Synthesis and characterization of CdS-TiO2 materials and their application.

Cadmium sulfide–titanium dioxide (CdS–TiO₂ ) composite materials have emerged as
highly attractive semiconductor systems for photocatalytic and optoelectronic
applications due to their complementary optical band gaps, efficient charge separation
behavior, and tunable nanostructures. TiO₂ , a robust wide-band-gap semiconductor (Eg
≈ 3.0–3.2 eV), exhibits high chemical stability, non-toxicity, and excellent
photocatalytic activity under UV illumination; however, its practical utility is restricted
by limited absorption of visible light and rapid electron–hole recombination. In contrast,
CdS, with a narrow band gap of 2.3–2.4 eV, effectively absorbs visible light but suffers
from photo corrosion and limited stability. Integrating CdS with TiO₂ offers a
synergistic strategy to overcome the individual shortcomings of each material by
forming heterojunctions that facilitate directional charge transfer, broaden the spectral
response, and enhance photocatalytic efficiencies.
Comprehensive characterization of CdS–TiO₂ systems is carried out using
complementary spectroscopic, microscopic, and electrochemical techniques. Powder Xray
diffraction (XRD) confirms the formation of crystalline anatase/rutile TiO₂ and
hexagonal CdS phases, as well as verifying heterojunction formation. UV–Vis diffuse
reflectance spectroscopy reveals extended visible-light absorption and reduced band-gap
energies compared to pristine TiO₂ . Photoluminescence (PL) spectroscopy provides
information on recombination kinetics, with reduced PL intensity indicating suppressed
electron–hole recombination.