Os autores reconhecem com gratidão da National Science Foundation (DMR-1409034) para suporte deste projecto. Também reconhecemos o apoio do Instituto Nacional de padrões e tecnologia, E.U. departamento do comércio, em fornecer as instalações USANS usadas neste trabalho, onde estas facilidades são suportadas em parte pela Fundação Nacional de ciência no âmbito do acordo Não. DMR-0944772. Os experimentos SANS desta pesquisa foram concluídos em alta Isotope Reactor do ORNL de fluxo, que foi patrocinado pela divisão de instalações científicas usuário, escritório de ciências básicas de energia, do departamento de energia.

Qualquer manuseio de produtos químicos deve proceder com os equipamentos de proteção individual adequado e dentro de uma capa de segurança. Todas as amostras expostas à radiação ionizante devem ser manipuladas sob a supervisão dos técnicos instalações controle radioativo. Este protocolo foi realizado por indivíduos que tinham completado o treinamento de segurança de radiação apropriado.
1. preparação de P3HT em d-ODCB soluções
<ol>
	<li>Aquisição de amostra
	<ol>
		<li>Compra 1 g de regioregularity alto (&#62; 90%) P3HT no peso molecular escala 15-40 K.</li>
		<li>Compra de 5 g de alta pureza (&#62; 90% do átomo deuterado) 1,2-ODCB d-4.</li>
	</ol>
	</li>
	<li>Preparação da amostra
	<ol>
		<li>Filtre toda solução de d-ODCB com 0,45 µm peneira dentro de um frasco de vidro.</li>
		<li>Combine 0,34 g de P3HT em 1,66 g de d-ODCB em um frasco de vidro de 5 g com tampa de alumínio forrado. Nota: Durante o processo de criação e transferência de amostra, minimize a intensidade da luz ambiente ao qual a amostra é exposta em todos os momentos.</li>
		<li>Adicionar uma barra de agitação magnética para o frasco, fixar a tampa e lacre com parafilme.</li>
		<li>Enrole o frasco inteiramente em papel de alumínio para evitar qualquer exposição à luz, a solução.</li>
		<li>Colocar a amostra na placa quente a 70 ° C, durante 1-3 h com barra de agitação magnética ativada.</li>
		<li>Retire do fogo e mexendo uma vez que a solução é completamente homogênea (de preferência deixando o pernoite de aquecimento/agitação de amostra para assegurar a dispersão completa).</li>
		<li>Transferir a solução do frasco para um limpado corretamente (com lavagens separadas de acetona e água) 1 ou 2 mm espessura quartzo banjo célula usando uma pipeta de vidro. Nota: Imediatamente antes de transferência simplifica esse processo de aquecimento a pipeta de vidro em um forno de aquecimento a 70 ° C.</li>
		<li>Apor a tampa do celular banjo e selar com parafilme.</li>
		<li>Célula de banjo lugar na escuridão completa (ou seja, dentro de uma caixa selada ou embrulhado em papel de alumínio).</li>
		<li>De forma semelhante, monte uma amostra que contém somente d-ODCB (lotado) e uma célula vazia banjo, para atuar como o fundo solvente e célula vazia, respectivamente, para os experimentos de espalhamento.</li>
	</ol>
	</li>
</ol>
2. experimentos de espalhamento de nêutrons
<ol>
	<li>SANS experimentos no ambiente "escuro"
	<ol>
		<li>Com a ajuda do cientista instrumento, certifique-se de que uma fase de amostra é afixada com os controles de temperatura necessária capazes de dirigir uma rampa de temperatura de 70-20 ° C.</li>
		<li>Coloque as células do banjo no blocos de exploração de tamanho adequado, seguros e etiqueta.</li>
		<li>Embrulhe um bloco inteiro com papel de alumínio grosso de 0,1 mm para garantir que nenhuma luz ambiente é incidente para a amostra. Minimize deformações da película para assegurar a correcta montagem do bloco envolvido na fase de amostra. Coloque este bloco embrulhado e amostra dentro do palco da amostra.</li>
		<li>Com a ajuda do cientista instrumento, completa o instrumento adequado alinhamento e calibração usando as medições padrão apropriadas. Definir a distância de detector perto de seu máximo de configuração (por exemplo em 18 m) para garantir o acesso à região mais baixa do Q (~0.001 Å-1), em última análise, permitindo uma gama completa de Q de aproximadamente 0.001-0.1 Å-1. Isso permitirá que a sondagem de comprimento escalas até ~ 500 nm.</li>
		<li>Com a ajuda do cientista instrumento, cobrar taxas de contagem para o P3HT e o solvente de amostras e executar cálculos para determinar a quantidade de tempo de dispersão necessária para alcançar a total detector contagens por amostra de cerca de 500.000 a 1.000.000, garantindo boa qualidade estatística nos dados.</li>
		<li>Com esta informação, crie um script de exemplo que irá direcionar o processo de coleta da rampa e dados da temperatura do 70-20 ° C. Escolha que uma faixa de temperatura discreta aponta para melhor cobertura toda a gama dentro as restrições de tempo determinado, por exemplo cada 2 ° C. Para cada ponto na rampa fazer 3 entradas separadas no script: uma mudança para a temperatura desejada, um período de espera (~ 15 minutos) para permitir que o sistema equilibrar termicamente antes de dispersão é coletado e a medida de dispersão em si realizado sobre o duração de tempo adequado para atingir o detector necessário conta</li>
		<li>Uma vez que o instrumento e o script são preparados, executar o script e começar o experimento. Certifique-se a coletar dados para a célula vazia e solvente também (sem subida de temperatura). Além disso, coletar dados de transmissão para cada amostra e medição um feixe bloqueados.</li>
