Particle size dependence of the charging of Au nanoparticles immobilized on a modified ITO electrode

Abstract

Citrate-stabilized gold nanoparticles (Au-NPs) of a nearly spherical shape with four different diameters (3.7, 11.0, 21.7, and 40.8 nm) were immobilized on a 4-aminobutylsiloxane monolayer-modified indium-tin oxide (ITO) electrode. From the results of coulometric measurements using potential step sequences, the number of electrons per particle to be transferred to attain a new equilibrium state after applying a potential step was found to increase in proportion to the square of the diameter. The double layer integral capacitance of the Au-NP surface per unit area in the potential range from −0.4 V to 0.6 V (Ag/AgCl/sat'd KCl) is ca. 70 μF cm -2 , being independent of the particle size. The differential capacitance of the Au-NP surface is a function of the potential with a maximum at 0.32 V, while the function is again independent of the particle size. The kinetics of the charging was discussed using the analysis of the potential step transient current. The potential dependent shift of the plasmon absorption band obtained by constant-potential and potential-modulated transmission-absorption spectroscopic measurements revealed that a smaller Au-NP exhibits a greater blue-shift of the plasmon band when applying more negative potentials, being in line with the Mie-Drude theory.

Gold nanoparticles-enhanced photocurrent at a dye-sensitized liquid|liquid interface

“…The core size of Au-NPs was an average diameter of 17±3 nm determined by analyzing the TEM image. The plasmon absorption band of Au-NPs was observed at 522 nm for a colloidal aqueous solution in agreement with the estimated particle size [13].…”

Charging gold nanoparticles in ZnO by electric fields

“…Extrapolating the measurements of Toyota et al [58] a blue shift of 1.8 nm per electron is estimated for a 2.3 nm gold nanoparticle. Therefore, the shift of 7 nm observed here at maximum applied voltage corresponds to 3.8 electrons per particle on average.…”

A Convenient Electrochemiluminescent Immunosensor for Detecting Methamphetamine Antibody

“…This immunosensor is arranged for antibody test based on the recognition of immobilized antigen protein. [39][40][41] Since MA is a small molecule and does not have immunogenicity, we need to combine the MA molecule into a biological macromolecule without losing its antigenic activity. Firstly, a hapten was formed by introducing a carboxyl group onto the second amino group of MA, then the holoantigen (MA-BSA) was prepared by conjugation of carrier protein (BSA) via a carbodiimide (EDPC) method.…”