M. M. Rashad

Concordantly fabricated heterojunction ZnO–TiO2 nanocomposite electrodes via a co-precipitation method for efficient stable quasi-solid-state dye-sensitized solar cells

This manuscript is concerned with the successful attempts we have made to fabricate nanostructured spheres composed of mixed metal oxides. ZnO/TiO2 nanocomposites supported on an FTO substrate are used as the photoanode electrode for quasi-solid-state dye-sensitized solar cells (QS-DSSCs). The phase purity of the ZnO and TiO2 phases of the composite shell has been studied by X-ray diffraction peak analysis. A novel gel polymer electrolyte based on a poly(acrylamide)–poly(ethylene glycol) composite and a binary organic solvent was prepared. The polymer gel electrolyte based on the composite of poly(acrylamide)–poly(ethylene glycol), the binary organic solvent of ethylene carbonate and propylene carbonate and the additive of 4-tert-butylpyridine has been employed to fabricate a quasi-solid-state dye-sensitized solar cell. The conversion efficiency of the dye-sensitized solar cells with nanocomposites is 6.5% which is more than double compared with that of bare ZnO nanoparticle photoanodes (3.8%). We believe that this improvement comes from the synergetic effect between ZnO and TiO2, which increases dye absorption, electron transport and electron lifetime, as discussed with the EIS and loaded absorption results. From the current–voltage and incident photon-to-current conversion efficiency (IPCE) measurement, the conductivity of the nanocomposite ZnO–TiO2 was shown to be higher compared to the nanostructured ZnO itself. This simple method can be universally adopted for all quasi-solid-state electrolyte-based DSSCs in order to improve their performance and durability.

Tuning the optical and dielectric properties of calcium copper titanate CaxCu3−xTi4O12 nanopowders

Calcium copper titanate CaxCu3−xTi4O12 (CCTO) nanopowders have been synthesized using the organic acid precursor method based on commercially available materials. The results revealed that cubic CCTO phase was accomplished for the formed citrate precursors annealed at 1000 °C for 2 h. The crystallite size of the formed powders was found to increase from 44.2 to 64.8 nm upon increasing the molar ratio of Ca2+ ion from 1.0 to 2.0. A slight increase in the lattice parameter “a” and unit cell volume were observed, while a slight decrease in the porosity was evidenced as a result of increasing Ca2+ ion concentration. FE-SEM observations of these powders confirmed their homogeneous regular cubic-like structure. It can be noted that the transmittance of the sample was around 85% with Ca2+ ratio 1.0. Furthermore, the band gap energy increased from 3.8 to 4.2 eV, and the DC resistivity was increased from 6.4 × 104 to 6.8 × 104 cm Ω with increasing calcium content. We demonstrate that without any dopant, only by controlling the chemistry and engineering of the interfacial regions at the grain boundaries, the dielectric loss was suppressed remarkably while retaining the giant dielectric constant. These investigations would allow the application of these materials in transparency, microelectronics and memory devices.

Tailoring optical, magnetic and electric behavior of lanthanum strontium manganite La1−xSrxMnO3 (LSM) nanopowders prepared via a co-precipitation method with different Sr2+ ion contents

Lanthanum strontium manganite (LSM) nanopowders La1−xSrxMnO3 (x = 0.2, 0.5, 0.8) have been synthesized using the co-precipitation method based on methyl amine as a base at a pH value 12. The effect of Sr2+ ion concentration on the crystal structure, microstructure, optical, magnetic and the electrical properties was investigated. Typically, in all of the formed LSM powders, XRD revealed that a pure single perovskite LSM phase was obtained after annealing at 1000 °C for 2 h. This temperature was relatively low compared to what has been reported elsewhere. The microstructure of the produced LSM nanopowders depends on the Sr2+ concentration. The observations of these powders confirmed their rough surface. Meanwhile, the transmittance of the sample was around 40% for LSM with an Sr2+ ratio of 0.8. Furthermore, the band gap energy of this powder was 2.6 eV. The refractive index was decreased with an enhanced Sr2+ ion content. Indeed, the saturation magnetization of the LSM powders was increased on increasing the Sr2+ ion concentration. Electrochemical impedance spectroscopy (EIS) evinced that the electrode specific polarization resistance of the LSM samples was increased by increasing the Sr2+ ion concentration from 3.10 to 8.56 Ω cm2.