	</ol>
	</li>
	<li>SANS experimentos no ambiente de "luz"
	<ol>
		<li>Após a conclusão do experimento "escuro", mover as amostras do palco, coloque sobre uma bancada de segura e remover toda a folha de alumínio, enquanto observa a radiação protocolos de segurança.</li>
		<li>Posicione um iluminador óptico com uma fonte de luz halógena perto do palco de amostra tal que os condutores efetivamente iluminam o slot de amostra na fase associado à posição de coleção de dispersão.</li>
		<li>Usando um medidor de luz calibrado, registro a intensidade da luz fornecida pelo iluminador na intensidade máxima na posição onde a amostra se sentará. Valores de intensidade variará com iluminador e exemplo de configuração de palco, no entanto, a intensidade de iluminação pelo menos 5.000 lux é desejada.</li>
		<li>Uma vez que esta configuração de iluminação está montada corretamente, retornar as amostras para o palco, garantir que o iluminador é corretamente a iluminação da amostra ativa, aqueça novamente a 70 ° C, permitem o equilíbrio adequado e repita o procedimento de coleta de dados realizado no escuro amostras, com a óptica iluminador fornecimento ininterrupta exposição de luz direta completa toda a duração desta etapa.</li>
	</ol>
	</li>
	<li>Experiências USANS
	<ol>
		<li>Preparar amostras USANS em uma forma similar, usando células de quartzo banjo e coloque em blocos de cobre ou titânio dentro de um estágio de amostra de temperatura controlada.</li>
		<li>Com a ajuda do cientista instrumento, alinhar e calibrar o instrumento empregando o número exigido de buffers no comprimento de onda determinado nêutrons, para permitir a análise dos valores de Q de aproximadamente 10-5 - 10-3 Å-1, permitindo o comprimento escalas da ordem de micra para ser analisados.</li>
		<li>Desenvolva o script experimental em uma forma similar para os experimentos SANS, permitindo equilíbrio térmico e coleta de dados a cada temperatura estudada anteriormente.</li>
		<li>Replicar as experiências SANS novamente, execute o script uma vez sob condições "escuras" e novamente em "condições de"luz".</li>
	</ol>
	</li>
</ol>
3.Análise e redução de dados
<ol>
	<li>SANS redução e análise
	<ol>
		<li>Usando o programa de redução do respectivo,32 entrada os arquivos de dados para o espalhamento, plano de fundo (solvente), célula vazia, feixe bloqueado e medições de transmissão para realizar a subtração de fundo apropriada e conversão de dados de dispersão absoluta unidades de intensidade em cm-1.</li>
		<li>Com os dados apropriadamente reduzidos, começar a análise por encaixe os dados experimentais de espalhamento para um modelo que é a adição linear de duas equações de encaixe, uma representando os nanofibril agregados através do modelo de cilindro elíptico,33 e outra levando em conta as cadeias livres em solução através do polímero excluídos modelo de volume. 34 , 35 a equação abaixo descreve esta abordagem de modelo de combinação: 
		<img alt="Equation 1" src="/files/ftp_upload/56163/56163eq1.jpg"> Nesta equação, ϕP3HT descreve a fração do volume total de P3HT na solução, <img alt="Equation 2" src="/files/ftp_upload/56163/56163eq2.jpg"> é a fração de volume de agregados P3HT presentes e modelado como um cilindro elíptico, PPEV é o volume corrente livre excluído fator de forma para P3HT, PECM descreve o fator de forma de cilindro elíptico para os agregados, e <img alt="Equation 3" src="/files/ftp_upload/56163/56163eq3.jpg"> e <img alt="Equation 4" src="/files/ftp_upload/56163/56163eq4.jpg"> são o contraste de densidade (SLD) de comprimento de dispersão entre agregados de P3HT e o solvente e entre o livre P3HT correntes e solvente, respectivamente. Valores SLD para todos os componentes do sistema podem ser calculados com um conhecimento de sua química composição e massa de densidade e o uso de uma calculadora SLD disponível como parte da maioria dos programas de análise de nêutrons ou on-line. 36</li>
		<li>Após os procedimentos de instalação adequada usando esta Igor encaixe as macros37 ou o programa de instalação SASView, adquirir valores para os principais parâmetros estruturais para o sistema gelificado em todas as temperaturas na luz e escuridão, permitindo a quantificação do evolução morfológica, ocorrendo em todo este processo como uma função da temperatura e da exposição à luz. Esses parâmetros estruturais incluem as áreas transversais do nanofibrils, livre de cadeia raio de giração (Rg) e expoente de Porod e uma avaliação qualitativa da quantidade total de material presente na fase nanofibril.</li>
	</ol>
	</li>
	<li>Análise e redução de USANS
	<ol>
		<li>Usando o programa de redução do respectivo, entrada de dispersão de dados e os dados de fundo para cada buffer mesclar os dados em uma única curva reduzida em unidades de intensidade absoluta de cm-1.</li>
		<li>Analise os dados usando um modelo de lei de poder de Guinier-Porod que permite uma avaliação quantitativa dos padrões de dispersão agregado sondados pela escala de comprimento de USANS e permite a aquisição de valores agregados deg R. 38 se encaixam usando este método através de Igor esta montagem macros37 ou o programa de instalação SASView para permitir a comparação de macroagregado Rg em todas as temperaturas e as condições de iluminação.</li>
	</ol>
	</li>
</ol>

