Fabrication and characterization of a NiO-ZnO/PANI-CNTs composite for sensing of methanol in an aqueous environment.

In this study, we fabricated a composite of NiO-ZnO/PANI-CNTs on a fluorine tin oxide (FTO) electrode and examined the electrochemical sensing behavior of the modified electrode to detect methanol in aqueous solution. The structural, morphological, and electrochemical properties of the composite were characterized using various methods such as X-ray diffraction (XRD), EDS, FTIR, X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and electrochemical techniques such as cyclic voltammetry (CV) and chronoamperometry (CA). The composite-based electrode showed excellent electrocatalytic activity and selectivity for methanol oxidation. The calibration equation obtained was ΔI = 0.0003 × CMeOH + 0.02811, with a high correlation coefficient of 0.9993, over a wide detection range of 0 to 500 mM. The material exhibits great potential for the fabrication of sensors to detect methanol in commercial products. Real gasoline samples have been selected to evaluate the practical performance and feasibility of this as-prepared sensor. The experimental data indicated that the recovery of gasoline samples is about 98%, indicating this to be an appropriate detection procedure for effective electrochemical determination of MeOH in real gasoline samples.

Reaction of quinaldine with 4,6-di(tert-butyl)-3-nitro-1,2-benzoquinone. Dependence of the outcome on the reaction conditions and a deeper insight into the mechanism.

Condensation of quinaldine with 4,6-di (tert-butyl)-3-nitro-1,2-benzoquinone results in the formation of 5,7-di (tert-butyl)-2-(quinoline-2-yl)-1,3-tropolone, 5,7-di (tert-butyl)-4-nitro-2-(quinoline-2-yl)-1,3-tropolone, 3,3-dimethyl-2-(5-hydroxy-4-nitro-3-tert-butyl-6-quinoline-2-yl-pyridine-2-yl)butanoic acid, 6-(2,2-dimethylprop-3-yl)-5-tert-butyl-4-nitro-2-(quinoline-2-yl)-pyridine-3-ol, 1,7-di (tert-butyl)-3-(quinoline-2-yl)-2-azabicyclo-[3.3.0]octa-2,7-diene-4,6-dione-N-oxide. The formation of 1,3-tropolone and pyridine-2-yl butanoic acid derivatives proceeds through a ring expansion and 2-azabicyclo [3.3.0]octa-2,7-diene-4,6-dione-N-oxide via the contraction of the o-quinone ring. The structure of the heterocyclic compounds obtained was justified by X-ray diffraction analysis, NMR spectroscopy, IR- and HRMS-spectrometry, and the proposed mechanisms of their formation include the participation of an intermediate product of the expansion reaction of the o-quinone cycle - 5,7-di (tert-butyl)-4-nitro-2-(quinoline-2-yl)-cyclohepta-1,3,5-triene-1,3-diol, which was first isolated preparatively. The DFT/B3LYP/6-311++G** methods were used to determine the thermodynamic stability of tautomeric forms of intermediate products, as well as the relative stability of NH and OH tautomers of 5,7-di (tert-butyl)-2-(quinolin-2-yl)-1,3-tropolone and 5,7-di (tert-butyl)-4-nitro-2-(quinolin-2-yl)-1,3-tropolone.

Preparation and spectroscopic investigation of CdS/CdSe/CdS quantum-dot quantum-well heterostructures.

CdS/CdSe/CdS quantum-dot quantum-well heterostructures with the different thicknesses of CdSe well layers were synthesized by using the colloidal chemical method. The absorption, photoluminescence and Raman scattering spectra of CdS cores, and CdS/CdSe, CdS/CdSe/CdS structures were investigated. A comparative study of their optical properties confirmed the formation of CdSe well and exterior CdS shell. Raman spectra of the nanostructures exhibit the quantum confinement of the optical phonons and the appearance of the surface phonons. It was found that the temperature dependence of the photoluminescence emission energy is described by Varshni relation with the different temperature coefficients for CdS/CdSe and CdS/CdSe/CdS structures. Upconversion luminescence was observed at low temperatures. The optical and vibrational properties of quantum-dot quantum-well heterostructures have been discussed.

