Tuning the Surface State and Zeta Potential of Aged CuO Nanoparticles by Additive-Free Surface Treatments as Guided
Anastasia S Batenkova1,2, Bastian Rheingans1, Claudia Cancellieri1
1Laboratory for Joining Technologies and Corrosion, Empa - Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, CH-8600, Switzerland.
Abstract:
Broad application of nanoparticles, for e.g., catalysis, antimicrobial coatings, medicine, electronics, batteries, and nanojoining technologies, is hindered by their limited shelf-life due to ambient aging. This study traces the changes in the surface chemistry of nanoparticles during atmospheric aging by monitoring the changes in the C 1s, O 1s, Cu 2p core-level spectra using XPS. The atmospheric aging of nanoparticles proceeds via hydroxylation and the adsorption of organic-O surface species, which introduces defects in the subsurface region. The position and shape of the main Cu 2p3/2 peak and its satellite provide a sensitive fingerprint of the nanoparticle surface state, while the O 1s spectra reveal the formation of subsurface O defect species. Air annealing at 300°C and room-temperature ozonation provide additive-free, environmentally friendly surface treatments that can convert arbitrarily aged surface back to well-defined (pristine) CuO nanoparticle surface states. Thus, reproducible dispersion characteristics of CuO nanoparticles in ethanol can be obtained independently of the aging history. These findings help to extend the shelf-life of nanoparticles and enable reproducible processing routes for CuO nanopowders to be established for advancing nanotechnologies such as nanoporous oxide membranes, catalysts, functional coatings, and batteries.
