Bifunctional oxidase-peroxidase mimicking Fe-Ce MOF on paper-based analytical devices to intensify luminol chemiluminescence: Application for measuring different sugars with a smartphone readout.

This study presents a potent paper-based analytical device (PAD) for quantifying various sugars using an innovative bi-nanozyme made from a 2-dimensional Fe/Ce metal-organic framework (FeCe-BTC). The MOF showed excellent bifunctional peroxidase-oxidase activities, efficiently catalyzing luminol's chemiluminescence (CL) reaction. As a peroxidase-like nanozyme, FeCe-BTC could facilitate the dissociation of hydrogen peroxide (H2O2) into hydroxyl radicals, which then oxidize luminol. Additionally, it was also discovered that when reacting with H2O2, the MOF turns into a mixed-valence MOF, and acts as an oxidase nanozyme. This activity is caused by the generated Ce4+ ions in the structure of MOF that can directly oxidize luminol. The MOF was directly synthesized on the PAD and cascaded with specific natural enzymes to establish simple, rapid, and selective CL sensors for the measurement of different sugars. A cell phone was also used to record light intensities, which were then correlated to the analyte concentration. The designed PAD showed a wide linear range of 0.1-10 mM for glucose, fructose, and sucrose, with detection limits of 0.03, 0.04, and 0.04 mM, respectively. It showed satisfactory results in food and biological samples with recovery values ranging from 95.8 to 102.4 %, which makes it a promising candidate for point-of-care (POC) testing for food control and medicinal purposes.

AuNRs attached TiO2 NPs modified by cobalt-imidazolate frameworks as exceptional materials to improve the energy conversion efficiency of dye-sensitized solar cells.

This work reports a significant improvement in both the open-circuit voltage (VOC) and current density (J) of dye-sensitized solar cells (DSSCs) using gold nanorod-modified TiO2 nanoparticles (TiO2/AuNRs) together with a cobalt-imidazolate framework (ZIF-67) as an efficient photoanode. It was demonstrated that adding ZIF-67 (8 wt%) to TiO2 NPs increased the VOC by 160 mV and J by 2.5 times. This observation was described based on the significant increase in the amount of adsorbed dye in the presence of highly porous ZIF-67, which boosts the photoanode's light harvesting. Modifying TiO2 NPs with AuNRs also caused a remarkable enhancement in J (∼ 2.8 times), which can be explained via electron transfer between the TiO2 conduction band and AuNRs. It can result in a more efficient inhibiting effect on the interfacial charge recombination processes in TiO2/AuNRs/ZIF-67 because of the formation of a Schottky barrier at the interface between TiO2 and Au. These effects were confirmed by the reduction in the photoluminescence intensity of TiO2 in the presence of AuNRs. More reduction in the photoluminescence intensity was observed when ZIF-67 was added. The prepared photoanode showed an outstanding improvement in the overall efficiency of the DSSC (η) to 8.38% compared to the bare TiO2-based photoanode (1.83%). The notable improvement in the TiO2/AuNRs/ZIF-67 performance confirmed its practicality for high-efficiency DSSCs.

Novel amino-functionalized magnetic metal-organic framework/layered double hydroxide adsorbent for microfluidic solid phase extraction: Application for vitamin D3.

Vitamin D deficiency is highly prevalent worldwide, especially with limited sun exposure and sun avoidance. Thus, reliable monitoring of vitamin D levels in food and biological samples is vital for medicinal diagnosis. Herein, a potent method for the extraction and determination of vitamin D3 is presented using a microchip-based solid-phase extraction (SPE) device followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) detection. A new magnetic adsorbent based on Fe3O4 magnetic nanoparticles (MNPs) modified ZnFe layered double hydroxide (LDH)/2-aminoterephthalic acid-Zn2+ metal-organic framework (IRMOF-3) composite (IRMOF-3@MLDH) was successfully synthesized and fixed inside a rectangular micro-column (4 × 2 × 12 mm). The porous structure and high surface area of IRMOF-3@MLDH provide abundant adsorbing sites and make it a potent SPE adsorbent, with an exceptional ability to retain vitamin D3. The adsorption isotherm showed that the composite was highly efficient at extracting vitamin D3 with an extraction capacity of 126 mg g-1. The designed extraction microchip simplified the SPE process, paving the way for automated SPE systems. The developed method presented a broad linear range of 5-2000 ng mL-1, with a detection limit of 1.4 ng mL-1. In comparison to conventional silica-based adsorbents, a higher sensitivity was obtained in the determination of vitamin D3 using the IRMOF-3@MLDH adsorbent. The selectivity of the method was also satisfactory, enabling the measurement of vitamin D3 in food and blood samples with high recovery values in the range from 95.2 to 101%. Thus, the newly developed adsorbent and method offer an efficient alternative to the commonly used C18-based approach.

