Current Nanoscience - Volume 8, Issue 3, 2012

The research presents an experimental study on the heat transfer and pressure drop characteristics of Al2O3-water nanofluids flowing through a microchannel heat sink (MCHS). The effects of Reynolds number and particle concentrations on the heat transfer and flow behavior are investigated. Comparison of the heat transfer coefficient obtained from water-cooled MCHS and nanofluids-cooled MCHS is also presented. MCHS with rectangular flow channel made from aluminum with dimension of 50x50 mm is used as the test section. Al2O3-water nanofluids with particle concentrations of 1.0, 2.0 and 3.0 wt.% are tested. Two electric heaters each with a capacity of 50 W are used to supply heat to the test section. The results indicate that the heat transfer performance of MCHS increases with increasing Reynolds number as well as particle concentrations. Compared with pure water, the results indicate that at particle concentration of 3.0 wt%, the heat transfer coefficient for nanofluid-cooled MCHS is range between 1,100-1,700 W/m2K which is higher than that of water by about 7 – 15%. The pressure drop is between 8 and 25 kPa which is close to the water.

Copper loaded nanostructure TiO2 thin films were deposited on glass substrates using the dip-coating method. The crystalline structure and surface morphology of Cu-loaded TiO2 thin film was characterized by X-ray diffraction analysis and Field emission scanning electron microscopy. X-ray photoelectron spectroscopy was used to evaluate the surface properties of the film surfaces. The transmittance spectra of the films were obtained by UV-vis spectrophotometer. Water contact angle on the film surfaces during irradiation and storage in a dark place was measured by a contact angle analyzer. The XPS results indicated that the hydroxyl content for TiO2 and copper loaded TiO2 thin films was calculated to be 14 % and 20 %, respectively. The transmittance results showed that copper loading enhanced the absorption of TiO2 at about 450 and 700-800 nm. The water contact angle results indicated that copper loading had a significant effect on the hydrophilicity of TiO2 thin film and maintaining it in a dark place for a long time.

This article addresses the flow of nanofluid towards a radially stretching sheet with convective boundary conditions. The Brownian motion and thermophoresis effects are taken into consideration. The governing equations are reduced to a system of coupled ordinary differential equations through similarity transformations. Analytic solutions valid for all the values of embedding parameters have been obtained by homotopy analysis method (HAM). In addition numerical solutions are computed through a shooting technique using computational software Mathematica. The behaviors of key parameters such as Brownian motion parameter (Nb), thermophoresis parameter (Nt), Biot number (Bi), Prandtl number (Pr) and Lewis number (Le) have been thoroughly examined. It is observed that increase in the strength of Brownian motion effect rises the temperature significantly. However rate of heat transfer and nanoparticles concentration at the sheet is reduced when Nb is increased. Moreover it is noticed that temperature and nanoparticles concentration are increasing functions of Biot number (Bi). A comparative study between analytic and numerical solution shows an excellent agreement.

A simple thermal process for the one-step preparation of highly concentrated (up to 0.21 M) but well-stable silver colloids with a bimodal size distribution is developed for the first time, carried out by directly heating an aqueous solution of concentrated AgNO3 and poly[(2-ethyldimethylammonioethyl methacrylate ethyl sulfate)-co- (1-vinylpyrrolidone)] (PQ11), a kind of cationic polyelectrolyte, at 100 °C without the extra introduction of other reducing agents and protective agents. Time-dependent UV-vis spectra were collected to gain further insight into the Ag nanoparticles (AgNPs) formation process. Most importantly, it is found that the colloidal solution can form stable films on bare electrode surfaces and the AgNPs contained therein exhibit notable catalytic activity toward the reduction of H2O2, leading to a H2O2 sensor with a fast amperometric response time of less than 2 s. The linear detection range is estimated to be from 100 μM to 150 mM (r = 0.9995), and the detection limit is estimated to be 1.8 μM at a signal-to-noise ratio of 3.

