Current Nanoscience - Volume 11, Issue 1, 2015

Cellulose considered as one of the most abundant renewable resources have great potential for the production of bio-fuels and chemical building blocks bearing a diverse range of applications. Among various approaches for the efficient transformation of cellulose, nanoparticles on ordered porous materials with high surface area and unique particle morphology employed as heterogeneous catalysts exhibit dramatic improvement of catalytic activity and selectivity. In this review, selective conversion of cellulose as well as cellobiose through different types of reactions including hydrolysis, isomerization, dehydration, hydrogenation/hydrogenolysis, oxidation, hydrogenation-dehydration, and gasification/pyrolysis promoted by mono- or bi-functional nanocatalysts has been described. Emphasis is also paid to discuss plausible reaction pathways catalyzed by functionalized nanoparticles in these catalytic processes.

Nanotechnology has shown tremendous scope in healthcare offering numerous possibilities to significantly improve diagnosis of many dreadful diseases including Tuberculosis (MTB). Nanomedicine has made the current drug regimen more effective against tuberculosis particularly tuberculosis meningitis with attributes like sustained release, increased half life, higher drug concentrations at target sites, reduced toxicity and lesser side effects. However because of the severity of the disease, there is a strong urge to develop better approaches with some concomitant regimens using nano-particles to diagnose, treat and manage tuberculosis meningitis (TBM) patients. The rate of drug resistance is also reportedly higher in case of TBM, which may further reduce the patient compliance and therapeutic failure of the current regimen. Hence there is an urgent need to develop effective ways to counter TBM. The current review highlights some of the evolving strategies in the field of nanomedicine offering promising alternatives to the existing TBM regimens. The study also emphasizes upon the need to design more effective biocompatible and biodegradable nanocarriers which can effectively cross the blood brain barrier to counter TBM.

Carbon nanotubes have been increasingly used in the fields of nanorobotics, electrochemical catalysis, microarray chips, and green adsorbents for pollutants, sensors and optoelectronics. Complicated physico-chemical aspects and novel schemes to synthesize controlled featured carbon nanotubes have added new ambiguities to their characterizations and applications and these must be resolved on an urgent basis. Most of the characterization tools such as scanning electron microscopy, transmission electron microscopy, scanning tunneling microscopy and atomic force microscopy probes only for characterizing the local features of carbon nanotubes. However, X-ray powder diffraction can reveal the local and global features of microstructure’s lattice and crystalline phases, domain sizes, and impurities. Thus it is worthwhile to highlight this technique for better understanding and utilization of its benefit to unravel the carbon nanotube ambiguities. To the best of our knowledge, no comprehensive reviews or systematic description of X-ray powder diffraction on carbon nanotubes characterization have been published yet. In this review, we filled-up this gap and provided a systematic presentation of X-ray powder diffraction application in carbon nanotubes characterization. This could be used as a reference guide for the utilization of X-ray powder diffraction to probe the various features of carbon nanotubes and carbon nanotubes based materials.

In this paper a procedure for RF characterization of Carbon NanoTube Field Effect Transistors is illustrated and applied to a back-gate CNTFET. S parameters measurements up to 12 GHz are performed and a new lumped element active two-port network is proposed and deduced from these measurements. To obtain the intrinsic RF behavior of the device, we perform a straightforward static de-embedding procedure, applicable to any other CNTFET structures. In this way it is possible to evaluate the intrinsic model to implement directly in simulation software for electronic circuits CAD.

