Cu-doping effect on the structural, optical and photoluminescence properties of Sn0.98Cr0.02O2 nanoparticles by co-precipitation method

Sn_0.98-xCr_0.02Cu_xO₂ nanoparticles were prepared by co-precipitation method with different Cu concentrations from x = 0 to 0.05 and annealed at 600°C for 2 h in air atmosphere. The prepared particle were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectra, UV–visible spectrophotometer, and Fourier transform infrared spectroscopy. The XRD measurement reveals that the prepared nanoparticles have different microstructure without changing a tetragonal structure. The calculated average crystalline size decreased from 12.2 to 10.5 nm for x = 0–0.02 then gradually increased up to 16.8 nm for x = 0.05 which were confirmed by Scanning electron microscope. The optical studies were done by UV–visible spectrometer and the energy band gap values were calculated from absorption spectra. A small red shift from 3.52 eV (Cu = 0) to 3.49 eV (Cu = 0.02, ΔE_g = 0.03 eV) at lower Cu concentrations and a remarkable blue shift from 3.49 eV (Cu = 0.02) to 3.71 eV (Cu = 0.05, ΔE_g = 0.22 eV) at higher Cu concentrations is due to Cu-doping in Cr–SnO₂ matrix. The presence of functional groups and the chemical bonding is confirmed by Fourier transforms infrared spectra. PL spectra of Sn_0.98-xCr_0.02Cu_xO₂ nanoparticle described the shift in UV emission from 366 to 381 nm (red shift) and a shift in blue band emission from 458 to 482 nm (red shift) which confirms the Cu-doping in Cr–SnO₂ matrix. The doping of Cu in the present system is useful to tune the emission wavelength and hence is appreciable for the fabrication of nano-optoelectronic devices and photo-catalytic applications.