Current Nanoscience - Volume 9, Issue 3, 2013

The properties of nanoscale titanium dioxide particles generated in-situ during a polycondensation process are explored and the compounds obtained are investigated as UV-stabilizing additives for the formation of ultradurable powder coatings. Beneficial effects of TiO2 nanoparticles for the long-term photoprotection of polyester composite materials under accelerated weathering conditions could be clearly demonstrated. These results are of considerable interest for the development of new hybrid organic-inorganic systems to be used as transparent coatings for outdoor applications such as UV-resistant protection layers stabilized with functional nanoparticles based on cheap, environmentally benign and abundant compounds.

Nano-structured titania (TiO2) has received considerable attention in the field of biomedical research because of its numerous advantages and few health concerns. To produce good biocompatible biomaterial, we synthesized different structural nano-TiO2 and TiO2–chitosan (CH) nanocomposite by precipitation, hydrothermal, and in situ sol–gel methods. The prepared samples were characterized comprehensively. Nano-TiO2 prepared by precipitation and hydrothermal methods (sintered at 673 K) showed an anatase phase with spherical morphology, whereas precipitation at 393 K confirmed amorphous phase. In situ synthesized composites were amorphous and had irregular morphology. The samples were further analyzed for in vitro bioactivity, antibacterial activity, and cytotoxicity. The characterization after bioactivity study confirmed formation of stoichiometric ratio of hydroxyapatite on TiO2–CH nanocomposite compared with other TiO2 samples. No significant cytotoxic effect of all the samples on gastric adenocarcinoma (AGS) human cell line was observed. This study shows that method of synthesis has no significant effect on the bioactivity and antibacterial activity, whereas it influences cytotoxicity. However, TiO2–CH nanocomposite has an important function in conferring better biocompatibility. Thus, TiO2-based polymer composites prepared with appropriate synthesis methods are recommended for implant and tissue engineering applications.

A diverse pool of six semiconductor GaN nanopowders was synthesized by the thermally-driven pyrolysis of gallium imide at various temperatures. The XRD-derived average crystallite sizes for the nanopowders were in the range 1-17 nm. Standard nitrogen adsorption measurements at 77 K yielded the basic characteristics of the powder pore structures including the BET surface areas that spanned 23-287 m2/g. Rare studies of adsorption of water vapor, carbon dioxide, and hydrogen on the nitride nanopowders were carried out. The data on water vapor adsorption at 295 K supported chemisorption of water molecules on the primary adsorption centers and physisorption on the secondary centers. The data on carbon dioxide adsorption at 273 K and hydrogen adsorption at 77 K were used to determine the selectivity of adsorption for these gases defined as the ratio of the respective Henry’s constants calculated from the Langmuir equation. The GaN nanopowders showed remarkably diverse pore structure characteristics and adsorption properties that could be linked to the nitride’s average crystallite size and crystallite agglomeration, the latter supported by helium density data.

The bilayer structures of graphenes and boron nitride nanosheets (BNNSs) with different interlayer spacings are optimized, and their Young’s moduli are calculated using the molecular dynamics method. The optimized results indicate that the optimal interlayer distances are about 0.343 nm for bilayer graphenes and 0.354 nm for bilayer BNNSs. A comparison of the binding energy, van der Waals interactions between layers, and radial distribution function (RDF) revealed that bilayer BNNSs can achieve a more stable combined structure than bilayer graphenes. The Young’s moduli of bilayer graphenes were 1029 and 1032 GPa and those of bilayer BNNSs were 944 and 957 GPa along the zigzag and armchair directions, respectively. The moduli for the bilayer nanosheets were all slightly lower than those of the corresponding monolayer ones, wherein the reduction of BNNSs was always smaller than that of graphenes. The bilayer structure, specially bilayer graphenes, can markedly weaken the anisotropy of the elastic property. These phenomena can be rationally analyzed based on system energy, RDF, deformation electron density, and chemical bonding theory.

WO3-MoO3 nanocomposite films with good electrochromic properties were prepared by the electrodeposition method. The surface morphologies and composition of the composite films were characterized by scanning electron microscope (SEM) and energydispersive X-ray analysis (EDS). Spectroelectrochemistry and electrochromic properties of the WO3-MoO3 nanocomposite films were characterized using cyclic voltammetry (CV) and spectral optical absorbance. The effect the content of MoO3 in the composite films on the electrochromic properties has been studied. It has been observed that the electrochromic properties of the composite films could be adjustable by changing the MoO3 quantity in the composite films.

