Name: facet-to-facet linking of shape-anisotropic colloidal cadmium chalcogenide nanostructures
Uploaded: 2017-08-10T14:00:00.000+00:00
Duration: 9 min 12 s
Description: Watch this Scientific Journal Video about Facet-to-facet Linking of Shape-anisotropic Colloidal Cadmium Chalcogenide Nanostructures at JoVE.com

Este trabalho foi apoiado pela JCO A * STAR Investigatorship conceder (projeto n. º 1437 00135), A * STAR ciência & engenharia Conselho setor público financiamento da investigação (projecto n. º 1421200076) e projectos conjuntos de investigação um JSPS-NUS concede (WBS R143-000-611-133).

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	<li>Figuerola, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=End-to-End+Assembly+of+Shape-Controlled+Nanocrystals+via+a+Nanowelding+Approach+Mediated+by+Gold+Domains.">End-to-End Assembly of Shape-Controlled Nanocrystals via a Nanowelding Approach Mediated by Gold Domains.</a> Adv. Mat. 21, 550-554 (2009).</li><li>Tang, Z., Kotov, N. A., Giersig, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spontaneous+Organization+of+Single+CdTe+Nanoparticles+into+Luminescent+Nanowires.">Spontaneous Organization of Single CdTe Nanoparticles into Luminescent Nanowires.</a> Science. 297, 237-240 (2002).</li><li>Kim, D., Kim, W. D., Kang, M. S., Kim, S. -. H., Lee, D. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Self-Organization+of+Nanorods+into+Ultra-Long+Range+Two-Dimensional+Monolayer+End-to-End+Network.">Self-Organization of Nanorods into Ultra-Long Range Two-Dimensional Monolayer End-to-End Network.</a> Nano Lett. 15, 714-720 (2015).</li><li>Schliehe, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrathin+PbS+Sheets+by+Two-Dimensional+Oriented+Attachment.">Ultrathin PbS Sheets by Two-Dimensional Oriented Attachment.</a> Science. 329, 550-553 (2010).</li><li>Chakrabortty, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Facet+to+facet+Linking+of+Shape+Anisotropic+Inorganic+Nanocrystals+with+Site+Specific+and+Stoichiometric+Control.">Facet to facet Linking of Shape Anisotropic Inorganic Nanocrystals with Site Specific and Stoichiometric Control.</a> Nano Lett. 16, 6431-6436 (2016).</li><li>Leatherdale, C. A., Woo, W. K., Mikulec, F. V., Bawendi, M. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=On+the+Absorption+Cross+Section+of+CdSe+Nanocrystal+Quantum+Dots.">On the Absorption Cross Section of CdSe Nanocrystal Quantum Dots.</a> J Phys Chem B. 106, 7619-7622 (2002).</li><li>Dabbousi, B. O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=(CdSe)ZnS+Core-Shell+Quantum+Dots:+Synthesis+and+Characterization+of+a+Size+Series+of+Highly+Luminescent+Nanocrystallites.">(CdSe)ZnS Core-Shell Quantum Dots: Synthesis and Characterization of a Size Series of Highly Luminescent Nanocrystallites.</a> J Phys Chem B. 101, 9463-9475 (1997).</li><li>Carbone, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+and+Micrometer-Scale+Assembly+of+Coilloidal+CdSe/CdS+Nanorods+Prepared+by+Seeded+Grwoth+Approach.">Synthesis and Micrometer-Scale Assembly of Coilloidal CdSe/CdS Nanorods Prepared by Seeded Grwoth Approach.</a> Nano Lett. 7, 2942-2950 (2007).</li><li>Shaviv, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Absorption+properties+of+Metal-Semiconductor+Hybrid+Nanoparticles.">Absorption properties of Metal-Semiconductor Hybrid Nanoparticles.</a> ACS Nano. 5, 4712-4719 (2011).</li><li>Lim, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controlled+Synthesis+of+CdSe+Tetrapods+with+High+Morphological+Uniformity+by+the+Persistent+Kinetic+Growth+and+the+Halide-Mediated+Phase+Transformation.">Controlled Synthesis of CdSe Tetrapods with High Morphological Uniformity by the Persistent Kinetic Growth and the Halide-Mediated Phase Transformation.</a> Chem Mat. 25, 1443-1449 (2013).</li></ol>

