The effect of ethylene glycol/citric acid molar ratio in the initial precursor of TiO2 nanoparticle paste synthesized by a polymerizable complex method on the photovoltaic properties of dye-sensitized solar cells

A polymerizable complex method, also known as a Pechini method, was employed to synthesize titanium-sol (Ti-sol) as a matrix for TiO₂ nanoparticle paste, suitable for fabrication of semiconducting mesoporous TiO₂ layer as a photoanode of dye-sensitized solar cells (DSSCs). The purpose of the present work was to investigate the effect of ethylene glycol (EG)/citric acid (CA) molar ratio (Z), in the initial Ti-sol precursor, on the photovoltaic properties of DSSCs. From viscosity (µ) measurement and Fourier transform infrared (FTIR) spectrum of Ti-sols it was revealed that the amount of polyester in the sol decreases with increasing Z. The higher polyester content in the Ti-sols with lower Z ratios led to their higher surface tension (γ) and as a result the higher contact angle (α). The low wettability of fluorine doped tin oxide (FTO) coated glass with Ti-sol was the main reason of micro-cracking of TiO₂ layers after sintering. This effect was significant for lower Z ratios. Micro-cracks increase the back electron–hole recombination rate. Also, at higher Z ratio, the back electron–hole recombination rate increased, which was due to the lower Ti⁴⁺ ions in the Ti-sol precursor and poor interconnection between TiO₂ nanoparticles. Therefore, the maximum short circuit current density (I_sc) and the maximum conversion efficiency (η) were obtained for Z=4. Fill factor (FF) decreased with increasing Z. But, open circuit voltage (V_oc) was nearly independent of Z.     

Comparison of structural,spectral and magnetic properties of NiO nanofibers obtained by sol–gel electrospinning from two different polymeric binders

NiO is a p-type semiconductor with wide band gap energy. In this study, nickel oxide nanofibers were fabricated by sol–gel electrospinning followed by high temperature calcination, using two sacrificial polymeric binders. Poly(2-ethyl-2-oxazoline) (PEtOx) in water and styrene-acrylonitrile random copolymer (SAN) in N,N- dimethylformamide (DMF) along with nickel (II) acetate tetrahydrate (NATH), as metal oxide precursor, were the two distinct polymeric systems used in this study. The morphological and structural properties of NiO fibers obtained from the aforementioned systems were compared with each other. The degradation behavior of the sacrificial polymeric binder imparted a significant effect on the properties of the obtained NiO fibers. The grain sizes and the activation energies for grain growth of NiO fibers from two systems were different. The non-stoichiometric NiO fibers obtained from the SAN/NATH system had a better ferromagnetic behavior as compared with that produced from the PEtOx/NATH system. This non-stoichiometry made a difference also in the optical band gap energies of the NiO nanofibers.     

Removal of zirconium from spent fuel solution by alginate gel polymer

The uptake behaviour of zirconium (Zr) in alginate gel polymer and removal of Zr from spent fuel solution have been studied by the batch and column methods. As a first step, alginate gel polymer was synthesized and conditioned. The uptakes of Zr were examined in several concentrations of HNO₃ solution (from 0.01 M to 9 M HNO₃) by a batch method. Stronger affinity of Zr was shown than strontium (Sr), cobalt (Co), uranium (U) and iron (Fe) in 1 M HNO₃. It has been reported that cation binding was stronger with ions of higher charge in the alginate gel polymer. In contrast, the free aqueous ion, Zr⁴⁺, is the dominant form of the Zr species in very acidic solution. Therefore, the strong affinity of Zr is explained. The uptake rate of Zr was also evaluated in 2.6 M HNO₃ solution, which was close to the HNO₃ concentration in actual HLLW from fuel reprocessing. The uptake of Zr reached equilibrium within 2 h. For the column experiment, fission products (FPs) solution containing rare earth elements (REEs), platinum group metals, alkaline metals, alkaline earth metals and the other elements was prepared from actual spent fuel and the concentration of HNO₃ was adjusted to 2.6 M. In the column experiment, the alginate gel polymer was packed into a column, and then a chromatographic experiment was performed using the FPs solution prepared from actual spent fuel. As a result, over 95% of the Zr was removed from the FPs solution. Molybdenum (Mo), technetium (Tc), yttrium (Y), palladium (Pd), tellurium (Te), cesium (Cs) and REEs were eluted by the successive use of H₂O, and 1 M and 3 M HNO₃.     

Efficient dye-sensitized solar cells based on CNTs and Zr-doped TiO2 nanoparticles

The light scattering, harvesting and adsorption effects in dye-sensitized solar cells (DSSCs) are studied by preparation of coated carbon nanotubes (CNTs) with TiO₂ and Zr-doped TiO₂ nanoparticles in the forms of mono- and double-layer cells. X-ray diffraction (XRD) analysis reveals that the phase composition of Zr-doped TiO₂ electrode is a mixture of anatase and rutile phases with major rutile content, whereas it is the same mixture with major anatase content for coated CNTs with TiO₂. Furthermore, the average crystallite size of Zr-doped TiO₂ electrode is slightly decreased with Zr introduction. Field emission scanning electron microscope (FE-SEM) images show that the porosity of Zr-doped TiO₂ electrodes is higher than that of undoped electrode, enhancing dye adsorption. UV–visible spectroscopy analysis reveals that the absorption onset of Zr-doped TiO₂ electrodes is slightly shifted to longer wavelength (the red-shift) in comparison with that of undoped TiO₂ electrode. Moreover, the band gap energy of TiO₂ nanoparticles is decreased by Zr introduction, enhancing light absorption. It is found that electron injection of monolayer TiO₂ electrode is improved by introduction of 0.025 mol% Zr, resulted in enhancement of its power conversion efficiency (PCE) up to 6.81% compared with 6.17% for pure TiO₂ electrode. Moreover, electron transport and light scattering are enhanced by incorporation of 0.025 wt% coated CNTs with TiO₂ in the over-layer of double layer electrode. Therefore, double layer solar cell composed of 0.025 mol% Zr-doped TiO₂ nanoparticles as the under-layer and mixtures of these nanoparticles and 0.025 wt% coated CNTs with TiO₂ as the over-layer shows the highest PCE of 8.19%.     

