L. John Kennedy

Bio: L. John Kennedy is an academic researcher from VIT University. The author has contributed to research in topics: Diffuse reflectance infrared fourier transform & Crystallite. The author has an hindex of 48, co-authored 168 publications receiving 6401 citations. Previous affiliations of L. John Kennedy include Central Leather Research Institute.

Synthesis of hierarchical ZSM-5 hexagonal cubes and their catalytic activity in the solvent-free selective oxidation of toluene

Abstract: In the present work, ZSM-5 with hexagonal cubic morphology was successfully synthesized by the hydrothermal method in the presence of tetrapropylammonium hydroxide and nonionic surfactant as mesopore template. The structural, textural, morphological and thermal properties of the as-synthesized zeolite samples were evaluated by XRD, XRF, FT-IR, N2 adsorption, HR-TEM, HR-SEM and TGA. The powder X-ray diffraction and FT-IR analysis confirms the formation of pure ZSM-5 zeolite without any impurities present. The surface area analysis showed that the mesoporous surface area was evidently increased without intensively destroying the microporosity in the surfactant-assisted zeolite. The catalytic performance of the ZSM-5 zeolites was evaluated in the liquid phase selective oxidation of toluene using tert-butyl hydroperoxide as an oxidant. The surfactant-assisted ZSM-5 shows a higher toluene conversion and benzaldehyde selectivity at optimum conditions.

Studies on the Structural, Morphological, Optical, and Magnetic Properties of α -Fe 2 O 3 Nanostructures by a Simple One-Step Low Temperature Reflux Condensing Method

Abstract: Uniform hematite (α-Fe2O3) nanoparticles have been successfully synthesized through a simple one-step low temperature reflux condensing method which requires no surfactants or templates. The crystallite size was calculated by using Debye–Sherrer formula, and it showed the range of 4–27 nm. The lattice parameters of the samples were measured by Rietveld analysis. The morphology of the products was studied by high resolution scanning electron microscopy (HR-SEM), and it was confirmed by high resolution transmission electron microscopy (HR-TEM). The HRTEM images exhibit the well defined lattice fringes of α-Fe2O3 particles that confirm their high crystallinity. The formation of pure α-Fe2O3 was further confirmed by using energy dispersive X-ray (EDX) analysis. The optical properties and the bandgap energy were measured by UV-Visible diffuse reflectance spectra (DRS) and photoluminescence (PL) spectra. The bandgap energy was measured by using Kubelka–Munk method, and the value was found to be 2.26 eV. Magnetic hysteresis (M–H) loops revealed that the as-prepared α-Fe2O3 samples displayed ferromagnetic behavior. These results show that the prepared hematite possess good magnetic properties.

Alcohol sensing properties of sol–gel prepared Sr(II)-added cobalt aluminate spinel composites

Abstract: Strontium(II)-added CoAl 2 O 4 composites prepared by sol–gel technique were investigated for the sensing properties to alcohols like methanol, ethanol, isopropanol and butanol. X-ray diffraction, scanning electron microscopy and nitrogen adsorption/desorption isotherms at 77 K were employed to identify the structural phases, surface morphology and BET surface area of the composites, respectively. The composites were prepared with the molar ratios of Co:Sr as 1.0:0.0, 0.0:1.0, 0.8:0.2, 0.6:0.4, 0.4:0.6, and 0.2:0.8, keeping the aluminum molar ratio as constant and were labeled as CoSA1, CoSA2, CoSA3, CoSA4, CoSA5 and SA, respectively. The samples sintered at 900 °C for 5 h, were subjected to dc resistance measurements in the temperature range from 30 to 250 °C to study the alcohol vapor sensing characteristics. The results revealed that the sensitivity factor ( S f ) increased with temperature up to the optimum temperature at which maximum sensitivity is obtained and thereafter decreased. The sensitivity factor was found to increase with increase in concentration from 100 to 5000 ppm at the respective operating temperatures. Among the composites prepared CoSA5 showed the maximum sensitivity factor towards alcohols. The sensitivity factor and response and recovery characteristics showed that the order of sensing alcohols by the composites was butanol > isopropanol > ethanol > methanol, which could be explained on the basis of oxidation of alcohols. The stability of the most sensitive composite CoSA5 was also discussed along with the mechanism of sensing. The response and recovery characteristics of CoSA1, CoSA5 and SA to alcohols were also reported.

Ultracapacitors: Why, How, and Where is the Technology

Abstract: The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

X-Ray Diffraction

Abstract: Interpretation of X-ray Powder Diffraction Patterns . By H. Lipson and H. Steeple. Pp. viii + 335 + 3 plates. (Mac-millan: London; St Martins Press: New York, May 1970.) £4.

A review of ZnO nanoparticles as solar photocatalysts: Synthesis, mechanisms and applications

Abstract: Persistent organic pollutants (POPs) are carbon-based chemical substances that are resistant to environmental degradation and may not be completely removed through treatment processes. Their persistence can contribute to adverse health impacts on wild-life and human beings. Thus, the solar photocatalysis process has received increasing attention due to its great potential as a green and eco-friendly process for the elimination of POPs to increase the security of clean water. In this context, ZnO nanostructures have been shown to be prominent photocatalyst candidates to be used in photodegradation owing to the facts that they are low-cost, non-toxic and more efficient in the absorption across a large fraction of the solar spectrum compared to TiO 2 . There are several aspects, however, need to be taken into consideration for further development. The purpose of this paper is to review the photo-degradation mechanisms of POPs and the recent progress in ZnO nanostructured fabrication methods including doping, heterojunction and modification techniques as well as improvements of ZnO as a photocatalyst. The second objective of this review is to evaluate the immobilization of photocatalyst and suspension systems while looking into their future challenges and prospects.

Applications of hierarchically structured porous materials from energy storage and conversion, catalysis, photocatalysis, adsorption, separation, and sensing to biomedicine

Abstract: Over the last decade, significant effort has been devoted to the applications of hierarchically structured porous materials owing to their outstanding properties such as high surface area, excellent accessibility to active sites, and enhanced mass transport and diffusion. The hierarchy of porosity, structural, morphological and component levels in these materials is key for their high performance in all kinds of applications. The introduction of hierarchical porosity into materials has led to a significant improvement in the performance of materials. Herein, recent progress in the applications of hierarchically structured porous materials from energy conversion and storage, catalysis, photocatalysis, adsorption, separation, and sensing to biomedicine is reviewed. Their potential future applications are also highlighted. We particularly dwell on the relationship between hierarchically porous structures and properties, with examples of each type of hierarchically structured porous material according to its chemical composition and physical characteristics. The present review aims to open up a new avenue to guide the readers to quickly obtain in-depth knowledge of applications of hierarchically porous materials and to have a good idea about selecting and designing suitable hierarchically porous materials for a specific application. In addition to focusing on the applications of hierarchically porous materials, this comprehensive review could stimulate researchers to synthesize new advanced hierarchically porous solids.