المجلد السابع والعشرون-2007-المجلة القطرية للكيمياء National Journal of Chemistry,2007, Volume 27 ,474-482 Generation of Photocurrent using Rhodamine B Dye and visible Light Hassan A. Habeb Saja S. Jabbar Al-Taweel Nabeel A. Abed –Al-rudha College of Education? College of Scienc College of Education University o f Al- Qadisiya (NJC) (Receivedon 29/5/2007) (Accepted for publication on 22/8 /2007) Abstract The photo galvanic effect was studied in a system of photogalvanic cell, containing rhodamine B as photosensitizer, EDTA as reductant, and sodium lauryl sulphate as surfactant. The electrical outputs of this cell were 210 mV and 70μA respectively. The storage capacity of the cell was 20 min in dark after 55 min of illumination. The effect of different parameters on electrical output of this system were studied such as; pH, temperature, light intensity, concentration of dye, concentration of EDTA, and concentration of NaLS. Also, a mechanism of generation of photocurrent in this cell has been proposed. الخالصة ليم م م م م ممة ليا يم م م م م ممة و م م م م م ممب ة EDTA ال ليم م ممام م م م م م مماث ي تم م م م م ممو اام ممةن رك مما مماي رو ممبةمر لم70ولت و مممممم ال م م م م م ممو وا يةل ممةن ي مما ممو تم م م م م ممث د ارسم م م م م ممة التم م م م م ممليةر الكليم م م م م مما مت س ممو Rhodamine.B(RB)الم مرودامةن . مر ب عال سط ياNaLS عامل م تزل و بريتات لوريل ال ودةوث مل210 لهذه ال لية ا ا تمت د ارسمة بعم. دقيقمة55 ال ممث بعمد شم ن ال ليمة لممد باسممت داث هممذه ال ليممة وشممملت تممليةر الدالممة ال ام ممية ودرجممة والتيار ال و وجد إن الجهد ال و دقيقة20 إن سعة ال زن لهذه ال لية ه. التوال يمماء تولةممد التيممار ال ممو العوامممل الم م ير ل م تث و ممع يليممة ا ت ار ممية. لم الت موالNaLS وEDTA ال مرار وشممد ال مموء السمماقك تر ةممز ممل مممن ال ممب ة و .هذه ال لية 474 لعملية تولةد التيار ال و المجلد السابع والعشرون-2007-المجلة القطرية للكيمياء National Journal of Chemistry,2007, Volume 27 ,474-482 The photogalvanic effect of photoredox Introduction The generation of electrical energy by couples have also investigated by many conversion and storage of solar radiation workers all over the world, for instance has a good attention from chemist and Potter and Thaller , Kaneko and Yamada 11) , Aliwi et al energy is one from many renewable of energy especially , Ikawa and Yamase (6) physician scientists. The utility of solar sources (4) (12) (7) , Ameta et al (8- Gangotri et al (13-14) Meena et al.(15) ,and Genwa and Chouhan in (16) photogalvanic cells, so the photogalvanic . In all works, the conversion efficiency cells are worthwhile source of energy and of these cells are quite low (0.03-0.1%) (11) have future applications and uses. The which due to the fast back electron transfer photogalvanic the and other deactivated physical processes excitation of a molecule by photon and a beside the special phenomenon of dyes chemical reaction occurs to yielding new such as lower stability of absorbers and chemicals (high-energy products) which aggregates of dye molecule around the save the chemical energy. electrodes. Recently, an attention has been effect involves paid The photogalvanic effect was first reported by Rideal and Williams (1) to use photosensitizers but of systems (dyes & containing complexes), first reductants (EDTA, ascorbic acid, etc) and photogalvanic cell in 1940 at USA by micelles (surfactants) for improved the using thionine –Fe+2 system which serve as solar energy conversion and storage (17-19). (2,3) Rabinowitch made the and The present work aims to study the conversion the energy to Fe+2 ions and the rhodamine B-EDTA-NaLS system in a results of this cell were 1.09 V and 1.73 photogalvanic cell for conversion and μA mW/cm2). storage of solar energy. The effect of dye first observed in 1839 the concentration, pH, temperature, incident generation and flow of current between light intensity, EDTA concentration, and unsymmetrical NaLS concentration have been studied. absorber of under Becquerel incident sun (4,5) light photons (70 illuminated metal electrodes in sun