The bacterial photosynthetic reaction center (RC)1 is a membrane spanning protein that, upon illumination, promotes the reduction of a quinone molecule withdrawing electrons from cytochrome c. This reaction has been often exploited in suitably designed photoelectrochemical cells, to generate photocurrents sustained by the reduction at the working electrode of the photo-oxidized electron donor or by the oxidation of the electron acceptor. A number of PECs employing the bacterial RC as photoactive component have been developed in the last decade 2. Much effort has been devoted to the optimization of protein/electrode electrical communication by suitable protein immobilization strategies 3. Several ways to interface RCs to electrodes have been described including immobilization by Layer-by-Layer and Langmuir-Blodgett techniques, by encapsulation in nanoporous and nanostructured materials, by entrapment in sol-gel media, and by employment of suitable electrode/protein linkers. Despite the huge amount of investigations driven in recent years on bio-photovoltaic devices based on immobilized RCs and relevant models describing their behaviour,4 the scientific literature is relatively poor of reports focused on photocurrent generation by means of photoactive proteins dissolved in the electrolyte solution.5 In this work we have explored in more detail the factors affecting the photocurrent generation in commercially available screen-printed electrochemical cells containing an electrolyte solution where RC proteins are solubilized. In particular, the role of the applied potential and the influence of concentration and structure of acceptor and donor molecules have been assessed. We show that efficient generation of cathodic photocurrents occurs at an applied potential of 0 V versus quasi-ref Ag (the open circuit voltage of the system in the dark) in presence of ferrocenemethanol and decylubiquinone, which proved to guarantee high performances as electron donor and acceptor respectively. Moreover, a set of differential equations, describing reaction and diffusion processes, has been employed for modelling with high accuracy the chronoamperometry profiles recorded at variables RC concentrations. This model allowed to estimate the kinetic parameters relevant to the chemical reactions triggered by light and to get a snapshot of the electrolyte composition in the different cell compartments (bulk and electrode surroundings) at different times from the light exposure. The characteristic time course of the photocurrent, showing a peak value followed by a slow decay, has been therefore explained as the result of the strict interconnection between the dynamical processes involved. This investigation represents a further contribution to the comprehension of factors that regulate light energy conversion in protein-based and bio-inspired photoelectrochemical devices. On the other side, the generated photocurrents represent a good physical observable for the selective detection of herbicides and specific environmental pollutants, able to inhibit the reaction center photoactivity. 1.Feher, G.; Allen, J. P.; Okamura, M. Y.; Rees, D. C., Structure and function of bacterial photosynthetic reaction centres. Nature 1989, 339, 111-116. 2.Ravi, S. K.; Tan, S. C., Progress and perspectives in exploiting photosynthetic biomolecules for solar energy harnessing. Energy Environ. Sci. 2015, 8 (9), 2551-2573. 3.Yehezkeli, O.; Tel-Vered, R.; Michaeli, D.; Willner, I.; Nechushtai, R., Photosynthetic reaction center-functionalized electrodes for photo-bioelectrochemical cells. Photosynth. Res. 2013. 4.Caterino, R.; Csiki, R.; Lyuleeva, A.; Pfisterer, J.; Wiesinger, M.; Janssens, S. D.; Haenen, K.; Cattani-Scholz, A.; Stutzmann, M.; Garrido, J. A., Photocurrent generation in diamond electrodes modified with reaction centers. ACS Appl Mater Interfaces 2015, 7 (15), 8099-107. 5.Takshi, A.; Madden, J. D. W.; Mahmoudzadeh, A.; Saer, R.; Beatty, J. T., A Photovoltaic Device Using an Electrolyte Containing Photosynthetic Reaction Centers. Energies 2010, 3 (11), 1721-1727.
Photo-electrochemical cell based on detergent-solubilized photosynthetic reaction centers.
F Milano;M Trotta;A Agostiano;
2018
Abstract
The bacterial photosynthetic reaction center (RC)1 is a membrane spanning protein that, upon illumination, promotes the reduction of a quinone molecule withdrawing electrons from cytochrome c. This reaction has been often exploited in suitably designed photoelectrochemical cells, to generate photocurrents sustained by the reduction at the working electrode of the photo-oxidized electron donor or by the oxidation of the electron acceptor. A number of PECs employing the bacterial RC as photoactive component have been developed in the last decade 2. Much effort has been devoted to the optimization of protein/electrode electrical communication by suitable protein immobilization strategies 3. Several ways to interface RCs to electrodes have been described including immobilization by Layer-by-Layer and Langmuir-Blodgett techniques, by encapsulation in nanoporous and nanostructured materials, by entrapment in sol-gel media, and by employment of suitable electrode/protein linkers. Despite the huge amount of investigations driven in recent years on bio-photovoltaic devices based on immobilized RCs and relevant models describing their behaviour,4 the scientific literature is relatively poor of reports focused on photocurrent generation by means of photoactive proteins dissolved in the electrolyte solution.5 In this work we have explored in more detail the factors affecting the photocurrent generation in commercially available screen-printed electrochemical cells containing an electrolyte solution where RC proteins are solubilized. In particular, the role of the applied potential and the influence of concentration and structure of acceptor and donor molecules have been assessed. We show that efficient generation of cathodic photocurrents occurs at an applied potential of 0 V versus quasi-ref Ag (the open circuit voltage of the system in the dark) in presence of ferrocenemethanol and decylubiquinone, which proved to guarantee high performances as electron donor and acceptor respectively. Moreover, a set of differential equations, describing reaction and diffusion processes, has been employed for modelling with high accuracy the chronoamperometry profiles recorded at variables RC concentrations. This model allowed to estimate the kinetic parameters relevant to the chemical reactions triggered by light and to get a snapshot of the electrolyte composition in the different cell compartments (bulk and electrode surroundings) at different times from the light exposure. The characteristic time course of the photocurrent, showing a peak value followed by a slow decay, has been therefore explained as the result of the strict interconnection between the dynamical processes involved. This investigation represents a further contribution to the comprehension of factors that regulate light energy conversion in protein-based and bio-inspired photoelectrochemical devices. On the other side, the generated photocurrents represent a good physical observable for the selective detection of herbicides and specific environmental pollutants, able to inhibit the reaction center photoactivity. 1.Feher, G.; Allen, J. P.; Okamura, M. Y.; Rees, D. C., Structure and function of bacterial photosynthetic reaction centres. Nature 1989, 339, 111-116. 2.Ravi, S. K.; Tan, S. C., Progress and perspectives in exploiting photosynthetic biomolecules for solar energy harnessing. Energy Environ. Sci. 2015, 8 (9), 2551-2573. 3.Yehezkeli, O.; Tel-Vered, R.; Michaeli, D.; Willner, I.; Nechushtai, R., Photosynthetic reaction center-functionalized electrodes for photo-bioelectrochemical cells. Photosynth. Res. 2013. 4.Caterino, R.; Csiki, R.; Lyuleeva, A.; Pfisterer, J.; Wiesinger, M.; Janssens, S. D.; Haenen, K.; Cattani-Scholz, A.; Stutzmann, M.; Garrido, J. A., Photocurrent generation in diamond electrodes modified with reaction centers. ACS Appl Mater Interfaces 2015, 7 (15), 8099-107. 5.Takshi, A.; Madden, J. D. W.; Mahmoudzadeh, A.; Saer, R.; Beatty, J. T., A Photovoltaic Device Using an Electrolyte Containing Photosynthetic Reaction Centers. Energies 2010, 3 (11), 1721-1727.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
