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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.

A comparative study of the interactions of the cationic gemini surfactant tetramethylene-1,4-bis(dimethyltetradecylammonium bromide) (14-4-14) with anionic polymer sodium carboxymethylcellulose (NaCMC), with two different molar masses, was performed in water and isopropanol (IP)–water media. The interaction process was studied in detail using conductometry, tensiometry, turbidimetry and viscometry. At very low concentration, 14-4-14 monomers interact with the polymer. Above the critical aggregation concentration (cac), small micelle-like aggregates form complexes with the polymer. During the interaction process, coacervates are formed beyond Cs (polymer saturation concentration), which initially grow by aggregation and stay in the solution throughout the process. The interaction process is affected by addition of isopropanol into the medium. The intrinsic viscosities of the two NaCMCs were determined by using Huggins and Kraemer equations. Dynamic light scattering (DLS) study helps to determine the hydrodynamic size of the dispersed polymer and its surfactant-interacting complexes. The hydrodynamic size of the dispersed polymer and its interacting complex in IP–water media is lower than that obtained in aqueous solution. The surface morphology of the solvent removed polymer and its surfactant-interacting complex were examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The pattern of the morphologies depends on the polymer–surfactant composition and the solvent environment.

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.

The micellar and surface properties of single as well as equimolar binary mixed systems of some cationic gemini and monomeric ionic surfactants have been studied by conductivity, surface tension and fluorescence measurements at 300 K. The critical micelle concentration (CMC), Γmax (maximum surface excess), Amin (minimum surface area per molecule), πcmc (surface pressure at the CMC) and thermodynamic parameters viz. standard Gibbs free energies of adsorption ( Δ G ads ° ), standard Gibbs free energies of micellization ( Δ G m ° ) and minimum free energy of the surface ( Δ G min ( s ) ) of gemini with cationic monomeric surfactants were also evaluated. The negative values of Δ G ads ° and Δ G m ° indicate the spontaneity and stability of the mixed micelle. The experimental CMC values are less than the ideal CMC values, indicating negative deviation from ideal behavior for all the equimolar binary surfactant systems. Aggregation number (Nagg) and Stern–Volmer quenching constant (Ksv) have been evaluated by Fluorescence measurement. The solubilization capacities of selected single and equimolar binary surfactant systems toward polycyclic aromatic hydrocarbons (PAHs), i.e., naphthalene, anthracene and pyrene have been evaluated and discussed in terms of the molar solubilization ratio (MSR), the micelle-water partition coefficient (K(m)), the deviation ratio (R), and the free energy of solubilization ( Δ G s ° ) of PAHs. The negative value of Δ G s ° shows spontaneity of solubilization process.

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.