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A tyrosinase-activatable fluorescent probe with endoplasmic reticulum targetability was developed for the first time. It can ratiometrically fluoresce and hence be used to monitor refluxed tyrosinase into the endoplasmic reticulum. [ABSTRACT FROM AUTHOR]

Herein, we develop a Rh(III)-catalyzed intermolecular regioselective dearomative spirocyclization of 2-aryl-3-nitrosoindoles with alkynes, featuring the redox-neutral and atom-economic construction of spiroindoline-3-one oximes bearing a C2 spirocyclic quaternary carbon center under mild conditions. Both aryl alkyl alkynes and 1,3-diynes generally proceeded smoothly in the reaction with moderate to good regioselectivities. DFT calculations provided in-depth insights into the reaction mechanism and disclosed the origins of the regioselectivities. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) were fabricated with a hierarchical flower-like hollow structure, possessing a large specific surface area, high porosity, and excellent environmental stability. In situ growth of noble silver nanoparticles (AgNPs) onto COFs was conducted yielding COF–Ag nanozymes. The structural advantages of COFs can ensure the uniform dispersion and effective size control of AgNPs. More interestingly, the oxidase-like catalytic activity of the obtained COF–Ag nanozymes could be enhanced in the presence of Hg2+ ions, which could specifically interact with AgNPs to form Ag–Hg alloys. A COF–Ag catalysis-based colorimetric platform was thereby constructed for highly selective and sensitive analysis of Hg2+ ions, showing a linear concentration range from 0.050 to 10.0 μM, with a limit of detection of about 3.7 nM. Besides, the developed colorimetric strategy was successfully applied for detecting Hg2+ ions in human blood with favorable detection recoveries, indicating its potential for applications in the biomedical analysis, environmental monitoring, and food safety fields. [ABSTRACT FROM AUTHOR]

The coupling of benzyl mercaptans to disulfide compounds is an important reaction in the production of pharmaceuticals, life medicine and other valuable fine chemicals. However, the coupling of benzyl mercaptans to disulfide compounds under aerobic and mild conditions remains a great challenge. Herein, we use cyclotriphosphazene as the basic skeleton to connect pyrimidine rings through ether bonds to form porous organic polymers (OBCPs). Research shows that OBCP samples not only exhibit fast carrier mobility, but also build up more negative reduction potential as well as low oxidation potential. In the photocatalytic reaction of benzyl mercaptans, OBCP sample generates the coupling of benzyl mercaptan to disulfide compounds rather than thiol oxidation products. Meanwhile, OBCPs also showed excellent photocatalytic reduction of CO2 to produce CH4. This work highlights that the dipole modulation of monomer molecules is important for designing polymers for excellent photocatalytic reactions. [ABSTRACT FROM AUTHOR]

The stoichiometric coupling of readily available methylarenes and diverse acid chlorides into α-aryl ketones, a valued structural motif present in pharmacologically relevant molecules, has been developed. The utility of this protocol is demonstrated by the late-stage acylation of biologically active molecules in a stoichiometric manner. Mechanistic investigation reveals that the photocatalytically generated bromine radical acts as a hydrogen atom abstraction reagent and delivers a nucleophilic benzyl radical, which is intercepted by nickel-catalyzed cross coupling to accomplish benzylic acylation. [ABSTRACT FROM AUTHOR]

Nitrogen-enriched carbon dots (NCDs) with green fluorescence were prepared with an average diameter of 4.8 nm by a room temperature self-polymerization method using catechol and ethylenediamine as precursors. It was found that the green fluorescence of NCDs can be quenched directly by uric acid (UA). A facile and fast fluorescent enzyme-free sensor has been developed for the detection of UA in the linear concentration range of 0–30 μM, with a limit of detection of 0.22 μM. High sensitivity, stability and selectivity can also be achieved for the detection of UA. In addition, the mechanism of fluorescence quenching of NCDs induced by UA was the dynamic quenching type according to the linearity of the Stern–Volmer equation and the change of the lifetime of NCDs after adding UA. Furthermore, UA in saliva samples was successfully detected using this established fluorimetric method, showing the feasible detection of UA in complicated body fluid samples. This NCD-based fluorimetric non-invasive method can be used for the highly selective determination of UA in the clinical laboratory. [ABSTRACT FROM AUTHOR]

