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A Fine Size Selection of Brightly Luminescent Water-Soluble Ag-In-S and Ag-In-S/ZnS Quantum Dots

A size-selected series of water-soluble luminescent Ag–In–S (AIS) and core/shell AIS/ZnS QDs were produced by a precipitation technique. Up to 10–11 fractions of size-selected AIS (AIS/ZnS) QDs emitting in a broad color range from deep-red to bluish-green were isolated with the photoluminescence (PL) quantum yield reaching 47% for intermediate fractions. The size of the isolated AIS (AIS/ZnS) QDs varied from ~2 nm to ~3.5 nm at a roughly constant chemical compo- sition of the particles throughout the fractions as shown by the X-ray photoelectron spectroscopy.
The decrease of the mean AIS QD size in consecutive fractions was accompanied by an increase of the structural QD imperfection/disorder as deduced from a notable Urbach absorption “tail” below the fundamental absorption edge. The Urbach increased from 90–100 meV for the largest QDs up to 350 meV for the smallest QDs, indicating a broadening of the distribution of sub-bandgap states. Both the Urbach energy and the PL bandwidth of the size-selected AIS QDs increased with QD size reduction from 3–4 nm to ~2 nm and a distinct correlation was observed between these parameters.
A study of size-selected AIS and AIS/ZnS QDs by UV photoelectron spectroscopy on Au and FTO substrates revealed their valence band level EVB at ~6.6 eV (on Au) and ~7 eV (on FTO) and pinned to the Fermi level of conductive substrates resulting in a masking of any possible size- dependence of the valence band edge position.

Identiferoai:union.ndltd.org:DRESDEN/oai:qucosa.de:bsz:14-qucosa-226647
Date11 August 2017
CreatorsRaevskaya, Alexandra, Lesnyak, Vladimir, Haubold, Danny, Dzhagan, Volodymyr, Stroyuk, Oleksandr, Gaponik, Nikolai, Zahn, Dietrich R.T., Eychmüller, Alexander
ContributorsAmerican Chemical Society ,
PublisherSaechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden
Source SetsHochschulschriftenserver (HSSS) der SLUB Dresden
LanguageEnglish
Detected LanguageEnglish
Typedoc-type:article
Formatapplication/pdf
SourceThe journal of physical chemistry C, Nanomaterials and interfaces (2017), 121(16). S. 9032-9042. ISSN 1932-7455. DOI: 10.1021/acs.jpcc.7b00849.

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