A comparative study on the microstructure and magnetic properties of FePt-MgO and FePt-Ag thin film sputtered onto glass substrate has been carried out systematically in this paper. FePt-MgO thin film shows better (001) orientation of L10-ordered FePt phase, narrower c-axis orientation distribution, higher out-of-plane coercivity, higher remanence ratio and larger hysteresis slope α than the FePt-Ag thin film. The results of angular variation of coercivity indicate that the magnetization reversal behavior of FePt-MgO thin film is closer to the Stoner–Wohlfarth rotation model than that of FePt-Ag thin film. The magnetic domain size in FePt-MgO thin film (∼80nm) is smaller than that in FePt-Ag thin film (∼160nm) due to the isolated grain structure. From this point of view, the FePt-MgO thin film is more suitable than the FePt-Ag thin film for the application of high density recording media.

Intranasal administration is a non-invasive and effective way for the delivery of drugs to brain that circumvents the blood– brain barrier (BBB). Taking this into account it was planned to formulate a thermodynamically stable and infinite dilutable nanoemulsion (o/w) encapsulating Ropinirole (rop), an anti-Parkinson drug, using a surfactant in a minimum concentration that could improve its solubility, stability and intransnasal flux. Various surfactants, co-surfactants and their mixtures were screened for their ability to emulsify the selected oil. Ternary phase diagrams were constructed to locate the area of nanoemulsion for. The optimized formulation contained 2 mg of Ropinirole along with Sefsol 218 (10% v/v), tween 80 (18% v/v), Transcutol (18% v/v) and water (54% v/v) as matrix, surfactant, cosurfactant and aqueous phase respectively. The optimized formulation showed adequate drug release (72.23±9.56%), globule size (58.61±5.18), polydispersity (0.201), viscosity (31.42±6.97 mpas), and infinite dispersion capability. The ex vivo study showed significant high (p<0.005) drug translocation in different parts of Wister rat brain. From in vitro, ex vivo and in vivo results conclude the promising approach of intranasal Ropinirole nanoemulsion as a better management option for Parkinson’s disease.

Water-soluble, highly fluorescent (FL) and very stable biopolymer-conjugated CdS quantum dots (QDs) were prepared via ligand exchange process of CdS-TG QDs with a biopolymer based ligand. The salep biosource polymer can attach to the surface of CdS QDs to yield quantum dots having great properties. To provide evidences for the occurrence of ligand exchange process, the prepared bioconjugate CdS nanocrystals were characterized by thermo gravimetric analysis (TGA), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR).

Cu(0) metal nanoparticles were prepared inside p(2-acrylamido-2-methyl-1-propansulfonic acid) hydrogel networks. The p(2- acrylamido-2-methyl-1-propansulfonic acid)-Cu composites were used in the reduction of 4-nitrophenol and 2-nitrophenol, as model reactions in the presence of excess NaBH4, and showed excellent catalytic activity. The reduction rate of 4-nitrophenol with p(2- acrylamido-2-methyl-1-propansulfonic acid)-Cu composites, even in the presence of a very low amount of catalyst (1.1 mg Cu(0)) at close to room temperature (30 °C), resulted in a very high value (0.1032 min-1) in comparison to Co(0) and Ni(0) catalysts prepared under very similar conditions. The kinetic parameters were determined at different reaction temperatures and the activation energies for 4- nitrophenol and 2-nitrophenol were found to be 28.2 and 39.2 kJmol-1, respectively.

