Este trabalho foi apoiado pela Universidade de Helsinque e pela Fundação Jane e Aatos Erkko. S.H. agradece os fundos da ERASMUS+ UE pela bolsa.

1. Síntese de Ag-Pd/ZrO2 NPs 
NOTA: Neste procedimento, o Pd mol% em Ag-Pd correspondeu a 1%, e o carregamento Ag-Pd no ZrO2 correspondeu a 3 wt.%.
<ol><li>Coloque 1 g de ZrO2 em pó em um béquer de 250 mL.</li>
	<li>Adicione 50 mL de uma solução AgNO3 (aq) (0,0059 mol/L) e 9,71 mL de uma solução K2PdCl4 (aq) (0,00031 mol/L) ao béquer sob forte agitação magnética (500 rpm) à temperatura ambiente.</li>
	<li>Adicione 10 mL de solução aquosa de lisina (0,53 M).</li>
	<li>Mantenha a mistura sob agitação vigorosa (500 rpm) por 20 minutos.</li>
	<li>Após 20 min, use uma pipeta para adicionar à suspensão 10 mL de uma solução nabh4 (aq) (aq) (0,035 M) recém-preparada, a uma taxa de 1 mL/min. Mantenha a suspensão em movimento (500 rpm) durante todo o processo.</li>
	<li>Deixe a mistura mexer por 30 minutos em temperatura ambiente.</li>
</ol>2. Separação e purificação do catalisador
<ol><li>Transfira a suspensão para tubos de centrífugas e separe os sólidos da mistura por centrifugação a 3.260 x g por 10 min.</li>
	<li>Remova cuidadosamente a fase líquida com uma pipeta e adicione 15 mL de água desionizada aos tubos.<ol>
<li>Agite vigorosamente até que a dispersão do sólido seja obtida. Se uma boa dispersão não for alcançada, coloque os tubos em um banho ultrassônico por 5 minutos.</li>
		<li>Centrifugar a dispersão a 3.260 x g por 10 min.</li>
	</ol>
</li>
	<li>Repita as etapas de lavagem (2.2. a 2.2.2.) mais duas vezes usando água deionizada, depois uma vez usando etanol em vez de água.</li>
	<li>Retire o etanol e seque o sólido em forno a 60 °C por 12h.</li>
	<li>Caracterize os NPs Ag-Pd/ZrO2 NPs preparados por uma variedade de técnicas microscopia, elementar e espectroscópica.</li>
</ol>3. Síntese de Ag/ZrO2 NPs 
NOTA: Neste procedimento, o carregamento ag no ZrO2 correspondeu a 3 wt.%.
<ol><li>Coloque 1 g de ZrO2 em pó em um béquer de 250 mL.</li>
	<li>Adicione 50 mL de uma solução AgNO3 (aq) (0,0059 mol/L) ao béquer sob agitação magnética vigorosa (500 rpm) à temperatura ambiente.</li>
	<li>Adicione 10 mL de solução aquosa de lisina (0,53 M).</li>
	<li>Mantenha a mistura sob agitação vigorosa (500 rpm) por 20 minutos.</li>
	<li>Após 20 min, use uma pipeta para adicionar à suspensão 10 mL de uma solução nabh4 (aq) (aq) (0,035 M) recém-preparada, a uma taxa de 1 mL/min. Mantenha a suspensão em movimento (500 rpm) durante todo o processo.</li>
	<li>Deixe a mistura mexer por 30 minutos em temperatura ambiente.</li>
</ol>4. Separação e purificação do catalisador
<ol><li>Transfira a suspensão para tubos de centrífugas e separe os sólidos da mistura por centrifugação a 3.260 x g por 10 min.</li>
	<li>Remova cuidadosamente a fase líquida com uma pipeta e adicione 15 mL de água desionizada aos tubos.<ol>
<li>Agite vigorosamente até que a dispersão do sólido seja observada. Se uma boa dispersão não for alcançada, coloque os tubos em um banho ultrassônico por 5 minutos.</li>
		<li>Centrifugar a dispersão a 3.260 x g por 10 min.</li>
	</ol>
</li>
	<li>Repita as etapas de lavagem (4.2. a 4.2.2.) mais duas vezes usando água deionizada, depois uma vez usando etanol em vez de água.</li>
	<li>Retire o etanol e seque o sólido em forno a 60 °C por 12h.</li>
	<li>Os NPs Ag/ZrO2 preparados podem então ser caracterizados por uma variedade de técnicas microscopia, elementar e espectroscópica.</li>
</ol>5. Investigação do desempenho catalítico plasmônico para a redução de nitrobenzeno sob excitação LSPR (iluminação de luz)
<ol><li>Coloque 30 mg de catalisador em um frasco de fundo redondo de 25 mL, juntamente com uma barra de agitação magnética.</li>
	<li>Adicione 5 mL de uma solução de nitrobenzeno (0,03 mol/L) em álcool isopropílico (IPA) ao reator.</li>
	<li>Em seguida, adicione 11,22 mg de koh em pó (0,0002 mol).</li>
	<li>Purgue o reator borbulhando a suspensão com um fluxo de argônio por 1 min. Imediatamente após a purga, sele o frasco.</li>
	<li>Coloque o reator em um banho de óleo aquecido a 70 °C acima de um agitador magnético controlado pela temperatura (500 rpm).</li>
	<li>Irradie o tubo usando lâmpadas LED de 4 led com um comprimento de onda de 425 nm como fonte de luz, e uma intensidade leve de 0,5 W/cm2. A distância das lâmpadas ao frasco de reação deve ser de 7 cm.</li>
	<li>Deixe a reação prosseguir por 2,5 h a 70 °C sob agitação magnética vigorosa (500 rpm).</li>
	<li>Em seguida, desligue a luz, abra o reator e use uma seringa e uma agulha para coletar uma amostra de 1 mL. Filtre-o através de um filtro de 0,45 μm, para remover as partículas catalisadoras, em um frasco de cromatografia gasosa.</li>
</ol>6. Reação na ausência de excitação LSPR (condições escuras)
<ol><li>Siga os mesmos passos descritos em 5, mas sem irradiação leve. Enrole o tubo de reação com papel alumínio para evitar qualquer exposição à luz.</li>
</ol>7. Preparação para análise de cromatografia gasosa (GC)
<ol><li>Prepare uma solução IPA contendo aproximadamente 30 mmol/L nitrobenzeno (NB), 30 mmol/L de anilina (AN) e 30 mmol/L de azobenzeno (AB).</li>
	<li>Execute uma análise gc da solução usando um método adequado. Diferentes métodos podem ser testados variando os programas de temperatura e fluxo de gás da coluna. O método selecionado deve ser capaz de separar os picos correspondentes ao IPA, NB, AN e AB no período mínimo de retenção.</li>
	<li>Uma vez selecionado o método, prepare um conjunto de soluções de 50 mM, 25 mM, 10 mM, 5 mM e 2,5 mM NB no IPA, e outro conjunto de soluções de AN e AB em IPA com as mesmas concentrações.</li>
	<li>Execute uma análise gc das soluções preparadas. Cada cromatograma deve apresentar 2 picos: o maior corresponde ao IPA e o inferior corresponde a NB, AN ou AB. Para cada cromatograma, observe o tempo de retenção e a área de pico de todos os picos.</li>
	<li>Rastreie as curvas de calibração de NB, AN e AB, traçando a concentração versus área de pico de cada amostra.</li>
</ol>8. Análise GC
<ol><li>Execute uma análise de GC nas amostras coletadas nas etapas 5. e 6. com o mesmo método utilizado para as etapas 7.2. e 7,4.</li>
	<li>Para cada cromatograma, observe o tempo de retenção e a área de pico e use as curvas de calibração traçadas anteriormente para determinar a concentração de NB, AN e AB nas amostras.</li>
	<li>Calcule a conversão de nitrobenzeno, bem como a seletividade anilina e azobenzena usando as equações: <img alt="Equation 1" src="/files/ftp_upload/61712/61712eq1.jpg"> <img alt="Equation 2" src="/files/ftp_upload/61712/61712eq2.jpg"> <img alt="Equation 3" src="/files/ftp_upload/61712/61712eq3.jpg"> Onde <img alt="Equation 4" src="/files/ftp_upload/61712/61712eq4.jpg"> está a concentração inicial de NB (0,03 mol/L) e C NB, CAN, CAB correspondem às concentrações de NB, AN e AB, respectivamente, após 2,5 horas de reação pela análise de GC.</li>
</ol>

