Current Nanoscience (v.9, #2)

Polished (111) surfaces of monocrystalline cubic gallium arsenide GaAs platelets and a powdered microcrystalline form ofGaAs were nitrided towards gallium nitride GaN under a flow of ammonia at temperatures in the range 600-900 °C for one to several tensof hours. The progress of nitridation was followed mainly by grazing incidence X-ray diffraction GIXD and powder X-ray diffractionXRD. 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. Thesubstrate/temperature/time related interplay in the formation of the cubic and hexagonal GaN polytypes from cubic GaAs and conditionsfavoring the metastable cubic GaN polytype are delineated.

Enhanced Luminescent Properties of Solution Combustion Synthesized Nanocrystalline Y3Al5O12:Eu3+ Phosphors by Sumei Wang, Xurong Zhao, Shengming Zhou, Limin Zhou, Guodong Xia (183-186).
Nanocrystalline Y<sub>3</sub>Al<sub>5</sub>O<sub>12</sub>:Eu<sup>3+</sup> phosphors with particle size about 20-40 nm have been synthesized by a facile solution combustionmethod. XRD and TEM studies show that Y<sub>3</sub>Al<sub>5</sub>O<sub>12</sub> nanocrystals can directly form at a low temperature of 825 &deg;C and highlycrystalline at 850 &deg;C. With the increase of annealing temperature, the charge transfer band shows a blue shift due to the dielectric confinementeffect. The color purity of Y<sub>3</sub>Al<sub>5</sub>O<sub>12</sub>:Eu<sup>3+</sup> phosphors can be improved by decreasing the grain size of nanocrystals. Furthermore,the high concentration doping of Eu<sup>3+</sup> can be realized in Y<sub>3</sub>Al<sub>5</sub>O<sub>12</sub> nanocrystals, which will enhance the luminescent intensity. This workdemonstrated that solution combustion is a feasible method to synthesize europium rare earth doped Y<sub>3</sub>Al<sub>5</sub>O<sub>12</sub> nanocrystals with enhancedoptical properties.

Effect of Gold Nanoparticles Density Grown Directly on the Surface on the Performance of Organic Solar Cell by Vivi Fauzia, Akrajas Ali Umar, Muhamad Mat Salleh, Muhammad Yahaya (187-191).
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 nanoparticlesgrown in the device had a certain critical effect on the performance of the device; where the performance increases with highernanoparticle density and is optimum when the nanoparticles are grown up for 30 min, which produces a nanoparticle density as high asca. 125 particles/ &mu;m<sup>2</sup>. In these conditions, an improvement as high as 83&percnt; of the original device can be obtained. The size of thenanoparticles was also found to have a profound effect on the device performance, in which an increase in nanoparticle correlates with adecrease in performance. This is attributed to an increase in the surface roughness at the interface between the active materials and thePEDOT:PSS as the size increases. Gold nanoparticle preparation and a possible mechanism underlying the improvement of the deviceperformance 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 metalplates. On the other hand, bimetallic nanoalloys consisting of Au&ndash;Ag and Au&ndash;Pt have been synthesized by irradiation of the preparednanoparticles under UV light, which leads to an alloy type of structure. The optical characterization and particle sizes were determined byusing absorption spectroscopy and transmission electron microscopy.

Perchloric acid adsorbed on magnetic Fe<sub>3</sub>O<sub>4</sub> nano-particles coated with silica (Fe<sub>3</sub>O<sub>4</sub>&#64;SiO<sub>2</sub>-HClO<sub>4</sub>) as a magnetically separablenano-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 undersolvent-free conditions; recycle of the catalyst, through convenient magnetic decantation, shows non-significant loss in activity. Theprepared nano-composite has been subjected for thorough characterization with X-ray diffraction (XRD) and Field Emission ScanningElectron Microscope (FE-SEM) techniques. The average particle size of nano-particles was obtained as 70 nm.

