Dual-Mode LSPR–SERS Sensor Based on Silver Nanoislands for Gas-Phase VOC Detection

In this letter, we report a dual-mode sensor integrating localized surface plasmon resonance (LSPR) and surface-enhanced Raman scattering (SERS) for gas-phase detection of volatile organic compounds (VOCs). The sensor is fabricated by sequential silver sputtering (5 nm per cycle) and annealing at 250°C, forming silver nanoislands on glass substrates. As the number of deposition cycles increases, the nanoislands grow and interparticle gaps narrow, enhancing plasmonic effects. The substrate prepared with four sputtering–annealing cycles exhibited the strongest SERS response when tested with 100 nM 4-aminothiophenol, while a fifth cycle led to performance degradation due to excessive aggregation. This optimized substrate was employed to detect ∼28 ppm of anethole vapor and ∼4 ppm of 4-ethylbenzaldehyde vapor. The LSPR measurements revealed rapid spectral shifts upon exposure, while SERS captured the characteristic Raman peaks. These results demonstrate the sensor’s dual capability: fast, label-free detection via LSPR and high molecular specificity via SERS. The silver nanoisland-based platform, thus, offers a promising approach for selective and sensitive VOC sensing in the gas phase.