Effect of Y3+, Gd 3+ and La3+ dopant ions on structural, optical and electrical properties of o-mullite nanoparticles

Abstract Dielectric ceramics of M(x)Al6(1–x)Si2O13 doped mullite were synthesized via co-precipitation technique. The X-ray diffraction profiles revealed that these nanoparticles were crystallized well and the volume of mullite unit cell was increased as a function of the ionic radius of dopant ion. TEM images showed regular orthorhombic crystal morphology for the pure mullite sample. Meanwhile, the doped samples exhibited slightly distorted crystal morphology of larger particle sizes. DSC thermograms evinced that the exothermic peak temperature of mullite was shifted to the lower value with M3+ ion insertion. The photoluminescence spectra were studied for mullite samples, and it was found that the intensity of the emission spectra was affected by the M3+ ion type. It was found that, Y3+ doped mullite achieved the minimum dielectric loss value of 0.01 in the radio wave frequency region (1 MHz). Meanwhile, Gd3+ doped mullite achieved the minimum dielectric loss value of 0.09 in the microwave frequency region (1 GHz).

Organic acid precursor synthesis and environmental photocatalysis applications of mesoporous anatase TiO2 doped with different transition metal ions

Abstract Mn2+ and Co2+ ions doped titania (TiO2) nanopowders were synthesized using organic acid precursor route for the first time. The results revealed that TiO2 with metal dopants were reduced grain size and increased the surface area of TiO2. The band gap energy values of doped TiO2 were higher than the pure TiO2 and show a blue shift. The photocatalytic performance of TiO2 in the degradation of the rhodamine B dye was tested. Moreover, the efficiency was enhanced by adding Mn and Co to TiO2.

Copper-Substituted Lead Perovskite Materials Constructed with Different Halides for Working (CH3NH3)2CuX4-Based Perovskite Solar Cells from Experimental and Theoretical View

Toxicity and chemical instability issues of halide perovskites based on organic-inorganic lead-containing materials still remain as the main drawbacks for perovskite solar cells (PSCs). Herein, we discuss the preparation of copper (Cu)-based hybrid materials, where we replace lead (Pb) with nontoxic Cu metal for lead-free PSCs, and investigate their potential toward solar cell applications based on experimental and theoretical studies. The formation of (CH3NH3)2CuX4 [(CH3NH3)2CuCl4, (CH3NH3)2CuCl2I2, and (CH3NH3)2CuCl2Br2] was discussed in details. Furthermore, it was found that chlorine (Cl-) in the structure is critical for the stabilization of the formed compounds. Cu-based perovskite-like materials showed attractive absorbance features extended to the near-infrared range, with appropriate band gaps. Green photoluminescence of these materials was obtained because of Cu+ ions. The power conversion efficiency was measured experimentally and estimated theoretically for different architectures of solar cell devices.

An easy synthesis of nanostructured magnetite-loaded functionalized carbon spheres and cobalt ferrite

An easy method in a solvothermal system has been developed to synthesize nanostructured magnetite (Fe3O4)-loaded functionalized carbon spheres (CSs) and cobalt ferrite (CoFe2O4). Surface-tunable CSs loaded with iron oxide (Fe3O4) nanoparticles were prepared using an acetylferrocene Schiff base (OPF), whereas spinel cobalt ferrite (CoFe2O4) was synthesized via metal complexes of a ferrocenyl Schiff base with phenol moiety (Co-OPF). The formed composite powder was investigated using X-ray powder diffraction, Raman spectrometry, Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and vibrating sample magnetometry. It was found that most of the iron oxide nanoparticles were evenly distributed upon the surface of the CSs. Furthermore, the surface of the iron oxide-loaded CSs has large numbers of functional groups. Good saturation magnetization was achieved for the formed magnetic nanoparticles.

