Ahmed Mourtada Elseman

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.

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.

Microwave-assisted spent black tea leaves as cost-effective and powerful green adsorbent for the efficient removal of Eriochrome black T from aqueous solutions

Abstract In this work, microwave-assisted spent black tea leaves (MASTL) were used as effective low-cost green adsorbents for the removal of Eriochrome Black T (EBT) from aqueous solutions and adequately characterized. The pHpzc of MASTL was found to be 4.6. The experimental conditions, such as pH, contact time, temperature, adsorbent dose and EBT concentration, were optimized to evaluate the interaction of EBT with MASTL. The adsorption isotherms were simulated by Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models. The results showed that the Langmuir model best fitted the adsorption data. The monolayer adsorption capacity was calculated to be 242.72 mg/g at 25 °C. The thermodynamic data calculated from the temperature-dependent adsorption isotherms indicated that the adsorption process was spontaneous, endothermic and physicochemical in nature. The results revealed that the MASTL could be used as low-cost green adsorbents for the efficient removal of EBT from aqueous solutions in environmental pollution clean-up.

A novel heterometallic compound for design and study of electrical properties of silver nanoparticles-decorated lead compounds

A new heterometallic compound AgPb(C2O4)(NO3) (AgPb-1) was constructed for the first time using a precipitation reaction. Then, different silver nanoparticles (Ag-NPs)-decorated lead compounds were obtained from AgPb-1via thermal annealing at different temperatures. The compounds Ag·PbCO3 (AgPb-2), Ag·α-PbO (AgPb-3), Ag·α-PbO + β-PbO (AgPb-4) and Ag·β-PbO (AgPb-5) were obtained by annealing at 523 K, 623 K, 723 K and 873 K, respectively. The formed powders were investigated using X-ray powder diffraction (XRD), scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy and thermogravimetric analysis (TGA). The dispersion of Ag-NPs on the surface of lead compounds as decorated layers was proven by SEM and TEM micrographs. The electrical conductivity and dielectric constant of the precursor in the temperature range of 293–673 K were investigated. Furthermore, the electrical behaviours of the different phases are described.

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.

Computational Study of Ternary Devices: Stable, Low-Cost, and Efficient Planar Perovskite Solar Cells

Although perovskite solar cells with power conversion efficiencies (PCEs) more than 22% have been realized with expensive organic charge-transporting materials, their stability and high cost remain to be addressed. In this work, the perovskite configuration of MAPbX (MAu2009=u2009CH3NH3, Xu2009=u2009I3, Br3, or I2Br) integrated with stable and low-cost Cu:NiOx hole-transporting material, ZnO electron-transporting material, and Al counter electrode was modeled as a planar PSC and studied theoretically. A solar cell simulation program (wxAMPS), which served as an update of the popular solar cell simulation tool (AMPS: Analysis of Microelectronic and Photonic Structures), was used. The study yielded a detailed understanding of the role of each component in the solar cell and its effect on the photovoltaic parameters as a whole. The bandgap of active materials and operating temperature of the modeled solar cell were shown to influence the solar cell performance in a significant way. Further, the simulation results reveal a strong dependence of photovoltaic parameters on the thickness and defect density of the light-absorbing layers. Under moderate simulation conditions, the MAPbBr3 and MAPbI2Br cells recorded the highest PCEs of 20.58 and 19.08%, respectively, while MAPbI3 cell gave a value of 16.14%.

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

Ion‐Migration Inhibition by the Cation–π Interaction in Perovskite Materials for Efficient and Stable Perovskite Solar Cells

Migration of ions can lead to photoinduced phase separation, degradation, and current-voltage hysteresis in perovskite solar cells (PSCs), and has become a serious drawback for the organic-inorganic hybrid perovskite materials (OIPs). Here, the inhibition of ion migration is realized by the supramolecular cation-π interaction between aromatic rubrene and organic cations in OIPs. The energy of the cation-π interaction between rubrene and perovskite is found to be as strong as 1.5 eV, which is enough to immobilize the organic cations in OIPs; this will thus will lead to the obvious reduction of defects in perovskite films and outstanding stability in devices. By employing the cation-immobilized OIPs to fabricate perovskite solar cells (PSCs), a champion efficiency of 20.86% and certified efficiency of 20.80% with negligible hysteresis are acquired. In addition, the long-term stability of cation-immobilized PSCs is improved definitely (98% of the initial efficiency after 720 h operation), which is assigned to the inhibition of ionic diffusions in cation-immobilized OIPs. This cation-π interaction between cations and the supramolecular π system enhances the stability and the performance of PSCs efficiently and would be a potential universal approach to get the more stable perovskite devices.

A novel magnetite nanorod-decorated Si-Schiff base complex for efficient immobilization of U(VI) and Pb(II) from water solutions

A novel silicon Schiff base complex (Si-SBC) and magnetite nanorod-decorated Si-SBC (M/SiO2-Si-SBC) were synthesized and well characterized in detail. The synthesized materials were applied for the removal of U(vi) and Pb(ii) from water solutions under various experimental conditions. The monolayer maximum adsorption capacities of M/SiO2-Si-SBC (6.45 × 10-4 mol g-1 for Pb(ii) and 4.82 × 10-4 mol g-1 for U(vi)) obtained from the Langmuir model at 25 °C and pH = 5.00 ± 0.05 were higher than those of Si-SBC (5.18 × 10-4 mol g-1 for Pb(ii) and 3.70 × 10-4 mol g-1 for U(vi)). Moreover, DFT calculations showed that the high adsorption energies (Ead) of 7.61 kcal mol-1 for Pb2+-(Si-SBC) and 2.72 kcal mol-1 for UO22+-(Si-SBC) are mainly attributed to stronger electrostatic interactions. The results revealed that the Si-SBC and M/SiO2-Si-SBC could be used as efficient adsorbents for the effective elimination of U(vi) and Pb(ii) from contaminated wastewater. High sorption capacity and reusability indicated the practical applications of the synthesized materials in environmental pollution cleanup.

Superior Stability and Efficiency Over 20% Perovskite Solar Cells Achieved by a Novel Molecularly Engineered Rutin-AgNPs/Thiophene Copolymer

Abstract Perovskite solar cells (PSCs) with efficiencies greater than 20% have been realized mostly with expensive spiro‐MeOTAD hole‐transporting material. PSCs are demonstrated that achieve stabilized efficiencies exceeding 20% with straightforward low‐cost molecularly engineered copolymer poly(1‐(4‐hexylphenyl)‐2,5‐di(thiophen‐2‐yl)‐1H‐pyrrole) (PHPT‐py) based on Rutin–silver nanoparticles (AgNPs) as the hole extraction layer. The Rutin–AgNPs additive enables the creation of compact, highly conformal PHPT‐py layers that facilitate rapid carrier extraction and collection. The spiro‐MeOTAD‐based PSCs show comparable efficiency, although their operational stability is poor. This instability originated from potential‐induced degradation of the spiro‐MeOTAD/Au contact. The addition of conductive Rutin–AgNPs into PHPT‐py layer allows PSCs to retain >97% of their initial efficiency up to 60 d without encapsulation under relative humidity. The PHPT‐py/ Rutin–AgNPs‐based devices surpass the stability of spiro‐MeOTAD‐based PSCs and potentially reduce the fabrication cost of PSCs.