Current Nanoscience - Volume 9, Issue 2, 2013

Polished (111) surfaces of monocrystalline cubic gallium arsenide GaAs platelets and a powdered microcrystalline form of GaAs were nitrided towards gallium nitride GaN under a flow of ammonia at temperatures in the range 600-900 ° C for one to several tens of hours. The progress of nitridation was followed mainly by grazing incidence X-ray diffraction GIXD and powder X-ray diffraction XRD. Morphology changes were examined with scanning electron microscopy supplemented with energy dispersive analysis SEM/EDX. Thermogravimetric and differential thermal analyses TGA/DTA were used to evaluate a thermal stability of the GaAs substrate. The substrate/temperature/time related interplay in the formation of the cubic and hexagonal GaN polytypes from cubic GaAs and conditions favoring the metastable cubic GaN polytype are delineated.

Nanocrystalline Y3Al5O12:Eu3+ phosphors with particle size about 20-40 nm have been synthesized by a facile solution combustion method. XRD and TEM studies show that Y3Al5O12 nanocrystals can directly form at a low temperature of 825 °C and highly crystalline at 850 °C. With the increase of annealing temperature, the charge transfer band shows a blue shift due to the dielectric confinement effect. The color purity of Y3Al5O12:Eu3+ phosphors can be improved by decreasing the grain size of nanocrystals. Furthermore, the high concentration doping of Eu3+ can be realized in Y3Al5O12 nanocrystals, which will enhance the luminescent intensity. This work demonstrated that solution combustion is a feasible method to synthesize europium rare earth doped Y3Al5O12 nanocrystals with enhanced optical properties.

The plasmonic effect of gold nanoparticles has been used in this work to enhance light energy absorption in organic solar cells, to compensate for high light-transmissivity in the active material due to its low thickness. It was found that the density of the nanoparticles grown in the device had a certain critical effect on the performance of the device; where the performance increases with higher nanoparticle density and is optimum when the nanoparticles are grown up for 30 min, which produces a nanoparticle density as high as ca. 125 particles/ μm2. In these conditions, an improvement as high as 83% of the original device can be obtained. The size of the nanoparticles was also found to have a profound effect on the device performance, in which an increase in nanoparticle correlates with a decrease in performance. This is attributed to an increase in the surface roughness at the interface between the active materials and the PEDOT:PSS as the size increases. Gold nanoparticle preparation and a possible mechanism underlying the improvement of the device performance upon the presence of gold nanoparticles will be discussed.

Gold, silver and platinum nanoparticles were fabricated by a laser-induced breakdown technique of Au, Ag and Pt metal plates. On the other hand, bimetallic nanoalloys consisting of Au–Ag and Au–Pt have been synthesized by irradiation of the prepared nanoparticles under UV light, which leads to an alloy type of structure. The optical characterization and particle sizes were determined by using absorption spectroscopy and transmission electron microscopy.

Perchloric acid adsorbed on magnetic Fe3O4 nano-particles coated with silica (Fe3O4@SiO2-HClO4) as a magnetically separable nano-catalyst was prepared and used for the preparation of 1,4-dihydropyridine derivatives via multi-component reaction of cinnamaldehyde, aromatic amines and methyl / ethyl acetoacetate in high yields. Quantitative conversion of the reactants was achieved under solvent-free conditions; recycle of the catalyst, through convenient magnetic decantation, shows non-significant loss in activity. The prepared nano-composite has been subjected for thorough characterization with X-ray diffraction (XRD) and Field Emission Scanning Electron Microscope (FE-SEM) techniques. The average particle size of nano-particles was obtained as 70 nm.

