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The key to developing sensors for chiral drug determination is to exclude interference from enantiomers. In this study, metal–organic frameworks (MOFs) and molecularly imprinted polymer (MIP) were introduced to prepare a chiral sensor for levofloxacin detection. The MIP was electropolymerised on the surface of the Cu/Fe-benzene-1,3,5-tricarboxylate MOF (Cu/Fe-BTC)-modified Au electrode using levofloxacin as a template molecule. After eluting the levofloxacin, a chiral sensor with recognition sites for levofloxacin was obtained. With this site as a switch, a novel method for detecting levofloxacin was established. Because of the enhanced recognition effect, the sensor can effectively exclude the enantiomeric interference of d-ofloxacin. Moreover, Cu/Fe-BTC can effectively amplify the current response signal and improve the sensitivity of the sensor. The linear range of the sensor was 5 to 4000 × 10−11 mol L−1, and the detection limit was 2.07 × 10−11 mol L−1. When applied to detecting levofloxacin in actual samples, the sensor showed a 92.7–109.8% recovery. [ABSTRACT FROM AUTHOR]

A highly sensitive kanamycin electrochemiluminescence (ECL) switch sensor was constructed. A signal element consisting of ordered mesoporous carbon loaded with indium oxide nanoparticles/carbon quantum dots (OMC/In2O3/C-dots) was assembled on the surface of a gold electrode. Then, a molecularly imprinted polymer (MIP) was prepared on the modified electrode surface using kanamycin as the template molecule and o-aminophenol as the functional monomer. After kanamycin elution, the prepared sensor retained specific kanamycin recognition sites. OMC/In2O3 effectively amplified the ECL signal of the C-dots, thereby enhancing the detection sensitivity, whereas kanamycin quenched the signal. Therefore, the imprinted sites acted as a switch, providing a new method for detecting kanamycin. Under the optimal experimental conditions, the concentration of kanamycin was proportional to the degree of ECL quenching within a linear range of 5–4500 × 10−12 mol L−1 at 0.8 V (vs. Ag/AgCl electrode electrode), and the detection limit was 5.8 × 10−13 mol L−1. When applied to the detection of kanamycin in actual samples, such as chicken, duck, pork, and milk, the recovery for spiked samples was in the range 92.7–110%. [ABSTRACT FROM AUTHOR]

Considering the limitations associated with existing methods for the detection of trace amounts of trichlorfon, this paper proposes a novel molecularly imprinted electrochemiluminescence (ECL) sensor for the detection of trichlorfon by utilizing the double enhancement effect of trichlorfon and Ag nanoparticles supported by multi-walled carbon nanotubes (MWCNTs/Ag NPs) in a luminol–H2O2 ECL system. Here, trichlorfon was electropolymerized on the surface of the MWCNT/Ag NP–modified gold nanoelectrode with o-phenylenediamine to prepare the molecularly imprinted polymer-based sensor. After eluting the trichlorfon, imprinted holes for the identification of trichlorfon were retained on the sensor, which were used as signal switches to obtain different ECL intensities through the adsorption of different concentrations of trichlorfon. The ECL signal of the sensitized luminol–H2O2 was doubly enhanced by the MWCNTs/Ag and trichlorfon, improving the sensitivity of the sensor. The trichlorfon concentration was positively correlated with the enhanced ECL intensity of the sensor in the range 5.0 × 10−8–5.0 × 10−11 mol L−1, and the detection limit of trichlorfon was 3.9 × 10−12 mol L−1. Moreover, the proposed sensor was successfully applied to the detection of trichlorfon residues in real samples, and the recovery ranged between 91.8 and 109%. A molecularly imprinted electrochemiluminescence sensor for trichlorfon detection by utilizing the double enhancement effect of trichlorfon and Ag nanoparticles supported by multi-walled carbon nanotubes in a luminol–H2O2 ECL system. The dual enhancement of the ECL signal improved the sensitivity of the sensor. [ABSTRACT FROM AUTHOR]

The rapid detection of insecticides such as parathion-methyl (PM) requires methods with high sensitivities and selectivities. Herein, a dual catalytic amplification strategy was developed using Fe3O4 nanozyme-supported carbon quantum dots and silver terephthalate metal–organic frameworks (Fe3O4/C-dots@Ag-MOFs) as current amplification elements. Based on this strategy, a novel electrochemical microfluidic paper-based chip was designed to detect PM. Fe3O4/C-dots@Ag-MOFs were synthesised by a hydrothermal method, and a molecularly imprinted polymer (MIP) was then synthesised on the surface of Fe3O4/C-dots@Ag-MOFs using PM as a template molecule. Finally, the reaction zone of a chip was modified with MIP/Fe3O4/C-dots@Ag-MOFs. PM from a sample introduced into the reaction zone was captured by the MIP, which generated a reduction current response at − 0.53 V in a three-electrode system embedded in the chip. Simultaneous catalysis by Fe3O4/C-dots and Ag-MOFs significantly enhanced the signal. The chip had a detection limit of 1.16 × 10−11 mol L−1 and was successfully applied to the determination of PM in agricultural products and environmental samples with recovery rates ranging from 82.7 to 109%, with a relative standard deviation (RSD) of less than 5.0%. This approach of combining a dual catalytic amplification strategy with an MIP significantly increased the sensitivity as well as selectivity of chips and can potentially be used to detect a wide variety of target analytes using microfluidic paper-based chips. [ABSTRACT FROM AUTHOR]

Fluorescence intensity and selective recognition ability are crucial factors in determining the analytical techniques for fluorescent probes. In this study, a core–shell fluorescent material, composed of silver nanoparticles@nitrogen-doped graphene quantum dots (Ag NPs@N/GQDs), was synthesised using mango leaves as the raw material through a thermal cracking method, resulting in strong fluorescence luminescence intensity. By employing noradrenaline as a template molecule and using a surface molecular imprinting technique, a molecularly imprinted membrane (MIP) was formed on the surface of the fluorescent material, that was subsequently eluted to obtain a highly specific, fluorescent probe capable of recognising noradrenaline. The probe captured various concentrations of noradrenaline using the MIP, which decreased the fluorescence intensity. Then a method for detecting trace amounts of noradrenaline was established. This method exhibited a linear range from 0.5 –700 pM with a detection limit of 0.154 pM. The proposed method was implemented in banana samples. Satisfactory recoveries were confirmed at four different concentrations. The method presented a relative standard deviation (RSD) of less than 5.0%. [ABSTRACT FROM AUTHOR]

A highly selective and amplification strategy levamisole sensor using an electrode modified with a Cu/Zn-trimesic-acid MOF and an molecularly imprinted polymer. Cu/Zn-BTC fixed the conformation of levamisole in the first step of the recognition, whereas the MIP formed weak hydrogen bonds with levamisole in the second stage in the sensor. The combination of these two recognition processes effectively improved the levamisole-recognising ability of the sensor. Additionally, the bimetallic MOF material doubly amplified the probe signal, effectively improving the detection sensitivity. The sensor showed excellent chiral recognition attributes and high sensitivity for levamisole. [Display omitted] • An electrochemical sensor was built to distinctly detect the trace levamisole enantiomer. • A molecularly imprinted polymer and Cu-Zn/BTC were used for improving selectivity of sensor. • Cu-Zn/BTC can effectively amplify the current response signal of the sensor. • The sensor showed excellent selectivity for levamisole and excluded dextramisole interference. We used an enhanced recognition strategy to fabricate a novel levamisole-detecting chiral electrochemical sensor featuring a metal–organic framework (MOF) combined with a molecularly imprinted polymer (MIP). We first synthesised a Cu/Zn-[benzene-1,3,5-tricarboxylic acid] (Cu/Zn-BTC) MOF as the molecular immobilisation and signal-amplifying unit, and then prepared the MIP (molecular recognition unit) using levamisole as the template on a glassy carbon electrode modified with Cu/Zn-BTC. We obtained a composite chiral sensor with enhanced recognition capability for levamisole after template removal. Using the templated sites as the switch and K 3 [Fe(CN) 6 ]/K 4 [Fe(CN) 6 ] as a probe, we established a new method for detecting levamisole in meat products and water bodies. The linear detection range and detection limit of our chiral sensor are 5 to 6000 × 10-11 mol/L and 1.65 × 10−12 mol/L, respectively. Moreover, the sensor exhibited 93.8–109.0% recovery in the detection of levamisole in chicken and other real samples. [ABSTRACT FROM AUTHOR]

