Name: synthesis of cd-free inp/zns quantum dots suitable for biomedical applications
Uploaded: 2016-02-06T14:00:00.000+00:00
Duration: 10 min 56 s
Description: Watch this Scientific Journal Video about Synthesis of Cd-free InP/ZnS Quantum Dots Suitable for Biomedical Applications at JoVE.com

Os autores agradecem o Departamento de Química e da Faculdade de Pós-Graduação da Universidade Estadual do Missouri para o seu apoio a este projeto. Reconhecemos também o Electron Microscopy Laboratório do Laboratório Nacional Frederick para Pesquisa do Câncer para o uso de seu microscópio eletrônico de transmissão e redes revestidas de carbono.

1. Síntese de fosfeto de índio / Zinc Sulfide (INP / ZnS) Quantum Dots <ol><li> Síntese de fosfeto de índio (InP) Quantum Dot Cores <ol><li> Caber um fundo redondo de 100 ml, 3-neck, garrafa com um condensador de 12 polegadas. Adicionar 30 ml de oleilamina (OLA), cloreto de 0,398 g de índio (III) (incl 3), (II), cloreto de 0,245 g de zinco (ZnCl2) e agita-se durante a evacuação, à TA utilizando um vácuo durante 1 hora. A solução deve aparecer incolor com um precipitado branco. </li><li> Usando uma manta de aquecimento, com um termopar e controlador de temperatura proporcional-integral-derivativo (PID), aumentar a temperatura da solução a 120 ° C. Evacuar a solução sob vácuo durante 20 min para remover as impurezas de baixo ponto de ebulição que podem afectar o crescimento do núcleo. Nota: Embora seja possível utilizar um banho de areia e termómetro, usando uma manta de aquecimento e PID aumenta a uniformidade e a reprodutibilidade dos produtos da reacção. </li><li> Sob um gás inerte (por exemplo,, N2), refluxo a solução e aumentar a temperatura para 220 ° C durante 15 min. O InCl3 e ZnCl2 dissolver completamente, resultando numa solução amarelo pálida. Permitir que a temperatura estabilize, durante 10 min. </li><li> Purgar a, 3 ml seringa de plástico descartável e 4 polegadas, 22 G agulha com gás nitrogênio. Usando a seringa, para entregar rapidamente 0,5 ml de tris (dimetilamino) fosfina (TDMAP) à solução de InCl3. A temperatura da solução diminui ligeiramente e retorna a 220 ° C. A solução muda de transparente, amarelo pálido a opaco, preto. </li><li> Após 9,5 min, remover o balão de reacção a partir da manta de aquecimento até que a temperatura diminui abaixo de 200 ° C. Para proteger a integridade dos núcleos de InP, seguir diretamente para a etapa de revestimento de ZnS em 1.2.1. </li></ol></li><li> Síntese de Sulfeto de zinco Conchas (ZnS) quantum dot <ol><li> Colocar o balão de reacção a partir do passo 1.1.5 em uma manta de aquecimento e estabilizar o temperatura a 200 ° C. Adiciona-se lentamente 3,58 g dodecanotiol (DDT) ao longo de 15 seg para a solução contendo InP QDs. Permitir que a solução reagir durante 1 h. Nota: a espessura da casca de ZnS pode ser variado aumentando ou diminuindo a quantidade de estearato de zinco adicionado no passo 1.2.4. Alterando a quantidade de ZnCl2 ou dodecanotiol em passos 1.1.1 e 1.2.1 podem ter impacto significativo na qualidade de QDs alterando a cinética da reacção. <ol><li> Depois, remover o balão de reacção a partir da manta de aquecimento e deixar a solução arrefecer até cerca de 60 ° C. </li></ol></li><li> Uma vez que a solução de InP / ZnS atinge ~ 60 ° C, adicionar 10 ml de hexanos e transferir toda a solução de cerca de 45 ml para um tubo de centrífuga de polipropileno de 50 ml. Centrifugar a amostra (3000 xg durante 10 min) para remover os precursores sólidos que não reagiram. </li><li> Transferir cuidadosamente o sobrenadante para um frasco de 250 ml de centrífuga de polipropileno, adicionar 200 ml de acetona, e a solução de centrífuga (3.000 xg durante 10 min) para precipitar QDs InP / ZnS. Este volume também pode ser dividido uniformemente em quatro tubos de 50 ml para centrifugação se uma centrífuga com as necessárias rotor / acessórios não está disponível. Decantar o sobrenadante e o sedimento secar QD cuidadosamente com azoto gasoso para remover a acetona. </li><li> Volte a suspender as QDs em 20 ml OLA usando sonicação, transferir para um fundo redondo de 50 ml, 3-pescoço, frasco contendo 0,474 g estearato de zinco, e mexa. Evacuar a solução sob vácuo durante 20 min à temperatura ambiente. </li><li> Sob atmosfera de azoto, aumentar a temperatura para 180 ° C e deixar a reacção prosseguir durante 3 horas. Embora não existam alterações visuais perceptíveis à solução de reacção que ocorrem durante esta reacção, a adição de estearato de zinco aumenta a espessura da casca de ZnS, aumentando, assim, QY, melhorando a passivação de superfície 12. QDs. Uma vez que a reacção está completa, remover o balão da manta de aquecimento e deixar a solução arrefecer até cerca de 60 ° C. </li><li> Uma vez que a solução que InP / ZnSno ~ atinge 