In this article, dispersive Raman imaging microscopy was used in characterizing the structures of: Polyaniline (PAni), MgFe2O4, and PAni/MgFe2O4 nanocomposite designed in the form of core-shell, and is used also in explaining their electrical conductivity properties. MgFe2O4 nanoparticles have been incorporated into the PAni polymer for capping and stabilizing the ferrite nanoparticles, and for tailoring the polymer's properties as well. Electrical conductivity results revealed that after an applied voltage of 0.98 V, equivalent to threshold electric field (E) of 5.5 V.cm-1, PAni/MgFe2O4 core-shell nanocomposite showed enhanced electrical conductivity (σ) of 4.39x10-1 S.cm-1, which is higher than the conductivity obtained from both parents materials at equivalent electric field values (σ = 3.9x10-1 and 5.81x10-10 S.cm-1 at E = 5.5 V.cm-1 for PAni and MgFe2O4 nanoparticles respectively). Moreover, at applied voltage of 1.3 volt, high conductivity values up to 8.7x10-1 S.cm-1 were obtained from the prepared PAni/MgFe2O4 core-shell nanocomposite after being stated in literature that it is difficult to simultaneously obtain high conductivity (>0.01 S.cm-1) for the PAni composites, and despite the insulating property of MgFe2O4, which was assumed to lower the net electrical conductivity of the synthesized core-shell nanocomposite. This value of relatively high conductivity is reached due to the core-shell design of the samples, and due to the changes that occurred in the PAni structure after coating MgFe2O4 nanoparticles. Dispersive Raman imaging spectroscopy operating in the microscopic mode assisted in understanding the electrical conductivity behavior showed by PAni/MgFe2O4 core-shell nanocomposite, as it revealed that shelling MgFe2O4 with PAni resulted in a weak interfacial interaction between the core and the shell materials, which might change the molecular conformation of PAni from being of compact coil structure to an expanded coil like structure, that resulted in better conductivity of the core-shell nanocomposite, while XRD Patterns proved that MgFe2O4 nano-filler reduced the crystallinity of PAni, and acted as an oxidizing agent that enhanced the intermolecular component of the bulk conductivity in PAni/MgFe2O4 core-shell nanocomposite. This combination between the Raman spectral data, and the electrical conductivity data is considered as an approach in using and getting usefulness from the Raman microscopy spectroscopic data, and in interpreting electrical conductivity results as well.

The nanocomposites of chitosan and its derivatives with layered silicate have gained increasing attention since they showed many attracting properties. For the first time, the present study was carried out to investigate the intercalation of chitosan monomer (Dglucosamine hydrochloride, DGH) into organic rectorite (OREC). XRD, TEM, FTIR, 13C NMR, SEM and TGA were performed to characterize the microstructure, morphology and properties of DGH/OREC nanocomposites. The results showed that DGH monosaccharide could insert into the interlayer of OREC, and intercalation result was similar to that of chitosan/OREC nanocomposites. The interlayer distance of DGH/OREC nanocomposites was not proportional to the mass ratio of DGH to OREC, it increased firstly to reach a peak value before it decreased with the increase of the DGH amount. The largest spacing of 6.13 nm was obtained when the mass ratio of DGH to OREC was at 12:1. The direct observation by TEM and SEM also confirmed the intercalated but not exfoliated DGH/OREC nanocomposites. Noteworthily, most strong crystals of DGH in DGH/OREC nanocomposites were destroyed greatly, but its two weak crystals were stronger. TGA result indicated that the thermal stability of DGH/OREC nanocomposites were higher than that of pristine DGH.

In this communication, we report on the preparation of Ag nanoparticle-decorated 2,4,6-tris (2-pyridyl)-1,3,5-triazine nanobelts (AgNP-TPTNBs) by mixing a AgNO3 aqueous solution and pre-formed TPTNBs with the aid of sodium hydroxide in the absence of any external reducing agent. The formation mechanism of AgNP-TPTNBs is discussed from the seed-mediated growth and considering the reduction potential of triazine and Ag(I) ions under alkaline conditions. It is found that the resultant AgNP-TPTNBs show great potential of Surface-enhanced Raman scattering (SERS) technique with high sensitivity up to 1.0x10-10 M by using p-aminothiophenol (p-ATP) as the model Raman probe.

Mn3O4 Nanoparticles were synthesized from Mn(OAc)2 by hydrothermal method in water in the presence and absence of ionic liquids (ILs) as template for controlling the size and the shape of nanoparticles. In order to produce nanoparticles which are more similar and uniform in distribution and morphology, ionic liquids have been used. The ionic liquid [BMIm][Cl] caused more uniform nanoparticles as well as small nanoparticles. Structural characterizations revealed that the synthesized nanoparticles were of tetragonal Mn3O4 structure and that they were uniform in the presence of ionic liquid.

