Arun Bera

Tuning of electrical and optical properties of polyaniline incorporated functional paper for flexible circuits through oxidative chemical polymerization

An organic semiconductor material made of polyaniline with outstanding physical properties was prepared on a flexible paper substrate. Oxidative chemical polymerization, a straightforward and cost effective technique for large scale synthesis has been employed for the preparation of the polymer on the paper substrate. CuCl2 has been chosen as a polymerizing agent for the oxidative chemical polymerization process. The prepared polymer semiconductor has become an ideal system to explore this outstanding recipe of chemistry and physics. Formation of polaron and bipolaron defect energy states in the polymer lattice facilitates exceptional electrical hole transport through the polymer chain, providing an electrical sheet resistance varying from 5.0 × 105 Ω □−1 to 2.8 × 107 Ω □−1. The optical band gap as obtained from the absorbance study was found to be in the range of 2.49 eV to 2.62 eV, which is suitable for the design of semiconductor devices. Most importantly, this article reports an effective way of tuning the optical and electrical properties of the prepared semiconductor, achieved through controlling the degree of oxidation during polymerization and thus bringing a control over the defect energy states. Along with the controllable electrical and optical properties, the flexibility of the paper substrates provides an extra merit to such polymer systems for designing paper based low cost flexible devices.

Facile additive-free synthesis of hematite nanoparticles for enhanced adsorption of hexavalent chromium from aqueous media: Kinetic, isotherm, and thermodynamic study

ABSTRACT Facile additive-free synthesis of hematite nanoparticles via a chemical co-precipitation technique is reported for adsorptive removal of Cr(VI) from aqueous media, and adsorption capacity as much as 43.05 mg/g at solution pH 2.0 is observed. Langmuir isotherm model was fitted nicely with adsorption experimental data, whereas kinetic studies reveal that both surface adsorption and intra-particle diffusion are involved in the adsorption mechanism. Thermodynamic studies established the favorability, spontaneity, and exothermic nature of the adsorption process. Regeneration studies revealed the stability of the adsorbent up to three consecutive cycles, indicating it as a potential adsorbent for Cr(VI)-contaminated wastewater remediation.

DISPERSION IN IMPEDANCE SPECTRA OF ISOTYPE CdO–ZnO THIN FILM HETEROSTRUCTURE ON APPLIED DC BIAS

Radio frequency magnetron sputtering technique has been used to prepare n–n isotype heterostructure of CdO–ZnO thin film on glass substrate. The energy band structure analysis shows the formation of charge accumulation and charge depletion region created near the interface of CdO–ZnO n–n isotype heterostrucure which leads to the formation of a junction capacitance. The impedance spectroscopic studies of CdO–ZnO isotype heterostructure show an excellent dispersion in the impedance spectra as observed in the Nyquist plot depending on applied DC bias voltage. The frequency response of impedances has been explained from band structure and equivalent electrical circuit model of the heterostructure. These studies will be highly significant in exploring the possibility of application of such isotype interfaces in optimizing the functionality of organic and inorganic electronic devices and solar cells.