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Herein, Fe3O4@MOF-2 (MOF: metal-organic framework) nanocomposite, as a heterogeneous nanocatalyst, was applied to activate persulfate (PS) in the attendance of ultrasonic (US) irradiation (Fe3O4@MOF-2/US/PS) for degradation of diazinon. The evaluation results showed that, in the acidic solution (pH = 3), the reaction rate constant of Fe3O4@MOF-2/US/PS system (0.0546 min−1) was more than 6-folds than that of the US/PS system (0.0079 min−1). Reducing the diazinon concentration, along with raising the Fe3O4@MOF-2 dosage and the US bath power favored the degradation of diazinon. It was found that Fe3O4@MOF-2 had fine catalytic performance and reuseibility. The diazinon decomposition pathway was proposed by GC–MS analysis.

Herein, high performance peroxidase-like activity of zinc and cobalt bi-metal metal-organic framework (ZnCo MOF) is reported and applied for the sensitive measurement of atropine. ZnCo MOF was synthesized by the reaction of 2-methylimidazole with Zn and Co (II) cations in aqueous media. The colorimetric and fluorometric experiments were applied to investigate the catalytic activity of obtained MOF, using o-phenylenediamine (OPD) and terephthalic acid (TA) peroxidase substrates, respectively. The results demonstrated the more efficient mimetic behavior of ZnCo MOF compared with common Zn or Co MOFs. Besides, it was found that atropine hindered the catalytic action of ZnCo MOF and this effect was intensified by increasing the atropine concentration. So, it was considered to design a sensitive analytical assay for atropine detection. To assure a high specific recognition, molecularly imprinted polymer (MIP)-based extraction using magnetic graphene oxide supports was applied to extract atropine before its determination. The combination between the high specific extraction and great catalytic activity of ZnCo MOF led to the ultrasensitive and reliable determination of atropine. The best linear range of calibration graph was achieved using fluorometric detection system for 0.1–45 ng mL−1 atropine concentrations, and detection limit (3Sb/m) was 27 pg mL−1. The relative standard deviations (RSD %) for the determination of 1, and 10 ng mL−1 atropine (n = 5) were 2.13% and 3.08%, respectively. The explained fluorometric assay was examined for the measurement of atropine in biological fluids (Recoveries were in the range of 95.90–103.57%), and the results were validated by an official method.

Herein, a novel metal-organic framework (MOF) based nanocomposite with efficient catalytic behavior is reported including flake-like copper (II) MOF (CuMOF) and graphitic C3N4 nanosheets (g-C3N4). The g-C3N4@MOF nanocomposite was simply prepared by solvothermal synthesis of CuMOF in the presence of g-C3N4. The characterization analyses using scanning electron microscopy (SEM), X-ray diffractometry (XRD) and some other techniques demonstrated a nano-porous flake-like structure for the synthesized CuMOF, which enveloped the g-C3N4 nanosheets. Furthermore, the investigation of catalytic behavior of synthesized nanomaterial was implemented on H2O2 based reactions. The fluorometric and colorimetric experimentations illustrated that the accompanying of g-C3N4 with CuMOF had a remarkable positive effect on the catalytic behavior of obtained g-C3N4@MOF. This effect was described based on the improved affinity of nanocomposite to adsorb H2O2 and also synergistic action of its components on the dissociation of H2O2 to hydroxyl radicals. Finally, the analytical application of high catalytic activity of new g-C3N4@MOF was designed for the rapid and simple measurement of glucose in blood. After the enzymatic oxidation of glucose, the fluorometric method was applied for the analysis of produced H2O2 using terephthalic acid as peroxidase substrate. The system led to the ultrasensitive glucose determination in the concentration range of 0.1–22 μM, with a detection limit (3S/m) of 59 nM.

Developing a new detection system for reliable recognition of threatening organophosphate poisons (OPs) is a challenging subject for analysts to control their undesirable effects. Here, a sensitive analytical assay for OPs was reported based on the high mimetic behavior of layered double hydroxides supported ZIF-8 nanocomposite (LDH@ZIF-8). The well-known inhibiting effect of OP analytes on the enzymatic activity of acetylcholinesterase (AChE) was exerted to gain a suitable selectivity. Following that, efficient chemiluminescence (CL) system assisted by LDH@ZIF-8 was employed to monitor the variation in the amount of produced H2O2. It is found that the synthesized LDH@ZIF-8 possess a high effective peroxidase-like activity and can remarkably enhance the emission of the ultra-weak rhodamine B (RhoB)-H2O2 CL reaction. More studied was done using fluorometric to ratify the mimetic properties of LDH@ZIF-8 nanocomposite. The high catalytic effect of developed nanocomposite assured the high efficacy of the CL system to detect the small changes in H2O2 concentration, resulting in a high sensitivity in the detection of OPs. The low-priced and simple synthesized LDH@ZIF-8 catalyst, as well as a simple and easy-to-use CL system can be beneficial in the development of an on-site and portable detection tools. A wide linear range of 0.5–300 nM was achieved for the determination of diazinon (as a model OP), and the detection limit was as low as 0.22 nM. The method showed high reproducibility and was reassured by its application for the analysis of environmental samples.

