Current Nanomaterials - Volume 1, Issue 2, 2016

Polymer-clay nanocomposites (PCN) are the most important nanomaterials of the current decade with wide range of applications. Montmorillonite, vermiculite, sepiolite, laponite, bentonite and attapulgite are the main classes of clay used as reinforcement in polymer nanocomposites. Clay nanocomposites show characteristic features of thermal stability, flame retardancy, barrier and anticorrosive properties. This work comprehensively review current developments and applications of polymer-clay nanocomposites in automotive, sporting goods, coating technology, packaging, insulation, building construction, electrochemical, biomedical and environmental. This work also aims to describe the importance of polymer clay nanocomposites in various fields, especially for environmental applications. Polymer clay based nanocomposites also have the potential to decontaminate and remediate aqueous systems, therefore purification and remediation of contaminated soil and air with the help of clay based nanocomposites have also been discussed.

Background: Hydrogen is considered as the fuel of the future since it has about three times higher energy per mass relative to gasoline. However, it is difficult to be stored and there is intense effort to find materials that can store as much as possible hydrogen. Lithium-Aluminium and -Boron hydrides are some of the most important compounds used in hydrogen storage with promising hydrogen weight percentages and low desorption energies. Methods: The Density Functional Theory (DFT) have been used to calculate the desorption energies of Hydrogen in Lithium-Aluminium, and -Boron nanoparticles. Results: The type of nanoparticles studied were LinMnHxn with M = Al or B, n varying from 1 up to 20 and x between 0 and 4. Complex nanoparticles LinAln-yByH4n have been also examined. These type of nanoparticles try to combine the low weight of LinBnH4n with the low desorption energies of LinAlnH4n. Finally, NanAlnH4n nanoparticles have been studied. For all these cases, several different geometries were examined and the lowest energy geometry was chosen. Conclusion: For the fully hydrogenated NPs (x=4), the desorption energy reduces as n increases saturating to about 135 and 47 kJ/mol for Li20B20H80 and Li20Al20H80, respectively, in close agreement with measurements.

Background: Carbonaceous nanomaterials (activated carbons, carbon molecular sieves, activated carbon fibers) are amorphous solids consisting of micro crystallites with a graphite lattice. They differ from graphite by having a random imperfect structure which is highly porous over a broad range of pore sizes, as well as various surface functional groups. They are most often produced from natural feed stocks, such as hard coal, lignite, wood, peat, stones, and peels of the fruits by carbonization and activation. Methods: Many investigations have been performed to explore polymers as raw materials, and to optimize the preparation conditions, and to obtain nanomaterials with the desired porous properties. Results: The possibility to use the composites of coal-tar pitch modified with different types of waste polymers for the preparation of carbonaceous nanomaterials was studied. The influence of polymeric precursor, the mass ratio pitch/polymer, carbonization and activation conditions, type of activation agent used, on the porous texture were investigated. The surface functional groups were also determined. Conclusion: Composites of coal-tar pitch and polymer waste can be converted to nanoporous carbonaceous adsorbents. These results allow to devise processes for a proper utilization of polymeric wastes, which is a very important issue both for economy and ecology.

Background: Graphene synthesis via wet chemical route needs chemical reduction of graphene oxide in the presence of reducing agents. To minimize the environmental impacts, natural antioxidants are potential alternatives than the currently used hazardous materials for the reduction of graphene oxide. Cow urine inherently owns excellent anti-oxidant properties by virtue of its high natural nitrogenous content and has researched well for urine therapy throughout the history of mankind. Methods: The reductive ability of cow urine has been used to reduce graphene oxide into graphene nanosheets with ultrasonication followed by heat treatment. Results: Raman analysis reveals that the maximum reduction of graphene oxide is observed at 140 °C by cow urine, with a Raman D to G band intensity ratio of ~ 1.27. XPS analysis validates the Raman signature of maximum removal of oxygen species from graphene oxide, and reveals the attainment of the C/O ratio of ~ 5.25. Conclusion: A simple green and cost effective approach has been demonstrated for the reduction of graphene oxide via cow urine as a natural reducing agent. The reduction degree of graphene oxide is found to be high as processing temperature increases. The maximum reduction of oxygen species from graphene oxide is found at 140 °C. Hence, cow urine offers potential alternative chemicals to avoid the use of hazardous reducing agents for the synthesis of graphene nanosheets at large scale.

Background: Nanoparticle aggregation affects nanofluid thermal conductivity. Objective: Several aspects of aggregation modeling pertinent to nanofluid thermal conductivity estimation are to be discussed. Method: Mathematical analysis is performed using the macroscopic aggregation equations. Results: Some plausable types of models are identified and their positive and negative features evaluated. A number of explicit solutions relevant to nanofluid thermal conductivity modeling are presented. Conclusion: Modeling techniques of varying levels of sophistication exist which should be further pursued and evaluated.

