Carbon nanomaterial-enabled pesticide biosensors: Design strategy, biosensing mechanism, and practical application

Novel, fast, and reliable electrochemical dsDNA biosensor based on O-terminated pristine nanocrystalline boron-doped diamond electrode for DNA interaction studies

We present a novel application of a nanocrystalline boron-doped diamond electrode (B-NCDE) for the construction of an electrochemical DNA biosensor based on double-stranded DNA (dsDNA) for various bioanalytical applications. Surface characterization of the transducer surface (prior and after the fabrication of negatively charged O-terminated surface - O-B-NCDE) was performed by scanning electron microscopy (SEM), Raman spectroscopy, and linear sweep voltammetry (LSV) that was further used for the voltammetric determination, scan rate dependence investigation, and repeatability examination of dsDNA electrochemical oxidation at the O-B-NCDE. The fabrication of a dsDNA/O-B-NCDE biosensor via electrostatic adsorption of dsDNA involved a thorough optimization process of deposition potential (Edep), deposition time (tdep), and optimal saturation concentration (cg(satur)) with optimal values of 0.3 V, 3 min, and 10 mg/mL. The bioanalytical applicability of the fabricated dsDNA/O-B-NCDE biosensor was verified by examining the nature of the interaction between dsDNA and five selected DNA intercalators - namely thioridazine hydrochloride (TR), trimipramine maleate (TRIM), levomepromazine maleate (LEV), imipramine hydrochloride (IMI), and prochlorperazine maleate (PER) - where intercalation was proven for all of the five tested compounds. Moreover, the proposed novel bioanalytical test offers the possibility to selectively distinguish between the phenothiazine representatives (TR, LEV, and PER) and representatives of tricyclic antidepressants group (TRIM and IMI).

Novel electrochemiluminescence sensing platform for ultrasensitive detection of malathion residue in tea based on SiO2NSs doped Luminol/AgNPs as a signal amplification strategy

To address the potential hazards of organophosphorus pesticides (OPs) residues in tea, an electrochemiluminescence (ECL) aptasensor based on functionalized nanomaterials was constructed in this work. Firstly, gold nanoparticles (AuNPs) were attached on the surface of multi-walled carbon nanotubes (MWCNTs) by the constant potential electrodeposition to form a compound, and it was utilized to provide excellent immobilization sites for complementary DNA (cDNA). Subsequently, composite nanomaterials were synthesized by a one-pot method with aminated Luminol/silver nanoparticles@silica nanospheres (NH2-Luminol/Ag@SiO2NSs). Finally, NH2-Luminol/Ag@SiO2NSs was combined with a malathion aptamer (Apt) to obtain signal probes (SPs) for the construction of an aptasensor. The aptasensor had a wide linear range (1×10-3-1×103 ng/mL) and a low limit of detection (LOD) (0.3×10-3 ng/mL). It had the virtues of high sensitivity, wonderful stability and excellent specificity, which could be used for the detection of malathion residue in tea. The work provides a proven way for the construction of a rapid and ultrasensitive aptasensor with low-cost.

Carbon dots-based stimuli-responsive hydrogel for in-situ detection of thiram on fruits and vegetables

Stimuli-responsive hydrogel possesses a strong loading capacity to embed luminescent indicators for constructing food safety sensors, which are suitable for field application. In this work, a fluorescent hydrogel sensor was fabricated by incorporating Ag+-modified carbon dots (CDs-Ag+) into a sodium alginate (SA) hydrogel for in-situ detection of thiram. The fluorescence of CDs was quenched due to the combined effects of electrostatic adsorption and electron transfer between Ag+ and CDs. The formation of an AgS bond between thiram and Ag+ facilitates the release of CDs, causing subsequently fluorescence recovery. Combined with smartphone and analysis software, the fluorescence color change of the hydrogel sensor was converted into data information for quantitative detection of thiram. Such a sample-to-result step is completed within 10 min. Notably, the in-situ detection experiment of thiram in fruit and vegetable samples confirmed the practical application of the hydrogel sensor. Therefore, the hydrogel sensor provides a new research direction for the in-situ detection of pesticide residues in the monitoring of food safety.

Fe-MOF/AuNP-based ratiometric electrochemical immunosensor for the detection of deoxynivalenol in grain products

A ratiometric assay was designed to improve the sensitivity and reliability of electrochemical immunosensors for deoxynivalenol (DON) detection. The indicator signal caused by the Fe-based metal-organic framework nanocomposites loaded with gold nanoparticles and the internal reference signal from the [Fe(CN)6]3-/4- in the electrolyte came together at the immunosensor. When immunoreactivity occurred, the indicator signals decreased as the concentration of DON increased, while the internal reference signals increased slightly. The ratio of the indicator signal to the internal reference signal was available for reproducible and sensitive monitoring of DON. The prepared immunosensor showed excellent performance in the range from 0.5 to 5000 pg mL-1, and the detection limit was 0.0166 pg mL-1. The immunosensor achieved satisfactory detection toward DON in spiked and actual samples and has a promising application in the control of DON in grain products.

Silver-nanoparticle-coated Fe3O4/chitosan core-shell microspheres for rapid and ultrasensitive detection of thiram using surface magnetic solid-phase extraction-surface-enhanced Raman scattering (SMSPE-SERS)

We report a surface magnetic solid-phase extraction-surface-enhanced Raman scattering (SMSPE-SERS) method based on silver-nanoparticle-coated Fe3O4/chitosan (Fe3O4/CS@Ag) microspheres as the substrate, and this method integrates all steps from sample pretreatment to detection. Fe3O4/CS was synthesized by a one-step solvothermal method in which chitosan (CS) was used as a surface modifier and adsorbent. Fe3O4/CS@Ag microspheres exhibit both adsorption ability and SERS activity. Therefore, we used the SMSPE-SERS method to detect pesticide residues on fruit peel. The procedures of capturing, separating and enriching pesticides, as well as detection, are all integrated. In addition, the SERS substrate allows label-free detection of thiram pesticide in both fruit peel and apple juice. Owing to the uniform distribution of Ag NPs and the adsorption ability of CS, the thiram-detection sensitivity was sufficiently high to detect the lowest concentration of 1.2 ng/cm2, which was significantly lower than the maximum thiram residue limit (7 μg/cm2) in fruits. The method was comparable to high-performance liquid chromatography with recovery ranging from 86.60 to 109.69 %.

