Tweezing and Manipulating Nanomaterials on Tapered Optical Fiber to Develop SurfaceEnhanced Raman Spectroscopy (SERS) Substrate

Abstract

A compact and cost-effective fiber-based probe was manufactured for the detection of chemicals at low concentrations using Surface-Enhanced Raman Spectroscopy (SERS). Multi-mode optical fiber was tapered with a dynamic etching process using Hydrofluoric (HF) acid. The desired length, tip diameter, and cone angle of the tapered fiber were obtained by using this process. The SERS substrate was prepared by depositing Gold Nanorods (GNRs) on the tapered fiber surface by the phenomenon called Optical Tweezing (OT). The tapered fiber was characterized by using a Scanning Electron Microscope (SEM) and Optical Microscope. Light from a a He-Ne laser was coupled to the untapered end of the tapered fiber to study the distribution of GNRs using the Optical Microscope. The effect of different tweezing wavelengths, and the tapered length on the distribution of GNRs on the tapered fiber surface was investigated. It was observed that the maximum surface area of tapered fiber was covered with GNRs when tweezed consecutively with two different wavelengths (1064 nm and 632 nm). The application of the tapered fiber covered with GNRs as a SERS substrate was investigated for a chemical and material, Rhodamine 6G (R6G) and Graphite, respectively. Furthermore, we presented the tweezing of an another compound Zn (OH)2 on the tapered fiber surface when mixed with GNRs solution using two lasers consecutively.