A hybrid dewetting approach to generate highly sensitive plasmonic silver nanoparticles with a narrow size distribution

Highlights: • A hybrid dewetting method to generate Ag nanoparticles from a thin film is presented. • The nanoparticles exhibit a strong plasmonic resonance peak owing to their narrow size distribution. • The refractive index sensitivity of the particles is measured to be 118 nm/RIU (RIU = refractive index unit). Laser dewetting is a simple and efficient method for transforming a metal thin film into nanoparticles. However, the particles obtained via laser dewetting typically exhibit a wide size distribution. This study shows that a combination of thermal and laser dewetting processes can be used to generate more uniform metal nanoparticles. A 10-nm-thick Ag film deposited on glass was irradiated by an Nd:YAG laser pulse to produce nanoparticles with sizes in the range of 35–145 nm. When the film was thermally annealed at 250 °C in an Ar atmosphere before laser irradiation, Ag nanoparticles with a much narrower size distribution were obtained (mean size = 48 nm and standard deviation = 10.5 nm), which was attributed to the island structure formed by the pre-annealing step. X-ray photoelectron spectroscopy confirmed the absence of particle oxidation. An important feature associated with this hybrid dewetting approach was that the obtained Ag nanoparticles showed a strong single plasmonic resonance peak owing to their narrow size distribution. As a plasmonic sensing platform, they exhibited much enhanced refractive index sensitivity and figure of merit than the particles produced via laser dewetting.