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J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Defect+chemistry+and+Plasmon+physics+of+colloidal+metal+oxide+Nanocrystals.">Defect chemistry and Plasmon physics of colloidal metal oxide Nanocrystals.</a> Journal of Physical Chemistry Letters. 5 (9), 1564-1574 (2014).</li><li>Rej, 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=Determining+Plasmonic+Hot+Electrons+and+Photothermal+Effects+during+H2+Evolution+with+TiN-Pt+Nanohybrids.">Determining Plasmonic Hot Electrons and Photothermal Effects during H2 Evolution with TiN-Pt Nanohybrids.</a> ACS Catalysis. 10 (9), 5261-5271 (2020).</li><li>Barragan, A. 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=Photochemistry+of+Plasmonic+Titanium+Nitride+Nanocrystals.">Photochemistry of Plasmonic Titanium Nitride Nanocrystals.</a> The Journal of Physical Chemistry C. 123 (35), 21796-21804 (2019).</li></ol>

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Os achados descritos neste método demonstram que a atividade catalítica intrínseca do PD (ou outro metal catalítico, mas não plasmônico) pode ser significativamente aprimorada pela excitação LSPR através da irradiação de luz visível em NPs35bimetálicas . Neste caso, ag (ou outro metal plasmônico) é capaz de colher energia a partir da irradiação de luz visível via excitação LSPR. A excitação LSPR leva à formação de portadores de carga quente (elétrons e orifícios quentes)...

