Nous reconnaissons le soutien financier de l&#39;Institut de Zernike des matériaux avancés, de l&#39;Université de Groningen.

1. Préparation et caractérisation de PS-b-P4VP (PDP) Complexes avec Double Gyroid Morphologie <ol><li> Peser le polystyrène-bloc-poly (4-vinylpyridine) (PS-b-P4VP) et pentadécylphénol (PDP, M r = 304,51 g / mol). Afin d&#39;obtenir la morphologie Gyroid, choisir soigneusement le montant de PDP devrait être (la fraction de poids de P4VP (PDP) bloc (f P4VP (PDP)) doit être ca. 0,6 selon le diagramme de phase de copolymères linéaires diblocs AB). Habituellement, de 0,15 à 0,2 g d&#39;un PS-b-P4VP conduit à PS-b-P4VP (PDP) des films de 50 à 100 um d&#39;épaisseur (étant donné que le diamètre d&#39;une boîte de Petri utilisé dans l&#39;étape 5-6 est de 1,3 cm). Calculer la quantité de PDP selon l&#39;une des équations suivantes: <img alt="Equation 1" src="/files/ftp_upload/50673/50673eq1.jpg" /> <img alt="Equation 2" src="/files/ftp_upload/50673/50673eq2.jpg" /> <img alt="Equation 3" src="/files/ftp_upload/50673/50673eq3.jpg" /><br/&gt; <img alt="Equation 4" src="/files/ftp_upload/50673/50673eq4.jpg" /></li><li> Dissoudre PS-b-P4VP et PDP dans le chloroforme et remuez pendant quelques heures à la température ambiante. Maintenir la concentration de polymère au-dessous de 2% en poids pour assurer la formation d&#39;un complexe homogène. </li><li> Verser la solution dans une boîte de Pétri en verre. </li><li> Placer le plat dans une atmosphère saturée de chloroforme. </li><li> Après environ une semaine, sortez la boîte de Pétri. Un film de complexe supramoléculaire est formé. </li><li> Sécher le film sous vide à 30 ° C pendant une nuit. </li><li> Placez le film dans un conteneur spécialement conçu, retirer l&#39;air du récipient et remplissez-le avec de l&#39;azote. Recuire le film pendant 4 jours à l&#39;étuve à 120 ° C sous atmosphère de N2 à 1 bar de surpression. </li><li> Couper le petit morceau du film, incorporer en époxy et guérir une nuit à 40 ° C. </li><li> Microtome l&#39;échantillon à une épaisseur d&#39;environ 80 nm à l&#39;aide d&#39;un couteau diamant à la température ambiante. The section microtome flotte sur l&#39;eau. Ramassez-les et placez sur des grilles de Cu. </li><li> Mettez les grilles contenant les sections microtomée dans un bocal avec de l&#39;iode. Après 45 min d&#39;échantillons sont colorés et prêts pour la microscopie électronique à transmission. </li><li> Insérer les grilles de Cu avec coupes colorées dans le microscope électronique à transmission fonctionnant à une tension d&#39;accélération de 120 kV et une image de l&#39;échantillon. </li><li> Insérez le morceau du film (obtenu après l&#39;étape 1.7) dans le porte-échantillon pour les petits angles de diffusion de rayons X et le fixer avec une bande Kapton. Placer le porte-échantillon préparé dans la machine pour SAXS. Ouvrez le volet de rayons X et d&#39;acquérir le modèle de diffusion 2D. Intégrer le modèle 2D obtenu et analyser la position des pics dans le modèle 1D. </li></ol> 2. Génération et caractérisation de la structure poreuse <ol><li> Mettez le morceau de film (obtenu après l&#39;étape 1.7) dans de l&#39;éthanol et le garder pendant trois jours. </li><li> Sécher l&#39;échantillon. </li><li> Préparer les échantillons pour une mesure H RMN. Dissoudre la poudre PDP, poudre PS-b-P4VP, PS-b-P4VP (PDP) (après l&#39;étape 1.7), et poreux film complexe supramoléculaire (après l&#39;étape 2.2) dans CDCl3. Enregistrement des spectres RMN 1 H à température ambiante. </li><li> Analyser poudre PS-b-P4VP, supramoléculaire complexe PS-b-P4VP (PDP) (après l&#39;étape 1.7), et le film poreux (après l&#39;étape 2.2) par calorimétrie différentielle à balayage. Utiliser un mode modulé avec un taux de chauffage / refroidissement de 1 ° C / min, une amplitude d&#39;oscillation de 0,5 ° C, et une période d&#39;oscillation de 60 