Electrochemical Detection of Atrazine by Platinum Nanoparticles/Carbon Nitride Nanotubes with Molecularly Imprinted Polymer

Rapid Determination of 15 Herbicides in Blood and Soil by Direct Analysis in Real Time-Tandem Mass Spectrometry

RATIONALE

The rampant abuse of herbicides in agricultural practices has resulted in frequent incidents of both unintended and deliberate poisoning, posing dual threats to ecosystems and human health. This underscores an urgent need for efficient herbicide detection methods.

METHODS

A direct analysis in real time coupled with tandem mass spectrometry (DART-MS/MS) method was developed for the simultaneous detection of 15 herbicides in blood and soil. Systematic optimization of mass spectrometric parameters established optimal detection conditions in multiple reaction monitoring (MRM) mode, with the ion source temperature set at 450°C. Following liquid-liquid extraction of blood or soil samples, the processed supernatant was analyzed directly.

RESULTS

The method demonstrated excellent linearity (R² ≥ 0.99) across a wide concentration range. Sensitivity was validated with limits of detection (LODs) of 1-20 ng/mL in blood and 1-10 ng/g in soil, and limits of quantification (LOQs) of 1-50 ng/mL in blood and 1-20 ng/g in soil. Satisfactory recovery rates and controlled matrix effects met toxicological requirements. In 2024, the method was successfully applied to four real cases of herbicide poisoning.

CONCLUSIONS

This study established the first DART-MS/MS method for simultaneous analysis of 15 herbicides in biological (blood) and environmental (soil) matrices. The complete analytical workflow required only 20 minutes from sample preparation to detection, significantly advancing forensic applications of DART-MS/MSwhile providing a reliable technical solution for herbicide screening in forensic investigations.

A Comparative Analysis of Optical Biosensors for Rapid Detection of SARS-CoV-2 and Influenza

Airborne pathogens, such as influenza and SARS-CoV-2, pose significant health risks. While traditional diagnostic methods have limitations, optical biosensors offer a promising solution due to their rapid, sensitive, and cost-effective nature. This review focuses on the application of optical biosensors, including colorimetry, surface plasmon resonance, surface-enhanced Raman spectroscopy, and fluorescence techniques, for the detection of influenza and SARS-CoV-2. We discuss the advantages of these techniques, such as their potential for point-of-care testing and early disease detection. By addressing the limitations of existing methods and exploring emerging technologies, optical biosensors can play a crucial role in combating the spread of airborne pathogens. This review provides a comprehensive overview of optical biosensor techniques for the detection of both SARS-CoV-2 and influenza, addressing a significant gap in the literature.

Low-tech innovation: biomimetic solid-contact potentiometric sensor for nanomolar-level atrazine detection

Despite the fact that there are already a number of solid-contact-based ion-selective electrodes designed for atrazine detection, our ground-breaking contribution lies in introducing the first-ever atrazine potentioselectrode, enabling the ultra-sensitive detection of atrazine at nanomolar levels. Solid-contact ion-selective electrodes can offer advantages, such as improved stability, reproducibility, sensitivity, and selectivity compared to their liquid-contact counterparts. Here, a biomimetic potentiometric sensor for Atrazine was developed using economic, light weight, and flexible carbon cloth as solid-contact material. Our methodology entails the synthesis of a molecularly imprinted polymer (MIP) through straightforward precipitation polymerization, showcasing a streamlined and efficient method for creating highly specific molecular recognition elements. The validation of template removal is confirmed via meticulous analysis employing EDX and FTIR techniques, ensuring the efficacy of our methodology. The resulting sensing membrane are casted by dispersing the MIP in 2-nitrophenyl octyl ether plasticizer and embedding it within a PVC matrix containing sodium tetraphenyl borate as a lipophilic additive. The developed sensor responds to atrazine in the pH range of 2.8-3.3 over a wide concentration range of 1 × 10-8 M to 1 × 10-5 M & 1 × 10-5 M to 1 × 10-1 M with respective slopes of 29.2 mv & 58.7 mV and a limit of detection of 1 × 10-9 M. An impressive feature of this sensor lies in its swift response time, registering a rapid reaction within a mere 10 s. Emphasize the sensor's commendable attributes of reproducibility, selectivity, and sensitivity underscoring its successful application in field monitoring.

