DFT and TD-DFT Investigations for the Limitations of Lengthening the Polyene Bridge between N,N-dimethylanilino Donor and Dicyanovinyl Acceptor Molecules as a D-π-A Dye-Sensitized Solar Cell.

One useful technique for increasing the efficiency of organic dye-sensitized solar cells (DSSCs) is to extend the π-conjugated bridges between the donor (D) and the acceptor (A) units. The present study used the DFT and TD-DFT techniques to investigate the effect of lengthening the polyene bridge between the donor N, N-dimethyl-anilino and the acceptor dicyanovinyl. The results of the calculated key properties were not all in line with expectations. Planar structure was associated with increasing the π-conjugation linker, implying efficient electron transfer from the donor to the acceptor. A smaller energy gap, greater oscillator strength values, and red-shifted electronic absorption were also observed when the number of polyene units was increased. However, some results indicated that the potential of the stated dyes to operate as effective dye-sensitized solar cells is limited when the polyene bridge is extended. Increasing the polyene units causes the HOMO level to rise until it exceeds the redox potential of the electrolyte, which delays regeneration and impedes the electron transport cycle from being completed. As the number of conjugated units increases, the terminal lobes of HOMO and LUMO continue to shrink, which affects the ease of intramolecular charge transfer within the dyes. Smaller polyene chain lengths yielded the most favorable results when evaluating the efficiency of electron injection and regeneration. This means that the charge transfer mechanism between the conduction band of the semiconductor and the electrolyte is not improved by extending the polyene bridge. The open circuit voltage (VOC) was reduced from 1.23 to 0.70 V. Similarly, the excited-state duration (τ) decreased from 1.71 to 1.23 ns as the number of polyene units increased from n = 1 to n = 10. These findings are incompatible with the power conversion efficiency requirements of DSSCs. Therefore, the elongation of the polyene bridge in such D-π-A configurations rules out its application in solar cell devices.

N-doped TiO2/rGO: synthesis, structure, optical characteristics, and humidity sensing applications.

In the current study, the effect of rGO ratio on the N-dopped TiO2has been synthesized through sol-gel method. The prepared N-doped TiO2/rGO composites were examined for humidity sensing applications. The relationship between optical properties and the humidity sensing properties was studied. The structure, morphology, and bonding interaction have been examined using XRD, FT-IR, PL and HRTEM respectively. The average particle size as estimated from XRD and HRTEM was found to be about 9 nm. The optical properties have been studied using UV/ Vis. Spectroscopy. Further, optical parameters including refractive index and optical band gap energy have been estimated. The humidity sensing behavior of the resultant composites were evaluated in a wide range of humidity (7%-97% RH) at different testing frequencies. The optical band gap was found to be decreased as the amount of rGO increase. Among all prepared samples, both the optical parameters and humidity sensing experiments confirmed that the 0.5% rGO@N-dopped TiO2sample is the best candidate for the humidity sensing applications. The best optimum testing frequency was demonstrated to be 50 Hz. The sensor demonstrates a fast response and recovery times of 13 s and 33 s with low hysteresis and large sensitivity. The humidity sensing mechanism was studied using complex impedance spectroscopy at different RH levels under testing frequency range from 50 Hz to 5 MHz and testing voltage of 1 VAC. The produced structure demonstrated a promising material for humidity measuring devices.

Polyelectrolyte membranes based on phosphorylated-PVA/cellulose acetate for direct methanol fuel cell applications: synthesis, instrumental characterization, and performance testing.

Designing and synthesis of cost-effective and improved methanol permeable and proton conductive membranes are the main challenges for preparation of polymeric electrolyte membrane (PEM). Herein, a cost-effective PEM membrane based on phosphorylated polyvinyl alcohol (PVA)-grafted-cellulose acetate (CA) was prepared by a solution-casting technique. Water and methanol uptakes of phosphorylated PVA/CA membranes were characterized as function with the molar ratio of CA. Additionally, structure and morphology of phosphorylated PVA/CA (Ph-PVA/CA) membranes were verified by FT-IR analysis, SEM investigation. Furthermore, ion exchange capacity (IEC), proton conductivity and methanol permeation of Ph-PVA/CA membranes were examined based on the concentration of OPA basically. The results manifested a perceptible improvement in proton conductivity from 0.035 to 0.05 S/cm at 25 and 70 °C, respectively using 600 µL of OPA, and IEC of 2.1 meq/g using 400 µL of OPA at ambient temperature. On the other hand, methanol permeability (P = 1.08 × 10-10 cm2/s) was lower than Nafion 117 admirably. The optimum OPA concentration was 200 µL according to conductivity measurements (at 10% PVA, 150 µL GA, and CA 7%). Finally, prepared Ph-PVA/CA membranes exhibited enhancement in critical natures such as proton conductivity and IEC combined with its low-cost materials, which make them excellent candidate as PEM for DMFCs application.

Current stress minimization for isolated dual active bridge DC-DC converter.

