Facile synthesis of glutathione-l-cysteine co-capped CdTe Core shell system: Study on optical and structural morphology

Semiconductor nanoparticles also known as quantum dots (QDs) have been used in diverse areas of application due to their good optical and photo-physical properties. The synthesis of core-shell QDs have assisted to improve the stability of most nano-particles but the size and long term stability of such materials have been problematic. However, thiol-capped CdTe QDs have been regarded as some of the most widely synthesized nanoparticles due to their unique optical properties. The use of un-stable tellurium source such as NaHTe or highly toxic H₂Te gas makes the reaction condition cumbersome. In this study, we prepared some CdTe QDs and core-shell QDs using K₂TeO₃ as a stable source of tellurium without inert gas protection. This was done using a co-capped bio-compatible coating such as cysteine and glutathione following a modified standard method to produce QDs in the yields of about 60 to 80%. All the synthesized materials were subsequently characterized using various characterization techniques. The systematic optimization of the reaction parameters such as reaction time, pH and mole ratio results with a drastic red shift in wavelength (546-600 nm) by the CdTe core proved that an extra material has been deposited unto the surface of the CdTe core. The 60 days stability test conducted demonstrated that the core-shell nanoparticles were quite stable. Since this reaction was performed under open air conditions and no special ligand or buffer solution was used, it may suitably be applied on an industrial scale.