The authors wish to acknowledge the competitive faculty-initiated collaboration (FIC) grant from KAUST.

1. Preparação de Pré-dopado SrTiO 3 Pó <ol><li> A fim de preparar 10 g de Sr 0,95 Pr 0,05 TiO 3 em pó, pesar as quantidades estequiométricas de SrCO 3 em pó (7,53407 g), TiO 2 nanopowder (4,28983 g), e Pr 2 O 3 protuberância sinterizado (0,44299 g) a seguir à reacção para X = 0,05: </li></ol><img alt="Equação 1" fo:content-width="5in" src="/files/ftp_upload/52869/52869eq1.JPG" width="550" /><ol start="2"><li> Triture os pesados ​​Pr 2 O 3 caroços sinterizados a partículas finas utilizando um almofariz e pilão de ágata. </li><li> Adicionar o pesava SrCO3 pó e de TiO 2 nanopowder ao Pr 2 O 3 e continuar moagem e mistura utilizando um almofariz de ágata e pilão até um pó visualmente homogénea é conseguido. </li><li> Carregar o pó moído em um frasco de vidro e mistura utilizando um dispositivo de turbulência durante 30 minutos para homogeneizar the mistura. </li><li> Carregar o pó misturado resultante num cuidadosamente limpos e polidos de aço inoxidável fieira (1 polegada de diâmetro) e que sanduíche entre dois êmbolos de aço inoxidável. </li><li> Imprensa fria o pó usando uma prensa sob uma carga de aproximadamente 1 tonelada métrica. </li><li> Ejetar o pellet prensado a frio, colocando a matriz em um cilindro de aço inoxidável oco e empurrando os êmbolos e a pelota para fora do topo usando uma haste de empurrar. Após a ejecção do pelete prensado a frio (corpo verde) a partir da matriz, limpar qualquer contaminação na superfície circunferencial do pelete, cobrindo suavemente o sedimento com um pequeno pedaço de fita adesiva e, a remoção de uma camada fina por rasgar a fita. </li><li> Coloque o pellet verticalmente em um barco de alumina preenchido com comprada comercialmente SrTiO 3 em pó como a barreira entre o barco alumina ea imprensa pelota frio. </li><li> Inserir o barco num forno tubular, aquecer até 1300 ° C em 3 horas e mantê-lo a esta temperatura durante 15h. Permitir que o sedimento de arrefecer até à temperatura ambiente no interior do forno quando a calcinação acabou. Este passo é referido como o &quot;processo de calcinação&quot; posteriormente. </li><li> Moer o pellet usando o almofariz de ágata e pilão e carregar o pó resultante em um frasco de vidro para posterior mistura usando a turbulência. </li><li> Carregar o pó para dentro da matriz de aço inoxidável e prensado a frio sob uma cerca de 3 toneladas métricas de carga. </li><li> Repetir o passo de 1,9 mais uma vez a 1400 ° C em 3 horas e guarda-se a esta temperatura durante 20 horas. </li><li> Moer o pellet usando o almofariz de ágata e pilão. </li><li> Repita os passos 1.11, 1.12, 1.13 e mais uma vez para a reacção em estado sólido para atingir a conclusão. </li></ol> 2. Preparação de massa policristalino Pr-dopado SrTiO 3 Ceramic <ol><li> Pesar 1,6 g de pó de AS-preparada (para um disco de 2 mm de espessura e 12,7 mm de diâmetro). </li><li> Prepare pedaços graphoil circulares para cobrir a parte superior e inferior interface dos êmbolos de pó de grafite e colada no grafite morrer. Além disso, uma outra parte preparar graphoil rectangular para cobrir a parede interna do molde de grafite. </li><li> Carregar o pó como preparada num molde de grafite (12.7 mm de diâmetro interno) e o pó de sanduíche entre dois êmbolos de grafite do mesmo tamanho. Perfurar um furo de 2 mm no meio do comprimento da matriz de grafite e a partir da superfície exterior da matriz de cerca de 2 mm da superfície interna para a leitura de temperatura. Nota: Ajustar o comprimento dos êmbolos de grafite que fiquem fora do molde e posicionar o centro do cilindro de pó ensanduichada em que o orifício é colocado para obter uma leitura precisa da temperatura. Os rostos dos êmbolos de grafite precisam ser meticulosamente nivelada durante a usinagem das peças. Qualquer desalinhamento pode resultar na quebra da pastilha sinterizada durante a sinterização plasma pulsado. </li><li> Cold-prima suavemente o pó (carga &lt;200 kg) utilizando uma prensa antes da montagem sobre a centelhaplaca de sinterização plasma no interior da câmara. Use planas polidas placas de suporte de aço inoxidável entre a parte superior e inferior e êmbolos do palco imprensa para evitar danificar os êmbolos de grafite. </li><li> Enrole um pedaço de feltro de grafite em torno da matriz para o isolamento e prenda-o com fios de grafite. Conceber uma janela sobre o feltro de grafite pelo corte de uma peça rectangular de feltro onde a leitura da temperatura orifício é colocado sobre o molde. </li><li> Coloque o molde de grafite e êmbolos carregados na câmara de sinterização plasma pulsado. Mover o palco para a posição final. </li><li> Concentre-se e alinhar o círculo alvo Pyrometer no buraco leitura da temperatura do molde. Verifique se a configuração emissividade do pirômetro está definido para grafite. </li><li> Feche a câmara e colocar uma carga de 7,7 kN (aproximadamente 60 MPa) sobre a amostra. Vácuo e purgar a câmara com Ar três vezes e saem da câmara sob vácuo dinâmico de 6 Pa. </li><li> Aumentar a temperatura, aumentando a corrente (manualmente ou utilizando umprograma). Use 250 A min -1 (correspondendo a aproximadamente 300-400 ° C min-1) para as amostras optimizados. Este é o passo mais importante no processo de sinterização plasma pulsado. </li><li> Manter a temperatura a 1500 ° C durante 5 min, ajustando manualmente a corrente ou utilizando o programa. No final do período de detenção de 5 min, fechou a atual off e solte rapidamente a carga de 7,7 kN para evitar rachaduras da amostra durante o arrefecimento. Deixe o fresco de exemplo para RT no interior da câmara. </li><li> Solte o pellet granel do grafite morrer suavemente com a imprensa fria. Isto é feito colocando o molde de grafite em um cilindro de aço oca e ejectar o sedimento e os êmbolos de grafite utilizando uma vareta de aço que empurra a partir do topo. </li><li> Remover o graphoil nas faces superior e inferior do sedimento, bem como a superfície circunferencial usando uma lâmina afiada. </li><li> Polir a amostra usando um papel áspero areia (400 grade) para baixo para 0,3-0,5 mm de cada lado para garantira remoção completa do graphoil. Limpar a amostra com acetona. </li></ol> 3. Caracterização de eletrônicos e Transporte Thermal Ceramics Propriedades de massa <ol><li> Determinar a densidade do disco cerâmico, ρ, utilizando o método de Arquimedes. </li><li> Medir o peso da amostra, W seco, e então o peso da amostra submersa em água, W molhado, em um sistema de medição de densidade estabilizada e calcular a densidade a partir de Arquimedes </li></ol><img alt="Equação 2" fo:content-width="2.1in" src="/files/ftp_upload/52869/52869eq2.JPG" width="260" /> onde a água ρ é a densidade da água à temperatura de medição (por exemplo, igual a 1 g cm -3 a 300 K). 