NANOSCALE
Year:2019 | Volume:6 | Issue:3 |Papers Count:12

Porous coordination polymers, called metal-organic frameworks, have attracted considerable attention due to high volume of pore, regular pore framework with uniform size, high surface area, simultaneous presence of organic and inorganic groups, and it have the wide application. In this research, metal-organic frameworks based on zinc metal [Zn2(bdc)2(dabco)]n were synthesized by solution (at room temperature) and solvothermal (at 90 ° C) and then zinc oxide nanoparticles (ZnO) were dissolved by thermal degradation and removal of organic section. The samples were investigated by Fourier transform infrared (FTIR) for investigation functional groups, X-ray diffraction (XRD) for determination of crystalline structure, scanning electron microscopy (SEM) for studding of size and morphology, X-ray diffusion spectroscopy (EDS) for investigation of chemical composition, and Diffuse reflection spectroscopy (DRS) for determination of ultraviolet radiation absorption. Antibacterial activity of zinc oxide nanoparticles was evaluated against Escherichia coli (E. coli). The results indicated that thermal degradation of metal-organic frameworks based on zinc metal can be used successfully to preparation of zinc oxide nanoparticles and final nanoparticles have an appropriate antibacterial activity against E. coli and UV-blocking, and can have a good potential for different applications.

In this study, nanocrystalline Li0. 5Fe2. 5O4 ferrite powders have been prepared by sol-gel, selfcombustion and hydrothermal synthesis methods. The influence of synthesis method on the structure and the properties has been investigated in details. Based on the X-ray diffraction (XRD) data, the cubic crystal structure with P4332 space group is obtained for Li ferrite produced by sol-gel method, while P4332 space group is observed for the powders prepared by self-combustion and hydrothermal methods. In addition, a significant amount of impurity is detected for the hydrothermally synthesized powders which is contrary to that observed by two other methods. The microstructure of the produced powder has been investigated by a field emission scanning electron microscope (FESEM). A plate-like and spongy morphology with numerous porosity is observed in the Li ferrite powder clusters produced by sol-gel and auto-combustion synthesis methods, respectively. According to the magnetic measurements, the highest saturation magnetization (57 emu/g) and the lowest crystallite size (26 nm) is detected for the self-combustion powders. The results also show that dielectric constant and AC electrical conductivity of the selfcombustion Li ferrite is moderately higher that those recorded for the the sol-gel Li ferrite in the all measured frequencies.

The aim of this study was the evaluation of the antibacterial effect of Zn-doped TiO2 nanoparticles immobilized on the bentonite prepared via molten salt method. The prepared nanocomposites were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDX), UV-Vis diffusive reflectance spectrometer (UV-Vis DRS). SEM was showed that agglomeration of TiO2 nanoparticles formed on the bentonite surface. The band gap energy of TiO2 nanoparticles and TiO2/bentonite was about 3. 2 eV. After doping of 5 and 10% Zn, the band gap was decreased to 3. 04 eV, respectively. According to XRD results, the crystalline phase of the TiO2 nanoparticles in all of the nanocomposites was anatase. The crystalline size of nanoparticles was less than 50 nm. Finally, doping of Zn in the nanocomposites increased their antibacterial activity.

Topological indices have significant applications in QSAR/QSPR studies, which allow the prediction of physical ad chemical properties for many chemical structures based on statically validated analysis starting from a small data set. With regard to nano structures, the problem is that the calculation of an index, which is the first step towards its application, usually is an immensely complicated subject. Consequently, computing the value of the index, will be the central issue rather than considering its application or comparing with other easycomputing indices. In this paper, the arithmetic-geometric indices and their generalizations in relation to the single-walled zig-zag nanotubes (TUHC_6 [2p, q]) have been investigated. Our results proved that the values of these families of indices are approximately equal to the number of the edges of their molecular graphs. From this point of view, the computation of such indices, for single-walled Zig-Zag nanotubes, is worthless. Instead, an edge version of distance-based topological indices has been purposed. We found and compared relationships between some of these new indices and the total energy of TUHC_6 [2p, q] nanotubes.

