Recent advances in coupling light-harvesting microorganisms with electronic components have led to a new generation of biohybrid devices based on microbial photocatalysts. These devices are limited ...by the poorly conductive interface between phototrophs and synthetic materials that inhibit charge transfer. This study focuses on overcoming this bottleneck through the metabolically-driven encapsulation of photosynthetic cells with a bio-inspired conductive polymer. Cells of the purple non sulfur bacterium
Rhodobacter sphaeroides
were coated with a polydopamine (PDA) nanoparticle layer via the self-polymerization of dopamine under anaerobic conditions. The treated cells show preserved light absorption of the photosynthetic pigments in the presence of dopamine concentrations ranging between 0.05–3.5 mM. The thickness and nanoparticle formation of the membrane-associated PDA matrix were further shown to vary with the dopamine concentrations in this range. Compared to uncoated cells, the encapsulated cells show up to a 20-fold enhancement in transient photocurrent measurements under mediatorless conditions. The biologically synthesized PDA can thus act as a matrix for electronically coupling the light-harvesting metabolisms of cells with conductive surfaces.
Living photovoltaics are microbial electrochemical devices that use whole cell–electrode interactions to convert solar energy to electricity. The bottleneck in these technologies is the limited ...electron transfer between the microbe and the electrode surface. This study focuses on enhancing this transfer by engineering a polydopamine (PDA) coating on the outer membrane of the photosynthetic microbe
Synechocystis
sp. PCC6803. This coating provides a conductive nanoparticle shell to increase electrode adhesion and improve microbial charge extraction. A combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Vis absorption, and Raman spectroscopy measurements were used to characterize the nanoparticle shell under various synthesis conditions. The cell viability and activity were further assessed through oxygen evolution, growth curve, and confocal fluorescence microscopy measurements. The results show sustained cell growth and detectable PDA surface coverage under slightly alkaline conditions (pH 7.5) and at low initial dopamine (DA) concentrations (1 mM). The exoelectrogenicity of the cells prepared under these conditions was also characterized through cyclic voltammetry (CV) and chronoamperometry (CA). The measurements show a three-fold enhancement in the photocurrent at an applied bias of 0.3 V (vs. Ag/AgCl 3 M KCl) compared to non-coated cells. This study thus lays the framework for engineering the next generation of living photovoltaics with improved performances using biosynthetic electrodes.
In the development of semi-artificial biophotovoltaic assemblies, deeper understanding of electrochemical processes is required to achieve functional and efficient devices. Evaluation of photosystem ...2 embedded in an Os-complex modified redox polymer using scanning photoelectrochemical microscopy (SPECM) provides insight into the intricate electrochemical processes of the immobilized protein complex and its electrical communication pathways with the redox tethers of the polymer matrix. The use of local irradiation during an SPECM array scan prevents sample inactivation prior to analysis. Moreover, the simultaneously possible collection of partially reduced oxygen species in the form of hydrogen peroxide confirms the presence of competing charge transfer pathways involved in the reduction of oxygen at the chlorophyll pigments upon irradiation of the sample. In addition, evaluation of photocurrent in the presence of an inhibitor that blocks the terminal plastoquinone QB binding site of the photosystem reveals electrochemical communication between the intermediate plastoquinone QA and the redox polymer. The obtained information proves to be relevant for further design and optimization of devices for technological applications.
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A Biogenic Photovoltaic Material Srivastava, Sarvesh Kumar; Piwek, Przemyslaw; Ayakar, Sonal R. ...
Small (Weinheim an der Bergstrasse, Germany),
06/2018, Volume:
14, Issue:
26
Journal Article
Peer reviewed
A proof‐of‐concept for the fabrication of genetically customizable biogenic materials for photovoltaic applications is presented. E. coli is first genetically engineered to heterologously express the ...carotenoid biosynthetic pathway from plants. This modification yields a strain that overproduces the photoactive pigment lycopene. The pigment‐producing cells are then coated with TiO2 nanoparticles via a tryptophan‐mediated supramolecular interface, and subsequent incorporation of the resulting biogenic material (cells@TiO2) as an anode in an I−/I3−‐based dye‐sensitized solar cell yields an excellent photovoltaic (PV) response. This work lays strong foundations for the development of bio‐PV materials and next‐generation organic optoelectronics that are green, inexpensive, and easy to manufacture.
A new class of biogenic photovoltaics has been developed by coating lycopene‐producing E. coli cells with TiO2 nanoparticles using supramolecular chemistry.
Here, we report the development of a novel photoactive biomolecular nanoarchitecture based on the genetically engineered extremophilic photosystem I (PSI) biophotocatalyst interfaced with a single ...layer graphene via pyrene-nitrilotriacetic acid self-assembled monolayer (SAM). For the oriented and stable immobilization of the PSI biophotocatalyst, an His
-tag was genetically engineered at the
-terminus of the stromal PsaD subunit of PSI, allowing for the preferential binding of this photoactive complex with its reducing side towards the graphene monolayer. This approach yielded a novel robust and ordered nanoarchitecture designed to generate an efficient direct electron transfer pathway between graphene, the metal redox center in the organic SAM and the photo-oxidized PSI biocatalyst. The nanosystem yielded an overall current output of 16.5 µA·cm
for the nickel- and 17.3 µA·cm
for the cobalt-based nanoassemblies, and was stable for at least 1 h of continuous standard illumination. The novel green nanosystem described in this work carries the high potential for future applications due to its robustness, highly ordered and simple architecture characterized by the high biophotocatalyst loading as well as simplicity of manufacturing.
