Non-biological fluorescent chemosensors for pesticides detection

A "turn-on" fluorescent sensor for herbicide quizalofop-p-ethyl based on cyanostilbene-pyridine macrocycle

Quizalofop-p-ethyl is a widely used herbicide that also poses a risk to human health and environmental safety. However, there is still a lack of simple and in-situ detecting method for quizalofop-p-ethyl so far. In this work, the fluorescent sensor was firstly developed on detection of quizalofop-p-ethyl based on cyanostilbene-pyridine macrocycle (CPM). CPM was prepared by the "1 + 1" condensation of pyridine-substituted cyanostilbene derivative with 4,4'-Bis(chloromethyl)biphenyl in 68 % yield. The weak fluorescence of CPM in aqueous media transferred to strong orange fluorescence after sensing quizalofop-p-ethyl. This sensing behavior exhibited high selectivity among 28 kinds of herbicides and ions. The limitation of detection (LOD) was 2.98 × 10-8 M and the limitation of quantification (LOQ) was 9.94 × 10-8 M (λex = 390 nm, λem = the maximum emission between 512 nm and 535 nm) with a dynamic range of 0.01-0.9 eq. The binding constant (Ka) of quizalofop-p-ethyl to the sensor CPM was 3.2 × 106 M-1. The 1:1 sensing mechanism was confirmed as that quizalofop-p-ethyl was located in the cavity of CPM, which enhanced aggregating effect and reduced the intramolecular rotation of aromatic groups for better AIE effect. The sensing ability of CPM for quizalofop-p-ethyl had been efficiently applied in test paper experiments, agricultural product tests and real water samples, revealing that CPM has good application prospect for simple and in-situ detection of quizalofop-p-ethyl in real environment.

Recent Progress in Detecting Enantiomers in Food

The analysis of enantiomers in food has significant implications for food safety and human health. Conventional analytical methods employed for enantiomer analysis, such as gas chromatography and high-performance liquid chromatography, are characterized by their labor-intensive nature and lengthy analysis times. This review focuses on the development of rapid and reliable biosensors for the analysis of enantiomers in food. Electrochemical and optical biosensors are highlighted, along with their fabrication methods and materials. The determination of enantiomers in food can authenticate products and ensure their safety. Amino acids and chiral pesticides are specifically discussed as important chiral substances found in food. The use of sensors replaces expensive reagents, offers real-time analysis capabilities, and provides a low-cost screening method for enantiomers. This review contributes to the advancement of sensor-based methods in the field of food analysis and promotes food authenticity and safety.

A simple AIE probe to pesticide trifluralin residues in aqueous phase: Ultra-fast response, high sensitivity, and quantitative detection utilizing a portable platform

The threat from pesticide trifluralin residues to ecological environment and public health is becoming a growing problem. Thus, rapid and sensitive detection, particularly a simple and portable detected platform for trifluralin residues, are highly desired. Here, a small organic aggregation-induced emission (AIE) molecule (TPETPy) is facilely synthesized and applied to detect trifluralin both in lab and in actual water systems. Based on the photo-induced electron transfer (PET) mechanism, the emissive peak of TPETPy located at 475 nm in tetrahydrofuran (THF)/water mixture (ƒw = 90 %) under the excitation of 340 nm, decreases dramatically upon trace trifluralin addition and exhibits ultra-fast response (3 s), high sensitivity and selectivity, and good anti-interference ability. The fluorescence sensing correlation with the concentration of trifluralin shows good linearity in the range of 20-90 μg L-1 with the limit of detection of 6.28 μg L-1. Moreover, a portable smartphone-integrated detected platform based on fluorescent pattern Red/Green/Blue (RGB) values is first employed to realize the real-time and on-site quantitative fluorescent detection of trifluralin in actual water sources, featuring good accuracy and reproducibility. Hereby, this work provides not only a highly efficient trifluralin residues fluorescent probe but also a portable and straightforward operating platform to detect trifluralin pesticides quantitatively.

