Surface-Enhanced Infrared Absorption and Density Functional Theory Study of Dihydroxybenzene Isomer Adsorption on Silver Nanostructures

A combination of surface-enhanced infrared absorption (SEIRA) and density functional theory (DFT) was used to study the adsorption of the dihydroxybenzene (DH) isomers on silver nanostructures (SNSs). No evidence was observed for the oxidation of any of the DH isomers during adsorption on SNSs. It was found that the SNSs weakened intermolecular hydrogen bonding in thin DH layers adsorbed on SNSs versus the bulk powders with the effect being more pronounced for para-dihydroxybenzene (PDH) than ortho-dihydroxybenzene (ODH) and meta-dihydroxybenzene (MDH). DFT simulations of the infrared spectra of ODH and MDH dimers were good reproductions of the SEIRA spectra and infrared spectra of ODH/MDH powder, but DFT dimer infrared simulations were less effective at modeling the PDH results due to the large variations of hydrogen bonding between PDH films formed on SNSs versus PDH powder. Hydrogen bonding effects were observed between acetone and both PDH and ODH in thin layers adsorbed on SNSs, and C-H center dot center dot center dot O hydrogen bonding was also seen between n-heptane and PDH and ODH in adsorption experiments SNSs. These hydrogen bonding effects were not detected between MDH and either acetone or n-heptane due to differences in resonance effects between MDH versus ODH and PDH.