Titanium Dioxide Nanomaterials: Synthesis, Properties, Modifications, and Applications

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Principles Of Fluorescence Spectroscopy

Two-photon excitation provides a means of activating chemical or physical processes with high spatial resolution in three dimensions and has made possible the development of three-dimensional fluorescence imaging, optical data storage, and lithographic microfabrication. These applications take advantage of the fact that the two-photon absorption probability depends quadratically on intensity, so under tight-focusing conditions, the absorption is confined at the focus to a volume of order λ3 (where λ is the laser wavelength). Any subsequent process, such as fluorescence or a photoinduced chemical reaction, is also localized in this small volume. Although three-dimensional data storage and microfabrication have been illustrated using two-photon-initiated polymerization of resins incorporating conventional ultraviolet-absorbing initiators, such photopolymer systems exhibit low photosensitivity as the initiators have small two-photon absorption cross-sections (δ). Consequently, this approach requires high laser power, and its widespread use remains impractical. Here we report on a class of π;-conjugated compounds that exhibit large δ (as high as 1, 250 × 10−50 cm4 s per photon) and enhanced two-photon sensitivity relative to ultraviolet initiators. Two-photon excitable resins based on these new initiators have been developed and used to demonstrate a scheme for three-dimensional data storage which permits fluorescent and refractive read-out, and the fabrication of three-dimensional micro-optical and micromechanical structures, including photonic-bandgap-type structures.

Two-photon polymerization initiators for three-dimensional optical data storage and microfabrication

A surface science perspective on TiO2 photocatalysis

Polymeric ionic liquids: Broadening the properties and applications of polyelectrolytes

We report a novel, non-hydrolytic route to ZnO nanocrystals by means of thermal decomposition of zinc acetate (ZnAc2) in alkylamines, in the presence of tert-butylphosphonic acid (TBPA). The slow heating of an alkylamine/TBPA/ZnAc2 mixture is a simple, safe, and scalable approach to synthesize ZnO nanocrystals from handy chemicals. The obtained ZnO nanocrystals were characterized by UV-vis absorption, photoluminescence (PL) and infrared (FT-IR) spectroscopies, and by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The growth of ZnO particles in the nanoscopic regime and their final size were governed by the TBPA/ZnAc2 molar ratio in the reaction mixtures. The various roles played by TBPA in the conditions of the synthesis are discussed on the basis of the experimental evidence. The presented synthetic approach provides a unique tool for designing the synthesis of ZnO crystals of a desired size in the nanoscale regime and can be potentially extended to other nanoscale materials.

ZnO Nanocrystals by a Non-hydrolytic Route: Synthesis and Characterization

Nano-objects on a round trip from water to organics in a polymeric ionic liquid vehicle.

The controversial nature of the fluorescent properties of carbon dots (CDs), ascribed either to surface states or to small molecules adsorbed onto the carbon nanostructures, is an unresolved issue. To date, an accurate picture of CDs and an exhaustive structure–property correlation are still lacking. Using two unconventional spectroscopic techniques, fluorescence correlation spectroscopy (FCS) and time-resolved electron paramagnetic resonance (TREPR), we contribute to fill this gap. Although electron micrographs indicate the presence of carbon cores, FCS reveals that the emission properties of CDs are based neither on those cores nor on molecular species linked to them, but rather on free molecules. TREPR provides deeper insights into the structure of carbon cores, where C sp2 domains are embedded within C sp3 scaffolds. FCS and TREPR prove to be powerful techniques, characterizing CDs as inherently heterogeneous systems, providing insights into the nature of such systems and paving the way to standardiza...

Spectroscopic Insights into Carbon Dot Systems.

An extensive optical and photoelectrochemical study of blended systems composed of organic-capped TiO2 nanocrystals with either a spherical or rodlike morphology and a conjugated polymer, MEH-PPV, ...

M. Lucia Curri

Papers

ZnO Nanocrystals by a Non-hydrolytic Route: Synthesis and Characterization

Nano-objects on a round trip from water to organics in a polymeric ionic liquid vehicle.

Spectroscopic Insights into Carbon Dot Systems.

Colloidal TiO2 nanocrystals/MEH-PPV nanocomposites: photo(electro)chemical study.

Efficient charge storage in photoexcited TiO2 nanorod-noble metal nanoparticle composite systems