Sharif Digital Repository

The phase-pure multiple ternary or quaternary metal selenides in energy boosting, have not been reported yet. Here, self-supported porous crystalline Zn–Ni–Co/Cu selenides microballs arrays were constructed by selenation of the designed tubular Cu(OH)2 arrays decorated with ultrathin Zn–Co–Ni tri-metallic hydroxide on carbon cloth substrate. For this rational engineering, a novel precursor sample was firstly prepared by conversion of deposited Cu layer to hollow tubular Cu(OH)2 arrays on carbon cloth, then, Zn-Co–Ni layered ternary hydroxides with a thin layer structure was deposited around this tubular arrays. The selenation with an exciting morphology change from amorphous tube to highly... 

High-performance wearable electronic devices with the capability of converting mechanical force into electrical energy have been gaining increasing attention for biomedical monitoring applications. We present a novel wearable piezoelectric sensor based on a poly(vinylidene fluoride) (PVDF) nanofibrous membrane containing microporous zirconium-based metal-organic frameworks (MOFs) for arterial pulse monitoring. It is shown that the incorporation of 5 wt % of MOF greatly enhances the piezoelectric constant of the polymer fibrous mat by 3.4-fold without significant loss in its flexibility. The nanofibrous composite exhibits a peak-to-peak voltage of 600 mV under an applied force of 5 N, which... 

Self-assembled dandelion-like hydroxyapatite (HAp) nanostructures were successfully synthesized via a mild template-free hydrothermal process, using ethylenediaminetetraacetic acid (EDTA) as the surfactant. The obtained dandelion-like HAp nanostructures were between 5 and 8 μm in diameter and were composed of radially oriented nanorods with an average diameter of about 200 nm. The X-ray diffraction analysis and Fourier transform infrared spectroscopy were used to characterize the crystalline phase and purity of the synthesized nanostructures. The Brunauer-Emmett-Teller surface area of the dandelion-like nanostructures was measured to be about 39 m2/g. The results of thermal analysis revealed... 

Antibacterial activity of sol-gel synthesized Ag-TiO2 nanocomposite layer (30nm) deposited on rough anatase (a) TiO2 thin film (~200nm in thickness) was investigated against Escherichia coli bacteria, in dark and also in exposure to UV light. The nanocomposite thin films were transparent with a surface plasmon resonance absorption band at a wavelength of 410nm. The metallic silver nanoparticles with an average diameter of 30nm and fcc crystalline structure were self-accumulated on surface of a mesoporous and aqueous TiO2 layer with a capillary pore structure having a pore radius of 3.0nm. By adding the silver nanoparticles in the TiO2 layer, recombination of the photoexcited electron-hole... 

A highly water stable metal-organic framework (MOF) based on zirconium, i.e. UiO-66, was synthesized and then employed to adsorptive removal of an anionic dye, methyl orange (MO), and a cationic dye, methylene blue (MB), from aqueous solution. In this work, for the first time, the long term stability of UiO-66 in water was investigated for 12 months. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and N2 adsorption/desorption analysis were employed to monitor the textural alteration of UiO-66 during water aging. The results indicated that the structure of UiO-66 was mostly retained and its adsorption capacity toward dyes exhibited minor loss after long term water... 

5-Ammonium valeric acid (AVA) is a frequently used additive in the preparation of lead halide perovskites. However, its microscopic role as passivating, cross-linking, or templating agent is far from clear. In this work, we provide density functional theory-based structural models for the Ruddlesden-Popper (RP) phases of AVA2(CH3NH3)n-1PbnI3n+1 for n = 1, 2, and 3 and validate with experimental data on polycrystalline samples for n = 1. The structural and electronic properties of the AVA-based RP phases are compared to the ones of other linker families. In contrast to aromatic and aliphatic spacers without additional functional groups, the RP phases of AVA are characterized by the formation... 

Hydrolysis of titanium isopropoxide alcoholic solution has been used to prepare the crystallized TiO2 nanoparticles at low temperature. Concentration ratio was used to control the pathway of sol-gel process and change the physical characteristics of TiO2 nanopowders. The crystallinity, morphology and size of aged TiO2 nanopowders were studied by X-ray diffraction and Scanning Electron Microscopy (SEM). FTIR and, Thermo-Gravimetric (TG) analysis were used to identify the functional groups and thermal behavior of prepared samples. Experimental results have shown that high crystalline TiO2 nanomaterial with anatase polymorph can be obtained at room temperature. It has been found that the... 

