Integration of gold nanoparticles into SnS for enhanced peroxidase-like activity and colorimetric detection of ascorbic acid in fruit juice.

A gold/tin(ii) sulfide (AuNPs/SnS) nanocomposite was developed as an efficient peroxidase-mimicking nanozyme for colorimetric sensing. Uniformly dispersed Au nanoparticles (∼12.0 nm) on the SnS surface created a synergistic interface that significantly enhanced catalytic performance compared with individual components. Under optimized conditions, the nanozyme exhibited a strong peroxidase-like response toward the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2, showing excellent linearity (0-1.14 mM, R 2 = 0.9996) and a low detection limit (LOD) of 0.0022 mM. The system was further applied for ascorbic acid (AA) quantification through ox-TMB reduction, achieving a detection limit of 1.94 μM, a quantification limit of 6.48 μM, and recovery values of 99.7-102.3% in commercial fruit juices. Results were in good agreement with HPLC analysis, confirming analytical reliability. This study highlights the AuNPs/SnS nanocomposite as a robust, cost-effective, and sensitive alternative to natural peroxidases for practical food analysis and colorimetric biosensing.