Sonochemical and mechanical stirring synthesis of liquid metal nanograss structures for low‐cost SERS substrates

Abstract

Micro‐nanofabrication technologies are frequently used to prepare surface‐enhanced Raman scattering (SERS)‐active substrates with specially shaped microstructures, whose characteristics of high sensitivity and good reproducibility are our unswerving pursuit of the goal. However, these techniques suffer from high cost and low throughput, which limits the fabrication of large‐area SERS substrates and restricts their practical application in detection analysis. Therefore, a low‐cost, facile, and environmentally friendly fabrication strategy for SERS‐active substrates by sonochemical treatment in conjunction with mechanical stirring without surfactants is proposed for the detection of low concentrations of molecules. Liquid metal alloys were employed as SERS‐active substrate materials and are easily oxidized to form an oxide film in air, resulting in good dispersion of the nanoparticles. In addition, nanograss consisting of rod‐like structures and nanogaps formed on the micro/nanoparticle surface, providing numerous SERS‐active sites. The shape, size, and surface nanostructure of the micro/nanoparticles could be tuned by controlling the ultrasonication time and the stirring speed. The performance of the SERS substrate coated with Au film was evaluated by using rhodamine 6G as a probe. The resulting limit of rhodamine 6G detection for the optimized nanograss‐structured substrate by Raman analysis was as low as 10−7 M, and the standard deviation was 8–15.5%, which meets the requirements for the trace detection of analytes. This facile, large‐scale, low‐cost, and green synthesis of a liquid metal nanograss‐structured substrate with high SERS activity and sensitivity makes it a perfect choice for practical SERS detection applications.

Emerging Role of Liquid Metals in Sensing

“…The robust SERS effect observed for Ga NPs and their composites has been applied in several studies to enable sensitive and ultrasensitive detections. In one such case study, NPs of Galinstan, featuring a textured surface consisting of nanorods and nanogaps, were prepared through sonication . The surface of Galinstan NPs was coated with a Au film and was applied for SERS detection of R6G.…”

“…In one such case study, NPs of Galinstan, featuring a textured surface consisting of nanorods and nanogaps, were prepared through sonication. 151 The surface of Galinstan NPs was coated with a Au film and was applied for SERS detection of R6G. Here the textured structure provided numerous active sites for SERS, resulting in a LOD of 10 −7 M. In another study, the surface of Ga particles with oxide coatings (in their work, the authors referred them as Ga particles), deposited on a silicon substrate by CVD method, was coated by Au NPs and used for SERS detection.…”

Nano‐Biomedicine based on Liquid Metal Particles and Allied Materials

“…For example, coating nanograss on LMNPs surface would alter the surface morphology and further enable surface‐enhanced Raman scattering (SERS)‐active sites for molecular detection. [ 88 ] Besides the physical or chemical intervention, the temperature provides an autonomous texture regulation on the surface structure, roughness, and composition. Two tiers of surface texture are demonstrated under heating.…”

“…[ 105 ] In another work, a facile and low‐cost modification method was proposed to prepare the SERS substrate, in which the surface of LMNPs is modified with rod‐like nanograss morphology. [ 88 ] The fabricated substrate can enable stable and sensitive properties, as well as a lower detection limit, which can be used to detect molecules and biomolecules.…”

Recent advances in linear and nonlinear Raman spectroscopy. Part XIII

“…Chen and co‐workers used sonochemical and mechanical stirring for the synthesis of liquid metal nanograss structures as low‐cost SERS substrates. The method is a facile, large scale, low cost, and green synthesis of a liquid metal nanograss‐structured substrate with high SERS activity that makes it an ideal choice for practical SERS detection applications . Guo and coworkers used ion‐inducing surface interactions for improved SERS detection of melamine in fertilizer and soil.…”