Graphitic carbon nitride-based electrochemical sensors: A comprehensive review of their synthesis, characterization, and applications

Graphitic carbon nitride (g-C3N4) has garnered much attention as a promising 2D material in the realm of electrochemical sensors. It contains a polymeric matrix that can serve as an economical and non-toxic electrode material for the detection of a diverse range of analytes. However, its performance is impeded by a relatively limited active surface area and inherent instability. Although electrochemistry involving metal-doped g-C3N4 nanomaterials is rapidly progressing, it remains relatively unexplored. The metal doping of g-C3N4 augments the electrochemically active surface area of the resulting electrode, which has the potential to significantly enhance electrode kinetics and bolster catalytic activity. Consequentially, the main objective of this review is to provide insight into the intricacies of synthesizing and characterizing metal-doped g-C3N4. Furthermore, we comprehensively delve into the fundamental attributes of electrochemical sensors based on metal-doped g-C3N4, with a specific focus on healthcare and environmental applications. These applications encompass a meticulous exploration of detecting biomolecules, drug molecules, and organic pollutants.

Unveiling carcinogenic pollutant levels in environmental water samples through facile fabrication of gold nanoparticles on sulfur-doped graphitic carbon nitride

Extensive utilization of pesticides and herbicides to boost agricultural production increased the environmental health risks, which can be mitigate with the aid of highly sensitive detection systems. In this study, an electrochemical sensor for monitoring the carcinogenic pesticides in the environmental samples has been developed based on sulfur-doped graphitic-carbon nitride-gold nanoparticles (SCN-AuNPs) nanohybrid. Thermal polycondensation of melamine with thiourea followed by solvent exfoliation via ultrasonication leads to SCN formation and electroless deposition of AuNPs on SCN leads to SCN-AuNPs nanohybrid synthesis. The chemical composition, S-doping, and the morphology of the nanohybrid were confirmed by various microscopic and spectroscopic tools. The as-synthesized nanohybrid was fabricated with glassy carbon (GC) electrode for determining the carcinogenic hydrazine (HZ) and atrazine (ATZ) in field water samples. The present sensor exhibited superior electrocatalytic activity than GC/SCN and GC/AuNPs electrodes due to the synergism between SCN and AuNPs and the amperometric studies showed the good linear range of detection of 20 nM-0.5 mM and 500 nM-0.5 mM with the limit of detection of 0.22 and 69 nM (S/N = 3) and excellent sensitivity of 1173.5 and 13.96 μA mM-1 cm-2 towards HZ and ATZ, respectively. Ultimately, the present sensor is exploited in environmental samples for monitoring HZ and ATZ and the obtained results are validated with high-performance liquid chromatography (HPLC) technique. The excellent recovery percentage and close agreement with the results of HPLC analysis proved the practicability of the present sensor. In addition, the as-prepared materials were utilized for the photocatalytic degradation of ATZ and the SCN-AuNPs nanohybrid exhibited higher photocatalytic activity with the removal efficiency of 93.6% at 90 min. Finally, the degradation mechanism was investigated and discussed.

Internet-of-things-integrated molecularly imprinted polymer-based electrochemical nano-sensors for pesticide detection in the environment and food products

To ensure environmental and health safety, relevant pollutants such as pesticides must be screened thoroughly to set their permissible limit. Various approaches have been used to identify pesticides such as capillary electrophoresis, gas and liquid-liquid chromatography, high-performance liquid chromatography, and enzyme-linked immune-absorbent tests. However, these techniques have some drawbacks, including time-consuming difficult steps, expensive bulky equipment, expert personnel, and a lack of selectivity. Recent advances in the field of biosensing have introduced biosensors for the onsite detection of pesticides which offer several advantages including rapid, simple, selective, sensitive, low-cost operation, and on-site detection. With the advent of molecularly imprinted polymer which substituted the traditional biorecognition elements (BREs) such as enzymes and antibodies, biosensors' sensitivity, selectivity, and reproducibility enhanced many folds. Molecularly imprinted polymers (MIP) are artificial polymer molecules that resemble natural BREs. They are synthesized when functional monomers are polymerized in the presence of a target analyte. Owing to the advantages of MIP, in this paper, the development of MIP-based electrochemical biosensors for pesticide detection is reviewed critically. A brief introduction to pesticides and the use of MIPs-based electrochemical sensors for pesticide detection is presented along with pros and cons. Further, Internet of Things (IoT) integrated MIP-based nanosensors for pesticide detection and information distribution have been discussed. In the end, future perspectives and challenges while implementing MIP-based nanosensors for onsite pesticide recognition have eventually been highlighted.

