A novel colloid was synthesized using a two-step photoinduced reducting method with irradiation of ultraviolet and visible light. Characterized by a surface plasmon band in the near-infrared wavelength range, the linear nanoparticle aggregations in the silver colloid was found to occur with high efficient near-infrared surface- enhanced Raman scattering (NIR-SERS) effect and high biocompatibility for human serum albumin (HSA), which provides a potential active substrate for investigating the structure, conformation and interfacial interactions of bio-macromolecules. For the adsorbed HSA, the obtained NIR-SERS spectrum indicates that the majority of peptide- back bone adopts an ct-helical structure, which keeps the native conformation^ characteristic of normal HSA, the microenvironments of some aromatic amino residues are induced to approach the surface of silver nanoparticles. In addition, the detected Raman shifts for COO- and C-S provide evidences that deprotonated carboxyl oxygen atoms and sulphur atoms in the disulfide bridges have the direct interfacial interactions with the silver nanoparticles.

Key words: SILVER, NANOPHASE MATERIALS, SURFACE ENHANCED RAMAN SCATTERING, UV