Preparation and characterization of temperature-induced ultrasensitive SERS large-scale vertical Au nanosphere dimers

Plasmonic dimers have a very wide range of applications as a unique platform for studying the fundamental effects of plasmonics. Most dimer structures are prepared by chemical methods and direct-writing methods, such as coupling agents and lithography. These methods are often complex and expensive. Here, we prepared Au nanospheres (AuNSs) by layer-by-layer (LBL) deposition, used polymethyl methacrylate (PMMA) as a spacer layer, and then annealed the deposited AuNSs to orient the assembly and integrate them together. In this paper, suitable PMMA spin coating conditions and optimal annealing temperatures were explored, and large-scale AuNSs-PMMA-AuNSs(NSs-P-NSs) composed of vertical Au nanosphere dimers were prepared successfully. The detection limits of this substrate can reach 4 × 10−12 M/L and 4 × 10−10 M/L for Rhodamine 6 G (R6G) and Crystal Violet (CV), respectively, demonstrating excellent Raman activity. In addition, the sensitivity of detecting aspartame (APM) is 0.015625 g/L. This method is not only simple to operate but also allows the preparation of a large-scale uniform substrate with excellent detection capabilities.