Remarkable surface-enhanced Raman scattering on self-assembled {201} anatase

Semiconductors exhibit great potential as a surface-enhanced Raman scattering (SERS) substrate due to their low cost, stability, and biocompatibility. However, their application has been essentially restricted by their intrinsically low SERS sensitivity (10-10 2 ). Herein, sea urchin-like TiO 2 was obtained by a self-assembled growth of crystals enclosed with the {201} facet. The high-symmetric spiny spheres exhibited appreciable Raman enhancement factors (EFs) of 1.6 × 10 6 , three orders of magnitude higher than those asymmetric TiO 2 with exposed {101}, {001}, and {100} facets. The greatest charge transfer upon dopamine adsorption occurred on {201} TiO 2 due to its high density of unoccupied t 2g orbitals, partly contributing to the excellent SERS performance. More importantly, the sea urchin-like spheres created high-density hotspots evenly distributed in the vicinity of sharp tips and at narrow gaps between the spines, enabling a strong electromagnetic field enhancement (1.4 × 10 4 ). Benefiting from the specific electronic and morphologic properties, the self-assembled {201} TiO 2 exhibited superior SERS performance in terms of both intensity and reproducibility. The insights gained from this study open a new avenue to improve the SERS performance of semiconductors for applications in biomedical analysis, food detection, and toxicity tests. The self-assembled sea urchin-like {201} TiO 2 exhibits Raman enhancement factors at 1.6 × 10 6 , ascribed to shape-dependent electromagnetic enhancement with high-density hotspots in the vicinity of sharp tips and at narrow gaps between spines.