Biosolar Cell Research Articles

Bimodal functionality of highly conductive nanostructured silver film towards improved performance of photosystem I-based graphene photocathode

We present the novel design of photosystem I (PSI)-based biosolar cell, whereby conductive transparent electrode materials, such as ITO or FTO, are replaced with glass covered with silver island film. This nanostructured metallic layer combines high electric conductance with enhancing the absorption efficiency of the PSI biocatalyst via the plasmonic effect. We demonstrate strong enhancement of the photocurrent generated in the biohybrid electrode composed of oriented layers of PSI reaction centers due to plasmonic interactions of the PSI fluorophores and redox centres with the conductive silver island film.

Engineering cyanobacteria as a new platform for producing taxol precursors directly from carbon dioxide

Taxol serves as an efficient natural anticancer agent with extensive applications in the treatment of diverse malignancies. Although advances in synthetic biology have enabled the de novo synthesis of taxol precursors in various microbial chassis, the total biosynthesis of taxol remains challengable owing to the restricted oxidation efficiency in heterotrophic microbes. Here, we engineered Synechocystis sp. PCC 6803 with modular metabolic pathways consisting of the methylerythritol phosphate pathway enzymes and taxol biosynthetic enzymes for production of taxadiene-5α-ol (T5α-ol), the key oxygenated intermediate of taxol. The best strain DIGT-P560 produced up to 17.43 mg/L of oxygenated taxanes and 4.32 mg/L of T5α-ol. Moreover, transcriptomic analysis of DIGT-P560 revealed that establishing a oxygenated taxane flux may enhance photosynthetic electron transfer efficiency and central metabolism in the engineered strain to ameliorate the metabolic disturbances triggered by the incorporation of exogenous genes. This is the first demonstration of photosynthetic production of taxadiene-5α-ol from CO2 in cyanobacteria, highlighting the broad prospects of engineered cyanobacteria as bio-solar cell factories for valuable terpenoids production and expanding the ideas for further rational engineering and optimization.

Enhancing bio-photovoltaic cell efficiency: A study in transport property

Recently, bio-solar cells have garnered significant attention owing to their relatively high efficiency and cost-effectiveness, positioning them as alternative devices for solar energy harvesting. This study delves into the optical and electrical transport characteristics of a novel bilayer bio-solar cell using the total system transfer matrix method, theoretically. These bilayer bio-solar cells consist of two distinct layers of Chlorophyll-a and Chlorophyll-b, forming a heterojunction in the bio-solar cell architecture. Within these solar cells, photon absorption by the active layers of chlorophyll generates excitons and quasi-particles (bound electron and hole pairs), which subsequently diffuse through the collecting layer, resulting in significant recombination losses. The influence of the thickness of chlorophyll adsorbent active layers on the short circuit current density and quantum efficiency is examined through numerical calculations. Furthermore, we develop models for the solar cell parameters of thin film heterojunction photovoltaic devices based on Chlorophyll-a/Chlorophyll-b. The results indicate efficient short circuit current and quantum efficiency values (or power conversion efficiency) of 72 A/m2 and 3.30 %, respectively. It is demonstrated that optimizing the thickness of bio-solar cells based on these findings may enhance electron transport, leading to higher photocurrents and improved overall efficiency. These simulation outcomes pave the way for optimizing the thickness of bio-solar cells and advancing towards higher efficiencies.

Review on green resources and AI for biogenic solar power

The need for clean and renewable energy has grown dramatically over the past few years. As potential candidates for producing green energy in this region, photovoltaic and bio-solar energy technologies have arisen. This review presents a novel approach for designing and developing photovoltaics and bio-solar cells using eco-friendly materials and artificial intelligence (AI) techniques. An intriguing architecture is outlined for a bio-solar cell that fuses photovoltaic electronics with photosynthetic organisms. A recyclable thin-film solar cell serves as the basis of our photovoltaic system. To further maximize the effectiveness of the device, we use AI algorithms. According to statistical calculations, the proposed bio-solar cell can produce a sizable amount of electricity while being ecologically sound. This paper outlines significant advances in developing solar cells and photovoltaics using green nanomaterials and AI, which provide exciting potential for improving energy harvesting capacity. This review also presents an overview of the effects of the potential commercialization of our strategy, its social and environmental benefits, and its pitfalls.