Dosage-sensitive and simultaneous detection of multiple small-molecule pollutants in environmental water and agriproducts using portable SERS-based lateral flow immunosensor

The co-contamination of pesticide residues and mycotoxins in agricultural products is a global concern, with the potential for cumulative and synergistic damaging effects, imposing substantial health and economic burdens to the public. The dosage-sensitive and simultaneous detection of multiple pollutants, with a heightened sensitivity in real samples, poses a significant demand and challenge. Herein, we propose a portable detection method integrating surface-enhanced Raman scattering (SERS)-with lateral flow immunoassay (LFIA), offering high sensitivity and multiplex analysis capabilities. This approach enables the simultaneous detection of imidacloprid (IMI), pyraclostrobin (PYR) and aflatoxin B1 (AFB1) through a single test strip. Utilizing the immune-specific binding between antigen and antibodies, we immobilised antibody- conjugated SERS nanotags on three test lines of the strips to generate Raman signal amplification in the proposed biosensor. Accurate quantitative analysis was performed by measuring the SERS signal intensity on the test lines. The limits of detection were 8.6 pg/mL for IMI, 97.4 pg/mL for PYR and 8.9 pg/mL for AFB1, exhibiting sensitivities 12-fold, 102-fold and11-fold higher than the colorimetric signals, respectively. Importantly, the SERS-LFIA immunosensor demonstrated robust performance when applied to real samples, yielding recoveries ranging from 86.16 % to 115.0 %, with relative standard deviation values below 8.67 %. These results underscore the excellent stability, high selectivity and reliability the proposed SERS-LFIA immunosensor. Consequently, it holds promise for the detection of multiple pesticides and mycotoxins in both environmental and agricultural samples.

A novel self-enhanced electrochemiluminescent aptamer sensor based on ternary nanocomposite PEI/RuSi-MWCNTs for the detection of profenofos residues in vegetables

In this work, a novel ternary nanocomposite of PEI/RuSi-MWCNTs was designed and synthesized for the first time, which an ultrasensitive and self-enhanced electrochemiluminescent (ECL) aptasensor was developed for the detection of profenofos residues in vegetables. The self-enhanced complex PEI-Ru (II) enhanced the emission and stability of ECL, and the multi-walled carbon nanotubes (MWCNTs) acted as an excellent carrier and signal amplification. The PEI/RuSi-MWCNTs were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive spectrometer (EDS). The incorporation of gold nanoparticles (AuNPs) improved the performance of the sensor and provided a platform for the immobilization of the aptamer. The results of the experiment showed that the presence of profenofos significantly suppressed the electrochemiluminescence intensity of the sensor. The detection sensitivity of the aptamer sensor was in the range of 1 × 10-2 to 1 × 103 ng/mL. Under optimal conditions, the limit of detection (LOD) of the sensor for profenofos was 1.482 × 10-3 ng/mL. The sensor had excellent stability, reproducibility and specificity. The recoveries of the sensor ranged from 92.29 % to 106.47 % in real sample tests.

Nano-size cobalt-doped cerium oxide particles embedded into graphitic carbon nitride for enhanced electrochemical sensing of insecticide fenitrothion in environmental samples: An experimental study with the theoretical elucidation of redox events

In the present work, a nanocomposite, based on embedding Co-doped CeO2 nanoparticles into graphitic carbon nitride (g-C3N4), was applied to functionalize commercial glassy carbon paste. This is the first application of the electrochemical sensor, developed through the proposed procedure, in electrochemical sensing. The sensor was utilized for the electrochemical determination of organophosphate pesticide fenitrothion (FNT). Cyclic voltammetry identified reversible oxidation of FNT (oxidation at 0.18 V and reduction at 0.13 V) and additional reduction at -0.62 V vs. Ag/AgCl in HCl solution (pH = 1). Theoretical calculations were carried out to model and elucidate experimentally observed redox processes. Special attention was devoted to modeling experimental conditions, and based on the obtained results, a detailed redox mechanism of the investigated analyte was proposed. This represents the first complete and unambiguous elucidation of the FNT redox mechanism, supported by joined experimental and theoretical data. Square wave voltammetry (SWV) was utilized for quantification, whereby the FNT oxidation peak was chosen for monitoring the analyte concentration. The developed sensor provided a nanomolar detection limit (3.2 nmol L-1), a wide linear concentration range (from 0.01 to 13.7 μmol L-1), and good precision, repeatability, and selectivity towards FNT. Practical application possibility was explored by testing the sensor performance for examining tap water and apple samples. Recovery tests, conducted during the FNT-spiked sample assays, showed a great application capability of the developed sensor for real-time monitoring of FNT traces in environmental samples.

High sensitivity, low-cost, and disposability: A novel screen-printed electrode developed for direct electrochemical detection of the antibiotic ceftriaxone

This study describes the development of a novel disposable and low-cost electrochemical platform for detecting the antibiotic ceftriaxone. The screen-printed electrode has been modified with a novel hybrid nanostructure containing silicon oxide (SiO2), zirconium oxide (ZrO2), and nitrogen-doped carbon quantum dots (Cdot-N). Different techniques like Fourier-transform infrared spectroscopy, Raman spectroscopy, and transmission electron microscopy characterized the hybrid nanostructure used in the sensor surface modifier material. The hybrid nanostructure showed an excellent synergistic effect that contributed to the oxidation reaction of ceftriaxone. The screen-printed electrode modified with SiO2/ZrO2/Cdot-N nanostructure presented high sensitivity with a detection limit of 0.2 nmol L-1 in the linear range of 0.0078-40.02 μmol L-1. The measurements have been performed by square wave voltammetry technique. Studies on real samples of synthetic urine, urine, and tap water showed 95%-105% recovery without applying any sample pretreatment. The sensor demonstrated excellent selectivity in the antibiotic ceftriaxone determination in the presence of possible interferences cationic, Na+, K+, Ca2+, Mg2+, Cu2+, Pb2+, Mn2+, Zn2+, Co2+, and biological, glucose, caffeine, uric acid, and ascorbic acid. The developed sensor becomes a selective, sensitive, and applicable tool in determining the antibiotic ceftriaxone.

