Sensitive Detection Of Organophosphorus Pesticides Research Articles

Apple polysaccharide stabilized palladium nanoparticles for sensitive detection of organophosphorus pesticide

The widespread application of organophosphorus pesticides (OPs) has inflicted significant damage on human well-being and food security. Hence, it is imperative to develop a friendly and accessible biosensor for the detection of OPs. Herein, apple polysaccharide (AP) stabilized palladium nanoparticles (AP-PdnNPs) with a particle size of 2.75–5.95 nm were prepared using AP as a stabilizer and reducing agent. AP-Pd30NPs exhibited good peroxidase-like activity and effectively decomposed H2O2 to ·OH, which catalyzed the 3,3′,5,5′-tetramethylbenzidine system to become blue. The catalytic kinetics of AP-Pd30NPs conformed to the typical Michelis-Menten equation. Furthermore, OPs directly inhibited the peroxidase-like activity of AP-Pd30NPs. Thus, a highly effective colorimetric biosensor was developed for the detection of OPs. The detection range of the biosensor was 0.050 μg/L - 200 mg/L, and the limit of detection was extremely low to 0.010 μg/L. Compared with other nanomaterials, the detection platform based on AP-Pd30NPs can effectively detect organophosphorus pesticides without coupling natural enzymes；this method is more economical and practical. Therefore, this established method explores good perspective for the detection of OPs.

Highly sensitive detection of organophosphorus pesticides in water using a carboxyl-functionalized magnetic covalent organic framework

The development of novel methods for the precise quantification of organophosphate pesticides (OPPs), with enhanced accuracy, sensitivity, and efficiency, is crucial for environmental monitoring and human health risk assessment. In this study, Fe3O4@SiO2@COF-COOH magnetic core–shell nanoparticles were synthesized by coating a carboxyl-functionalized covalent organic framework (COF-COOH) onto the surface of amino-modified silica-coated iron(III) oxide particles (Fe3O4@SiO2-NH2). The incorporation of carboxyl groups, covalent organic framework and magnetic properties imparted superior performance to the adsorbent in magnetic solid-phase extraction (MSPE) of polar compounds from complex sample matrices. An analytical method based on Fe3O4@SiO2@COF-COOH coupled with GC–MS/MS was developed for the determination of eight organophosphate pesticide residues in river water near farmland. The established method displays good linearity in the range of 0.1–500 ng/mL for four OPPs and 1–2000 ng/mL for the other four, with correlation coefficients between 0.9903–0.9983. The LODs (S/N = 3) and LOQs (S/N = 10) were determined to be in the ranges of 0.53–9.6 ng/L and 1.8–31.9 ng/L, respectively. The adsorption mechanism was characterized by density functional theory calculations. Furthermore, the established method was successfully applied to analyze the distribution of trace OPPs in real river water samples collected from various cities in Henan Province. Its rapid, straightforward, and efficient ability to enrich trace levels of OPPs from complex real-world samples makes it a valuable tool for environmental monitoring, food safety, and human health management.

A new composite electrode based on hemin/copper nanoparticles/oxidized graphitic nitride for sensitive detection of organophosphorus pesticide

A new composite of Hemin, copper oxide nanoparticle, and oxidized g-C3N4 (He/CuO/Oxi-gC3N4) is fabricated and successfully employed for electrocatalysis of the chlorinated Organo-Phosphorous pesticide, Dichlorvos. Hemin (He) is a well-known metalloporphyrin, which has an electroactive center of Fe3+. Pure hemin aggregates easily due to its poor solubility in an aqueous solution and hence is usually composited with other electroactive materials. The composite electrode has been thoroughly characterized including SEM, AFM, FT-IR, Raman spectroscopy, XPS, and Voltammetric techniques for the determination of Dichlorvos in water sample. Herein we have used a composite of Hemin with green synthesized copper oxide nanoparticle, (CuO)-Nps adsorbed on a porous oxidized graphitic carbon nitride surface (Oxi-gC3N4). The obtained linear range for Dichlorvos was found to be 2.5 × 10−10 to 62.5 × 10−10 M with a detection limit of 0.83×10−11 M. The composite electrode performance was further extended for use in real samples like lake water, well water, and tap water containing Dichlorvos. The analysis was carried out based on the standard addition method. Good recovery ranges from 99.0 to 100.0% were observed. Also, the He/CuO/Oxi-gC3N4 showed very good antibacterial activity against gram-positive and gram-negative bacteria.