Progress in environmental monitoring and mitigation strategies for herbicides and insecticides: A comprehensive review

Herbicides and insecticides are pervasively applied in agricultural sector to increase the yield by controlling or eliminating bug vermin and weeds. Although, resistance development occurs, direct and indirect impact on human health and ecosystem is clearly visible. Normally, herbicides and pesticides are water soluble in nature; accordingly, it is hard to decrease their deadliness and to dis-appear them from the environment. They are profoundly specific, and considered as poisonous to various peoples in agricultural and industrial work places. In order to substantially reduce the harmful impacts, it is crucial to thoroughly examine the detection and mitigation measures for these compounds. The primary objective of this paper is to provide an overview of various herbicide and pesticide detection techniques and associated remedial techniques. A short summary on occurrence and harmful effects of herbicides/insecticides on ecosystem has been included to the study. The conventional and advanced, rapid techniques for the detection of insecticides and herbicides were described in detail. A detailed overview on several mitigation strategies including advanced oxidation, adsorption, electrochemical process, and bioremediation as well as the mechanism behind the strategic approaches to reduce the effects of growing pesticide pollution has been emphasized. Regardless of the detection techniques and mitigation strategies, the recent advances employed, obstacles, and perspectives have been discussed in detail.

Preparation of surface molecular imprinting fluorescent sensor based on magnetic porous silica for sensitive and selective determination of catechol

A magnetic fluorescent molecularly imprinted sensor was successfully prepared and implemented to determine catechol (CT). Fe3O4 nanoparticles were synthesized by the solvothermal technique and mesoporous Fe3O4@SiO2@mSiO2 imprinted carriers were prepared by coating nonporous and mesoporous SiO2 shells on the surface of the Fe3O4 subsequently. The magnetic surface molecularly imprinted fluorescent sensor was created after the magnetic mesoporous carriers were modified with γ-methacryloxyl propyl trimethoxy silane to introduce double bonds on the surface of the carries and the polymerization was carried out in the presence of CT and fluorescent monomers. The magnetic mesoporous carriers were modified with γ-methacryloxyl propyl trimethoxy silane and double bonds were introduced on the surface of the carriers. After CT binding with the molecularly imprinted polymers (MIPs), the fluorescent intensity of the molecularly imprinted polymers (Ex = 400 nm, Em = 523 nm) increased significantly. The fluorescent intensity ratio (F/F0) of the sensor demonstrated a favorable linear correlation with the concentration of CT between 5 and 50 μM with a detection limit of 0.025 μM. Furthermore, the sensor was successfully applied to determine CT in actual samples with recoveries of 96.4-105% and relative standard deviations were lower than 3.5%. The results indicated that the research of our present work provided an efficient approach for swiftly and accurately determining organic pollutant in water.

3D nanocake-like Au-MXene/Au pallet structure-based label-free electrochemical aptasensor for paraquat determination

3D nanocake-like Au-MXene and Au pallet (Au-MXene/AuP) nanocomposite-modified screen-printed carbon electrodes (SPCEs) were utilized to construct an ultrasensitive label-free electrochemical aptasensor through a self-assembly procedure for trace paraquat (PQ) residue detection. Benefiting from the excellent electrochemical (EC) performances (e.g., high conductivity and large surface area) of Au-MXene nanocomposites and AuP substrate, the developed Apt/Au-MXene/AuP/SPCE-based EC aptasensor displayed excellent specificity and anti-interference ability, good repeatability, and stability. A linear relationship between the log value of the change in current intensity [lg (ΔI)] and the log value of the concentration of PQ [lg (CPQ)] was obtained in the range 0.05-1000 ng/mL. The limit of detection was 0.028 ng/mL, and the sensitivity was 255.5 μA/(μM·cm2). Practical applications in malt and mint samples confirmed the accuracy of the EC aptasensor in complex matrices for PQ detection, providing a universal analytical tool for other trace pesticides in different food samples by simply replacing the corresponding aptamers.

