Gli autori ringraziano il Dipartimento di Chimica e il laureato in Missouri State University per il loro sostegno di questo progetto. Riconosciamo anche la microscopia Laboratorio Electron presso il Laboratorio Nazionale di Federico per la Ricerca sul Cancro per l&#39;utilizzo del loro microscopio elettronico a trasmissione e griglie di carbonio rivestiti.

1. Sintesi di fosfuro di indio / solfuro di zinco (INP / ZnS) Quantum Dots <ol><li> Sintesi di fosfuro di indio (InP) Quantum Dot Cores <ol><li> Montare un fondo da 100 ml rotondo, 3-collo, pallone con un condensatore da 12 pollici. Aggiungere 30 ml oleilammina (OLA), 0,398 g di indio (III) cloruro (compresi 3), 0,245 g di zinco (II) cloruro (ZnCl 2) e mescolare mentre evacuare a temperatura ambiente usando un vuoto per 1 ora. La soluzione deve apparire incolore con un precipitato bianco. </li><li> Utilizzando un mantello di riscaldamento con una termocoppia e regolatore di temperatura proporzionale-integrale-derivativa (PID), aumentare la temperatura della soluzione a 120 ° C. Evacuare la soluzione sotto vuoto per 20 minuti per eliminare le impurezze a basso punto di ebollizione che possono influenzare la crescita nucleo. Nota: Mentre è possibile utilizzare un bagno di sabbia e termometro, con un mantello riscaldante e PID aumenta l&#39;uniformità e la riproducibilità dei prodotti di reazione. </li><li> Sotto gas inerte (ad esempio, N 2), riflusso della soluzione e aumentare la temperatura a 220 ° C per 15 min. Il Incl 3 e ZnCl 2 completamente dissolvono, per ottenere una soluzione di colore giallo pallido. Lasciare che la temperatura si stabilizzi per 10 minuti. </li><li> Purge una siringa monouso da 3 ml di plastica e 4 pollici, 22 G ago con azoto gassoso. Usando la siringa, fornire rapidamente 0,5 ml tris (dimetilammino) fosfina (TDMAP) alla soluzione incl 3. La temperatura della soluzione diminuisce leggermente e ritorna a 220 ° C. I cambiamenti soluzione da trasparente, giallo pallido a opaco, nero. </li><li> Dopo 9,5 min, togliere il pallone di reazione dal mantello di riscaldamento fino a quando la temperatura scende al di sotto di 200 ° C. Per proteggere l&#39;integrità dei nuclei InP, procedere direttamente al rivestimento ZnS nel passaggio 1.2.1. </li></ol></li><li> Sintesi di solfuro di zinco Conchiglie (ZnS) Quantum Dot <ol><li> Porre il pallone di reazione dal punto 1.1.5 su un mantello riscaldante e stabilizzare il temperature a 200 ° C. Aggiungere lentamente 3,58 g dodecantiolo (DDT) nel corso di 15 sec per la soluzione contenente InP QD. Lasciare la soluzione di reagire per 1 ora. Nota: spessore del guscio ZnS può essere variata aumentando o diminuendo la quantità di stearato di zinco aggiunto nel passaggio 1.2.4. Che modifica l&#39;importo di ZnCl 2 o dodecantiolo in passi 1.1.1 e 1.2.1 può avere un impatto significativo sulla qualità della QD, modificando la cinetica di reazione. <ol><li> In seguito, rimuovere il pallone di reazione dal mantello di riscaldamento e lasciar raffreddare la soluzione a circa 60 ° C. </li></ol></li><li> Una volta che la soluzione InP / ZnS raggiunge ~ 60 ° C, aggiungere 10 ml esano e trasferire