A microfluidic device for simultaneous analysis of total flavonoids and total phenolic acids is presented for the first time. The process was based on the utilization of magnetic zinc-imidazole frameworks (ZIF-4), as a highly efficient media for on-line separation of phenolic acids and flavonoids, which were subsequently detected by a sensitive chemiluminescence (CL) method. Acrylate-based polymeric microchips containing a separation column (12.5 mm length, 3 mm width and 1 mm depth) were fabricated using a 3D-printer, and magnetic ZIF-4 was fixed into the column. The high porosity of the magnetic ZIF-4 made it a suitable adsorbent, guaranteeing an effective separation. The detection limits were in the range of 0.04–0.10 µg mL−1 with relative standard deviation values of (2.19–4.38%). The system was successfully applied for the analysis of flavonoids and phenolic acids in tea and honey samples. The recovery was from 95.4 to 104.1%, indicating a good accuracy of the developed method.

Herein, a novel paper-based chemiluminescence (CL) assay is reported using a smartphone readout for on-site and reliable analytical applications. The CL system was based on the high-performance improving effect of cobalt-imidazole metal-organic framework (CoMOF) on luminol-hydrogen peroxide (H2O2) CL emission. The CoMOF was grown on paper and used as a support for the CL reaction, which led to an intense CL emission and good reproducibility. More importantly, the stability of luminol, as the CL reagent, was greatly improved in the presence of CoMOF. This high stability, along with the high-yield CL emission, makes the device highly suitable for commercialization. Furthermore, using a smartphone as the detector for the developed device made the process easier and more accessible for public usage. In this work, the new paper-based CL smartphone device was used for the detection of the total phenolic content of food samples. Phenolic compounds (PC) are hydroxyl radical scavengers that can effectively quench the CL emission of the luminol–H2O2–CoMOF system. After optimizing the reaction conditions, the system could detect PC at the μg mL−1 level. Detection limits of 0.12, 0.28, 0.46, 0.85, and 1.23 μg mL−1 were obtained for gallic acid, quercetin, catechin, kaempferol, and caffeic acid, respectively. This work is the first report on the practical application of smartphone CL assays for the estimation of PC. The proposed assay is an easy-to-use, low-cost, portable, and suitable assay for on-site screening purposes.

Two highly sensitive and selective methods based on fluorescence (FL) and chemiluminescence (CL) emissions of 8-mercaptoquinoline-capped CdS quantum dots (MCQ-CdS QDs) were described for the determination of copper (II) after it’s preconcentration. High fluorescent CdS QDs, synthesized in an aqueous medium, generated a relatively intense CL emission in the presence of potassium permanganate as an oxidant. Furthermore, low quantities of copper (II) ions showed a remarkable quenching effect on both of the CL and FL emissions of MCQ-CdS QDs. Based on this effect, two selective and simple methods were established for Cu2+, and the detection limits of 0.28 and 0.026 ng mL−1 were obtained for the FL and CL methods, respectively. Also, due to the high propensity of MCQ to Cu2+, good selectivity was obtained and no sensible interfering effects from other metal ions were observed. To more sensitize the developed method, an efficient preconcentration process was designed based on the high-yield ultrasound-assisted temperature-controlled ionic liquid dispersive liquid–liquid microextraction (UA-TIL-DLLME) method. Under the optimum conditions, the extracted Cu2+ showed a suppressing effect on the FL and CL emissions of CdS QDs proportional to its initial concentration over the ranges of 0.008–1.4 and 0.001–1.4 ng mL−1, respectively. The limits of detection of 3.7 and 0.37 pg mL−1, respectively, were also achieved. The established methods showed great features and were satisfactorily applied to the monitoring of ultratrace Cu2+ in some different environmental samples.

