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Metal–organic frameworks (MOFs) show excellent catalytic activity and have been widely applied in diagnosis of diseases and tumors. However, current assay methods usually involve cumbersome configurations and complicated procedures, which inhibit their practical applications. Hence, a Cu–Ni MOF/carbon printed electrode (CPE)-based integrated electrochemical immunosensor was constructed for highly sensitive and efficient determination of carcinoembryonic antigen (CEA). First, highly conductive carbon ink was screen-printed onto a polyethylene terephthalate substrate to manufacture a CPE. Afterward, an aminated Cu-Ni MOF was prepared by a typical solvothermal strategy and modified on the CPE. Owing to its excellent peroxidase activity, the Cu–Ni MOF can catalytically oxidize hydroquinone using hydrogen peroxide, which greatly amplifies the peak current signal. Then the formation of an immune complex inhibited the catalytic activity of the MOF, thus enabling the quantitative determination of CEA content with a wide linear range of 0.5 pg mL−1–500 ng mL−1 and a low detection limit of 0.16 pg mL−1. Furthermore, the Cu–Ni MOF/CPE-based integrated portable electrochemical immunosensor also showed satisfactory performance in the detection of CEA in clinical serum samples with excellent accuracy, showing great potential for application in point-of-care disease diagnosis. [ABSTRACT FROM AUTHOR]

The extension application of perovskites in aqueous media such as bioassays requires the development of a water-stable perovskite with a simple preparation process and low cost. However, the degradation of perovskites in aqueous solution is still a thorny problem. Here, we develop a methylimidazole-assisted two-step synthesis protocol to prepare CsPbBr3@PbBrOH nanorods with superior water stability and remarkable optical properties at room temperature. The synergy of 2-methylimidazole (2-MIM), an N-donor ligand, with water can not only facilitate CsPbBr3 formation and suppress CsPb2Br5 or Cs4PbBr6 formation, but also promote the formation of a PbBrOH shell capping CsPbBr3. 2-MIM is ionized into 2-MIM− in DMF and 2-MIM+ in water. They passivated the surface defects and changed the crystallization environment, leading to water-stable CsPbBr3@PbBrOH. The obtained CsPbBr3@PbBrOH nanorods can still maintain 91% PL intensity after being stored in water for more than 2 months. Furthermore, the CsPbBr3@PbBrOH nanorods show excellent stability in polar solvents, water, and phosphate buffer solution in a wide pH range, as well as better thermal and irradiation stability. In addition, the CsPbBr3@PbBrOH nanorods are further functionalized with polydopamine (PDA) for biomolecular immobilization and immunoassay studies. The resulting assay shows a detection limit of 0.003 ng mL−1 for IgG detection, illustrating important progress towards expanding fluorescence labeling application of perovskite nanomaterials for immunoassays. [ABSTRACT FROM AUTHOR]

In this research, dual-strategy biosensing of glucose was proposed based on multifunctional CuWO4 nanoparticles (CuWO4 NPs), which were prepared for the application of electrochemical and colorimetric sensing of glucose. CuWO4 NPs show large specific surface area and good conductivity as well as excellent peroxidase-like activity. A sensitive and selective electrochemical glucose biosensor was fabricated with the immobilization of glucose oxidase (GOx) on a CuWO4 NP modified electrode for enhancing the direct electron transfer behavior. A wide linear range of 0.005–1.8 mM with a low detection limit of 1.5 μM and a high sensitivity of 28.02 mA M−1 cm−2 were achieved by using the electrochemical biosensor. Meanwhile, a colorimetric and visual glucose biosensor was constructed based on the GOx/CuWO4 cascade nanozyme, which shows a linear range of 0.05–1.0 mM with excellent selectivity. CuWO4 NPs as a promising matrix open up a dual-strategy biosensor for sensitive and selective detection of glucose. [ABSTRACT FROM AUTHOR]

Possessing prominent customization in structural design as well as unique physicochemical properties, covalent organic frameworks (COFs) show great potential in the biosensing field. In this study, we prepared a novel COF-based electrochemical enzymatic composite (denoted as Fe3O4@COF@HRP), where spherical magnetic COF was functionalized with horseradish peroxidase (HRP). The resultant composite was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. Thereinto, the Fe3O4 nanoparticles with remarkable conductivity could accelerate the charge transfer, while HRP with good catalytic activity could enhance the sensitivity of the as-prepared biosensor. With such a design, the Fe3O4@COF@HRP-based biosensor exhibits excellent analytical properties for the determination of hydroquinone. The extended linear detection range was 0.5–300 μmol L−1, and the limit of detection was down to 0.12 μmol L−1 (S/N = 3). Furthermore, the electrochemical enzymatic biosensor was used to detect low-abundance hydroquinone in environmental water samples with a satisfactory consequence, suggesting great promise in sensing applications. [ABSTRACT FROM AUTHOR]