14 <ol start="2"><li> Medir a difusividade térmica da amostra, d, usando a técnica de inflamação do laser transiente sob uma 75 ml min -1 fluxo de Ar. Medir a espessurada amostra, G, com precisão primeiro usando um micrómetro digital. Nota: As amostras Paralelo-confrontados com diferentes tamanhos e formas (por exemplo, discos redondos 12,7 milímetros de diâmetro ou quadrada 10 x 10 mm 2 discos) e espessuras entre 0,5 e 5 mm pode ser facilmente medido. <ol><li> Na técnica de inflamação do laser difusividade térmica, irradiação de uma face da amostra por um curto (~ 1 mseg) pulso de laser e registar o aumento de temperatura na face oposta por um detector de infra-vermelhos. Em seguida, calcular difusividade térmica pelo software de interface de inflamação do laser a partir da espessura da amostra e o perfil de subida de temperatura-tempo utilizando a equação 15 Parker </li></ol></li></ol><img alt="Equação 3" fo:content-width="1.9in" src="/files/ftp_upload/52869/52869eq3.JPG" width="220" /> em que L representa a espessura do disco e t 1/2 representa a meia-altura da elevação máxima de temperatura do outro side da amostra. Nota: O modelo de 15 Parker assume condições ideais de amostra adiabatic e aquecimento de pulso instantânea, outros modelos têm sido propostos ao longo dos anos, que representam várias perdas na medição, como as perdas de calor, duração de pulso finito, aquecimento de pulso não uniforme e não homogénea estruturas. Temos utilizado o modelo Cowan 16 com correção de pulso, que é um dos métodos mais avançados. Deve notar-se que, a fim de maximizar a quantidade de energia térmica transmitida a partir da superfície frontal e para maximizar o sinal observado pelo detector de IR, as superfícies das amostras deve ser altamente emissiva. Normalmente, isto requer a aplicação de uma fina camada de grafite para as superfícies das amostras. Uma incerteza de 2% -5% na medição da difusividade térmica existe, provenientes da determinação da dimensão. 17 <ol start="3"><li> Cortar o sedimento utilizando uma serra de disco de diamantes em barras rectangulares, 2 x 2 x 103 mm, a condutividade eléctrica e medições de coeficiente de Seebeck, bem como um disco de quadrado, de 4 x 4 x 1,5 mm3 para o calor específico de alta temperatura e uma peça rectangular fina, 8 x 5 x 1 mm3 para medidas Hall. </li><li> Medir o calor específico, C p, da amostra sobre a peça quadrada plana e polida-espelho (4 x 4 x 1,5 mm3) utilizando uma calorimetria de varrimento diferencial (DSC) sob fluxo de árgon. 18 <ol><li> Usar uma taxa de aquecimento de 5 K min -1-se a 40 ° C durante uma preensão isotérmica durante 10 min para permitir que a amostra atingir o equilíbrio térmico, seguido por 20 K min -1 taxa de aquecimento até 500 ° C, com uma taxa de arrefecimento exacta que se seguiu. Executar a medição sob o fluxo de árgon (50 ml min -1 é sugerido). </li></ol></li></ol> Nota: devido à sensibilidade do método utilizado para a análise, conduzir três medições para determinar a capacidade de calor<html> incluindo (1) uma medição de linha de base para subtrair o fundo, (2) a medição do calor específico de um material padrão (tais como safira) com um conhecido C P, e (3) medição do calor específico da amostra. Certifique-se de que as amostras são planas e, a fim de fazer um contacto ideal, com o fundo do cadinho de medição (panelas de Pt / Rh com Al 2 O 3 cadinhos utilizados neste trabalho) polido-espelho. Mais detalhes sobre a estrutura exacta da fase de DSC, uma comparação das técnicas de DSC para os outros, e instruções precisas para a medição de uma amostra pode ser encontrada em várias fontes 19. <ol start="5"><li> Calcular a condutividade térmica a alta temperatura, κ, da amostra a partir dos valores medidos de difusividade térmica, d, o calor específico, C P, e a densidade, utilizando 20 ρ </li></ol>/52869/52869eq4.JPG &quot;Width =&quot; 200 &quot;/&gt; <ol start="6"><li> Placa de ouro sondas aos pontos de contacto (4) sobre a contactos 2 x 2 x 10 mm de 3 peças cortadas a partir da amostra para aliviar os problemas de resistência de contacto. <ol><li> A fim de pulverização catódica ouro apenas nas áreas de contato desejados, enrole uma scotch-fita ao redor da amostra 2 x 2 x 10 mm 3 para usar como um estêncil. Deixe a 2 x 2 milímetros dois rostos un-coberto. Usando uma lâmina de barbear, cortar dois orifícios muito pequenos (aproximadamente 1 mm de diâmetro) no centro da face 2 x 10 mm 2, ao longo de uma linha separada pela distância sondas. </li><li> 21 por pulverização catódica, uma película de ouro ~ 200 nm de espessura usando uma unidade de pulverização de ouro de bancada. </li></ol></li><li> Medem-se as propriedades de transporte eléctrico, ou seja, a condutibilidade eléctrica e de coeficiente de Seebeck) da amostra, como uma função de temperatura 22,23. <ol><li> Medir a condutividade eléctrica através do método de quatro terminais. Medir o coeficiente de Seebeck com a same configuração usando as medições de temperatura e de tensão através dos dois termopar média &quot;sondas&quot;. Meça a distância entre estas duas sondas que utilizam um microscópio digital. Mais detalhes sobre as medidas de transporte elétricas podem ser encontradas em outros lugares 22,23. </li></ol></li><li> 24 medir a concentração de portadores Hall como uma função da temperatura sobre a 8 x 5 x 1 mm3 amostra usando um sistema de medição de propriedades físicas. </li></ol>

