Highly sensitive hydrogel surface-enhanced Raman scattering chips with multi-analyte detection ability

Surface-enhanced Raman spectroscopy (SERS) is a powerful analytical technique, however, the development of substrates that integrate high sensitivity, uniformity, stability, and multi-analyte applicability remains challenging. In this study, highly sensitive hydrogel SERS chips with multi-analyte detection ability were fabricated by embedding aggregated silver nanocages (a-AgNCs) into a polyvinyl alcohol hydrogel matrix via a physical cross-linking method. The a-AgNCs exhibited excellent dispersibility and stability in the hydrogel, a main LSPR peak centered at 495 nm, which couples well with the 532 nm laser for strong electromagnetic enhancement. Along with the chemical enhancement driven by photo-induced charge transfer, the substrate exhibits an excellent SERS activity. The resulting hydrogel SERS chips demonstrate an ultrahigh enhancement factor of 2.12 × 10¹⁰, exceptional signal uniformity (RSD = 1.22%), outstanding inter-batch reproducibility (RSD = 4.84%), and long-term stability (up to 6 weeks at 4 °C and more than 16 weeks at -20 °C). Moreover, the substrate exhibits excellent multi-analyte detection performance toward various antibiotics and pesticides at trace concentrations. Practical applicability was validated through the quantitative detection of triazophos in food samples, with a limit of detection of 2.1 ng/mL and recovery rates of 91-101% achieved. This work establishes hydrogel SERS chips as a robust and versatile platform for high-sensitivity, multi-analyte sensing in real-world applications.