Developing a selective and sensitive tool for recognizing 2,4,6-trinitrotoluene (TNT) is of great importance from both security and contamination viewpoints. Here, a novel molecularly imprinted polymer (MIP) based chemiluminescence (CL) assay is described for the determination of TNT in environmental samples. ZnO quantum dots (QDs) were synthesized using a simple and economical process and applied as efficient supports for the MIP layer. The MIP layer was produced using (3-aminopropyl)triethoxysilane (APTES) as a monomer and tetraethoxysilane (TEOS) as a cross-linker, in the presence of TNT as the template. The MIP-labeled ZnO QD composite (MIP@QDs) was characterized using photoluminescence emission, X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The prepared composite showed a remarkable promoting effect on the weak chemiluminescence emission of an alkaline permanganate–rhodamine B (RB) system. This effect was described based on the catalytic activity of the composite. Moreover, in the presence of TNT, its molecules were adsorbed onto specific sites of the MIP and placed near the QDs, resulting in a noticeable decrease in the CL intensity of the KMnO4–RB–MIP@QDs system. Based on this effect, a selective and highly sensitive CL assay was introduced for the TNT determination. Under the optimal conditions, a linear relationship was obtained between the decreased CL intensity and TNT concentration in the ranges 0.02–50 and 50–200 ng mL−1 with a detection limit (3σ) of 6.8 pg mL−1. This method had good selectivity towards TNT but not towards similar species such as 2-nitrotoluene, 2,4-dinitrotoluene, etc.

Herein, a two dimensional metal-organic framework (2D MOF) is introduced as an efficient adsorbent for simultaneously extraction of fluoroquinolones (FQs) from milk samples. The proposed MOF was synthesized by solvothermal method. The high surface area and high accessible sites of prepared MOF offered a unique adsorbent for solid phase extraction (SPE). The experiments showed the great ability of 2D MOF for the retention of ofloxacin (OF), ciprofloxacin (CIP) and norfloxacin (NOR). It was also found that acetic acid (ACA) solution can effectively elute the adsorbed FQs with a high recovery, eliminating the need for other toxic organic elution solvents, which are utilized for the common C18 cartridges. A 3D printed microchip containing a microcolumn was also examined for the SPE process using magnetic composite of 2D MOF, which was fix inside the column using simple magnet. The extracted analytes were gathered to be analyzed by high performance liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS), as the potent detection system. The results demonstrated the great ability of MOF toward the extraction of tested FQs with a breakdown point of 1200 ng mL−1 for each analyte in their mixed solution. The method showed an acceptable selectivity toward the FQs and no interfering effect was observed by other compounds. It was able to detect OF, NOR and CIP in the range of 0.5–1000 ng mL−1 in milk samples and the detection limits were 0.012, 0.009 and 0.016 ng mL−1, respectively.

A novel spectrofluorimetric probe based on Ag nanoparticle (AgNPs)-enhanced terbium (III) (Tb) fluorescence was introduced for the sensitive determination of folic acid (FA). The effect of gold and silver nanoparticles in different size was investigated on the well-known Tb sensitized fluorescence emission of 1, 10-phenantroline (Phen). The greatest fluorescence intensity was observed in the presence of AgNPs with a diameter of ~6 nm maybe due to their highest surface area. Furthermore, it's discovered that FA can form Tb-Phen -FA ternary complexes and cause a notable diminution in this enhanced fluorescence system. Based on this finding, a high sensitive and selective method was developed for the determination of FA. Effects of various parameters like Ag NPs, Phen and Tb(3+) concentration and pH of media were investigated. In the optimum circumstances, the fluorescence emission of AgNPs-Phen-Tb collection was declined linearly by increasing the concentration of FA in the range of 0.5 to 110 nmol L(-1). Limits of detection and quantification were achieved to be 0.21 and 0.62 nmol L(-1), respectively. The method has good linearity, recovery, reproducibility and sensitivity, and was adequately exploited to follow FA content in pharmaceutical, fortified flour and human urine samples.

Development of a sensitive detection method for the reliable screening of widely used organophosphorus (OP) toxins is a crucial request to control their side-effects. Herein, a novel fluorometric assay based on the acetylcholinesterase (AChE) inhibited enzymatic activity and the new peroxidase-like Fe3O4 nanoparticles@ZIF-8 composite (Fe3O4 NPs@ZIF-8) was developed for the determination of OPs. Magnetic Fe3O4 NPs were encapsulated into ZIF-8 and the high mimetic activity of produced composite was assessed on the oxidation of substrates. This observation was applied to the rapid detection of diazinon as a model OP compound. The sensing tool contains AChE and choline oxidase (CHO) enzymes, peroxidase colorimetric or fluorometric substrate, and Fe3O4 NPs@ZIF-8 as the catalyst. In the presence of mimic Fe3O4 NPs@ZIF-8, the generated H2O2 from the enzymatic reactions of acetylcholine is decomposed to hydroxyl radicals. The radicals oxidize the peroxidase substrates to generate a detectable signal. However, due to the inhibition effect of OPs on the enzymatic activity of AChE, lower H2O2 amounts are produced in the presence of diazinon. Using the fluorometric detection system, the generated signal is decreased proportionally by increasing diazinon concentration in the range of 0.5–500 nM. The limit of detection was obtained 0.2 nM. Consequently, the usage of high performance peroxidase-mimic Fe3O4 NPs@ZIF-8 provided a sensitive bio-assay with a potential to be applied as screening tool for toxic OP compounds. The developed assay was successfully applied for the determination of diazinon in water and fruit juices.