Atorvastatin-Loaded Oleic Acid Nanoglobules for Oral Administration: In Vitro Characterization and Biopharmaceutical Evaluation by Pradum Pundlikrao Ige, Nilesh Ashok Bachhav, Hitendra Shaligram Mahajan, Pankaj Padmakar Nerkar, Surendra Ganeshlal Gattani (202-210).
Poorly water-soluble drugs like atorvastatin with low bioavailability needs novel approach for enhancement of bioavailabilityand therapeutic efficacy. The use of nanotechnology to formulate as nanoemulsions offer an opportunity to address the issues associatedwith BCS class II drugs. Nanoemulsion of atorvastatin was developed by spontaneous emulsification method with the aim of enhancingthe 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 &lsaquo; 0.01) as compared to the pure drug. The optimized formulation codeNE3 containing 5&percnt; Oleic acid, 20&percnt; [Cremophore EL: ethanol (1:1)], and 75&percnt; of aqueous phase had enhanced solubility from 41.8 &plusmn;2.45 to 69.07 &plusmn; 1.41. Globule size and zeta potential of the optimized nanoemulsion formulation were found to be 153.9 &plusmn; 1.02 nm and &ndash;32.9 mV, respectively. Biopharmaceutical evaluation of the optimized nanoemulsion formulation was performed by a triton&ndash;induced hypercholesterolemiamodel in male albino wistar rats. The optimized nanoemulsion showed significantly reduced serum lipid levels ascompared to pure atorvastatin. In conclusion, the developed nanoemulsion could be an alternative for the enhancement of solubility andbioavailability 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 significantlyhigh entrapment of hydrophilic drugs within solid lipid nanoparticles (SLNs). Methods and Materials: Isoniazid was selectedas a representative hydrophilic drug with a high solubility of 230 mg/ml and a log P of -0.402 at 25&deg;C (determined as per OECD TG 105and 107 respectively). Three lipids/fatty acids (Glyceryl monostearate, Compritol 888 ATO&reg; and stearic acid) were evaluated out ofwhich Compritol 888 ATO&reg; and stearic acid showed favorable interactions (FTIR and DSC studies) with isoniazid. The two lipids wereused alone or in combination for preparing SLNs. Formulation of SLNs by microemulsification, method involved pouring the hot microemulsioninto cold water under constant stirring, which may result in expulsion of the hydrophilic drug from the lipid matrix; hence, partitioningof isoniazid from the hot lipid melts into cold water was also determined. Results and Discussion: Results indicate that combiningstearic acid with Compritol 888 ATO&reg; in certain ratio (1:4) led to significant entrapment efficiency (EE) of 84.0&plusmn;1.1&percnt;. The formulationswere subjected to morphological, physiochemical and in vitro drug release studies. Developed SLNs were found to be stable for 1year at 4 &deg;C. Conclusion: The study demonstrates the benefit of excipient screening techniques in improving entrapment efficiency of ahydrophilic 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 (&plusmn;)-propranolol, a kind of commonly used β-blockers, has beenachieved on abovementioned reagents impregnated silica gel GF254 layers. The solvent system tert-butanol-acetonitrile with variousvolume ratios was further investigated. By detecting the spots at 254 nm with a UV lamp, the obtained chiral separation factors indicatedoxidized multi-walled carbon nanotubes and β-cyclodextrin derivatives impregnated TLC plates could be used for effectively chiral recognitionof racemic compounds.

Shear History Effect on the Viscosity of Carbon Nanotubes Water-based Nanofluid by Patrice Estelle, Salma Halelfadl, Nimeti Doner, Thierry Mare (225-230).
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 preshearhistory effect are studied: the influence of stress rate during preshear and the effect of resting time before viscosity measurement. Itis 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 alsoobserved that the nanofluid can reform at rest after preshear following the resting time and the rate or preshear applied to the nanofluid.