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D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Illumination+of+Conjugated+Polymer+in+Solution+Alters+Its+Conformation+and+Thermodynamics.">Illumination of Conjugated Polymer in Solution Alters Its Conformation and Thermodynamics.</a> Macromolecules. 49 (9), 3490-3496 (2016).</li><li>Ilavsk, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phase+Transition+in+Swollen+Gels.+2.+Effect+of+Charge+Concentration+on+the+Collapse+and+Mechanical+Behavior+of+Polyacrylamide+Networks.">Phase Transition in Swollen Gels. 2. Effect of Charge Concentration on the Collapse and Mechanical Behavior of Polyacrylamide Networks.</a> Macromolecules. 15, 782-788 (1982).</li><li>Tanaka, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Collapse+of+Gels+and+the+Critical+Endpoint.">Collapse of Gels and the Critical Endpoint.</a> Phys. Rev. Lett. 40 (12), 820-823 (1978).</li><li>. SANS &amp; USANS Data Reduction and Analysis Available from: <a target="_blank" href="https://www.ncnr.nist.gov/programs/sans/data/red_anal.html">https://www.ncnr.nist.gov/programs/sans/data/red_anal.html</a> (2017)</li><li>Feigin, L., Svergun, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Structure Analysis by Small-Angle X-Ray and Neutron Scattering. , (1987).</li><li>Mittelbach, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zur+Rontgenkleinwinkelstreuung+verdunnter+kolloider+systeme.">Zur Rontgenkleinwinkelstreuung verdunnter kolloider systeme.</a> Acta Phys. Austriaca. 14, 185-211 (1961).</li><li>Schulz, G. Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=&#220;ber+die+Kinetik+der+Kettenpolymerisationen.">&#220;ber die Kinetik der Kettenpolymerisationen.</a> Z. Phys. Chem. 43, 25 (1935).</li><li>. Neutron activation and scattering calculator Available from: <a target="_blank" href="https://www.ncnr.nist.gov/resources/activation">https://www.ncnr.nist.gov/resources/activation</a> (2017)</li><li>Kline, S. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reduction+and+Analysis+of+SANS+and+USANS+Data+Using+IGOR+Pro.">Reduction and Analysis of SANS and USANS Data Using IGOR Pro.</a> J. Appl. Crystallogr. 39 (6), 895-900 (2006).</li><li>Guinier, A., Fournet, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Small-Angle Scattering of X-Rays. , (1955).</li></ol>

Os autores não têm nada para divulgar.

Primeiro, olhando para os dados SANS em função da temperatura, o aumento no fator de escala modelo de cilindro elíptico indica um aumento na quantidade de P3HT presentes na fase de nanofibril, que isconsistent com a progressão da gelificação da processo . Simultaneamente, a diminuição da cadeia livre Rg emparelhado com um aumento de Porod expoente revela que as condições termodinâmicas deterioração associadas com temperatura diminuem está causando um colapso da cadeia em cadeias de P3HT ainda pre...

