Reconhecemos o apoio financeiro do Instituto de Zernike de Materiais Avançados, da Universidade de Groningen.

1. Preparação e Caracterização de PS-b-P4VP (PDP) Complexos com duplo Gyroid Morfologia <ol><li> Pesar de poliestireno-bloco-poli (4-vinilpiridina) (PS-b-P4VP) e pentadecilfenol (PDP, Mr = 304,51 g / mol). De modo a obter a morfologia gyroid, seleccionar cuidadosamente a quantidade de PDP deve ser (a fracção de peso de P4VP (PDP) bloco (f P4VP (PDP)) deve ser ca. 0,6 de acordo com o diagrama de fases de copolímeros em dibloco lineares AB). Normalmente, 0,15-0,2 g de um PS-b-P4VP leva a PS-b-P4VP (PDP), os filmes de 50-100 mm de espessura (uma vez que o diâmetro de um prato Petri usado no passo 1.3 é 5-6 cm). Calcular a quantidade de PDP de acordo com as seguintes equações: <img alt="Equação 1" src="/files/ftp_upload/50673/50673eq1.jpg" /> <img alt="Equação 2" src="/files/ftp_upload/50673/50673eq2.jpg" /> <img alt="Equação 3" src="/files/ftp_upload/50673/50673eq3.jpg" /><br/&gt; <img alt="Equação 4" src="/files/ftp_upload/50673/50673eq4.jpg" /></li><li> Dissolver PS-b-P4VP e PDP em clorofórmio e mexa por um par de horas a temperatura ambiente. Manter a concentração de polímero inferior a 2% em peso, para assegurar a formação de um complexo homogéneo. </li><li> Despeje a solução numa placa de Petri de vidro. </li><li> Colocar a cápsula num ambiente saturado de clorofórmio. </li><li> Após cerca de uma semana, retire a placa de Petri. Um filme do complexo supramolecular é formado. </li><li> Seca-se a película no vácuo a 30 ° C durante a noite. </li><li> Coloque o filme em um recipiente especialmente projetado, retire o ar do recipiente e, em seguida, preenchê-lo com nitrogênio. Recozer o filme durante 4 dias na estufa a 120 ° C sob atmosfera de N 2, com 1 bar de pressurização. </li><li> Cortar o pequeno pedaço da película, incorporar em epóxi e curá-la durante a noite a 40 ° C. </li><li> Micrótomo a amostra com uma espessura de cerca de 80 nm, usando uma faca de diamante, à temperatura ambiente. The seção microtomed irá flutuar na água. Buscá-las e colocar grades de Cu. </li><li> Coloque as grades contendo os cortes microtomed em uma jarra com iodo. Após 45 minutos as amostras são e pronto para microscopia eletrônica de transmissão. </li><li> Insira as grades de Cu com cortes corados no microscópio eletrônico de transmissão operando com uma tensão de aceleração de 120 kV e imagem da amostra. </li><li> Insira a parte do filme (obtido após o passo 1.7) no suporte da amostra para pequenas ângulo de espalhamento de raios-X e corrigi-lo com uma fita Kapton. Coloque o suporte de amostra preparada para a máquina de SAXS. Abra o obturador de raios-X e adquirir o padrão de espalhamento 2D. Integrar o padrão de 2D obtido e analisar a posição dos picos de padrão de 1D. </li></ol> 2. Geração e caracterização da estrutura porosa <ol><li> Coloque a peça da película (obtido após o passo 1.7) em etanol e mantê-lo durante três dias. </li><li> Seca-se a amostra. </li><li> Préaparar as amostras para um medições H RMN. Dissolve-se pó de PDP, PS-b-P4VP pó, PS-b-P4VP (PDP) (depois do passo 1.7), e porosa filme complexo supramolecular (após o passo 2.2) em CDCl3. Ficha 1 H espectros RMN à temperatura ambiente. </li><li> Analise PS-b-P4VP pó, complexo supramolecular PS-b-P4VP (PDP) (depois do passo 1.7), e película porosa (após o passo 2.2) por meio de calorimetria diferencial de varrimento. Usar um modo modulado com uma velocidade de aquecimento / arrefecimento de 1 ° C / min, uma amplitude de oscilação de 0,5 ° C, e um período de oscilação de 60 seg. Equilibrar as amostras à temperatura de -30 ° C, aquecer até 180 ° C, arrefecer a -30 ° C, e em seguida aquecer de novo a 180 ° C. Usar os dados a partir do segundo ciclo de aquecimento para a análise. </li><li> Desgaseificar a amostra porosa (após o passo 2.2) durante 8 horas à temperatura ambiente e durante 18 horas a 70 ° C e realizar medições de adsorção de azoto a 77 K. </li><li> Use o software apropriado (por exemplo, WinADP) e modelos para analisar as isotermas obtidas. </li><li> Seca-se a amostra porosa (após o passo 2.2) a 50 ° C durante 8 horas e desgaseifica-la à temperatura ambiente e à pressão de 0,5 Pa, durante 2 horas. </li><li> Realizar porosimetria de mercúrio. </li></ol> 3. Inserção de níquel no modelo Polymer <ol><li> Pesar de cloreto de estanho (SnCl2, Mr = 189,60 g / mol) e preparar uma solução aquosa (0,1 M SnCl 2 / HCl 0,1 M, 1,896 g de SnCl 2, 0,8 ml de HCl, e 100 ml de H2O). Colocar a solução em um dia para o outro agitador para garantir a dissolução completa de SnCl2. </li><li> Pesar o cloreto de paládio (PdCl2, Mr = 177,33 g / mol) e preparar uma solução aquosa (0,0014 M PdCl2 / 0,25 M de HCl; 0,025 g PdCl 2, 2 mL de HCl e 100 mL de H 2 O). </li><li> Prepare a parte 1 do banho de níquel: pesar 6,78 g de sulfato de níquel hexahidratado (NISO 4 • 6H 2 O, M r = 2620,85 g / mol) e 2 g de citrato de sódio (Na 3 C 6 H 5 O 7, Mr = 258,06 g / mol) e dissolvê-los em 80 ml ​​de água. Adicionar 828 ul de 85% de ácido láctico (C 3 H 6 O 3, M r = 90,08 g / mol). </li><li> Prepare a parte 2 do banho níquel: peso fora 0,2 g complexo dimetilamina borano ((CH 3) 2 NHBH 3, M r = 58,92 g / mol) e dissolvê-la em 20 ml de água. Complexo dimetilamina Borane deve ser tratado em um exaustor bem ventilado. </li><li> Mergulha-se o filme poroso (após o passo 2.2) em solução aquosa de cloreto de estanho (passo 3.1), durante 1 hora. </li><li> Lavar a película completamente com água desionizada. </li><li> Mergulha-se o filme da solução aquosa de cloreto de paládio (passo 3.2), durante 1 hora. </li><li> Lavar a película completamente com água desionizada. </li><li> Misture parte 1 (3.3) e parte 2 (3.4) do banho de níquel. Ajustar o pH para 7,0 utilizando hidróxido de amónio. </li><li> Mergulha-se o filme no banho de niquelagem, durante 1 hora. </li><li> Lavar a película completamente com água desionizada. </li><li> Seca-se a amostra. </li><li> Preparar a amostra inoculada, em microscopia electrónica, tal como descrito nos passos 1,8-1,9. </li><li> Imagem da amostra, tal como descrito no passo 1.11. </li><li> Coloque grades Cu contendo as seções da amostra banhado na alta resolução de microscópio eletrônico de transmissão. Adquirir microscopia eletrônica de transmissão de alta resolução. Observar a amostra sob o microscópio e escolher a área para análise elementar por EDX (Energia Dispersiva Análise de Raios-X). Realize a análise EDX da área escolhida e analisar o padrão obtido. </li></ol> 4. Exposição do Inverso Gyroid Nickel Foam <ol><li> Coloque a película de níquel (após o passo 3.12) num forno a 350 ° C e mantê-lo a partir de 1 hora até 4 dias. </li><li> Prenda a amostra para o titular da amostra usando um colar de prata. </li><li> Insira a amostra no microfone eletrônica de varreduraroscope. Adquirir várias imagens da amostra. </li><li> Coloque a amostra no microscópio eletrônico de varredura. Observe o exemplo sob o microscópio e escolher a área para análise elementar por EDX. Realize a análise EDX da área escolhida e analisar o padrão obtido. </li></ol>