Disposable nanosensor for the electrochemical determination of the interaction between DNA, and a mycotoxin, patulin

Silicon dioxide nanoparticles were synthesized and disposable screen-printed electrodes were modified with these nanoparticles to electrochemically detect the interaction between DNA and patulin, a mycotoxin. Firstly, the synthesized silicon dioxide nanoparticles were chemically characterized by X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR). Microscopic characterization of the nanoparticles was performed by Transmission Electron Microscopy (TEM) and Energy-dispersive X-ray spectroscopy (EDX). The surface of the silicon dioxide nanoparticle-modified screen-printed electrode was characterized by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). SiNP modification resulted in a 2-fold increase in surface area and a 2.3-fold enhancement in the signal. The detection limit (LOD) for the electrochemical patulin determination was calculated as 1.15 µg/mL, and the linear concentration range was found to be 3.2-20 µg/mL. The mode of interaction between patulin and dsDNA was determined through a molecular docking study. After the interaction between patulin and dsDNA, approximately 86 % and 23 % decreases were observed in patulin and guanine oxidation signals, respectively. The S % value for patulin was calculated by utilizing the decrease in the guanine signal after the interaction.

Portable multichannel detection instrument based on time-resolved fluorescence immunochromatographic test strip for on-site detecting pesticide residues in vegetables

In this work, a portable multichannel detection instrument based on time-resolved fluorescence immunochromatographic test strip (TRFIS) was proposed for on-site detecting pesticide residues in vegetables. Its hardware consisted of a silicon photodiode and excitation light source array, a mainboard of the lower machine with STMicroelectronics 32 (STM32) and a linear stepping motor. While detecting, cardboard with 6-channel TRFIS was pulled into the cassette by the stepping motor. The peak area of the test (T) line and control (C) line of each TRFIS was sampled and calculated by software, then the concentration of the detected pesticide was obtained according to the ratio of the T to C value. This instrument could sample 6-channel TRFIS within 30 s simultaneously, and it exhibited excellent accuracy with a 2.5% average coefficient of variation for each channel (n = 12). In addition, the TRFIS was constructed by using europium oxide time-resolved fluorescent microspheres to label the monoclonal antibody against acetamiprid and form a fluorescent probe, which was fixed on the binding pad. The TRFIS was used for the detection of acetamiprid in celery cabbage, cauliflower and baby cabbage. This instrument was used to complete the qualitative and quantitative analysis of the TRFIS, so as to enhance the practical application of the detection method. This TRFIS possessed excellent linearity ranging from 0.25 mg kg-1 to 1.75 mg kg-1 for the detection of acetamiprid, and the limit of detection were 0.056-0.074 mg kg-1 in the different vegetable matrix. The platform combines the accuracy and portability of traditional test strips with the highly sensitive and efficient fluorescence intensity recognition function of detection equipment, which shows a great application prospect of multi-channel rapid detection of small molecule pollutants in the field.

One-Pot Hydrothermal Method Preparation of Cerium-Nitrogen-Codoped Carbon Quantum Dots from Waste Longan Nucleus as a Fluorescent Sensor for Sensing Drug Rifampicin

Currently, the large-scale application of carbon quantum dots (CQDs) is usually limited by their low quantum yield and detection limit. Herein, the abandoned longan nucleus was used as a carbon source to synthesize cerium-nitrogen-codoped carbon quantum dots (Ce/N-CQDs) with strong luminescence intensity. In this work, the fluorescent properties and fluorescent quantum yield of CQDs may be improved by the single cerium-doped carbon quantum dots (Ce-CQDs) and the single nitrogen-doped carbon quantum dots (N-CQDs). Nevertheless, the Ce/N-CQDs exhibited intense fluorescence with a high quantum yield. Compared with CQDs, the quantum yield of Ce/N-CQDs was significantly increased from 5 to 32% and showed high photostability and good water solubility. The Ce/N-CQDs can be used for the direct detection of rifampicin (RFP) in human serum. The concentration demonstrated a good linear relationship in the range of 1.0 × 10-7-9.0 × 10-6 mol/L, with a detection limit of 9.6 × 10-8 mol/L.

Catalytic electrodes' characterization study serving polluted water treatment: environmental healthcare and ecological risk assessment

Pesticide residues in the environment have irreparable effects on human health and other organisms. Hence, it is necessary to treat and degrade them from polluted water. In the current work, the electrochemical removal of the fenitrothion (FT), trifluralin (TF), and chlorothalonil (CT) pesticides were performed by catalytic electrode. The characteristics of SnO2-Sb2O3, PbO2, and Bi-PbO2 electrodes were described by FE-SEM and XRD. Dynamic electrochemical techniques including cyclic voltammetry, electrochemical impedance spectroscopy, accelerated life, and linear polarization were employed to investigate the electrochemical performance of fabricated electrodes. Moreover, evaluate the risk of toxic metals release from the catalytic electrode during treatment process was investigated. The maximum degradation efficiency of 99.8, 100, and 100% for FT, TF, and CT was found under the optimal condition of FT, TF, and CT concentration 15.0 mg L-1, pH 7.0, current density 7.0 mA cm-2, and electrolysis time of 120 min. The Bi-PbO2, PbO2, and SnO2-Sb2O3 electrodes revealed the oxygen evolution potential of 2.089, 1.983, 1.914 V, and the service lifetime of 82, 144, and 323 h, respectively. The results showed that after 5.0 h of electrolysis, none of the heavy metals such as Bi, Pb, Sb, Sn, and Ti were detected in the treated solution.

A Colorimetric Sensor Enabled with Heterogeneous Nanozymes with Phosphatase-like Activity for the Residue Analysis of Methyl Parathion

In this study, a colorimetric sensor was developed for the detection of organophosphorus pesticides (OPs) using a heterogeneous nanozyme with phosphatase-like activity. Herein, this heterogeneous nanozyme (Au-pCeO2) was obtained by the modification of gold nanoparticles on porous cerium oxide nanorods, resulting in synergistic hydrolysis performance for OPs. Taking methyl parathion (MP) as the target pesticide, the catalytic performance and mechanism of Au-pCeO2 were investigated. Based on the phosphatase-like Au-pCeO2, a dual-mode colorimetric sensor for MP was put forward by the analysis of the hydrolysis product via a UV-visible spectrophotometer and a smartphone. Under optimum conditions, this dual-mode strategy can be used for the on-site analysis of MP with concentrations of 5 to 200 μM. Additionally, it can be applied for MP detection in pear and lettuce samples with recoveries ranging from 85.27% to 115.87% and relative standard deviations (RSDs) not exceeding 6.20%, which can provide a simple and convenient method for OP detection in agricultural products.

