Potentiometric determination of mefenamic acid in pharmaceutical formulation by membrane sensor based on ion-pair with basic dye

The characteristics,performance and application of membrane sensors based on ion-pair Brilliant Green mefenamate are described.The sensor’s response to the mefenamate ion has the sensitivity of （86.0±2.0） mV/pC over the range of 9×10^-5-1×10^-2moI/Land the detection limit of 4.5×10^-5mol/L at pH 8.5-12.The sensor is easily assembled at a relatively low cost and has fast response time（5-10 s）.The proposed sensor displayed good selectivity for mefenamate ion in the presence of different substances.It was used to determine mefenamic acid in pharmaceuticals.     

Fabrication of an Electrochemical L‐Cysteine Sensor Based on Graphene Nanosheets Decorated Manganese Oxide Nanocomposite Modified Glassy Carbon Electrode

The graphene nanosheets/manganese oxide nanoparticles modified glassy carbon electrode (GC/GNSs/MnOx) was simply prepared by casting a thin film of GNSs on the GC electrode surface, followed by performing electrodeposition of MnOx at applied constant potential. The GC/GNSs/MnOx modified electrode shows high catalytic activity toward oxidation of L ‐cysteine. Hydrodynamic amperometry determination of L ‐cysteine gave linear responses over a concentration range up to 120 µM with a detection limit of 75 nM and sensitivity of 27 nA µM^?1. The GC/GNSs/MnOx electrode appears to be a highly efficient platform for the development of sensitive, stable and reproducible L ‐cysteine electrochemical sensors.     

Facile Fabrication of Multi‐targeted and Stable Biochemical SERS Sensors

The direct transfer of single‐crystalline Au nanowires (NWs) onto Au substrates was achieved by a simple attachment and detachment process. In the presence of a lubricant, Au NWs grown vertically on a sapphire substrate were efficiently moved to an Au substrate through van der Waals interactions. We demonstrate that the transferred Au NWs on the Au substrate can act as sensitive, reproducible, and long‐term‐stable surface‐enhanced Raman scattering (SERS) sensors by detecting human α‐thrombin as well as Pb²⁺ and Hg²⁺ ions. These three biochemically and/or environmentally important analytes were successfully detected with high sensitivity and selectivity by Au NW‐SERS sensors bound by a thrombin‐binding aptamer. Furthermore, the as‐prepared sensors remained in working order after being stored under ambient conditions at room temperature for 80 days. Because Au NWs can be routinely transferred onto Au substrates and because the resultant Au NW‐SERS sensors are highly stable and provide with high sensitivity and reproducibility of detection, these sensors hold potential for practical use in biochemical sensing.     

Dual pH‐ and Temperature‐Responsive Metallosupramolecular Block Copolymers with Tunable Critical Micelle Temperature by Modulation of the Self‐Assembly of NIR‐Emissive Alkynylplatinum(II) Complexes Induced by Changes in Hydrophilicity and Electrostatic Effects

Terpyridylplatinum(II)‐based metallosupramolecular triblock copolymers with hydrophilic alkynyl ligands have been synthesised and characterised. As a result of the intrinsic properties of Pluronics, reversible temperature‐induced micellisation occurred at high temperature leading to aggregation of the platinum(II) complex moieties through Pt???Pt and π–π interactions, resulting in significant UV/Vis absorption and near‐infrared (NIR) emission spectral changes. The critical micelle temperatures of the complexes were found to vary from 21 to 30 °C due to differences in the hydrophilicity of the alkynyl ligands and the electrostatic repulsions between the positively charged platinum(II) complex moieties. One of the complexes with pH‐responsive CH₂NMe₂ groups on the alkynyl ligand was found to show NIR emission that is sensitive to both pH and temperature. Such dual‐responsive behaviour has been ascribed to the modulation of the self‐assembly of the complex moieties by temperature‐induced micellisation and the changes in the hydrophilicity as well as electrostatic interactions upon protonation/deprotonation of the CH₂NMe₂ groups on the alkynyl ligand.     

