Dongen Zhang

Electrochemical nonenzymatic sensor based on CoO decorated reduced graphene oxide for the simultaneous determination of carbofuran and carbaryl in fruits and vegetables

A novel nonenzymatic sensor based on cobalt (II) oxide (CoO)-decorated reduced graphene oxide (rGO) was developed for the detection of carbofuran (CBF) and carbaryl (CBR). Two well-defined and separate differential pulse voltammetric peaks for CBF and CBR were obtained with the CoO/rGO sensor in a mixed solution, making the simultaneous detection of both carbamate pesticides possible. The nonenzymatic sensor demonstrated a linear relationship over a wide concentration range of 0.2-70 μM (R=0.9996) for CBF and 0.5-200 μM (R=0.9995) for CBR. The lower detection limit of the sensor was 4.2 μg/L for CBF and 7.5 μg/L for CBR (S/N=3). The developed sensor was used to detect CBF and CBR in fruit and vegetable samples and yielded satisfactory results.

Enhanced simultaneous detection of ractopamine and salbutamol - Via electrochemical-facial deposition of MnO2 nanoflowers onto 3D RGO/Ni foam templates

In this paper, we report a facile method to successfully fabricate MnO2 nanoflowers loaded onto 3D RGO@nickel foam, showing enhanced biosensing activity due to the improved structural integration of different electrode materials components. When the as-prepared 3D hybrid electrodes were investigated as a binder-free biosensor, two well-defined and separate differential pulse voltammetric peaks for ractopamine (RAC) and salbutamol (SAL) were observed, indicating the simultaneous selective detection of both β-agonists possible. The MnO2/RGO@NF sensor also demonstrated a linear relationship over a wide concentration range of 17 nM to 962 nM (R=0.9997) for RAC and 42 nM to 1463 nM (R=0.9996) for SAL, with the detection limits of 11.6 nM for RAC and 23.0 nM for SAL. In addition, the developed MnO2/RGO@NF sensor was further investigated to detect RAC and SAL in pork samples, showing satisfied comparable results in comparison with analytic results from HPLC.

Supported ionic-liquid layer on polystyrene–TEMPO resin: a highly efficient catalyst for selective oxidation of activated alcohols with molecular oxygen

We report a facile, efficient procedure for selective oxidation of activated alcohols by use of a novel supported ionic-liquid catalyst produced by coating polystyrene–TEMPO resin with the ionic liquid [bmim]PF6 and CuCl2. The oxidation affords aldehydes or ketones in excellent yield and with high selectivity. It is worthy of note that the supported ionic-liquid layer substantially enhances catalytic activity, and the catalyst can easily be recycled.Graphical abstract

High Durable Ternary Nanodendrites as Effective Catalysts for Oxygen Reduction Reaction

Exploiting high catalytic activities and superior durability is significant for the lifetime and the cost of electro-catalysts for oxygen reduction reaction (ORR). Pt-Ni nanocrystals have attracted considerable attention owing to their exceptionally catalytic performance. However, the durability of Pt-Ni nanoparticles in acid media is still far below satisfaction. Consequently, improving the durability is extremely urgent for the application of Pt-Ni catalysts. To this end, we herein develop Pt-Ni-Ir ternary nanocrystals with dendritic shape, which are synthesized through a facile one-pot strategy. Such nanostructures featured with multibranches show an area specific activity of 1.58 mA cm(-2), seven times more than that of the commercial Pt/C catalyst (0.21 mA cm(-2)). More importantly, the dendritic Pt-Ni-Ir catalyst displays extraordinarily high durability. In contrast to the commercial Pt/C counterparts, which exhibit losses of 53.2% in EASA and 41% in area specific activity after 12 000 cycles of sweeping in the potential range of 0.6-1.1 V, only respective losses of 5.5% and 6% are detected for our dendritic Pt-Ni-Ir catalyst. The high activity and remarkable durability are mainly attributed to the dendritic morphology and the introduction of Ir. This work demonstrates that the Pt-Ni-Ir dendritic nanostructures are promising electro-catalysts for ORR.

One-Pot Synthesis of Concave Platinum–Cobalt Nanocrystals and Their Superior Catalytic Performances for Methanol Electrochemical Oxidation and Oxygen Electrochemical Reduction

Exploring highly efficient electro-catalysts is of significant urgency for the widespread uptake of the direct methanol fuel cells (DMFCs). Pt-Co nanocrystals have attracted considerable attentions because of their superior catalytic performance toward both methanol oxidation and oxygen reduction in the preliminary assessments. This Research Article presents a Pt-Co bimetal catalyst that is synthesized through a facile coreduction strategy. The Pt-Co nanocrystals have concave cubic shape with a high uniform size of 7-9 nm and Pt-rich surfaces. The catalysis of the concave cubic Pt-Co nanoparticles toward both methanol electrochemical oxidation reaction (MOR) and oxygen electrochemical reduction reaction (ORR) is evaluated. In comparison with the commercial Pt/C catalyst (Johnson Matthey), the present concave cubic Pt-Co catalyst displays superior performances in not only catalytic activity but also durability. The concave Pt-Co catalyst also shows higher activities than spherical and cubic Pt-Co nanoparticles. The dramatic enhancement is mainly attributed to its alloyed composition, Pt-rich surface and the concave nanostructure. The results of our research indicate that the concave Pt-Co nanocrystal could be a promising catalyst for both MOR and ORR. The present work might also raise more concerns on exploiting morphology and composition of nanocrystal catalysts, which are expected to provide high catalytic performance in electrochemical reactions.

