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Here, a simple and portable paper-based analytical device (PAD) based on the inherent capability of carbon quantum dots (CQDs) to serve as a great emitter for the bis(2,4,6-trichlorophenyl)oxalate (TCPO)-hydrogen peroxide (H₂O₂) chemiluminescence (CL) reaction is introduced for the detection of harmful mercury ions (Hg

Bendiocarb, a type of carbamate pesticide, plays a crucial role in controlling a wide range of pests. Due to its harmful impact on humans and the environment, the need for inexpensive, portable, efficient and easy-to-use analytical devices has become essential. In this study, an environmentally friendly paper-based analytical device (PAD) with a chemiluminescence (CL) sensing platform was investigated and characterized for the facile, reliable and sensitive detection of the bendiocarb pesticide. It is based on the enhancing effect of SO32- on the CL reaction of sulfur, nitrogen-doped carbon quantum dots (S,N-CQDs)-KMnO4 in acidic media. According to the experiments, S,N-CQDs and SO32- both are oxidized by KMnO4 to generate (S,N-CQDs*) and (SO2*) in their excited states, emitting at 510 nm. This indicates that an energy transfer process is taking place from SO2* to S,N-CQDs, resulting in a remarkably intensified CL emission. Interestingly, another emission was also observed around 660 nm contributing to about 20 to 25% of the total CL emission. This emission is related to the Mn2+* species produced by reducing MnO4-. The established multi-emission CL system was tested for analytical applications. Under optimal experimental conditions, a good linear relationship was observed between the bendiocarb concentration and the CL intensity of the established CL system. The linear detection range was 0.1-10 μg mL-1, with a limit of detection (LOD) of 0.02 μg mL-1. Finally, the method was successfully applied for the measurements of bendiocarb in water and juice samples. The obtained recovery values (97.5-105.5) verified the suitable accuracy of the results.

In this work, we prepare composites of ZnO–GO and ZnO–rGO through an economic and facile route and comparatively study their gas sensitivity towards ethanol. The morphological, compositional and structural properties of the prepared composites are investigated using scanning electron microscopy (SEM), energy–dispersive X–ray (EDX) spectroscopy, and X–ray diffraction (XRD) analysis. The optimal work temperature of 300˚C was observed for the prepared samples. ZnO–GO–based sensor shows higher sensitivity than ZnO–rGO. Also, the variation of response and recovery time with the gas concentration is investigated. As is expected, the sensitivity increases as the gas concentration increases. Besides, it was revealed that the response and recovery time is a function of the surface morphology.

This study reports an economical and portable point-of-care (POC) monitoring device based on artificial multi-enzyme cascade systems for multiple detection purposes. The device was made up of a disposable three dimensional microfluidic paper-based analytical device (3D μPAD) with multiple detection zones and a smartphone readout. On-paper synthesis of a multifunctional mimetic composite, based on the CeO

Herein, a novel lab-on-a-chip (LoC) device fabricated by 3D printing based on H

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.

Introducing novel mimic materials as alternatives for natural enzymes challenges the analysts. Study on the peroxidase-like materials is an active field in analytical research areas. Herein, Au/Cu bimetal nanoclusters (Au/Cu NCs) are introduced as highly efficient peroxidase mimics, which were investigated using fluorometric and colorimetric techniques. A comprehensive comparison between the catalytic activity of Au, Cu, and their bimetal NCs, with different ratios of Au/Cu was performed using some different peroxidase substrates (including 3,3′,5,5′-tetramethylbenzidine (TMB), o-phenylenediamine dihydrochloride (OPD), and terephthalic acid (TA)). Additionally, different capping agents were applied for the synthesis of NCs, and it was found that penicillamine-capped NCs with 50% Cu have higher activity than other synthesized NCs. Analytical application of the novel mimic for H2O2 detection caused a linear calibration in a wide linear range of 0.001–3 μmol/L, and a great detection limit (3S) of 0.18 nmol/L, using a sensitive fluorescence system. The developed system was also sensitive for recognizing glucose and cholesterol in blood samples, after their enzymatic oxidation and production of H2O2. Detection limits of 55 and 15 nmol/L were obtained for glucose and cholesterol, respectively. The presented method also showed good reliability, which was validated by certified reference materials.

