•Nitrogen (N) and sulfur (S) co-doped reduced graphene oxide (NS-rGO) was prepared by a one-step thermal annealing procedure.•NS-rGO is expected to replace precious metal nanoparticles as electrode materials because its comparable electrocatalytic activity, low cost, and straightforward synthetic steps.•NS-rGO modified glassy carbon electrode (NS-rGO/GCE) showed superior electrochemical performance in H2O2 determination than some noble metal nanoparticles based electrochemical sensors.•NS-rGO/GCE had desirable selectivity, repeatability and stability, and was utilized for H2O2 determination in human serum.Hydrogen peroxide (H2O2) is becoming significant due to its extensive applications, so determination of H2O2 is very important topic in analytical chemistry. Metal-free “graphene alloy” – nitrogen (N) and sulfur (S) heteroatoms co-doped reduced graphene oxide (NS-rGO) was produced via a simple one-step thermal annealing procedure using a mixture of 5-amino-2-mercapto-1,3,4-thiadiazole (AMT) and graphene oxide (GO). The obtained metal-free NS-rGO composite showed better electrocatalytic activity toward the reduction of H2O2 compared with the reduced graphene oxide (rGO). The enhanced performance was caused by the synergistic effect of N and S co-doping. Under optimum conditions, the constructed sensor demonstrated a linear response to H2O2 in the range of 7–18000 μM, with a lower detection limit of 0.45 μM (S/N=3), even better than some reported sensors based on noble metal nanoparticles. Moreover, the proposed sensor exhibited excellent analytical performance in terms of acceptable selectivity, excellent reproducibility and long-time stability. These results indicated that the NS-rGO composite was a promising metal-free electrocatalytic material for constructing H2O2 sensors. Additionally, NS-rGO composite was expected to be applied as catalysts for fuel cell applications, even for applications beyond fuel cells.

A highly selective fluorescent probe 2-(2-(2-aminoethylamino)ethyl)-3′,6′-bis(ethylamino)-2′,7′-dimethylspiro[isoindoline-1,9′-xanthen]-3-one (ABDO) for Se (IV) had been synthesized in our earlier report. In this study, this fluorescent sensor is applied on analysis fluorescent imaging of Se (IV) in Hela cells. The experiment conditions, such as the MTT assay, different concentration of saline, incubated time of Hela cells with ABDO and Se (IV), and intracellular action position of Se (IV), are investigated. Through a series of experiments, the fluorescent image of Se (IV) in Hela cells can be observed when the cells cultured by 2 μM ABDO and 2 μM Se (IV) for 210 min. And the intracellular action position of Se (IV) is verified after the co-localization experiments are done. It is mitochondria. These experimental results show that ABDO will be an eagerly anticipated sensor for fluorescent imaging analysis of selenium ion in living cells. Besides, we also can use the complexes of ABDO-Se to observe morphology and distribution of mitochondria in cells like JG-B.

•A water-soluble conjugated polymer PPE-OBS was synthesized.•An off-on probe is developed for Cys, Hcy and GSH detection using PPE-OBS-Hg2 + system.•The method exhibits high sensitivity and selectivity to Cys, Hcy and GSH.•This probe can be applied in food samples with excellence accuracy and precision.In this work, a turn on fluorescent sensor, based on Hg2 + coordination conjugated polymer, was developed to detect cysteine-containing compounds. The fluorescence of conjugated polymer (poly(2,5-bis (sodium 4-oxybutyrate) -1,4 - phenylethynylene-alt-1,4-phenyleneethynylene; PPE-OBS) would be quenched by Hg2 + because of the coordination-induced aggregation and electron transfers of PPE-OBS toward Hg2 +. When there were some cysteine-containing compounds in PPE-OBS-Hg2 + system, the fluorescence of PPE-OBS would be recovered. It indicated that the PPE-OBS-Hg2 + system could be used to detect cysteine-containing compounds. Under the optimized conditions, the experiment results showed that there were particularly linear range, high sensitivity and selectivity over other amino acids. The limit of detection (LOD) of cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) were 0.725 μmol L− 1, 0.982 μmol L− 1 and 1.21 μmol L− 1 by using this sensor. In addition, Cys standard recovery in several green tea drink and honey samples was also demonstrated. The recovery of Cys was range from 96.3 to 105.0% and RSD was less than 3.25%. The satisfactory results demonstrated that the proposed method could be as a potential fluorescent method for determining cysteine-containing compounds in real samples.Download high-res image (284KB)Download full-size image

