Theoretical Description of the Role of Halides, Silver, and Surfactants on the Structure of Gold Nanorods

Density functional theory simulations including dispersion provide an atomistic description of the role of different compounds in the synthesis of gold-nanorods. Anisotropy is caused by the formation of a complex between the surfactant, bromine, and silver that preferentially adsorbs on some facets of the seeds, blocking them from further growth. In turn, the nanorod structure is driven by the perferential adsorption of the surfactant, which induces the appearance of open {520} lateral facets

Combination of HAADF-STEM and ADF-STEM Tomography for Core–Shell Hybrid Materials

Characterization of core–shell type nanoparticles in 3D by transmission electron microscopy (TEM) can be very challenging. Especially when both heavy and light elements coexist within the same nanostructure, artifacts in the 3D reconstruction are often present. A representative example would be a particle comprising an anisotropic metallic (Au) nanoparticle coated with a (mesoporous) silica shell. To obtain a reliable 3D characterization of such an object, a dose-efficient strategy is proposed to simultaneously acquire high-angle annular dark-field scanning TEM and annular dark-field tilt series for tomography. The 3D reconstruction is further improved by applying an advanced masking and interpolation approach to the acquired data. This new methodology enables us to obtain high-quality reconstructions from which also quantitative information can be extracted. This approach is broadly applicable to investigate hybrid core–shell materials

XPS characterization of Au (core)/SiO2 (shell) nanoparticles

Core-shell nanoparticles with ca. 15-nm gold core and 6-nm silica shell were prepared and characterized by XPS. The Au/Si atomic ratio determined by XPS is independent of the electron takeoff angle because of the concentric spherical shape of the nanoparticles. The formula given by Wertheim and DiCenzo (Phys. Rev. B 1988, 37, 844) for spherical nanoparticles and the modified one by Yang et al. (J. Appl. Phys. 2005, 97, 024303) for core-shell nanoparticles are used to correlate the XPS-derived composition with the geometry of the nanoparticles only after significantly modifying either the bulk density of the silica shell or the attenuation length of the photoelectrons. © 2005 American Chemical Society

Cancer Cell Internalization of Gold Nanostars Impacts Their Photothermal Efficiency In Vitro and In Vivo: Toward a Plasmonic Thermal Fingerprint in Tumoral Environment

Gold nanoparticles are prime candidates for cancer thermotherapy. However, while the ultimate target for nanoparticle-mediated photothermal therapy is the cancer cell, heating performance has not previously been evaluated in the tumoral environment. A systematic investigation of gold nanostar heat-generating efficiency in situ is presented: not only in cancer cells in vitro but also after intratumoral injection in vivo. It is demonstrated that (i) in aqueous dispersion, heat generation is governed by particle size and exciting laser wavelength; (ii) in cancer cells in vitro, heat generation is still very efficient, but irrespective of both particle size and laser wavelength; and (iii) heat generation by nanostars injected into tumors in vivo evolves with time, as the nanostars are trafficked from the extracellular matrix into endosomes. The plasmonic heating response thus serves as a signature of nanoparticle internalization in cells, bringing the ultimate goal of nanoparticle-mediated photothermal therapy a step closer. ¸ 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Lectin-gated and glycan functionalized mesoporous silica nanocontainers for targeting cancer cells overexpressing Lewis X antigen