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C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Landau+theory+of+the+orthorhombic+Fddd+phase.">Landau theory of the orthorhombic Fddd phase.</a> Phys. Rev. E. 74, 011803 (2006).</li><li>Kim, M. I., 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=Stability+of+the+Fddd+Phase+in+Diblock+Copolymer+Melts.">Stability of the Fddd Phase in Diblock Copolymer Melts.</a> Macromolecules. 41, 7667-7670 (2008).</li></ol>

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Complexos supramoleculares são aplicadas com êxito como precursores de nanofoams de metal bem ordenadas. Neste método, o passo crucial é adquirir o modelo apropriado, ou seja, um molde com morfologia gyroid. No diagrama de fases de copolímeros em bloco da região gyroid é muito pequeno e é bastante difícil de atingir. Isto significa que, se os copolímeros em bloco convencionais são utilizados como materiais de partida, a síntese bastante elaborada tem de ser repetido até que a composição desejada,...

Existem várias técnicas disponíveis para a preparação de nanofoams metálicos: dealloying 1-3, sol-gel aproxima de 4,5, nanosmelting 6,7, e a síntese de combustão 8. No processo dealloying, o material de partida é geralmente uma liga binária, por exemplo, uma liga de prata e de ouro. O metal menos nobre, prata, neste caso, pode ser removido quimicamente ou electroquimicamente, resultando numa espuma de ouro poroso desordenado com ligamentos nanométricas. Na síntese de combustão, o metal é misturado com um precursor energético que liberta energia durante a sua decomposição e conduz à formação de metais nanofoam 8. Estudos sobre o comportamento mecânico de espumas de metal indicam que em arquitecturas desordenados tensões não podem ser transmitidas de forma eficaz a partir do ligamento à nanoescala macroescala geral 9-11. Assim nanofoams metálicos bem ordenadas se espera que tenham propriedades mecânicas superiores, em comparação com oos desordenados. A idéia aqui representada é empregar copolímeros em bloco que se auto-organizar em nanoestruturas ordenadas como precursores de nanofoams metal. Dependendo da composição de um copolímero em bloco, o número total de unidades de monómeros e o grau de repulsão entre os blocos quimicamente ligados, várias morfologias parecem tais como: esférica, cilíndrica, lamelar, duplo gyroid, hexagonal lamelar perfurada, e os outros 12-14 . Além disso, os blocos de polímero pode ser degradado selectivamente levando a materiais nanoporos 15. Os métodos mais comuns incluem: ozonólise 16-18, irradiação UV 19, corrosão iônica reativa 20-22, 23-26 e dissolução. As estruturas porosas gerados podem ser utilizados no enchimento com diversos materiais inorgânicos. Óxidos metálicos (por exemplo, SiO 2, TiO 2) são normalmente introduzidos através de método de sol-gel para os canais do molde 27-29. Elchapeamento electroless ectrochemical e são comumente usados ​​para depositar metal em ou em modelos de 30-33. Finalmente, o polímero restante pode ser removido a partir do polímero / nanohíbrido inorgânico através de pirólise 2, dissolução 34,35, 28,29 degradação de UV, etc Em nossa abordagem, vamos começar a partir de um complexo supramolecular de poliestireno-bloco-poli (4-vinil-piridina) (PS-b-P4VP) copolímero diblock e pentadecilfenol anfifílico (PDP) moléculas. Este complexo é um resultado da ligação de hidrogénio entre PDP e anéis de piridina (Figura 1a). A composição de copolímero em bloco de partida e a quantidade de agregado PDP são escolhidos de tal maneira que o sistema de auto-montagem obtidos na morfologia gyroid dupla bicontinua com uma rede PS e uma matriz de P4VP (PDP) (Figura 1b). Moléculas PDP ficar dissolvido seletivamente em etanol e P4VP cadeias colapso na rede PS (A Figura 1c). Subsequentemente, utilizando o método de revestimentos de níquel é depositado no interior dos poros da matriz (Figura 1d). Após a remoção do polímero remanescente através de pirólise, uma nanofoam níquel gyroid bem ordenado é obtido (Figura 1e).

