Synthesis of Polyoxometalate‐Protected Gold Nanoparticles by a Ligand‐Exchange Method: Application to the Electrocatalytic Reduction of Bromate

Abstract

Gold nanoparticles (AuNPs) protected by an alkanethiol in nonaqueous solvent are converted to AuNPs with a surrounding layer of a polyoxometalate, AuNP-POM, by ligand exchange and liquid -liquid extraction into aqueous solution without changing the size of the metal core. With glassy carbon electrodes modified with PMo 12 -AuNP (PMo 12 ¼ H 3 PMo 12 O 40 ), the reduction of bromate was mediated by the first redox process of the Mo VI centers; the reduction occurred at a lower overpotential and yielded a higher cathodic current than that observed with PMo 12 alone as the mediator. This synergistic electrocatalysis, which approached a linear diffusion-controlled process, was used to demonstrate the feasibility of the determination of bromate. A detection limit of 3 mM (k ¼ 3 criterion) was achieved by pulse voltammetry.

Modification of glassy carbon electrode with polyaniline/multi-walled carbon nanotubes composite: Application to electro-reduction of bromate

“…Several approaches have been evaluated to eliminate bromate pollution, such as filtration [6], UV irradiation [7], photo-catalytic decomposition [8], coagulation [9], ion exchange [10], biodegradation [11,12], chemical and electrochemical reduction [13,14]. Among them, the use of electrochemical approach is considered attractive, since they are relatively clean, environment-friendly and often cost efficient [15].…”

Preparation and electrocatalytic application of composites containing gold nanoparticles protected with rhodium-substituted polyoxometalates

“…Analogous to our procedure for preparing polyoxometalate-protected AuNPs [5], the TMSP-protected gold nanoparticles were synthesized by a combination of the Brust-Schiffrin method [29] and a ligand place-exchange reaction [30] by which a hexanethiol (RSH) monolayer on the AuNP core was replaced by the TMSP. The AuNP-SR nanoparticles were synthesized by reduction of HAuCl 4 with NaBH 4 in aqueous solution in contact with toluene, into which AuNP-SR was extracted.…”

“…Expanding on early reports [3,4], numerous applications in electrochemistry have been devised, the bases of which primarily relate to their favorable electron-transfer kinetics and ability to strongly adsorb to a wide range of electrode materials. In concert, these properties have led to fabrication of surface-modified electrodes that are capable of mediating numerous electrochemical reductions [5]. The surface activity of POMs has been employed in the formation [6,7] and stabilization [8-11] of nanoparticles.…”

“…The surface activity of POMs has been employed in the formation [6,7] and stabilization [8-11] of nanoparticles. Indeed, the interaction of Keggin-type lacunary PW 11 O 39 7- with silver is sufficient to displace the ligand from citrate-protected silver nanoparticles [8], and PMo 12 displaces the alkanethiol (RSH) from gold nanoparticles in a place-exchange reaction that facilitates a phase transfer of AnNP centers from non-polar solvent into aqueous solution [5]. Adsorption of PMo 12 is the driving force that converts aggregates of a conventional carbon black suspension into anionic monolayer-protected nanoparticles [6] and of a suspension of platinum black into PtNPs in the 5 - 10 nm domain [7].…”

Fundamental Aspects of Electrodeposition for the Realization of Plasmonic Nanostructures

“…Firstly, a colloidal solution was obtained following the procedure reported in ref. [16], where Au nanoparticles are stabilized by a surrounding layer of adsorbed phosphodecanomolybdenic acid. The subsequent adsorption on the Si surface was performed by potential scanning between À0.1 and À0.25 V in the dark, after adding an aliquot of the colloidal solution to the water containing cell.…”