A new method was developed to grow zinc oxide (ZnO) nano-flowers via an organic solvent assisted growth technique. Flower-like ZnO nanostructures were successfully prepared from the solution method, without using surfactant, complexing agent or stabilizer. The influences of different organic solvents on the growth of ZnO nanostructures were investigated. A simple growth mechanism was proposed, to demonstrate the role of solvent molecules in the growth of flower-like ZnO. The structural and photoluminescence properties of synthesized flower-like ZnO were analyzed, using X-ray diffraction, photoluminescence studies, field emission scanning electron microscopy and transmission electron microscopy. For photocatalytic activity, flower-like ZnO nanomaterials, upon ultraviolet irradiation, act as an excellent photocatalyst for the decomposition of two commercial organic dyes, 4-[(4-dimethylaminophenyl) phenylmethyl]- N,N-dimethylaniline (malachite green) and 4-[(4-Aminophenyl)-(4-imino-1-cyclohexa-2,5-dienylidene)methyl] aniline hydrochloride (basic fuchsin); and these were investigated. Upon UV irradiation, a significant enhancement in photocatalytic activity was observed in both dyes.

Owing to its special photoelectric properties, ZnO nanostructrues have attracted extensive attention. Here we reported a study on the effect of substrates and seeding layers’ thickness on the morphology of the resultant ZnO nanostructures. The atomic layer deposition (ALD) was used to pre-synthesized seed layers on different substrates, including polyethylene terephthalate (PET), graphene/PET, Ag/PET, Al/PET and Al2O3/PET. Chemical solution route was employed to synthesize ZnO nanostructures. When the thickness of seed layers was 10 nm, nanorods, nanowalls and nanosheets were obtained. Nevertheless, when the thickness of seed layer was increased to 100 nm, well-aligned ZnO nanorods with homogeneous dimension were achieved on all the studied substrates. The possible growth mechanism of ZnO nanostructure was discussed and a feasible way to control the morphology and structure of ZnO was proposed.

We report, strong ultraviolet (UV) emission from ZnO nanoparticle thin film obtained by a green synthesis, where the film is formed by the microwave irradiation of the alcohol solution of the precursor. The deposition is carried out in non-aqueous medium without the use of any surfactant, and the film formation is quick (5 min). The film is uniform comprising of mono-disperse nanoparticles having a narrow size distribution (15-22 nm), and that cover over an entire area (625 mm2) of the substrate. The growth rate is comparatively high (30-70 nm/min). It is possible to tune the morphology of the films and the UV emission by varying the process parameters. The growth mechanism is discussed precisely and schematic of the growth process is provided.

Metal oxide semiconductor nanofibers obtained by electrospinning are excessively used in organic-inorganic photovoltaic (PV) devices due to large surface area with low production cost. Performance of these devices depends upon the thickness of the active layer and polymer infiltration through the pores of nanofibers mat, which is controlled by electrospinning time. The parameters of hybrid photovoltaic devices, fabricated by poly (3-hexylthiophene) (P3HT) and TiO2/ Di-tetrabutylammonium cis-bis(isothiocyanato)bis(2,2'- bipyridyl-4,4'-dicarboxylato)ruthenium(II) (N719) composite nanofibers was analyzed by considering infiltration of polymer through the electrospun nanofibrous network. Power conversion efficiency (PCE) was improved from 0.13% to 0.93%. Open circuit voltage and short circuit current density were also improved to 0.61V and 3.64mA/cm2 respectively. Longer electrospinning time resulted in an increased number of fiber layers, i.e. increased thickness of the active layer. This results in higher light absorption but reduced infiltration of polymer through the nanofibrous pores up to the lowest layer due to covering up by the top layers. These factors introduce defects and increased series resistance, contributing toward decrease in device efficiency.

The detection of hexanal has attracted much attention because hexanal has an important effect on food quality and human health. In this paper, nano-SnO2 flat-type coplanar hexanal gas sensor arrays at the ppb level were fabricated by a screen-printing technique based on nano-SnO2 powders prepared by a sol-gel method. The test results show that the nano-SnO2 flat-type coplanar gas sensor arrays have good hexanal gas-sensing characteristics such as short response time, low detection limit, high sensitivity. Especially, the gas sensitivity of the nano-SnO2 gas sensor arrays to 50 ppb hexanal reached 9.5 at a working temperature of 200°C. Nanometer-size effects, lattice distortion of nano-SnO2, and the natural properties of hexanal caused the ppb-level hexanal gas-sensing characteristics.