[EN] Gated mesoporous silica nanoparticles can deliver payload upon the application of a predefined stimulus, and therefore are promising drug delivery systems. Despite their important role, relatively low emphasis has been placed on the design of gating systems that actively target carbohydrate tumor cell membrane receptors. We describe herein a new Lewis X (Le(x)) antigen-targeted delivery system comprising mesoporous silica nanoparticles (MSNs) loaded with ATTO 430LS dye, functionalized with a Le(x) derivative (1) and capped with a fucose-specific carbohydrate-binding protein (Aleuria aurantia lectin (AAL)). This design takes advantage of the affinity of AAL for Le(x) overexpressed receptors in certain cancer cells. In the proximity of the cells, AAL is detached from MSNs to bind Le(x), and selectins in the cells bind Le(x) in the gated MSNs, thereby inducing cargo delivery. Gated MSNs are nontoxic to colon cancer DLD-1 cells, and ATTO 430LS dye delivered correlated with the amount of Le(x) antigen overexpressed at the DLD-1 cell surface. This is one of the few examples of MSNs using biologically relevant glycans for both capping (via interaction with AAL) and targeting (via interaction with overexpressed Le(x) at the cell membrane).The authors thank the Spanish Government (Projects MAT2015-64139-C4-1-R and MAT2013-46101-R (MINECO/ FEDER)), Fondo de Investigacion Sanitaria (PI15/00480) and Generalitat Valenciana (Project PROMETEOII/2014/047 and project GVA/2014/13) for support. R. B. is thankful to Svagata. Eu (Erasmus Mundus Action-II program) for his fellowship. The authors also thank the Electron Microscopy Service at the UPV for support.Bhat, R.; García, I.; Aznar, E.; Arnáiz, B.; Martínez-Bisbal, M.; Liz-Marzán, L.; Penadés, S.... (2018). Lectin-gated and glycan functionalized mesoporous silica nanocontainers for targeting cancer cells overexpressing Lewis X antigen. Nanoscale. 10(1):239-249. https://doi.org/10.1039/c7nr06415bS239249101Argyo, C., Weiss, V., Bräuchle, C., & Bein, T. (2013). Multifunctional Mesoporous Silica Nanoparticles as a Universal Platform for Drug Delivery. Chemistry of Materials, 26(1), 435-451. doi:10.1021/cm402592tAznar, E., Martínez-Máñez, R., & Sancenón, F. (2009). Controlled release using mesoporous materials containing gate-like scaffoldings. Expert Opinion on Drug Delivery, 6(6), 643-655. doi:10.1517/17425240902895980Aznar, E., Oroval, M., Pascual, L., Murguía, J. R., Martínez-Máñez, R., & Sancenón, F. (2016). Gated Materials for On-Command Release of Guest Molecules. Chemical Reviews, 116(2), 561-718. doi:10.1021/acs.chemrev.5b00456Wang, X., Tan, L.-L., Li, X., Song, N., Li, Z., Hu, J.-N., … Yang, Y.-W. (2016). Smart mesoporous silica nanoparticles gated by pillararene-modified gold nanoparticles for on-demand cargo release. Chemical Communications, 52(95), 13775-13778. doi:10.1039/c6cc08241fChen, X., Sun, H., Hu, J., Han, X., Liu, H., & Hu, Y. (2017). Transferrin gated mesoporous silica nanoparticles for redox-responsive and targeted drug delivery. Colloids and Surfaces B: Biointerfaces, 152, 77-84. doi:10.1016/j.colsurfb.2017.01.010Prasad, R., Aiyer, S., Chauhan, D. S., Srivastava, R., & Selvaraj, K. (2016). Bioresponsive carbon nano-gated multifunctional mesoporous silica for cancer theranostics. Nanoscale, 8(8), 4537-4546. doi:10.1039/c5nr06756aAgostini, A., Mondragón, L., Coll, C., Aznar, E., Marcos, M. D., Martínez-Máñez, R., … Amorós, P. (2012). Dual Enzyme-Triggered Controlled Release on Capped Nanometric Silica Mesoporous Supports. ChemistryOpen, 1(1), 17-20. doi:10.1002/open.201200003García-Fernández, A., García-Laínez, G., Ferrándiz, M. L., Aznar, E., Sancenón, F., Alcaraz, M. J., … Orzáez, M. (2017). Targeting inflammasome by the inhibition of caspase-1 activity using capped mesoporous silica nanoparticles. Journal of Controlled Release, 248, 60-70. doi:10.1016/j.jconrel.2017.01.002Ultimo, A., Giménez, C., Bartovsky, P., Aznar, E., Sancenón, F., Marcos, M. D., … Murguía, J. R. (2016). Targeting Innate Immunity with dsRNA-Conjugated Mesoporous Silica Nanoparticles Promotes Antitumor Effects on Breast Cancer Cells. Chemistry - A European Journal, 22(5), 1582-1586. doi:10.1002/chem.201504629Polo, L., Gómez-Cerezo, N., Aznar, E., Vivancos, J.