2.1. Nanomaterials synthesis

A series of inorganic metal oxides, ZTO CANP, ZTO NP, TiO₂ NP, and ZnO NP, were synthesized using the solvothermal method. All chemicals were supplied by Sigma, Australia. The choice of precursors was based on our previous reports in the literature. Briefly, to synthesize ZTO CANP, 1 mmol of zinc acetate dihydrate and 1 mmol of sodium stannate were dissolved in ethanol and water (1:1 v/v). The mixture was solvothermally heated to 180°C for 12 hours, and then centrifuged, dried, and calcinated at 400°C for 6 hours [21]. For ZTO NP, a modified solvothermal procedure was used to create a precursor solution. The process involved dissolving 0.15 M of zinc acetate dihydrate and 0.08 M of tin chloride pentahydrate in ethanol, stirring continuously for 2 hours, adding 0.5 M of sodium hydroxide, and subjecting the solution to solvothermal treatment at 180°C for 12 hours [25]. To prepare TiO₂ NP, 1.5 g of titanium isopropoxide (TTIP) was added into a solvent of ethanol and acetic acid (2:1 v/v), followed by stirring for 1 hour at ambient temperature. The solution was transferred to a Teflon-lined stainless-steel autoclave (Parr Instrument Co., USA), heated to 200°C, and maintained at this temperature for 9 hours. The precipitate was collected, washed three times with distilled water and ethanol, dried overnight at 90°C, and then subjected to calcination at 500°C in an air environment for three hours. To prepare ZnO NP, a solution of zinc acetate dihydrate was prepared at a concentration of 0.1 M by dissolving it in 100 ml of distilled water. The solution was continuously stirred for 15 minutes with the application of heat as an assisting factor. The solution was solvothermally heated to 150°C for 9 hours, and then centrifuged, dried, and calcinated at 400°C for 3 hours.