Room temperature ionic liquids are currently used as functional materials in several application and their optical investigation can provide a better understanding of their physical and chemical behavior. Absorption and emission properties of imidazolium-based ILs have been attributed to the imidazolium moiety and related to the presence of energetically different aggregates. Here, time-integrated and time-resolved investigation has been carried out on 1-alkyl-3-methylimidazolium tetrafluoroborate and hexafluorophosphate ionic liquids with different chain lengths in order to probe the occurrence of energy transfer processes, and hence to disclose the presence of various states with different energy. Such a study contributes to provide relevant insight on the effect of alkyl chain and anion type on the emission characteristics, and, hence, on the presence of associated structures.

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Original nanocomposites have been obtained by direct incorporation of pre-synthesized oleic acid capped TiO(2) nanorods into properly functionalized poly(methyl methacrylate) copolymers, carrying carboxylic acid groups on the repeating polymer unit. The presence of carboxylic groups on the alkyl chain of the host functionalized copolymer allows an highly homogeneous dispersion of the nanorods in the organic matrix. The prepared TiO(2)/PMMA-co-MA nanocomposites show high optical transparency in the visible region, even at high TiO(2) nanorod content, and tunable linear refractive index depending on the nanoparticle concentration. Finally measurements of nonlinear optical properties of TiO(2) polymer nanocomposites demonstrate a negligible two-photon absorption and a negative value of nonlinear refractive index, highlighting the potential of the nanocomposite for efficient optical devices operating in the visible region.

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.