Redox polymer/protein biophotoelectrochemistry was used to analyse forward electron transfer of isolated PSII complexes with natural PsbA-variants. PsbA1- or PsbA3-PSII was embedded in a redox ...hydrogel that allows diffusion-free electron transfer to the electrode surface and thus measurement of an immediate photocurrent response. The initial photocurrent density of the electrode is up to ~2-fold higher with PsbA1-PSII under all tested light conditions, the most prominent under high-light 2,300 μmol(photon) m
–2
s
–1
illumination with 5 μA cm
–2
for PsbA3-PSII and 9.5 μA cm
–2
for PsbA1-PSII. This indicates more efficient electron transfer in low-light-adapted PsbA1-PSII. In contrast, the photocurrent decays faster in PsbA1-PSII under all tested light conditions, which suggests increased stability of high-light-adapted PsbA3-PSII. These results confirm and extend previous observations that PsbA3-PSII has increased P680
+•
/Q
A
–•
charge recombination and thus less efficient photon-to-charge conversion, whereas PsbA1-PSII is optimised for efficient electron transfer with limited stability.
A fabrication strategy of photoactive biohybrid electrodes based on the immobilization of the bacterial reaction center (RC) onto indium tin oxide (ITO) is proposed. The RC is an integral photoenzyme ...that converts photons into stable charge‐separated states with a quantum yield close to one. The photogenerated electron–hole pair can be eventually exploited, with suitable redox mediators, to produce photocurrents. To this purpose, RC must be effectively anchored on the electrode surface and simple strategies for its stable immobilization ensuring prolonged enzyme photoactivity are strongly desired. In this work, polydopamine (PDA), a polymer reminiscent of the natural melanin, is used to anchor the RC on the electrode surface. PDA is easily prepared in situ by spontaneous polymerization of dopamine in slightly alkaline aerated buffered RC solution. This reaction, carried out in the presence of an ITO substrate dipped into the solution, directly leads to a stable RC‐PDA/ITO photoelectrode with 20 nm film thickness and 50% of fully functional RC occupancy. Photocurrents densities recorded using this photoelectrode are comparable to those obtained with far more sophisticated immobilization techniques. The RC‐PDA films are fully characterized by visible–near‐infrared absorption spectroscopy, ellipsometry, atomic force, and scanning electron microscopies.
A simple, biocompatible, and cheap in situ strategy for the assembly of indium tin oxide photoelectrodes is based on polydopamine films encapsulating the photosynthetic reaction center. The photoelectrodes produce intense photocurrents that become very stable when the redox mediators and the photoenzyme are coencapsulated into the film onto the electrode surface.
Biophotovoltaic methods rely on the fact that photosynthetic microorganisms, like many others, can export small amounts of electric current. For photosynthetic organisms, this current usually ...increases on illumination. This "exoelectrogenic" property may be of biotechnological interest, and may also provide useful experimental insights into the physiological status of the cell. We describe how to construct biophotovoltaic devices, and the kinds of measurements that are typically made.
The necessity for sustainable energy production has driven the rapid development of technologies to harness solar energy effectively. The microphotosynthetic power cells (μPSC) aim to harness solar ...energy from living photosynthetic cells. Currently, the power density of the μPSC is low, due to several factors. One of the major impediments and challenges of the μPSC is its lower charge transfer efficiency between the photosynthetic microorganisms and the electrodes. Herein, the proposed strategy explores the interaction of gold nanoparticles (Au NPs) with photosynthetic microorganisms for enhanced power generation from the μPSC. Herein, the intracellular biocompatible, efficient light absorbers in the form of Au NPs are introduced. Translocation of gold colloidal solution of 25 μL of 50 μg mL−1 (253.8 μmol mL−1) concentration into 2 mL whole liquid culture of algal cells (Chlamydomonas reinhardtii: ≈1 million cells mL−1) enhances operational quantum yield (ϕ0) of the algal cells by 30.2% and power generation capability by 15.2% in μPSCs. Internalized Au NPs in the algal cells quench chlorophyll fluorescence, thereby contributing to increased photosynthetic efficiency. With multiple advantages such as light absorption capability, biocompatibility, and ability to transfer the electrons, Au NPs can efficiently harvest sunlight for enhanced power generation from the μPSC.
Microphotosynthetic power cells (μPSC) aim to harness the solar energy from living photosynthetic cells. Herein, the interaction of gold nanoparticles with photosynthetic microorganisms for enhanced power generation from the μPSC is explored. With multiple advantages such as light absorption capability, biocompatibility, and ability to transfer the electrons, gold nanoparticles efficiently harvest sunlight for enhanced power generation from the μPSC.
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•Fully reversible currents were observed only with a dual microbial community.•Cathodic oxygen reduction occurs at high working electrode potential.•Cathodic current is likely ...associated with γ-proteobacterium Congregibacter.•Anodic current reflects biofilm capability to indirectly convert light to electricity.•The highest solar bioanode (>100mAm−2)/oxygen biocathode currents (>1000mAm−2).
