Ti-Si-Zr-Zn Nanometallic Glass Substrate with a Tunable Zinc Composition for Surface-Enhanced Raman Scattering of Cytochrome c

As a remarkably powerful analytical technique, surface-enhanced Raman scattering (SERS) continues to find applications from molecular biology and chemistry to environmental and food sciences. In search of reliable and affordable SERS substrates, the development has moved from noble metals to other diverse types of structures, e.g., nano-engineered semiconductor materials, but the cost of the enhancement factors (EF) substantially decreasing. In this work, we employ biocompatible thin films of Ti-Si-Zr-Zn nanometallic glasses as the SERS substrates, while tuning the Zn composition. Aided by quartz crystal microbalance, we find that the composition of 4.3% Zn (Ti-Si-Zr-Zn_4.3) gives an ultrasensitive detection of Cytochrome c (Cyt c) with an EF of 1.38 × 10⁴, 10-fold higher than the previously reported EF in the semiconducting metal oxide nanomaterials, such as TiO₂, and even comparable to the reported noble-metal-assisted semiconducting tungsten oxide hydrate. Ti-Si-Zr-Zn_4.3 exhibits a stronger adhesion force toward Cyt c, which ensures the strong binding of Cyt c to the surface, facilitating the Cyt c adsorption onto the surface and thus enhancing the SERS signal. The high separation efficiency of photoinduced electrons and holes in Ti-Si-Zr-Zn_4.3 is also acknowledged for promoting the SERS activity.