The performance of an electrochemiluminescent reagent directly affects the performance of its corresponding electrochemiluminescent (ECL) sensor. In this study, Fe/Zn-benzene-1,3,5-tricarboxylic acid metal–organic framework@C-dots (Fe/Zn-BTC@C-dots), which consist of a nano-loaded carbon quantum dot material with an excellent luminescence performance, were synthesised for the first time. Subsequently, they were used to modify the surface of a glassy carbon electrode, and combined with a single-chain thiamethoxam DNA aptamer to construct a biosensor. A novel method for the detection of thiamethoxam was established based on control of the excellent luminescence signal of the Fe/Zn-BTC@C-dots by specific recognition of the aptamer by the target molecule (a signal switch). Upon capturing thiamethoxam, the electrochemical luminescence intensity of the sensor was quenched. The ability of Fe/Zn-BTC to effectively catalyse and amplify the electrochemical luminescence of the C-dots significantly improved the sensitivity of the sensor, while the specific recognition of the target by the aptamer imparted the sensor with an excellent selection ability. Such an advanced approach is promising for the detection of thiamethoxam, with a linear range of 5–5000 × 10−11 mol/L and a sensitivity of 9.81 × 10−12 mol/L being achieved. Moreover, the sensor exhibited recovery rates of 90.5–109.3% upon the detection of thiamethoxam in actual samples. [Display omitted] • Fe/Zn-BTC@C-dot composites were prepared to construct an ECL sensor. • This DNA-adapted sensor was applied in the sensitive detection of thiamethoxam. • The sensor exhibited a remarkable reproducibility, selectivity, and stability. [ABSTRACT FROM AUTHOR]

The use of dual recognition and multiple detection modes is an attractive strategy for realising sensors with improved selectivity and accuracy. Herein, a molecularly imprinted polymer (MIP)-based sensor is developed for amoxicillin detection based on two detection modes (fluorescence and electrochemiluminescence) and dual recognition. First, graphene oxide loaded with CdTe quantum dots/gold nanoparticles (GO/CdTe/Au NPs) is coated onto an indium tin oxide (ITO) electrode. Then, 4-mercapto-calix[6]arene is bonded to GO/CdTe/Au NPs as the first recognition element, which then form a host–guest complex with the target molecule amoxicillin. Subsequently, as the second recognition element, an MIP is prepared on the ITO electrode. After amoxicillin is removed from the MIP, specific identification sites for amoxicillin are obtained. Furthermore, the GO/CdTe/Au NPs can generate fluorescence and electrochemiluminescence signals that are effectively quenched by amoxicillin. Therefore, on/off switching of these signals can be achieved through the elution or adsorption of amoxicillin. The dual detection modes are complementary and provide mutual authentication, which can improve the detection accuracy and application scope. Moreover, the dual recognition sites for amoxicillin, improve detection selectivity. The fluorescence and electrochemiluminescence modes have detection ranges of 5–1000 × 10−11 mol L−1 and 5–1500 × 10−11 mol L−1, respectively, with detection limits of 9.2 × 10−12 mol L−1 and 8.3 × 10−12 mol L−1, respectively. Image 1 • An amoxicillin sensor is fabricated based on two detection modes, with GO/CdTe/Au NPs used as an optical element. • Dual fluorescence and electrochemiluminescence detection modes improve accuracy. • Dual recognition sites (4-mercapto-calix[6]arene /molecularly imprinted polymer) impart selectivity. [ABSTRACT FROM AUTHOR]

A luminescent double recognition nanoprobe is described as a new strategy for the selective determination of chiral molecules. C-dots/Ir/Au fluorescent nanoparticles, synthesised under hydrothermal conditions, are used as a high-performance probe in combination with a molecularly imprinted polymer (MIP) and calix[6]arene as a double recognition element. Thiolated calix[6]arene is grafted on C-dots/Ir/Au as the first recognition element, which then forms a host–guest complex with the target molecule levodopa (L-DOPA). Subsequently, an MIP is prepared on the C-dots/Ir/Au (MIP/C-dots/Ir/Au) by chemical polymerisation. After the removal of L-DOPA, double recognition imprinting cavities are formed. The fluorescence intensity at 478 nm of the nanoprobe is effectively quenched by adsorption of L-DOPA on MIP/C-dots/Ir/Au, which provides a method for L-DOPA determination. Owing to the double recognition strategy, this method has excellent selectivity which can effectively avoid interference from enantiomer D-DOPA, and a imprinting factor of 7.1 is obtained for L-DOPA. This accurate and reliable method, with a wide linear range (5 × 10−10 to 1.2 × 10−7 mol L−1) and a low limit of detection (1.45 × 10−10 mol L−1), was successfully applied to the determination of L-DOPA in real samples, giving standard recoveries of 89.7–110.0%. Thus, the proposed sensing method provides a viable approach for the determination of a single enantiomer. [ABSTRACT FROM AUTHOR]

A fluorometric assay is described for the determination of Cd(II) in environmental and agricultural samples. It is making use of a molecularly imprinted polymer (MIP) and aptamer as dual recognition units, while carbon quantum dots (co-doped with sulphur and nitrogen) and gold nanoparticles (SN-CQD/Au) act as the fluorophores. The aptamer-modified MIP was placed on an SN-CQD/Au-modified indium tin oxide glass electrode. Cd(II) was detected with high selectivity by the recognition sites of the aptamer in the MIP. Fluorescence, with excitation/emission peaks at 370/430 nm, is quenched by Cd(II). Response is linear in the 20 pM to 12 nM concentration range. The detection limit is 1.2 pM. The sensor is selective for Cd(II), and recoveries from spiked waters, soils and vegetables real-world samples range between 82.1 and 113.9%. [ABSTRACT FROM AUTHOR]

An electrochemiluminescence (ECL) switch sensor with a dual-recognition mechanism was developed based on complexation reactions and a molecular imprinted film (MIP). The MIP was prepared on a gold electrode with ferroferric oxide/carbon quantum dots (Fe 3 O 4 /C-dots) via electrochemical polymerization. An L -canavanine–trinitrobenzene complex was used as the template molecule and o -phenylenediamine was used as the functional monomer. Further, C-dots were used as the ECL signal elements and the L -canavanine–trinitrobenzene complex could quench the ECL signal. Subsequently, by using the elution and re-adsorption of the template molecule as the control switch, it was possible to control the ECL intensity of the sensor, and establish a new method for rapidly measuring L -canavanine. A sensor that combined complexation recognition and imprinting recognition demonstrated excellent performance in terms of recognizing specific target molecules. The detection limits of this method reached 7.32 × 10−11 mol L−1, and the measurement results for practical samples were satisfactory. • A novel molecularly imprinted molecular switch sensor is fabricated for biotoxin L -canavanine determination. • The dual-recognition system between molecular imprinting polymers and trinitrobenzene is the first studied. • Fe 3 O 4 /C-dots act as electrochemiluminescence element, and establish a new method for measuring L -canavanine sensitively. [ABSTRACT FROM AUTHOR]