Solar Energy Is Effectively Converted to Electricity and Hydrogen Using Cyanobacteria

We present solar energy conversion for electricity generation and hydrogen production from water using Anabaena variabilis (A. variabilis), an oxygenic photosynthetic cyanobacterium. Electrons from water oxidation by the light reactions that take place in thylakoid membranes (TMs) undergo a series of electron transfer pathway called Z-schme. We devised a method in which electrons are directed to the external electrode. In order to extract electrons from TMs, we found that double mediators are very effective in transferring electrons to the electrode from TMs. Dimethylbenzoquinone, the first mediator, can take electrons from the Z-scheme and delivers them to ferricyanide, the second mediator. Thus transferred electrons move to the cathode where oxygen reduction reaction takes place. Figure shows how biosolar cell (BSC) is operating under illumination.Electricity generation was achieved by simply attaching an external load between the anode and the cathode. When A. variabilis was dispersed in solution, the maximum photocurrent up to 2.14 mA cm-2 upon one sun light intensity. A complete cell produced Pmaxof 160 mW cm-2 at 750 mA cm-2 with a quantum efficiency of 4.8% over a whole spectral range and turnover frequency of 17 per PSII for water molecule oxidation. The same concept was also applied to the hydrogen production. When operated in a double-chamber reactor under anaerobic condition, pure hydrogen gas was produced from water with high energy efficiencies and high production rates upon voltage bias. The maximum H2 production rate of 122 mmol H2(mg Chla)-1h-1 at anode potential of 0.4 V vs. Ag/AgCl was achieved. Energy efficiency exceeded 100% at lower anode potentials. We expect that this study opens a new way of utilizing cyanobacteria for appreciable electricity and hydrogen production. The same concept could be extended to other oxygenic cyanobacteria. Figure 1

A Nano-Biohybrid-Based Bio-Solar Cell to Regulate the Electrical Signal Transmission to Living Cells for Biomedical Application.

Bio-solar cells are studied as sustainable and biocompatible energy sources with significant potential for biomedical applications. However, they are composed of light-harvesting biomolecules with narrow absorption wavelengths and weak transient photocurrent generation. In this study, a nano-biohybrid-based bio-solar cell composed of bacteriorhodopsin, chlorophyllin, and Ni/TiO2 nanoparticles is developed to overcome the current limitations and verify the possibility of biomedical applications. Bacteriorhodopsin and chlorophyllin are introduced as light-harvesting biomolecules to broaden the absorption wavelength. As a photocatalyst, Ni/TiO2 nanoparticles are introduced to generate a photocurrent and amplify the photocurrent generated by the biomolecules. The developed bio-solar cell absorbs a broad range of visible wavelengths and generates an amplified stationary photocurrent density (152.6nAcm-2 ) with a long lifetime (up to 1month). Besides, the electrophysiological signals of muscle cells at neuromuscular junctions are precisely regulated by motor neurons excited by the photocurrent of the bio-solar cell, indicating that the bio-solar cell can control living cells by signal transmission through other types of living cells. The proposed nano-biohybrid-based bio-solar cell can be used as a sustainable and biocompatible energy source for the development of wearable and implantable biodevices and bioelectronic medicines for humans.

Powering the internet of things in aquatic environments: Solar energy harvesting through a buoyant biosolar cell array

Despite the development of supportive technologies of the Internet of Things (IoT), the maximum potential of the IoT networks has been limited by the absence of integrative, sustainable, environmentally safe, and economical electrical energy sources to operate these networks independently. Conventional batteries have proven to be costly on a large scale, environmentally toxic, and unsustainable. As the IoT becomes more widespread and branches into domains such as aquatic environments, batteries are becoming less favorable as a power supply for IoT nodes. Similarly, most common energy harvesting methods have struggled as an energy solution because of their difficulty in integration, hazardous nature, and inconsistent performance. In this project, we introduce a miniaturized buoyant bio-solar cell array for solar energy harvesting through photosynthetic electrogenic bacteria in a microbial consortium. The bio-solar cell (BSC) can generate up to ∼90 μW/cm2 of constant output which is the highest power density achieved by a BSC so far. The BSC array can connect multiple cells powering a long-range wireless system transferring sensor data across ∼470 m. The proposed BSC's unique design allows it to be seamlessly integrated into aquatic environments operating for two months making it a great energy source for IoT nodes in lentic ecosystems.