Progress on Electrochemical Biomimetic Nanosensors for the Detection and Monitoring of Mycotoxins and Pesticides

Monitoring agricultural toxins such as mycotoxins is crucial for a healthy society. High concentrations of these toxins lead to the cause of several chronic diseases; therefore, developing analytical systems for detecting/monitoring agricultural toxins is essential. These toxins are found in crops such as vegetables, fruits, food, and beverage products. Currently, screening of these toxins is mostly performed with sophisticated instrumentation such as chromatography and spectroscopy techniques. However, these techniques are very expensive and require extensive maintenance, and their availability is limited to metro cities only. Alternatively, electrochemical biomimetic sensing methodologies have progressed hugely during the last decade due to their unique advantages like point-of-care sensing, miniaturized instrumentations, and mobile/personalized monitoring systems. Specifically, affinity-based sensing strategies including immunosensors, aptasensors, and molecular imprinted polymers offer tremendous sensitivity, selectivity, and stability to the sensing system. The current review discusses the principal mechanisms and the recent developments in affinity-based sensing methodologies for the detection and continuous monitoring of mycotoxins and pesticides. The core discussion has mainly focused on the fabrication protocols, advantages, and disadvantages of affinity-based sensing systems and different exploited electrochemical transduction techniques.

Bio-engineered sensing of Atrazine by green CdS quantum dots: Evidence from electrochemical studies and DFT simulations

The present investigation reports a comprehensible and responsive strategy for identifying atrazine in several conditions using an extensive electrochemical method. CdS Quantum dots were synthesized via a greener approach, and their formation was endorsed by numerous characterization techniques such as FTIR, SEM, Raman, UV-Vis, and XRD. Owing to the splendid electrocatalytic behavior, Green CdS quantum dots (QDs) of crystallite size ∼2 nm was opted as the sensor material and were, therefore, incorporated on the bare carbon paste electrode's surface. The developed sensor demonstrated an impressive outcome for atrazine sensing accompanied by superior selectivity and sensitivity. The lower detection limit (LLOD) of 0.53 μM was attained using the developed sensor in a linear concentration range of 10-100 μM. Furthermore, the practical pertinence of the developed sensor was examined on distilled water, wastewater, and fresh liquid milk, resulting in a tremendous retrieval of atrazine (91.33-99.8%).

Exploring the potential of molecularly imprinted polymers and metal/metal oxide nanoparticles in sensors: recent advancements and prospects

Metal/metal oxide nanoparticles have gained increasing attention in recent years due to their outstanding features, including optical and catalytic properties, as well as their excellent conductivity. The implementation of metal/metal oxide nanoparticles, combined with molecularly imprinted polymers (MIPs) has paved the way for a new generation of building blocks to engineer and enhance the fascinating features of advanced sensors. This review critically evaluates the impact of combining metal/metal oxide nanoparticles with MIPs in sensors. It covers synthesis strategies, advantages of coupling these materials with MIPs, and addresses questions about the selectivity of these hybrid materials. In the end, the current challenges and future perspectives of this field are discussed, with a particular focus on the potential applications of these hybrid composites in the sensor field. This review highlights the exciting opportunities of using metal/metal oxide nanoparticles along with MIPs for the development of next-generation sensors.

Alternative methods of monitoring emerging contaminants in water: a review

Anthropogenic activities have steadily increased the release of emerging contaminants (ECs) in aquatic bodies, and these ECs may have adverse effects on humans even at their trace (μg L^-1) levels. Their occurrence in wastewater systems is more common, and the current wastewater treatment facilities are inefficient in eliminating many of such persistent ECs. "Gold standard" techniques such as chromatography, mass spectrometry, and other high-resolution mass spectrometers are used for the quantification of ECs of various kinds, but they all have significant limitations. This paper reviews the alternative methods for EC detection, which include voltammetry, potentiometry, amperometry, electrochemical impedance spectroscopy (EIS) based electrochemical methods, colorimetry, surface-enhanced Raman spectroscopy (SERS), fluorescence probes, and fluorescence spectroscopy-based optical techniques. These alternative techniques have several advantages over conventional techniques, including low sample volume, excludes solid phase extraction procedure, high sensitivity, selectivity, portability, reproducibility, rapidity, low cost, and the ability to monitor ECs in real time. This review summarises each of the alternative methods for detecting ECs in water samples and their respective limits of detection (LODs). The sensitivity of each technique varied depending on the type of EC measured, type of electrochemical probe and electrode, substrates, type of nanoparticle (NP), the physicochemical parameters of water samples tested, and more. Nevertheless, this paper also focuses on some of the current challenges encountered by these alternative methods in monitoring ECs.

Preparation of porous carbon-based molecularly imprinted polymers for separation of triazine herbicides in corn

A synthesis route of using cellulose as the precursor to prepare porous carbon (PC) had been established in this study. The as-prepared PC was introduced as carriers in the synthesis process of porous carbon-molecularly imprinted polymers (PC-MIPs), which greatly improved the absorption capacity of MIPs. Triazine pesticides in corn were extracted with matrix solid-phase dispersion (MSPD) using the PC-MIPs as dispersants and determined by ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Under the optimal MSPD condition for extracting six kinds of triazines (simazine, terbutryn, simetryne, prometryne, ametryn, and atrazine), the detection limits were 0.005-0.02 ng g^-1, while the precisions were 1.2-5.9%, and the recoveries were 92.6-104.7%. The method has been extensively applied to analyze various corn samples. Atrazine residue (1.2 μg kg^-1) was detected in one corn sample, which was lower than the maximum residual limit indicated by the Chinese stated standards (50 μg kg^-1).