Carbon dots-modified paper-based chemiluminescence device for rapid determination of mercury (II) in cosmetics.

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 (Hg2+ ). The energy is transferred from the unstable reaction intermediate (1,2-dioxetanedione) to CQDs, as acceptors, and an intensive orange-red CL emission is generated at ~600 nm, which is equal to the fluorescence emission wavelength of CQDs. The analytical applicability of this system was examined for the determination of Hg2+ . It was observed that Hg2+ could significantly quench the produced emission, which can be attributed to the formation of a stable and nonluminescent Hg2+ -CQDs complex. Accordingly, a simple and rapid PAD was established for monitoring Hg2+ , with a limit of detection of 0.04 µg ml-1 . No interfering effect on the signal was found from other examined cations, indicating the acceptable specificity of the method. The designed assay was appropriately utilized to detect Hg2+ ions in cosmetic samples with high efficiency. It was characterized by its low cost, ease of use, and was facile but accurate and high selective for the detection of Hg2+ ions. In addition, the portability of this probe makes it suitable for on-site screening purposes.

On paper synthesis of multifunctional CeO2 nanoparticles@Fe-MOF composite as a multi-enzyme cascade platform for multiplex colorimetric detection of glucose, fructose, sucrose, and maltose.

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 CeO2 nanoparticles embedded in the amino-functionalized Fe metal-organic frameworks (CeO2@NH2-MIL-88B(Fe)), for cascade reactions was the main achievement of this work. The 3D µPAD was applied for simultaneous quantification of glucose, fructose, sucrose and maltose, and the detection process consisted of the enzymatic reaction of each sugar by anchored enzymes on the metal-organic frameworks (MOF) and successive oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). Utilizing the new artificial mimicking system improved the color development uniformity and resulted in a reliable detection tool, with excellent detection limits in the range of 20-280 µM. It was directly applied to analyze the sugars levels of human total blood, urine, semen, honey and juice samples with the relative errors of less than 7.7% compared with the HPLC method. The cost-effective and easy-to-use µPAD has a great potential to be used in either medical diagnostics or the food industry. Also, it can be considered as a competitive POC method for patients in disadvantaged communities or emergencies.

A handheld 3D-printed microchip for simple integration of the H2O2-producing enzymatic reactions with subsequent chemiluminescence detection: Application for sugars.

Herein, a novel lab-on-a-chip (LoC) device fabricated by 3D printing based on H2O2-producing enzymatic reactions with sensitive chemiluminescence (CL) detection was developed to measure different sugars, including glucose, fructose, sucrose, and maltose, in honey, juice, and rice flour samples. The pumpless microchip included two main parts, separated by new cone-shape blocking valves; part A for sample introduction and subsequent enzymatic reaction, besides the CL reagent (luminol) container, and part B for detection. The specific enzyme(s) were embedded into the pores of the zinc zeolite-imidazole framework (ZIF-8) to improve their storage stability. By opening the valves, H2O2 produced by enzymatic reaction and luminol could flow through the designed channels into the detection zone on part B, where a 2D cobalt-imidazole framework was embedded to improve the luminol-H2O2 CL emission. The obtained signal was proportional to the considered sugar concentration, with the detection limits range of 20-268 µM.

On paper synthesis of metal-organic framework as a chemiluminescence enhancer for estimating the total phenolic content of food samples using a smartphone readout.

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.

A paper-based chemiluminescence detection device based on S,N-doped carbon quantum dots for the selective and highly sensitive recognition of bendiocarb.

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.

Magnetic zinc based 2D-metal organic framework as an efficient adsorbent for simultaneous determination of fluoroquinolones using 3D printed microchip and liquid chromatography tandem mass spectrometry.

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.

Simultaneous determination of total phenolic acids and total flavonoids in tea and honey samples using an integrated lab on a chip device.

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.

