Biochar (BC), a stable, carbon-rich material produced by heating biomass, is increasingly used in electrochemical sensing, particularly in hybrid nanocomposite forms, because hybridization can improve electrical conductivity, catalytic activity, surface area, and interfacial charge-transfer characteristics, making it well-suited as advanced functional sensing materials. In particular, their nanoarchitecture and functionality can be precisely controlled during synthesis to meet specific sensing requirements, including selective target interactions, elemental composition, and nanoscale dimensions, thereby demonstrating their versatility as next-generation sensing materials. Unlike previous reviews that focus on synthesis and general applications, this review summarizes recent advances in BC-based nanohybrids for electrochemical sensing, covering their synthesis methods, nanoarchitectures, and functions, with a particular focus on those incorporating graphene, carbon nanotubes, graphite, polymers, metal–organic frameworks, and noble metals. The roles of these materials in improving the detection efficiency of environmental contaminants, including toxic metals, pesticides, agrochemicals, pharmaceuticals, organics, and emerging pollutants, are discussed, along with their detection limits and dynamic ranges. The review also provides electrode surface modification strategies to produce effective electrode films and highlights the potential for developing a conductive, low-cost BC-based ink as an alternative to commercial graphene ink. Future perspectives address the need for sustainable synthesis strategies and the integration of computational chemistry to design practical BC nanohybrid systems for smart, eco-friendly electrochemical sensing applications. Also, we highlight the emergence of environmental contaminants and the challenges they pose, emphasizing the need for stronger action to address these serious concerns.

The existing methodologies for detecting foodborne pathogens often involve laborious and time-consuming procedures, underscoring the need for rapid and effective detection techniques. Herein, we present a super-hydrophobic magneto-flow system integrated with an electrochemical aptasensor designed for simple, sensitive, yet controlled detection of Salmonella enterica serovar Typhimurium (Salmonella) in food samples. A super-hydrophobic surface created through a chemical gold reduction method on a polydimethylsiloxane substrate enabled a distinct fluid orientation within a microfluidic device that prevents merging, thereby reducing contamination and enhancing detection rates. A laminate magneto-driven microfluidic device was fabricated using laser cutting and assembled to establish channel barriers that allow for precise control of magnetic flow direction using magnetic force, rather than relying on external pumps or absorbent pads. Aptamers specifically targeting Salmonella were conjugated to magnetic beads and aligned on the superhydrophobic surface with a custom-designed pattern to facilitate one-time spotting of the requisite reagents. Using a single introduced platform, the entire operation, including Salmonella-aptamer capturing, washing, and electrochemical measurement, can be performed sequentially, akin to a move-pause station. The aptasensing system operated in a label-free format, demonstrated the capability to detect Salmonella in food samples, achieving high sensitivity successfully (limit of detection = 10.01 CFU/mL), selectivity, a rapid response time (30 min), and a broad linearity range (10-105 CFU/mL), verified by standard approaches. This device embodies a cutting-edge immunosensing platform that facilitates precise operational control and features simple fabrication processes, rendering it a viable alternative suitable for complex multi-step procedures.

As health and environmental challenges become more complex, the demand for innovative sensing technologies capable of simultaneously detecting multiple disease indicators and contaminants is critical. This research introduces a wireless dual laser-induced graphene (LIG) aptasensor, utilizing LIG electrodes (LIGEs) for sensitive and selective detection of two significant foodborne pathogens: Salmonella enterica serovar Typhimurium (S. Typhimurium) and Shigella dysenteriae (S. dysenteriae). The aptasensor features a four-electrode configuration, enabling portable and simultaneous measurements. LIGEs outperform traditional screen-printed graphene electrodes (SPGEs), offering enhanced sensitivity, sustainability, and scalability. To further enhance these properties, plasma treatment was applied to address the hydrophobic nature of LIG, improving its surface characteristics prior to functionalization. Silver nanocorals (AgNCs) were electrodeposited, serving as immobilization platforms for specific aptamers and efficient signal tags. Thiolated aptamers were self-assembled onto the modified LIGE, followed by a two-step blocking process with mercaptohexanol (MCH) and skim milk (SM) for effective antifouling. The aptasensor detected electrochemical signal changes from AgNC oxidation using rapid linear sweep voltammetry (LSV). It demonstrated excellent linearity for simultaneous detection of S. Typhimurium and S. dysenteriae at concentrations from 101 to 105 CFU/mL, with low detection limits (LODs) of 1.24 and 1.26 CFU/mL, respectively. With good repeatability, high specificity, and stability, this portable aptamerbased sensing platform shows promise for on-site evaluation of disease indicators and environmental contaminants in clinical, food, and environmental samples.

