Biosolar Cell Research Articles

Photocurrent generation in diamond electrodes modified with reaction centers.

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.

A micro-sized bio-solar cell for self-sustaining power generation.

Self-sustainable energy sources are essential for a wide array of wireless applications deployed in remote field locations. Due to their self-assembling and self-repairing properties, "biological solar (bio-solar) cells" are recently gaining attention for those applications. The bio-solar cell can continuously generate electricity from microbial photosynthetic and respiratory activities under day-night cycles. Despite the vast potential and promise of bio-solar cells, they, however, have not yet successfully been translated into commercial applications, as they possess persistent performance limitations and scale-up bottlenecks. Here, we report an entirely self-sustainable and scalable microliter-sized bio-solar cell with significant power enhancement by maximizing solar energy capture, bacterial attachment, and air bubble volume in well-controlled microchambers. The bio-solar cell has a ~300 μL single chamber defined by laser-machined poly(methyl methacrylate) (PMMA) substrates and it uses an air cathode to allow freely available oxygen to act as an electron acceptor. We generated a maximum power density of 0.9 mW m(-2) through photosynthetic reactions of cyanobacteria, Synechocystis sp. PCC 6803, which is the highest power density among all micro-sized bio-solar cells.

Electromicrobiology: An Emerging Reality—A Review

Electromicrobiology is the study of the interactions between the novel electrical properties of microorganisms and electronic devices. A diversity of microorganisms such as Geobacter and Shewanella species is capable of interacting electrically with the environment. Many recent advances in Electromicrobiology stem from studying Microbial Fuel Cells (MFCs) which are a device designed for the harvesting of electric current from organic compounds. Three types of Microbial Fuel Cells are known which are heterotrophic microbial fuel cells, photosynthetic microbial fuel cells (bio-solar cells) designed to harness the most abundant and promising energy source (solar irradiation) of earth and the hybrid microbial fuel cell. Electric microorganisms especially Sporomusa ovata can use electron derived from electrodes to reduce carbondioxide to multicarbon extracellular organic compounds in a process known as Microbial Electrosynthesis. The mechanism of electron transfer to electrodes by electric microbes is either by the use of electron shuttling molecules, redox-active proteins or via conductive pili. Conductive microorganisms and/or their nanowires have a number of potential practical applications but additional basic research will be necessary for rational applications. This review looks at the Microbial Fuel Cells, the associated mechanisms and applications.

Toward the design of bio-solar cells: high efficiency cascade energy transfer among four donor–acceptor dyes self-assembled in a highly ordered protein–DNA matrix

Artificial antenna complexes built via self-assembly are reported, indicating efficient cascade energy transfer, unprecedented thermal stability, and ease of formation.

Oriented assembly of bacteriorhodopsin on ZnO nanostructured electrode for enhanced photocurrent generation.

Bacteriorhodopsin (bR) is a photoactive protein that has great potential to be used in bioelectronics applications. For the first time, a monolayer of bR created by the Langmuir-Blodgett method is immobilized on a ZnO nanoporous film. Scanning electron microscopy and atomic force microscopy analyses are used to study the morphological properties of the electrodes. In addition, an efficient biosolar cell is designed and fabricated, and the performance of produced nano-biohybrid electrode is investigated by the measurement of power conversion efficiency of biosolar cell. Under AM1.5 irradiation, a short-circuit current of 0.39 mA cm(-2) , open-circuit voltages of 0.5 V, fill factor of 0.52, and an overall energy conversion efficiency of 0.1% are achieved.

Immobilization of photosystem I or II complexes on electrodes for preparation of photoenergy-conversion devices

Photosystems, PSI and PSII isolated from Thermosynechococcus elongatus were successfully immobilized on a TiO2 nanostructured film for use in dye-sensitized biosolar cells (DSBCs). The photosystem complexes were also immobilized on an ITO electrode modified with 3-aminopropyltriethoxysilane by utilizing the interactions between the electrode and the surface of the PSI or PSII polypeptide. Illumination of the PSI and PSII complexes immobilized on the ITO electrode resulted in action spectra in the presence of methyl viologen, which corresponded to the absorption spectra of the complexes. Compared with the ITO electrode, PSI or PSII complexes assembled on the TiO2 electrode had much higher energy-conversion efficiency in the presence of an iodide/triiodide redox system of an ionic-liquid-based electrolyte. This could have interesting applications in the development of DSBCs.

