Chemical preparation and characterization of fibrous poly(3-methylthiophene) decorated by TiO2 nanoparticles

In this article, we report on the chemical oxidative polymerization of 3-methylthiophene (3MTh) in a concentrated TiO₂/CHCl₃ homogeneous suspension with an oxidant/monomer mole ratio of 3 at room temperature. According to the scanning electron microscopy images, in this condition, poly(3-methylthiophene) (P3MTh) was prepared with fibrous morphology decorated by nano-dimensional TiO₂ particles. P3MTh/TiO₂ was also characterized by Fourier transform infrared spectroscopy and X-ray diffraction techniques. It was found that no aggregation of nanoparticles occurred during the polymerization process. In addition, the thermal stability of P3MTh/TiO₂ nanocomposite was investigated by thermogravimetric analysis and compared with that of an analogously prepared neat P3MTh. The thermal degradation of P3MTh in the temperature range of 300–550°C decreases significantly due to the presence of the TiO₂ nanoparticles in the polymer composite.     

Application of spinel-structured MgFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles for simultaneous electrochemical determination diclofenac and morphine

The paper describes a sensitive method for simultaneous sensing of morphine (MOR) and diclofenac (DCF). The surface of a MgFe₂O₄/graphite paste electrode was modified with multi-walled carbon nanotubes, and the resulting sensor was characterized by cyclic voltammetry, differential pulse voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. The electrode showed an efficient synergistic effect in term of oxidation of DCF and MOR, with sharp oxidation peaks occurring at +0.370 and 0.540 V (vs Ag/AgCl) at pH 7.0. The calibration plot for MOR is linear in the 50 nM to 920 μM concentration range, and the detection limit is 10 nM (at a signal-to-noise ratio of 3). The respective data for DCF are 100 nM to 580 μM, with a 60 nM LOD. The sensor was applied to the determination of MOR and DCF in spiked serum and urine samples, with recoveries ranging between 91.4 and 100.7 %.

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Graphical abstract A sensitive method for simultaneous sensing of morphine (MOR) and diclofenac (DCF) is described. The surface of MgFe₂O₄/graphite paste electrode was modified with multi-walled carbon nanotubes, and the resulting sensor showed an efficient synergistic effect in terms of oxidation of DCF and MOR. The calibration plot for MOR is linear in the 50 nM to 920 μM concentration range, and the detection limit is 10 nM. The respective data for DCF are 100 nM to 580 μM, with a 60 nM LOD.

     

Luciferin‐Regenerating Enzyme Crystal Structure Is Solved but its Function Is Still Unclear

Contribution of luciferin‐regenerating enzyme (LRE) for in vitro recycling of D‐luciferin has been reported. According to crystal structure of LRE, it is a beta‐propeller protein which is a type of all β‐protein architecture. In this overview, reinvestigation of the luciferase‐based LRE assays and its function is reported. Until now, sequence of LRE genes from four different species of firefly has been reported. In spite of previous reports, T‐LRE (from Lampyris turkestanicus) was cloned and expressed in Escherichia coli as well as Pichia pastoris in a nonsoluble form as inclusion body. According to recent investigations, bioluminescent signal of soluble T‐LRE–luciferase‐coupled assay increased and then reached an equilibrium state in the presence of D‐cysteine. In addition, the results revealed that both D‐ and L‐cysteine in the absence of T‐LRE caused a significant increase in bioluminescence intensity of luciferase over a long time. Based on activity measurements and spectroscopic results, D‐cysteine increased the activity of luciferase due to its redox potential and induction of conformational changes in structure and kinetics properties. In conclusion, in spite of previous reports on the effect of LRE (at least T‐LRE) on luciferase activity, most of the increase in luciferase activity is caused by direct effect of D‐cysteine on structure and activity of firefly luciferase. Moreover, bioinformatics analysis cannot support the presence of LRE in peroxisome of photocytes in firefly lanterns.     

