. –, Photocurrent enhancement linescans along the length of the wedge taken at λo = 700 nm (), λo = 750 nm (), λo = 800 nm (). Horizontal dotted lines demarcate the narrow end of the wedge structure at w = 50 nm. Arrows in and indicate photocurrent enhancement resonances observed at w = 95 nm and w = 320 nm. * Figure 3: Analysis of resonant behaviour using two-dimensional FDFD simulations. , Simulated photocurrent enhancement ratio (Ja/Jo) and equivalent in-coupling cross-section (σi) as a function of strip width at λo = 700 nm. –, Cross-sectional time-averaged magnetic field maps of resonant metallic strips placed on the SOI detector. The strip widths are 620 nm (), 350 nm (), 90 nm (), and the illumination wavelength is λo = 700 nm. Scale bars, 50 nm. * Figure 4: Theoretical and experimental photocurrent enhancement maps. ,, Theoretical () and experimental () photocurrent enhancement maps, showing the enhancement ratio (Ja/Jo) in photocurrent produced by a wedge at different incident wavelengths and strip widths, given an illumination spot size of 1.2 µm. The dotted line at w = 50 nm denotes the start of the wedge antenna. Overlaid lines are predictions from a Fabry–Pérot resonator model. Solid and dashed lines correspond to different order resonances (m = 1 and m = 3, respectively). * Figure 5: Spatial and spectral mapping of photocurrent enhancement from a silicon nanowire optical antenna. , Optical microscope image of silicon nanowires on top of a detector platform. Scale bar, 5 µm. Two different nanowires are labelled '1' and '2'. , Photocurrent enhancement map at λo = 800 nm of the region in . Units are nanometres of in-coupling cross-section, σi. Polarization is denoted by a red arrow. Scale bar, 5 µm. , Experimentally measured in-coupling cross-section of silicon nanowire antenna of wire 1 with an electric-field polarization parallel (TM) to the wire (45° from horizontal). , Simulated TM in-coupling cross-section of 90 nm silicon nanowire on a detector platform. Red vertical lines in and highlight resonant wavelengths of the nanowire. ,, Full field simulations of the TM-illuminated nanowire on the detector platform at λo = 500 nm () and λo = 800 nm (). Time-averaged longitudinal (out-of-plane) electric field is shown. Panels and illustrate how wire resonances create high near-field intensities in the active detector layer. Author information * Abstract * Author information * Supplementary information Affiliations * Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA * Edward S. Barnard, * Ragip A. Pala & * Mark L. Brongersma Contributions E.S.B. and M.L.B. conceived and designed the experiments. E.S.B. and R.A.P. designed and fabricated the samples. E.S.B. performed the optical experiments. E.S.B. and M.L.B. co-wrote the manuscript. Competing financial interests The authors declare no competing financial interests. Corresponding author Correspondence to: * Mark L. Brongersma Author Details * Edward S. Barnard Search for this author in: * NPG journals * PubMed * Google Scholar * Ragip A. Pala Search for this author in: * NPG journals * PubMed * Google Scholar * Mark L. Brongersma Contact Mark L. Brongersma Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (518 KB) Supplementary information Additional data - Ferri-liposomes as an MRI-visible drug-delivery system for targeting tumours and their microenvironment
- Nat Nanotechnol 6(9):594-602 (2011)
Nature Nanotechnology | Article Ferri-liposomes as an MRI-visible drug-delivery system for targeting tumours and their microenvironment * Georgy Mikhaylov1 * Ursa Mikac2, 3 * Anna A. Magaeva4 * Volya I. Itin4 * Evgeniy P. Naiden4 * Ivan Psakhye1, 13 * Liane Babes5 * Thomas Reinheckel5, 6 * Christoph Peters5, 6 * Robert Zeiser7 * Matthew Bogyo8 * Vito Turk1, 9 * Sergey G. Psakhye4, 10 * Boris Turk1, 9, 11, 12 * Olga Vasiljeva1 * Affiliations * Contributions * Corresponding authorsJournal name:Nature NanotechnologyVolume: 6,Pages:594–602Year published:(2011)DOI:doi:10.1038/nnano.2011.112Received31 January 2011Accepted16 June 2011Published online07 August 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg The tumour microenvironment regulates tumour progression and the spread of cancer in the body. Targeting the stromal cells that surround cancer cells could, therefore, improve the effectiveness of existing cancer treatments. Here, we show that magnetic nanoparticle clusters encapsulated inside a liposome can, under the influence of an external magnet, target both the tumour and its microenvironment. We use the outstanding T2 contrast properties (r2 = 573–1,286 s−1 mM−1) of these ferri-liposomes, which are ~95 nm in diameter, to non-invasively