Here, a specific and reliable fluorometric method for the rapid determination of amikacin was developed based on the molecularly imprinting polymer (MIP) capped g-C3N4 quantum dots (QDs). g-C3N4 QDs were obtained by facile and one-spot ethanol-thermal treatment of bulk g-C3N4 powder and showed a high yield fluorescence emission under UV irradiation. The MIP layer was also created on the surface on QDs, via usual self-assembly process of 3-aminopropyl triethoxysilane (APTES) functional monomers and tetraethyl ortho-silicate (TEOS) cross linker in the presence of amikacin as template molecules. The synthesized MIP-QDs composite showed an improved tendency toward the amikacin molecules. In this state, amikacin molecules located adjacent to the g-C3N4 QDs caused a remarkable quenching effect on the fluorescence emission intensity of QDs. This effect has a linear relationship with amikacin concentration and so, formed the basis of a selective assay to recognize amikacin. Under optimized experimental conditions, a linear calibration graph was obtained as the quenched emission and amikacin concentration, in the range of 3–400 ng mL−1 (4.4–585.1 nM) with a detection limit of 1.2 ng mL−1 (1.8 nM). The high selectivity of MIP sites as well as individual fluorescence properties of g-C3N4 QDs offers a high specific and sensitive monitoring method for drug detection. The method was acceptably applied for the measurement of amikacin in biological samples.

Herein, a high performance chemiluminescence (CL) system is developed for the sensitive detection of tramadol. The CL reaction is based on the direct oxidation of rhodamine 6 G (R6 G) by potassium permanganate (KMnO4), producing an ultra-weak emission. It was found that copper nanoclusters encapsulated in copper-based two-dimensional metal-organic frameworks (CuNCs@CuMOF) create a tremendous enhancing effect on the observed emission. A probable mechanism was also suggested for CL emission based on the catalytic effects of nanomaterial and chemiluminescence resonance energy transfer (CRET) events. Besides, it was observed that tramadol caused a relatively selective increasing effect on the CL emission of R6 G-KMnO4-CuNCs@CuMOF system. In order to guarantee a selective response for tramadol, an extraction process using molecularly imprinted polymer modified Fe3O4@SiO2 nanoparticles (MIP-Fe3O4@SiO2 NPs) was applied before the CL analysis. The dispersed MIP-Fe3O4@SiO2 NPs showed high specificity for the extraction of tramadol from its samples. The combination between the high improved CL detection system and the efficient extraction process caused an ultrasensitive and selective determination method for tramadol. The best linear calibration graph was obtained in the concentration range of 0.0030–2.5 μM tramadol, with a detection limit (3Sb/m) of 0.80 nM. The illustrated CL method was tested for the quantification of tramadol in biological fluids, which led to the acceptable and reliable results.

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.

The less stability and robustness, high-cost preparation and maintenance of natural enzymes, especially horseradish peroxidase (HRP), challenge researchers to introduce effective alternatives for their wide applications. Herein, the peroxidase-like activity of AuCu bimetal nanoclusters (AuCu NCs) was investigated in the rhodamine B-H2O2 chemiluminescence (CL) system. AuCu NCs could effectively catalyzed the CL reaction, and a high intensive emission intensity was obtained. A comprehensive study was implemented to examine the effects of different stabilizing ligands and Au/Cu ratios on the catalytic activity of obtained NCs. Comparison experiments were also expanded to include Au and Cu nanoparticles with different sizes, too. The results verified the superior catalytic activity of penicillamine-stabilized AuCu bimetal NCs containing 50% cu atoms. Finally, the analytical application of the introduced CL system showed great sensitivity for H2O2 detection, with a detection limit of 0.13 nM. Moreover, the developed CL method was able to measure glucose and xanthine over wide concentration ranges of 0.1 - 400 and 0.1 - 200 μM, respectively. The method also indicated satisfactory reliability, confirmed by standard reference materials.