-L., Sancenón, F., Arcos, D., … Martínez-Máñez, R. (2017). Molecular gates in mesoporous bioactive glasses for the treatment of bone tumors and infection. Acta Biomaterialia, 50, 114-126. doi:10.1016/j.actbio.2016.12.025Luo, Z., Ding, X., Hu, Y., Wu, S., Xiang, Y., Zeng, Y., … Zhao, Y. (2013). Engineering a Hollow Nanocontainer Platform with Multifunctional Molecular Machines for Tumor-Targeted Therapy in Vitro and in Vivo. ACS Nano, 7(11), 10271-10284. doi:10.1021/nn404676wZhang, Q., Neoh, K. G., Xu, L., Lu, S., Kang, E. T., Mahendran, R., & Chiong, E. (2014). Functionalized Mesoporous Silica Nanoparticles with Mucoadhesive and Sustained Drug Release Properties for Potential Bladder Cancer Therapy. Langmuir, 30(21), 6151-6161. doi:10.1021/la500746eGuillet-Nicolas, R., Popat, A., Bridot, J.-L., Monteith, G., Qiao, S. Z., & Kleitz, F. (2013). pH-Responsive Nutraceutical-Mesoporous Silica Nanoconjugates with Enhanced Colloidal Stability. Angewandte Chemie International Edition, 52(8), 2318-2322. doi:10.1002/anie.201208840Bringas, E., Köysüren, Ö., Quach, D. V., Mahmoudi, M., Aznar, E., Roehling, J. D., … Stroeve, P. (2012). Triggered release in lipid bilayer-capped mesoporous silica nanoparticles containing SPION using an alternating magnetic field. Chemical Communications, 48(45), 5647. doi:10.1039/c2cc31563gOroval, M., Climent, E., Coll, C., Eritja, R., Aviñó, A., Marcos, M. D., … Amorós, P. (2013). An aptamer-gated silica mesoporous material for thrombin detection. Chemical Communications, 49(48), 5480. doi:10.1039/c3cc42157kHe, D., He, X., Wang, K., Chen, M., Zhao, Y., & Zou, Z. (2013). Intracellular acid-triggered drug delivery system using mesoporous silica nanoparticles capped with T–Hg2+–T base pairs mediated duplex DNA. Journal of Materials Chemistry B, 1(11), 1552. doi:10.1039/c3tb00473bChen, L., Zhou, X., Nie, W., Zhang, Q., Wang, W., Zhang, Y., & He, C. (2016). Multifunctional Redox-Responsive Mesoporous Silica Nanoparticles for Efficient Targeting Drug Delivery and Magnetic Resonance Imaging. ACS Applied Materials & Interfaces, 8(49), 33829-33841. doi:10.1021/acsami.6b11802Croissant, J. G., Zhang, D., Alsaiari, S., Lu, J., Deng, L., Tamanoi, F., … Khashab, N. M. (2016). Protein-gold clusters-capped mesoporous silica nanoparticles for high drug loading, autonomous gemcitabine/doxorubicin co-delivery, and in-vivo tumor imaging. Journal of Controlled Release, 229, 183-191. doi:10.1016/j.jconrel.2016.03.030Oroval, M., Díez, P., Aznar, E., Coll, C., Marcos, M. D., Sancenón, F., … Martínez-Máñez, R. (2016). Self-Regulated Glucose-Sensitive Neoglycoenzyme-Capped Mesoporous Silica Nanoparticles for Insulin Delivery. Chemistry - A European Journal, 23(6), 1353-1360. doi:10.1002/chem.201604104Chen, C., Geng, J., Pu, F., Yang, X., Ren, J., & Qu, X. (2010). Polyvalent Nucleic Acid/Mesoporous Silica Nanoparticle Conjugates: Dual Stimuli-Responsive Vehicles for Intracellular Drug Delivery. Angewandte Chemie International Edition, 50(4), 882-886. doi:10.1002/anie.201005471Yang, X., Liu, X., Liu, Z., Pu, F., Ren, J., & Qu, X. (2012). Near-Infrared Light-Triggered, Targeted Drug Delivery to Cancer Cells by Aptamer Gated Nanovehicles. Advanced Materials, 24(21), 2890-2895. doi:10.1002/adma.201104797Deng, Z., Zhen, Z., Hu, X., Wu, S., Xu, Z., & Chu, P. K. (2011). Hollow chitosan–silica nanospheres as pH-sensitive targeted delivery carriers in breast cancer therapy. Biomaterials, 32(21), 4976-4986. doi:10.1016/j.biomaterials.2011.03.050Palanikumar, L., Choi, E. S., Cheon, J. Y., Joo, S. H., & Ryu, J.