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Zeitschriftenartikel:

K. Kocsis, M. Niedermaier, V. Kasparek, J. Bernardi, G. Redhammer, M. Bockstedte, T. Berger, O. Diwald:
"From Anhydrous Zinc Oxide Nanoparticle Powders to Aqueous Colloids: Impact of Water Condensation and Organic Salt Adsorption on Free Exciton Emission";
Langmuir, 35 (2019), S. 8741 - 8747.



Kurzfassung englisch:
Variations in the composition and structure of
ZnO nanoparticle interfaces have a key influence on the
materials´ optoelectronic properties and are responsible for
high number of discrepant results reported for ZnO-based
nanomaterials. Here, we conduct a systematic study of the
room-temperature photoluminescence of anhydrous ZnO
nanocrystals, as synthesized in the gas phase and processed
in water-free atmosphere, and of their colloidal derivatives in
aqueous dispersions with varying amounts of organic salt
admixtures. A free exciton band at hν = 3.3 eV is essentially
absent in the anhydrous ZnO nanocrystal powders measured
in vacuum or in oxygen atmosphere. Surface hydration of the nanoparticles during colloid formation leads to the emergence of
the free exciton band at hν = 3.3 eV and induces a small but significant release in lattice strain as detected by X-ray diffraction.
Most importantly, admixture of acetate or citrate ions to the aqueous colloidal dispersions not only allows for the control of the
ζ-potential but also affects the intensity of the free exciton emission in a correlated manner. The buildup of negative charge at
the solid−liquid interface, as produced by citrate adsorption, increases the free exciton emission. This effect is attributed to the
suppression of electron trapping in the near-surface region, which counteracts nonradiative exciton recombination. Using welldefined
ZnO nanoparticles as model systems for interface chemistry studies, our findings highlight water-induced key effects
that depend on the composition of the aqueous solution shell around the semiconducting metal oxide nanoparticles.


"Offizielle" elektronische Version der Publikation (entsprechend ihrem Digital Object Identifier - DOI)
http://dx.doi.org/10.1021/acs.langmuir.9b00656


Erstellt aus der Publikationsdatenbank der Technischen Universität Wien.