Dual-function 2D cobalt metal-organic framework embedded on paper as a point-of-care diagnostic device: Application for the quantification of glucose.

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.

Mesoporous MIP-capped luminescent MOF as specific and sensitive analytical probe: application for chlorpyrifos.

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.

Metal-Organic Framework Loaded by Rhodamine B As a Novel Chemiluminescence System for the Paper-Based Analytical Devices and Its Application for Total Phenolic Content Determination in Food Samples.

Herein, a novel paper-based chemiluminescence (CL) device has been reported for the estimation of total phenolic content of food samples. The CL system implemented on the paper was based on a hydrogen peroxide (H2O2)-rhodamine b (RhoB)-cobalt metal organic framework (CoMOF) reaction. It was found that the reaction of H2O2 with RhoB molecules, loaded into the nanopores of CoMOF (R@CoMOF), can produce an intensive CL emission. The experiments on the paper indicated that in the presence of CoMOF, the CL emission was greatly increased. In addition to this strong catalyzing effect, application of CoMOF on the paper improved the stability of the CL system for several days. As a useful analytical application for the obtained paper-based CL device (PCD), it was examined for the detection of phenolic antioxidants. It was observed that the addition of 5 µL of phenolic compounds (PC) on the paper containing the CL reagents can remarkably decrease the CL intensity. This effect was applied to design a simple analytical assay for PC. After the optimization process, the best sensitivity was obtained for gallic acid, quercetin, catechin, kaempferol, and caffeic acid with detection limits of 0.98, 1.36, 1.48, 1.81, and 2.55 ng mL-1, respectively. The relative standard deviations (RSD%) were also less than 5%. This study is the first report on the practical application of PCD using a nanomaterial assisted CL reaction. It is simple, portable, and low-cost and consumes a very low amount of reagents and sample solution. The device was successfully applied in the investigation of total antioxidant capacity of molasses and honey samples.

Application of surface molecular imprinted magnetic graphene oxide and high performance mimetic behavior of bi-metal ZnCo MOF for determination of atropine in human serum.

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.

A Highly Efficient Chemiluminescence System Based on an Enhancing Effect of Ag Nanoclusters/Graphene Quantum Dots Mixture for Ultrasensitive Detection of Rabeprazole.

Herein, an efficient chemiluminescence (CL) reaction with a high emission intensity is reported based on a synergistic improving effect of silver nanoclusters (AgNCs) and graphene quantum dots (GQDs). First, the syntheses of AgNCs and GQDs were simply performed by the chemical reducing of AgNO3 and a thermal treatment of glucose, respectively. After the characterization steps, the beneficial behavior of the prepared nanomaterial was investigated in CL systems. The oxidation reaction of KMnO4-rhodamine B produced weak CL emission. However, the presence of AgNCs and GQDs led to a synergetic enhancing effect, and thus higher emission was obtained. A possible mechanism was investigated for this effect using absorption and fluorescence experiments. Furthermore, rabeprazole showed a relatively selective enhancing impact on the CL emission. The CL intensity was linearly increased in the rabeprazole concentration range of 4 - 133 ng mL-1 with a detection limit (3Sb/m) of 1.1 ng mL-1. The developed CL method was utilized for the measurement of Rbp in biological samples with acceptable precision and accuracy.

Specific fluorometric assay for direct determination of amikacin by molecularly imprinting polymer on high fluorescent g-C3N4 quantum dots.

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.

A Chemiluminescent Method for the Detection of H2O2 and Glucose Based on Intrinsic Peroxidase-Like Activity of WS2 Quantum Dots.

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 1⁻1.5 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⁻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 0⁻1000 nmol·L-1, with a detection limit of 2.4 nmol·L-1. Using this CL assay, a linear relationship was obtained between the intensity of the CL emission and glucose concentration in the range of 0.01⁻30 nmol·L-1, with a limit of detection (3S) of 4.2 nmol·L-1.

Ultrasensitive chemiluminescence assay for cimetidine detection based on the synergistic improving effect of Au nanoclusters and graphene quantum dots.

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.

Synthesis of g-C3N4@CuMOFs nanocomposite with superior peroxidase mimetic activity for the fluorometric measurement of glucose.

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.

CdSe quantum dots-sensitized chemiluminescence system and quenching effect of gold nanoclusters for cyanide detection.

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.