The development of flexible substrate materials and nanomaterials with high electrochemical performance is of great significance for constructing efficient wearable electrochemical sensors for real-time health monitoring. Herein, a wearable electrochemical sweat sensor based on a Ni–Co MOF nanosheet coated Au/polydimethylsiloxane (PDMS) film was prepared for continuous monitoring of the glucose level in sweat with high sensitivity. First, a stretchable Au/PDMS film based three-electrode system was prepared by chemical deposition of a gold layer on the hydrophilic treated PDMS. Then, Ni–Co MOF nanosheets with high electrocatalytic activity were synthesized by a facile solvothermal method and modified on the Au/PDMS electrode. The electrocatalytic activity of the Ni–Co MOF nanosheets synthesized under different Ni : Co ratios was investigated. The Ni–Co MOF/Au/PDMS (NCAP) film electrode showed excellent electrochemical performance for glucose detection with a wide linear range of 20 μM to 790 μM and a high sensitivity of 205.1 μA mM−1 cm−2. In addition, the flexible sensor shows high stability and a good electrochemical response to glucose when stretched and bent to different levels. Moreover, it maintained long-term stability and high selectivity for glucose monitoring. Lastly, a sweat-absorbent cloth was used to cover the working area of the sensor and was fixed with a needle and thread to form a wearable sweat glucose sensor. The sensor can be attached to the skin for stable, accurate and continuous monitoring of glucose levels in human sweat for one day. This work validates the potential of our high-performance wearable sensor for out-of-clinic health monitoring. [ABSTRACT FROM AUTHOR]

The poor stability and aqueous-quenching of fluorescence of perovskite nanocrystals (NCs) hinder their application in bio-detection and bio-imaging. Herein, through the synergistic effects of polymer surface ligand and silica encapsulation, highly stable and enhanced aqueous fluorescent CsPbBr3-mPEG@SiO2 NCs were synthesized and used as a novel "on–off–on" fluorescent probe for highly sensitive and selective detection of mercury ions (Hg2+) and glutathione (GSH) in aqueous solutions. The effects of the methoxypolyethylene glycol amine (mPEG-NH2) ligand and silica encapsulation on the stability and aqueous fluorescence of the CsPbBr3 NCs were studied. It indicated that the aqueous fluorescence of perovskite NCs was increased by 2.59 times. The water stability was also greatly improved, with the NCs maintaining 73% of their original fluorescence after storage for 30 days in water. X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR) analyses further demonstrated that the NCs were successfully passivated by mPEG-NH2 and silica. The fluorescence of the CsPbBr3-mPEG@SiO2 nanocrystals was effectively quenched by Hg2+ which is attributed to the electron transfer process between NCs and Hg2+. Then, through the interaction between Hg2+ and GSH, the restoration of fluorescence for CsPbBr3-mPEG@SiO2 was realized. The "on–off–on" fluorescent probe can be used for the detection of Hg2+ and GSH with a low detection limit of 0.08 nM and 0.19 μM, respectively. It also shows a fast response time and high accuracy for practical sample detection. The simple and sensitive fluorescent probe of CsPbBr3-mPEG@SiO2 shows great potential in environmental and biological sensing. [ABSTRACT FROM AUTHOR]

A novel hedgehog-shaped bismuth sulfide (HS-Bi2S3) nanostructure was for the first time explored as an electrode material for biosensing. Using cetyltrimethyl ammonium bromide (CTAB)-trimellitic acid as a composite soft template, the HS-Bi2S3 nanostructure was synthesized by a hydrothermal route. Using glucose oxidase (GOx) as the model, the HS-Bi2S3 nanostructure was employed to immobilize GOx for the development of a sensitive electrochemical glucose biosensor. The characterization of HS-Bi2S3 and the biosensor was performed by scanning electron microscopy, X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy and cyclic voltammetry. The hedgehog-shaped nanostructure of Bi2S3 has a large specific surface area to trap a large number of enzyme molecules, and at the same time greatly enhances the direct-electron-transfer action of enzymes. The HS-Bi2S3-based biosensor shows a wide linear range of 0.005–1.7 mmol L−1 and a low detection limit of 1.6 μmol L−1 for glucose at −0.37 V, which presents much better assay performance in comparison with the glucose biosensor without HS-Bi2S3. The present electrochemical biosensor displays high selectivity, good repeatability and stability, which can be used to measure blood glucose in real serum samples. [ABSTRACT FROM AUTHOR]

