(608i) Single Enzyme Biomineralization of Size Controlled, Water Soluble Quantum Dots

Single Enzyme Biomineralization of Size Controlled, Water Soluble
Quantum Dots

Robert Dunleavy, Leah Spangler, Zhou Yang, Li Lu,
Christopher J. Kiely, Bryan W. Berger, Steven McIntosh.

Biological systems have evolved
several unique mechanisms to mineralize, primarily structural, inorganic
nanomaterials. These biomineralization processes are inherently “green”,
enabling low-cost and scalable production of nanomaterials under benign
conditions in aqueous solutions. However, extending from these processes to
achieve the regulated control necessary for reproducible, scalable biosynthesis
of functional nanomaterials remains a central challenge. This is especially
true of quantum dots (QDs), where precise size and crystal quality control is
required to achieve the desired electronic properties. While several studies
have described production of QDs from biological systems, the majority of these
add a reactive chemical precursor, typically Na₂S, or do not provide
the necessary tight control over particle size.

In this work, we describe a
single enzyme capable of both the mineralization and templating of cadmium,
lead, and zinc sulfide quantum dots within the quantum confined size range. The
quantum dots are synthesized in the aqueous phase from normally unreactive
metal acetate and L-cysteine precursors and are only formed upon the addition
of the enzyme. The mineralization mechanism is proposed to consist of enzymatic
turnover of L-cysteine to form reactive H₂S and is coupled to
enzymatic templating of nanocrystal growth. We further demonstrate the
flexibility of this approach to form core-shell and alloy nanoparticles. The biomineralized materials demonstrate aqueous phase band gap
and quantum yield similar to chemically prepared materials.