-H. (2014). Noncovalent Polymer-Gatekeeper in Mesoporous Silica Nanoparticles as a Targeted Drug Delivery Platform. Advanced Functional Materials, 25(6), 957-965. doi:10.1002/adfm.201402755Li, L.-L., Xie, M., Wang, J., Li, X., Wang, C., Yuan, Q., … Tan, W. (2013). A vitamin-responsive mesoporous nanocarrier with DNA aptamer-mediated cell targeting. Chemical Communications, 49(52), 5823. doi:10.1039/c3cc41072bHäuselmann, I., & Borsig, L. (2014). Altered Tumor-Cell Glycosylation Promotes Metastasis. Frontiers in Oncology, 4. doi:10.3389/fonc.2014.00028Haltiwanger, R. S., & Lowe, J. B. (2004). Role of Glycosylation in Development. Annual Review of Biochemistry, 73(1), 491-537. doi:10.1146/annurev.biochem.73.011303.074043A. Varki , R.Kannagi and B. P.Toole , Glycosylation Changes in Cancer , Cold Spring Harbor Laboratory Press , 2009A. Varki and J. B.Lowe , Biological Roles of Glycans , Cold Spring Harbor Laboratory Press , 2009Gary-Bobo, M., Hocine, O., Brevet, D., Maynadier, M., Raehm, L., Richeter, S., … Durand, J.-O. (2012). Cancer therapy improvement with mesoporous silica nanoparticles combining targeting, drug delivery and PDT. International Journal of Pharmaceutics, 423(2), 509-515. doi:10.1016/j.ijpharm.2011.11.045Brevet, D., Gary-Bobo, M., Raehm, L., Richeter, S., Hocine, O., Amro, K., … Durand, J.-O. (2009). Mannose-targeted mesoporous silica nanoparticles for photodynamic therapy. Chemical Communications, (12), 1475. doi:10.1039/b900427kHocine, O., Gary-Bobo, M., Brevet, D., Maynadier, M., Fontanel, S., Raehm, L., … Frochot, C. (2010). Silicalites and Mesoporous Silica Nanoparticles for photodynamic therapy. International Journal of Pharmaceutics, 402(1-2), 221-230. doi:10.1016/j.ijpharm.2010.10.004Park, I. Y., Kim, I. Y., Yoo, M. K., Choi, Y. J., Cho, M.-H., & Cho, C. S. (2008). Mannosylated polyethylenimine coupled mesoporous silica nanoparticles for receptor-mediated gene delivery. International Journal of Pharmaceutics, 359(1-2), 280-287. doi:10.1016/j.ijpharm.2008.04.010Luo, Z., Cai, K., Hu, Y., Zhao, L., Liu, P., Duan, L., & Yang, W. (2010). Mesoporous Silica Nanoparticles End-Capped with Collagen: Redox-Responsive Nanoreservoirs for Targeted Drug Delivery. Angewandte Chemie International Edition, 50(3), 640-643. doi:10.1002/anie.201005061PENG, J., WANG, K., TAN, W., HE, X., HE, C., WU, P., & LIU, F. (2007). Identification of live liver cancer cells in a mixed cell system using galactose-conjugated fluorescent nanoparticles. Talanta, 71(2), 833-840. doi:10.1016/j.talanta.2006.05.064Yu, M., Jambhrunkar, S., Thorn, P., Chen, J., Gu, W., & Yu, C. (2013). Hyaluronic acid modified mesoporous silica nanoparticles for targeted drug delivery to CD44-overexpressing cancer cells. Nanoscale, 5(1), 178-183. doi:10.1039/c2nr32145aHe, Q., Ma, M., Wei, C., & Shi, J. (2012). Mesoporous carbon@silicon-silica nanotheranostics for synchronous delivery of insoluble drugs and luminescence imaging. Biomaterials, 33(17), 4392-4402. doi:10.1016/j.biomaterials.2012.02.056Wu, S., Huang, X., & Du, X. (2013). Glucose- and pH-Responsive Controlled Release of Cargo from Protein-Gated Carbohydrate-Functionalized Mesoporous Silica Nanocontainers. Angewandte Chemie International Edition, 52(21), 5580-5584. doi:10.1002/anie.201300958Li, J., Qu, X., Payne, G. F., Zhang, C., Zhang, Y., Li, J., … Liu, C. (2015). Biospecific Self-Assembly of a Nanoparticle Coating for Targeted and Stimuli-Responsive Drug Delivery. Advanced Functional Materials, 25(9), 1404-1417. doi:10.1002/adfm.201403636Burchell, J., Poulsom, R., Hanby, A., Whitehouse, C., Cooper, L., Clausen, H., … Taylor-Papadimitriou, J. (1999). An  2,3 sialyltransferase (ST3Gal I) is elevated in primary breast carcinomas. Glycobiology, 9(12), 1307-1311. doi:10.1093/glycob/9.12.1307Pinho, S. S., Reis, C. A., Paredes, J., Magalhaes, A. M., Ferreira, A. C., Figueiredo, J., … Seruca, R. (2009). The role of N-acetylglucosaminyltransferase III and V in the