Correction to: A molecularly imprinted polymer with integrated gold nanoparticles for surface enhanced Raman scattering based detection of the triazine herbicides, prometryn and simetryn.

The published version of this article, unfortunately, contains error. Author name was corrected as "A. M. Abd EI-Aty" - upper case of "i" in "EI-Aty", instead of "A. M. Abd El-Aty" - lower case of "L". Given in this paper is the correct author name.

A disposable electrochemical sensor based on electrospinning of molecularly imprinted nanohybrid films for highly sensitive determination of the organotin acaricide cyhexatin.

Nanofibrous polyporous membranes imprinted with cyhexatin (CYT) were formed via the ordered distribution of the imprints in electrospun nanofibers. The MIPs have a high mass transfer rate and enhanced adsorption capacity. In addition, a printed carbon electrode with enhanced sensitivity was developed via electrochemical fabrication of reduced graphene oxide (rGO) and gold nanoparticles (AuNPs). The molecularly imprinted sensor exhibits excellent selectivity and sensitivity for CYT. The structure and morphology of the nanohybrid films were characterized by using scanning electron microscopy, atomic force microscopy and chronoamperometry. The sensing performances were evaluated by cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy by using hexacyanoferrate(IV) as an electrochemical probe. The electrode, best operated at a working potential of around 0.16 V (vs. Ag/AgCl), has a linear response in the 1-800 ng mL-1 CYT concentration range and a detection limit of 0.17 ng mL-1 (at S/N = 3). The sensor demonstrated satisfactory recoveries when applied to the determination of CYT in spiked pear samples. Graphical abstract Schematic presentation of the electrochemical sensor for detection of CYT.

Rapid colorimetric determination of the pesticides carbofuran and dichlorvos by exploiting their inhibitory effect on the aggregation of peroxidase-mimicking platinum nanoparticles.

A novel and highly sensitive enzyme inhibition assay was developed for the rapid detection of the organophosphate pesticide dichlorvos and the carbamate pesticide carbofuran. It achieves signal amplification by the secondary catalysis of platinum nanoparticles. Acetylcholinesterase (AChE) is capable of catalyzing the hydrolysis of acetylthiocholine to form thiocholine. Thiocholine causes the aggregation of citrate-capped platinum nanoparticles which then lose their peroxidase-mimicking properties. After addition of pesticides, the activity of AChE is inhibited, less thiocholine is produced, less aggregation occurs, and the peroxidase-mimetic properties are increasingly retained. In the presence of tetramethylbenzidine and H2O2, a deep blue coloration with an absorption maximum at 650 nm will be formed. The assay was applied to the determination of dichlorvos and carbofuran, and detection limits of 2.3 µg·L-1 and 1.4 µg·L-1 were obtained, respectively. Recovery experiments with spiked tap water and pears gave satisfactory relative standard deviations. Graphical abstract The blue product formed by platinum nanoparticle-catalyzed oxidation of 3,3'5,5'-tetramethylbenzidine (TMB) by H2O2 is reduced if acetylthiocholine (ATCh) is hydrolyzed by acetylcholinesterase (AChE) to form thiocholine. However, if AChE is inhibited by pesticides, color formation will recover.

A molecularly imprinted polymer with integrated gold nanoparticles for surface enhanced Raman scattering based detection of the triazine herbicides, prometryn and simetryn.

A class-specific molecular imprinted polymer (MIP) is described for simultaneous recognition of prometryn and simetryn prior to their determination via a fingerprint signal (at 974 cm-1 and 1074 cm-1) in the surface enhanced Raman scattering (SERS) spectra that were acquired in the presence of gold nanoparticles. The imprinted nanoparticles were applied to the analysis of rice and wheat samples spiked with both herbicides. The method has fairly good recoveries (72.7-90.9%) with a relative standard deviation of 1.7-7.8%, and a 20 µg·kg-1 limit of detection. The imprint factors (compared to non-imprinted polymers) are 5.3 for prometryn and 4.2 for simetryn (both at 10 µg·mL-1 of the initial solution). Graphical abstract A MIP-SERS method was developed for simultaneous detection of triazine herbicides (prometryn and simetryn) in food samples.

