Photocurrent generation based on a light-driven proton pump in an artificial liquid membrane

Journal name:
Nature Chemistry
Volume:
6,
Pages:
202–207
Year published:
DOI:
doi:10.1038/nchem.1858
Received
Accepted
Published online

Abstract

Biological light-driven proton pumps use light to move protons across a cell membrane, creating a proton gradient. Although photochromic compounds such as spiropyrans can reversibly convert between two structures with differing pKa values, spiropyrans have not been used to generate either a light-driven proton pump or an electrical current. Here, we report an artificial light-harvesting system based on a supported liquid membrane doped with a spiropyran. Irradiating the membrane with ultraviolet light induces a ring-opening reaction, converting spiropyran to merocyanine, whereas irradiation with visible light induces the reverse reaction. When the membrane is irradiated with ultraviolet and visible light on opposite sides, H+ is taken up by merocyanine, carried through the polymeric membrane and released on the other side. We show that this system produces a light-induced proton flux, an electrical current with an efficiency of ∼0.12%, an open-circuit voltage of ∼210 mV and a membrane gradient of ∼3.6 ΔpH units. Alternating the sides illuminated with ultraviolet and visible light generates an alternating current.

At a glance

Figures

  1. Scheme demonstrating the photocurrent generation principle.
    Figure 1: Scheme demonstrating the photocurrent generation principle.

    The left side of the membrane is illuminated with ultraviolet light and the right with visible light or kept in the dark. The membrane contains 5 mg Sp, 6.5 mg ETH 500 and 3 mg K+R in 50 mg NPOE as solvent. The aqueous solutions both contain 0.1 M HCl. For simplicity, ETH 500 and Cl are not shown. Dashed arrows represent mass transport of the species.

  2. Light-induced voltage and current due to a light-driven proton gradient within the spiropyran-doped polypropylene membrane.
    Figure 2: Light-induced voltage and current due to a light-driven proton gradient within the spiropyran-doped polypropylene membrane.

    a, Representation of the flow cell used to measure the photocurrent generated by the light-harvesting membrane. b, Photocurrents generated when the membrane is placed in 0.1 M HCl and illuminated with ultraviolet light on one side. c, Photocurrent generated with illumination by visible light (482 ± 35 nm) on one side of the membrane. d, Observed open-circuit voltage when the membrane is illuminated with ultraviolet on one side and subsequently with visible on the other.

  3. Experimental and theoretical photocurrent evolution characteristics.
    Figure 3: Experimental and theoretical photocurrent evolution characteristics.

    a, Photocurrent evolution from numerical simulation showing the difference between ultraviolet irradiation on one side only (ring-opening rate constant k1 = 10−1.1 s−1, ring-closing rate constant k2 = 1 s−1) and asymmetric illumination with ultraviolet and visible (k1 = 10−1.1 s−1, k2 = 10−6 s−1). b, Experimental photocurrent generated when the membrane is illuminated with the light sequence indicated in the figure.

  4. Evaluation of conversion efficiency for the light-harvesting system.
    Figure 4: Evaluation of conversion efficiency for the light-harvesting system.

    a, Current density characteristics for the light-harvesting cell under light illumination (10 mW cm−2) and in the dark. b, Corresponding power density–voltage relationship under light irradiation.

  5. Changing the direction of the proton gradient in the membrane.
    Figure 5: Changing the direction of the proton gradient in the membrane.

    The direction reverses when illuminated with ultraviolet or visible light, so an alternating current can be generated using light sequences composed of ultraviolet and visible light. The figure shows alternating photocurrent generation by the membrane in 0.1 M HCl with alternating ultraviolet and visible light (ultraviolet for 2 s + off for 4 s + visible for 1 s + off for 4 s) illuminating one side of the membrane.

  6. The presence of an interfering ion can cause transport of the interfering ion in a direction opposite to the proton flux.
    Figure 6: The presence of an interfering ion can cause transport of the interfering ion in a direction opposite to the proton flux.

    Such a counter flux will reduce the net photocurrent density. a, Scheme demonstrating light-induced counter-diffusion in a direction opposite to the proton flux, which competes with the proton pumping, thereby reducing the current. b, Observed photocurrent density from the membrane under ∼0.2 mW cm−2 illumination as a function of pH in the two identical buffer solutions (2.5 mM boric acid + 2.5 mM citric acid + 2.5 mM NaH2PO4), with the Na+ background fixed at 2 M. The counter-diffusion process becomes more important at high pH and results in a lower current density.

