Nanoscience & Nanotechnology-Asia - Volume 3, Issue 1, 2013

The performance and reliability of energy storage systems largely depend on the characteristics and properties of the electrode materials that constitute the system. Nanostructured materials have greatly influenced the overall performance of these systems by enhancing surface processes and improving the transport kinetics of the ions/molecules involved. Vanadium based materials have received considerable attention, particularly as electrode materials in high energy density Lithium ion batteries (LIB) and supercapacitors because of their cost effectiveness, efficient energy utilization and special structural characteristics. In this review, the applications of vanadium based materials as electrode components in energy storage systems have been described; their utilization in LIB and supercapacitors has been particularly highlighted. Recent developments in the field of vanadium based nanoelectrode materials are also discussed.

Carbon nanostructures have become one of the most exciting and rapidly expanding research topics since the discoveries of fullerene and carbon nanotubes. In particular, carbon nanotubes, graphene, and mesoporous carbons are the most important classes of carbon nanostructures in terms of synthesis and practical applications. Due to their excellent chemical, physical, mechanical, and electrical properties, carbon nanostructures have been considered as promising candidate materials for energy devices. Therefore, it is important to summarize and review the previous research on carbon nanomaterials in energy storage, conversion, and generation. Herein, the typical fabrication procedures for carbon nanostructures, and the characteristics and performances of those carbon nanomaterials as major components in energy devices are briefly described. The wet-type approaches to carbon nanomaterials are discussed extensively because the chemical vapor deposition and template methods have already been reported frequently. In addition, recent research on the improvement of batteries, capacitors, and solar cells will be concisely reviewed.

Nanodimensional materials such as transition metal oxides, polyanionic based materials and metal fluorides can be used as cathode while metal nanoparticles, alloys and metal oxides are preferred as anode for next-generation lithiumion batteries (LIBs) in order to obtain high reversible capacity, rate capability, safety, and longer cycle life. These nanomaterials can offer relatively short ionic and electronic pathways which leads to better transportation of both lithium ions and electrons to the particles core. This article emphasize on the effect of nanodimension on the electrochemical performance of cathode and anode materials. Their synthesis processes, electrochemical properties and electrode reaction mechanisms are briefly discussed and summarized. Furthermore, the article highlights recent past scientific works and new progresses in the field of LIBs. It also highlights the direction to overcome the existing issues of current lithium storage technology. In future, we may overcome all the existing issues of LIBs and can deliver excellent cathode and anode combinations to fulfill maximum practical efficiency with low cost and ultimate safety for high end applications.

Lithium ion batteries are the key components of the portable, entertainment, computing and telecommunication equipment required by today's information-rich and mobile society. Highly flexible batteries would free product designers from the constraints of rigid and predetermined forms. In addition, powerful and light-weight batteries made from inherently safe materials could facilitate quickly advance development of electric vehicles and other transportation applications. In this mini-review, some advances on flexible and light-weight batteries are reported and discussed.

Nanomaterials are receiving great attention in terms of research and development over the past few years in Polymeric Electrolyte Membrane (PEM) for Fuel Cells and Electrolyzers applications. The addition of inorganic nanofillers (SiO2, ZrO2 and TiO2), clays (montmorrillonite, bentonite, etc.), heteropolyacids (including cesium salts) and carbon nanotubes to the membrane structure have demonstrated to be ways of enhancing the system performance. In H2- based PEMFC, the water retention capacity can be significantly increased, opening up the possibility of operating the system above the water boiling point under low humidity conditions without a dramatic drop in the performance. In Direct Alcohol Fuel Cell (DAFC), its application intends to address the detrimental alcohol crossover that depolarizes the cathode without inadmissibly depressing the membrane conductivity. Good results can be obtained when including SiO2 and TiO2 nanoparticles, metallic nanoparticles, zeolites and clays such as plain and sulfonated-montmorillonite. For high temperature PEMFC based on phosphoric acid-doped polybenzimdazole, the presence of the nanocomponents helps to achieve higher conductivities compared to the pristine material under severe anhydrous conditions, which is reflected in larger power density peaks. Finally, a section for the PEM electrolyzer depicts the importance of SiO2 and TiO2 nanoparticles for improving the performance of this system without the additional consumption of electricity by allowing the operation above 100 °C.

