Dimensionality switching through a thermally induced reversible single-crystal-to-single-crystal phase transition in a cyanide complex

The heterometallic hexanuclear cyanide-bridged complex {[Mn(bpym)(H(2)O)](2)[Fe(HB(pz)(3))(CN)(3)](4)} (1), its C(15)N and D(2)O enriched forms {[Mn(bpym)(H(2)O)](2)[Fe(HB(pz)(3))(C(15)N)(3)](4)} (2) and {[Mn(bpym)(D(2)O)](2)[Fe(HB(pz)(3))(CN)(3)](4)} (3), and the hexanuclear derivative complex {[Mn(bpym)(H(2)O)](2)[Fe(B(pz)(4))(CN)(3)](4)}·4H(2)O (4) [bpym = 2,2'-bipyrimidine, HB(pz)(3)(-) = hydrotris(1-pyrazolyl)borate, B(pz)(4)(-) = tetra(1-pyrazolyl)borate] have been synthesized. Their structures have been determined through single-crystal X-ray crystallography at different temperatures. Whereas 3 and 4 maintain a discrete hexanuclear motif during the entire temperature range investigated (down to 95 K), 1 and 2 exhibit a thermally induced reversible single-crystal to single-crystal phase transition driven by a remarkable concerted rearrangement of hydrogen and cyanide coordination bonds. While hexanuclear complexes are observed in the high temperature phases (noted 1a and 2a) above 200 K, the low temperature phases are composed of one-dimensional coordination polymers noted 1b and 2b. The magnetic properties of the four compounds have been investigated in the 2-300 K range, and they reveal the occurrence of an overall antiferromagnetic behavior. The thermal dependence of the optical reflectivity and the FT-IR absorbance have been studied for 1 in the range 10-300 K and 130-300 K, respectively. A comparative analysis of the structural and electronic properties for 1-4 clearly underlines the major role of the intermolecular interactions in the topological and dimensional rearrangement observed during the structural phase transition. This result opens new perspectives in the design of cyanide-based switchable magnetic materials using coordination bonds rearrangements.     

BiVO4/TiO2 core-shell heterostructure: wide range optical absorption and enhanced photoelectrochemical and photocatalytic performance

In the present study, pristine BiVO₄, TiO₂ and BiVO₄/TiO₂ core-shell heterostructured nanoparticles are prepared by hydrothermal methods and studied for structural, morphological, optical, photoelectrochemical water splitting and photocatalytic degradation of methylene blue as an organic pollutant. Both pristine BiVO₄ and TiO₂ exhibit poor PEC and PC performance under visible light illumination. However, an enhanced PEC and PC activity in BiVO₄/TiO₂ core-shell heterostructure is observed due to high solar energy absorption and superior charge separation properties in core-shell nanoparticles. The photoelectrode prepared using BiVO₄/TiO₂ core-shell nanoparticles exhibit a photocathode behavior and produced cathodic photocurrent, however, the pristine BiVO₄ and TiO₂ photoelectrodes act as photoanode and produced anodic photocurrent. This behavior of change in current direction is also observe in the Mott-Schottky analysis where the BiVO₄/TiO₂ core-shell nanoparticles photoelectrode exhibits the positive slow showing p-type semiconducting behavior. The change in cathodic photoresponse in core-shell nanoparticles in comparison to anodic photoresponse of BiVO₄ and TiO₂ nanoparticles is explained in terms of the variations in the work function values. These results highlight the advantages of core-shell nanoparticle of suitable materials for photocatalytic and photoelectrochemical applications.     

Nigella sativa L. and COVID-19: A Glance at The Anti-COVID-19 Chemical Constituents,Clinical Trials,Inventions, and Patent Literature

COVID-19 has had an impact on human quality of life and economics. Scientists have been identifying remedies for its prevention and treatment from all possible sources, including plants. Nigella sativa L. (NS) is an important medicinal plant of Islamic value. This review highlights the anti-COVID-19 potential, clinical trials, inventions, and patent literature related to NS and its major chemical constituents, like thymoquinone. The literature was collected from different databases, including Pubmed, Espacenet, and Patentscope. The literature supports the efficacy of NS, NS oil (NSO), and its chemical constituents against COVID-19. The clinical data imply that NS and NSO can prevent and treat COVID-19 patients with a faster recovery rate. Several inventions comprising NS and NSO have been claimed in patent applications to prevent/treat COVID-19. The patent literature cites NS as an immunomodulator, antioxidant, anti-inflammatory, a source of anti-SARS-CoV-2 compounds, and a plant having protective effects on the lungs. The available facts indicate that NS, NSO, and its various compositions have all the attributes to be used as a promising remedy to prevent, manage, and treat COVID-19 among high-risk people as well as for the therapy of COVID-19 patients of all age groups as a monotherapy or a combination therapy. Many compositions of NS in combination with countless medicinal herbs and medicines are still unexplored. Accordingly, the authors foresee a bright scope in developing NS-based anti-COVID-19 composition for clinical use in the future.     

