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

Abstract

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 CO₂ 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 (H₂ase) 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 H₂ase 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 H₂ase activity photosynthesized acetic acid the fastest. These results suggest a two-pathway mechanism: a high quantum efficiency charge-transfer pathway to H₂ase generating H₂ as a molecular intermediate that dominates at longmore » 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:

Kornienko, Nikolay ^[1]; Sakimoto, Kelsey K. ^[1]; Herlihy, David M. ^[1]; Nguyen, Son C. ^[1]; Alivisatos, A. Paul ^[2]; Harris, Charles. B. ^[1]; Schwartzberg, Adam ^[3]; Yang, Peidong ^[2]

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+ Show Author Affiliations

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:

Mon Oct 03 00:00:00 EDT 2016

Research Org.:

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); National Science Foundation (NSF)

OSTI Identifier:

1377542

Grant/Contract Number:  

AC02-05CH11231; DMR-1507914

Resource 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)

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