Herein, a sensitive and reliable fluorometric probe based on the molecular imprinted polymer capped terbium metal-organic frameworks (MIP@TbMOF-76) was introduced for the measurement of cefixime. The MIP@TbMOF-76 composite was prepared by simple co-polymerization of definite monomers and cross-linkers in the presence of TbMOF-76 as support and cefixime as the model template molecules. After the removing of template molecules, the obtained composite had an intense fluorescence emission corresponding to the terbium emission spectra which undergo a sensible diminution in the presence of cefixime. The prepared MIP@TbMOF-76 indicated a great affinity to adsorb cefixime molecules, which could linearly quench the emission intensity. Moreover, an extraction process using magnetic Fe3O4@SiO2 modified graphene oxide (Fe3O4/GO) was applied for the efficient preconcentration of cefixime from aqueous solution to access its very low concentrations. Based on this procedure, an ultrasensitive and selective probe was designed for cefixime. After optimization of key factors, a calibration graph was achieved in the concentration range of 0.8–90 ng mL−1 cefixime, with a detection limit (3 s) of 0.34 ng mL−1. The developed probe had a good precision (RSD%

Specific recognition of organophosphate pesticides (OPs) is a significant challenge for analytical researchers. Herein, surface imprinted terbium-based luminescent metal-organic framework (MOF-76) are presented as a highly specific probe for the measurement of chlorpyrifos (CP). A mesoporous molecular imprinted polymer (mMIP) layer was generated on the surface of nano-sized MOF-76 using CP, as template. The resulting mMIP-capped MOF-76 (mMIP@MOF-76) contained specific sites for adsorption of CP molecules, guaranteeing the selectivity of the designed probe. The high porosity of rod-shape MOF-76, as well as the mesoporous structure of the MIP layer improved the diffusion process and caused the high sensitivity of the probe. The detection process is based on the remarkable quenching effect of CP on the fluorescence emission of mMIP@MOF-76. Plotting the CP concentration against the fluorescence intensity (λex = 285 nm and λem = 544 nm) gave a linear curve in the concentration range 10–1000 ng mL−1 CP, with 3.41 ng mL−1 limit of detection. The designed probe was utilized for CP determination in fruit juice and environmental samples. The combination of the stable MOF-based support, as well as its remarkable fluorescence features and specific MIP sites, led to a highly selective and ultrasensitive detection system. Graphical abstract

Point-of-care (POC) diagnostic devices play significant roles in delivering vital surveillance information and providing proper and timely care to patients. There is a challenge in the development of new diagnostic tools to overcome their current shortcomings in terms of cost issues, accuracy and performance. Herein, a highly efficient paper-based analytical device based on a 2D metal-organic framework (MOF) has been reported for the colorimetric/fluorometric monitoring of glucose. Because of the inherent bifunctional activity of cobalt-terephthalate MOF (CoMOF) nanosheets, great improvements were made to the stability and performance of glucose oxidase (GOX) and to its catalytic effect on the reaction of o-phenylenediamine (OPD) and H2O2. The exceptional behavior of 2D CoMOF, along with a precise smartphone readout, led to the rapid and sensitive colorimetric/fluorometric detection of glucose in biological samples. Paper modified by CoMOF and GOX was stable for a long time, and a yellow-brown color and a high fluorescence emission were observed after the addition of a low volume of sample and OPD solutions. The probe showed a wide linear effectiveness range of 50 μM-15 mM, with colorimetric and fluorometric detection limits of 16.3 and 3.2 μM, respectively. Despite its great simplicity, the developed probe showed high performance and accuracy for the quantification of glucose.

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.

Developing a novel non-enzyme mimetic in biosensors is of great significance. Here, a synergetic peroxidase-like activity was disclosed for mixed MoS2 quantum dots (MoS2 QDs) and graphene quantum dots (GQDs). The high catalytic effect of this mixture was studied on the chemiluminescence system. It was observed that the simultaneous presence of MoS2 QDs and GQDs had a powerful enhancing effect on the chemiluminescence (CL) emission of rhodamine B (RB)-H2O2 reaction. MoS2 QDs and GQDs mixture (prepared with a ratio of 3:2) showed a superior catalytic activity when compared to each of the constituents. A linear relationship was acquired between the CL emission intensity and H2O2 concentration in the range of 1.5-460nmolL-1. On the other hand, since the enzymatic oxidation of cholesterol leads to the production of H2O2; the offered CL system was examined to detect cholesterol after its oxidation by cholesterol oxidase (ChOx) enzyme. Herein, a further improvement was achieved by MoS2 nanosheets. The MoS2 nanosheets increased the performance of ChOx in cholesterol oxidation process. The obtained results confirmed a highly selective and sensitive determination of cholesterol concentration in a linear dynamic range of 0.08-300µmolL-1, with a detection limit (3S) of 35nmolL-1. The developed method was successfully applied for the detection of cholesterol level in human serum samples.

