Research Journal of Recent Sciences ______ ______________________________ ______ ___ __ _ ISSN 2277 - 2502 Vol. 1( ISC - 2011 ), 62 - 6 6 (201 2 ) Res.J. Recent .Sci. International Science Congress Association 62 Role of Carmine in Tween 60 – Ascorbic Acid System f or Energy Conversion Genwa K.R. and Sagar C.P. Department of Chemistry, Jai Narain Vyas University, Jodhpur, Rajasthan, INDIA Available online at: www.isca.in (Received 29 th September 2011, revised 10 th January 2012 , accepted 25 th January 2012 ) Abstract The photogalvanic effect studied in H - cell containing Ascorbic acid as reductant and Carmine as photosensitizer. The photopotential and photocurrent generated in cell were 884.0 mV and 190.0 μA, respectively. The observed conversion efficienc y 0.8184% and the maximum outpu t (power) of the cell was 85.12 μW. The photogalvanic cell can be used at this power level for 170 minutes. The effect of different parameters of electrical output of the cell was investigated and a cell photoreaction mechan ism for the generation of the ph otocurrent in this photogalvanic cell has also been proposed. Keywords: Ascorbic acid, c armine, conversion efficiency, t ween 60. Introduction Solar energy presents a scientific challenge beyond the efficient conversion of solar photon to electricity fuel and heat. Once conversion on a large scale is achieved, we must find ways to store the large quantities of electricity and heat that we will pr oduce. Access to solar energy is interrupted by natural cycles of day - night cloudy sunny and winter summer variation that are often out of phase with energy demand. Solar fuel production automatically store energy in chemical bonds. Electricity and heat, however are much more diffic ult store cost effectively storing even a fraction of our peak demand for electricity of heat for 24 hours is a task well beyond present technology 1 . The Photoelectrochemical process is a visible means of converting solar energy directly into ele ctricity 2 - 3 . The physical chemical princip al of photovoltaic conversion with nanoparticales, mesop orous dye sensitized solar cell 4 . Whereas Mayer . have presented the molecular approaches to solar energy conversion and stora ge in photogalv anic cell 5 . Later on s tudies on solar energy conversion and storage in photogalvanic cell reported time to time 6 - 9 . Efficiency of light conversion in photog alvanic cell, water cleavage system and c onve rsion of light into electricity was reported by Dung and Kozak 10 . Ghosh et al. studied the role of nonionic micelles of tweens in photogalvanic gen eration using fluorescien dye 11 . Studies of photochemical conversion of solar energy into electrical energy reported by Balzani et al. 12 . S ome ne w photogalva nic systems reported recently 13 - 16 . In present work electronic output of Tween 60 – Carmine – Ascorbic acid system examined experimentally the storage performance and to development cost effective photogalvanic cell system for sustainable development. M aterial and Methods The solution of Carmine, Tween 60, Ascorbic acid and NaOH having concentration 7.2x10 - 5 M, 1.24x10 - 3 M, 1.96x10 - 3 M and 1.0 N were used respectively. All solutions were prepared by direct weighing and prepared in double distilled water, and kept in amber c olou red container to protect from light. Photogalvanic effect of dye was studied using H - shaped glass tube which consist known amount of the solution of Carmine, t ween 60, a scorbic acid, NaOH. A p latinum electrode (1.0x1.0 cm 2 ) was dip ped in one limb and a saturated calomel electrode (SCE) is immersed in another limb of the H - tube. The terminals of the electrodes were then connected to a digital pH meter and the whole cell is placed in dark. The photopotential was measured in dark when the cell attains a stable potential. The limb containing platinum electrode was focused to the light source (projector Tungsten lamp). The intensity of light was measured in laboratory with the help of solar intensity meter (Surya Systems, Ahmadabad ). A water filter placed between the illuminated chamber and the light source to cut off thermal radiation upto with radiations is observed by cell itself. Photopotential and photocurrent were measured by digital pH meter (Systonics modal 335) and digital amme