Entre as diversas aplicações de nanopartículas metálicas (NPs), a catálise merece atenção especial. A catálise desempenha um papel central em um futuro sustentável, contribuindo para o menor consumo de energia, melhor aproveitamento das matérias-primas e possibilitando condições de reação mais limpas1,2,3,4. Assim, o progresso na catálise pode fornecer ferramentas para aumentar a eficiência atômica dos processos químicos, tornando-os mais limpos, economicamente viáveis e mais ecológicos. NPs metálicos que englobam prata (Ag), ouro (Au) ou cobre (Cu) podem exibir propriedades ópticas interessantes na faixa visível que surgem da forma única como esses sistemas interagem com a luz na nanoescala através da excitação de ressonância de plasmon de superfície localizada (LSPR)5,6,7,8. Nestes NPs, chamados de NPs plasmônicos, o LSPR compreende a interação ressonante entre os fótons incidentes (a partir de uma onda eletromagnética de entrada) com o movimento coletivo dos elétrons5,6,7,8. Esse fenômeno ocorre em uma frequência característica que depende do tamanho, forma, composição e constante dielétrica do ambiente9,10,11. Por exemplo, para Ag, Au e, essas frequências podem variar do visível ao near-IR, abrindo possibilidades para a utilização da energia solar para excitar sua LSPR5,6,7,8,12,13.
Recentemente, foi demonstrado que a excitação LSPR em NPs plasmônicos pode contribuir para acelerar as taxas e controlar a seletividade das transformações moleculares5,14,15,16,17,18,19. Isso deu origem a um campo chamado catálise plasmônica, que se concentra no uso de energia da luz para acelerar, dirigir e/ou controlar transformações químicas5,14,15,16,17,18,19. Neste contexto, foi estabelecido que a excitação LSPR em NPs plasmônicos pode levar à formação de elétrons e buracos quentes energéticos, chamados de portadores quentes animados por LSPR. Esses portadores podem interagir com espécies adsorvidas através da ativação eletrônica ou vibracional15,16. Além do aumento das taxas de reação, esse processo também pode fornecer vias alternativas de reação não acessíveis através de processos tradicionais movidos a termoquímica, abrindo novos caminhos para o controle sobre a seletividade de reação20,21,22,23,24,25. É importante ressaltar que a decadência do plasmon também pode levar à dissipação térmica, levando a um aumento de temperatura nas proximidades dos NPs que também pode contribuir para acelerar as taxas de reação15,16.
Devido a essas características interessantes, a catálise plasmônica tem sido empregada com sucesso para uma variedade de transformações moleculares18. No entanto, um desafio importante permanece. Enquanto NPs plasmônicos como Ag e Au exibem excelentes propriedades ópticas nas faixas visível e próxima de IR, suas propriedades catalíticas são limitadas em termos do escopo das transformações. Em outras palavras, eles não exibem boas propriedades catalíticas para várias transformações. Além disso, metais importantes na catálise, como paládio (Pd) e platina (Pt), não suportam excitação LSPR nas faixas visível ou próxima de IR. Para preencher essa lacuna, NPs bimetálicos contendo um metal plasmônico e catallítico representam uma estratégia eficaz20,26,27,28,29. Nestes sistemas, o metal plasmônico pode ser empregado como uma antena para colher energia da excitação da luz através do LSPR, que é então usado para conduzir, acelerar e controlar transformações moleculares no metal catalítico. Portanto, essa estratégia nos permite estender a catálise plasmônica para além do metal plasmônico tradicional NPs20,26,27,28,29.
Este protocolo descreve a síntese fácil de NPs bimetálicos de prata-paládio (Ag-Pd) suportados no ZrO2 (Ag-Pd/ZrO2) que podem atuar como um sistema plasmônico-catallítico para catálise plasmônica. Os NPs Ag-Pd/ZrO2 foram preparados pela co-impregnação dos precursores metálicos correspondentes no suporte ZrO2 seguidos de redução simultânea30. Esta abordagem levou à formação de NPs bimetálicos de cerca de 10 nm de tamanho (diâmetro) diretamente na superfície do suporte ZrO2. Os NPs foram compostos por 1 mol% de DP para minimizar a utilização do metal catalítico, maximizando as propriedades ópticas dos NPs Ag-Pd resultantes. Foi demonstrado um protocolo para a aplicação dos NPs Ag-Pd/ZrO2 em catálise plasmônica para a redução do nitrobenzeno. Empregamos iluminação LED de 425 nm para a excitação LSPR. A cromatografia gasosa foi realizada para monitorar a conversão e seletividade da reação de redução sob as condições de irradiação escura e clara. A excitação LSPR levou a um desempenho catalítico aprimorado e controle sobre a seletividade em Ag-Pd/ZrO2 NPs em relação a condições puramente conduzidas termicamente. O método descrito neste protocolo baseia-se em uma simples configuração de reação fotocatalítica aliada à cromatografia gasosa e pode ser adaptado a uma ampla gama de transformações moleculares e composições de NPs. Assim, este método possibilita a caracterização da atividade fotocatalítica, em termos de conversividade e seletividade de reação, de diferentes NPs e para uma miríade de transformações de fase líquida. Acreditamos que este artigo fornecerá importantes diretrizes e insights para os recém-chegados e cientistas mais experientes no campo.

