We report on the preparation of luminescent collectors based on poly(methyl methacrylate) (PMMA) thin films doped with a red-emitting 2-amino-7-acceptor-9-silafluorene, where the amino group is -N(CH3)(2) and the acceptor is -CH=C(CN)(2). The results obtained from photophysical investigations of the dye in different solvents and in PMMA are very encouraging as the silafluorene dyes turn out to be highly dispersed in the solid matrix, stable upon irradiation and highly emissive. QY and lifetime investigations demonstrate that autoabsorption phenomena moderately occur with SilaFluo content, and the optical features still maintained very significant, also at the highest fluorophore concentration (QY similar to 65%). Study of the LSCs features yields excellent optical efficiencies of 9.6% attained for 25 mm thick PMMA films containing the 1.5 wt% of SilaFluo. This performance is at the top level with respect to the current state-of-art of similar devices based on perylene-based fluorophores such as Lumogen Red.

The unique size-and shape-dependent electronic properties of nanocrystals (NCs) make them extremely attractive as novel structural building blocks for constructing a new generation of innovative materials and solid-state devices. Recent advances in material chemistry has allowed the synthesis of colloidal NCs with a wide range of compositions, with a precise control on size, shape and uniformity as well as specific surface chemistry. By incorporating such nanostructures in polymers, mesoscopic materials can be achieved and their properties engineered by choosing NCs differing in size and/or composition, properly tuning the interaction between NCs and surrounding environment. In this contribution, different approaches will be presented as effective opportunities for conveying colloidal NC properties to nanocomposite materials for micro and nanofabrication. Patterning of such nanocomposites either by conventional lithographic techniques and emerging patterning tools, such as ink jet printing and nanoimprint lithography, will be illustrated, pointing out their technological impact on developing new optoelectronic and sensing devices.

The interaction between plasmons and excitons in photonic crystal structures is demonstrated to benefit the light extraction capabilities of polymer-based light emitting components. An enhancement of up to a factor of 40 is reported in structures fabricated by nanoimprint lithography. © 2011 IEEE.

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 TiO2 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 TiO2 nanorods. This increase has been shown to directly depend on TiO2 load and has been ascribed to charge-transfer phenomena from photoexcited TiO2 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.

We investigated the excitation density dependence of the photoluminescence spectra of hybrid poly(9,9-dioctylfluorene)-CdSe/ZnS nanocrystals (PF8-NCs) thin films. We demonstrate that this experiment allows the determination of the efficiency of all the CdSe/ZnS NCs excitation processes and that the presence of amplified spontaneous emission (ASE) from the PF8 leads to a strong dependence of the NC excitation processes from the laser excitation density. Below the PF8 ASE threshold only about 6% of the excitons in the NCs are due to pump laser absorption, while about 94% of the NC excitation is due to the interaction with the PF8, and it is due for about 58% to PF8 -> NC Forster resonant energy transfer (FRET) and for about 37% to reabsorption by the NCs of the PF8 luminescence. ne presence of PF8 ASE significantly modifies this scenario by strongly decreasing the FRET importance and strongly increasing the reabsorption one. The interplay between reduced FRET and increased reabsorption overall decreases the NC excitation due to PF8 indicating that ASE from the donors should be avoided if efficient NCs excitation under strong pumping is wished.

Titanium and its alloys are widely employed materials for implants in orthopedic or dental surgery due to their mechanical properties, resistance to corrosion and osseointegration capability. However adverse reactions at the tissue/implant interface may occur, which limit the success of the osseointegration process. Therefore, different strategies have to be used to overcome these drawbacks. In this work, we developed two different liposome-based coatings on titanium surfaces as drug or bioactive molecule deposits for dental/orthopedic implant applications. The first one is a supported vesicular layer (SVL), obtained by liposome adhesion on passivated Ti surface, the second one is a covalently bonded vesicular layer (CBVL) grafted on properly functionalized Ti. Photoluminescence spectroscopy and atomic force microscopy investigations demonstrated the effective anchoring of intact liposomes in both systems. Cytotoxicity assays, performed after 48h, showed a MG63 cell viability higher than 75% and 70% on SVLs and CBVLs, respectively. Scanning electron microscopy investigation revealed numerous and spread MG63 cells after 48h on SVL modified Ti surface and a lower cell adhesion on samples coated with CBVL. The cellular uptake capability of liposome content was proved by fluorescence microscopy using carboxyfluorescein loaded SVLs and CBVLs. Finally, we demonstrated that these liposome-modified Ti surfaces were able to deliver a model bioactive molecule (phosphatidylserine) to adherent cells, confirming the potentiality of developed systems in bone related prosthetic applications.

