| Abstract [eng] |
The purpose of this work was to generate hybrid gold-silver nanoparticles from thin metallic films in water using nanosecond laser pulses and compare the plasmonic properties, energy dependency and stability of the formed particles. Nanoparticles of gold and silver precious metals have a high area-to-volume ratio, electrical conductivity, chemical stability, catalytic functions and good biocompatibility. The optical properties of metal nanoparticles depend on the localized surface plasmon resonance (LSPR). The absorption of gold and silver nanoparticles occurs in different areas of the visible electromagnetic spectrum. Hybrid gold-silver nanoparticles are used to extend the resonant wavelength range. For this research a nanosecond pulsed laser was used to scan thin hybrid Au-Ag metal films (100 nm) on a glass substrate in aqueous solution. This process does not require chemical reagents or stabilizers. Laser parameters for each film were the same: the laser wavelength was 1064 nm, 500 mm/ s laser scan speed, 50 µm hatch, 10 kHz frequency. The energy was gradually changed from 50 µJ to 300 µJ (every 50 µJ). The obtained nanoparticles were characterized by transmission electron microscopy (TEM) and spectrophotometer. The formed hybrid nanoparticles have colors between gold (pink) and silver (yellow) nanoparticles due to their unique absorption and scattering. The abundance of color indicates the variety of localized surface plasmon resonance (LSPR) at different wavelengths that we can observe in the extinction spectra. It has been ascertained that the incorporation of a gold layer into the silver film weakens the particle absorption, promotes redshift and particle size dispersion. Nanoparticle generation from thin films depends on energy: increasing the energy increases the concentration, but when it is too high (from 250 µJ), part of the energy is absorbed during plasma shielding, thus reducing efficiency. Judging from the narrow and high spectra, the strongest LSPR was recorded in nanoparticles generated from the film made of 75 nm silver and 25 nm gold layer, using a pulse energy of 150 µJ. The results of the stability test showed that the hybrid particles remain stable for one week, after which the aggregation processes begin. The best stability result (4–5 weeks) is achieved with higher (250-300 µJ) pulse energy. |
