The highest photocurrent to date on a bare metal electrode is reported by R. N. Frese and co‐workers. Plasmon‐enhanced light harvesting in a photosynthetic pigment protein on a nanoporous silver ...substrate results in record photocurrents up to 416 μA cm−2, representing a breakthrough in the field of biohybrid photoelectrodes. This is significant for the development of potential bioelectronic devices such as biohybrid solar cells and biosensors.
Putting Photosystem I to Work: Truly Green Energy Teodor, Alexandra H.; Bruce, Barry D.
Trends in biotechnology (Regular ed.),
December 2020, 2020-12-00, 20201201, 2020-12-01, Volume:
38, Issue:
12
Journal Article
Peer reviewed
Open access
Meeting growing energy demands sustainably is one of the greatest challenges facing the world. The sun strikes the Earth with sufficient energy in 1.5 h to meet annual world energy demands, likely ...making solar energy conversion part of future sustainable energy production plans. Photosynthetic organisms have been evolving solar energy utilization strategies for nearly 3.5 billion years, making reaction centers including the remarkably stable Photosystem I (PSI) especially interesting for biophotovoltaic device integration. Although these biohybrid devices have steadily improved, their output remains low compared with traditional photovoltaics. We discuss strategies and methods to improve PSI-based biophotovoltaics, focusing on PSI-surface interaction enhancement, electrolytes, and light-harvesting enhancement capabilities. Desirable features and current drawbacks to PSI-based devices are also discussed.
Studies of alternative electrode and semiconductor materials have improved PSI orientation and activity on electroactive surfaces.Stable, photoactive dense packing of PSI on electrode and semiconductor surfaces is difficult. Crosslinking, redox polymer hydrogels, 3D semiconductor architectures, and biocompatible electrolytes could improve PSI-based device stability and output.Native PSI utilizes chlorophylls a and b for its light-harvesting antenna, leaving a 'green gap' in its absorption spectrum. Dyes and nanoparticles that can use this green gap and transfer their energy to PSI can enhance the photoactivity of PSI in vitro.PSI reduction kinetics post-photoexcitation are slow and limiting, and novel redox mediators and modified proteins to improve kinetics could improve photosensitizer regeneration rates and enhance photocurrent densities in PSI-based devices.
The Cover Feature illustrates the production of extracellular electrons from photosynthetic microorganisms or subcellular fractions located on an electrode. Methods for studying extracellular ...electron production, developments in electrode design, the pathway for electron transfer to the electrode, and prospects for scale‐up are discussed in more detail in the article by L. Wey et al. More information can be found in the Minireview by L. T. Wey et al. on page 5375 in Issue 21, 2019 (DOI: 10.1002/celc.201900997).
A critical selection of the recent literature reports on the use of photosynthetic and photoresponsive bacteria as a source of materials for optoelectronics and photonic devices is discussed, ...together with the applications foreseen in solar energy conversion and storage and light information technologies. The use of both photoactive cellular components and entire living cells is reviewed, aiming to highlight the great conceptual impact of these studies. These studies point out possible deep changes in the paradigm of design, and synthesis of materials and devices for optoelectronics. Although the possible technological impact of this technology is still hard to be predicted, these studies advance the understanding of photonics of living organisms and develop new intriguing concepts in biomaterials research.
Photosynthetic and photoresponsive bacteria can be used as a source of materials for optoelectronics and photonics. Applications of either photoactive cellular components or metabolically active photosynthetic bacterial cells in devices for solar energy conversion and storage and in light information technologies are presented. Emphasis on new concepts in materials design and device architectures emerging from recent research is given.
Photosynthetic hydrogen (photoH2) production is an elegant approach to storing solar energy. The most efficient strategy is to couple the hydrogen‐producing enzyme, the hydrogenase (H2ase), directly ...to photosystem I (PSI), which is a light‐driven nanomachine found in photosynthetic organisms. PSI–H2ase fusions have been tested in vivo and in vitro. Both approaches have each their specific advantages and drawbacks. Here, a system to combine both approaches by assembling PSI–H2ase fusions in vivo for in vitro photoH2 production is established. For this, cyanobacterial PSI–H2ase fusion mutants are generated and characterized concerning photoH2 production in vivo. The chimeric protein is purified and embedded in a redox polymer on an electrode where it successfully produces photoH2 in vitro. The combination of in vivo and in vitro processes comes along with reciprocal benefits. The in vivo assembly ensures that the chimeric protein is fully functional and suited for the fabrication of bioelectrodes in vitro. At the same time, the photoelectrochemical in vitro characterization now permits to analyze the assemblies in detail. This will open avenues to optimize in vivo and in vitro approaches for photoH2 production in a target‐oriented manner in the future.
Cyanobacterial mutants that express photosystem I and hydrogenase assembled in vivo are created. The chimeric fusion protein is purified and embedded in a redox polymer over an electrode, which is used for successful photoH2 production in vitro. Photoelectrochemical characterizations now permit a detailed analysis of the assemblies enabling optimization of in vivo and in vitro approaches for photoH2 production.