Exploring Various Photochemical Processes in Optical Sensing of Pesticides by Luminescent Nanomaterials: A Concise Discussion on Challenges and Recent Advancements

Food safety is a burning global issue in this present era. The prevalence of harmful food additives and contaminants in everyday food is a significant cause for concern as they can adversely affect human health. More particularly, among the different food contaminants, the use of excessive pesticides in agricultural products is severely hazardous. So, the optical detection of residual pesticides is an effective strategy to counter the hazardous effect and ensure food safety. In this perspective, nanomaterials have played a leading role in defending the open threat against food safety instigated by the reckless use of pesticides. Now, nanomaterial-based optical detection of pesticides has reached full pace and needs an inclusive discussion. This Review covers the advancement of photoprocess-based optical detection of pesticides categorically using nanomaterials. Here, we have thoroughly dissected the photoprocesses (aggregation and aggregation-induced emission (AIE), charge transfer and intramolecular charge transfer (ICT), electron transfer and photoinduced electron transfer (PET), fluorescence resonance energy transfer (FRET), hydrogen bonding, and inner filter effect) and categorically demarcated their significant role in the optical detection of pesticides by luminescent nanomaterials over the last few years.

High-efficiency SERS platform based on 3D porous PPDA@Au NPs as a substrate for the detection of pesticides on vegetables

Nowadays, the presence of highly toxic and persistent residues of pesticides in water and food around the world is becoming a serious problem, and so their rapid and sensitive detection is critical to human health. In this work, a 3D composite nanoparticle of porous PDA (polydopamine) microspheres and Au NPs (PPDA@Au NPs) was proposed as a SERS substrate to detect pesticides. Porous PDA as a substrate was first synthesized with F127 (Pluronic F127), dopamine hydrochloride, and 1,3,5-TMB (1,3,5-trimethylbenzene) under weakly alkaline conditions by a one-step method. Then, HAuCl4 was in situ reduced in the pores of PPDA spheres and grew sequentially for effecting the reducibility of PPDA. As a result, uniform 3D PPDA@Au NPs with "hot spots" were successfully synthesized as SERS substrates, which could effectively avoid the agglomeration of gold nanoparticles to greatly improve the sensitivity and uniformity of the SERS platform. At the same time, methyl parathion, 4-chlorophenol, and 2,4-D as representatives of pesticides were detected with the proposed PPDA@Au NP-based SERS platform, with detection limits lower than 7.26, 7.52, and 11 ng mL-1, separately. The current work presents a simple preparation method to prepare sensitive and uniform SERS platform PPDA@Au NPs, which have potential for applications in actual pesticide and drug testing.

Anti-interference and non-destructive identification of textile fabrics using front-face excitation-emission matrix fluorescence spectroscopy combined with multi-way chemometrics

The identification of trace textile fabrics discovered at crime scenes plays a crucial role in the case of forensic investigations. Additionally, in practical situations, fabrics may be contaminated, making identification more challenging. To address the aforementioned issue and promote the application of fabrics identification in forensic analysis, front-face excitation-emission matrix (FF-EEM) fluorescence spectra coupled with multi-way chemometric methods were proposed for the interference-free and non-destructive identification of textile fabrics. Common commercial dyes in the same color range under different materials (cotton, acrylic, and polyester) that cannot be visually distinguished were investigated, and several binary classification models for the identification of dye were established using partial least squares discriminant analysis (PLS-DA). The identification of dyed fabrics in the presence of fluorescent interference was also taken into consideration. In each kind of pattern recognition model mentioned above, the classification accuracy (ACC) of the prediction set was 100%. The alternating trilinear decomposition (ATLD) algorithm was executed to separate mathematically and remove the interference, and the classification model based on the reconstructed spectra attained an accuracy of 100%. These findings indicate that FF-EEM technology combined with multi-way chemometric methods has broad prospects for forensic trace textile fabric identification, especially in the presence of interference.

