Au/SBA-15 Based Robust and Convenient- to-Use Nanopowder Material for Surface Enhanced Raman Scattering (SERS) with High SERS Enhancement Factor

Powdered nanocomposite materials composed of SBA-15 mesoporous silica and different types of Au nanoparticles within the mesoporous channel pores (Au/SBA-15) are shown to serve as robust and efficient substrates for surface-enhanced Raman spectroscopy (SERS). Using the Au/SBA-15 samples as SERS substrates and 4-mercaptopyridine (4-Mpy) as SERS reporter molecule, SERS enhancement factors as high as ∼105 are obtained. The degree of SERS enhancement is found to depend on the size of the Au nanoparticles as well as the synthetic procedures employed to synthesize the Au/SBA-15 materials. The high SERS enhancement given by the Au/SBA-15 as compared to any other powered SERS substrates appears to be the result of the formation of SERS “hot spots” due to the side-by-side alignment of Au nanoparticles within the cylindrical channel pores of the SBA-15 mesoporous silica host. Because of their powdered forms, longevity, simple sample preparation procedures, easily tunable surface, and high SERS enhancement factors, Au/SBA-15 can also be expected to serve as simple and convenient-to-use substrates for SERS-based analysis of various analytes, besides 4-Mpy. Furthermore, this work demonstrates the synthesis of supported “naked” Au nanoparticles and their use as SERS substrate directly and without any further chemical modification.