Phosphine-Free Synthesis of Metal Chalcogenide Quantum Dots by Directly Dissolving Chalcogen Dioxides in Alkylthiol as the Precursor

Semiconductor quantum dots (QDs) are competitive emitting materials in developing new-generation light-emitting diodes (LEDs) with high color rendering and broad color gamut. However, the use of highly toxic alkylphosphines cannot be fully avoided in the synthesis of metal selenide and telluride QDs because they are requisite reducing agents and solvents for preparing chalcogen precursors. In this work, we demonstrate the phosphine-free preparation of selenium (Se) and tellurium (Te) precursors by directly dissolving chalcogen dioxides in the alkylthiol under the mild condition. The chalcogen dioxides are reduced to elemental chalcogen clusters, while the alkylthiol is oxidized to disulfides. The chalcogen clusters further combine with the disulfides, generating dispersible chalcogen precursors. The resulting chalcogen precursors are suitable for synthesizing various metal chalcogenide QDs, including CdSe, CdTe, Cu₂Te, Ag₂Te, PbTe, HgTe, and so forth. In addition, the precursors are of high reactivity, which permits a shorter QD synthesis process at lower temperature. Owing to the high quantum yield (QYs) and easy tunability of the photoluminescence (PL), the as-synthesized QDs are further employed as down-conversion materials to fabricate monochrome and white LEDs

Facile Synthesis of Cu₂GeS₃ and Cu₂MGeS₄ (M = Zn, Mn, Fe, Co, and Ni) Hollow Nanoparticles, Based on the Nanoscale Kirkendall Effect

Hollow nanostructures have shown charming properties beyond their solid counterparts, but the synthesis of multinary chalcogenide semiconductors with hollow nanostructures remains challenging, because of their complex components. In this work, we demonstrate a facile one-pot method to synthesize Cu₂GeS₃ hollow nanoparticles (NPs) based on Kirkendall effect by using dissolved GeO₂ as the Ge source. A theory model according to the diffusion kinetic and reaction kinetic is established to investigate the growth mechanism of Cu₂GeS₃ hollow NPs. By using Cu₂GeS₃ hollow NPs as the template, quaternary Cu₂MGeS₄ (M = Zn, Ni, Co, Fe and Mn) hollow NPs are further produced, which are more difficult to prepare, because of their excessive ion species. Furthermore, Cu₂GeS₃ hollow NP-based gas sensors are prepared, which exhibit outstanding sensitivity for the detection of ethanol gas, because of their large surface-to-volume ratio and small grain size