سال:1392 | دوره: | شماره: |تعداد مقالات:12

Synthesis and application of mesoporous silicate nanoparticles are important areas of research in many fields such as drug delivery, medicine, catalysis, and optic. The method of synthesis strongly affects the properties of a product. In this work, the mesoporous silica nanoparticles were synthesized by means of a hydrogel. The obtained product was characterized by X-ray diffraction, scanning electron microscopy, and nitrogen physisorption. The results show that highly ordered mesoporous silica nanoparticles were synthesized by means of a hydrogel.

Highly crystalline Gd3+-doped cadmium oxide micro-structure was synthesized by calcining the obtained precursor of a sol–gel reaction. The reaction was carried out with cadmium nitrate (Cd (NO3) 2·4H2O), gadolinium oxide, and ethylene glycol (C2H6O2) reactants without any additives at 80oC for 2 h. The resulting gel was calcined at 900oC with increasing temperature rate of 15oC/min for 12 h in a furnace. As a result of heating, the organic section of the gel was removed, and the Gd3+-doped cadmium oxide micro-structure was produced. The obtained compound from the sol–gel technique possesses a cubic crystalline structure at a micro scale. XRD study indicates that the obtained Gd3+-doped CdO has a cubic phase. Also, the SEM images showed that the resulting material is composed of particles with cluster structure. Also, FT-IR spectroscopy was employed to characterize the Gd3+-doped CdO micro-structures

During the past decade, much attention has been paid to the replacement of homogeneous catalysts by solid acid catalysts. Friedel-Crafts benzylation of toluene with benzyl chloride (BC) in liquid phase was carried out over highly active, nano-crystalline sulfated titania systems. These catalysts were prepared using the sol gel method. Modification was done by loading 3% of transition metal oxides over sulfated titania. Reaction parameters such as catalyst mass, molar ratio, temperature, and time have been studied. More than 80% conversion of benzyl chloride and 100% selectivity are shown by all the catalysts under optimum conditions. Catalytic activity is correlated with Lewis acidity obtained from perylene adsorption studies. The reaction appears to proceed by an electrophile, which involves the reaction of BC with the acidic titania catalyst. The catalyst was regenerated and reused up to four reaction cycles with equal efficiency as in the first run. The prepared systems are environmentally friendly and are easy to handle.

It has been possible to incorporate cadmium ions in ZnS quantum dots (QDs). It is studied how the substitution of Cd2+ ions by zinc ions affects the structural, morphological, and optical properties of ZnS QDs. Zn1-xCdxS QDs are prepared by a simple beaker chemistry approach and characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy, and UV-visible and photoluminescence (PL) spectroscopies. XRD studies confirmed that all the prepared samples are in zinc-blende phase. With the increase of cadmium content, the diffraction peaks shifted towards lower diffraction angles and the lattice constant increased linearly. Optical studies revealed that the strong absorption edge also shifted towards the higher wavelength region with the increase of Cd content. Hence, the optical bandgap of the QDs decreases with the increase of Cd content. Due to the quantum confinement of the carriers in the QDs, the bandgap energy is higher than that of the corresponding bulk material. The PL spectrum of the undoped ZnS QDs contains five peaks (centered at 365, 400, 420, 450, and 470 nm) which are attributed to the recombination of the defect states of ZnS.

In this paper, we have designed an all-optical controllable gas detector by doping 3-level Λ type nanocrystals in the moving arms' mirror of Michelson interferometer and used electromagnetically induced transparency (EIT) phenomenon to change its refractive index. By this means, we have created a controllable phase difference between light beams in two arms of the Michelson interferometer, where reflection phase of the EIT-based mirror changes about p radiant. Also, the signal reflection from EIT-based mirror changes between 0% and 100% approximately, while the second arm's signal is reflected completely. This EIT-based mirror's refractive index change can be a good alternative for conventional Michelson interferometer-based gas detector with one mechanical moving arm mirror (Undergraduate Instrumental Analysis, 6th edn. Marcel Dekker, New York, 2005), where long response time and unfix moving speed were its main drawbacks. While, in this scheme, not only these disadvantages are removed but also the response time can reach the electron transient time between the atomic energy levels. Then, by this all-optical tunable gas detector, we have achieved many modifications such as response time in sub-nanoseconds, high resolution, and high accuracy, or less cross sensitivity to other gas species.

The present study is aimed to investigate the formulation andin vitro anticancer activities of solid lipid nanoparticles (SLNs) of 5-fluorouracil (5-FU) prepared using glyceryl monostearate (GMS) and cetyl palmitate (CP) by hot homogenization method. The lipids were selected based on the partition coefficient of 5-FU in lipids. The lipid nanoparticles were optimized for process and formulation parameters. The optimized nanoparticles were characterized for their zeta potential, morphology, release kinetics, and anticancer activity. Higher entrapments were achieved using a combination of emulsifiers. The zeta potential of the optimized CP and GMS SLN formulation were -8.26 and -9.35 mV, respectively. Both the optimized formulations were spherical. The in vitro release studies of SLNs of both the lipid carriers followed Peppas-Korsenmeyer equation when carried out at pH 3.5 and 7.4. The chemosensitivity assay carried out in B16F10 cell lines revealed that CP SLNs had better cytotoxicity than 5-FU solution and GMS SLNs at 48 h of incubation. Subtoxic concentration of 5-FU-loaded CP SLNs (0.12 mg/mL) possessed comparable antimigrational activity, colony inhibition activity, and cytopathic as that of 5-FU solution effects. The results indicated that encapsulating 5-FU in CP would be a promising delivery system for delivering 5-FU.