A novel and powerful chemiluminescence (CL) system was developed based on the promoting effect of graphene quantum dots (GQDs)/bisulfite on rhodamine B (RB)-H2O2 CL reaction. GQDs were synthesized by a simple, green and affordable approach and characterized using their distinctive absorption and emission patterns. X-ray diffraction (XRD), Fourier transform infrared (FT-IR) transmission and transmission electron microscopy (TEM) analysis were implemented for complementary studies on the structural and morphological characteristics of GQDs. The simultaneous enhancing effect of the synthesized GQDs and bisulfite on the CL emission of RB-H2O2 reaction provided a more strong and efficient CL system. The mechanism of CL emission was described. Furthermore, HCHO as a well-known pollutant, could selectively diminish the developed CL system. This effect was linearly proportional to HCHO concentration which turned the introduced CL system to a susceptible chemosensor for HCHO. Under the optimized operational condition, the linear changing of CL response was obtained in HCHO concentration ranges of 0.02–5 μg L−1 and 5–11 μg L−1, with limit of detection (LOD) and quantification (LOQ) of 6 ng L−1 and 20 ng L−1, respectively. Ultimately, presented CL chemosensor was served as an accurate tool for determination of formaldehyde concentration in water and wastewater samples.

The development of novel non-enzyme mimics for (bio)sensing applications is of great practical importance. Herein, an efficient chemiluminescence (CL) system is presented according to the significant mimetic behavior of the copper metal-organic framework decorated with cobalt oxide nanoparticles (Co3O4@CuMOF). The catalytic activity of nanocomposite was proved by its strengthening effect on the CL emission of rhodamine B (RB)-hydrogen peroxide (H2O2) reaction. More documents were also obtained using colorimetric and fluorometric peroxidase substrates. The presence of Cu and Co in the Co3O4@CuMOF structure, as well as the high porosity and great surface area of the obtained composite, was responsible for the observed synergetic catalytic activity. The Michaelis-Menten constant (Km) for the composite (0.108 mM) was remarkably lower than that of pristine CuMOF and Co3O4 NPs, illustrating its superior affinity towards H2O2. A linear correlation was found between the CL intensity and H2O2 concentration in the extensive range of 1–250 nM, with a detection limit (3S) of 0.244 nM. Furthermore, the developed system was exploited as a reliable sensing device for individual measurement of cholesterol and glucose after their enzymatic oxidations. The obtained data verified the high sensitivity and selectivity of the probe, which could be linked to the presence of high-performance Co3O4@CuMOF and the accompanying enzymes, respectively. The designed method was appropriately applied to measure cholesterol and glucose levels in human serum samples, and its accuracy was validated by analyzing the standard materials.

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.

In this work, an attempt was made to develop a powerful method for the determination of cefixime, as a widely used cephalosporin antibiotic. The method was based on the facile extraction and preconcentration of cefixime using Zn metal–organic framework doped magnetic graphene oxide composite (ZnMOF@MGO), followed by its determination using high-performance liquid chromatography (HPLC). The high surface area, great stability, and distinct features of the new adsorbent made it ideal for very efficient interactions with analyte molecules. ZnMOF@MGO was able to effectively extract cefixime from the complex matrix of real samples. Furthermore, the application of the magnetic-solid phase extraction (MSPE) process provided a low-cost and simple extraction process with a reduced extraction time. The combination of a high-performance extraction with a potent HPLC system resulted in a highly sensitive and selective analytical detection method. The method was able to detect cefixime in a linear range of 0.5–130 ng mL−1, with a detection limit of 0.11 ng mL−1, no important interfering effect was caused by other examined drugs. It was examined for the analysis of cefixime content of pharmaceutical and biological samples and acceptable recovery values were obtained.

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.