Interaction of Buffalo Brain Cystatin with Serotonin by Fakhra Amin, Aabgeena Naim, Bilqees Bano (231-234).
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 explorethe serotonin induced cystatin dysfunction.When 1&mu;M of cystatin was treated with increasing concentrations of serotonin, the cystatin showed increase in fluorescence intensity anddecrease in absorbance, functional study shows a continues loss in antiproteolytic activity with increasing concentration of serotonin resultsindicated 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 ofneurotransmitters usually follows arrival of an action potential at the synapse, Serotonin is a monoamine neurotransmitter. It is synthesizedin serotonergic neurons in the central nervous system (CNS) where it has various functions, including control of appetite, mood andanger. 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 regulatethe activities of cysteine proteinases.

Iron-doped Anatase Titania Nanostructures: Synthesis and Characterization by S.D. Delekar, H.M. Yadav, P.P. Hankare (235-240).
Titania nanostructures doped with iron in optimum composition (0.0 mole&percnt; &ndash; 3.0 mole&percnt;) have been synthesized using sol-gelmethod from sodium dodecyl sulfate as a surfactant and titanium (IV) isopropoxide precursor. XRD studies of all samples demonstratethe characteristic features of nanocrystalline titanium dioxide in tetragonal anatase phase. XRD with magnetic measurements reveal thehomogeneous substitution of few Ti<sup>4+</sup> sites by Fe<sup>3+</sup> dopant ions in titania host lattice. Pure titania and doped titania samples were studiedby TEM and energy dispersive X-ray spectroscopy (EDS) for morphological and compositional analysis; respectively. TEM measurementsshowed that the particle size is in the range of 7&ndash;15 nm. Raman bands at 637 cm<sup>-1</sup>, 517 cm<sup>-1</sup>, and 397 cm<sup>-1</sup> confirm the anatasephase of titania in all samples. Surface area and pore volume of 3.0 mole&percnt; 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 furtherenhanced with iron content in the titania matrix.

Climate is likely to render a number of physiological responses in plants affecting various phytohormones, such as ethylenewhich influences the growth and phytochemical properties of plants. Certain compounds are found to be effective in alleviating the effectsof ethylene e.g. silver nitrate, which saves the plants from the hazardous effects of ethylene and helps in modifying their growth andmetabolism. Silver nanoparticles are considered as novel silver compounds that were developed with the help of nanotechnology. In a recentstudy, the foliar application of silver nanoparticles and silver nitrate during seed growth has been reported to minimize the rate ofseed abscission and to maximize the seed yield of borage. The study has therefore been aimed to find out the comparison between the effectsof the foliar application of silver nanoparticles and silver nitrate on the vegetative and phytochemical properties of borage. Differentconcentrations of silver nitrate (0, 10, 20, and 30 mM) and silver nanoparticles (0, 0.2, 0.4, and 0.6 mM) were taken into considerationsfor finding out their efficacy; the aerial parts of borage plants were sprayed with these solutions at the onset of the flowering stage (65days after cultivation) and were maintained un till flowering (98 days after cultivation). These solutions were reported to significantly enhancethe 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 wasobserved with 0.6 mM concentrationof silver nanoparticles than the ones with other treatments regarding the maximization of the measuredproperties of borage.

Impact of Viscosity and Refractive Index on Droplet Size and Zeta Potential of Model O/W and W/O Nanoemulsion by Faiyaz Shakeel, Nazrul Haq, Mohd Ali, Fars K. Alanazi, Ibrahim A. Alsarra (248-253).
This study was aimed to evaluate the impact of viscosity and refractive index on the magnitude of droplet size and zeta potentialof 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 potentialanalyzer. Objective was achieved by adopting two control approaches. For studying the effects of viscosity, the refractive index was keptconstant while changing the viscosity and in case of refractive index, magnitude of viscosity was held constant and changing the refractiveindex. 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 changedfrom 1.29 to 1.43. The zeta potential of model nanoemulsions was not found to be measurable by increasing or decreasing the refractiveindex. These results indicate that care must be taken while performing such type of measurements especially in case of emulsion-basedformulation, 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 elementmethod (FEM). To this end, atomistic model for both zigzag and armchair chiralities of the single walled boron nitride nanotubes forfixed-free boundary condition is analyzed and their natural frequencies and corresponding mode shapes are obtained. The fixed-freeSWBNNTs with different aspect ratios (length/diameter) for both types of chairality are modeled as space frames by considering threedimensional elastic beams and point masses. The elastic properties for beam element are considered based on mechanical characteristicsof 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. Implementingthe 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 differentchiralities can be easily incorporated in terms of real atomic structures. The results shows, that as the size of fixed free SWBNNTs interms of length as well as diameter increases the natural frequencies of free vibration decreases, and the zigzag form of fixed-freeSWBNNTs are more sensitive compare to armchair form.

