Surface-Enhanced Raman Scattering Fiber Probe Based on Silver Nanocubes

Surface-enhanced Raman scattering (SERS) provides a novel method for low concentration molecular detection. The performances were highly dependent on the sizes, geometries and distributions of metal nanostructures. Here, highly sensitive SERS fiber probe based on silver nanocubes (Ag NCs) was fabricated, by assembled nanostructures on planar and tapered fiber tips. Ag NCs were synthesized by polyol method, and controlled by reductant content, reaction temperatures and crystal growth durations. Tapered fibers with different cone angles were prepared by chemical etching. The electromagnetic distribution simulation indicated that nanocubes had stronger electric field between two cubes and vertex corners than nanosphere, under 532 nm laser excitation. The intensity could reach 53.52 V/m, for cubes with 70 nm edge length. The SERS performance of probes was characterized using crystal violet analyte. The detectable lowest concentration could reach 10–9 and 10–10 M for planar and tapered fiber probes, respectively. The corresponding enhancement factor could be 9.02 × 107 and 6.22 × 108. The relationship between SERS peak intensities and analyte concentrations showed well linear, which indicated both fiber probes could be applied for both qualitative and quantitative analysis. Furthermore, optimal cone angle of tapered fiber SERS probe was 8.3°. The tapered fiber SERS probes have highly sensitive activity and great potential in substance detection.