Characterization of Organic Molecules Attached to Gold Nanoparticle Surface Using High Resolution Magic Angle Spinning 1H NMR

Structural elucidation of molecules attached to nanoparticle surface holds key to the successful chemical modifications of nanomaterial surface. In this investigation, we effectively optimized H-1 HRMAS NMR conditions and applied one- and two-dimensional techniques to fully characterize ligand structures on surfaces of gold nanoparticles (GNPs). We found that there are significant differences in detection sensitivity depending on the distance between the surface of GNP and protons in the ligand molecule, with the loss of sensitivity for protons closer to the nanoparticles. Furthermore, NMR spectra of aromatic protons in ligands attached to GNP seem to have a broad base compared with aliphatic ligands, indicating some degree of potential pi-pi stacking effects. Our results demonstrate that 1H HRMAS NMR is an irreplaceable method for fully characterizing nanoparticle surface-bound molecules.