To optimize the utilization of thermal conversion systems, it is essential to integrate them with thermal energy storage. Among many types of base materials, the phase change materials are the most satisfactory mediums to store and release the thermal energy due to their high latent heat of fusion. In general, the phase change materials have low thermal conductivity. Nanoadditives have been investigated to further enhance the thermal properties of the phase change materials. This paper reviews the research development of the various types of phase change materials, nanoadditives, nanofluids, and nanocomposites as possible materials for efficient thermal energy storage. Some deficit in the literature has been noticed on the dispersion of various types of nanoparticles in the various types of base materials. It is also recommended that further studies are required to understand the stability of the nanofluids and nanocomposites due to a large number of thermal cycles.

A significant proportion of drugs present in market, are poorly soluble. Formulation development of these drugs is also a demanding challenge. Nanosuspensions have revealed their potential to problems, associated with poorly soluble drugs. Media milling and high pressure homogenization techniques have been used extensively for producing the nanosuspensions. This article reviews the various aspects related to nanosuspensions and their potential as a strategic approach for poorly soluble drugs.

It is new approach to combine one or multiple drugs onto the same drug-delivery nanocarrier in accurately controllable manner, by covalently preconjugating one or multiple therapeutic agents by covalent bond to form drug conjugates. It provides the advantages of nano size system with the targeted delivery of drug with great precision. The conjugation system allows the modification in the metabolic path way in the blood stream and can target the delivery to the heart, liver or brain. The cleavable covalent bond allows the therapeutic activity of the individual drugs to be resumed after the drug conjugates are delivered into the target site and get separated from the carriers. The characters of drug conjugated system are (a) a covalent bond between drug and carrier moiety, (b) in vitro cleavage of the bond, (c) optimum release of drug at site of action to ensure effectiveness, (d) no alteration in drug action. As a proof of the concept, synthesis and characterization of stearic acid/oleic acid- diminazene conjugates nanoparticles are demonstrated. It is shown that after conjugation with lipid and/or polymer and synthesized to nanoparticles there is significant improvement in cyctotoxicity and targeted controlled delivery of drug than the free drug.

Quantum dots (QDs) are a landmark development in the field of nanotechnology. These zero-dimensional semiconductors, unlike their physical attributes, have enormous capacity to store energy within themselves. This energy is contained in several thousands of electrons that constitute the nanoparticles. QDs are synthesized by both organic and inorganic methods, the choice being dependent upon the desired efficacy of the resultant product. The process of synthesis is auto regulated by the phenomenon of nucleation threshold, whilst quality control occurs through ostwald ripening, given by Gibbs Thompson equation. The optical and electronic properties of these particles are dependent upon the transitions of constituent electrons between the valence and conductance bands and this phenomenon is exploited in synthesizing QDs to be employed as biomarkers. Fluorescence is obtained when electrons return to the ground state from the lowest vibrational level of an excited state, emitting quanta of radiation in the process. As wavelength varies with each energy state, a rainbow of fluorescence is seen with quantum dots of different sizes and shapes. The properties of these nanoparticles are largely attributed to their high surface area to volume ratio, with the former parameter being subjected to modifications like capping and functionalization. This not only enhances their quantum yield but also multiplies their fluorescing abilities. As biomarkers, these particles find many clinical applications, in an array of in vivo and in vitro techniques, ranging from drug delivery systems to interstitial target tracking. However, one special clinical application of QDs that demands reverence for their utility, is their specific and selective cancer cell imaging activity. Photosensitizers may be linked to QDs, bound to monoclonal antibodies, and targeted to cancer cells, where they may generate reactive oxygen species (ROS) upon exposure to light. This could help in the treatment of metastatic malignancies and form a part of photodynamic therapy. On the other side lies the toxic effect of these particles that can be traced to their heavy metal crystalline cores. However, pursuit is on, to overcome this drawback, so that QDs can be used more effectively in vivo for a longer period of time.

