Fabrication of Gyroid-Structured Metal/Semiconductor Nanoscaffolds with Ultrasensitive SERS Detection via Block Copolymer Templating

摘要

Surface-enhanced Raman scattering (SERS) is a label-free and powerful techniquefor monitoring dynamic molecular processes with high sensitivity andreproducibility. SERS has diverse applications in medicine, molecular science,biology, and chemical sensing. In this study, a template-based approach tocreate an ultrasensitive SERS-active substrate is proposed which involvescombining nanostructured semiconductors and noble metals. A nanoporouspolymer obtained from hydrolyzed gyroid-forming polystyrene-blockpoly(l-lactide) (i.e., PS-b-PLLA) is used as a template for Ag reduction andTiO_2 sol–gel reaction. After calcination to remove the polymeric template, TiO_2nanoscaffolds appear as self-supporting 3D nanoobjects with homogeneouslyand closely distributed Ag nanoparticles, providing a high density of regionswith intense local field enhancement (hotspots). Rhodamine 6G molecules areused as probe molecules to demonstrate the SERS performance, revealing amarkedly high average enhancement factor of up to 10~(14). The intrinsic photocatalyticproperties of TiO_2 can degrade target organic chemicals for theself-cleaning and reproduction of SERS-active substrates. Moreover, a simplehydrazine reduction-based approach is applied for the formation of regeneratedAg/TiO_2 nanoscaffolds to reduce the use of Ag-based SERS-active substrates,decreasing the costs associated with relevant industrial processes.