ter (Osaw). Absorption spectra were recorded using Systonics Spectrophotometer 106 with the matched pair of silica cuvetts (path length 1cm). All spectral measurements were duplicated in a constant temperature water bath maintained with in ±1 0 C and mean values were processed for data analysis. The dye observed absorption peak (λ max ) in visible region with maximum at 515 nm. Maximum absorption is recorded at Carmine - Tween 60 combination of concentration 7.2x10 - 5 M + 1.24x10 - 3 M. Research Journal of Recent Sciences ______ _ _ _______________________________ ______________ _ ______ ISSN 2277 - 2502 Vol. 1( ISC - 2011 ), 62 - 6 6 (201 2 ) Res.J.Recent.Sci International Science Congress Association 63 Results and Discussion Effect of variation of dye (Carmine), surfactant (Tween 60), and reductant (Ascorbic acid) concentration: Effects of dye, surfactant and reductant concentrations are shown in t able - 1 . It was observed that the photopotential and photocurrent of t ween 60 – c armine – a scorbic acid system for the better performance of the photogalvanic cell proper concentration of dye needed. Experimentally, photopotential and photocurrent increased with increase in concentration of the c armine. A maxima was obtained at certain dye concentration. On future increasing in concentration of dye a decrease in the electrical output is observed. On the lower concentration range of photosensitizer, there are limited number of dye molecules to absorb the major portion of the light in t he path and therefore, there is minimum electrical output, where as high concentration of dye again resulted in a decreased in electrical output due to intensity of light reaching the molecule near the electrode decreased due to absorption of the major por tion of the light by the dye molecules present in the path. Therefore corresponding fall in the power of the cell was observed. Tween 60 is used as a surfactant in the system. The photopotential and photocurrent of the cell was increased on increasing the concentration of t ween 60. A maxima was obtained at a certain value and decrease on further increase in surfactant concentration. The most important properties of miceller systems are the ability to solubilize a variety of molecules and substantial cataly tic effect on chemical reaction. With the increase electricity output of the cell also depend on variation of reductant ( a scorbic acid) concentration of the ascorbic acid photopotential and Photocurrent was found to increase to maximum value of Photopotent ial of 884.0 mV and photocurrent of 190.0 μA and then decrease in electrical output because fever reductant molecule, were available for electron donation to photosensitizer (Dye) molecule. Higher concentration of reductant again resulted in a decrease in electrical output, due to the large number of reductant molecules hinder the dye molecule from reaching electrode in the desired time limit. Ascorbic acid is a better photochemical reducing agent in photogalvanic cell. The effect of variation of electrode area on the current parameters of the cell also studied using thin platinum electrodes of different diameters. Experimentally it is observed that with increase electrode area the value of maximum photocurrent (i max ) was f ound to increase and (i eq ) is all most independent to change in electrode cell. However, photocurrents of system, the results are summarized in t able - 2. Table - 1 Effect of variation of electrode area and light intensity Concentration Photopotential (mV) Photocurrent (µA) [Carmine] x 10 - 5 M 6.4 816 104 6.8 843 146 7.2 884 190 7.6 851 152 8.0 825 118 [Tween 60] x 10 - 3 M 1.16 762 126 1.20 828 164 1.24 884 190 1.28 845 176 1.32 812 151 [Ascorbic acid] x 10 - 3 M 1.88 802 143 1.92 832 159 1.96 884 190 2.00 849 163 2.04 822 147 Table – 2 Effect of electrode area Tween 60 – Carmine - Ascorbic acid System Electrode area (cm 2 ) 0.25 0.64 1.00 1.21 1.96 Maximum photocurrent i max (μA) 197 223 250 262 314 Equilibrium photocurrent I eq (μA) 136 162 190 201 252 a [Tween 60] = 1.24 x 10 - 3 M, b [Carmine] = 7.2 x 10 - 5 M, c [Ascorbic Acid] = 1.96 x 10 - 3 M, d Light Intensity = 10.4 mW cm - 2 , e Temp. = 298 K, f pH = 10.04. The intensity of light is also affects the electrical output of the cell. This effect was observed by using