<ol>
	<li>Ohta, S., Nomura, T., Ohta, H., Koumoto, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-temperature+Carrier+Transport+and+Thermoelectric+Properties+of+Heavily+La-or+Nb-doped+SrTiO3+Single+Crystals.">High-temperature Carrier Transport and Thermoelectric Properties of Heavily La-or Nb-doped SrTiO3 Single Crystals.</a> J. Appl. Phys. 97, (2005).</li><li>Wang, H. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhancement+of+Thermoelectric+Figure+of+Merit+by+Doping+Dy+in+La0.1Sr0.9TiO3+Ceramic.">Enhancement of Thermoelectric Figure of Merit by Doping Dy in La0.1Sr0.9TiO3 Ceramic.</a> Mater. Res. Bull. 45, 809-812 (2010).</li><li>Bhattacharya, S., Mehdizadeh Dehkordi, A., Alshareef, H. N., Tritt, T. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis&#8211;Property+Relationship+in+Thermoelectric+Sr1&#8722;xYbxTiO3&#8722;&#948;+Ceramics.">Synthesis&#8211;Property Relationship in Thermoelectric Sr1&#8722;xYbxTiO3&#8722;&#948; Ceramics.</a> J. Phys. D: Appl. Phys. 47, 385302 (2014).</li><li>Wang, Y., Lee, K. H., Ohta, H., Koumoto, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermoelectric+Properties+of+Electron+Doped+SrO(SrTiO3)n+(n=1,2)+Ceramics.">Thermoelectric Properties of Electron Doped SrO(SrTiO3)n (n=1,2) Ceramics.</a> J. Appl. Phys. 105, 1037011-1037016 (2009).</li><li>Wang, N., 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=Effects+of+YSZ+Additions+on+Thermoelectric+Properties+of+Nb-Doped+Strontium+Titanate.">Effects of YSZ Additions on Thermoelectric Properties of Nb-Doped Strontium Titanate.</a> J. Electron. Mater. 39, 1777-1781 (2010).</li><li>Muta, H., Kurosaki, K., Yamanaka, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermoelectric+Properties+of+Rare+Earth+Doped+SrTiO3.">Thermoelectric Properties of Rare Earth Doped SrTiO3.</a> J. Alloys Compd. 350, 292-295 (2003).</li><li>Shang, P. -. P., Zhang, B. -. P., Li, J. -. F., Ma, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+Sintering+Temperature+on+Thermoelectric+Properties+of+La-doped+SrTiO3+Ceramics+Prepared+by+Sol-gel+Process+and+Spark+Plasma+Sintering.">Effect of Sintering Temperature on Thermoelectric Properties of La-doped SrTiO3 Ceramics Prepared by Sol-gel Process and Spark Plasma Sintering.</a> Solid State Sciences. 12, 1341-1346 (2010).</li><li>Wang, Y., Fan, H. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sr1-xLaxTiO3+Nanoparticles:+Synthesis,+Characterization+and+Enhanced+Thermoelectric+Response.">Sr1-xLaxTiO3 Nanoparticles: Synthesis, Characterization and Enhanced Thermoelectric Response.</a> Scripta Materialia. 65, 190-193 (2011).</li><li>Kikuchi, A., Okinakab, N., Akiyama, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Large+Thermoelectric+Figure+of+Merit+of+La-doped+SrTiO3+Prepared+by+Combustion+Synthesis+with+Post-Spark+Plasma+Sintering.">A Large Thermoelectric Figure of Merit of La-doped SrTiO3 Prepared by Combustion Synthesis with Post-Spark Plasma Sintering.</a> Scripta Materialia. 63, 407-410 (2010).</li><li>Obara, H., 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=Thermoelectric+Properties+of+Y-Doped+Polycrystalline+SrTiO3.Jpn.">Thermoelectric Properties of Y-Doped Polycrystalline SrTiO3.Jpn.</a> J. Appl. Phys. 43, L540-L542 (2004).</li><li>Koumoto, K., Wang, Y., Zhang, R., Kosuga, A., Funahashi, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oxide+Thermoelectric+Materials:+A+Nanostructuring+Approach.">Oxide Thermoelectric Materials: A Nanostructuring Approach.</a> Annu. Rev. Mater. Res. 40, 363-394 (2010).</li><li>Mehdizadeh Dehkordi, 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=Large+Thermoelectric+Power+Factor+in+Pr-Doped+SrTiO3&#8722;&#948;+Ceramics+via+Grain-Boundary-Induced+Mobility+Enhancement.">Large Thermoelectric Power Factor in Pr-Doped SrTiO3&#8722;&#948; Ceramics via Grain-Boundary-Induced Mobility Enhancement.</a> Chem. Mater. 26, 2478-2485 (2014).</li><li>Mehdizadeh Dehkordi, A., Bhattacharya, S., He, J., Alshareef, H. N., Tritt, T. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Significant+Enhancement+in+Thermoelectric+Properties+of+Polycrystalline+Pr-doped+SrTiO3+Ceramics+Originating+from+Nonuniform+distribution+of+Pr+dopants.">Significant Enhancement in Thermoelectric Properties of Polycrystalline Pr-doped SrTiO3 Ceramics Originating from Nonuniform distribution of Pr dopants.</a> Appl. Phys. Lett. 104, 1939021-1939024 (2014).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Standard Test Methods for Density of Compacted or Sintered Powder Metallurgy (PM) Products Using Archimedes&#8217; Principle. , (2015).</li><li>Parker, W. J., Jenkins, R. J., Butler, C. P., Abbott, G. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flash+Method+of+Determining+Thermal+Diffusivity,+Heat+Capacity+and+Thermal+Conductivity.">Flash Method of Determining Thermal Diffusivity, Heat Capacity and Thermal Conductivity.</a> J. Appl. Phys. 32, 1679-1684 (1961).</li><li>Cowan, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pulse+Method+of+Measuring+Thermal+Diffusivity+at+High+Temperatures.">Pulse Method of Measuring Thermal Diffusivity at High Temperatures.</a> J. Appl. Phys. 34, 926-927 (1963).</li><li>Mehdizadeh-Dehkordi, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> An Experimental Investigation Towards Improvement of Thermoelectric Properties of Strontium Titanate Ceramics. , (2014).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> DSC Pegasus 404C Operating Manual. , (1999).</li><li>Daw, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurement+of+Specific+Heat+Capacity+Using+Differential+Scanning+Calorimeter.">Measurement of Specific Heat Capacity Using Differential Scanning Calorimeter.</a> Report of US Department of Energy. , (2008).</li><li>Tritt, T. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Thermal Conductivity: Theory, Properties and Applications. , (2004).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> SC7610 Sputter Coater Operating Manual. , (2002).</li><li>Tritt, T. M., Rowe, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrical+and+Thermal+Transport+Measurement+Techniques+for+Evaluation+of+the+figure-of-Merit+of+Bulk+Thermoelectric+Materials.">Electrical and Thermal Transport Measurement Techniques for Evaluation of the figure-of-Merit of Bulk Thermoelectric Materials.</a> Thermoelectrics Handbook: Macro to Nano. , 23-1-23-17 (2006).</li><li>Burkov, A. T., Rowe, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurements+of+Resistivity+and+Thermopower:+Principles+and+Practical+Realization.">Measurements of Resistivity and Thermopower: Principles and Practical Realization.</a> Thermoelectrics Handbook: Macro to Nano. , 22-1 (2006).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Physical Property Measurement System: AC Transport Option User&#8217;s Manual. , (2003).</li><li>Ohta, S., Ohta, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Grain+Size+Dependence+of+Thermoelectric+Performance+of+Nb-doped+SrTiO3.">Grain Size Dependence of Thermoelectric Performance of Nb-doped SrTiO3.</a> Polycrystals. J. Ceram. Soc. Jpn. 114, 102 (2006).</li><li>Wang, N., He, H., Ba, Y., Wan, C., Koumoto, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermoelectric+Properties+of+Nb-doped+SrTiO3+Ceramics+Enhanced+by+Potassium+Titanate+Nanowires+Addition.">Thermoelectric Properties of Nb-doped SrTiO3 Ceramics Enhanced by Potassium Titanate Nanowires Addition.</a> J. Ceram. Soc. Jpn. 118, 1098 (2010).</li><li>Ohta, 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=Large+Thermoelectric+Performance+of+Heavily+Nb-doped+SrTiO3+Epitaxial+Film+at+High+Temperature.">Large Thermoelectric Performance of Heavily Nb-doped SrTiO3 Epitaxial Film at High Temperature.</a> Appl. Phys. Lett. 87, 092108 (2005).</li><li>Kovalevsky, A., Yaremchenko, A., Populoh, S., Weidenkaff, A., Frade, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhancement+of+Thermoelectric+Performance+in+Strontium+Titanate+by+Praseodymium+Substitution.">Enhancement of Thermoelectric Performance in Strontium Titanate by Praseodymium Substitution.</a> J. Appl. Phys. 113, 053704 (2013).</li><li>Kovalevsky, A. V., 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=Towards+a+High+Thermoelectric+Performance+in+Rare-Earth+Substituted+SrTiO3:+Effects+Provided+by+Strongly-Reducing+Sintering+Conditions.">Towards a High Thermoelectric Performance in Rare-Earth Substituted SrTiO3: Effects Provided by Strongly-Reducing Sintering Conditions.</a> Phys. Chem. 16, 26946 (2014).</li><li>Dawson, J. A., Tanaka, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Local+Structure+and+Energetics+of+Pr-+and+La-Doped+SrTiO3+Grain+Boundaries+and+the+Influence+on+Core–Shell+Structure+Formation.">Local Structure and Energetics of Pr- and La-Doped SrTiO3 Grain Boundaries and the Influence on Core–Shell Structure Formation.</a> J. Phys. Chem. C. 118, 25765-25778 (2014).</li><li>Mehdizadeh Dehkordi, 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=New+Insights+on+the+Synthesis+and+Electronic+Transport+in+Bulk+Polycrystalline+Pr-doped+SrTiO3&#8722;&#948;.">New Insights on the Synthesis and Electronic Transport in Bulk Polycrystalline Pr-doped SrTiO3&#8722;&#948;.</a> Appl. Phys. Lett. 117, 055102 (2015).</li></ol>