References

  1. Alberts, B. et al. in Molecular Biology of the Cell (eds Anderson, M. & Granum, S.) Chs 11,14 (Garland Science, Taylor & Francis, 2007).
  2. Garg, V. et al. Conformationally constrained macrocyclic diporphyrin–fullerene artificial photosynthetic reaction center. J. Am. Chem. Soc. 133, 29442954 (2011).
  3. Moore, G. F. et al. A bioinspired construct that mimics the proton coupled electron transfer between P680•+ and the TyrZ–His190 pair of photosystem II. J. Am. Chem. Soc. 130, 1046610467 (2008).
  4. Rutherford, A. W. & Moore, T. A. Mimicking photosynthesis, but just the best bits. Nature 453, 449 (2008).
  5. Moore, G. F. & Brudvig, G. W. Energy conversion in photosynthesis: a paradigm for solar fuel production. Annu. Rev. Condens. Matter Phys. 2, 303327 (2011).
  6. Steinberg-Yfrach, G. et al. Conversion of light energy to proton potential in liposomes by artificial photosynthetic reaction centres. Nature 385, 239241 (1997).
  7. Bennett, I. M. et al. Active transport of Ca2+ by an artificial photosynthetic membrane. Nature 420, 398401 (2002).
  8. Tan, S. C., Crouch, L. I., Mahajan, S., Jones, M. R. & Welland, M. E. Increasing the open-circuit voltage of photoprotein-based photoelectrochemical cells by manipulation of the vacuum potential of the electrolytes. ACS Nano 6, 91039109 (2012).
  9. LeBlanc, G., Chen, G., Gizzie, E. A., Jennings, G. K. & Cliffel, D. E. Enhanced photocurrents of photosystem I films on p-doped silicon. Adv. Mater. 24, 59595962 (2012).
  10. Tan, S. C., Crouch, L. I., Jones, M. R. & Welland, M. Generation of alternating current in response to discontinuous illumination by photoelectrochemical cells based on photosynthetic proteins. Angew. Chem. Int. Ed. 51, 66676671 (2012).
  11. Valentin, M. D. et al. Photoinduced long-lived charge separation in a tetrathiafulvalene–porphyrin–fullerene triad detected by time-resolved electron paramagnetic resonance. J. Phys. Chem. B 109, 1440114409 (2005).
  12. Berkovic, G., Krongauz, V. & Weiss, V. Spiropyrans and spirooxazines for memories and switches. Chem. Rev. 100, 17411745 (2000).
  13. Kalisky, Y., Orlowski, T. E. & Williams, D. J. Dynamics of the spiropyran–merocyanine conversion in solution. J. Phys. Chem. 87, 53335338 (1983).
  14. Mistlberger, G., Crespo, G. A., Xie, X. & Bakker, E. Photodynamic ion sensor systems with spiropyran: photoactivated acidity changes in plasticized poly(vinyl chloride). Chem. Commun. 48, 56625664 (2012).
  15. Xie, X., Mistlberger, G. & Bakker, E. Reversible photodynamic chloride-selective sensor based on photochromic spiropyran. J. Am. Chem. Soc. 134, 1692916932 (2012).
  16. Mistlberger, G., Xie, X., Pawlak, M., Crespo, G. A. & Bakker, E. Photoresponsive ion extraction/release systems: dynamic ion optodes for calcium and sodium based on photochromic spiropyran. Anal. Chem. 85, 29832990 (2013).
  17. Toei, M., Saum, R. & Forgac, M. Regulation and isoform function of the V-ATPases. Biochemistry 49, 47154723 (2010).
  18. Turina, P., Samoray, D. & Graber, P. H+/ATP ratio of proton transport-coupled ATP synthesis and hydrolysis catalysed by CF0F1-liposomes. EMBO J. 22, 418426 (2003).
  19. Weinberg, D. R. et al. Proton-coupled electron transfer. Chem. Rev. 112, 40164093 (2012).
  20. Morgan, J. E., Vakkasoglu, A. S., Lugtenburg, J., Gennis, R. B. & Maeda, A. Structural changes due to the deprotonation of the proton release group in the M-photointermediate of bacteriorhodopsin as revealed by time-resolved FTIR spectroscopy. Biochemistry 47, 1159811605 (2008).
  21. Dencher, N. A. The five retinal-protein pigments of Halobacteria: bacteriorhodopsin, halorhodopsin, P 565, P 370, and slow-cycling rhodopsin. Photochem. Photobiol. 38, 753768 (1983).
  22. Oesterhelt, D. Bacteriorhodopsin als Beispiel einer lichtgetriebenen Protonenpumpe. Angew. Chem. 88, 1624 (1976).
  23. Trisll, H-W. & Montal, M. Electrical demonstration of rapid light-induced conformational changes in bacteriorhodopsin. Nature 266, 655657 (1977).
  24. Gregg, B. A. & Hanna, M. C. Comparing organic to inorganic photovoltaic cells: theory, experiment, and simulation. J. Appl. Phys. 93, 36053614 (2003).
  25. He, F. & Yu, L. How far can polymer solar cells go? In need of a synergistic approach. J. Phys. Chem. Lett. 2, 31023113 (2011).
  26. Nazeeruddin, M. K., Baranoff, E. & Grätzel, M. Dye-sensitized solar cells: a brief overview. Solar Energy 85, 11721178 (2011).
  27. Levitus, M., Talhavini, M., Negri, R. M., Atvars, T. D. Z. & Aramendia, P. F. Novel kinetic model in amorphous polymers. Spiropyran–merocyanine system revisited. J. Phys. Chem. B 101, 76807686 (1997).
  28. Giordani, S., Cejas, M. A. & Raymo, F. M. Photoinduced proton exchange between molecular switches. Tetrahedron 60, 1097310981 (2004).
  29. McCoy, C. P., Donnelly, L., Jones, D. S. & Gorman, S. P. Synthesis and characterisation of polymerisable photochromic spiropyrans: towards photomechanical biomaterials. Tetrahedron Lett. 48, 657661 (2007).

Download references

Author information

Affiliations

  1. Department of Inorganic and Analytical Chemistry, University of Geneva, Quai E. Ansermet 30, CH-1211 Geneva, Switzerland

    • Xiaojiang Xie,
    • Gastón A. Crespo,
    • Günter Mistlberger &
    • Eric Bakker

Contributions

X.X. and E.B. designed the research and wrote the manuscript. X.X. and G.A.C. performed the experiments. G.M. helped with designing the experiment.

Competing financial interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to:

Author details

Supplementary information

PDF files

  1. Supplementary information (1,188 KB)

    Supplementary information

Additional data