Selective Synthesis of Gold Nanoparticles in Water/Alcohol Binary Solution Systems by Ultrasonic Irradiation

Abstract

We have synthesized stable gold nanoparticles (AuNPs) by a simple ultrasonic irradiation in water/alcohol binary solutions without additive stabilizer agents. Methanol, ethanol, and 1-propanol are used as solvents. The morphology and optical properties of the sonochemically synthesized AuNPs are characterized using SEM and UVvis spectroscopy. The average particle diameter of as-prepared AuNPs was 36 ± 10 nm for water/methanol system (methanol: 25 vol%), 56 ± 17 nm for water/ethanol system (ethanol:35 vol%), and 24 ± 7 nm for water/1-propanol system (1-propanol: 35 vol%). The water/1-propanol system give the smallest average particle diameter together with the narrowest particle size distribution. This fact also support that the hydrophobicity of 1-propanol is higher, because the side chain of 1-propanol is longer than those in the other alcohols. Thus, it can be concluded that the dispersion of AuNPs is enhanced and their aggregation and growth are suppressed.

Surfactant-Free Colloidal Syntheses of Gold-Based Nanomaterials in Alkaline Water and Mono-alcohol Mixtures

“…Following the G reen C hemistry principles for the development of NPs, we observed that 30 vol % is also a suitable amount of polyols for the development of surfactant-free syntheses. Furthermore, 35 vol % EtOH was found to be the optimal content in previous studies to favor fast kinetics of reduction, e.g., using sonication . In another study using plasma synthesis, faster kinetics of reduction were observed for a mole fraction of ROH around ∼0.09.…”

“…Furthermore, 35 vol % EtOH was found to be the optimal content in previous studies to favor fast kinetics of reduction, e.g., using sonication. 65 In another study using plasma synthesis, 66 faster kinetics of reduction were observed for a mole fraction of ROH around ∼0.09. Note that 30 vol % ROH corresponds to a mole fraction of ∼0.11.…”