l&#39;intera soluzione di circa 45 ml in una provetta da centrifuga da 50 ml in polipropilene. Centrifugare il campione (3000 xg per 10 min) per rimuovere precursori solidi non reagiti. </li><li> trasferire con cautela il surnatante in una bottiglia in polipropilene centrifuga da 250 ml, aggiungere 200 ml di acetone, e centrifugare la soluzione (3.000 xg per 10 minuti) per far precipitare QD InP / ZnS. Questo volume può essere diviso equamente in quattro 50 ml provette per centrifugazione se una centrifuga con le necessarie rotore / accessori non è disponibile. Decantare il surnatante e asciugare il pellet QD a fondo con azoto per eliminare l&#39;acetone. </li><li> Risospendere le QD in 20 ml OLA utilizzando sonicazione, il trasferimento ad un fondo da 50 ml rotondo, 3-collo, pallone contenente 0.474 g di zinco stearato, e mescolate. Evacuare la soluzione sotto vuoto per 20 minuti a RT. </li><li> Sotto azoto gassoso, aumentare la temperatura a 180 ° C e lasciare che la reazione di procedere per 3 ore. Mentre non ci sono cambiamenti visivi notevoli alla soluzione di reazione che si verificano durante questa reazione, l&#39;aggiunta di stearato di zinco aumenta ZnS spessore del guscio, aumentando così QY migliorando passivazione della superficie di QD 12.. Una volta che la reazione è completa, togliere il pallone dal mantello di riscaldamento e lasciare raffreddare la soluzione a circa 60 ° C. </li><li> Una volta che i soluti InP / ZnSsulla raggiunge ~ 60 ° C, aggiungere 20 ml esano e trasferire in una provetta da centrifuga da 50 ml in polipropilene. Centrifugare il campione (3000 xg per 10 min) per rimuovere stearato di zinco non reagito. </li><li> Trasferire accuratamente surnatante in un flacone da centrifuga da 250 ml polipropilene, aggiungere 200 ml di acetone, e centrifugare la soluzione (3000 xg per 10 min) per precipitare InP / ZnS QD. decantare con cautela il surnatante e asciugare accuratamente con azoto per eliminare l&#39;acetone. </li><li> Sciogliere il pellet InP / ZnS QD in 30 ml di esano. Vortex e Sonicare la soluzione per breve tempo per garantire la completa dispersione. </li><li> purificazione Ripetere i punti 1.2.6-1.2.8 altre due volte per assicurare la rimozione completa di leganti organici in eccesso. Le interazioni tra il polimero amfifilico ed il QD nel passo 1.2 possono essere compromessi in presenza di leganti eccesso. </li><li> Con calcoli dettagliati da Xie, et al. 16, determinare la dimensione e la concentrazione dei QD InP / ZnS sintetizzati mediante Spettroscopia UV-Vis. <br/&gt; Nota: La caratteristica spettrale importante per questa analisi è la spalla del picco di assorbimento. Il valore di lunghezza d&#39;onda e l&#39;assorbanza del massimo della spalla è utilizzato per calcolare le dimensioni e la concentrazione dei QD rispettivamente. Questa reazione produce tipicamente di circa 5 micromole di QD con un picco di emissione a 600 nm. Per sintetizzare QD di diversi colori, la durata e / o la temperatura della reazione può essere cambiato. Un tempo di reazione più lungo e / o superiore temperatura dei risultati della soluzione in un picco di emissione rossa spostata. Ad