Ag dots array fabricated using laser interference technique for biosensing

An interference lithography technique was adopted to fabricate Ag dots array. It has advantages of mask free, cost effective, and good controllability compared to the conventional nanosphere lithography (NSL) method. One-dimensional (1D) grating structures, two-dimensional (2D) grid patterns, and 2D dots array were obtained on the photoresist film by means of direct exposing the resist using the interference patterns. Then the photoresist patterns were transferred to the quartz substrate by wet etching and reactive ion etching. Atomic force microscope (AFM) was employed for geometrical characterization of the patterns generated in the steps from pattern generation to pattern transfer, respectively. The Ag dots array was formed by depositing an Ag thin film of ∼25 nm in thickness on the quartz. Our experimental results showed that wavelength shifts in the extinction spectra is acceptable for the applications of localized surface plasmon resonance (LSPR)-based immunoassay and binding detection.