Cu2+-assisted sensing of fungicide Thiram in food, soil, and plant samples and the ratiometric detection of Hg2+ in living cells by a low cytotoxic and red emissive fluorescent sensor

Metal ions and pesticides are extensively used in many industries and agriculture. However, they cause significant environmental pollution and various adverse health effects. Therefore, the development of sensitive and selective techniques to detect them is necessary for human health and the ecosystem. In this paper, we report a novel red-emitting fluorescence probe with a large Stokes shift (∼220 nm) based on rhodamine and isophorone units. The probe shows a ratiometric fluorescence response toward Hg²⁺ ions; however, Cu²⁺ ions quench the red fluorescence signal. The decomposition of the probe-Cu²⁺ complex allows detection of Thiram followed by recovery of the red fluorescence signal of the probe. In addition, the probe shows a good linear response to Hg²⁺, Cu²⁺, and Thiram, with detection limits of 122.0 nM, 29.0 nM, and 72.0 nM, respectively. The practical applicability of the probe has been successfully tested in real samples. Moreover, smartphone detection and light-responsive capsule fabrication have been established, for easy and quick detection. The probe possesses very low cytotoxicity and allows visualization of Hg²⁺ and Cu²⁺ ions in HeLa cells. Therefore, the present probe is expected to be an effective tool assisting in easy, quick, and reliable detection of Thiram, Hg²⁺, and Cu²⁺ ions.

Luminescent Guests Encapsulated in Metal-Organic Frameworks for Portable Fluorescence Sensor and Visual Detection Applications: A Review

Metal-organic frameworks (MOFs) have excellent applicability in several fields and have significant structural advantages, due to their open pore structure, high porosity, large specific surface area, and easily modifiable and functionalized porous surface. In addition, a variety of luminescent guest (LG) species can be encapsulated in the pores of MOFs, giving MOFs a broader luminescent capability. The applications of a variety of LG@MOF sensors, constructed by doping MOFs with LGs such as lanthanide ions, carbon quantum dots, luminescent complexes, organic dyes, and metal nanoclusters, for fluorescence detection of various target analyses such as ions, biomarkers, pesticides, and preservatives are systematically introduced in this review. The development of these sensors for portable visual fluorescence sensing applications is then covered. Finally, the challenges that these sectors currently face, as well as the potential for future growth, are briefly discussed.

Metal-porphyrinic framework nanotechnologies in modern agricultural management

Metal-porphyrinic frameworks are an important subclass of metal-organic frameworks (MOFs). These porous materials exhibit a large number of applications for sustainable development and related environmental considerations. Their attractive features include (1) as a free base or metalated with zinc(II) or iron(II or III), they are environmentally benign, and (2) they absorb visible light and are emissive and semi-conducting, making them convenient tools for sensing agrochemicals. But the key feature that makes these nano-sized pristine materials or their composites in many ways superior to most MOFs is their ability to photo-generate reactive oxygen species with visible light, including singlet oxygen. This review describes important issues related to agriculture, including controlled delivery of pesticides and agrochemicals, detection of pesticides and pathogenic metals, elimination of pesticides and toxic metals, and photodynamic antimicrobial activity, and has an important implication for food safety. This comprehensive review presents the progress of the rather rapid developments of these functional and increasingly nano-sized materials and composites in the area of sustainable agriculture.

Recent advances in morphology, aperture control, functional control and electrochemical sensors applications of carbon nanofibers

Among many nanomaterials, electrospun carbon nanofibers (CNFs) have become one of the hot spots in nanoscience research because of their interesting physicochemical and biological properties such as large specific surface area, easy functionalization and biocompatibility. Polyacrylonitrile（PAN) has also become the most widely used precursor fiber for CNF manufacturing. In this paper, the latest advances in the synthesis of CNF by electrospinning were reviewed, including using template method, heat treatment, coaxial spinning technology to control the morphology and aperture, as well as the functionalization of electrospinning doped with chemical substances such as heteroatoms, nanoparticles (NPs), carbon nanotubes (CNTs) and grapheme (Gr), in order to further expand its application scope. The application of electrospun CNFs as electrochemical sensing platform for toxic and harmful substances in food and environment was also briefly introduced.