Impedimetric Sensors for Cyclocreatine Phosphate Determination in Plasma Based on Electropolymerized Poly(o-phenylenediamine) Molecularly Imprinted Polymers

Cyclocreatine and its water-soluble derivative, cyclocreatine phosphate (CCrP), are potent cardioprotective drugs. Based on recent animal studies, CCrP, FDA-awarded Orphan Drug Designation, has a promising role in increasing the success rate of patients undergoing heart transplantation surgery by preserving donor hearts during transportation and improving the recovery of transplanted hearts in recipient patients. In addition, CCrP is under investigation as a promising treatment for creatine transporter deficiency, an X-linked inborn error resulting in a poor quality of life for both the patients and the caregiver. A newly designed molecularly imprinted polymer (MIP) material was fabricated by the anodic electropolymerization of o-phenylenediamine on screen-printed carbon electrodes and was successfully applied as an impedimetric sensor for CCrP determination to dramatically reduce the analysis time during both the clinical trial phases and drug development process. To enhance the overall performance of the proposed sensor, studies were performed to optimize the electropolymerization conditions, incubation time, and pH of the background electrolyte. Scanning electron microscopy, electrochemical impedance spectroscopy, and cyclic voltammetry were used to characterize the behavior of the developed ultrathin MIP membrane. The CCrP-imprinted polymer has a high recognition affinity for the template molecule because of the formation of 3D complementary cavities within the polymer. The developed MIP impedimetric sensor had good linearity, repeatability, reproducibility, and stability within the linear concentration range of 1 × 10^-9 to 1 × 10^-7 mol/L, with a low limit of detection down to 2.47 × 10^-10 mol/L. To verify the applicability of the proposed sensor, it was used to quantify CCrP in spiked plasma samples.

A sensitive sensor based on molecularly imprinted polypyrrole on reduced graphene oxide modified glassy carbon electrode for nevirapine analysis

A molecularly imprinted polymer (MIP) sensor was offered for nevirapine (NVP) analysis based on the electropolymerization of pyrrole (Py) on electrochemically reduced graphene oxide (ErGO) immobilized on a glassy carbon electrode (GCE). Electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and atomic force microscope (AFM) were applied to characterize the proposed sensor (MIP/ErGO/GCE). The electrochemical operation of this sensor for NVP analysis was tested using differential pulse voltammetry (DPV) and cyclic voltammetry (CV) methods in an alkaline medium. The prepared MIP/ErGO/GCE exhibited better analytical performance than other modified electrodes toward NVP detection. The offered sensor depicted a linearity range between 0.005 µM and 400 µM with a limit of detection (LOD) of 2 nM under optimal conditions. Notably, the offered sensor illustrated excellent selectivity, good reproducibility, acceptable repeatability, and reliable long-term performance. These experiments depicted the constructed sensor as a favorable and good sensing element towards NVP monitoring in pharmaceutical and serum samples.

Dummy Molecularly Imprinted Polymers Using DNP as a Template Molecule for Explosive Sensing and Nitroaromatic Compound Discrimination

This work reports a rapid, simple and low-cost voltammetric sensor based on a dummy molecularly imprinted polymer (MIP) that uses 2,4-dinitrophenol (DNP) as a template for the quantification of 2,4,6-trinitrotoluene (TNT) and DNP, and the identification of related substances. Once the polymer was synthesised by thermal precipitation polymerisation, it was integrated onto a graphite epoxy composite (GEC) electrode via sol–gel immobilisation. Scanning electron microscopy (SEM) was performed in order to characterise the polymer and the sensor surface. Responses towards DNP and TNT were evaluated, displaying a linear response range of 1.5 to 8.0 µmol L−1 for DNP and 1.3 to 6.5 µmol L−1 for TNT; the estimated limits of detection were 0.59 µmol L−1 and 0.29 µmol L−1, for DNP and TNT, respectively. Chemometric tools, in particular principal component analysis (PCA), demonstrated the possibilities of the MIP-modified electrodes in nitroaromatic and potential interfering species discrimination with multiple potential applications in the environmental field.