Insertion of an Anionic Analogue of the Antimicrobial Peptide PGLa in Lipid Architectures Including S-Layer Supported Lipid Bilayers by Angelika Schrems, Vanessa-D. Larisch, Uwe B. Sleytr, Martin Hohenegger, Karl Lohner, Bernhard Schuster (262-270).
The membrane &ndash; peptide insertion behavior of an artificial antimicrobial peptide analogue in liposomes, planar free-standingbilayer and planar lipid membranes supported by a crystalline bacterial surface layer, termed S-layer, was investigated. The template forthis peptide was peptidyl-glycine-leucine-carboxyamide (PGLa) where all lysine residues were replaced by glutamic acid resulting in anegatively charged analogue termed PGLa(-). Zeta potential measurements and calcein release experiments on liposomes revealed thatthe insertion of PGLa(-) can be compared to that of native antimicrobial peptides. Patch clamp recordings on free-standing lipid membranesprovided 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 byPGLa(-) interaction. In line with other studies on the action of membrane active peptides, the rupture of the lipid membrane was stronglyinfluenced by the peptide concentration. S-layer supported lipid membranes were utilized to perform combined surface-sensitive (quartzcrystal microbalance with dissipation measurements) and electrical (impedance spectroscopy) measurements. These data evidenced notonly the attachment and/or insertion of PGLa(-) in the supported lipid membrane but also indicated toroidal pore formation in a concentrationdependent fashion. Hence, S-layer supported lipid membranes constitute a promising platform for studying the interaction and insertionof antimicrobial peptides.

Synthesis and Characterization of Magnetite-Polysulfone Micro- and Nanobeads with Improved Chemical Stability in Acidic Media by Denisa Ficai, Anton Ficai, Roxana Trusca, Bogdan Stefan Vasile, Gorgeta Voicu, Cornelia Guran, Ecaterina Andronescu (271-277).
The phase-inversion process initiating form magnetite nanoparticles (MNPs) and polysulfone, in dimethylformamide (DMF)15&percnt;w was performed to obtain the more chemically stable Fe<sub>3</sub>O<sub>4</sub>/polysulfone (PSf) micro and nanobeads. Finally, by spraying the polysulfone-magnetite suspension into distilled water the Fe<sub>3</sub>O<sub>4</sub>/PSf micro and nanobeads were formed. The polysulfone plays dual role, suchas the one that's of protecting magnetite in acidic media and the other of supporting the immobilization of the active groups which are involvedin water purification. The presence of the polymeric shell maximizes the stability of these micro and nanobeads in acidic, syntheticenvironment to a great extent. The characterization of these Fe<sub>3</sub>O<sub>4</sub>/PSf suprastructures was performed by Fourier transform infraredspectroscopy (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 thedevelopment of new Fe<sub>3</sub>O<sub>4</sub>/polysulfone micro and nanobeads with increased chemical stability in acidic media. In acidic media,Fe<sub>3</sub>O<sub>4</sub>/polysulfone micro and nanobeads are reported to become 500 times more chemically stable as compared to the pure Fe<sub>3</sub>O<sub>4</sub>nanoparticles. The results of this research are promising enough to hope that the functionalization of these materials would be quite beneficialin environmental applications &ndash; such as the removal of heavy metal from water and its purification.

