title: Surface-enhanced Raman scattering of coumarin 343 on silver colloidal nanoparticles.
abstract: Surface-enhanced Raman scattering (SERS) of coumarin 343 (C343) adsorbed on silver colloidal nanoparticles reduced by sodium citrate was investigated and the surface adsorption geometry of C343 on Ag was sought by optimizing C343-Ag complexes for neutral and deprotonated C343 molecules in the DFT simulations. The SERS of C343 showed a number of spectral changes upon solution pH change. We found that deprotonated C343 adsorbs on the Ag nanoparticles through the carboxylate group keeping a perpendicular geometry to the surface. When protonated, the adsorption geometry of C343 is changed into more or less flat to the surface as the cyclic ester group becomes a preferred surface adsorption site.
authors.affiliation: Department of Physics and Photon Science, Gwangju Institute of Science and Technology, 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea.
authors.forename: Shafqat
authors.initials: S
authors.lastname: Hussain
authors.affiliation: Department of Chemistry, Gwangju Institute of Science and Technology, 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea. Electronic address: ypang@gist.ac.kr.
authors.forename: Yoonsoo
authors.initials: Y
authors.lastname: Pang
keywords: Ag colloidal nanoparticles; Coumarin 343; Surface adsorption geometry; Surface-enhanced Raman scattering