Silver nanoparticles, exhibiting unusual properties of ionic ability associated with the particle suspension, have been extensively used as the anti-microbial agent in medicine. The present study addressed the elicitation potential of nanosilver particles for the enhancing plant secondary metabolite production. Ag-SiO2 core–shell nanoparticles (AgNPs) with an average size of 101.8 ± 8.9 nm were prepared as elicitor to the hairy root cultures of Artemisia annua. Artemisinin content in the cultures was increased from 1.67 mg/g dry wt to 2.86 mg/g dry wt by the stimulation of AgNPs at 900 mg/L for 3 d. AgNP elicitation was related to the released dissolved Ag+ and nanoparticulate nature of AgNPs introduced to the cultures. AgNP treatment induced oxidative stress (H2O2 production) resulting in lipid peroxidation (increased malonyldialdehyde (MDA) accumulation), enhanced activities of catalase (CAT) and increased artemisinin content in hairy roots. The elicitor stimulated artemisinin production in 20-day-old hairy root cultures up to 13.3 mg/L, a 3.9-fold increase over the control. These results suggest that Ag nanoparticles can be used as a novel effective elicitor in plant biotechnology for the production of plant secondary metabolites.

La/Sm-doped strontium-ferrite/poly-m-toluidine) (PMT) composites were synthesized by in-situ chemical polymerization of m-toluidine in the presence of La/Sm-doped strontium-ferrite particles. Structural, morphological and electro-magnetic properties of nanocomposites were performed by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), four-probe conductivity tester and vibrating sample magnetometer (VSM). The results of XRD indicated that La3+ and Sm3+ had entered into the lattice of strontium ferrite. FTIR spectra demonstrated that there were interactions between ferrite particles and PMT. SEM studies showed that the composites presented the core-shell structure. Under applied magnetic field, nanocomposite exhibited the hystereric loops of the ferromagnetic behavior. The saturation magnetization and coercivity of nanocomposites varied with the content of (LaSm)0.06SrFe11.88O19particles.

There might be amorphous solid He-4 formed in around 6 nm (diameter) pore as reported recently. By treating the solid He-4 in confined nanodomains locally as an amorphous matter and using the Eyring's model together with the activation energies and volumes, we can observe sudden changes of the shearing stresses (which relate to the resistance) as well as shear viscosities (which relate to the rigidity) at corresponding onset temperature of solid He-4. We demonstrated that there might be almost frictionless transport of locally amorphous solid He-4 in confined nanopores at temperature ∼ 0.08 K.

Gd-substituted Mn-Zn ferrite (Mn0.5Zn0.5Gd0.02Fe1.98O4) nanoparticles were synthesized using chemical co-precipitation. Measurements of magnetization as a function of the applied field were performed at several temperatures. As expected, the saturation magnetization was found to decrease with temperature. However, fitting the magnetization data to a single Langevin function yielded an anomalous increase in the average magnetic moment per particle. The increased magnetic moment is attributed to thermally increased nanoparticle volume which is caused by thermally induced aggregation of the nanoparticles. Inter-particles dipolar interactions, responsible for clustering, are believed to increase with thermally induced surface layer spin. This agglomeration is thermally reversible up to a critical temperature after which thermal energy overcomes dipolar interactions. Thermally induced agglomeration can be used as temperature sensor.

Degradation of C.I. Direct Red 23 (DR23) was investigated by photoelectro-Fenton (PEF) process in the presence of citrate catalyst under visible light irradiation of 6W. Multi walled carbon nanotubes (CNTs) were characterized by transmission electron microscopy (TEM), which had approximately internal and external diameters of 6 nm and 22 nm, respectively. CNTs were stabilized on carbon paper utilizing polytetrafluoroethylene (PTFE) and stabilization was confirmed by scanning electron microscopy (SEM). Results revealed that the degradation efficiency followed the order of PEF/citrate > PEF > EF at the same operational conditions after 90 min treatment of 20 mg/L DR23. The effect of some operational parameters such as applied current, initial pH, initial dye concentration and Fe(III) to citrate ratio on PEF/citrate process was studied. Artificial neural network (ANN) was applied not only to develop a model to predict the degradation efficiency with reasonable performance (R2= 0.988), but also to determine the relative importance of operational parameters for PEF/citrate process.

