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The paper explored the mechanism of working of dye sensitizers for the improvement of efficiency of environmentally benign dye-sensitized solar cells (DSSC). The identified natural dyes namely anthocyanin (A), betalain (B) and chlorophyll (C) were extracted from Roselle (Hibiscus sabdariffa L.), spinach (Spinacia oleracea) and beetroot (Beta vulgaris) respectively. Light absorption performance of dyes was recorded by ultraviolet-visible (UV-vis) spectroscopic analysis followed by direct and indirect band gap calculation. The effect of functional groups present in the dyes studied by Fourier transform infrared spectroscopy (FTIR) and binding of the dyes on TiO 2 through surface morphology of sheets was identified employing field emission scanning electron microscopy (FESEM). Photovoltage characteristics (I-V) and induced photon to current efficiency (IPCE) measurements were also noted followed by the stability studies. The N3 (synthetic dye chosen for the reference) dye-based cell showed the highest efficiency of 6.19% out of all of 11 cells fabricated using different sensitizers. The DSSC fabricated using the novel mixed dye (ABC) mixture gave the highest efficiency of 3.73%, however it showed similar drop (almost 22%) in efficiency as that with of N3 dye in stability studies. The mechanism for the increase in the overall power conversion efficiency of DSSC was also suggested.

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A new calix [4]resorcinarene bearing eight hydroxamic acid groups (C4RAHA) has been synthesized and characterized by FT-IR, 1 H-NMR and elemental analysis. Its analytical properties were investigated, and showed high affinity and selectivity toward thorium(IV) in the presence of large quantities of associated metal ions. Thorium(IV) was extracted from an ethyl acetate solution of C4RAHA at pH 4.5. The λmax and molar absorptivity (ε) for thorium(IV) were 341 nm and 7120 l mol -1 cm -1 . The complexation of thorium(IV) with C4RAHA has a 4:1 metal:ligand stoichiometry, which is relatively rare. The extracts were directly aspirated in the plasma for ICP-AES measurements for thorium(IV) in the presence of a diversified matrix. The system obeyed Beer's law over the range 0.1 -6.5 µg ml -1 of thorium(IV) with a Sandell sensitivity of 0.0325 µg cm -2 . The preconcentration factor and overall stability constant evaluated at 25˚C for thorium(IV) were 133 and 15.86, respectively. The complexation was characterized by a favorable enthalpy change. A liquid-membrane transport study of thorium(IV) was carried out from the source to the receiving phase under controlled conditions, and a mechanism of transport proposed. To check the validity of the proposed method, thorium(IV) was determined in monazite sand, rare earth sand and water samples.

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