Organic semiconducting material orange dye was dissolved in distilled H2O at room temperature and solutions were prepared with concentrations from 0.019 to 0.155 mol dm-3. The electrical conduction of these aqueous solutions were investigated in a temperature scope of 23 – 62oC, at a frequence of 5 – 1000 Hz, and a electromotive force runing from 0 – 2.3 V. The length, breadth and tallness of the dip type conductance cell for measuring of the opposition were equal to 2, 1 and 1 centimeter severally. It was found that the electrical conduction of the OD solution addition with temperature, frequence and the applied electromotive force. Conductivity – concentration relationship showed a maximal conduction at 0.05 mol dm-3. The conduction mechanism can be explained on the footing of relaxation, cataphoretic effects and dual bed formation at the electrode-solution interface. An tantamount circuit of the cell was developed and simulation surveies of its electric resistance were carried out.
Cardinal words: concentration ; conduction ; frequence ; orange dye solution ; organic semiconducting material ; temperature ; electromotive force.
A big figure of academic documents have reported surveies of organic photo-electrochemical and electro-chemical cells. This is chiefly due to their low cost, easy device fiction and interesting electrical and optical belongingss. The transition of visible radiation to electricity by cis-X2 Bis ( 2,2′-bipyridyl-4,4′-dicarboxylate ) Ru composites on nanocrystalline TiO2 electrodes have been reported by Nazeeruddin et Al. ( 1993 ) . A solar-to-electric energy transition efficiency of 10 % was achieved by these writers. The photo-electrochemistry of individual crystal C60 and fullerene photo-electrochemical solar cells belongingss were studied by Sinke et Al. ( 1998 ) . The belongingss of dye-TiO2 organic solar cell were investigated by Sinke et Al. ( 1998 ) . This survey had shown a record efficiency of 11 % and 6.5 % for a 0.25 and 1.6 cm2 cell countries severally. Photoelectric behaviour of n-GaAs and n-AlxGa1-xAs in CH3CH has been investigated by Casagrande et Al. ( 2000 ) , who reported an open-circuit electromotive force of 0.83 V, a short-circuit current denseness of 20 mA cm-2 and an energy transition efficiency of & gt ; 10 % at 88 mW cm-2 of fake AM 1.5 solar light. Historical background, present position and development chances for the new coevals of photo-electrochemical cells, including dye-sensitized nanocrystaline TiO2 movie, was reviewed by M.Gratzel, 2001.
Using orange dye ( OD ) a figure of devices have been fabricated: Electrochemical Zn/Orange Dye Aqueous Solution / Carbon cell ( Karimov et al. 2006 ) , orange dye thin movie electrochemical hygrometers ( Karimov et al. 2005 ) and photoelectric n-Si and p-Si/Orange dye / Conductive glass cells ( Sayyad et al. 2005 ) have been investigated. In other surveies the high conduction of inorganic-organic polymer electrolyte ( interpolation of poly ( ethene ) oxide into LiV3O8 ) ( Yang et al. 2005 ) have been reported and the voltammetry curves of organic electrolytes with Li ions were investigated ( Lee et al. 2002 ) . To optimise the belongingss of devices based on OD aqueous solutions it would be desirable to look into their electrical conduction. This paper presents surveies of the electrical belongingss of OD aqueous solution.
Distilled H2O and commercially produced organic semiconducting material orange dye ( OD ) , C17H17N5O2 ( Figure 1 ) with molecular weight of 323 g/mole was used for readying of solution in concentration scope from 0.019 to 0.155 mol dm-3 at room temperature. The electrical conduction of orange dye aqueous solution was investigated in a temperature scope of 23 – 62oC, a frequence scope of 5 – 1000 Hz, and in a electromotive force scope of 0 – 2.3 V. The length, breadth and tallness of the dip type conductance cell with aluminium electrodes ( aluminium was stable in the solution ) were equal to 2, 1 and 1 centimeter severally. Conventional digital instruments were used to mensurate the electrical conduction of the sample.
Figure 1: Molecular construction of orange dye ( OD ) .
RESULTS AND DISCUSSION
Figure 2 shows the conduction – concentration relationship at T=25 oC at a frequence and electromotive force of 10 Hz and 1 V severally. It is seen that conduction is maximal at concentrations from 0.038 to 0.077 mol dm-3.
Figure 2: Orange dye aqueous solution conduction – concentration relationship at T=25 oC and applied frequence and electromotive force of 10 Hz and 1 V severally.
As the solutions concentration is increased from a lower value, the figure of ions additions which increases the conduction but when the ion concentration becomes big ( above 0.077 mol dm-3 ) their speed lessenings and therefore a lessening in conduction is observed ( it may be due to beef uping of cataphoretic consequence ) that is seen from the undermentioned look ( Krasnov 1982 ) :
I? = 10-3 I± degree Celsius F ( vc + Virginia ) , ( 1 )
Where F is a changeless, I± is dissociation changeless, degree Celsius is concentration of the solution ( in mol dm-3 ) , vc and Virginias are speed of cations and anions severally. Figure 3 shows the conduction – temperature relationships for 0.019, 0.038, 0.077 and 0.155 mol diabetes mellitus -3 at 10 Hz and 1 V.
Figure 3: Orange dye aqueous solution conduction – temperature relationships at concentration of 0.019 mol dm-3 ( 1 ) , 0.038 mol dm-3 ( 2 ) , 0,077 mol dm-3 ( 3 ) and 0.155 mol dm-3 ( 4 ) , and applied frequence and electromotive force of 10 Hz and 1 V severally.