Weatherability of hybrid organic–inorganic silica protective coatings on glass

Currently, there is a growing interest in the application of silicon-based technologies for the development of advanced hybrid organic–inorganic coatings with strong weatherability. In this study, the sol–gel process is used to prepare such coatings on glass and their resistance to weathering effects is assessed afterwards. Various sols were prepared by mixing a silica-based inorganic matrix (tetraethyl orthosilicate) with different quantities of silica alkoxides functionalised with various organic groups. Subsequently, the sols were dip-coated onto glass samples at low temperatures without any heat treatment. The coatings prepared were analysed before and after three model ageing tests simulating various weathering parameters. After ageing, the best performing coatings showed good overall homogeneity and transparency (optical microscopy, SEM), improved water repellency and adhesion to the glass substrate (static contact angle measurements, cross-cut tape tests) and no colour or chemical composition changes (UV–VIS, FTIR). Compared with commercial hybrid silica products, the alkyl- and methacryloxy-functionalised silica coatings particularly displayed improved homogeneity, elasticity and barrier properties. Thus, these low temperature coatings, easily applicable to thin films, appear to fulfil the main requirements for the protection of the glass exposed to weathering phenomena.     

Fabrication of CuInS2/CNTs absorber layers by sol–gel method

In this work, CuInS₂/multiwalled carbon nanotube (MWCNT) layers are fabricated by the sol–gel spin-coating method. We introduce two forms of MWCNTs into a CIS₂ solution, washed functional multiwalled carbon nanotubes (W-FMWCNTs) and unwashed-functional multiwalled carbon nanotubes (UW-FMWCNTs), in order to investigate the effects of MWCNTs and an acidic environment on the physical properties of the CIS₂ absorber layers. The structure and morphology of the samples are investigated by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), respectively. The XRD study shows that all samples crystallize in a tetragonal structure. The results obtained from the optical, thermo-electric, and electrical measurements indicate that the two groups of CIS₂ layers prepared using W- and UW-FMWCNTs show the opposite behaviors. The Seebeck coefficient (SC) measurements indicate possible formation of a p–n junction.     

Weak Delocalization in Graphene on a Ferromagnetic Insulating Film

Graphene has been predicted to develop a magnetic moment by proximity effect when placed on a ferromagnetic film, a promise that could open exciting possibilities in the fields of spintronics and magnetic data recording. In this work, the interplay between the magnetoresistance of graphene and the magnetization of an underlying ferromagnetic insulating film is studied in detail. A clear correlation between both magnitudes is observed but through a careful modeling of the magnetization and the weak localization measurements, that such correspondence can be explained by the effects of the magnetic stray fields arising from the ferromagnetic insulator is found. The results emphasize the complexity arising at the interface between magnetic and 2D materials.     

Long-term sustained-released in situ gels of a water-insoluble drug amphotericin B for mycotic arthritis intra-articular administration: preparation,in vitro and in vivo evaluation

Amphotericin B (AMB) was often used in intra-articular injection administration for fungal arthritis, because it could often bring a satisfactory therapeutic efficacy and a minimum systemic toxic side effect. However, because of the multiple operations and the frequent injections, the compliance of the patients was bad. Therefore, to develop a long-term sustained-released preparation of AMB for mycotic arthritis intra-articular administration is of great significance. The purpose of present study was to develop a long-term sustained-released in situ gel of a water-insoluble drug AMB for mycotic arthritis intra-articular administration. Based on the evaluations of the in vitro properties of the formulations, the formulation containing 10% (w/w) ethanol, 15% (w/w) PG, 0.75% (w/w) HA, 5% (w/w) purified soybean oil, 0.03% (w/w) α-tocopherol, 15% (w/w) water and 55% (w/w) glyceryl monooleate was selected as a suitable intra-articular injectable in situ gel drug delivery system for water-insoluble drug AMB. Furthermore, the results of the in vivo study on rabbits showed that the selected formulation was a safe and effective long-term sustained-released intra-articular injectable AMB preparation. Therefore, the presented in situ AMB gel could reduce the frequency of the administration in the AMB treatment of fungal arthritis, and then would get a good patient compliance.     

Sol–gel synthesis of Nd-doped BiFeO3 multiferroic and its characterization

Neodymium doped bismuth ferrite (BiFeO₃, BFO) nanoparticles were successfully synthesized by a facile sol–gel route. The influence of annealing temperature, time, Bi content and solvent on the crystal structure of BFO was studied. Results indicated that the optimum processing condition of BFO products was 550–600 °C/1.5 h with excess 3–6% Bi and ethylene glycol as solvent. On the other hand, Nd³⁺ ion was introduced into the BFO system and the effect of Nd³⁺ concentration on the structure, magnetic and dielectric properties of BFO were investigated. It was found that the magnetization of BFO was enhanced significantly with Nd³⁺ substitution, being attributed to the suppression of the spiral cycloidal magnetic structure led by the crystal structure transition. Furthermore, with increasing Nd³⁺ content, the dielectric constant was found to decrease while the dielectric loss was enhanced, which was mainly due to the hoping conduction mechanism with the reduction of oxygen vacancies.