Assessment of aflatoxin B1 contamination in rice and maize / Evaluación de la contaminación por aflatoxina B1 en arroz y maíz

Introduction: Aflatoxins B1 are among the most common poisonous mycotoxins produced by certain fungi that harm animals and crops. Mycotoxins can cause a variety of adverse health effects and pose a serious health threat to humans. The Maximum Residue Limits of aflatoxin B1 in processed cereals and ingredients are 2 parts per billion (ppb) and 5 ppb, respectively. Objectives: To evaluate the status of aflatoxin B1 contamination in rice, corn and staple food produced in Ha Giang province compared with the maximum permitted levels. Methods: A total of 210 rice and maize samples were analyzed to quantify the level of aflatoxin B1. Analysis of mycotoxins was conducted by High Performance Liquid Chromatography using a fluorescence detector. Results: It was found that rice, rice products, maize, and maize products had a mean aflatoxin B1 content of 1.79 ppb, 2.55 ppb, 2.19 ppb, and 6.35 ppb, respectively. The results also showed that 71.9 percent of samples were contaminated with mycotoxins, and 14.28 percent of samples exceeded the maximum allowable limit. Conclusion: The concentration of aflatoxin B1 in 14.28 percent of the samples are over permissible limits by nationwide regulations (AU)

Introducción: La aflatoxina B1 se encuentra entre las micotoxinas más comunes y venenosas producidas por ciertos hongos que dañan a los animales y los cultivos. Las micotoxinas pueden causar una variedad de efectos adversos para la salud y representar una grave amenaza para la salud de los seres humanos. Los límites máximos de residuos de aflatoxina B1en cereales e ingredientes procesados son de 2 ppb y 5 ppb, respectivamente. Objetivos: Evaluar el estado de contaminación por aflatoxina B1 en arroz, maíz y alimentos básicos producidos en la provincia de Ha Giang, en comparación con los niveles máximos permitidos. Métodos: Se analizaron un total de 210 muestras de arroz y maíz para cuantificar el nivel de aflatoxina B1. El análisis de micotoxinas se realizó mediante cromatografía líquida de alta resolución, utilizando un detector de fluorescencia. Resultados: Se encontró que el arroz, los productos de arroz, el maíz y los productos de maíz tenían un contenido medio de aflatoxin B1, de 1,79 ppb, 2,55 ppb, 2,19 ppb y 6,35 ppb, respectivamente. Los resultados también mostraron que el 71,9 por ciento de las muestras estaban contaminadas con micotoxinas y el 14,28 por ciento de las muestras excedieron el límite máximo permitido. Conclusión: La concentración de aflatoxina B1 en el 14,28 por ciento de las muestras está por encima de los límites permisibles por la norma nacional(AU)

Assessment of arsenic contamination of milk and dairy products / Evaluación de la contaminación por arsénico de la leche y productos lácteos

ABSTRACTS Introduction: Milk and dairy products are nutritious and can play a significant role in a healthy diet. The safety of milk decreases with increasing concentration of arsenic. The Maximum Residue Limits of arsenic is 500 parts per billion (ppb). Objectives: To evaluate the status of arsenic contamination of milk and dairy products produced and processed in some provinces and cities of Vietnam. Methods: A total of 367 samples were tested. Samples were digested before analysis to remove organic compounds, and the total arsenic content determined by atomic absorption spectrophotometry. Results: The average concentrations of total arsenic in liquid milk were 139.32 ppb; in yogurt, 169.81 ppb; in cheese, 221.38 ppb; in milk cake, 232.80 ppb; and in milk powder, 35.43 ppb, respectively. Conclusion: The arsenic concentrations in some samples are higher than the maximum permitted levels according to national regulations.

RESUMEN Introducción: La leche y los productos lácteos son nutritivos y pueden desempeñar un papel importante en una dieta saludable. La seguridad de la leche disminuye con el aumento de la concentración de arsénico. Los límites máximos de residuos de arsénico son 500 ppb. Objetivos: Evaluar el estado de contaminación por arsénico de la leche y los productos lácteos producidos y procesados ​​en algunas provincias y ciudades de Vietnam. Métodos: Se analizaron un total de 367 muestras. Las muestras se digirieron antes del análisis, para eliminar los compuestos orgánicos y se determinó el contenido total de arsénico mediante espectrofotometría de absorción atómica. Resultados: Las concentraciones promedio de arsénico total en la leche líquida fueron 139,32 ppb; en el yogur, 169,81 ppb; en el queso, 221,38 ppb; en el pastel de leche, 232,80 ppb; y en la leche en polvo, 35,43 ppb, respectivamente. Conclusión: Las concentraciones de arsénico en algunas muestras superan los niveles máximos permitidos según la normativa nacional.