Ionic liquid assisted growth of poly(3,4-ethylenedioxythiophene)/reduced graphene oxide based electrode: An improved electro-catalytic performance for the detection of organophosphorus pesticides in beverages

MIL-88B(Fe) MOF modified screen-printed electrodes for non-enzymatic electrochemical sensing of malathion

An enzyme-free electrochemical approach for ultra-trace quantification of the organophosphate insecticide malathion is proposed in this study. It is premised on screen-printed carbon electrodes modified by the MIL-88B(Fe) metal-organic framework (MOF). A one-pot solvothermal method was used to synthesise MIL-88B(Fe). The surface modification of electrodes allowed for increased electroactive surface area and accelerated electron transport on the electrode. Inhibition in the redox signal of MIL-88B(Fe) was observed due to the affinity between metal centres of the MOF and the functional groups of malathion, leading to an accurate determination of malathion. The proposed sensor effectively quantified malathion in the wide concentration range of 1 × 10-12 M to 1 × 10-6 M. The limit of detection for malathion was 0.79 pM. The proposed sensor also possessed excellent stability, repeatability, and anti-interference characteristics. Furthermore, the proposed sensor demonstrated satisfactory malathion recovery in spiked vegetable samples.

Synergistic integration of ZrO2-enriched reduced graphene oxide-based nanostructures for advanced photodegradation of tetracycline hydrochloride

The escalating demand for the antibiotic drug tetracycline hydrochloride (TCH) contributes to an increased release of its residues into land and water bodies, which poses risks to both aquatic life and human health. Therefore, it is precedence to effectively degrade TCH residues to protect environment from their long-term impacts. In this aspect, the present study entails the synthesis of zirconia (ZrO2) nanostructures and focuses on the enhancement in the catalytic performance of ZrO2 nanostructures by employing reduced graphene oxide (RGO) as a solid support to synthesize ZrO2-enriched RGO-based photocatalysts (ZrO2-RGO) for the degradation of TCH. The study delves into comprehensive spectroscopic and microscopic investigations and their photodegradation assessments. Powder XRD and HR-TEM studies depicted the phase crystallinity and also displayed uniform distribution of ZrO2 nanostructures with spherical morphology within ZrO2-RGO. This corresponds to high surface-to-volume ratios, providing a substantial number of active sites for light absorption and generation of e--h+ pairs. Moreover, the heterojunctions created between RGO and ZrO2 nanostructures promoted the interspecies electron transfer which prolonged the recombination time of e- and h+ than pure ZrO2 nanostructures, accounted for enhanced degradation of TCH using ZrO2-RGO. The photocatalytic activity of as-synthesized materials were examined under visible and UV light irradiation. The degradation efficiency of ~ 73.82% was achieved using ZrO2-RGO-based photocatalyst with rate constant k = 0.007023 min-1 under visible-light illumination. Moreover, under UV-light, the degradation rate was explicated to be k = 0.01017 min-1 with ~ 85.56% degradation of TCH antibiotics within 180 mins. Hence, the synthesized ZrO2-enriched RGO-based photocatalysts represents a promising potential for the effective degradation of pharmaceutical compounds, particularly TCH under visible and UV-light irradiation.

Promotion effect of ultraviolet light on graphene oxide aggregation in the presence of different climatic zone's humic and fulvic acid

Aggregation of graphene oxide (GO) is significantly affected by dissolved organic matter (DOM) in natural waters, while DOM's climate zone and light irradiation is seldom considered. This study investigated the effect of humic/fulvic acid (HA/FA) from various climate zones of China on aggregation of small (200 nm) and large (500 nm) GO under 120-h UV irradiation. GO aggregation was promoted by HA/FA because UV irradiation decreased hydrophilicity of GO and steric forces among particles. GO generated electron and hole pair under UV irradiation, which reduce GO with more hydrophilic oxygen-containing functional group (C-O) to rGO with high hydrophobicity and oxidize DOM into organic matter with smaller molecular weight. Most severe GO aggregation was observed with Makou HA from Subtropical Monsoon climate zone and Maqin FA from Plateau and Mountain climate zone, which was primarily because HA/FA's high molecular weight and aromaticity dispersed GO initially that facilitated UV penetration. GO aggregation ratio was positively correlated with graphitic fraction content (R2 = 0.82-0.99) and negatively correlated with C-O group content (R2 = 0.61-0.98) in the presence of DOM under UV irradiation. This work highlights different dispersity of GO during photochemical reactions in various climate zones, providing new insight into the environmental implications of nanomaterial release.