Structural, magnetic properties, and induction heating behavior studies of cobalt ferrite nanopowders synthesized using modified co-precipitation method

ABSTRACT Nanocrystalline cobalt ferrite CoFe2O4 powders have been successfully synthesized via modified co-precipitation at low temperature. Obviously, well crystalline CoFe2O4 phase was obtained from the precipitated precursors at pH 10 using 5 M NaOH as a base thermally treated at 80°C for 1 h in aqueous medium in the absence and the presence of 1000 ppm cetyl trimethyl ammonium bromide (CTAB) as well as sodium dodecyl sulfate (SDS) as cationic and anionic surfactants, respectively. Meanwhile, the spinel ferrite was observed with the similar conditions using ethylene glycol as an organic solvent. The microstructures of the formed powders exhibited nanospheres like structure with narrow size distribution from 6 to 10 nm. The magnetic properties of the formed cobalt ferrite powders strongly depend on the synthesis conditions. For instance, the highest saturation magnetization (Ms = 36.2 emu/g) was achieved in the aqueous medium, whereas the lowest saturation magnetization (Ms = 16.2 emu/g) was accomplished in the ethylene glycol medium. Indeed, heating properties of the CoFe2O4 samples in an alternating magnetic field (AMF) at 160 kHz were estimated. Of note, it is clear that the specific heat rate SAR values were in the range from 104.5 to 302.0 W/g at different synthesis conditions, making co-ferrite appropriate for hyperthermia treatment of cancer.

Structure evaluation of bismuth telluride (Bi2Te3) nanoparticles with enhanced Seebeck coefficient and low thermal conductivity

ABSTRACT Bismuth telluride (Bi2Te3) nanoparticles with different morphologies were synthesized using solvothermal process. The composition, the size and the micro-structure of the synthesized nanoparticles were investigated using X-ray diffraction (XRD) and scanning electron microscope (SEM). Band gap energy was determined using UV-vis spectrometer. The absorption peaks were shifted from 278 to 284 nm which confirm that the effect of the size and the nanostructure morphology. Moreover, the direct band gap (E g ) of ST–Bi2Te3, STEd–Bi2Te3, STNaEd–Bi2Te3, STPv–Bi2Te3 and STNaPv–Bi2Te3 were equal to 3.95,4.7,4.8,4.7 and 4.5 eV. Thermal and electrical conductivity of the prepared nanoparticles were also investigated at room temperature. Plainly, thermal conductivity measurement concludes that thermal conductivity of ST–Bi2Te3 sample prepared without any additives was high. The study revealed that, the addition of NaOH to the reaction medium as an alkali modifier has a great effect on the morphology and the size of the produced nanoparticles. The additions of PVP in absence and in presence of NaOH strongly affect the size and the morphology of the product. The effect of changing the morphology and the particle size were determined on the band gap energy and the Seebeck coefficient of the prepared samples and the negative sign of all Seebeck coefficients indicate n-type semiconductor.

Innovations in graphene-based nanomaterials in the preconcentration of pharmaceuticals waste

ABSTRACT Generally, pharmaceuticals (PhAs) have been extensively detected in various food and wastewater samples. In this regard, solid-phase extraction (SPE) is an excellent choice for their preconcentration, extraction, and fractionation. Typical, graphene-based nanomaterials (GBNMs) have been spaciously utilized as the efficient SPE adsorbents for the extraction of PhAs. Magnetic solid-phase extraction (MSPE) is found to reduce the time and cost of the operation by skipping the centrifugation step. Of note, this review summarizes the current research on the preconcentration of PhAs by GBNMs and provides valuable information about their applications in the determination and analysis of PhAs in various samples of health and environmental importance. Finally, the different analytical techniques used for the preconcentration of PhAs as well as their adsorption mechanism, and different environmental factors affecting the adsorption, have been studied and discussed in details. GRAPHICAL ABSTRACT