Microfluidic Synthesis and Catalytic Application of PVP-Stabilized, ∼1 nm Gold Clusters

Abstract

Small PVP-stabilized gold clusters were successfully prepared by the homogeneous mixing of continuous flows of aqueous AuCl 4 (-) and BH 4 (-) in a micromixer. Spectroscopic characterization revealed that microfluidic synthesis could yield monodisperse Au:PVP clusters with an average diameter of approximately 1 nm, which is smaller than clusters produced by conventional batch methods. These approximately 1 nm Au:PVP clusters exhibited higher catalytic activity for the aerobic oxidation of p-hydroxybenzyl alcohol than did Au:PVP clusters prepared by batch methods.

Toward an Atomic-Level Understanding of Size-Specific Properties of Protected and Stabilized Gold Clusters

“…The two solutions were mixed by microfluidic mixing (route a) 146 or conventional batch mixing (route b). 143145 By overlaying laminated substreams with a thickness of 70¯m, the microfluidic mixer mixes the two solutions more homogeneously than is possible by batch mixing.…”

Heterogeneous photocatalytic removal and reaction kinetics of Rhodamine-B dye with Au loaded TiO2 nanohybrid catalysts

“…The values of k and K are used to explain the coeffi cients defi ning the rate determining reaction events and pre--equilibrium adsorption within an adsorbed monolayer at the oxide material surface and the aqueous solution interface. The effect of light intensity is also incorporated in k and K which accounts for the equilibrium constant for fast adsorption-desorption processes between surface monolayer and bulk solution 14 . After integration of the above formula it is transformed to: (2) if the solution is highly diluted or C is very small especially as the initial concentration (C 0 ) of RhB dye is a millimolar solution (C 0 «0.1 mmol L -1 ), and in this case K .…”

Microreactors for Gold Nanoparticles Synthesis: From Faraday to Flow

“…Deviations of the local concentration of reactants, particularly strong reducing agents like sodium borohydride, influence the kinetics of the cluster formation and are detrimental to the size distribution. Tsunoyama et al presented a microfluidic method to produce ultra-small PVP-stabilized gold nanoparticles using a SIMM-V2 micromixer (IMM, Figure 2A) [32]. In this micromixer, the total flow of HAuCl 4 gold precursor, PVP and an aqueous solution of sodium borohydride was split in a multitude of parallel substreams with a thickness below 100 µm.…”

“…However, sodium borohydride is known to decompose in water and produce hydrogen gas bubbles. Generation of additional gas phase in single phase operation may enhance convective mixing between liquid elements, however in a rather irregular manner [32]. Such unpredictable and irregular mixing between liquid reactants would make the process unreliable for sustained and reproducible synthesis.…”