Preparation of homogeneous ZnSeTeS quantum dots.

Quantum dots (QDs) have emerged as promising candidates for next-generation display owing to their exceptional optoelectronic properties. However, despite substantial advancements in QD synthesis, the blue-emitting QDs, especially heavy-metal-free blue ones, still underperform compared with their red and green counterparts. ZnSeTe QDs offer a viable ecofriendly alternative for blue emissions, but their performance is limited by spectrum broadening (linewidth >20 nm) and structural instability. These issues stem from compositional inhomogeneity, which is primarily induced by Te aggregation during synthesis. Recently, we realized the synthesis of homogeneous quaternary-alloyed ZnSeTeS QDs through a synergistic strategy of reactivity modulation and isoelectronic control. This Protocol enables precise bandgap tuning in the blue spectral region (450-475 nm) by controlling the Te ratio, while ensuring high color purity and stability of QDs. Furthermore, the as-prepared ZnSeTeS QDs exhibit outstanding electroluminescence performance, with a peak external quantum efficiency of 24.7% and half-life of 29,600 h at 100 cd cm-2, and demonstrate strong potential for applications such as solid-state lighting and bioimaging owing to their high stability and low toxicity. Here we detail a synthesis Protocol for ZnSe0.94Te0.03S0.03/ZnSe/ZnS core/shell/shell QDs via a hot-injection method using zinc carboxylate and anionic phosphine precursor, systematically outlining the design and preparation of precursors and QDs, post treatments (including purifications) and characterization methods, including time-resolved photoluminescence spectroscopy. The entire process typically requires 11-12 h for QD synthesis and 6 h for characterizations, demanding only accessible chemistry knowledge and routine colloidal synthesis techniques.