Disubstituted thiourea as a suitable sulfur source in the gram-scale synthesis of yellow- and red-emitting CdTeS/CdxZn1−xS core/shell quantum dots

Abstract

The key parameters of semiconductor quantum dots (QDs) that determine the suitability and efficiency for the design of most optoelectronic devices are the spectral positions of absorbance (ABS) and photoluminescence (PL) maxima, Stokes shift, photoluminescence quantum yield (PL QY) and photoluminescence lifetime (PL LT). All these parameters have been considered in the design of new ternary core CdTeS and core/shell CdTeS/Cd_xZn_1−xS QDs. One-pot synthesis conducted in an organic medium at 160 °C using substituted thioureas as new, highly reactive sulfur sources allowed for the formation of a series of size- and emission-tunable CdTe_0.05S_0.95 QDs. Gram-scale synthesis of yellow-red emitting CdTe_0.06S_0.94 and CdTe_0.12S_0.88 cores was performed through the manipulation of their precursor ratio for the controllable formation of CdTeS/Cd_xZn_1−xS (x = 0.1, 0.2, and 0.3) core/shell QDs. The development of the designed nanomaterials was carried out with a special emphasis on their optical properties, in particular a high PL QY up to 87% and extremely large Stokes shift, reaching ≈280 nm for core/shell QDs. Promisingly, for biolabeling and diagnostics, the synthesized core/shell QDs were transferred into water via surface ligand modification with the expected loss of photoluminescence efficiency. The results indicated that the availability of initial components, high yield of the desired product, stability in the organic phase, and high optical characteristics can scale up the synthesis of the developed nanomaterials from the laboratory level to industrial production.