International Journal of Nano Dimension
Year:2016 | Volume:7 | Issue:1|Papers Count:10

Photocatalytic degradation of toxic organic compounds in water, soil and air by semiconductor catalysts such as TiO2 and ZnO has received much attention over the last two decades. However, the low quantum yield, easy agglomeration and difficult post-separation of these inorganic catalysts limit their application for large-scale applications.Metal-organic frameworks (MOFs) are the latest class of ordered porous solids that being intensively studied as a novel class of hybrid inorganic-organic material with ultrahigh porosity, enormous internal surface areas, together with the extraordinary tailorability of structure, dimension, size and shape. Recently exploring performance of MOF as a new nanophotocatalyst is attracting interest of researchers working in the fields of chemistry, chemical engineering, material scienceand others. Although the photocatytic application of MOF materials is still at the early stage compared with the other applications of them such as gas storage, separation, biomedical application and heterogeneous catalysis, the currently available results have revealed that the design and construction of MOFs for photocatalyst functionality are very active. The present review aims tointroduce MOF materials, the synthesized methods and highlights the progress attempts for using the mas a nanophotocatalyst for degradation of pollutants.

Li2Ni8O10 and LiMn2O4 Nanoparticles as cathode materials for lithium ion battery were successfully synthesized using lithium acetate, nickel and manganese acetate as Li, Ni and Mn sources and stearic acid as a complexing reagent. The structure of the obtained products was characterized by FT-IR and XRD. The shape, size and distribution of the Li2Ni8O10 and LiMn2O4 nanoparticles were observed by SEM. Optical band gap and magnetic properties were determined by diffuse reflectance spectroscopy (DRS) and vibrating sample magnetometer (VSM). Li2Ni8O10 and LiMn2O4 spinels were identified as the main crystalline phases. The particles size of both, Li2Ni8O10 and LiMn2O4 nanoparticles is around 24 to 32 nm. Optical band gap of Li2Ni8O10 andLiMn2O4 are 1.40 eV and 1.16 eV, respectively.Therefore, lithium nickel and lithium manganese oxide nanoparticles can be used as semiconductor materials in electrical devices. VSM curve showed paramagnetic behavior of LiMn2O4 nanoparticles. Moreover, color parameters were obtained by colorimetric analysis of LiMn2O4 indicating characteristic values of L*=25.820, a*=1.607 and b*=-1.143.

In this work the synthesis of polyaniline/chitosan/functionalized single- walled carbon nanotube nanocomposite is carried out. For this purpose, single -walled carbon nanotubes were reacted with thionyl chloride to change the hydroxyl to acyl chloride groups for improving the react ability. In other step, aniline monomers and chitosan were polymerized in the presence of Iron (III) Chloride to synthesize the chitaline copolymer. The synthesized chitaline then reacted with functionalized single- walled carbon nanotube to prepare chitaline-single walled carbon nanotube nanocomposite. The synthesized nanocomposite was also characterized to evaluate the structure and morphology by Fourier infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and thermo gravimetric analysis (TGA). The results showed that the formation of the composite in nano scale can be good carbon materials with high adsorption capacity in porous surfaces for improving the properties as a good candidate such as nano bio filter for removing the organic and inorganic wastes from water.

S-doped and baremesoporous TiO2 were prepared using titaniumtetraisopropoxideand thiocarbamide as raw materials. Prepared materials were characterized by means of fourier transform infrared spectroscopy FT-IR, thermogravimetry-differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), UV-Vis absorption spectroscopy, Brunauer-Emmett-Teller (BET) specific surface area and Barrett–Joyner-Halenda (BJH) pore size distribution analyses, scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX). The band gap of S-doped was estimated from UV-Vis spectroscopy data to be 2.8 eV. The specific surface area of S-doped TiO2 nanoparticles obtained via the BET method, calculated to be 181.3 m2/g and its pore size distribution curve revealed that the average diameter of the pores is 12.3 nm using BJH method. Photocatalytic efficiency of synthesized S-doped mesoporous TiO2 was tested for degradation of Congoredazo dye under ultraviolet and visible lights. The results revealed that the S-doped mesoporous TiO2 is the most effective under visible lightin comparison withbareone.

Protonation of the highly reactive 1: 1 intermediates, produced in the reaction between triphenylphosphine and acetylenic esters, by NH-acids such as azathioprine, imidazole or theophylline leads to the formation of vinyltriphenylphosphonium salts, which undergo a Michael addition reaction with a conjugate base to produce phosphorus ylides. Silica nanoparticles (silica NPs were prepared by thermal decomposition of rice hulls) was found to catalyze the conversion of the phosphorus ylides to electron-poor N -vinyl imidazoles in solvent-free conditions under thermal (90oC, 30 min) conditions. It may be speculated that the polar amphoteric surface (OH groups of the silica NPs) facilitates the interaction of adsorbed weak acidic and basic components due to stabilization of the corresponding transition states and intermediates by H-bonding. It seems that the interactions with the neighboring silanol groups are plausible factors in the rate acceleration. Participation of two proximate silanol groups (one as an Hbond donor and the other as an H-bond acceptor) in the reaction mechanism also seems to be plausible.