Poorly water-soluble drugs like atorvastatin with low bioavailability needs novel approach for enhancement of bioavailability and therapeutic efficacy. The use of nanotechnology to formulate as nanoemulsions offer an opportunity to address the issues associated with BCS class II drugs. Nanoemulsion of atorvastatin was developed by spontaneous emulsification method with the aim of enhancing the solubility and oral bioavailability of atorvastatin. Pseudo ternary phase diagrams were constructed to identify the nanoemulsion region. The desired formulations of nanoemulsion region were developed and characterized by globule size, scanning electron microscopy, partition coefficient, clarity, viscosity, percent drug entrapment efficiency, in vitro drug release and in vivo pharmacodynamic studies. The release of drug from nanoemulsion had significantly higher (p ‘ 0.01) as compared to the pure drug. The optimized formulation code NE3 containing 5% Oleic acid, 20% [Cremophore EL: ethanol (1:1)], and 75% of aqueous phase had enhanced solubility from 41.8 ± 2.45 to 69.07 ± 1.41. Globule size and zeta potential of the optimized nanoemulsion formulation were found to be 153.9 ± 1.02 nm and – 32.9 mV, respectively. Biopharmaceutical evaluation of the optimized nanoemulsion formulation was performed by a triton–induced hypercholesterolemia model in male albino wistar rats. The optimized nanoemulsion showed significantly reduced serum lipid levels as compared to pure atorvastatin. In conclusion, the developed nanoemulsion could be an alternative for the enhancement of solubility and bioavailability for the oral drug delivery in management of atherosclerosis.

Introduction: Premise of the present study was to suitably select or modify the constitution of the lipid matrix to achieve significantly high entrapment of hydrophilic drugs within solid lipid nanoparticles (SLNs). Methods and Materials: Isoniazid was selected as a representative hydrophilic drug with a high solubility of 230 mg/ml and a log P of -0.402 at 25°C (determined as per OECD TG 105 and 107 respectively). Three lipids/fatty acids (Glyceryl monostearate, Compritol 888 ATO® and stearic acid) were evaluated out of which Compritol 888 ATO® and stearic acid showed favorable interactions (FTIR and DSC studies) with isoniazid. The two lipids were used alone or in combination for preparing SLNs. Formulation of SLNs by microemulsification, method involved pouring the hot microemulsion into cold water under constant stirring, which may result in expulsion of the hydrophilic drug from the lipid matrix; hence, partitioning of isoniazid from the hot lipid melts into cold water was also determined. Results and Discussion: Results indicate that combining stearic acid with Compritol 888 ATO® in certain ratio (1:4) led to significant entrapment efficiency (EE) of 84.0±1.1%. The formulations were subjected to morphological, physiochemical and in vitro drug release studies. Developed SLNs were found to be stable for 1 year at 4 °C. Conclusion: The study demonstrates the benefit of excipient screening techniques in improving entrapment efficiency of a hydrophilic drug.

By using oxidized multi-walled carbon nanotubes and β-cyclodextrin derivatives (methyl-β-cyclodextrin or hydroxypropyl-β- cyclodextrin) as impregnating reagents, high efficiently resolution of (±)-propranolol, a kind of commonly used β-blockers, has been achieved on abovementioned reagents impregnated silica gel GF254 layers. The solvent system tert-butanol-acetonitrile with various volume ratios was further investigated. By detecting the spots at 254 nm with a UV lamp, the obtained chiral separation factors indicated oxidized multi-walled carbon nanotubes and β-cyclodextrin derivatives impregnated TLC plates could be used for effectively chiral recognition of racemic compounds.

Experimental results on the steady-state rheological behaviour of carbon nanotube (CNT) water-based nanofluid are presented. We have investigated the influence of a controlled preshear history on the viscosity of CNT water-based nanofluid. Two types of preshear history effect are studied: the influence of stress rate during preshear and the effect of resting time before viscosity measurement. It is revealed that CNT water-based nanofluid behaves as a viscoelastic media at low shear rate and it is shear-thinning at higher shear rate. This behaviour is strongly dependent on shear history due to the breakdown in the structural network of nanofluid agglomerates. It is also observed that the nanofluid can reform at rest after preshear following the resting time and the rate or preshear applied to the nanofluid.

Cystatins interfere in the functioning of antidepressant (MAOI) therefore MAOI may not be able to act on monoamine Oxidase (MAO) and the destruction of Serotonin continues which leads to depression. The effect of neurotransmitter has been studied to explore the serotonin induced cystatin dysfunction. When 1μM of cystatin was treated with increasing concentrations of serotonin, the cystatin showed increase in fluorescence intensity and decrease in absorbance, functional study shows a continues loss in antiproteolytic activity with increasing concentration of serotonin results indicated unfolding of cystatin which may not be able to regulate the activity of cathepsins leading to protease- antiprotease imbalance, which may be a cause of several diseases. Neurotransmitters are endogenous chemicals which relay, amplify, and modulate signals between a neuron and another cell. Release of neurotransmitters usually follows arrival of an action potential at the synapse, Serotonin is a monoamine neurotransmitter. It is synthesized in serotonergic neurons in the central nervous system (CNS) where it has various functions, including control of appetite, mood and anger. Cystatins are the inhibitors of cysteine proteinases most of which form equimolar complexes with their target enzymes. They are the members of cystatin super family. They are present in a variety of tissues, body fluids of human beings and animals to regulate the activities of cysteine proteinases.

