Colloidal synthesis of high quality CdSe nanocrystals with controllable size and tunable properties have been one of the most important topics of research over the last decade, in view of its huge technological potentials. CdSe is one of the most studied nanocrystals of this category because of its photoluminescence tunability across the visible spectrum. We have synthesized CdSe nanocrystals using CdO precursor in a noncoordinating solvent and studied the effect of the reaction temperature on the size and optical properties of the nanocrystals. The size of the nanocrystals could be varied systematically in the range of 3.5 to 6.6 nm diameter with a remarkably narrow size distribution by controlling only the reaction temperature, without any need for a post-synthesis processing. The band gap and the corresponding band edge emission could be tuned across the entire visible range by tuning the size of the nanocrystals. The narrow width of the photoluminescence emissions of different colours (blue to red) make these nanocrystals a potential candidate for different optical and optoelectronic devices.

Quantum Dots (QDs) are recently emerging as the alternative to organic fluorescent probes in bio imaging applications. In the present study, CdTe QDs were prepared in aqueous phase using a stable tellurium source in presence of a capping agent capable of stabilizing and regulating its growth in the pH range of 6.0–8.0, such that it is amenable for use in biological systems. The spectroscopic and microstructural studies confirmed the formation of CdTe nanoparticles capped by mercaptosuccinic acid (MSA) of average size 2.5 nm with narrow size distribution. These MSA– CdTe QDs have shown tunable fluorescence with high quantum yield, broad absorption and symmetric fluorescence spectra. Of the different QDs emitting varied luminescence, the yellow, orange and red QDs were taken up for further characterization, to assess their potential in bioimaging applications. The cytotoxicity assays in mammalian lymphocytes showed that these QDs have a very high order cell viability and low level of toxicity when incubated with varying QD concentrations (20–130 nm).

No abstract

No abstract

Introduction of intra bandgap state in semiconductor nanocrystals provides an efficient way to control the separation or recombination of charge carriers and enhances their applicability for light emitting, harvesting, and sensing purposes. This manuscript presents the conversion of ternary CIZS nanocrystals to doped binary alloyed nanocrystals and studies the change in the defect/dopant state induced light-emission activities. Adopting an in situ transformation process by facile ion exchange protocol, the ternary CIZS nanocrystals (Cu >10%) are converted to alloyed binary nanocrystals with <2% Cu, and the change in their excitation, de-excitation processes, and consequent photophysical properties are continuously monitored with the variation in composition. Finally, it is concluded that when the ternary CIZS nanocrystals change to doped nanocrystals, the position of the defect state changes and this influences the optical properties of the nanocrystals.