A relationship based on the modified couple stress theory is developed to investigate the flexural sensitivity of an atomic force microscope (AFM) with assembled cantilever probe (ACP). This ACP comprises a horizontal cantilever, two vertical extensions and two tips located at the free ends of the extensions, which forming a caliper. An approximate solution to the flexural vibration problem is obtained using the Rayleigh–Ritz method. The results show that the sensitivities of AFM ACP obtained by the modified couple stress theory are smaller than those evaluated by the classical beam theory at the lower contact stiffness. The results also indicate that the flexural sensitivities of the proposed ACP are strong size dependant when the thickness of the cantilever is close to the material length scale, especially at lower contact stiffness. Furthermore, the greatest flexural modal sensitivity occurs at a small contact stiffness of the system, in which the ratio of the cantilever thickness to the material length scale and the distance between the vertical extensions are also small. In this situation, the distance between the vertical extensions and the clamped end of the cantilever and also the vertical extensions lengths are large. The results reveal that the sensitivity of the right sidewall tip is higher than that of the left one.

Research in convective heat transfer using suspensions of nanometer-sized solid particles in base liquids started only over the past decade. Recent investigations on nanofluid, suspensions are often called, show that the suspended nanoparticles remarkably change the transport properties and heat transfer characteristics of the suspension. Bending walls can also improve heat transfer by raising the total heat transfer from a surface and changing the behavior of the flow. In this paper two-dimensional incompressible nanofluid flow in a confined sinusoidal converging jet in turbulent flow regime is numerically investigated. Results showed for the flow structure at different Reynolds numbers for steady asymmetric jet development at various values of the duct-to-jet width ratio (aspect ratio), different amplitudes of surface undulation and different volume fractions of nanoparticles. For considering unsteady treatment of the flow, the streamlines and temperature contours result for the unsteady problem is presented and compared with the steady results. The present computations are in a good agreement with experimental results in open literature. The results show that by increasing the Reynolds number, aspect ratio, amplitude and volume fraction the average the Nusselt number will increase.

Dipolar-dephasing method provides some information about the strength of dipolar coupling in solids.Dipolar dephasing technique measures the time for a polarized carbon nucleus to lose its magnetization once the proton locking field is terminated. The dynamics of guest molecules adsorbed within the cavities and channels of nanoprous zeolite strongly depend on the structure and chemical composition of the nonporous zeolite. In this work solid-state 13C NMR spectroscopy and dipolar dephasing technique were used to determine the extent of motion 1-chlroadamantane loaded in nanoprous zeolite-Y. Loading of 1-chlroadamantane into the supercages of the zeolite-Y (with R=100 and R=2.35, R=Si/Al) was carried out by a vapor phase impregnation and solution impregnation methods. The accuracy of dipolar dephasing method was first investigated with the aid of pure 1-chlroadamantane to determine the degree of motion in the nanoprous of zeolite-Y. Results indicated that the Cd signal of the 1-chlroadamantane in the nonporous zeolite-Y decays faster than that the C and C, demonstrating that dipolar interaction for this carbon (Cd) is stronger.However, the rate of signal decay Cd for the 1-chlroadamantane loaded in zeolite -Y (R=2.35) is less than that loaded in zeolite-Y (R=100).

In this study, the adsorption of 1-chloro-4-nitrobenzene (1C4NB) on carbon nanofibers (CNFs), was investigated in a batch system. The combined effects of operating parameters such as contact time, pH, initial 1C4NB concentration, and CNFs dosage on the adsorption of 1C4NB by CNFs were analyzed using response surface methodology (RSM). The analysis of variance results confirmed that there was significant agreement between the model and experimental data. In addition, it was indicated that the residuals followed a normal distribution. The screening experiments showed that significant factors in 1C4NB removal were CNFs dosage, interaction between initial 1C4NB concentration-CNFs dosage and CNFs dosage-contact time. High efficiency removal (>90%) was obtained under optimal value of process parameters in the first 6 min of the removal process. The results indicate that RSM is a suitable method for modeling and optimizing the process, so that experimental design by RSM leads to time and cost saving. Non-linear form of Langmuir, Freundlich and Temkin models were fitted to adsorption equilibrium data. The results showed that the isotherm data can be well described by Freundlich isotherm equation.

In the present work, a prototype of a new type of solar collectors called Direct Absorption Solar Collector, was built and its thermal performance is experimentally compared with conventional flat plate solar collector under transient and steady state conditions. Different volume fractions of multi wall carbon nanotubes in water and ethylene glycol mixture (70%: 30% in volume) were used as working fluid of direct absorption solar collector. The transient comparison show that the efficiency of the direct absorption solar collector becomes about 7% (in average) more than that of flat plate solar collector at 72 l/hr flow rate. The steady state performance tests were performed in different flow rates from 54 to 90 l/hr, based on the procedure of EN 12975-2 standard. Under similar operating conditions, a direct absorption solar collector using 100 ppm carbon nanotube nanofluid has the zero-loss efficiency of 23% higher than that of a flat plate collector; whereas, the zero-loss efficiency of a direct absorption solar collector using the base fluid is 4.4% lower than that of a flat plate collector. Based on the results, the performance of a direct absorption solar collector using carbon nanotube nanofluids is better than a flat-plate solar collector.