Instant Visual Detection of Picogram Levels of Trinitrotoluene by Using Luminescent Metal–Organic Framework Gel‐Coated Filter Paper

There is an ongoing need for explosive detection strategies to uncover threats to human security including illegal transport and terrorist activities. The widespread military use of the explosive trinitrotoluene (TNT) for landmines poses another particular threat to human health in the form of contamination of the surrounding environment and groundwater. The detection of explosives, particularly at low picogram levels, by using a molecular sensor is seen as an important challenge. Herein, we report on the use of a fluorescent metal–organic framework hydrogel that exhibits a higher detection capability for TNT in the gel state compared with that in the solution state. A portable sensor prepared from filter paper coated by the hydrogel was able to detect TNT at the picogram level with a detection limit of 1.82 ppt (parts per trillon). Our results present a simple and new means to provide selective detection of TNT on a surface or in aqueous solution, as afforded by the unique molecular packing through the metal–organic framework structure in the gel formation and the associated photophysical properties. Furthermore, the rheological properties of the MOF‐based gel were similar to those of a typical hydrogel.     

Rational Design of an “OFF–ON” Phosphorescent Chemodosimeter Based on an Iridium(III) Complex and Its Application for Time‐Resolved Luminescent Detection and Bioimaging of Cysteine and Homocysteine

Biothiols, such as cysteine (Cys) and homocysteine (Hcy), play very crucial roles in biological systems. Abnormal levels of these biothiols are often associated with many types of diseases. Therefore, the detection of Cys (or Hcy) is of great importance. In this work, we have synthesized an excellent “OFF‐ON” phosphorescent chemodosimeter 1 for sensing Cys and Hcy with high selectivity and naked‐eye detection based on an Ir^III complex containing a 2,4‐dinitrobenzenesulfonyl (DNBS) group within its ligand. The “OFF‐ON” phosphorescent response can be assigned to the electron‐transfer process from Ir^III center and C^N ligands to the DNBS group as the strong electron‐acceptor, which can quench the phosphorescence of probe 1 completely. The DNBS group can be cleaved by thiols of Cys or Hcy, and both the ³M LCT and ³LC states are responsible for the excited‐state properties of the reaction product of probe 1 and Cys (or Hcy). Thus, the phosphorescence is switched on. Based on these results, a general principle for designing “OFF‐ON” phosphorescent chemodosimeters based on heavy‐metal complexes has been provided. Importantly, utilizing the long emission‐lifetime of phosphorescence signal, the time‐resolved luminescent assay of 1 in sensing Cys was realized successfully, which can eliminate the interference from the short‐lived background fluorescence and improve the signal‐to‐noise ratio. As far as we know, this is the first report about the time‐resolved luminescent detection of biothiols. Finally, probe 1 has been used successfully for bioimaging the changes of Cys/Hcy concentration in living cells.     

Borylated Arylisoquinolines: Photophysical Properties and Switching Behavior of Promising Tunable Fluorophores

A series of nine borylated arylisoquinolines has been prepared with systematic variation in their electronic properties and their photophysical properties were investigated. The color of their fluorescence can be finely tuned by changing the properties of the aryl moiety, which is involved in internal‐charge‐transfer processes. For example, methoxy‐substituted compound 5 showed an intense green emission, whereas dimethylamino‐substituted compound 6 showed an orange‐red emission. These new fluorophores were tested for their potential as molecular switches with external ionic stimuli, such as protons and fluoride ions. On the one hand, protonation of the isoquinoline moiety led to fluorescence enhancement for compounds that showed weak charge transfer and fluorescence quenching for compounds that showed strong charge transfer. On the other hand, the formation of ate complexes with fluoride led to strong fluorescence quenching in all of the investigated cases.     

Well‐Dispersed Pt Cubes on Porous Cu Foam: High‐Performance Catalysts for the Electrochemical Oxidation of Glucose in Neutral Media

