Laser synthesis of surfactant-free silver nanoparticles for toxic dyes degradation and SERS applications

Abstract

Surfactant-free silver nanoparticles (NPs) were synthesized by ablating a silver target placed in pure water by nanosecond pulsed Nd:YAG laser beam. UV–Vis spectroscopy and scanning electron microscopy (SEM) were employed to characterize the NPs. The diagnostics revealed that the NPs concentration in liquid linearly increases with the laser pulse energy up to 40 mJ and then starts to decrease with further increase of the laser energy. The diameter of NPs ranges from approximately 20 to 100 nm, with the average diameter of 50 nm. The average diameter of NPs does not seem to vary with the laser pulse energy. The surfactant-free Ag NPs were used to degrade methylene blue (MB) and methyl orange (MO) dyes. The surfactant-free Ag NPs showed high catalytic activity and completely degraded MB and MO. Furthermore, the SERS study of Rhodamine 6G using Ag NPs as a substrate resulted in significant Raman enhancement. In order to demonstrate that the surfactant-free nature of the Ag NPs is responsible for their better catalytic ability, a cationic surfactant is attached to the Ag NPs, which resulted in substantial reduction of its catalytic ability. These results confirm that the better catalytic ability and Surface Enhanced Raman Spectroscopy (SERS) signal enhancement is primarily due to the surfactant-free nature of the Ag NPs synthesized by pulse laser ablation.