Simple and low-cost sensor based on activated biochar for the stripping voltammetric detection of caffeic acid

Exploring wood-derived biochar potential for electrochemical sensing of fungicides mancozeb and maneb in environmental water samples

The sustainable material, biochar (BC) from a hardwood source, was synthesized via pyrolysis process at 400 °C (BC400) and 700 °C (BC700) and used as a modifier during the electrochemical sensor design. The prepared BCs were characterized by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) analysis, and elemental analysis (CHNS). The development of rapid analytical techniques for detecting pesticides employing a low-cost carbon paste electrode (CPE) modified with BC is a novel strategy to provide a sensitive response to water pollution. The prepared working electrodes (unmodified CPE, BC400-CPE, and BC700-CPE) were compared for selected fungicides mancozeb (MCZ) and maneb (MAN) sensing, and BC700-CPE provides the most favorable analytical response of target analytes. Cyclic voltammetric investigations revealed that the electrode reaction is irreversible and controlled by the adsorption of MCZ and MAN at the surface of the BC700-CPE, which led to an optimization of the differential pulse adsorptive stripping voltammetric (DP-AdSV) method. The obtained working linear concentration ranges were 25-2780 μg L-1 MCZ and 49-1840 μg L-1 MAN in Britton-Robinson buffer pH 7.0 using CPE modified with 10 % BC700. The evaluated limit of detection was 7.5 μg L-1 for MCZ and 15.0 μg L-1 for MAN. Investigated interferences did not significantly affect the MCZ and MAN oxidation signal intensity. The developed DP-AdSV method was successfully applied to determine selected fungicides in spiked river water and wastewater samples, with good recovery and reproducibility.

Biochar-based electrochemical sensors: a tailored approach to environmental monitoring

Biochar (BC), often obtained via thermochemical conversion methods of biomass, has emerged as a versatile material with significant potential in electrochemical sensing applications. This review critically examines the recent advancements in the development of BC-based sensors for the electrochemical determination of pharmaceuticals, pesticides, heavy metals, phenolic compounds, and microplastics. BC-based electrochemical sensors have emerged as a promising alternative due to their sustainability, cost-effectiveness, and excellent electrochemical properties. The unique physicochemical properties of BC, including its high surface area, porosity, and functional groups, contribute to its effectiveness as a sensor material. The review begins with an overview of the synthesis methods for BC, highlighting the activation strategies on its structural and electrochemical properties. Next, the functionalization of BC and its integration into electrochemical sensor platforms are explored. The performance of BC-based sensors is evaluated using electrochemical focusing on their sensitivity, selectivity, detection limits, and stability. Future directions for research are proposed, emphasizing the need for further optimization, miniaturization, and integration of BC-based sensors into portable and on-site analytical devices.

Emerging carbonaceous material based on residual grape seed applied in selective and sensitive electrochemical detection of fenamiphos

Fenamiphos (FNP) is a pesticide applied for soil pest control, particularly nematodes, and sucking insects, including aphids and thrips. Despite its use being banned in several countries due to its highly toxic nature for living beings, including mammals, because of its acetylcholine-inhibiting action, it is still marketed for use in agriculture. Therefore, a carbon paste electrode modified with residual grape seed biochar (bSU), served as an electrochemical sensor (E-bSU) for the quantification of fenamiphos in grape juice, tap water, and river water samples. The bSU underwent comprehensive characterization employing elemental, morphological, and spectroscopic analysis techniques. The impact of electrode modification and the electrochemical behavior of the FNP were systematically assessed through cyclic voltammetry, electrochemical impedance spectroscopy and differential pulse voltammetry. The biochar manifested a microporous surface adorned with dispersed functional groups, enhancing its affinity for organic compounds, particularly the investigated pesticide. Electrode modification and the optimization of analysis parameters resulted in a notable 6-fold amplification of the electrochemical signal of FNP relative to initial conditions, underscoring the efficacy of the E-bSU. The developed methodology attained limits of detection and quantification of 0.3 and 0.9 nmol L⁻1, respectively. Repeatability and reproducibility assays demonstrated relative standard deviations below 5%, underscoring the reliability of the applied electrode. The sensor showcased recoveries ranging from 99.75% to 109.9% across the analyzed samples, highlighting the utility of this selective, stable, and reproducible sensor for fenamiphos determination.