Using the QSPR Approach for Estimating the Density of Azole‐based Energetic Compounds

The relationship between density of energetic azole‐based compounds and their molecular structure is investigated through quantitative structure‐property relationship (QSPR) approach. The methodology of this work introduces a new model, which related density of azole‐based energetic compounds to the optimum elemental composition, the degree of unsaturation (DoU) of the compounds, presence of nitroimino group in the structural formula, as well as several non‐additive structural parameters. The presence of nitroimino functional group and also increasing the value of n_O/n_N in the formula of these compounds can enhance their density. The correlation is derived on the basis of experimental density values of 100 azole‐based energetic compounds with different molecular structure as training set. The determination coefficient of the new correlation is 0.923. Also, it has the root mean square deviation (RMSD) and the average absolute deviation (AAD) of 0.038 and 0.030 g · cm^–3, respectively. In addition, the correlation gives good predictions for further 25 azole‐based energetic compounds as test set (Q²_EXT = 0.901). The predictive ability of the correlation is checked using a cross validation method (Q²_LMO = 0.918). The proposed method can also apply for designing novel azole‐based energetic compounds.     

Synthesis,characterization and in vitro DNA binding studies of a new copper(II) complex containing antioxidant ferulic acid

A mononuclear Cu(II) complex, [Cu(FA)₂(NO₃)₂], in which FA is ferulic acid ((E)-3-(4-hydroxy-3-methoxy-phenyl)prop-2-enoic acid), was synthesized and characterized by spectroscopic methods. The main structures of the ligand and its complexes with Cu²⁺ were optimized by QM calculations. The calculations on the structures of the [Cu(FA)₂(NO₃)₂] complexes forms and the intercalating with DNA profile were undertaken by UHF/PM6 and MMFF94 methods, respectively. In vitro studies (UV-vis spectroscopy, emission titration, circular dichroism techniques, and viscometry) under physiological conditions (Tris-HCl buffer solutions, pH 7.4) showed that the complex interacts with calf-thymus DNA (ct-DNA) via an intercalative binding mode. The thermodynamic parameters, enthalpy change (ΔH), and entropy change (ΔS) showed that the acting forces between Cu(II) complex and ct-DNA mainly included van der Waals interactions and hydrogen bonds. Methylene blue (MB) displacement studies revealed that Cu(II) complex can substitute MB probe in the MB-DNA complex which was indicative of intercalative binding. The theoretical data confirm the experimental results with respect to the mechanism of binding.     

Impact of modified electrodes on boosting power density of microbial fuel cell for effective domestic wastewater treatment:A case study of Tehran

Utilizing microbial fuel cells (MFCs) is a promising technology for energy-efficient domestic wastewater treatment, but it still faces practical barriers such as low power generation. In this study, the LaMnO₃ perovskite-type oxide nanoparticles and nickel oxide/carbon nanotube/polyaniline (NCP) nanocomposite (the cathode and anode catalysts, respectively) have been prepared and used to enhance power density of MFC. The prepared La-based perovskite oxide catalysts were characterized by X-ray diffraction (XRD) and scanning electron microscopies (SEM). The electrocatalytic properties of the prepared catalysts were investigated through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) and Tafel plot at ambient temperature. Results show the exchange current densities of LaMnO₃/carbon cloth cathode and NCP nanocomposite/carbon cloth anode were 1.68 and 7 times more compared to carbon cloth cathode, respectively. In comparison to the bare carbon cloth anode, the MFC with the modified electrodes shows 11 times more enhancement in power density output which according to electrochemical results, it can be due to the enhancement of the electron transfer capability. These cathodic and anodic catalysts were examined in batch and semi-continuous modes to provide conditions close to industrial conditions. This study suggests that utilizing these low cost catalysts has promising potential for wastewater treatment in MFC with high power generation and good COD removal efficiency.     