Titania nanostructures doped with iron in optimum composition (0.0 mole% – 3.0 mole%) have been synthesized using sol–gel method from sodium dodecyl sulfate as a surfactant and titanium (IV) isopropoxide precursor. XRD studies of all samples demonstrate the characteristic features of nanocrystalline titanium dioxide in tetragonal anatase phase. XRD with magnetic measurements reveal the homogeneous substitution of few Ti4+ sites by Fe3+ dopant ions in titania host lattice. Pure titania and doped titania samples were studied by TEM and energy dispersive X–ray spectroscopy (EDS) for morphological and compositional analysis; respectively. TEM measurements showed that the particle size is in the range of 7–15 nm. Raman bands at 637 cm–1, 517 cm–1, and 397 cm–1 confirm the anatase phase of titania in all samples. Surface area and pore volume of 3.0 mole% Fe–doped titania sample, significantly higher than lower iron- doped or –undoped titania samples. Optical absorption of iron–doped titania is shown in the visible region of solar spectrum which further enhanced with iron content in the titania matrix.

Climate is likely to render a number of physiological responses in plants affecting various phytohormones, such as ethylene which influences the growth and phytochemical properties of plants. Certain compounds are found to be effective in alleviating the effects of ethylene e.g. silver nitrate, which saves the plants from the hazardous effects of ethylene and helps in modifying their growth and metabolism. Silver nanoparticles are considered as novel silver compounds that were developed with the help of nanotechnology. In a recent study, the foliar application of silver nanoparticles and silver nitrate during seed growth has been reported to minimize the rate of seed abscission and to maximize the seed yield of borage. The study has therefore been aimed to find out the comparison between the effects of the foliar application of silver nanoparticles and silver nitrate on the vegetative and phytochemical properties of borage. Different concentrations of silver nitrate (0, 10, 20, and 30 mM) and silver nanoparticles (0, 0.2, 0.4, and 0.6 mM) were taken into considerations for finding out their efficacy; the aerial parts of borage plants were sprayed with these solutions at the onset of the flowering stage (65 days after cultivation) and were maintained un till flowering (98 days after cultivation). These solutions were reported to significantly enhance the vegetative (leaf number, greenness of leaves, plant dry weight, inflorescence dry weight, and petal abscission) and phytochemical (phenol, tannin and alkaloid content, mucilage percentage and swelling index) properties of borage. A stronger beneficial effect was observed with 0.6 mM concentrationof silver nanoparticles than the ones with other treatments regarding the maximization of the measured properties of borage.

This study was aimed to evaluate the impact of viscosity and refractive index on the magnitude of droplet size and zeta potential of model indomethacin loaded oil-in-water (o/w) nanoemulsion and 5-fluorouracil (5-FU) loaded water-in-oil (w/o) nanoemulsion. Droplet size and zeta potential of model nanoemulsions were determined using Brookhaven 90 plus/zeta plus particle size/zeta potential analyzer. Objective was achieved by adopting two control approaches. For studying the effects of viscosity, the refractive index was kept constant while changing the viscosity and in case of refractive index, magnitude of viscosity was held constant and changing the refractive index. The droplet size of model o/w or w/o nanoemulsions was found to vary nonlinearly by increasing or decreasing the viscosity. The droplet size and polydispersity index were also found to be changed significantly when refractive index of medium was changed from 1.29 to 1.43. The zeta potential of model nanoemulsions was not found to be measurable by increasing or decreasing the refractive index. These results indicate that care must be taken while performing such type of measurements especially in case of emulsion-based formulation, because small changes in setting parameters can significantly change the results of analysis.