Mn-modified porphyrin metal–organic framework mediated colorimetric and photothermal dual-channel probe for sensitive detection of organophosphorus pesticides

Herein, a novel dual-mode probe for organophosphorus pesticides (OPs) colorimetric and photothermal detection was developed based on manganese modified porphyrin metal–organic framework (PCN-224-Mn). PCN-224-Mn had excellent oxidase-like activity and oxidized colorless 3,3,5,5-tetramethylbenzidine (TMB) to blue–green oxidation state TMB (oxTMB), which exhibited high temperature under near-infrared irradiation. l-ascorbate-2-phosphate was hydrolyzed by acid phosphatase to produce ascorbic acid, which weakened colorimetric and photothermal signals by impacting oxTMB generation. The presence of OPs blocked the production of ascorbic acid by irreversibly inhibiting the activity of acid phosphatase, causing the restoration of chromogenic reaction and the increase of temperature. Under the optimal conditions, the probe showed a good linear response to OPs in the concentration range of 5 ∼ 10000 ng/mL, using glyphosate as the analog. The detection limits of glyphosate in colorimetric mode and photothermal mode were 1.47 ng/mL and 2.00 ng/mL, respectively. The probe was successfully used for sensitive identification of OPs residues in tea, brown rice, and wheat flour. This work proposes a simple and reliable colorimetric/photothermal platform for OPs identification, which overcomes the problem that single-mode detection probes are susceptible to external factors, and has broad application potential in the field of food safety.

A Multienzyme Reaction-Mediated Electrochemical Biosensor for Sensitive Detection of Organophosphorus Pesticides.

Ethephon (ETH), a commonly employed growth regulator, poses potential health risks due to its residue in fruits and vegetables, leading to both acute and subchronic toxicity. However, the detection accuracy of ETH is compromised by the color effects of the samples during the detection process. In this work, a multienzyme reaction-mediated electrochemical biosensor (MRMEC) was developed for the sensitive, rapid, and color-interference-resistant determination of ETH. Nanozymes Fe3O4@Au-Pt and graphene nanocomplexes (GN-Au NPs) were prepared as catalysts and signal amplifiers for MRMEC. Acetylcholinesterase (AChE), acetylcholine (ACh), and choline oxidase (CHOx) form a cascade enzyme reaction to produce H2O2 in an electrolytic cell. Fe3O4@Au-Pt has excellent peroxidase-like activity and can catalyze the oxidation of 3,3',5,5'-tetramethvlbenzidine (TMB) in the presence of H2O2, resulting in a decrease in the characteristic peak current of TMB. Based on the inhibitory effect of ETH on AChE, the differential pulse voltammetry (DPV) current signal of TMB was used to detect ETH, offering the limit of detection (LOD) of 2.01 nmol L-1. The MRMEC method effectively analyzed ETH levels in mangoes, showing satisfactory precision (coefficient of variations, 2.88-15.97%) and recovery rate (92.18-110.72%). This biosensor holds promise for detecting various organophosphorus pesticides in food samples.

Smartphone-assisted colorimetric biosensor for the determination of organophosphorus pesticides on the peel of fruits

Nowadays, the widespread use of organophosphorus pesticides (OPs) in agricultural production leads to varying degrees of residues in crops, which pose a potential threat to human health. Conventional methods used in national standard for the detection of OPs in fruits and vegetables require expensive instruments or cumbersome sample pretreatment steps for the analysis. To address these challenges, in this work, we took advantage of the peroxidase-like activity of PtCu3 alloy nanocrystals (NCs) for a colorimetric and smartphone assisted sensitive detection of OPs. With the assist of a smartphone, the concentration of OPs on the peel of fruits could be obtained by comparing the B/RG value (the brightness value of blue divided by those of red and green) of a test strip with a calibration curve. This work not only provides a facile and cost-effective method to detect pesticides but also makes a positive contribution to food safety warning.

A smartphone-integrated colorimetric sensor for sensitive detection of organophosphorus pesticides based on large-scale synthesized Fe-N/C single-atom nanozymes

Single-atom nanozymes (SAzymes) have been wildly used to design high-performance biosensors for the quantification of organophosphorus pesticides (OPs) recently. However, the low yield and low metal loading of SAzymes often limit their practical use in biosensing field. Herein, a large-scale synthesis (6.60 g) of Fe-N /C SAzymes (Fe loading of 3.9 wt%) was achieved by using carbon black as a template. This prepared Fe-N/C SAzymes exhibit efficient oxidase-like activity that could catalyze the oxidation reaction of 3,3′,5,5′-tetramethylbenzidine (TMB) along with color variation. On this basis of Fe-N/C SAzymes, a colorimetric biosensor was designed for OPs detection. Then a smartphone combined with RGB analysis was used to digitize the color information. The B/ (R + G) value shows good linear detection range (1–100 nM) and low detection limit (0.4177 nM). More importantly, the large-scale synthetic approach and excellent catalytic performance of Fe-N/C SAzymes are significant for promoting the marketability of biosensors.

