Low temperature aqueous synthesis of size-controlled nanocrystals through size focusing: a quantum dot biomineralization case study

Abstract

Traditional quantum dot synthesis techniques rely on the separation of nucleation and growth to control nanocrystal size. Herein we demonstrate that similar control can be achieved through the continuous generation of reactive precursors throughout synthesis.

Scalable Biomineralization of CdS Quantum Dots by Immobilized Cystathionine γ-Lyase

“…34% through cycle 6. The sustained cyclic activity of CSE-TiO 2 , albeit less than that which is achievable with the freely dispersed enzyme, may be sufficient to provide a continuous, low-level source of H 2 S, and thus reactive HS – , that is important for CdS particle nucleation and size control …”

“…Engineered and purified strains of cystathionine γ-lyase (CSE) were employed for the synthesis of CdS QDs following previous reports. ,,,,, Specifically, QD synthesis was initiated from a solution of 1 mM cadmium acetate (Alfa Aesar, 99.999% Puratronic), 7 mM l -cysteine (Spectrum Chemicals), and 0.05 mg mL –1 CSE in 0.1 M Tris-HCl (pH 8.0, VWR) buffer. The solution was incubated at 37 °C for 2 h. The concentration of QDs in the solution was computed from UV–vis absorbance measurements based upon published calibrations .…”

“…Herein, we demonstrate the cyclic biomineralization of CdS QDs by facile immobilization of CSE on inexpensive, nontoxic TiO 2 supports. , By leveraging the unique irreversibility of CSE physisorption onto TiO 2 under nominal synthesis conditions, we demonstrate that the retained activity of the immobilized CSE for turnover of l -cysteine is sufficient for the slow, continuous endogenous production of H 2 S in buffered solutions of Cd acetate that is required to keep the CdS biomineralization system in the size-focusing regime . The system enables the cyclic synthesis of CdS QDs with remarkable batch-to-batch consistency of particle size and narrow size distribution.…”

Tailored Coupling of Biomineralized CdS Quantum Dots to rGO to Realize Ambient Aqueous Synthesis of a High-Performance Hydrogen Evolution Photocatalyst

“…The CdS nanoparticles were found to have a diameter in the 2−4 nm range, which is consistent with the optical properties reported in Figure 1 and with our previously reported size distributions for the biomineralized CdS nanocrystals. 19,38,39 Low-magnification HAADF-STEM and high-angle annular bright-field (HAABF)-STEM clearly demonstrate that CdS is associated with rGO (Figure S3a−d). STEM images show that the distribution of CdS on rGO is not homogenous and that the particles are most likely attaching to both sides of the sheet.…”

“…We have previously demonstrated a single-enzyme-based aqueous route for the synthesis of a variety of quantum-confined, semiconducting nanocrystals, including CdS and the reduction of graphene oxide to rGO. − Both CdS and CdS/rGO photocatalysts, although unstable over long periods of use, have been widely studied for water splitting, providing a basis for this demonstration of the potential for bioinspired and biological synthesis. rGO is often used in chemically synthesized photocatalysts as a support that can accept photoexcited electrons from CdS to suppress charge recombination, increase exciton lifetime, and ultimately increase H 2 production rates .…”