Advances in the synthesis and applications of 2D MXene-metal nanomaterials

MXenes, two-dimensional (2D) materials that consist of transition metal carbides, nitrides and/or carbonitrides, have recently attracted much attention in energy-related and biomedicine fields. These materials have substantial advantages over traditional carbon graphenes: they possess high conductivity, high strength, excellent chemical and mechanical stability, and superior hydrophilic properties. Furthermore, diverse functional groups such as -OH, -O, and -F located on the surface of MXenes aid the immobilization of numerous noble metal nanoparticles (NP). Therefore, 2D MXene composite materials have become an important and convenient option of being applied as support materials in many fields. In this review, the advances in the synthesis (including morphology studies, characterization, physicochemical properties) and applications of the currently known 2D MXene-metal (Pd, Ag, Au, and Cu) nanomaterials are summarized based on critical analysis of the literature in this field. Importantly, the current state of the art, challenges, and the potential for future research on broad applications of MXene-metal nanomaterials have been discussed.

Dual-ratiometric aptasensor for simultaneous detection of malathion and profenofos based on hairpin tetrahedral DNA nanostructures

Due to the diversification and complexity of organophosphorus pesticide residues brings great challenges to the detection work. Therefore, we developed a dual-ratiometric electrochemical aptasensor that could detect malathion (MAL) and profenofos (PRO) simultaneously. In this study, metal ions, hairpin-tetrahedral DNA nanostructures (HP-TDN) and nanocomposites were used as signal tracers, sensing framework and signal amplification strategy respectively to develop the aptasensor. Thionine (Thi) labeled HP-TDN (HP-TDNThi) provided specific binding sites for assembling Pb2+ labeled MAL aptamer (Pb2+-APT1) and Cd2+ labeled PRO aptamer (Cd2+-APT2). When the target pesticides were present, Pb2+-APT1 and Cd2+-APT2 were dissociated from the hairpin complementary strand of HP-TDNThi, resulting in reduced oxidation currents of Pb²⁺ (I_Pb²⁺) and Cd²⁺ (I_Cd²⁺), respectively, while the oxidation currents of Thi (I_Thi) remained unchanged. Thus, I_Pb²⁺/I_Thi and I_Cd²⁺/I_Thi oxidation current ratios were used to quantify MAL and PRO, respectively. In addition, the gold nanoparticles (AuNPs) encapsulated in the zeolitic imidazolate framework (ZIF-8) nanocomposites (Au@ZIF-8) greatly increased the catch of HP-TDN, thereby amplifying the detection signal. The rigid three-dimensional structure of HP-TDN could reduce the steric hindrance effect on the electrode surface, which could greatly improve the recognition efficiency of the aptasensor for the pesticide. Under the optimal conditions, the detection limits of the HP-TDN aptasensor for MAL and PRO were 4.3 pg mL-1 and 13.3 pg mL-1, respectively. Our work proposed a new approach to fabricating a high-performance aptasensor for simultaneous detection of multiple organophosphorus pesticides, opening a new avenue for the development of simultaneous detection sensors in the field of food safety and environmental monitoring.

Advancements in nanomaterial-based aptasensors for the detection of emerging organic pollutants in environmental and biological samples

The combination of nanomaterials (NMs) and aptamers into aptasensors enables highly specific and sensitive detection of diverse pollutants. The great potential of aptasensors is recognized for the detection of diverse emerging organic pollutants (EOPs) in different environmental and biological matrices. In addition to high sensitivity and selectivity, NM-based aptasensors have many other advantages such as portability, miniaturization, facile use, and affordability. This work showcases the recent advances achieved in the design and fabrication of NM-based aptasensors for monitoring EOPs (e.g., hormones, phenolic contaminants, pesticides, and pharmaceuticals). On the basis of their sensing mechanisms, the covered aptasensing systems are classified as electrochemical, colorimetric, PEC, fluorescence, SERS, and ECL. Special attention has been paid to the fabrication processes, analytical achievements, and sensing mechanisms of NM-based aptasensors. Further, the practical utility of aptasensing approaches has also been assessed based on their basic performance metrics (e.g., detection limits, sensing ranges, and response times).

Multiplex strategy electrochemical platform based on self-assembly dual-site DNA tetrahedral scaffold for one-step detection of diazinon and profenofos

In the work, based on self-assembly dual-site DNA tetrahedral scaffold (DTS), thionine (Thi), and 6-(Ferrocenyl)hexanethiol (Fc6S), a multiplex strategy electrochemical platform was fabricated for the simultaneous detection of profenofos (PFF) and diazinon (DZN). Thi and Fc6S were used to label aptamers for the synthesis of probes respectively. Notably, Thi and Fc6S engendered recognizable DPV peaks at different potentials to achieve simultaneous detection of PFF and DZN. In addition to increasing the conductivity of the electrode, the combination of carboxylic acid functionalized multi-walled carbon nanotubes and ferroferric oxide nanoparticles could also increase its higher specific surface area of the electrode interface to adsorb more DTS. Because of the mechanical rigidity of the DTS, the DTS could keep a complementary chain upright and provide more binding sites for aptamers, the binding efficiency between the complementary chain and 2 binding aptamers could be improved. Comparing the aptasensors performance of single-strand DNA with that of the DTS with complementary strands, the benefits of the DTS were highlighted in this system. Under optimal conditions, the detection limits of PFF and DZN were both 3.33 pg/mL and the detection ranges were both 1.00 × 10¹-1.00 × 10⁷ pg/mL. Meanwhile, the recoveries of PFF and DZN were 87.15%-117.34% and 91.20%-114.19%, respectively. The aptasensor could realize the simultaneous detection of PFF and DZN in vegetables. Furthermore, the aptasensor also had good stability and selectivity. This strategy could provide a good reference for developing effective aptasensors for the simultaneous detection of other small molecules and toxins.