Photothermal effect-enhanced peroxidase-like performance for sensitive detection of organophosphorus pesticides on a visual test strip

Pesticides pose a serious risk to public health, even in trace amounts. The sensitive, rapid, visual, and on-site detection of pesticides in a real sample remains a challenge. Herein, we report a visual and rapid organophosphorus pesticide (OP) sensing device with excellent sensitivity, ease of application, and specificity based on a photothermal effect-based peroxidase (POD) mimetic. The ultrathin MIL-101-NH2(Fe) (Fe-MOF) shell-coated Au nanobipyramide (NBP) not only possesses POD-like activity, but also exhibits excellent photothermal effect under near-infrared (NIR) light. The results reveal that the excellent photo-to-thermal conversion of the Au NBPs can rapidly heat the MIL-101-NH2(Fe) shell, which subsequently induces a markedly enhanced POD-like activity. Using paraoxon-ethyl as model OP, the combination of the OP inhibition effect on the biocatalytic activity of acetylcholinesterase with the inhibition effect of thiocholine on the colorimetric assays of the POD-mimicking Fe-MOF leads to a significant improved selectivity for OP sensing. In particular, the NIR light irradiation increased the OP detection sensitivity by 100 times. Importantly, based on this detection strategy, a visual test strip with high sensitivity was developed and enabled real-time detection through a simple color analysis software on a smartphone. The successful detection of OP residues in fruit peel using this test strip further confirmed its application potential in real sample analysis.

Complementary Homogeneous Electrochemical and Photothermal Dual-Modal Sensor for Highly Sensitive Detection of Organophosphorus Pesticides via Stimuli-Responsive COF/Methylene Blue@MnO2 Composite.

Credible and on-site detection of organophosphorus pesticides (OPs) in complex matrixes is significant for food security and environmental monitoring. Herein, a novel COF/methylene blue@MnO2 (COF/MB@MnO2) composite featured abundant signal loading, a specific recognition unit, and robust oxidase-like activity was successfully prepared through facile assembly processes. The multifunctional composite acted as a homogeneous electrochemical and photothermal dual-mode sensing platform for OPs detection through stimuli-responsive regulation. Without the presence of OPs, the surface MnO2 coating could recognize thiocholine (TCh), originating from acetylcholinesterase (AChE)-catalyzed hydrolysis of acetylthiocholine (ATCh), and exhibited a distinctly amplified diffusion current due to the release of plentiful MB; while the residual MnO2 nanosheets could only catalyze less TMB into oxidized TMB (oxTMB) with a typical near-infrared (NIR) absorption, enabling NIR-driven photothermal assay with a low temperature using a portable thermometer. Based on the inhibitory effect of OPs on AChE activity and OP-regulated generation of TCh, chlorpyrifos as a model target can be accurately detected with a low limit of detection of 0.0632 and 0.108 ng/mL by complementary electrochemical and photothermal measurements, respectively. The present dual-mode sensor was demonstrated to be excellent for application to the reliable detection of OPs in complex environmental and food samples. This work can not only provide a complementary dual-mode method for convenient and on-site detection of OPs in different scenarios but also expand the application scope of the COF-based multifunctional composite in multimodal sensors.

Rapid, sensitive detection of organophosphorus pesticides through auto-inductive cascade signal amplification approach and a sensitized behavior of Tb3+ hydrogel in point-of-care

A strategy for detecting trace amount OPs was designed and developed by combining auto-inductive cascade signal amplification approach and a sensitization behavior of Tb3+ hydrogel, which could greatly improve the sensitivity and convenience of OPs detection. Due to the promotion by CA-PhSH, the process of auto-inductive cascade and luminescence response could be completed only in 3 min and 5 min respectively, which had greatly improved the efficiency of OPs detection. The lowest detection limit of BK@Tb3+/hydrogel platform with the auto-inductive cascade approach for OPs was only 0.39 nM. In addition, a portable smartphone system had also developed by this hydrogel platform and had successfully applied to detect OPs in vegetable, fruit samples and accurately monitor the degradation process of OPs in cabbage leaves. The good results demonstrated that BK@Tb3+/hydrogel platform with the auto-inductive signal amplification approach was a powerful tool in the application of OPs detection.

