IS-embedded core-shell SERS for precision pesticide quantification in foods: a review

Surface-enhanced Raman scattering (SERS) offers sensitive molecular fingerprinting for rapid pesticide-residue detection, but quantitative reliability remains limited by hot-spot heterogeneity, substrate variation, analyte adsorption, and complex food matrices. Internal-standard (IS)-embedded core-shell nanostructures enable ratiometric correction of common-mode fluctuations, while their shells can regulate analyte transport, resist fouling, sieve molecules, and promote selective enrichment. This review summarizes recent advances in IS-embedded core-shell SERS, with particular attention to IS location, shell chemistry, local electromagnetic fields, and mass transport. Reported systems are further evaluated in terms of limit of quantification (LOQ), recovery, precision, matrix effects, reproducibility, uncertainty, regulatory relevance, and comparison with established reference methods. Current evidence positions IS-SERS as a calibratable platform for rapid screening and near-site quantification, complementary to LC-MS/MS or GC-MS/MS confirmation. Future priorities include MRL-relevant and validated LOQ, interbatch and interinstrument reproducibility, storage stability, and scalable manufacturing.