title: Spectroscopic elucidation of energy transfer in hybrid inorganic-biological organisms for solar-to-chemical production.
abstract: 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 CO2to 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-1spectral 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 H2as 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). This work represents a promising platform to utilize conventional spectroscopic methodology to extract insights from more complex biotic-abiotic hybrid systems.
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720.
authors.forename: Nikolay
authors.initials: N
authors.lastname: Kornienko
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720.
authors.forename: Kelsey K
authors.initials: KK
authors.lastname: Sakimoto
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720.
authors.forename: David M
authors.initials: DM
authors.lastname: Herlihy
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720.
authors.forename: Son C
authors.initials: SC
authors.lastname: Nguyen
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720; Department of Materials Science and Engineering, University of California, Berkeley, CA 94720; Kavli Energy NanoSciences Institute, Berkeley, CA 94720.
authors.forename: A Paul
authors.initials: AP
authors.lastname: Alivisatos
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720.
authors.forename: Charles B
authors.initials: CB
authors.lastname: Harris
authors.affiliation: Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.
authors.forename: Adam
authors.initials: A
authors.lastname: Schwartzberg
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720; Department of Materials Science and Engineering, University of California, Berkeley, CA 94720; Kavli Energy NanoSciences Institute, Berkeley, CA 94720; p_yang@berkeley.edu.
authors.forename: Peidong
authors.initials: P
authors.lastname: Yang
keywords: CO2 reduction; biohybrid systems; catalysis; energy conversion; spectroscopy