A novel molecularly imprinted electrochemiluminescence sensor based on cobalt nitride nanoarray electrode for the sensitive detection of bisphenol S

A substitute for bisphenol A (BPA), bisphenol S (BPS) has endocrine disruptive and toxic effects and could pose potential risk on human health and the environment. Herein, we fabricated a sensitive molecularly imprinted electrochemiluminescence (MIECL) sensor for the determination of BPS. CoN nanoarray with outstanding electrical conductivity was prepared and it directly served as the sensor platform. Especially, due to the high surface area of the porous CoN nanoarray, the ECL probe of Ru(bpy)3 2+ could be absorbed on the electrode. By means of the cation exchange of Nafion membrane and utilizing tripropylamine (TPrA) as co-reactant, boosted ECL signals were obtained. Meanwhile, by combining with molecularly imprinted polymers (MIPs), the constructed sensor achieved specific recognition of BPS. On the basis of the superior properties of the CoN nanoarray-based electrode, the ECL signal of the proposed sensor was linearly proportional to the BPS concentration from 2.4 × 10-9 to 5.0 × 10-5 mol L-1 (R 2 = 0.9965) with a low limit of detection (LOD) of 8.1 × 10-10 mol L-1 (S/N = 3). To test the accuracy of the proposed method, the HPLC method was adopted to analyze drinking water samples as a comparison. The t-test result proved that discrepancies between HPLC analysis and the method using the fabricated MIECL sensor were acceptable. The developed MIECL sensor with the sensitive, selective, reproducible, and stable analytical performance provides a potential pathway for the detection of BPS and other BPA substitutes in drinking water samples.

Sensitive simultaneous voltammetric determination of the herbicides diuron and isoproturon at a platinum/chitosan bio-based sensing platform

Phenylurea herbicides are persistent contaminants, which leads their transport to the surface and ground waters, affecting human and aquatic organisms. Different analytical methods have been reported for the detection of phenylureas; however, several of them are expensive, time-consuming, and require complex pretreatment steps. Here, we show a simple method for the simultaneous electrochemical determination of two phenylurea herbicides by differential pulse adsorptive stripping voltammetry (DPAdSV) using a modified platinum/chitosan electrode. The one-step synthesized platinum/chitosan PtNPs/CS was successfully characterized by TEM, XRPD, and FT-IR, and applied through the sensing platform designated as PtNPs/CS/GCE. This bio-based modified electrode is proposed for the first time for the individual and/or simultaneous electrochemical detection of the phenylurea herbicides diuron and isoproturon compounds extensively used worldwide that present a very similar chemical structure. Electrochemical and interfacial characteristics of the modified electrode were evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). It was found that the oxidation mechanism of diuron and isoproturon occurs in two different pathways, with a peak-to-peak definition of ca. 0.15 V. Under differential pulse adsorptive stripping voltammetry (DPAdSV) optimized conditions, the limit of detection (LOD) was estimated as 7 μg L^-1 for isoproturon and 20 μg L^-1 for diuron (E_d = +0.8 V; t_d = 100 s). The proposed method was successfully applied to the determination of both analytes in river water samples, at three different levels, with a recovery range of 90-110%. The employment of the bio-based sensing platform PtNPs/CS/GCE allows a novel and easy analytical method to the multi-component phenylurea herbicides detection.

Graphitic carbon nitride nanotubes: a new material for emerging applications

We provide a critical review of the current state of the synthesis and applications of nano- and micro-tubes of layered graphitic carbon nitride. This emerging material has a huge potential for light-harvesting applications, including light sensing, artificial photosynthesis, selective photocatalysis, hydrogen storage, light-induced motion, membrane technologies, and can become a major competitor for such established materials as carbon and titania dioxide nanotubes. Graphitic carbon nitride tubes (GCNTs) combine visible-light sensitivity, high charge carrier mobility, and exceptional chemical/photochemical stability, imparting this material with unrivaled photocatalytic activities in photosynthetic processes, such as water splitting and carbon dioxide reduction. The unique geometric GCNT structure and versatility of possible chemical modifications allow new photocatalytic applications of GCNTs to be envisaged including selective photocatalysts of multi-electron processes as well as light-induced and light-directed motion of GCNT-based microswimmers. Closely-packed arrays of aligned GCNTs show great promise as multifunctional membrane materials for the light energy conversion and storage, light-driven pumping of liquids, selective adsorption, and electrochemical applications. These emerging applications require synthetic routes to GCNTs with highly controlled morphological parameters and composition to be available. We recognize three major strategies for the GCNT synthesis including templating, supramolecular assembling of precursors, and scrolling of nano-/microsheets, and outline promising routes for further progress of these approaches in the light of the most important emerging applications of GCNTs.

All-electrochemical synthesis of a three-dimensional mesoporous polymeric g-C3N4/PANI/CdO nanocomposite and its application as a novel sensor for the simultaneous determination of epinephrine, paracetamol, mefenamic acid, and ciprofloxacin

mpg-C₃N₄/PANI/CdO nanocomposite was electrochemically synthesized and used for simultaneous determination of EPI, PAR, MFA, and CIP. Also, HOMO and LUMO eigenvalues of the EPI, PAR, MFA and CIP molecules have been evaluated using the DFT method.