secondes. Equilibrer les échantillons à -30 ° C, température à 180 ° C, refroidir à -30 ° C, puis chauffer à nouveau à 180 ° C. Utiliser les données provenant du second cycle de chauffage pour l&#39;analyse. </li><li> Dégazer l&#39;échantillon poreux (après l&#39;étape 2.2) pendant 8 heures à la température ambiante et pendant 18 heures à 70 ° C et à effectuer des mesures d&#39;adsorption d&#39;azote à 77 K. </li><li> Utilisez le logiciel approprié (par exemple, WinADP) et des modèles pour analyser les isothermes obtenues. </li><li> Sécher l&#39;échantillon poreux (après l&#39;étape 2.2) à 50 ° C pendant 8 heures et dégazer à température ambiante et à la pression de 0,5 Pa pendant 2 heures. </li><li> Effectuer porosimétrie au mercure. </li></ol> 3. Insertion Nickel dans le modèle de polymère <ol><li> Peser le chlorure d&#39;étain (SnCl 2, M r = 189,60 g / mol) et de préparer une solution aqueuse (SnCl 2 / HCl 0,1 M à 0,1 M; 1,896 g de SnCl 2, 0,8 ml de HCl et 100 ml H 2 O). Mettre la solution pendant une nuit sur ​​un agitateur pour assurer la dissolution complète du SnCl 2. </li><li> Peser le chlorure de palladium (PdCl 2, M r = 177,33 g / mol) et de préparer une solution aqueuse (M PdCl 2 M HCl 0,0014 / 0,25; 0,025 g de PdCl2, 2 ml d&#39;HCl et 100 ml H 2 O). </li><li> Préparer la partie 1 de la salle de bain de nickelage: peser 6,78 g de sulfate de nickel hexahydraté (NiSO4 • 6H 2 O, M r = 2620,85 g / mol) et 2 g de citrate de sodium (Na 3 C 6 H 5 O 7, M r = 258,06 g / mol) et les dissoudre dans 80 ml ​​d&#39;eau. Ajouter 828 ul de 85% d&#39;acide lactique (C 3 H 6 O 3, M r = 90,08 g / mol). </li><li> Préparer la partie 2 du bain de nickelage: poids rupture complexe borane diméthylamine de 0,2 g de ((CH 3) 2 NHBH 3, M r = 58,92 g / mol) et le dissoudre dans 20 ml d&#39;eau. Complexe de diméthylamine borane doit être manipulé dans une hotte bien ventilée. </li><li> Immerger le film poreux (après l&#39;étape 2.2) dans la solution aqueuse de chlorure d&#39;étain (étape 3.1) pendant 1 heure. </li><li> Rincer le film à fond avec de l&#39;eau désionisée. </li><li> Immerger le film dans la solution aqueuse de chlorure de palladium (étape 3.2) pendant 1 heure. </li><li> Rincer le film à fond avec de l&#39;eau désionisée. </li><li> Mélanger une partie (3.3) et la partie 2 (3.4) du bain de nickelage. Ajuster le pH à 7,0 avec de l&#39;hydroxyde d&#39;ammonium. </li><li> Immerger le film dans le bain galvanique de nickel pendant 1 heure. </li><li> Rincer le film à fond avec de l&#39;eau désionisée. </li><li> Sécher l&#39;échantillon. </li><li> Préparer l&#39;échantillon plaqué pour la microscopie électronique en suivant les étapes 1.8 à 1.9. </li><li> L&#39;image de l&#39;échantillon tel que décrit à l&#39;étape 1.11. </li><li> Insérer des grilles de Cu contenant les sections de l&#39;échantillon plaqué dans le microscope électronique à transmission à haute résolution. Acquérir micrographies TEM haute résolution. Observer l&#39;échantillon sous le microscope et choisir la zone pour l&#39;analyse élémentaire par EDX (analyse par dispersion d&#39;énergie des rayons X). Effectuer l&#39;analyse EDX de la zone choisie et analyser le motif obtenu. </li></ol> 4. L&#39;exposition de la mousse de nickel inverse Gyroid <ol><li> Mettre le film de nickel plaqué (après l&#39;étape 3.12) dans un four à 350 ° C et l&#39;empêcher de 1 heure à 4 jours. </li><li> Attacher l&#39;échantillon sur le porte-échantillon en utilisant une pâte d&#39;argent. </li><li> Insérez l&#39;échantillon dans le micro électronique à balayageroscope. L&#39;acquisition de plusieurs images de l&#39;échantillon. </li><li> Introduire l&#39;échantillon dans le microscope électronique à balayage. Observer l&#39;échantillon sous le microscope et choisir la zone pour l&#39;analyse élémentaire par EDX. Effectuer l&#39;analyse EDX de la zone choisie et analyser le motif obtenu. </li></ol>

