3.1. Variation of Dye-Methylene blue (photosensitizer) concentration on the PGS: It was observed that when we increase the concentration of dye MB, the electrical output also increases and attains maximum value on particular concentration value and then decreases in D-Xylose+MB+Brij-35+NaLS system. On a lower concentration range of methylene blue (MB < 4.00 ×10-5 M), the low number of Dye-Methylene blue limits the absorption of the light source, so the electrical output is low. In contrast, at a higher concentration range of methylene blue (MB > 4.00 ×10-5 M), there are so many molecules present that the desired light source does not reach the molecule near the electrode. At intermediate range of methylene blue concentration (MB = 4.00×10-5 M), there are optimum molecules present that the optimum light source does reach the molecule near the electrode and maximum photopotential (696.00 mV), maximum photocurrent (311.00 mA) and maximum power (142.00 µW) were obtained. Table 1 and graphical figure 2 shows the variation of photosensitizer concentration in the D-Xylose+MB +Brij-35+NaLS system.
3.2. Variation of D-xylose (Reductant) concentration on the PGS: It was observed that when we increase the concentration of reductant (D-xylose), the electrical output also increases and attains maximum value on particular concentration value and then decreases in D-Xylose+MB+Brij-35+NaLS system. On a lower concentration range of Reductant (D-xylose < 2.00 ×10-3 M), a smaller number of reductant molecules being available for electron donation to methylene blue to form the cationic form. In contrast, at a higher concentration range of Reductant (D-xylose < 2.00 ×10-3 M) there are a larger number of reductant molecules being available for electron donation to methylene blue to form the cationic form which hinders the methylene blue. At intermediate range of Reductant concentration (D-xylose= 2.00 ×10-3 M) there are optimum number of reductant molecule present that form favorable condition for semi or leuco form of dye molecules and maximum photopotential (696 mV), maximum photocurrent (311.00 mA) and maximum power (142.00 µW) were obtained. Table 1 and graphical figure 2 shows the variation of xylose concentration on the D-Xylose+MB + Brij-35+NaLS system.
3.3. Variation of (NaLS+Brij-35) concentration on the PGS: The electric power of the PG cell havingD-Xylose+MB+Brij-35+NaLSsystem was increased on increasing the concentration of Brij-35 keeping NaLS concentration constant (around its CMC value) and reached at optimum position and decreased on further increase the concentration of Brij-35. Then the concentration of NaLS was increased keeping Brij-35 concentration constant till it reached at optimum position and decreased on further change in concentration of NaLS. On a lower concentration range of both surfactants (NaLS < 6.40×10-4M), and (Brij-35 < 9.00 ×10-4M), less ability to solubilize the molecules for electron transfer process in hydrophilic hydrophobic interaction. In contrast, at a higher concentration range of both surfactants (NaLS > 6.40×10-4M), and (Brij-35 > 9.00 ×10-4M), there are a larger number of surfactant molecules being available for electron transfer process in hydrophilic hydrophobic interaction which may reduce electron transfer. At the intermediate range of surfactant concentration (NaLS = 6.40×10-4M), and (Brij-35 = 9.00 ×10-4M), there are significant effects on electrical output for the photogalvanic system. This is because surfactant can help to separate photoproducts through hydrophilic –hydrophobic interaction of the micelles interface. Generally, the electrical output increases in presence of a particular surfactant, due to increase in solubilization and stabilization properties of dye molecules in the water. The Table 4 and graphical figure 3 and 4 show the variation of mixed surfactant in D-Xylose+MB+Brij-35+NaLS system.
3.4. Variation of pH on the PGS: It was observed that when we increase the pH, the electrical output also increases and attains a maximum value of particular value (pH=13.00 at max.) and then decreases in D-Xylose+MB+Brij-35+NaLS system. On a lower range (PH < 12.84) of PH and higher range of PH (PH > 12.84) not good results are obtained. In contrast, at an intermediate range of PH (PH = 12.84)), maximum photopotential, maximum photocurrent and maximum power were obtained. The intermediate range of ph is slightly higher than the pka value. The may be caused by availability of reductants in an anionic form, which is a better electron donor than its neutral form. Table I shows the variation of pH on D-Xylose+MB+Brij-35+NaLS system.
3.5. Variation of diffusion length on the PGS: The current parameter of the cell (imax, ieq) and initial rate of generation of photocurrent of PG cell having D-Xylose+MB+ Brij-35+NaLS system was observed with change in diffusion lengths (distance between two electrodes). It was found that with an increase in diffusion length maximum photocurrent (imax) and rate (μA min-1) go on increasing but the equilibrium photocurrent (ieq) shows negligible small decreasing trends. So, virtually it may be considered unaffected by the change in diffusion length. On a lowest diffusion length (35mm), the lowest number of dye molecules limits the absorption of the light source, so the photocurrent is obtained as minimum value (262.00 mA). In contrast, at a highest diffusion length (55mm), there are highest numbers of dye molecule absorption of the light source, so the photocurrent is maximum value (280.00 mA). At highest diffusion length, maximum photocurrent (280.00 µA) equilibrium photocurrent (225.00 µA), and initial generation of photocurrent (7.78 A/min) were obtained. Table 2 shows the variation of diffusion length on D-Xylose+MB+Brij-35+NaLS system.
3.6. Variation of electrode area of the cell on the PGS: The current parameter – maximum photocurrent (imax), equilibrium photocurrent (ieq) of PG cell having D-Xylose+MB+Brij-35+NaLSsystem was observed that these were regular increase in maximum photocurrent but equilibrium photocurrent was almost independent on increase in electrode area rather affected in reverse direction. Table 3 shows the variation of electrode area on D-Xylose+MB+Brij-35+NaLSsystem.
3.7. (i-V) characteristics (current–voltage) of the PGS: In the PG cell having D-Xylose+MB +Brij-35+NaLS system, the short circuit current isc is measured by microammeter keeping the circuit closed and open circuit voltage Voc by digital pH meter keeping other circuit open. It is observed that the highest value of photopotential Vpp and photocurrent were measured by applying an eternal load with the help of carbon pot (log 470 K) connected in the circuit. The highest value of potential obeyed in the circuit is known as potential at power point corresponding to highest value of short circuit current is known as current at power point ipp. These four vales (isc, Voc, Vpp and ipp,) were used in formula in one the determine the fill factor of PGS and formula to determine the power point of pgs. The value of fill factor of cell (h) = 0.4521 was observed and the power point of cell (pp) = 64.23mW was obtained for the PGS. The fill-factor was calculated using the following formula:
Where :
Vpp is value of potential, ipp is current at power point, Voc is represent open circuit voltage, isc is short circuit current
3.9. Cell performance and conversion efficiency on the PGS: The D-Xylose+MB+Brij-35+NaLS system was terminated the light source at the value of photocurrent so observed at power point of the PG cell by applying electric load from light source. The time was recorded at which the photogalvanic cell has reached to a half the value of the power in off light mode. The performance of the cell was determined in term of t1/2. The determined value was 120.00 min. The Table IV and graphical Figure 2 show the performance of the PG cell in D-Xylose+MB+ Brij-35+NaLSSystem. Determination of PG cell performance is shown by figure-2 in term of t1/2 and its observed value was 126.00 minutes in dark. PG cell conversion efficiency was determined as 0.6769 % using the following formula:
Where :
Vpp, is photopotential at power point of cell, ipp is Photocurrent at power point of cell, A is used electrode area of cell.