Preparation of uniform Ag nanoparticles with enhanced plasmon resonance intensity and antibacterial efficiency via two-step dewetting process

•Ag thin films were processed by three different dewetting methods: thermal aging, pulse-laser irradiation, and two-step dewetting (thermal aging and laser irradiation)•The two-step dewetting process resulted in the formation of small nanoparticles with a narrow size distribution and a strong SPR intensity.•The two-step dewetted film showed a better antibacterial efficiency against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa bacteria than the films processed by thermal aging or laser dewetting alone.•The ROS generation of the two-step dewetted film was significantly greater than that of the laser irradiated film and thermal aged film. Ag thin films were deposited on glass substrates by a high vacuum sputtering system. The films were then processed by three different dewetting methods: thermal aging, pulse-laser irradiation, and two-step dewetting (thermal aging and laser irradiation). The morphologies, crystalline structures, optical properties, Raman signal intensity, and antibacterial efficiency of the dewetted Ag films were analyzed and compared. The island structures of the as-sputtered Ag film were transformed into nanoparticles as the annealing temperature increased. Furthermore, the nanoparticle size decreased with an increasing laser energy. The two-step dewetting process resulted in the formation of small nanoparticles with a narrow size distribution and a strong SPR intensity. A strong Raman peak was also observed for a 1000 ppm melamine aqueous solution deposited on the dewetted surface. The two-step dewetted film showed a better antibacterial efficiency against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa bacteria than the films processed by thermal aging or laser dewetting alone. Moreover, the two-step dewetted Ag film induced a greater ROS generation rate after contact with the Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa bacteria for 24 hr. The greater antibacterial efficiency and Raman signal intensity of the two-step dewetted film were both attributed to the effect of the small nanoparticles in increasing the contact area between the dewetted surface and the bacteria or melamine solution, respectively. Overall, the two-step dewetting process appears to be a promising approach for the fabrication of uniform small-sized nanoparticles for a wide range of applications.