Few polymers with practical and technological appeal can be electrospun into nanofibers from water solutions. The production of polymer nanofibers from water solution is considered green, up-scalable and versatile. From this point of view, the use of nanoparticles in the form of water colloidal suspension instead of nano-powder should be more affordable and safer. The combination of these two aspects makes a breakthrough in materials science on electrospun nanomaterials. In this work, multi-component organic/inorganic nanofibers were produced by electrospinning water solutions of a protein extracted from wool (i.e. keratin) containing nanosols of titanium dioxide and metal silver. In order to improve electrospinnability, poly(ethylene oxide) was added to the solutions. Colloidal stability was studied in depth to preserve nanoparticle dimension as smaller as possible in the electrospinning solutions. Resulting hybrid keratin-based nanofibers were made water insoluble by treatments at high temperature, expanding the range of applications of such a nanomaterial. In this way, it was also possible to wash out poly(ethylene oxide) from nanofibers maintaining a nanofibrous structure and small-sized porosity comparable to the as-spun materials. Finally, the functional properties of electrospun hybrid nanofibers were evaluated. Both antibacterial and photo-catalytic activities of titanium dioxide nanoparticles embedded into the nanofibers were quantified, as well as antibacterial property of nano-silver. The results demonstrate that nanoparticle functionalities were maintained in electrospun keratin nanofibers.

Photonics has experienced rapid growth in recent years and market promotion. Photonics is an emerging field of science which deals with nanoscale fabrication and characterization techniques. The aim of this paper is to overview some achievements on light harnessed in photonic nanostructures. We present the results from recent papers and from seminal papers. Successful approaches from relevant literature, together with results from our own research are presented. Our research was performed by numerical integrations with the MIT codes and dealt especially with light confinement in nanostructures. This progress has brought with it a renewed interest in surface plasmon-polaritons that allow electromagnetic energy to be localized, confined, and guided on subwavelength scales. Moreover, the locally enhanced field intensities observed in plasmonic structures promise potential for molecular biosensing, surface enhanced Raman spectroscopy, and nonlinear optical device applications.

A study on the application of Response Surface Methodology (RSM) for the optimization of the process parameters of the preparation of 2,4,5-triphenyl-1H-imidazole over BaSO4 nanoparticles as catalyst was explored. A threelevel, three-factor, Box–Behnken experimental design has been employed to determine the effects of process parameters namely temperature (20-130 °C), catalyst dosage (0.01-0.5) and initial NH4OAc concentration (2-4 mmol). The second order mathematical model was developed by regression analysis of the experimental data obtained from 30 runs. Highest yield of product and lowest time of process were obtained at the optimum conditions as: temperature (130 °C), catalyst dosage (0.5 mmol) and NH4OAc concentration (4 mmol).

Microbicidal tissue paper is made by a simple method of impregnating biosynthesized silver nanoparticles with the conventional tissue paper. A number of infections are being transmitted by conventional tissue paper especially through hospitals. Silver nanoparticles were synthesized by green synthetic route using the leaf extract of Eichornia crassipes, further characterized using UV Vis spectroscopy exhibiting a SPR peak at 413 nm and HRTEM having a size between 20 to 50 nm. We have developed a hybrid tissue paper for control of spreading of hospital infections. The hybrid tissue paper was characterized by X – Ray Diffraction and Field Emission Scanning Electron Microscopy in which the size of the nanoparticles present in the tissue paper was found to be ranging from 20 nm to 50 nm. Antimicrobial activity was evaluated against clinical pathogens - Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa and release studies of nanoparticles from the hybrid tissue paper were carried out to ascertain the antimicrobial nature.

Among all separation techniques, membrane technology has been shown to reduce CO2 emissions without any phase changes due to its rapid, energy efficient process. The membrane-based gas separation must consist of a defect-free, thin, dense skin layer that is supported by a porous sub-layer that allows an excellent permeation rate and selectivity. This study is aimed at developing a defect-free, thin-skinned layer of mixed matrix membrane (MMM) from cellulose acetate (CA) polymer and functionalized multi walled carbon nanotubes (MWCNTs) as inorganic filler. The influences of membrane casting thickness (150-300) µm and CA polymer concentration (7-17) wt.% on membrane morphologies were first investigated. The outcome of these dominant parameters were then used to synthesize the MMM. The results showed that the defect-free, thin, dense skin thickness of membrane could be achieved with a casting thickness of 250 µm and CA polymer concentration of 10 wt.%. By considering both dominant parameters, the synthesized MMM proved to have a thin selective layer, whereby it showed a high permeance and selectivity for CO2/N2 gas separation.

