Direct visual evidence of end-on adsorption geometry of pyridine on silver surface investigated by surface enhanced Raman scattering and density functional theory calculations

Snehasis Bhunia; Stefan Forster; Nidhi Vyas; Hans-Christian Schmitt; Animesh K Ojha

doi:10.1016/j.saa.2015.07.019

Direct visual evidence of end-on adsorption geometry of pyridine on silver surface investigated by surface enhanced Raman scattering and density functional theory calculations

Spectrochim Acta A Mol Biomol Spectrosc. 2015 Dec 5:151:888-94. doi: 10.1016/j.saa.2015.07.019. Epub 2015 Jul 4.

Authors

Snehasis Bhunia¹, Stefan Forster², Nidhi Vyas³, Hans-Christian Schmitt², Animesh K Ojha⁴

Affiliations

¹ Department of Physics, Motilal Nehru National Institute of Technology, Allahabad 211004, India.
² Institute of Physical and Theoretical Chemistry, University of Wuerzburg, Am Hubland, D-97074 Wuerzburg, Germany.
³ Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India.
⁴ Department of Physics, Motilal Nehru National Institute of Technology, Allahabad 211004, India. Electronic address: animesh198@gmail.com.

PMID: 26184474
DOI: 10.1016/j.saa.2015.07.019

Abstract

Fourier transform Raman (FT-Raman) spectra of neat pyridine (Py) and surface enhanced Raman scattering (SERS) spectra of Py with silver nanoparticles (AgNPs) solution at different molar concentrations (X=1.5M, 1.0M, 0.50 M, 0.25 M, and 0.125 M) were recorded using 1064 nm excitation wavelength. The intensity of Raman bands at ∼1003 (ν11) and ∼1035 (ν21) cm(-1) of Py is enhanced in the SERS spectra. Two new Raman bands were observed at ∼1009 (ν12) and ∼1038 (ν22) cm(-1) in the SERS spectra. These bands correspond to the ring breathing vibrations of Py molecules adsorbed at the AgNPs surface. The value of intensity ratios (I12/I11) and (I21/I22) is increased with dilution and attains a maximum value at X=0.5M and upon further dilution (0.25 and 0.125 M) it drops gradually. The theoretically calculated Raman spectra were found to be in good agreement with experimentally observed Raman spectra. Both, experimental and theoretical investigations have confirmed that the Py interacts with AgNPs via the end-on geometry.

Keywords: AgNPs; DFT; Pyridine; SERS.

Publication types

Research Support, Non-U.S. Gov't