The authors have nothing to disclose.

Neste protocolo, apresentamos os passos da estratégia de síntese, a fim de preparar com êxito policristalinos granel dopado-PR SrTiO 3 cerâmica apresentando melhores propriedades eletrônicas e termoelétricas. As principais etapas do protocolo incluem (i) a síntese em estado sólido do dopado SrTiO 3 em pó em ar sob pressão atmosférica e (ii) aproveitando as capacidades de técnica de sinterização plasma pulsado para densificar o pó preparado como em alta densidade de massa cerâmica e ...

Thermoelectrics óxido foram mostrados para ser candidatos promissores para aplicações termelétricas de alta temperatura, de estabilidade e de custo perspectivas para propriedades de transporte eletrônico. Entre as termelétricas de óxido do tipo n, altamente dopado titanato de estrôncio (STO) tem atraído muita atenção devido às suas intrigantes propriedades eletrônicas. No entanto, uma grande condutividade térmica total (κ ~ 12 W K -1 m -1 a 300 K para cristais individuais) 1 e uma baixa mobilidade do transportador (μ ~ 6 centímetros 2 V 1 s-1 a 300 K para cristais individuais) 1 afectar prejudicialmente o desempenho termoeléctrico que é avaliado por uma figura de mérito adimensional, ZT = α 2 σT / κ, onde α é o coeficiente de Seebeck, σ a condutividade eléctrica, T a temperatura absoluta em graus Kelvin, e κ a condutividade térmica total. Nós aqui definir o numerador como o fator de potência, PF = α 263; T. A fim de que este material termoeléctrico óxido de competir com outros thermoelectrics de alta temperatura (tais como ligas de SiGe), são requeridos um aumento mais pronunciado no factor de potência e / ou diminuição da condutividade térmica da estrutura. A maioria dos estudos experimentais, a fim de melhorar as propriedades termoeléctricas de STO têm-se centrado principalmente na redução da condutividade térmica através estirpe de campo e espalhamento flutuação massa de fonões. Estas tentativas incluem: (i) simples ou duplas de doping do Sr 2+ e / ou Ti 4+ locais, como os principais esforços no que diz respeito a esta direção, 2,3 (ii) Síntese de superrede naturais estruturas Ruddlesden-Popper a fim de reduzir ainda mais a conductividade térmica através de camadas isolantes SRO, 4 e (iii) de engenharia composto por adição de uma segunda fase de nanoparticulado. 5 No entanto, até recentemente, nenhuma estratégia de reforço tem sido relatada a substantially aumentar o fator de energia termelétrica nestes óxidos. Os valores do fator de potência máxima registada (PF) em única massa e STO poli-cristalino foram confinados a um limite máximo de PF &lt;1,0 W m -1 K -1. Uma variedade de abordagens de síntese e técnicas de processamento têm sido utilizados para implementar as ideias tentativas acima. As rotas de síntese pó incluem reação de estado sólido convencional, 6 sol-gel, 7 hidrotermal, 8 e síntese de combustão, enquanto que 9 sinterização convencional, 6 prensagem a quente 10 e recentemente sinterização plasma faísca 12 estão entre as técnicas comuns usadas para densificar as pós em massa cerâmica. No entanto, para um dopante semelhante (por exemplo, La) e a concentração de dopante, os massa cerâmica resultantes exibem uma gama de propriedades de transporte electrónicos e térmicas. Isto é, em grande devido à química defeito fortemente dependente do processo de SrTiO &lt;sub&gt; 3, que resulta em propriedades dependentes de síntese. Há apenas um punhado de relatórios otimizando os parâmetros de síntese e processamento de beneficiar transporte termelétrica. Vale ressaltar que, devido ao muito pequeno phonon livre percurso médio em SrTiO 3 (l ph ~ 2 nm a 300 K), 11 nanoestruturação não é uma opção viável para a melhoria do desempenho TE de cerâmica grandes quantidades STO principalmente através da redução da condutividade térmica da estrutura. Recentemente, nós relataram melhora mais de 30% na termelétrica figura de mérito em não uniforme Pr-dopados SrTiO 3 cerâmica provenientes de um fator de potência termelétrica reforçada simultaneamente e condutividade térmica reduzida 12,13. Neste protocolo de vídeo detalhado, apresentamos e discutir os passos de nossa estratégia de síntese para a preparação destes Pr-dopado cerâmica STO que exibem melhores propriedades electrónicas e termoeléctricos.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>SrCO3 Powder, 99.9%</td>
			<td>Sigma Aldrich</td>
			<td>472018</td>
			<td></td>
		</tr>
		<tr>
			<td>TiO2 Nanopowder, 99.5%</td>
			<td>Sigma Aldrich</td>
			<td>718467</td>
			<td></td>
		</tr>
		<tr>
			<td>Pr2O3 Sintered Lumps, 99.9%</td>
			<td>Alfa Aesar</td>
			<td>35663&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Name of&#160; Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Spark Plasma Sintering&#160;</td>
			<td>Dr. Sinter Lab</td>
			<td>SPS-515S</td>
			<td></td>
		</tr>
		<tr>
			<td>Resistivity/Seebeck Coefficient Measurement System</td>
			<td>Ulvac-Riko</td>
			<td>ZEM-2</td>
			<td></td>
		</tr>
		<tr>
			<td>Laser Flash Thermal Diffusivity Measurement System</td>
			<td>Netzsch</td>
			<td>LFA-457 Microflash</td>
			<td></td>
		</tr>
		<tr>
			<td>Differential Scanning Calorimetry (DSC) System</td>
			<td>Netzsch</td>
			<td>404C Pegasus</td>
			<td></td>
		</tr>
		<tr>
			<td>Physical Property Measurement system (PPMS)</td>
			<td>Quantum Design</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Field Emission Scanning Electron Microscope (FE-SEM)</td>
			<td>Hitachi</td>
			<td>SU-6600</td>
			<td></td>
		</tr>
		<tr>
			<td>Energyy-dispersive X-ray Spectroscopy (EDS)</td>
			<td>Oxford Instruments</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>X-ray Diffractometer</td>
			<td>Rigaku</td>
			<td>Ultima IV</td>
			<td></td>
		</tr>
		<tr>
			<td>Bench-top Sputter Coater</td>
			<td>Denton Vacuum</td>
			<td>Desk II</td>
			<td></td>
		</tr>
		<tr>
			<td>Diamond&#160; Wheel Saw</td>
			<td>South Bay Technology</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

