Laser-induced assembly of Au nano-polyhedron clusters as stable 3D superstructures with ultrabroadband plasmonic resonance for promoting multi-band SERS

Abstract

Multi-band surface-enhanced Raman spectroscopy (SERS) via multiple excitation wavelengths operated on broadband resonant substrate can empower a high-dimensional comprehensive molecular diagnosis of complex analytes. Herein, we demonstrate an extraordinary multi-resonant SERS active substrate that is composed of three-dimensional (3D) hierarchical plasmonic Au superstructures (SS) with both horizontal and vertical close-packed nano-polyhedron clusters on fluorine-doped tin oxide-coated (FTO) support. The stable solid-state Au SS can be simplistically developed by ultraviolet laser irradiation of FTO plate in HAuCl4 solution that facilitates photoexcited reduction of Au ions and then anisotropic nucleation of Au atoms. The 3D Au SS with ultrabroadband plasmonic resonance ranging from visible light to near-infrared region (400∼2000nm) provide remarkable enhanced multi-band SERS performances under 532, 633 and 785 nm excitation wavelengths, in comparison with the reference normal Au nanoparticles (NPs). Especially, the 785 nm NIR excitation of the generated SERS substrate enables the ultra-low detection limit of crystal violet (CV) molecules to be achieved as low as 10−16 M, which is obviously better than many previous works. The ultrahigh multi-band SERS activity is highly related the strong synergetic coupling effects of these interconnected Au nano-polyhedrons with hybridized multiple plasmonic modes. Besides, the ingenious Au configuration also possesses excellent SERS spatial uniformity, long-term stability and reproducibility, having more promising potentials for practical operation. Therefore, the versatile 3D plasmonic SS may grant attractive alternative pathway toward robust multi-band SERS analyses in the near future.