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			<td height="42" style="height:42px;width:427px;">2-Propanol (anhydrous, 99.5%)</td>
			<td style="width:96px;">Sigma-Aldrich</td>
			<td style="width:114px;">278475</td>
			<td style="width:89px;">CAS Number 67-63-0</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:427px;">Aniline (for synthesis)</td>
			<td style="width:96px;">Sigma-Aldrich</td>
			<td style="width:114px;">8.22256</td>
			<td style="width:89px;">CAS Number 62-53-3</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:427px;">Azobenzene (98%)</td>
			<td style="width:96px;">Sigma-Aldrich</td>
			<td style="width:114px;">424633</td>
			<td style="width:89px;">CAS Number 103-33-3</td>
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		<tr height="42">
			<td height="42" style="height:42px;width:427px;">Ethanol</td>
			<td style="width:96px;">Honeywell</td>
			<td style="width:114px;">32221</td>
			<td style="width:89px;">CAS Number 64-17-5</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:427px;">Hydrochloric acid (37%)</td>
			<td style="width:96px;">VWR</td>
			<td style="width:114px;">PRLSMC310066</td>
			<td style="width:89px;">CAS Number 7647-01-0</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:427px;">L-Lysine (crystallized, &#8805;98.0% (NT))</td>
			<td style="width:96px;">Sigma-Aldrich</td>
			<td style="width:114px;">62840</td>
			<td style="width:89px;">CAS Number 56-87-1</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:427px;">Nitric acid (65%)</td>
			<td style="width:96px;">Merck</td>
			<td style="width:114px;">100456</td>
			<td style="width:89px;">CAS Number 7697-37-2</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:427px;">Nitrobenzene</td>
			<td style="width:96px;">Sigma-Aldrich</td>
			<td style="width:114px;">8.06770</td>
			<td style="width:89px;">CAS Number 98-95-3</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:427px;">Potassium hydroxide</td>
			<td style="width:96px;">Fisher</td>
			<td style="width:114px;">10448990</td>
			<td style="width:89px;">CAS Number 1310-58-3</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:427px;">Potassium tetrachloropalladate (II) (98%)</td>
			<td style="width:96px;">Sigma-Aldrich</td>
			<td style="width:114px;">205796</td>
			<td style="width:89px;">CAS Number 10025-98-6</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:427px;">Silver nitrate (ACS reagent, &#8805;99.0%)</td>
			<td style="width:96px;">Sigma-Aldrich</td>
			<td style="width:114px;">209139</td>
			<td style="width:89px;">CAS Number 7761-88-8</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:427px;">Sodium borohydride (fine granular for synthesis)</td>
			<td style="width:96px;">Sigma-Aldrich</td>
			<td style="width:114px;">8.06373</td>
			<td style="width:89px;">CAS Number 16940-66-2</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:427px;">Zirconium (IV) oxide (nanopowder, &#60;100 nm particle size (TEM))</td>
			<td style="width:96px;">Sigma-Aldrich</td>
			<td style="width:114px;">544760</td>
			<td style="width:89px;">CAS Number 1314-23-4</td>
		</tr>
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preparation of silver-palladium alloyed nanoparticles for plasmonic catalysis under visible-light illumination

A ressonância de plasmon de superfície localizada (LSPR) em nanopartículas plasmônicas (NPs) pode acelerar e controlar a seletividade de uma variedade de transformações moleculares. Isso abre possibilidades para o uso de luz visível ou quase-IR como uma entrada sustentável para conduzir e controlar reações quando nanopartículas plasmônicas que suportam excitação LSPR nessas faixas são empregadas como catalisadores. Infelizmente, este não é o caso de vários metais catalíticos, como o paládio (Pd). Uma estratégia para superar essa limitação é empregar NPs bimetálicos contendo metais plasmônicos e catalíticos. Neste caso, a excitação LSPR no metal plasmônico pode contribuir para acelerar e controlar transformações impulsionadas pelo componente catalítico. O método aqui relatado se concentra na síntese de NPs bimetálicos de prata-paládio (Ag-Pd) suportados no ZrO2 (Ag-Pd/ZrO2) que atua como um sistema plasmônico-catallítico. Os NPs foram preparados por co-impregnação de precursores metálicos correspondentes no suporte ZrO2 seguido de redução simultânea levando à formação de NPs bimetálicos diretamente no suporte ZrO2. Os NPs Ag-Pd/ZrO2 foram então usados como catalisadores plasmônicos para a redução de nitrobenzeno sob iluminação de 425 nm por lâmpadas LED. Utilizando cromatografia gasosa (GC), a conversão e seletividade da reação de redução sob as condições de irradiação escura e clara podem ser monitoradas, demonstrando o desempenho catalítico aprimorado e o controle sobre a seletividade sob excitação LSPR após a liga pd não plasmônica com metal plasmônico Ag. Esta técnica pode ser adaptada a uma ampla gama de transformações moleculares e composições de NPs, tornando-a útil para a caracterização da atividade catalítica plasmônica de diferentes tipos de catálise em termos de conversão e seletividade.