A Review on Cs-Based Pb-Free Double Halide Perovskites: From Theoretical and Experimental Studies to Doping and Applications

Despite the progressive enhancement in the flexibility of Pb-based perovskites for optoelectronic applications, regrettably, they are facing two main challenges; (1) instability, which originates from using organic components in the perovskite structure, and (2) toxicity due to Pb. Therefore, new, stable non-toxic perovskite materials are demanded to overcome these drawbacks. The research community has been working on a wide variety of Pb-free perovskites with different molecular formulas and dimensionality. A variety of Pb-free halide double perovskites have been widely explored by different research groups in search for stable, non-toxic double perovskite material. Especially, Cs-based Pb-free halide double perovskite has been in focus recently. Herein, we present a review of theoretical and experimental research on Cs-based Pb-free double halide perovskites of structural formulas Cs₂M⁺M³⁺X6 (M⁺ = Ag⁺, Na⁺, In⁺ etc.; M³⁺= Bi³⁺, In³⁺, Sb³⁺; X = Cl⁻, Br⁻, I¯) and Cs₂M⁴⁺X₆ (M⁴⁺ = Ti⁴⁺, Sn⁴⁺, Au⁴⁺ etc.). We also present the challenges faced by these perovskite compounds and their current applications especially in photovoltaics alongside the effect of metal dopants on their performance.     

Label-free and sensitive impedimetric nanosensor for the detection of cocaine based on a supramolecular complexation with β-cyclodextrin,immobilized on a nanostructured polymer film

Cocaine, a powerful addictive stimulant drug, has a variety of adverse effects on the body, thus its sensitive detection is very important. Here, we report on a simple, label-free, and sensitive impedimetric sensor for determination of cocaine based on its affinity to form an inclusion complex with β-cyclodextrin (β-CD). First, we prepared nanostructured poly N-acetylaniline film via electropolymerization of its monomer on a glassy carbon electrode (PNAANI/GC), subsequently overoxidized it, and conjugated β-CD to the polymer backbone. The designed and synthesized nanostructured PNAANI film serves a dual function in the sensor: on one hand, it maintains a high effective surface area on a geometrically small electrode that significantly enhances the number of β-CD molecules immobilized on the electrode; on the other hand, it provides an upright-oriented β-CD conjugation to the polymer backbone, thus all the β-CD receptors are actively involved in responding to the target. Sensitivity of the sensor was further enhanced by preconcentration of cocaine on the modified electrode surface. We attributed the changes in the interfacial charge transfer resistance (R _ct) of the electrode to cocaine concentration. Under optimized condition (pH 7.4, 5-min accumulation at an open circuit voltage), the sensor responded to cocaine concentration in the range of 100 nM–1.0 mM with a detection limit of 50 nM. Selectivity of the sensor for cocaine relative to some potential inferring compounds was also investigated, and the results were promising. The proposed approach exhibited an extended dynamic range, low detection limit, good sensitivity, and a desirable selectivity, which provides an efficient application prospect for on-field cocaine sensing.     

Molecularly imprinted stir bar sorptive extraction coupled with high-performance liquid chromatography for trace analysis of naphthalene sulfonates in seawater

In this paper, a novel molecularly imprinted polymer coated stir bar has been used to selectively extract naphthalene sulfonates (NS_s) directly from seawater sample. 1-Naphthalene sulfonic acid (1-NS) was used as template molecule. The effects of different parameters were optimized on the extraction efficiency and the optimum conditions were established as: the absorption and desorption times were fixed, respectively, at 10 and 15 min, stirring speed was 700 rpm, pH was adjusted to 4.1, amount of NaCl was 1 mol L^?1 and extraction process was performed at a temperature of 50 °C. The linear ranges were 2–250 µg L^?1 for 3,6-NDS-1-OH (1-naphthol-3,6-disulfonic acid), 4–250 µg L^?1 for 2-NS (2-naphthalene sulfonate) and 3–250 µg L^?1 for 1-NS. The detection limits were within the range of 0.32–0.95 µg L^?1. Under optimum conditions, the detection limits of the NSs were 0.84, 0.95 and 0.32 µg L^?1 with the enrichment factor of 117-, 41- and 77-fold for 2-NS, 1-NS, and 6-NDS-1-OH, respectively. The repeatability of the method was satisfactory (0.53 ≤ RSD ≤6.0 %, n = 10). The method has been successfully applied for the analysis of trace amounts of three naphthalene sulfonates in seawater of Chabahar Bay.