<table border="1">
 <tbody>
 <tr>
 <td>REAGENTS:</td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>PS-b-P4VP, CAS: 26222-40-2</td>
 <td>Polymer Source Inc.</td>
 <td>P9009-S4VP 
 P136-S4VP 
 P5462-S4VP 
 P3912-S4VP</td>
 <td>additional information are provided in a separate table</td>
 </tr>
 <tr>
 <td>PDP</td>
 <td>Aldrich</td>
 <td>P4402-100G-A</td>
 <td>recrystallized twice from petroleum ether</td>
 </tr>
 <tr>
 <td>SnCl2</td>
 <td>Acros Organics</td>
 <td>196981000</td>
 <td></td>
 </tr>
 <tr>
 <td>PdCl2</td>
 <td>Aldrich</td>
 <td>76050</td>
 <td></td>
 </tr>
 <tr>
 <td>NiSO4 x H2O</td>
 <td>Sigma-Aldrich</td>
 <td>227676</td>
 <td></td>
 </tr>
 <tr>
 <td>lactic acid</td>
 <td>Aldrich</td>
 <td>W261106</td>
 <td></td>
 </tr>
 <tr>
 <td>citric acid trisodium salt</td>
 <td>Sigma-Aldrich</td>
 <td>C3674</td>
 <td></td>
 </tr>
 <tr>
 <td>borane dimethyl amine complex</td>
 <td>Aldrich</td>
 <td>180238</td>
 <td></td>
 </tr>
 <tr>
 <td>PS-b-P4VP catalogue number</td>
 <td>Mn (PS), g/mol</td>
 <td>Mn(P4VP), g/mol</td>
 <td>PDI</td>
 </tr>
 <tr>
 <td>P9009-S4VP</td>
 <td>24000</td>
 <td>9500</td>
 <td>1.1</td>
 </tr>
 <tr>
 <td>P136-S4VP</td>
 <td>31900</td>
 <td>13200</td>
 <td>1.08</td>
 </tr>
 <tr>
 <td>P5462-S4VP</td>
 <td>37500</td>
 <td>16000</td>
 <td>1.3</td>
 </tr>
 <tr>
 <td>P3912-S4VP</td>
 <td>41500</td>
 <td>17500</td>
 <td>1.07</td>
 </tr>
 </tbody>
</table>

gyroid nickel nanostructures from diblock copolymer supramolecules

Espumas metálicas Nanoporosos possuem uma combinação única de propriedades, - eles são cataliticamente activas, termicamente e electricamente condutor, e, além disso, têm uma elevada porosidade, elevada relação de superfície-para-volume e resistência-peso. Infelizmente, as abordagens comuns para a preparação de nanoestruturas metálicas tornar materiais com arquitetura altamente desordenado, o que pode ter um efeito adverso em suas propriedades mecânicas. Os copolímeros em bloco têm a capacidade de se auto-organizar em nanoestruturas ordenadas e pode ser aplicado como modelo para a preparação de nanofoams metálicos bem ordenadas. Aqui descreve-se a aplicação de um complexo supramolecular bloco baseado em copolímero - poliestireno-bloco-poli (4-vinilpiridina) (pentadecilfenol) PS-b-P4VP (PDP) - como um precursor para nanofoam níquel bem ordenada. Os complexos supramoleculares exibem um comportamento de fase semelhante a copolímeros em bloco convencionais e pode auto-montar em bicontinua o engenho morfologia gyroidh duas redes PS colocados numa matriz de P4VP (PDP). PDP pode ser dissolvido em etanol, levando à formação de uma estrutura porosa, que pode ser preenchido com metal. Usando a técnica de chapeamento electrolítico, níquel pode ser introduzido nos canais do molde. Finalmente, o polímero restante pode ser removida através de pirólise a partir de polímero / inorgânico nanohíbrido resultando em espuma de níquel nanoporoso com morfologia gyroid inversa.

A morfologia de complexos supramoleculares PS-b-P4VP (PDP) x é examinada por TEM e SAXS Figuras 2a e 2b apresentam padrões gyroid típicos de um complexo supramolecular representativo:. Da onda duplo e os padrões vagão rodas que são conhecidos para representar projecções através do (211) e o plano (111) da célula unitária gyroid, respectivamente. Os domínios bloco PS aparecer brilhante enquanto os P4VP gerados (PDP) domínios Bloco X aparecem escuras devido a manchas...

