Current Nanoscience - Volume 14, Issue 6, 2018

Background: Photocatalytic materials can be prepared in the supported form in wastewater treating devices. The quartz sphere can be regarded as a suitable support for photocatalytic material since it is transparent to UV irradiation. Methods: Gd2Ti2O7 was supported on quartz spheres by a sol-gel method in this work to study the effects of calcination temperature on the properties of the composite 30%Gd2Ti2O7/SiO2. The materials were characterized using scanning electron microscopy, transmission electron microscopy, Xray powder diffraction, FT-IR/Far IR spectroscopy, UV-Vis spectrometry, fluorescence spectrophotometry, and surface area and pore analyses. Results: Crystallization of pyrochlore structured Gd2Ti2O7 starts at 800oC. The FT-IR absorptions of Gd2Ti2O7 occur in the spectra of the samples calcined over 800oC. Band gap energy of the 30%Gd2Ti2O7/SiO2 decreases from 3.66 eV at 600oC to 3.43 eV at 1000oC. The sample calcined at 800oC has the maximum photocatalytic degradation efficiency of 59.5% after 30 min of irradiation. Conclusion: The increase of calcination temperature leads to a slight cell expansion of pyrochlore structured Gd2Ti2O7 crystals that forms above 800oC. The increase in calcination temperature leads to constant reducing band gap energy of 30%Gd2Ti2O7/SiO2. The maximum amount of hydroxyl radical is produced in the solution containing 30%Gd2Ti2O7/SiO2 calcined at 800oC, accompanied with the maximum ofloxacin degradation efficiency on that sample.

Background: As a new type of micron/nanofiber preparation technology, solutionblowing has attracted more and more attention and applied in wide application field. Compared with electrospinning, it has such advantages as simple equipment, easy accessibility and low energy consumption. Objective: In this paper, the modified poly(arylene ether sulfone) polymers are expected to be prepared and converted into nanofibers via solution-blowing technology, and can be applied in microfiltration and oil-water separation. Methods: We synthesized a series of linear high molecular weight ternary poly(arylene ether sulfone) via adding different content of phthalein group, and then successfully fabricated the corresponding nanofibers via solution-blowing technology. The concentration of spinning solution was optimized to obtain the uniform and smooth nanofibers. The membranes were characterized by Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Wide-angle X-ray diffraction (WAXD), Differential scanning calorimetry (DSC), Thermogravimetric analysis (TGA), and Water contact angle (WCA), etc. Furthermore, the filtration experiment and oil-water separation test were executed to verify the membranes practical application value. Results: The results showed the spinning solution with polymers concentration of 25 wt% was suitable to prepare nanofibers with well appearance and the membranes had a higher glass transition temperature (Tg) and better thermal stability with the increase content of phthalein groups. The oil-water separation experiments of membranes showed fast and efficient separation ability for oil-water mixtures at special scale. Conclusion: The nanofibrous membranes of modified poly (arylene ether sulfone) with cardo group in the main chain were successfully prepared via solution-blowing technology and exhibited great application potential in microfiltration.

Background: Among the mixed transition metal oxides, ZnFe2O4 as a binary metal oxide with a spinel structure has a wide range of application prospects in materials science and technology. The microstructure, energy band structure, optical properties and magnetic properties of ZnFe2O4 can be modified by element doping. Objective: In this work, the influences of Ni doping upon the structure, morphology, optical and magnetic properties of ZnFe2O4 were studied. Methods: Pure and Ni-doped Zn1-xNixFe2O4 nanoparticles with different concentration (x = 0, 0.1, 0.3 and 0.5) were successfully synthesized by hydrothermal method. XRD, HRTEM, XEDS, UV– vis, FT-IR and VSM were utilized to investigate the Zn1-xNixFe2O4 nanocrystals samples. Results: The experimental results show that all Zn1-xNixFe2O4 nanoparticles have cubic spinel structure with good crystallization. Ni2+ successfully substituted for the lattice site of Zn2+ and generated single-phase ZnFe2O4 without other impurity phases. After Ni doping, the grain size distribution increased, the bandwidth increased and ferromagnetism increased. Conclusion: The crystalline size increased as Ni concentration increased, while its the lattice constant occurshrink expansion. The energy band gap of Zn1-xNixFe2O4 nanocrystals increased as Ni concentration increased, and blue shift occurred compared to that of the pure ZnFe2O4. Pure ZnFe2O4 nanocrystals showed superparamagnetic properties, while the doped Zn1-xNixFe2O4 samples have obvious ferromagnetic properties at room temperature.