An ultrasensitive biosensor for colorimetric detection of Salmonella in large-volume sample using magnetic grid separation and platinum loaded zeolitic imidazolate Framework-8 nanocatalysts

Salmonella is the leading risk factor in food safety. Rapid, sensitive and accurate detection of Salmonella is a key to prevent and control the outbreaks of foodborne diseases caused by Salmonella. In this study, we reported a colorimetric biosensor for ultrasensitive detection of Salmonella Typhimurium using a magnetic grid separation column to efficiently separate target bacteria from large volume of sample and platinum loaded zeolitic imidazolate framework-8 (Pt@ZIF-8) nanocatalysts to effectively amplify biological signal. The target Salmonella cells in large volume of sample were first separated and concentrated using the magnetic grid separation column with immune magnetic particle chains, then conjugated with the immune Pt@ZIF-8 nanocatalysts to mimic peroxidase for catalysis of hydrogen peroxide-3,3',5,5'-tetramethylbenzidine, and finally determined by measuring the catalysate at characteristic wavelength of 450 nm. This proposed biosensor was able to separate ∼70% of target Salmonella cells from 50 mL of bacterial sample and quantitatively detect Salmonella from 10¹ to 10⁴ CFU/mL in 2.5 h with the lower detection limit of 11 CFU/mL. The mean recovery for Salmonella in spiked chicken carcass was about 109.8%. This new magnetic grid separation method was first time reported for efficient separation of target bacteria from very large volume of sample to greatly improve the sensitivity of this biosensor and could be used with various biosensing assays for practical applications in routine detection of foodborne pathogens without any bacterial pre-enrichment.

Electrochemical sensors for improved detection of paraquat in food samples: A review

Paraquat (1,10-dimethyl-4,40-dipyridinium chloride), also known as methyl viologen, is widely used as a quaternary ammonium herbicide (broadleaf weed killer) all over the world owing to its excellent effect in plant cells for crop protection and horticultural use. However, it is dangerous because of its high acute toxicity even at low concentrations. Its detection in the environment is therefore necessary. As a consequence of its widespread usage, it causes genotoxic, teratogenic as well as other environmental and ecological adverse impacts. Exposure to PQ leads to a high mortality rate because no specific drug is effective for treatment. Excessive consumption of PQ can cause cellular damage and necrosis in the brain, heart, lungs, liver, and kidneys. The diversity and sensitivity of the analyses currently required have forced the experimenter to use more advanced and efficient techniques, which can provide qualitative and quantitative results in complex environments. Electrochemical methods generally meet these criteria while offering other advantages to achieve excellent accuracy and fast handling. This paper provides an overview of the determination of PQ using electrochemical methods combined with several modified electrodes in food samples, including milk, apple juice, tomato juice, and potato juice. Emphasis was placed on the most relevant modifiers used to generate high selectivity and sensitivity such as noble metals, metallic nanoparticles, polymers, biomolecules, clay, and apatite minerals. Comprehensively, it is strongly convincing that the synergy between the sensor substrate and the modifier architecture gives the electrodes a high capacity to detect paraquat in complex matrices such as food. In line with the context, information's on the mechanism of electrooxidation or reduction of PQ has been reported with the discussion of some future prospects and some insights. To the best of our knowledge, there is no review article relating the electrochemical determination of paraquat.

Preparation and applications of electrochemical chemosensors based on carbon-nanomaterial-modified molecularly imprinted polymers

The past few decades have witnessed a rapid development in electrochemical chemosensors (ECCSs). The integration of carbon nanomaterials (CNMs) and molecularly imprinted polymers (MIPs) has endowed ECCSs with high selectivity and sensitivity toward target detection. Due to the integrated merits of MIPs and CNMs, CNM-modified MIPs as ECCSs have been widely reported and have excellent detection applications. This review systematically summarized the general categories, preparation strategies, and applications of ECCSs based on CNM-modified MIPs. The categories include CNM-modified MIPs often hybridized with various materials and CNM-encapsulated or CNM-combined imprinting silica and polymers on working electrodes or other substrates. The preparation strategies include the polymerization of MIPs on CNM-modified substrates, co-polymerization of MIPs and CNMs on substrates, drop-casting of MIPs on CNM-modified substrates, self-assembly of CNMs/MIP complexes on substrates, and so forth. We discussed the in situ polymerization, electro-polymerization, and engineering structures of CNM-modified MIPs. With regard to potential applications, we elaborated the detection mechanisms, signal transducer modes, target types, and electrochemical sensing of targets in real samples. In addition, this review discussed the present status, challenges, and prospects of CNM-modified MIP-based ECCSs. This comprehensive review is desirable for scientists from broad research fields and can promote the further development of MIP-based functional materials, CNM-based hybrid materials, advanced composites, and hybrid materials.