Fruit-Based Fermented Beverages: Contamination Sources and Emerging Technologies Applied to Assure Their Safety

The food and beverage market has become broader due to globalization and consumer claims. Under the umbrella of consumer demands, legislation, nutritional status, and sustainability, the importance of food and beverage safety must be decisive. A significant sector of food production is related to ensuring fruit and vegetable conservation and utilization through fermentation. In this respect, in this review, we critically analyzed the scientific literature regarding the presence of chemical, microbiological and physical hazards in fruit-based fermented beverages. Furthermore, the potential formation of toxic compounds during processing is also discussed. In managing the risks, biological, physical, and chemical techniques can reduce or eliminate any contaminant from fruit-based fermented beverages. Some of these techniques belong to the technological flow of obtaining the beverages (i.e., mycotoxins bound by microorganisms used in fermentation) or are explicitly applied for a specific risk reduction (i.e., mycotoxin oxidation by ozone). Providing manufacturers with information on potential hazards that could jeopardize the safety of fermented fruit-based drinks and strategies to lower or eliminate these hazards is of paramount importance.

A scientometric study on application of electrochemical sensors for detection of pesticide using graphene-based electrode modifiers

Pesticide testing is an important topic in environmental protection and food safety. The development of green, accurate and reliable pesticide residue detection methods is an important technical support for implementing of agricultural quality supervision. Electrochemical sensors are a very promising analytical method for pesticide detection due to their high sensitivity, speed, low cost and portability. Performance enhancement of electrochemical sensors is often accompanied by research advances in materials science. Among them, carbon material is a very important electrode material for the fabrication of electrochemical sensors. The discovery of graphene makes it the most promising candidate among carbon materials for sensor performance enhancement. The topic of this review is the use of graphene-modified electrochemical sensors for pesticide detection in the last decade. Traditional literature summaries and bibliometric analyses were used for an in-depth analysis of this topic. In addition to the introduction of different sensor types and performance comparisons, this review also parses the authors' country, keywords and publication frequency. The related research experienced rapid growth several years ago and has now reached a relatively stable stage. We also discuss the perspectives on this topic.

Recent advances in electrochemical and optical sensing of the organophosphate chlorpyrifos: a review

Chlorpyrifos (CP) is one of the most popular organophosphorus pesticides that is commonly used in agricultural and nonagricultural environments to combat pests. However, several concerns regarding contamination due to the unmitigated use of chlorpyrifos have come up over recent years. This has popularized research on various techniques for chlorpyrifos detection. Since conventional methods do not enable smooth detection, the recent trends of chlorpyrifos detection have shifted toward electrochemical and optical sensing techniques that offer higher sensitivity and selectivity. The objective of this review is to provide a brief overview of some of the important and innovative contributions in the field of electrochemical and optical sensing of chlorpyrifos with a primary focus on the comparative advantages and shortcomings of these techniques. This review paper will help to offer better perspectives for research in organophosphorus pesticide detection in the future.

New analytical strategies Amplified with 2D carbon nanomaterials for electrochemical sensing of food pollutants in water and soils sources

