I tried to synthesize AuNPs by a galvanostatic method on glassy carbon electrode, The deposit gave a Zeta potential of -2.4 mV, When i carried out a UV absorbance study, I didn't get any UV absorbance peak at around 500-530 nm (the fingerprint region for AuNps)? But very small (size varies from 0.1-2nm) sized particles in TEM were visible. Are these gold nano-particles or just gold cluster without any reduction?
Hello Sai Prasad Nayak
One of the problems for growing heterostructures on electrode is the discontinuity of the crystal lattice.
The atomic packing of graphite is different from gold, hence there is no epitaxy. There must be an adequate balance between applied electrical potential and electrode surface energy.
Generally, for the growth of nanoparticles on electrodes, surface modifications are made with groups containing thiols or amines. And by chemical reduction, there is the formation of nanoparticles.
Another approach for the formation of films on vitreous carbon is the introduction of small doping nuclei on the surface. Or even small grooves, which increase the surface potential locally at the edges. Using a sweep linear voltammetry procedure.
As for your TEM images, yes, you may have formed very small gold particles, but a confirmation would be by EDX spectra.
Follow some references:
https://doi.org/10.1039/C7RA07544H
https://doi.org/10.1016/j.bios.2004.10.021
https://doi.org/10.1016/S0022-0728(79)80167-9
Article Organized self-assembling monolayers on electrodesPart I. Oc...
Dear Sai Prasad Nayak from a chemists point of view I would say that you cannot obtain elemental gold (nanoparticles or other sizes) from e.g. HAuCl4 without any reduction step. In any case reduction from Au3+ to Au0 must have taken place one or the other way. Well-defined gold nanoclusters can be synthesized by chemical means when sulfur-containing ligands are present which protect the gold nanoclusters. This has been reported e.g. in the following article which is freely accessible on RG:
Controlled reduction for size selective synthesis of thiolate-protected gold nanoclusters Au n (n = 20, 24, 39, 40)
Article Controlled reduction for size selective synthesis of thiolat...
The synthesis of gold nanoparticles (AuNPs) by a galvanostatic method on a glassy carbon electrode has been described e.g. in the following research articles:
Gold nanoparticles electrodeposited on glassy carbon using cyclic voltammetry: Application to Hg(II) trace analysis
Article Gold nanoparticles electrodeposited on glassy carbon using c...
and
Electrodeposited gold nanoparticles on glassy carbon: Correlation between nanoparticles characteristics and oxygen reduction kinetics in neutral media
Conference Paper Electrodeposited gold nanoparticles on glassy carbon: Correl...
These papers have not been posted as public full texts on RG. However, most of the authors have RG files. If these papers are of interest to you, you can certainly request the full texts directly from one of the authors via RG.
Good luck with your work and best wishes, Frank Edelmann
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