2.3. Evaluation of Photocatalytic Water Splitting 6507 2.3.1. Photocatalytic Activity 6507 2.3.2. Photocatalytic Stability 6507 3. UV-Active Photocatalysts for Water Splitting 6507 3.1. d0 Metal Oxide Photocatalyts 6507 3.1.1. Ti-, Zr-Based Oxides 6507 3.1.2. Nb-, Ta-Based Oxides 6514 3.1.3. W-, Mo-Based Oxides 6517 3.1.4. Other d0 Metal Oxides 6518 3.2. d10 Metal Oxide Photocatalyts 6518 3.3. f0 Metal Oxide Photocatalysts 6518 3.4. Nonoxide Photocatalysts 6518 4. Approaches to Modifying the Electronic Band Structure for Visible-Light Harvesting 6519

Semiconductor-based Photocatalytic Hydrogen Generation

Lanthanide-based luminescent hybrid materials.

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Lanthanide single-molecule magnets.

Gold nanorods: Synthesis, characterization and applications

Noble metal nanoparticles are capable of confining resonant photons in such a manner as to induce coherent surface plasmon oscillation of their conduction band electrons, a phenomenon leading to two important properties. Firstly, the confinement of the photon to the nanoparticle's dimensions leads to a large increase in its electromagnetic field and consequently great enhancement of all the nanoparticle's radiative properties, such as absorption and scattering. Moreover, by confining the photon's wavelength to the nanoparticle's small dimensions, there exists enhanced imaging resolving powers, which extend well below the diffraction limit, a property of considerable importance in potential device applications. Secondly, the strongly absorbed light by the nanoparticles is followed by a rapid dephasing of the coherent electron motion in tandem with an equally rapid energy transfer to the lattice, a process integral to the technologically relevant photothermal properties of plasmonic nanoparticles. Of all the possible nanoparticle shapes, gold nanorods are especially intriguing as they offer strong plasmonic fields while exhibiting excellent tunability and biocompatibility. We begin this review of gold nanorods by summarizing their radiative and nonradiative properties. Their various synthetic methods are then outlined with an emphasis on the seed-mediated chemical growth. In particular, we describe nanorod spontaneous self-assembly, chemically driven assembly, and polymer-based alignment. The final section details current studies aimed at applications in the biological and biomedical fields.

Gold Nanorods: From Synthesis and Properties to Biological and Biomedical Applications

Hydrogen production by photocatalytic alcohol reforming has been studied in the presence of a Pt/TiO2 photocatalyst. Nanocrystalline titania was deposited on glass slides by using a sol–gel process in the presence of surfactant template. Band-gap excitation of titania was made by using a low-energy Black-Light source. Water–ethanol mixtures proved the most efficient substrate for hydrogen production. This system demonstrated an impressive efficiency, which reached up to 74% active electron to incident photon ratio and 32% energy conversion efficiency.

Hydrogen production by photocatalytic alcohol reforming employing highly efficient nanocrystalline titania films

Strongly Luminescent Poly(ethylene glycol)-2,2′-bipyridine Lanthanide Ion Complexes

Steady-state luminescence spectroscopy and luminescence decay analysis have been employed to study the association of two rare earth ions (i.e., Eu3+ and Tb3+) with poly(ethylene glycol) in the absence and in the presence of 2,2‘-bipyridine, which acted as an antenna of near-UV radiation. Three different systems have been studied at various polymer concentrations, i.e., aqueous solutions, transparent composite organic/inorganic sol−gel matrixes made by hydrolysis of tetramethoxysilane, and polymer matrixes. The photophysical behavior of the luminescent species has been studied in conjunction with the poly(ethylene glycol) content. In both aqueous solutions and silica matrixes, luminescence intensity and decay time were found to increase by increasing polymer concentration. Addition of 2,2‘-bipyridine resulted in complex formation between the ligand and the lanthanide ions. This complex was stabilized by association with the polymer chains. Excitation at the ligand absorption wavelength (337 nm) resulted i...

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Intensely Luminescent Materials Obtained by Combining Lanthanide Ions, 2,2‘-Bipyridine, and Poly(ethylene glycol) in Various Fluid or Solid Environments

Hybrid organic/inorganic sol−gel materials have been synthesized by carboxylic acid solvolysis of (aminopropyl)triethoxysilane or ureasil precursors The hybrid nature of these gels is expanded with the introduction of silica esters A main feature of the ensuing materials is the formation of hybrid organic/inorganic nanoclusters, which are founded on silica backbone but they are facilitated and assisted also by forces arising from hydrophilic/hydrophobic balance and hydrogen-bonding interactions The silicious domains of these clusters with attached functional groups, for example, amino groups, are luminescence centers Some precursor compounds bearing amino groups without silicious groups but with a tendency to form clusters in solution also emit luminescence Luminescence is the result of electron−hole recombination on delocalized states so that emission wavelength depends on excitation wavelength Luminescence can thus be emitted in almost the entire visible spectrum and it can be tuned by choosing ex

Photoluminescence from Sol−Gel Organic/Inorganic Hybrid Gels Obtained through Carboxylic Acid Solvolysis

The mechanism of formation of gold particles by reduction of AuIII in solutions of alcyltrimethylammonium chloride surfactants was studied in the absence and in the presence of NaCl. AuIII anions interact strongly with trimethylammonium cations forming insoluble ion pairs (Torigoe et al. Langmuir 1992, 8, 59). Above the surfactant critical micelle concentration, the ion pairs are solubilized in the micelles returning to the solution. Gold particles were produced by photochemical reduction of the clear micellar solutions. The coupling between surfactant aggregation and inorganic crystallization phenomena in these systems was investigated using transmission electron microscopy (TEM), UV−vis, and time-resolved fluorescence spectroscopy. At concentrations close to the phase boundary of the L1 phase with the lyotropic liquid crystalline phases many gold particles have a threadlike morphology, as previously noted by Esumi et al. (Langmuir 1995, 11, 3285). The presence of NaCl modifies the micellar size and affe...

Vlasoula Bekiari

Papers

Hydrogen production by photocatalytic alcohol reforming employing highly efficient nanocrystalline titania films

Strongly Luminescent Poly(ethylene glycol)-2,2′-bipyridine Lanthanide Ion Complexes

Intensely Luminescent Materials Obtained by Combining Lanthanide Ions, 2,2‘-Bipyridine, and Poly(ethylene glycol) in Various Fluid or Solid Environments

Photoluminescence from Sol−Gel Organic/Inorganic Hybrid Gels Obtained through Carboxylic Acid Solvolysis

Gold colloids from cationic surfactant solutions. 1. Mechanisms that control particle morphology