Voltammetric sensor for the monitoring of hazardous herbicide triclopyr (TCP)

The herbicide Triclopyr (TCP) is widely applied to minimize the growth of woody plants. Monitoring of TCP is of major environmental concern due to its adverse impact on aquatic organisms, soils and animals. Electrochemical behavior of TCP was investigated at C₇₀ decorated PANI modified glassy carbon sensor (PANI/C₇₀/GC). The experimental parameters, such as concentration, pH, amplitude, frequency, deposition potential were optimized. The modified sensor exhibited an excellent catalytic response towards the reduction of TCP with a well-defined reduction peak at 1.72 V. The developed sensor was characterized by scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS). The electrochemical measurements were carried out using square wave (SWV) and cyclic voltammetry (CV). The modified sensor exhibited linear calibration curve for TCP over a concentration range of 10 ngmL^-1-100 ngmL^-1 with detection limit of 1.9 ngmL^-1. The developed sensor could detect TCP efficiently without any interference from the common metabolites. The voltammetric procedure was applied successfully to real sample analysis with high sensitivity and good selectivity.

Recent Advances in Electrosynthesized Molecularly Imprinted Polymer Sensing Platforms for Bioanalyte Detection

The accurate detection of biological materials has remained at the forefront of scientific research for decades. This includes the detection of molecules, proteins, and bacteria. Biomimetic sensors look to replicate the sensitive and selective mechanisms that are found in biological systems and incorporate these properties into functional sensing platforms. Molecularly imprinted polymers (MIPs) are synthetic receptors that can form high affinity binding sites complementary to the specific analyte of interest. They utilise the shape, size, and functionality to produce sensitive and selective recognition of target analytes. One route of synthesizing MIPs is through electropolymerization, utilising predominantly constant potential methods or cyclic voltammetry. This methodology allows for the formation of a polymer directly onto the surface of a transducer. The thickness, morphology, and topography of the films can be manipulated specifically for each template. Recently, numerous reviews have been published in the production and sensing applications of MIPs; however, there are few reports on the use of electrosynthesized MIPs (eMIPs). The number of publications and citations utilising eMIPs is increasing each year, with a review produced on the topic in 2012. This review will primarily focus on advancements from 2012 in the use of eMIPs in sensing platforms for the detection of biologically relevant materials, including the development of increased polymer layer dimensions for whole bacteria detection and the use of mixed monomer compositions to increase selectivity toward analytes.

Facile Fabrication of Surface-Imprinted Macroporous Films for Chemosensing of Human Chorionic Gonadotropin Hormone

We present an improved approach for the preparation of highly selective and homogeneous molecular cavities in molecularly imprinted polymers (MIPs) via the combination of surface imprinting and semi-covalent imprinting. Toward that, first, a colloidal crystal mold was prepared via the Langmuir-Blodgett (LB) technique. Then, human chorionic gonadotropin (hCG) template protein was immobilized on the colloidal crystal mold. Later, hCG derivatization with electroactive functional monomers via amide chemistry was performed. In a final step, optimized potentiostatic polymerization of 2,3'-bithiophene enabled depositing an MIP film as the macroporous structure. This synergistic strategy resulted in the formation of molecularly imprinted cavities exclusively on the internal surface of the macropores, which were accessible after dissolution of silica molds. The recognition of hCG by the macroporous MIP film was transduced with the help of electric transducers, namely, extended-gate field-effect transistors (EG-FET) and capacitive impedimetry (CI). These readout strategies offered the ability to create chemosensors for the label-free determination of the hCG hormone. Other than the simple confirmation of pregnancy, hCG assay is a common tool for the diagnosis and follow-up of ectopic pregnancy or trophoblast tumors. Concentration measurements with these EG-FET and CI-based devices allowed real-time measurements of hCG in the range of 0.8-50  and 0.17-2.0 fM, respectively, in 10 mM carbonate buffer (pH = 10). Moreover, the selectivity of chemosensors with respect to protein interferences was very high.

Development of a quantum dot molecularly imprinted polymer sensor for fluorescence detection of atrazine

Atrazine is a common agricultural pesticide which has been reported to occur widely in surface drinking water, making it an environmental pollutant of concern. In the quest for developing sensitive detection methods for pesticides, the use of quantum dots (QDs) as sensitive fluorescence probes has gained momentum in recent years. QDs have attractive and unique optical properties whilst coupling of QDs to molecularly imprinted polymers (MIPs) has been shown to offer excellent selectivity. Thus, the development of QD@MIPs based fluorescence sensors could provide an alternative for monitoring herbicides like atrazine in water. In this work, highly fluorescent CdSeTe/ZnS QDs were fabricated using the conventional organometallic synthesis approach and were then encapsulated with MIPs. The CdSeTe/ZnS@MIP sensor was characterized and applied for selective detection of atrazine. The sensor showed a fast response time (5 min) upon interaction with atrazine and the fluorescence intensity was linearly quenched within the 2-20 mol L^-1 atrazine range. The detection limit of 0.80 × 10^-7  mol L^-1 is comparable to reported environmental levels. Lastly, the sensor was applied in real water samples and showed satisfactory recoveries (92-118%) in spiked samples, hence it is a promising candidate for use in water monitoring.