A new molecularly imprinted polymer electrochemiluminescence (ECL) sensor was developed for the detection of clopyralid (CPD) based on enzyme-biocatalyzed amplification. CdTe quantum dots were immobilized on the surface of an electrode by reaction with p-aminothiophenol preadsorbed on the electrode. Then a molecularly imprinted film was formed by electrochemical polymerization of o-phenylenediamine in the presence of CPD on the CdTe-modified gold electrode. During the analytical cycle, horseradish peroxidase (HRP)-labeled CPD was replaced by CPD in the sample. The amount of HRP on the molecularly imprinted polymer electrode decreased, and then less H2O2 was catalytically decomposed. Subsequently, the ECL intensity of the CdTe-H2O2 system was enhanced. There was a good linear relationship between ECL intensity and the concentration of CPD in the range from 2.0 × 10-11 to 2.5 × 10-10 mol/L and in the range from 2.5 × 10-10 to 3.5 × 10-8 mol/L. The detection limit was 4.1 × 10-12 mol/L. The sensor was applied to determine CPD in vegetable samples.A molecularly imprinted electrochemiluminescence sensor was fabricated for ultratrace clopyralid determination. The sensitivity was significantly improved with the enhancement of the ECL intensity of quantum dot via the enzymatic reaction of HRP [ABSTRACT FROM AUTHOR]

The degradation of bifenthrin (BF) and chlorpyrifos (CP), either together or individually, by a bacterial strain (CB2) isolated from activated sludge was investigated. Strain CB2 was identified as belonging to genus Pseudomonas based on the morphological, physiological, and biochemical characteristics and a homological analysis of the 16S rDNA sequence. Strain CB2 has the potential to degrade BF and CP, either individually or in a mixture. The optimum conditions for mixture degradation were as follows: OD600nm = 0.5; incubation temperature = 30°C; pH = 7.0; BF-CP mixture (10 mg L−1 of each). Under these optimal conditions, the degradation rate constants (and half-lives) were 0.4308 d−1 (1.61 d) and 0.3377 d−1 (2.05 d) for individual BF and CP samples, respectively, and 0.3463 d−1 (2.00 d) and 0.2931 d−1 (2.36 d) for the BF-CP mixture. Major metabolites of BF and CP were 2-methyl-3-biphenylyl methanol and 3,5,6-trichloro-2-pyridinol, respectively. No metabolite bioaccumulation was observed. The ability of CB2 to efficiently degrade BF and CP, particularly in a mixture, may be useful in bioremediation efforts. [ABSTRACT FROM AUTHOR]

The authors describe an electrochemiluminescence (ECL) based aptasensor for the pesticide aldicarb. The method is based on effective ECL energy transfer that occurs between the ruthenium(II) bipyridyl complex [referred to as Ru(bpy) ] and gold nanoparticles (AuNPs). More specifically, multiwalled carbon nanotubes were modified with dendritic poly( L-arginine) labeled with Ru(bpy) , and the aptamers were taggedd with AuNPs. In the absence of aldicarb, the ECL emitted by Ru(bpy) is enhanced by AuNPs under peak wavelength at at a wavelength of 610 nm. In the presence of aldicarb, the capture and competitive binding of aldicarb to the DNA aptamers causes their separation from the DPA6/Ru(bpy) /MWCNT. As a result, ECL intensity decreases linearly with increasing aldicarb concentrations in the range between 40 pM and 4 nM, with a detection limit of 9.6 pM. This aptamer switch is highly sensitive, selective and inexpensive. Conceivably, it can be adapted to formats for the determination of other pesticide residues by using different DNA aptamers. [ABSTRACT FROM AUTHOR]

In this study, a biosensor with a dual recognition system comprising a molecularly imprinted polymer (MIP) and aptamers selective for lincomycin was fabricated. The MIP was synthesized by electropolymerization of carbon dots (C-dots)-tagged DNA aptamers combined with lincomycin and o -aminophenol on the gold-nanoparticle-functionalized graphene oxide (Au-GO)-modified electrode. Electrogenerated chemiluminescence (ECL) resonance energy transfer was observed between Au-GO and C-dots. After the C-dots accepted the energy, they acted as a signal indicator and exhibited enhanced signal intensity in the presence of target lincomycin. When lincomycin was competitively bound to DNA aptamers and MIP, it blocked the transfer of energy, and a decreased ECL signal was observed. Hence, a dual recognition method for the detection of lincomycin is realized. Using this strategy, the sensor exhibited a linear ECL response to lincomycin at concentrations from 5.0 × 10 −12 mol/L to 1.0 × 10 −9 mol/L. The detection limit of this assay was found to be 1.6 × 10 −13 mol/L. This method was utilized to determine lincomycin residuals in meat samples with satisfactory results. [ABSTRACT FROM AUTHOR]

The authors describe an electrochemical sensor for the neonicotinoid insecticide imidacloprid (IMI) based on Pt-In catalytic nanocomposite film and Bromophenol blue amplification. The Pt-In nanocomposite film was deposited on the surface of a modified glassy carbon electrode. The composite molecularly imprinted polymer (MIP) was prepared by electro-polymerization using bromophenol blue doped o-aminophenol as functional monomer and 4-tert-butylcalix[6]arene-IMI supramolecular inclusion complex as template molecule. The experimental results showed that the current intensity of IMI was clearly amplified in the potential range from −0.3 to −1.8 V, because of the double amplification, based on the Pt-In film and Bromophenol blue catalysis. Moreover, the double recognition ability of the sensor, which relied on the MIP and the vacuum structure of 4-tert-butylcalix[6]arene, effectively increased the specific recognition performance. The feasibility of its practical applications has been demonstrated by the analysis of vegetable samples. [ABSTRACT FROM AUTHOR]

In this study, an electrogenerated chemiluminescence (ECL) sensing platform for carbofuran detection was constructed based on ECL energy transfer (ECRET) and carbon dot (C-dot)-tagged aptamers as the recognition element. Fullerene (C60)-loaded gold nanoparticles (C60-Au) were used as the energy donor, modified on a glassy carbon electrode. C-dot-tagged DNA aptamers were used as the receptor, and ECRET then occurred between C60-Au and C-dots. After accepting the energy, the C-dots acted as a signal indicator and showed decreased signal intensity in the presence of targets, which competitively bound to DNA aptamers and blocked energy transfer. Using this robust, straight-forward strategy, the sensor showed a linear ECL response to carbofuran at concentrations from 2.0 × 10 −11 mol L −1 to 8.0 × 10 −9 mol L −1 . The detection limit of this assay was shown to be 8.8 × 10 −13 mol L −1 . Thus, the sensing approach described in this study could be adapted for use in the detection of various pesticide residue targets. [ABSTRACT FROM AUTHOR]

We present novel magnetic composite nanospheres for the preparation of a nanoiron oxide/carbon dots/β-cyclodextrin/molecularly imprinted polymer for the selective solid-phase extraction kelthane and pyridaben from vegetables. The molecularly imprinted polymer was synthesized on the surface of nano-iron oxide/carbon dots via a chemical polymerization procedure, where kelthane-β-cyclodextrin and pyridaben-β-cyclodextrin inclusion complexes were used as template molecules, and their adsorption behavior was investigated in detail. Characterization analysis and binding experiments revealed that magnetic composite nanospheres had outstanding magnetic properties, a large adsorption capacity, and high competitive selectivity for kelthane and pyridaben. The magnetic composite nanospheres were employed as an adsorbent in solid-phase extraction for the determination of kelthane and pyridaben in vegetable samples. The recoveries of kelthane and pyridaben were 92.8-105.2 and 94.4-104.6%, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • GO/Au NPs/β-CD modified electrode base-electrochemical sensor for imidacloprid determination reported for the first time. • Multiple amplification strategy enhanced sensitivity. • Excellent range of response, limit of detection, repeatability, and selectivity. The key to improving the sensitivity of electrochemical sensors for direct detection is the introduction of catalytically amplified nanomaterials. Accordingly, in this study, a new strategy for the preparation of electrochemical sensors with multiple amplification effects is proposed. Graphene oxide (GO), gold nanoparticles (Au NPs), and β-cyclodextrin (β-CD) were introduced to the surface of a glassy carbon electrode via cyclic voltammetry to prepare a modified electrode sensor with a GO/Au NPs/β-CD thin film. The prepared sensor effectively catalyzed and amplified the reduction current of imidacloprid in a B-R buffer with pH = 5.0 owning to the multiple amplification effects of GO/Au NPs/β-CD. A good linear relationship was observed the level of the reduction current response and the imidacloprid at concentrations ranging from approximately 5 × 10−10 to 3000 × 10−10 mol/L; thus, a new imidacloprid detection method using an electrochemical sensor was established. The new method, whose detection limit reached 1.33 × 10−10 mol/L, was tested on actual samples, achieving recoveries of 92.0 % to 110.0 %. [ABSTRACT FROM AUTHOR]