Yttria stabilized zirconia (YSZ) nanostructured and conventional coatings have been prepared by atmospheric plasma spraying (APS) on NiCoCrAlY-coated superalloy substrates. Bonding strength test was carried out based on the ASTM-C-633-01. To evaluate thermal insulation value of coatings, the thermal insulation capability test was designed and administered. Field emission scanning electron microscope (FESEM) and X-ray diffractometry (XRD) were employed to characterize the microstructures and the phase compositions of the powders and coatings. Nanostructured YSZ coating exhibited a bimodal microstructure consisting of nanosized particles retained from the powder and microcolumnar grains formed through the resolidification of the molten part of powder, whereas the microstructure of conventional YSZ coating consisted of columnar-grain splats. Both nanostructured and conventional YSZ coatings consisted of the non-transformable tetragonal phase. The results revealed that nanostructured coating, due to unique microstructure container of nanozones, presented improved bonding strength and thermal insulation capability as compared to the conventional coating.

Nano-poly(3-methoxythiophene) (NPMOT) was electrochemically synthesized on an ITO surface in the ionic liquid 1-butyl-3- methyl-imidazolium tetrafluoroborate ([BMIM]BF4) by a potentiodynamic polymerization method. NPMOT was characterized by fourier- transform infrared spectroscopies (FTIR) and scanning electron microscopy (SEM). Spectroelectrochemistry and electrochromic properties of the NPMOT films were characterized using various experiment techniques in [BMIM]BF4. The thin films were red at its neutral state. After oxidization of the NPMOT films, the films underwent reversible change to the blue. Via kinetic studies, switching time and the maximum optical contrast % ΔT were found to be 2.4 s and 33.1% for NPMOT films.

ZnO flower like and doubly pointed microneedles (DPNs) were prepared on Cu2O and glass substrates respectively via facile hydrothermal route. Cu2O substrate was prepared through thermal oxidation method from the Cu sheet. The structure and morphologies of ZnO microstructures were characterized by X-ray diffraction and scanning electron microscopy. The average size of flower-like structure was measured to be 2 μm, whereas the doubly pointed microneedles (DPNs) exhibited a tip diameter of 150-250 nm. The flower-like ZnO microstructures showed the photoluminescence emission spectra UV band at 383 nm along with a strong yellow emission band at 580 nm. Correspondingly, the DPNs ZnO microstructure showed UV emission peak at 396 nm associated with a blue emission peak at 469 nm. The photon-to-hydrogen efficiency was found to be 0.04% for flower like microstructure.

Nano-sized cuprous oxide (nano-Cu2O) materials with different morphologies such as hollow spheres, two-dimensional (2D) sheets and octahedrons were synthesized using a simple hydrothermal method in a Cu-citrate complex solution by making small adjustments to the solution’s pH value under alkaline conditions. The morphology of the Cu2O was observed using scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The crystalline features of the materials were characterized by X-ray diffraction (XRD). The formation mechanism related to these materials was also discussed. The photoelectrochemical experiments showed that the hollow Cu2O structure synthesized under a pH range of 8-11 exhibited n-type semiconductor characteristics. Alternatively, solid octahedral Cu2O formed in the presence of strong alkaline conditions (i.e. pH greater than or equal to 12) and exhibited p-type behavior. The nanosheet Cu2O possesses the same n-type semiconductor properties as hollow spherical Cu2O and displays a larger photo-response. This indicated that nanosheet Cu2O is a promising material for photoelectric applications.

The nanoimprint process of (CH2)n polymer is studied using molecular dynamics (MD) simulations based on the finitely extensible non-linear elastic (FENE) potential. To consider the effect of the anti-adhesion layer, a self-assembled monolayer (SAM) was coated on a stamp and imprinted onto a specimen. The effects of the imprinting temperature, loading and unloading velocities, and aspect ratio of the stamp are evaluated in terms of molecular trajectories, imprinting force, and elastic recovery ratio. Simulation results show that the weights of the reactive force are 62 % and 38 % for the specimen and the SAM, respectively, for a stamp with a length of 5 nm and a height of 9 nm; the weight of the reactive force for the specimen increases with increasing stamp length. During the imprinting process, the required loading force decreases with increasing imprinting temperature and decreasing imprinting velocity. The formation of the pattern is more stable for imprinting at room temperature than that at high temperature due to lower elastic recovery and adhesion during unloading. High-velocity imprinting leads to non-uniform elastic recovery of an imprinted pattern.