As a source of several valuable products, photosynthetic microorganisms (microalgae and cyanobacteria) have many applications in biomedical, electrochemical, and urban-space fields. Microalgal and ...cyanobacterial (photoautotrophs) implementations have been the subject matter of several reviews, which mainly focused on exploring effective methods of their harvesting, optimal cultivation conditions, energy conversion efficiency, and new strategies for microalgal health-promoting compound recovery. This review highlights recent investigations into biomedical, urban, environmental, and electrical engineering microalgae and cyanobacteria applications over the last seven years. A brief historical outline of advances in photoautotroph-based technologies is presented prior to an exploration of the important role of these microorganisms in combating global warming and food and energy insecurity. Special attention is given to the photosynthetic oxygen production of algae and the possibility of treating hypoxia-associated diseases such as cancer or tissue injuries. Photoautotroph applications in microrobotics, drug delivery and wound healing systems, biosensors, and bioelectronics are also introduced and discussed. Finally, we present emerging fabrication techniques, such as additive manufacturing, that unleash the full potential of autotrophic, self-sufficient microorganisms at both the micro- and macroscales. This review constitutes an original contribution to photoautotroph biotechnology and is thought to be impactful in determining the future roles of microalgae and cyanobacteria in medical, electrical, or urban space applications.
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•Current trends and prospects in microalgae-based systems and devices are presented.•Microalgae can be used in a broad range of biotechnological applications.•Microalgae-based biomedical and pharmaceutical applications are highlighted.•Emerging biofabrication techniques allow for tuning specific microalgal functions.
The field of biophotoelectrochemistry and its application in biophotovoltaics and biosensors has gained more and more attention in recent years. Knowledge of the redox potentials of the catalytically ...active protein cofactors in biophotovoltaic devices is crucial for accurate modelling and in discerning the mechanisms of their operation. Here, for the first time, we used spectroelectrochemical methods to investigate thermodynamic parameters of a biophotoelectrode in situ. We determined redox potentials of two elements of the system: the primary electron donor in photosynthetic reaction centers (RCs) of the bacterium Rhodobacter sphaeroides and osmium-complex based redox mediators that are bound to a hydrogel matrix. We observe that the midpoint potential of the primary donor is shifted towards more positive potentials in comparison to literature data for RCs solubilized in buffered water solution, likely due to interaction with the polymer matrix. We also demonstrate that the osmium-complex modified redox polymer efficiently wires the RCs to the electrode, maintaining a high Internal Quantum Efficiency with approximately one electron per two photons generated (IQE=50±12%). Overall, this biophotoelectrode may be attractive for controlling the redox state of the protein when performing other types of experiments, e.g. time resolved absorption or fluorescence measurements, in order to gain insights into kinetic limitations and thereby help in the rational design of bioelectronic devices.
The successful interfacing of electronics with biology is the next frontier for microelectronics and nanotechnology. Melanin, a naturally occurring conjugated polymer composed of different structural ...subunits, may be an ideal candidate for such interfacing. In the solid-state, the large broadband molar attenuation coefficient of melanin over the visible spectrum implicates potential applications as a semiconductor for light harvesting and light detection. Additionally, the conductance of melanin has been shown to increase with hydration, making this irregular polymer a hybrid electronic-protonic conductor. While the precise mechanism of charge transfer in melanin is not well understood, the hydration dependence of conductance has been tapped to utilize melanin-based devices in a variety of roles, such as humidity sensors and pH detectors. The applications of melanin active layers in OLEDs, OPVs and OFETs have been explored. The viability of this polymer has also been validated inside biological systems, showing the potential for creating electronic devices that are biocompatible. This paper reviews the status of melanin towards achieving biocompatible electronics.
•Clear and concise review of the state of the field in melanin-based electronics.•Both electronic and protonic charge transport in melanin covered.•Concise discussion of the structure and physico-chemical properties of melanin.•Unique survey of melanin utilization in OPV, OLED, OFET and OECT devices.•Applications of melanin in electronic sensing and biocompatible devices.
In a quest to fabricate novel solar energy materials, the high quantum efficiency and long charge separated states of photosynthetic pigment‐proteins are being exploited through their direct ...incorporation in bioelectronic devices. In this work, a biohybrid photocathode comprised of bacterial reaction center‐light harvesting 1 (RC‐LH1) complexes self‐assembled on a nanostructured silver substrate yields a peak photocurrent of 166 μA cm−2 under 1 sun illumination, and a maximum of 416 μA cm−2 under 4 suns, the highest reported to date on a bare metal electrode. A 2.5‐fold plasmonic enhancement of light absorption per RC‐LH1 complex is observed on the rough silver substrate. This plasmonic interaction is assessed using confocal fluorescence microscopy, revealing an increase of fluorescence yield, and radiative rate of the RC‐LH1 complexes, signatures of plasmon‐enhanced fluorescence. Nanostructuring of the silver substrate also enhanced the stability of the protein under continuous illumination by almost an order of magnitude relative to a nonstructured bulk silver control. Due to its ease of construction, increased protein loading capacity, stability, and more efficient use of light, this hybrid material is an excellent candidate for further development of plasmon‐enhanced biosensors and biophotovoltaic devices.
A novel biohybrid photocathode consisting of photosynthetic complexes is revealed on a nanostructured silver electrode. This photocathode nets record photocurrents up to 416 μA cm−2 in part thanks to a 2.5‐fold plasmon‐enhanced light harvesting efficiency.
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