Reactive Blue 21 Dye Degradation and Surface Modification of Cu and Ag/Cu Thin Films Prepared by Pulsed Laser Deposition

Abstract

In the present work, the potential applications of Cu thin films and Ag/Cu bilayer thin films obtained by the pulsed laser deposition (PLD) technique are investigated in terms of the physicochemical effects resulting from their interaction with an aqueous solution containing Reactive Blue 21 (RB21) dye and sodium bicarbonate (NaHCO₃). The thin-film deposition process was carried out using a Q-switched Nd:YAG laser system operating at a wavelength of λ = 532 nm, with a pulse duration of τ = 10 ns, a repetition rate of ν = 10 Hz, a pulse energy of E = 180 mJ, a laser spot diameter of d = 336 μm, and an angle of incidence of α = 45°. Two types of thin films were prepared: a Cu thin film and an Ag/Cu bilayer thin film. The thermal effects induced by the interaction of the laser beam with the target materials were investigated by numerical simulations performed in COMSOL, allowing the evaluation of melt-phase formation for each material separately and providing a better understanding of the morphology and topography of the deposited thin films. The simulation results were validated through scanning electron microscopy (SEM) observations and surface roughness analyses. The two thin films were subsequently treated with an aqueous solution containing 10 g/L RB21 dye and 10 g/L NaHCO₃. Physicochemical analyses performed after treatment, including scanning electron microscopy (SEM), optical microscopy (OM), profilometry, Fourier-transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDS), and UV–Vis spectroscopy, revealed significant degradation of the RB21 dye accompanied by corrosion of the thin films, with the corrosion process being more pronounced in the case of the Cu thin film. The obtained results indicate that the method analyzed in this study may represent an alternative approach for the decomposition of recalcitrant organic dyes using thin Cu films, without relying on conventional photocatalytic processes. Equally important are the potential applications of the RB21/NaHCO₃ solution as an etching and patterning medium for thin Cu layers, while the Ag overlayer may provide a protective effect during such processes. These findings may contribute to the development of novel fabrication techniques for optoelectronic components, including solar cells, photovoltaic windows, and other industrial and laboratory applications.