Fabrication of a highly sensitive electrochemical sensor based on electropolymerized molecularly imprinted polymer hybrid nanocomposites for the determination of 4-nonylphenol in packaged milk samples.

Herein, an imprinted electrochemical sensor based on graphene-Au nanoparticles incorporated with molecularly imprinted polymer (MIP) was fabricated for determination of 4-nonylphenol (4-NP). Grafted MIP electropolymerized on nanoscale multilayer films electrode was achieved using 4-NP as a template and P-aminothiophenol as a functional monomer. The electrochemical properties of the MIP nanoscale multilayer membrances were characterized and measured by cyclic voltammetry and differential pulse voltammetry techniques; using ferrocyanide/ferricyanide-redox marker. Several important parameters were optimized and investigated to improve the performance of the sensor. Under the optimized conditions, the developed sensor showed an excellent linear response over the concentration ranges of 50-500 ng mL-1 (4-NP) with a detection limit of 0.01 ng mL-1(S/N = 3). The developed sensor showed a good selective recognition of 4-NP compared with structural analogue, exhibited a good reproducibility and accuracy with long-term stability. At last, the feasibility of the proposed methodology was successfully applied fordetection of 4-NP in milk and its packaging materials.

SERS-active metal-organic frameworks with embedded gold nanoparticles.

Surface-enhanced Raman scattering (SERS) has been widely used in the detection of targets and strongly depends on the interaction and the distance between the targets and nanoparticles. Herein, metal-organic frameworks (MOFs) were first easily synthesized on a large scale via a water bath method, especially Uio-66 and Uio-67. MOFs embedded with gold nanoparticles (AuNPs) for SERS enhancement were successfully fabricated via an impregnation strategy. The synthesized AuNPs/MOF-199, AuNPs/Uio-66, and AuNPs/Uio-67 composites, with LSPR properties and high adsorption capability of MOFs to preconcentrate the analytes close to the surface of the AuNPs, exhibited excellent SERS activity. The effects of the reducing concentrations of sodium citrate on the SERS activity, and the stability and reproducibility of the AuNP/MOFs have been discussed via the detection of acetamiprid. The SERS intensity enhanced by the composites was retained for more than 40 days under ambient conditions with the reducing concentrations of sodium citrate at 0.16%, 0.20%, and 0.16%. The limits of detection with the signal/noise ratio higher than 3 at the characteristic peak 632 cm-1 were 0.02 µM, 0.009 µM, and 0.02 µM for acetamiprid. Most interestingly, the AuNP/MOF-199 composites, whose morphology was long tube sheet, exhibited excellent SERS activity. These novel composites with high sensitivity, stability, and reproducibility provide a new route for the detection of pesticides via the SERS technology.

One-pot synthesis of magnetic zeolitic imidazolate framework/grapheme oxide composites for the extraction of neonicotinoid insecticides from environmental water samples.

Magnetic zeolitic imidazolate framework 67/graphene oxide composites were synthesized by one-pot method at room temperature for the first time. Electrostatic interactions between positively charged metal ions and both negatively charged graphene oxide and Fe3 O4 nanoparticles were expected to chemically stabilize magnetic composites to generate homogeneous magnetic products. The additional amount of graphene oxide and stirring time of graphene oxide, Co2+ , and Fe3 O4 solution were investigated. The zeolitic imidazolate framework 67 and Fe3 O4 nanoparticles were uniformly attached on the surface of graphene oxide. The composites were applied to magnetic solid-phase extraction of five neonicotinoid insecticides in environmental water samples. The main experimental parameters such as amount of added magnetic composites, extraction pH, ionic strength, and desorption solvent were optimized to increase the capacity of adsorbing neonicotinoid insecticides. The results show limits of detection at signal-to-noise ratio of 3 were 0.06-1.0 ng/mL under optimal conditions. All analytes exhibited good linearity with correlation coefficients of higher than 0.9915. The relative standard deviations for five neonicotinoid insecticides in environmental samples ranged from 1.8 to 16.5%, and good recoveries from 83.5 to 117.0% were obtained, indicating that magnetic zeolitic imidazolate framework 67/graphene oxide composites were feasible for analysis of trace analytes in environmental water samples.

Dual-template imprinted polymers for class-selective solid-phase extraction of seventeen triazine herbicides and metabolites in agro-products.