Polímeros conjugados prometem materiais funcionais que podem ser utilizados em uma ampla gama de dispositivos, tais como orgânico luz emitida por diodos, semicondutores orgânicos, sensores químicos e orgânica energia fotovoltaica. 1 , 2 , 3 , 4 , 5 , 6 um aspecto crucial do desempenho destes equipamentos é a ordenação e a embalagem do polímero conjugado no estado sólido na camada ativa. 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 esta morfologia é largamente pre-determinada por ambos a conformação da cadeia do polímero em solução, bem como as estruturas que evoluem à medida que estas soluções são lançadas a um substrato e o solvente é removido. Ao estudar as estruturas presentes ao longo de uma transição sol-gel típica de um polímero de optoeletrônicos de modelo em um solvente adequado, estes sistemas podem ser efetivamente modelados e um vislumbre de quantitativo a auto-montagem que ocorre durante a deposição de material pode ser obtido. 15 , 16 , 17 , 18 , 19 , 20
Especificamente, nós examinamos o benchmark de polímero conjugado P3HT na solvente deuterado orto-diclorobenzeno (ODCB), um sistema de polímero-solvente, que viu o uso extensivo devido à sua adequação para uma variedade de fabricação de dispositivos eletrônicos orgânicos técnicas. 23 , 24 , 25 neste ambiente de determinado solvente, P3HT correntes começam a agregar-se em cima de um estímulos ambientais adequadas, tais como temperatura diminuição ou perda da qualidade de solvente. O mecanismo exato para este processo de montagem está sob investigação, com uma das principais vias propostas acreditado para ser um processo gradual, onde individuais P3HT moléculas π-pilha para formar nano-agregados lamelares, conhecidos como nanofibrils, que então se aglomeram-se para formar a maior micron escala macroagregados. 24 compreender esses caminhos e as resultantes estruturas formadas é chave para predizer corretamente e influenciando a formação de morfologias de camada ativa do dispositivo ideal.
Para este objetivo final de mais precisamente dirigindo a formação dessas arquiteturas de camada ativa, existe uma necessidade de desenvolver métodos experimentais e industriais adicionais não-destrutivamente alterar morfologia polímero conjugado in situ. Uma relativamente nova metodologia centros em torno do uso de exposição à luz como um meio barato para alterar a morfologia de cadeia do polímero, com resultados computacionais e experimentais apontam para sua viabilidade. 25 , 26 , 27 recente trabalho por nosso laboratório indicou a existência de uma leve alteração induzida da interação polímero-solvente conjugada em uma solução diluída, levando a uma mudança notável no tamanho de cadeia do polímero sobre iluminação. 30 , 31 aqui, apresentamos um protocolo para continuar este trabalho monitorando eficazmente os efeitos de expor uma solução muito mais concentrada de polímero conjugado à luz direta durante todo um processo de gelificação que é dirigido por um termóstato controlado rampa de temperatura. Empregamos a dispersão de nêutrons como permite análise robusta de parâmetros estruturais do sistema sol-gel de polímero-solvente em escalas de comprimento de Angstrons a microns, uma habilidade não é possível através de outro mais comuns rheological ou espectroscópico instrumental métodos. 16 , 17 , 30 , 31 assim, comparando o ângulo pequeno e ultra pequeno devidamente analisado dados de nêutrons para a montagem de géis formaram sob a iluminação para idênticos dados coletados em completa escuridão, diferenças estruturais provocadas pela iluminação-driven efeitos podem ser exaustivamente identificados e quantificados.

<table><tbody><tr><td>M(106) poly(3-hexylthiophene-2,5-diyl) (P3HT)</td><td>Ossila</td><td>104934-50-1</td><td>Conjugated polymer</td></tr><tr><td>deuterated 1,2 ortho-dichlorobenzene (ODCB)</td><td>Sigma Aldrich</td><td>AC321260050</td><td>solvent</td></tr></tbody></table>

monitoring the effects of illumination on the structure of conjugated polymer gels using neutron scattering

Vamos demonstrar um protocolo para controlar eficazmente o processo de gelificação de uma solução de alta concentração de polímero conjugado tanto na presença e ausência de exposição à luz branca. Instituindo uma rampa de temperatura controlada, a gelificação destes materiais pode ser precisamente monitorada como proceder através desta evolução estrutural, que espelha efetivamente as condições experientes durante a fase de deposição de solução de orgânicos fabricação de dispositivos eletrônicos. Usando a dispersão de nêutrons de ângulo pequeno (SANS) e a dispersão de nêutrons de ângulo ultra pequeno (USANS) juntamente com protocolos de encaixe apropriado podemos quantificar a evolução dos parâmetros estruturais selecionados em todo este processo. Minuciosa análise indica que a continuada exposição à luz durante todo o processo de gelificação significativamente altera a estrutura do gel, finalmente, formado. Especificamente, o processo de agregação de agregados de nano-escala de poly(3-hexylthiophene-2,5-diyl) (P3HT) é negativamente afetado pela presença de iluminação, finalmente tendo por resultado o retardo de crescimento em microestruturas de polímero conjugado e o formação de clusters de macroagregado de escala menores.