Two novel, simple and sensitive fluorescence (FL) and chemiluminescence (CL) procedures were established for methamphetamine (MA) determination. l -Cysteine capped CdS quantum dots (QDs) were synthesized by a simple one-step hydrothermal procedure and characterized by their specific absorption and emission spectra. The structure and morphology of QDs were investigated using X-ray diffraction (XRD) pattern, transmission electron microscopy (TEM) and scanning electron microscope (SEM). It is found that the prepared CdS QDs have a remarkable promoting effect on rhodamine B (RhoB)-cetyltrimethylammonium bromide (CTAB)-KMnO4 CL reaction. Based on this influence, a new efficient CL system was introduced. On the other hand, the FL and CL emission intensities of QDs undergo a remarkable alteration in the presence of low quantities of MA. The optimization of the effective parameters was performed and the high sensitivity was obtained in 0.013 mol L− 1 Tris buffer at pH = 6.5 with 0.2 mmol L− 1 CdS QDs. In this condition, MA had a notable linear quenching effect on the FL emission of QDs which formed the basis of simple FL probe for sensitive determination of MA in the range of 6.7–400 ng mL− 1. Also, MA can remarkably enhance the intensity of developed CL system. Under the optimized conditions (0.15 mol L− 1 H2SO4, 0.15 mmol L− 1 RhoB, 0.13 mmol L− 1 QDs, 0.3 mmol L− 1 CTAB and 0.4 mmol L− 1 KMnO4), the improved CL intensity was proportional to the concentration of MA in the range of 0.25–125 ng mL− 1 with limit of detection (3 s) of 0.086 ng mL− 1, which is over 20 times better than the introduced FL method. The developed FL and CL methods were exploited for accurate determination of MA in human urine samples.

A novel and efficient chemiluminescence (CL) probe was developed based on the sensitizing effect of graphene quantum dots (GQDs) on the morin–KMnO4 CL reaction for cypermethrin (CYPM). GQDs were prepared using an economic and green procedure, and characterized with the help of their distinctive emission and absorption patterns. Advanced morphological and structural investigations of the GQDs were conducted using X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and transmission electron microscopy (TEM) analysis. The synthesized GQDs showed a remarkable promoting influence on the CL emission of the morin–KMnO4 reaction in the presence of cetyltrimethylammonium bromide (CTAB), offering a powerful and efficient new CL system. The mechanism of the sensitized CL system was described based on the electron transfer processes. In addition, CYPM, as a potent pollutant, could linearly suppress the emission of the KMnO4–morin–CTAB–GQD CL system. This turned the introduced CL system into a susceptible chemosensor for CYPM. Under the selected operating conditions, a linear relation of the CL response was attained over the CYPM concentration range of 0.3–22.0 mg L−1 with a limit of detection (LOD) of 0.08 mg L−1. The proposed method showed good features for the determination of CYPM and was satisfactorily employed for CYPM evaluation in real environmental water 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.

A novel and sensitive chemiluminescence (CL) procedure based on the synergetic catalytic effects of gold nanoclusters (Au NCs) and graphene quantum dots (GQDs) was developed for the reliable measurement of cimetidine (CM). The initial experiments showed that the KMnO4 -based oxidation of alkaline rhodamine B (RhoB) generated a very weak CL emission, which was intensively enhanced in the simultaneous presence of Au NCs and GQDs. CL intermediates can be adsorbed and gathered on the surface of Au NCs, becoming more stable. GQDs participate in the energy transferring processes and facilitate them. These improving effects were simultaneously obtained by adding both Au NCs and GQDs into the RhoB-KMnO4 reaction. Consequently, the increasing effect of the Au NCs/GQDs mixture was more than that of pure Au NCs or GQDs, and a new nano-assisted powerful CL system was achieved. Furthermore, a marked quenching in the emission of the introduced CL system was observed in the presence of CM, so the system was examined to design a sensitive sensor for CM. After optimization of influencing parameters, the linear lessening in CL emission intensity of KMnO4 -RhoB-Au NCs/GQDs was verified for CM concentrations in the range 0.8-200 ng ml-1 . The limit of detection (3Sb /m) was 0.3 ng ml-1 . Despite being a simple CL method, good sensitivity was obtained for CM detection with reliable results for CM determination in human urine samples.

Currently, researchers are looking for nanomaterials with peroxidase-like activity to replace natural peroxidase enzymes. For this purpose, WS2 quantum dots (WS2 QDs) were synthesized via a solvothermal method, which improved the mimetic behavior. The resulting WS2 QDs with a size of 1&ndash, 1.5 nm had a high fluorescence emission, dependent on the excitation wavelength. WS2 QDs with uniform morphology showed a high catalytic effect in destroying H2O2. The peroxidase-like activity of synthesized nanostructures was studied in H2O2 chemical and electrochemical reduction systems. The mimetic effect of WS2 QDs was also shown in an H2O2&ndash, rhodamine B (RB) chemiluminescence system. For this aim, a stopped-flow chemiluminescence (CL) detection system was applied. Also, in order to confirm the peroxidase-like effect of quantum dots, colorimetry and electrochemical techniques were used. In the enzymatic reaction of glucose, H2O2 is one of the products which can be determined. Under optimum conditions, H2O2 can be detected in the concentration range of 0&ndash, 1000 nmol&middot, L&minus, 1, with a detection limit of 2.4 nmol&middot, 1. Using this CL assay, a linear relationship was obtained between the intensity of the CL emission and glucose concentration in the range of 0.01&ndash, 30 nmol&middot, 1, with a limit of detection (3S) of 4.2 nmol&middot, 1.

