We used both localized and periodic calculations on a series of monovalent (Li+, Na+, K+, Rb+, Cs+) and divalent (Mg2+, Ca2+, Sr2+, Ba2+) cations to monitor their effect on the swelling of clays. The activity order obtained for the exchangeable cations among all the monovalent and divalent series studied: Ca2+ > Sr2+ > Mg2+ > Rb+ > Ba2+ > Na+ > Li+ > Cs+ > K+. We have shown that, in case of dioctahedral smectite, the hydroxyl groups play a major role in their interaction with water and other polar molecules in the presence of an interlayer cation. We studied both type of clays, with a different surface structure and with/without water using a periodic calculation. Interlayer cations and charged 2:1 clay surfaces interact strongly with polar solvents; when it is in an aqueous medium, clay expands and the phenomenon is known as crystalline swelling. The extent of swelling is controlled by a balance between relatively strong swelling forces and electrostatic forces of attraction between the negatively charged phyllosilicate layer and the positively charged interlayer cation. We have calculated the solvation energy at the first hydration shell of an exchangeable cation, but the results do not correspond directly to the experimental d-spacing values. A novel quantitative scale is proposed with the numbers generated by the relative nucleophilicity of the active cation sites in their hydrated state through Fukui functions within the helm of the hard soft acid base principle. The solvation effect thus measured show a perfect match with experiment, which proposes that the reactivity index calculation with a first hydration shell could rationalize the swelling mechanism for exchangeable cations. The conformers after electron donation or acceptance propose the swelling mechanism for monovalent and divalent cations.

A series of highly ordered mesoporous gallium-containing MCM-41 molecular sieves with variable Si/Ga (100−10) ratios have been synthesized at room temperature. The synthesized Ga−MCM-41 was investigated by powder X-ray diffraction, transmission electron microscopy, thermal analysis, N2 adsorption measurement, and 29Si and 71Ga nuclear magnetic resonance (NMR); optimal synthesis conditions have thus been established. We were successful in synthesizing highly ordered material at room temperature using gallium nitrate as the source of gallium, and the surfactant was the cetyltrimethylammonium cation [(C16H33N(CH3)3]+. 71Ga NMR of calcined and uncalcined Ga−MCM-41 demonstrated that gallium was substituted for Si with tetrahedral coordination in the Ga−MCM-41 structure. N2 adsorption measurements indicate that high mesoporosity exists over the entire range of Ga−MCM-41 with an average pore diameter of 38.3 Å.

Hydrothermal synthesis of brookite was performed at 110-200 °C within 24 h using amorphous TiO2 and sodium salts as the starting material. Brookite was obtained as an almost single phase at 200 °C and TiO2 / NaOH mole ratio ≅ 1. By the results of XPS and UV-vis measurements, brookite was considered to be formed from sodium titanate by releasing Na+ and H+ of the surface accompanied by oxidation of Ti in the structure.

Hydrothermal synthesis of potassium hexatitanate was carried out under various subcritical and supercritical water conditions using potassium hydroxide and titanium tetraisopropoxide as starting materials. Characterization of these hydrothermally synthesized potassium hexatitanates by XRD, SEM, TEM, and thermal analysis showed that long, felted-like fibers of potassium hexatitanates were formed and these fibers are thermally stable up to 1273 K. The use of these fibers as photocatalysts in water decomposition was investigated using ruthenium oxide as the catalytic active phase. Photocatalytic activitiy in the water decomposition reaction was found to be much higher in comparison with the solid state synthesized photocatalyst. Activites of more than 13-fold were obtained for the photocatalysts synthesized under subcritical water conditions and between 27- and 59-fold for those synthesized under supercritical water conditions for water decomposition.

We report a "ship-in-a-bottle" synthesis where encapsulation of copper phthalocyanines (CuPc) into mesoporous channels of silicate MCM-41 was achieved by chemical vapor deposition (CVD) using 1,2-dicyanobenzene (DCNB). Silanol protons of MCM-41 were ion-exchanged with copper ions before CVD, and when the initial amount of DCNB was much larger than that of copper ions, CuPc molecules in the channels were found to form a cofacial structure that was confirmed by diffuse reflectance spectra.