Shigella dysenteriae (S. dysenteriae) is a significant pathogen associated with foodborne diseases, yet it is often overlooked, posing a risk of widespread outbreaks. Traditional detection methods rely on complex and lengthy cell culture techniques. In response, we have developed a cost-effective, portable, and versatile paper-based aptasensor that utilizes silver-decorated magnetic nanobeads (Ag/MBs) for S. dysenteriae detection. This aptasensor was designed to enable voltammetric and impedance analyses, offering rapid screening and sensitive detection of S. dysenteriae in food samples. Ag is chemically decorated on carboxyl-functionalized MBs, with aptamer probes attached. The current response from Ag indicated the presence of the pathogen, while bacterial binding reduced the Ag signal due to insulating properties, measured via differential pulse voltammetry (DPV). Concurrently, the formation of immunocomplexes increased charge transfer resistance, facilitating electrochemical impedance spectroscopy (EIS) measurement within a single device and lowering the detection limit. MB-based assays helped concentrate S. dysenteriae, thus achieving broad linearity (DPV = 102-108 CFU/mL, EIS = 101-109 CFU/mL) and high sensitivity (DPV = 90 CFU/mL, EIS = 8.09 CFU/mL) while maintaining specificity. The aptasensor also integrated near-field communication technology for convenient on-site analyses, making it an effective, sensitive, yet portable platform for detecting S. dysenteriae and other microorganisms.

Salmonella Typhimurium (S. Typhimurium) is a pathogenic bacterium associated with food contamination and severe illnesses. Given its low infectious dose, monitoring this bacterium is critical. Conventional detection methods often involve labor-intensive and time-consuming enzyme-linked immunoassays, further highlighting the need for more efficient alternatives. In this study, we developed a paper-based electrochemical aptasensor utilizing a label-free format, enhanced with carboxyl (COOH)-functionalized cellulose nanocrystals, as an innovative platform for detecting S. Typhimurium. The device was custom-designed and fabricated using a wax printing technique on Whatman filter paper, yielding a disposable and desirable paper-based analytical device (PAD). COOH-cellulose nanocrystals were applied to the PAD surface to directly immobilize an aptamer probe specific to Salmonella, employing effective EDC/NHS standard chemistry without requiring additional modifications. The subsequent formation of a half-sandwich immunocomplex (aptamer/Salmonella) induces a highly insulated layer on the PAD surface, suppressing the redox mediator signal response of [Fe(CN)6]3-/4- in a Salmonella concentration-dependent manner, with detectable ranges from 10 to 109 CFU/mL and an ultra-low detection limit of 3.50 CFU/mL, as evaluated by differential pulse voltammetry. This aptasensor successfully detects the presence of Salmonella in food samples, demonstrating remarkable sensitivity, selectivity, rapid response times (30 min), and portability.

Label -free electrochemical sensors have gained popularity as point-of-care devices because they do not require complicated labeling procedures. However, they have difficulties detecting multiple analytes simultaneously. In this study, we developed a novel label -free electrochemical immunosensor on an origami paper-based analytical device (oPAD) for the simultaneous detection of quinolone antibiotics, in which norfloxacin (Nor) and enrofloxacin (Enr) were used as a model. The oPAD was designed with two antibody zones, each zone contains different antibodies. The oPAD has two thionine- and ferrocenecarboxylic acid-coated reagent zones, as redox species, which will generate the response current signals for the detection of quinolone antibiotics. The simultaneous current responses of thionine and ferrocenecarboxylic acid decreased proportionately when exposed to Nor and Enr concentrations, respectively. Under optimal conditions, this device provided linear range at concentrations of 0.01-10 mu g/mL for the detection of Nor and Enr and limit of detection was calculated as 2.02 and 1.70 ng/mL, respectively. Moreover, this device demonstrates performance comparable to standard methods for the simultaneous detection of Nor and Enr in milk, honey, and fish. Therefore, label -free electrochemical immunosensors provide a highly potent, inexpensive, and portable method for detecting multiple quinolone antibiotics simultaneously on a single device.