synthesis of non-uniformly pr-doped srtio3 ceramics and their thermoelectric properties

We demonstrate a novel synthesis strategy for the preparation of Pr-doped SrTiO3 ceramics via a combination of solid state reaction and spark plasma sintering techniques. Polycrystalline ceramics possessing a unique morphology can be achieved by optimizing the process parameters, particularly spark plasma sintering heating rate. The phase and morphology of the synthesized ceramics were investigated in detail using X-ray diffraction, scanning electron microcopy and energy-dispersive X-ray spectroscopy. It was observed that the grains of these bulk Pr-doped SrTiO3 ceramics were enhanced with Pr-rich grain boundaries. Electronic and thermal transport properties were also investigated as a function of temperature and doping concentration. Such a microstructure was found to give rise to improved thermoelectric properties. Specifically, it resulted in a significant improvement in carrier mobility and the thermoelectric power factor. Simultaneously, it also led to a marked reduction in the thermal conductivity. As a result, a significant improvement (> 30%) in the thermoelectric figure of merit was achieved for the whole temperature range over all previously reported maximum values for SrTiO3-based ceramics. This synthesis demonstrates the steps for the preparation of bulk polycrystalline ceramics of non-uniformly Pr-doped SrTiO3.

Padrões de difracção de raios-X foram recolhidos como para os pós preparados e as correspondentes massa cerâmica em função do conteúdo-Pr (Figura 1), a fim de estudar o efeito do Pr-dopagem na SrTiO 3 estrutura, a solubilidade do Pr em SrTiO 3 e a formação da fase secundária (s). Os padrões de confirmar a formação de SrTiO 3 fase em todos os pós preparados como onde as reflexões podem ser indexados para uma rede cúbica com grupo espacial (Figura ...

Watch this Scientific Journal Video about Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties at JoVE.com

Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties

A protocol for the synthesis and processing of polycrystalline SrTiO3 ceramics doped non-uniformly with Pr is presented along with the investigation of their thermoelectric properties.

Síntese de não-uniforme Pr-dopado SrTiO<sub&gt; 3</sub&gt; Cerâmica e suas propriedades termoelétricas

We demonstrate a novel synthesis strategy for the preparation of Pr-doped SrTiO3 ceramics via a combination of solid state reaction and spark plasma ...

synthesis-non-uniformly-pr-doped-srtio3-ceramics-their-thermoelectric

Research

JoVE Journal

Chemistry

Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties

9.7K visualizações.  Clemson University. A protocol for the synthesis and processing of polycrystalline SrTiO3 ceramics doped non-uniformly with Pr is presented along with the investigation of their thermoelectric properties.

Vídeo: Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties

Amide Coupling Reaction for the Synthesis of Bispyridine-based Ligands and Their Complexation to Platinum as Dinuclear Anticancer Agents

Amide coupling reactions can be used to synthesize bispyridine-based ligands for use as bridging linkers in multinuclear platinum anticancer drugs. Isonicotinic acid, or its derivatives, are coupled to variable length diaminoalkane chains under an inert atmosphere in anhydrous DMF or DMSO with the use of a weak base, triethylamine, and a coupling agent, 1-propylphosphonic anhydride. The products precipitate from solution upon formation or can be precipitated by the addition of water. If desired, the ligands can be further purified by recrystallization from hot water. Dinuclear platinum complex synthesis using the bispyridine ligands is done in hot water using transplatin. The most informative of the chemical characterization techniques to determine the structure and gross purity of both the bispyridine ligands and the final platinum complexes is 1H NMR with particular analysis of the aromatic region of the spectra (7-9 ppm). The platinum complexes have potential application as anticancer agents and the synthesis method can be modified to produce trinuclear and other multinuclear complexes with different hydrogen bonding functionality in the bridging ligand.

