Surface enhanced Raman scattering of 2,2′-biphenyl dicarboxylic acid on silver surfaces: Structure and orientation upon adsorption

초록

The SERS spectrum of 2,2'-biphenyl dicarboxylic acid (22-BPDC) adsorbed on Ag nanoparticles has been measured and the observed bands are identified and assigned referred to the ordinary Raman spectrum and to the previously measured SERS spectrum of 4,4'-biphenyl dicarboxylic acid (44-BPDC). [J. Mol. Struct. 1050, 2013, 128] As in the case of 44-BPDC, quantum chemical density functional theory calculations have also been performed to figure out structures and to calculate vibrational wavenumbers and eigenvectors in 22-BPDC. The observed SERS spectra could successfully be simulated from the models for adsorption of 22-BPDC to Ag and three Ag atom clusters. As opposed to 44-BPDC adsorbed flat on the Ag surfaces through both the COO-Ag and phenyl it-electron-metal interactions, the two phenyl rings remain twisted in 22-BPDC upon adsorption on the Ag surfaces with less pi-electron-metal interaction because of small space allowances for the two closely located carboxyl groups compared to 44-BPDC. (C) 2016 Elsevier B.V. All rights reserved.

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