Recent advances in carbon-based materials derived from diverse green biowaste for sensing applications: a comprehensive overview from the perspective of synthesis method and application

The rapid increase in global waste, driven by population growth, has raised significant environmental concerns. Among different types of wastes, green biowastes (BWs) containing organic matter have attracted considerable attention. The conversion of BW, particularly from herbaceous and animal sources, to carbon-based materials (CBMs) introduces a suitable platform for waste management and resource recovery. Furthermore, this strategy creates valuable materials from low-value waste for various applications, sensing included. The abundance of these wastes provides a sustainable and affordable raw material and enhances the feasibility of fabricating these materials. Generally, the presence of carbon in their structure can present an accessible resource for producing different carbon materials, especially carbon dots (CDs), carbon quantum dots (CQDs), and graphene quantum dots (GQDs). The performance of these CBMs has been enhanced by optimizing synthesis processes, incorporating functional groups, and integrating various materials. The synthesized CBMs possess desirable features, such as biocompatibility, excellent physical, chemical, and electrical conductivity. These materials have been used in different sensors such as electrochemical (EC) and optical sensors for presenting high performance sensing probes with several benefits such as real-time monitoring, rapid detection, and high sensitivity. The first section of this review is dedicated to the preparation of CBMs, derived from green BWs, by different synthesized methods for use in different fields including biomedical application, food safety, and environmental monitoring. In addition, the challenges, limitations, and future directions in the development of these CBMs were completely discussed to improve their performance.

Electrochemical detection of FTO with N3-kethoxal labeling and MazF cleavage

N6-Methyladenosine (m6A) is a prevalent modification in eukaryotic mRNAs and is linked to various human cancers. The fat mass and obesity-associated protein (FTO), a key m6A demethylase, is crucial in m6A regulation, affecting many biological processes and diseases. Detecting FTO is vital for clinical and research applications. Our study leverages the specific cleavage properties of the MazF endoribonuclease to design an electrochemical method with signal amplification guided by streptavidin-horseradish peroxidase (SA-HRP), intended for FTO detection. Initially, the compound N3-kethoxal is employed for its reversible tagging ability, selectively attaching to guanine (G) bases. Subsequently, dibenzocyclooctyne polyethylene glycol biotin (DBCO-PEG4-Biotin), is introduced through a reaction with N3-kethoxal. HRP is then employed to catalyze the redox system to enhance the current response further. A promising linear correlation between the peak current and the FTO concentration was observed within the range of 7.90 × 10-8 to 3.50 × 10-7 M, with a detection limit of 5.80 × 10-8 M. Moreover, this method assessed the FTO inhibitor FB23's inhibitory effect, revealing a final IC50 value of 54.73 nM. This result aligns with the IC50 value of 60 nM obtained through alternative methods and is very close to the values reported in the literature. The study provides reference value for research into obesity, diabetes, cancer, and other FTO-related diseases, as well as for the screening of potential therapeutic drugs.

Efficient anode material derived from nutshells for bio-energy production in microbial fuel cell

Biochar is a carbonaceous solid that is prepared through thermo-chemical decomposition of biomass under an inert atmosphere. The present study compares the performance of biochar prepared from Peanut shell, coconut shell and walnut shell in dual chamber microbial fuel cell. The physicochemical and electrochemical analysis of biochar reveals that prepared biochar is macroporous, amorphous, biocompatible, and electrochemically conductive. Polarization studies show that Peanut shell biochar (PSB) exhibited a maximum power density of 165 mW/m2 followed by Coconut shell biochar (CSB) Activated Charcoal (AC) and Walnut shell biochar (WSB). Enhanced power density of PSB was attributed to its surface area and suitable pore size distribution which proved conducive for biofilm formation. Furthermore, the high electrical capacitance of PSB improved the electron transfer between microbes and anode.

Investigation of Health Effects of Major Phenolic Compounds in Foods: Extraction Processes, Analytical Approaches and Applications

The escalating costs of healthcare services and a growing awareness of personal health responsibilities have led individuals to explore natural methods alongside conventional medicines for health improvement and disease prevention. The aging global population is experiencing increased health needs, notably related to conditions like diabetes, heart disease, and hypertension. Lifestyle-related diseases, poor dietary habits, and sedentary lifestyles underscore the importance of foods containing nutrients that can aid in preventing and managing these diseases. Phenolic compounds, a fundamental group of phytochemicals, are prominent in the chemical diversity of the natural world and are abundant in functional foods. Widely distributed in various plant parts, these compounds exhibit important functional and sensory properties, including color, taste, and aroma. Their diverse functionalities, particularly antioxidant activity, play a crucial role in mitigating cellular oxidative stress, potentially reducing damage associated with serious health issues such as cardiovascular disease, neurodegenerative disea23ses, and cancer. Phenolic compounds exist in different forms, some combined with glycosides, impacting their biological effects and absorption. Approximately 8000 polyphenols isolated from plants offer significant potential for natural medicines and nutritional supplements. Therefore, their extraction process and selective and sensitive food determination are very important. This review focuses on the extraction processes, analytical methods, and health effects of major phenolic compounds in foods. The examination encompasses a comprehensive analysis of analytical approaches and their applications in elucidating the presence and impact of these compounds on human health.

