Cadmium telluride quantum dot-doped glass by the sol-gel technique

CdTe quantum dot (QD)-doped sodium borosilicate (NBS) glasses with particle sizes ranging from 2.4 nm to 8.5 mn were synthesized by the sol-gel technique. Two sol-gel methods were developed. Method (a) involves the immersion of CdO-doped gels in Na2Te/methanol (MeOH) solution for 1 to 4 days at 60 degrees C, followed by heat-treatment at 540 degrees C or 570 degrees C for 6 to 12 hours in an inert atmosphere. In method (b), CdTe QDs were directly formed at various temperatures (520 degrees C to 570 degrees C) under a reducing atmosphere. The synthesis of CdTe QDs in the NBS glass was accomplished using cadmium nitrate (Cd(NO3)(2)) and telluric acid (H6TeO6) as the starting materials. The number density and particle size distribution of the CdTe nanocrystallites depend on the heat-treatment conditions for the reduction of Te6+ to Te2- ions and their subsequent ions react with Cd2+ ions to form CdTe. The absorption edges of these glasses were blue-shifted due to quantum confinement depending on the concentration of the initial salt and the heat-treatment conditions.