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A vinculação técnica descrita neste trabalho permite cádmio forma anisotrópica calcogênio nanopartículas podem sofrer de permuta catiónica com Ag+ a serem Unidas, faceta-para-facet, em assemblies como cadeias lineares ou redes ramificadas. Falha para formar módulos (assemblies) de nanopartículas vinculadas faceta-para-faceta bem dispersos, extensa é muitas vezes devido a duas razões: (i) o ODPA não é dispersa bem na solução contendo NR, que pode ser resolvida com sonicating a mistura para o pre...

Assembleia dirigida do semicondutor coloidal NCs oferece um caminho sintético para a fabricação de nanoestruturas cujas propriedades físico-químicas ou são a soma coletiva de ou radicalmente diferente da sua individual de blocos de construção de NC1 , 2 , 3 , 4. entre as diversas abordagens para montagem de nanopartículas, o método de fixação orientada - em quais NCs são essencialmente fundidos uns com os outros - se destaca como um que permite o acoplamento eletrônico interpartícula. No entanto, acessório orientado convencional geralmente exige o delicado equilíbrio de partícula dipolo, ligante e interações solvente-baseado que são geralmente difíceis de executar e tornar aplicáveis aos diferentes sistemas de NC.
Recentemente desenvolvemos um método molhado-química de unir covalentemente cádmio forma anisotrópica calcogênio NCs introduzindo um intermediário reativo inorgânico através de um processo de nucleação local-seletivo. As partículas estão ligadas posteriormente pela fusão espontânea do reativo inorgânicos intermediário domínios5. Embora a técnica ainda é baseada em um mecanismo de fixação orientada, há muito menos necessidade de considerar interações interpartícula fracas, permitindo mais flexibilidade e controle. A ligação do cádmio forma anisotrópica calcogênio NCs é realizada pelo primeiro converter suas facetas de ponta de prateado calcogênio através de um processo de troca de cátion parcial (em solução); Isto é seguido pela remoção seletiva de ligantes passivação da superfície. Os NCs então se reúnem através da fusão das facetas calcogênio prata expostos, resultando em módulos (assemblies) de cádmio calcogênio NCs vinculados-to-end.
Neste protocolo, demonstramos que a vinculação técnica pode ser aplicada a uma variedade de cádmio forma anisotrópica calcogênio NCs (i.e., CdSe-semeado CdS NRs e NRs de CdSe CdSe-semeado ou TPs), produzindo cadeias NR tempo lineares ou altamente ramificada TP redes. Estes resultados sugerem que a técnica pode ser estendida a uma grande variedade de formas de NC e metal chalcogenides passível de troca de cátion prata.