Experiências através de SANS e USANS, o processo de gelificação de P3HT em d-ODCB foi efetivamente monitorado do estado solução dispersos a 70 ° C para um estado totalmente gelificado a 20 ° C. Esses experimentos foram conduzidos em ambos completa escuridão e sob iluminação de luz branca. Figura 1 exibe algumas curvas de dados exemplo SANS reduzido destas experiências, com uma curva exemplo mostrado na Figura 2. Estes...

Watch this Scientific Journal Video about Monitoring the Effects of Illumination on the Structure of Conjugated Polymer Gels Using Neutron Scattering at JoVE.com

Monitoring the Effects of Illumination on the Structure of Conjugated Polymer Gels Using Neutron Scattering

Um protocolo de análise de géis formados a partir do optoelectronic conjugados polímero poly(3-hexylthiophene-2,5-diyl) (P3HT) usando pequenas e dispersão de nêutrons ultra pequeno ângulo na presença e na ausência de iluminação é apresentado.

Monitorização dos efeitos de iluminação sobre a estrutura do polímero conjugado géis usando Neutron Scattering

We demonstrate a protocol to effectively monitor the gelation process of a high concentration solution of conjugated polymer both in the presence and ...

monitoring-effects-illumination-on-structure-conjugated-polymer-gels

Universidad de Cartagena UDEC

Research

JoVE Journal

Chemistry

5.6K visualizações.  University of Tennessee, Knoxville. Um protocolo de análise de géis formados a partir do optoelectronic conjugados polímero poly(3-hexylthiophene-2,5-diyl) (P3HT) usando pequenas e dispersão de nêutrons ultra pequeno ângulo na presença e na ausência de iluminação é apresentado.

Vídeo: Monitoring the Effects of Illumination on the Structure of Conjugated Polymer Gels Using Neutron Scattering

Using Neutron Spin Echo Resolved Grazing Incidence Scattering to Investigate Organic Solar Cell Materials

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped crystallites. Neutrons are passed through two well defined regions of magnetic field; one before and one after the sample. The two magnetic field regions have opposite polarity and are tuned such that neutrons travelling through both regions, without being perturbed, will undergo the same number of precessions in opposing directions. In this case the neutron precession in the second arm is said to &#34;echo&#34; the first, and the original polarization of the beam is preserved. If the neutron interacts with a sample and scatters elastically the path through the second arm is not the same as the first and the original polarization is not recovered. Depolarization of the neutron beam is a highly sensitive probe at very small angles (&#60;50&#160;&#956;rad) but still allows a high intensity, divergent beam to be used. The decrease in polarization of the beam reflected from the sample as compared to that from the reference sample can be directly related to structure within the sample.
In comparison to scattering observed in neutron reflection measurements the SERGIS signals are often weak and are unlikely to be observed if the in-plane structures within the sample under investigation are dilute, disordered, small in size and polydisperse or the neutron scattering contrast is low. Therefore, good results will most likely be obtained using the SERGIS technique if the sample being measured consist of thin films on a flat substrate and contain scattering features that contains a high density of moderately sized features (30 nm to 5 &#181;m) which scatter neutrons strongly or the features are arranged on a lattice. An advantage of the SERGIS technique is that it can probe structures in the plane of the sample.

Progress has been made in utilizing spin echo resolved grazing incidence scattering (SERGIS) as a neutron scattering technique to probe the length-scales in irregular samples. Crystallites of [6,6]-phenyl-C61-butyric acid methyl ester have been probed using the SERGIS technique and the results confirmed by optical and atomic force microscopy.

Usando neutron spin echo resolvi a dispersão da incidência de pastagem para investigar materiais orgânicos de células solares

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped ...

Engenharia

Measurement of Scattering Nonlinearities from a Single Plasmonic Nanoparticle

Plasmonics, which are based on the collective oscillation of electrons due to light excitation, involve strongly enhanced local electric fields and thus have potential applications in nonlinear optics, which requires extraordinary optical intensity. One of the most studied nonlinearities in plasmonics is nonlinear absorption, including saturation and reverse saturation behaviors. Although scattering and absorption in nanoparticles are closely correlated by the Mie theory, there has been no report of nonlinearities in plasmonic scattering until very recently. 
Last year, not only saturation, but also reverse saturation of scattering in an isolated plasmonic particle was demonstrated for the first time. The results showed that saturable scattering exhibits clear wavelength dependence, which seems to be directly linked to the localized surface plasmon resonance (LSPR). Combined with the intensity-dependent measurements, the results suggest the possibility of a common mechanism underlying the nonlinear behaviors of scattering and absorption. These nonlinearities of scattering from a single gold nanosphere (GNS) are widely applicable, including in super-resolution microscopy and optical switches. 
In this paper, it is described in detail how to measure nonlinearity of scattering in a single GNP and how to employ the super-resolution technique to enhance the optical imaging resolution based on saturable scattering. This discovery features the first super-resolution microscopy based on nonlinear scattering, which is a novel non-bleaching contrast method that can achieve a resolution as low as l/8 and will potentially be useful in biomedicine and material studies.