Current electroanalytical approaches in the carbamates and dithiocarbamates determination

Pesticides are a suitable tool for controlling plagues and disease vectors. However, their inappropriate use allows for contamination of the environment, soil, water, and foods. Carbamates and dithiocarbamates pesticides present accumulative effects in the human body resulting in hormonal, neurological and reproductive disorders, and some are still suspected or proven to give carcinogenic or mutagenic effects. This review provides a current electroanalytical approach in the carbamates and dithiocarbamates determination, showing the use of voltammetric techniques such as amperometry, cyclic and linear scan, differential pulse, and square wave voltammetry, indicating their advantages, disadvantages, and perspectives in electroanalytical detection of carbamates and dithiocarbamates in natural water and foods. Also are reported the different materials used in the preparation of working electrodes since their choice has an important impact on the success of the analytical applications, resulting in suitable sensitivity, selectivity, stability, and robustness.

Sensitive electrochemical assay of acetaminophen based on 3D-hierarchical mesoporous carbon nanosheets

Acetaminophen plays a key role in first-line Covid-19 cure as a supportive therapy of fever and pain. However, overdose of acetaminophen may give rise to severe adverse events such as acute liver failure in individual. In this work, 3D-hierarchical mesoporous carbon nanosheet (hMCNS) microspheres with superior properties were fabricated using simple and quick strategy and applied for sensitive quantification of acetaminophen in pharmaceutical formulation and rat plasmas after administration. The hMCNS microspheres are prepared via chemical etching of zinc oxide (ZnO) nanoparticles from a zinc-gallic acid precursor composite (Zn-GA) synthesized by high-temperature anaerobic pyrolysis. The obtained hMCNS could enhance analytes accessibility and accelerate proton transfer in the interface, hence increasing the electrochemical performance. Under optimized experimental conditions, the proposed electrochemical sensor achieves a detection limit of 3.5 nM for acetaminophen. The prepared electrochemical sensor has been successfully applied for quantification of acetaminophen in pharmaceutical formulations and the rat plasma samples before and after administration. Meanwhile, this sensor is compared with high-performance liquid chromatography (HPLC) as a reference technology, showing an excellent accuracy. Such an electrochemical sensor has great potential and economic benefits for applications in the fields of pharmaceutical assay and therapeutic drug monitoring (TDM).

Using Nanomaterials as Excellent Immobilisation Layer for Biosensor Design

The endless development in nanotechnology has introduced new vitality in device fabrication including biosensor design for biomedical applications. With outstanding features like suitable biocompatibility, good electrical and thermal conductivity, wide surface area and catalytic activity, nanomaterials have been considered excellent and promising immobilisation candidates for the development of high-impact biosensors after they emerged. Owing to these reasons, the present review deals with the efficient use of nanomaterials as immobilisation candidates for biosensor fabrication. These include the implementation of carbon nanomaterials-graphene and its derivatives, carbon nanotubes, carbon nanoparticles, carbon nanodots-and MXenes, likewise their synergistic impact when merged with metal oxide nanomaterials. Furthermore, we also discuss the origin of the synthesis of some nanomaterials, the challenges associated with the use of those nanomaterials and the chemistry behind their incorporation with other materials for biosensor design. The last section covers the prospects for the development and application of the highlighted nanomaterials.

Simultaneous electrochemical degradation of pesticides from the aqueous environment using Ti/SnO2-Sb2O3/PbO2/Bi electrode; process modeling and mechanism insight

In this work, modified Bi-PbO₂ electrode was fabricated and employed for simultaneous degradation of fenitrothion (FT), trifluralin (TF), and chlorothalonil (CT) from synthetic and pesticide wastewater through the anodic oxidation process. A novel high-performance liquid chromatography method was developed and optimized to identify the pesticides simultaneously. Quadratic models were developed to investigate the effects of main operating parameters and predict the degradation efficiencies of the treatment processes. The R² of the degradation efficiencies were obtained of 0.9847, 0.9910, and 0.9821 for FT, TF, and CT, respectively, which indicates the degree of conformity between the experimental and the actual values of degradation efficiencies, and the adjusted R² values for the degradation efficiency of FT, TF, and CT in proposed models were 0.9826, 0.9898, and 0.9796, and the values of the predicted R² were 0.9792, 0.9875, and 0.9755, respectively. The maximum degradation efficiencies of 99.7, 100, and 100% obtained for FT, TF, and CT, respectively, under the optimal operating condition of FT, TF, and CT concentration of 10.0, 6.0, and 8.0 mg L^-1, respectively, pH 6.0, the current density 6.0 mA cm^-2, and electrolysis time of 60 min. Chemical oxygen demand removal and energy consumption were 64.7% and 5.1 kWh m^-3. Eventually, the generated intermediates and other produced species of pesticides through the treatment process was evaluated using a gas chromatography-mass spectrometry method, and their degradation pathways were proposed.

Biosensors Based on Acetylcholinesterase Immobilized on Clay-Gold Nanocomposites for the Discrimination of Chlorpyrifos and Carbaryl

This work aims at evaluating a utilization of diverse clay mineral/gold nanoparticles/acetylcholinesterase (clay/AuNPs/AChE) biosensors by using principal component analysis (PCA) for the discrimination of pesticide types and their concentration levels both in the synthetic and real samples. Applications of simple and low-cost clay/AuNP composites of different characteristics as modified-electrode materials are highlighted. Four types of clay minerals, namely, platelike kaolinite (Kaol: 1:1 aluminum phyllosilicate), globular montmorillonite (Mt: 2:1 aluminum phyllosilicate), globular bentonite (Bent: 2:1 aluminum phyllosilicate), and fibrous sepiolite (Sep: 2:1 inverted ribbons of magnesium phyllosilicate), were selected as the base materials. Due to the distinct characteristics of the selected clay, the derived clay/AuNP composites resulted in different physical morphologies, AuNP sizes and loadings, matrix hydrophobicity, and active AChE loading per electrode. These, in turn, caused divergent electrochemical responses for the pesticide determination; hence, no other enzymes apart from AChE were necessary for the fabrication of distinct biosensors. Physical and chemical characterizations of clay/AuNPs were conducted using scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy techniques. The electrochemical information was recorded by cyclic voltammetry and amperometry techniques. The enzyme inhibition results obtained from the pesticides were treated and used as input data to obtain PCA results. The four fabricated clay/AuNPs/AChE biosensors were able to discriminate chlorpyrifos and carbaryl and their concentration levels for synthetic pesticides and real samples. It was disclosed that a high enzyme inhibition and a high hydrophobic modified-electrode material affect a highly sensitive pesticide biosensor. The hydrophobic/hydrophilic character of the modified-electrode material plays a major role in discriminating the pesticide types and their concentration levels by the proposed single-enzyme sensor system. The PCA results illustrated that PC2 described the different types of pesticides, and PC1 showed the level of pesticide concentration with high first two principal components. The mixed pesticides could be identified at an especially low total concentration of 0.5 ng/mL in real samples.