60 ° C, adicionar 20 ml de hexanos e transferir para um tubo de centrífuga de polipropileno de 50 ml. Centrifugar a amostra (3000 xg durante 10 min) para remover o estearato de zinco que não reagiu. </li><li> Transferir cuidadosamente o sobrenadante para um frasco de centrífuga de polipropileno de 250 ml, adicionar 200 ml de acetona, e centrifuga-se a solução (3000 xg durante 10 min) para precipitar InP / ZnS QDs. Cuidadosamente decantar o sobrenadante e completamente seco com azoto gasoso para remover a acetona. </li><li> Dissolve-se o sedimento InP / ZnS QD em 30 ml de hexano. Vortex e sonicar a solução rapidamente para assegurar a dispersão completa. </li><li> Repita os passos de purificação 1.2.6-1.2.8 mais duas vezes para assegurar a remoção completa do excesso de ligandos orgânicos. As interacções entre o polímero anfifílico e o QD na etapa 1.2 pode ser comprometida, na presença de ligandos em excesso. </li><li> Com cálculos detalhado por Xie, et al. 16, determinar o tamanho ea concentração dos QDs InP / ZnS sintetizados usando UV-Vis. <br/&gt; Nota: A característica espectral importante para esta análise é o ombro do pico de absorção. O valor do comprimento de onda e da absorvância máxima deste ombro é utilizada para calcular o tamanho e a concentração dos QDs, respectivamente. Esta reacção produz tipicamente cerca de 5 umol de QDs com um pico de emissão a 600 nm. Para sintetizar QDs de cores diferentes, a duração e / ou a temperatura da reacção pode ser alterada. Um maior tempo de reacção e / ou temperatura mais elevada dos resultados solução num pico de emissão vermelho-deslocado. Por exemplo, aumentando a temperatura da reacção a 240 ° C e mantendo o tempo de reacção de 10 min irá resultar em QDs com um pico de 680 nm no máximo as emissões. Da mesma forma, reduzindo o tempo de reacção de 2 min e dobrando o cloreto de zinco utilizado irá resultar em QDs com um pico de emissão máxima 470 nm. Estes QDs InP / ZnS são estáveis ​​durante pelo menos um mês a 4 ° C no escuro sob atmosfera de gás inerte. </li></ol></li></ol> 2. águaSolubilização de InP / ZnS Quantum Dots Usando um polímero anfifílico <ol><li> A solubilização de água <ol><li> Usando os QDs InP / ZnS do passo 1.2.10, diluir uma parte dos QDs com hexanos para se obter 1 ml de 1 uM QDs. <ol><li> Num tubo de centrífuga, transferir 0,25 ml de InP / ZnS QDs em cada tubo. Adicionar 1 ml de acetona ou metanol para o tubo de centrífuga e centrifuga-se (3000 xg durante 10 min). remover cuidadosamente o sobrenadante e dissolve-se cada um precipitado em 1 ml de tetra-hidrofurano (THF). </li><li> Transfira os QDs InP / ZnS dissolvidos em THF em um frasco de 100 ml de fundo redondo e diluir com 16 ml THF. Para reduzir o número de agregados em solução, sonicar as QDs durante 5-10 min. </li></ol></li><li> Dissolve-se 30 mg de poli (maleico alt andhydride- -1-octadeceno), 3- (dimetilamino) -1-propilamina (PMAL-d) em 10 ml de água de grau molecular. Banho-maria de ultra-sons ou agitação suave até a solução estar translúcida é suficiente para dissolver completamente o polímero. outilização de vortex ou agitação vigorosa pode produzir muitas bolhas, o que dificulta a interacção do polímero com o QD. Adicionar a solução de polímero de 10 ml para os 100 ml balão de fundo redondo contendo InP / ZnS QDs em THF. </li><li> Evapora-se a solução de THF de QD / polímero utilizando um evaporador rotativo. Colocar o balão num banho de gelo enquanto evaporação para facilitar a interacção entre o polímero e QD. Dependendo da força do vácuo, a maioria de THF é evaporado após 10 minutos e a solução aparece turvo. <ol><li> Uma vez que a solução é evaporada para 10 ml, retirar o balão do evaporador rotativo e adicionar 30 ml de água de grau molecular. Devolver o balão no evaporador rotativo e continuar a evaporar-se a 2 ml. Esta etapa evaporação final pode levar várias horas; assegurar o banho de gelo é mantida. </li></ol></li><li> Remover os QDs InP / ZnS solúveis em água a partir do balão de fundo redondo com uma pipeta. Filtra-se a solução QD utilizando uma seringa de plástico de 3 ml ligado a um SY de nylon de 0,1 umRinge filtrar para um tubo de centrífuga de 5 ml. </li><li> Coloque as QDs em uma unidade de diálise de membrana de MWCO 20000 e diálise contra tampão de borato 0,05 M pH 8,5 para remover o excesso de polímero. (Lentamente adicionar tetraborato decahidrato de sódio 0,05 M a 0,05 M de ácido bórico, com agitação vigorosa, até que o pH é de 8,5 a tornar esta solução tampão de borato.) Utilizando um concentrador de vácuo, concentrar os QDs em tampão de borato a 1 ml. </li><li> Para o armazenamento, purgar a solução com azoto antes da selagem com Parafilm. Os QDs InP / ZnS solúveis em água são estáveis ​​durante pelo menos 4 meses a 4 ° C no escuro. </li></ol></li></ol>