solar intensity meter. Results are reported in f igure - 1. It was observed that photocurrent showed a linear increasing behavior with the increase in light intensity whereas photopotential increase in logarithmic manner. Research Journal of Recent Sciences ______ _ _ _______________________________ ______________ _ ______ ISSN 2277 - 2502 Vol. 1( ISC - 2011 ), 62 - 6 6 (201 2 ) Res.J.Recent.Sci International Science Congress Association 64 Figure - 1 Variation of photocurrent and log V with light intensity Figure - 2 Current - potential ( I - V) curve of the cell 2.8 2.9 2.9 3.0 3.0 120 140 160 180 200 220 240 260 280 2.0 5.0 8.0 11.0 14.0 17.0 20.0 23.0 26.0 29.0 log V g Tween 60 - Carmine - Ascorbic acid System Photocurrent ( m A) g Light intensity (mW cm - 2 ) g Photocurrent log V 0 30 60 90 120 150 180 210 240 270 0.0 100.0 200.0 300.0 400.0 500.0 600.0 700.0 800.0 900.0 1000.0 1100.0 Photocurrent ( m A) g Potential (mV) g PP = 85 . 12 m W Tween 60 - Carmine - Ascorbic acid System Research Journal of Recent Sciences ______ _ _ _______________________________ ______________ _ ______ ISSN 2277 - 2502 Vol. 1( ISC - 2011 ), 62 - 6 6 (201 2 ) Res.J.Recent.Sci International Science Congress Association 65 Figure - 3 Time - power curve of the cell Current – voltage (i - V) characteristics of the cell : The open circuit voltage (V oc 1040.0 mV) and short circuit current (i sc 190.0 µA ) of the photogalvanic cell were measured under the continuous illumination of light, with the help of digital pH meter (keeping the circuit open) and a micro ammeter (keeping the circuit closed), respectively. The external parameters (photopotential and photocurrent) of the photogalvanic cell in between this two extreme values (V pp and i pp ) were recorded with the help of a carbon pot (log 407K) connected in the circuit of micro ammeter, through which an external load applied on it. i - V curve is shown in f igure - 2 i - V curve deviated from its regular rectangular shape. A point in the i - V curve, called power point(pp), was determined where the product of current and potential was maximum and the fill - factor was calculated as 0.43 and conversion efficiency o f the cell was determined as 0.8184% using the following relationship Fill - factor (f f) = V pp x i pp / V oc x i sc …………….. (1) V pp x i pp Conversion efficiency ( η ) = x 100% A x 10.4 mWcm - 2 …………………… (2) Where V pp , i pp and A are photopotential at power point, Photocurrent at power point and electrode area respectively. Storage capacity (Performance) of the cell : The performance of photogalvanic cell containing t ween 60 – c armine - a scorbic acid system have current and potential corresponding to the power point after removing illumination. The power output is observed to half of its original value of the power point in the dark. It was observed that the cell can be used in dark for 1 70 minutes using Tween 60 - c armine – a scorbic acid system in photogalvanic cell. Performance of the cell observed graphically in time – power curve shown in f igure - 3. Conclusion Renewable energy can be used again and again without duplication they are fr ee and they are abundant. The use of nonrenewable energy source like sunlight not only limited to the production of electricity. The sunlight is directly converted into the electricity by photogalvanic and photovoltaic cells. The photovoltaic cell are wild ly used in the hilly and desert place, but saying to there storage capacity and commercial viability, the photogalvanic cell are edge over the others because they are cost effective, economic and have added advantage of inherent storage capacity. The power conversion efficiency of photogalvanic cell containing a t ween 60 – c armine – a scorbic acid was t 1/2 = 170min 10 20 30 40 50 60 70 80 90 100 0 . 0 20 . 0 40.0 60.0 80.0 100.0 120.0 140.0 160 . 0 180 . 0 200.0 220.0 240.0 Power ( m W) g Time (Min.) g Tween 60 - Carmine - Ascorbic acid System Research Journal of Recent Sciences ______ _ _ _______________________________ ______________ _ ______ ISSN 2277 - 2502 Vol. 1( ISC - 2011 ), 62 - 6 6 (201 2 ) Res.J.Recent.Sci International Science Congress Association 66 calculated as 0.8184% and storage of light energy in this system recorded 75.0 min. 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