It is seen that conduction additions with temperature linearly. Normally the addition in conduction is due to increase in ions speed ( Eq.1 ) and this behaviour is described with the undermentioned look ( Krasnov 1982 ) :
I?2 = I?A1 [ 1 + A ( T2-T1 ) ] , ( 2 )
Where I?1 and I?A2 are the conduction values at T1 and T2 severally, A is temperature conductance coefficient, that is equal to 0.0141, 0.0111, 0.0081 and 0.111/oC for the concentrations of 0.019, 0.038, 0.077 and 0.155 mol dm-3 severally. These temperature conductance coefficients are close to the values obtained for acids, bases and salts ( Krasnov 1982 ) .
Fig.4 shows conduction – frequence relationships of the solution at a concentration of 0.019, 0.038, 0.077 and 0.155 mol dm-3 at 25oC and 1 V. It is seen that conduction additions in each instance and the initial rate besides depends on concentration. Normally, electrolytes conduction enhances at high frequence electric field ( above 1 MHz ) when ionic ambiance can non be re-established ( Hibbert 1993 ) .
Figure 4: Orange dye aqueous solution conduction – frequence relationships at concentration of 0.019 mol dm-3 ( 1 ) , 0.038 mol dm-3 ( 2 ) , 0,077 mol dm-3 ( 3 ) and 0.155 mol dm-3 ( 4 ) , and T=25 o C, and applied electromotive force of 1 V.
The addition in conduction in this instance may be due to diminish in the dual bed electrical capacity, electric resistance and opposition of the electrolyte due to weakening of the relaxation consequence ( Hibbert 1993 ) and increase in the ions speed ( Eq.1 ) with frequence. In the well-known tantamount circuit of the electrochemical cell ( Figure 5, Hibbert 1993 & A ; Christensen & A ; Hamnett 1994 ) an electrode-solution junction electrical capacity ( Cj ) may be added due to the presence of Al2O3 movie on the surface of aluminium electrode that may besides lend to the frequence dependance of the conduction.
Figure 5: An tantamount electrical circuit to an electrochemical cell: RSol is opposition of the solution, Cj and CD is the electrode-solution junction electrical capacity and dual bed electrical capacity severally, RCT is charge-transfer opposition, Zw is the Warburg electric resistance. ( Hibbert 1993 & A ; Christensen & A ; Hamnett 1994 ) .
Figure 6 shows the current – electromotive force features of the OD solutions at concentration of 0.019, 0.038, 0.077 and 0.155 mol dm-3, at T=25 oC and applied frequence of 10 Hz. The curves are ace additive significance that the conduction increases with applied electromotive force or electric field.
Figure 6: Orange dye aqueous solution current – electromotive force features at concentration of 0.019 mol dm-3 ( 1 ) , 0.038 mol dm-3 ( 2 ) , 0,077 mol dm-3 ( 3 ) and 0.155 mol dm-3 ( 4 ) , and T=25 o C, and applied frequence of 10 Hz.
It is well-known that high electric field ( around of 1-10kV/cm ) affects conduction ( Hibbert 1993 ) , foremost, due to the retarding consequence of the Attic ambiance on ions gesture and addition in the ions speed, it is the first Wein consequence that is seen largely in strong electrolytes, 2nd, due to heighten dissociation or increase in the ion concentration, it is the 2nd Wein consequence that has been observed in weak electrolytes. Actually, the consequence of the electric field depends on nature of ions and ionic ambiance. From physical point of position, it may be assumed that ions are in possible Wellss ( Neamen 1992 ) and the lessenings in the possible barriers height may increase the conduction as the ions speed additions. On the other manus, injection of charges from electrodes may increase due to electric field, like the infinite charge limited current phenomenon in OD movies ( Moiz et al. 2005 ) , that in bend addition the conduction due to increase in ions concentration.
Figure 7 shows that the magnitude of solution ‘s electric resistance ( Z ) decreases with frequence. It means that the capacitive reactance dominates over the solution ‘s opposition ( Rsol ) , but is much lower than the charge-transfer opposition ( RCT ) , and Zw the Warburg electric resistance.
Figure 7: Orange dye aqueous solution electric resistance – frequence relationship at concentration of 0.038 mol dm-3, at room temperature and applied electromotive force of 1 Volts: 1 – experimental, 2- simulation.
Therefore we can, as a first estimate, simplify the tantamount circuit ( Figure 5 ) to a series connexion of the solution opposition and effectual electrical capacity of the junction and dual bed electrical capacities. At low frequence we may anticipate that the electric resistance is equal to capacitive reactance and at high frequence to the solution ‘s opposition alternatively. Using these estimates a fake information was obtained ( Figure 7 ) for comparing with experimental informations. Both curves show similar behaviour with frequence.
Presently, for aluminium electrolytic capacitances, which can supply high values of electrical capacity in a little volume, a moistened borax paste electrolyte is used ( Irwin & A ; Wu 1999 ) . Study of electrical belongingss of orange dye aqueous solution made in the current research shows that OD may besides be used. This may be considered as one of the new application of this stuff. Designation of the nature, concentration and speed of the ions is a particular undertaking that may be carried out in farther probes.
It was found that the electrical conduction of orange dye aqueous solution additions with temperature, applied frequence and electromotive force. The conduction is maximal at a concentration of 0.038 mol dm-3. Electrical conduction mechanism of the OD solutions is explained on the footing of relaxation and cataphoretic effects in the solution, junction and dual beds electrical capacities in the electrode-solution interface. The tantamount circuit of the cell was developed and simulation of the electrical behaviour of OD solution was carried out. As efficiency of a figure of photo- and electro-chemical cells, depends on conduction of the electrolyte, the current informations obtained allows to optimise parametric quantities of the orange dye aqueous solution with regard to concentration, applied electromotive force, frequence and temperature.