Crop protection against insect pest is a priority and due to the adverse impact of chemical insecticides, use of biopesticdes is increasing. Bacillus thuringiensis (Bt) based biopesticides have utmost importance and occupy almost 97% of the world biopesticide market. Environmental contamination, food safety concerns, and pest resistance to conventional insecticides have caused a steady increase in demand for Bt-based insecticides. Despite extensive research in the field of Bt biopesticides, many formulations don’t deliver effectively in field owing to various environmental stresses (for example agriculture and forestry). Insecticides formulated with Bt account for less than 1% of the total insecticides used each year worldwide because of high cost, narrow host range, and comparatively low efficacy. The recent escalation of commercial interest in Bt has resulted in more persistent and efficacious formulations. In this context, nanotech applications and products are strongly promoted on the basis of their environmental benefits. Bt as NANOPARTICLES in agriculture especially for plant protection is an under explored area, and needs further exploration. This short concept note discussed on various aspects of Bt as nanoparticles covering the prospect, integration and future strategies for the effective utilization to the benefits of human welfare.

Carbon Nanotube Field-Effect Transistor (CNTFET) is a promising candidate for future electronic devices, so it is used for both analog and digital circuit application. This paper presents a Verilog-A implementation of a physical compact model for the Conventional Carbon Nanotube Field Effect Transistor. This device is then used to design a carbon nanotube FET based Operational Amplifier (Op Amp). The CNTFET Op Amp performances are tuned in term of the CNT diameter in order to obtain a gain of 48dB and a bandwidth of 200MHz. The performances in term of the power dissipation are much better compared to AOP circuit using CMOS technology.

TiO2-Al2O3 composite material was prepared by a sol-gel method using a sol mixture derived from tetrabutyl titanate and aluminium isopropoxide. Crystalline structure, surface morphology, composition, BET surface area, and pore size distribution of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Xray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), and N2-adsoption and desorption. The composite materials are composed of anatase TiO2 and amorphous Al2O3. There is no apparent difference in surface morphology among the samples calcinated at different temperature. Titanium is in its full oxidation state and there is no reduced titanium state existing in TiO2-Al2O3 composite. The existence of Al2O3 causes binding energies shift to higher energy end for Ti2p3/2, Ti2p1/2, and O1s levels. Specific surface area of the composite samples decreases and TiO2 crystallite size increases with increasing calcination temperature. The TiO2-Al2O3 composite sample calcinated at 500 °C for 3 h shows both the maximum adsorption capacity and photocatalytic activity. Nearly all of the initial methyl orange is removed from TiO2-Al2O3 composite after a certain time period. As compared with pure TiO2, photocatalytic activity and adsorption capacity of TiO2-Al2O3 composite are enhanced obviously.

Magnetic MnFe2O4 with functionalized graphene (MnFe2O4-G) was prepared by solvothermal treatment of inorganic salts with graphene oxide as a starting material. The as- prepared product was then characterized by using X-ray powder diffraction (XRD) and Field Emission Scanning electron microscopy (FE-SEM). FE-SEM observations show that manganous ferrite nanoparticles with sizes of 10-40 nm were well dispersed on graphene sheets. The obtained hybrid was further tested for its photocatalytic activity against malachite green (MG) dye degradation. Results show that the photocatalytic activity of as- prepared product (MnFe2O4-G) has about 67% of dye degradation. This research would provide a new easy separating platform for wastewater decontamination. The combination of the superior adsorption of graphene and the magnetic properties of MnFe2O4 nanoparticles can be used as a good adsorbent and separation tool to deal with water pollution.