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Revisiting the conformational adsorption of L ‐ and D ‐cysteine on Au nanoparticles by Raman spectroscopy
Author(s) -
RodríguezZamora P.,
SalazarAngeles B.,
Buendía F.,
CorderoSilis C.,
Fabila J.,
BazánDíaz L.,
FernándezDíaz L.M.,
PazBorbón L.O.,
Díaz G.,
Garzón I.L.
Publication year - 2020
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.5782
Subject(s) - raman spectroscopy , cysteine , adsorption , chemistry , colloidal gold , molecule , nanoparticle , density functional theory , spectroscopy , thiol , infrared spectroscopy , sulfur , crystallography , inorganic chemistry , nanotechnology , materials science , computational chemistry , organic chemistry , physics , quantum mechanics , optics , enzyme
Understanding the physical mechanisms of thiolated molecules adsorption on metal surfaces has required copious research, particularly on Au–cysteine systems due to the affinity of sulfur molecules to gold surfaces, as well as the interesting structural modifications that this strong interaction induces and the peculiar optical, chiroptical, and electronic properties of Au(SR) systems. Here, we present vibrational experimental data on the adsorption of L ‐ and D ‐cysteine on small gold nanoparticles (<2 nm) by means of Raman spectroscopy. L ‐ and D ‐cysteine molecules adopt the same strained conformation upon adsorption on colloidal gold nanoparticles, regaining structure due to the stabilization that the gold nanoparticle induces on the cysteine, reflected in the recuperation of vibrational bands from their polymorphically distinctive crystalline forms. Through the analysis of Raman vibrational modifications after adsorption, we found experimental evidence that confirms a stabilized cysteine conformation locating the carboxyl group in the antiposition (P C isomeric rotamer) for both molecules. This result is supported by extensive density functional theory (DFT) calculations and simulated Raman spectra, considering zwitterionic cysteine adsorbed on a Au 34 cluster, emulating experimental nanoparticle sizes. Our Raman spectroscopy experimental and DFT results determine one of the oxygen atoms of the carboxyl group as a second adsorption site after the sulfur atom, confirming that independent of its polymorphism and enantiomerism, zwitterionic cysteine interacts with gold nanoparticles through the thiol group and the carboxyl group as adsorption sites.