<table><tbody><tr><td>Cadmium oxide (CdO), 99.5%</td><td>Sigma Aldrich</td><td></td><td>Highly toxic</td></tr><tr><td>Tri-n-octylphosphine oxide (TOPO), 90 % and 99%</td><td>Sigma Aldrich</td><td></td><td>Technical and analytical grade</td></tr><tr><td>Cadmium acetylacetonate (Cd(acac)&lt;sub&gt;2&lt;/sub&gt;), 99.9%</td><td>Sigma Aldrich</td><td></td><td>Highly toxic</td></tr><tr><td>Hexadecanediol (HDDO), 90%</td><td>Sigma Aldrich</td><td></td><td>Technical grade</td></tr><tr><td>1-octadecene (ODE), 90%</td><td>Sigma Aldrich</td><td></td><td>Technical grade</td></tr><tr><td>Dodecylamine (DDA), 98%</td><td>Sigma Aldrich</td><td></td><td>Toxic</td></tr><tr><td>Cadmium nitrate tetrahydrate ((CdNO&lt;sub&gt;3&lt;/sub&gt;)&lt;sub&gt;2&lt;/sub&gt;.4H&lt;sub&gt;2&lt;/sub&gt;O), 98%</td><td>Sigma Aldrich</td><td></td><td>Highly toxic</td></tr><tr><td>Myristic acid (MA), 99%</td><td>Sigma Aldrich</td><td></td><td>Analytical grade</td></tr><tr><td>Octyl phosphonic acid (OPA), 97%</td><td>Sigma Aldrich</td><td></td><td>Analytical grade</td></tr><tr><td>Oleylamine (Oly), 70%</td><td>Sigma Aldrich</td><td></td><td>Technical grade</td></tr><tr><td>Hexadecyltrimethylammonium bromide (CTAB), 95%</td><td>Sigma Aldrich</td><td></td><td>Toxic</td></tr><tr><td>Selenium pellets (Se, 5 mm), 99.99%</td><td>Sigma Aldrich</td><td></td><td>Analytical grade</td></tr><tr><td>Hexadecylamine (HDA), 90%</td><td>Alfa Aesar</td><td></td><td>Technical grade, toxic</td></tr><tr><td>n-tetradecylphosphonic acid (TDPA), 98%&amp;nbsp;</td><td>Alfa Aesar</td><td></td><td>Analytical grade</td></tr><tr><td>Silver nitrate (AgNO&lt;sub&gt;3&lt;/sub&gt;), 99.9%</td><td>Alfa Aesar</td><td></td><td>Analytical grade</td></tr><tr><td>Oleic acid (OA), 90%</td><td>Alfa Aesar</td><td></td><td>Technical grade</td></tr><tr><td>Tri-n-octylphosphine (TOP), 97%</td><td>Strem</td><td></td><td>Analytical grade, toxic, air sensitive</td></tr><tr><td>n-hexylphosphonic acid (HPA), 97%</td><td>Strem</td><td></td><td>Analytical grade</td></tr><tr><td>n-octadecylphosphonic acid (ODPA), 97%</td><td>Strem</td><td></td><td>Analytical grade</td></tr><tr><td>Tellurium powder (Te), 99.9%</td><td>Strem</td><td></td><td>Air sensitive</td></tr><tr><td>Tri-n-butylphosphine (TBP), 99%</td><td>Strem</td><td></td><td>Analytical grade, highly toxic, air sensitive</td></tr><tr><td>Diisooctylphosphonic acid (DIPA), 90%</td><td>Fluka</td><td></td><td>Technical grade, toxic</td></tr></tbody></table>

facet-to-facet linking of shape-anisotropic colloidal cadmium chalcogenide nanostructures

Aqui, descrevemos um protocolo que permite para cádmio forma anisotrópica calcogênio nanocristais (NCs), tais como nanorods (NRs) e tetrápodes (TPs), ligadas covalentemente e site-specifically através de suas facetas de fim, resultando em polímeros como lineares ou ramificados correntes. O procedimento de ligação começa com um processo de permuta catiónica em que as facetas de final do calcogênio de cádmio NCs primeiro são convertidos em prateado calcogênio. Isto é seguido pela remoção seletiva de ligantes em sua superfície. Isso resulta em cádmio calcogênio NCs com final altamente reativo calcogênio prata facetas que fundem-se espontaneamente em contato uns com os outros, estabelecendo um anexo de faceta-para-faceta interpartícula. A escolha criteriosa das concentrações de precursor, através de uma extensa rede de NCs vinculados pode ser produzida. Caracterização estrutural de NCs vinculados é realizada através de baixa e alta resolução microscopia eletrônica de transmissão (TEM), bem como a espectroscopia de raio-x-energia dispersiva, que confirmam a presença de prata calcogênio domínios entre cadeias de cádmio calcogênio NCs.