The investigation of highly efficient catalysts for the electrochemical oxidation of glucose is the most critical challenge to commercialize nonenzymatic glucose sensors, which display a few attractive superiorities including the sufficient stability of their properties and the desired reproducibility of results over enzyme electrodes. Herein we propose a new and very promising catalyst: Pt cubes well‐dispersed on the porous Cu foam, for the the electrochemical oxidation reaction of glucose in neutral media. The catalyst is fabricated in situ on a homemade screen‐printed carbon electrode (SPCE) substrate through initially synthesizing the three‐dimensional (3D) porous Cu foam using a hydrogen evolution assisted electrodeposition strategy, followed by electrochemically reducing the platinic precursor simply and conveniently. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) proofs demonstrate that Pt cubes, with an average size (the distance of opposite faces) of 185.1 nm, highly dispersed on the macro/nanopore integrated Cu foam support can be reproducibly obtained. The results of electrochemical tests indicate that the cubic Pt‐based catalyst exhibits significant enhancement on the catalytic activity towards the electrooxidation of glucose in the presence of chloride ions, providing a specific activity 6.7 times and a mass activity 5.3 times those of commercial Pt/C catalysts at ?0.4 V (vs. Ag/AgCl). In addition, the proposed catalyst shows excellent stability of performance, with only a 2.8 % loss of electrocatalytic activity after 100 repetitive measurements.     

Leveraging Material Properties in Fluorescence Anion Sensor Arrays: A General Approach

As the demand for probes suitable for sensor development increases, investigation of approaches that utilize known successful receptors gains in general importance. This study describes a two‐prong approach that can be used as a guide to developing sensors from known receptors. First, the conversion of a simple receptor, calix[4]pyrrole, into a fluorescent probe to establish a ratiometric signal is described. Secondly, the sensors that employ an output from a single ratiometric calix[4]pyrrole probe are fabricated by using poly(ether‐urethane) hydrogel copolymers. These hydrogels are designed to absorb, internalize and transport aqueous electrolytes. A sensor array of ten different poly(ether‐urethane) matrices with varying comonomer proportions were doped with a single probe and were exposed to eight different anions: acetate, benzoate, fluoride, chloride, phosphate, pyrophosphate, hydrogen sulfide, and cyanide, eight urine samples and anti‐inflammatory drugs (NSAIDs). The poly(ether‐urethane) matrices comprise different proportions of anion‐binding urethane moieties and different hydrophilicity given by the ratio between ethylene glycol ether and butylene glycol ether. This diversity in the hydration behavior provides different environment polarity, in which the recognition and self‐assembly processes display enough diverse behavior to allow for unique response of the probe to the analytes. Furthermore, a single probe is shown to recognize eight different aqueous anions and eight urine samples when embedded in ten different polyurethanes in an array that displays 100 % classification accuracy. To demonstrate the potential of the concept for quantitative studies, an estimation of non‐steroidal anti‐inflammatory drugs ibuprofen and diclofenac in water and in saliva was performed. A limit of detection of 0.1 ppm and a dynamic range of 0.1–0.6 and 0.05–60 ppm was observed, respectively. Given the general difficulty of chemosensors to recognize aqueous anions, the fact that one probe recognizes eight different analytes attests to an enormous effect of the polymer environment on the recognition process. This method could be used to generate a variety of sensor arrays for various analyses including species that are difficult to recognize, such as small‐molecule‐ and inorganic anions.     

A Rapid and Efficient Way to Dynamic Creation of Cross‐Reactive Sensor Arrays Based on Ionic Liquids

Based on the simple counterion exchange of ionic liquids, a rapid, facile, and efficient strategy to create a cross‐reactive sensor array with a dynamic tunable feature was developed, and exemplified by the construction of a sensor array for the identification and classification of nitroaromatics and explosives mimics. To achieve a good sensing system with fast response, good sensitivity, and low detection limit, the synthesized ionic liquid receptors were tethered onto a silica matrix with a macro‐mesoporous hierarchical structure. Through the facile anion exchange approach, abundant ionic‐liquid‐based individual receptors with diversiform properties, such as different micro‐environments, diverse molecular interactions, and distinctive physico‐chemical properties, were easily and quickly synthesized to generate a distinct fingerprint of explosives for pattern recognition. The reversible anion exchange ability further endowed the sensor array with a dynamic tunable feature as well as good controllability and practicality for real‐world application. With the assistance of statistical analysis, such as principal component analysis (PCA) and linear discrimination analysis (LDA), an optimized‐size array with a good resolution was rationally established from a large number of IL‐based receptors. The performed experiments suggested that the ionic‐liquid‐based sensing protocol is a general and powerful strategy for creating a cross‐reactive sensor array that could find a wide range of applications for sensing various analytes or complex mixtures.