The less stability and robustness, high-cost preparation and maintenance of natural enzymes, especially horseradish peroxidase (HRP), challenge researchers to introduce effective alternatives for their wide applications. Herein, the peroxidase-like activity of AuCu bimetal nanoclusters (AuCu NCs) was investigated in the rhodamine B-H

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 paper-based analytical device (PADs) combined with a powerful chemiluminescence (CL) system was established for the determination of deltamethrin (DM), based on the enhancing effect of polyphosphate (PP) on graphene quantum dots (GQDs)-KMnO4 CL reaction. A possible mechanism for the obtained emission was proposed using the CL spectra, fluorescence and ultraviolet-visible patterns. The reaction of KMnO4 and GQDs can lead to generation of GQDs in excited state (GQDs*), which can emit at 490 nm. Interestingly, PP changes the CL mechanism and the main emitter becomes Mn2+ instead of GQDs leading to a strong emission at 695 nm. Furthermore, the obtained multi-emission CL system was examined for analytical applications. The initial experiments showed that the amplified CL emission of the GQDs-KMnO4 system was selectively quenched in the presence of trace levels of DM, probably due to its effective interaction with GQDs or reaction with KMnO4. This observation led to a facile, reliable and sensitive PADs-CL probe, developed for the determination of DM residue in food samples. Using this CL system and under the optimized experimental conditions, the generated signal is decreased by increasing DM concentration in the range of 0.3−10 μg mL-1 with limit of detection (LOD) of 0.15 μg mL-1.

Designing simple and selective sensors for on-site recognition of organophosphate toxins (OPs) is of great importance. Here, molecularly imprinted polymer (MIP)-capped CoZn bimetal imidazolate framework (CoZn ZIF) has been introduced as a specific probe for the quantification of dimethoate. The detection is based on its diminishing effect on the catalytic action of ZIF in 3,3′,5,5′-Tetramethylbenzidine (TMB)-hydrogen peroxide (H2O2) reaction. CoZn ZIF catalyzes the dissociation of H2O2 to hydroxyl radicals, which can then oxidize TMB and create a blue colored product. It was demonstrated that the catalytic performance of bimetal metal organic framework (MOF) is higher than that of single metal MOF of Co (ZIF-67) or Zn (ZIF-8). On the other hand, adsorbing dimethoate in the specific MIP sites on the surface of CoZn ZIF declines its catalytic action. This effect was exploited to design a selective colorimetric assay for dimethoate determination in fruit and wastewater samples. The decrease in the absorption intensity of final solution was proportional to the dimethoate concentration in the range of 0.02–1.2 μM, with a detection limit of 5.6 nM. The high specificity of MIP technique and great catalytic activity of CoZn ZIF, as well as the simplicity of colorimetric method led to a reliable screening assay.

A rapid and efficient solid phase extraction method was established for the preconcentration of codeine prior to its simple determination by spectrophotometry. The extraction process is based on the multi-walled carbon nanotubes (CNTs) containing –COOH functional groups. These CNTs showed a great affinity for the low quantities of codeine in certain condition. Various extraction factors including buffer type, concentration and its pH, ionic buffer, incubation time, and eluent were optimized to achieve high sensitivity. The calibration graph was linear in the codeine concentration range of 0.001–4 mg·L−1, with a detection limit (3s) of 0.4 μg·L−1. The relative standard deviation (RSD %) for the repetitive determination of 0.01, 0.5, and 2 mg·L−1 codeine (n = 5) were 1.56%, 2.01%, and 1.63%, respectively. Furthermore, comparison with other reported methods showed that the presented method has suitable characteristics. Finally the method was successfully used to accurately determine codeine in pharmaceutical and human urine samples.

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.

