B. Mondal

Potential use of polyphenol oxidases (PPO) in the bioremediation of phenolic contaminants containing industrial wastewater

The present review emphasizes on the use of Polyphenol oxidase (PPO) enzyme in the bioremediation of phenolic contaminants from industrial wastewater. PPO is a group of enzyme that mainly exists in two forms; tyrosinase (E.C. 1.14.18.1) and laccase (E.C. 1.10.3.1) which are widely distributed among microorganisms, plants and animals. These oxidoreductive enzymes remain effective in a wide range of pH and temperature, particularly if they are immobilized on some carrier or matrices, and they can degrade a wide variety of mono and/or diphenolic compounds. However, high production costs inhibit the widespread use of these enzymes for remediation in industrial scale. Nevertheless, bench studies and field studies have shown enzymatic wastewater treatment to be feasible options for biodegradation of phenols through biological route. Nanomaterials-PPO conjugates have been also applied for removal of phenols which has successfully lower down the drawbacks of enzymatic water treatment. Therefore in this article various approaches and current state of use of PPO in the bioremediation of wastewater, as well as the benefits and disadvantages associated with the use of such enzymes have been overviewed.

Visible light absorption and photo-sensitizing properties of spinach leaves and beetroot extracted natural dyes.

Herein, chlorophyll and betalain dyes are extracted from fresh spinach leaves and beetroots. Fourier transform infrared spectra are used to identify the characteristic peaks of the extracted dyes. UV-vis light absorption characteristics of the dyes and their mixed counterpart are investigated by varying their pH and temperature. These dyes are used as photo sensitizer for fabrication of zinc oxide photo-anode based dye sensitized solar cells (DSSCs). The photo-voltaic characteristics of the developed DSSCs are measured under simulated solar light (power of incident light 100 mW cm(-2) from Air Mass 1.5G). The solar to electric conversion efficiencies for the chlorophyll, betalain and mixed dye based solar cells are estimated as 0.148%, 0.197% and 0.294% respectively. The highest conversion efficiency for mixed dye based solar cell is attributed due to the absorption of wider range of solar spectrum.

Facile synthesis of pseudo-peanut shaped hematite iron oxide nano-particles and their promising ethanol and formaldehyde sensing characteristics

Herein, pseudo-peanut shaped hematite iron oxide nano-particles are prepared through a facile cost effective wet chemical synthesis route. The synthesized particles are characterized in terms of their phase formation behavior, morphological features and also used for sensing ethanol and formaldehyde vapors. The sensing characteristics (response %, response time, recovery time, selectivity coefficient) are investigated by varying the operating temperature (300–375 °C) of the sensor and concentration (20–200 ppm) of the studied vapors. The sensor shows promising response towards ethanol and formaldehyde vapors. In the studied operating temperature range, the response of the sensor towards ethanol is found to be better than formaldehyde. The cross-selectivity issue of the sensor has been addressed using the variation of selectivity coefficient with the exposure time of the vapors. For sensing ethanol and formaldehyde vapors, the response of the pseudo-peanut shaped particles is compared with poly-disperse type hematite particles. As compared to the poly-disperse particles, peanut like structures are found to be superior for sensing the studied vapors.

Physico-chemical characterization and biological response of Labeo rohita -derived hydroxyapatite scaffold

The chemically treated Labeo rohita scale is used for synthesizing hydroxyapatite (HAp) biomaterials. Thermogravimetric and differential thermal analyses of fish scale materials reveal the different phase changes with temperature and find out the suitable calcination temperatures. The composition and structures of wet ball-milled calcined HAp powders are characterized by Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray analysis (EDX). The EDX as well as chemical analysis of fish scale-derived apatite materials confirms that the Ca/P ratio is 1.71. The compressive stress, hardness and porosity have been evaluated on sintered HAp biomaterials. The cell attachment on HAp surfaces, cytotoxicity evaluation and MTT assay, which are carried out in RAW macrophage-like cell line media demonstrate good biocompatibility. The histological analysis also supports the bioaffinity of processed HAp biomaterials in Wistar rat model for investigating the contact reaction and stability at the artificial or natural prosthesis interface.

Morphology induced light scattering by zinc oxide polydisperse particles: Promising for dye sensitized solar cell application

In the present work, polydisperse zinc oxide composed of nano and submicron size particles is used to prepare photo-anode for dye sensitized solar cell. The particles are synthesized through auto-combustion route and characterized in terms of their phase formation behavior as well as morphological properties. UV-vis diffused reflectance spectra of the prepared photo-anode show its promising dye uptake and incident light scattering behavior. The prepared cells reveal ∼3.2% solar to electric conversion efficiency. The fairly acceptable efficiencies of the cells are attributed due to the efficient scattering of incident light and reasonable dye uptake within polydisperse particulate photo-anode.

