Review report for Bioregenerative. A sustainable source of energy. Afshin Khan School of Environment Washington State University

Transcription

1 Review report for Bioregenerative Solar cells: A sustainable source of energy Afshin Khan School of Environment Washington State University

2 Table of Contents 1. Abstract 2. Reviewed Models 3. Conclusion 4. References

3 1. Abstract Building bio-regenerative solar panels for harnessing energy for deep space research instrumentation is one of the goals being pursued by space research agencies worldwide. Photosynthesis is being employed as the major path towards photochemical energy conversion and different architectural designs are being explored as a guide towards future energy conversion devices. This is a new approach towards building photovoltaic cells by utilizing nature s methods to harness Sun s energy. These models will incorporate protein biotechnology to accomplish instruments that are engineered to be efficient in their functionality and have a longer lifetime than the existing models. Recently, analytical methods used by Neil Johnson et al in the University of Miami elucidated the role of purple bacteria in making green solar cells (Caycedo-Soler, et al. 2010). This report is divided into two parts to review available models with the potential of building sustainable solar cells. The first part of the review provides an insight into a synthetic photochemical complex consisting of the light harvesting protein of purple bacteria, lipids and carbon nanotubes as demonstrated by Ham et al. In this system the photoconversion efficiency was observed to go up to 300% and an extended lifetime of the system indefinitely (Ham, et al. 2010). The second part of the review is about chlorophyll-d producing cyanobacteria Acaryochloris marina that show the ability to thrive in extreme shade or less availability of light and also adapt to strong light, as demonstrated by Kuhl et al in It was found that the energy storage efficiency of the photosynthetic light reactions in A. marina

4 is comparable to or higher than that of typical Chl a-utilizing oxygenic phototrophs. (Behrendt, et al. 2012).

5 2. Reviewed Models 2.1 Autonomously Regenerating Photoelectrochemical Complex for Solar Energy Conversion Photosynthetic systems use elaborate pathways of self-repair to limit photo-damage. Selfrepair systems in photosynthetic bacteria use molecular recognition and metastable thermodynamic states to make protein complexes that can be repaired repeatedly by partial disassembly and reassembly with new components initiated by chemical signals. In 2012, Moon-Ho Ham et al. demonstrated a complex consisting of two recombinant proteins, phospholipids and carbon nanotubes that were used to develop the first synthetic photoelectrochemical complex capable of mimicking the self-repair cycle. This technique could prove valuable insights in building sustainable bio-regenerative solar cells. To develop the complex, the use of phospholipid-based light harvesting nanostructures were explored and successfully achieved with the discs assembling onto a single walled carbon nanotube, which creates a platform for attaching proteins. Previous work has demonstrated that the dialysis of phospholipids such as 1,2-dimyris- toyl-sn-glycero-3- phosphocholine in the presence of an amphipathic apolipoprotein (membrane scaffold protein) creates a lipid bilayer nanodisc. The protein of interest for photoelectrochemical conversion is the photosynthetic reaction center isolated from the purple bacteria, Rhodobacter sphaeroides. Upon photoabsorption, the complex acts as a photoconverter, shuttling the formed excitation to the other side of the reaction center through an electron transfer reaction. It was found that incorporating the reaction center into the nanodisc locates the hole injection site such that it s directly facing the carbon nanotube, like a molecular hole conducting wire. A

6 parallel arrangement of the nanodiscs along the nanotube surface was observed. This allows for maximum scattering of photons of light. Figure 1: Schematic of self-assembled photoelectrochemical complexes. System can disassemble upon the addition of a surfactant and reassemble upon its removal over an indefinite number of cycles. In the assembled state, complexes exhibit photoelectrochemical activity. The system described above can disassemble upon the addition of a surfactant and reassemble upon its removal over an indefinite number of cycles. The assembly is thermodynamically metastable and can only transition reversibly if the rate of surfactant removal exceeds a threshold value. Only in the assembled state do the complexes exhibit photoelectrochemical activity.

7 Figure 2: Optical signatures of the assembled complex. a, Photoluminescence excitation contour of carbon nanotubes before (top) and after (bottom) dialysis. b, fluorescence wavelength shifts upon nanodisc formation on SWNTs, identified from photoluminescence excitation spectra. c, photoluminescence maxima in a spectral window of 985 1,015 nm as a function of time during serial self-assembly and decomposition. d, nitial structure of DMPC (based on simulation), with the axis oriented at 258 relative to the graphene lattice vector (upper panel). The lower panel shows that the energy-minimized structure based on simulation has both DMPC tails aligned to the carbon atoms of the graphene lattice. Through this work the first synthetic photoelectrochemical complex capable of chemically triggered disassembly and oriented reassembly based on intermolecular forces and thermodynamic equilibrium was achieved. The reversal assembly and disassembly process enables synthesis of a photoelectrochemical cell that can autonomously regenerate. Future investigations to mimic the dynamics of photosynthetic systems will help in building more robust and fault tolerant solar energy conversion systems.

