Ознаки квантово-розмірного квантування в спектрах ЕПР та UV-vis наносистем Al/Au

Композитна наносистема Al/Au, синтезована методом співвідновлення з розчину (з використанням таніну та цитрату натрію як відновників), вивчалась методами ЕПР-спектроскопії та спектроскопії електронного поглинання світла в УФ та видимому діапазонах. Виявлену тонку структуру лінії з g = 2.062 (пов’язаної з наночастинками, парамагнітні властивості яких викликані непарною кількістю атомів золота в нанокластері) віднесено до наявності дискретності електронних станів неспареного електрону в об’єднаній електронній оболонці багатоатомної наночастинки. Ця тонка структура проявляється як послідовність резонансних сигналів з близькими значеннями g-факторів. Електронні спектри оптичного поглинання розчину нанокомпозиту Al/Au складались зі смуг поглинання, які слідували еквідистантно з різницею енергій фотонів, що відповідають максимумам сусідніх смуг 0.73-0.74 еВ. Виявлені спектральні особливості пов’язані з квантово-розмірними ефектами в нанокомпозитній системі Al/Au. Оцінки, зроблені на основі експериментальних даних, показують, що розмір кластерів золота, відповідальних за парамагнітні властивості, становить близько декількох нм у діаметрі.The composite Al/Au nanosystems synthesized by co-reduction from solution (with tannin and sodium citrate as reducing agent) are studied by electron paramagnetic resonance (EPR) and UV-vis electron absorption spectroscopies. A fine structure revealed in line with g = 2.062 (associated with particles whose paramagnetism originates from odd number of gold atoms) is attributed to the discrete electronic states of an unpaired electron in a joint electron structure of a polyatomic nanoparticle. This fine structure manifests itself as a sequence of the resonance signals with close values of their g-factors. The UV-vis absorption spectra of the Al/Au nanocomposite solution contain equidistant absorption bands with 0.73-0.7 eV energy differences between the adjacent peaks. These features are attributed to the quantum confinement effects in the Al/Au nanocomposite system. The estimates made on the basis of the experimental data outline the size of the gold containing nanoclusters which in their paramagnetic form are of several nm in diameter

A New Approach to the Assessment of the Safety of Tea, Coffee, Cocoa, and Vegetable Oils, Based on the Rapid Screening of Samples for the Total Concentration of Fluorine-, Chlorine-, and Bromine-Containing Organic Compounds

Abstract: We propose a new approach to assessing the contamination of tea, coffee, cocoa, and vegetable oils with F-, Cl-, Br- and S-containing organic pesticides and other hazardous anthropogenic and natural compounds at a trace level. The approach ensures the rapid screening of test samples for the total concentration of all halogen and sulfur organic compounds present in the samples. Sample preparation is excluded. The procedure is based on the direct high-temperature oxidative conversion of a test sample under oxygen; the absorption of inorganic salts present in the sample in a reactor; the absorption of the conversion products of organic compounds of the sample, including the analyzed ones, by deionized water with the formation of F–, Cl–, Br– and SO42- acccccon in the absorbate by ion chromatography. This approach ensures the simultaneously reliable determination of all volatile, medium-volatile, and nonvolatile organohalogen and organosulfur compounds present in one sample and, thereby, improves the reliability of detection by eliminating their losses during the analysis. © 2021, Pleiades Publishing, Ltd

Determination of the Total Concentration of Halogen- and Sulfur-Organic Compounds in Vegetable Oils of Different Degrees of Purity—a New Approach to Assessing Their Safety

Abstract: A methodology is proposed for the highly selective, sensitive, and reliable determination of the total concentration of halogen and sulfur organic compounds in vegetable oils in the presence of inorganic salts, based on the direct high-temperature conversion of an oil sample in a stream of pure oxygen, absorption of inorganic salts in a reactor, absorption of the products of analyte conversion with deionized water to form F–, Cl–, Br–, and S$${\text{O}}_{4}^{{2 - }}$$ anions, and their determination in the absorbate by ion chromatography. An increase in the reliability of the determination of F–, Cl–, and Br– anions is provided by combining the registration of retention times in the direct determination of anions with an analysis of the flow of the same absorbate after the selective removal of F–, Cl–, and Br– anions (together) using corresponding adsorption columns packed with cation exchangers R–Al3+ (for F–) and R–Ag+ (for Cl– and Br–) (possibility of distortion of the determination result of these anions due to potentially coeluted components is excluded). Using the proposed methodology, the total concentration of halogen and sulfur organic compounds is determined in samples of vegetable oils of varying degrees of purity. It ranged from 2 × 10–6 to 6.0 × 10–2% (in terms of element), depending on the sample and element, at a sample volume of 1 μL. A possibility of increasing sample volume by up to 15 times and lowering the limits of detection to 10–7% (in terms of element) is shown. © 2020, Pleiades Publishing, Ltd