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It is highly required to rationally design fluorescent probes via a molecular engineering strategy with desired analytical performance for applications in sensing and imaging. Reaction-based fluorescent probes for highly selective sensing of cysteine (Cys) are mainly based on the participation of Cys in reactions such as, addition–cyclization with acrylates, cyclization with aldehydes, coordination displacement, Michael addition reactions, and cleavage reactions. Cys-triggered reactions with the O atoms of ether bonds has also been used to construct reaction-based fluorescent probes based on the substitution of the ether with the nucleophilic thiolate of Cys. However, many of the developed probes still suffer from long response times, interference from homocysteine (Hcy) and glutathione (GSH), high background fluorescence, and a lack of two-photon absorption (TPA) properties. Herein, we successfully design a Cys-sensitive two-photon fluorescent probe (F-BTD) using a donor–acceptor–donor (D–A–D) type π-extended benzothiadiazole framework as the fluorophore, with nitrobenzofuran (NBD) as the recognition unit. The proposed F-BTD probe displays some advantages over other probes including a rapid response time, high selectivity, low background fluorescence, and two-photon imaging capability. The F-BTD probe is applied to the two-photon fluorescence imaging of endogenous and exogenous Cys in HeLa cells with satisfactory results. For comparison, commonly used biothiol recognition groups including 2,4-dinitrobezensulfonyl and 2,4-dinitrophenyl are also used to construct S-BTD and N-BTD probes, respectively. The response mechanism of F-BTD to Cys is studied in detail through kinetic studies and transition-state analysis. This study may provide an example of how to design fluorescent probes with desired analytical performance by considering the recognition group as an important index of the design. [ABSTRACT FROM AUTHOR]

Herein, polyvinylpyrrolidone-stabilized Au nanorods were controllably implanted into ZIF-8 to form a well-uniformed AuNRs@ZIF-8 electrocatalyst with a multicore-shell structure. After characterizing the chemical and physical properties, a novel electrochemical sensing platform was fabricated for 2-chlorophenol (2-CP) monitoring based on the AuNRs@ZIF-8 modified glassy carbon electrode. Due to the unique electrochemical property of AuNRs cores and ultra-porous architecture of ZIF-8 shell, the electrocatalyst would effectively accelerate the electron transfer and greatly improve the electrochemical response of 2-CP. Under the optimized experimental conditions, the oxidation peak current of 2-CP enhanced linearly with the increase of its concentration between 0.010 and 40 lM, and the limit of detection was 3.6 nM based on S/N = 3. Meanwhile, the prepared AuNRs@ZIF-8 electrode showed favorable stability, reproducibility, and selectivity, which could be applied to the accurate analysis of 2-CP in aquaculture with standard addition recovery ranging from 96.67% to 104.0%. Key words: Au nanorods, ZIF-8, core-shell structure, 2-chlorophenol, electrochemical determination. Dans le cadre des présents travaux, nous avons implanté de façon contrôlable des nanobâtonnets d'or (NB-Au) stabilisés par la poly(vinylpyrrolidone) dans un réseau d'imidazolate zéolitique (ZIF-8 pour zeolitic imidazolate framework-8) pour former un électrocatalyseur uniforme de type NB-Au@ZIF-8 présentant une structure multi-coeurs--coquille. Après caractérisation des propriétés chimiques et physiques, nous avons réalisé un nouveau système de détection électrochimique pour le dosage du 2-chlorophénol (2-CP) reposant sur une électrode de carbone vitreux modifiée par le composite NB-Au@ZIF-8. Grâce aux pro-priétés électrochimiques uniques des coeurs formés par les NB-Au et l'architecture ultraporeuse de la coquille de ZIF-8, l'électrocatalyseur accélérerait efficacement le transfert d'électrons et améliorerait grandement la réponse électrochimique du 2-CP. Dans les conditions expérimentales optimisées, l'amplification du courant de crête de l'oxydation du 2-CP était pro-portionnelle à l'augmentation de la concentration de ce dernier dans le domaine de linéarité de 0,010 à 40 lM, la limite de détection étant de 3,6 nM si l'on considère un rapport signal/bruit de 3. Par ailleurs, l'électrode à base de NB-Au@ZIF-8 que nous avons pré-parée a montré une stabilité, une reproductibilité et une sélectivité favorables. Elle pourrait ainsi être appliquée au dosage précis du 2-CP en aquaculture, avec un taux de récupération par ajouts dosés allant de 96,67 % à 104,0 %. [Traduit par la Rédaction] Mots-clés : nanobâtonnets d'or, ZIF--8, structure coeur-coquille, 2-chlorophénol, dosage électrochimique., Introduction Chlorophenols are an important class of aquatic contaminants released to the environment mainly during the manufacturing of pesticides, herbicides, disinfection, glue, leather, paint, and wood preservation and are presentinaquatic [...]