Watch this Scientific Journal Video about Gyroid Nickel Nanostructures from Diblock Copolymer Supramolecules at JoVE.com

Gyroid Nickel Nanostructures from Diblock Copolymer Supramolecules

Este artigo descreve a preparação de nanofoams níquel bem ordenadas por deposição química de metal para modelos nanoporous obtidos a partir supramoléculas base de copolímeros diblock auto-montados.

Gyroid Nickel Nanoestruturas de dibloco copolímero supramoléculas

Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, ...

gyroid-nickel-nanostructures-from-diblock-copolymer-supramolecules

Research

JoVE Journal

Chemistry

12.3K visualizações.  University of Groningen.  Este artigo descreve a preparação de nanofoams níquel bem ordenadas por deposição química de metal para modelos nanoporous obtidos a partir supramoléculas base de copolímeros diblock auto-montados. 

Vídeo: Gyroid Nickel Nanostructures from Diblock Copolymer Supramolecules

Nucleoside Triphosphates - From Synthesis to Biochemical Characterization

The traditional strategy for the introduction of chemical functionalities is the use of solid-phase synthesis by appending suitably modified phosphoramidite precursors to the nascent chain. However, the conditions used during the synthesis and the restriction to rather short sequences hamper the applicability of this methodology. On the other hand, modified nucleoside triphosphates are activated building blocks that have been employed for the mild introduction of numerous functional groups into nucleic acids, a strategy that paves the way for the use of modified nucleic acids in a wide-ranging palette of practical applications such as functional tagging and generation of ribozymes and DNAzymes. One of the major challenges resides in the intricacy of the methodology leading to the isolation and characterization of these nucleoside analogues.
	
	In this video article, we present a detailed protocol for the synthesis of these modified analogues using phosphorous(III)-based reagents. In addition, the procedure for their biochemical characterization is divulged, with a special emphasis on primer extension reactions and TdT tailing polymerization. This detailed protocol will be of use for the crafting of modified dNTPs and their further use in chemical biology.

The protocol described herein aims to explain and abridge the numerous obstacles in the way of the intricate route leading to modified nucleoside triphosphates. Consequently, this protocol facilitates both the synthesis of these activated building-blocks and their availability for practical applications.

Nucleosídeos Trisfosfatos - Da síntese à Caracterização Bioquímica

The  traditional strategy for the introduction of chemical functionalities is the  use of solid-phase synthesis by appending suitably modified ...

Química

Synthesis of Ligand-free CdS Nanoparticles within a Sulfur Copolymer Matrix

Aliphatic ligands are typically used during the synthesis of nanoparticles to help mediate their growth in addition to operating as high-temperature solvents. These coordinating ligands help solubilize and stabilize the nanoparticles while in solution, and can influence the resulting size and reactivity of the nanoparticles during their formation. Despite the ubiquity of using ligands during synthesis, the presence of aliphatic ligands on the nanoparticle surface can result in a number of problems during the end use of the nanoparticles, necessitating further ligand stripping or ligand exchange procedures. We have developed a way to synthesize cadmium sulfide (CdS) nanoparticles using a unique sulfur copolymer. This sulfur copolymer is primarily composed of elemental sulfur, which is a cheap and abundant material. The sulfur copolymer has the advantages of operating both as a high temperature solvent and as a sulfur source, which can react with a cadmium precursor during nanoparticle synthesis, resulting in the generation of ligand free CdS. During the reaction, only some of the copolymer is consumed to produce CdS, while the rest remains in the polymeric state, thereby producing a nanocomposite material. Once the reaction is finished, the copolymer stabilizes the nanoparticles within a solid polymeric matrix. The copolymer can then be removed before the nanoparticles are used, which produces nanoparticles that do not have organic coordinating ligands. This nascent synthesis technique presents a method to produce metal-sulfide nanoparticles for a wide variety of applications where the presence of organic ligands is not desired.

Herein we present a method to synthesize ligand-free cadmium sulfide (CdS) nanoparticles based on a unique sulfur copolymer. The sulfur copolymer operates as a high temperature solvent and a sulfur source during the nanoparticle synthesis and stabilizes the nanoparticles after the reaction.

Síntese de CDs Nanopartículas sem ligando dentro de uma matriz de copolímero de Enxofre

Aliphatic ligands are typically used during the synthesis of nanoparticles to help mediate their growth in addition to operating as high-temperature ...