Due to the emergency need in early diagnosis of illnesses, the need for high performance biosensors is one of the researchers' goals. In this paper, a structure consisting of graphene-gold grating, which formed strong plasmons in the near infrared region, was proposed to detect the refractive indexes' changes (and consequently the concentration) biomolecule and, in general, all materials with a refractive index of 1. 000-1. 600. Sensitivity and quality factor of the proposed sensor have been calculated and the effects of structural parameters and incident light characteristics on these factors have been considered. The best result has been obtained for materials with 1. 100 refractive index with 9750 quality factor. Also, the possibility of detection for some biological molecules with this sensor, such as water, glucose, MDCK and blood, with a refractive index variation of 1. 000 to 1. 600 has been investigated which the quality factors for these molecules have been achieved upper than 6000.

The core-shell nanofibers consist of titanium dioxide and tin dioxide were fabricated by electrospinning method in order to enhance photocatalytic activity under ultraviolet (UV) irradiation. The morphology and microstructure of the produced nanofibers were investigated using scanning electron microscopy (SEM), transition electron microscopy (TEM) and X-ray diffraction (XRD). According to SEM images, the fabricated samples have core-shell TiO2-SnO2 structures with diameters ranging from 120 to 70 nm. The XRD analyzes show that synthesized nanostructures have a crystalline dominant phase after thermal treatment. Furthermore, the results of ultraviolet-visible (UV-Vis) spectroscopy show that the changes in absorption peaks of Rhodamine b, Methylene blue and Methyl orange have been considerably reduced in presence of core-shell nanofibers TiO2-SnO2. These results confirm that the photocatalytic properties of nanofibers eventually led to a reduction in concentration of the model dye.

In this paper, preparing process of the PANI@MgO/TiO2 nanocomposite film and its application as a lead (II) ion adsorbent from aqueous solutions is reported. The MgO/TiO2 nanocomposite was synthesized by sol-gel method. In order to prevent the dispersion of synthesized nanocomposite in the environment, the PANI @MgO/TiO2 nanocomposite film was prepared using a cyclic voltammetry in a phosphoric acid and potassium chloride medium at a concentration of 0. 5 M as a carrier electrolyte on a graphite electrode in the potential range of-0. 2 to 1 volt. Various methods were used to identify the microstructure of resulting film. The XRD pattern confirmed the presence of magnesium oxide and crystallized titanium dioxide in the nanocomposite. The FESEM image showed that the nanocomposite was formed in a uniform spherical form with an average diameter of 61nm. The EDX analysis confirmed the presence of magnesium, titanium and oxygen elements. The FT-IR spectra showed the expected fine structure. The prepared nanocomposite film was used to remove lead (II) ion from aqueous solution and the factors affecting removal were optimized. Temperature of 25° C, 15 min contact time, pH range of 4 to 5, and nano-adsorbent amount 0. 066g were obtained as optimal conditions for removal of Pb 2+ ion. In these conditions, the sorption capacity was 48. 5 mg/gsorbent. Also, the study revealed that the presence of interference ions doesn’ t affect on removal process and the ability of nano-adsorbent in the samples with complex matrix is significant. The study of nano-sorption isotherms showed that the equilibrium results are consistent with the Langmuir and Freundlich equations.

Two-dimensional materials such as transition metal dichalcogenides (TMDCs) with direct band gaps have opened a new horizon for application in photonics and optoelectronic elements. Of various TMDCs, the WSe2 monolayer is chosen to study its absorption in the presence of the gold as a plasmonic layer and SiO2 as the spacer layer with alternative layer’ s positions. Optical properties of these structures are calculated based on the transfer matrix method, TMM, in the visible wavelength region. We found that the presence of the spacer layer between the WSe2 and gold layer enhances the absorption significantly. In an optimal design and in the wavelength of 324 nm, while thickness of the spacer layer is 38 nm, the absorption is reached to 97%. Our findings can be applied for designing any desirable optical absorbers for high performance photovoltaic devices.