Designing Hierarchically Porous Single Atoms of Fe-N5 Catalytic Sites with High Oxidase-like Activity for Sensitive Detection of Organophosphorus Pesticides.

Recently, single-atom catalysts (SACs) have been used to construct biosensors for the determination of organophosphorus pesticides (OPs). However, most nanozymes including SACs are peroxidase-like enzymes and require highly toxic and unstable hydrogen peroxide (H2O2) as a co-reactant to generate reactive oxygen species. Inspired by the heme site of cytochrome c oxidases (Ccos), the construction of Fe-N5-coordinated SACs by introducing axial N ligands is expected to bind O2 to generate active metal-oxygen intermediates. Herein, a SAC with an Fe-N5 active center confined by hierarchically porous carbon nanoframes (Fe SAs/N5-pC-4) was prepared by a polymerization-pyrolysis-evaporation-etching strategy, and its underlying enzyme-like mechanism was uncovered through experiments and density functional theory calculations. The 100% metal atom utilization, increased accessible active sites, accelerated mass transfer, excellent hydrophilicity, and an electron-driven mechanism of axial N endow the SAC with enhanced oxidase-like activity. Notably, its catalytic rate constant (0.398 s-1) is 569 times greater than that of the commercial Pt/C catalyst. Similar to the catalytic mechanism of Ccos, O2 can be converted into reactive oxygen species, avoiding the use of co-reactant H2O2 effectively. In addition, based on the inhibitory effect of thiols on the active site of Fe SAs/N5-pC-4, a biosensor was constructed and applied to the colorimetric analysis of OPs. This provides a facile, cost-effective method for efficient OP screening at sites to help control their contamination.

Sensitive detection of organophosphorus pesticides based on the localized surface plasmon resonance and fluorescence dual-signal readout

In this work, a dual-signal visual biosensor was designed for organophosphorus pesticides (OPs) detection using DNA functionalized Ag/Au bimetallic nanoparticles (Ag/Au NPs) as multifunctional nanoprobe. The dual-signal detection strategy was based on the inhibition of enzyme-induced H2O2 generation by OPs in the detection solution containing acetylcholinesterase (AChE), choline oxidase (CHO), acetylcholine (ACh) and nanoprobe. H2O2 produced by enzyme-catalyzed reaction could trigger the etching of Ag and dissociation of carboxyfluorescein (FAM)-labeled aptamer from the nanoprobe, resulting in significant localized surface plasmon resonance (LPRR) and fluorescence (FL) signal responses. In the presence of OPs, AChE activity was inhibited to disrupt the enzymatic generation of H2O2, which allowed to simultaneous quantitative measure OPs through the LSPR peak shifts and FL intensity variations of the nanoprobe. The LSPR/FL dual-signal biosensor showed great selectivity and sensitivity for OPs detection. In addition, two distinct colour changes were visually observed to match the LSPR/FL spectra signal responses, which was a feasible means for visual analysis of OPs. Consequently, the work provided a dual-signal visual biosensor via the combination of multifunctional nanoprobe, and had significant potential to monitor pesticide residue with high anti-interference capability and detection accuracy.

Ultrathin graphdiyne nanosheets confining Cu quantum dots as robust electrocatalyst for biosensing featuring remarkably enhanced activity and stability

There is an urgent need for developing electrochemical biosensor based on the acetylcholinesterase (AChE) inhibition to real-time analysis of organophosphorus pesticides (OPs), but it is suffered from the sluggish electrode kinetics and high oxidation potential toward signal species. Herein, a nanocomposite of ultrafine Cu quantum dots (QD) uniformly loaded on three-dimensional ultrathin graphdiyne (GDY) nanosheets (denoted as Cu@GDY) was synthesized via a one-step strategy, which showing high-density of active sites with persistent stability. Then an AChE biosensor based on Cu@GDY was fabricated to detect OPs, and the results revealed that the Cu@GDY nanocomposite can significantly amplifies electrochemical signal and reduces the oxidation potential for OPs. The strong interaction between active site of Cu@GDY and thiocholine signal species caused rapid analyte aggregation and decreased the reaction activation energy of thiocholine electro-oxidation. Benefiting from the excellent catalytic activity of Cu@GDY nanocomposite and reasonable regulation of enzyme inhibition kinetics, the biosensor achieved rapid and sensitive detection of OPs with a detection limit of 1 μg L−1 for paraoxon. Furthermore, the biosensor demonstrated great reproducibility, good stability and high recovery rate for OPs detection in real samples. Cu@GDY based sensor also displayed high catalytic activities and good selectivity to the non-enzymatic detection of glucose in alkaline medium. Cu@GDY offers a versatile and promising platform for sensors and biosensors featuring remarkably enhanced activity and stability, and can be applied to many other fields as desirable electrocatalyst.