Anionic Polymerization of an Amphiphilic Copolymer for Preparation of Block Copolymer Micelles Stabilized by &#960;-&#960; Stacking Interactions

In this study, an amphiphilic copolymer that includes a core-forming block with phenyl groups was synthesized by living anionic polymerization of phenyl glycidyl ether (PheGE) on methoxy-polyethylene glycol (mPEG-b-PPheGE). Characterization of the copolymer revealed a narrow molecular distribution (PDI &#60; 1.03) and confirmed the degree of polymerization of mPEG122-b-(PheGE)15. The critical micelle concentration of the copolymer was evaluated using an established fluorescence method with the aggregation behavior evaluated by dynamic light scattering and transmission electronic microscopy. The potential of the copolymer for use in drug delivery applications was evaluated in a preliminary manner including in vitro biocompatibility, loading and release of the hydrophobic anti-cancer drug doxorubicin (DOX). A stable micelle formulation of DOX was prepared with drug loading levels up to 14% (wt%), drug loading efficiencies &#62; 60% (w/w) and sustained release of drug over 4 days under physiologically relevant conditions (acidic and neutral pH, presence of albumin). The high drug loading level and sustained release is attributed to stabilizing &#960;-&#960; interactions between DOX and the core-forming block of the micelles.

Anionic Polymerization of an Amphiphilic Copolymer for Preparation of Block Copolymer Micelles Stabilized by &amp;#960;-&amp;#960; Stacking Interactions

The key steps of living anionic polymerization of phenyl glycidyl ether (PheGE) on methoxy-polyethylene glycol (mPEG-b-PPheGE) are described. The resulting block copolymer micelles (BCMs) were loaded with doxorubicin 14% (wt%) and sustained release of drug over 4 days under physiologically relevant conditions was obtained.

Aniônico polimerização de um copolímero anfifílicas para Preparação de copolímero em bloco As micelas estabilizada por interacções de empilhamento π-¸

In this study, an amphiphilic copolymer that includes a core-forming block with phenyl groups was synthesized by living anionic polymerization of phenyl ...

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

Here, we describe a protocol that allows for shape-anisotropic cadmium chalcogenide nanocrystals (NCs), such as nanorods (NRs) and tetrapods (TPs), to be covalently and site-specifically linked via their end facets, resulting in polymer-like linear or branched chains. The linking procedure begins with a cation-exchange process in which the end facets of the cadmium chalcogenide NCs are first converted to silver chalcogenide. This is followed by the selective removal of ligands at their surface. This results in cadmium chalcogenide NCs with highly reactive silver chalcogenide end facets that spontaneously fuse upon contact with each other, thereby establishing an interparticle facet-to-facet attachment. Through the judicious choice of precursor concentrations, an extensive network of linked NCs can be produced. Structural characterization of the linked NCs is carried out via low- and high-resolution transmission electron microscopy (TEM), as well as energy-dispersive X-ray spectroscopy, which confirm the presence of silver chalcogenide domains between chains of cadmium chalcogenide NCs.

A protocol detailing how shape-anisotropic colloidal cadmium chalcogenide nanocrystals can be covalently linked via their end facets is presented here.

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 ...

Synthesis of Platinum-nickel Nanowires and Optimization for Oxygen Reduction Performance

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen reduction reaction. Spontaneous galvanic displacement was used to deposit Pt layers onto Ni nanowire substrates. The synthesis approach produced catalysts with high specific activities and high Pt surface areas. Hydrogen annealing improved Pt and Ni mixing and specific activity. Acid leaching was used to preferentially remove Ni near the nanowire surface, and oxygen annealing was used to stabilize near-surface Ni, improving durability and minimizing Ni dissolution. These protocols detail the optimization of each post-synthesis processing step, including hydrogen annealing to 250 &#176;C, exposure to 0.1 M nitric acid, and oxygen annealing to 175 &#176;C. Through these steps, Pt-Ni nanowires produced increased activities more than an order of magnitude than Pt nanoparticles, while offering significant durability improvements. The presented protocols are based on Pt-Ni systems in the development of fuel cell catalysts. These techniques have also been used for a variety of metal combinations, and can be applied to develop catalysts for a number of electrochemical processes.