Objective: The aim of this study is to analyze the local and global bifurcation for the physiological flow of nanofluid in channel and tube having porous medium with slip conditions. Methods: Of concern in this paper, simultaneous effects of surface slip and mixed convection on the streamline patterns along their bifurcations for peristaltic flow of blood base nanofluid have been investigated in a homogenous porous medium. The flow is supposed to be in a vertical twodimensional symmetric channel. The flow systems are reduced by employing the estimation of low Reynolds number and long wavelength. For the discourse of the path of particle in the wave frame, an arrangement of nonlinear independent differential equations is built up and the strategies for dynamical frameworks are utilized to examine the local bifurcations and their topological changes. Flow situations marked as backward flow, trapping or augmented flow. Results: Graphically, a wide range of topological changes of bifurcations are examined. The analysis is disclosed that the number and size of trapped bolus increases in planner channel by increasing Grashof number and slip parameter. Conclusion: The place of the bifurcation point changes with the variation of the slip parameter. Increase of Darcy number leads to increase the size of trapped bolus. The decreasing behavior of temperature is depicted with respect to slip parameter, which clarify the nanofluid as a cooling agent. Graphically, a wide range of topological changes of bifurcations are examined.

Background: Suzuki–Miyaura cross-coupling reactions are reliable and powerful methods to minimize their surface energy, especially during the catalytic reaction at high temperature. They could easily lead to deactivation or loss of the catalytic activity. Objective: To solve this problem, adopting new supporting substrate is a possible strategy especially for nanometer-sized catalysts. Methods: Here we focused upon the uses of oxides of a sp2- and sp hybridized graphyne-like porous carbon-rich network (GYLPCO) as the supporting materials because they have lower reduction potentials than Pd2+ ions and could enable electroless deposition of Pd in a technically simple way without the use of surfactants or extra reductants or catalysts, while maintaining high activity. Results: We demonstrate that GYLPCO can be used as an excellent substrate for electroless deposition of ultrafine Pd nanoparticles. The as-formed Pd/GYLPCO nanocomposite is found to be an excellent catalyst for highly efficient Suzuki–Miyaura couplings. Conclusion: The unique Pd/GYLPCO exhibits very high catalytic activity for a broad scope of Suzuki–Miyaura reactions in aqueous media under aerobic conditions with short reaction time and good yields. The strong interaction between Pd and GYLPCO carbon-carbon triple bonds prevents the agglomeration or leaching of Pd nanoparticles and enables the Pd/GYLPCO catalyst to remain highly active even after the catalyst is kept in air for a long time.

Background: Gold nanoparticles (GNPs) of different sizes and shapes are very important for technological applications. They possess unique catalytic behavior under mild conditions and also they are considered catalysts of choice due to higher stability and negligible poisoning as compared to other metal nanoparticles (NPs). Objective: The main aim of the work is to synthesize GNPs using the flower extract of the harmful invasive wild growing plant, Lantana camara as a reducing and stabilizing agent under ambient conditions and use them for catalytic applications. Methods: The as-synthesized GNPs were characterized using various spectroscopic, microscopic and diffractometric techniques. UV-vis spectroscopy was used to monitor the progress of the catalytic dye reduction reactions. Results: UV-vis spectroscopic results indicated that optical properties of GNPs can be tuned by varying the concentration of extract in the reaction medium. Zeta potential measurement confirmed that the surfaces of these GNPs are negatively charged which imparts stability to the colloids. Microscopic results confirmed that varying the concentration of flower extract; size and shape of the formed GNPs can be systematically tuned. Selected area electron diffraction analysis of spherical and polygonal GNPs indicated that spherical GNPs are mainly polycrystalline in nature whereas polygonal GNPs are single crystalline.X-ray diffraction analyses confirmed the formation of pure face-centered cubic gold. These GNPs showed excellent catalytic activity in the borohydride reduction of organic dye molecules. Conclusion: At higher extract concentration, spherical GNPs are formed predominantly. But when the concentration of extract is lowered, GNPs of mixed morphology are formed. Further lowering in the concentration of extract resulted in polygonal GNPs only. These gold nanoparticles can be used as an efficient catalyst for borohydride reduction of toxic organic dyes in an aqueous medium.

