A cubic Sm@CdS Q-dot glass as a photocatalyst for solar H2 generation

Abstract

The cubic Sm@CdS quantum dots (QDs) are grown in a glass matrix with good thermal stability for the first time. The band gap of CdS particles embedded in glass is observed to be in the range of 3.8 to 2.4 eV. The present system is compared with CdS/Sm nanocrystals (NCs) doped in a silica-based glass system. The CdS quantum dots, having a size in the range of 3–6 nm, are grown in the silica glass. Structural characterization has been carried out using X-ray diffraction (XRD), which shows the cubic structure of Sm@CdS quantum dots in glass, whereas the pristine CdS Q-dot glass shows hexagonal structure. The optical characterization of the glasses has been carried out using a UV-visible spectrophotometer. A spectroscopic study showed a shift in optical transmittance due to thermal treatment, i.e., due to the growth of CdS quantum dots in the glass matrix. The semiconductor crystals are uniform in size and distributed evenly in the glass matrix. The size quantization effect has been seen in both systems. There is a drastic change in the optical band gap with the size of the quantum dots. Under natural sunlight, the hydrogen production experiment was conducted, and an increase of 42.5% in the hydrogen evolution rate was observed from 1 wt% Sm³⁺ doped CdS (3769.2 μmol h⁻¹ g⁻¹) heat-treated at 525 °C when compared to the CdS Q-dot glass with a similar heat treatment temperature (2626 μmol h⁻¹ g⁻¹). Such cubic CdS QD–glass nanocomposites have great significance owing to their potential applications in solar cells, LEDs, and other optoelectronic devices.