Benoy B. Bhowmik

Molecular interaction of phenosafranin with surfactants and its photogalvanic effect

Abstract The spectrophotometric studies of phenosafranin (PSF) dye in aqueous solutions containing three different types of surfactants such as CTAB (cationic), SLS (anionic), and Triton X-100 (neutral) show that PSF forms a 1:1 molecular complex with Triton X-100 and SLS, and there is no interaction of PSF with CTAB. The thermodynamic and spectrophotometric properties of these complexes suggest that PSF forms a strong charge-transfer complex with Triton X-100 whereas the interaction of PSF with SLS is coulombic in nature. The photogalvanic and photoconductivity effects in PSF-surfactants aqueous systems have been studied using platinum electrodes for both chambers, illuminated and dark, at room temperature (25°C); the PSF + Triton X-100 system only generates photovoltage and photoconductivity and it is almost reversible for a number of cycles.

Kinetics of photoinduced electron transfer in a photoelectrochemical cell consisting of thiazine dyes and Triton X-100 surfactant

Abstract Systems consisting of thiazine dyes in an aqueous solution of Triton X-100 generate photovoltage when studied in a photoelectrochemical cell arrangement. The growth and decay of the photovoltage follow functional forms related to the relaxation times. The rate constants of the forward light reaction and backward dark reaction have been calculated using the relaxation times. A possible mechanism of photovoltage generation involves the photoinduced electron transfer from Triton X-100 surfactant to the thiazine dye through a charge transfer (CT) interaction. A good correlation between the photovoltage, determined by photoelectrochemical studies, and the equilibrium constant, determined by kinetic and spectral studies, confirms this mechanism.

Studies on storage photoelectrochemical cell consisting of phenazine dye-EDTA and different redox couples

A new type of photoelectrochemical cell has been developed using phenazine dye and EDTA aqueous solution and aqueous solution of different redox couples separated by a Pyrex sintered glass membrane (porosity G-4). The different phenazine dyes used are phenosafranin. safranin-O, safranin-T, and neutral red. The redox couples used are Cu+Cu2+, Fe(CN)64−Fe(CN)63−, I−I2, and solFe2+Fe3+. An interesting observation is that the growth of maximum photovoltage takes 15–25 min, whereas the decay to the original dark voltage requires two to three days. Cell characteristics such as open-circuit voltage, short-circuit current, fill factor, power efficiency, and solar energy efficiency have been determined.

Temperature effect on phenosafranine-EDTA photogalvanic cell

The photogalvanic effect in phenosafranine—EDTA aqueous system has been studied in deoxygenated solutions using platinum electrodes for both chambers, illuminated and dark, at different temperatures. For temperature variations between 20 and 49°C, the values of open circuit photovoltage Voc, change from 543 to 870 mV and that of steady state photocurrent I, from 1.58 to 3.24 μA. The present results show that with increasing temperature the photovoltage and photocurrent increase linearely, the time to attain both the equilibrium values also diminishes gradually. Photovoltage and photocurrent appear only in unstirred solutions. An attempt has been made to analyse the effect of pH, light intensity and solvent to understand the temperature dependence of photovoltage. Power conversion efficiency is only 0.24μW cm−2 and solar energy efficiency 10−3%. The current—potential curve indicates high activation overpotential responsible for low efficiency of the cell. Calculation of thermodynamic parameters show large negative entropy for cell reaction.

Enhancement in power output of solar cells consisting of mixed dyes

A new type solar cell consisting of dye-redox system have been developed. Instead of single dye, mixture of two dyes along with a reducing agent, EDTA was taken in the illuminated compartment of an H-shaped cell in which I−/I2 redox couple in the dark compartment are separated by glass membrane (Porosity G-4). The dyes used for mixed system are of four classes: phenazine, thiazine, xanthene and acridine. Calculated solar energy efficiency (SEE) and other cell characteristics of mixed dye-solar cell is larger in comparison to the cell with single dye.

Liposome formation of egg lecithin and its interaction with iodine

The sonicated dispersion of egg lecithin (phosphatidylcholine) in water forms 1:1 molecular complex with iodine, when its concentration is above 1.6 X 10(-5) M. The thermodynamic and spectrophotometric properties of this complex have been determined. The thermodynamic values are: K (25 degrees C) = 1.6 X 10(3) 1 X mol-1, delta G degrees = -18.4 KJ X mol-1, delta H degrees = -27.4 KJ X mol-1 and delta S degrees = -30.0 J X mol-1 X deg-1. The complex shows two absorption bands: one at 293 nm, which is the charge transfer band and the other at 370 nm, which is the blue shifted visible iodine band at 460 nm in water.

Solvent effects on charge-transfer intensities and heats of formation of chloranil complexes with aromatic hydrocarbons

Abstract The spectrophotometric and thermodynamic properties of the charge-transfer complexes of chloranil with aromatic hydrocarbons such as benzene, toluene, xylenes (o-, m- and p-) and mesitylene have been studied in n-heptane solvent to make a correlation between the charge-transfer intensities and the heats of formation of the complexes. The results disagree with M ulliken s prediction—the charge-transfer intensities decrease with increase of heats of formation. An attempt has been made to calculate the thermodynamic as well as spectrophotometric properties of these complexes free from the influence of chloranil—solvent interaction and the results thus obtained show a good correlation between the charge-transfer intensities and the heats of formation of the complexes.

Solvent effect on the charge-transfer complexes of chloranil with mesitylene and benzene

Abstract The thermodynamic and spectrophotometric properties of the charge-transfer (CT) complexes of chloranil with mesitylene and benzene have been studied in different solvents such as n -hexane, cyclohexane, n -heptane, carbon tetrachloride, chloroform, dichloromethane and in addition, the properties of the former complex have been studied in benzene. The results show that the oscillator strengths ( f ) of the CT absorption bands of these complexes in different solvents increase with the heats of formation (− Δ H °). The role of the solvent in changing both thermodynamic as well as spectrophotometric properties of these complexes is assumed to be due to the solvent interaction with chloranil. An attempt has been made to calculate the thermodynamic and spectrophotometric properties of the solvent—chloranil interaction. Moreover, the CT absorption band positions of chloranil complexes with mesitylene and benzene in the gas phase have been determined from the corresponding values in different solvents.

Photoinduced interaction of thionine with phospholipid and cholesterol in artificial membranes.

The photoinduced interaction of thionine dye with phosphatidylcholine (PC) (and its components, e.g. lysoPC, phosphorylcholine and choline) and oxidized cholesterol was studied in artificial membranes using spectrophotometric and photoelectrochemical methods. The results show that the dye (electron acceptor) in its singlet excited state forms 1:1 electron donor-acceptor (EDA) complexes with the lipids (electron donor). The electrode kinetics of the photoinduced redox reactions in the cell were also studied to confirm the mechanism of photoinduced interaction between the dye and the lipid.

Double-electrode behavior of the bilayer lipid membrane in electrolytic solution

Abstract The electrical conductivity across the bilayer lipid membrane of oxidized cholesterol in the presence of different electrolytes in aqueous solution is a function of the standard electrode potential of the ions of the electrolytes. The same correlation follows in the presence of these electrolytic solutions containing iodine although the conductivity value increases manyfold. The results can be satisfactorily explained in the light of electronic conduction through the bilayer membrane which acts as a double electrode.