Optical properties of aluminum nanostructures modified by polymer coatings

In this research, optical properties of Al films based on Al nanoparticles (Al NPs) with a particle size of 55 nm were studied by analyzing the absorption spectra before and after deposition of polymer coatings. Plasmonic Al nanostructures films were fabricated using spin-coating on quartz substrates, followed by sequential deposition of polymer using poly-
L-lysine (PLL) and dextran. The obtained results showed that dextran coating did not induce significant spectral changes, whereas PLL provided a shift in the absorption resonance peak of Al films from 230 nm to 300 nm. Additionally, at an excitation wavelength of 325 nm, the photoluminescence enhancement of ZnO nanocrystals with 27 nm in particle size was investigated in the presence of Al nanostructures with and without PLL film as intermediate film. The results demonstrated that the increase in photoluminescence enhancement factor at an emission wavelength of 377 nm in the presence of PLL film between ZnO and Al films up to 68%. These findings proved that polymer coatings have a significant impact on the optical response of aluminum nanostructures. The obtained results provide a promising methodology for tuning their optical properties and plasmon-enhanced photoluminescence factor for many plasmonic and biosensing applications in the ultraviolet region.