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Este protocolo detalha a síntese das altamente fluorescentes QDs InP / ZnS que podem ser utilizados em muitos sistemas biológicos. Os produtos sintetizados QD aqui exibiu um único pico de emissão de fluorescência centrada a 600 nm com um FWHM de 73 nm (Figura 1), que é comparável a outras sínteses descritas anteriormente 12. O tempo de reacção e temperatura da reacção são extremamente passos cruciais, devido ao seu profundo efeito sobre a qualidade de síntese QD e repetibilidade...

A correction was made to: <a href="http://www.jove.com/video/53684/synthesis-cd-free-inpzns-quantum-dots-suitable-for-biomedical" target="_blank">Synthesis of Cd-free InP/ZnS Quantum Dots Suitable for Biomedical Applications</a>. There was an error with an author's given name. The author's name was corrected to:
Katye M. Fichter
from:
Kathryn M. Fichter

A correction was made to: <a href="http://www.jove.com/video/53684/synthesis-cd-free-inpzns-quantum-dots-suitable-for-biomedical" target="_blank">Synthesis of Cd-free InP/ZnS Quantum Dots Suitable for Biomedical Applications</a>.

Erratum: Synthesis of Cd-free InP/ZnS Quantum Dots Suitable for Biomedical Applications

Os pontos quânticos (QDs) são semicondutor nanocristais que exibem propriedades fluorescentes quando irradiado com luz 1. Devido ao seu pequeno tamanho (2-5 nm), que é semelhante a muitas biomoléculas grandes, e facilidade de biofunctionalization, QDs são uma ferramenta extremamente atraente para aplicações biomédicas. Eles têm encontrado utilização na rotulagem biológica, imagem única molécula-célula viva, a entrega de drogas, imagem in vivo, detecção de patógenos e rastreamento de celular, entre muitos outros usos 2-8. QDs baseada em CD foram mais comumente usados ​​em aplicações biomédicas devido à sua intensa fluorescência e larguras de pico de emissão estreitas 9. No entanto, as preocupações foram levantadas devido ao potencial de toxicidade do Cd 2+ 10 que pode ser introduzida através da degradação das nanopartículas. Recentemente, QDs baseados em InP têm sido explorados como uma alternativa para QDs baseadas em CD porque eles mantêm muitas características de fluorescênciade QDs Cd-baseado e pode ser mais biocompatível 11. QDs baseadas em CD foram encontrados para ser significativamente mais tóxica do que QDs baseados em InP em ensaios in vitro para concentrações tão baixas quanto 10 pM, após apenas 48 h 11. A cor de emissão de fluorescência de QDs é tamanho-ajustável 1. Isto é, como o tamanho das QD aumenta, a emissão de fluorescência é vermelho-deslocado. O tamanho e dimensão dispersibilidade dos produtos QD pode ser modificada alterando a temperatura, duração da reacção, ou em condições de concentração de precursor durante a reacção 12. Embora o pico de emissão de InP QDs é tipicamente mais ampla e menos intensa do que QDs baseadas em CD, InP QDs pode ser feita numa grande variedade de cores, destinadas a evitar sobreposição espectral, e são suficientemente intensa para a maioria das aplicações biomédicas 12. A síntese detalhada neste protocolo produz QDs com um pico de emissão vermelha centrado em 600 nm. Várias medidas são tomadas afsíntese ter dos núcleos QD para manter a integridade óptica dos QDs e torná-los compatíveis para aplicações biológicas. A superfície do núcleo QD deve ser protegida contra a oxidação ou defeitos superficiais, que podem causar têmpera; portanto, uma concha ZnS é revestido sobre o núcleo para produzir InP / ZnS (core / shell) qds 13. Este revestimento tem sido demonstrado para proteger o fotoluminescência do produto QD. A presença de iões de zinco, durante a síntese InP QD foi mostrado para limitar os defeitos de superfície, bem como a distribuição do tamanho de redução 12. Mesmo com a presença de Zn2 + no meio de reacção, a síntese de InZnP são altamente improvável 12. Depois do revestimento, resultantes QDs InP / ZnS são revestidos em ligandos hidrofóbicos, tais como o óxido de trioctilfosfina (TOPO) ou oleilamina 12,14. Um polímero anfifílico pode interagir com ligandos hidrófobos na superfície do QD, bem como moléculas de água em massa para conferir solubilidade em água 15. polímeros anfifílicos com carbogrupos químicos xylate pode ser utilizado como &quot;alças&quot; químicas para funcionalizar ainda mais os QDs. Este protocolo detalha a síntese e funcionalização de solúveis em água InP / ZnS QDs com emissão de fluorescência muito intenso e relativamente pequeno em tamanho dispersity. Estes QDs são potencialmente menos tóxico do que QDs CdSe / ZnS vulgarmente utilizados. Nisto, a síntese de InP / ZnS QDs fornece uma alternativa prática para QDs baseadas em CD para aplicações biomédicas.