The generation of high-calorific-value hydrocarbon fuels is still limited by poor photoinduced carrier transport in organic polymers. Herein, 2D polymers with different porous structures were synthesized by adopting a good-solvent/poor-solvent control strategy, and the photocatalytic CO2 reduction behavior was further compared. It was verified that the ultrafine porous structure in the 2D polymer (D1M4-PC) is responsible for the selective formation of CH4. The CH4 yield of the D1M4-PC sample reached 6733 μmol g−1, and the CH4 selectivity was near 100%. Experiments and theoretical calculations show that the ultrafine porous structure can provide an extremely short carrier transport distance and has accessible active sites, which enables the photoinduced carrier migration to the trapped CO2 molecules rapidly, enabling high selectivity photocatalytic CO2 conversion. This work offers a promising strategy for designing polymers for the conversion of CO2 into high-calorific-value hydrocarbon fuels with high selectivity and activity. [ABSTRACT FROM AUTHOR]

Nowadays, test strips are widely applied, but their use is mostly limited to the qualitative or half-quantitative analysis of targets. The main reason for their limited use is the "Coffee Ring Effect" (CRE) of probe materials, which leads to a heterogeneous probe distribution and poor testing reproducibility and sensitivity. In the present work, a fluorescent test strip was fabricated with a suppressed CRE of silver nanocluster (AgNC) probes coated by gelatin (Gel) under vacuum-aided fast lyophilization. Uniform and stable deposition of AgNC probes was achieved onto the test strips with a high loading capacity. The AgNCs displayed specific responses to Hg2+ ions, allowing sensitive and quantitative analysis in the linear concentration ranges from 0.20 to 50000 nM with a limit of detection of 0.10 nM. Given the advantages of rapid and facile preparation, CRE suppression, high biocompatibility, and cost-effectiveness, such a fabrication protocol may pave the way for the design of various test strips-based devices for point-of-care analytical applications in the fields of environmental monitoring, food quality analysis, and clinical diagnostics. [ABSTRACT FROM AUTHOR]

A high-throughput and selective fluorimetric platform has been constructed for the analysis of ammonia in blood by using a polymer-stabilized metal–organic framework (MOF) of porous NH2-MIL-125, which was coated onto a wettable microwells array constructed on an indium tin oxide (ITO) substrate. It was found that the nitrogen plasma treatment for the ITO substrate could create a super-hydrophilic interface that combined with the hydrophobic pattern yielded a wettable microwells array, enabling the condensation-based enrichment of targets from the sample droplets. Moreover, the NH2-MIL-125 MOF encapsulated using polymers could be firmly coated onto the microwells to act as fluorescent probes for sensing NH3 with enhanced responses. In addition, the use of the polymer polyvinyl pyrrolidone could protect and stabilize the crystals of NH2-MIL-125 probe in aqueous media, revealing the improved hydrophilicity and significantly depressed signal background. The as-developed fluorimetric platform, containing a MOF-coated microwells array, can enable the detection of ammonia in blood, with concentrations ranging linearly from 0.10 to 300 μM. More importantly, this plasma treatment-based fabrication route may hold promise for designing different wettable microwells arrays for the high-throughput detection of multiple targets in the fields of biomedical analysis and environmental monitoring. [ABSTRACT FROM AUTHOR]