A miniaturized bionic ocean-battery mimicking the structure of marine microbial ecosystems

Marine microbial ecosystems can be viewed as a huge ocean-battery charged by solar energy. It provides a model for fabricating bio-solar cell, a bioelectrochemical system that converts light into electricity. Here, we fabricate a bio-solar cell consisting of a four-species microbial community by mimicking the ecological structure of marine microbial ecosystems. We demonstrate such ecological structure consisting of primary producer, primary degrader, and ultimate consumers is essential for achieving high power density and stability. Furthermore, the four-species microbial community is assembled into a spatial-temporally compacted cell using conductive hydrogel as a sediment-like anaerobic matrix, forming a miniaturized bionic ocean-battery. This battery directly converts light into electricity with a maximum power of 380 μW and stably operates for over one month. Reproducing the photoelectric conversion function of marine microbial ecosystems in this bionic battery overcomes the sluggish and network-like electron transfer, showing the biotechnological potential of synthetic microbial ecology.

Electropolymerized chlorophyll derivative biopolymers for supercapacitors

Chlorophylls (Chls) have rarely been prepared and studied in the polymeric phase. We demonstrate for the first time the preparation of four polymerized thin films of chlorophyll derivatives, via the electrochemical coupling of peripheral vinyl or ethynyl groups at the C3-position of the tetrapyrrole ring. The characterization of these PolyChl (polymerized chlorophylls) films suggests that Zn-based PolyChls remain in the chlorin macrocycle, whereas Ni-based PolyChls turn into porphyrin macrocycles during the electropolymerization processes. Employing these PolyChls as the working electrodes in a three-electrode system, the highest capacitance 466 F g−1 at 5 mV s−1 is obtained for PolyNiChl-A. To fully verify the practical value and environment-friendly property, we also fabricate a novel bio-inspired solar light-to-electricity conversion-storage device using a PolyNiChl-A solid-state symmetric supercapacitor and a previously developed all-Chl-based biosolar cell. The device shows excellent photo-charging-discharging behavior under different light illumination intensities. Using non-toxic, degradable, sustainable and pollution-free Chls as dominating material, transferring solar energy to electricity and storing it in supercapacitor, the hybrid energy conversion and storage device suggests a promising way on construction of future clean energy system. Meanwhile this study also creates a novel family of biopolymers with the most abundant, environmentally friendly, and multi-functional Chl derivatives.

Enhancement of power conversion efficiency by chlorophyll and carotenoid co-sensitization in the biosolar cells

Photosynthetic pigment-based biosolar cells (BSCs) have attracted much attention over the past few years in the field of artificial photosynthesis. To further improve the power conversion efficiency (PCE) of chlorophyll (Chl)-based bilayer BSCs, co-sensitization effects of three carboxylated chromophores, methyl trans-32-carboxy-pyropheophorbide-a (H2Chl-1), methyl 7-deformyl-7-(trans-carboxyethenyl)-pyropheophorbide-b (H2Chl-2), and β-apo-8′-carotenoic acid (Car) were investigated as H2Chl-1:H2Chl-2, H2Chl-1:Car, and H2Chl-2:Car combinations. The homogeneously co-sensitized mesoporous TiO2 (m-TiO2) layer (TiO2–H2Chl:Car) serves as the photoactive and electron extraction layer, while a Chl-a derivative, zinc methyl 3-devinyl-3-hydroxymethyl-pyropheophorbide-a (ZnChl) forms J-type self-aggregation film and acts as electron donor layer. The light absorption and electron injection efficiency of the TiO2 sensitized H2Chl-1:Car blends are better than those of other types of co-sensitization after optimizing the blend ratio of each type. The electron absorption spectrum of TiO2–(H2Chl-1:Car) at the best mass ratio of 10:3 (molar ratio of 12:5) showed wider absorption band in 350–450 nm region compared to the spectrum of sole TiO2–(H2Chl-1). The charge transfer resistance was significantly reduced when TiO2–(H2Chl-1:Car) was applied for BSCs. The best PCE of 2.13% was achieved using TiO2–(H2Chl-1:Car = 10:3), which corresponds to 40% increase of PCE compared to the device using TiO2–(H2Chl-1) without Car.

Photobioanodes Based on Nanoimprinted Electrodes and Immobilized Chloroplasts

AbstractAs the global energy demand continues to increase, the interest in photosynthetic energy conversion is growing accordingly. Chloroplasts, photosynthetic organelles present in plants and algae, are attractive candidates for construction of bio solar cells; however, they have been less studied because of their complex membrane system, which restricts electrochemical communication with an electrode surface. Nevertheless, in this work photobioanodes based on planar and nanoimprinted gold substrates modified with chloroplasts were designed and evaluated. Apparently, nanoimprint lithography contributed to higher photocurrent densities, not only owing to the enlarged real surface area, but also due to boosting electrochemical communication between the photosynthetic organelles and the electrode. Combining chloroplast‐modified nanoimprinted gold electrodes with a capacitive part made of a planar gold substrate, coated with a conductive polymer, resulted in a dual‐feature photobioanode providing a lower open‐circuit potential, i. e., −0.11 V vs. Ag|AgCl|KClsat, and an enhanced capacitance of ca. 37 F m−2 upon illumination of 400 W m−2.

