Structural and Antibacterial behaviors of Tin Dioxide Thin Films on Copper Substrates

Tin dioxide (SnO2) thin films were deposited on copper substrates using a spin-coating technique, where a precursor solution of tin chloride (SnCl2) in methanol and distilled water was applied. The films were annealed at 300°C to enhance crystallinity. The study investigates how varying SnO2 layer thicknesses (3 and 9 layers) on Cu substrate influence structural, optical, and antibacterial properties. Characterization techniques included X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscope (AFM), UV-visible spectroscopy, and Fourier-transform infrared (FTIR). The study specifically examines the effects of varying SnO2 layer numbers (3 and 9) on the properties of the composite. Results indicate that increasing SnO2 layers affect surface roughness, grain size, optical characteristics, and antibacterial efficacy. XRD analysis revealed a shift in the diffraction pattern, indicating lattice expansion with more layers. SEM analyses identify increased porosity and decreased density, while AFM confirms an increase in roughness with the number of layers. The multilayer system exhibits anisotropic magnetic properties suitable for magnetic and spintronic applications, as evidenced by SQUID magnetometer measurements that reveal a 100 Oe difference in coercive fields between parallel and perpendicular field orientations. As SnO2 thickness increases, bandgap energies decrease from 3.93 eV (Cu) to 3.89 eV (3 layers) and 3.81 eV (9 layers), as determined by Tauc plots assuming direct transitions (αhν)2 vs hν, indicating tunable optical properties. The FTIR spectra of SnO2/Cu films display characteristic SnO2 bands and hydroxyl-related peaks, with increased SnO2 layers resulting in reduced transmittance and more pronounced peaks. Antibacterial activity (n=5 replicates) of the SnO2/Cu composite against Pseudomonas aeruginosa improves with additional SnO2 layers, showing statistically significant (p