S.K. Samdarshi

Nickel oxide nanoparticles: A novel antioxidant

We investigated a novel inorganic (nickel oxide) nanoparticles as a potential antioxidant in the biosystems. The particles were synthesized using self-propagating high-temperature synthesis (SHS) method at 650 degrees C. The antioxidant property of the nickel oxide particles was investigated in an in vitro system, using modified DPPH method for insoluble solid materials.

A green precursor for carbon nanotube synthesis

Abstract The present work aims to explore a natural renewable precursor for the synthesis of multiwalled carbon nanotubes (MWCNTs), conforming to the principles of green chemistry. MWCNTs were synthesized by chemical vapor deposition using a natural renewable precursor (coconut oil). Nitrogen gas was used as an inert atmosphere as well as a carrier for the evaporated precursor (flow rate: 100 mL/min). The synthesized MWCNTs are characterized by scanning and transmission electron microscopy, electron dispersive X-ray analysis, and Raman spectroscopy. The diameters of the synthesized nanotubes are in the range of 80 nm to 90 nm under optimum conditions.

Computer simulation of salt gradient solar pond's thermal behaviour

This paper investigates a few mathematical aspects of computer simulation of salt gradient solar pond’s thermal behavior. The basic equation governing heat flow in the non-convective zone of solar pond is solved by finite difference approach using the Crank–Nicholsen method. Stability and convergence of the method, specifically for the case of solar pond, is examined over a wide range of depth difference (Δx) and time difference (Δt). It is observed that the mesh ratio parameter (r = K Δt/ρCpΔx2) which is used to define the stability and convergence of the method does not have an absolute value, rather its value varies with Δx. While using an actual set of Δx and Δt, the stability must be tested with reference to the set being used. Few other mathematical aspects pertaining to the actual application of the method are also investigated. Also, the effect of fineness of ambient input data on long term performance of the pond is investigated. It is observed that the diurnal variation of ambient input data yields the same accuracy as the hourly variation. Different approaches of calculating the heat losses from upper convective zone are compared for long term performance of the pond. A simple method is suggested to calculate the radiation flux at a depth which results due to multiple reflections between bottom and surface of the pond. The method saves computational time when used for simulation and is also suitable for hand calculations.

Non-hydrolytic synthesis of hierarchical TiO2 nanostructures using natural cellulosic materials as both oxygen donors and templates

Non-hydrolytic reactions between TiCl4 and cellulosic natural materials acting as both oxygen-donors and templates lead to hierarchical TiO2 nanostructures by a mineralization process.

Synthesis and characterization of plasmonic visible active Ag/ZnO photocatalyst

Ag deposited ZnO nanoparticles (NPs) have been synthesized by simple sol–gel method for visible light active photocatalytic application. X-ray diffraction (XRD), TEM, UV–DRS and PL studies have been used to characterize the photocatalyst. The results show that Ag/ZnO NPs are wurtzite phase (WZ) of ZnO with Ag NPs in the surface region forming a hetero-interface of Ag–WZ (ZnO). Visible light activity of the material has been studied using photocatalytic degradation kinetics of methylene blue as a probe pollutant. Ag/ZnO NPs exhibit five times higher visible-light driven photocatalytic activity than pristine ZnO and four times than the reference Degussa P-25, under identical conditions. The high visible activity of Ag/ZnO may be attributed to the surface plasmon effect complemented sensitization in the presence of metallic Ag and effective charge separation through Ag–WZ hetero-interfaces.

Simple methods for estimation of radiation flux in solar ponds

Abstract Two simple formulations for estimation of net available radiation at a depth in solar pond are proposed. The first formulation uses the correlation of Bryant and Colbeck [Solar Energy 19 (1977) 321] and extends the same to incorporate the reflected part of radiation coming from bottom and surface of the pond. The other formulation is an empirical fourth order polynomial function. The universal functions of Hull [Solar Energy 29 (5) (1982) 385] are taken as a base line for comparison of accuracy in estimation of radiation flux. The proposed formulations provide a substantial saving of computational time, much simplicity in analytical calculations, and reasonably good accuracy in estimation of radiation flux at a depth in solar pond. Their impact of these formulations is also analyzed on accuracy in prediction of pond’s long-term thermal behavior and gain in terms of computational speed. It provides a 20–25% saving in computational time as compared to Hull’s method with comparable accuracy.

Enhanced visible light photocatalytic disinfection of gram negative, pathogenic Escherichia coli bacteria with Ag/TiV oxide nanoparticles

Silver sensitized titanium vanadium mixed Ag/TiV oxide photocatalyst was synthesized using sol-gel technique. The catalyst was characterized using XRD, SEM, EDAX, HRTEM, UV-DRS, XPS, and PL analysis which reveal the formation of a predominantly rutile mixed phase nanoparticles of 25-30 nm crystallite size. The catalyst showed a marked red-shift in the absorption spectrum compared to Degussa P25. It exhibited a remarkable enhancement in the visible light photocatalytic activity in inactivating Escherichia coli, a gram-negative pathogenic bacterium, too. The conclusions are supported by a comparison with an identically synthesized TiV oxide sample. A microbicidal photonic efficiency (MPE) has been defined and a method for its determination has been proposed to facilitate quantification of the performance of the photocatalyst and the disinfection system taking into account the response of the catalyst to the radiation intensity.

Combined effect of bottom reflectivity and water turbidity on steady state thermal efficiency of salt gradient solar pond

Abstract In salt gradient solar ponds, the clarity of water and absorptivity of the bottom are important concerns. However, both are practically difficult to maintain beyond a certain limit. The reflectivity of the bottom causes the loss of a fraction of the incident radiation flux, resulting in lower absorption of flux in the pond. Turbidity hinders the propagation of radiation. Thereby it decreases the flux reaching the storage zone. Both these factors lower the efficiency of the pond significantly. However, the same turbidity also prevents the loss of radiation reflected from the bottom. Hence, the combined effect is compensatory to some extent. The present work is an analysis of the combined effect of the bottom’s reflectivity and water turbidity on the steady state efficiency of solar ponds. It is found that in the case of a reflective bottom, turbidity, within certain limits, improves the efficiency of pond. This is apparently contradictory to the conventional beliefs about the pond. Nevertheless, this conclusion is of practical importance for design and maintenance of solar ponds.

Ultrasonication: Enhances the antioxidant activity of metal oxide nanoparticles

The present work is a modification for Serpen et al.s method for antioxidant activity determination for insoluble materials with special reference to metal oxide nanoparticles. As reported in our former publications the mixing procedures were followed as mentioned by Serpen et al. A new mixing procedure was followed for enhancing the reaction between metal oxide nanoparticles and DPPH in the solution. The sonication inside a water bath enhances the DPPH scavenging capacity of metal oxide nanoparticles up to 13.94% and 18.96% in case of ferric oxide and nickel oxide nanoparticles respectively. The control DPPH solution without any nanoparticles does not show any degradation due to sonication.

Optimum size of non-convective zone for improved thermal performance of salt gradient solar pond

The salt gradient solar pond is a long-term heat storage system with a considerable warm-up time. A pond is efficient when it reaches the desired temperature quickly and maximum heat is subsequently retrieved at steady state. This requires optimum sizing of the non-convective zone. In the present work, the optimum size of the non-convective zone for fast warm-up is determined. This is found to differ considerably from the optimum size of the steady state criterion. The possibility of achieving both performance parameters, i.e. fast warm-up and maximum heat collection later on, is analyzed. It is suggested that when commissioning a pond, the size of the non-convective zone should at first be the optimum value from the warm-up rate criterion, but may later be changed to the optimum size from the steady state criterion.