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 nm were synthesized by the sol-gel technique. Two sol-gel methods were developed. Method (1) involves the immersion of CdO-doped gels in Na2Te/methanol (MeOH) solution for 1 to 4 days at 60 degrees Celsius, followed by heat-treatment at 540 degree Celsius or 570 degrees Celsius for 6 to 12 hours in an inert atmosphere. In method 2, CdTe QDs were directly formed at various temperatures (520 degrees Celsius to 570 degrees Celsius) 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.