Thylakoid direct photobioelectrocatalysis: utilizing stroma thylakoids to improve bio-solar cell performance.

Thylakoid membranes from spinach were separated into grana and stroma thylakoid fractions which were characterized by several methods (pigment content, protein gel electrophoresis, photosystem activities, and electron microscopy analysis) to confirm that the intact thylakoids were differentiated into the two domains. The results of photoelectrochemical experiments showed that stroma thylakoid electrodes generate photocurrents more than four times larger than grana thylakoids (51 ± 4 nA cm(-2) compared to 11 ± 1 nA cm(-2)). A similar trend was seen in a bio-solar cell configuration with stroma thylakoids giving almost twice the current (19 ± 3 μA cm(-2)) as grana thylakoids (11 ± 2 μA cm(-2)) with no change in open circuit voltage.

Photosynthetic protein complexes as bio-photovoltaic building blocks retaining a high internal quantum efficiency.

Photosynthetic compounds have been a paradigm for biosolar cells and biosensors and for application in photovoltaic and photocatalytic devices. However, the interconnection of proteins and protein complexes with electrodes, in terms of electronic contact, structure, alignment and orientation, remains a challenge. Here we report on a deposition method that relies on the self-organizing properties of these biological protein complexes to produce a densely packed monolayer by using Langmuir-Blodgett technology. The monolayer is deposited onto a gold electrode with defined orientation and produces the highest light-induced photocurrents per protein complex to date, 45 μA/cm(2) (with illumination power of 23 mW/cm(2) at 880 nm), under ambient conditions. Our work shows for the first time that a significant portion of the intrinsic quantum efficiency of primary photosynthesis can be retained outside the biological cell, leading to an internal quantum efficiency (absorbed photon to electron injected into the electrode) of the metal electrode-protein complex system of 32%.

The role of biosolar technologies in future energy supply making scenarios for the Netherlands: Energy port and energy farm

This paper assesses the possible roles of biosolar energy systems in the Netherlands in the coming years. The appraisal is made in the light of EU Directives on renewable energy and reduction of CO2 emissions, and the new Dutch Energy Agreement for Sustainable Growth. The assessment is made within the Dutch BioSolar Cells (BSCs) research programme on photosynthesis and its application in fuel production. Part of the programme is committed to societal debate by considering different options and uses of biosolar technology. To provide building blocks for these discussions, we conducted a comprehensive desk study supplemented with key expert interviews, and we identified and articulated the main drivers for the Dutch transition towards more sustainable energy supply. Next, these drivers were used to develop two futures: energy port and energy farm, representing institutional settings in which BSC technology could be implemented. Both represent fundamentally different types of innovation and are useful in assessing the effect of policies on future energy systems. Both scenarios were used in workshops with BSC researchers and policymakers. Their possible implications for the BSC programme itself, as well as the broader policy significance of the use of biosolar technologies in the Netherlands, are indicated.

Thyalkoid-Based Bio-Solar Cells

Thylakoid bio-solar cells have been developed previously which are capable of direct solar energy conversion through photosynthesis. However, the current output of these cells is quite small compared to mediated systems. Several methods have been implemented to improve the performance. Incorporation of fluorescent carbon quantum dots leads to an increase in photocurrent generation. The conductive quantum dots allow for greater transfer of electrons. Additionally, the quantum dots absorb at wavelengths not necessary for photosynthesis but emit light at wavelengths at which the photosystems of the thylakoids absorb. This makes it possible for the electrodes to use more of the light spectrum. A second method involved the intercalation of conjugated oligoelectrolytes into the thylakoid membrane. These molecules allow for greater electron transfer through the membrane which decreases the resistance in the thylakoid bio-solar cell. Additionally, the photocurrent produced by the thylakoid electrodes increased as well. A third method involves separating thylakoids into stacked regions (grana) and non-stacked regions (stroma) which have very different composition of photosynthetic components. Electrodes modified with stroma thylakoids give much larger currents, up to three times larger than full thylakoid membranes.