Background: Since last two decades, there has been rigorous efforts are going on to develop a hydrogen storage system for large-scale application in fuel cells, mobiles and for automotive uses. The early experimental data on hydrogen storage using CNTs contradicted theoretical calculations, and there has been a large variation in the CNT hydrogen storage capacity reported by various research groups. In present work, a comparative study on hydrogen storage and release characteristics of bare as well as three transition metals viz. Ni, Cu & Fe nanoparticles decorated MWCNT at ambient temperature i.e. 298K and pressure range of 9-16 atm has been studied. Methods: Synthesis, characterization and hydrogen adsorption-desorption behavior of bare as well as transition metal (Ni, Cu and Fe) decorated multiwalled carbon nanotubes has been studied systematically. Results: The maximum hydrogen storage capacities of finely dispersed Ni, Cu, and agglomerated Fe decorated and bare multiwalled carbon nanotubes measured at 298K were 0.812 wt% (at 15.85 atm), 2.59 wt% (at 12.64 atm), 0.909 wt % (at 15.45atm) and 0.654 wt% (at 12.84 atm) respectively. A mechanism invoking metal nanoparticle mediated dissociation of hydrogen molecule and its subsequent storage in carbon structure as well as defect sites has been proposed to explain hydrogen storage and release behavior of metal-decorated multiwalled carbon nanotubes. Conclusion: The nature and morphology of metal nanoparticle has significant role in controlling hydrogen adsorption-desorption characteristic of decorated multiwalled carbon nanotubes.

Background: Nano biosensors are highly sensitive and cost effective nanostructured metal oxides because of their excellent properties such as optical, electrical, selectivity and surface to volume ratio. Apart from these properties can also possess other unique properties like biocompatibility, nontoxic, high iso electric point (iep) (~9.2). Now most of the researchers are attracted towards core-shell nps, since these fabrics have emerged in many areas such as fluorescence imaging. Method: Synthesis of ceria-titania (CeO2-TiO2) Core-Shell Nano Particles (CSNPs) from the wet chemical precipitation method using cerium-nitrate hexa-hydrate and Titanium tetra isopropoxide (TTIP) as precursors. Results: Chemically synthesized biocompatible ceria-titania (CeO2-TiO2) CSNPs were characterized by High resolution transmission electron microscopy (HRTEM), Scanning electron microscopy (SEM), UV-Visible spectroscopy and Cyclic Voltammetry (CV) techniques. A novel glucose biosensor based ceria-titania CSNPs was developed by immobilizing glucose 6 phosphate dehydrogenase (G6PD) with nicotinamide adenine dinucleotide phosphate (NADPH) on CSNPs via covalent linkage. Conclusion: The glucose sensing performance of an electrochemical biosensor with nano-interface was successfully investigated by fabricating NADPH/G6PD/TiO2 coated CeO2 core shell NPs/Pt bioelectrode. The developed biosensor exhibited high sensitivity (2.11 V mM-1), Limit of detection (2.98μM) and with a linear dynamic range of 0.5-2.5mM. As the detection limit is very low, this sensor can detect glucose from this lower limit. In addition, the normal range of blood glucose is about 3.9- 7.8mM. Owing to its high response, the fabricated TiO2 coated CeO2 core shell nano-interface based bio-electrode can be used as a sensitive handheld miniaturize system for the detection of glucose in blood samples.

Background: In the upcoming era carbon nanotubes have proved to be the most promising material in the field of science and technology. In the analysis of carbon nanotube, nonlocal elasticity is found to be highly effective as it regards the small scale effects in the analysis. The small scale effect is found to be considered via nonlocal elasticity in both axial and radial direction. Objective: In the present article, radial nonlocal effect on the vibration of carbon nanotubes supported in Winkler type elastic foundation is studied. Method: In the analysis, Timoshenko beam theory is employed to derive the governing differential equations. Finite element model is developed. Results: It is observed radial nonlocal effect has a dominating effect over Winkler modulus parameter and at higher diameter, the effect of Winkler modulus disappears. Conclusion: The observation indicates that radial scale effect has significant influence in the vibration analysis of carbon nanotubes supported on Winkler foundation.

Background: CaTiO3, being a member of perovskite family, has a broad range of properties and can be used in different applications such as biomedical, photocatalytic and communication equipment operating at microwave frequencies. CaTiO3 is one of the important components for the immobilization of high level radioactive wastes and is extensively used in electronic ceramic materials. CaTiO3 has been investigated for biocompatible and luminescent material and exhibits a combination of high permittivity and modest dielectric loss. CaTiO3 could be of great usefulness for the development of integrated circuits in microelectronic industry in the future. Method: Perovskite CaTiO3 has been synthesized via facile solution combustion synthesis using titanium peroxo complex. Results: The X-ray diffraction pattern revealed the pure perovskite structure. Microstructures with porous morphology were observed using a scanning electron microscopy. Transmission electron microscopy images showed a uniform particle size distribution with average particle sizes varying in the range of 30-70 nm. The surface area ~30.89 m2/g was measured by BET method. The band gap of 3.54 eV was calculated using the diffuse reflectance spectrum of CaTiO3. The photoluminescence spectra of CaTiO3 powder exhibited a violet shift and blue shift at 441 nm and 483 nm with an excitation wavelength at 351 nm. An investigation on frequency dependence of dielectric constant (έ) and tangent loss (tan δ) showed a dispersive behavior at low frequencies. The photocatalytic degradation of methylene blue (MB) using CaTiO3 as photocatalyst showed 98 % of decolourisation only in the presence of solar radiation. Conclusion: The prepared CaTiO3 reveals good properties and application which act as a good photocatalyst in the presence of natural sunlight. This material can act as a noble candidate for next generation.