title: Diazonium-derived aryl films on gold nanoparticles: evidence for a carbon-gold covalent bond.
abstract: Tailoring the surface chemistry of metallic nanoparticles is generally a key step for their use in a wide range of applications. There are few examples of organic films covalently bound to metal nanoparticles. We demonstrate here that aryl films are formed on gold nanoparticles from the spontaneous reduction of diazonium salts. The structure and the bonding of the film is probed with surface-enhanced Raman scattering (SERS). Extinction spectroscopy and SERS show that a nitrobenzene film forms on gold nanoparticles from the corresponding diazonium salt. Comparison of the SERS spectrum with spectra computed from density functional theory models reveals a band characteristic of a Au-C stretch. The observation of this stretch is direct evidence of a covalent bond. A similar band is observed in high-resolution electron energy loss spectra of nitrobenzene layers on planar gold. The bonding of these types of films through a covalent interaction on gold is consistent with their enhanced stability observed in other studies. These findings provide motivation for the use of diazonium-derived films on gold and other metals in applications where high stability and/or strong adsorbate-substrate coupling are required.
authors.affiliation: Department of Chemistry and National Institute for Nanotechnology, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Lars
authors.initials: L
authors.lastname: Laurentius
authors.forename: Stanislav R
authors.initials: SR
authors.lastname: Stoyanov
authors.forename: Sergey
authors.initials: S
authors.lastname: Gusarov
authors.forename: Andriy
authors.initials: A
authors.lastname: Kovalenko
authors.forename: Rongbing
authors.initials: R
authors.lastname: Du
authors.forename: Gregory P
authors.initials: GP
authors.lastname: Lopinski
authors.forename: Mark T
authors.initials: MT
authors.lastname: McDermott
mesh_terms: D002244:Carbon / Q000737:chemistry*; D003460:Crystallization / Q000379:methods*; D003979:Diazonium Compounds / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D013499:Surface Properties
chemical_list: D003979:Diazonium Compounds; D046911:Macromolecular Substances; D002244:Carbon; D006046:Gold