In this study, the structure of the inverted planer solar cell was used because of its prominent features, such as low temperature construction and low cost construction, the effect of two layers of PDOT: PSS and PTAA (as the underlying perovskite) on the morphology perovskite layer and parameters affecting solar cell performance (Jsc, Voc, FF, PCE) were investigated. SEM and AFM images showed that Proper morphology and high coverage of perovskite film with PTAA compared to perovskite film with PEDOT: PSS resulted in increased light absorption and efficiency in perovskite solar cell with PTAA. Their yields reached 11. 37%, while the maximum PDOT: PSS-based solar cell efficiency was 9. 23%.

in this study, Ni-Cu/Cu multilayers from a single sulfate/sulfamate bath using electrodeposition method from two solutions; ultrapure solution (without impurity of Co) and impure solution (with 0. 2% Co) in galvanostat/potentiostat (G/P) mode was prepared at optimized Cu deposition potential. Magnetoresistance (MR) measurements were performed at room temperature for the Ni-Cu/Cu multilayers as a function of (Cu) layer thickness for both ultrapure and impure electrolytes. The magnetoresistance curves represent an anisotropic magnetoresistance (AMR) for multilayered samples prepared by ultrapure electrolyte and giant magnetoresistance (GMR) by impure electrolyte, so that the maximum GMR value was obtained for Ni-Cu/Cu multilayer with 3. 0nm/4. 2nm thickness. The X-ray diffraction pattern (XRD) was used for structural analysis of multilayer films. The XRD pattern confirmed the presence of satellite peaks, indicating the existence of a superlattice structure. The nominal thickness of the multilayers (Λ nominal) was compared with the thickness of the X-ray diffraction pattern (Λ XRD), which was significantly consistent. . The morphology of the samples was performed using scanning electron microscopy (SEM) which implies uniformity of deposition during the layering process. The results showed that with decreasing thickness of nonmagnetic layer (Cu) the coercivity decreased and saturation magnetization increased.

In this work, core (SiO2) – shell (CuS) nanostructures have beendeveloped using a simple wet chemical route. X-ray diffraction analysis (XRD), diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), EDS and fourier transform infrared (FT-IR) were used to characterize the products. The morphological studies revealed theuniformity in size distribution with core size of 250 nm andshell thickness of 7. 5-17 nm. The structural studies indicate hexagonal structure of covellite (CuS) shell with no other trace for impurities in the crystalstructure. This CuS layer exhibit the band gap energy of3. 1 eV, due to quantum confinement and numerousdefects presence. Photocatalytic activity of nanocomposites was studied for degradation of Methylene Blue (MB) under visible light. Several parameters were examined, catalyst amount (0. 1– 1 g L-1 ), pH (1– 13) and initial concentration of MB (0. 96– 10 ppm). The extent of degradation was estimated from the residual concentration by spectrophotometrically.

Recently, upconversion nanoparticles have attracted tremendous attention and have been employed for verity of applications. Here, we investigate the impact of applying different temperatures on the optical function of NaYF4: Yb upconversion nanoparticles. Therefore, upconversion nanoparticles are doped in a polymer matrix and excited with a 980 nm laser beam. Its fluorescence spectrum comprises of 4 peaks in the red, green and blue bands and appeared in green color. Then, the temperature was slowly increased from 25C° up to 75C° and subsequently decreases to investigate the fluorescence intensity at two wavelength peaks of 525 nm and 541 nm. Results indicates that the fluorescence intensity 3+ 3+, Er decreases by increasing the temperature, due to non-radiative decays induces by thermal de-excitation in the NaYF4 host matrix, and increase again by reducing the temperature.