An approach for patterning surfaces with prepared nanoparticles is described. Chitosan-stabilized gold nanoparticles (Au/chitosan NPs) were locally deposited on stainless steel (StSt), indium tin oxide (ITO), and highly-ordered pyrolytic graphite (HOPG). Deposition was driven by local pH gradient formed between a surface and a scanning electrochemical microscopy tip set in the direct mode. The pH at the substrate was increased upon biasing the surface by negative potentials, which caused the reduction of water. As the pH on the surface exceeded that of pKchitosanH+e6:3 deprotonation of the amino groups of chitosan caused the irreversible deposition of the chitosan/AuNPs. The effect of different parameters, such as tip-surface distance and time, on deposition was studied. While the potential duration showed no clear influence, smaller tip-substrate distance and more negative potentials applied to the surface caused larger deposits. The overpotential needed for the deposition of nanoparticles on HOPG was the highest while that for StSt was the lowest. On the former, the sluggish kinetics caused the deposition of ringshaped structures while disk-shaped deposits were formed on the other surfaces.
Bibliographical noteFunding Information:
This work was supported by the Israel Science Foundation (1150/11) and by the United States-Israel Binational Science Foundation (BSF), Award 2008039. The Harvey M. Krueger Family Centre for Nanoscience and Nanotechnology of the Hebrew University is acknowledged.
- Au nanoparticles
- Local deposition
- Scanning electrochemicalmicroscopy