Plasmonic carbon nanohybrids from laser-induced deposition: controlled synthesis and SERS properties

A novel single-step, laser-induced and solution-based process is presented for synthesizing complex hybrid metal/carbon nanostructures. The process relies on simply illuminating the interface between a substrate and a liquid solution of the supramolecular complex [Au13Ag12(C2Ph)20(PPh2(C6H4)3PPh2)3][PF6]5 (hereinafter abbreviated as SMC) with an unfocussed He–Cd laser having a wavelength of 325 nm and an intensity of I = 0.5 W/cm2. The process results in hybrid nanostructures of well-controlled morphology: nanoparticles (NP) and 2D flakes, which may also grow jointly to form 3D morphologically complex multipetal ‘flower-like’ structures. At the atomic scale, the obtained metamaterials are complex in composition and structure, i.e., they contain bimetallic Au–Ag nanoclusters of diameter 3–5 nm incorporated inside a carbonaceous matrix. This matrix can be amorphous or crystalline, and the details of the compositional outcome can be controlled and steered by the laser deposition parameters. Au–Ag nanoclusters show plasmonic behavior including the enhancement of electromagnetic fields of visible light. This leads to the enhancement of Raman scattering by the Au–Ag nanoparticle ensemble within the carbonaceous matrix. This enables a 3D architecture for stimulating surface-enhanced Raman scattering (SERS).