Ultrasensitive electrochemiluminescence aptasensor based on ABEI reduced silver nanoparticles for the detection of profenofos

An ultrasensitive electrochemiluminescence (ECL) aptasensor for detection of profenofos was constructed by the reducibility and chemiluminescence property of N-(aminobutyl)-N-(ethylisoluminol) (ABEI). ABEI was used to reduce silver nitrate (AgNO₃) to silver nanoparticles (AgNPs), which could be adsorbed on the lattice of graphene oxide (GO) to form ABEI-AgNPs-GO complex. This compound could achieve excellent luminescence. The aptamer (Apt) modified (5') by sulfhydryl groups could be immobilized on AgNPs to capture profenofos. When profenofos was present, the ECL signal of the aptasensor would be weakened. To further demonstrate the successful construction of the aptasensor, cyclic voltammetry tests were performed on an electrochemical workstation and an ECL analyzer, respectively. The standard curve and specificity experiment both showed that the sensor had the advantages of low limit of detection (LOD) and good specificity. Under the optimal conditions, the aptasensor had a good linear response for profenofos in the range of 1 × 10^-1-1 × 10⁴ ng/mL. It also had a LOD of 6.7 × 10^-2 ng/mL and a correlation coefficient (R²) of 0.9991. The aptasensor had been successfully applied to the detection of profenofos in vegetables. The recovery range of the proposed ECL aptasensor was 98 % ~ 107.4 %.

Ternary heterostructures of 1D/2D/2D CuCo2S4/CuS/Ti3C2 MXene: Boosted amperometric sensing for chlorpyrifos

Multicomponent heterogeneous Ti₃C₂ transition metal carbide (MXene)-based materials are receiving extensive research attention due to their interesting synergistic interactions and catalytic properties. However, the morphology-controllable synthesis of heterostructures as structural stabilizers for Ti₃C₂ MXene remains a challenge owing the complicated synthesis procedure. In this work, a kind of ternary heterogeneous nanomaterials CuCo₂S₄/CuS/Ti₃C₂ MXene with a nanorod/nanoplate/nanosheet hybrid architecture is constructed through a one-step low-temperature solvothermal method. The well-designed ternary one-dimensional (1D)/two-dimensional (2D)/2D CuCo₂S₄/CuS/Ti₃C₂ MXene heteromaterials exhibit synergistic improvements in substrate-catalyzed reactions for electrochemical acetylcholinesterase (AChE) biosensor. The Michaelis-Menten constant for the Nafion/AChE/CuCo₂S₄/CuS/Ti₃C₂ MXene/GCE biosensor is 228 μM, which is smaller than ones reported in previous literatures, indicating a higher affinity of the fabricated enzyme biosensor to acetylthiocholine chloride. The biosensor exhibits a well linear relationship with chlorpyrifos concentration ranging from 2.852 × 10^-12 M to 2.852 × 10^-6 M. The multicomponent 1D/2D/2D CuCo₂S₄/CuS/Ti₃C₂ MXene heteromaterial may shine a light in more electrochemical applications.

Fluorescence Assay for Detecting Four Organophosphorus Pesticides Using Fluorescently Labeled Aptamer

In this work, we reported a rapid and sensitive fluorescence assay in homogenous solution for detecting organophosphorus pesticides by using tetramethylrhodamine (TAMRA)-labeled aptamer and its complementary DNA (cDNA) with extended guanine (G) bases. The hybridization of cDNA and aptamer drew TAMRA close to repeated G bases, then the fluorescence of TAMRA was quenched by G bases due to the photoinduced electron transfer (PET). Upon introducing the pesticide target, the aptamer bound to pesticide instead of cDNA because of the competition between pesticide and cDNA. Thus, the TAMRA departed from G bases, resulting in fluorescence recovery of TAMRA. Under optimal conditions, the limits of detection for phorate, profenofos, isocarbophos, and omethoate were 0.333, 0.167, 0.267, and 0.333 µg/L, respectively. The method was also used in the analysis of profenofos in vegetables. Our fluorescence design was simple, rapid, and highly sensitive, which provided a means for monitoring the safety of agricultural products.

Enhanced Optical Biosensing by Aerotaxy Ga(As)P Nanowire Platforms Suitable for Scalable Production

Sensitive detection of low-abundance biomolecules is central for diagnostic applications. Semiconductor nanowires can be designed to enhance the fluorescence signal from surface-bound molecules, prospectively improving the limit of optical detection. However, to achieve the desired control of physical dimensions and material properties, one currently uses relatively expensive substrates and slow epitaxy techniques. An alternative approach is aerotaxy, a high-throughput and substrate-free production technique for high-quality semiconductor nanowires. Here, we compare the optical sensing performance of custom-grown aerotaxy-produced Ga(As)P nanowires vertically aligned on a polymer substrate to GaP nanowires batch-produced by epitaxy on GaP substrates. We find that signal enhancement by individual aerotaxy nanowires is comparable to that from epitaxy nanowires and present evidence of single-molecule detection. Platforms based on both types of nanowires show substantially higher normalized-to-blank signal intensity than planar glass surfaces, with the epitaxy platforms performing somewhat better, owing to a higher density of nanowires. With further optimization, aerotaxy nanowires thus offer a pathway to scalable, low-cost production of highly sensitive nanowire-based platforms for optical biosensing applications.