The authors describe a nanomaterial for solid-phase extraction of carbendazim. Magnetic molecularly imprinted polymer nanoparticles (mag-MIP-NPs) were obtained by immobilizing the MIP and a thiolated β-cyclodextrin on the surface of magnetite (FeO) nanoparticles coated with gold nanoparticles. Both the recognition sites of the MIP and the hydrophobic cavities in the β-cyclodextrin contribute to the specific molecular recognition and extraction of carbendazim. The mag-MIP-NPs have an apparent adsorption capacity of 190 mg⋅g‾. Spiked vegetables were analyzed by using this material for extraction of carbendazim prior to its determination by ultra performance liquid chromatography (UHPLC). Recoveries range from 90.5 % to 109 %, and the detection limit is 3.0 pg⋅mL‾. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A novel supramolecular imprinted electrochemical sensor was developed for carbofuran (CBF) determination based on a multiwalled carbon nanotube-supported Pd-Ir nanocomposite catalyst (MWCNT/Pd-Ir) with methylene blue (MB) signal amplification. First, MWCNT/Pd-Ir composite nanoparticles were synthesized and used to modify the surface of a glassy carbon electrode; then, a molecular imprinted polymer for CBF was prepared by electropolymerization, with MB-doped o -phenylenediamine as the functional monomer and a 4-tert-butylcalix[8]arene-CBF (4TB[8]A-CBF) supramolecular complex as the template. The electrical signals were controlled though the elution and re-adsorption of CBF. Due to the double catalysis by the MWCNT/Pd-Ir and MB, the current intensity for CBF was obviously amplified. Additionally, because of the double recognition by the 4TB[8]A and MIP, the sensors showed outstanding CBF identification properties. The method was applied to detect CBF in agricultural products, and the satisfactory results were obtained. [ABSTRACT FROM AUTHOR]

A novel fluorescence switch sensor was constructed for detecting the fungicide fenaminosulf (FM), based on a dye-doped molecularly imprinted polymer (MIP) and silver nanofilm amplification. The MIP was prepared by electropolymerization of hydroquinone doped with neutral red on the silver nanofilm modified electrode. A fluorescence signal was produced by the neutral red and the fluorescence intensity was diminished by the ion pair that formed via electrostatic forces between FM and the dye. Therefore, elution and adsorption of FM by the MIP acted as a switch to control the fluorescence intensity, which was effectively amplified by the silver nanofilm. The decrease in fluorescence intensity was linear with the FM concentration, establishing a new method for FM detection. Under optimal conditions, good linear correlation was obtained for FM concentrations over the range from 2.0×10 −10 to 4.0×10 −8 mol/L, with a detection limit of 1.6×10 −11 mol/L. This method was utilized to determine residual FM in vegetable samples, and recoveries ranging from 92.0% to 110% were obtained. [ABSTRACT FROM AUTHOR]

Schematic presentation of the sensor for the detection of CFX. [Display omitted] • An electrochemiluminescence sensor for ciprofloxacin determination was developed. • Aggregation-induced luminescence and nanozyme amplification enhanced sensitivity. • A molecularly imprinted polymer provided selectivity. • A linear detection range of 2–3000 pM was achieved with detection limit of 0.598 pM. To broaden the applicability of electrochemiluminescence (ECL) sensors toward the sensitive and selective detection of trace antibiotic residues, new ECL reagents are required. Herein, a novel molecularly imprinted sensor based on an aggregation-induced ECL reagent was fabricated for the sensitive detection of ciprofloxacin (CFX). A covalent organic framework with aggregation-induced ECL (COF-AIECL) was synthesised using a boric acid condensation dehydration reaction. Then, an electrode surface was modified with COF-AIECL as a signal element and nanozymatic ferriferrous oxide@platinum nanoparticles (Fe 3 O 4 @Pt NPs) as a signal amplification element. Subsequently, using CFX as a template molecule, a molecularly imprinted polymer (MIP) was fabricated on the modified electrode. The ECL signal of COF-AIECL was catalytically amplified by the Fe 3 O 4 @Pt NPs, whereas CFX effectively quenched this signal. Consequently, the ECL signal was controlled by CFX elution from and adsorption by the MIP, thus establishing a new method for CFX detection. The sensitivity of the sensor was greatly enhanced by the aggregation-induced luminescence effect and nanozyme amplification, whereas the MIP effectively improved the selectivity for CFX. Under optimal conditions, the electrochemical sensor exhibited a linear detection range of 2 × 10−12 to 3 × 10−9 mol L−1, with a detection limit of 5.98 × 10−13 mol L−1. Furthermore, in untreated milk samples, CFX recoveries of 92.0%–111% were achieved. Thus, the developed sensor exhibited good reproducibility, stability, and selectivity for CFX detection. [ABSTRACT FROM AUTHOR]

A new molecularly imprinted sensor was developed based on an electroluminescent molecularly imprinted polymer (MIP) membrane and used for doxycycline determination. The MIP was prepared by electropolymerization of pyrogallol doped with alizarin red. An electrochemiluminescence (ECL) signal was produced by the oxidation of the poly-pyrogallol polymer and reaction with alizarin red. The luminescence intensity was enhanced by doxycycline molecules which were re-adsorbed in cavities in MIP due to the energy transfer of the doxycycline oxidized intermediate to alizarin red. The changes of ECL intensities were linear with the concentrations of doxycycline in the range of 2 × 10−10 to 5 × 10−8 mol L−1. The detection limit was 5.17 × 10−11 mol L−1. This method was utilized to determine doxycycline residuals in fish muscles with satisfactory results. [ABSTRACT FROM AUTHOR]

A novel molecularly imprinted fluorescent sensor was developed for dimethoate determination based on fluorescence resonance energy transfer. First, a doped molecular template polymer was prepared by electropolymerization. During dimethoate detection, a competitive reaction occurred between dimethoate and carbon dot labeled dimethoate. Fluorescence resonance energy transfer between residual carbon dots labeled dimethoate in the sensor and methyl red on the doped molecularly imprinted polymer then occurred, enhancing the fluorescence signal of the sensor. The fluorescence intensity decreased when the carbon dots labeled dimethoate molecules were replaced by dimethoate molecules in the samples. Under optimal conditions, good linear correlation was obtained for dimethoate over the concentration range from 6 × 10 −10 mol/L to 3.4 × 10 −8 mol/L with a detected limit of 1.83 × 10 −11 mol/L. This sensor was used to detect for dimethoate in actual samples, for which recoveries ranging from 95.0% to 106.0% were obtained. [ABSTRACT FROM AUTHOR]