light kept in amber-coloured containers for Methodology Rhodamine B dye (RB) (Figure protect it from sun light (16) . A mixture of (1)), EDTA, sodium hydroxide supplied by dye solution and other additives were taken Aldrich. Sodium lauryl sulphate (NaLS) in an H-shaped glass tube of capacity 50 and citrate buffer were supplied by Fluka cm3 (11). Two platinum electrodes (1x1cm) AG. All the chemicals were used without were further purification and all the solutions electrodes. The wholly cell was placed in were prepared in doubly distilled water and a 475 used as thermostat illuminated water path and dark (HAAKE المجلد السابع والعشرون-2007-المجلة القطرية للكيمياء National Journal of Chemistry,2007, Volume 27 ,474-482 (20) circulator) .The whole system was first described by Haatchard . Cintra-5 GBC placed in dark till a stable potential was Scientific equipment spectrophotometer obtained, then the one arm of the cell was was used to recording the UV-visible exposed to a 200W tungsten lamp and the spectra of dye in wavelength range The between 300 –800 nm by using 1 cm path photopotentials were measured by a digital length quartz cell. In all experiments the multimeter were cell was irradiated with tungsten lamp for measured by digital pH meter (PW 9420 55 minutes by variation of pH, light pH intensity, other one was kept in dark meter). and (15) . photocurrents The two half-cell were concentration of dye, separated by a sintered glass disc. The concentration of EDTA, concentration of electrodes were pretreated by immersed NaLS, and temperature. them in dilute hydrochloric acid solution for 1 h (12) .The incident light intensity was measured actinometrically by the method COOH ClN O N Figure (1): The chemical structure of Rhodamine B The electrical output of Results and Discussion The spectrum of rhodamine B dye photogalvanic cells is affected by several locates in the visible range with λmax factors involves effect of pH, temperature, 545nm and and high coefficient ε (1.9x10 molar 4 absorption -1 -1 l.mol cm ). The light intensity, concentration of reductant, concentration of surfactant, and rhodamine B dye shows a good stability on concentration irradiation with tungsten lamp as shown in efficiency of present cell was examined by Figure (2). From these data, the use of this following the variation of photopotential dye as photosensitizer in performance of and photocurrent with time. Figure (3) photogalvanic cell is worthwhile. illustrate the variation of electrical output of photosensitizer. with irradiation time. 476 The المجلد السابع والعشرون-2007-المجلة القطرية للكيمياء National Journal of Chemistry,2007, Volume 27 ,474-482 It is seen that electrical output of From the obtained results Figure (7), it present photogalvanic cell is found to seen that a linear relation increase as the pH increases. It is observed electrical output and temperature. But the from Figure (4) that the photopotential and photocurrent photocurrent reach the maximum value at photopotential decreases. This attributed to pH=10, and then decreases on further decreased in internal resistance of the cell increase in pH. It is clear that this at higher temperature (16). increases between and the photogalvanic cell is sensitive to the pH The dependence of electrical output variation. Generally the pH of optimum on variation of dye concentration has been condition for reductant has a relation with studied. It is seen from Figure (8) that its pKa and the best pH is higher than pKa lower concentrations of rhodamine B dye (15, 16) causes a decreases of photopotential and . The electrical output of present photocurrent due to lowering of dye photogalvanic cell also affected by the molecule in the excited stat and donate the change of concentration of reductant electrons to electrode, and the greater EDTA. Figure (5) shows that at lower concentration concentration of EDTA causes decreasing decreasing in electrical output because the in photopotential and photocurrent as a high number of dye