A Figura 1A mostra fotografias digitais das amostras sólidas contendo o óxido ZrO2 puro (esquerda) e os NPs Ag-Pd/ZrO2 (à direita). Esta mudança de cor de branco (em ZrO2) para marrom (Ag-Pd/ZrO2) fornece a evidência qualitativa inicial sobre a deposição de NPs Ag-Pd na superfície ZrO2. A Figura 1B mostra os espectros de absorção visível UV dos NPs Ag-Pd/ZrO2 (traço azul), bem como ZrO...

Watch this Scientific Journal Video about Preparation of Silver-Palladium Alloyed Nanoparticles for Plasmonic Catalysis under Visible-Light Illumination at JoVE.com

Preparation of Silver-Palladium Alloyed Nanoparticles for Plasmonic Catalysis under Visible-Light Illumination

Apresentado aqui é um protocolo para a síntese de nanopartículas de alossa de prata -paládio (Ag-Pd) suportadas no ZrO2 (Ag-Pd/ZrO2). Este sistema permite a colheita de energia da irradiação de luz visível para acelerar e controlar transformações moleculares. Isto é ilustrado pela redução de nitrobenzeno sob irradiação leve catalisada por Ag-Pd/ZrO2 NPs.

Preparação de Nanopartículas de Aliga de prata-paládio para catálise plasmônica sob iluminação de luz visível

Localized surface plasmon resonance (LSPR) in plasmonic nanoparticles (NPs) can accelerate and control the selectivity of a variety of molecular ...

preparation-silver-palladium-alloyed-nanoparticles-for-plasmonic

Research

JoVE Journal

Chemistry

5.4K visualizações.  University of Helsinki. Apresentado aqui é um protocolo para a síntese de nanopartículas de alossa de prata -paládio (Ag-Pd) suportadas no ZrO2 (Ag-Pd/ZrO2). Este sistema permite a colheita de energia da irradiação de luz visível para acelerar e controlar transformações moleculares. Isto é ilustrado pela redução de nitrobenzeno sob irradiação leve catalisada por Ag-Pd/ZrO2 NPs.

Vídeo: Preparation of Silver-Palladium Alloyed Nanoparticles for Plasmonic Catalysis under Visible-Light Illumination

Gyroid Nickel Nanostructures from Diblock Copolymer Supramolecules

Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, have high porosity, high surface-to-volume and strength-to-weight ratio. Unfortunately, common approaches for preparation of metallic nanostructures render materials with highly disordered architecture, which might have an adverse effect on their mechanical properties. Block copolymers have the ability to self-assemble into ordered nanostructures and can be applied as templates for the preparation of well-ordered metal nanofoams. Here we describe the application of a block copolymer-based supramolecular complex - polystyrene-block-poly(4-vinylpyridine)(pentadecylphenol) PS-b-P4VP(PDP) - as a precursor for well-ordered nickel nanofoam. The supramolecular complexes exhibit a phase behavior similar to conventional block copolymers and can self-assemble into the bicontinuous gyroid morphology with two PS networks placed in a P4VP(PDP) matrix. PDP can be dissolved in ethanol leading to the formation of a porous structure that can be backfilled with metal. Using electroless plating technique, nickel can be inserted into the template&#39;s channels. Finally, the remaining polymer can be removed via pyrolysis from the polymer/inorganic nanohybrid resulting in nanoporous nickel foam with inverse gyroid morphology.

This article describes the preparation of well-ordered nickel nanofoams via electroless metal deposition onto nanoporous templates obtained from self-assembled diblock copolymer based supramolecules.

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, ...

Química

Preparation of Silica Nanoparticles Through Microwave-assisted Acid-catalysis

Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle diameters ranging from 30-250 nm by varying the reaction conditions. Through the selection of a microwave compatible solvent, silicic acid precursor, catalyst, and microwave irradiation time, these microwave-assisted methods were capable of overcoming the previously reported shortcomings associated with synthesis of silica nanoparticles using microwave reactors. The siloxane precursor was hydrolyzed using the acid catalyst, HCl. Acetone, a low-tan &#948; solvent, mediates the condensation reactions and has minimal interaction with the electromagnetic field. Condensation reactions begin when the silicic acid precursor couples with the microwave radiation, leading to silica nanoparticle sol formation. The silica nanoparticles were characterized by dynamic light scattering data and scanning electron microscopy, which show the materials&#39; morphology and size to be dependent on the reaction conditions. Microwave-assisted reactions produce silica nanoparticles with roughened textured surfaces that are atypical for silica sols produced by St&#246;ber&#39;s methods, which have smooth surfaces.