&#160; The protocol describes the synthesis and electrochemical testing of platinum-nickel nanowires. Nanowires were synthesized by the galvanic displacement of a nickel nanowire template. Post-synthesis processing, including hydrogen annealing, acid leaching, and oxygen annealing were used to optimize nanowire performance and durability in the oxygen reduction reaction.

Síntese de nanofios de níquel e platina e otimização de desempenho de redução do oxigênio

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen ...

Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area

We demonstrate a method for the synthesis of NixNb1-xO catalysts with sponge-like and fold-like nanostructures. By varying the Nb:Ni ratio, a series of NixNb1-xO nanoparticles with different atomic compositions (x = 0.03, 0.08, 0.15, and 0.20) have been prepared by chemical precipitation. These NixNb1-xO catalysts are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The study revealed the sponge-like and fold-like appearance of Ni0.97Nb0.03O and Ni0.92Nb0.08O on the NiO surface, and the larger surface area of these NixNb1-xO catalysts, compared with the bulk NiO. Maximum surface area of 173 m2/g can be obtained for Ni0.92Nb0.08O catalysts. In addition, the catalytic hydroconversion of lignin-derived compounds using the synthesized Ni0.92Nb0.08O catalysts have been investigated.

Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area

A protocol for the synthesis of sponge-like and fold-like Ni1-xNbxO nanoparticles by chemical precipitation is presented.

Método de precipitação química para a síntese do Nb2O5 modificado catalisadores de níquel em massa com alta área de superfície específica

We demonstrate a method for the synthesis of NixNb1-xO catalysts with sponge-like and fold-like nanostructures. By varying the Nb:Ni ratio, a series of ...

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We present methods for depositing and passively manipulating C60 molecules on rippled graphene that advance the pursuit of realizing applications involving 1D C60/graphene hybrid structures. The techniques applied in this exposition are geared towards high vacuum systems with preparation areas capable of supporting molecular deposition as well as thermal annealing of the samples. We focus on C60 deposition at low pressure using a homemade Knudsen cell connected to a scanning tunneling microscopy (STM) system. The number of molecules deposited is regulated by controlling the temperature of the Knudsen cell and the deposition time. One-dimensional (1D) C60 chain structures with widths of two to three molecules can be prepared via tuning of the experimental conditions. The surface mobility of the C60 molecules increases with annealing temperature allowing them to move within the periodic potential of the rippled graphene. Using this mechanism, it is possible to control the transition of 1D C60 chain structures to a hexagonal close packed quasi-1D stripe structure.

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Here we present a protocol for the fabrication of C60/graphene hybrid nanostructures by physical thermal evaporation. Particularly, the proper manipulation of deposition and annealing conditions allow the control over the creation of 1D and quasi 1D C60 structures on rippled graphene.

Preparação e caracterização de nanoestruturas de híbrido C60/Graphene

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We ...

Disentangling High Strength Copolymer Aramid Fibers to Enable the Determination of Their Mechanical Properties

Traditionally, soft body armor has been made from poly(p-phenylene terephthalamide) (PPTA) and ultra-high molecular weight polyethylene. However, to diversify the fiber choices in the United States body armor market, copolymer fibers based on the combination of 5-amino-2-(p-aminophenyl) benzimidazole (PBIA) and the more conventional PPTA were introduced. Little is known regarding the long-term stability of these fibers, but as condensation polymers, they are expected to have potential sensitivity to moisture and humidity. Therefore, characterizing the strength of the materials and understanding their vulnerability to environmental conditions is important for evaluating their use lifetime in safety applications. Ballistic resistance and other critical structural properties of these fibers are predicated on their strength. To accurately determine the strength of the individual fibers, it is necessary to disentangle them from the yarn without introducing any damage. Three aramid-based copolymer fibers were selected for the study. The fibers were washed with acetone followed by methanol to remove an organic coating that held the individual fibers in each yarn bundle together. This coating makes it difficult to separate single fibers from the yarn bundle for mechanical testing without damaging the fibers and affecting their strength. After washing, fourier transform infrared (FTIR) spectroscopy was performed on both washed and unwashed samples and the results were compared. This experiment has shown that there are no significant variations in the spectra of poly(p-phenylene-benzimidazole-terephthalamide-co-p-phenylene terephthalamide) (PBIA-co-PPTA1) and PBIA-co-PPTA3 after washing, and only a small variation in intensity for PBIA. This indicates that the acetone and methanol rinses are not adversely affecting the fibers and causing chemical degradation. Additionally, single fiber tensile testing was performed on the washed fibers to characterize their initial tensile strength and strain to failure, and compare those to other reported values. Iterative procedural development was necessary to find a successful method for performing tensile testing on these fibers.

