Electrochemical Size Discrimination of Gold Nanoparticles Attached to Glass/Indium−Tin-Oxide Electrodes by Oxidation in Bromide-Containing Electrolyte

Abstract

Here we describe the electrochemical oxidation of an assembly of gold nanoparticles (Au NPs) attached to glass/indium-tin-oxide (ITO) electrodes as a function of particle size. We synthesized Au NP arrays with NP diameters ranging from 8 to 250 nm by electrodeposition of Au from HAuCl(4) in H(2)SO(4) at potentials of -0.2 to 0.8 V versus Ag/AgCl using chronocoulometry to keep the amount of Au deposited constant. The average Au NP size increased with increasing deposition potential. The chemical reduction of HAuCl(4) by NaBH(4) in trisodium citrate solution led to 4 nm average diameter Au NPs, which we chemisorbed to the glass/ITO electrode. Linear sweep voltammograms (LSVs) obtained on the glass/ITO/Au NP (4 to 250 nm) electrodes (with a constant coverage of Au in terms of Au atoms per cm(2)) from 0.5 to 1.1 V in 0.01 M potassium bromide plus 0.1 M HClO(4) showed a positive shift in oxidation potential from 734 +/- 1 mV to 913 +/- 19 mV with increasing Au NP diameter. The shift agrees qualitatively with that predicted by a shift in the redox potential based on a difference in free energy associated with a change in surface energy as a function of particle size. On the basis of the charge during Au deposition versus the charge during oxidation, the oxidation process produces a mixture of Au(III)Br(4)(-) (25%) and Au(I)Br(2)(-) (75%). A glass/ITO electrode coated with a mixture of 4 and 250 nm Au NPs revealed 2 oxidation peaks, consistent with the two Au NP size populations present on the surface.

Displacement of voltammetric peaks with nanoparticles size: a nonextensive thermodynamic approach

“…Figure 3 : experimental of peak potentials for the system (solid points) described in ref. [22]. The solid curve is calculated from eq.26.…”

“…The second study by the same authors, reported here, considers gold nanoparticles [22]. In this paper, the authors describe the electrochemical oxidation of an assembly of gold nanoparticles (Au NPs) attached to glass/indium-tin-oxide (ITO) electrodes as a function of particle size.…”

“…We have exploited data reported by these authors for the electrodeposition made at 0.8V, taking as the value of the peak potential, 926 mV, and as E° those corresponding to the one-electron exchange (i.e., 963 mV) [22]. The graphical exploitation of the eq.…”

Gold Nanoparticle-Based Colorimetric Sensors for Detection of DNA and Small Molecules

“…53,246 The UV-Vis spectrometer is used to characterize the concentration of the AuNPs. The maximum absorption peak of the prepared AuNP was located at 504 nm ( Figure 16A).…”

The unique electrochemical reactivity of small metal nanoparticles.

“…34,35 In our group we were studying the effect of size dependence on the change of the Ep value. [36][37][38] It is very well know that in many cases the reactivity of metal nanoparticles is directly correlated to the decrease in size. A decrease in size changes the coordination number of the atoms at the surface of the nanoparticle.…”