Photomicrobial fuel cells (p-MFCs) are devices that use photosynthetic organisms (such as cyanobacteria or algae) to turn light energy into electrical energy. In a p-MFC, the anode accepts electrons ...from microorganisms that are either growing directly on the anode surface (biofilm) or are free floating in solution (planktonic). The nature of both the anode and cathode material is critical for device efficiency. An ideal anode is biocompatible and facilitates direct electron transfer from the microorganisms, with no need for an electron mediator. For a p-MFC, there is the additional requirement that the anode should not prevent light from perfusing through the photosynthetic cells. The cathode should facilitate the rapid reaction of protons and oxygen to form water so as not to rate limit the device. In this paper, we first review the range of anode and cathode materials currently used in p-MFCs. We then present our own data comparing cathode materials in a p-MFC and our first results using porous ceramic anodes in a mediator-free p-MFC.
Photosynthesis is the natural eternal process of conversion of solar energy into Chemical energy by living chlorophyllous organisms. The direct conversion of sunlight into electrical current by using ...photosynthetic organisms has the potential to produce green energy. Conventional bio-photovoltaic cells have utilized unicellular photosynthetic microorganisms such as cyanobacteria and unicellular green algae. This study describes electricity generation through a quasi-solid-state device by utilizing live freshwater macroalgae. Here, we fabricated a simple bio-photovoltaic device with filamentous macroalgae Pithophora roettleri as photoactive materials. The filamentous alga Pithophora belonging to the family of green algae, is generally found growing at the bottom or forming dense mats on the surface of aquatic habitats. The algae were collected from a pond located in the neighbourhood and fabricated a device by sandwiching the algal biofilm between activated carbon-coated copper (Cu) and titanium oxide (TiO2) coated fluorine-doped tin oxide (FTO) coated glass slide. The fabricated optimized device has exhibited a considerable amount of photo-generated current and photo-generated voltage generation under the white light and UV light irradiation The optimized device (with 1 cm2 area) exhibits 10.19 μA short circuit photocurrent and 0.35 V open circuit photovoltage in white light (100 mW/cm2) irradiance and exhibits 1.25 mA photocurrent and 0.5 V photovoltage in UV light (365 nm LED with 20 mW/cm2 intensity). To understand applicability, 10 devices were connected in a series that delivered 5.53 V in outdoors under natural sunlight with 0.6 Sun intensity.
•Bioelectricity generation from fresh water macro algae.•Bioelectricity generated using the photosynthetic organism from sandwiched device.•Macroalgae sandwiched between carbon-coated copper and TiO2-coated FTO electrode.•The best device exhibited a photocurrent of 1.25 mA and a photovoltage of 0.5V•A series of 10 devices was enhanced the voltage output to 5.53V under open sun light.
Photoactive reaction centers (RCs) are protein complexes in bacteria able to convert sunlight into other forms of energy with a high quantum yield. The photostimulation of immobilized RCs on ...inorganic electrodes result in the generation of photocurrent that is of interest for biosolar cell applications. This paper reports on the use of novel electrodes based on functional conductive nanocrystalline diamond onto which bacterial RCs are immobilized. A three-dimensional conductive polymer scaffold grafted to the diamond electrodes enables efficient entrapment of photoreactive proteins. The electron transfer in these functional diamond electrodes is optimized through the use of a ferrocene-based electron mediator, which provides significant advantages such as a rapid electron transfer as well as high generated photocurrent. A detailed discussion of the generated photocurrent as a function of time, bias voltage, and mediators in solution unveils the mechanisms limiting the electron transfer in these functional electrodes. This work featuring diamond-based electrodes in biophotovoltaics offers general guidelines that can serve to improve the performance of similar devices based on different materials and geometries.
Recent advances in materials science lead to the emergence of novel materials to address current energy and environmental challenges, such as energy-intensive manufacturing processes, use of ...hazardous materials, and greenhouse gas (GHG) emissions of photovoltaic (PV) technology. New materials that are more environmentally sustainable and abundant in nature are being integrated into PV technologies, especially in dye-sensitized solar cells. Carbon nanomaterials and biomolecules, specifically the photosystem I (PSI) and the bacteriorhodopsin (bR) proteins, are discussed in this review for bio-sensitized solar cells (bio-SSCs). Nanostructured carbon materials show enormous potential because of their allotropic diversity, compatible wide bandgap levels that facilitate light absorption, and excellent electrical properties, whereas the PSI and bR are promising as sensitizers because of their chromophores, high quantum yield, and chemical stability. This review addresses the role of these renewable materials for the development of bio-SSCs. The low photoconversion efficiency of bio-SSCs remains a challenge and is explained on energy mismatch, low surface density of sensitizer, and high-resistance interfacial electron transport between photoanode and electrolyte. By comparing the effect of various morphologies of photoanode semiconductors and protein modifications in the performance of bR-sensitized solar cells, we appraise how far bio-SSCs may progress in the future.
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•Replacing toxic materials in dye-sensitized solar cells by renewable carbon discussed.•Nanostructured carbons have multiple functions in these devices.•Photosystem I and bacteriorhodopsin (bR) proteins are promising solar light harvesters.•Protein mutation and immobilization approaches improve bR-solar cells performance.•Low bR surface density, energy mismatch, and photoelectron recombination limit performance.
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