post-transcriptional modifications of E-cadherin. Human Molecular Genetics, 18(14), 2599-2608. doi:10.1093/hmg/ddp194Takahashi, M., Kuroki, Y., Ohtsubo, K., & Taniguchi, N. (2009). Core fucose and bisecting GlcNAc, the direct modifiers of the N-glycan core: their functions and target proteins. Carbohydrate Research, 344(12), 1387-1390. doi:10.1016/j.carres.2009.04.031Li, M., Song, L., & Qin, X. (2010). Glycan changes: cancer metastasis and anti-cancer vaccines. Journal of Biosciences, 35(4), 665-673. doi:10.1007/s12038-010-0073-8Nagao, K., Itoh, Y., Fujita, K., & Fujime, M. (2007). Evaluation of urinary CA19-9 levels in bladder cancer patients classified according to the combinations of Lewis and Secretor blood group genotypes. International Journal of Urology, 14(9), 795-799. doi:10.1111/j.1442-2042.2007.01840.xGao, W., Liang, J., & Liang, Y. (2016). Clinicopathological and prognostic significance of sialyl Lewis X overexpression in patients with cancer: a meta-analysis. OncoTargets and Therapy, 3113. doi:10.2147/ott.s102389Sozzani, P., Arisio, R., Porpiglia, M., & Benedetto, C. (2008). Is Sialyl Lewis x Antigen Expression a Prognostic Factor in Patients With Breast Cancer? International Journal of Surgical Pathology, 16(4), 365-374. doi:10.1177/1066896908324668Yusa, A., Miyazaki, K., Kimura, N., Izawa, M., & Kannagi, R. (2010). Epigenetic Silencing of the Sulfate Transporter Gene DTDST Induces Sialyl Lewisx Expression and Accelerates Proliferation of Colon Cancer Cells. Cancer Research, 70(10), 4064-4073. doi:10.1158/0008-5472.can-09-2383Golijanin, D., Sherman, Y., Shapiro, A., & Pode, D. (1995). Detection of bladder tumors by immunostaininc of the lewis x antigen in cells from voided urine. Urology, 46(2), 173-177. doi:10.1016/s0090-4295(99)80189-7Hittelet, A., Camby, I., Nagy, N., Legendre, H., Bronckart, Y., Decaestecker, C., … Yeaton, P. (2003). Binding Sites for Lewis Antigens Are Expressed by Human Colon Cancer Cells and Negatively Affect Their Migration. Laboratory Investigation, 83(6), 777-787. doi:10.1097/01.lab.0000073129.62433.39De la Torre, C., Casanova, I., Acosta, G., Coll, C., Moreno, M. J., Albericio, F., … Martínez-Máñez, R. (2014). Gated Mesoporous Silica Nanoparticles Using a Double-Role Circular Peptide for the Controlled and Target-Preferential Release of Doxorubicin in CXCR4-Expresing Lymphoma Cells. Advanced Functional Materials, 25(5), 687-695. doi:10.1002/adfm.201403822De la Fuente, J. M., & Penadés, S. (2002). Synthesis of Lex-neoglycoconjugate to study carbohydrate–carbohydrate associations and its intramolecular interaction. Tetrahedron: Asymmetry, 13(17), 1879-1888. doi:10.1016/s0957-4166(02)00480-9Zhu, T., & Boons, G.-J. (2000). A Novel and Efficient Synthesis of a Dimeric LexOligosaccharide on Polymeric Support. Journal of the American Chemical Society, 122(41), 10222-10223. doi:10.1021/ja001930lMartínez-Ávila, O., Hijazi, K., Marradi, M., Clavel, C., Campion, C., Kelly, C., & Penadés, S. (2009). GoldManno-Glyconanoparticles: Multivalent Systems to Block HIV-1 gp120 Binding to the Lectin DC-SIGN. Chemistry - A European Journal, 15(38), 9874-9888. doi:10.1002/chem.200900923Cory, A. H., Owen, T. C., Barltrop, J. A., & Cory, J. G. (1991). Use of an Aqueous Soluble Tetrazolium/Formazan Assay for Cell Growth Assays in Culture. Cancer Communications, 3(7), 207-212. doi:10.3727/095535491820873191Malich, G., Markovic, B., & Winder, C. (1997). The sensitivity and specificity of the MTS tetrazolium assay for detecting the in vitro cytotoxicity of 20 chemicals using human cell lines. Toxicology, 124(3), 179-192. doi:10.1016/s0300-483x(97)00151-0Sakuma, K., Aoki, M., & Kannagi, R. (2012). Transcription factors c-Myc and CDX2 mediate E-selectin ligand expression in colon cancer cells undergoing EGF/bFGF-induced epithelial-mesenchymal transition. Proceedings of the National Academy of Sciences, 109(20), 7776-7781. doi:10.1073/pnas.111113510