esempio, aumentando la temperatura di reazione a 240 ° C e mantenendo il tempo di reazione di 10 min comporterà QD con nm picco 680 emissioni massime. Analogamente, riducendo il tempo di reazione per 2 min e raddoppiando cloruro di zinco utilizzato comporterà QD con nm picco massimo di emissione 470. Questi QD InP / ZnS sono stabili per almeno un mese a 4 ° C al buio sotto gas inerte. </li></ol></li></ol> 2. acquaSolubilizzazione del InP / ZnS Quantum Dots Utilizzando un Amphiphilic Polymer <ol><li> solubilizzazione acqua <ol><li> Usando i QD InP / ZnS dal passaggio 1.2.10, diluire una parte dei QD con esano per ottenere 1 ml di 1 pM QD. <ol><li> In una provetta da centrifuga, trasferire 0,25 ml InP / ZnS QD in ogni provetta. Aggiungere 1 ml di acetone o metanolo al tubo da centrifuga e centrifugare (3000 xg per 10 min). Rimuovere con attenzione il surnatante e sciogliere ogni precipitato in 1 ml di tetraidrofurano (THF). </li><li> Trasferire i QD InP / ZnS disciolto in THF in un 100 ml pallone da fondo e diluire con 16 ml di THF. Per ridurre il numero di aggregati in soluzione, sonicare i QD per 5-10 min. </li></ol></li><li> Sciogliere 30 mg di poli (maleica andhydride- alt -1-ottadecene), 3- (dimetilammino) -1-propilammina (PMAL-d) in 10 ml di acqua grado molecolare. Bagnomaria sonicazione o blanda agitazione fino a quando la soluzione è trasparente è sufficiente per sciogliere completamente il polimero. iluso di vortice o vigorosa agitazione può produrre molte bolle, che ostacola l&#39;interazione del polimero con il QD. Aggiungere la soluzione di polimero 10 ml ai 100 ml rotonda pallone a fondo contenente InP / ZnS QDs in THF. </li><li> Evaporare THF dalla soluzione QD / polimero utilizzando un evaporatore rotante. Collocare la beuta in un bagno di ghiaccio evaporando facilitare l&#39;interazione tra il polimero e QD. A seconda della forza del vuoto, più THF viene evaporato dopo 10 minuti e la soluzione appare torbida. <ol><li> Una volta che la soluzione viene evaporata a 10 ml, togliere il matraccio dall&#39;evaporatore rotante e aggiungere 30 ml di acqua molecolare. Riportare il pallone evaporatore rotante e continuare ad evaporare a 2 ml. Questa fase di evaporazione finale può richiedere molte ore; assicurare il bagno di ghiaccio viene mantenuta. </li></ol></li><li> Rimuovere i QD InP / ZnS idrosolubili dal pallone a fondo tondo con una pipetta. Filtrare la soluzione QD usando una siringa di plastica 3 ml collegata ad un nylon sy 0,1 umRinge filtrare in una provetta da centrifuga da 5 ml. </li><li> Mettere i QD in una unità di dialisi membrana 20.000 MWCO e dializzare contro 0,05 M tampone borato pH 8,5 per rimuovere l&#39;eccesso di polimero. (Aggiungere lentamente 0,05 M di sodio tetraborato decaidrato a M di acido borico 0.05, sotto vigorosa agitazione, fino a quando il pH è 8,5 a rendere questa soluzione tampone borato.) Utilizzando un concentratore a vuoto, concentrare gli QD in tampone borato a 1 ml. </li><li> Per la conservazione, eliminare la soluzione con azoto prima di sigillare con parafilm. I QD InP / ZnS idrosolubili sono stabili per almeno 4 mesi a 4 ° C al buio. </li></ol></li></ol>