Background: Al-F co-doped ZnO systems are investigated by the first principles calculations. Synchronously, we successfully prepared Al-F co-doped ZnO thin films using the aerosolassisted chemical vapor deposition technique. The computational results reveal that the Fermi energy of the Al-F co-doped ZnO system shifts to the conduction band in the electronic band structure, which illustrates that the Al-F co-doped ZnO system is an n-type semiconductor. Furthermore, Al-F co-doped ZnO system has much smaller minimum band gap than pure ZnO system and Al, F monodoped ZnO systems, which indicates its better conductive performance. Experimental results confirm the Al-F co-doping ZnO thin film has the smallest sheet resistance. More importantly, for the optical properties, the strong absorption of Al mono-doped and F mono-doped ZnO systems occurs in the UV region, while the obvious absorption of Al-F co-doped ZnO system happens in the visible-light region. Experimental results of photoluminescence spectroscopy can confirm the conclusion. These results suggest that Al-F co-doped ZnO system has excellent electrical conductivity and optical properties. Objective: Our work mainly concentrates on the Al-F co-doping ZnO system and its electronic band structure and optical properties in terms of experimental studies and theoretical calculations simultaneously. Methods: The ultrasoft pseudopotentials and CASTEP code of plane wave are used to execute all calculations, and depositing ZnO thin films on a glass substrate used by a cold wall aerosol assisted chemical vapor deposition method. Results: We use first principles and experimental results to study ZnO:Al, ZnO:F and ZnO:Al-F systems. We found that F and Al co-doped ZnO thin films resulted in the decrease of both the resistivity and the optical absorption in the visible range compared with the mono-doping systems (ZnO:Al, ZnO:F). It indicates that the Al-F co-doping ZnO system shows better conductive and optical performances in the visible light range. Conclusion: In summary, first principles calculations and experimental results have been performed to study the electronic band structure and optical properties of the ZnO:Al-F system. The electronic band structures show that ZnO:Al-F system exhibits n-type semiconductor, whereas the Fermi level shifts to the conduction band and exhibits metal-like characteristics with Al-F co-doping. The calculated optical properties indicate that the optical energy gap increases with Al-F co-doping. More importantly, a strong absorption in the visible-light region has been found with Al-F co-doping, which originates mainly from the transition between F 2p and Al 3p states. Our calculations provide electronic structure evidence that, in addition to the usage as optoelectronic devices, the ZnO:Al-F system could be a potential candidate for photo-electrochemical application due to the nature of the activity in the visible-light region.

Background: Substituted Mg nanoferrite attracted attention recently according to their capability for using in high-density magnetic recording applications, biotechnological applications and microwave control components. Objective: This article studied the temperature dependence of photoluminescence and Raman scattering of Zn2+ and Al3+substituted Mg nano spinel ferrites using a 325- and 758-nm He–Cd laser as an excitation source. Methods: Zn2+ and Al3+-substituted Mg nano spinel ferrites were fabricated at different ratios by coprecipitation method, the resulted powder was ground and sintered at 600°C for 10 h. The structure, particle size, and morphology of the spinel ferrites were confirmed with X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Results: The photoluminescence at different temperatures was investigated by studying the energy, intensity, and bandgap. The spectra exhibited a broadband consisting of two bands at 1.8 and 2.2 eV, indicated by their redshift. An Arrhenius model was used to fit the integrated photoluminescence as a function of the inverse temperature to calculate the activation energy. The Raman spectra reasonably fit the spinel ferrite structure of the synthesized nano spinel ferrites. The modes at 798 and 802 cm-1 exhibited a softening with increasing temperature owing to the effect of the substituted ions on the spinel microstructure.

Background: Silver nanoparticles find enormous applications in medicine, anti-bacterial coatings, paints, textiles and packaging industry. Synthesis of such nanoparticles through green approach provides the additional advantage of being non-toxic. Methods: In the present pursuit, we have synthesized silver nanoparticles by using leaves extract of Eugenia reinwardtiana. Such nanoparticles were further used to prepare nanocomposites with TOPAS to explore their potential for food packaging applications. Nanoparticles, as well as nanocomposites, were characterized using Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier- Transform Infrared Spectroscopy (FTIR), UV-Vis spectroscopy, tensile testing, water vapor permeability test and antimicrobial testing. Results: Mechanical testing, antimicrobial testing and water vapor permeability tests were carried out to probe into the properties of nanocomposites films essential for packaging applications. Water vapor permeability was found to decrease with increasing content of silver nanoparticles. Mechanical properties of the nanocomposite films demonstrated considerable increment with the addition of silver nanoparticles. Such nanocomposite films showed enhanced antimicrobial behavior as compared to pure TOPAS film. Conclusions: The results indicated the potential of nanocomposites films to be used in the food packaging applications.

Background: Heavy metal removal from wastewaters can be achieved by conventional processes such as chemical precipitation, ion exchange, flocculation, and so on. These methods have significant disadvantages, which are, for instance, incomplete removal, high-energy requirements, and production of toxic sludge. Nowadays, numerous approaches have been studied for the development of cheaper and more effective technologies. Adsorption has shown one of the alternative treatments. Basically, adsorption is a mass transfer process by which a substance is transferred from the liquid phase to the surface of a solid, and becomes bound by physical and/or chemical interaction. Methods: In this work, a simple method for determination of cadmium in petroleum effluent samples using multi-wall carbon nanotubes modified by anthraquinone followed by atomic absorption spectrometry is described. The structure, morphology and composition of nanosorbents were characterized by SEM and FT-IR techniques. A Taguchi L-16 method was used for selecting the best experimental condition. Effects of experimental parameters including pH, amount of the adsorbent, type of the adsorbent, removal temperature and removal time were investigated. Results: The results obtained by AAS indicated that the 2, 6-AQ-MWCNTs had much higher adsorption capacity for Cd(II) ions. The potential interfering ion on the removal efficiency of cadmium was studied. Conclusion: The method was successfully applied for the determination of cadmium in different petroleum effluent samples. The applicability of this sorbent was also investigated in some different real samples.