8 Figure 3: Photoelectrochemical activity of a RC ND SWNT complex that autonomously regenerates. a, Schematic of the photoelectrochemical system, which comprises a photoelectrochemical cell incorporating two recirculating membrane dialyzers. b. Temporal photoresponse of the RC ND SWNT with and without regeneration. Without regeneration (black curve), the photocurrent decreases sharply, falling to 50% after 5 h and 10% after 80 h. Deactivation is comparable to dye-sensitized solar cell (DSSC) data published in the literature (green curve)

9 2.2 Unique photosystem of Acaryochloris marina Michael Kuhl et al. describe the role of chlorophyll d in cyanobacteria, Acaryochloris marina that is a unique phototroph and photosynthesizes in far red light. Further work done by Lars Behrendt et al. and published in 2012, shows a detailed biochemical and biophysical characterization of A. marina. In their paper, they describe the A. marina type strain MBIC11017 inoculated in alginate beads to form dense biofilm like cluster as in their natural environment, characterized by strong oxygen concentration gradients that change with irradiance. Biofilm growth under visible radiation and near infrared radiation yielded maximal cell specific growth rate and the photosynthetic efficiency values. Figure 4: Scanning electron micrographs of cross sections through alginate beads with immobilized A. marina cells (A, C, and E) and naturally occurring biofilms from the underside of

10 the didemnid ascidian Lissoclinum patella (B, D, and F). (A, C) Typical cell clusters of A. marina growing within the alginate matrix; note the laminar layers of alginate enclosing the cell clusters. (E) Growth of unidentified bacteria in alginate beads kept under visible light. (B, D, F) naturally occurring biofilms found on the underside of the didemnid ascidian L. patella; note the round A. marina-like cells (1 to 2 m in size) that closely resemble A. marina cells growing in alginate (see A, C, and E). Figure 5: Photosynthesis of A. marina in alginate beads. (A) Gross photosynthesis was measured with an O2 microsensor placed at a depth of 2 to 500 m using the light-dark shift method. NIR was administered in increasing intensities by altering the distance of three collimated LEDs to the beads, while blue light was provided through an optical fiber placed directly at the bead surface. (B) Relative electron transport rates (retr) measured on the bead surface using a fiber-optic PAM fluorometer. retr was measured after a steady-state condition for O2 production under

11 either NIR or blue light was observed. Three independent biological replicates were used to generate the data displayed in panels A and B. Figure 6: Models for pigment arrangement in photosystems of (A, B) A. marina and (C) typical cyanobacteria Some of the other properties of A. marina have been characterized and its been determined that photosynthesizing pigment of these cyanobacteria belong to CP43 family of proteins have a similar photosystem, like that of purple bacteria (Ohashi 2008). In it s unique photosystem, chlorophyll-d dominates 99% of cellular chlorophyll and the energy storage efficiency of the photosynthetic light reactions in A. marina is comparable to or higher than that of typical Chl a-utilizing oxygenic phototrophs. Also higher photosynthetic efficiencies under low-light conditions have been observed (Fig 5).

12 3. Conclusion With the review of the above photosynthetic models it can be hypothesized that for the synthetic regenerative photosynthetic complex, the photoelectrochemical conversion protein can be derived from the chlorophyll-d producing cyanobacteria Acaryochloris marina that show the ability to thrive in extreme shade or less availability of light and also adapt to strong light, are well adapted to oxygen conditions ranging from anoxia to hyperoxia. This is would certainly prolong the longevity of the solar cells and makes them functional in infrared light. The solar cells would be ideal for deeper space missions, for example, orbiters to satellites of the far Solar System, Uranus and Neptune. Also they would be useful for terrestrial areas with scarcity of sunlight, as a cleaner source of harnessing energy.

13 Works Cited 1. Behrendt, Lars, Verena Schrameyer, Klaus Qvortrup, and et al. "Biofilm growth and near infrared radiation driven photosynthesis of the chlorophyll-d containing Cyanobacterium Acaryochloris marina." Applied and Environmental Microbiology 78 (2012): Caycedo-Soler, Felipe, Ferney J. Rodriguez, Luis Quiroga, and Neil F. Johnson. "Light-harvesting mechanism of Bacteria exploits a critical interplay between the dynamics of transport and trapping." Physical Review Letters 104 (2010): Ham, Moon-Ho, Jong Hyun Choi, Ardemis A. Boghossian, and et al. "Photoelectrochemical complexes for solar energy conversion that chemically and autonomously regenerate." Nature Chemistry 2 (2010): Kuhl, Michael, Min Chen, Peter J Ralph, Ulrich Schreiber, and Anthony W.D. Larkum. "A niche for cyanobacteria containing chlorophyll d." Nature 433 (2005): Sension, Roseanne J. "Quantum path to Photosynthesis." Nature 446 (April 2007): Swingley, Wesley D., Min Chen, and et al. "Niche adaptation and genome expansion in the chlorophyll d-producing cyanobacterium Acaryochloris marina." PNAS 105 (2008): Ohashi, S. et al "Unique photosystems in Acaryochloris marina." Photosynth Res 98 (2008): Aro, E. M., Virgin, I. & Andersson, B. Photoinhibition of photosystem II. Inactivation, protein damage and turnover. Biochim. Biophys. Acta Bioenerg (1993), Melis, A. Dynamics of photosynthetic membrane composition and function. Biochem. Biophys. Acta Bioenerg. 1058(1991), Richard, C., Balavoine, F., Schultz, P., Ebbesen, T. W. & Mioskowski, C. Supramolecular self-assembly of lipid derivatives on carbon nanotubes. Science 300(2003),

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