Correlation coefficients (r) are shown for organochlorine concentrations (ng l −1 ) in snow and site elevation (m.a.s.l.) for the equation conc: ¼ ae b Elev: , where a and b are fitted constants. Asterisks show significance at P р 0:05, for 19 degrees of freedom. Sub-cooled liquid vapour pressures are included for pesticides at 20 ЊC (ref. 21) and PCBs at 25 ЊC (ref. 22). Published vapour pressures vary considerably, so these values represent mean reported values for all PCBs in that class. Ranges of published vapour pressures for each PCB category are shown in brackets.Only compounds with mean sample concentrations that were ten times higher than blanks were considered. † Present addresses:

A new series of panchromatic ruthenium(II) sensitizers derived from carboxylated terpyridyl complexes of tris-thiocyanato Ru(II) have been developed. Black dye containing different degrees of protonation [(C(2)H(5))(3)NH][Ru(H(3)tcterpy)(NCS)(3)] 1, [(C(4)H(9))(4)N](2)[Ru(H(2)tcterpy)(NCS)(3)] 2, [(C(4)H(9))(4)N](3)[Ru(Htcterpy)(NCS)(3)] 3, and [(C(4)H(9))(4)N](4)[Ru(tcterpy)(NCS)(3)] 4 (tcterpy = 4,4',4' '-tricarboxy-2,2':6',2' '-terpyridine) have been synthesized and fully characterized by UV-vis, emission, IR, Raman, NMR, cyclic voltammetry, and X-ray diffraction studies. The crystal structure of complex 2 confirms the presence of a Ru(II)N6 central core derived from the terpyridine ligand and three N-bonded thiocyanates. Intermolecular H-bonding between carboxylates on neighboring terpyridines gives rise to 2-D H-bonded arrays. The absorption and emission maxima of the black dye show a bathochromic shift with decreasing pH and exhibit pH-dependent excited-state lifetimes. The red-shift of the emission maxima is due to better pi-acceptor properties of the acid form that lowers the energy of the CT excited state. The low-energy metal-to-ligand charge-transfer absorption band showed marked solvatochromism due to the presence of thiocyanate ligands. The Ru(II)/(III) oxidation potential of the black dye and the ligand-based reduction potential shifted cathodically with decreasing number of protons and showed more reversible character. The adsorption of complex 3 from methoxyacetonitrile solution onto transparent TiO(2) films was interpreted by a Langmuir isotherm yielding an adsorption equilibrium constant, K(ads), of (1.0 +/- 0.3) x 10(5) M(-1). The amount of dye adsorbed at monolayer saturation was (n(alpha) = 6.9 +/- 0.3) x 10(-)(8) mol/mg of TiO(2), which is around 30% less than that of the cis-di(thiocyanato)bis(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II) complex. The black dye, when anchored to nanocrystalline TiO(2) films achieves very efficient sensitization over the whole visible range extending into the near-IR region up to 920 nm, yielding over 80% incident photon-to-current efficiencies (IPCE). Solar cells containing the black dye were subjected to analysis by a photovoltaic calibration laboratory (NREL, U.S.A.) to determine their solar-to-electric conversion efficiency under standard AM 1.5 sunlight. A short circuit photocurrent density obtained was 20.5 mA/cm(2), and the open circuit voltage was 0.72 V corresponding to an overall conversion efficiency of 10.4%.

No abstract

During the past five years, we have developed in our laboratory a new type of solar cell that is based on a photoelectrochemical process. The light absorption is performed by a monolayer of dye (i.e., a Ruthenium complex) that is adsorbed chemically at the surface of a semiconductor (i.e., titanium oxide (TiO2)). When excited by a photon, the dye has the ability to transfer an electron to the semiconductor. The electric field that is inside the material allows extraction of the electron, and the positive charge is transferred from the dye to a redox mediator that is present in solution. A respectable photovoltaic efficiency (i.e., 10%) is obtained by the use of mesoporous, nanostructured films of anatase particles. We will show how the TiO2 electrode microstructure influences the photovoltaic response of the cell. More specifically, we will focus on how processing parameters such as precursor chemistry, temperature for hydrothermal growth, binder addition, and sintering conditions influence the film porosity, pore‐size distribution, light scattering, and electron percolation and consequently affect the solar‐cell efficiency.

A preparation technique of TiO2 screen‐printing pastes from commercially‐available powders has been disclosed in order to fabricate the nanocrystalline layers without cracking and peeling‐off over 17 µm thickness for the photoactive electrodes of the dye‐sensitised solar cells. A conversion efficiency of 8·7% was obtained by using a single‐layer of a semi‐transparent‐TiO2 film. A conversion efficiency of 9·2% was obtained by using double‐layers composed of transparent and light‐scattering TiO2 films for a photon‐trapping system. Copyright © 2007 John Wiley & Sons, Ltd.