A new high sensitive, selective, and simple method based on the inhibited effect of gold nanoparticles (Au NPs) on rhodamine B (RB)–ferricyanide (Fe(CN)63 −) chemiluminescence (CL) system has been developed for the determination of Hg2 + in environmental samples. This study is the analytical exploiting of Au NPs inhibiting effect on CL system. RB–Fe(CN)63 − causes a high emission intensity in alkaline condition but undergoes an intense extinction in the presence of Au NPs. This decreasing effect can be attributed to the energy transfer and collisions between RB molecules and Au NPs. Moreover, it is observed that the CL intensity is gradually restored in the presence of mercury (II) due to RB molecules release from the surfaces of Au NPs. Based on this effect, sensitive, and selective turn-on CL assay was developed for the determination of Hg2 +. Under the optimized conditions, CL calibration curve was drawn as a function of Hg2 + concentration, which is linear over the range of 0.013–4.67 μg L− 1 (0.067–23.3 nmol L− 1) with limit of detection (3s) and quantification (10s) of 5.42 and 18 ng L− 1, respectively. The relative standard deviations (RSD%, n = 5) were about 0.7–2.1% for the different concentrations of Hg2 +. The presented assay was satisfactorily applied to the quantification of Hg2 + in the environmental (tap, rain, and river) water samples, which shows good sensitivity and reliability in comparison with the other nanoparticle-based methods; the recoveries were 97–102%.

A fluorescence resonance energy transfer (FRET) system between carbon dots (C-dots) and amine-capped gold nanoparticles (AuNPs) was developed for the selective determination of 2,4,6-trinitrotoluene (TNT). C-dots have an intrinsic florescence emission depending on their exciting wavelength. In the presence of AuNPs, C-dots adsorb on the Au surfaces, and NPs treat as energy acceptor, which can receive light emitted by C-dots, leading to decrease the fluorescence intensity of C-dots. Furthermore, it is observed that nitroaromatic compounds, especially TNT, could restore this fluorescence due to selective interaction with AuNPs via amine groups, and so releasing the C-dots. Based on this effect, a sensitive and selective fluorescence turn-on probe was designed for the determination of TNT. Some important factors including AuNPs and C-dot concentrations and media pH, which would affect the efficiency of the probe, were optimized. Under the optimum experimental conditions, good linear relationships in the range of 7 - 250 nmol L(-1) TNT with the detection limit of 2.2 nmol L(-1) were obtained. The proposed method was satisfactorily applied to the determination of TNT in the environmental water samples. Compared with previous reports, the developed method has relatively high sensitivity, short analysis time, low cost and ease of operation.

A simple and selective method was described for the rapid determination of morphine based on its extraction and preconcentration by molecularly imprinted polymers (MIPs) on multi-walled carbon nanotubes (MWCNTs) prior to its chemiluminometric recognition. MIP–MWCNTs composite was obtained by copolymerization of certain monomers on the surface of vinyl modified MWCNTs using morphine as template molecule. Dispersed MIP–MWCNTs indicated good tendency and selectivity to low amounts of morphine in relatively acidic condition. Some important factors containing buffer and its pH, ionic buffer, incubation time, eluent, etc., were optimized for extraction step. KMnO4–carbon dots (C-dots) chemiluminescence (CL) reaction was applied as recognition device for extracted morphine. Morphine can linearly quench the CL emission of this system via its interaction with C-dots. The calibration graph was obtained in the range of 0.003–1.2 mg L−1 morphine concentration with a detection limit (3 s) of 0.82 μg L−1. The relative standard deviation (RSD%) for five determinations of 0.01, 0.1, and 0.8 mg L−1 morphine were 1.11%, 2.54% and 1.98%, respectively. The developed method has acceptable features in comparison with other reported methods and was satisfactorily applied to the accurate determination of morphine in pharmaceutical and urine samples.