As a key reactive oxygen species (ROS), hypochlorous acid (HClO) plays a vital role in living systems. Ratiometric and endoplasmic reticulum-targeting probes for highly sensitive detection of hypochlorous acid are in demand. In this paper, we constructed a novel reticulum-targeting and ratiometric fluorescent probe for determining hypochlorous acid. The probe applied 4-aminonaphthalimide as the fluorescent group, employed the (2-aminoethyl)thiourea group as a specific recognition unit, and used the p-toluenesulfonamide group as the localization group of the endoplasmic reticulum. When HClO is absent, the probe underwent an intramolecular charge transfer (ICT) process and displayed green emission. In the presence of HClO, the ICT process was inhibited, which induced a 49 nm blue-shift of fluorescence emission from 533 nm to 484 nm. The ratiometric fluorescent probe exhibited high sensitivity and selectivity for HClO. Furthermore, the ratiometric fluorescent probe could work in a wide pH range. The fluorescence intensity ratios (I484nm/I533nm) exhibited a linear response to the concentration of HClO from 5.0 × 10−7 to 1.0 × 10−5 mol L−1. The detection limit was evaluated to be 1.0 × 10−7 mol L−1 for HClO. In addition, the probe displayed an excellent endoplasmic reticulum-targeting ability, and has been successfully applied for the confocal imaging of HClO in the endoplasmic reticulum of PC-12 cells with almost no cell toxicity. All of such outstanding properties demonstrated that it could be employed to sense HClO in the endoplasmic reticulum of living cells. [ABSTRACT FROM AUTHOR]

In the present study, a simple strategy was developed for Ni/Co layered double hydroxides (LDHs) as a substitute for natural peroxidase. The obtained Ni/Co LDHs exhibited ease of preparation, low-cost, and water-solubility; importantly, this material showed high catalytic activity in neutral pH solutions (phosphate buffer, Tris–HCl buffer, and even water). Benefitting from Ni/Co LDHs having a similar pH and temperature with specificity oxidase, such as glucose oxidase, choline oxidase, acetylcholinesterase, etc., a novel one-step method for a biosensor was developed in water. Glucose detection was selected as an application model system to evaluate the performance of this method, which showed a linear detection range from 0.5 μM to 100 μM with a detection limit (DL) of 0.1 μM. We also extended the one-step method to detect acetylcholine (ACh) by taking advantage of the specific catalytic reaction of acetylcholinesterase (AChE) and choline oxidase (ChOx). The linear detection range was from 10 μM to 150 μM with the DL of 1.62 μM. The proposed method had ease of operation, simple steps, and was rapid for glucose and ACh detection in real samples. On the basis of these advantages and virtues, Ni/Co LDHs could become attractive nanozymes in biotechnology and bioassays, and create a great influence on the next generation of enzyme mimetic systems. [ABSTRACT FROM AUTHOR]

A high-throughput and selective fluorimetric platform has been constructed for the analysis of ammonia in blood by using a polymer-stabilized metal-organic framework (MOF) of porous NH2-MIL-125, which was coated onto a wettable microwells array constructed on an indium tin oxide (ITO) substrate. It was found that the nitrogen plasma treatment for the ITO substrate could create a super-hydrophilic interface that combined with the hydrophobic pattern yielded a wettable microwells array, enabling the condensation-based enrichment of targets from the sample droplets. Moreover, the NH2-MIL-125 MOF encapsulated using polymers could be firmly coated onto the microwells to act as fluorescent probes for sensing NH3 with enhanced responses. In addition, the use of the polymer polyvinyl pyrrolidone could protect and stabilize the crystals of NH2-MIL-125 probe in aqueous media, revealing the improved hydrophilicity and significantly depressed signal background. The as-developed fluorimetric platform, containing a MOF-coated microwells array, can enable the detection of ammonia in blood, with concentrations ranging linearly from 0.10 to 300 μM. More importantly, this plasma treatment-based fabrication route may hold promise for designing different wettable microwells arrays for the high-throughput detection of multiple targets in the fields of biomedical analysis and environmental monitoring.