In view of the core–shell nanocomposites can complement the functions of the core and shell components, we here demonstrate a facile self-template strategy for synthesizing a one-dimensional rod-like hierarchical ZnO@ZIF-8 core–shell structure composed of a stabilized core and an active shell. The ZnO nanorods not only served as the template, but also as source of Zn ions for the in situ formation of zeolitic imidazolate framework-8 (ZIF-8) crystal shell, and the well-stabilized ZnO core preserved its own nature during the growth of the ZIF-8 shell. Furthermore, a sensing platform using ZnO@ZIF-8 as electrocatalyst was developed, which demonstrated salient electrocatalytic activity for diethylstilbestrol (DES) oxidation. The concentration of DES was directly proportional to its anodic peak current in the range of 2 nmol/L to 2 µmol/L, and ultralow detection limit of 0.73 nmol/L (S/N = 3) was achieved. The proposed method also gave excellent selectivity, reproducibility, and stability, showing promising analytical performance for the measurement of DES in food samples of animal origin. [ABSTRACT FROM AUTHOR]

We report an integrated ratiometric lysosomal nitric oxide (NO) nanoprobe based on engineered semiconducting polymer dots (Pdots), LyNO-Pdots, which consist of a newly designed NO-responsive dye, a fluorescent conjugated polymer and two functional polymers. The developed probe LyNO-Pdots exhibit high specificity and stability, good photostability and favorable blood–brain barrier (BBB) penetration ability. The LyNO-Pdots are successfully applied to ratiometric imaging of lysosomal NO variations in brain-derived endothelial cells, brain tissues and mice brains with Alzheimer's disease (AD). The results demonstrate that the NO content in the brains of AD mice is considerably higher than that in normal mice. [ABSTRACT FROM AUTHOR]

In this work, the Ag@Cu particles with yolk-shell nanostructure was prepared by facile solvothermal method, which was modified on glassy carbon electrode (GCE) to fabricate electrochemical sensor for the convenient and fast determination of p-aminobenzoic acid (PABA). The surface morphology and electrochemical properties of the as-prepared Ag@Cu nanocomposite modified electrode were characterized by scanning electron microscopy, transmission electron microscopy, chronocoulometry, and electrochemical impedance spectroscopy. Further, the electrochemical sensing of PABA was performed on the Ag@Cu/GCE using cyclic voltammetry and differential pulse voltammetry techniques, showing high catalytic activity. Under the optimal conditions, the sensor exhibited a wide linear range, high sensitivity, and low detection limit of 0.315 [micro]mol/L for PABA. The developed sensor was also successfully applied for PABA detection in anesthetic and cosmetics with satisfactory results.Key words: yolk-shell structure, Ag, Cu, p-aminobenzoic acid, electrochemical sensor.Dans le cadre des présents travaux, nous avons préparé des particules d'Ag@Cu présentant une nanostructure d'oeuf à coquille par une méthode solvothermale simple. Avec ces particules, nous avons ensuite modifié une électrode de graphite vitrifié (EGV) afin de fabriquer un capteur électrochimique pour le dosage rapide et pratique de l'acide p-aminobenzoïque (PABA). Nous avons caractérisé la morphologie de surface et les propriétés électrochimiques de cette électrode modifiée par le nano-composite dAg@Cu, telle que nous l'avons préparée, par microscopie électronique à balayage, microscopie électronique en transmission, chronocoulométrie et spectroscopie d'impédance électrochimique. De plus, nous avons effectué la détection électrochimique du PABA sur l'EGV/Ag@Cu par des techniques de voltampérométrie cyclique et de voltampérométrie pulsée différentielle, qui ont révélé une activité catalytique élevée. En conditions optimisées pour le dosage du PABA, le capteur a présenté un large intervalle linéaire, une sensibilité élevée et une faible limite de détection (0,315 [micro]mol/L). Le capteur que nous avons mis au point, lorsqu'appliqué à la détection du PABA dans des anesthésiques et des cosmétiques, a produit des résultats satisfaisants. [Traduit par la Rédaction]Mots-clés : structure d'oeuf à coquille, Ag, Cu, acide p-aminobenzoïque, capteur électrochimique., Introductionp-Aminobenzoic acid (PABA) distributes widely in the nature as a non-protein amino acid. It is assigned to the vitamin family as a small quantity of it is present as the [...]