A novel dual-template molecularly imprinted polymer (DMIP) was prepared with atrazine and prometryn as the template and applied as a class-specific adsorbent for simultaneously selective solid-phase extraction of seventeen triazine herbicides and metabolites from complex matrices. For comparison, a non-imprinted polymer (NIP) and two single-template imprinted polymers (SMIPs) were also synthesized using the same procedure of DMIP, but in the absence of the template (NIP) or with one template (SMIP). Various parameters affecting the extraction performance of DMIP-SPE were investigated in detail. Under the optimum conditions, the enrichment efficiency, class-selectivity and reusability of DMIP-SPE were evaluated. Only DMIP-SPE possessed high affinity and good selective recognition ability for all the seventeen targets including chloro-, thiomethyl- and methoxy- triazines. Further, a DMIP-SPE-LC-MS/MS method was developed for simultaneously determining trace triazine herbicides and metabolites in maize, wheat and cottonseed samples. The method showed good linearity (r>0.9941) in the range of 10-200 µg kg-1, high sensitivity with low limits of detection of 0.5-8.8 µg kg-1, and satisfactory recoveries of 61.3-105.9% with relative standard deviations of 2.1-10.7%. These results highlighted the good application prospect of the multi/dual-template imprinting strategy in the high-throughput analysis of various concerned contaminants in agro-products.

Sensitive and Simple Competitive Biomimetic Nanozyme-Linked Immunosorbent Assay for Colorimetric and Surface-Enhanced Raman Scattering Sensing of Triazophos.

The biomimetic enzyme-linked immunosorbent assay (BELISA) is widely used for detection of small-molecule compounds as a result of low cost and reagent stability of molecularly imprinted polymers (MIPs). However, enzyme labels used in BELISA still suffer some drawbacks, such as high production cost and limited stability. To overcome the drawbacks, a biomimetic nanozyme-linked immunosorbent assay (BNLISA) based on MIPs and nanozyme labels was first proposed. For nanozyme labels, platinum nanoparticles (PtNPs) acted as peroxidase by catalyzing the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) into an ideal surface-enhanced Raman scattering (SERS) marker. Blue TMB2+ and bovine serum albumin (BSA)-hapten showed superior selectivity when competing with targets for binding sites on MIPs, named the Pt@BSA-hapten probe. The BNLISA method was employed to detect triazophos with a limit of detection of 1 ng mL-1 via colorimetric and SERS methods. Replacing traditional enzymes with nanozymes for combination with MIPs may bring about a new prospect for other compound analyses.

"Off-On" non-enzymatic sensor for malathion detection based on fluorescence resonance energy transfer between ß-cyclodextrin@Ag and fluorescent probe.

Here, we developed a novel non-enzymatic rapid testing method for determination of organophosphate pesticide (malathion) in water. In principle, target molecule can block the Fluorescence resonance energy transfer (FRET) between chemical fluorescent probe (energy donor) and ß-cyclodextrin-coated silver nanoparticles (@AgNP) (receptor). The effects of malathion on the dynamics of fluorescent probe and ß-cyclodextrin@AgNP were evaluated and their properties were further characterized. The current methodology showed a good sensitivity of 0.01 µg/mL represented as a limit of detection (LOD) and the calibration curve was linear over the concentration range of 0.1-25 µg/mL. Recovery rate from water samples spiked at 3 different concentration levels (0.3, 0.4, and 0.6 µg/mL) showed satisfactory range between 83% and 101%.

A dummy molecularly imprinted solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry for selective determination of four pyridine carboxylic acid herbicides in milk.

We aim to develop a solid-phase extraction (SPE) based on a dummy molecularly imprinted polymer (MIP) and liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS) for selective determination of four pyridine carboxylic acid herbicides (aminopyralid, picloram, fluroxypyr, and clopyralid) in milk samples. Using picloram as the dummy template, MIP nanocomposites with highly selective recognition and adsorption for the target molecule and its structural analogs were successfully synthesized by precipitation polymerization. Adsorption isotherms and kinetics were used to determine the adsorption performance and specific recognition mechanism of both MIPs and non-molecularly imprinted polymers (NIP). The Scatchard plot analysis revealed that two different binding sites were formed in the MIP with maximum binding capacity (Qmax) of 1171.8 µg·g-1 and 3022.5 µg·g-1, respectively. Recovery at three spiking levels of 10, 20, and 50 µg·L-1 ranged between 75.3 and 89.8% with relative standard deviations (RSDs) <14.3%.The limit of detection (LOD) was estimated to be 0.124 µg·L-1. Finally, the feasibility of the proposed methodology was successfully applied to quantify aminopyralid and another three pyridine carboxylic acid herbicides in milk.