Biocontainment of Engineered Synechococcus elongatus PCC 7942 for Photosynthetic Production of α-Farnesene from CO2.

Biocontainment systems have been developed to mitigate the concerns regarding biosafety and environmental risk because of the possible escape of genetically modified organisms into the environment following large-scale outdoor cultivation. Here, we present a biocontainment system entailing genetically modified Synechococcus elongatus PCC 7942, also engineered for α-farnesene production using a de-evolutionary strategy. In this approach, the gene cluster encoding the β-carboxysome and the associated carbon concentrating mechanism (CCM) were deleted in the α-farnesene-producing cyanobacteria, resulting in no cell growth and no α-farnesene production at ambient CO2 concentrations (100% air bubbling). However, cell growth and α-farnesene production were detected in the CCM-deficient strains at high CO2 concentrations (5% CO2 [v/v], 10% CO2 [v/v]), albeit at levels lower than those of the parental control. To overcome this limitation, the overexpression of carbonic anhydrase and bicarbonate transporter genes in the CCM-deficient strains restored cell growth and the production level of α-farnesene (5.0 ± 0.6 mg/L) to that of the parental control. The production of α-farnesene in the later strains strictly depended on CO2 concentration in the photobioreactor and did not rely on a chemical induction process. Thus, next generation bio-solar cell factories could be promoted with the suggested biocontainment system.

Charge-Transfer Mechanism in Chlorophyll Derivative-based Biosolar Cells with Hole-Transporting P3HT Revealed by Sub-Picosecond Transient Absorption Spectroscopy

The photovoltaic performance of chlorophyll (Chl)-based biosolar cells (BSCs) is increased greatly by introducing a P3HT layer on a base architecture of indium tin oxide (ITO)/compact TiO2/mesoporo...

A Logic NAND Gate for Controlling Gene Expression in a Circadian Rhythm in Cyanobacteria.

To enable circadian control of gene expression in cyanobacteria, we constructed a genetic logic gate (NAND) using orthogonal promoters via modular CRISPR interference. The NAND gates were tested in Synechococcus elongatus PCC 7942 using a fluorescent reporter. The NAND gate dynamics were characterized based on the affinity of the dCas9 complex to the output element. Upon connecting tight gene repressions with the circadian promoter (the purF gene; peak expression at dawn), inversed peak expressions were obtained as an output of the NAND gate although the retroactivities were shown in the ON and OFF states. A dark-responsive genetic element of the NAND gate was also expanded to an AND gate in S. elongatus PCC 7942. These cyanobacterial NAND and AND gates could facilitate the control of gene expressions in dynamic metabolic engineering technologies, thereby enabling the cyanobacteria to serve as biosolar cell factories.

Construction of a Bioelectrochemical Dihydrogen/Formate Interconversion System and a Bio-Solar Cell