Schematic diagram of GQDs/C-dots system for imidacloprid detection by FRET. [Display omitted] • A fluorescence resonance energy transfer system base on GQDs/C-dots was developed. • A fluorescence method to detect traces of imidacloprid was designed base on fluorescence quenching. • The fluorescence probe exhibited high sensitivity, and selectivity for imidacloprid. Herein, a fluorescent probe was investigated for the detection of imidacloprid based on the fluorescence resonance energy transfer (FRET) between two carbon-based quantum dots, namely graphene- and carbon quantum dots (GQDs/C-dots). In an HAc-NaAc buffer solution at pH = 5.0, an effective FRET occurred between the GQDs and C-dots, significantly enhancing the C-dot fluorescence. When imidacloprid was added to the FRET system, the fluorescence intensity of the C-dots was quenched in a linear imidacloprid concentration-dependent manner, which allowed for the establishment of a new method for the determination of imidacloprid by GQD/C-dot FRET. Under optimised experimental conditions, the linear range of imidacloprid was 5–4000 × 10−9 mol L−1, with a correlation coefficient r and a detection limit of 0.998 and 8.23 × 10−10 mol L−1, respectively. This method was applied to the detection of imidacloprid residues in real samples, and a satisfactory recovery rate of standard additions was found between 93.0% and 105.6%. [ABSTRACT FROM AUTHOR]

Highlights: [•] An electrochemiluminescence immunosensor for detection of SCCA was first reported. [•] CdTe@CDs nanocomposite and ERET of CdTe@CDs was introduced for electrochemiluminescence immunosensor at the first time. [•] CdTe@CDs composite nanocomposite has relatively good electro-optical properties. [•] The Fe3O4 magnetic nanoparticles enrichment enhances the ECL signal intensity. [ABSTRACT FROM AUTHOR]

Cancer is still one of the leading causes of death in the world. There are over 200 types of cancers currently known according to the National Cancer Institute. However, early diagnosis continues to be an important integral part of cancer treatment even though many advances in therapeutics have been made in the past decade. Quick diagnosis and early prevention are critical for the control of the disease status. Biomarkers are commonly indicative of a particular disease process and the cancer biomarkers are also widely used in oncology to help detecting the presence of various carcinomas. The detection of cancer biomarkers plays an important role in clinical diagnoses and evaluation of treatment for patients. Many immunoassay methods are developed for detection of cancer biomarkers. As the detection devices are normally viewed with high sensitivity, simple preparation and rapid response, electrochemical biosensors are increasingly used for the detection of cancer markers. This review describes the status, the latest research and trends of electrochemical sensors in the quantitation of cancer markers in recent years. In particular, the strategy to improve the sensitivities of the electrochemical biosensors by the aid of enzymatic amplification, nanoparticle amplification, ultilization of magnetic microspheres etc. is described herein. At last, we discuss some special features and limitations associated with the described systems that summarize the application and the development prospects of electrochemical immunoassay technology. [ABSTRACT FROM AUTHOR]

A new molecularly imprinted electrochemical luminescence sensor (MIP-ECL sensor) was developed for isoproturon (IPU) determination based on the competition reaction between IPU and glucose oxidase labeled IPU (GOD-IPU). After competition, hydrogen peroxide produced by residual GOD-IPU on the MIP reacted with luminol to emit electrochemiluminescence (ECL) signal. The ECL intensity decreased when the GOD-IPU molecules were replaced by IPU molecules in the samples. IPU could be determined in the concentration range from 9×10−11 mol/L to 5.1×10−9 mol/L with a detection limit of 3.78×10−12 mol/L. Water samples were assayed and recoveries ranging from 98.5 % to 102.1 % were obtained. [ABSTRACT FROM AUTHOR]

Excessive pesticide residues in agricultural products could accumulate in organisms through the food chain, causing potential harm to human health. The investigation of dissipation kinetics and residues of pesticides in crops is crucial for the scientific application of pesticides and the mitigation of their adverse effects on human health. In vivo solid-phase microextraction (in vivo SPME) has unique advantages, but the research on field plants is still lacking and the quantitative correction methods need to be further developed. A method combining in vivo solid-phase microextraction with ultra-performance liquid chromatography-tandem mass spectrometry (in vivo SPME-UPLC-MS/MS) was developed to monitor the presence of acetamiprid, cyromazine, thiamethoxam and imidacloprid in cowpea fruits grown in the field. The sampling rates (R s) were determined using both in vitro SPME in homogenized cowpea samples and in vivo SPME in intact cowpea fruit samples. The in vivo-R s values were significantly higher than the in vitro-R s for the same analyte, which were used for in vivo SPME correction. The accuracy of this method was confirmed by comparison with a QuEChERS-based approach and subsequently applied to trace pesticide residues in field-grown cowpea fruits. The residual concentrations of each pesticide positively correlated with application doses. After 7 days of application at two different doses, all of the pesticides had residual concentrations below China's maximum residue limits. Both experimental data and predictions indicated that a safe preharvest interval for these pesticides is 7 days; however, if the European Union standards are to be met, a safe preharvest interval for cyromazine should be at least 13 days. This study highlights the advantages of in vivo SPME for simultaneous analysis and tracking of multiple pesticides in crops under field conditions. This technique is environmentally friendly, minimally invasive, highly sensitive, accurate, rapid, user-friendly, cost-effective, and capable of providing precise and timely data for long-term pesticide surveillance. Consequently, it furnishes valuable insights to guide the safe utilization of pesticides in agricultural production. [Display omitted] • An in vivo SPME-UPLC-MS/MS method was constructed for pesticide tracking in cowpea. • Its accuracy is proved by comparison with the QuEChERS-UPLC-MS/MS method. • It is more convenient, easy, quick, eco-friendly, sensitive and cheap. • The safe preharvest intervals for pesticides can be both detected and predicted. • The tracking method prevents the risk of pesticide residues in food. [ABSTRACT FROM AUTHOR]

Combining electrochemiluminescence (ECL) with nanozyme amplification provides unique advantages for the detection of antibiotic residues. Herein, a molecularly imprinted chloramphenicol (CAP) sensor was established based on aggregation-induced (AI)-ECL and nanozyme amplification. Covalent organic framework materials with AI-ECL groups (COF-AI-ECL) and nanozyme Co 3 O 4 were synthesised as the signal element and the amplification element, respectively. Subsequently, using CAP as a template molecule, a molecularly imprinted polymer (MIP) was fabricated on the electrode surface modified with COF-AI-ECL and Co 3 O 4. The ECL signal of COF-AI-ECL was catalytically amplified by Co 3 O 4 , whereas CAP effectively quenched this signal. Consequently, the ECL signal was controlled by the elution and adsorption of CAP by the MIP, thus establishing a new method for CAP detection. Unlike traditional ECL reagent, COF-AI-ECL exhibited a stable and strong ECL signal. Therefore, COF-AI-ECL in combination with the MIP provided greater sensitivity and enhanced selectivity. The linear range of the developed CAP sensor was 5 × 10−13 to 4 × 10−10 mol/L, with a detection limit of 1.18 × 10−13 mol/L. Moreover, the recoveries range of 85.0%–106.2% were obtained for the detection of CAP in real honey, milk, and chicken samples, indicating the potential of this sensor design for the detection of trace antibiotic residues in food safety applications. • A chloramphenicol sensor base on COF-AI-ECL materials was developed. • The ECL reagent provided a stable signal that was amplified by nanozyme Co 3 O 4. • A molecularly imprinted polymer enhanced the selectivity for chloramphenicol. • The sensor exhibited high sensitivity, stability, and reproducibility. [ABSTRACT FROM AUTHOR]