This paper illustrates the vibrational behavior of single walled boron nitride nanotubes (SWBNNTs) using finite element method (FEM). To this end, atomistic model for both zigzag and armchair chiralities of the single walled boron nitride nanotubes for fixed-free boundary condition is analyzed and their natural frequencies and corresponding mode shapes are obtained. The fixed-free SWBNNTs with different aspect ratios (length/diameter) for both types of chairality are modeled as space frames by considering three dimensional elastic beams and point masses. The elastic properties for beam element are considered based on mechanical characteristics of the BN bond in the hexagonal lattice. The masses of B and N atoms are assumed as point masses at the ends of BN bond. Implementing the finite element simulation approach, the natural frequencies of fixed-free SWBNNTs are computed. Results pertaining to bending, torsional and axial modes of vibration are reported with discussions. The present approach is found to be time saving and different chiralities can be easily incorporated in terms of real atomic structures. The results shows, that as the size of fixed free SWBNNTs in terms of length as well as diameter increases the natural frequencies of free vibration decreases, and the zigzag form of fixed-free SWBNNTs are more sensitive compare to armchair form.

The membrane – peptide insertion behavior of an artificial antimicrobial peptide analogue in liposomes, planar free-standing bilayer and planar lipid membranes supported by a crystalline bacterial surface layer, termed S-layer, was investigated. The template for this peptide was peptidyl-glycine-leucine-carboxyamide (PGLa) where all lysine residues were replaced by glutamic acid resulting in a negatively charged analogue termed PGLa(-). Zeta potential measurements and calcein release experiments on liposomes revealed that the insertion of PGLa(-) can be compared to that of native antimicrobial peptides. Patch clamp recordings on free-standing lipid membranes provided evidence of pore formation at a lipid to peptide ratio (L/P) of 1600 with a single pore conductance of 25 pS. However, also a lower conductance at a high L/P (3200) was observed which might be explained by membrane disordering effects caused by PGLa(-) interaction. In line with other studies on the action of membrane active peptides, the rupture of the lipid membrane was strongly influenced by the peptide concentration. S-layer supported lipid membranes were utilized to perform combined surface-sensitive (quartz crystal microbalance with dissipation measurements) and electrical (impedance spectroscopy) measurements. These data evidenced not only the attachment and/or insertion of PGLa(-) in the supported lipid membrane but also indicated toroidal pore formation in a concentration dependent fashion. Hence, S-layer supported lipid membranes constitute a promising platform for studying the interaction and insertion of antimicrobial peptides.

The phase-inversion process initiating form magnetite nanoparticles (MNPs) and polysulfone, in dimethylformamide (DMF) 15%w was performed to obtain the more chemically stable Fe3O4/polysulfone (PSf) micro and nanobeads. Finally, by spraying the polysulfone- magnetite suspension into distilled water the Fe3O4/PSf micro and nanobeads were formed. The polysulfone plays dual role, such as the one that’s of protecting magnetite in acidic media and the other of supporting the immobilization of the active groups which are involved in water purification. The presence of the polymeric shell maximizes the stability of these micro and nanobeads in acidic, synthetic environment to a great extent. The characterization of these Fe3O4/PSf suprastructures was performed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEMHRTEM) and also according to their chemical stability in acidic and synthetic environment. This manuscript has been aimed towards the development of new Fe3O4/polysulfone micro and nanobeads with increased chemical stability in acidic media. In acidic media, Fe3O4/polysulfone micro and nanobeads are reported to become 500 times more chemically stable as compared to the pure Fe3O4 nanoparticles. The results of this research are promising enough to hope that the functionalization of these materials would be quite beneficial in environmental applications – such as the removal of heavy metal from water and its purification.

