(471e) Applying Protein Systems for Controllable Biomineralization of Semiconductor Quantum Dots

Light harvesting devices, such as photovoltaics and photocatalysts, have achieved high efficiencies in recent years; however, such efficiencies require specialized inorganic materials synthesized at high temperatures and pressures with toxic precursors or solvents. Here, I demonstrate an alternative approach to synthesize functional materials in a scalable and sustainable way that uses proteins found in biological systems. In the first part of my talk, I will demonstrate the synthesis of semiconductor quantum dots using a protein found in nature. Originally identified in the bacteria Stenotrophomonas maltophila, the biomineralization process was found to rely on a single enzyme, cystathionine gamma-lyase, which catalyzes nanocrystal growth by producing reactive sulfur from the amino acid L-cysteine. Biomineralization was used to generate many types of semiconductor quantum dots including cadmium sulfide, lead sulfide, copper indium sulfide and the first reported fully biomineralized lead sulfide/cadmium sulfide core/shell quantum dots. In the second part of my talk, I will demonstrate an alternative biomineralization approach that uses the artificially designed de novo protein, Construct K (ConK), to produce CdS quantum dots. ConK was not designed for function but found to catalyze production of reactive sulfur from L-cysteine precursors, enabling biomineralization of metal sulfide nanocrystals. Because de novo proteins are created by design to fold into stable structures, they are highly tolerant to mutations in their amino acid sequence, making them ideal candidates for future addition of new functionalities and properties. For both systems, I will present results that include nanocrystal characterization (Absorbance and fluorescence spectroscopy, TEM) and in-depth protein characterization, including identification of the active site.