This paper presents a new phase-shift modulation for isolated dual active bridge (DAB) direct current-direct current (DC-DC) converter. The proposed technique aims to minimize the maximum current stress of the converter, which could directly increase the efficiency and reduce the device losses. This modulation technique controls the converter power through only two phase-shift angles or two degrees of freedom; one phase shift is used between the legs of its first bridge and the other one between the legs of the second bridge. Although the traditional single-phase shift (SPS) technique has only one degree of freedom, it suffers from many drawbacks in terms of high current stress and reverse circulating power flow, which decrease the converter efficiency. On the other hand, increasing the number of phase-shift angles can enhance the system performance but also increase the control complexity. Thus, a comparative analysis between the proposed modulation technique and the traditional SPS was conducted; the new method showed better performance in terms of current stress reduction, along with implementation simplicity.

WiScope® single use digital flexible ureteroscope versus reusable flexible ureteroscope for management of renal stones: a prospective randomized study.

OBJECTIVES: To compare the clinical performance and surgical outcomes of the new digital single use flexible ureteroscope (WiScope®) with a reusable digital flexible ureteroscope. PATIENT AND METHODS: Our prospective study includes patients with renal stones less than 2 cm who underwent retrograde flexible ureteroscopy and laser lithotripsy. Patients were randomized into two groups: group A included patients who underwent laser lithotripsy using WiScope® Single use digital flexible ureteroscope and group B included patients who underwent laser lithotripsy using reusable flexible ureteroscope. Image quality, deflection, ease of insertion, maneuverability, and overall performance were assessed using either a visual analog or Likert scale. Operative outcomes and complications were collected and analyzed in both groups. RESULTS: A total of 242 patients were included in our study. There were 121 patients in the WiScope® group and 121 patients in reusable ureteroscope group. The WiScope® had higher maneuverability (9.3 ± 0.7 vs. 7.2 ± 0.8, P < 0.001) and less limb fatigue but had lower image quality when compared to reusable digital flexible ureteroscope (7.6 ± 0.9 vs. 9.2 ± 0.6, P < 0.001). There were no differences in operative time, complication rates and rates of relook ureteroscopy. CONCLUSIONS: The WiScope® single use flexible ureteroscope has comparable outcomes to the reusable flexible ureteroscope with regard to maneuverability, limb fatigue, and deflection. However, it has a lower image quality.

Talented Bi0.5Na0.25K0.25TiO3/oxidized cellulose films for optoelectronic and bioburden of pathogenic microbes.

We study the microstructure, optical, thermal, dielectric, and mechanical properties of flexible oxidized cellulose (OC) films loaded with different mass fractions of cubic structure Bi0.5Na0.25K0.25TiO3 by blending solution technique and casting method. The films were characterized using infrared, X-ray diffraction, scanning electron microscopy, and UV-visible spectroscopy. The optical results confirmed the formation of crystalline bismuth sodium titanate/OC semiconductor films with a direct energy bandgap (3.002-3.276 eV) and have the ability for optoelectronic applications. The dielectric constant and dielectric loss of OC /BNKT film decreased obviously with increasing frequency. However, the ferroelectric state of the BNKT and its correlation with structure verified the existence of a relaxer behavior to this ratio. OC film with 20% dopped BNKT displayed energetic bactericidal activity against Gram-positive and Gram-negative bacteria. The presented study suggested that this film can be used as an antibacterial packaging material to diminish packaging's adverse environmental impacts with non-cytotoxicity.

New fabrication method for di-indium tri-sulfuric (In2S3) thin films.

Di-indium tri-sulfuric (In2S3) thin films are fabricated with annealing indium thin films in a sulfur environment. The effect of both annealing temperature and pressure on the structure, morphology, Raman, and photoluminescence (PL) spectroscopy has been studied. The X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) of the prepared thin films showed different structural phases and morphology with varying annealing temperature and pressure. Energy dispersive X-ray (EDX) analysis confirmed the chemical composition and the atomic ratio of In/S for the In2S3 thin films. The optimum annealing conditions of In2S3 thin films are 550 °C and 100 Torr. The outcome results revealed a new good growth method for In2S3 thin films to be used for different applications.

From Center-to-Multilayer Chirality: Asymmetric Synthesis of Multilayer Targets with Electron-Rich Bridges.

Asymmetric synthesis of new atropisomerically multilayered chiral targets has been achieved by taking advantage of the strategy of center-to-multilayer chirality and double Suzuki-Miyaura couplings. Diastereomers were readily separated via flash column chromatography and well characterized. Absolute configuration assignment was determined by X-ray structural analysis. Five enantiomerically pure isomers possessing multilayer chirality were assembled utilizing anchors involving electron-rich aromatic connections. An overall yield of 0.69% of the final target with hydroxyl attachment was achieved over 11 steps from commercially available starting materials.

Ischemic Priapism Progressing to Penile Gangrene in a Patient with COVID-19 Infection: A Case Report with Literature Review.

