Fabrication of the TiN-Ag Double-Shell Hollow Nanosphere Structure As the Highly Sensitive Substrate

Abstract

Surface plasmon resonance (SPR) effect has been intensively studied in recent years due to its wide applications in sensing or optical regimes, such as surface-enhance Raman scattering (SERS) for molecular detection 1, 2, plasmonic optical tweezers3 and so on. It has been well accepted that the noble metals, such as Ag and Au, especially Ag, are the ideal plasmonic materials in SERS detection 4. But, Ag generally exhibits poor chemical and thermal stability, which would deteriorate its SERS activity5. So, alternative plamonic materials or passivation strategy were often proposed to resolve those issues. TiN, besides its good chemical stability, high melting point, and high hardness as other metal nitrides, also exhibits a metal-like optical properties in the visible and longer wavelengths6, 7 and thus might be considered as a potential plasmonic material. In this work, the surface modification on Ag hollow nanosphere (HNS) arrays was carried out by coating a thin layer of TiN, which presents high and stable sensitivity on molecular detection, including R6G and b-agonists. Theoretically and experimentally, it has been founded that the TiN coating layer can effectively manipulate the local field distribution and intensity near the Ag HNS, as well as the multiple plasmonic resonances on the composite hollow structure.8 Further Raman characterizing indicated that the multiple coupling effect between the plasmonic cavities and the charge-transfer process between the TiN/Ag shells enable the substrate to be a good SERS substrate with intensively enhanced local filed and Raman activity comparing with the bare Ag HNS arrays.