Pharmaceutical and food pollutants have threatened global health. Pharmacotherapy has left a positive impression in the field of health and life of people and animals. However, the many unresolved problems brought along with residues of pharmaceuticals in the environmental and food. Consumption of the world's freshwater resources, toxic chemicals, air pollution, plastic waste directly affects water and soil resources. Pesticides have a wide role in pollutants. Therefore, the determination of pesticides is significant to eliminate their negative effects on living things. Nowadays, there are many analytical methods available. However, new analysis methods are still being researched due to certain limitations of traditional methods. Electrochemical sensors have drawn attention because of their superior properties, such as short analysis time, affordability, high sensitivity, and selectivity. The development of new analytical strategies for assessing risks from pharmaceutical to food pollutants in water and soil sources is important for the measurement of different pollutants. Moreover, the 2D-carbon nanomaterials used in the development of electrochemical sensors are widely utilized to enlarge the surface area, increase porosity, and make easy immobilization. Graphene (graphene derivations) and carbon nanotubes integrated nanosensors are widely used for the determination of pesticides. 2D-carbon nanomaterials can be tailored according to the purpose of the study. The characterization and synthesis methods of 2D-carbon nanomaterials are widely explained. Furthermore, enzyme nanobiosensors, especially Acetylcholinesterase (AChE), are widely used to determine pesticides. The three main topics are focused on in this review: 2D-carbon nanomaterials, pesticides that threaten life, and the application of 2D-carbon nanomaterials-based electrochemical sensors. The various developed 2D-carbon nanomaterials-based electrochemical sensors were applied in pharmaceutical forms, fruits, tap/lake water, beverages, and soils sources. This work aims to indicate the recently published paper related to pesticide analysis and highlight the importance of 2D-nanomaterials on sensors.

2-(Anthracen-9-yl)benzothiazole-modified graphene oxide-nickel ferrite nanocomposite for anodic stripping voltammetric detection of heavy metal ions

A novel electrochemical sensor, 2-(anthracen-9-yl)benzothiazole (ABT)-modified nickel ferrite reduced graphene oxide (NF@rGO) has been designed for the individual and simultaneous detection of Cd²⁺, Cu²⁺, and Hg²⁺ ions. Herein, NF@rGO nanocomposite, synthesized by a simple hydrothermal methodology, was hooked to ABT under easy and simple stirring conditions. Chelation of active functional groups of ABT with metal ions was augmented with higher adsorption and conductivity provided by NF@rGO. The created synergy resulted in analytical signals via selective oxidation of the ions within a potential ranging from - 1.2 to + 1.2 V vs sat. KCl. The proposed protocol exhibited a wide linear range from 0.05 to 1250 nM with excellent detection limit of 123, 54.1, and 86.6 pM via anodic stripping voltammetry for the simultaneous determination of Cd²⁺, Cu²⁺, and Hg²⁺ ions, respectively. Simple cost-effective synthetic approach, improved sensitivity with high selectivity, noteworthy repeatability (RSD less than 3%), and reproducibility (RSD less than 7%) equipped with successful real time monitoring (apparent recovery more than 90%) bring about a spiffing sensing platform for the detection of hazardous metal ions.

Immobilization of bovine hemoglobin on Au nanoparticles/MoS2 nanosheets - Chitosan modified screen-printed electrode as chlorpyrifos biosensor

In this paper a quick and disposable electrochemical biosensor based on bovine hemoglobin (BHb) is proposed for the determination of chlorpyrifos (CP). The bioelectrode (denoted as AuNPs/MoS₂-CS/BHb/SPE) has been designed by immobilizing BHb on the screen printed electrode (SPE) surface modified by gold nanoparticles (AuNPs) and Molybdenum disulfide (MoS₂) nanosheets - chitosan (CS) mixture (MoS₂-CS). Field emission scanning electron microscopy (FESEM) and electrochemical characterization demonstrate the successful grafting of AuNPs/MoS₂-CS/BHb/SPE. Detailed electrochemical impedance spectroscopy (EIS) analysis and cyclic voltammetry (CV) tests show that the proposed bioelectrode exhibits decent electrochemical properties, such as well conductivity and large specific surface area. In-depth electrochemical analysis reveals the redox reaction occurring on the surface of the bioelectrode and the mechanism that CP binds with BHb forming the thin film to inhibit the peak current. The proposed biosensor exhibits sensitive and stable responses for electrochemical assay of CP ranging from 0.004 μM to 28.52 μM, with a limit of detection (LOD) as 5.6 nM. The electrochemical biosensor passes the repeatability, reproducibility, stability and anti-interference ability test experiments with good performance. The biosensor also shows its credibility for detecting CP in real vegetable samples (Cabbage and Leek) with recovery (%) ranging from 87% to 109%. The proposed biosensor is of great potential application values for detecting CP and the study is of great reference value for the research and development of biosensors for quantitative detection of organophosphate pesticides (OPs).

