Semiconducting CuClxBr1−x (x = 0–1) nanocrystals in thin films: synthesis and characterization

Abstract

Thin films containing semiconducting nanocrystals of CuCl_xBr_1−x (x = 0–1) were synthesized by the sol–gel process, by stepwise substitution of chloride ions by bromide ions. Cuprous oxide was used as the precursor for copper, HCl and HBr as halide sources, and the matrix sol was synthesized from 3-glycidoxypropyl(trimethoxy)silane (GPTS) and tetraethoxysilane (TEOS). The films were characterized using ultraviolet–visible (UV-VIS) spectroscopy, high-resolution transmission electron microscopy (HR-TEM) and X-ray diffraction analysis. Thin films (thickness 0.7–1.0 µm) containing cubic CuCl_xBr_1−x (x = 1–0) nanoparticles were obtained. For the samples having no bromide, the absorption spectrum showed a sharp absorption edge at 371 nm. Addition of HBr shifted the peak towards a higher wavelength, giving a peak that is characteristic of CuCl_xBr_1−x; the addition of 1.85 × 10⁻² mole of HBr leads to the complete substitution of chloride by bromide ions. The same observations were also made using X-ray diffraction.