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Aqueous synthesis of glutathione-capped CdTe…

T1 - Aqueous synthesis of glutathione-capped CdTe/CdS/ZnS and CdTe/CdSe/ZnS core/shell/shell nanocrystal heterostructures

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Biomimetic, Mild Chemical Synthesis of CdTe-GSH …

An efficient bacterial synthesis method to harvest cadmium telluride (CdTe) quantum dots (QDs) with tunable fluorescence emission using Escherichia coli is demonstrated. Ultraviolet-visible, photoluminescence, X-ray diffraction and transmission electron microscopy analysis confirmed the superior size-tunable optical properties, with fluorescence emission from 488 to 551 nm, and the good crystallinity of the as synthesized QDs. A surface protein capping layer was confirmed by hydrodynamic size, ζ potential and Fourier transform infrared spectroscopy measurements, which could maintain the viability (92.9%) of cells in an environment with a QD concentration as high as 2 μM. After functionalization with folic acid the QDs were used to image cultured cervical cancer cells in vitro. Investigations of bacterial growth and morphology and the biosynthesis of CdTe QDs in Luria-Bertani medium containing E. coli-secreted proteins showed that extracellular synthesis directly relied on the E. coli-secreted proteins, and a mechanism for protein-assisted biosynthesis of QDs is proposed. This work provides an economical approach to fabricate highly fluorescent biocompatible CdTe QDs via an environmentally friendly production process. The biosynthesized QDs may have great potential in broad bio-imaging and bio-labeling applications.

Biomimetic, mild chemical synthesis of CdTe-GSH quantum dots with improved biocompatibility.

Here we demonstrate the aqueous synthesis of colloidal nanocrystal heterostructures consisting of the CdTe core encapsulated by CdS/ZnS or CdSe/ZnS shells using glutathione (GSH), a tripeptide, as the capping ligand. The inner CdTe/CdS and CdTe/CdSe heterostructures have type-I, quasi-type-II, or type-II band offsets depending on the core size and shell thickness, and the outer CdS/ZnS and CdSe/ZnS structures have type-I band offsets. The emission maxima of the assembled heterostructures were found to be dependent on the CdTe core size, with a wider range of spectral tunability observed for the smaller cores. Because of encapsulation effects, the formation of successive shells resulted in a considerable increase in the photoluminescence quantum yield; however, identifying optimal shell thicknesses was required to achieve the maximum quantum yield. Photoluminescence lifetime measurements revealed that the decrease in the quantum yield of thick-shell nanocrystals was caused by a substantial decrease in the radiative rate constant. By tuning the diameter of the core and the thickness of each shell, a broad range of high quantum yield (up to 45%) nanocrystal heterostructures with emission ranging from visible to NIR wavelengths (500-730 nm) were obtained. This versatile route to engineering the optical properties of nanocrystal heterostructures will provide new opportunities for applications in bioimaging and biolabeling.

Microwave-assisted synthesis of high-quality CdTe…

Biomimetic, mild chemical synthesis of CdTe-GSH …

N2 - Here we demonstrate the aqueous synthesis of colloidal nanocrystal heterostructures consisting of the CdTe core encapsulated by CdS/ZnS or CdSe/ZnS shells using glutathione (GSH), a tripeptide, as the capping ligand. The inner CdTe/CdS and CdTe/CdSe heterostructures have type-I, quasi-type-II, or type-II band offsets depending on the core size and shell thickness, and the outer CdS/ZnS and CdSe/ZnS structures have type-I band offsets. The emission maxima of the assembled heterostructures were found to be dependent on the CdTe core size, with a wider range of spectral tunability observed for the smaller cores. Because of encapsulation effects, the formation of successive shells resulted in a considerable increase in the photoluminescence quantum yield; however, identifying optimal shell thicknesses was required to achieve the maximum quantum yield. Photoluminescence lifetime measurements revealed that the decrease in the quantum yield of thick-shell nanocrystals was caused by a substantial decrease in the radiative rate constant. By tuning the diameter of the core and the thickness of each shell, a broad range of high quantum yield (up to 45%) nanocrystal heterostructures with emission ranging from visible to NIR wavelengths (500-730 nm) were obtained. This versatile route to engineering the optical properties of nanocrystal heterostructures will provide new opportunities for applications in bioimaging and biolabeling.

N2 - An efficient bacterial synthesis method to harvest cadmium telluride (CdTe) quantum dots (QDs) with tunable fluorescence emission using Escherichia coli is demonstrated. Ultraviolet-visible, photoluminescence, X-ray diffraction and transmission electron microscopy analysis confirmed the superior size-tunable optical properties, with fluorescence emission from 488 to 551 nm, and the good crystallinity of the as synthesized QDs. A surface protein capping layer was confirmed by hydrodynamic size, ζ potential and Fourier transform infrared spectroscopy measurements, which could maintain the viability (92.9%) of cells in an environment with a QD concentration as high as 2 μM. After functionalization with folic acid the QDs were used to image cultured cervical cancer cells in vitro. Investigations of bacterial growth and morphology and the biosynthesis of CdTe QDs in Luria-Bertani medium containing E. coli-secreted proteins showed that extracellular synthesis directly relied on the E. coli-secreted proteins, and a mechanism for protein-assisted biosynthesis of QDs is proposed. This work provides an economical approach to fabricate highly fluorescent biocompatible CdTe QDs via an environmentally friendly production process. The biosynthesized QDs may have great potential in broad bio-imaging and bio-labeling applications.