The present work aims at designing of a novel hexagonal porous structure of alumina to improve the efficiency of dehydrogenation catalysts. Alumina was prepared by solvent thermal method under supercritical conditions in presence of ethanol. X-ray diffraction was used to identify alumina after calcinations at 600 °C. Scanning electron microscopy images confirmed that the alumina particles are in the nano-scale and showed strong aggregates of the nanoparticles. The hexagonal porous structure of alumina was confirmed by field emission scanning electron microscopy (FESEM) after coating with a thin film of platinum. Agreeing with the FESEM images, the results of the nitrogen adsorption-desorption isotherm indicated that the mesoporous structures of the alumina and the nano catalyst were built from aggregates of plate-like particles or slit shape of particles. Development of the dehydrogenation catalyst was achieved by supporting 0.6 wt.% platinum metal over the prepared alumina. The results of catalytic activity revealed that the nanocatalyst based on the hexagonal porosity was efficient and selective toward dehydrogenation reaction. Where, the catalytic activity and selectivity toward cyclohexane dehydrogenation reaction were 100% at moderate temperature 350 °C. Our results concluded that the nanocatalyst based on hexagonal porosity of alumina is convenient for dehydrogenation reaction.

The present study aims to investigate the drug-loaded mechanism of ion–cross-linked nanoparticles (NPs) in the presence of polyvinylpyrrolidone K30 (PVP K30) and set up the optimal PVP-coated norcantharidin (NCTD) chitosan NPs method. We compared and assessed PVP-coated norcantharidin chitosan NP (PVP-NCTD-NP) with norcantharidin chitosan nanoparticles (NCTD-CS-NP) using Xray diffraction (XRD) and atomic force microscopy (AFM). The results show that both kinds of nanoparticles were spherical, with an average size ranging from 100 nm to 250 nm. However, the entrapment efficiency of the PVP-NCTD-NP (67.33% ± 1.41%) was higher than that of NCTD-CS-NP (52.61% ± 1.28%), probably because of the PVP-coating effect on the surface of the NPs. The cumulative release percentages of PVP-NCTD-NP in vitro within 2 h, 4 h, and 6 h were 74%, 89%, and 92%, respectively. Those of NCTD-CS-NP within 40 min and 190 min were 67% and 90%, respectively. Thus, the PVP-NCTD-NP with dual physical drug-loaded mechanisms (physical encapsulation and coating of PVP) possessed higher drug content and showed longer sustained release.

We investigated top-contact pentacene-based organic thin-film transistor (OTFTs) with bi-layer MoO3/Au electrodes. The device performance including field effect mobility, threshold voltage, and On/Off ratio was highly improved in a device with 5 nm MoO3 layer which showed the highest field-effect mobility of 0.72 cm2 V-1s-1. In addition, from temperature dependence characteristics, we observed that the barrier height was dramatically decreased from 0.12 eV (without MoO3) to 0.03 eV in device with 5 nm MoO3 layer. This improved device performance was attributed to significant reduction in barrier height at Au/pentacene interfaces and surface roughness of pentacene layer after inserting a suitable MoO3 layer between pentacene and gold electrodes.

For a molecular graph G with vertex set V (G) , we denote by dG (u,v ) the distance between vertices u and v in G ...

Polymerase chain reaction is a critical scientific technique in molecular biology. With the higher demand of PCR, recently, researchers have demonstrated various effects that take place when nanomaterials (NNMTs) are used as additives in PCR, which is defined here as Nano-PCR. Quantitative and qualitative understanding of the effect of NNMTs on PCR after adding different NNMTs into PCR systems has also emerged. Nano-PCR has become a hot topic in the fields of nanotechnology and biotechnology. In addition, understanding the fundamental mechanism of the effects of NNMTs on PCR is of paramount importance because these effects impact directly the ability to develop nano-PCR systems with high specificity, efficiency, sensitivity, fidelity and repeatability and to optimize NNMTs. In this paper, we review the effect of NNMTs on important PCR profiles, and their underlying mechanisms of action.