A Novel CdSe/ZnS Quantum Dots Fluorescence Assay Based on Molecularly Imprinted Sensitive Membranes for Determination of Triazophos Residues in Cabbage and Apple.

In the present study we have developed a direct competitive CdSe/ZnS quantum dot (QD) fluorescence assay based on micro-array-imprinted membranes for the determination of triazophos in cabbage and apple. The imprinted membranes were directly synthesized on the surface of a 96-well plate by thermal polymerization using triadimefon as the dummy template. Under optimal conditions, the assay showed an excellent linear response over the concentration ranges of 0.1-10,000 µg L-1 with a good coefficient of determination (R 2= 0.982). The sensitivity (IC50) and limit of detection (LOD, expressed as IC15) of the developed assay were 3.63 mg L-1 and 0.31 µg L-1, respectively. The applicability of the developed approach was tested for detecting triazophos in incurred samples. The method showed excellent recoveries (109.6-118.9%) and relative standard deviations (RSDs) between 9.9 and 19.5%. The obtained results correlated well with those obtained by LC-MS/MS (R 2= 0.9995). The competitive assay using CdSe/ZnS QDs as fluorescence-labeled probe showed good sensitivity, steady and fast response, and excellent anti-interference ability compared to conventional fluorescence-quenching methods. Finally, the feasibility of the proposed methodology was successfully applied for detection of triazophos in real samples.

Metal-organic framework UiO-66 for rapid dispersive solid phase extraction of neonicotinoid insecticides in water samples.

UIO-66 crystals were explored for the first time to adsorb neonicotinoid insecticides in environmental water samples. HPLC coupled with tandem MS was used for quantification and determination of neonicotinoid insecticides. UiO-66 crystals was successfully synthesized by a simple constant-temperature bath method. Synthesized UiO-66 was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry and nitrogen adsorption porosimetry (NAP), which demonstrated a uniform particle size, a large Brunauer-Emmett-Teller (BET) surface area and high thermostability. The adsorbing results showed that UIO-66 crystals could be used as a promising adsorbents for rapid extraction of neonicotinoid insecticides and be reused at least 10 times. Under the optimized conditions, the limits of detection (LODs, S/N = 3) and limits of quantification (LOQs, S/N = 10) for the five insecticides were found to be 0.02-0.4 ng/mL and 0.05-1.0 ng/mL, respectively. This developed approach not only provided more simple and sensitive method, as well as possessing satisfactory recovery for neonicotinoid insecticides, but also for other traces in environmental samples.

Biomimetic enzyme-linked immunoassay based on a molecularly imprinted 96-well plate for the determination of triazophos residues in real samples.

In this study, a direct competitive biomimetic enzyme-linked immune-sorbent assay (BELISA) based on a molecularly imprinted nanomembrane as an artificial antibody was developed for the determination of triazophos in real samples. The imprinted film was directly synthesized on the well surface of a 96-well plate using a dummy molecular template under the conditions of thermal polymerization. The developed BELISA using a hapten of triazophos as an enzyme-labeled probe is much more sensitive, simple, quick, steady and inexpensive than the other instrumental and immuno assay methods. Under optimal conditions, the linear range of the method was 0.001-10 000 µg L-1 with a good regression coefficient of 0.977. The sensitivity (IC50) and the limit of detection (LOD) of BELISA were 428 µg L-1 and 0.001 µg L-1, respectively. This method was performed to detect triazophos in cabbage and apple samples, and showed excellent recovery and relative standard deviations (RSDs) ranging from 70.5 to 119.8% and from 5.2 to 19.7%, respectively. The results correlated well with those obtained using high performance liquid chromatography-tandem mass spectrometry.