A covalent organic framework (COF) is a promising type of porous material with customizable surface characteristics. Confining multiple catalytic units within a mesoporous COF can generate abundant active sites and improve the catalytic performance. In this work, a COF with both metalloporphyrin and a metal nanoparticle complex denoted as hemin/TAPB-DMTP-COF/AuNPs (TAPB: 1,3,5-tris(4-amino-phenyl)benzene, DMTP: 2,5-dimethoxyterephaldehyde, AuNPs: Au nanoparticles) has been successfully fabricated through a hierarchical encapsulation method. The as-synthesized composite was then employed to construct an electrochemical sensing platform for the efficient detection of bisphenol A (BPA). Under the optimal conditions, the hemin/TAPB-DMTP-COF/AuNP sensor presented a linear range of 0.01–3 μmol L−1 and a low detection limit of 3.5 nmol L−1. The satisfactory signal amplification is based on a triple-signaling amplification strategy due to the abundant Fe3+ sites of Fe-porphyrin, high conductivity of AuNPs and a large specific surface area of the TAPB-DMTP-COF. The proposed method was used to measure the content of BPA in different water samples with a satisfactory recovery from 95.5 to 104.0%, suggesting the great potential of the sensor in practical applications. [ABSTRACT FROM AUTHOR]

In this research, a novel manganese dioxide nanorod-anchored graphene oxide (MnO2 NRs/GO) composite was synthesized by a simple hydrothermal method for electrochemical sensing application. A highly sensitive electrochemical sensor for dopamine (DA) was constructed by modifying glassy carbon electrode (GCE) with MnO2 NRs/GO. The morphology and performance of the composite material and modified GCEs were investigated by using scanning electron microscopy (SEM), X-ray diffraction (XRD) and cyclic voltammetry (CV), respectively. The resultant MnO2 NRs/GO composite has a large electroactive area and shows excellent electrochemical activity toward DA. Under the optimal conditions, the DA sensor shows a linear response in the DA concentration ranges of 0.1 μM–0.08 mM and 0.08–0.41 mM with a low detection limit of 0.027 μM and a high sensitivity of 602.4 μA·mM−1·cm−2. The MnO2 NRs/GO composite provides a promising platform for the construction of a highly sensitive and selective sensor of DA. [ABSTRACT FROM AUTHOR]

In this research, we reported effective streptavidin-functionalized tin disulfide nanoflakes (SnS2 NFs) to develop an ultrasensitive electrochemical immunosensor for the bioanalysis of tumor markers. The streptavidin-functionalized SnS2 platform and immunosensor were characterized by scanning electron microscopy, electrochemical impedance spectroscopy, static water contact angle measurements and cyclic voltammetry. Biofunctionalized SnS2 NFs displayed a large specific surface area and outstanding hydrophilicity. These characteristics enhanced the loading efficiency and capacity of antibodies on the biosensing platform and ensured the biological activity of the immobilized protein biomolecules. Carcinoembryonic antigen (CEA) was chosen as the model analyte, and a wide linear range of 0.006–3.0 ng mL−1 with a low detection limit of 5 pg mL−1 for CEA was exhibited by the immunosensor. Human serum sample analysis was achieved through the CEA immunosensor with satisfactory results. Streptavidin-functionalized SnS2 NFs offer a potential platform for the expansion of electrochemical immunosensor applications. [ABSTRACT FROM AUTHOR]

The fabrication of chemically stable metal–organic frameworks for electrochemical sensors is essential to broaden their applications. In this study, the integration of a Zr-based metal–organic framework (UiO-66-NH2) with multi-walled carbon nanotubes (MWCNTs) was achieved by a one-pot solvothermal reaction. This composite was then characterized by scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, and contact angle measurements. The porous structure and unreacted amine groups provided by UiO-66-NH2 frameworks accompanied by the excellent conductivity of MWCNTs have made this composite an ideal electrode material for lead detection. After the optimization of MWCNT content and the detection conditions, the oxidation peak currents were proportional to lead concentrations in the range of 0.001–0.8 μmol L−1 with a low detection limit of 0.5 nmol L−1 (S/N = 3). More importantly, the well-preserved crystallinity of MWCNTs@UiO-66-NH2 after 80 cycles and after being soaked in different pH aqueous solutions indicates the promising application of this sensor for real samples. Satisfactory recoveries were achieved when this sensor was used to detect lead in real samples. Furthermore, the excellent stability of this composite makes it possible to be employed in other fields, including extreme acidic media. [ABSTRACT FROM AUTHOR]

Herein, we report the synthesis of novel nanosized reduced graphene oxide@polystyrene nanospheres (rGO@PS NSs) through an electrostatic interaction method, and further their exploitation for highly sensitive label-free electrochemical immunoassay applications. These rGO@PS NSs provide a universal and promising carrier platform to develop excellent biosensors for clinical screening and diagnostic applications. [ABSTRACT FROM AUTHOR]

