Preparation of TiO₂ Nanoparticles Coated with Ionic Liquids: A Supramolecular Approach

Coated TiO₂ nanoparticles by dicationic imidazolium-based ionic liquids (ILs) were prepared and studied by differential scanning calorimetry (DSC), dynamic light scattering (DLS), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), and scanning electron microscopy (SEM). Three ILs with different hydrophobicity degrees and structural characteristics were used (IL-1, IL-2, and IL-3). The interaction between IL molecules and the TiO₂ surface was analyzed in both solid state and in solution. The physical and chemical properties of coated nanoparticles (TiO₂ + IL-1, TiO₂ + IL-2, and TiO₂ + IL-3) were compared to pure materials (TiO₂, IL-1, IL-2, and IL-3) in order to evaluate the interaction between both components. Thermal behavior, diffraction pattern, and morphologic characteristics were evaluated in the solid state. It was observed that all mixtures (TiO₂ + IL) showed different behavior from that detected for pure substances, which is an evidence of film formation. DLS experiments were conducted to determine film thickness on the TiO₂ surface comparing the size (hydrodynamic radius, <i>R</i>_h) of pure TiO₂ with coated nanoparticles (TiO₂ + IL). Results showed the thickness of the film increased with hydrophobicity of the IL compound. TEM images support this observation. Finally, X-ray diffraction patterns showed that, in coated samples, no structural changes in TiO₂ diffraction peaks were observed, which is related to the maintenance of the crystalline structure. On the contrary, ILs showed different diffraction patterns, which confirms the hypothesis of interactions happening between IL and the TiO₂ nanoparticles surface

How Mechanical and Chemical Features Affect the Green Synthesis of 1<i>H</i>‑Pyrazoles in a Ball Mill

This work investigated the chemical and mechanical factors that affect cyclocondensation reactions in a ball mill. Chemical characteristics such as the use or non-use of a catalyst, amount of catalyst and reactants, and product formation, as well as the yield and mechanical factors such as rotation frequency and the number, diameter, and material of the milling balls were evaluated. It was found that a rotation frequency of 450 rpm is efficient for energy transfer to the reactants because the conversion is higher at this rotation. The reaction was highly dependent on the time (3 min) and amount of <i>p</i>-TSA (<i>p</i>-toluenesulfonic acid) utilized as catalyst (10 mol %). Five steel balls of 10 mm were considered to be the ideal number for the efficient mixing of the particles. For this work, the ideal conditions determined were used for the green synthesis of a series of 1<i>H</i>-pyrazoles