Two-Dimensional Cobalt-Doped Ti3C2 MXene Nanozyme-Mediated Homogeneous Electrochemical Strategy for Pesticides Assay Based on In Situ Generation of Electroactive Substances

Common homogeneous electrochemical (HEC) sensors usually suffer from the drawbacks of high background signal, low signal-to-noise ratio, and even false positive results due to the preaddition of electroactive substances. Thus, it is necessary to develop novel HEC sensors based on in situ generation of electroactive substances to overcome these shortcomings, which, however, is underexplored. In this work, two-dimensional (2D) nanozymes, i.e., cobalt-doped 2D Ti₃C₂ MXene nanosheets (CMNSs), with excellent peroxidase-like properties were utilized to develop HEC sensors based on the in situ generation of electroactive substances for organophosphate pesticides (OPs) detection. The 2D CMNSs were synthesized via a template-directed wet chemical approach and displayed outstanding features of hydrophilia and water dispersibility, which could catalyze the oxidation of o-phenylenediamine (OPD) to generate significantly increased reduction current. Interestingly, the 2D CMNSs with peroxidase-like properties exhibited a unique response to thiol compounds and were thus employed as highly efficient catalysts to develop HEC sensors for OPs based on the hydrolysis of acetylthiocholine (ATCh) to form thiocholine catalyzed by acetylcholinesterase (AChE) and the inhibition of AChE activity by OPs. The recovery for OPs analysis of pakchoi extract solutions ranged from 97.4% to 103.3%. The as-proposed HEC sensor based on in situ generation of electroactive substances will provide a new way for the development of high-performance electrochemical sensors and demonstrate potential applicability for the determination of pesticide residues in real samples.

A novel label-free electrochemiluminescence aptasensor using a tetrahedral DNA nanostructure as a scaffold for ultrasensitive detection of organophosphorus pesticides in a luminol-H2O2 system

In this work, a new type of Au-tetrahedral DNA nanostructure (Au-TDN) was originally proposed and successfully applied in an electrochemiluminescence aptasensor to detect organophosphorus pesticides (Ops). The aptamers modified with -SH could be covalently bonded with gold nanoparticles (AuNPs) to form a tetrahedron structure, and there were independent probes at each vertex of the tetrahedron, which could increase the probability of specific binding with Ops. The originally designed structure could not only maintain a stable tetrahedral configuration, but also combined with the target to improve the sensitivity of the sensor. Meanwhile, silver nanoparticles (AgNPs) could catalyze the chemical reaction between luminol and H₂O₂ to generate a variety of intermediates called reactive oxygen species (ROS) for signal enhancement. Factors that had important influences on the aptasensor, such as the concentration of Au-TDN, the incubation time, and the pH value of the buffer, were optimized in this trial. According to the final results, the limit of detection (LOD) of 3 pg mL^-1 (S/N = 3) for methyl parathion, the LOD of 0.3 pg mL^-1 (S/N = 3) for parathion and the LOD of 0.03 pg mL^-1 (S/N = 3) for phoxim were obtained, respectively. Moreover, the novel tetrahedral structure could be replaced by different types of aptamers to expand its application range and lay a foundation for the development of portable rapid detection devices for pesticide residues.

Dual-mode fluorescence and colorimetric detection of pesticides realized by integrating stimulus-responsive luminescence with oxidase-mimetic activity into cerium-based coordination polymer nanoparticles

The great threat of pesticide residues to the environment and human health has drawn widespread interest to explore approaches for pesticide monitoring. Compared to commonly developed single-signal pesticide assays, multi-mode detection with inherent self-validation and self-correction is expected to offer more reliable and anti-interference results. However, how to realize multi-mode analysis of pesticides still remains challenging. Herein, we propose a dual-mode fluorescence and colorimetric method for pesticide determination by integrating stimulus-responsive luminescence with oxidase-mimetic activity into cerium-based coordination polymer nanoparticles (CPNs(Ⅳ)). The CPNs(Ⅳ) exhibit good oxidase-like activity of catalyzing the colorless 3,3',5,5'-tetramethylbenzidine (TMB) oxidation to its blue oxide, offering a visible color signal; by employing acid phosphatase (ACP) to hydrolyze ascorbic acid 2-phosphate (AAP), the generated ascorbic acid (AA) can chemically reduce the CPNs(Ⅳ) to CPNs(Ⅲ), which exhibit a remarkable fluorescence signal but lose the oxidase-mimicking ability to trigger the TMB chromogenic reaction; when pesticides exist, the enzymatic activity of ACP is restrained and the hydrolysis of AAP to AA is blocked, leading to the recovery of the catalytic TMB chromogenic reaction but the suppression of the fluorescence signal of CPNs(Ⅲ). According to this principle, by taking malathion as a pesticide model, dual-mode 'off-on-off' fluorescence and 'on-off-on' colorimetric detection of the pesticide with good sensitivity was realized. Excellent interference-tolerance and reliability were verified by applying it to analyze the target in real sample matrices. With good performance and practicability, the proposed dual-mode approach shows great potential in the facile and reliable monitoring of pesticide residues.

Recent advances in synthesis and modification of carbon dots for optical sensing of pesticides

Serious threat from pesticide residues to the ecosystem and human health has become a global concern. Developing reliable methods for monitoring pesticides is a world-wide research hotspot. Carbon dots (CDs) with excellent photostability, low toxicity, and good biocompatibility have been regarded as the potential substitutes in fabricating various optical sensors for pesticide detection. Based on the relevant high-quality publications, this paper first summarizes the current state-of-the-art of the synthetic and modification approaches of CDs. Then, a comprehensive overview is given on the recent advances of CDs-based optical sensors for pesticides over the past five years, with a particular focus on photoluminescent, electrochemiluminescent and colorimetric sensors regarding the sensing mechanisms and design principles by integrating with various recognition elements including antibodies, aptamers, enzymes, molecularly imprinted polymers, and some nanoparticles. Novel functions and extended applications of CDs as signal indicators, catalyst, co-reactants, and electrode surface modifiers, in constructing optical sensors are specially highlighted. Beyond an assessment of the performances of the real-world application of these proposed optical sensors, the existing inadequacies and current challenges, as well as future perspectives for pesticide monitoring are discussed in detail. It is hoped to provide powerful insights for the development of novel CDs-based sensing strategies with their wide application in different fields for pesticide supervision.

Carbon Nanomaterial-Based Drug Sensing Platforms Using State-of-the- Art Electroanalytical Techniques

Background:

Currently, nanotechnology and nanomaterials are considered as the most popular and outstanding research subjects in scientific fields ranging from environmental studies to drug analysis. Carbon nanomaterials such as carbon nanotubes, graphene, carbon nanofibers etc. and non-carbon nanomaterials such as quantum dots, metal nanoparticles, nanorods etc. are widely used in electrochemical drug analysis for sensor development. Main aim of drug analysis with sensors is developing fast, easy to use and sensitive methods. Electroanalytical techniques such as voltammetry, potentiometry, amperometry etc. which measure electrical parameters such as current or potential in an electrochemical cell are considered economical, highly sensitive and versatile techniques.