A simple and selective colorimetric method for the detection of perilous peroxide explosives was developed using the peroxidase mimetic activity of silver nanoparticles/flake-like zinc metal-organic framework nanocomposite (Ag@ZnMOF). The synthesis of Ag@ZnMOF contained the formation of silver nanoparticles (AgNPs) inside the fine pores of Zn metal-organic framework (ZnMOF). High reactive AgNPs as well as great surface area of MOFs provided a synergetic and high improved catalytic activity for the composite which was studied as a peroxidase mimic in hydrogen peroxide (H2O2)-based oxidations. The achieved system was used for detection of Triacetone triperoxide (TATP) as one of the most hazardous peroxide explosives. TATP was decomposed in an acidic condition to generate H2O2, which was then applied to oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of the Ag@ZnMOF as a catalyst. This reaction led to the production of well-known blue colored charge transfer complex (oxTMB), which was recognized by the colorimetric technique. A linear relationship was obtained between the absorption intensity of the produced blue solution and the TATP concentration in the range of 0.4–15 mg L−1, with a detection limit of 0.1 mg L−1. A portable test kit was prepared using the same reagents for TATP measurement in real samples.

Here, Ag nanoparticle/flake-like Zn-based MOF nanocomposite (AgNPs@ZnMOF) with great peroxidase-like activity was applied as an efficient support for molecularly imprinted polymer (MIP) and successfully used for selective determination of patulin. AgNPs@ZnMOF was simply synthesized by creating Ag nanoparticles (Ag NPs) inside the nano-pores of flake-like (Zn)MOF. The high surface area of MOF remarkably improved the catalytic activity of Ag NPs which was assessed by fluorometric, colorimetric and electrochemical techniques. Furthermore, it was observed that patulin could strangely reduce the catalytic activity of AgNPs@ZnMOF, probably due to its electron capturing features. This outcome was the motivation to design an assay for patulin detection. In order to make a selective interaction with patulin molecules, MIP layer was created on the surface of AgNPs@ZnMOF by co-polymerization reaction of 3-aminopropyl triethoxysilane (APTES) and tetraethyl orthosilicate (TEOS) monomers wherein patulin was applied as template agent. Combination between the selective identifying feature of MIP and outstanding peroxidase-like activity of novel AgNPs@ZnMOF nanocomposite as well as the sensitive fluorescence detection system was led to the design of a reliable probe for patulin. The prepared MIP-capped AgNPs@ZnMOF catalyzed the H2O2-terephthalic acid reaction which produced a high florescent product. In the presence of patulin, the fluorescence intensity was decreased proportional to its concentration in the range of 0.1-10µmolL-1 with a detection limit of 0.06µmolL-1. The proposed method was able to selectively measure patulin in a complex media without significant interfering effects from analogue compounds.

We describe a new turn off-on chemiluminescence (CL) method for the sensitive and selective determination of cyanide based on the inhibiting effect of gold nanoparticles (AuNPs) on rhodamine B (RohB)-ferricyanide (Fe(CN)6(3-)) reaction. Free RohB can generate strong chemiluminescence emission when oxidized with Fe(CN)6(3-), but undergoes an intense extinction in the presence of AuNPs. Energy transfer and collisions between RohB molecules and AuNPs are probably the reason for this decreasing effect. Furthermore, it was found that CL intensity gradually recovered in the presence of cyanide due to its interaction with the AuNPs. The relation between the decreased CL intensity and cyanide concentration was exploited to develop a method for the determination of cyanide in the 16.7 - 1333 nmol L(-1) concentration range, with a detection limit of 13.6 nmol L(-1). In comparison with other nanoparticle-based methods, the presented assay shows good sensitivity and reliability for the determination of cyanide. The method was satisfactorily applied to the determination of cyanide in environmental and biological samples.