The present work was aimed to develop, explore & compare the use of multifuctional nanoparticles (MNPs) (drug loaded) made of the conjugate poly (lactide-co-glycolide) (PLGA) - polyethylene glycol (PEG) & – folic acid with PLGA nanoparticles (NPs) (drug loaded) for targeting solid tumor. For that first optimum cytotoxic concentration of PLGA (polymer) and cisplatin (drug) were optimized through MTT assay. The optimum size and percent entrapment efficiency were found to be 170±6.5 nm and 74.9±2.3% for PLGA NPs and 186±4.2 nm and 76.9±3.1% for MNPs. The in vitro cytotoxic activity of MNPs and PLGA NPs were investigated & compared with drug solution (cisplatin) on MDA-MB-231 breast cancer cells, which revealed that MNPs are more cytotoxic in a time dependent manner. The rhodamine B isothiocyanate loaded NPs and MNPs were prepared & compared for cell uptake studies which conformed that targeted NPs (MNPs) were more taken up by the MDA-MB-231 cells. To determine the effect of ligand (folic acid) on internalization, cells were incubated with MNPs, NPs and 10 fold excess folic acid with MNPs. Results confirmed that the presence of ligand gradually increases internalization of carriers and exhibited maximum uptake of MNPs whereas, little difference was observed on uptake between NPs and excess folate treated cells. Results suggesting that MNPs are promising approach for targeting solid tumor & to achieve deeper cellular internalization.

In this work, the oxidation of styrene by anhydrous hydrogen peroxide as an environmental friendly oxidant on γ-aluminasupported VxOy nanoparticles catalysts was performed with the continuous adsorption of water by anhydrous MgSO4. This catalyst, with a surface area of 174 m2/g, showed good selectivity for benzaldehyde. Poor styrene conversion and benzaldehyde selectivity due to the presence of water can be enhanced by the addition of a water scavenger such as MgSO4. Response surface methodology (RSM) was employed to examine the effect of anhydrous H2O2 concentration (from 20 to 80mmol), reaction time (from 2.5 to 6h), temperature (from 45 to 90°C), amount of anhydrous MgSO4 (from 8 to 33mmol) and catalyst concentration (from 0.014 to 0.036 g/ml) on the conversion of styrene and the selectivity of benzaldehyde and styrene oxide. Based on the RSM analysis, the optimum conditions for obtaining maximum styrene conversion (61.7%) and benzaldehyde selectivity (84.2%) were as follows: a reaction temperature of 63°C, a reaction time of 4.9h, a H2O2/styrene/anhydrous MgSO4 molar ratio of 2.7:1:1.08 and a catalyst concentration of 0.024g/ml.

Multi-walled carbon nanotubes (MWCNTs) prepared by chemical vapor deposition (CVD) were sprayed on C wafers. Then, an 8 nm-thick CNx coating was deposited on MWCNTs by ion beam deposition (IBAD). The cell adhesion and hemocompatibility of MWCNTs with and without CNx coating were investigated using contact-angle measurements, cell- and platelet-adhesion assays, and hemolytic-rate testing. The results showed that mouse fibroblast cells (L929) cultured on MWCNTs with CNx coating displayed a higher cell-adhesion strength, viability, proliferation, and spreading than those on MWCNTs without CNx coating, indicating that CNx coating induced MWCNTs showed an increase in cytocompatibility. Despite MWCNTs with CNx coating displayed higher hemolytic and platelet adsorption rates than those on MWCNTs without CNx coating, its hemolytic rate values below 5% were acceptable. And CNx coating inhibited red blood cell adhesion and deformation. Good cell growth and hemocompatibility on MWCNTs with CNx coating were probably related to the positive contribution of nitrogen functional groups to hydrophilicity and the three-dimensional network configuration.