<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>

Les auteurs déclarent aucun intérêt financier concurrents.

Complexes supramoléculaires sont appliquées avec succès en tant que précurseurs pour nanomousses métalliques bien ordonnées. Dans ce procédé, l&#39;étape essentielle consiste à acquérir le gabarit approprié, à savoir un modèle de morphologie Gyroid. Dans le diagramme de phase de copolymères séquences de la région Gyroid est très faible et il est assez difficile à cibler. Cela signifie que si les copolymères à blocs conventionnels sont utilisés comme matières de départ, la synthèse tout ...

Il existe plusieurs techniques disponibles pour la préparation d&#39;nanomousses métalliques: dealloying 1-3, sol-gel se rapproche de 4,5, 6,7 nanosmelting, et la synthèse de combustion 8. Dans le procédé de dealloying, le matériau de départ est généralement un alliage binaire, par exemple, un alliage d&#39;argent et d&#39;or. Le métal le moins noble, l&#39;argent, dans ce cas, peut être éliminé par voie chimique ou par voie électrochimique résultant en une mousse d&#39;or poreuse désordonnée avec ligaments de taille nanométrique. Dans la synthèse par combustion, le métal est mélangé avec un précurseur d&#39;énergie qui libère de l&#39;énergie lors de sa décomposition et entraîne la formation de nanomousse métallique 8. Des études sur le comportement mécanique des mousses métalliques indiquent que dans les architectures de troubles contraintes ne peuvent pas être transmises efficacement de l&#39;échelle nanométrique de ligament à l&#39;échelle macroscopique global 9-11. Ainsi nanomousses métalliques bien ordonnées sont censés avoir des propriétés mécaniques supérieures par rapport à lales troubles. L&#39;idée représentée ici est d&#39;employer des copolymères à blocs qui s&#39;auto-assemblent en nanostructures ordonnées comme précurseurs d&#39;nanomousses métalliques. En fonction de la composition d&#39;un copolymère à blocs, le nombre total d&#39;unités monomères et de l&#39;étendue de la répulsion entre les blocs chimiquement liés, apparaissent différentes morphologies telles que: sphérique, cylindrique, à lamelles, double Gyroid, lamellaire hexagonale perforée, et d&#39;autres de 12 à 14 . En outre, des blocs de polymères peuvent être dégradés de manière sélective conduisant à des matériaux nanoporeux 15. Les méthodes les plus courantes sont: 16-18 ozonolyse, une irradiation UV 19, gravure ionique réactive de 20 à 22, 23 à 26 et de dissolution. Les structures poreuses générés peuvent être remblayées avec divers matériaux inorganiques. Les oxydes métalliques (par exemple SiO 2, TiO 2) sont généralement introduits par procédé sol-gel dans les canaux de la modèle 27-29. Elle placage autocatalytique ectrochemical et sont couramment utilisés pour déposer du métal sur ou dans des modèles de 30 à 33. Enfin, le polymère restant peut être éliminé du polymère nanohybride / inorganique par l&#39;intermédiaire de deux pyrolyse, dissolution 34,35, 28,29 dégradation par les UV, etc Dans notre approche, nous partons d&#39;un complexe supramoléculaire de polystyrène-bloc-poly (4-vinyl-pyridine) (PS-b-P4VP) copolymère dibloc et pentadécylphénol amphiphile (PDP) des molécules. Ce complexe est le résultat de la liaison hydrogène entre PDP et cycles pyridine (Figure 1a). La composition du copolymère à blocs de départ et la quantité d&#39;ajouter PDP sont choisis de telle sorte que le système s&#39;auto-assemble obtenus en double morphologie Gyroid bicontinue avec un réseau de PS et d&#39;une matrice P4VP (PDP) (figure 1b). Molécules PDP se dissoudre sélectivement dans de l&#39;éthanol et P4VP chaînes effondrement sur le réseau PS (Figure 1c). Par la suite, en utilisant la méthode de placage sans courant, le nickel est déposé dans les pores de la matrice (figure 1d). Après l&#39;élimination du polymère restant par pyrolyse, un nanomousse de nickel Gyroid bien ordonnée est obtenue (figure 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