<table><tbody><tr><td>Oleylamine</td><td>Acros</td><td>129540010</td><td></td></tr><tr><td>Zinc(II) chloride</td><td>Sigma</td><td>030-003-00-2</td><td></td></tr><tr><td>Indium(III) chloride</td><td>Chem-Impex</td><td>24560</td><td></td></tr><tr><td>Tris(dimethylamino)phosphine</td><td>Encompass</td><td>50-901-10500</td><td></td></tr><tr><td>1-dodecanethiol</td><td>Acros</td><td>117625000</td><td></td></tr><tr><td>Hexanes</td><td>Fisher Sci</td><td>H292-4</td><td></td></tr><tr><td>Acetone</td><td>TransChemical</td><td>UN 1090</td><td></td></tr><tr><td>Zinc Stearate</td><td>Aldrich Chem</td><td>307564-1KG</td><td></td></tr><tr><td>Tetrahydrofuran</td><td>Acros</td><td>34845-0010</td><td></td></tr><tr><td>Molecular Water</td><td>Fisher Sci</td><td>BP2470-1</td><td></td></tr><tr><td>Poly(maleic anhyrdride-&lt;em&gt;alt&lt;/em&gt;-1-tetradecene), 3-(dimethylamino)-1-propylamine derivative</td><td>Sigma</td><td>90771-1G</td><td></td></tr><tr><td>Boric acid</td><td>Fisher Sci</td><td>BP168-500</td><td></td></tr><tr><td>Sodium Tetraborate Decahydrate</td><td>Fisher Sci</td><td>BP175-500</td><td></td></tr><tr><td>Rhodamine B</td><td>Aldrich Chem</td><td>R95-3</td><td></td></tr><tr><td>Nitrogen gas</td><td>Airgas</td><td>UN1066</td><td></td></tr><tr><td>Trypan blue</td><td>Thermo Sci</td><td>SV30084.01</td><td></td></tr><tr><td>3 ml plastic Luer-lock syringe</td><td>BD</td><td>309657</td><td></td></tr><tr><td>Luer-lock Needle</td><td>Air-Tite</td><td>8300014471</td><td>4 inch, 22 gauge</td></tr><tr><td>50 ml polypropyene centrifuge tube</td><td>Falcon</td><td>352098</td><td></td></tr><tr><td>250 ml centrifuge bottle</td><td>Thermo Sci</td><td>05-562-23</td><td>Nalgene PPCO</td></tr><tr><td>5 ml centrifuge tubes</td><td>Argos-Tech</td><td>T2076</td><td></td></tr><tr><td>1.5 ml microcentrifuge tubes</td><td>Bio Plas</td><td>4150</td><td></td></tr><tr><td>0.1 &amp;mu;m Syringe filter</td><td>Whatman</td><td>6786-1301</td><td>Puradisc 13 mm nylon filter</td></tr><tr><td>Slide-A-Lyzer MINI Dialysis Unit</td><td>Thermo Sci</td><td>69590</td><td>20,000 MWCO</td></tr><tr><td>Rotary Evaporator</td><td>Heidolph</td><td></td><td></td></tr><tr><td>Centrifuge 5072</td><td>Eppendorf</td><td></td><td>Swinging Bucket with 50&amp;nbsp;ml tube adapters</td></tr><tr><td>Lambda 650 UV/VIS Spectrometer</td><td>Perkin Elmer</td><td></td><td>UV-Vis Spectrophotometer</td></tr><tr><td>LS 55 Fluorescence Spectrometer</td><td>Perkin Elmer</td><td></td><td>Fluorometer</td></tr><tr><td>Axio Observer.A1</td><td>Zeiss</td><td></td><td>epifluorescence microscope</td></tr><tr><td>AxioCam MRm</td><td>Zeiss</td><td></td><td>CCD Camera</td></tr><tr><td>Tecnai TF20 Microscope</td><td>FEI</td><td></td><td>Transmisison Electron Miscroscope</td></tr><tr><td>TEM Eagle CCD</td><td>FEI</td><td></td><td>TEM CCD Camera</td></tr><tr><td>NanoBrook Omni DLS</td><td>Brookhaven</td><td></td><td>Dynamic Light Scattering Instrument</td></tr></tbody></table>