In situchemical deposition sol-gel method has been used to prepare graphene oxide-BaCrO4 (GO-BaCrO4), which was then reduced to graphene-BaCrO4 (RGO-BaCrO4) under visible-light irradiation. X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscopy were used to study the morphological characteristics of the prepared composite material. This synthesis method offers effortless incorporation of a visible light active photocatalyst in a composite, the reduction of GO to RGO was carried out under visible light as well. Graphene sheets with high specific surface area and unique electronic properties can be used as a good support for BaCrO4 and enhance the photocatalytic activity for the degradation of methylene blue dye compared to pure BaCrO4. The poor photocatalytic activity of pure BaCrO4 is due to its fast charge recombination. Enhanced photocatalytic degradation activity is attributed predominantly to the presence of graphene, which serves as an electron collector and transporter to lengthen efficiently the lifetime of the photogenerated charge carriers from BaCrO4 nanoparticles. The modified surface of BaCrO4 acts as a good photocatalyst compared to unmodified BaCrO4. The optimum reaction time for synthesis and GO concentration in the composite to enhance photocatalytic activity are presented in this article.

Zinc oxide nanoparticles were synthesized using a simple precipitation method with zinc sulfate and sodium hydroxide as starting materials. The synthesized sample was calcined at different temperatures for 2 h. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and proton-induced X-ray emission (PIXE) analysis. SEM images show various morphological changes of ZnO obtained by the above method. The average crystallite sizes of the samples were calculated from the full width at half maximum of XRD peaks by using Debye-Scherrer's formula and were found to be in the nanorange. EDS shows that the above route produced highly pure ZnO nanostructures. PIXE technique was used for trace elemental analysis of ZnO. The optical band gaps of various ZnO powders were calculated from UV-visible diffuse reflectance spectroscopic studies.

In this study, direct precipitation technique was used to synthesize Ag nanoparticles supported by carbon nanotubes. After distinguishing the best situation in the synthesis of Ag nanoparticles, carbon nanotubes as the support were used to control the Ag nanoparticle size. The prepared carbon nanotubes and Ag nanoparticles were investigated by using X-ray diffraction, transmission electron microscopy, and scanning electron microscopy. The results showed that carbon nanotubes can play an important role in controlling the morphology and size of the obtained powders, and the size of Ag nanoparticles synthesized on the carbon nanotubes is smaller.

Highly mono-shaped straw bundle-like silinaite micro-rods have been synthesized using an aqueous mixture of silicic acid, lithium sulfate, and sodium hydroxide under hydrothermal conditions at 180oC. The synthesized materials were characterized by powder X-ray diffraction technique and Fourier transform infrared spectroscopy. The morphologies of the synthesized materials were studied by field emission scanning electron microscopy technique. The synthesized micro-rods are composed of long, fine nanosheets. Electronic absorption and photoluminescence spectra of the synthesized materials were also studied. With increasing reaction time, a blueshift was observed in the UV–vis electronic absorption and emission spectra of the synthesized materials.

Micro-cantilever arrays with different dimensions are fabricated by micro-machining technique onto a silicon<100>substrate. These sputtered gold-coated micro-cantilevers were later surface-functionalized. Scanning electron microscopy, atomic force microscopy (AFM), and optical diffraction using a laser source are employed to characterize the morphology and image measurement of the micro-cantilever arrays. The spatial resolution produced in the proposed image measurement method is approaching 1mm, and the repeatable precision is nanometer confirmable. Compared with conventional AFM and SPM measurement techniques, the proposed method has demonstrated sufficient flexibility, repeatability, and reliability. The experimental results have been analyzed and presented in this paper for microelectromechanical system (MEMS) micro-cantilevers. The scanning white light interferometry-based two-point high-resolution optical method is presented for characterizing micro-cantilevers and other MEMS micro-structures. In this letter, we investigate the microstructure fabrication and image measurement of length, width, and step height of micro cantilever arrays fabricated using bulk micro-machining technique onto a silicon<100> substrate.

In this article, we have discussed blood flow in the nano-Prandtl fluid flow analysis in tapered stenosed arteries. The occurrence of nanoparticle fraction and heat transfer was found. Gravitational effects were also considered because the tube was taken vertically upward. Homotopy perturbation method was used to find the analytical solution of coupled nonlinear differential equations. Physical fea-tures have been discussed through graphs of concentration profile s, velocity profile w, resistance impedance l, temperature profile q, wall shear stress Srz, wall shear stress at the stenosis throat ts, and the stream lines.