In this work, a water stable zirconium metal–organic framework functionalized with thiol groups was synthesized by a solvent-assisted ligand incorporation technique. The composites were characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy, specific surface area measurement and field emission scanning electron microscopy. The prepared material was then used as a novel adsorbent for Cu(ii) removal from water. The experimental parameters associated with adsorption capability, such as the initial solution pH, contact time, and the presence of competing cations were investigated in detail. Under the optimal conditions, the adsorption follows a pseudo-second-order kinetics, and the equilibration time for the adsorption is 15 min. The Langmuir adsorption model was in better correlation with the isothermal adsorption data than the Freundlich model. The maximum Cu(ii) adsorption capacity reached up to 42.70 mg g−1. Quantitative recovery of Cu(ii) was achieved by using 0.1 mol L−1 HCl. The prepared adsorbent has fast adsorption efficiency, high adsorption capacity, and exceptional stability up to 50 adsorption/desorption cycles. It can be used as a promising candidate material for heavy metal ion removal and water treatment. [ABSTRACT FROM AUTHOR]

We report a new concept of a chemiluminescence imaging nanozyme immunoassay (CINIA), in which nanozymes are exploited as catalytic tags for simultaneous multiplex detection of cytokines. The CINIA provides a novel and universal nanozyme-labeled multiplex immunoassay strategy for high-throughput detection of relevant biomarkers and further disease diagnosis. [ABSTRACT FROM AUTHOR]

In this study, mesoporous silica nanospheres (MSNs) are synthesized and biofunctionalized with streptavidin for the development of an ultrasensitive chemiluminescence (CL) immunoassay. The streptavidin-functionalized MSNs have a large specific surface area and exhibit excellent hydrophilicity, which are favourable to effectively capture biotinylated antibodies and retain their bioactivity. We used α-fetoprotein (AFP) as a model analyte, which can be detected in a wide linear range of 0.01–5.0 ng mL−1 with a very low detection limit down to 9 pg mL−1 (S/N = 3). The assay results of clinical human serum samples using the present method are in acceptable agreement with the reference values obtained from the hospital. This biofunctionalized MSN-based CL immunoassay provides a promising approach for early screening of tumor diseases. [ABSTRACT FROM AUTHOR]

In this work, a conductive electrochemical sensor, UiO-66-NH2@PANI, was successfully prepared by polymerizing the conductive polyaniline (PANI) polymer around the metal–organic framework UiO-66-NH2. Fourier transform infrared spectra, X-ray diffraction patterns, and X-ray photoelectron spectral data support the formation of UiO-66-NH2@PANI. Additionally, scanning and transmission electron microscopy investigations confirm that PANI uniformly coated the surface of UiO-66-NH2. The resultant material was applied to construct a novel electrochemical sensor for the reliable detection of cadmium ions due to the chelation mechanism between metal cations and amine groups. Under optimized conditions, a linear detection of Cd2+ concentration range of 0.5–600 μg L−1 was repeatable with a 0.3 μg L−1 lowest level detection limit. Little to no interference effects from other co-existing ions allow the sensor to work in varying environments for practical application. This method of coating metal–organic frameworks may show utility for constructing highly sensitive electrochemical sensors for the detection of heavy metal ions and more. [ABSTRACT FROM AUTHOR]

MoS2 nanosheet–Au nanorod (MoS2–Au) hybrids were utilized to immobilize catalase (CAT) to construct a sensitive hydrogen peroxide (H2O2) electrochemical biosensor for the reliable determination of H2O2 released from living cells. The fabricated biosensor was characterized by transmission electron microscopy (TEM), UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy, it was observed that the MoS2–Au hybrid provides excellent matrixes for the adsorption of CAT and the entrapped CAT maintains its native structure and bioactivity. The results of direct electrochemical measurements indicate that on the CAT/MoS2–Au modified electrode, CAT exhibits a surface controlled and fast electron transfer process towards H2O2 reduction. The MoS2–Au hybrid has a large surface area and provides a biocompatible microenvironment for accelerating direct electron transfer between the enzyme and the electrode. The detection limit of the constructed H2O2 biosensor is 1 × 10−7 M (signal-to-noise = 3) with a wide linear range from 5 × 10−7 M to 2 × 10−4 M and a high sensitivity of 187.4 mA M−1 cm−2. The fabricated H2O2 biosensor also exhibits excellent selectivity, good reproducibility and long-time stability. Furthermore, the biosensor was used to perform real-time monitoring of H2O2 released from SP2/0 cells, indicating the MoS2–Au hybrid is an attractive material for application in the efficient immobilization of biomolecules and construction of high-performance biosensors. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks/titanium dioxide (UiO-66-NH2/TiO2) nanocomposites have been prepared by a simple hydrothermal reaction and they exhibit excellent electrocatalytic activity for chlorogenic acid oxidation due to the synergic effect of UiO-66-NH2 and TiO2. Under the optimal conditions, the sensor can be employed in the quantification of chlorogenic acid in the ranges of 0.01–1.0 μmol L−1 and 1.0–15 μmol L−1 with an ultralow detection limit of 7 nmol L−1 (S/N = 3). Moreover, UiO-66-NH2/TiO2 nanocomposites demonstrate significant stability in acidic buffer solution and maintain their electrocatalytic activities at least up to 90 cycles. The potential utility was validated by the analysis of coffee and tea samples and good recoveries were obtained from different spiked values. The UiO-66-NH2/TiO2 based sensor with highly sensitive, selective and stable consecutive monitoring of chlorogenic acid is a promising candidate for the construction of highly active electrocatalyst in electrochemical biosensors. [ABSTRACT FROM AUTHOR]