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dettagli Questo protocollo sintesi altamente fluorescenti QD InP / ZnS che possono essere utilizzati in molti sistemi biologici. I prodotti QD sintetizzati qui esposti un singolo picco di emissione di fluorescenza centrato a 600 nm con una FWHM di 73 nm (figura 1), che è paragonabile ad altre sintesi precedentemente descritti 12. Tempo di reazione e temperatura di reazione sono passi estremamente importanti a causa del loro effetto profondo sulla qualità sintesi QD e ripetibilità. Dopo sol...

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

Punti quantici (QDs) sono semiconduttori nanocristalli che presentano proprietà fluorescenti quando irradiato con luce 1. A causa delle loro piccole dimensioni (2-5 nm), che è simile a molte biomolecole più grandi, e facilità di biofunzionalizzazione, QD sono uno strumento estremamente interessante per applicazioni biomediche. Hanno trovato l&#39;uso in etichettatura biologica, imaging singola molecola live-cell, la somministrazione di farmaci, imaging in vivo, il rilevamento degli agenti patogeni, e il monitoraggio delle cellule, tra molti altri usi 2-8. QD basata su CD sono stati più comunemente usato in applicazioni biomediche a causa della loro intensa fluorescenza e una ridotta larghezza picco di emissione 9. Tuttavia, le preoccupazioni sono state sollevate a causa della potenziale tossicità del Cd 2+ ioni 10 che possono essere immesse attraverso la degradazione della nanoparticella. Recentemente, QD InP basati sono stati esplorati come alternativa alla QD Cd basati perché mantengono molte caratteristiche fluorescenzadi QD Cd-based e può essere più biocompatibile 11. QD basata su CD sono stati trovati per essere significativamente più tossico QD InP a base di saggi in vitro a concentrazioni basse quanto 10:00, dopo solo 48 ore 11. Il colore emissione di fluorescenza di QD è formato-sintonizzabile 1. Cioè, come la dimensione degli aumenti QD, l&#39;emissione di fluorescenza è spostata verso il rosso. Le dimensioni e la dimensione dispersity dei prodotti QD può essere modificata variando la temperatura, la durata di reazione, o condizioni di concentrazione precursori durante la reazione 12. Mentre il picco di emissione di InP QD è in genere più ampio e meno intensa rispetto QD basata su CD, InP QD può essere fatta in una grande varietà di colori progettate per evitare la sovrapposizione spettrale, e sono sufficientemente intenso per la maggior parte delle applicazioni biomediche 12. La sintesi descritto in questo protocollo produce QD con un picco di emissione rosso centrato a 600 nm. Diversi passaggi sono prese afSintesi ter delle anime QD per mantenere l&#39;integrità ottica dei QD e la compatibilità per applicazioni biologiche. La superficie del nucleo QD deve essere protetto da difetti di ossidazione o di superficie che possono causare tempra; di conseguenza, un guscio di ZnS è rivestito sopra il nucleo di produrre InP / ZnS (core / shell) QD 13. Questo rivestimento è stato dimostrato di proteggere la fotoluminescenza del prodotto QD. La presenza di ioni zinco durante la sintesi InP QD ha dimostrato di limitare difetti superficiali, nonché distribuzione dimensionale diminuzione 12. Anche con la presenza di Zn 2+ nel mezzo di reazione, sintesi di InZnP sono altamente improbabili 12. Dopo il rivestimento, con conseguente QD InP / ZnS sono rivestiti in ligandi idrofobici come l&#39;ossido di trioctylphosphine (TOPO) o oleilammina 12,14. Un polimero amfifilico può interagire con leganti idrofobi sulla superficie QD e molecole di acqua bulk per conferire solubilità in acqua 15. polimeri anfifilici con carbogruppi chimici xylate possono essere utilizzate come &quot;maniglie chimici&quot; di funzionalizzare ulteriormente i QD. Dettagli Questo protocollo la sintesi e funzionalizzazione di idrosolubili InP / ZnS QD con molto intensa emissione di fluorescenza e dimensioni relativamente piccole-dispersity. Questi QD sono potenzialmente meno tossici comunemente usati QD CdSe / ZnS. Qui, la sintesi di InP / ZnS QD offre una pratica alternativa per QD Cd-based per applicazioni biomediche.

<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.

I nuclei InP non rivestiti non dimostrano sostanziale fluorescenza visibile ad occhio. Tuttavia, InP / ZnS (core / shell) punti quantici sembrano fluorescenza brillantemente ad occhio sotto irraggiamento UV. La fluorescenza di InP / ZnS QD è stato caratterizzato mediante spettroscopia di fluorescenza. Lo spettro di fluorescenza della QDs in esani (figura 1) eccitato a 533 nm mostra un picco principale centrato a 600 nm con una larghezza a metà massimo (FWHM) di 73 nm. ...

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.

Sintesi di Cd-libera InP / ZnS Quantum Dots adatto per applicazioni biomediche

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 Views.  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.

Video: 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.

Compact Quantum Dots per singola molecola Imaging

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

Ricerca

Ingegneria

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.

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

Chimica

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.

Sintesi, Caratterizzazione, e funzionalizzazione di ibrida UA / CdS e Au / ZnS core / shell nanoparticelle

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.

Solubilizzazione e Bio-coniugazione dei punti quantici e test di tossicità batterica curva di crescita e conta in piastra

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

Bioingegneria

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.

Sintesi di CdS nanoparticelle libera-ligando all&#39;interno di una matrice zolfo Copolimero

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.

Iniezione di elettroni avanzata e confinamento eccitone per diodi emettitori di luce pura blu Quantum-Dot introducendo parzialmente ossidato catodo in alluminio

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.

Produzione e Targeting di monovalente 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.

A getto d'inchiostro stampa tutti gli inchiostri di Perovskite alogenuro inorganici per applicazioni fotovoltaiche

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.

Sintesi di in37P20(O2CR)51 cluster e la loro conversione in 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 ...

Nanosfere di punti quantici per una maggiore sensibilità nel rilevamento di biomarcatori

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.

Autore in primo piano: Nanosfere a punti quantici di alta qualità per saggi immunologici a flusso laterale fluorescenti sensibili

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.

Immunodosaggio fluorescente a flusso laterale basato su nanosfere di punti quantici

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

Sintesi di Cd-libera InP / ZnS Quantum Dots adatto per applicazioni biomediche

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