Plasmonic Au-Ag alloy nanostars based high sensitivity surface enhanced Raman spectroscopy fiber probes

The noble metal substrate components and geometries have a critical effect on surface enhanced Raman spectroscopy, for ultra-trace molecular detection. In present work, Au-Ag alloy nanostars were synthesized, and homogenously assembled on silica optical fibers for fiber probes fabrication. The Au-Ag alloy nanostars were controlled synthesized by the ratio of Au and Ag. The fiber probes with uniform and dense distribution of Au/Ag alloy nano-stars were fabricated through PVP dispersant addition in metal nanostructure solution and fiber surface siliconizing. The limitation of detection of fiber probes for crystal violet (CV) and Rhodamine 6 G (R6G) are 10(-9) M and 10(-8) M, respectively, under 633 nm laser excitation. The relationship between analyte concentrations and Raman intensities showed nearly linear, which indicates potential applications for quantitative analysis. In addition, the fiber probes showed well reproducibility, with maximum 8.43% deviation from different probes. The electromagnetic field distribution simulation revealed much stronger electric field from nanostar tip top than sphere nanoparticles, even greater field from closed and crossed tip top between two nanostars, which was responsible for the high sensitivity of the fiber probes. The fiber probes could be applied for ultra-trace, single molecular detections for chemistry, biology and others. (C) 2021 Elsevier B.V. All rights reserved.