Quaternized carboxymethyl chitosan/organic rectorite (QCMC/OREC) nanocomposites with different ratios were rapidly prepared under microwave irradiation for 70min. The whole preparation proceeded in water without any organic solvent. The structures of QCMC/OREC nanocomposites were characterized by XRD, TEM and FT-IR. The results showed that the QCMC chains were inserted into silicate layers to form the intercalated or exfoliated nanocomposites, and there were hydrogen bonds and electrostatic interaction between QCMC and OREC. The interlayer distance of the layered silicates in QCMC/OREC nanocomposites was not proportional to the amount of QCMC; it increased firstly to reach a peak value before it decreased with the increase of the QCMC amount; when the weight ratio of QCMC to OREC was 4:1, the exfoliated QCMC/OREC nanocomposite was obtained. The thermogravimetric analysis revealed that the thermal stability of QCMC/OREC nanocomposites was higher as compared to QCMC. In vitro antimicrobial assay showed that QCMC/OREC nanocomposites had stronger antimicrobial activity than original QCMC, particularly against Gram-positive bacteria. With the increase of the amount and the interlayer distance of the layered silicate, the nanocomposites showed stronger antibacterial effect. Therefore, this work provides important basis for developing new antibacterial materials.

This report described a polysilicon nanogap biosensor for the detection of target DNA hybridization which is a key step in biodiagnostics, gene expression profiling, environmental monitoring and forensic investigation. The detection was performed with a low cost dielectric analyzer which measured the changes in capacitance, conductance and permittivity of the nanogap electrodes upon target DNA hybridization. A conventional lithography coupled with thermal oxidation-based size reduction technique was used to fabricate the polysilicon nanogap electrodes. A layer of self-assembled amine functionalities coupled with non-covalently adsorbed gold nanoparticles was added onto the nanogap surface to create a binding chemistry for the thiol-modified probe DNA and to enhance the detection signal. The hybridization detection discrimination among the complementary, noncomplementary and single mismatch targets was reflected through the differences in capacitance, conductance and permittivity profiles of the biosensor. The detection limit of the polysilicon nanogap biosensor was 5 nmol/L of target DNA.

The fabrication, characterization and application of nanostructured zinc oxide (ZnO) thin films on interdigitated silver electrodes were described for the determination of phosphate buffer saline (PBS) concentration. The ZnO thin films were synthesized on a silicon dioxide wafer using a sol-gel spin coating technique. Two different seed solutions were prepared by dissolving Zn-acetate dihydrate in methanol and isopropanol in presence of a stabilizer, monoethanolamine. The field emission scanning electron microscope, atomic force microscope, X-ray diffractometer and Fourier transform infrared characterization revealed the presence of hexagonal ZnO nano-crystals in all thin films. However, the smaller sized and homogeneous ZnO nano-crystals were observed in isopropanol derived thin films. These thin films were used to discriminate the concentrations of different PBS solutions and the discriminatory signals were captured using a low-cost dielectric analyzer and a source meter. The frequency-capacitance curve reflected 2.85 fold increase in capacitance values when the sensor was exposed to 1000-fold diluted PBS in deionized water. A change in PBS concentration from 1000 fold to 10 fold increased the current flow from 6uF to 122uF. Thus the capacitance and current flow demonstrated a proportional relationship with the concentration of PBS, suggesting the application of the fabricated sensor in the determination and discrimination of chemicalspecies concentration in various solutions.

Phytoestrogens are the most important therapeutic molecules that are richly present in soya based foods. Genistein (GEN) is one among the prominent constituent of soybean. Isolated form of Genistein has poor bioavailability because of its low aqueous solubility, absorption and limited clinical efficacy. Encapsulated GEN could be used for colloidal drug delivery for the treatment of diseases including breast cancer. In the present study we have prepared poly lactic acid based nanoparticles with Genistein by emulsion diffusion method. The obtained genistein-loaded nanoparticles (GEN-PLA-NPs) were characterized for their size (PCS/ Zetasizer), shape (SEM) and other physical properties using FTIR and DSC. Encapsulation efficiency, release characteristics The sizes of the particles were ranged between 100 nm and 380 nm due to different solvents that were used during the preparation of nanoparticles. Under optimal conditions, different sizes of the particles (259.7 nm, 122.3 nm and 105.7 nm) were formed with encapsulation efficiency (73.9%, 57.9% and 61.4%, respectively). The drug and polymer interaction studies were performed by FTIR and DSC. When percent release of encapsulated drug was studies in PBS (pH 7.4), it was found to be biphasic pattern (Korsmeyer-Peppas model) with 21.27% release at 37°C in 24 h. In hemolysis experiment, Genistein loaded poly (lactic acid) nanoparticles exhibited non-toxic nature. These results demonstrated the feasibility of encapsulation of GEN and its non-toxic in vitro studies.