Here we report the synthesis and characterization of five new organic dyes based on 2-(1,1-dicyanomethylene)rhodanine, which simultaneously serves as an efficient electron-acceptor moiety and anchoring unit to the TiO2. Triphenylamine was used as the electron donor and a vinylthiophene unit was introduced to increase the pi-conjugation of the system and to widen the absorption region. The dye containing two 2-(1,1-dicyanomethylene)rhodanine units and no thiophene units showed the best photovoltaic performance with a short-circuit photocurrent density of 7.76 mA/cm(2), an open circuit photovoltage of 0.62 V, and a fill factor of 0.68, corresponding to an overall conversion efficiency of 3.78% under AM 1.5 irradiation (100 mW/cm(2)). (C) 2014 Elsevier Ltd. All rights reserved.

Four new organic dyes, 1–4, containing triphenylamine (TPA) donors connected through different acetylene linkages to fluorene bridges and cyanoacrylic acid acceptors were designed and synthetized for photoconversion in dye sensitized solar cells (DSSCs). Their absorption spectra, electrochemical and photovoltaic properties were investigated. Shortening the bridge between the TPA moiety and the anchoring group leads to a dramatic increase in the overall photoconversion efficiency (1>3>4>2).

The soft chemical route was used in the synthesis of undoped and 5% Mn doped ZnO nanocrystalline powders. XRD, TEM, TGA/DTA, FTIR, and superconducting quantum interference device techniques were used to study the structural, nano/microstructural, thermal decomposition and metastability aspects as a function of calcination temperatures (400-1100 degrees C) and magnetic properties. The evolution of the major wurtzite phase (ZnO) and minor non-stoichiometric nanocrystalline defect cubic spinel phase (ZnMnO3-) at various temperatures is clearly seen. The magnetic hysteresis loop is observed at room temperature in the undoped and doped samples calcined at 400 degrees C. Interestingly, the hysteresis loop parameters (M-s, H-c) are found to enhance dramatically as soon as the concentration of the minor phase is large enough up to the calcination temperature 700 degrees C. In contrast, the magnetic hysteresis loop vanishes slowly for the sample calcined at 1000 degrees C, it disappears completely. The room temperature ferromagnetic behavior at 400 degrees C is understood in terms of intrinsic cationic/anionic defects, extrinsic defects associated with the various species chemisorbed on the surface of the nanoparticles of undoped and Mn doped ZnO. During thermal annealing a nanocrysatllline seconadary phase of non-stoichiometric defect cubic spinel ZnMnO3- is formed, contributing to the enhancement of ferromagnetic behavior. All our experimental results are discussed in terms of model comparing various structural and localized electronic defects formed in the nanocrystalline powder. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

A simple two step strategy was developed to introduce carboxyl groups via Vilsmeier-Haack formylation on the commercially available conjugated polymer BEHP-co-MEH PPV followed by Knoevenagel condensation. Adsorption of the carboxyl-modified polymer onto TiO2 film and J-V curves were studied for the dye sensitized solar cell and compared with the base polymer BEHP-co-MEH PPV. Carboxyl-modification of BEHP-co-MEH PPV resulted in significant enhancement in the efficiency (3%), compared to the base polymer which showed an efficiency of only 0.3%. The details of the synthetic procedure, characterization and the photovoltaic property measurements are presented and discussed.

Anatase TiO2 nanoparticles dressed with gold nanoparticles were synthesized by hydrothermal process by using mixed precursor and controlled conditions. Diffused Reflectance Spectra (DRS) reveal that in addition to the expected TiO2 interband absorption below 360 nm gold surface plasmon feature occurs near 564 nm. It is shown that the dye sensitized solar cells made using TiO2-Au plasmonic nanocomposite yield superior performance with conversion efficiency (CE) of similar to 6% (no light harvesting), current density (J(SC)) of similar to 13.2 mA/cm(2), open circuit voltage (V-oc) of similar to 0.74 V and fill factor (FF) 0.61; considerably better than that with only TiO2 nanoparticles (CE similar to 5%, J(SC) similar to 12.6 mA/cm(2), V-oc similar to 0.70 V, FF similar to 0.56). (C) 2012 Elsevier Ltd. All rights reserved.

Thin anatase TiO2 nanoleaves (NLs) with high surface area (similar to 93 m(2)/g) are synthesized by hydrothermal route and dye-sensitized solar cells (DSSC) made using such NLs are compared with those made with hydro-thermally synthesized TiO2 nanoparticles and the Degussa P25 powder. The NLs-based DSSCs show increment of 16% and 24% in the total conversion efficiency over the cells made with NPs and P25 respectively. Interestingly, the highest increment in the conversion efficiency (similar to 35%) is achieved for cells made using a 50:50 (wt/wt) mixture of NLs and NPs. In this case the dye loading is found to be >50% higher than the case of NP films. Moreover the DC resistance of diffusion of I-3(-) in electrolyte (as revealed by the electrochemical impedance spectroscopy) is substantially lower than the NP film case, other cell parameters being nominally comparable. (C) 2011 Elsevier Ltd. All rights reserved.