Silica nanoparticles were prepared using acid-catalysis of a siloxane precursor and microwave-assisted synthetic techniques resulting in the controlled growth of nanomaterials ranging from 30-250 nm in diameter. The growth dynamics can be controlled by varying the initial silicic acid concentration, time of the reaction, and temperature of reaction.

Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle ...

Synthesis of Immunotargeted Magneto-plasmonic Nanoclusters

Magnetic and plasmonic properties combined in a single nanoparticle provide a synergy that is advantageous in a number of biomedical applications including contrast enhancement in novel magnetomotive imaging modalities, simultaneous capture&#160;and detection of circulating tumor cells (CTCs),&#160;and multimodal molecular imaging combined with photothermal therapy of cancer cells. These applications have stimulated significant interest in development of protocols for synthesis of magneto-plasmonic nanoparticles with optical absorbance in the near-infrared (NIR) region and a strong magnetic moment. Here, we present a novel protocol for synthesis of such hybrid nanoparticles that is based on an oil-in-water microemulsion method. The unique feature of the protocol described herein is synthesis of magneto-plasmonic nanoparticles of various sizes from primary blocks which also have magneto-plasmonic characteristics. This approach yields nanoparticles with a high density of magnetic and plasmonic functionalities which are uniformly distributed throughout the nanoparticle volume. The hybrid nanoparticles can be easily functionalized by attaching antibodies through the Fc moiety leaving the Fab portion that is responsible for antigen binding available for targeting.

Here, we describe a protocol for synthesis of magneto-plasmonic nanoparticles with a strong magnetic moment and a strong near-infrared (NIR) absorbance. The protocol also includes antibody conjugation to the nanoparticles through the Fc moiety for various biomedical applications which require molecular specific targeting.

Síntese de Immunotargeted magneto-plasmónico Nanoclusters

Magnetic and plasmonic properties combined in a single nanoparticle provide a synergy that is advantageous in a number of biomedical applications ...

Preparation and Characterization of SDF-1&#945;-Chitosan-Dextran Sulfate Nanoparticles

Chitosan (CS) and dextran sulfate (DS) are charged polysaccharides (glycans), which form polyelectrolyte complex-based nanoparticles when mixed under appropriate conditions. The glycan nanoparticles are useful carriers for protein factors, which facilitate the in vivo delivery of the proteins and sustain their retention in the targeted tissue. The glycan polyelectrolyte complexes are also ideal for protein delivery, as the incorporation is carried out in aqueous solution, which reduces the likelihood of inactivation of the proteins. Proteins with a heparin-binding site adhere to dextran sulfate readily, and are, in turn, stabilized by the binding. These particles are also less inflammatory and toxic when delivered in vivo. In the protocol described below, SDF-1&#945; (Stromal cell-derived factor-1&#945;), a stem cell homing factor, is first mixed and incubated with dextran sulfate. Chitosan is added to the mixture to form polyelectrolyte complexes, followed by zinc sulfate to stabilize the complexes with zinc bridges. The resultant SDF-1&#945;-DS-CS particles are measured for size (diameter) and surface charge (zeta potential). The amount of the incorporated SDF-1&#945; is determined, followed by measurements of its in vitro release rate and its chemotactic activity in a particle-bound form.

Preparation and Characterization of SDF-1&amp;#945;-Chitosan-Dextran Sulfate Nanoparticles

The objective of this protocol is to incorporate SDF-1&#945;, a stem cell homing factor, into dextran sulfate-chitosan nanoparticles. The resultant particles are measured for their size and zeta potential, as well as the content, activity, and in vitro release rate of SDF-1&#945; from the nanoparticles.

Preparação e Caracterização de SDF-1α-Quitosana As nanopartículas de sulfato de dextrano

Chitosan (CS) and dextran sulfate (DS) are charged polysaccharides (glycans), which form polyelectrolyte complex-based nanoparticles when mixed under ...

A Simple Method for the Size Controlled Synthesis of Stable Oligomeric Clusters of Gold Nanoparticles under Ambient Conditions

Reducing dilute aqueous HAuCl4 with sodium thiocyanate (NaSCN) under alkaline conditions produces 2 to 3 nm diameter nanoparticles. Stable grape-like oligomeric clusters of these yellow nanoparticles of narrow size distribution are synthesized under ambient conditions via two methods. The delay-time method controls the number of subunits in the oligoclusters by varying the time between the addition of HAuCl4 to alkaline solution and the subsequent addition of reducing agent, NaSCN. The yellow oligoclusters produced range in size from ~3 to ~25 nm. This size range can be further extended by an add-on method utilizing hydroxylated gold chloride (Na+[Au(OH4-x)Clx]-) to auto-catalytically increase the number of subunits in the as-synthesized oligocluster nanoparticles, providing a total range of 3 nm to 70 nm. The crude oligocluster preparations display narrow size distributions and do not require further fractionation for most purposes. The oligoclusters formed can be concentrated &#62;300 fold without aggregation and the crude reaction mixtures remain stable for weeks without further processing. Because these oligomeric clusters can be concentrated before derivatization they allow expensive derivatizing agents to be used economically. In addition, we present two models by which predictions of particle size can be made with great accuracy.