Saturable and reverse saturable scattering were discovered in isolated plasmonic particles and adopted as a novel non-bleaching contrast method in super-resolution microscopy. Here the experimental procedures of detecting and extracting nonlinear scattering are explained in detail, as well as how to enhance resolution with the aid of saturated excitation microscopy.

Medição da Dispersão Não-linearidades de um Nanoparticle plasmonic Individual

Plasmonics, which are based on the collective oscillation of electrons due to light excitation, involve strongly enhanced local electric fields and thus ...

Synthesis and Characterization of Supramolecular Colloids

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

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

Síntese e Caracterização de Supramoleculares Colloids

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

Química

Controlled Synthesis and Fluorescence Tracking of Highly Uniform Poly(N-isopropylacrylamide) Microgels

Stimuli-sensitive poly(N-isopropylacrylamide) (PNIPAM) microgels have various prospective practical applications and uses in fundamental research. In this work, we use single particle tracking of fluorescently labeled PNIPAM microgels as a showcase for tuning microgel size by a rapid non-stirred precipitation polymerization procedure. This approach is well suited for prototyping new reaction compositions and conditions or for applications that do not require large amounts of product. Microgel synthesis, particle size and structure determination by dynamic and static light scattering are detailed in the protocol. It is shown that the addition of functional comonomers can have a large influence on the particle nucleation and structure. Single particle tracking by wide-field fluorescence microscopy allows for an investigation of the diffusion of labeled tracer microgels in a concentrated matrix of non-labeled microgels, a system not easily investigated by other methods such as dynamic light scattering.

Controlled Synthesis and Fluorescence Tracking of Highly Uniform PolyN-isopropylacrylamide Microgels

Non-stirred precipitation polymerization provides a rapid, reproducible prototyping approach to the synthesis of stimuli-sensitive poly(N-isopropylacrylamide) microgels of narrow size distribution. In this protocol synthesis, light scattering characterization and single particle fluorescence tracking of these microgels in a wide-field microscopy setup are demonstrated.

Síntese controlada e Fluorescência de rastreamento de Poly altamente uniforme (<em&gt; N</em&gt; -isopropylacrylamide) microgéis

Stimuli-sensitive poly(N-isopropylacrylamide) (PNIPAM) microgels have various prospective practical applications and uses in fundamental research. In this ...

Advanced Compositional Analysis of Nanoparticle-polymer Composites Using Direct Fluorescence Imaging

The fabrication of polymer-nanoparticle composites is extremely important in the development of many functional materials. Identifying the precise composition of these materials is essential, especially in the design of surface catalysts, where the surface concentration of the active component determines the activity of the material. Antimicrobial materials which utilize nanoparticles are a particular focus of this technology. Recently swell encapsulation has emerged as a technique for inserting antimicrobial nanoparticles into a host polymer matrix. Swell encapsulation provides the advantage of localizing the incorporation to the external surfaces of materials, which act as the active sites of these materials. However, quantification of this nanoparticle uptake is challenging. Previous studies explore the link between antimicrobial activity and surface concentration of the active component, but this is not directly visualized. Here we show a reliable method to monitor the incorporation of nanoparticles into a polymer host matrix via swell encapsulation. We show that the surface concentration of CdSe/ZnS nanoparticles can be accurately visualized through cross-sectional fluorescence imaging. Using this method, we can quantify the uptake of nanoparticles via swell encapsulation and measure the surface concentration of encapsulated particles, which is key in optimizing the activity of functional materials.

Here we present a reliable method to monitor the incorporation of nanoparticles into a polymer host matrix via swell encapsulation. We show that the surface concentration of cadmium selenide quantum dots can be accurately visualized through cross-sectional fluorescence imaging.

Avançado Análise da composição dos compósitos de nanopartículas de polímero através da tecnologia Direct Fluorescência de imagem

The fabrication of polymer-nanoparticle composites is extremely important in the development of many functional materials. Identifying the precise ...