Optical response of Ag-Au bimetallic nanoparticles to electron storage in aqueous medium

Composition and structure dependence of the shift in the position of the surface plasmon resonance band upon introduction of NaBH 4 to aqueous solutions of gold and silver nanoparticles are presented. Silver and gold nanoalloys in different compositions were prepared by co-reduction of the corresponding salt mixtures using sodium citrate as the reducing agent. After addition of NaBH 4 to the resultant nanoalloys, the maximum of their surface plasmon resonance band, ranging between that of pure silver (ca. 400 nm) and of pure gold (ca. 530 nm), is blue-shifted as a result of electron storage on the particles. The extent of this blue shift increases non-linearly with the mole fraction of silver in the nanoparticle, parallel to the trends reported previously for both the frequency and the extinction coefficient of the plasmon band shifts. Gold(core)@silver(shell) nanoparticles were prepared by sequential reduction of gold and silver, where addition of NaBH 4 results in relatively large spectral shift in the plasmon resonance band when compared with the nanoalloys having a similar overall composition. The origin of the large plasmon band shift in the core-shell is related with a higher silver surface concentration on these particles. Hence, the chemical nature of the nanoparticle emerges as the dominating factor contributing to the extent of the spectral shift as a result of electron storage in bimetallic systems. Copyright © 2008 American Scientific Publishers All rights reserved