monitor drug delivery in vivo. We also visualize the targeting of the tumour microenvironment by the drug-loaded ferri-liposomes and the uptake of a model probe by cells. Furthermore, we used the ferri-liposomes to deliver a cathepsin protease inhibitor to a mammary tumour and its microenvironment in a mouse, which substantially reduced the size of the tumour compared with systemic delivery of the same drug. View full text Subject terms: * Nanomedicine Figures at a glance * Figure 1: Characterization of the magnetic nanocarrier system. Schematic on the left corresponds to the experimental data on the right. , Transmission electron micrographs of FMIO nanoparticles. Inset: corresponding electron diffraction pattern. , Size distribution of FMIO nanoparticles (average size, D = 6.65 nm). , Field-emission gun scanning electron microscopy of the aqueous colloidal system of FMIO nanoparticles. , DLS measurement of FMIO colloidal dispersion showing the distribution of diameters of the nanoparticle clusters and their average size (D = 56.56 nm). , AFM image of liposome-encapsulated FMIO nanoparticles (ferri-liposome). , Liposome size as determined by DLS (average size, D = 92.3 nm). * Figure 2: MR contrast properties of electrostatically stabilized FMIO nanoparticles. , Spin–lattice 1/T1 (left) and spin–spin 1/T2 (right) relaxation rates of 39 nm and 57 nm FMIO nanoparticles at different concentrations, compared to commercially available MR contrast agents (Ferridex17 and Magnevist). Relaxivity rates r1 and r2 were obtained by comparing the measured (symbols) and theoretical (lines) values. , T1- and T2-weighted MR images of agarose phantoms at different concentrations of 39 nm and 57 nm FMIO nanoparticles. , Schematic (left) and T2-weighted MR image (right) of four phantom-probes containing 1% agarose (samples 1 and 3), and 3.4 mM FMIO nanoparticles either injected into the centre of the 1% agarose gel (sample 2) or diffused into the 1% agarose in the presence of a magnetic field (sample 4). Bottom panel shows signal intensity profiles along lines i and ii. Sample 5 is a small probe containing a solution of CuSO4·H2O in the phantom. * Figure 3: Monitoring the targeting and release of ferri-liposomes in vivo. , T2-weighted MR images of an MMTV-PyMT transgenic mouse before and 1 h and 48 h after intraperitoneal injection of ferri-liposomes followed by 1 h of magnetic field application to the lower right tumour (white arrow). Inset: red rectangle shows the region of the MRI images. , Fluorescence images of primary MMTV-PyMT tumour cells and MEFs incubated with Alexa Fluor 555-functionalized ferri-liposomes for 3 h at 37 °C. Scale bar, 20 µM. Data are representative of three separate experiments. , Optical imaging of FVB.luctg/+;PyMTtg/+ mice that have been intraperitoneally administered with ferri-liposomes (FL) carrying D-luciferin in the presence (targeted FL) and absence (non-targeted FL) of magnet application. A high-intensity luciferase signal was detected only in the tumour region exposed to the magnet (black arrow). The scale is in photons s−1 sm−2 sr−1. * Figure 4: Anti-tumour effect of magnetically targeted ferri-liposomes containing cysteine protease inhibitor JPM-565. , Schematic showing the treatment experiment design. Cells from the transgenic (Tg) MMTV-PyMT mouse with multifocal tumours were cultured and inoculated into an immunocompetent FVB/N mouse to form a model with a monofocal tumour that can be easily monitored. , Table showing the treatment groups. Mice were treated with stabilizing buffer containing different compounds and magnetic targeting combinations as represented by the ' + ' and ' − ' signs. , Tumour volumes for each treatment day for the different treatment groups. *P < 0.05, **P < 0.01 and **P < 0.001, compared with the other groups. , Activity of cysteine cathepsins in tumour tissue after JPM-565 administration (NS, not significant). , The percentage of Ki67+ cells as calculated by computer-assisted data analyses. Data are presented as means and standard errors, n = 5. Statistics were analysed using Student's t-test. NS, not significant. , Fluorescent images of control tumours and tumours treated with JPM-5! 