(216a) Bioinspired, Non-Enzymatic, ‘Green’ Synthesis of Size Tunable CdS Quantum Dots

Quantum dots (QDs) are beneficial for a wide range of applications including bioimaging, photocatalysis, LEDs, and solar cells due to their unique optical and electronic properties.¹ While QD synthesis tends to rely on high-temperature organometallic processing, associated toxic organic solvents, energy intensive high-temperature operations, and complex purification steps required to concentrate and transfer QDs among solvents results in biocompatibility, scalability, and sustainability problems in addition to increased production cost.^1–4 Alternatively, enzymatic production of H₂S in metabolic processes has been exploited as an intrinsically ‘green’ and sustainable mode for biomineralization of functional metal sulfide quantum dots (QDs).^5–8 However, even with demonstrations of strategies for improving enzymatic lifetime and recovery through immobilization, enabling cyclic QD synthesis,⁹ the reliance on enzymes tends to limit the efficacy of the synthesis to narrow, physiologically constrained temperature and pH windows, with implications on functionality, stability, and tunability (i.e., size, composition) of the resulting products.

Drawing inspiration from a previously unexploited non-enzymatic biochemical route to H₂S¹⁰ that also contributes to metabolic processing, in this study, we demonstrate the efficacy of bioinspired non-enzymatic H₂S production from L-cysteine catalyzed by PLP and Fe (III) for the synthesis of CdS QDs as a novel bioinspired synthesis approach. In addition to demonstrating the successful synthesis of CdS QDs, we elucidate kinetics of the nucleation and growth process and the impact of pH, and temperature. We conclude by exploring the robustness and sensitivity of the process to synthesis solution composition, temperature, and pH, underscoring the versatility of the non-enzymatic route to aqueous production of H₂S for the tunable synthesis of QDs. Ultimately, this study offers a green and scalable approach for the synthesis of size and compositionally tunable functional QDs.

References

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