Optimisation of process parameters for fabrication of nanocrystalline TiO2–hydoxyapatite based scaffold using response surface methodology

Abstract The present study focuses on the application of central composite design of response surface methodology for optimisation of process parameters to develop a hybrid mechanically stable biocompatible porous scaffold. The scaffolds are developed by varying the composition of fish scale derived HAp and nanocrystalline TiO2 powders. The effects of sintering temperature, dwell time on the porosity and compressive strength of the scaffolds are investigated. Various diagnostic tools (e.g. thermogravimetric/differential thermal analysis, Fourier transform infrared spectroscopy, X-ray diffraction and field emission scanning electron microscopy /energy dispersive X-ray spectroscopy) are used for composition, phase conformity and microstructure evaluation of green as well as sintered materials. The desirability function optimisation study reveals that at 60∶40 (TiO2∶HAp) concentration with sintering temperature of 1100°C for 90 min provides the maximum compressive strength of 78·5 MPa and maximum porosity of 33·5%.

Zinc oxide thin film based nonenzymatic electrochemical sensor for the detection of trace level catechol

In the present work, a novel zinc oxide thin film based nonenzymatic, electrochemical sensor is developed for the detection of catechol. The zinc oxide thin film electrode on FTO conducting substrate is prepared by a simple and cost effective spin coating technique. The developed sensor exhibits promising cyclic voltammetric as well as amperometric response when the concentration of the catechol in phosphate buffer (pH ∼ 7) is varied in the range of 2 to 15 μM. The interference of the sensor for the detection of catechol is compared in presence of chlorophenol and formaldehyde. The repeatability of the sensor performance towards catechol is also investigated at different time intervals. To understand the underlying mechanism of catechol sensing by the ZnO thin film, we have studied the phase, micro-structural and optical features of the electrode before and after electrochemical sensing experiments. It has been observed that the XRD pattern, morphology and optical transmittance of the electrode changes significantly after electrochemical interaction with catechol. Specifically, the 2D thin film morphology upon electrochemical interaction with catechol starts changing to a 1D nanowire like morphology which in turn influences the phase, optical transmittance as well as sensing performance. The modulation of structural, optical features and sensing performances of the developed electrode are again supported by electrochemical impedance spectroscopy.

Hierarchical zinc oxide nano-tips and micro-rods: hydrothermal synthesis and improved chemi-resistive response towards ethanol

In the present work, a novel hierarchical architecture of zinc oxide has been synthesized through a spherical carbon template assisted two step hydrothermal process. The architecture can be represented visually as a combination of secondary phase nano-tips grown on initially prepared zinc oxide micro rods. An attempt has been made here to understand the mechanism for the formation of the said zinc oxide architecture. As compared to the zinc oxide micro rods, the enhanced surface activity of the hierarchical architecture has been reflected during its improved chemi-resistive response towards ethanol. The sensing characteristics are measured by varying the sensor operating temperature (250–350 °C) and ethanol concentrations (50–200 ppm). The prepared micro rods and hierarchical architecture show 47 and 59% responses towards 50 ppm ethanol at their optimum operating temperature of 325 °C.

Chemi-resistive response of rutile titania nano-particles towards isopropanol and formaldehyde: a correlation with the volatility and chemical reactivity of vapors

The performance of phase pure rutile titania nano-particles for gas/vapor sensing is not well explored in open literature, mostly because of their moderate chemical activity. However, the high thermal stability of rutile titania could be beneficial towards making a stable chemi-resistive sensor, operable generally at higher temperature. Herein, we have investigated the chemi-resistive response characteristics of rutile phase titania nano-particles for the detection of isopropanol and formaldehyde vapors. Titania nano-particles are synthesized through a hydrothermal route and characterized in terms of their phase formation behavior and micro-structural features. The sensing characteristics of the particles are measured by varying the operating temperature (275 °C–350 °C) of the sensor and concentrations (20–200 ppm) of the vapors, using a static flow gas sensing measurement set-up. The rutile titania particles are found more responsive towards isopropanol than formaldehyde. An attempt is made here to correlate the sensing performance of titania sensors with the volatility and chemical reactivity of studied vapors. The higher response of the sensor towards isopropanol is predicted, due to its comparatively lower volatility and more suitable chemical structure for oxidation on the sensor surface.

Response surface modeling of Cu(II) removal from wastewater using fish scale-derived hydroxyapatite: application of Box–Behnken experimental design

The present study illustrates the potential use of hydroxyapatite (HAp) synthesized from fish scale for Cu(II) removal with optimal efficiency. Batch experiments were conducted to determine the eff...