Tiny CuO/CeO2 modified bovine serum albumin with oxidase-like activity for reliable recognition of ascorbic acid and S2− in food

Food health and safety is one of the hottest topics to affect human life nowadays. To reliably detect toxic S 2− and to normalize bioactive ascorbic acid (AA), a kind of tiny CuO/CeO 2 modified bovine serum albumin (CuO/CeO 2 @BSA) was prepared under microwave-assisted conditions. Not only did the modification of BSA to CuO/CeO 2 nanospheres endow CuO/CeO 2 @BSA with high stability and an average mesoporous pore of 3.88 nm, it exhibited outstanding oxidase-like activity to catalyze the oxidization of 3,3′,5,5′-tetramethyl benzidine (TMB) with V max / K m of 0.15 mM/5.96 × 10 −8  M·s −1 . The presence of trace S 2− or AA could exclusively deteriorate the characteristic UV–vis absorbance intensity at 652 nm ( A 652 ) of CuO/CeO 2 @BSA-TMB with obvious hypochromic effect from dark blue to light blue. Under the optimal oxidase-mimic conditions, CuO/CeO 2 @BSA-TMB was applied for potable UV–vis spectral/smartphones-assisted red-green-blue (RGB) monitoring of S 2− or AA in complex agricultural products with detection limits as low as 9.2 × 10 −9 /4.0 × 10 −8  M or 6.1 × 10 −8 /7.2 × 10 −8  M. The analysis accuracy was reliable from comparing their F and t values and the detection mechanisms were proposed. It will shed a potential for portable monitoring of analytes in food samples practically.