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Title: Spectroscopic elucidation of energy transfer in hybrid inorganic–biological organisms for solar-to-chemical production

We present that the rise of inorganic–biological hybrid organisms for solar-to-chemical production has spurred mechanistic investigations into the dynamics of the biotic–abiotic interface to drive the development of next-generation systems. The model system, Moorella thermoacetica–cadmium sulfide (CdS), combines an inorganic semiconductor nanoparticle light harvester with an acetogenic bacterium to drive the photosynthetic reduction of CO 2 to acetic acid with high efficiency. In this work, we report insights into this unique electrotrophic behavior and propose a charge-transfer mechanism from CdS to M. thermoacetica. Transient absorption (TA) spectroscopy revealed that photoexcited electron transfer rates increase with increasing hydrogenase (H 2ase) enzyme activity. On the same time scale as the TA spectroscopy, time-resolved infrared (TRIR) spectroscopy showed spectral changes in the 1,700–1,900-cm -1 spectral region. The quantum efficiency of this system for photosynthetic acetic acid generation also increased with increasing H 2ase activity and shorter carrier lifetimes when averaged over the first 24 h of photosynthesis. However, within the initial 3 h of photosynthesis, the rate followed an opposite trend: The bacteria with the lowest H 2ase activity photosynthesized acetic acid the fastest. These results suggest a two-pathway mechanism: a high quantum efficiency charge-transfer pathway to H 2ase generating H 2 asmore » a molecular intermediate that dominates at long time scales (24 h), and a direct energy-transducing enzymatic pathway responsible for acetic acid production at short time scales (3 h). Lastly, this work represents a promising platform to utilize conventional spectroscopic methodology to extract insights from more complex biotic–abiotic hybrid systems.« less
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [1] ;  [3] ;  [2]
  1. Univ. of California, Berkeley, CA (United States). Department of Chemistry
  2. Univ. of California, Berkeley, CA (United States). Department of Chemistry and Department of Materials Science and Engineering; Kavli Energy NanoSciences Institute, Berkeley, CA (United States)
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Molecular Foundry
Publication Date:
Grant/Contract Number:
AC02-05CH11231; DMR-1507914
Type:
Accepted Manuscript
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 113; Journal Issue: 42; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 59 BASIC BIOLOGICAL SCIENCES; 14 SOLAR ENERGY; 30 DIRECT ENERGY CONVERSION; energy conversion; spectroscopy; CO2 reduction; biohybrid systems; catalysis
OSTI Identifier:
1377542