A new label-free chemiluminescence (CL) immunoassay method is proposed for the cheap, convenient and sensitive detection of proteins through the co-immobilization of a capture antibody and horseradish peroxidase on a sensing interface. The specific immunoreaction on the interface effectively inhibits the enzymatic CL reaction, thus causing a decrease in CL signals. [ABSTRACT FROM AUTHOR]

In this work, we illustrate how to anchor –SO3H functional groups onto the pore surface of MOF for cadmium removal from aqueous solution via the approach of sequential post-synthetic modification and oxidation as exemplified in the context of functionalizing the MOF, Cu3(BTC)2 with sulfonic acid. The resultant sulfonic acid functionalized MOF, Cu3(BTC)2–SO3H demonstrates a high cadmium uptake capacity of 88.7 mg g−1, surpassing that of the benchmark adsorbents. In addition, it exhibits a fast kinetics with the kinetic rate constant k2 of 0.6818 g mg−1 min, which is 1–3 orders of magnitude higher than existing adsorbent materials for adsorbing cadmium ions from aqueous solution. Moreover, it demonstrates high selectivity of cadmium ions in the presents of other background metal ions, and can be readily regenerated and recycled without significant loss of cadmium uptake capacity. Our work thus paves a way for developing functionalized MOFs as a new type of platform for removing cadmium from wastewater. [ABSTRACT FROM AUTHOR]

Carbon functionalized metal organic frameworks (C/Al-MIL-53-(OH)2) were successfully prepared for the first time by a solvothermal technique and characterized by Fourier transform infrared spectroscopy, X-ray diffraction spectrometry, and scanning electron microscopy. This composite was coated with a Nafion film so as to form a Nafion/C/Al-MIL-53-(OH)2 modified glassy carbon electrode. The modified electrode was then used as a novel electrocatalyst for dopamine (DA) oxidation in phosphate buffer solution. Due to the synergistic effects of the different materials, including the high conductivity of carbon, the large surface area of Al-MIL-53-(OH)2, and the film-forming ability of a cation-exchange polymer, the modified electrode exhibited a remarkable enhancement effect on voltammetric response of DA. Under the optimal conditions, the response peak currents had a linear relationship with the DA concentration in the range from 3.0 × 10−8 to 1.0 × 10−5 mol L−1. The limits of detection and quantitation for DA were found to be 0.8 × 10−8 mol L−1 and 2.6 × 10−8 mol L−1, respectively. The analytical utilities of the proposed biosensor were achieved by analyzing the content of DA in biological fluids. [ABSTRACT FROM AUTHOR]

In this work, a novel chemically modified electrode is constructed based on metal–organic frameworks and β-cyclodextrin (Cu3(BTC)2/β-CD, BTC = benzene-1,3,5-tricarboxylate) composite material. The electrode was used for simultaneous determination of guanine and adenine in a sequential injection lab-on-valve format and exhibited sensitive responses to guanine and adenine oxidation due to the π–π stacking interaction of Cu3(BTC)2 and the inclusion behavior of β-CD. The analytical performance was assessed with respect to the supporting electrolyte and its pH, accumulation time and accumulation potential, and the fluid flow rates. Under optimal conditions, linear calibration ranges for both guanine and adenine were from 1.0 × 10−7 to 1.0 × 10−5 mol L−1, and detection limits (S/N = 3) were found to be 5.2 × 10−8 and 2.8 × 10−8 mol L−1, respectively. The proposed sensor showed advantages of high sensitivity, simple sample preparation protocol, enhanced throughput and good reproducibility. Finally, the practical application of the proposed sensor has been performed for the determination of guanine and adenine in real samples with satisfactory results. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks have been the subject of intense research because of their unique physicochemical properties. The presented study investigates the application of multi-wall carbon nanotubes and metal–organic frameworks (MWCNTs@Cu3(BTC)2) nanoparticles-modified electrode for the determination of trace levels of lead. The nanocomposites were prepared by solvothermal synthesis and characterized in detail. The experimental procedure was carried out by accumulating lead on the electrode surface and subsequently measuring with differential pulse anodic stripping voltammetry in a lab-on-valve format. The main parameters affecting the analytical performance, including the amount of MWCNTs@Cu3(BTC)2 suspension, supporting electrolyte and its pH, stripping mode, and flow rate, have been investigated in detail. Under the optimum conditions, the oxidation peak current displayed a calibration response for lead over a concentration range from 1.0 × 10−9 to 5.0 × 10−8 mol L−1 with a excellent detection limit of 7.9 × 10−10 mol L−1. The relative standard deviation of 7 successive scans was 3.10% for 1.0 × 10−8 mol L−1 lead. The established method showed a great improvement in sensitivity and sample throughput for lead analysis. [ABSTRACT FROM AUTHOR]