The surface and interface could be designed to enhance properties of electrocatalysts, and they are regarded as the key characteristics. This report describes surface modification of a bifunctional rht-type metal–organic framework (MOF, Cu-TDPAT) with nanosized electrochemically reduced graphene oxide (n-ERGO). The hybrid strategy results in a Cu-TDPAT–n-ERGO sensor with sensitive and selective response toward hydrogen peroxide (H2O2). Compared with Cu-TDPAT, Cu-TDPAT–n-ERGO exhibits significantly enhanced electrocatalytic activities, highlighting the importance of n-ERGO in boosting their electrocatalytic activity. The sensor shows a wide linear detection range (4–12 000 μM), and the detection limit is 0.17 μM (S/N = 3) which is even lower than horseradish peroxidase or recently published noble metal nanomaterial based biosensors. Moreover, the sensor displays decent stability, excellent anti-interference performance, and applicability in human serum and urine samples. Such good sensing performance can be explained by the synergetic effect of bifunctional Cu-TDPAT (open metal sites and Lewis basic sites) and n-ERGO (excellent conductive property). It is expected that rht-type MOF-based composites can provide wider application potential for the construction of bioelectronics devices, biofuel cells, and biosensors.Keywords: electrochemical; hydrogen peroxide; nanosized graphene; rht-type metal−organic framework; synergetic effect;

Petal-like graphene–Ag (p-GR–Ag) composites with highly exposed active edge sites were designed and constructed in this work. Petal-like graphene (p-GR) was prepared using a HCl assisted hydrothermal method, which was made of basal planes and highly reactive edge planes to provide more active sites. Then the p-GR can be intentionally utilized as nucleation sites for subsequent Ag nanoparticles (NPs) deposition via modified silver mirror reaction. The composites were characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and electrochemical methods. The combination of zero-dimensional (0D) Ag NPs on a two-dimensional (2D) graphene (GR) support that came into being three-dimensional (3D) structure created a sensor for electrochemical detection of metronidazole. The designed sensor exhibited well bimodal linear behaviour in the metronidazole concentration range between 0.05 to 10 μM and 10 to 4500 μM with a detection limit of 28 nM (S/N = 3). The mechanism and the heterogeneous electron transfer kinetics constant of the metronidazole reduction were discussed in the light of the rotating disk electrode (RDE) experiments. Moreover, validation of the applicability of the prepared sensor was carried out by detecting metronidazole in human urine and local lake water samples.

Water soluble porphyrins have many perfect analytical figures of merit. A water-soluble sulfonated porphyrin (H2TEHPPS) was used to build a novel platform for sensitive assays of hydrogen peroxide and glucose based on the different effects of Fe2+ and Fe3+ on H2TEHPPS. H2O2 or Fe2+ alone cannot induce a fluorescence change in H2TEHPPS, but Fe3+ can quench the fluorescence of H2TEHPPS significantly. Interestingly, glucose is oxidized to gluconolactone by GOD and generates an equivalent hydrogen peroxide, and the produced H2O2 also oxidizes Fe2+ to Fe3+ and causes the fluorescence quenching of H2TEHPPS. According to this, a sensitive sensor for hydrogen peroxide and glucose has been demonstrated, which can determine H2O2 and glucose in a relative simple and sensitive way. The detection limits were 1.3 × 10−7 M and 3.2 × 10−7 M for H2O2 and glucose, respectively. In addition, the glucose in serum samples was determined successfully using this sensing platform. It is also noteworthy that H2O2 can be released in almost all oxidations catalyzed by oxidases, which suggests that this newly proposed H2O2 probe can be readily extended to sense other oxidases and their specific substrates.

A novel water-soluble porphyrin[5,10,15,20-tetra(3-ethoxy-4-hydroxy-5-sulfonate)phenyl porphyrin, H2TEHPPS]_was designed and synthesized, which could be used as a potential fluorescence sensor to detect temperature changes. The studies were performed in solution phase and the concentration of H2TEHPPS was 2.0×10−5 mol/L. The optical properties of H2TEHPPS were investigated based on the UV and fluorescence spectra. The results show that the fluorescence intensity of H2TEHPPS is directly proportional to temperature in the range of 293–353 K. So H2TEHPPS can be used as a molecular temperature sensor in biomedical and other fields.

A water-soluble bidentate pyridine–acid ligand (1) was synthesized. The ligand 1 had a stronger interaction with Mo6+ than with other metal ions. Subsequently, we found that a linear increase in the fluorescence intensity of complex (1-Mo) was observed upon addition of bovine serum albumin (BSA).

A novel silica-coated multiwall carbon nanotube (MWNTs) with CdTe quantum dots nanocomposite was synthesized in this paper. Here, we show the in situ growth of crystalline CdTe quantum dots on the surfaces of oxidized MWNTs. The approach proposed herein differs from previous attempts to synthesize nanotube assemblies in that we mix the oxidized MWNTs into CdCl2 solution of CdTe nanocrystals synthesized in aqueous solution. Reinforced the QD–MWNTs heterostructures with silica coating, this method is not invasive and does not introduce defects to the structure of carbon nanotubes (CNTs), and it ensures high stability in a range of organic solvents. Furthermore, a narrow SiO2 layer on the MWNT–CdTe heterostructures can eliminate the biological toxicity of quantum dots and carbon nanotubes. This is not only a breakthrough in the synthesis of one-dimensional nanostructures, but also taking new elements into bio-nanotechnology.

A water-soluble bidentate pyridine–acid ligand (1) was synthesized. The ligand 1 had a stronger interaction with Mo6+ than with other metal ions. Subsequently, we found that a linear increase in the fluorescence intensity of complex (1-Mo) was observed upon addition of bovine serum albumin (BSA).