We describe a simple method for producing highly stable oligomeric clusters of gold nanoparticles via the reduction of chloroauric acid (HAuCl4) with sodium thiocyanate (NaSCN). The oligoclusters have a narrow size distribution and can be produced with a wide range of sizes and surface coats.

Um método simples para o tamanho Síntese controlada de estáveis ​​Oligoméricas Clusters de nanopartículas em condições ambientais

Reducing dilute aqueous HAuCl4 with sodium thiocyanate (NaSCN) under alkaline conditions produces 2 to 3 nm diameter nanoparticles. Stable grape-like ...

Atom Transfer Radical Polymerization of Functionalized Vinyl Monomers Using Perylene as a Visible Light Photocatalyst

A standardized technique for atom transfer radical polymerization of vinyl monomers using perylene as a visible-light photocatalyst is presented. The procedure is performed under an inert atmosphere using air- and water-exclusion techniques. The outcome of the polymerization is affected by the ratios of monomer, initiator, and catalyst used as well as the reaction concentration, solvent, and nature of the light source. Temporal control over the polymerization can be exercised by turning the visible light source off and on. Low dispersities of the resultant polymers as well as the ability to chain-extend to form block copolymers suggest control over the polymerization, while chain end-group analysis provides evidence supporting an atom-transfer radical polymerization mechanism.

A method for the atom transfer radical polymerization of functionalized vinyl monomers using perylene as a visible-light photocatalyst is described.

Polimerização Radical por Transferência de Átomos de Monômeros Vinílicos Funcionalizados Usando Perileno como Fotocatalisador de Luz Visível

A standardized technique for atom transfer radical polymerization of vinyl monomers using perylene as a visible-light photocatalyst is presented. The ...

HKUST-1 as a Heterogeneous Catalyst for the Synthesis of Vanillin

Vanillin (4-hydoxy-3-methoxybenzaldehyde) is the main component of the extract of vanilla bean. The natural vanilla scent is a mixture of approximately 200 different odorant compounds in addition to vanillin. The natural extraction of vanillin (from the orchid Vanilla planifolia, Vanilla tahitiensis and Vanilla pompon) represents only 1% of the worldwide production and since this process is expensive and very long, the rest of the production of vanillin is synthesized. Many biotechnological approaches can be used for the synthesis of vanillin from lignin, phenolic stilbenes, isoeugenol, eugenol, guaicol, etc., with the disadvantage of harming the environment since these processes use strong oxidizing agents and toxic solvents. Thus, eco-friendly alternatives on the production of vanillin are very desirable and thus, under current investigation. Porous coordination polymers (PCPs) are a new class of highly crystalline materials that recently have been used for catalysis. HKUST-1 (Cu3(BTC)2(H2O)3, BTC = 1,3,5-benzene-tricarboxylate) is a very well known PCP which has been extensively studied as a heterogeneous catalyst. Here, we report a synthetic strategy for the production of vanillin by the oxidation of trans-ferulic acid using HKUST-1 as a catalyst.

The conversion of trans-ferulic acid to vanillin was achieved by heterogeneous catalysis. HKUST-1 was employed in this synthesis and the essential step in the catalytic process was the generation of unsaturated metal sites. Thus, when the catalyst was activated under vacuum, full vanillin conversion (yield of 95%) was obtained.

HKUST-1 como um catalisador heterogéneo para a Síntese de vanilina

Vanillin (4-hydoxy-3-methoxybenzaldehyde) is the main component of the extract of vanilla bean. The natural vanilla scent is a mixture of approximately ...

Facile Synthesis of Worm-like Micelles by Visible Light Mediated Dispersion Polymerization Using Photoredox Catalyst

Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins with the synthesis of a hydrophilic poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) homopolymer using reversible addition-fragmentation chain-transfer (RAFT) polymerization. Under mild visible light irradiation (&#955; = 460 nm, 0.7 mW/cm2), this macro-chain transfer agent (macro-CTA) in the presence of a ruthenium based photoredox catalyst, Ru(bpy)3Cl2 can be chain extended with a second monomer to form a well-defined block copolymer in a process known as Photoinduced Electron Transfer RAFT (PET-RAFT). When PET-RAFT is used to chain extend POEGMA with benzyl methacrylate (BzMA) in ethanol (EtOH), polymeric nanoparticles with different morphologies are formed in situ according to a polymerization-induced self-assembly (PISA) mechanism. Self-assembly into nanoparticles presenting POEGMA chains at the corona and poly(benzyl methacrylate) (PBzMA) chains in the core occurs in situ due to the growing insolubility of the PBzMA block in ethanol. Interestingly, the formation of highly pure worm-like micelles can be readily monitored by observing the onset of a highly viscous gel in situ due to nanoparticle entanglements occurring during the polymerization. This process thereby allows for a more reproducible synthesis of worm-like micelles simply by monitoring the solution viscosity during the course of the polymerization. In addition, the light stimulus can be intermittently applied in an ON/OFF manner demonstrating temporal control over the nanoparticle morphology.

