High-performance electrochemical sensor based on electrodeposited iron oxide nanoparticle: catecholamine as analytical probe

In this paper, we report the synthesis and electrocatalytic activity of electrodeposited Fe₂O₃ nanoparticles modified on a glassy carbon electrode as highly sensitive sensors for determination of catecholamines. Results showed that the Fe₂O₃ nanoparticles on a glassy carbon electrode exhibit excellent catalytic activity toward catecholamines oxidation, including levodopa, dopamine, and epinephrine, resulting in a marked lowering in the peak potential and considerable improvement of the peak current as compared to the electrochemical activity at the bare glassy carbon electrode. The electrochemical characterizations of catecholamines were performed using cyclic voltammetry, chronoamperometry, and differential pulse voltammetry techniques. The electrocatalytic currents increase linearly with the levodopa, dopamine, and epinephrine concentrations in the ranges of 0.0625–1000, 0.25–1500, and 0.125–1000 µM, respectively, and the detection limits (3σ) were 24 ± 2, 14 ± 2, and 12 ± 2 nM, respectively.     

Comparative macrocycle binding of the anticancer drug phenanthriplatin by cucurbit[<Emphasis Type="Italic">n</Emphasis>]urils, β-cyclodextrin and <Emphasis Type="Italic">para</Emphasis>-sulfonatocalix[4]arene: a <Superscript>1</Superscript>H NMR and molecular modelling study

The potential anticancer drug phenanthriplatin, [cis-(NH₃)₂(phenanthridine)Cl]⁺, forms supramolecular complexes with cucurbit[n]urils (CB[n], n?=?7 or 8), β-cyclodextrin and para-sulfonatocalix[4]arene (sCX[4]) as determined by ¹H NMR spectroscopy and molecular modeling. The results show that cucurbit[7]uril binds over the long arm of the drug, where hydrophobic effects and two hydrogen bonds stabilise binding. For cucurbit[8]uril, two phenanthriplatin molecules can bind simultaneously within the macrocycle’s cavity. Unfortunately, Na⁺ was able to displace the drug from both CB[7] and CB[8] making the macrocycles unsuitable as delivery vehicles for phenanthriplatin. Drug binding to β-cyclodextrin occurs at the portal of the macrocycle with no part of the phenanthriplatin located within the cavity. Phenanthriplatin binding to sCX[4] occurs in a 2-to-1, macrocycle-to-drug, ratio with the formation of a capsule-like complex where each sCX[4] binds over opposing ends of the drug. The results indicate that para-sulfonatocalix[4]arene is the only suitable macrocycle of the four studied for further research into phenanthriplatin drug delivery.     

Ultrasound-assisted dispersive liquid–liquid microextraction and multivariate optimization for determination of Sodium Closantel in biological samples and pharmaceutical formula

A fast and simple ultrasound-assisted dispersive liquid–liquid microextraction method for determination of Sodium Closantel has been developed. High-performance liquid chromatography with ultraviolet detector has been used for the determination of Sodium Closantel. The effect of influencing parameters such as type and volume of extraction and disperser solvents, pH of sample solution, extraction time and amount of salt was also investigated. Optimization of method was performed using Plackett–Burman experimental design and surface response methodology. Under the optimal conditions, the linear dynamic range of Sodium Closantel was from 10 to 3000 µg L^?1 with a correlation coefficient of 0.997 and a detection limit of 1.0 µg L^?1. The relative standard deviation was less than 3.5% (n = 5). The method has been successfully applied for determination of Sodium Closantel in real samples. The enrichment factor was 48 under optimal conditions.     

KIT-6-anchored sulfonic acid groups as a heterogeneous solid acid catalyst for the synthesis of aryl tetrazoles

In the current study, a simple, environmentally benign and cost-effective method is presented for the preparation of 5-substituted-1H-aryltetrazoles. To this goal, mesoporous KIT-6 silica anchored with sulfonic acid (–SO₃H) groups via post-grafting modification was synthesized using the sol–gel method and characterized by XRD, TGA, FTIR, BET, TEM and SEM techniques. For the preparation of tetrazole derivatives, the effect of various parameters such as catalyst amount, aryl nitrile:azide ratio, temperature and reaction time was tested. The hybrid organic/inorganic catalyst could be recovered easily through a simple filtration and reused multiple times without significant loss in activity.     

