Measurement on the structural,morphological, electrical and optical properties of PANI-CSA nanofilms

Camphorsulfonic acid doped polyaniline (PANI-CSA) prepared by chemical oxidative polymerization is spin coated on glass plates with four different PANI:CSA weight ratios (1:1, 1:2, 1:4 and 1:8) and measurements on the structural and optical properties are done. Thickness of the films measured <100 nm are termed as nanofilms. Fourier transform infrared spectroscopy indicated the presence of dopant and an increase in degree of polymerization with increase in dopant ratio. X-ray diffraction studies revealed the change of amorphous nature of the film to crystalline nature with increase in CSA dopant ratio. Scanning electron microscopy showed the change of very smooth morphology of the film to rough root-like morphology with increase in CSA dopant ratio. Hall-effect analysis showed that the increase in CSA weight ratio appreciably increases the conductivity of PANI-CSA films due to increase in carrier concentration and it also represents the semiconductivity (P-type) nature in all the films. UV–visible absorption studies reveal the broadening of absorption spectrum in visible region with maximum CSA dopant ratio (1:8). Photoluminescence spectra of PANI-CSA films excited using 300 nm, revealed that the change in intensity and position of emission peaks are due to transition of semiconducting nature of the film to conducting nature with an increase in CSA dopant ratio from 1:1 to 1:8.     

Synergistic effect of composite template and La-doping on microdynamic behavior of photogenerated carriers in mesoporous nano-TiO2

The traditional view that the role of the composite template that is adopted in the preparation of nano-TiO₂ is only for forming a pore structure and increasing the material's specific surface area is challenged by this study. The complex impact of the composite template and La-doping on the microdynamic behavior of photo-generation free charge carriers (FCCs) in the mesoporous nano-TiO₂ is investigated using the transient photovoltaic (TPV) technique, supplemented by electric field-induced surface photovoltaic spectroscopy and a computer simulation method. The experimental results reveal that utilizing an appropriate composite template, such as polyethylene glycol and octadecylamine with a molar ratio of 1:1, may result in the rapid separation and prolonged diffusion distance of electron–hole pairs that were excited by a 355 nm and 50 μJ laser pulse. These may be responsible for the stronger and broader TPV response in the microsecond and millisecond regions of the La-doped nano-TiO₂ in TPV spectroscopy, as compared with that for materials that used other composite templates. This response is closely related to the reduced content of the surface state located at 367 nm. A suitable level of La-doping, however, was only responsible for the stronger and broader TPV response in the microsecond region of the spectrum of the nano-TiO₂. The computer simulation results confirm that the photo-generation FCCs microdynamic characteristics in the microsecond region may partially originate from the state density distribution of both the d-electron in the antibonding orbital and the p-electron in the bonding orbital moving up to higher levels, and from a broader band-gap after La-doping in the anatase lattice cell.     

Facile synthesis of luminescent TiO2 nanorods using an anionic surfactant: Their photosensitization and photocatalytic efficiency

Mixed phase (rutile/anatase) TiO₂ nanorods have been synthesized using an anionic surfactant template. Nanorod synthesis has been achieved using mild reaction conditions and without using any rod-shaped template. The shape and crystallinity of the TiO₂ nanomaterials can be modulated by careful control of the surfactant concentration. The novelty of the present work is that the anatase/rutile mixed phase nanorods were formed without using the well-known layer by layer assembly method or the hydrothermal method. These mixed phase TiO₂ nanorods are highly luminescent, can be easily sensitized by fluorescent dyes, show significant dye adsorption ability and function as efficient photocatalysts.     

Synthesis and characterization of soluble polypyrrole–poly(ɛ-caprolactone) polymer blends with improved electrical conductivities

Polypyrrole–poly(?-caprolactone) (PPy–PCL) blends were prepared through an in situ deposition technique wherein different amounts of poly(?-caprolactone) were added during the polymerization of pyrrole. Ammonium persulfate was used as an oxidant in the polymerization of polypyrrole (PPy). Compared with pure PPy, the blends showed higher solubility in many organic solvents. The composition and structural characteristics of PPy–PCL were determined by Fourier transform infrared, ultraviolet–visible, and X-ray photoelectron spectroscopic methods. Scanning electron and transmission electron microscopic methods were performed to observe the morphology of the PPy–PCL blends. The temperature-dependent conductivity of the PPy–PCL blends was measured at 300–500 K. The conductivity increased with increasing PCL concentration in the blends, which can be explained by the increased mobility of charge carriers at high PCL concentrations. Based on the temperature dependence of the electrical conductivity, hopping may be the conduction mechanism involved in the PPy–PCL blending process.     

