ABSTRACT
Organosilica spheres functionalized with two different photoactive units, diphenylanthracene, DPA@SPH, and viologen, VIO@SPH, covalently linked to the silica framework are prepared. These new materials have a uniform diameter, 300 nm for the DPA@SPH and 550 nm for the VIO@SPH, and exhibit the typical photochemical response of the organic moieties. It is observed that organic radical cations incorporated in the structure of the functionalized silica spheres are remarkably persistent. Due to their morphology and regular diameter DPA@SPH do not tend to aggregate and they form a highly regular, ordered and homogeneous multilayer film of high surface coverage which is employed as the active layer for the preparation of an electroluminescence cell.
ABSTRACT
Two layered zirconium phosphates containing Ru(bpy)(3)(2+) mono- or diphosphonates and diquat, {Ru(bpy)(3)(2+)[]/ZrP/DQ(++)} and Ru(bpy)(3)(2+)[]/ZrP/DQ(++), covalently attached to the phosphate layers exhibit notable photovoltaic response (the maximum V(OC), J(SC), and FF were 0.093 V, 16.8 microA cm(-2) and 0.33, respectively). The photocurrent spectra indicate that the photovoltaic response is due predominantly to direct photoexcitation of gamma-ZrP host, Ru(bpy)(3)(2+) and diquat acting as hole and electron traps, respectively, for the charge separated state of the semiconductor.
ABSTRACT
Tin oxide nanoparticles (2-5 nm) have been structured using CTAB surfactant into mesoporous mpSnO(2) materials that exhibit lower electrical resistivity than the precursors SnO(2) nanoparticles and over nine orders the magnitude lower than that of mesoporous MCM-41 silica. The superior performance of these conductive mesoporous mpSnO(2) materials as hosts is clearly manifested by the fact that a conjugated polymer with 2,5-dimethoxyphenylenevinylene structure emits light at voltages below 10 V direct current when incorporated in mpSnO(2) materials, but not in analogous mesoporous MCM-41 silica or when adsorbed on the nonporous precursor SnO(2) nanoparticles.
ABSTRACT
Although the [CB(11)H(12)](-) carborane does not exhibit an absorption band in UV, its triplet excited state can be generated upon 308 nm laser excitation; also unexpectedly carborane acts as electron donor forming a charge transfer complex with methylviologen that upon illumination gives rise to viologen radical cation.
ABSTRACT
2,4,6-Triphenylpyrylium (TP(+)) forms host-guest complexes with cucurbiturils (CBs) in acidic aqueous solutions. (1)H NMR spectroscopic data indicates that complexation takes place by encapsulation of the phenyl ring at the four position within CB. Formation of the complex with CB[6] and CB[7] leads to minor shifts in the fluorescence wavelength maximum (lambda(fl)) or quantum yield (Phi(fl)). In sharp contrast, for complexes with CB[8], the emission results in the simultaneous observation of fluorescence (lambda(fl)=480 nm, Phi(fl)=0.05) and room-temperature phosphorescence (lambda(ph)=590 nm, Phi(ph)=0.15). The occurrence of room-temperature phosphorescence can be used to detect the presence of CB[8] visually in solution. Molecular modeling and MM2 molecular mechanics calculations suggest that this effect arises from locking the conformational mobility of the 2- and 6-phenyl rings as a result of CB[8] encapsulation. The remarkably high room-temperature phosphorescence quantum yield of the TP(+)@CB[8] complex has been advantageously applied to develop an electroluminescent cell that contains this host-guest complex. In contrast, analogous cells prepared with TP(+) or TP(+)@CB[7] fail to exhibit electroluminescence.
ABSTRACT
We have used porous anodised Al(2)O(3) membranes as inert matrix for constructing and organizing spatially ternary donor/conductor/acceptor (DCA) systems exhibiting photovoltaic cell activity on the micrometric-length scale. These DCA triads were built stepwise by first growing a conducting polymer inside the membrane pores, thus forming nanorods that completely fill the internal pore space of the membrane. Then, an electron donor and an electron acceptor were adsorbed one on each side of the membrane, so that they were separated by a distance equal to the membrane thickness (ca. 60 microm), but electronically connected through the conductive polymer. When this device was placed between two electrodes and irradiated with visible light, electrons jumped from the donor molecule, crossed the membrane from side to side through the conductive polymer (a journey of about 60 microm!) until they finally reach the acceptor molecule. In so doing, an electric voltage was generated between the two electrodes, capable of maintaining an electric current flow from the membrane to an external circuit. Our DCA device constitutes the proof of a novel concept of photovoltaic cells, since it is based on the spatial organization at the micrometric scale of complementary, but not covalently linked, electron-donor and electron-acceptor organic species. Thus, our cell is based in translating photoinduced electron transfer between donors and acceptors, which is known to occur at the molecular nanometric scale, to the micrometric range in a spatially organised system. In addition our cell does not need the use of liquid electrolytes in order to operate, which is one of the main drawbacks in dye-sensitised solar cells.