• The sensor detection method for ethephon based on molecularly imprinted switch was established for the first time. • Au NPs-amplification effect was proposed in the sensor to improve sensitivity. • This sensor can be used as a general strategy to detect other target molecules. A highly sensitive molecularly imprinted ethephon sensor based on the amplification effect of gold nanoparticle (Au NPs) was designed in this study. An ethephon molecularly imprinted polymer (MIP) was prepared on a surface by electropolymerisation with Au NPs as the carriers and ethephon as the template molecule. Elution of the template molecule gave an MIP sensor that retains imprinted sites for specific recognition of ethephon. The sensor forms a current switch through adsorption of different concentrations of ethephon molecules to obtain different current responses, thereby establishing a new method for ethephon detection. The results indicated that using Au NPs as a carrier in the ethephon imprinted sensor could permit the loading of more MIP and increase the electron-transfer rate. The sensitivity of the sensor prepared with Au NPs was increased by three orders of magnitude compared to conventional MIP sensors without a carrier. Using potassium ferricyanide as a probe, the oxidation peak intensity of the probe molecule and the negative logarithm of the ethephon concentration exhibited a linear relationship within the concentration range from 1.0 × 10−13 to 1.0 × 10−9 mol L−1. The linear equation was ΔI (10−5 A) = −1.7838 × (−lg c) + 26.1216, and the detection limit was 2.78 × 10−14 mol L−1. In addition, the sensor successfully measured the ethephon content in apples. [ABSTRACT FROM AUTHOR]

A dual selection/recognition effect is described for cobalt (II) ions (Co2+). It is based on bovine serum albumin-metal-Co2+ coordination (BSA-Co2+) and the use of a molecularly imprinted polymer (MIP). An electrochemiluminescence (ECL) switch sensor was designed for detecting nanomolar levels of Co2+. The BSA-Co2+ coordination complex was chosen as a template to prepare a MIP modified switch sensor. The coordination reaction between BSA and Co2+ provides the first step in recognition, and MIP provides the second step for Co2+. This leads to a strong improvement in selectivity of the sensor. A multi-walled carbon nanotube/Cu nanoparticles/carbon quantum dots nanocomposite (MWCNT/Cu/C-dots) acts as an ECL device, and the BSA-Co2+ complex quenches the ECL signal. Therefore, the elution and resorption of BSA-Co2+ can be used as a switch to control ECL. Additionally, a method was established to detect Co2+, with the detection limit as low as 3.07 × 10−10 mol/L. The method was applied to the analysis of spiked environmental water, soil samples, and agricultural products. The recovery rates of the method were in the range of 87.5–111.3%. • A novel switch sensor base on MIP and BSA-Co2+ coordination as recognition elements is fabricated for Co2+ determination. • MWCNT/Cu/C-dots are act as electrochemiluminescence element for measuring Co2+ sensitively. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe/B/N codoped hierarchical porous carbon spheres (B-N-Fe-HPCs) were coated onto a gold electrode. • B-N-Fe-HPCs amplified the electrochemiluminescence (ECL) signal of calcein. • The sensor showed very high sensitivity and good selective for the detection of florfenicol. • The sensor had a linear range of 1–8000 × 10−12 mol/L and a detection limit of 4.65 × 10−13 mol/L. Electrochemiluminescence (ECL) signal amplification is an important method for improving sensor sensitivity. In this study, an ECL sensor was developed for florfenicol detection based on the aggregation-induced electrochemiluminescence of calcein and Fe/B/N codoped hierarchical porous carbon spheres (B-N-Fe-HPCs). First, B-N-Fe-HPCs were prepared by a simple high-temperature synthesis method, attached to the gold electrode surface, and used as a signal amplification element. Then, a molecularly imprinted polymer (MIP) was prepared using florfenicol as a template molecule and phthalylenediamine as a functional monomer and doped with calcein on the B-N-Fe-HPC-modified electrode. After the elution of florfenicol, the sensor retains an imprinted site that specifically recognizes florfenicol can readsorb florfenicol in the sample. Because calcein aggregates in the MIP to generate an ECL signal, B-N-Fe-HPCs effectively amplifies this ECL signal. Thus, because the ECL signal of the sensor can be quenched, a new method for detecting florfenicol was established. The sensor used for florfenicol showed very high sensitivity and good selective performance, with a linear range of 1–8000 × 10−12 mol/L and a detection limit of 4.65 × 10−13 mol/L. The sensor was applied to detect actual samples, such as chicken, and the results were satisfactory, with the recovery rate of the spike from 91.2 % to 105.3 %. [ABSTRACT FROM AUTHOR]

A series of arecoline derivatives with amino acid moieties were designed and synthesised using an acylamide condensation strategy, taking arecoline as the foundational structure. The insecticidal efficacy of these compounds against Aphis craccivora and Tetranychus cinnabarinus was evaluated. Notably, derivatives 3h and 3i demonstrated superior insecticidal activity compared with arecoline. Additionally, 3h and 3i showed good fungicidal effectiveness against two types of plant fungi. Moreover, molecular docking analyses suggested that 3h and 3i could affect the nervous systems of A. craccivora and T. cinnabarinus by binding to neuronal nicotinic acetylcholine receptors. These findings suggest that compounds 3h and 3i represent promising leads for further development in insecticide and fungicide research. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) exhibit excellent photoelectrically active structures and serve as channels for photon capture and charge carrier transport. However, their relatively high charge-carrier recombination rates and lack of specific recognition sites limit their application in photoelectrochemical sensing. This paper reports a functionalized donor–acceptor (D-A) COF comprising electron-rich polycyclic aromatic moieties and electron-deficient triazines (Tz) incorporating boronic acid through ligand exchange. The number of aromatic rings in the polycyclic aromatic moiety is crucial for establishing an efficient D-A system within COF. In the absence of an external electron donor, the anthracene-based COF exhibited a five-fold enhancement in photocurrent compared to the naphthalene-based COF. The resulting anthracene-based D-A COF exhibited enhanced orbital overlap and electron push–pull interactions, facilitating more effective charge separation. Furthermore, introducing boronic acid enabled the selective enrichment of low-concentration external electron donors, such as dopamine, in the inner Helmholtz plane. This ingenious approach establishes a unique dual-channel D-A system that allows direct measurement of dopamine in serum. Under optimized conditions, the test platform achieves good correspondence for dopamine at 1 to 100 nM and 0.5 to 100 μM with a detecting limit of 0.36 nM (3σ/S, n = 11). This strategy introduces a novel dimension to photoelectrochemical sensing, focusing on the effect of spatial separation between the external electron donor and the photoelectrode interface that intricately shapes the behavior and enhances the performance of the photoelectric system. A boric acid functionalized dual channel D-A COF by incorporating a condensed aromatic hydrocarbon as the electron donor moiety and triazine as the electron acceptor have been synthesized and successfully applied in specific sensing of trace dopamine in serum. [Display omitted] [ABSTRACT FROM AUTHOR]

The authors describe a method of electrochemiluminescent quantitation of the antibiotic sulfaquinoxaline (SQX). It relies on the use of a molecularly imprinted polymer and a Cu(II)-anchored unzipped covalent triazine framework (UnZ-CCTF) with excellent dispersibility, electrical conductivity, and peroxidaze-like activity. The framework was prepared by unzipping a covalent triazine framework under retention of basic triazine units. It was morphologically and structurally characterized by a range of instrumental techniques. The excellent peroxidase-mimicking effect of UnZ-CCTF on the electrochemiluminescence of the luminol/H2O2 system was exploited to design an ultrasensitive SQX assay with a 1.0-20 pM detection range and a detection limit of 0.76 pM (at 3δ/m). The technique was used for SQX quantitation in spiked milk samples, achieving recoveries of 94.0-104.8%.Scheme of the sulfaquinoxaline molecularly imprinted electrochemiluminescence sensor based on Cu-anchored unzipped covalent triazine frameworks. [ABSTRACT FROM AUTHOR]

