Convective Self-Assembly of 2D Non-Close-Packed Binary Au Nanoparticle Array with Tunable Optical Properties

Field emission scanning electron microscopy (FE-SEM, Sirion 200) was used to characterize the morphologies of the products. A sputtering device (Quorum, K550X) was employed to deposit the thin Au film on the PS crystal colloidal monolayer. The optical absorption spectra of the products were obtained with an ultraviolet–visible–near-infrared (UV–Vis–NIR) spectrophotometer (Varian, Cary 500). Reflection spectra were collected using the R1 angle-resolved spectroscopy system (R1-A-UV). A confocal microprobe Raman spectrometer (Renishaw Invia) was used to determine the SERS properties. The laser wavelength was 785 nm, and SERS spectra were obtained after integration for 5 s and accumulated 1 time. The laser power was 0.25 mW.