Trace analysis of the MIF analogue pareptide in blood plasma by high-performance liquid chromatography and short-wavelength excitation fluorometry

A high-performance liquid chromatographic procedure was developed and applied to analysis of the pharmacologically active MIF analogue pareptide in human plasma. The procedure involves formation of a fluorescent 7-chloro-4-nitrobenzyl-2-oxa-1,3-diazole (NBD-Cl) pareptide derivative followed by separation of the NBD derivative from plasma components on a 30-cm microparticle octadecylsilane bonded column. The separated derivative was quantitated using a short-wavelength excitation fluorometric detector. The detection limit of pareptide in plasma samples was 5 ng or 17 pmoles per ml of plasma. In the absence of plasma, the corresponding on-column detection limit was 0.5 pmoles.     

Characterization of BCN films synthesized by radiofrequency plasma enhanced chemical vapor deposition

Boron carbonitride (BCN) films have been synthesized on Si(1 0 0) substrate by radio frequency plasma enhanced chemical vapor deposition using tris-(dimethylamino)borane (TDMAB) as a precursor. The deposition was performed at the different RF powers of 400-800 W, at the working pressure of 2×10⁻¹ Torr. The formation of the sp²-bonded BCN phase was confirmed by Fourier transform infrared spectroscopy. X-ray photoelectron spectroscopy measurements showed that B atoms were bonded to C and N atoms to form the BCN atomic hybrid configurations with the chemical compositions of B₅₂C₁₂N₃₆ (sample 1; prepared at the RF power of 400 W), B₅₂C₁₀N₃₈ (sample 2; at 500 W) and B₄₆C₁₈N₃₆ (sample 3; at 800 W), respectively. Near-edge X-ray absorption fine structure (NEXAFS) measurements indicated that B atoms were bonded not only to N atoms but also to C atoms to form various configurations of sp²-BCN atomic hybrids. The polarization dependence of NEXAFS suggested that the predominant hybrid configuration of sp²-BCN films oriented in the direction perpendicular to the Si substrate.     

Nanotextured multicrystalline Al‐BSF solar cells reaching 18% conversion efficiency using industrially viable solar cell processes

We report recent achievements in adapting industrially used solar cell processes on nanotextured surfaces. Nanostructures were etched into c‐Si surfaces by dry exothermic plasma‐less reaction of F species with Si in atmospheric pressure conditions and then modified using a short post‐etching process. Nanotextured multicrystalline wafers are used to prepare Al‐BSF solar cells using industrially feasible solar cell proc‐ essing steps. In comparison to the reference acidic textured solar cells, the nanostructured cells showed gain in short circuit current (J_sc) of up to 0.8 mA/cm² and absolute gain in conversion efficiency of up to 0.3%. The best nanotextured solar cell was independently certified to reach the conversion efficiency of 18.0%. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Trace element evaluation of rice and husk by INAA

An instrumental neutron activation analysis technique has been utilized to study the prevailing levels of certain inorganic trace elements in different varieties of rice produced in Pakistan. The data have been compared with those of other countries. The elemental ratios within rice and rice to husk have been computed to evaluate indirectly the impact of soil and environment on the rice crops. The dietary spectum for the inhabitants of Rawalpindi/Islamabad areas has been evaluated by estimating the daily intake and comparing with allowances suggested in the literature.     

Lateritic minerals for decontamination of radionuclides

Naturally available lateritic minerals (LM) have been used on laboratory scale for the removal of Ce, Gd and Lu radionuclides from nuclear industry and reactor effluents. The adsorption behavior using radiotracers is reported, describing factors such as the nature and strength of acids, particle size, temperature and equilibration time which influence the adsorption mechanism. The interference of various anions and organic complexing agents on sorption of these radiotracers has also been considered. The optimized physico-chemical conditions and high loading capacities suggest an, effective use of LM for the isolation of the radionuclides from industrial and reactor effluents. Leaching studies made on pelletized LM loaded with the radionuclides indicate their potential for disposal in reduced solid form for a longer period.     

Top and bottom quark condensates

It is possible that electroweak symmetry might be broken dynamically by a condensate of top quarks. We extend a previous study of top quark dynamics to include the bottom quark. The simultaneous gap equations in dressed ladder approximation for∑ _t (p),∑ _b (p) are studied numerically and analytically in various regions of parameter space, and the solutions are used to determine \(\langle \bar tt\rangle ,\langle \bar bb\rangle \) and the decay constantsF _±,F ₀, as well as the top and bottom masses. We discuss the question of fine-tuning, and show how our approach can be extended to other quark and lepton masses.     

Cytotoxicity,In vitro anti-Leishmanial and fingerprint HPLC- photodiode array analysis of the roots of Trillium govanianum

Trillium govanianum Wall. ex D. Don (Melanthiaceae alt. Trilliaceae), commonly known as ‘nagchhatry’ or ‘teen patra’, distributed from Pakistan to Bhutan about 2500–3800 m altitude is indigenous to Himalayas region. In folk medicine the plant has been reported for the treatment of wound healing, sepsis and in various sexual disorders. This paper reports, for the first time, to evaluate the cytotoxicity, in vitro anti-leishmanial (promastigotes) and fingerprint HPLC-photodiode array analysis of the MeOH extract of the roots of T. govanianum and its solid phase extraction fractions. Reverse phase HPLC-PDA based quantification revealed the presence of significant amount of quercetin, myrecetin and kaemferol ranging from 0.221to 0.528 μg/mg DW. MeOH extract revealed distinguishable protein kinase inhibitory activity against Streptomyces 85E strain with 18 mm bald phenotype. The remarkable toxicity profile against brine shrimps and leishmanial was manifested by MeOH extract with LC₅₀ 10 and 38.5 μg/mL, respectively.