synthesis of cd-free inp/zns quantum dots suitable for biomedical applications

Fluorescent nanocrystals, specifically quantum dots, have been a useful tool for many biomedical applications. For successful use in biological systems, quantum dots should be highly fluorescent and small/monodisperse in size. While commonly used cadmium-based quantum dots possess these qualities, they are potentially toxic due to the possible release of Cd2+ ions through nanoparticle degradation. Indium-based quantum dots, specifically InP/ZnS, have recently been explored as a viable alternative to cadmium-based quantum dots due to their relatively similar fluorescence characteristics and size. The synthesis presented here uses standard hot-injection techniques for effective nanoparticle growth; however, nanoparticle properties such as size, emission wavelength, and emission intensity can drastically change due to small changes in the reaction conditions. Therefore, reaction conditions such temperature, reaction duration, and precursor concentration should be maintained precisely to yield reproducible products. Because quantum dots are not inherently soluble in aqueous solutions, they must also undergo surface modification to impart solubility in water. In this protocol, an amphiphilic polymer is used to interact with both hydrophobic ligands on the quantum dot surface and bulk solvent water molecules. Here, a detailed protocol is provided for the synthesis of highly fluorescent InP/ZnS quantum dots that are suitable for use in biomedical applications.

Os núcleos de InP não revestidos não demonstram fluorescência visível substancial a olho nu. No entanto, InP / ZnS (core / shell) pontos quânticos parecem apresentam forte fluorescência por olho sob irradiação UV. A fluorescência de InP / ZnS QDs foi caracterizado usando espectroscopia de fluorescência. O espectro de fluorescência de QDs em hexanos (Figura 1) excitado a 533 nm demonstra um pico principal centrado a 600 nm com uma largura total a meia altura (...

Watch this Scientific Journal Video about Synthesis of Cd-free InP/ZnS Quantum Dots Suitable for Biomedical Applications at JoVE.com

Synthesis of Cd-free InP/ZnS Quantum Dots Suitable for Biomedical Applications

In this protocol, the synthesis of Cd-free InP/ZnS quantum dots (QDs) is detailed. InP-based QDs are gaining popularity due to the toxicity of Cd2+ ions that may be released through nanoparticle degradation. After synthesis, QDs are solubilized in water using an amphiphilic polymer for use in biomedical applications.

Síntese de Cd-livre InP / ZnS Quantum Dots Indicado para aplicações biomédicas

Fluorescent nanocrystals, specifically quantum dots, have been a useful tool for many biomedical applications. For successful use in biological systems, ...

synthesis-cd-free-inpzns-quantum-dots-suitable-for-biomedical

Research

JoVE Journal

Chemistry

13.6K visualizações.  Missouri State University. In this protocol, the synthesis of Cd-free InP/ZnS quantum dots (QDs) is detailed. InP-based QDs are gaining popularity due to the toxicity of Cd2+ ions that may be released through nanoparticle degradation. After synthesis, QDs are solubilized in water using an amphiphilic polymer for use in biomedical applications.

Vídeo: Synthesis of Cd-free InP/ZnS Quantum Dots Suitable for Biomedical Applications