Nitrogen Doped Porous Biochar/β-CD-MOFs Heterostructures: Bi-Functional Material for Highly Sensitive Electrochemical Detection and Removal of Acetaminophen

Acetaminophen (AC) is one of the most common over-the-counter drugs, and its pollutant in groundwater has attracted more attention due to its serious risk to human health. Currently, the research on AC is mainly focused on its detection, but few are concerned about its removal. In this work, for the first time, nitrogen-doped Soulangeana sepals derived biochar/β-cyclodextrin-Metal-organic frameworks (N-SC/β-CD-MOFs) composite was proposed for the simultaneous efficient removal and detection of AC. N-SC/β-CD-MOFs combined the properties of host-guest recognition of β-CD-MOFs and porous structure, high porosity, and large surface area of N-SC. Their synergies endowed N-SC/β-CD-MOFs with a high adsorption capacity toward AC, which was up to 66.43 mg/g. The adsorption type of AC on the surface of N-SC/β-CD-MOFs conformed to the Langmuir adsorption model, and the study of the adsorption mechanism showed that AC adsorption on N-SC was mainly achieved through hydrogen bonding. In addition, the high conductivity, large specific surface area and abundant active sites of N-SC/β-CD-MOFs were of great significance to the high-performance detection of AC. Accordingly, the sensor prepared with N-SC/β-CD-MOFs presented a wide linear range (1.0-30.0 μM) and a low limit of detection of 0.3 nM (S/N = 3). These excellent performances demonstrate that N-SC/β-CD-MOFs could act as an efficient dual-functional material for the detection and removal of AC.

One-step potentiostatic electrodeposition of NiS-NiS2 on sludge-based biochar and its application for a non-enzymatic glucose sensor

Conventional nanomaterials are available in electrochemical glucose nonenzymatic sensing, but their broad applications are limited due to their high cost and complicated preparation procedures. In this study, NiS-NiS₂/sludge-based biochar/GCE was fabricated by one-step potentiostatic electrodeposition on biochar and used as an interface material for non-enzymatic sensing of glucose in 0.1 M NaOH. With an electrodeposition time of 300 s, the as-prepared sensors delivered the best electrochemical performance toward glucose due to the synergistic effects of NiS-NiS₂ and sludge-based biochar. The as prepared NiS-NiS₂/sludge-based biochar surface morphology, surface composition, and electrochemical properties were characterized by SEM elemental mapping, XPS and cyclic voltammetry. Under optimized conditions, the linearity between the current response and the glucose concentration has been obtained in the range of 5-1500 μM with a detection limit of 1.5 μM. More importantly, the fabricated sensor was successfully utilized to measure glucose in serum of sweetened beverages and human blood. Accordingly, NiS-NiS₂/sludge-based biochar/GCE can hopefully be applied as a normal enzyme-free glucose sensor with excellent properties of sensitivity, reproducibility, stability, as well as sustainability.

Recent Advances of Biochar-Based Electrochemical Sensors and Biosensors

In the context of accelerating the global realization of carbon peaking and carbon neutralization, biochar produced from biomass feedstock via a pyrolysis process has been more and more focused on by people from various fields. Biochar is a carbon-rich material with good properties that could be used as a carrier, a catalyst, and an absorbent. Such properties have made biochar a good candidate as a base material in the fabrication of electrochemical sensors or biosensors, like carbon nanotube and graphene. However, the study of the applications of biochar in electrochemical sensing technology is just beginning; there are still many challenges to be conquered. In order to better carry out this research, we reviewed almost all of the recent papers published in the past 5 years on biochar-based electrochemical sensors and biosensors. This review is different from the previously published review papers, in which the types of biomass feedstock, the preparation methods, and the characteristics of biochar were mainly discussed. First, the role of biochar in the fabrication of electrochemical sensors and biosensors is summarized. Then, the analytes determined by means of biochar-based electrochemical sensors and biosensors are discussed. Finally, the perspectives and challenges in applying biochar in electrochemical sensors and biosensors are provided.

Electrochemical sensors based on sewage sludge-derived biochar for the analysis of anthocyanins in berry fruits

The reutilization of waste and the reduction of the general environmental impact of every production are fundamental goals that must be achieved in the framework of a circular economy. Recycled carbon-rich materials may represent a promising alternative to other less-sustainable carbonaceous materials used in the production of electrochemical sensing platforms. Herein, we propose an innovative carbon paste electrode (CPE) composed of biochar derived from biological sludge obtained from municipal and industrial wastewater treatment plants. The physicochemical properties of the biochar after a chemical treatment with an acidic solution obtained from industrial by-products were investigated. The electrode surface characterization was carried out by analyzing common redox probes and multiple phenols bearing varying numbers of –OH and –OCH₃ groups in their structure. Furthermore, the CPE was also tested on the evaluation of the phenolic fingerprints of Vaccinium myrtillus, Vaccinium uliginosum subsp. gaultherioides, and Fragaria × ananassa. Standard anthocyanin mixtures and extracts of the aforementioned fruits were analyzed to provide a phenolic characterization of real samples. The obtained results show that the sewage sludge–derived biochar can be a promising material for the development of electroanalytical sensors.