Ultrasensitive direct determination of BTEX in polluted soils using a simple and novel pressure-controlled solid-phase microextraction setup

A pressure-controlled headspace solid-phase microextraction (PC-HS-SPME) setup was developed, by reconsidering the strengths and weaknesses points of the similar reported systems. The new setup was coupled with gas chromatography–flame ionization detection (GC–FID) for direct analysis of benzene, toluene, ethylbenzene and xylene (BTEX) in contaminated soils, without any sample preparation step. The important experimental factors, affecting the performance of the method, including volumes of extraction and vacuum vials, type of SPME fiber, extraction time and temperature, moisture content of the sample, and sonication time were studied and optimized. Under the optimal conditions, good linearity of the calibration curves (R² > 0.997) was obtained in the concentration range of 0.1–20,000 ng g^?1. The limits of detections were found to be 0.001–0.08 ng g^?1. The relative standard deviations, for six repetitive analyses of 100 ng g^?1 BTEX, were obtained to be 5.7–12.3%. The PC-HS-SPME–GC–FID procedure was successfully applied for the extraction and determination of BTEX in the polluted soil samples.     

Removal of chromate from aqueous solution by reduction with nanoscale Fe–Al layered double hydroxide

Nanoscale layered double hydroxides of Fe^II and Al^III (Fe–Al LDH) have been applied for removal of chromate (Cr^VI) from aqueous solution. Given the reaction stoichiometry, Cr^VI was completely reduced to Cr^III and coprecipitated with Fe^III and Al^III oxyhydroxides. The extent of Cr^VI removal decreased with increasing initial pH and decreasing molar ratio of Cr^VI/structural Fe^II in the LDH. The chromate reduction rate at different initial concentrations of Cr^VI was well described by the pseudo-second-order model with reaction rate constant ranging from 197.4 to 13.53 (mmol min)^?1. Initial pH and substitution of various amounts of Fe^III in the LDH structure had little effect on the reaction rate. Backtransformation of Cr^III to Cr^VI by birnessite Mn oxide (δ-MnO₂) after 40 days of reaction was less than 1% of the initial Cr (as Cr^III solid), indicating high stability of the final reaction products and high efficiency of nanoscale Fe–Al LDHs for removal of chromate from aqueous solution.     

Design and Analysis of the Integrated Plasma Wave Micro-Optical Modulator/Switch

Feasibility of a new integrated amplitude modulator/switch operating up to the visible spectrum, based on the absorption of light due to the linear interaction of the incident laser and a two-dimensional plasma layer is demonstrated. Plasma layers are generated via the Muller effect at the waveguide's interfaces. A plasma wave is excited in the two-dimensional gas when it is illuminated by electromagnetic radiation. Thus, due to the energy transfer from the electromagnetic wave to the plasma wave, the output light intensity can be controlled. The device is capable of amplitude modulation of guided beams in dielectric waveguides. Analysis based on both full-classical and semiclassical approaches are performed and are compared.     

2,6-Dicarboxypyridinium chlorochromate: an efficient and selective reagent for the oxidation of thiols to disulfides and sulfides to sulfoxides

2,6-Dicarboxypyridinium chlorochromate (2,6-DCPCC) was found to be an efficient reagent for the conversion of thiols to disulfides and sulfides to sulfoxides under neutral and anhydrous conditions in good to excellent yields. Selective oxidation of thiols in the presence of sulfides at room temperature is also observed with this reagent.     

Fourier transform infrared emission spectra of MnH and MnD

Fourier transform infrared emission spectra of MnH and MnD were observed in the ground X⁷Σ⁺ electronic state. The vibration-rotation bands from v = 1 → 0 to v = 3 → 2 for MnH and from v = 1 → 0 to v = 4 → 3 for MnD were recorded at an instrumental resolution of 0.0085 cm⁻¹. Spectroscopic constants were determined for each vibrational level and equilibrium constants were found from a Dunham-type fit. The equilibrium vibrational constant (ω_e) for MnH was found to be 1546.84518(65) cm⁻¹, the equilibrium rotational constant (B_e) is 5.6856789(103) cm⁻¹ and the eqilibrium bond distance (r_e) was determined to be 1.7308601(47) Å.     

A novel method for preparation of 8-hydroxyquinoline functionalized mesoporous silica: Aluminum complexes and photoluminescence studies

8-Hydroxyquinoline (8-HQ) was attached to mesoporous silica by sulfonamide bond formation between 8-hydroxyquinoline-5-sulfonyl chloride (8-HQ-SO₂Cl) and aminopropyl functionalized SBA-15 (designated as SBA-SPS-Q) and then aluminum complexes of 8-HQ was covalently bonded to SBA-SPS-Q using coordinating ability of grafted 8-HQ.The prepared materials were characterized by powder X-ray diffraction (XRD), nitrogen adsorption-desorption, Fourier transform infrared (FT-IR), thermal analysis (TGA-DTA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), elemental analysis and fluorescence spectra. The environmental effects on the emission spectra of grafted 8-HQ and its complexes were studied and discussed in details.