Compact Quantum Dots for Single-molecule Imaging

Single-molecule imaging is an important tool for understanding the mechanisms of biomolecular function and for visualizing the spatial and temporal heterogeneity of molecular behaviors that underlie cellular biology 1-4. To image an individual molecule of interest, it is typically conjugated to a fluorescent tag (dye, protein, bead, or quantum dot) and observed with epifluorescence or total internal reflection fluorescence (TIRF) microscopy. While dyes and fluorescent proteins have been the mainstay of fluorescence imaging for decades, their fluorescence is unstable under high photon fluxes necessary to observe individual molecules, yielding only a few seconds of observation before complete loss of signal. Latex beads and dye-labeled beads provide improved signal stability but at the expense of drastically larger hydrodynamic size, which can deleteriously alter the diffusion and behavior of the molecule under study.
Quantum dots (QDs) offer a balance between these two problematic regimes. These nanoparticles are composed of semiconductor materials and can be engineered with a hydrodynamically compact size with exceptional resistance to photodegradation 5. Thus in recent years QDs have been instrumental in enabling long-term observation of complex macromolecular behavior on the single molecule level. However these particles have still been found to exhibit impaired diffusion in crowded molecular environments such as the cellular cytoplasm and the neuronal synaptic cleft, where their sizes are still too large 4,6,7.
Recently we have engineered the cores and surface coatings of QDs for minimized hydrodynamic size, while balancing offsets to colloidal stability, photostability, brightness, and nonspecific binding that have hindered the utility of compact QDs in the past 8,9. The goal of this article is to demonstrate the synthesis, modification, and characterization of these optimized nanocrystals, composed of an alloyed HgxCd1-xSe core coated with an insulating CdyZn1-yS shell, further coated with a multidentate polymer ligand modified with short polyethylene glycol (PEG) chains (Figure 1). Compared with conventional CdSe nanocrystals, HgxCd1-xSe alloys offer greater quantum yields of fluorescence, fluorescence at red and near-infrared wavelengths for enhanced signal-to-noise in cells, and excitation at non-cytotoxic visible wavelengths. Multidentate polymer coatings bind to the nanocrystal surface in a closed and flat conformation to minimize hydrodynamic size, and PEG neutralizes the surface charge to minimize nonspecific binding to cells and biomolecules. The end result is a brightly fluorescent nanocrystal with emission between 550-800 nm and a total hydrodynamic size near 12 nm. This is in the same size range as many soluble globular proteins in cells, and substantially smaller than conventional PEGylated QDs (25-35 nm).

We describe the preparation of colloidal quantum dots with minimized hydrodynamic size for single-molecule fluorescence imaging. Compared to conventional quantum dots, these nanoparticles are similar in size to globular proteins and are optimized for single-molecule brightness, stability against photodegradation, and resistance to nonspecific binding to proteins and cells.

Compactas pontos quânticos para uma única molécula de imagem

Single-molecule imaging is an important tool for  understanding the mechanisms of biomolecular function and for visualizing the  spatial and temporal ...

Engenharia

Seeded Synthesis of CdSe/CdS Rod and Tetrapod Nanocrystals

We demonstrate a method for the synthesis of multicomponent nanostructures consisting of CdS and CdSe with rod and tetrapod morphologies. A seeded synthesis strategy is used in which spherical seeds of CdSe are prepared first using a hot-injection technique. By controlling the crystal structure of the seed to be either wurtzite or zinc-blende, the subsequent hot-injection growth of CdS off of the seed results in either a rod-shaped or tetrapod-shaped nanocrystal, respectively. The phase and morphology of the synthesized nanocrystals are confirmed using X-ray diffraction and transmission electron microscopy, demonstrating that the nanocrystals are phase-pure and have a consistent morphology. The extinction coefficient and quantum yield of the synthesized nanocrystals are calculated using UV-Vis absorption spectroscopy and photoluminescence spectroscopy. The rods and tetrapods exhibit extinction coefficients and quantum yields that are higher than that of the bare seeds. This synthesis demonstrates the precise arrangement of materials that can be achieved at the nanoscale by using a seeded synthetic approach.

A protocol for the seeded synthesis of rod-shaped and tetrapod-shaped multicomponent nanostructures consisting of CdS and CdSe is presented.

Semeado Síntese de CdSe / CdS Rod e tetrápodes Nanocristais

We demonstrate a method for the synthesis of multicomponent nanostructures consisting of CdS and CdSe with rod and tetrapod morphologies. A seeded ...

Química

Synthesis, Characterization, and Functionalization of Hybrid Au/CdS and Au/ZnS Core/Shell Nanoparticles

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large extinction coefficients which can be tuned across the visible spectrum. Research into the plasmonic enhancement of optical transitions has become popular, due to the possibility of altering and in some cases improving photo-absorption or emission properties of nearby chromophores such as molecular dyes or quantum dots. The electric field of the plasmon can couple with the excitation dipole of a chromophore, perturbing the electronic states involved in the transition and leading to increased absorption and emission rates. These enhancements can also be negated at close distances by energy transfer mechanism, making the spatial arrangement of the two species critical. Ultimately, enhancement of light harvesting efficiency in plasmonic solar cells could lead to thinner and, therefore, lower cost devices. The development of hybrid core/shell particles could offer a solution to this issue. The addition of a dielectric spacer between a gold nanoparticles and a chromophore is the proposed method to control the exciton plasmon coupling strength and thereby balance losses with the plasmonic gains. A detailed procedure for the coating of gold nanoparticles with CdS and ZnS semiconductor shells is presented. The nanoparticles show high uniformity with size control in both the core gold particles and shell species allowing for a more accurate investigation into the plasmonic enhancement of external chromophores.

The synthesis of uniform gold nanoparticles coated with semiconductor shells of CdS or ZnS is performed. The semiconductor coating is conducted by first depositing a silver sulfide shell and exchanging the silver cations for zinc or cadmium cations.