Electrochemical detection of methyl parathion via a novel biosensor tailored on highly biocompatible electrochemically reduced graphene oxide-chitosan-hemoglobin coatings

A quick electrochemical sensing tool by utilizing novel bioelectrode based on redox active protein hemoglobin (Hb) has been offered here for the determination of methylparathion (MP). The bioelectrode has been designed by immobilizing Hb on electrochemically reduced graphene oxide-chitosan (ERGO-CS/Hb/FTO) based biocompatible coatings. Fourier transform-infrared analyses (FTIR), field emission scanning electron microscopy (FESEM), UV-visible and electrochemical characterization reveal the successful grafting of ERGO-CS/Hb/FTO. A detailed impedimetric analysis shows low charge transfer resistance (R_CT) and solution resistance (Rs) for the fabricated biosensor, thus pointing towards improved electrochemical performance and sensitivity. In-depth elucidation of redox analysis has been presented in terms of surface concentration of redox moiety (2.92 × 10^-9 mol cm^-2) and heterogeneous electron transfer rate constant (0.0032 s^-1) which indicate enhanced surface coverage and better charge transfer properties of the proposed electrochemical biosensor. The sensor is equipped with a low limit of detection of 79.77 nM and a high sensitivity of 45.77 Acm^-2 μM^-1 with excellent reproducibility. The modified biosensor also offered its credibility towards detection of MP in vegetable samples with recovery (%) ranging from 94% to 101%. The designed biosensor hereby, evolves as a promising approach for the recognition of MP.

Development of a molecularly imprinted polymer electrochemical sensor and its application for sensitive detection and determination of malathion in olive fruits and oils

Malathion (MAL) is an organophosphorus (OP) insecticide. It is a cholinesterase inhibitor, which can pose serious health and environmental problems. In this study, a sensitive and selective molecular imprinted polymer (MIP) based on screen-printed gold electrodes (Au-SPE) for MAL detection in olive oils and fruits, was devised. The MIP sensor was prepared using acrylamide as the functional monomer and MAL as the template. Subsequently, the morphology of the electrode surface was studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The electrochemical characterization of the developed MIP sensor was performed by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) techniques. The operational repeatability and stability of the sensor were studied. It was found to have a dynamic concentration range of (0.1 pg mL^-1-1000 pg mL^-1) and a low limit of detection (LOD) of 0.06 pg mL^-1. Furthermore, the sensor was employed to determine MAL content in olive oil with a recovery rate of 87.9% and a relative standard deviation of 8%. It was successfully applied for MAL determination in real samples and promise to open new opportunities for the detection of OP pesticides residues in various food products, as well as in environmental applications.

A Schiff base modified graphene oxide film for anodic stripping voltammetric determination of arsenite

A protocol is described for chemical modification of graphene oxide with a Schiff base derived from diethylenetriamine and 2-hydroxy-4-methoxybenzophenone. The base was grafted onto an indium tin oxide (ITO) film and applied to electroanalytical determination of arsenite. Successful grafting was confirmed by Fourier transform-infrared spectroscopy, spectrophotometry, field emission scanning electron microscopy and cyclic voltammetry. Secondly, the coated ITO film served as a working electrode for the stripping voltammetric determination of arsenite. The analytical signal is generated by selective oxidation of metal species via multi-donor sites present in the derivatized Schiff base. The electroanalytical protocol was optimized by investigating the effects of deposition time, working potential, frequency and amplitude of square wave anodic stripping voltammetry. The method has attractive features including (a) the usage of a non-metallic, non-toxic and cost-effective material; (b) improved sensitivity (with limit of detection as low as 156 pM) due to better adsorption of arsenite in the Schiff base pockets on the ITO, and (c) the application to the determination of arsenite in real samples. Graphical abstract Schematic representation of the fabrication of a Schiff base-functionalized graphene oxide on an indium tin oxide (SB@SiO2@GO@ITO) electrode for selective electrochemical sensing of arsenite due to adsorption on multi-donor sites.