Priapism is considered a rare disorder and even more rare when it occurs as a complication of COVID-19. To the best of our knowledge, only eight studies have reported priapism as a complication of COVID-19. Here, we report the case of a 66-year-old male with COVID-19 who presented with neglected priapism for three days. On local examination, penile erection was apparent in association with blackened areas on the glans penis extending to the midpenile shaft denoting penile gangrene. A clear line of demarcation was noticed at the midpenile shaft. Penile duplex was performed, showing no blood flow in both cavernosal arteries. Penile aspiration was performed, and the cavernosal blood sample showed evidence of ischemic priapism. Given the presence of penile gangrene extending to the midshaft of the penis and the poor general condition of the patient, the decision was made to perform partial penectomy and suprapubic tube placement. We recommend the establishment of a guideline for the diagnosis and prevention of thrombotic diseases in patients with COVID-19 infection as there is increasing evidence of COVID-19-related thrombotic manifestations.

Asymmetric synthesis of functionalized 2,3-dihydrobenzofurans using salicyl N-phosphonyl imines facilitated by group-assisted purification (GAP) chemistry.

In this work, we present a strategy for the preparation of functionalized 2,3-dihydrobenzofuran derivatives via the Cs2CO3-catalyzed domino annulation of enantiopure chiral salicyl N-phosphonyl imines with bromo malonates, which offers an avenue for the construction of 2,3-dihydrobenzofurans. Nineteen examples were synthesized in impressive chemical yields and diastereoselectivity. The products were purified simply by washing the crude mixtures with hexanes following group-assisted purification chemistry/technology to bypass traditional separation methods which often result in a loss of product. The absolute configuration was unambiguously assigned by X-ray structural analysis.

Asymmetric [4 + 2] cycloaddition synthesis of 4H-chromene derivatives facilitated by group-assisted-purification (GAP) chemistry.

In this work, we present a strategy for the preparation of functionalized 4H-chromene derivatives via a Cs2CO3-catalyzed [4 + 2] cycloaddition of enantiopure chiral salicyl N-phosphonyl imines with allenoates. Fifteen examples were achieved in excellent yields and diastereoselectivity. The products were purified simply by washing the crude mixture with hexanes following the Group-Assisted Purification (GAP) chemistry/technology to bypass traditional separation methods. The absolute configuration was unambiguously determined by X-ray structure analysis.

Recent Advances in the Application of Selectfluor as a "Fluorine-free" Functional Reagent in Organic Synthesis.

Selectfluor, [1-chloromethyl-4-fluoro-1,4-diazoniabicyclo-[2.2.2]octane bis(tetrafluoroborate)], is not only an important electrophilic fluorinating agent but also a facile and efficient "fluorine-free" functional reagent in other organic reactions. In this Minireview, we will present a brief history of Selectfluor as a transition metal oxidant, fluorine cation and radical initiator in "fluorine-free" functionalizations over the last five years.

Influences of Ag-NPs doping chitosan/calcium silicate nanocomposites for optical and antibacterial activity.

Chitosan (CS)/calcium silicate nanocomposites pure and doped with Ag ions (1, 2mol%) were prepared via sol-gel method. The prepared CS/calcium silicate nanocomposites were investigated through X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The XRD results, indicating that after increasing the Ag ions in the CS/calcium silicate nanocomposite the crystallinity degree increased regularly in the prepared nanocomposites accompanying to the continuously rearrangement in the internal structure of nanocomposite under the effect of inorganic nanoparticles. Correspondingly, the optical properties of the prepared nanocomposites films were measured using UV/vis spectroscopy. The reflectance increased while the energy band gap decreased from 3.96eV to 2.43eV with Ag-ions concentration. More over the transition type changed from direct into indirect by adding Ag-ions, indicate that new band between valence and conduction band were formed. In addition, the optical parameters showed an increase in refractive indices and decrease in the surface and volume energies losses with increasing Ag-ions. Correspondingly, the prepared nanocomposites exhibited good antibacterial activity against gram positive (Staphylococcus aureus), gram negative (Pseudomonas aeruginosa) bacteria and fungi (Candidia albicans). The results suggested that the prepared CS/calcium silicate nanocomposites can be a promised candidate for optical sensors applications and smart packaging materials.

Optimization of tungsten dual poly-metal gates in memory devices with Ti/Wn/WSiN barrier metal.

Due to the demand of high-speed/high-density and low power application of memory devices, tungsten dual poly gate (W-DPG; W/barrier metals/n+ and p+ poly-Si) electrode could be a good solution in order to reduce gate sheet resistance (Rs). Process optimization is completed for a diffusion barrier metal in a W-DPG. A new noble WSiN layer is inserted between the Ti/WN barrier metal and the tungsten gate electrode to maintain large grain size of W deposited by physical vapor deposition. The annealed WSiN during post-processing changes into crystallized WSi(x) mixed with SiN, which can make vertical conductive path between top and bottom interface, contributing to low vertical contact resistance (Rc) and low gate Rs adequate for high speed requirement of memory device. The Ti/WN/WSiN barrier is found to have the same electrical performance, ring oscillator singal delay as complicated multi-layes barrier metal, Ti/WN/TiN/WSi(x)/WN reported earlier. Therefore, the gate stack can be optimized by introducing a simpler diffusion barrier metal.