Many properties provided by supramolecular chemistry, nanotechnology and catalysis only appear in solids exhibiting large surface areas and regular porosity at the nanometre scale. In nanometre-sized particles, the ratio of the number of atoms in the surface to the number in the bulk is much larger than for micrometre-sized materials, and this can lead to novel properties. Here we report the preparation of a hierarchically structured mesoporous material from nanoparticles of CeO(2) of strictly uniform size. The synthesis involves self-assembly of these 5-nm CeO(2) pre-treated nanoparticles in the presence of a structure directing agent (poly(alkylene oxide) block polymer). The walls of this hexagonal structured CeO(2) material are formed from the primary nanoparticles. The material possesses large pore volumes, high surface areas, and marked thermal stability, allowing it to be easily doped after synthesis whilst maintaining textural and mechanical integrity. It also exhibits a photovoltaic response, which is directly derived from the nanometric particle size-normal CeO(2) does not show this response. We have constructed operational organic-dye-free solar cells using nanometric ceria particles (in both mesostructured or amorphous forms) as the active component, and find efficiencies that depend on the illuminating power.

Chitosan is a N-containing biopolymer that can form high-quality films on glass, quartz, metals and other hydrophilic surfaces. Pyrolysis of chitosan films under argon at 800 °C and under inert atmosphere gives rise to high-quality single layer N-doped graphene films (over 99% transmittance) as evidenced by XPS, Raman spectroscopy, and TEM imaging.

The field of multifunctional materials has seen very rapid progress since the discovery of structures with a variety of technologically useful properties such as nanoporosity, [1][2][3] luminescence, and magnetism for sensors, [4][5][6] lasers, [7,8] nonlinear optics, [9] displays, [10] and electroluminescent devices.[11]After these discoveries, one of the most appealing aims is to explore multifunctionality, especially in designed materials, which combine in the same crystal a set of well-defined properties for specific applications. Lanthanide-based porous metal-organic frameworks (Ln-MOFs) [12][13][14][15][16][17] are excellent candidates to create multifunctional materials for sensors, provided that their photoluminescence and emission lifetimes are not influenced at ambient conditions by the presence of water. [5,[18][19][20] Existing Ln-MOF materials are thermally stable in air only up to approximately 673 K, [5,18,21] while pore diameters are too small to allow the diffusion of molecules of interest. [21,22] These properties preclude their use in luminescence sensors working in the presence of moisture at ambient temperature.MOFs that combine magnetic and anisotropic properties with high emission quantum yields under ambient conditions will open new possibilities for low-cost sensors.[23] Herein, we have synthesized, by rational design, novel crystalline MOFs containing rare-earth ions that combine hydrophobicity, high adsorption capacity, high thermal resistance, anisotropic photoluminescence, and magnetic properties. These materials preserve their photoluminescence properties in the presence of water and show excellent sensor capabilities.For achieving the above properties, we have chosen an organic spacer that fulfils the following requirements: high hydrophobicity, antenna effect, strong interaction with the metal center, and at least two coordination centers in order to obtain microporous 3D structures. High hydrophobicity was attained with ultrahydrophobic ligands, such as multiaromatic and C(sp 3 ) fluorinated spacers. The antenna effect can be present in a spacer with aromatic or multiaromatic groups. Moreover, rare-earth ions have high affinity for oxygencontaining molecules, for example those with carboxy groups, which produce robust framework architectures.[24] One spacer that fulfills the above requirements and that can be adequate to synthesize MOFs [25][26][27] is 4,4'-(hexafluoroisopropylidene)-bis(benzoic acid) (HFIPBB).Herein, under appropriate synthesis conditions and in the presence of HFIPBB, new Ln 3+ -based materials ITQMOF-1 and ITQMOF-2 (ITQMOF = Instituto de Tecnologia Quimica Metal Organic Framework), with similar properties but different crystallographic structures, have been obtained. To obtain the desired properties (luminescence and magnetism), different samples have been prepared with all the Ln elements except for the radioactive promethium. For mixed Ln 3+ samples, their molar composition (%) is given in parenthesis.The ITQMOF-1 material was obtained by reacting the HFIPBB...

The physical origin of the open‐circuit voltage in bulk heterojunction solar cells is still not well understood. While significant evidence exists to indicate that the open‐circuit voltage is limited by the molecular orbital energies of the heterojunction components, it is clear that this picture is not sufficient to explain the significant variations which often occur between cells fabricated from the same heterojunction components. We present here an analysis of the variation in open‐circuit voltage between 0.4–0.65 V observed for a range of P3HT/PCBM solar cells where device deposition conditions, electrode structure, active‐layer thickness and device polarity are varied. The analysis quantifies non‐geminate recombination losses of dissociated carriers in these cells, measured under device operating conditions. It is found that at open‐circuit, losses due to non‐geminate recombination are sufficiently large that other loss pathways may effectively be neglected. Variations in open‐circuit voltage between different devices are shown to arise from differences in the rate coefficient for non‐geminate recombination, and from differences in the charge densities in the photoactive layer of the device. The origin of these differences is discussed, particularly with regard to variations in film microstructure. By separately quantifying these differences in rate coefficient and charge density, and by application of a simple physical model based upon the assumption that open‐circuit is reached when the flux of charge photogeneration is matched by the flux of non‐geminate recombination, we are able to calculate correctly the open‐circuit voltage for all the cells studied to within an accuracy of ±5 mV.

A soluble, functionalized Py-SWNT has been synthesized and characterized by solution (1)H and (13)C NMR, FT-Raman, and electron microscopy. Experimental data indicate that Py-SWNT has short tubes with pentyl esters at the tips and pyridyl isoxazolino units along the walls. The synthesis of Py-SWNT is based on a 1,3-dipolar cycloaddition of a nitrile oxide on the SWNT walls, similar to 1,3-dipolar cycloadditions that are common for fullerene functionalization. The resulting Py-SWNT forms a complex with a zinc porphyrin (ZnPor) in a way similar to that reported for pyridyl-functionalized [60]-fullerenes. Formation of this metal-ligand complex was firmly established by a detailed electrochemical study. However, in contrast to the behavior observed for the ZnPor/Py-C(60) complex, photochemical excitation of the complex between ZnPor/Py-SWNT does not lead to electron transfer with the generation of charge-separated states. Fluorescence and laser flash studies indicate that the main process is energy transfer from the singlet ZnPor excited state to the Py-SWNT with observation of emission from Py-SWNT. Triplet ZnPor excited-state quenching by Py-SWNT is only observed in polar solvents such as DMF, but not in benzonitrile.

A round robin for the performance of roll-to-roll coated flexible large-area polymer solar-cell modules involving 18 different laboratories in Northern America, Europe and Middle East is presented. The study involved the performance measurement of the devices at one location (Risø DTU) followed by transportation to a participating laboratory for performance measurement and return to the starting location (Risø DTU) for re-measurement of the performance. It was found possible to package polymer solar-cell modules using a flexible plastic barrier material in such a manner that degradation of the devices played a relatively small role in the experiment that has taken place over 4 months. The method of transportation followed both air-mail and surface-mail paths

No abstract

No abstract