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

Abstract

A size-selected series of water-soluble luminescent Ag–In–S (AIS) and core/shell AIS/ZnS quantum dots (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 to ∼3.5 nm at a roughly constant chemical composition 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 energy 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 ...