Síntese, caracterização e funcionalização de híbrida UA / CDS e Au / ZnS Núcleo / Shell Nanopartículas

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large ...

Solubilization and Bio-conjugation of Quantum Dots and Bacterial Toxicity Assays by Growth Curve and Plate Count

Quantum dots (QDs) are fluorescent semiconductor nanoparticles with size-dependent emission spectra that can be excited by a broad choice of wavelengths. QDs have attracted a lot of interest for imaging, diagnostics, and therapy due to their bright, stable fluorescence1,2 3,4,5. QDs can be conjugated to a variety of bio-active molecules for binding to bacteria and mammalian cells6.
QDs are also being widely investigated as cytotoxic agents for targeted killing of bacteria. The emergence of multiply-resistant bacterial strains is rapidly becoming a public health crisis, particularly in the case of Gram negative pathogens 7. Because of the well-known antimicrobial effect of certain nanomaterials, especially Ag, there are hundreds of studies examining the toxicity of nanoparticles to bacteria 8. Bacterial studies have been performed with other types of semiconductor nanoparticles as well, especially TiO2 9,10-11, but also ZnO12 and others including CuO 13. Some comparisons of bacterial strains have been performed in these studies, usually comparing a Gram negative strain with a Gram positive. With all of these particles, mechanisms of toxicity are attributed to oxidation: either the photogeneration of reactive oxygen species (ROS) by the particles or the direct release of metal ions that can cause oxidative toxicity. Even with these materials, results of different studies vary greatly. In some studies the Gram positive test strain is reportedly more sensitive than the Gram negative 10; in others it is the opposite 14. These studies have been well reviewed 15.
In all nanoparticle studies, particle composition, size, surface chemistry, sample aging/breakdown, and wavelength, power, and duration of light exposure can all dramatically affect the results. In addition, synthesis byproducts and solvents must be considered16 17. High-throughput screening techniques are needed to be able to develop effective new nanomedicine agents.
CdTe QDs have anti-microbial effects alone18 or in combination with antibiotics. In a previous study, we showed that coupling of antibiotics to CdTe can increase toxicity to bacteria but decrease toxicity to mammalian cells, due to decreased production of reactive oxygen species from the conjugates19. Although it is unlikely that cadmium-containing compounds will be approved for use in humans, such preparations could be used for disinfection of surfaces or sterilization of water.
In this protocol, we give a straightforward approach to solubilizing CdTe QDs with mercaptopropionic acid (MPA). The QDs are ready to use within an hour. We then demonstrate coupling to an antimicrobial agent.
The second part of the protocol demonstrates a 96-well bacterial inhibition assay using the conjugated and unconjugated QDs. The optical density is read over many hours, permitting the effects of QD addition and light exposure to be evaluated immediately as well as after a recovery period. We also illustrate a colony count for quantifying bacterial survival.

Nanoparticles such as semiconductor quantum dots (QDs) can be used to create photoactivatable agents for anti-microbial or anti-cancer applications. This technique shows how to water-solubilize cadmium telluride (CdTe) QDs, conjugate them to an antibiotic, and perform a bacterial inhibition assay based upon growth curves and plate count.

Solubilização e Bio conjugação de pontos quânticos e ensaios de toxicidade bacterianas por curva de crescimento e Contagem

Quantum dots (QDs) are fluorescent semiconductor nanoparticles with size-dependent emission spectra that can be excited by a broad choice of wavelengths. ...

Bioengenharia

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

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

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

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

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

Enhanced Electron Injection and Exciton Confinement for Pure Blue Quantum-Dot Light-Emitting Diodes by Introducing Partially Oxidized Aluminum Cathode

Stable and efficient red (R), green (G), and blue (B) light sources based on solution-processed quantum dots (QDs) play important roles in next-generation displays and solid-state lighting technologies. The brightness and efficiency of blue QDs-based light-emitting diodes (LEDs) remain inferior to their red and green counterparts, due to the inherently unfavorable energy levels of different colors of light. To solve these problems, a device structure should be designed to balance the injection holes and electrons into the emissive QD layer. Herein, through a simple autoxidation strategy, pure blue QD-LEDs which are highly bright and efficient are demonstrated, with a structure of ITO/PEDOT:PSS/Poly-TPD/QDs/Al:Al2O3. The autoxidized Al:Al2O3 cathode can effectively balance the injected charges and enhance radiative recombination without introducing an additional electron transport layer (ETL). As a result, high color-saturated blue QD-LEDs are achieved with a maximum luminance over 13,000 cd m-2, and a maximum current efficiency of 1.15 cd A-1. The easily controlled autoxidation procedure paves the way for achieving high-performance blue QD-LEDs.

A protocol is presented for fabricating high-performance, pure blue ZnCdS/ZnS-based quantum dots light-emitting diodes by employing an autoxidized aluminum cathode.