We report on a method to enhance the light-emission efficiency of printable thin films of a polymer doped with luminescent (CdSe)ZnS nanocrystals via metallic nanoparticles and nanoimprinted photonic crystals. We experimentally show a strong fluorescence enhancement of nanocrystals by coupling exciton-plasmon with the localized surface plasmon of metallic nanoparticles. The emitted light is efficiently diffracted by photonic crystals structures directly imprinted in the nanocomposite polymer. By combining the field susceptibility technique with optical Bloch equations, we examine the interaction of the quantum and plasmonic entities at small distances.

Nanocrystalline titania (TiO2) synthesized via sol-gel, by using an alkoxide precursor were deposited ontocommercially available silica and alumina fibers, namely E-Glass and Nextel 650, respectively. Differentprocessing conditions and material preparation parameters, such as amount of TiO2, film composition andannealing temperature were tested in order to obtain nanocrystalline TiO2 with different morphologicaland structural characteristics. The materials were characterized by scanning electron microscopy (SEM),X-ray diffraction (XRD), and the Brunauer, Emmett, and Teller (BET) surface area measurements. Thephotocatalytic activity of the obtained coated fibers was investigated by monitoring the degradationof a model molecule, an azo dye (Methyl Red), under UV irradiation in aqueous solution. The detectedphotocatalytic performance of the sol-gel derived nanocrystalline TiO2 was explained on the basis ofmechanism associated to the photocatalytic decomposition of organic molecules using semiconductoroxides and accounted for the structural and morphological characteristics of the TiO2 based coating. Thematerials with the most suited characteristics for photocatalysis were used to scale up the depositiononto a larger sample of fiber and then tested in a photocatalytic reactor. A commercially available TiO2standard material (TiO2 P25 Degussa) was used as reference, in order to ultimately assess the viability ofthe coating process for real application.

Two colloidal methods, namely one pot and two steps approaches, have been exploited to synthesize light emitting CdSe/ZnS core-shell nanocrystals, differing in growth process of the inorganic ZnS shell and, therefore in the resulting surface chemistry of the two types of nanocrystals. The synthesized nanocrystals have been incorporated, by using an "ex situ" procedure, in different thermoplastic PMMA-based polymers, including PMMA co-polymer specifically functionalized by means of groups having high chemical affinity to nanocrystal surface, and the resulting nanocomposites have been processed in thin films. Spectroscopic steady state and time-resolved investigations, carried out both on nanocomposite solution and thin film samples, indicate as a change in the optical properties of the two steps nanocrystals is observed upon incorporation in polymers, especially in PMMA homopolymer, where significant aggregation of inorganic nanostructures occurs. On the contrary, the one pot CdSe/ZnS nanocrystals preserve in all investigated samples their long-lived radiative emission. Such nanocrystals result homogeneously dispersed in the polymers, providing high quality films and thus representing ideal candidates for future optical applications.

This study reports for the first time the use of a red-emitting AIEgen, i.e. TPE-AC, for the realization of efficient luminescent solar concentrators (LSCs) based on poly(methyl methacrylate) (PMMA) and polycarbonate (PC) thin films (25 +/- 5 mu m). TPE-AC is an AIEgen with D-A features that absorbs visible light in the range between 400 and 550 nm and emits fluorescence peaked at 600-620 nm, with a maximum quantum yield (QY) of 50% when dispersed (0.1-1.5 wt%) in PMMA and PC matrices. QY and lifetime investigations demonstrated that fluorescence quenching occurred with varying the TPE-AC concentration, even if the optical features were still significant even at the highest fluorophore content. Study of the LSCs' performances yielded worthy optical efficiencies of 6.7% for the TPE-AC/PC systems due to their superior light harvesting features and the compatibility of the AIEgen within the PC matrix.

A growing interest is devoted to the study of imidazolium-based ionic liquids as innovative materials to combine with functional elements for advanced technological applications. Materials based on semiconductor and oxide nanocrystals in ionic liquids can be promising for their integration in lithium batteries, as well as in innovative solar cells. Although the physical chemical properties and the solvation dynamics of bare ionic liquids have been extensively studied, their combination with colloidal nanocrystals still remains almost unexplored. Here, the optical properties of organic-capped luminescent cadmium selenide nanocrystals coated by a shell of zinc sulfide (CdSe(ZnS)) dispersed in 1,3-dialkyl imidazolium ionic liquids have been investigated, also in dependence of the alkyl chain length on the imidazolium ring and of the anion nature, by using both time-integrated and time-resolved optical spectroscopy. The observed variations in decay profiles of the ionic liquid in presence of colloidal nanocrystals suggest that the dispersion of the nanostructures induces modifications in the ionic liquid structural order. Finally, atomic force microscopy analysis has provided insight into the topography of the investigated dispersions deposited as film, confirming the organization of the ionic liquids in super-structures, also upon nanocrystal incorporation.

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.