An electrochemical microfluidic chip is described for the determination of the insecticide carbofuran. It is making use of a molecularly imprinted film (MIP) and a DNA aptamer as dual recognition units. The analyte (carbofuran) is transported to the MIP and captured at the identification site in the channel. Then, carbofuran is eluted with carbinol-acetic acid and transported to the DNA aptamer on the testing position of the chip. It is captured again, this time by the aptamer, and detected by differential pulse voltammetry (DPV). The dual recognition (by aptamer and MIP) results in outstanding selectivity. Additionally, graphene oxide-supported gold nanoparticles (GO-AuNPs) were used to improve the sensitivity of electrochemical detector. DPV response is linear in the 0.2 to 50 nM carbofuran concentration range at a potential of −1.2 V, with a 67 pM detection limit. The method has attractive features such as its potential for high throughput, high degree of automation, and high integration. Conceivably, the method may be extended to other analytes for which appropriate MIPs and aptamers are available.Schematic of an electrochemical microfluidic chip for carbofuran detection based on a molecularly imprinted film (MIP) and a DNA aptamer as dual recognition units. In the chip, targets were recognized by MIP and aptamer, respectively. It shows promising potential for the design of electrochemical devices with high throughput, high automation, and high integration. [ABSTRACT FROM AUTHOR]

[Display omitted] • An electrochemical Cu2+ sensor is developed using a dual recognition strategy. • Bovine serum albumin and an ion-imprinted polymer provide selective Cu2+ recognition. • Amplification by graphene oxide-loaded gold nanoparticles increases sensitivity. • The linear range is 1–8000 × 10−14 mol/L with a 1.12 × 10−15 mol/L detection limit. Despite the promise of ion imprinting technology for the development of electrochemical sensors for heavy metals, improved selectivity and stability are required for practical applications. Herein, a dual recognition strategy based on a protein and an ion-imprinted polymer (IIP) was proposed to develop highly sensitive sensors for copper(II) ions (Cu2+). On Bovine serum albumin (BSA) and graphene oxide (GO)-loaded gold nanoparticles (GO/Au NPs) modify the gold electrode surface, an a Cu2+ IIP was formed on the electrode by electropolymerization. After Cu2+ was removed from IIP, the imprinted holes with a specific recognition ability for Cu2+ were obtained. In the prepared sensor, Cu2+ recognition sites were present in both BSA and the IIP, thus providing a dual recognition strategy for selective Cu2+ detection. Furthermore, owing to the amplification effect of GO/Au NPs, the sensor showed high sensitivity. With potassium ferricyanide/potassium ferrocyanide as a probe, the logarithm of the Cu2+ concentration was proportional to the sensor current response within the range of 1–8000 × 10−14 mol/L, and the detection limit was 1.12 × 10−15 mol/L. Moreover, for Cu2+ detection in actual samples, the sensor exhibited a recovery rate of 93.2–105.6 %. [ABSTRACT FROM AUTHOR]

A total 206 samples of green, yellow, white, black, and Oolong teas were utilized to acquire hyperspectral imaging, and five tea categories were identified based on visible and near-infrared (NIR) hyperspectral imaging, combined with classification pattern recognition. The characteristic spectra were extracted from the region of interest (ROI), and the standard normal variate (SNV) method was preprocessed to reduce background noise. Four dominant wavelengths (589, 635, 670, and 783 nm) were selected by principal component analysis (PCA) as spectral features. Textural features were extracted by the Grey-level co-occurrence matrix (GLCM) from images at selected dominant wavelengths. Linear discriminant analysis (LDA), library support vector machine (Lib-SVM), and extreme learning machine (ELM) classification models were established based on full spectra, spectral features, textural features, and data fusion, respectively. Lib-SVM was the best model with the input data fusion, and the correct classification rate (CCR) achieved 98.39%. The results implied that visible and NIR hyperspectral imaging combined with Lib-SVM has the capability of rapidly and non-destructively classifying tea categories. [ABSTRACT FROM AUTHOR]

A photoelectrochemical sensing platform based on ligand-variable metal clusters charge transfer was established for the quantitative assay of ronidazole (RNZ) using Ce-porphyrin-metal–organic frameworks/silver nanowires (Ce-Por-MOFs/AgNWs). Rod-like Ce-Por-MOFs and well-dispersed sub-50 nm AgNWs were prepared using a hydrothermal method and polyol strategy, and then through simple drop coating to yield Ce-Por-MOFs/AgNWs nanocomposites. We investigated the intrinsic semiconducting properties of the composites. More importantly, it was found that the variable-valence metal node can provide electronic defect states similar to those caused by multi-metal doping, synergizing with the surface plasmon effect of AgNWs, which significantly improved the photoelectric conversion efficiency, thereby resulting in excellent optoelectronic properties. In combination with molecular imprinting, a competitive type trace photoelectrochemical sensor for RNZ was constructed using Fe2+ as the electron donor and probe. Under optimal conditions, the sensor response is proportional to the logarithm of RNZ concentration in the range 0.1–104 nM with a detected limit of 0.038 nM. The recoveries ranged from 87.2 to 116% with relative standard deviations (RSDs) < 6.5% (n = 3) in milk sample. This work reveals the charge-transfer process of variable-valence metal nodes in MOFs during photoelectrochemical processes, which will provide new insights for the sensing application of variable-valence metal MOFs. [ABSTRACT FROM AUTHOR]

In this work a simple, rapid, and environmentally friendly method has been established for the determination of chlorpyrifos residue in green tea by dispersive liquid–liquid microextraction and gas chromatography-flame photometric detection. Some experimental parameters that influence extraction efficiency, such as the kind and volume of disperser solvents and extraction solvents, extraction time, addition of salt and pH, were investigated. And the optimal experimental conditions were obtained, quantitative analysis was carried out using external standard method. The correlation coefficient of the calibration curves was 0.999 with in 0.05 mg/kg to 5 mg/kg. The results showed that under the optimum conditions, the enrichment factors of the chlorpyrifos was about 554.51, the recoveries for standard addition fell in the range from 91.94 to 104.70% and the relative standard deviations was 4.61%. The limit of quantification of chlorpyrifos in green tea was 0.02 μg/mL at the signal/noise ratio of 3. [ABSTRACT FROM AUTHOR]

The residue levels of nine pesticides (imidacloprid, acetamiprid, carbendazim, diflubenzuron, chlorbenzuron, phoxim, pyrimethanil, abamectin and iprodione) in 117 samples of three minor tropical fruits (starfruits, wax apples and Indian jujubes) from Hainan, Fujian, Guangdong and Guangxi provinces in China were analyzed using ultra-high performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) after multi-residue extraction procedures. A total of 78 (66.7%) samples were positive, with residues above the limit of quantification. Indian jujube was the fruit with the highest percentage of positive samples (81.6%), followed by starfruit (61.0%) and finally wax apple (57.9%). Carbendazim was the most frequently detected residue found in 51 (43.6%) samples in the concentration ranges of 34.0–443.8 μg/kg. Diflubenzuron, phoxim, pyrimethanil and abamectin were not detected in any sample. Twenty-nine (24.8%) samples were contaminated with multiple pesticide residues, and the simultaneous occurrence of three different residues was found in one wax apple and two starfruit samples. Estimation of the potential health risks associated with the exposure to the analyzed pesticides was carried out and the estimated daily intakes (EDIs) were very low, ranging from 0.020% of the acceptable daily intakes (ADIs) for chlorbenzuron to 1.13% for carbendazim. These results indicate that despite a high occurrence of pesticides in starfruit, wax apple and Indian jujube, the contamination levels do not contribute significantly to pesticide intakes and are unlikely to have public health effects. Nevertheless, measures should be taken to hasten the registration of pesticides for use on minor fruit crops. The findings also indicate that routine monitoring of pesticide residues in minor fruits is necessary to prevent, control and reduce pesticide contamination and to minimize health risks. [ABSTRACT FROM AUTHOR]