PPT - Synthesis of CdTe quantum dots and study of …

We present here the simplest, fast and economical method for CdTe QDs synthesis described to date

Here, we investigated a facial way to directly and continuously synthesize the CdTe/CdS/ZnS core/shell/shell QDs using a modified chemical aerosol flow method. In this integrated synthesis system, the Cd, Te precursors were first carried into the chemical aerosol flow system to result CdTe/CdS core/shell quantum dots. Then, they were brought out into a vessel containing Zn, S precursor solution for coating a shell of ZnS. The obtained core/shell/shell QDs were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectrometer (EDS), and PL spectra to confirm the core/shell/shell structure.

In a typical synthetic procedure, the stock solution containing Cd(MPA) complex and NaHTe was carefully transferred to the equipment and nebulized into microdroplets by a 1.7-MHz ultrasonic generator (Yuyue 402AI, Shanghai Yuyue Co. Ltd). The mist was carried to the furnace by a N2 flow at designed rate through a quartz tube located in a tube furnace kept at appointed temperature, and in the furnace, the solvent evaporated, then the reaction took place, and subsequently CdTe/CdS core/shell quantum dots were obtained; in the following collection and further reaction stage, the synthesized CdTe/CdS QDs were pumped into a three-neck flask containing the Zn and S precursor stock solution with continuous stirring and kept at about 80°C, capping a shell of ZnS was realized in this stage.

Synthesis of CdTe quantum dots and study of their stability
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Preparation of Quantum Dot/Drug Nanoparticle …

AB - Photocathodic stripping of a pre-deposited tellurium film on a gold electrode in 0.1 M Na2SO4 electrolyte containing Cd 2+ ions and poly(vinyl pyrrolidone) (PVP) was used as a route to the photoelectrosynthesis of CdTe nanoparticles. Thus illumination of a Te-modified gold surface generated Te2- species, which were removed from the surface into the bulk electrolyte containing Cd2+and PVP by vigorous stirring. The reaction of Te2-and Cd2+ produced PVP-protected nanosized CdTe particles dispersed in solution in the size range 20-40 nm. In this approach, PVP played a critical role as a stabilizer to form discrete CdTe particles instead of larger (agglomerated) ones. Electrochemical quartz crystal microgravimetry was used to monitor stripping of Te films during the light illumination and the synthesized CdTe nanoparticles were characterized by scanning electron microscopy, energy dispersive X-ray analyses and laser Raman spectroscopy.

Journal of Nanoscience and Nanotechnology

AB - Here we demonstrate the aqueous synthesis of colloidal nanocrystal heterostructures consisting of the CdTe core encapsulated by CdS/ZnS or CdSe/ZnS shells using glutathione (GSH), a tripeptide, as the capping ligand. The inner CdTe/CdS and CdTe/CdSe heterostructures have type-I, quasi-type-II, or type-II band offsets depending on the core size and shell thickness, and the outer CdS/ZnS and CdSe/ZnS structures have type-I band offsets. The emission maxima of the assembled heterostructures were found to be dependent on the CdTe core size, with a wider range of spectral tunability observed for the smaller cores. Because of encapsulation effects, the formation of successive shells resulted in a considerable increase in the photoluminescence quantum yield; however, identifying optimal shell thicknesses was required to achieve the maximum quantum yield. Photoluminescence lifetime measurements revealed that the decrease in the quantum yield of thick-shell nanocrystals was caused by a substantial decrease in the radiative rate constant. By tuning the diameter of the core and the thickness of each shell, a broad range of high quantum yield (up to 45%) nanocrystal heterostructures with emission ranging from visible to NIR wavelengths (500-730 nm) were obtained. This versatile route to engineering the optical properties of nanocrystal heterostructures will provide new opportunities for applications in bioimaging and biolabeling.

Program | 6th World Congress and Expo on …

AB - An efficient bacterial synthesis method to harvest cadmium telluride (CdTe) quantum dots (QDs) with tunable fluorescence emission using Escherichia coli is demonstrated. Ultraviolet-visible, photoluminescence, X-ray diffraction and transmission electron microscopy analysis confirmed the superior size-tunable optical properties, with fluorescence emission from 488 to 551 nm, and the good crystallinity of the as synthesized QDs. A surface protein capping layer was confirmed by hydrodynamic size, ζ potential and Fourier transform infrared spectroscopy measurements, which could maintain the viability (92.9%) of cells in an environment with a QD concentration as high as 2 μM. After functionalization with folic acid the QDs were used to image cultured cervical cancer cells in vitro. Investigations of bacterial growth and morphology and the biosynthesis of CdTe QDs in Luria-Bertani medium containing E. coli-secreted proteins showed that extracellular synthesis directly relied on the E. coli-secreted proteins, and a mechanism for protein-assisted biosynthesis of QDs is proposed. This work provides an economical approach to fabricate highly fluorescent biocompatible CdTe QDs via an environmentally friendly production process. The biosynthesized QDs may have great potential in broad bio-imaging and bio-labeling applications.

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