Synthetic Azo Dyes as Factors of Environmental Pollution

В настоящей статье рассмотрены основные области применения азокрасителей и их вред для человека и окружающей среды. Проанализированы способы их удаления.This article discusses the main areas of azo dyes application and their harm to human and the environment. The ways of their removal are analyzed

The effect of the antioxidant activity of plant extracts on the properties of gold nanoparticles

Synthesis of gold nanoparticles (phyto-AuNPs) with the use of leaf extracts (phytosynthesis) is based on the concept of Green Chemistry. The present study is conducted to discuss how antioxidant activity (AOA) of extracts from plant leaves impacts on the kinetics of phytosynthesis, the size of the formed nanoparticles, and the stability of their nanosuspensions. Results show that the formation rate of phyto-AuNPs suspensions accelerate due to the increase in the AOA of the extracts. Accompanying the use of transmission electron microscopy (TEM), UV-Vis-spectrophotometry and dynamic light scattering (DLS), it also has been found that higher AOA of the extracts leads to a decrease in the size of phyto-AuNPs, an increase in the fraction of small (d ≤ 5 nm), and a decrease in the fraction of large (d ≥ 31–50 nm) phyto-AuNPs, as well as an increase in the zeta potential in absolute value. Phyto-AuNPs suspensions synthesized with the use of extracts are more resistant to destabilizing electrolytes and ultrasound, as compared to suspensions synthesized using sodium citrate. Thus, the AOA of the extract is an important parameter for controlling phytosynthesis and predicting the properties of phyto-AuNPs. The proposed approach can be applied to the targeted selection of plant extract that will be used for synthesizing nanoparticles with desired properties. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.Russian Foundation for Basic Research, RFBR: 17-03-00679_АFunding: This research was funded by the Russian Foundation for Basic Research, grant number 17-03-00679_А

Electrochemical sensor based on a carbon veil modified by phytosynthesized gold nanoparticles for determination of ascorbic acid

An original voltammetric sensor (Au-gr/CVE) based on a carbon veil (CV) and phytosynthesized gold nanoparticles (Au-gr) was developed for ascorbic acid (AA) determination. Extract from strawberry leaves was used as source of antioxidants (reducers) for Au-gr phytosynthesis. The sensor was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy and electrochemical methods. Optimal parameters of AA determination were chosen. The sensor exhibits a linear response to AA in a wide concentration range (1 µM–5.75 mM) and a limit of detection of 0.05 µM. The developed sensor demonstrated a high intra-day repeatability of 1 µM AA response (RSD = 1.4%) and its stability during six weeks, selectivity of AA determination toward glucose, sucrose, fructose, citric, tartaric and malic acids. The proposed sensor based on Au-gr provides a higher sensitivity and a lower limit of AA detection in comparison with the sensor based on gold nanoparticles synthesized by the Turkevich method. The sensor was successfully applied for the determination of AA content in fruit juices without samples preparation. The recovery of 99%–111% and RSD no more than 6.8% confirm the good reproducibility of the juice analysis results. A good agreement with the potentiometric titration data was obtained. A correlation (r = 0.9867) between the results of AA determination obtained on the developed sensor and integral antioxidant activity of fruit juices was observed. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Russian Foundation for Basic Research, RFBR: 17-03-00679This research was partially funded by RFBR grant number 17-03-00679

VOLTAMPEROMETRIC DETERMINATION OF NITRITE IONS IN NATURAL WATERS

The article discusses the main sources of environmental pollution with nitrite ions. The need for monitoring the nitrite content in environmental objects is shown, since nitrite ions are toxic substances that can harm human health. The development of an electrochemical sensor for the fast and accurate determination of nitrite ions in natural waters is discussed.В статье рассматриваются основные источники загрязнения окружающей среды нитрит-ионами. Показана необходимость контроля за содержанием нитритов в объектах окружающей среды, так как нитрит-ионы относятся к токсичным веществам, способным нанести вред здоровью человека. Обсуждается разработка электрохимического сенсора для быстрого и точного определения нитрит-ионов в природных водах

Eco-Friendly Synthesis of Metal Nanoparticles

Нанотехнология - активно развивающаяся область науки и техники. Приоритетным направлением её развития является разработка и совершенствование eco-friendly безопасных и экономически выгодных способов синтеза металлических наночастиц, к числу которых относится «зеленый» синтез с использованием экстрактов растений. Проведено сравнение характеристик золотых наночастиц, полученных с помощью «зеленого» синтеза и по методу Туркевича. Установлено, что фитосинтезированные наночастицы являются более стабильными и электрохимически активными.Nanotechnology is an actively developing area of science and technology. The priority direction of its evolution is the development and improvement of eco-friendly safe and cost-effective methods for the synthesis of metal nanoparticles, which include the “green” synthesis using plant extracts. Comparison of the characteristics of gold nanoparticles obtained by “green” synthesis and by the Turkevich method is carried out. It was found that phytosynthesized nanoparticles are more stable and electrochemically active

Carbon Paper Modified with Functionalized Poly(diallyldimethylammonium chloride) Graphene and Gold Phytonanoparticles as a Promising Sensing Material: Characterization and Electroanalysis of Ponceau 4R in Food Samples

This paper presents a novel eco-friendly sensing material based on carbon paper (CP) volumetrically modified with a composite nanomodifier that includes functionalized poly(diallyldimethylammonium chloride) graphene (PDDA-G) and phytosynthesized gold nanoparticles (phyto-AuNPs). The functionalization of graphene was justified by Fourier-transform infrared spectroscopy. The phyto-AuNPs (d = 6 nm) were prepared by “green” synthesis with the use of strawberry leaf extract. The sensing material was characterized using scanning electron microscopy, electrochemical impedance spectroscopy, and voltammetry. The research results indicated a more than double increase in the electroactive surface area; a decrease in the resistance of electron transfer on nanocomposite-modified CP, compared to bare CP. The phyto-AuNPs/PDDA-G/CP was used for the electrosensing of the synthetic dye Ponceau 4R. The oxidation signal of colorant enhanced 4-fold on phyto-AuNPs/PDDA-G/CP in comparison to CP. The effect of the quantity of nanomodifier, solution pH, potential scan rate, accumulation parameters, and differential pulse parameters on the peak current of Ponceau 4R was studied. Under optimal conditions, excellent sensory characteristics were established: LOD 0.6 nM and LR 0.001–2 μM for Ponceau 4R. High selectivity and sensitivity enable the use of the sensor for analyzing the content of Ponceau 4R in food products (soft drinks, candies, and popsicles) without additional sample preparation. © 2022 by the authors