Usando CdSe-semeado CdS NRs como um sistema de modelo, como ilustrado na Figura 1(um), demonstrámos que podemos usar um processo de troca parcial Ag+ para transformar especificamente as facetas com as pontas NR para Ag2S. As facetas de2S Ag são tampadas por DDA, que reage com ODPA através de uma reação ácido-base, para formar um sal insolúvel5. Isso faz com que os ligantes DDA de...

Watch this Scientific Journal Video about Facet-to-facet Linking of Shape-anisotropic Colloidal Cadmium Chalcogenide Nanostructures at JoVE.com

Facet-to-facet Linking of Shape-anisotropic Colloidal Cadmium Chalcogenide Nanostructures

Um protocolo detalhando como forma anisotrópica cádmio coloidal calcogênio nanocristais podem ser ligado covalentemente através de suas facetas de fim é apresentado aqui.

Faceta-para-faceta vinculando de forma anisotrópica cádmio coloidal calcogênio nanoestruturas

Here, we describe a protocol that allows for shape-anisotropic cadmium chalcogenide nanocrystals (NCs), such as nanorods (NRs) and tetrapods (TPs), to be ...

facet-to-facet-linking-shape-anisotropic-colloidal-cadmium

Universidad San Sebastian

Research

JoVE Journal

Chemistry

7.6K visualizações.  National University of Singapore. Um protocolo detalhando como forma anisotrópica cádmio coloidal calcogênio nanocristais podem ser ligado covalentemente através de suas facetas de fim é apresentado aqui.

Vídeo: Facet-to-facet Linking of Shape-anisotropic Colloidal Cadmium Chalcogenide Nanostructures

Compact Quantum Dots for Single-molecule Imaging

Single-molecule imaging is an important tool for understanding the mechanisms of biomolecular function and for visualizing the spatial and temporal heterogeneity of molecular behaviors that underlie cellular biology 1-4. To image an individual molecule of interest, it is typically conjugated to a fluorescent tag (dye, protein, bead, or quantum dot) and observed with epifluorescence or total internal reflection fluorescence (TIRF) microscopy. While dyes and fluorescent proteins have been the mainstay of fluorescence imaging for decades, their fluorescence is unstable under high photon fluxes necessary to observe individual molecules, yielding only a few seconds of observation before complete loss of signal. Latex beads and dye-labeled beads provide improved signal stability but at the expense of drastically larger hydrodynamic size, which can deleteriously alter the diffusion and behavior of the molecule under study.
Quantum dots (QDs) offer a balance between these two problematic regimes. These nanoparticles are composed of semiconductor materials and can be engineered with a hydrodynamically compact size with exceptional resistance to photodegradation 5. Thus in recent years QDs have been instrumental in enabling long-term observation of complex macromolecular behavior on the single molecule level. However these particles have still been found to exhibit impaired diffusion in crowded molecular environments such as the cellular cytoplasm and the neuronal synaptic cleft, where their sizes are still too large 4,6,7.
Recently we have engineered the cores and surface coatings of QDs for minimized hydrodynamic size, while balancing offsets to colloidal stability, photostability, brightness, and nonspecific binding that have hindered the utility of compact QDs in the past 8,9. The goal of this article is to demonstrate the synthesis, modification, and characterization of these optimized nanocrystals, composed of an alloyed HgxCd1-xSe core coated with an insulating CdyZn1-yS shell, further coated with a multidentate polymer ligand modified with short polyethylene glycol (PEG) chains (Figure 1). Compared with conventional CdSe nanocrystals, HgxCd1-xSe alloys offer greater quantum yields of fluorescence, fluorescence at red and near-infrared wavelengths for enhanced signal-to-noise in cells, and excitation at non-cytotoxic visible wavelengths. Multidentate polymer coatings bind to the nanocrystal surface in a closed and flat conformation to minimize hydrodynamic size, and PEG neutralizes the surface charge to minimize nonspecific binding to cells and biomolecules. The end result is a brightly fluorescent nanocrystal with emission between 550-800 nm and a total hydrodynamic size near 12 nm. This is in the same size range as many soluble globular proteins in cells, and substantially smaller than conventional PEGylated QDs (25-35 nm).

