Enhanced SERS performance of Ag nanoparticles using hybrid dewetting process for melamine detection

•Pure Ag thin films were deposited on glass substrates.•Pure Ag films were dewetted using both a regular laser irradiation approach and a hybrid dewetting process.•The hybrid dewetting process resulted in the formation of a mixture of small-sized (∼20 nm) and large-sized NPs (142–167 nm).•The AEF and LOD for the hybrid dewetting process was 1.9 × 105 and 10−7 M, respectively. A thermal evaporation system was used to deposit Ag thin films on glass substrates. The films were dewetted using both a regular laser irradiation approach and a hybrid dewetting process that involved laser irradiation followed by Ag thermal deposition. The study would evaluate and compare the optical characteristics and efficiency in melamine detection within these dewetted films. In the traditional dewetting process, as the laser power increased from 15 to 25 W, the nanoparticles (NPs) size decreased from 162 to 125 nm. Furthermore, an evident optical absorption peak range of 540–600 nm was also observed. Through the hybrid dewetting process, a mixture of small NPs (20 nm) and larger NPs (142–167 nm) were formed. It resulted in two distinct Surface Plasmon Resonance (SPR) peaks at 460 nm and 660 nm, respectively. Notably, a strong Raman peak at 701 cm−1 emerged when a melamine aqueous solution was placed on the hybrid dewetted surface. Comparing the two methods, the hybrid dewetted sample exhibited enhanced fingerprint peak intensity and a higher analytical enhancement factor (AEF). When operating at laser power of 25 W and a scanning speed of 100 mm/s, the maximum AEF value reached 1.9 × 105. The limit of detection for melamine solution in the hybrid dewetted sample was established at 10−7 M. Hence, the hybrid dewetting process is a potential method to produce the mixed-sized nanoparticles for diverse applications.