Comparative study of thylakoids from higher plants for solar energy conversion and herbicide detection

Thylakoid membranes were isolated from seven plant species. The isolated thylakoids were immobilized onto carbon paper electrodes and the photocurrent was measured. Spinach thylakoids showed the largest photocurrent, 80±10μA per mg protein and 430±60μA per mg chlorophyll. The electrodes were also tested in a bio-solar cell configuration. Open circuit voltages were the same regardless of the thylakoid source, and spinach thylakoid bio-solar cells had the largest currents. Exposure of the electrodes to diuron, a commonly used herbicide, showed that sensitivity varied by thylakoid source, with spinach having the highest sensitivity and green chard and beet greens having the lowest.

Photosensitizers from Spirulina for Solar Cell

Spirulina is a kind of blue-green algae with good photosynthetic efficiency and might be used for photovoltaic power generation. So this paper used living spirulina as novel photosensitizer to construct spirulina biosolar cell. The results showed that spirulina had the photoelectric conversion effect, and could let the spirulina biosolar cell have 70 μA photocurrent. Meanwhile, adding glucose sucrose or chitosan in the spirulina anode chamber, they could make the maxima current density of the cell greatly increased by 80 μA, 100 μA, and 84 μA, respectively, and the sucrose could improve the maximum power density of the cell to 63 mW/m−2. Phycobiliprotein played an important role in the photosynthesis of spirulina. So in this paper phycobiliprotein was extracted from spirulina to composite with squaraine dye to sensitize nanocrystalline TiO2photoanode for building dye sensitized solar cell, and the photoelectric properties of the cell also were investigated.

Improved Performance of a Thylakoid Bio-Solar Cell by Incorporation of Carbon Quantum Dots

Carbon quantum dots (CQDs) were incorporated into thylakoid bioanodes capable of direct photobioelectrocatalysis in order to increase the photocurrent generation. More thylakoids are in contact with the increased surface area which allows for greater direct electron transfer (DET). Additionally, the fluorescent quantum dots redshift the light which allows for the thylakoid/CQD electrodes to use more of the solar spectrum, increasing the photocurrent. The current density was more than twice as large when CQDs were

Photocurrent activity of light-harvesting complex II isolated from spinach and its pigments in dye-sensitized TiO2 solar cell

Light-harvesting complex II (LHCII) was used as sensitizer in biosolar cell. To improve the cell performance, we studied the adsorbing conditions and compared the photocurrent activity of LHCII and its pigments. The maximum adsorbances were achieved at the concentration over 80μg chl/ml with 96h incubation for LHCII and at the concentration over 120μg chl/ml with 24h incubation for pigments. The initial performance of pigment-sensitized solar cell was superior to that of LHCII-sensitized solar cell. With the increase of adsorbance, both the short-circuit current and efficiency increased for LHCII-sensitized solar cell and pigment-sensitized solar cell. The best short-circuit current, open-circuit voltage, fill factor and efficiency were 2.26mA/cm2, 0.53V, 0.69 and 0.79% for pigment-sensitized solar cells and 0.80mA/cm2, 0.59V, 0.58 and 0.27% for LHCII-sensitized solar cells, respectively. The adsorption models of LHCII and pigments on TiO2 are proposed, and the strategies for further study are briefly discussed.

On the Use of Metabolic Control Analysis in the Optimization of Cyanobacterial Biosolar Cell Factories

Oxygenic photosynthesis will have a key role in a sustainable future. It is therefore significant that this process can be engineered in organisms such as cyanobacteria to construct cell factories that catalyze the (sun)light-driven conversion of CO2 and water into products like ethanol, butanol, or other biofuels or lactic acid, a bioplastic precursor, and oxygen as a byproduct. It is of key importance to optimize such cell factories to maximal efficiency. This holds for their light-harvesting capabilities under, for example, circadian illumination in large-scale photobioreactors. However, this also holds for the "dark" reactions of photosynthesis, that is, the conversion of CO2, NADPH, and ATP into a product. Here, we present an analysis, based on metabolic control theory, to estimate the optimal capacity for product formation with which such cyanobacterial cell factories have to be equipped. Engineered l-lactic acid producing Synechocystis sp. PCC6803 strains are used to identify the relation between production rate and enzymatic capacity. The analysis shows that the engineered cell factories for l-lactic acid are fully limited by the metabolic capacity of the product-forming pathway. We attribute this to the fact that currently available promoter systems in cyanobacteria lack the genetic capacity to a provide sufficient expression in single-gene doses.