This protocol describes the use of amide coupling reactions of isonicotinic acid and diaminoalkanes to form bridging ligands suitable for use in the synthesis of multinuclear platinum complexes, which combine aspects of the anticancer drugs BBR3464 and picoplatin.

Acoplamento de amida de reacção para a síntese de ligandos baseados em Bispyridine e sua complexação com platina como agentes anticancerígenos dinucleares

Amide coupling reactions can be used to synthesize bispyridine-based ligands for use as bridging linkers in multinuclear platinum anticancer drugs. ...

Química

Synthesis and Characterization of Supramolecular Colloids

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

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

Síntese e Caracterização de Supramoleculares Colloids

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

Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level

We demonstrate a method for the synthesis of cyclic polymers and a protocol for characterizing their diffusive motion in a melt state at the single molecule level. An electrostatic self-assembly and covalent fixation (ESA-CF) process is used for the synthesis of the cyclic poly(tetrahydrofuran) (poly(THF)). The diffusive motion of individual cyclic polymer chains in a melt state is visualized using single molecule fluorescence imaging by incorporating a fluorophore unit in the cyclic chains. The diffusive motion of the chains is quantitatively characterized by means of a combination of mean-squared displacement (MSD) analysis and a cumulative distribution function (CDF) analysis. The cyclic polymer exhibits multiple-mode diffusion which is distinct from its linear counterpart. The results demonstrate that the diffusional heterogeneity of polymers that is often hidden behind ensemble averaging can be revealed by the efficient synthesis of the cyclic polymers using the ESA-CF process and the quantitative analysis of the diffusive motion at the single molecule level using the MSD and CDF analyses.

A protocol for the synthesis and characterization of diffusive motion of cyclic polymers at the single molecule level is presented.

Síntese de polímeros cíclicos e Caracterização do seu movimento difusivo no estado fundido na molécula de nível único

We demonstrate a method for the synthesis of cyclic polymers and a protocol for characterizing their diffusive motion in a melt state at the single ...

Synthesis and Characterization of Fe-doped Aluminosilicate Nanotubes with Enhanced Electron Conductive Properties

The goal of the protocol is to synthesize Fe-doped aluminosilicate nanotubes of the imogolite type with the formula (OH)3Al2-xFexO3SiOH. Doping with Fe aims at lowering the band gap of imogolite, an insulator with the chemical formula (OH)3Al2O3SiOH, and at modifying its adsorption properties towards azo-dyes, an important class of organic pollutants of both wastewater and groundwater.
Fe-doped nanotubes are obtained in two ways: by direct synthesis, where FeCl3 is added to an aqueous mixture of the Si and Al precursors, and by post-synthesis loading, where preformed nanotubes are put in contact with a FeCl3&#8226;6H2O aqueous solution. In both synthesis methods, isomorphic substitution of Al3+ by Fe3+ occurs, preserving the nanotube structure. Isomorphic substitution is indeed limited to a mass fraction of ~1.0% Fe, since at a higher Fe content (i.e., a mass fraction of 1.4% Fe), Fe2O3 clusters form, especially when the loading procedure is adopted. The physicochemical properties of the materials are studied by means of X-ray powder diffraction (XRD), N2 sorption isotherms at -196 &#176;C, high resolution transmission electron microscopy (HRTEM), diffuse reflectance (DR) UV-Vis spectroscopy, and &#950;-potential measurements. The most relevant result is the possibility to replace Al3+ ions (located on the outer surface of the nanotubes) by post-synthesis loading on preformed imogolite without perturbing the delicate hydrolysis equilibria occurring during nanotube formation. During the loading procedure, an anionic exchange occurs, where Al3+ ions on the outer surface of the nanotubes are replaced by Fe3+ ions. In Fe-doped aluminosilicate nanotubes, isomorphic substitution of Al3+ by Fe3+ is found to affect the band gap of doped imogolite. Nonetheless, Fe3+ sites on the outer surface of nanotubes are able to coordinate organic moieties, like the azo-dye Acid Orange 7, through a ligand-displacement mechanism occurring in an aqueous solution.

Here, we present a protocol to synthesize and characterize Fe-doped aluminosilicate nanotubes. The materials are obtained by either sol-gel synthesis upon addition of FeCl3&#8226;6H2O to the mixture containing the Si and Al precursors or by post-synthesis ionic exchange of preformed aluminosilicate nanotubes.

Síntese e Caracterização de Fe-dopado alumino nanotubos com propriedades condutoras aprimorados Electron

The goal of the protocol is to synthesize Fe-doped aluminosilicate nanotubes of the imogolite type with the formula (OH)3Al2-xFexO3SiOH. Doping with Fe ...

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

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

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

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

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

Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles

Bicyclic aziridinium ions were generated by the removal of an appropriate leaving group through internal nucleophilic attack by nitrogen atom in the aziridine ring. The utility of bicyclic aziridinium ions, specifically 1-azoniabicyclo[3.1.0]hexane and 1-azoniabicyclo[4.1.0]heptane tosylate highlighted in the aziridine ring openings by the nucleophile with the release of the ring strain to yield the corresponding ring-expanded azaheterocycles such as pyrrolidine, piperidine and azepane with diverse substituents on the ring in regio- and stereospecific manner. Herein, we report a simple and convenient method for the preparation of the stable 1-azabicyclo[4.1.0]heptane tosylate followed by selective ring opening via a nucleophilic attack either at the bridge or at the bridgehead carbon to yield piperidine and azepane rings, respectively. This synthetic strategy allowed us to prepare biologically active natural products containing piperidine and azepane motif including sedamine, allosedamine, fagomine and balanol in highly efficient manner.