(ZnO)1-x(CdO)x nanofibers were fabricated via electrospinning of polymer precursor by subsequent annealing in air. Field emission scanning electron microscopy (FESEM) showed the smooth and beadless nanofibers and X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) showed the ZnO hexagonal and the CdO cubic structure. Diffuse reflectance spectroscopy (DRS) showed the band gap energy reduction by increasing the amount of CdO in (ZnO)1-x(CdO)x nanofibers that resulted in the photocatalytic activity under the visible light for dye degradation. Under the UV light CdO acted as both electron and hole sink in the (ZnO) 1-x(CdO)x nanofibers and a possible photocatalytic activity... 

Abstract In this study, adsorption of the CO2 and N2 gases on the MIL-53(Al) and its hybrid composite with the graphene nano-plates (GNP), MIL-53(Al)/GNP, adsorbents were investigated. These materials were synthesized using the solvothermal reaction method. The prepared samples were characterized by means of the powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM), N2 adsorption-desorption isotherms (BET-BJH surface area measurement) and Fourier transfer infrared (FT-IR) spectroscopy methods as well as; thermogravimetric analysis (TGA). Adsorption equilibrium of the CO2 and N2 on the sorbents were... 

In this work, the adsorption of benzoic acid (BA) over metal organic framework of chromium-benzenedicarboxylates (MIL-101) is reported for the first time. The influences of pH, contact time, initial concentration, and temperature of BA solution on the adsorption behavior were investigated. The Langmuir adsorption isotherm was adequate to represent the experimental data (R2 > 0.99) and the adsorption kinetics was well-represented by a pseudo-second order kinetic model (R2 > 0.96). The zeta potential of MIL-101 decreased with increasing pH confirming the importance of electrostatic interactions between MIL-101 and BA as well as the importance of the large pore volume (1.32 m3/g) and large... 

Decreasing particle size results in larger increase of external surface area and shorter diffusion path, both reducing mass and heat transfer resistances in catalysis and sorption. A rapid high-temperature hydrothermal synthesis method was developed to synthesize uniform nanoparticles of SAPO-34 zeolite with high crystallinity. To investigate the effects of temperature and synthesis time on purity and crystallinity of the final products, the crystallization temperature was increased from 468 to 673 K while the synthesis time was decreased from 24 h to 45 min. The products were characterized by XRD and SEM techniques. It was found that high temperature and short synthesis time reduce the... 

A rapid, environmental friendly and low-cost method to prepare hydroxyapatite nanoparticles is proposed. In this method, hydroxyapatite is produced in a sonicated pseudo-body solution. The sonication time was found effective in the formation of the crystalline phase of nanoparticles. In our experimental condition, 15 min sonication resulted in the most pure hydroxyapatite phase. Also it was shown that growth temperature is a crucial factor and hydroxyapatite crystallizes only at 37 °C. The particles formed by sonication were generally smaller and more spherical than those obtained without sonication. Sonication increased the hydroxyapatite crystal growth rate up to 5.5 times compared to... 

Radiopacity is sometimes an essential characteristic of biomaterials that can help clinicians perform follow-ups during pre- and post-interventional radiological imaging. Due to their chemical composition and structure, most bioceramics are inherently radiopaque but can still be doped/mixed with radiopacifiers to increase their visualization during or after medical procedures. The radiopacifiers are frequently heavy elements of the periodic table, such as Bi, Zr, Sr, Ba, Ta, Zn, Y, etc., or their relevant compounds that can confer enhanced radiopacity. Radiopaque bioceramics are also intriguing additives for biopolymers and hybrids, which are extensively researched and developed nowadays for... 

