Three-dimensional surface-enhanced Raman scattering substrates constructed by integrating template-assisted electrodeposition and post-growth of silver nanoparticles.

Ordered arrays of Ag nanoparticles-assembled cavities are fabricated by templated electrodeposition and post-growth. Oriented attachment and Ostwald ripening are proposed to drive the post-growth process. Such Ag cavity array shows high surface-enhanced Raman scattering sensitivity to pesticides (thiram and paraquat). [Display omitted] • Three-dimensional Ag nanostructure arrays have been fabricated by a simple method. • Ag nanoparticles-assembled micro-cavity arrays were achieved using templated electrodeposition and post-growth. • The three-dimensional substrate with dense hotspots showed high SERS sensitivity. • The fabricated SERS substrate showed high spectral uniformity and reproducibility. • Sensitive SERS detection of pesticide residues on fruits was realized. Three-dimensional (3D) plasmonic nano-arrays can provide high surface-enhanced Raman scattering (SERS) sensitivity, good spectral uniformity and excellent reproducibility. However, it is still a challenge to develop a simple and efficient method for fabrication of 3D plasmonic nano-arrays with high SERS performance. Here we report a facile approach to construct ordered arrays of silver (Ag) nanoparticles-assembled spherical micro-cavities using polystyrene (PS) sphere template-assisted electrodeposition and post-growth. The electrodeposited small Ag nanoparticles grow into bigger stable nanoparticles during the post-growth process, which could significantly improve the SERS sensitivity. The Ag nanoparticles-assembled 3D micro-cavity array provides much more hotspots in the excitation laser beam-covered volume than the two-dimensional counterpart. The relative standard deviation (RSD) of 612 cm−1 peak of rhodamine 6G (R6G) was calculated to be 8%, and the RSD of the characteristic peak taken from substrates of different batches was less than 10%. The detectable lower concentration as low as 1 fM was achieved for an aqueous solution of R6G. Such SERS substrate also showed high sensitivity to thiram (fungicide) and paraquat (herbicide) in water with limits of detection of 0.067 nM and 2.5 nM respectively. Furthermore, it also demonstrated that SERS detection of pesticide residues on fruits can be realized, showing a potential application in rapid monitoring food safety. [ABSTRACT FROM AUTHOR]