Adsorption geometry of propranolol enantiomers on silver nanoparticles

In the present work we report an experimental and theoretical study on propranolol a widely used beta-blocking drug. Raman and Surface Enhanced Raman Spectroscopies (SERSs) have been employed for the detection of the molecular vibrations, while quantum chemical calculations based on density functional theory (DFT) have been used to determine the geometrical, energetic and vibrational characteristics of propranolol. Using a 785 nm laser line, the SERS spectra of the two propranolol enantiomers adsorbed on hydroxylamine reduced silver colloids have been measured in the 3–11 pH range. Based on DFT calculations performed at the B3LYP level of theory the FT-IR, Raman and SERS spectra of propranolol enantiomers were assigned. The adsorption geometry of both enantiomers onto the silver surface was predicted using the calculated molecular electrostatic potential (MEP) in association with data obtained from SERS.

► A complete assignment of the experimental vibrational bands is reported for propranolol.
► A model of molecular attachment of propranolol on the silver surface is proposed.
► The adsorption is done by a physisorbtion process through the implication of oxygen atoms.
► The naphthalene ring lies in a perpendicular orientation to the silver surface.