Mousses métalliques nanoporeux possèdent une combinaison unique de propriétés - ils sont à activité catalytique, thermiquement et électriquement conducteur, et, en outre, avoir une porosité élevée, rapport surface-volume et de force-à-poids. Malheureusement, des approches communes pour la préparation de nanostructures métalliques rendent matériaux à l&#39;architecture très désordonné, ce qui pourrait avoir un effet négatif sur leurs propriétés mécaniques. Les copolymères séquences ont la capacité de s&#39;auto-assembler en nanostructures ordonnées et peuvent être appliqués en tant que matrices pour la préparation des nanomousses métalliques bien ordonnées. Nous décrivons ici l&#39;application d&#39;un complexe supramoléculaire à base de copolymère-bloc - le polystyrène-bloc-poly (4-vinylpyridine) (pentadécylphénol) PS-b-P4VP (PDP) - en tant que précurseur pour bien ordonnée nanomousse de nickel. Les complexes supramoléculaires présentent un comportement de phase similaire à des copolymères à blocs classiques et peuvent s&#39;auto-assembler dans le bicontinue Gyroid morphologie esprith deux réseaux PS placés dans une matrice P4VP (PDP). PDP peut être dissous dans de l&#39;éthanol conduisant à la formation d&#39;une structure poreuse qui peut être rempli à nouveau avec le métal. En utilisant une technique de placage non électrolytique, le nickel peut être inséré dans les canaux du modèle. Enfin, le polymère restant peut être éliminé par pyrolyse du polymère / nanohybride inorganique résultant en mousse de nickel nanoporeux morphologie Gyroid inverse.

La morphologie des complexes supramoléculaires PS-b-P4VP (PDP) x est examiné par TEM et SAXS figures 2a et 2b afficher modèles Gyroid typiques d&#39;un complexe supramoléculaire représentant:. Double-ondes et les motifs wagon-roues qui sont connus pour représenter des saillies à travers le (211) et le plan (111) de la cellule unitaire Gyroid, respectivement. Les domaines de blocs de PS sont plus clairs que les P4VP (PDP) domaines de blocs de x apparaissent sombres en rai...

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

Gyroid Nickel Nanostructures from Diblock Copolymer Supramolecules

Cet article décrit la préparation de nanomousses de nickel bien ordonnés par dépôt électrolytique de métal sur des modèles nanoporeux obtenus à partir de la base supramolécules copolymère dibloc auto-assemblée.

Gyroid Nickel Nanostructures de copolymère dibloc supramolécules

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

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Chemistry

12.3K vues.  University of Groningen.  Cet article décrit la préparation de nanomousses de nickel bien ordonnés par dépôt électrolytique de métal sur des modèles nanoporeux obtenus à partir de la base supramolécules copolymère dibloc auto-assemblée. 

Vidéo: 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.

Nucléosidiques Triphosphates - de la synthèse à caractérisation biochimique

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

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Chimie

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.

Synthèse du ligand libre-CdS Nanoparticules dans une matrice de soufre Copolymer

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.

Anionique Polymérisation d&#39;un copolymère amphiphile pour la préparation du copolymère bloc micelles Stabilisé par π-tc Interactions Stacking

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.

Facet-à-facette reliant des Nanostructures de chalcogénure anisotropie forme colloïdale Cadmium

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.

Synthèse de nanofils Platinum-nickel et optimisation des performances de réduction de l’oxygène

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.

Méthode de précipitation chimique pour la synthèse de Nb2O5 modifiée catalyseurs Nickel en vrac avec le haute surface spécifique

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.

Préparation et caractérisation de Nanostructures hybrides de 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.

Démêler les fibres d’aramide de copolymère haute résistance afin de permettre la détermination de leurs propriétés mécaniques

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.

Motifs d’ADN stable, 1D et 2D Nanostructures construit à partir de molécules d’ADN circulaire petit

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.

Thérapie génique inspiré Polycation enduit pour la Protection de l’ADN Origami Nanostructures

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