Dithizone functionalized magnetic metal–organic frameworks (Fe3O4/Cu3(BTC)2–H2Dz) were successfully synthesized for the determination of trace levels of lead based on magnetic solid-phase extraction. The properties of the hybrid nanoparticles were characterized in detail by Fourier transform infrared spectroscopy, X-ray diffraction spectrometry, vibrating sample magnetometry, and scanning electron microscopy. The sorbents were conveniently separated from the complicated matrix easily with an external magnetic field. The metals were quantitatively desorbed and quantified by electrothermal atomic absorption spectrometry. The factors affecting the extraction process such as pH, sorbent amount, sample volume, eluent concentration and volume, and interfering ions were investigated and optimized. The adsorption capacity of Fe3O4/Cu3(BTC)2–H2Dz was found to be 1.67 mg g−1 for lead. The method had a linear calibration plot over the range of 0.01 to 5.0 μg L−1 with a relative standard deviation of 3.2% at 0.5 μg L−1 (n = 10). The detection limit was as low as 0.0046 μg L−1. The results indicated that the proposed method based on Fe3O4/Cu3(BTC)2–H2Dz was a novel, rapidly analysed, highly selective, and reliable assay for lead detection. [ABSTRACT FROM AUTHOR]

An indirect photoelectrochemical sensing platform for toxic hexavalent chromium was for the first time constructed based on its redox reaction with quercetin as both the electron donor and photosensitizer on a TiO2 photoanode, and thus inhibiting the photocurrent quantitatively and selectively. The presence of even 500-fold coexisting Cr(iii) does not interfere in the detection of Cr(vi). Under the optimum conditions, the electrode displayed a linear decrease response as the Cr(vi) concentration increased from 1 to 10 nmol L−1 and from 20 to 140 nmol L−1 with a detection limit of 0.24 nmol L−1. Many possible ions in drinking water did not interfere with the detection, and the real sample detection results agreed well with those obtained by GFAAS. This work provide a novel methodology for the simple, low-cost photoelectrochemical detection of Cr(vi) in drinking water. [ABSTRACT FROM AUTHOR]

We describe an automation-friendly chemiluminescent immunoassay method for sensitive and rapid determination of chicken interferon-γ at the sub-picogram per millilitre level based on the monoclonal antibody immobilized paramagnetic microspheres and flow-through system. [ABSTRACT FROM AUTHOR]

The extension application of perovskites in aqueous media such as bioassays requires the development of a water-stable perovskite with a simple preparation process and low cost. However, the degradation of perovskites in aqueous solution is still a thorny problem. Here, we develop a methylimidazole-assisted two-step synthesis protocol to prepare CsPbBr 3 @PbBrOH nanorods with superior water stability and remarkable optical properties at room temperature. The synergy of 2-methylimidazole (2-MIM), an N-donor ligand, with water can not only facilitate CsPbBr 3 formation and suppress CsPb 2 Br 5 or Cs 4 PbBr 6 formation, but also promote the formation of a PbBrOH shell capping CsPbBr 3 . 2-MIM is ionized into 2-MIM - in DMF and 2-MIM + in water. They passivated the surface defects and changed the crystallization environment, leading to water-stable CsPbBr 3 @PbBrOH. The obtained CsPbBr 3 @PbBrOH nanorods can still maintain 91% PL intensity after being stored in water for more than 2 months. Furthermore, the CsPbBr 3 @PbBrOH nanorods show excellent stability in polar solvents, water, and phosphate buffer solution in a wide pH range, as well as better thermal and irradiation stability. In addition, the CsPbBr 3 @PbBrOH nanorods are further functionalized with polydopamine (PDA) for biomolecular immobilization and immunoassay studies. The resulting assay shows a detection limit of 0.003 ng mL -1 for IgG detection, illustrating important progress towards expanding fluorescence labeling application of perovskite nanomaterials for immunoassays.