We describe the preparation of colloidal quantum dots with minimized hydrodynamic size for single-molecule fluorescence imaging. Compared to conventional quantum dots, these nanoparticles are similar in size to globular proteins and are optimized for single-molecule brightness, stability against photodegradation, and resistance to nonspecific binding to proteins and cells.

Compactas pontos quânticos para uma única molécula de imagem

Single-molecule imaging is an important tool for  understanding the mechanisms of biomolecular function and for visualizing the  spatial and temporal ...

Engenharia

Revealing Dynamic Processes of Materials in Liquids Using Liquid Cell Transmission Electron Microscopy

The recent development for in situ transmission electron microscopy, which allows imaging through liquids with high spatial resolution, has attracted significant interests across the research fields of materials science, physics, chemistry and biology. The key enabling technology is a liquid cell. We fabricate liquid cells with thin viewing windows through a sequential microfabrication process, including silicon nitride membrane deposition, photolithographic patterning, wafer etching, cell bonding, etc. A liquid cell with the dimensions of a regular TEM grid can fit in any standard TEM sample holder. About 100 nanoliters reaction solution is loaded into the reservoirs and about 30 picoliters liquid is drawn into the viewing windows by capillary force. Subsequently, the cell is sealed and loaded into a microscope for in situ imaging. Inside the TEM, the electron beam goes through the thin liquid layer sandwiched between two silicon nitride membranes. Dynamic processes of nanoparticles in liquids, such as nucleation and growth of nanocrystals, diffusion and assembly of nanoparticles, etc., have been imaged in real time with sub-nanometer resolution. We have also applied this method to other research areas, e.g., imaging proteins in water. Liquid cell TEM is poised to play a major role in revealing dynamic processes of materials in their working environments. It may also bring high impact in the study of biological processes in their native environment.

We have developed a self-contained liquid cell, which allows imaging through liquids using a transmission electron microscope. Dynamic processes of nanoparticles in liquids can be revealed in real time with sub-nanometer resolution.

Revelando processos dinâmicos de Materiais em Líquidos Usando líquido celular Microscopia Eletrônica de Transmissão

The recent development for in situ transmission electron microscopy, which allows imaging through liquids with high spatial resolution, has attracted ...

Seeded Synthesis of CdSe/CdS Rod and Tetrapod Nanocrystals

We demonstrate a method for the synthesis of multicomponent nanostructures consisting of CdS and CdSe with rod and tetrapod morphologies. A seeded synthesis strategy is used in which spherical seeds of CdSe are prepared first using a hot-injection technique. By controlling the crystal structure of the seed to be either wurtzite or zinc-blende, the subsequent hot-injection growth of CdS off of the seed results in either a rod-shaped or tetrapod-shaped nanocrystal, respectively. The phase and morphology of the synthesized nanocrystals are confirmed using X-ray diffraction and transmission electron microscopy, demonstrating that the nanocrystals are phase-pure and have a consistent morphology. The extinction coefficient and quantum yield of the synthesized nanocrystals are calculated using UV-Vis absorption spectroscopy and photoluminescence spectroscopy. The rods and tetrapods exhibit extinction coefficients and quantum yields that are higher than that of the bare seeds. This synthesis demonstrates the precise arrangement of materials that can be achieved at the nanoscale by using a seeded synthetic approach.

A protocol for the seeded synthesis of rod-shaped and tetrapod-shaped multicomponent nanostructures consisting of CdS and CdSe is presented.

Semeado Síntese de CdSe / CdS Rod e tetrápodes Nanocristais

We demonstrate a method for the synthesis of multicomponent nanostructures consisting of CdS and CdSe with rod and tetrapod morphologies. A seeded ...