Label-Free Aptasensor for Detection of Fipronil Based on Black Phosphorus Nanosheets

A label-free fipronil aptasensor was built based on Polylysine-black phosphorus nanosheets composition (PLL-BPNSs) and Au nanoparticles (AuNPs). A PLL-BP modified glassy carbon electrode (GCE) was fabricated by combining BP NSs and PLL, which included a considerable quantity of -NH₂. Au nanoparticles (AuNPs) were placed onto the GCE, and PLL-BPNSs bonded to Au NPs firmly by assembling. The thiolated primers were then added and fixed using an S-Au bond, and competitive binding of the fipronil aptamer was utilized for fipronil quantitative assessment. The sensor’s performance was evaluated using differential pulse voltammetry (DPV) method. The linear equation is ΔI (μA) = 13.04 logC + 22.35, while linear correlation coefficient R² is 0.998, and detection limit is 74 pg/mL (0.17 nM) when the concentration of fipronil is 0.1 ng/mL–10 μg/mL. This aptasensor can apply to quantitative detection of fipronil.

Optical sensing techniques for rapid detection of agrochemicals: Strategies, challenges, and perspectives

In recent years, the irrational use of agrochemicals has caused great harm to the environment and public health. Along with the rapid development of optical technology and nanotechnology, the research of optical sensing methods in agrochemical detection has been developed rapidly owing to its advantages of simplicity, fast response, and cost-effectiveness. In this review, the strategies of employing optical systems based on colorimetric sensor, fluorescence, chemiluminescence, terahertz spectroscopy, surface plasmon resonance, and surface-enhanced Raman spectroscopy for sensing agrochemicals were summarized. In addition, the challenges in the practical application of optical sensing technologies for agrochemical detection were discussed in-depth, and potential future trends and prospects of these techniques were addressed. A variety of nanomaterials have been developed for enhancing the sensitivity of optical sensing systems. The optical properties of nanomaterials are governed by their size, shape, and chemical structure. Although each optical sensing system holds its advantages, there are still many challenges that need to be overcome in practical applications. With the continuous developments in novel functional nanomaterials, sample preparation methods, and spectral processing algorithms, optical sensors are expected to have powerful potential for rapid testing of agrochemicals in the environment and foods.

Highly Selective Detection of Paraoxon in Food Based on the Platform of Cu Nanocluster/MnO2 Nanosheets

Selective and sensitive identification of paraoxon residue in agricultural products is greatly significant for food safety but remains a challenging task. Herein, a detection platform was developed by integrating Cu nanoclusters (Cu NCs) with MnO₂ nanosheets, where the fluorescence of Cu NCs was effectively quenched. Upon introducing butyrylcholinesterase and butyrylcholine into the system, their hydrolysate, thiocholine, leads to the decomposition of the platform through a reaction between the MnO₂ nanosheets and thiol groups on thiocholine. The electron-rich groups on thiocholine can further promote the fluorescence intensity of Cu NCs through host–guest interactions. Adding paraoxon results in the failure of fluorescence recovery and further promotion, which could be utilized for the quantitative detection of paraoxon, and a limit of detection as low as 0.22 ng/mL can be achieved. The detection platform shows strong tolerance to common interference species, which endows its applications for the detection of paraoxon in vegetables and fruit. These presented results not only open a new door for the functionalization of metal nanoclusters but also offer an inspiring strategy for analytic techniques in nanomedicine and environmental science.

A highly selective and sensitive CdS fluorescent quantum dot for the simultaneous detection of multiple pesticides

We presented one-pot prepared CdS fluorescent quantum dots (QDs) which can sensitively and selectively detect three different organic pesticides.