The primary goal of the study is to develop a protocol to prepare consistent specimens for accurate mechanical testing of high strength copolymer aramid fibers, by removing a coating and disentangling the individual fiber strands without introducing significant chemical or physical degradation.

Desembaraçar as fibras de aramida de copolímero de alta resistência para permitir a determinação de suas propriedades mecânicas

Traditionally, soft body armor has been made from poly(p-phenylene terephthalamide) (PPTA) and ultra-high molecular weight polyethylene. However, to ...

Stable DNA Motifs, 1D and 2D Nanostructures Constructed from Small Circular DNA Molecules

This article presents a detailed protocol for synthesis of small circular DNA molecules, annealing of circular DNA motifs, and construction of 1D and 2D DNA nanostructures. Over decades, the rapid development of DNA nanotechnology is attributed to the use of linear DNAs as the source materials. For example, the DAO (double crossover, antiparallel, odd half-turns) tile is well-known as a building block for construction of 2D DNA lattices; the core structure of DAO is made from two linear single-stranded (ss) oligonucleotides, like two ropes making a right hand granny&#160;knot. Herein, a new type of DNA tiles called cDAO (coupled DAO) are built using a small circular ss-DNA of c64nt or c84nt (circular 64 or 84 nucleotides) as the scaffold strand and several linear ss-DNAs as the staple strands. Perfect 1D and 2D nanostructures are assembled from cDAO tiles: infinite nanowires, nanospirals, nanotubes, nanoribbons; and finite nano-rectangles. Detailed protocols are described: 1) preparation by T4 ligase and purification by denaturing PAGE (polyacrylamide gel electrophoresis) of small circular oligonucleotides, 2) annealing of stable circular tiles, followed by native PAGE analysis, 3) assembling of infinite 1D nanowires, nanorings, nanospirals, infinite 2D lattices of nanotubes and nanoribbons, and finite 2D nano-rectangles, followed by AFM (Atomic Force Microscopy) imaging. The method is simple, robust, and affordable for most labs.

This article presents a detailed protocol for T4 ligation and denaturing PAGE purification of small circular DNA molecules, annealing and native PAGE analysis of circular tiles, assembling and AFM imaging of 1D and 2D DNA nanostructures, as well as agarose gel electrophoresis and centrifugation purification of finite DNA nanostructures.

Motivos de DNA estável, 1D e 2D nanoestruturas construídas a partir de moléculas de DNA Circular pequeno

This article presents a detailed protocol for synthesis of small circular DNA molecules, annealing of circular DNA motifs, and construction of 1D and 2D ...

Gene-therapy Inspired Polycation Coating for Protection of DNA Origami Nanostructures

DNA origami nanostructures hold an immense potential to be used for biological and medical applications. However, low-salt conditions and nucleases in physiological fluids induce denaturation and degradation of self-assembled DNA nanostructures. In non-viral gene delivery, enzymatic degradation of DNA is overcome by the encapsulation of the negatively charged DNA in a cationic shell. Herein, inspired by gene delivery advancements, a simple, one-step and robust methodology is presented for the stabilization of DNA origami nanostructures by coating them with chitosan and linear polyethyleneimine. The polycation coating efficiently protects DNA origami nanostructures in Mg-depleted and nuclease-rich media. This method also preserves the full addressability of enzyme- and aptamer-based functionalization of DNA nanostructures.

Here, a protocol for the protection of DNA origami nanostructures in Mg-depleted and nuclease-rich media using natural cationic polysaccharide chitosan and synthetic linear polyethyleneimine (LPEI) coatings is presented.

Gene-terapia inspirou Polycation revestimento para proteção de nanoestruturas de Origami de DNA

DNA origami nanostructures hold an immense potential to be used for biological and medical applications. However, low-salt conditions and nucleases in ...