Photothermal circular dichroism measurements of single chiral gold nanoparticles correlated with electron tomography

Chemically synthesized metal nanoparticles with morphological chiral features are known to exhibit strong circular dichroism. However, we still lack understanding of the correlation between morphological and chiroptical features of plasmonic nanoparticles. To shed light on that question, single nanoparticle experiments are required. We performed photothermal circular dichroism measurements of single chiral and achiral gold nanoparticles and correlated the chiroptical response to the 3D morphology of the same nanoparticles retrieved by electron tomography. In contrast to an ensemble measurement, we show that individual particles within the ensemble display a broad distribution of strength and handedness of circular dichroism signals. Whereas obvious structural chiral features, such as helical wrinkles, translate into chiroptical ones, nanoparticles with less obvious chiral morphological features can also display strong circular dichroism signals. Interestingly, we find that even seemingly achiral nanoparticles can display large g-factors. The origin of this circular dichroism signal is discussed in terms of plasmonics and other potentially relevant factors.Biological and Soft Matter Physic

Measuring Lattice Strain in Three Dimensions through Electron Microscopy

The three-dimensional (3D) atomic structure of nanomaterials, including strain, is crucial to understand their properties. Here, we investigate lattice strain in Au nanodecahedra using electron tomography. Although different electron tomography techniques enabled 3D characterizations of nanostructures at the atomic level, a reliable determination of lattice strain is not straightforward. We therefore propose a novel model-based approach from which atomic coordinates are

Real-Time Reconstruction of Arbitrary Slices for Quantitative and In Situ 3D Characterization of Nanoparticles

A detailed 3D investigation of nanoparticles at a local scale is of great importance to connect their structure and composition to th

Metallo-dielectric diamond and zinc-blende photonic crystals

It is shown that small inclusions of a low absorbing metal can have a dramatic effect on the photonic band structure. In the case of diamond and zinc-blende photonic crystals, several complete photonic band gaps (CPBG's) can open in the spectrum, between the 2nd-3rd, 5th-6th, and 8th-9th bands. Unlike in the purely dielectric case, in the presence of small inclusions of a low absorbing metal the largest CPBG for a moderate dielectric constant (epsilon<=10) turns out to be the 2nd-3rd CPBG. The 2nd-3rd CPBG is the most important CPBG, because it is the most stable against disorder. For a diamond and zinc-blende structure of nonoverlapping dielectric and metallo-dielectric spheres, a CPBG begins to decrease with an increasing dielectric contrast roughly at the point where another CPBG starts to open--a kind of gap competition. A CPBG can even shrink to zero when the dielectric contrast increases further. Metal inclusions have the biggest effect for the dielectric constant 2<=epsilon<=12, which is a typical dielectric constant at near infrared and in the visible for many materials, including semiconductors and polymers. It is shown that one can create a sizeable and robust 2nd-3rd CPBG at near infrared and visible wavelengths even for a photonic crystal which is composed of more than 97% low refractive index materials (n<=1.45, i.e., that of silica glass or a polymer). These findings open the door for any semiconductor and polymer material to be used as genuine building blocks for the creation of photonic crystals with a CPBG and significantly increase the possibilities for experimentalists to realize a sizeable and robust CPBG in the near infrared and in the visible. One possibility is a construction method using optical tweezers, which is analyzed here.Comment: 25 pp, 23 figs, RevTex, to appear in Phys Rev B. For more information look at http://www.amolf.nl/research/photonic_materials_theory/moroz/moroz.htm