Modification of the physical properties of semiconducting MgAl2O4 by doping with a binary mixture of Co and Zn ions

The effects of doping of MgAl₂O₄ by a binary mixture of Co and Zn ions on the absorbance, electrical resistivity, capacitance, thermal conductivity, heat capacity and thermal diffusivity are reported in this paper. The materials with the nominal composition Mg_1−2x(Co,Zn)_xAl₂O₄ (x = 0.0-0.5) are synthesized by solution combustion synthesis assisted by microwave irradiation. The substituted spinels are produced with a Scherrer crystallite size of 18-23 nm, as opposed to 45 nm for undoped samples, indicated by X-ray diffraction and confirmed by transmission electron microscopy. These materials also show better thermal stability in the temperature range of 298-1773 K. Three strong absorption bands at 536, 577 and 630 nm are observed for the doped samples which are attributed to the three spin allowed (⁴A₂ (F) → ⁴T₁ (P)) electronic transitions of Co²⁺ at tetrahedral lattice sites while pure magnesium aluminate remains transparent in the whole spectral range. The semiconducting behavior of the materials is evident from the temperature dependence of the electrical resistivity. Resistivity and activation energy are higher for the substituted samples. Fitting of the resistivity data is achieved according to the hopping polaron model of solids. Both dielectric constant and loss increase on account of doping. The dielectric data are explained on the basis of space charge polarization. The thermal conductivity and diffusivity are lowered and the heat capacity is increased in the doped materials. Wiedemann-Franz's law is used to compute the electronic and lattice contributions towards the total thermal conductivity.     

Preparation and photoelectrochemical properties of KTa5O13 microcones

Potassium tantalate (KTa₅O₁₃) microcones with a maximum diameter of about 47-85 μm were prepared by anodic oxidation of tantalum in (15-20 M) KOH solutions at the temperature of 70 °C and applied voltage of 20 V for 3 h. Different factors affecting on the morphology of tantalum surface were discussed. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffractometry (XRD) were used to characterize the structure of the microcones. The photoelectrochemical properties were studied through electrochemical workstation. The experimental results indicate KTa₅O₁₃ microcones have a good performance in photoelectricity. The possible formation mechanism of as-prepared KTa₅O₁₃ microcones was also presented.     

A novel lamella 2D Ag(I) coordination polymer of graphite-like structure featuring short interlayer distance

The reaction of Ag₂O with a mixture of benzene-1,3,5-tricarboxylic acid (H₃BTC) and 2-aminopyrazine (APYZ) under the ammoniacal conditions gives rise to a novel metal–organic coordination polymer Ag₆(BTC)₂(APYZ)₆·9H₂O (1). The structure of 1 possesses a high ordered lamella 2D structure with an interesting graphite-like 6³ net which is comprised of Ag₄ and Ag₆ fused hexagonal rings respectively. 1 exhibits photoluminescence maximized at 416 nm upon 330 nm excitation at room temperature, which may be mainly ascribed to ligand-to-ligand charge transfer (LLCT). Semiconducting behavior was also measured at ambient temperature with σ values of 5.56 × 10⁻⁷ S cm⁻¹ based on the π–π stacking and Ag(I)–π interactions.     

Superconductivity in polycrystalline diamond thin films

Superconductivity was discovered in heavily boron-doped diamond thin films deposited by the microwave plasma assisted chemical vapor deposition (MPCVD) method. Advantages of the MPCVD deposited diamond are the controllability of boron concentration in a wide range, and a high boron concentration, especially in (111) oriented films, compared to that of the high-pressure high-temperature method. The superconducting transition temperatures are determined to be 8.7 K for T_c onset and 5.0 K for zero resistance by transport measurements. And the upper critical field is estimated to be around 7 T.     

Capacitance and photoelectrochemical studies for the assessment of anodic oxide films on aluminium

Photoelectrochemical spectroscopy and capacitance measurements were used in this work to assess the electronic properties of the oxide films formed on 99.5% aluminium and 2024-T3 aluminium alloy by anodising in a sulphuric-boric bath. The morphology of these films was also studied by transmission electron microscopy cross-section observations.The results obtained indicate that the oxide films formed on aluminium show a n-type semiconductive behaviour, with bandgap energies that are identical for the oxides studied, despite their different characteristics.It was found out that capacitance measurements may be used as a valuable technique for the assessment of the quality of anodised layers, allowing the distinction between an efficient and an inefficient sealing. Therefore, they may be used to predict the corrosion resistance of these materials.     

Photoluminescence and electrochemistry behavior of well-dispersible poly-N-[5-(8-quinolinol)ylmethyl]aniline/nano-TiO2 composite

Well-dispersible poly-N-[5-(8-quinolinol)ylmethyl]aniline/nano-TiO₂ composite was synthesized by the surface modification of nano-TiO₂ particles using poly-N-[5-(8-quinolinol)ylmethyl] (PANQ), and it was characterized by Fourier-transform infrared spectroscopy, photoluminescence spectroscopy, thermogravimetric analysis and scanning electron microscope, as well as conductivity and cyclic voltammogram were given. The conductivity of this composite was 2.1 × 10⁻² S cm⁻¹ at 25 °C, and showed good redox reversibility. It was easy to cast a transparent conducting film with photoluminescent property.