In this research, dual-strategy biosensing of glucose was proposed based on multifunctional CuWO 4 nanoparticles (CuWO 4 NPs), which were prepared for the application of electrochemical and colorimetric sensing of glucose. CuWO 4 NPs show large specific surface area and good conductivity as well as excellent peroxidase-like activity. A sensitive and selective electrochemical glucose biosensor was fabricated with the immobilization of glucose oxidase (GOx) on a CuWO 4 NP modified electrode for enhancing the direct electron transfer behavior. A wide linear range of 0.005-1.8 mM with a low detection limit of 1.5 μM and a high sensitivity of 28.02 mA M -1 cm -2 were achieved by using the electrochemical biosensor. Meanwhile, a colorimetric and visual glucose biosensor was constructed based on the GOx/CuWO 4 cascade nanozyme, which shows a linear range of 0.05-1.0 mM with excellent selectivity. CuWO 4 NPs as a promising matrix open up a dual-strategy biosensor for sensitive and selective detection of glucose.

The poor stability and aqueous-quenching of fluorescence of perovskite nanocrystals (NCs) hinder their application in bio-detection and bio-imaging. Herein, through the synergistic effects of polymer surface ligand and silica encapsulation, highly stable and enhanced aqueous fluorescent CsPbBr 3 -mPEG@SiO 2 NCs were synthesized and used as a novel "on-off-on" fluorescent probe for highly sensitive and selective detection of mercury ions (Hg 2+ ) and glutathione (GSH) in aqueous solutions. The effects of the methoxypolyethylene glycol amine (mPEG-NH 2 ) ligand and silica encapsulation on the stability and aqueous fluorescence of the CsPbBr 3 NCs were studied. It indicated that the aqueous fluorescence of perovskite NCs was increased by 2.59 times. The water stability was also greatly improved, with the NCs maintaining 73% of their original fluorescence after storage for 30 days in water. X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR) analyses further demonstrated that the NCs were successfully passivated by mPEG-NH 2 and silica. The fluorescence of the CsPbBr 3 -mPEG@SiO 2 nanocrystals was effectively quenched by Hg 2+ which is attributed to the electron transfer process between NCs and Hg 2+ . Then, through the interaction between Hg 2+ and GSH, the restoration of fluorescence for CsPbBr 3 -mPEG@SiO 2 was realized. The "on-off-on" fluorescent probe can be used for the detection of Hg 2+ and GSH with a low detection limit of 0.08 nM and 0.19 μM, respectively. It also shows a fast response time and high accuracy for practical sample detection. The simple and sensitive fluorescent probe of CsPbBr 3 -mPEG@SiO 2 shows great potential in environmental and biological sensing.

This work investigated the feasibility and efficiency of a heterogeneous photo-Fenton catalyst, Fe/Si codoped TiO 2 , for the degradation of metronidazole (MNZ) under visible light irradiation. The Fe/Si codoped TiO 2 was prepared via a facile and simple sol-gel solvothermal process followed by annealing at 480 °C for 4 hours. High resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) measurements revealed that the photo-Fenton process did not change the structure, textural and surface morphologies of this catalyst. Elemental mapping results indicated the good dispersion of Fe and Si ions in TiO 2 . Nitrogen adsorption and desorption measurements indicated that Si doping increased the surface area of the catalysts. The Fe and Si doping narrowed the band gap of TiO 2 . They also facilitated the transfer of photo-generated electrons from TiO 2 to Fe(iii). Under visible light irradiation and the optimum operating conditions, MNZ could be completely degraded in 50 min by this catalyst within a wide pH range. Hydroxyl radicals and holes were verified to be responsible for degrading MNZ. The leaching of iron ions was less than 0.047 ppm even after illuminating the catalyst for 6 hours, indicating the good stability of the Fe/Si codoped TiO 2 . The as-prepared catalysts with excellent catalytic activity, and remarkable reusability and stability could provide a new insight into the preparation of photocatalysts and have wide applications for antibiotics removal., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

