<p> The&#xa0;synthesis of ZnO microspheres with different morphologies (spherical and flower-like) decorated with Au nanoparticles (hereafter referred to as S-ZnO–Au MPs and F-ZnO–Au MPs, respectively) as ultrasensitive SERS-active substrates are proposed&#xa0;for the trace-level detection and photocatalytic degradation of 2-mercaptobenzothiazole&#xa0;(MBT) in aquatic environments. Both spherical and flower-like ZnO microspheres were synthesized via a hydrothermal method. Subsequently, Au nanoparticles were deposited onto their surfaces through in situ reduction of chloroauric acid. Comparative analysis revealed that the S-ZnO–Au MPs exhibited superior SERS performance, with a high enhancement factor of 5.5 × 10⁷. Taking advantage of the synergistic effects of chemical enhancement from ZnO semiconductor and electromagnetic enhancement from AuNPs, the S-ZnO–Au MPs-based SERS assay for MBT demonstrates high sensitivity and reaches a limit of detection of 1.42 × 10⁻¹⁰&#xa0;mol/L, exhibiting a wide linear dynamic detection range from 1 × 10⁻⁸ to 1 × 10⁻⁴&#xa0;mol/L, with a correlation coefficient (<i>R</i>²) of 0.9901. S-ZnO–Au MPs enable highly efficient photocatalytic degradation of MBT (98% in 50&#xa0;min) via radical-mediated oxidation. The developed ZnO–Au MP structure exhibits significant potential as a multifunctional SERS substrate, enabling both the sensitive detection and subsequent photocatalytic degradation of MBT in aquatic environments.</p> Graphical Abstract <p></p>