Earth abundant and non-toxic kesterite Cu2ZnSnS4 (CZTS) thin films have been considered remarkably as the potential alternate to the conventional, expensive, and toxic absorber layers like CdTe, c-Si, CIGS etc. Formation of secondary phases along with poor electrical mobility are the main problems in fabrication of CZTS thin films by chemical methods. In the present study, single-phase high-hole-mobility CZTS thin films have been prepared by the facile low temperature sol-gel method with emphasizing on the role of monoethanolamine (MEA) and diethanolamine (DEA) as the stabilizer and the number of dip-coating. Results show the formation of high crystallinity single-phase CZTS thin films with DEA as the stabilizer. The thickness of the films prepared by DEA was higher than that of MEA. The compositional analysis of the films showed the formation of Cu-poor Zn-rich samples that are appropriate for solar cells by using of DEA. The surface analysis of the prepared thin films revealed an appropriate RMS roughness for capturing the major portion of the incident light. The evaluated bandgap of the films was in the optimum range for solar cell applications. D.C. electrical measurements showed very high-hole mobility for the samples prepared by DEA. The functionality of the prepared samples was investigated by performing a numerical simulation.

Herein, a novel metal-organic framework (MOF) based nanocomposite with efficient catalytic behavior is reported including flake-like copper (II) MOF (CuMOF) and graphitic C

An efficient chemiluminescence resonance energy transfer (CRET) induced chemiluminescence (CL) system was developed for the sensitive determination of cyanide ion (CN−) in environmental and biological samples. The selected CL reaction was hydrogen peroxide (H2O2)-bicarbonate (HCO3−) system with an ultra-weak emission at about 470 nm. It was found that glutathione-stabilized CdSe quantum dots (CdSe QDs) superbly increase the obtained CL intensity. The high performance CRET between the CL emitters and CdSe QDs with a broad absorption was mainly responsible for the observed improving effect. The absorption spectrum of QDs completely overlaps with the CL emission wavelength of H2O2-HCO3− system. Besides, CdSe QDs could also catalyze the CL reaction of H2O2-HCO3−, efficiently. On the other hand, it was observed that the gold nanoclusters (Au NCs) could prohibit the CRET system and turn off the CL emission. This diminishing effect can be useful for the analytical application. Herein, it was successfully exploited for the selective recognition of CN−, using its leaching effect on Au NCs. After efficient dissolution of NCs, the CRET to CdSe QDs restored and the CL emission was again turned on. This strategy resulted in a high sensitive and reliable measurement of CN− in the concentration range of 2–225 nM, with a detection limit of 0.46 nM.

Here, a specific and reliable fluorometric method for the rapid determination of amikacin was developed based on the molecularly imprinting polymer (MIP) capped g-C

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.

It is reported that a mixture of WS2 nanosheets (WS2 NS) and silver nanoclusters (AgNCs) displays strongly enhanced peroxidase-mimicking activity. The catalytic effect of the mixture was studied by colorimetry, fluorometry, chemiluminescence (CL) and electrochemistry. The effect is interpreted in terms of a difference between the Fermi energy level of the two nanomaterials. This leads to the formation of charge separation regions which act as active sites for enzyme mimetic interaction with the substrates. The mixture of WS2 NS and AgNCs was exploited for the non-enzymatic determination of H2O2 and glucose. A stopped-flow method was applied as a sensitive CL detection system using the bicarbonate-H2O2 reaction. The mixture has a powerful peroxidase mimicking activity on the bicarbonate-H2O2 CL reaction, and this effect is much larger than that of any single constituent. In addition, the CL emission is improved several times by using the stopped-flow technique. Under optimum condition, H2O2 can be determined in the 2.5–1500 nM concentration range. Moreover, glucose levels in human serum can be quantified via glucose oxidase based oxidation which leads to the generation of H2O2. Using this CL assay, a linear relationship was obtained between the intensity of the CL emission and glucose concentration in the range of 0.03–20 μM, with a limit of detection (3S) of 13 nM.

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.

Gold and silver nanoparticles (NPs) are shown to exert a positive effect on the chemiluminescence (CL) reaction of permanganate aldehydes. Interestingly, between various shapes examined, Au nanoprisms have the highest beneficial effect. This effect is even more notable in the presence of sodium dodecyl sulfate (SDS) surfactant. UV-vis spectra and transmission electron microscopy were used to characterize the NP shapes and sizes. Furthermore, it was observed that iron(III) ions can slightly increase CL emission of this system. This intensification is very effective in the presence of fluoride ions (F–). These observations form the basis of the method for the high sensitive determination of F– in the 6–1200 nmol L–1 concentration range, with a detection limit of 2.1 nmol L–1. The proposed method has good precision and was satisfactorily used in the selective determination of low concentrations of fluoride ion in real samples. Copyright © 2015 John Wiley & Sons, Ltd.