Ionic liquids for nano- and microstructures preparation. Part 1: Properties and multifunctional role

Visible‐Light Photocatalytic Activity of Ionic Liquid TiO2 Spheres: Effect of the Ionic Liquid's Anion Structure

“…Ionic liquids (ILs), owing to their unique physical and chemical properties such as low volatility, high thermal stability, high conductivity, and tunability, have attracted much interest for their use in the synthesis of metal and semiconductor nano‐ and microparticles . In this regard, the mode of action of the ILs in reaction mixtures and their influence on particle activity are the subject of intensive research.…”

“…It was shown that ILs can form protective layers owing to steric hindrance, electrostatic interactions, solvation forces, and viscous stabilization . ILs can act as structuring agents or soft templates, providing nano‐ and microstructures with uniform sizes and distributions, controlled morphologies, and, as a consequence, desired and improved properties . Moreover, changes in the physicochemical properties of ILs induced by confinement in nanoporous oxide matrices were also investigated…”

Preparation of Ag@mSiO 2 and Pt@mSiO 2 nano composites using trioctylmethyl ammonium hydrogen phthalate (TOMAHP) ionic liquid as reaction medium

“…The DLVO theory has limitation since it consider the ideal case only. According to DLVO theory, the nano particles are not effectively stabilized by only electrostatic repulsion due to the high ionic strength of IL [62,63]. Thus, the extra stabilization energy/force may arise from steric hindrance due to presence of bulky groups (anion, cation), solvation forces due to H-bonding, high viscosity and layer structure of IL.…”

Highly Active TiO2 Microspheres Formation in the Presence of Ethylammonium Nitrate Ionic Liquid

“…Additionally, it has been noted that a slower recombination rate and a larger surface area accounted for more active adsorption/desorption reactions and the surface transfer of photoexcited electrons [9,12,13], whereas the potential adverse effects that originate in the highly defective sites, typically developing with the growth of a large surface area, may be rectified by a higher crystallization of the particles [9].Ionic liquids (ILs) have gained increasing attention in terms of their assistance in TiO 2 synthesis as solvents as well as spatial and, perhaps, band structuring agents. Their high viscosity, dielectric constant, and thus polarity and dispersal capacity are widely recognized as the properties responsible for the charge, steric, and viscous stabilization of small-sized slow-growing crystallites, as well as the hindrance of aggregation and agglomeration processes that are disadvantageous for photocatalytic [7,10,11,[14][15][16][17][18][19][20][21][22][23].The synthesized photocatalysts in the presence of ILs nano-and microparticles are characterized by a larger specific surface area, higher crystallization level, and less crystalline defects [17]. Hence, with the assistance of ILs, the formation of the particles of the beneficial surface reactivity is promoted, inducing a more effective photon absorption, trapping, and their migration to the surface.…”

“…The generated reactive oxygen species (•OH and O 2 • − ) are crucial reagents in the photodegradation of pollutants [16,17,24].Notwithstanding, the direct relationship between the structure of the ILs and the size/morphology of the nano-and microparticles of the semiconductors, such as the TiO 2 photocatalysts, still remains ambiguous. Up until now, the following factors had been reported as predominant in effectuating the structure, and thus the activity of said particles, as follows: (1) IL anion type (the number of atoms it is composed o growth; apart from this, π-π stacking of imidazolium cations promotes the ILs role as templating agents); (3) cation-anion interaction energy where the frailer, the weaker the cation-anion interactions, the firmer the capping on growing the TiO 2 particles and the more efficient the inhibition/hampering of the unfavorable Ostwald ripening process; and (4) the type of overall interactions (π-π, van der Waals, coulomb and electrostatic forces, and hydrogen bonding) [15,16,21,25].Furthermore, the proposed fons et orgio of the influences on the TiO 2 photoactivity are tenable, as follows: (1) doping with N, C, and F elements after ILs thermal decomposition; (2) directly sensitizing the TiO 2 particles; (3) affecting the transfer of photo-generated charges through the bulk of particles; and (4) favoring oxygen vacancies and Ti 3+ species formation during synthesis [26][27][28]. However, an up to date kinetics of the formation of the TiO 2 particles during ionic liquid-assisted synthesis has not been presented and discussed.In this regard, in this study, the TiO 2 particles were synthesized solvothermally, with the assistance of the selected ionic liquid, ethylammonium nitrate [EAN] [NO 3 ], which is one of the earliest reported in the literature of protic ionic liquid [29,30].Apart from prevailing in studies on the topics of the synthesis process and characterization of the IL-assisted TiO 2 microparticles [22,[30][31][32], we focused on evaluating the functional properties of the obtained micro-particles, namely, their photoactivity.…”