A method for methanol detection by an inexpensive device using a nanomaterial modified by N-methylpolypyrrole (NMPPY) has been developed. Manganese-doped zinc sulfide quantum dots (Mn/ZnS-QDs) were synthesized and then characterized by a fluorescence spectrophotometer to study their spectroscopic properties. Mn/ZnS-QDs were modified with NMPPy and studied by digital-image colorimetry to optimize conditions for methanol detection. A 2 mL of 3000 mg∙L–1 Mn/ZnS-QDs modified with 300 μL of 1000 mg∙L-1 of NMPPy was chosen to be a detecting reagent for methanol determination. Under the optimum conditions, the linear range was found to be 2%v/v to 50%v/v of methanol with R-square of 0.9434 and the sensitivity of 3.569 ´ 10–3 (%v/v)-1, whilst the limit of detection (LOD) was 19.5%v/v. The selectivity of this method was also studied with several solvents; it was proven selective for methanol. Furthermore, a prototype device with simple and inexpensive has been created. The analytical performances were studied; the linearity of methanol detection was found in the range of 20%v/v to 80%v/v with R-square of 0.9918 and the sensitivity of 3.38 ´ 10-3 (%v/v)-1. Finally, the newly developed device was applied to analyze samples of hand sanitizer gel by digital-image colorimetry with acceptable results.

Foodborne illnesses caused by the ingestion of contaminated foods or beverages are a serious concern due to the millions of reported cases per year. It is essential to develop sensitive and rapid detection methods of foodborne pathogens to ensure food safety for producers and consumers. Unfortunately, current detection techniques still suffer from time-consuming operations and the need for highly skilled personnel. Here, we introduce a highly sensitive dual colorimetric/electrochemical detection approach for Salmonella enterica serovar typhimurium (S. typhimurium) based on a laser-induced graphene-integrated lateral flow immunoassay (LIG-LFIA) strip. The LIG electrode was fabricated by laser engraving on a polyimide tape containing a pseudo silver/silver chloride reference electrode from silver sintering and chlorination. Using double-sided tape inserted into the strip, automatic sequential reagent delivery was enabled for the dual-mode signal readout by single-sample loading. A gold-deposited gold nanoparticle strategy was first employed to simultaneously obtain a colorimetric signal for early screening and a signal turn-on electrochemical response for high-sensitivity and -quantitative analysis. A superior performance of the strip was established, characterized by a short analysis time (12 min assay +15 min sample preparation), a broad working concentration range (1 cfu/10 mL to 108 cfu/mL), and the lowest limit of detection (1 ± 0.5 cfu/10 mL; mean ± standard deviation, n = 3) among reported multimode S. typhimurium detection schemes. The strip was successfully applied in the analysis of various food products without any bacterial enrichment or amplification required, and the results were comparable to those of the standard culture method.

In this study, we developed a simple high-throughput and cost-effective method for monitoring toxic metal ion in an environmental aqueous sample. Mercury ion determination with Sequential Injection Analysis system (SIAs) coupled with the electrochemical detection on the modified screen-printed carbon working electrode (SPCE) is an alternative green analysis of mercury ion. The gold film was used as the modified material for improved mercury ion analysis in the automated system without memory effect on the electrode. Mercury oxidation signal was found at the potential of 0.7 V in 0.1 M HNO3 and 1.0 M HCl with the concentration low to 0.25 ± 0.18 mg×L-1. Online sample preparation and separation will study in the further experiment.