Development of Novel Nanocomposites Based on Graphene/Graphene Oxide and Electrochemical Sensor Applications

Background:

Until now, several methods such as spectroscopic methods and chromatographic techniques have been developed for the determination of biomolecules, drug or heavy metals. Nevertheless, the crucial interference problems are present in these methods. Due to these reasons, more sensitive, favorable portability, low-cost, simple and selective sensors based on nanocomposites are needed in terms of health safety. In the development of electrochemical nanosensor, the nanomaterials such as graphene/graphene oxide, carbon and carbon nitride nanotubes are utilized to improve the sensitivity.

Objective:

The nanomaterials such as graphene/graphene oxide, carbon and carbon nitride nanotubes have important advantages such as high surface area, electrical conductivity, thermal and mechanical stability. Hence, we presented the highly selective methods for sensitive sensor applications by molecular imprinting technology in literature. This technology is a polymerization method around target molecule. This method provides the specific cavities to analyte molecule on the polymer surface. Hence, the selective sensor is easily created for biomedical and other applications. Novel electrochemical sensors based on nanocomposite whose surface is coated with Molecular Imprinting Polymer (MIP) are developed and then applied to the selective and sensitive detection in this study. Until now, we have presented several reports about nanocomposite based sensor with MIP.

Advances in Molecularly Imprinting Technology for Bioanalytical Applications

In recent years, along with the rapid development of relevant biological fields, there has been a tremendous motivation to combine molecular imprinting technology (MIT) with biosensing. In this situation, bioprobes and biosensors based on molecularly imprinted polymers (MIPs) have emerged as a reliable candidate for a comprehensive range of applications, from biomolecule detection to drug tracking. Unlike their precursors such as classic immunosensors based on antibody binding and natural receptor elements, MIPs create complementary cavities with stronger binding affinity, while their intrinsic artificial polymers facilitate their use in harsh environments. The major objective of this work is to review recent MIP bioprobes and biosensors, especially those used for biomolecules and drugs. In this review, MIP bioprobes and biosensors are categorized by sensing method, including optical sensing, electrochemical sensing, gravimetric sensing and magnetic sensing, respectively. The working mechanism(s) of each sensing method are thoroughly discussed. Moreover, this work aims to present the cutting-edge structures and modifiers offering higher properties and performances, and clearly point out recent efforts dedicated to introduce multi-sensing and multi-functional MIP bioprobes and biosensors applicable to interdisciplinary fields.

Rational design and tailoring of imprinted polymeric enantioselective sensor layered on multiwalled carbon nanotubes for the chiral recognition of d-mandelic acid

Attempts have been made to investigate the feasibility of fabricating an enantiomeric sensor for the specific detection of d-mandelic acid layered on vinyl-MWCNT using molecular imprinting technology.

Development of cardiac troponin-I biosensor based on boron nitride quantum dots including molecularly imprinted polymer

The cardiac Troponin-I (cTnI) is one of the subunits of cardiac troponin complexes and a pivotal biochemical marker of acute myocardial infarction (AMI). Due to its myocardial specificity, cTnI is widely used for the diagnosis of AMI diseases. In this study, a novel imprinted biosensor approach based on boron nitride quantum dots (BNQDs) was presented for cTnI detection in plasma samples. Various characterization methods such as scanning electron microscope (SEM), transmission electron microscope (TEM), x-ray diffraction (XRD), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used for all characterizations of nanomaterials. After the characterization analysis, cTnI imprinted electrode was developed in the presence of 100.0 mM pyrrole containing 25.0 mM cTnI. After that, the analytical studies of cTnI in plasma samples were performed by using cTnI imprinted biosensor. The results of the study have revealed that 0.01-5.00 ng mL^-1 and 0.0005 ng mL^-1 were found as the linearity range and the detection limit (LOD). Moreover, the selectivity of cTnI imprinted glassy carbon electrode (GCE) was investigated for plasma sample analysis in the presence of other nonspecific and specific proteins including cardiac myoglobin (MYG), bovine serum albumin (BSA) and cardiac troponin T (cTnT), respectively. Furthermore, the prepared biosensor was examined in terms of stability, repeatability, reproducibility and reusability. Finally, the imprinted biosensor was applied to the plasma samples having high recovery.