Briefly, 0.3 g of polyvinylpyrrolidone (PVP) K30 was dissolved in the mixture of 2.54 ml of ethanol and 3.82 ml of acetic acid under continuous mag-netron stirring. About 10 min later, 7.0 ml of tetrabutyl titanate(Ti(oBu)4) was added, and the mixed solution was kept stirring for ca. 1 h to get a uniform PVP@TBT sol.