Quantitative detection of non-SERS-active plasticizer dioctyl terephthalate on a hierarchical cu/CuO@ag SERS...

The increasing replacement of regulated phthalate esters by alternative plasticizers such as dioctyl terephthalate (DOTP) in food contact materials has created an urgent need for rapid, on-site detection methods. However, DOTP is inherently non-SERS-active due to the lack of electrostatic adsorption moieties, precluding its direct detection on conventional SERS substrates. To address this critical gap, we develop a bifunctional Cu/CuO@Ag nanocomposite that integrates catalytic conversion and SERS enhancement in a single platform. The CuO component catalyzes the hydrazinolysis of non-SERS-active DOTP to SERS-active dihydrazide terephthalic acid (DDTP), while the hierarchical Cu/CuO@Ag structure simultaneously provides numerous SERS "hotspots" through the localized surface plasmon resonance (LSPR) from Ag nanoparticles and chemical enhancement through charge transfer at CuO interfaces, achieving an enhancement factor of 4.6 × 10⁶. Oxygen vacancies in CuO, confirmed XPS analysis, serve as electron traps and adsorption sites for selective molecular enrichment. This integrated catalytic-enrichment-detection strategy enables quantitative analysis of DOTP with a detection limit of 1.3 nM and a linear range of 5.0 nM to 0.50 μM. The method exhibits excellent selectivity against common food interferents and achieves satisfactory recoveries (91.2-107.5%) in real food samples including milk, ham sausage, fish fillet, and cooking wine. This work provides a stable, low-cost platform for on-site screening of trace DOTP in food matrices and offers a reference method for detecting other non-SERS-active contaminants through catalytic derivatization.