Química

Synthesis and Characterization of Supramolecular Colloids

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical properties for applications in photonics, drug delivery and coating technology. Here we present a new family of colloidal building blocks, coined supramolecular colloids, whose self-assembly is controlled through surface-functionalization with a benzene-1,3,5-tricarboxamide (BTA) derived supramolecular moiety. Such BTAs interact via directional, strong, yet reversible hydrogen-bonds with other identical BTAs. Herein, a protocol is presented that describes how to couple these BTAs to colloids and how to quantify the number of coupling sites, which determines the multivalency of the supramolecular colloids. Light scattering measurements show that the refractive index of the colloids is almost matched with that of the solvent, which strongly reduces the van der Waals forces between the colloids. Before photo-activation, the colloids remain well dispersed, as the BTAs are equipped with a photo-labile group that blocks the formation of hydrogen-bonds. Controlled deprotection with UV-light activates the short-range hydrogen-bonds between the BTAs, which triggers the colloidal self-assembly. The evolution from the dispersed state to the clustered state is monitored by confocal microscopy. These results are further quantified by image analysis with simple routines using ImageJ and Matlab. This merger of supramolecular chemistry and colloidal science offers a direct route towards light- and thermo-responsive colloidal assembly encoded in the surface-grafted monolayer.

A protocol for the synthesis and characterization of colloids coated with supramolecular moieties is described. These supramolecular colloids undergo self-assembly upon the activation of the hydrogen-bonds between the surface-anchored molecules by UV-light.

Síntese e Caracterização de Supramoleculares Colloids

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical ...

Creating Sub-50 Nm Nanofluidic Junctions in PDMS Microfluidic Chip via Self-Assembly Process of Colloidal Particles

Polydimethylsiloxane (PDMS) is the prevailing building material to make microfluidic devices due to its ease of molding and bonding as well as its transparency. Due to the softness of the PDMS material, however, it is challenging to use PDMS for building nanochannels. The channels tend to collapse easily during plasma bonding. In this paper, we present an evaporation-driven self-assembly method of silica colloidal nanoparticles to create nanofluidic junctions with sub-50 nm pores between two microchannels. The pore size as well as the surface charge of the nanofluidic junction is tunable simply by changing the colloidal silica bead size and surface functionalization outside of the assembled microfluidic device in a vial before the self-assembly process. Using the self-assembly of nanoparticles with a bead size of 300 nm, 500 nm, and 900 nm, it was possible to fabricate a porous membrane with a pore size of ~45 nm, ~75 nm and ~135 nm, respectively. Under electrical potential, this nanoporous membrane initiated ion concentration polarization (ICP) acting as a cation-selective membrane to concentrate DNA by ~1,700 times within 15 min. This non-lithographic nanofabrication process opens up a new opportunity to build a tunable nanofluidic junction for the study of nanoscale transport processes of ions and molecules inside a PDMS microfluidic chip.

We propose a simple self-assembly technique of silica colloidal nanoparticles to create a nanofluidic junction between two microchannels in polydimethylsiloxane (PDMS). Using this technique, a nanoporous bead membrane with a pore size down to ~45 nm was built inside a microchannel and applied to electrokinetic preconcentration of DNA samples.

Criação de Sub-50 nm nanofluidic Junções em PDMS Microfluidic Chip via processo de automontagem de coloidal Particles

Polydimethylsiloxane (PDMS) is the prevailing building material to make microfluidic devices due to its ease of molding and bonding as well as its ...

Self-assembling Morphologies Obtained from Helical Polycarbodiimide Copolymers and Their Triazole Derivatives

