title: Solvent Control of Surface Plasmon-Mediated Chemical Deposition of Au Nanoparticles from Alkylgold Phosphine Complexes.
abstract: Bottom-up approaches to nanofabrication are of great interest because they can enable structural control while minimizing material waste and fabrication time. One new bottom-up nanofabrication method involves excitation of the surface plasmon resonance (SPR) of a Ag surface to drive deposition of sub-15 nm Au nanoparticles from MeAuPPh3. In this work we used density functional theory to investigate the role of the PPh3 ligands of the Au precursor and the effect of adsorbed solvent on the deposition process, and to elucidate the mechanism of Au nanoparticle deposition. In the absence of solvent, the calculated barrier to MeAuPPh3 dissociation on the bare surface is <20 kcal/mol, making it facile at room temperature. Once adsorbed on the surface, neighboring MeAu fragments undergo ethane elimination to produce Au adatoms that cluster into Au nanoparticles. However, if the sample is immersed in benzene, we predict that the monolayer of adsorbed solvent blocks the adsorption of MeAuPPh3 onto the Ag surface because the PPh3 ligand is large compared to the size of the exposed surface between adsorbed benzenes. Instead, the Au-P bond of MeAuPPh3 dissociates in solution (Ea = 38.5 kcal/mol) in the plasmon heated near-surface region followed by the adsorption of the MeAu fragment on Ag in the interstitial space of the benzene monolayer. The adsorbed benzene forces the Au precursor to react through the higher energy path of dissociation in solution rather than dissociatively adsorbing onto the bare surface. This requires a higher temperature if the reaction is to proceed at a reasonable rate and enables the control of deposition by the light induced SPR heating of the surface and nearby solution.
authors.affiliation: †Department of Chemical and Biological Engineering, University of Colorado, 3415 Colorado Avenue, UCB 596, Boulder, Colorado 80309-0596, United States.
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Muhich
authors.affiliation: ‡Department of Chemistry and Center for Nanostructured Electronic Materials, University of Florida, 214 Leigh Hall, Gainesville, Florida 32611-7200, United States.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Qiu
authors.affiliation: †Department of Chemical and Biological Engineering, University of Colorado, 3415 Colorado Avenue, UCB 596, Boulder, Colorado 80309-0596, United States.|§Department of Chemistry and Biochemistry, University of Colorado, UCB 215, Boulder, Colorado 80309-0215, United States.
authors.forename: Aaron M
authors.initials: AM
authors.lastname: Holder
authors.affiliation: ‡Department of Chemistry and Center for Nanostructured Electronic Materials, University of Florida, 214 Leigh Hall, Gainesville, Florida 32611-7200, United States.
authors.forename: Yung-Chien
authors.initials: YC
authors.lastname: Wu
authors.affiliation: †Department of Chemical and Biological Engineering, University of Colorado, 3415 Colorado Avenue, UCB 596, Boulder, Colorado 80309-0596, United States.
authors.forename: Alan W
authors.initials: AW
authors.lastname: Weimer
authors.affiliation: ‡Department of Chemistry and Center for Nanostructured Electronic Materials, University of Florida, 214 Leigh Hall, Gainesville, Florida 32611-7200, United States.
authors.forename: Wei David
authors.initials: WD
authors.lastname: Wei
authors.affiliation: ‡Department of Chemistry and Center for Nanostructured Electronic Materials, University of Florida, 214 Leigh Hall, Gainesville, Florida 32611-7200, United States.
authors.forename: Lisa
authors.initials: L
authors.lastname: McElwee-White
authors.affiliation: †Department of Chemical and Biological Engineering, University of Colorado, 3415 Colorado Avenue, UCB 596, Boulder, Colorado 80309-0596, United States.|§Department of Chemistry and Biochemistry, University of Colorado, UCB 215, Boulder, Colorado 80309-0215, United States.
authors.forename: Charles B
authors.initials: CB
authors.lastname: Musgrave
keywords: bottom-up nanofabrication; density functional theory; organogold chemistry; organometallic chemistry; preferential molecular adsorption; thermal decomposition