Bicyclic aziridinium ions such as 1-azoniabicyclo[4.1.0]heptane tosylate were generated from 2-[4-tolenesulfonyloxybutyl]aziridine, which was utilized for the preparation of substituted piperidines and azepanes via regio- and stereospecific ring-expansion with various nucleophiles. This highly efficient protocol allowed us to prepare diverse azaheterocycles including natural products such as fagomine, febrifugine analogue and balanol.

Preparação de Íons Aziridínio Bicíclicos Estáveis e sua Abertura de Anel para a Síntese de Azaheterociclos

Bicyclic aziridinium ions were generated by the removal of an appropriate leaving group through internal nucleophilic attack by nitrogen atom in the ...

Synthesis of Substrate-Bound Au Nanowires Via an Active Surface Growth Mechanism

Advancing synthetic capabilities is important for the development of nanoscience and nanotechnology. The synthesis of nanowires has always been a challenge, as it requires asymmetric growth of symmetric crystals. Here, we report a distinctive synthesis of substrate-bound Au nanowires. This template-free synthesis employs thiolated ligands and substrate adsorption to achieve the continuous asymmetric deposition of Au in solution at ambient conditions. The thiolated ligand prevented the Au deposition on the exposed surface of the seeds, so the Au deposition only occurs at the interface between the Au seeds and the substrate. The side of the newly deposited Au nanowires is immediately covered with the thiolated ligand, while the bottom facing the substrate remains ligand-free and active for the next round of Au deposition. We further demonstrate that this Au nanowire growth can be induced on various substrates, and different thiolated ligands can be used to regulate the surface chemistry of the nanowires. The diameter of the nanowires can also be controlled with mixed ligands, in which another &#34;bad&#34; ligand could turn on the lateral growth. With the understanding of the mechanism, Au nanowire-based nanostructures can be designed and synthesized.

We report a solution-based method to synthesize substrate-bound Au nanowires. By tuning the molecular ligands used during the synthesis, the Au nanowires can be grown from various substrates with different surface properties. Au nanowire-based nanostructures can also be synthesized by adjusting the reaction parameters.

Síntese de nanofios de Au substrato ligados através de um mecanismo de crescimento ativo de superfície

Advancing synthetic capabilities is important for the development of nanoscience and nanotechnology. The synthesis of nanowires has always been a ...

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

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

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

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

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

Synthesis of In37P20(O2CR)51 Clusters and Their Conversion to InP Quantum Dots

This text presents a method for the synthesis of In37P20(O2C14H27)51 clusters and their conversion to indium phosphide quantum dots. The In37P20(O2CR)51 clusters have been observed as intermediates in the synthesis of InP quantum dots from molecular precursors (In(O2CR)3, HO2CR, and P(SiMe3)3) and may be isolated as a pure reagent for subsequent study and use as a single-source precursor. These clusters readily convert to crystalline and relatively monodisperse samples of quasi-spherical InP quantum dots when subjected to thermolysis conditions in the absence of additional precursors above 200 &#176;C. The optical properties, morphology, and structure of both the clusters and quantum dots are confirmed using UV-Vis spectroscopy, photoluminescence spectroscopy, transmission electron microscopy, and powder X-ray diffraction. The molecular symmetry of the clusters is additionally confirmed by solution-phase 31P NMR spectroscopy. This protocol demonstrates the preparation and isolation of atomically-precise InP clusters, and their reliable and scalable conversion to InP QDs.

Synthesis of In37P20O2CR51 Clusters and Their Conversion to InP Quantum Dots

A protocol for the synthesis of In37P20(O2C14H27)51 clusters and their conversion to indium phosphide quantum dots is presented.

Síntese de37P20(O2CR)51 clusters e sua conversão para pontos Quantum INP

This text presents a method for the synthesis of In37P20(O2C14H27)51 clusters and their conversion to indium phosphide quantum dots. The In37P20(O2CR)51 ...

Design, Synthesis, and Photochemical Properties of Clickable Caged Compounds

Caged compounds enable the photo-mediated manipulation of the cell physiology with high spatiotemporal resolution. However, the limited structural diversity of currently available caging groups and the difficulties in synthetic modification without sacrificing their photolysis efficiencies are obstacles to expanding the repertoire of caged compounds for live cell applications. As the chemical modification of coumarin-type photo-caging groups is a promising approach for the preparation of caged compounds with diverse physical and chemical properties, we report a method for the synthesis of clickable caged compounds that can be modified easily with various functional units via the copper(I)-catalyzed Huisgen cyclization. The modular platform molecule contains a (6-bromo-7-hydroxycoumarin-4-yl)methyl (Bhc) group as a photo-caging group, which exhibits a high photolysis efficiency compared to those of the conventional 2-nitrobenzyls. General procedures for the preparation of clickable caged compounds containing amines, alcohols, and carboxylates are presented. Additional properties such as the water solubility and cell targeting ability can be readily incorporated into clickable caged compounds. Furthermore, the physical and photochemical properties, including the photolysis quantum yield, were measured and were found to be superior to those of the corresponding Bhc caged compounds. The described protocol could therefore be considered a potential solution for the lack of structural diversity in the available caged compounds.

A protocol for the synthesis and measurement of the photochemical properties of modular caged compounds with clickable moieties is presented.