In this work we report on the synthesis of various ZnO mesostructures (rods, spheres, flakes and flower-like morphologies) by hydrothermal and co-precipitation methods and their remarkable and complete transformation into anatase TiO2 mesostructures with nominally similar shapes using controlled low temperature TiCl4 treatment. Various techniques are used to demonstrate the phase purity and morphology details. Based on the careful examination of the transformation of ZnO rods into TiO2 tubes we suggest a mechanism which embodies initial formation of a thin TiO2 shell on the ZnO surface by ion exchange (Ti4+-Zn2+) followed by Zn diffusion through the shell and its oxidation on the surface. We used these converted TiO2 mesostructures for light harvesting in Dye Sensitized Solar Cells (DSSCs) to enhance the conversion efficiency. It is shown that DSSCs made using a doctor bladed film of TiO2 nanoparticles with an overlayer of TiCl4 treated ZnO flowers yield a solar cell efficiency of 6.9% which is considerably higher than that with only TiO2 nanoparticle film (5.4%) of comparable thickness.

Stannic oxide (SnO2) nanoparticles have been suspended in polyvinyl alcohol (PVA) matrix in different PVA: SnO2 molar ratios ranging from 1:1 to 1:5 using simple chemical route. This suspension was deposited on ceramic substrate and upon drying was carefully detached from the substrate. SnO2-embedded self-standing, transparent and flexible thin films were hence synthesized. Transmission electron microscopy (TEM) and Xray diffraction (XRD) techniques show the rutile tetragonal structure of SnO2 with particle size similar to 5 nm. UV-Visible spectroscopy demonstrates the band gap of 3.9 eV, which does not alter when embedded in polymer. Fourier transform infrared spectroscopy (FTIR) reveals that the properties of SnO2 do not modify due to incorporation in the PVA matrix. The structures work as excellent humidity sensors at room temperature. For a critical PVA:SnO2 molar ratio of 1:3, the resistance changes to five times of magnitude in 92% humidity within fraction of second when compared with resistance at 11% humidity. The sample regains its original resistance almost instantaneously after being removed from humid chamber. Nanodimensions of SnO2 particles and percolation mechanism related to transport through polymer matrix and water molecule as a carrier has been used to understand the mechanism. (C) 2008 Elsevier B.V. All rights reserved.

A 50% enhancement in the conversion efficiency (4.9-7.37%) is realized in dye-sensitized solar cells using hydrothermally synthesized TiO(2)-multiwalled carbon nanotube (MWCNT) nanocomposites as compared to hydrothermally synthesized TiO(2) without MWCNT and Degussa P25. Several characterizations have been employed to reveal the nature of the modification imparted to the MWCNTs under hydrothermal processing conditions and the resulting TiO(2)-MWCNT conjugation through -COOH groups. Efficient charge transfer in the nanocomposite and efficient electron transport by MWCNT (significantly higher incident-photon-to-current conversion efficiency) are suggested to be the possible reasons for the enhancement.

The ZnO nanoflowers loaded with gold (Au) nanoparticles (NPs) are synthesized by a hydrothermal route using mixed precursors and controlled conditions. The dye-sensitized solar cells based on the ZnO nanoflowers with Au NPs show power conversion efficiency of 2.5%, which is considerably higher than that of ZnO nanoflowers without Au NPs. Detailed characterizations are performed, presented, and discussed.

Formation of CdS quantum dots (Q dots) on the vertically aligned ZnO nanorods electrode was carried out by chemical bath deposition. The diameter and thickness of ZnO nanorods are ∼100–150nm and ∼1.6μm, respectively, and CdS Q dots on ZnO nanorods have a diameter of smaller than 15nm. In application of the Q dots-sensitized solar cells, composite film exhibited a power conversion efficiency of 0.54% under air mass 1.5 condition (80mW/cm2), and incident-photon-to-current conversion efficiency showed 18.6%.

Fungal nanosynthesis of ternary CuAlO2 phase is achieved at 50 degrees C. This phase is chemically difficult to synthesize at low temperatures because of the incompatible oxidation chemistry of Cu and Al. The synthesized protein-capped water-dispersible nanoparticles show blue luminescence and radio-frequency absorption (see figure).

A nanosynthesis scheme is demonstrated which renders excellent control of nanoparticle shape, size, and dispersity in a solution based synthesis process. The scheme, termed as percolative microcavity synthesis, involves the use of a granular medium with percolative microcavities which facilitate nearly similar grain size/shape dependent reaction zones limiting intrinsic growth inhomogeneities, enabling particle size/shape control. The viability of the process is demonstrated for the synthesis of gold nanoparticles by a plant extract based biological method as well as a chemical method.