In this study, tungsten oxide films were deposited by pulsed-laser deposition (PLD) technique. The as-deposited films were annealed at 250 °C in air for 1 h. The surface morphology, microstructure, crystalline phase, and chemical composition of the films were characterized by SEM, XRD and XPS techniques. Pt nanoparticles were deposited onto the tungsten oxide films through a two-step process. First of all, a layer of PtCl2 was coated on the WO3 surface by drop-drying the PtCl2 solution onto the WO3 surface at 60 °C. Consequently, the reduction of the PtCl2 into the metallic Pt nanoparticles was performed at 200 °C. In this study, the effect of the temperature during hydrogen reduction of... 

In this study, maghemite (γ-Fe2O3) nanoparticles were produced using gelatin protein as an effective mediator. Size, shape, surface morphology and magnetic properties of the prepared γ-Fe2O3 nanoparticles were characterized using XRD, FT-IR, TEM, SEM and VSM data. The effects of furnace temperature and time of heating together with the amount of gelatin on the produced gelatin-Fe3O4 nanocomposite were examined to prove the fundamental effect of gelatin; both as a capping agent in the nanoscale synthesis and as the director of the spinel γ-Fe2O3 synthesis among possible Fe 2O3 crystalline structures  

In this study, lithium disilicate glass-ceramic in the TiO2-ZrO2-Li2O-CaO-Al2O3-SiO2 system was investigated for dentistry applications by incorporation of P2O5 and Nb2O5 as nucleation agent. The influence of the particles size (nano and submicron size) and nucleating agents on the crystalline phases, microstructure, crystallization mechanism and mechanical properties were investigated. Our data indicated that in ceramic glass with nano and submicron P2O5, the main crystalline phase was lithium disilicate. The results also showed that change of P2O5 particle's size had significant effect on the crystalline phases and microstructure. By replacement of submicron P2O5 with submicron Nb2O5,... 

Bacterial cellulose (BC) is an extracellular natural polymer produced by many microorganisms and its properties could be tailored via specific fabrication methods and culture conditions. There is a growing interest in BC derived materials due to the main features of BC such as porous fibrous structure, high crystallinity, impressive physico-mechanical properties, and high water content. However, pristine BC lacks some features, limiting its practical use in varied applications. Thus, fabrication of BC composites has been attempted to overcome these constraints. This review article overviews most recent advance in the development of BC composites and their potential in biomedicine including... 

A near fully dense mullite-TiB2-CNTs hybrid composite was prepared successfully trough spark plasma sintering. 1 wt%CNT and 10 wt%TiB2 were mixed with nano-sized mullite powders using a high energy mixer mill. Spark plasma sintering was carried out at 1350 °C under the primary and final pressure of 10 MPa and 30 MPa, respectively. XRD results showed mullite and TiB2 as dominant crystalline phases accompanied by tiny peaks of alumina. The microstructure of prepared composites demonstrated uniform distribution of TiB2 reinforcements in mullite matrix without any pores and porosities as a result of near fully densified spark plasma sintered composite. The fracture surface of composite revealed... 

A low cytotoxic metal–organic framework (MOF) UiO-66 (UiO stands for University of Oslo) and NH2-UiO-66, that showed high cell viability of HFF-2 via 3-(4, 5-dimethylthiazol-2-yl) 2, 5-diphenyl tetrazolium assay, was reported as an effective adsorbent (antidotal) agents. The structure of MOFs was confirmed by Fourier transform infrared, Field emission scanning electron microscopy (FESEM) and X-ray diffraction. Thermal behavior of MOFs was investigated using with thermogravimetric analyzer in nitrogen atmosphere to check the thermal stability. FESEM showed NH2-UiO-66 displayed symmetrical crystals with triangular base pyramid morphology, with the particle size around 100 nm and uniform size... 

A low cytotoxic metal–organic framework (MOF) UiO-66 (UiO stands for University of Oslo) and NH2-UiO-66, that showed high cell viability of HFF-2 via 3-(4, 5-dimethylthiazol-2-yl) 2, 5-diphenyl tetrazolium assay, was reported as an effective adsorbent (antidotal) agents. The structure of MOFs was confirmed by Fourier transform infrared, Field emission scanning electron microscopy (FESEM) and X-ray diffraction. Thermal behavior of MOFs was investigated using with thermogravimetric analyzer in nitrogen atmosphere to check the thermal stability. FESEM showed NH2-UiO-66 displayed symmetrical crystals with triangular base pyramid morphology, with the particle size around 100 nm and uniform size...