MoS 2 nanosheet-Au nanorod (MoS 2 -Au) hybrids were utilized to immobilize catalase (CAT) to construct a sensitive hydrogen peroxide (H 2 O 2 ) electrochemical biosensor for the reliable determination of H 2 O 2 released from living cells. The fabricated biosensor was characterized by transmission electron microscopy (TEM), UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy, it was observed that the MoS 2 -Au hybrid provides excellent matrixes for the adsorption of CAT and the entrapped CAT maintains its native structure and bioactivity. The results of direct electrochemical measurements indicate that on the CAT/MoS 2 -Au modified electrode, CAT exhibits a surface controlled and fast electron transfer process towards H 2 O 2 reduction. The MoS 2 -Au hybrid has a large surface area and provides a biocompatible microenvironment for accelerating direct electron transfer between the enzyme and the electrode. The detection limit of the constructed H 2 O 2 biosensor is 1 × 10 -7 M (signal-to-noise = 3) with a wide linear range from 5 × 10 -7 M to 2 × 10 -4 M and a high sensitivity of 187.4 mA M -1 cm -2 . The fabricated H 2 O 2 biosensor also exhibits excellent selectivity, good reproducibility and long-time stability. Furthermore, the biosensor was used to perform real-time monitoring of H 2 O 2 released from SP2/0 cells, indicating the MoS 2 -Au hybrid is an attractive material for application in the efficient immobilization of biomolecules and construction of high-performance biosensors.

Co(3)O(4) nanoparticles (NPs) with an average diameter of about 20 nm were synthesized by using MOFs as a template. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to characterize the as-prepared Co(3)O(4) NPs. Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) were used to confirm the structure of the Co(3)O(4) NPs. Then the Co(3)O(4) NPs were modified on a glassy carbon electrode (GCE) to obtain a non-enzymatic glucose and H(2)O(2) sensor. The NPs show electrocatalytic activity toward oxidation of glucose and H(2)O(2) in alkaline medium. For glucose detection, the developed sensor shows a short response time (less than 6 s), a high sensitivity of 520.7 μA mM(-1) cm(-2), a detection limit of 0.13 μM (S/N = 3), and good selectivity. The high concentration of NaCl does not poison the electrode. Its application for the detection of glucose in a human blood serum sample shows good agreement with the results obtained from the hospital. Furthermore, the proposed sensor was used for the detection of H(2)O(2). The results indicate that the detection limit and sensitivity for H(2)O(2) are 0.81 μM and 107.4 μA mM(-1) cm(-2), respectively. Determination of H(2)O(2) concentration in a disinfectant sample by the proposed biosensor also showed satisfactory result. The high sensitivity and low detection limit can be attributed to the excellent electrocatalytic performance of the as-prepared Co(3)O(4) NPs. These results demonstrate that the as-prepared Co(3)O(4) NPs have great potential applications in the development of sensors for enzyme-free detection of glucose and H(2)O(2).

In this study, an automated sequential injection lab-on-valve (SI-LOV) system was designed for the on-line matrix removal and preconcentration of quercetin. Octadecyl functionalized magnetic silica nanoparticles were prepared and packed into the microcolumn of the LOV as adsorbents. After being adsorbed through hydrophobic interaction, the analyte was eluted and subsequently introduced into the electrochemical flow cell by voltammetric quantification. The main parameters affecting the performance of solid-phase extraction, such as sample pH and flow rate, eluent solution and volume, accumulation potential and accumulation time were investigated in detail. Under the optimum experimental conditions, a linear calibration curve was obtained in the range of 1.0 × 10(-8) to 1 × 10(-5) mol L(-1) with R(2) = 0.9979. The limit of detection (LOD) and limit of quantitation (LOQ) were 1.3 × 10(-9) and 4.3 × 10(-9) mol L(-1), respectively. The relative standard deviation (RSD) for the determination of 1.0 × 10(-6) mol L(-1) quercetin was found to be 2.9% (n = 11) along with a sampling frequency of 40 h(-1). The applicability and reliability of the automated method described here had been applied to the determination of quercetin in human urine and red wine samples through recovery experiments, and the obtained results were in good agreement with those obtained by the HPLC method.

The miniaturized lab-on-valve (LOV) manifold well hyphenated with indirect biamperometry is presented for automated determination of trace level concentrations of organic environmental pollutants by programmable flow. The experimental procedure was carried out by means of taking o-phenylenediamine (OPDA) as a model analyte, relying on the Fe(iii)/Fe(ii) couple that served as an indicating redox system. The miniaturized electrochemical flow cell (EFC) designed and processed was integrated into the LOV module which is assembled with two identical polarized platinum electrodes between which a small potential difference (ΔE) was applied, to implement automated on-line analysis in a closed system. Factors affecting analytical performance are discussed, including indicating redox systems, concentration of indicating system, the acidity, the potential difference, and flow variables in the LOV. The calibration curve showed an excellent linearity in the concentration range of 5.0 × 10(-7) to 1.0 × 10(-4) mol L(-1) (R(2) = 0.9993). The limits of detection (LOD) and quantitation (LOQ) for OPDA were found to be 1.1 × 10(-7) and 3.7 × 10(-7) mol L(-1), respectively. A sampling frequency of 40 h(-1) was obtained along with an R.S.D. of 2.8% at 1.0 × 10(-6) mol L(-1) OPDA (n = 11). The proposed procedure was successfully applied to the assay of OPDA in industrial waste water.