Gold nanoparticles were synthesized, using a straightforward photoreduction protocol in the presence of mixedaddenda Preyssler heteropolyacid, H14[NaP5W29MoO110], (PMo). It acts as a reductive agent, as well as a photocatalyst and stabilizing agent. The obtained results showed that the construction rate, morphology and the size of the gold nanoparticles strongly depend on the volume of propan-2-ol amount, used as solvent in the reaction. The shapes of the synthesized gold nanoparticles in the low volume of the solvent were almost uniform spheres with the size of 40-60 nm. The morphologies of the gold nanoparticles in higher volume of the same solvent were found to involve a mixture of triangular, tubular, pentagonal and hexagonal structures along with spheres in range of 5-30 nm. Besides, the ability of the PMo as reductive agent for the syntheses of gold nanoparticles onto the surface of TiO2 via photochemical technique was investigated. The results showed that, PMo as a reducing catalytic linker could be bound onto titanium dioxide for syntheses of the desired gold nanoparticles. The synthesized gold nanoparticles and nanocomposites were characterized by TEM, XRD, SEM, UV and FTIR techniques. The photocatalytic activity of the synthesized nanocomposite was measured by photodegradation of the organic dye “malachite green” under UV-Vis light and was found to be excellent.

The semiconducting electronic properties of graphene nanoscroll (GNS) are very much related to its geometric structure. The aim of this study is to construct a GNS energy dispersion model within low-energy transport of 1 eV in identifying its electronic properties and carrier statistics. Non-parabolic energy dispersion is used to incorporate the Archimedean type-spiral model, and the band gap is assessed based on chirality and geometry effects. The energy band within low-energy transport indicates that GNS can achieve a quantum conductance limit of ~6.45 kΩ for ballistic transport. On the other hand, the numbers for three minimum sub-bands are attained based on non-parabolic energy dispersion, and the semi-metallic zig-zag GNS is found at chirality (3j + 1, 0). This work consistently predicts the semiconducting properties of the tight-binding model from previous work. The GNS overlapping region strongly affects its electronic properties. Constantly increasing the length of the overlapping region decreases the band gap exponentially, whilst semimetallic GNS forms when the overlap reaches a certain limit. The carrier density with temperature dependence is subsequently assessed at the intrinsic level, and found that the number of carriers in GNS shows a higher rate of increment (exponentially) compared to carbon nanotubes (CNT), in accordance to their diameter. The results are very useful in giving an intuitive understanding on GNS carrier statistics as subject to geometry changes.

The islands like barium aluminum oxide BaAl2O4 nano-spheres were grown on the surface of Al2O3-MgO composite via oil in water (O/W) micro-emulsion method. Hexane, 2-aminoethanol and ethanol were used as oil phase, non-anionic surfactant and co-surfactant respectively. The synthesized Ba Al2O4 nano-spheres were grown on the surface of Al2O3-MgO composite and have been characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and Energy-dispersive X-ray spectroscopy (EDAX). The BaAl2O4 nano-spheres grown on the surface of Al2O3-MgO composite exhibited high catalytic activity for the transformation of cinnamaldehyde, methyl/ethyl acetoacetate and aromatic amines as the starting materials to 1,4-dihydropyridine derivatives.

A modified sol-gel method was applied to prepare 0.3%La-3%In-TiO2 in order to investigate the effect of calcination temperature. The material was investigated by SEM, XRD, and N2 adsorption-desorption methods. The diffraction peaks of the sample are in accordance to the patterns of anatase TiO2. The anatase crystallite sizes are 5.5, 6.3, 11.1, and 15.6 nm for the samples calcinated at 350°C, 400°C, 500°C, and 600°C, respectively. Crystal cell expansion is found when calcination temperature increases from 350°C to 500°C. The increase of average pore size and decrease of pore volume with increasing calcination temperature are found for 0.3%La-3%In-TiO2. The 0.3%La-3%In-TiO2 calcinated at 400°C has satisfactory adsorption capacity and photocatalytic activity. 25.6% of the initial methyl orange can be adsorbed on the material after adsorption-desorption equilibrium. After that, the remaining methyl orange can be fully degraded after 40 min of irradiation.