A Review on Electrochemical Sensors and Biosensors Used in Assessing Antioxidant Activity

Currently, there is growing interest in screening and quantifying antioxidants from biological samples in the quest for natural and effective antioxidants to combat free radical-related pathological complications. Antioxidants play an important role in human health and provide a defense against many diseases. Due to the valuable dietary role of these compounds, the analysis and determination of their amount in food is of particular importance. In recent years, many attempts have been made to provide simple, fast, and economical analytical approaches for the on-site detection and determination of antioxidant activity in food antioxidants. In this regard, electrochemical sensors and biosensors are considered promising tools for antioxidant research due to their high sensitivity, fast response time, and ease of miniaturization; thus, they are used in a variety of fields, including food analysis, drug screening, and toxicity research. Herein, we review the recent advances in sensors and biosensors for the detection of antioxidants, underlying principles, and emphasizing advantages, along with limitations regarding the ability to discriminate between the specific antioxidant or quantifying total antioxidant content. In this work, both direct and indirect methods for antioxidants detecting with electrochemical sensors and biosensors are analyzed in detail. This review aims to prove how electrochemical sensors and biosensors represent reliable alternatives to conventional methods for antioxidant analysis.

A Low Cost Fe3O4-Activated Biochar Electrode Sensor by Resource Utilization of Excess Sludge for Detecting Tetrabromobisphenol A

Owing to its ubiquity in natural water systems and the high toxicity of its accumulation in the human body, it is essential to develop simple and low-cost electrochemical sensors for the determination of 3,3',5,5'-tetrabromobisphenol A (TBBPA). In this work, Fe3O4-activated biochar, which is based on excess sludge, was prepared and characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and BET analysis to analyze its basic features. Subsequently, it was used to fabricate an electrochemical sensor for the detection of TBBPA. The electrochemical test results revealed that the Fe3O4-activated biochar film exhibited a larger active surface area, a lower charge transfer resistance and a higher accumulation efficiency toward TBBPA. Consequently, the peak current of TBBPA was significantly enhanced on the surface of the Fe3O4-activated biochar. The TBBPA sensing platform developed using the Fe3O4-activated biochar composite film, with relatively a lower detection limit (3.2 nM) and a wider linear range (5-1000 nM), was successfully utilized to determine TBBPA levels in water samples. In summary, the effective application of Fe3O4-activated biochar provided eco-friendly and sustainable materials for the development of a desirable high-sensitivity sensor for TBBPA detection.

Validated Stability-Indicating GC-MS Method for Characterization of Forced Degradation Products of Trans-Caffeic Acid and Trans-Ferulic Acid

When dealing with simple phenols such as caffeic acid (CA) and ferulic acid (FA), found in a variety of plants, it is very important to have control over the most important factors that accelerate their degradation reactions. This is the first report in which the stabilities of these two compounds have been systematically tested by exposure to various different factors. Forced degradation studies were performed on pure standards (trans-CA and trans-FA), dissolved in different solvents and exposed to different oxidative, photolytic and thermal stress conditions. Additionally, a rapid, sensitive, and selective stability-indicating gas chromatographic-mass spectrometric method was developed and validated for determination of trans-CA and trans-FA in the presence of their degradation products. Cis-CA and cis-FA were confirmed as the only degradation products in all the experiments performed. All the compounds were perfectly separated by gas chromatography (GC) and identified using mass spectrometry (MS), a method that additionally elucidated their structures. In general, more protic solvents, higher temperatures, UV radiation and longer storage times led to more significant degradation (isomerization) of both trans-isomers. The most progressive isomerization of both compounds (up to 43%) was observed when the polar solutions were exposed to daylight at room temperature for 1 month. The method was validated for linearity, precision as repeatability, limit of detection (LOD) and limit of quantitation (LOQ). The method was confirmed as linear over tested concentration ranges from 1−100 mg L⁻¹ (r²s were above 0.999). The LOD and LOQ for trans-FA were 0.15 mg L⁻¹ and 0.50 mg L⁻¹, respectively. The LOD and LOQ for trans-CA were 0.23 mg L⁻¹ and 0.77 mg L⁻¹, respectively.