The influence of ultra-probe sonication and polyvinylpyrrolidone on dispersion stability and photocatalytic activity of Ag-TiO2 nanoparticles

Abstract

The growing use of silver-modified titanium dioxide nanoparticles (Ag-TiO2 NPs) raises environmental concerns. In industrial applications, ultrasonication and surfactant addition are widely employed to improve the efficiency of small amounts of Ag-TiO2 for better dispersion stability. Understanding the stability and dispersion of Ag-TiO2 NPs is crucial. The dispersion stability of Ag-TiO2 NPs is greatly influenced by ultra-probe sonication and polyvinylpyrrolidone (PVP). Ag-TiO2 NP concentrations from 0.1% to 10.0% m/v and PVP concentrations from 0.006% to 0.400% m/v were both used in this study. The effect of ultra-probe sonication presented a high sedimentation height ratio and turbidity below the settling time of 90 min for 0.1%Ag-TiO2 without PVP. A sonication amplitude of 35% and a sonication time of 15 and 30 min showed optimal conditions for good dispersion for 0.1% and 1.0% Ag-TiO2 whereas a sonication amplitude of 20% for 70 s and 140 s was suited for 5.0% and 10.0% Ag-TiO2, respectively. The concentration of PVP was found to be 0.04 times the concentration of Ag-TiO2 for good dispersion. Coordination bonds on the surface of Ag-TiO2 with the carbonyl group served as proof of the chemical adsorption of PVP and Ag-TiO2 NPs. The PVP-coated Ag-TiO2 NPs showed smaller particle sizes and a narrower size distribution than Ag-TiO2. The PVP-coated 1.0% Ag-TiO2 NPs provided lower methylene blue degradation ((5.06 ± 0.76) × 10−3 min−1) under visible light than those without PVP ((9.90 ± 0.74) × 10−3 min−1). These findings advance our understanding about how PVP affects dispersion and photocatalytic activity on Ag-TiO2 and suggest the potential applications as a water pollution coating material.