Hexagonal arrays of Pt nanocylinders on the top surface of PAA membranes using low vacuum sputter coating technique

Abstract

Localized surface plasmons at nanostructured surfaces are played a key role in a wide range of industrial applications. Here, hexagonal arrays of uniformly distributed Pt nanocylinders were fabricated on the top surface of nanoporous anodic alumina (PAA) membrane using low-cost sputter coating technique under low vacuum. Set of PAA membranes were synthesized at the same conditions and coated with Pt for different periods of time. The implemented growth mechanism allowed the vertical accumulation of Pt nanoparticles to form Pt nanocylinders on the active dots of PAA. SEM images showed nanocylinders of heights ranged from 10.0 ± 0.7 nm to 32.0 ± 2.1 nm based on sputtering time. The nanocylinders rate of growth is 1.22 ± 0.09 nm/min. According to SEM images, the uniformity of the nanocylinders decreased as the porosity of the PAA membrane increased. The optical properties of Pt nanocylinders/PAA membranes were investigated and showed strong transverse, longitudinal, and higher longitudinal surface plasmon modes. Relative to the previously reported SPRs for other Pt nanostructures, our Pt/PAA nanostructures showed stronger SPRs at longer wavelengths due to the using of PAA as a host material, the strong electromagnetic coupling between the very close Pt nanocylinders, and the strong coupling between SPRs and interfernce fringes. Moreover, the effects of sputtering time and membrane porosity on the SPR position, oscillation strength, and bandwidth were studied.