In this paper, three different morphological Co3O4 electrodes for oxygen evolution reaction (OER) have been synthesized. By comparing the three morphologies of Co3O4, the electrocatalytic properties show that the urchin-like spheres of Co3O4 electrode has relative low overpotential and good electrocatalysis stability, indicating that the structure of urchin-like Co3O4 spheres exhibit an easy OER for water splitting.

Iron oxide nanoparticles (IONs) are being used in medicine for magnetic resonance imaging, drug delivery and hyperthermia. There are contradictory data about cytotoxic effects of IONs on various cell lines. In this study a couple of IONs with two biocompatible coatings, L-lysine and 3-aminopropyltriethoxysilane, were synthesized by coprecipitation method in aqueous matrix and characterized. The MTT assay was used to evaluate the effects of the synthesised IONs on HepG2 cells. Cell culture illustrated that the growth of HepG2 cells can be promoted by IONs and nanoparticles with biocompatible coating have more biological benefit impacts than naked particles. By increase in concentration, cytotoxic effects will appear and reduce the growth promotion effects. Cytotoxic effects are in relation with agglomeration degree of nanoparticles, agglomeration can reduce cytotoxicity of IONs at high concentrations.

A super hydrophilic SiO2 aerogel (SHSA) was prepared using the sol-gel method and CO2 supercritical drying technology, yielding a specific surface area of 680.08 m2/g and a total pore volume of 3.95 cm3/g. The hydrophilic property of the SHSA was investigated and showed a maximum water adsorption capacity (qm) of 7.79 ml/g. NH3 adsorption tests were conducted and were compared with the results for pure SiO2 aerogel (PSA) under non-water vapor and water vapor treating conditions. The effect of water vapor on SHSA was found to be larger than its effect on PSA. A physicalchemical adsorption process of NH3 appeared in the presence of water vapor on the SHSA surface, giving a maximum adsorption capacity (Qm) of 193.66 mg/g. The regenerability of SHSA was also investigated, and the loss percentage of Qm was found to be 22.28% over 10-cycle adsorption tests. The results indicate that SHSA is a promising candidate for use as an NH3 sorbent.

In this study, MnO2 nanoparticles were synthesized on bio-silica by a simple one-step procedure using permanganate in the acidic medium. The synthesized catalyst was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The obtained results confirmed the nanostructure of MnO2 and its stabilization on the bio-silica as the support. The removal efficiency of acid orange 7 (AO7), using bare bio-silica and MnO2 coated bio-silica, was found to be 5 and 95%, respectively. The effect of operational parameters including AO7 concentration, catalyst dosage and process time of treatment process was also studied on the basis of efficiency. The results demonstrated that the color removal efficiency was decreased by increasing AO7 concentration, and increased by the enhancement of the process time. The optimal dosage of 0.8 g/L was chosen for the catalyst amount. Hydroxyl radicals played a significant role in the process based on the proposed mechanism. The spectral changes of AO7 during the process in UV-Vis region showed not only the efficient decolorization, but also the degradation of the dye after 50 min of the treatment.

Super hydrophilic multi-walled carbon nanotubes (MWCNTs) were bombarded by N ions through ion beam assisted deposition. MWCNTs were synthesized via chemical vapor deposition. Biological tests in vitro were performed on raw MWCNTs and N+-bombarded MWCNTs. Cellular adhesion was investigated both using human endothelial cells and mouse fibroblast cells. Results showed that N+-bombarded MWCNTs stimulated cell growth and proliferation, revealing superior cell adhesion. Antithrombogenicity of raw and N+-bombarded MWCNTs was evaluated by platelet conglutination, hemolysis and kinetic-clotting assays. Compared with raw MWCNTs, N+-bombarded MWCNTs displayed better morphology of platelets and red blood cells, longer kinetic blood-clotting time, which increased their thromboresistance, further antithrombogenicity.