Measurement of Particle Size Distribution in Turbid Solutions by Dynamic Light Scattering Microscopy

A protocol for measuring polydispersity of concentrated polymer solutions using dynamic light scattering is described. Dynamic light scattering is a technique used to measure the size distribution of polymer solutions or colloidal particles. Although this technique is widely used for the assessment of polymer solutions, it is difficult to measure the particle size in concentrated solutions due to the multiple scattering effect or strong light absorption. Therefore, the concentrated solutions should be diluted before measurement. Implementation of the confocal optical component in a dynamic light scattering microscope1 helps to overcome this barrier. Using such a microscopic system, both transparent and turbid systems can be analyzed under the same experimental setup without a dilution. As a representative example, a size distribution measurement of a temperature-responsive polymer solution was performed. The sizes of the polymer chains in an aqueous solution were several tens of nanometers at a temperature below the lower critical solution temperature (LCST). In contrast, the sizes increased to more than 1.0 &#181;m when above the LCST. This result is consistent with the observation that the solution turned turbid above the LCST.

A protocol for the direct measurement of particle size distribution in concentrated solutions using dynamic light scattering microscopy is presented.

Medição do Tamanho de Partículas Distribuição em turvas Solutions pela Dynamic dispersão de luz Microscopia

A protocol for measuring polydispersity of concentrated polymer solutions using dynamic light scattering is described. Dynamic light scattering is a ...

Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals

We discuss in this article the experimental measurements of the molecules in liquid crystal (LC) phase using the time-resolved infrared (IR) vibrational spectroscopy and time-resolved electron diffraction. Liquid crystal phase is an important state of matter that exists between the solid and liquid phases and it is common in natural systems as well as in organic electronics. Liquid crystals are orientationally ordered but loosely packed, and therefore, the internal conformations and alignments of the molecular components of LCs can be modified by external stimuli. Although advanced time-resolved diffraction techniques have revealed picosecond-scale molecular dynamics of single crystals and polycrystals, direct observations of packing structures and ultrafast dynamics of soft materials have been hampered by blurry diffraction patterns. Here, we report time-resolved IR vibrational spectroscopy and electron diffractometry to acquire ultrafast snapshots of a columnar LC material bearing a photoactive core moiety. Differential-detection analyses of the combination of time-resolved IR vibrational spectroscopy and electron diffraction are powerful tools for characterizing structures and photoinduced dynamics of soft materials.

Here, we present the protocols of differential-detection analyses of time-resolved infrared vibrational spectroscopy and electron diffraction which enable observations of the deformations of local structures around photoexcited molecules in a columnar liquid crystal, giving an atomic perspective on the relationship between the structure and the dynamics of this photoactive material.

Novas técnicas para observar a dinâmica estrutural de cristais líquidos de Photoresponsive

We discuss in this article the experimental measurements of the molecules in liquid crystal (LC) phase using the time-resolved infrared (IR) vibrational ...

Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization

We report a method to generate the N-heterocyclic carbene (NHC) 1,3-dimesitylimidazol-2-ylidene (IMes) under UV-irradiation at 365 nm to characterize IMes and determine the corresponding photochemical mechanism. Then, we describe a protocol to perform ring-opening metathesis polymerization (ROMP) in solution and in miniemulsion using this NHC-photogenerating system. To photogenerate IMes, a system comprising 2-isopropylthioxanthone (ITX) as the sensitizer and 1,3-dimesitylimidazolium tetraphenylborate (IMesH+BPh4-) as the protected form of NHC is employed. IMesH+BPh4- can be obtained in a single step by anion exchange between 1,3-dimesitylimidazolium chloride and sodium tetraphenylborate. A real-time steady-state photolysis setup is described, which hints that the photochemical reaction proceeds in two consecutive steps: 1) ITX triplet is photo-reduced by the borate anion and 2) subsequent proton transfer takes place from the imidazolium cation to produce the expected NHC IMes. Two separate characterization protocols are implemented. Firstly, CS2 is added to the reaction media to evidence the photogeneration of NHC through formation of the IMes-CS2 adduct. Secondly, the amount of NHC released in situ is quantified using acid-base titration. The use of this NHC photo-generating system for the ROMP of norbornene is also discussed. In solution, a photopolymerization experiment is conducted by mixing ITX, IMesH+BPh4-, [RuCl2(p-cymene)]2 and norbornene in CH2Cl2, then irradiating the solution in a UV reactor. In a dispersed medium, a monomer miniemulsion is first formed then irradiated inside an annular reactor to produce a stable poly(norbornene) latex.

We describe a protocol to photogenerate N-heterocyclic carbenes (NHCs) by UV irradiation of a 2-isopropylthioxanthone/imidazolium tetraphenylborate salt system. Methods to characterize the photoreleased NHC and elucidate the photochemical mechanism are proposed. The protocols for ring-opening metathesis photopolymerization in solution and miniemulsion illustrate the potential of this 2-component NHC photogenerating system.