This article describes a process for producing polymeric self-assembled nanoparticles using visible light mediated dispersion polymerization. Using low energy visible light to control the polymerization allows for the reproducible formation of self-assembled worm-like micelles at high solids content.

Síntese Facile de micelas Worm-like por luz visível Mediated Dispersão Polimerização Usando Photoredox Catalisador

Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins ...

Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry

With this protocol, a well-defined singlesite silica-supported heterogeneous catalyst [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)] is designed and prepared according to the methodology developed by surface organometallic chemistry (SOMC). In this framework, catalytic cycles can be determined by isolating crucial intermediates. All air-sensitive materials are handled under inert atmosphere (using gloveboxes or a Schlenk line) or high vacuum lines (HVLs, &#60;10-5 mbar). The preparation of SiO2-700 (silica dehydroxylated at 700 &#176;C) and subsequent applications (the grafting of complexes and catalytic runs) requires the use of HVLs and double-Schlenk techniques. Several well-known characterization methods are used, such as Fourier-transform infrared spectroscopy (FTIR), elemental microanalysis, solid-state nuclear magnetic resonance spectroscopy (SSNMR), and state-of-the-art dynamic nuclear polarization surface enhanced NMR spectroscopy (DNP-SENS). FTIR and elemental microanalysis permit scientists to establish the grafting and its stoichiometry. 1H and 13C SSNMR allows the structural determination of the hydrocarbon ligands coordination sphere. DNP SENS is an emerging powerful technique in solid characterization for the detection of poorly sensitive nuclei (15N, in our case). SiO2-700 is treated with about one equivalent of the metal precursor compared to the amount of surface silanol (0.30 mmol&#183;g-1) in pentane at room temperature. Then, volatiles are removed, and the powder samples are dried under dynamic high vacuum to afford the desired materials [(&#8801;Si-O-)Hf(&#951;2&#960;-MeNCH2)(&#951;1-NMe2)(&#951;1-HNMe2)]. After a thermal treatment under high vacuum, the grafted complex is converted into metal imido silica complex [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)]. [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)] effectively promotes the metathesis of imines, using the combination of two imine substrates, N-(4-phenylbenzylidene)benzylamine, or N-(4-fluorobenzylidene)-4-fluoroaniline, with N-benzylidenetert-butylamine as substrates. A significantly lower conversion is observed with the blank runs; thus, the presence of the imido group in [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)] is correlated to the catalytic performance.

A new group IV metal catalyst for imine metathesis is prepared by grafting amine metal complex onto dehydroxylated silica. Surface metal fragments are characterized using FT-IR, elemental microanalysis, and solid-state NMR spectroscopy. Further dynamic nuclear polarization surface enhanced NMR spectroscopy experiments complement the determination of the coordination sphere.

Metathesis de imine por catalisadores sílica-apoiados usando a metodologia da química organometálica de superfície

With this protocol, a well-defined singlesite silica-supported heterogeneous catalyst [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)] is designed and prepared ...

Performing Spectroscopy on Plasmonic Nanoparticles with Transmission-Based Nomarski-Type Differential Interference Contrast Microscopy

Differential interference contrast (DIC) microscopy is a powerful imaging tool that is most commonly employed for imaging microscale objects using visible-range light. The purpose of this protocol is to detail a proven method for preparing plasmonic nanoparticle samples and performing single particle spectroscopy on them with DIC microscopy. Several important steps must be followed carefully in order to perform repeatable spectroscopy experiments. First, landmarks can be etched into the sample substrate, which aids in locating the sample surface and in tracking the region of interest during experiments. Next, the substrate must be properly cleaned of debris and contaminants that can otherwise hinder or obscure examination of the sample. Once a sample is properly prepared, the optical path of the microscope must be aligned, using Kohler Illumination. With a standard Nomarski style DIC microscope, rotation of the sample may be necessary, particularly when the plasmonic nanoparticles exhibit orientation-dependent optical properties. Because DIC microscopy has two inherent orthogonal polarization fields, the wavelength-dependent DIC contrast pattern reveals the orientation of rod-shaped plasmonic nanoparticles. Finally, data acquisition and data analyses must be carefully performed. It is common to represent DIC-based spectroscopy data as a contrast value, but it is also possible to present it as intensity data. In this demonstration of DIC for single particle spectroscopy, the focus is on spherical and rod-shaped gold nanoparticles.

The goal of this protocol is to detail a proven approach for the preparation of plasmonic nanoparticle samples and for performing single particle spectroscopy on them with differential interference contrast (DIC) microscopy.

Realização de espectroscopia em nanopartículas Plasmonicas com microscopia de contraste de interferência diferencial de tipo Nomarski baseado em transmissão