The electrochemical activity of two seawater microbial consortia were investigated in three-electrode bioelectrochemical cells. Two seawater inocula – from the Sunshine Coast (SC) and Gold Coast (GC) shores of Australia – were enriched at +0.6V vs. SHE using 12/12hday/night cycles. After re-inoculation, the SC consortium developed a fully-reversible cathodic/anodic current, with a max. of −62mAm−2 during the day and +110mAm−2 at night, while the GC exhibited negligible daytime output but +98mAm−2 at night. Community analysis revealed that both enrichments were dominated by cyanobacteria, indicating their potential as biocatalysts for indirect light conversion to electricity. Moreover, the presence of γ-proteobacterium Congregibacter in SC biofilm was likely related to the cathodic reductive current, indicating its effectiveness at catalysing cathodic oxygen reduction at a surprisingly high potential. For the first time a correlation between a dual microbial community and fully reversible current is reported.
Living photovoltaics represent a growing class of microbial devices that are based on whole cell–electrode interactions. The limited charge transfer at the cell–electrode interface represents a ...significant bottleneck in realizing an efficient technology. This study focuses on the development of poly(3,4‐ethylenedioxythiophene) (PEDOT)‐based electrodes that are electrosynthesized in the presence of a sodium dodecyl sulphate (SDS) dopant. Potentiodynamic and potentiostatic electrochemical techniques, as well as scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy, and theoretical modelling of the electropolymerization transient, are employed to create and characterize PEDOT electrodes under various conditions. The electrodes are able to capture photosynthetically derived current under multiple light–dark cycles when interfaced with Synechocystis sp. PCC 6803. In the presence of the Synechocystis, the PEDOT electrodes show a sixfold and twofold enhancement over conventional graphite electrodes for both mediatorless and K3Fe(CN)6‐mediated conditions, respectively. The ability of these electrodes to enhance extracted photocurrent for both direct and indirect electron transfer mechanisms provides a versatile platform for improving various microbial devices.
Living photovoltaics are photovoltaics based on living organisms, such as light‐harvesting bacteria. Current microbial devices suffer from low efficiencies due to poor charge extraction from the living cell. This article discusses the engineering of electrodes based on conductive polymers that are able to increase charge extraction from living photosynthetic cells and improve device efficiency.
Interfacing proteins with electrode surfaces is important for the field of bioelectronics. Here, a general concept based on phage display is presented to evolve small peptide binders for immobilizing ...and orienting large protein complexes on semiconducting substrates. Employing this method, photosystem I is incorporated into solid‐state biophotovoltaic cells.
This work studies how extracellular electron transfer (EET) from cyanobacteria-dominated marine microbial biofilms to solid electrodes is affected by the availability of inorganic carbon (Ci). The ...EET was recorded chronoamperometrically in the form of electrical current by a potentiostat in two identical photo-electrochemical cells using carbon electrodes poised at a potential of +0.6 V versus standard hydrogen electrode under 12/12 h illumination/dark cycles. The Ci was supplied by the addition of NaHCO₃ to the medium and/or by sparging CO₂ gas. At high Ci conditions, EET from the microbial biofilm to the electrodes was observed only during the dark phase, indicating the occurrence of a form of night-time respiration that can use insoluble electrodes as the terminal electron acceptor. At low or no Ci conditions, however, EET also occurred during illumination suggesting that, in the absence of their natural electron acceptor, some cyanobacteria are able to utilise solid electrodes as an electron sink. This may be a natural survival mechanism for cyanobacteria to maintain redox balance in environments with limiting CO₂ and/or high light intensity.
The high quantum efficiency in converting light energy into a charge‐separated state is a major advantage in using photosynthetic proteins in biophotovoltaic applications. Photocurrents are typically ...measured at open circuit potential (OCP), where the electrochemical redox or faradaic currents are minimized. However, at potentials far from the OCP, the photocurrents produced by the proteins may be impossible to measure against the large background current, owing to electrochemical redox reactions of charge‐transfer mediators and/or sacrificial electron donors. Demonstrated here is a highly sensitive method using a sinusoidal‐modulated intensity of an LED excitation light source to isolate the protein‐based photocurrent component from the total current irrespective of electrode surface coverage. Using a genetically modified photochemical reaction center from Rhodobacter sphaeroides as a proof‐of‐concept, photocurrents up to 104–105 orders of magnitude smaller than the background electrochemical redox current (due to redox reactions directly on the electrode surface) were measured at applied voltages >0.4 V from the OCP. The phase relationship between the optical excitation and photocurrent response was also measured and shown to be analytically useful.
Isn′t it exciting! A method to accurately detect photocurrent signals 104–105‐fold smaller than background currents is presented. Bacterial photosynthetic reaction center proteins are bound to a gold electrode and optically excited at 13 Hz, resulting in electron transfer through the protein and to the electrode (see picture, arrows). A photocurrent signal is detected at the same frequency as the excitation signal and isolated from the background current.
Researchers at Kansas State University (Yiqun Yang, Jun Li, and Ryszard Jankowiak) and University of North Texas (Habtom B. Gobeze and Francis D'Souza) demonstrate harvesting sun light using ...artificial photosynthesis in a nanoscale forest in article 1600371. The performance of a “green” biosolar cell consisting of photosynthesis light‐harvesting complex sensitizers on TiO2 nanotrees is substantially enhanced by incorporating only ≈1 wt% plasmonic nanoparticles.
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