Pseudo-levitante de N-Heterocyclic carbenos: aplicação na polimerização de metátese de anel-abertura de participação

We report a method to generate the N-heterocyclic carbene (NHC) 1,3-dimesitylimidazol-2-ylidene (IMes) under UV-irradiation at 365 nm to characterize IMes ...

Light-mediated Formation and Patterning of Hydrogels for Cell Culture Applications

Click chemistries have been investigated for use in numerous biomaterials applications, including drug delivery, tissue engineering, and cell culture. In particular, light-mediated click reactions, such as photoinitiated thiol&#8722;ene and thiol&#8722;yne reactions, afford spatiotemporal control over material properties and allow the design of systems with a high degree of user-directed property control. Fabrication and modification of hydrogel-based biomaterials using the precision afforded by light and the versatility offered by these thiol&#8722;X photoclick chemistries are of growing interest, particularly for the culture of cells within well-defined, biomimetic microenvironments. Here, we describe methods for the photoencapsulation of cells and subsequent photopatterning of biochemical cues within hydrogel matrices using versatile and modular building blocks polymerized by a thiol&#8722;ene photoclick reaction. Specifically, an approach is presented for constructing hydrogels from allyloxycarbonyl (Alloc)-functionalized peptide crosslinks and pendant peptide moieties and thiol-functionalized poly(ethylene glycol) (PEG) that rapidly polymerize in the presence of lithium acylphosphinate photoinitiator and cytocompatible doses of long wavelength ultraviolet (UV) light. Facile techniques to visualize photopatterning and quantify the concentration of peptides added are described. Additionally, methods are established for encapsulating cells, specifically human mesenchymal stem cells, and determining their viability and activity. While the formation and initial patterning of thiol-alloc hydrogels are shown here, these techniques broadly may be applied to a number of other light and radical-initiated material systems (e.g., thiol-norbornene, thiol-acrylate) to generate patterned substrates.

We describe a sequential process for light-mediated formation and subsequent biochemical patterning of synthetic hydrogel matrices for three-dimensional cell culture applications. The construction and modification of hydrogels with cytocompatible photoclick chemistry is demonstrated. Additionally, facile techniques to quantify and observe patterns and determine cell viability within these hydrogels are presented.

Formação Light-mediada e padronização de hidrogéis para aplicações de cultura celular

Click chemistries have been investigated for use in numerous biomaterials applications, including drug delivery, tissue engineering, and cell culture. In ...

Bioengenharia

Measuring the Time-Evolution of Nanoscale Materials with Stopped-Flow and Small-Angle Neutron Scattering

This paper presents the use of a stopped-flow small-angle neutron-scattering (SANS) sample environment to quickly mix liquid samples and study nanoscale kinetic processes on time scales of seconds to minutes. The stopped-flow sample environment uses commercially available syringe pumps to mix the desired volumes of liquid samples that are then injected through a dynamic mixer into a quartz glass cell in approximately 1 s. Time-resolved SANS data acquisition is synced with the sample mixing to follow the evolution of the nanostructure in solution after mixing. 
To make the most efficient use of neutron beam time, we use a series of flow selector valves to automatically load, rinse, and dry the cell between measurements, allowing for repeated data collection throughout multiple sample injections. Sample injections are repeated until sufficient neutron scattering statistics are collected. The mixing setup can be programmed to systematically vary conditions to measure the kinetics at different mixing ratios, sample concentrations, additive concentrations, and temperatures. The minimum sample volume required per injection is approximately 150 &#181;L depending on the path length of the quartz cell. 
Representative results using this stopped-flow sample environment are presented for rapid lipid exchange kinetics in the presence of an additive, cyclodextrin. The vesicles exchange outer-leaflet (exterior) lipids on the order of seconds and fully exchange both interior and exterior lipids within hours. Measuring lipid exchange kinetics requires in situ mixing to capture the faster (seconds) and slower (minutes) processes and extract the kinetic rate constants. The same sample environment can also be used to probe molecular exchange in other types of liquid samples such as lipid nanoparticles, proteins, surfactants, polymers, emulsions, or inorganic nanoparticles. Measuring the nanoscale structural transformations and kinetics of exchanging or reacting systems will provide new insights into processes that evolve at the nanoscale.

This protocol presents the use of a stopped-flow sample environment to quickly mix multiple liquid solutions in situ during a small-angle neutron scattering measurement and to study kinetic processes on nanometer length scales and second time scales.

Medindo a evolução temporal de materiais em nanoescala com espalhamento de nêutrons de fluxo interrompido e de pequeno ângulo

This paper presents the use of a stopped-flow small-angle neutron-scattering (SANS) sample environment to quickly mix liquid samples and study nanoscale ...