A Study of the structural, optical, and photocatalytic properties of Cu3BiS3 nanoparticles by co-thermal decomposition of precursor complexes

In this study, Cu 3 BiS 3 (CBS) nanoparticles were synthesised by the co-thermal decomposition of Cu(II) and Bi(III) dithiocarbamate complexes at 200 °C using oleylamine (OLA) as both solvent and capping agent. The reaction was carried out at different reaction times (60, 90, and 120 min) to study the influence of synthesis time on the structural and optoelectronic properties of the nanomaterials. Powder X-ray diffraction (XRD) analysis of the ternary nanomaterial confirmed the formation of a single-phase orthorhombic wittichenite structure, with lattice parameters of a = 7.705 Å, b = 10.400 Å, and c = 6.730 Å, indicating high crystallinity and phase purity. Compositional analysis via energy-dispersive X-ray spectroscopy (EDX) corroborated the elemental makeup of Cu, Bi, and S in the synthesised nanoparticles. Optical absorption spectroscopy revealed a progressive blue shift in the absorption edge with decreasing reaction time, corresponding to an increase in band gap energies from 1.50 to 1.80 eV, attributed to size-dependent quantum confinement effects. Morphological study showed the formation of irregular rhombohedral particles with average sizes ranging from 49.86 to 50.04 nm according to transmission electron microscopy (TEM). The scanning electron microscopy (SEM) further revealed a microstructure composed of agglomerated, irregularly shaped spherical particles, enhancing surface area and active site accessibility. The as-synthesised CBS nanoparticles exhibited moderate photocatalytic performance in the degradation of methylene blue under visible light irradiation. The activity is attributed to their tailored band gap, high surface area, and porous morphology, rendering them promising candidates for improvement as photocatalysts in wastewater treatment applications. • Cu₃BiS₃ nanoparticles were synthesised at 200 °C via co-thermal decomposition in oleylamine. • XRD confirmed a single-phase orthorhombic wittichenite with high crystallinity. • Band gaps (1.50–1.80 eV) showed a blue shift with shorter reaction times, suggesting quantum confinement. • TEM showed ∼50 nm rhombohedral particles; SEM revealed agglomerated spheres. • Nanoparticles showed moderate visible-light degradation of methylene blue.