A facile method for the preparation of polycarbodiimide-based secondary structures (e.g., nano-rings, &#34;craters,&#34; fibers, looped fibers, fibrous networks, ribbons, worm-like aggregates, toroidal structures, and spherical particles) is described. These aggregates are morphologically influenced by extensive hydrophobic side chain-side chain interactions of the singular polycarbodiimide strands, as inferred by atomic force microscopy (AFM) and scanning electron microscopy (SEM) techniques. Polycarbodiimide-g-polystyrene copolymers (PS-PCDs) were prepared by a combination of synthetic methods, including coordination-insertion polymerization, copper(I)-catalyzed azide alkyne cycloaddition (CuAAC) &#34;click&#34; chemistry, and atom transfer radical polymerization (ATRP). PS-PCDs were found to form specific toroidal architectures at low concentrations in CHCl3. To determine the influence of a more polar solvent medium (i.e., THF and THF/EtOH) on polymer aggregation behavior, a number of representative PS-PCD composites have been tested to show discrete concentration-dependent spherical particles. These fundamental studies are of practical interest to the development of experimental procedures for desirable architectures by directed self-assembly in thin film. These architectures may be exploited as drug carriers, whereas other morphological findings represent certain interest in the area of novel functional materials.

Here, we present a protocol to prepare and visualize secondary structures (e.g., fibers, toroidal architectures, and nano-spheres) derived from helical polycarbodiimides. The morphology characterized by both atomic force microscopy (AFM) and scanning electron microscopy (SEM) was shown to depend on molecular structure, concentration, and the solvent of choice.

Morfologias de auto-montagem Obtidos a partir helicoidais policarbodiimida copolímeros e seus derivados triazólicos

A facile method for the preparation of polycarbodiimide-based secondary structures (e.g., nano-rings, &#34;craters,&#34; fibers, looped fibers, fibrous ...

Liquid-cell Transmission Electron Microscopy for Tracking Self-assembly of Nanoparticles

Drying a nanoparticle dispersion is a versatile way to create self-assembled structures of nanoparticles, but the mechanism of this process is not fully understood. We have traced the trajectories of individual nanoparticles using liquid-cell transmission electron microscopy (TEM) to investigate the mechanism of the assembly process. Herein, we present the protocols used for liquid-cell TEM studies of the self-assembly mechanism. First, we introduce the detailed synthetic protocols used to produce uniformly sized platinum and lead selenide nanoparticles. Next, we present the microfabrication processes used to produce liquid cells with silicon nitride or silicon windows and then describe the loading and imaging procedures of the liquid-cell TEM technique. Several notes are included to provide helpful tips for the entire process, including how to manage the fragile cell windows. The individual motions of nanoparticles tracked by liquid-cell TEM revealed that changes in the solvent boundaries caused by evaporation affected the self-assembly process of nanoparticles. The solvent boundaries drove nanoparticles to primarily form amorphous aggregates, followed by flattening of the aggregates to produce a 2-dimensional (2D) self-assembled structure. These behaviors are also observed for different nanoparticle types and different liquid-cell compositions.

Here we introduce experimental protocols for the real-time observation of a self-assembly process using liquid-cell transmission electron microscopy.

Microscopia eletrônica de transmissão de líquido-celular para rastreamento auto-montagem de nanopartículas

Drying a nanoparticle dispersion is a versatile way to create self-assembled structures of nanoparticles, but the mechanism of this process is not fully ...

Fabrication of Periodic Gold Nanocup Arrays Using Colloidal Lithography

Within recent years, the field of plasmonics has exploded as researchers have demonstrated exciting applications related to chemical and optical sensing in combination with new nanofabrication techniques. A plasmon is a quantum of charge density oscillation that lends nanoscale metals such as gold and silver unique optical properties. In particular, gold and silver nanoparticles exhibit localized surface plasmon resonances-collective charge density oscillations on the surface of the nanoparticle-in the visible spectrum. Here, we focus on the fabrication of periodic arrays of anisotropic plasmonic nanostructures. These half-shell (or nanocup) structures can exhibit additional unique light-bending and polarization-dependent optical properties that simple isotropic nanostructures cannot. Researchers are interested in the fabrication of periodic arrays of nanocups for a wide variety of applications such as low-cost optical devices, surface-enhanced Raman scattering, and tamper indication. We present a scalable technique based on colloidal lithography in which it is possible to easily fabricate large periodic arrays of nanocups using spin-coating and self-assembled commercially available polymeric nanospheres. Electron microscopy and optical spectroscopy from the visible to near-infrared (near-IR) was performed to confirm successful nanocup fabrication. We conclude with a demonstration of the transfer of nanocups to a flexible, conformal adhesive film.

