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).

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We have studied the optical properties of size-tunable undoped and Mn 2þ -doped cadmium telluride (CdTe) quantum dots (QDs) of monodisperse suspensions with emission wavelength varying between 500 and 680 nm. The role of the surface is investigated for obtaining size-tunable, bright, and stable CdTe QDs. Differentially tunable optical properties of doped and undoped CdTe QDs has been reported. Unlike the continuous redshifting in the absorption spectra of pristine CdTe system, an unusual blueshift is observed for doped CdTe system after a certain time period of refluxion, followed by again a redshift and the disappearance of earlier peak with further refluxing. The available size range and optical properties are significantly controlled through Mn 2þ doping. The surface adsorbed Mn promotes ripening of the doped system as well as disintegration into smaller fraction after saturation in growth occurs. An optimum size fraction is identified for both the systems based on their photoluminescence (PL) quantum yield. The photophysics of Mn 2þ -doped nanocrystals has been proposed.

Near white light emission (CIE 0.35, 0.29) has been achieved as a combination of intraligand transition, aggregate induced emission and dopant emission followed by surface complexation on Qdot surface.

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