A novel electrogenerated chemiluminescence (ECL) immunoassay based on enzyme amplification and magnetic nanoparticle enrichment was developed, and carbohydrate antigen 125 (CA125) was chosen as the analyte. FeO magnetic nanoparticles loaded with anti-CA125 were synthesized. The sandwich-type immunoassay was performed on the magnetic force-controlled carbon paste electrode via the immunoreactions among glucose oxidase-labeled anti-CA125, CA125, and anti-CA125 on the surface of magnetic nanoparticles. ECL was generated by the reaction between luminol and hydrogen peroxide. Hydrogen peroxide was produced during the enzymatic reaction with glucose and markedly increased in the presence of CA125 antigen. The CA125 concentrations were determined within the range of 0-10 mU mL, and the detection limit was 8.0 μU mL. The CA125 immunosensor was more sensitive than those previously reported. The proposed ECL method also provided a simple selectivity immunoassay protocol, which was applied in the determination of CA125 in clinical serum samples. [ABSTRACT FROM AUTHOR]

Highly-conductive two-dimensional covalent organic framework (COF) displays prominent applications in various fields of science and technology. This paper reports the design and liquid-liquid interface synthesis of a novel Zr-coordinated amide porphyrin-based 2D COF (Zr-amide-Por-based 2D COF). The COF adopts a graphene-like multilayer structure with the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) band gap of 1.6 eV. The ordered multilayer structure of the amide COF was confirmed through a series of characterization techniques, including scanning electron microscopy, high-resolution transmission electron microscopy, atomic force microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. In particular, the inherent-ordered structure of Zr-amide-Por-based 2D COF with Zr as the catalytically active center confers several distinct advantages to the material, such as high conductivity and high electrocatalysis performance. A molecularly imprinted tetracycline electrochemiluminescence sensor was constructed based on the Zr-amide-Por-based 2D COF, and gate control effect was used as a signal-generation mechanism. Under optimal conditions, the sensor showed a good linear relationship with tetracycline in the concentration range of 5–60 pM, with a detection limit of 2.3 pM. Because the sensor is rapid, cost-efficient, highly sensitive, and specific, it can be considered as a viable platform for veterinary drug residue monitoring. A molecularly imprinted tetracycline electrochemiluminescence sensor was constructed based on the efficient catalysis of Zr-coordinated amide porphyrin-based 2D COF on hydrogen peroxide. Image 1 • A amide 2D COFs was synthesized by liquid-liquid interfacial polymerization. • The prepared COFs with good conductivity and high catalytic activity were confirmed. • A tetracycline molecularly imprinted ECL sensor was constructed based on COFs. • The pM level of tetracycline was analyzed by the constructed sensor. [ABSTRACT FROM AUTHOR]

[Display omitted] • The polycentric affinity of PCN-224(Zn) on organophosphorus was confirmed. • Nb 4 C 3 was introduced into MOF-based heterojunction to enhance PEC properties. • Polycentric affinity cooperative MIPs achieves precise capture of targets. • The proposed sensor detects dimethoate at pM level in water & fruits. The analytical functionalization of metal organic frameworks (MOFs) has been an extremely attractive topic in photoelectrochemical (PEC) sensing. However, most PEC sensors based on photoactive MOFs are more focused on the acquisition and amplification of semiconductor photoelectric signals, and the study of affinity mechanisms for specific targets is more limited. Here, we find that PCN-224 (Zn) can effectively sense organophosphorus structures through a multicenter affinity mechanism, as evidenced by x-ray photoelectron spectroscopy (XPS) and computational chemistry. Further, we coupled PCN-224(Zn) to Nb 4 C 3 to form a Schottky junction that enhances the photoelectric signal response of the sensor. In particular, the heterojunction exhibited a higher photocurrent density than pristine PCN-224(Zn) (17.3 μA vs. 26.5 μA cm−2). On the basis, we developed a novel MOF-based polycentric-affinity PEC sensing strategy for dimethoate (DIM) detection in concert with molecular imprinting technology. The affinity effects of the Lewis acidic center sites (Zn(II), Zr(IV)) and spatial matching through molecular imprinting synergistically ensure that DIM is precisely captured. Ultimately, a trace DIM-PEC sensor was constructed by a competitive strategy using dopamine as an electron donor. The photocurrent intensity was linearly related to the logarithm of DIM concentration in the range of 0.1 nM to 1000 nM, with a low detection limit of 26.1 pM (3σ/S). This study demonstrates the potential of bifunctional polycentric-affinity MOF in the PEC sensing. [ABSTRACT FROM AUTHOR]

An ultrahigh-performance liquid chromatography/hybrid quadrupole time-of-fight mass spectrometry (UPLC/QTOF-MS) method for the simultaneous identification and quantification of 50 multi-class pesticides in minor fruits is reported. The method consists of a sample extraction step, followed by analysis of the pesticides by UPLC/QTOF-MS. Satisfactory chromatographic separation was achieved over a 20 min runtime. The pesticides were identified by the accurate mass measurements of the protonated molecules ([M+H] + ) and their main fragment ions, isotopic pattern analysis and retention time matching. The mass accuracy obtained was below 2 ppm error for all the pesticides analysed. The method was validated by spiking starfruit with the 50 analytes. Satisfactory results regarding sensitivity and linearity were obtained. The method was successfully applied to the analysis of 87 real-world starfruit and Indian jujube samples, demonstrating its applicability for the routine analysis of multiple pesticide residues in minor tropical fruits. [ABSTRACT FROM AUTHOR]

Owing to its unique features including low background noise, high signal-to-noise ratio, and rapid response, photoelectrochemical (PEC) sensing is a state-of-the-art platform for rapidly and accurately monitoring target compounds. Metal–organic frameworks (MOFs) and covalent organic frameworks (COFs) are key porous crystalline materials that show exceptional potential for application in PEC sensors. A timely and systematic review of the recent progress made and future research trends is valuable for accelerating MOF/COF-based PEC sensor development. This review first discusses the photoactive MOF/COF design principles and key PEC performance control factors by elucidating typical strategies for designing and fabricating photoactive MOFs/COFs to improve photoexcitation, charge separation/transfer. Then, an overview of the considerable progress made in applying MOF/COF-based materials to PEC sensing is presented including pristine MOFs/COFs, MOF/COF-based heterojunctions, MOF derivatives, and MOF/COF hybrids. Finally, the critical challenges for practical applications of MOF/COF-based PEC sensors and the research prospects are briefly discussed. • Recent advances reviewed for M/COF materials for PEC sensor applications. • Overview provides essential M/COF background information. • Key photoactive M/COF controlling factors are discussed. • Application of M/COF-based materials to PEC sensors is explored. • Research prospects proposed for developing commercial M/COF PEC sensor applications. [ABSTRACT FROM AUTHOR]

The fluorescence resonance energy transfer between fluorescent brightener (FB, donor) and CdTe quantum dots (CdTe QDs, acceptor) was studied and a new method for detecting Hg2+ ions in water samples was accordingly developed in this paper. It was found that the effective energy transfer occurred from FB to CdTe QDs in Tris–HCl buffer solution at pH=8.2, in which the QDs' fluorescence intensity increased greatly. Then the fluorescence quenching occurred as Hg2+ interacted with CdTe. Under the optimized conditions, there was a linear relationship between the fluorescence quenching intensity and the concentration of Hg2+. Hg2+ could be determined in the concentration range of 8.0×10−9–8.0×10−7 gL−1 with a detection limit of 6.6×10−10 gL−1 (S/N=3). The method was applied to the determination of Hg2+ in water samples via the standard addition method, and the recovery rate obtained was 97.3–105.5%. [ABSTRACT FROM AUTHOR]