65 targeted by ferri-liposomes (JPM + FLt). E-cadherin is stained green and nucleus is stained with Hoechst 33342 (blue). Higher-magnification images (right column) of white rectangles from the middle column illustrate the different patterns of E-cadherin localization. Scale bars, 100 µm and 25 µm (higher magnification images). * Figure 5: In vivo detection of fluorescent ferri-liposomes in tumours. , Fluorescent images of tissues confirm the presence of intraperitoneally administered Alexa Fluor 546-functionalized ferri-liposomes (red) in the tumour microenvironment. Inset: higher-magnification image of an individual cell of the tumour stroma outlined by the white rectangle in the main panel. , Haematoxylin and eosin staining of the corresponding section. Stromal (ST) and tumour (T) compartments of the tumour tissue are indicated, with their boundary demarcated by a dotted line. Scale bars in and , 200 µm and 20 µm (inset). ,, Uptake of Alexa Fluor 555-functionalized ferri-liposomes (red) by both stroma (white arrows) and tumour cells (pink arrows), after double intravenous injection of ferri-liposomes. Tissues were co-stained with tumour-associated macrophages (CD206-FITC; green) in and tumour cell marker (E-cadherin; green fluorescence) in . Scale bars in and , 40 µm. Author information * Abstract * Author information * Supplementary information Affiliations * Department of Biochemistry and Molecular and Structural Biology, Jozef Stefan Institute, SI-1000 Ljubljana, Slovenia * Georgy Mikhaylov, * Ivan Psakhye, * Vito Turk, * Boris Turk & * Olga Vasiljeva * Department of Condensed Matter Physics, Jozef Stefan Institute, SI-1000 Ljubljana, Slovenia * Ursa Mikac * Centre of Excellence EN-FIST, SI-1000 Ljubljana, Slovenia * Ursa Mikac * Tomsk Scientific Center, Siberian Branch of Russian Academy of Sciences, Tomsk 634055, Russia * Anna A. Magaeva, * Volya I. Itin, * Evgeniy P. Naiden & * Sergey G. Psakhye * Institut für Molekulare Medizin und Zellforschung, Albert-Ludwigs-Universität Freiburg, Freiburg 79104, Germany * Liane Babes, * Thomas Reinheckel & * Christoph Peters * BIOSS Centre for Biological Signalling Studies, Albert-Ludwigs-Universität Freiburg, Freiburg 79104, Germany * Thomas Reinheckel & * Christoph Peters * Department of Hematology and Oncology, University Medical Center Freiburg, Freiburg 79106, Germany * Robert Zeiser * Department of Pathology, Microbiology and Immunology, Stanford University School of Medicine, California 94305, USA * Matthew Bogyo * Center of Excellence CIPKEBIP, SI-1000 Ljubljana, Slovenia * Vito Turk & * Boris Turk * Institute of Strength Physics and Materials Science, Tomsk 634021, Russia * Sergey G. Psakhye * Faculty of Chemistry and Chemical Technology, University of Ljubljana, SI-1000 Ljubljana, Slovenia * Boris Turk * Center of Excellence Nanosciences and Nanotechnology, SI-1000 Ljubljana, Slovenia * Boris Turk * Present address: Department of Molecular Cell Biology, Max Planck Institute of Biochemistry, Martinsried 82152, Germany * Ivan Psakhye Contributions G.M., U.M., I.P., S.G.P., B.T. and O.V. conceived and designed the experiments. G.M., U.M., L.B. and O.V. performed the experiments. G.M., U.M., S.G.P., B.T. and O.V. analysed the data. T.R., C.P. and R.Z. contributed transgenic mouse models and animal imaging. M.B. contributed JPM-565 inhibitor. A.A.M., V.I.I., E.P.N. and S.G.P. supplied the magnetic nanoparticles. S.G.P., V.T., B.T. and O.V. supervised the project. G.M., S.G.P., B.T. and O.V. wrote the manuscript. All authors discussed the results and commented on the manuscript. Competing financial interests The authors declare no competing financial interests. Corresponding authors Correspondence to: * Boris Turk or * Olga Vasiljeva Author Details * Georgy Mikhaylov Search for this author in: * NPG journals * PubMed * Google Scholar * Ursa Mikac Search for this author in: * NPG journals * PubMed * Google Scholar * Anna A. Magaeva Search for this author in: * NPG journals * PubMed * Google Scholar * Volya I. Itin Search for this author in: * NPG journals * PubMed * Google Scholar * Evgeniy P. Naiden Search for this author in: * NPG journals * PubMed * Google Scholar * Ivan Psakhye Search for this author in: * NPG journals * PubMed * Google Scholar * Liane Babes Search for this author in: * NPG journals * PubMed * Google Scholar * Thomas Reinheckel Search for this author in: * NPG journals * PubMed * Google Scholar * Christoph Peters Search for this author in: * NPG journals * PubMed * Google Scholar * Robert Zeiser Search for this author in: * NPG journals * PubMed * Google Scholar * Matthew Bogyo Search for this author in: * NPG journals * PubMed * Google Scholar * Vito Turk Search for this author in: * NPG journals * PubMed * Google Scholar * Sergey G. Psakhye Search for this author in: * NPG journals * PubMed * Google Scholar * Boris Turk Contact Boris Turk Search for this author in: * NPG journals * PubMed * Google Scholar * Olga Vasiljeva Contact Olga Vasiljeva Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (3,237 KB) Supplementary information Additional data
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