•Carbon black is cheap, green, environmentally friendly, and incapable to secondary pollution.•The sp2-bonded carbon black possesses a great plenty of mesopores to enhance the sensing efficiency.•Carbon black as a metal-free electrocatalyst has an outstanding electrocatalytic performance for determination of Cr(VI).•High selectivity, good stability, wide linear range and high sensitivityHexavalent chromium is one of most toxic heavy metal contaminants in biological and environmental systems, thus the electrochemical method with high-sensitivity, excellent-accuracy, low-cost and easy-operation is desired to be developed for detecting Cr(VI). In this work, carbon black (CB) modified glassy carbon electrode (GCE), was proposed as a sensor for monitoring Cr(VI) concentrations. CB is cheap, green, environmentally friendly, and incapable to secondary pollution. Moreover, the sp2-bonded CB possesses a great plenty of mesopores as the charge transport channels in interior surface to enhance the sensing efficiency. Thus CB modified GCE demonstrated an outstanding electrocatalytic performance for reduction of Cr(VI), with a wide linear concentration range from 0.025 to 483.225 μM and a low detection limit (LOD) of 10 nM. The modified electrode also showed fast response, high stability, as well as good selectivity against interferences from other metal ions. These attributes suggest that CB as a metal-free electrocatalyst has an exciting prospects of sensing applications for determination of Cr(VI).Download high-res image (185KB)Download full-size image

Hexavalent chromium (Cr(VI)) is one of the most toxic heavy metal pollutants in groundwater, and thus the detection of Cr(VI) with high sensitivity, accuracy, and simplicity and low cost is of great importance. In this work, cheap bimetallic NiFe nanoparticles were synthesized and used for the electrochemical detection of Cr(VI). The reduction potential of Cr(VI) was negatively shifted to 0.00 V, and a wide linear concentration range for Cr(VI) from 0.025 to 98.3 μM with a detection limit of 0.01 μM was obtained. The results demonstrate that the NiFe nanoparticles have excellent sensing capability for Cr(VI). Their fast response and high reproducibility and stability, as well as great promise for the quantification of Cr(VI) in real samples, make the NiFe-based bimetallic catalysts promising candidates for sensing Cr(VI) in groundwater.

The electrochemical behaviors of m- and s-SWNTs obtained from as-prepared SWNTs using a novel binaphthyl based separation agent were studied. The s-SWNTs show higher capacitance but lower electrocatalytic activity, while m-SWNTs show the opposite. Their electrochemical properties can be further interconverted through changing the DOS by electron or hole doping.

•Small size Ni nanoparticles prepared via a facile and controlled route•The modified electrode was employed for simultaneous determination of AA, DA and UA.•High selectivity, good stability, wide linear range and high sensitivityA highly sensitive sensor based on carbon-supported Ni nanoparticles (Ni/C) with ultra-small size was prepared for the simultaneous determination of ascorbic acid (AA), dopamine (DA) and uric acid (UA). The electrochemical response showed excellent electrocatalytic activity toward the oxidation of AA, DA and UA with three well defined oxidation peaks and larger peak separation. Meanwhile, using the ultra-small Ni nanoparticles modified electrode with differential pulse voltammetry (DPV) method, the linear response ranges for the determination of AA, DA and UA were 20–2400, 1–55 and 5–180 μM in the coexistence systems of these three species under optimum condition and the detection limits (S/N = 3) were 5, 0.05 and 0.1 μM, respectively. Especially a much higher sensitivity for Ni/C modified electrode compared to other electrodes was also observed. Moreover, satisfactory results were achieved for the determination of AA, DA and UA in vitamin C tablet, DA hydrochloride injection, fetal bovine serum and human urine samples. The results demonstrated that the electrochemical sensor developed from the ultra-small Ni nanoparticles had advantages of high sensitivity and good selectivity for practical applications.

A diamine monomer o-phenylenedioxybis(5-amino-2-pyridine) was synthesized via reduction of a dinitro compound o-phenylenedioxybis(5-nitro-2-pyridine), producing a series of new polyimides from this diamine and various commercially available aromatic dianhydrides via conventional two-stage processes. The resulting polyimides are able to form tough and transparent films, with decomposition temperatures in the range of 529–551 °C, and can be dissolved in organic polar solvents. Meanwhile, these polyimides can be degraded in a hydrazine hydrate medium, a degradation mechanism proposed by analyzing the degradation products suggests that the degradable properties could be attributed to the phenyl-2-pyridyl ether structure in the polymer. In addition, the transformation of the compound structure from dinitro compound to damine monomer in the synthetic process is discussed in respect to X-ray structure.

•Small size NiCoO2 nanoparticles prepared via a facile and controlled route.•NiCoO2/C was employed for ascorbic acid determination.•High selectivity, good stability, wide linear range and high sensitivity.An electrochemical sensor for selective detection of ascorbic acid (AA) in the presence of dopamine (DA) and uric acid (UA) was fabricated by modifying the glassy carbon electrode (GCE) with carbon-supported NiCoO2 (NiCoO2/C) nanoparticles. The electrochemical impedance spectroscopic (EIS) studies reveal the little charge transfer resistance for the modified electrode. The electrocatalytic activity of the modified electrode for the oxidation of AA was investigated. The current sensitivity of AA was enhanced to about five times upon modification. The voltammetric response of AA was well resolved from the responses of DA and UA, and the oxidation potential of AA was negatively shifted to −0.20 V. The biosensor tolerated a wide linear concentration range for AA, from 1.0×10−5 M to 2.63×10−3 M (R2=0.9929), with a detection limit of 0.5 μM (S/N=3). Our results demonstrate that the NiCoO2/C nanomaterials has excellent AA sensing capability, including a fast response time, high reproducibility and stability, with great promise in the quantification of AA in real samples. That makes it a unique electrochemical sensor for the detection of AA which is free from the interference of DA, UA and other interferents.

Polyimides are widely used in electronic, semiconductor industry, however, with the wide application, the degradation of the polymer has become a serious problem people have to face. In this work, a series of new fast degradable polyimides were synthesized from diamine p-phenylenedioxybis(5-amino-2-pyridine) with various commercially available aromatic dianhydrides via a conventional two-stage process. The resulting polyimides could degrade at room temperature under a certain condition, and we proposed a degradation mechanism by analyzing the degradation products. Compared with the traditional method, here, we provided a facile and effective method for polyimide degradation. The result suggested that introducing a phenyl-2-pyridyl ether structure into polymer chains may become a class of new method for polymer degradation.

Cuprous oxide microsphere material was fabricated by electrochemical deposition using polystyrene particles as template. The samples are characterized by scanning electron microscope (SEM), X-ray diffraction, and UV–vis spectrophotometer. The SEM image shows the morphology and size of the microspheres, and the thickness of covered Cu2O layer is about 100 nm. Due to the unique microspherical structure, the surface area is larger, and the optical absorption is better in Cu2O microsphere material than in bulk Cu2O film, which makes the degradation of methylene blue faster and photoelectrocatalytic oxidation of glucose stronger on Cu2O microsphere material than on bulk Cu2O film under visible light illumination. The enhanced photo- and photoelectro-catalytic activity makes the Cu2O microsphere material more suitable for solar applications.

The electrochemical behaviors of m- and s-SWNTs obtained from as-prepared SWNTs using a novel binaphthyl based separation agent were studied. The s-SWNTs show higher capacitance but lower electrocatalytic activity, while m-SWNTs show the opposite. Their electrochemical properties can be further interconverted through changing the DOS by electron or hole doping.