Modern societies have energy and environmental issues such as fossil fuel depletion and excessive carbon dioxide (CO2) emissions. Therefore, an effective use of renewable energy resources instead of fossil fuels is essential for the development of a sustainable energy economy. Particularly, dihydrogen (H2), formic acid (HCOOH) and sunlight are expected to be new energy sources. These advantages are as follows; H2 emits no harmful substances in use; HCOOH has a high energy density and is a liquid fuel that can be easily stored and transported; sunlight is universally available on the ground. However, the electrochemical conversion of the above energy has the following problems; a catalyst for H2 oxidation, platinum, is expensive; byproducts such as carbon monoxide are generated in CO2 reduction at usual electrodes; solar cell materials are sometimes expensive and environmentally harmful. In order to overcome these problems, we focused on biocatalysts, which are ecofriendly, and have high catalytic performance and selectivity under mild conditions. Furthermore, we constructed two electro-enzymatic energy conversion devices: an H2/HCOO- interconversion system and a bio-solar cell.In an H2/HCOO- interconversion system, we applied two enzymes which catalyze bidirectional redox reactions: [NiFe]-hydrogenase from Desulfovibrio vulgaris Miyazaki F (H2ase; EC 1.12.2.1) and tungsten-containing formate dehydrogenase from Methylobacterium extorquens AM1 (FoDH1; EC 1.2.1.2). H2ase and FoDH1 catalyze the H+/H2 and CO2/HCOO- interconversion, respectively, and we attempted to generate HCOO- without external power supply by the coupling of two bioelectrocatalytic reactions: direct electron transfer (DET)-type H2 oxidation catalyzed by H2ase and mediated electron transfer (MET)-type CO2 reduction catalyzed by FoDH1 using benzyl viologen (BV) as a mediator (H2 + CO2 → HCOO- + H+). H2ase was adsorbed on a bioanode functionalized with p-phenylenediamine, which leads to orientations suitable for DET-type bioelectrocatalysis of H2ase, while FoDH1 and BV were adsorbed on a biocathode. In addition, gas-diffusion-type electrodes were employed for high-speed supply of gaseous substrates. The two electrodes were short-circuited in a cell, and CO2 and H2 gasses were spontaneously supplied from the outside of the biocathode and the bioanode, respectively. The amount of formate in the electrolyte solution increased almost linearly with the reaction time. On the other hand, when the feed gasses were replaced with Ar gas to remove CO2 and H2 from the system, the amount of formate decreased with the time. This is due to the reversed reaction: (HCOO- + H+ → H2 + CO2). These results mean that the difference in equilibrium potentials of the H+/H2 and CO2/HCOO- couples determines the driving force of the reaction, which is reversed depending on conditions, and the interconversion between H2 and HCOO- was experimentally demonstrated.A bio-solar cell is an electric energy device mimicking natural photosynthesis and extracts excited electrons outside the photosynthetic system. In this study, we constructed a bio-solar cell using the thylakoid membrane from spinach as an anodic photo-bioelectrocatalyst which oxidizes water (H2O) to dioxygen (O2) and the recombinant bilirubin oxidase (BOD; EC 1.3.3.5) produced by expressing the gene of BOD from Myrothecium verucarria in Pichia pastoris as a cathodic bioelectrocatalyst which reduces O2 to H2O. In addition, we investigated the characteristics of a thylakoid membrane-functionalized bioanode with a mediator of hexaammineruthenium(III/II) ion ([Ru(NH3)6]3+/2+), which has the following characteristics: fast electrode kinetics, high stability and solubility, and somewhat low redox potential. The photo-driven bioanode prepared by applying the mixture of thylakoid membranes and water-dispersed multi-walled carbon nanotubes on a gold-spattered indium tin oxide (ITO) electrode showed the photocurrent caused by MET-type photo-bioelectrocatalytic H2O oxidation in a buffer (pH 7.0) containing 5 mM Ru(NH3)6Cl3 under the light condition. The performance of the bioanode (0.2 mA cm- 2 at 0 V vs. Ag|AgCl|sat. KCl) is better than that in the previous report using 1,2-naphthoquinone as a mediator. Then, a bio-solar cell was constructed by combining the bioanode with the BOD-modified gas-diffusion-type biocathode, and O2 was spontaneously supplied from the outside of the biocathode. The cell exhibited an open-circuit voltage of 0.61 V and a maximum power density of 50 μW cm- 2 at a cell voltage of 0.42 V under quiescent conditions. To the best of our knowledge, the power density of our cell unit is the highest among those reported for the bio-solar cells to date.These works lead to the artificial photosynthetic system, which generates H2 or HCOO- from sunlight and H2O (and CO2), and they might be a breakthrough for the sustainable energy economy.

CRISPRi-dCas12a: A dCas12a-Mediated CRISPR Interference for Repression of Multiple Genes and Metabolic Engineering in Cyanobacteria.

In cyanobacteria, metabolic engineering using synthetic biology tools is limited to build a biosolar cell factory that converts CO2 to value-added chemicals, as repression of essential genes has not been achieved. In this study, we developed a dCas12a-mediated CRISPR interference system (CRISPRi-dCas12a) in cyanobacteria that effectively blocked the transcriptional initiation by means of a CRISPR-RNA (crRNA) and 19-nt direct repeat, resulting in 53-94% gene repression. The repression of multiple genes in a single crRNA array was also successfully achieved without a loss in repression strength. In addition, as a demonstration of the dCas12a-mediated CRISPRi for metabolic engineering, photosynthetic squalene production was improved by repressing the essential genes of either acnB encoding for aconitase or cpcB2 encoding for phycocyanin β-subunit in Synechococcus elongatus PCC 7942. The ability to regulate gene repression will promote the construction of biosolar cell factories to produce value-added chemicals.