Microfluidic paper-based analytical devices (μPADs) are promising biosensors that may be used in a variety of bioanalytical applications. A μPAD for automating the competitive enzyme-linked immunosorbent assay (ELISA) of small-sized target detection at the femtogram level using submicroliter samples is reported in this study. The proposed μPAD was integrated with a sucrose valve to automate the sequential delivery of reagents, providing simple control of reagent delivery time and simple operation. The use of a sample solution dropping location at the zones on the device that had been prepared with an antibody-conjugated enzyme before immersion in a running buffer allowed minimization of sample volume to 0.6 μL, while eliminating the possible loss of a target molecule by adsorption on the membrane, thus improving detection sensitivity. Furthermore, the proposed device was successfully applied to the automation of competitive ELISA for the detection of aflatoxin B1 (AFB1), a potent carcinogen that causes substantial health risks to humans worldwide, with a detection limit of 60 femtograms or 0.1 ng/mL. The method developed in this study provides high sensitivity, small sample volume, on-site and equipment-free measurements, low-cost operation, and user-friendliness. This approach could be used to analyze small-sized molecules in the fields of food safety and quality control, environmental monitoring, and clinical diagnostics.

We report for the first time a highly sensitive and rapid quantitative method for the detection ofSalmonella Typhimurium(S. Typhimurium) using a conductive immunosensor on a paper-based device (PAD).S. Typhimuriummonoclonal antibodies (MA) were first immobilized on a paper-based device and then captured byS. Typhimurium. After an immunoreaction on the device, the polyclonal antibody-colloidal gold conjugate (PA-AuNPs) was dropped to bind withS. Typhimurium. After a complete sandwich reaction, a dark red color appeared on the paper-based device, which can be observed by the naked eye for a rapid screening test. The electrical conductivity of PA-AuNPs between the screen-printed electrodes on the paper-based device was also measured for an accurate quantitative analysis. The electrical conductivity correlated well with the concentration ofS. Typhimurium, which was controlled by the amount ofS. Typhimuriumattached to the polyclonal antibody-colloidal gold conjugate. The device showed a linear correlation for the concentration of theS. Typhimuriumin the range of 10-10(8)CFU mL(-1)in a logarithmic plot, with anR(2)value of 0.9882 and a limit of detection (LOD) as low as 10 CFU mL(-1). This simple, highly sensitive, and rapid method for theS. Typhimuriumdetection was successfully performed within 30 min, and it can be developed into small portable measuring devices in order to facilitate preliminary screening tests.

A nanocomposite consisting of platinum particles, polyaniline and Ti3C2 MXene (Pt/PANI/MXene) was used to modify a screen-printed carbon electrode (SPCE) to obtain sensors for hydrogen peroxide and lactate. This nanocomposite was characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and X-ray powder diffraction (XRD) to determine the physical morphologies and the nanocomposite elements. The modified electrode exhibited the improved current response towards hydrogen peroxide (H2O2) compared with an unmodified electrode and provided a low detection limit of 1.0 μM. When lactate oxidase was immobilized on the modified electrode, the electrode responded to lactate via the H2O2 generated in the enzymatic reaction. The lactate assay was performed by amperometry at a constant potential of +0.3 V (vs. Ag/AgCl). The linear range was found to be from 0.005 to 5.0 mM with a detection limit of 5.0 μM for lactate. Ultimately, this biosensor was used for the determination of lactate in milk samples with high stability and reliability.

Stabilizing reagents that can be deposited onto paper is an important issue for researchers who depend on paper-based analytical devices (PADs), because long-term stability of the devices is essential in point-of-care testing. Here, we found that poly(vinyl alcohol) (PVA) would stabilize hydrogen peroxide placed on a paper substrate following exposure to air. Horseradish peroxidase was employed as a sample in colorimetric measurements of PADs after hydrogen peroxide and 3,3′,5,5′-tetramethylbenzidine were deposited as substrates in an enzymatic reaction. The addition of PVA to hydrogen peroxide significantly suppressed its degradation. Concentrations of PVA that ranged from 0.5 to 2%, increased the duration of the stability of hydrogen peroxide, and the results for a PVA concentration of 1% approximated those of 2% PVA. Storage of the PADs at 4 °C in a refrigerator extended the stability of the hydrogen peroxide containing 2% PVA by as much as 30 days. The stability of hydrogen peroxide without PVA was degraded after one day under room temperature.

