Controlled assembly of hydrogenase-CdTe nanocrystal hybrids for solar hydrogen production

Katherine A. Brown, Smita Dayal, Xin Ai, Garry Rumbles, Paul W. King

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Abstract

We present a study of the self-assembly, charge-transfer kinetics, and catalytic properties of hybrid complexes of CdTe nanocrystals (nc-CdTe) and Clostridium acetobutylicum [FeFe]-hydrogenase I (H2ase). Molecular assembly of nc-CdTe and H2ase was mediated by electrostatic interactions and resulted in stable, enzymatically active complexes. The assembly kinetics was monitored by nc-CdTe photoluminescence (PL) spectroscopy and exhibited first-order Langmuir adsorption behavior. PL was also used to monitor the transfer of photogenerated electrons from nc-CdTe to H 2ase. The extent to which the intramolecular electron transfer (ET) contributed to the relaxation of photoexcited nc-CdTe relative to the intrinsic radiative and nonradiative (heat dissipation and surface trapping) recombination pathways was shown by steady-state PL spectroscopy to be a function of the nc-CdTe/H2ase molar ratio. When the H2ase concentration was lower than the nc-CdTe concentration during assembly, the resulting contribution of ET to PL bleaching was enhanced, which resulted in maximal rates of H2 photoproduction. Photoproduction of H2 was also a function of the nc-CdTe PL quantum efficiency (PLQE), with higher-PLQE nanocrystals producing higher levels of H2, suggesting that photogenerated electrons are transferred to H2ase directly from core nanocrystal states rather than from surface-trap states. The duration of H 2 photoproduction was limited by the stability of nc-CdTe under the reactions conditions. A first approach to optimization with ascorbic acid present as a sacrificial donor resulted in photon-to-H2 efficiencies of 9% under monochromatic light and 1.8% under AM 1.5 white light. In summary, nc-CdTe and H2ase spontaneously assemble into complexes that upon illumination transfer photogenerated electrons from core nc-CdTe states to H2ase, with low H2ase coverages promoting optimal orientations for intramolecular ET and solar H2 production.

Original languageEnglish
Pages (from-to)9672-9680
Number of pages9
JournalJournal of the American Chemical Society
Volume132
Issue number28
DOIs
Publication statusPublished - Jul 21 2010

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ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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