Semisynthetic Chlorophyll Derivatives Toward Solar Energy Applications

Plenty of thin‐film solar cell technologies using organic materials have been developed to alleviate energy shortages. As developing devices for solar energy applications, artificial photosynthesis is a trend inspired from natural photosynthesis. Although the sophisticated system that exists in nature is fascinating, the development of photovoltaic devices focusing on the usage of natural chlorophylls has been quite limited, compared with the application of other counterparts such as artificial porphyrins or phthalocyanines. Herein, the development of semisynthetic chlorophyll derivatives as functional materials for solar cells are focused on. (Bacterio)chlorins possessing a carboxylic acid moiety as a binding site to semiconductors are synthesized to improve the efficiencies of dye‐sensitized solar cells, which are now leading to another application: photocatalysts for hydrogen evolution. In contrast, derivatives without a carboxy group can be applied to organic solar cells. As for the application for perovskite solar cells, self‐assembling aggregates of a kind of derivatives are proven to be suitable as hole‐transporting materials. In addition, a new type of solid‐state biosolar cells is proposed, in which chlorophyll derivatives act solely as the photoactive materials. This Report can enlarge the scope of advanced functional materials in the field of solar energy applications.

A chlorophyll derivative-based bio-solar energy conversion and storage device

Chlorophylls (Chls) are the most abundant natural photosynthetic pigments, with light harvesting and electron/energy transferring functions. We demonstrate a low-cost and environment friendly solar energy conversion and storage device, based entirely on Chl derivatives. To fabricate a hybrid capacitor, we employed zinc methyl 3-devinyl-3-hydroxymethyl-pyropheophorbide-a (Chl-1) aggregates as a positive electrode, in conjunction with an activated carbon-based negative electrode. The Chl-1 aggregates showed a typical battery characteristic with a pair of redox peaks in a three-electrode system. The gravimetric capacitance in 2 M KOH at 10 mV/s was 55.2 F/g. The hybrid capacitor, with a large potential window range from 0.6 to 1.7 V, was connected to a series trilayer Chl-based bio-solar cell for photo-charging and discharging tests. Under 1.5G illumination, the device reached its high potential window of 1.7 V in a short time and finished three charging/discharging cycles in 60 s. This study provides a unique approach for the future development of a sustainable society with green energy materials.

A miniaturized, self-sustaining, and integrable bio-solar power system

Abstract We demonstrate a practical and sustainable bacterial power source for low-power electronic applications. Self-sustainable electricity is produced from revolutionarily structured microliter-scale bio-solar cells using a co-culture of heterotrophic and autotrophic bacteria. Two bio-solar cells are integrated on a single chip and connected in series, continuously generating light-responsive electricity from heterotrophic bacterial respiration with the organic substrates produced by photosynthetic autotrophs. Agar-based anolyte, catholyte, and salt-bridge provided solid-state ionic environments for more efficient syntrophic interactions between co-cultures without bacterial competition, further enhancing the device performance and lifespan. The solid-phase platform allows versatile device configuration in a small footprint without a cumbersome fluidic feeding system and permits easy integration and operation with solid-state applications. The device is sealed with a gas-permeable polydimethylsiloxane (PDMS) membrane to facilitate gas exchange to the bacteria and cathodic reactions, even ideally allowing for replenishing bacterial gasses from environments for self-sustainable energy harvesting. A DC-DC booster circuit is integrated with the stacked bio-solar cells to increase the operational voltage (~500 mV) to a maximum output of >3 V for self-powering an on-chip, light-emitting diode (LED). This is the first demonstration of the microliter-scale bio-solar cell as a practical power source.

Chloroplast biosolar cell and self-powered herbicide monitoring.

Utilizing chloroplasts in biosolar cells offers a sustainable approach for sunlight harvesting. However, the limited electrochemical communication between these biological entities and an electrode surface has led to complex device setups, hindering their application in the field. Herein, a cross-linker enables a simple photoanode architecture with enhanced photoexcited electron transfer between chloroplasts and abiotic electrodes. The improved "wiring" of the photosynthetic electron transfer chain resulted in a five-fold increase in the biophotocurrent. The biophotoanode is applied in a Pt-free, portable biosolar cell allowing the in situ self-powered monitoring of diuron within limits set by the Environmental Protection Agency.