Preparation, Characterization and Antibacterial Activity of Quaternized Carboxymethyl Chitosan/Organic Rectorite Nanocomposites by Xiaoyun Li, Yang Han, Haoquan Zhong, Weijie Ye, Bo Liu, Xiaoying Wang, Runcang Sun (278-282).
Quaternized carboxymethyl chitosan/organic rectorite (QCMC/OREC) nanocomposites with different ratios were rapidly preparedunder microwave irradiation for 70min. The whole preparation proceeded in water without any organic solvent. The structures ofQCMC/OREC nanocomposites were characterized by XRD, TEM and FT-IR. The results showed that the QCMC chains were insertedinto silicate layers to form the intercalated or exfoliated nanocomposites, and there were hydrogen bonds and electrostatic interaction betweenQCMC and OREC. The interlayer distance of the layered silicates in QCMC/OREC nanocomposites was not proportional to theamount of QCMC; it increased firstly to reach a peak value before it decreased with the increase of the QCMC amount; when the weightratio of QCMC to OREC was 4:1, the exfoliated QCMC/OREC nanocomposite was obtained. The thermogravimetric analysis revealedthat the thermal stability of QCMC/OREC nanocomposites was higher as compared to QCMC. In vitro antimicrobial assay showed thatQCMC/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.

DNA Hybridization Detection Using 5-nm Polysilicon Nanogap Structure by Th. S. Dhahi, M. E. Ali, U. Hashim, N. Azah, I. M. Ali, M. J. Ashoor, A. Al-Roumy, H. A. Hadi (283-287).
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 lowcost dielectric analyzer which measured the changes in capacitance, conductance and permittivity of the nanogap electrodes upon targetDNA hybridization. A conventional lithography coupled with thermal oxidation-based size reduction technique was used to fabricate thepolysilicon nanogap electrodes. A layer of self-assembled amine functionalities coupled with non-covalently adsorbed gold nanoparticleswas 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 reflectedthrough the differences in capacitance, conductance and permittivity profiles of the biosensor. The detection limit of the polysiliconnanogap biosensor was 5 nmol/L of target DNA.

The fabrication, characterization and application of nanostructured zinc oxide (ZnO) thin films on interdigitated silver electrodeswere described for the determination of phosphate buffer saline (PBS) concentration. The ZnO thin films were synthesized on asilicon dioxide wafer using a sol-gel spin coating technique. Two different seed solutions were prepared by dissolving Zn-acetate dihydratein 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 ZnOnano-crystals in all thin films. However, the smaller sized and homogeneous ZnO nano-crystals were observed in isopropanol derivedthin films. These thin films were used to discriminate the concentrations of different PBS solutions and the discriminatory signals werecaptured using a low-cost dielectric analyzer and a source meter. The frequency-capacitance curve reflected 2.85 fold increase in capacitancevalues when the sensor was exposed to 1000-fold diluted PBS in deionized water. A change in PBS concentration from 1000 foldto 10 fold increased the current flow from 6uF to 122uF. Thus the capacitance and current flow demonstrated a proportional relationshipwith the concentration of PBS, suggesting the application of the fabricated sensor in the determination and discrimination of chemicalspeciesconcentration in various solutions.

Phytoestrogens are the most important therapeutic molecules that are richly present in soya based foods. Genistein (GEN) isone 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 includingbreast cancer. In the present study we have prepared poly lactic acid based nanoparticles with Genistein by emulsion diffusionmethod. 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 wereranged 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&percnt;, 57.9&percnt; and61.4&percnt;, respectively). The drug and polymer interaction studies were performed by FTIR and DSC. When percent release of encapsulateddrug was studies in PBS (pH 7.4), it was found to be biphasic pattern (Korsmeyer-Peppas model) with 21.27&percnt; release at 37&deg;C in 24 h. Inhemolysis experiment, Genistein loaded poly (lactic acid) nanoparticles exhibited non-toxic nature. These results demonstrated the feasibilityof encapsulation of GEN and its non-toxic in vitro studies.