An amplified fluorescence polarization assay for sensitive sensing of organophosphorus pesticides via MnO2 nanosheets

It is highly desirable to develop a simple, efficient and sensitive strategy for organophosphorus pesticides (OPs) in both environment pollution and human health. Herein, a novel amplified fluorescence polarization (FP) biosensor was established for highly sensitive detection of OPs using MnO2 nanosheets as the signal enhancer. In this system, OPs can suppress the activity of acetylcholinesterase (AChE) efficiently, blocking the hydrolysis reaction of acetylthiocholine (ATCh) to generate thiocholine (TCh) by AChE. TCh can lead the decomposition of MnO2 nanosheets to manganese ions. So, without the influence of TCh, MnO2 nanosheets can maintain its original shape and form a stable complex with FAM-DNA, which greatly enhanced the FP signal. This method can tremendously improve the sensitivity of FP with a detection limit of 0.01 ng/mL for diazinon. In addition, it was also applicable to determine other four OPs and investigate the level of diazinon in real water samples. Consequently, the proposed approach provides a new promising platform for detection of OPs and is expected to be used in application of environmental monitoring.

An Acetylcholinesterase-Functionalized Biosensor for Sensitive Detection of Organophosphorus Pesticides Based on Solution-Gated Graphene Transistors

In this work, a highly sensitive and selective organophosphorus pesticide (OP) biosensor based on a solution-gated graphene transistor (SGGT) has been successfully constructed. The electrochemical performance of the device is improved by immobilization of acetylcholinesterase (AChE) on the gold gate electrode with chitosan (CHIT) for detection of OPs. The AChE/CHIT-functionalized SGGT sensor shows an ultralow detection limit of 10 nM for OPs and a wide linear range from 300 nM to 3 μM. We also proved that the SGGT-based OP sensor has good selectivity and recovery performance for efficient evaluation of the level of OPs in actual rice samples. This sensor provides a promising detection platform for rapid and sensitive analysis of OPs in real samples with complex components and can be readily applied to many other important analytes for agricultural and food safety using the corresponding enzymes.

Unsymmetrically coordinated single Fe-N3S1 sites mimic the function of peroxidase

The development of highly active biomimetic catalysts with peroxidase (POD)-like activity and realization of vivid mimicking of the active sites of natural enzymes still remains a huge challenge. Herein, atomically dispersed Fe atoms on hierarchically S/N co-doped porous carbon (FeSNC) featured with the unsymmetrically coordinated Fe-N3S1 as active sites were synthesized by a template-assisted method. The resultant FeSNC exhibits higher POD-like activity than FeNC featured with Fe-N4 sites. Owing to the S doping-induced geometric/electronic effects, Fe-N3S1 not only lengthens the OO bonding distances of adsorbed H2O2 but also accelerates the electronic transfer between Fe and O, decreasing the energy barrier of the formation of the active intermediate and thus achieving the boosted POD-like activity. Finally, the sensitive detection of organophosphorus pesticides was performed by adjusting the POD-like activity of FeSNC, exhibiting satisfactory sensitivity and selectivity. This work provides great promise for the accurate design of single-atom catalysts for vivid mimicking the function of natural enzymes.

Multicolor enzyme-linked immunosorbent sensor for sensitive detection of organophosphorus pesticides based on TMB2+-mediated etching of gold nanorods

A multicolor enzyme-linked immunosorbent sensor was constructed to detect organophosphates pesticides (OPs) on base of TMB2+-mediated AuNRs etching. As the etching progresses, a rainbow-like color responses was generated. The naked eye limit of detection (LOD) of the sensing system is 0.25 ng mL−1. In particular, the longitudinal localized surface plasmon resonances (LSPR) peak shift of AuNRs is linearly correlated with the logarithm of OPs concentration in range of 104 to 5 × 106 pg mL−1 for parathion-methyl and fenitrothion, 5 × 104 to 107 pg mL−1 for fenthion, respectively. Compared with reported methods, this sensor displayed satisfactory linear ranges and detection limits. Average recoveries of this method ranged from 73.28% to 98.08% and relative standard deviations (RSDs) were below 8.0% as for food samples analysis without complicated pretreatments. Remarkably, the developed multicolor enzyme-linked immunosorbent sensor is capable of providing accurate and reliable assay for OPs in complex food samples.

