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A new bilayer-nanostructured photoanode with mesoporous titanium phosphate (MTP1) as overlayer and titanium dioxide (TiO2) as underlayer has been fabricated. Mesoporous titanium phosphate material with high surface area (442 m2 g−1) has been synthesized hydrothermally by using a new tailor made gemini surfactant under acidic pH conditions. HR TEM and N2 sorption analysis revealed the presence of disordered mesopores of dimension ca. 4.50 nm in MTP1 material. Open-circuit voltage decay (OCVD) spectroscopy is used to investigate the kinetic process of electron transport and recombination within TiO2/TiO2, MTP1/TiO2, or MTP1/MTP1 based DSSCs, revealing a faster electron transport rate and a lower recombination rate in the MTP1/TiO2 photoanode. The energy conversion efficiency of dye-sensitized solar cells (DSSCs) based on such a MTP1/TiO2 photoelectrode shows a significant enhancement (6.0%) compared to TiO2/TiO2 photoelectrode (5.5%) with similar thickness (∼7 μm), suggesting the favorable electron transport rate in former.

The interactions between myoglobin, a monomeric water soluble heme protein, and cationic gemini surfactants 14-3-14, 14-4-14, 14-5-14 have been studied in phosphate buffer at pH 7.4 using different techniques such as surface tension, UV–visible spectroscopy, fluorescence spectroscopy and circular dichroism. Myoglobin is a surface active protein and it is bound with surfactant molecules. The spin states of the heme group of myoglobin change depending on the concentration of surfactant. The unfolding process of protein in the presence of surfactant is observed from fluorescence spectra. With increasing surfactant concentration, α-helicity of myoglobin decreases with the appearance of β-sheet and random coil. The extent of interaction of myoglobin with gemini surfactant increases with increasing spacer length.

A comprehensive study of micellization and microemulsion formation of a cationic gemini surfactant (tetramethylene-1,4-bis(dimethyltetradecylammonium bromide; 14-4-14) in the absence or presence of hydrophobically modified polyelectrolyte, sodium carboxymethylcellulose (NaCMC), has been conducted by conductometry, tensiometry, microcalorimetry, and fluorimetry methods at different temperatures. Both critical micelle concentration and degree of ionization of the surfactant have been observed to increase with increasing temperature. The interfacial and thermodynamic parameters were evaluated. The standard Gibbs free energy of micellization (ΔGm°) is negative, which decreases with increase in temperature. Larger entropic contribution is observed compared to the enthalpy. The interaction of 14-4-14 with NaCMC produces coacervates which was determined from turbidimetry method. The pseudoternary phase behavior of the microemulsion systems comprising water (or NaCMC as additive), 14-4-14, isopropanol (IP) or n-butanol (Bu) as cosurfactant, and isopropyl myristate (IPM) were studied at 298 K. Phase diagrams reveal that IP derived microemulsions (in the absence of NaCMC) offer a large isotropic region compared to Bu-derived systems at comparable physicochemical conditions. Increasing the concentration of IP or Bu decreases the isotropic region in the phase diagram. NaCMC influences the microemulsion zone, depending upon its concentration, and type of cosurfactant and surfantant/cosurfactant ratio. Dynamic light scattering and conductometric measurements show the size of the droplet, threshold temperature of percolation, scaling parameters, and activation energy of the percolation process of 14-4-14/IP or Bu derived microemulsion systems without/with NaCMC at various physicochemical conditions. Bu exerts a greater effect to reduce θt than IP as a cosurfactant (in the absence of NaCMC) at comparable ω. On the other hand, IP showed better percolating effect than Bu in the presence of NaCMC. Bu and IP (as cosurfactant) and NaCMC (as additive) influenced the microemulsion droplet size (Dh) to different extents under comparable conditions. Temperature insensitive microemulsions have been reported at the studied temperature range (298–353 K). 14-4-14/IP (1:2)-derived microemulsion showed a fractured surface at fixed ω = 15, where ω is the water and surfactant molar ratio, and temperature (298 K); whereas, large scale mesospheres comprising multiple closely winded nanoslices and spheroid morphology were formed in 14-4-14/IP and 14-4-14/Bu microemulsions, respectively, in the presence of 0.01 g % NaCMC, at comparable conditions. These systems revealed good antimicrobial activity toward the strains of Gram-positive Bacillus subtilis and Gram-negative Escherichia coli bacteria at 298 K, and inhibitory effect was governed by ω, type of cosurfactant, and bacterial strains.

The effect of cosolvent (ethane-1,2-diol and dimethyl sulfoxide) on the self-assembly of three surfactants, N,N,N-trimethyl-1-dodecanaminium bromide (DTAB), sodium [dodecanoyl(methyl)amino]acetate (SDDS), and polyoxyethylene (20) sorbitan monolaurate (Tween-20) in aqueous solution have been investigated by conductometric, tensiometric, and viscometric techniques at 298 K. The main focus was on the effect of solvent on critical micelle concentration (cmc), free energy contribution to micellization (ΔGm0), tail transfer Gibbs free energy (ΔGtrans0), Gibbs adsorption energy (ΔGads0), and some micellar interfacial parameters, for example, Gibbs surface excess (Γmax), minimum area per surfactant molecule (Amin), surface pressure (Πcmc), and pC20(= −log(C20), where C20 is the surfactant molar concentration required to reduce the surface tension of mixed solvent by 20 mN m–1). With increasing concentration of cosolvent in the binary mixture, the cohesive force decreases, and surfactant molecules are more soluble...

The interaction of a cationic dye crystal violet, in aqueous solution with different types of surfactants, such as anionic, cationic, non-ionic, gemini and their mixtures has been investigated spectrophotometrically and fluorimetrically in premicellar and post micellar concentration regions. In the premicellar concentration region of anionic surfactants, the dimer of the dye is formed; in the micellar concentration region, the monomer of the dye predominates. With cationic and nonionic surfactants, crystal violet is solubilised primarily as the monomer. In case of anionic and nonionic mixture, stability of dye–surfactant complex increases with increase in mole fraction of anionic surfactant. Cationic surfactant, cetyltrimethylammonium bromide (CTAB) has no interaction with crystal violet.