Injeção eletrônica avançada e confinamento Exciton para ponto quântico puro azul diodos emissores de luz introduzindo parcialmente oxidado alumínio cátodo

Stable and efficient red (R), green (G), and blue (B) light sources based on solution-processed quantum dots (QDs) play important roles in next-generation ...

Production and Targeting of Monovalent Quantum Dots

The multivalent nature of commercial quantum dots (QDs) and the difficulties associated with producing monovalent dots have limited their applications in biology, where clustering and the spatial organization of biomolecules is often the object of study. We describe here a protocol to produce monovalent quantum dots (mQDs) that can be accomplished in most biological research laboratories via a simple mixing of CdSe/ZnS core/shell QDs with phosphorothioate DNA (ptDNA) of defined length. After a single ptDNA strand has wrapped the QD, additional strands are excluded from the surface. Production of mQDs in this manner can be accomplished at small and large scale, with commercial reagents, and in minimal steps. These mQDs can be specifically directed to biological targets by hybridization to a complementary single stranded targeting DNA. We demonstrate the use of these mQDs as imaging probes by labeling SNAP-tagged Notch receptors on live mammalian cells, targeted by mQDs bearing a benzylguanine moiety.

We provide detailed instructions for the preparation of monovalent targeted quantum dots (mQDs) from phosphorothioate DNA of defined length. DNA wrapping occurs in high yield, and therefore, products do not require purification. We demonstrate the use of the SNAP tag to target mQDs to cell-surface receptors for live-cell imaging applications.

Produção e Segmentação de Monovalent Quantum Dots

The multivalent nature of commercial quantum dots (QDs) and the difficulties associated with producing monovalent dots have limited their applications in ...

Inkjet Printing All Inorganic Halide Perovskite Inks for Photovoltaic Applications

A method for synthesizing photoactive inorganic&#160;perovskite quantum dot inks and an inkjet printer deposition method, using the synthesized inks, are demonstrated. The ink synthesis is based on a simple wet chemical reaction and the inkjet printing protocol is a facile step by step method. The inkjet printed thin films have been characterized by X-ray diffraction, optical absorption spectroscopy, photoluminescent spectroscopy, and electronic transport measurements. X-ray diffraction of the printed quantum dot films indicates a crystal structure consistent with an orthorhombic room temperature phase with (001) orientation. In conjunction with other characterization methods, the X-ray diffraction&#160;measurements show high quality films can be obtained through the inkjet printing method.

A protocol for synthesizing inorganic-lead-halide hybrid perovskite quantum dot inks for inkjet printing and the protocol for preparing and printing the quantum dot inks in an inkjet printer with post characterization techniques are presented.

Jato de tinta de impressão de todas as tintas de perovskita iodetos inorgânicos para aplicações fotovoltaicas

A method for synthesizing photoactive inorganic&#160;perovskite quantum dot inks and an inkjet printer deposition method, using the synthesized inks, are ...

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 ...

Nanoesferas de pontos quânticos para maior sensibilidade na detecção de biomarcadores

Fluorescent Lateral Flow Immunoassay Based on Quantum Dots Nanobeads

Quantum dots, also known as semiconductor nanocrystals, are novel fluorescent labels for biological imaging and sensing. However, quantum dot-antibody conjugates with small dimensions (~10 nm), prepared through laborious purification procedures, exhibit limited sensitivity in detecting certain trace disease markers using lateral flow immunoassay strips. Herein, we present a method for the preparation of quantum dot nanobeads (QDNB) using a one-step emulsion evaporation method. Using the as-prepared QDNB, a fluorescent lateral flow immunoassay was fabricated to detect disease biomarkers using C-reactive protein (CRP) as an example. Unlike single quantum dot nanoparticles, quantum dot nanobead-antibody conjugates are more sensitive as immunoassay labels due to signal amplification by encapsulating hundreds of quantum dots in one polymer composite nanobead. Moreover, the larger size of QDNBs facilitates easier centrifugation separation when conjugating QDNBs with antibodies. The fluorescent lateral flow immunoassay based on QDNBs was fabricated, and the CRP concentration in the sample was measured in 15 min. The test results can be qualitatively assessed under UV light illumination and quantitatively measured using a fluorescent reader within 15 min.

Autor em destaque: nanoesferas de pontos quânticos de alta qualidade para imunoensaios de fluxo lateral fluorescente sensível

Here, we describe a protocol for the preparation of quantum dot nanobeads (QDNB) and the detection of disease biomarkers using QDNB-based lateral flow immunoassay strips. The test results can be qualitatively assessed under UV light illumination and quantitatively measured using a fluorescent strip reader within 15 min.

Imunoensaio de fluxo lateral fluorescente baseado em nanoesferas de pontos quânticos

Quantum dots, also known as semiconductor nanocrystals, are novel fluorescent labels for biological imaging and sensing. However, quantum dot-antibody ...