Enzymatic Synthesis of CdS Quantum Dots By a Cystathionine Gamma-Lyase

Due to their highly photoluminescent properties, semiconductor nanocrystals or quantum dots (QDs) have received considerable attention in diverse areas such as cellular imaging and solar cells. The majority of commercially available quantum dots are synthesized in small batches of organic solvents leading to a large environmental and economic cost of synthesis. As such, the biosynthesis of quantum dots is advantageous for its scalability and low environmental cost.

Previously we have shown that an engineered strain of Stenotrophomonas maltophilia (SMCD1) is capable of production of extracellular, water-soluble CdS quantum dots. We report that cystathionine γ-lyase from SMCD1 produces CdS QDs in vitro upon incubation with L-cysteine and cadmium acetate. Control of particle synthesis through variation of capping agents such as L-cysteine and glutathione allows discrete sizes of CdS quantum dots from 1 to 4 nanometers to be produced. Optical properties and high resolution TEM imaging of produced nanoparticles shows well defined crystalline phases consistent with chemically synthesized CdS QDs. Future works involves investigating the mechanism of nanoparticle synthesis and applying this knowledge to the synthesis of other metal sulfide nanocrystals.