PH and Redox Dual-Response Disulfide Bond-Functionalized Red-Emitting Gold Nanoclusters for Monitoring the Contamination of Organophosphorus Pesticides in Foods.

Most of the fluorescence sensors require choline oxidase or quenchers to detect organophosphorus pesticides (OPs) based on a single hydrolysate and suffer from high cost, complex procedures, weak stability, and low sensitivity. Here, we proposed a brand-new fluorescence strategy for highly sensitive detection of OPs based on both hydrolysate-response disulfide bond-functionalized gold nanoclusters (S-S-AuNCs) without additional substances. S-S-AuNCs were synthesized via a facile one-step redox reaction and emitted bright red light with ultrasmall size and high water dispersion. Interestingly, S-S-AuNCs displayed a unique response to thiol compounds and low pH values and were thus pioneered as a high-efficiency sensor for OPs based on acetylcholinesterase (AChE)-catalyzed hydrolysis of acetylthiocholine into thiocholine and CH3COOH and OP inhibition of AChE activity. Further, S-S-AuNCs were employed to monitor the residue, distribution, and metabolization of methidathion in pakchoi with acceptable results. We believe that this work supplies a simpler and more highly sensitive approach for OP assay than the known ones and opens a new avenue to development of multistimulus-responsive and high-performance fluorescence substances.

PH-Response Quantum Dots with Orange-Red Emission for Monitoring the Residue, Distribution, and Variation of an Organophosphorus Pesticide in an Agricultural Crop.

Development of simple, sensitive, and reliable fluorescence sensors for monitoring the residue, distribution, and variation of organophosphorus pesticides (OPs) in agricultural crops is highly urgent but remains challenging, which is ascribed to deprivation of an ideal fluorophore and ingenious detection strategy. Herein, we report the fabrication of cadmium telluride quantum dots (CdTe QDs) with bright emission, good water dispersion, and long emission wavelength for OP screening based on the unique response of CdTe QDs to pH and the inhibition of OPs on acetylcholinesterase (AChE) activity. AChE catalyzed hydrolysis of acetylcholine (ACh) into CH3COOH, which protonated CdTe QDs to decline the fluorescence, whereas target OP impeded AChE from catalyzing hydrolysis of ACh into CH3COOH, making little influence in fluorescence of CdTe QDs. On the basis of the change in fluorescence, sensitive detection of OP was acquired, with the limit of detection at 0.027 ng/mL, which was comparable or lower than that of most known OP sensors. Furthermore, the CdTe-QD-based sensor was successfully applied for precisely monitoring the residue, distribution, and variation of methidathion in Chinese cabbage and cultivated soil. Therefore, the proposed sensor was anticipated to supply a promising alternative for food safety guarantee and was an valuable application for OP screening.

An OliGreen-responsive fluorescence sensor for sensitive detection of organophosphorus pesticide based on its specific selectivity towards T-Hg2+-T DNA structure

In this paper, it was found that OliGreen emitted much stronger fluorescence in rigid T-Hg2+-T DNA structure than that in the presence of poly T. Thus, an OliGreen-responsive label-free fluorescent sensor was proposed for sensitive detection of organophosphorus pesticides (OPs) by constructing T-Hg2+-T DNA structure. OliGreen emits strong fluorescence in T-Hg2+-T structures. The rigid DNA structure of T-Hg2+-T is prone to be destroyed by thiocholine (TCh) that hydrolyzed by acetylcholinesterase (AChE) because of the high affinity of TCh with Hg2+. As a result, T-Hg2+-T DNA structure broke down and the fluorescence intensity of OliGreen decreased greatly. With the inhibition of AChE by OPs, fluorescence intensity of OliGreen remained strong because of the rigid T-Hg2+-T DNA structure. Thus, a “turn-on” fluorescent sensor which avoids synthesis of nanomaterials and complex label procedures is proposed based on the fluorescence intensity of OliGreen. DDVP were detected with a wide linear range from 0.005 to 25.0 ng/mL and the detection limit was 2.9 pg/mL, which is more sensitive than previously reported methods.