We demonstrate the fabrication of periodic gold nanocup arrays using colloidal lithographic techniques and discuss the importance of nanoplasmonic films.

Fabricação de matrizes de periódicos Nanocup ouro usando litografia coloidal

Within recent years, the field of plasmonics has exploded as researchers have demonstrated exciting applications related to chemical and optical sensing ...

Ligand Nano-cluster Arrays in a Supported Lipid Bilayer

Currently there is considerable interest in creating ordered arrays of adhesive protein islands in a sea of passivated surface for cell biological studies. In the past years, it has become increasingly clear that living cells respond, not only to the biochemical nature of the molecules presented to them but also to the way these molecules are presented. Creating protein micro-patterns is therefore now standard in many biology laboratories; nano-patterns are also more accessible. However, in the context of cell-cell interactions, there is a need to pattern not only proteins but also lipid bilayers. Such dual proteo-lipidic patterning has so far not been easily accessible. We offer a facile technique to create protein nano-dots supported on glass and propose a method to backfill the inter-dot space with a supported lipid bilayer (SLB). From photo-bleaching of tracer fluorescent lipids included in the SLB, we demonstrate that the bilayer exhibits considerable in-plane fluidity. Functionalizing the protein dots with fluorescent groups allows us to image them and to show that they are ordered in a regular hexagonal lattice. The typical dot size is about 800 nm and the spacing demonstrated here is 2 microns. These substrates are expected to serve as useful platforms for cell adhesion, migration and mechano-sensing studies.

We present a protocol to functionalize glass with nanometric protein patches surrounded by a fluid lipid bilayer. These substrates are compatible with advanced optical microscopy and are expected to serve as platform for cell adhesion and migration studies.

Matrizes ligando Nano-fragmentação em uma bicamada lipídica Compatível

Currently there is considerable interest in creating ordered arrays of adhesive protein islands in a sea of passivated surface for cell biological ...

Bioengenharia

Fabrication of Zero Mode Waveguides for High Concentration Single Molecule Microscopy

In single molecule fluorescence enzymology, background fluorescence from labeled substrates in solution often limits fluorophore concentration to pico- to nanomolar ranges, several orders of magnitude less than many physiological ligand concentrations. Optical nanostructures called zero mode waveguides (ZMWs), which are 100&#8722;200 nm in diameter apertures fabricated in a thin conducting metal such as aluminum or gold, allow imaging of individual molecules at micromolar concentrations of fluorophores by confining visible light excitation to zeptoliter effective volumes. However, the need for expensive and specialized nanofabrication equipment has precluded the widespread use of ZMWs. Typically, nanostructures such as ZMWs are obtained by direct writing using electron beam lithography, which is sequential and slow. Here, colloidal, or nanosphere, lithography is used as an alternative strategy to create nanometer-scale masks for waveguide fabrication. This report describes the approach in detail, with practical considerations for each phase. The method allows thousands of aluminum or gold ZMWs to be made in parallel, with final waveguide diameters and depths of 100&#8722;200 nm. Only common lab equipment and a thermal evaporator for metal deposition are required. By making ZMWs more accessible to the biochemical community, this method can facilitate the study of molecular processes at cellular concentrations and rates.

Described here is a nanosphere lithography method for parallel fabrication of zero mode waveguides, which are arrays of nanoapertures in a metal-clad glass microscopy coverslip for single molecule imaging at nano- to micromolar concentrations of fluorophores. The method takes advantage of colloidal crystal self-assembly to create a waveguide template.

Fabricação de guias de ondas de modo zero para microscopia de molécula única de alta concentração

In single molecule fluorescence enzymology, background fluorescence from labeled substrates in solution often limits fluorophore concentration to pico- to ...