molecule are form an result of decreasing of available reducing inner filter and does not permit the photons agent molecule for donating the electrons to reaching the other dye molecules near for oxidized dye molecules. While, in the electrode. (15,16,21) higher concentration also a decreasing in of dye also causes a Different intensities of light were electrical out pout occur which attribute to used to deduce hindering the dye molecules from reaching photogalvanic cell. It is observed from the electrode surface by high number of Figure EDTA molecules (15). photocurrent on increase of light intensity, (9) the this linear on output increasing of of Figure (6) illustrates that electrical while the increasing of photopotential is output of this cell increases when the not linearly one. Generally the increasing concentration is of light intensity causes an increasing in increasing until reaching the optimum number of photons that collide with concentration, but on further increasing the photosensitizer photopotential electrode and hence causes an increasing in of surfactant and NaLS photocurrent are decreasing. The temperature electrical effect on of variation of photopotential, photocurrent and power has been studied. 477 molecule output besides values (16, the 21) . المجلد السابع والعشرون-2007-المجلة القطرية للكيمياء National Journal of Chemistry,2007, Volume 27 ,474-482 Figure (2): Electroinc spectra of rhodamine B (1 x 10-4 M) 250 photocurrent photopotential 200 150 100 mV 50 µA 0 0 25 50 75 100 Time(min) Figure (3): Effect of variation of irradiation time [RB] = 0.00005M, [NaLS] = 0.006 M, [EDTA] = 0.0075M, pH=9, light intensity =10.5µW/cm2, Temp=298K. 478 المجلد السابع والعشرون-2007-المجلة القطرية للكيمياء National Journal of Chemistry,2007, Volume 27 ,474-482 photocurrent photopotential 225 mV 150 75 µA 0 10-3M 0 5 10 15 pH Figure (4): Effect of variation of pH. [RB]=.00005M, [EDTA] =0.0075M, [NaLS] =0.006M, Light intensity=10.5µW/cm2, Temp=298K. photocurrent photopotential 250 200 150 100 mV 50 µA 0 0 1 2 3 4 [EDTA] x 0.001M Figure (5): Effect of variation of EDTA. Concentration. [RB]=0.00005M, [NaLS] =0.006 M, pH=9, Light intensity=10.5µW/cm2, Temp=298K. 479 المجلد السابع والعشرون-2007-المجلة القطرية للكيمياء National Journal of Chemistry,2007, Volume 27 ,474-482 photocurrent photopotential 250 mV 200 150 µA 100 50 0 0 5 10 103M [NaLS] x 0.001M 10-4M Figure (6): Effect of variation of NaLS concentration. [RB]=0.00005M, [EDTA] =0.00275 M, Light intensity=10.5µW/cm2, pH=9, Temp=298k. photocurrent photopotential 250 200 mV 150 100 µA 50 0 290 300 310 320 Temperature (K) Figure (7): Effect of variation of temperature. [RB]=0.00005M, [NaLS] =0.006M, [EDTA] =0.0075M, pH=9, light intensity=10.5µW/cm2. 480 المجلد السابع والعشرون-2007-المجلة القطرية للكيمياء National Journal of Chemistry,2007, 27 ,474-482 Volume photocurrent photopotential 250 200 mV 150 100 µA 50 0 0 0.2 0.4 0.6 0.8 [RB] x 0.0001M Figure (8): Effect of variation of dye concentration. [NaLS]= 0.006 M, [EDTA] = 0.00275M, pH= 9, light intensity= 10.5µW/cm2, Temp= 298K. photocurrent photopotential 400 mV 300 200 µA 100 0 0 10 20 30 light intensity(µW/cm ) Figure (9): Effect of variation of light intensity. [RB]= 0.00005M, [NaLS] = 0.006M, [EDTA] = 0.00275M, pH =9, Temp=298k. 481 National Journal of Chemistry,2007, 27 ,474-482 المجلد السابع والعشرون-2007-المجلة القطرية للكيمياء Volume Energy References 1- E.K.Riedel, and D.C. Williams, J. 12- 2- E.Rabinowitch, J.Chem.Phys.1940, and Solar Cells,1986,18,85. 3- E.Rabinowitch, J.Chem.Phys.1940, 13- K. M. Gangorti and R. C. Meena, 8,560. J.Photochem.Photobiol.,2001, A141 K.Becquerel,C.R.Acad.Sci.(Paris) ,175. 1839,9,14.(Cited by reference No. 14- K. M. Gangorti and O. P. Regar, 15). J.Indian.Chem.Soc.,2000,77,347. K.Becquerel,C.R.Acad.Sci.(Paris) 1839,9,561.(Cited by 15- R.C.Meena, S. Gautam, N. Tyagi reference and No. 15). Kumari, J.Chem.Sci. 16- K. R. Genwa and A. Chouhan, Chim. Acta, 1980,45,L55. 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