Interaction of TiO₂ Nanocrystals with Imidazolium-Based Ionic Liquids

Abstract

Semiconductor nanocrystals and room-temperature ionic liquids have been extensively investigated as promising materials for applications in the field of energy conversion and storage. Titanium dioxide nanoparticles are unquestionably the most used material for the fabrication of sensitized solar cells and batteries, in which room-temperature ionic liquids have been used to replace conventional electrolytes. The study of their interactions is, therefore, undoubtedly of large scientific and technological interest for their implementation in innovative energy devices. Here, a spectroscopic study focused on the interactions, in terms of charge and/or energy transfer, between titanium dioxide nanorods and imidazolium-based ionic liquids is reported. Anatase TiO 2 rodlike nanocrystals, synthesized by means of a colloidal synthetic procedure, have been dispersed at increasing loading in a series of dialkyl-substituted imidazolium-based ionic liquids, characterized by different anions and alkyl chain lengths. Time-resolved spectroscopic measurements have highlighted a significant increase of the photoluminescence decay times in the presence of TiO 2 nanorods. This increase has been shown to directly depend on TiO 2 load and has been ascribed to charge-transfer phenomena from photoexcited TiO 2 nanorods to imidazolium rings of ionic liquids. The obtained results are of considerable interest for designing batteries and solar cells based on nanostructured materials and ionic liquids.

Dispersion and Solvation Effects on the Structure and Dynamics of N719 Adsorbed to Anatase Titania (101) Surfaces in Room-Temperature Ionic Liquids: An ab Initio Molecular Simulation Study

“…RTILs are known for both their extremely long-range interfacial layering and relaxation times, 26,39 that can be on the order of hundreds of nanoseconds, if not milliseconds.…”

Fabrication and photoactivity of ionic liquid–TiO2 structures for efficient visible-light-induced photocatalytic decomposition of organic pollutants in aqueous phase

“…The intense absorption in the UV region can be assigned to the π–π* transition of the imidazolium ring. On the other hand, the long tail of the absorption spectra could be due to (i) the energy structure of the cation as well as the spatial arrangement of the anion and (ii) the presence of an impurity resulting from the IL synthesis [ 42 – 44 ].…”

The effect of pressure on cation–cellulose interactions in cellulose/ionic liquid mixtures

“…4,5 Negligible volatilities and a broad range of liquid states make ionic liquids attractive alternatives to volatile organic solvents, leading to discussions of ionic liquids as green solvents. [4][5][6][7][8][9] Various studies have been performed to elucidate the role of weak hydrogen bonding (C-HÁ Á ÁO or C-HÁ Á ÁX) in the structure of ionic liquids. Based on the results of previous studies, ionic liquids may possess hydrogen bonds, but the role of hydrogen bonding in ionic liquids is not well understood.…”

“…4,5 The most extensively studied ionic liquids are 1-alkyl-3-methylimidazolium salts which feature asymmetric cations. [4][5][6][7][8][9][10] With three hydrogen atoms bound to the imidazolium ring of 1-alkyl-3-methylimidazolium salts, the most acidic proton, i.e., the C 2 proton, may prefer to form hydrogen bonds with anions. [4][5][6][7][8][9] Various studies have been performed to elucidate the role of weak hydrogen bonding (C-HÁ Á ÁO or C-HÁ Á ÁX) in the structure of ionic liquids.…”

“…Based on the results of previous studies, ionic liquids may possess hydrogen bonds, but the role of hydrogen bonding in ionic liquids is not well understood. Self-assembly and the spatial microheterogeneity of ionic liquids have been suggested, 4,5,[7][8][9][10] and the alkyl side chain length seems to influence supramolecular aggregation behaviors which may lead to an ordered local environment. [4][5][6][7][8][9][10] With three hydrogen atoms bound to the imidazolium ring of 1-alkyl-3-methylimidazolium salts, the most acidic proton, i.e., the C 2 proton, may prefer to form hydrogen bonds with anions.…”