The bonding in thiolate protected gold nanoparticles from Au4f photoemission core level shifts.
ABSTRACT Density functional theory calculations are used to evaluate Au4f core level shifts of methyl thiolate protected Au(25), Au(102) and Au(144) nanoparticles. The shifts are found to provide sensitive fingerprints of the chemical environment. In particular, Au atoms in protective gold-thiolate complexes have higher binding energies than Au atoms with solely metal neighbors. The core level shifts for the nanoparticles are compared to the corresponding results for methyl thiolates adsorbed on Au(111) and implications for the understanding of the gold-sulfur bond is discussed.
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ABSTRACT: Metallic nanoparticles display distinct localized surface plasmon resonance (LSPR) properties that depend on their size, shape, and composition and that can be monitored to characterize their growth. Utilizing LSPR properties, we report the first investigation of ambient temperature formation of trioctylamine (TOA)-stabilized spherical silver nanoparticles (AgNPs) of ∼3.0-nm diameter by mild reduction of AgClO4 with the weak reducing agent heptamethyltrisiloxane in organic solvent. The appropriate choice of experimental conditions caused slow reduction, which allowed the study of the nanoparticle growth process by time-resolved UV–visible spectroscopy and transmission electron microscopy (TEM). The linear nanoparticle growth kinetics from 50 min to end of the reaction derived from LSPR changes, the absence of a bimodal size distribution during the initial stage of the reduction process from TEM analysis, and the single crystallinity of the resulting AgNPs suggested a diffusion-controlled Ostwald-ripening growth process. It was also found that in addition to its stabilizing ability, TOA acted as a catalyst and facilitated Ag+ reduction. Furthermore, a modest increase in reaction temperature caused a substantial enhancement in the AgNP formation rate, and low concentration of stabilizing ligand yielded an increase in size and dispersity.Plasmonics · 2.43 Impact Factor