This paper describes the development of a nanoscale optical pH probe based upon the surface-enhanced Raman scattering (SERS) properties of silica–gold core-shell nanoparticles. In this approach, a thin layer of gold is deposited onto a core of silica to form a metallic nanoshell with surface plasmon modes in the red-to-near-infrared spectral region. The surface of the nanoshell is functionalized with a pH-sensitive SERS reporter molecule, 4-mercaptopyridine (4-MPy). The SERS spectra of 4-MPy is shown to be sensitive to the pH of the surrounding media within the range of 3 to 7. In addition, it is shown that individual silica–gold core-shell nanoparticles yield more reliable SERS spectra than aggregates of core-shell nanoparticles.
Vol. 2, Iss. 9 Virtual Journal for Biomedical Optics
Rebecca A. Jensen, Jennifer Sherin, and Steven R. Emory, "Single Nanoparticle Based Optical pH Probe," Appl. Spectrosc. 61, 832-838 (2007)