In this study, Iron nanoparticles (FeNPs) were synthesized by green chemical method. A reducing and stabilizing agent from plant were used instead of toxic chemical reagent. It was observed that FeNPs was obtained at room temperature (25-35 °C) using bioreducing agent without voltammetric method. The optimum condition for FeNPs synthesis was studied. The nanoparticles have been preliminary characterized by UV-vis spectrophotometry.

The novel modified electrode of voltammetric technique was applied to detect p-nitrophenol quantity released from the synthetic substrate p-nitrophenyl-β-D-glucopyranoside (pNPG) for β-glucosidase activity measurement. The results from the developed bismuth film modified screen printed carbon electrode (Bi/SPCE) for p-nitrophenol detecting, can be used for enzyme activity assay during purification steps. The further work, the condition of convenient voltammetric method will be optimized the condition suitable for applying to the β-glucosidase enzyme purification from Terminalia ivorensis C. seeds.

Polyaniline/graphene quantum dots (PANI/GQDs) were used to modify a screen-printed carbon electrode (SPCE) in a flow-based system. A method for rapidly determining the Cr(VI) concentrations by using stopped-flow analysis has been developed using an Auto-Pret system coupled with linear-sweep voltammetry using the PANI/GQD-modified SPCE. The GQDs, synthesized in a botton-up manner from citric acid, were mixed with aniline monomer in an optimized ratio. The mixture was injected into an electrochemical flow cell in which electro-polymerization of the aniline monomer occurred. Under conditions optimized for determining Cr(VI), wide linearity was obtained in the range of 0.1-10 mg L(-1), with a detection limit of 0.097 mg L(-1). For a sample volume of 0.5 m L, the modified SPCE can be used continuously with a sample-throughput of more than 90 samples per hour. In addition, this proposed method was successfully applied to mineral water samples with acceptable accuracy, and the quantitative agreement was accomplished in deteriorated Cr-plating solutions with a standard traditional method for Cr(VI) detection.

: Bioreduction of silver nanoparticles (AgNPs) from silver ions (Ag+) using water extract of Thai basil leaf was successfully carried out. The basil leaf extract provided a reducing agent and stabilizing agent for a synthesis of metal nanoparticles. Silver nanoparticles received from cut and uncut basil leaf was compared. The resulting silver nanoparticles are characterized by UV-Vis spectroscopy. The maximum intensities of silver nanoparticle from cut and uncut basil leaf were 410 and 420, respectively. The techniques involved are simple, eco-friendly and rapid.

Authors : Wanida Wonsawat Abstract : This research describes a voltammetric approach to determine amounts of vitamin C (Ascorbic acid) in orange juice sample, using three screen printed electrode. The anodic currents of vitamin C were proportional to vitamin C concentration in the range of 0 – 10.0 mM with the limit of detection of 1.36 mM. The method was successfully employed with 2 μL of the working solution dropped on the electrode surface. The proposed method was applied for the analysis of vitamin C in packed orange juice without sample purification or complexion of sample preparation step.

Carbon nanopowder mixed with carbon ink was used as a working screen-printed electrode. This electrode consists of carbon nanopowder working electrode, carbon counter electrode, and silver/silver chloride reference electrode. The electrochemical behavior of ascorbic acid has been studied by cyclic voltammetry and differential pulse voltammetry with screen-printed carbon nanopowder electrode. The propose electrode will enhanced the sensitivity for antioxidance determination because increasing of the surface area of the working electrode. The voltammetric sensor offers several advantages to both the green chemistry and eco-friendly. The method was successfully employed with 2 microliter of the working solution dropped on the electrode surface. A linear concentration, limit of quantitation and limit of detection was sufficient for the ascorbic acid determination in the vitamin C tablet. The results obtained for the sample juices demonstrated that the powerful of the method.