Obviously Angular, Cuboid-Shaped TiO2 Nanowire Arrays Decorated with Ag Nanoparticle as Ultrasensitive 3D Surface-Enhanced Raman Scattering Substrates

In recent years, surface-enhanced Raman scattering (SERS) has received renewed attention, because of its nondestructive, ultrasensitive, and rapid analysis, detection, and imaging. Development of SERS substrates with high sensitivity and excellent stability is of great importance to realize its practical applications in trace analysis, bio diagnosis, and in vivo studies. In this work, we demonstrate wafer-scale Ag-nanoparticle-decorated, obviously angular, quasi-vertically aligned cuboid-shaped TiO 2 nanowire arrays (TiO 2 -NWs), as ultrasensitive and uniform 3D SERS substrates. A detection limit of 10 –15 M rhodamine 6G molecules and an analytical enhancement factor of 10 12 were achieved on the cuboid-shaped TiO 2 -NWs arrays with 9 min Ag-sputtering. This is the best result obtained among the literature values on Ag-modified semiconductor SERS substrates. More importantly, the optimized TiO 2 -Ag also exhibits excellent stability and uniformity. The excellent SERS performance is attributed to the “cusp” and “gaps” formed on the Ag-NPs coated TiO 2 nanowire arrays, which create a huge number of SERS “hot spots”. The experimental results were further confirmed by theoretical calculations of the spatial distributions of electromagnetic field intensity. The prepared TiO 2 -Ag SERS substrates with such low detection limit and high sensitivity will provide a promising candidate for practical chemical and biological detection.