High performance thylakoid bio-solar cell using laccase enzymatic biocathodes

Thylakoid membranes have previously been used for electrochemical solar energy conversion, but the current output and open circuit voltage are low, in part due to limitations of the cathode. In this paper, a thylakoid bioanode and laccase biocathode were combined in the construction of a bio-solar cell capable of light-induced generation of electrical power. This two-compartment cell showed a greater than 5-fold increase in short circuit current density and an open circuit voltage 0.275 V larger than that of a thylakoid bio-solar cell incorporating an air-breathing Pt cathode. The electrodes were then tested in several solutions of varying pH to evaluate the possibility of constructing a compartment-less bio-solar cell. This membrane-less cell, operating at pH 5.5, generated a short circuit photocurrent density of 14.0 ± 1.8 μA cm(-2) which is 25% larger than the two-compartment cell and a similar open circuit voltage of 0.720 ± 0.018 V.

Self-powered herbicide biosensor utilizing thylakoid membranes

A self-powered biosensor has been developed for the detection of herbicides in water. It consists of a bio-solar cell incorporating thylakoid membranes at the bioanode for direct photoelectrocatalysis with an air-breathing platinum cathode. The biosolar cell produces power in the presence of light, but inhibition of photosystems of the thylakoids by herbicides leads to a decrease in current output. This current decrease can be used to determine herbicide concentration. This sensor was able to detect several commercial herbicides, including: atrazine, bromacil, and diuron with a linear response up to concentrations of ∼15 μg L−1 and limits of detection (LOD) below 0.5 μg L−1, which are below the EPA limits.

Bio-Solar Cells Incorporating Catalase for Stabilization of Thylakoid Bioelectrodes during Direct Photoelectrocatalysis

Thylakoid membranes have been proposed for electrochemical solar energy conversion, but they have been plagued with short term instability. In this paper, thylakoid membranes extracted from Spinacia oleracea were physically adsorbed onto Toray paper electrodes with and without catalase, followed by entrapment in a vapor deposited silica matrix. The bioelectrodes were tested using voltammetry and amperometry and tested in a complete photobioelectrochemical cell. Upon subsequent polarization experiments, a significant decrease in the maximum current density from 1.53 ± 0.13 μAcm −2 to 0.75 ± 0.14 μAcm −2 was observed without catalase present. When catalase was included in the anode, this current decrease was not observed, showing the importance of catalase to scavenge reactive oxygen species produced by the thylakoids during photoelectrocatalysis.

Immobilization and Photocurrent Activity of a Light-Harvesting Antenna Complex II, LHCII, Isolated from a Plant on Electrodes.

A light-harvesting (LH) antenna complex II, LHCII, isolated from spinach was immobilized onto an indium tin oxide (ITO) electrode with dot patterning of 3-aminopropyltriethoxysilane (APS) by utilizing electrostatic interactions between the cationic surface of the electrode and the anionic surface of stromal side of the LHCII polypeptide. Interestingly, the illumination of LHCII assembled onto the ITO electrode produced a photocurrent response that depends on the wavelength of the excitation light. Further, LHCII was immobilized onto a TiO2 nanostructured film to extend for the development of a dye-sensitized biosolar cell system. The photocurrent measured in the iodide/tri-iodide redox system of an ionic liquid based electrolyte on the TiO2 system showed remarkable enhancement of the conversion efficiency, as compared to that on the ITO electrode.

Arginine interactions with anatase TiO2 (100) surface and the perturbation of 49Ti NMR chemical shifts – a DFT investigation: relevance to Renu-Seeram bio solar cell

Density functional theoretical calculations have been utilized to investigate the interaction of the amino acid arginine with the (100) surface of anatase and the reproduction of experimentally measured 49Ti NMR chemical shifts of anatase. Significant binding of arginine through electrostatic interaction and hydrogen bonds of the arginine guanidinium protons to the TiO2 surface oxygen atoms is observed, allowing attachment of proteins to titania surfaces in the construction of bio-sensitized solar cells. GIAO-B3LYP/6-31G(d) NMR calculation of a three-layer model based on the experimental structure of this TiO2 modification gives an excellent reproduction of the experimental value (-927 ppm) within +/- 7 ppm, however, the change in relative chemical shifts, EFGs and CSA suggest that the effect of the electrostatic arginine binding might be too small for experimental detection.Electronic supplementary materialThe online version of this article (doi:10.1007/s00894-010-0853-y) contains supplementary material, which is available to authorized users.