Methods:

Most recent researches and studies about electrochemical analysis of drugs with carbon-based nanomaterials were analyzed. Books and review articles about this topic were reviewed.

Results:

The most significant carbon-based nanomaterials and electroanalytical techniques were explained in detail. In addition to this; recent applications of electrochemical techniques with carbon nanomaterials in drug analysis was expressed comprehensively. Recent researches about electrochemical applications of carbon-based nanomaterials in drug sensing were given in a table.

Conclusion:

Nanotechnology provides opportunities to create functional materials, devices and systems using nanomaterials with advantageous features such as high surface area, improved electrode kinetics and higher catalytic activity. Electrochemistry is widely used in drug analysis for pharmaceutical and medical purposes. Carbon nanomaterials based electrochemical sensors are one of the most preferred methods for drug analysis with high sensitivity, low cost and rapid detection.

Recent advances and perspectives of enzyme-based optical biosensing for organophosphorus pesticides detection

The overuse or abuse of organophosphorus pesticides (OPs) can bring about severe contamination problems in foodstuff and the environment, which will seriously threaten human health and the ecosystem's cycle. Hence, it is in high demand to establish sensitive, portable, specific, and cost-effective methods for monitoring OPs to control food safety, protect the ecosystem, and prevent disease. The optical biosensor with enzyme as bio-recognition elements has been an effective alternative for OPs detection. Herein, we firstly introduce various enzymes, sensing mechanisms, advantages and disadvantages used as bio-recognition elements in optical sensing for OPs detection. Then, we review various optical biosensing strategies based on enzymes as recognition elements that were ingeniously designed and successfully utilized for OPs detection, with a particular emphasis on photoluminescence (PL), chemiluminescence (CL), electrochemiluminescence (ECL), and colorimetric (CM) biosensing strategies. We not only highlight the state-of-art developments and the construction strategies of the enzyme-based optical biosensing method but also summarize the existing deficiencies, current challenges, and the future perspectives of OPs detection.

A novel electrochemiluminescence aptasensor based on copper-gold bimetallic nanoparticles and its applications

In this work, a novel electrochemiluminescence (ECL) aptasensor was structured for the detection of four organophosphorus pesticides (OPs). Firstly, multi-walled carbon nanotubes (MWCNTs) were used to create a favorable loading interface for the fixation of tris (2, 2'-bipyridyl) ruthenium (II) (Ru (bpy)₃²⁺). At the same time, copper (core)-gold (shell) bimetallic nanoparticles (Cu@Au NPs) were synthesized in the aqueous phase for the sensor construction. Gold nanoparticles (Au NPs) could promote the electrochemiluminescence intensity of Ru (bpy)₃²⁺ with high efficiency by catalyzing the oxidation process of tri-n-propylamine (TPrA). Compared with the Au NPs, Cu@Au NPs increased the solid loading of Au NPs by virtue of the large specific surface area of copper nanoparticles (Cu NPs), which could further improve the sensitivity of aptasensor. When OPs were added, the ECL intensity was significantly reduced, and the concentration of OPs could be detected through the ECL intensity. Under the optimum conditions, the aptasensor had a wider dynamic range and ultra-low detection limit for the detection of four pesticides: profenofos, isocarbophos, phorate, and omethoate, and their detection limits were 3 × 10^-4 ng/mL, 3 × 10^-4 ng/mL, 3 × 10^-3 ng/mL, and 3 × 10^-2 ng/mL respectively (S/N = 3). The aptasensor had the merits of good stability, reproducibility, and specificity, and had a favorable recovery rate in detecting OPs residues in vegetables. This work provided an effective method for the construction of a simple, rapid, and sensitive biosensor.

Ligand-protected nanoclusters and their role in agriculture, sensing and allied applications

Nano biotechnology, when coupled with green chemistry, can revolutionize human life because of the vast opportunities and benefits it can offer to the quality of human life. Luminescent metal nanoclusters (NCs) have recently developed as a potential research area with applications in different areas like medical, imaging, sensing etc. Recently these new candidates have proved to be beneficial in the food supply chain enabling controlled release of nutrients, pesticides and as nanosensors for the detection of contaminants and play roles in healthy food storage and maintaining food quality. An assortment of nanomaterials has been employed for these applications and reviews have been published on the use of nanotechnology in agriculture. Ligand-protected metal nanoclusters are a distinctive class of small organic-inorganic nanostructures that garnered immense research interest in recent years owing to their stability at specific "magic size" compositions along with tunable properties that make them promising candidates for a wide range of nanotechnology-based applications. This review tries to consolidate the recent developments in the area of ligand-protected nanoclusters in connection with the detection of pesticides, food contaminants, heavy metal ions and plant growth monitoring for healthy agricultural practices. Its antimicrobial activity to manage the microbial contamination is highlighted. The review also throws light on the various perspectives by which food production and allied areas will be transformed in future.

Nanozyme-Participated Biosensing of Pesticides and Cholinesterases: A Critical Review

To improve the output and quality of agricultural products, pesticides are globally utilized as an efficient tool to protect crops from insects. However, given that most pesticides used are difficult to decompose, they inevitably remain in agricultural products and are further enriched into food chains and ecosystems, posing great threats to human health and the environment. Thus, developing efficient methods and tools to monitor pesticide residues and related biomarkers (acetylcholinesterase and butylcholinesterase) became quite significant. With the advantages of excellent stability, tailorable catalytic performance, low cost, and easy mass production, nanomaterials with enzyme-like properties (nanozymes) are extensively utilized in fields ranging from biomedicine to environmental remediation. Especially, with the catalytic nature to offer amplified signals for highly sensitive detection, nanozymes were finding potential applications in the sensing of various analytes, including pesticides and their biomarkers. To highlight the progress in this field, here the sensing principles of pesticides and cholinesterases based on nanozyme catalysis are definitively summarized, and emerging detection methods and technologies with the participation of nanozymes are critically discussed. Importantly, typical examples are introduced to reveal the promising use of nanozymes. Also, some challenges in the field and future trends are proposed, with the hope of inspiring more efforts to advance nanozyme-involved sensors for pesticides and cholinesterases.