Preparation of polyaniline modified BiOBr with enhanced photocatalytic activities

The polyaniline/bismuth oxybromide (PANI/BiOBr) hybrids materials have been synthesized hydrothermally in the presence of PANI. The PANI/BiOBr hybrids materials were confirmed by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy and ultraviolet–visible diffuse reflectance spectroscopies. Among the hybrid photocatalysts, PANI/BiOBr-0.2 showed the highest photocatalytic properties for the degradation of rhodamine B (RhB), and the increased photocatalytic properties could be due to photosensitization and the inhibited electron–hole recombination.

SOLVOTHERMAL PREPARATION OF CeO2 NANOCUBES AND THEIR CATALYTIC PROPERTIES

Cubic-like CeO2 nanocrystals about 11 nm long were successfully synthesized via an ethanolamine-assisted hydrothermal route using (NH4)Ce(NO3)4 as a precursor at 180°C for 24 h. The CeO2 nanocubes were modified onto the glassy carbon electrode by adsorption to fabricate the modified electrode. The reliability and stability of the CeO2 NC/GC electrode offer a good possibility for applying the technique on routine analysis of ascorbic acid (AA) in clinical use. In addition, the catalytic effect of the CeO2 nanocubes for thermal decomposition of ammonium perchlorate (AP) was investigated by DTA and TG. The catalytic performance of CeO2 nanocubes is superior to that of commercial CeO2 powder.

Synthesis and photocatalytic performance of Bi2S3/SnS2 heterojunction

Bi2S3/SnS2 heterostructured photocatalysts were synthesized from BiOI, SnCl4⋅5H2O and NH2CSNH2 using an economic and simple hydrothermal method. The as-synthesized samples were characterized by X-ray diffraction, scanning electron microscopy and ultraviolet-visible diffuse reflectance spectroscopy. The photodegradation activities of the Bi2S3/SnS2 heterostructured photocatalysts were estimated by degrading rhodamine B under simulated sunlight supplied by irradiating with a 350W Xe lamp. Bi2S3/SnS2 photocatalysts were prepared using varying percentages of Bi2S3. The sample containing 13% Bi2S3 had the most efficient photocatalyst performance among the tested samples. The photocatalytic mechanism involves heterojunctions formed in the Bi2S3/SnS2, which promoted effective separation of photoinduced electrons and holes.

Research on the self-assembly of exfoliated perovskite nanosheets (LaNb2O7−) and cobalt porphyrin utilized for the electrocatalytic oxidation of ascorbic acid

A sandwich-structured nanocomposite of LaNb2O7/CoTMPyP [5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrinato cobalt(III)] was fabricated via electrostatic interaction between a LaNb2O7− colloidal dispersion and a cobalt porphyrin aqueous solution. Several analytic techniques such as X-ray diffraction (XRD), Fourier transform infrared (IR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, and scanning electron microscopy (SEM) were used to characterize the obtained products and the existence of LaNb2O7− nanosheets was confirmed by atomic force microscopy (AFM) and transmission electron microscopy (TEM). Furthermore, the stable and well-dispersed colloidal suspension of the LaNb2O7− nanosheets, whose zeta potential value was −51.9 mV, was monitored with a Zetasizer Nano instrument. On the other hand, the cyclic voltammetry measurements of the LaNb2O7/CoTMPyP film modified GCE exhibited excellent electrocatalytic activities toward ascorbic acid oxidation with the oxidation peak potential shifting from 0.380 V (bare glass carbon electrode) to 0.044 V (modified electrode). The oxidation peak current increased linearly with the square root of the scan rate, implying a diffusion-controlled process. In addition, a detection limit of 4.99 × 10−5 M was obtained through differential pulse voltammetry with results in a concentration range of 5 × 10−5 to 9.09 × 10−3 M at a signal-to-noise ratio of 3.0.

Enhanced photocatalytic ability from carbon-doped ZnO photocatalyst synthesized without an external carbon precursor

We report a simple synthesis of C-doped ZnO composite nanoparticles by a solvothermal treatment of Zn(OAc)2 ⋅ 2H2O that provides a source of both zinc and carbon. The photocatalytic activities of the composites were evaluated by the degree of degradation rhodamine B in aqueous solutions at room temperature with near UV light irradiation. These nanocomposites exhibit higher photocatalytic activity compared with pure ZnO nanoparticles. The enhancement of photocatalytic activity of C-doped ZnO nanoparticles is mainly attributed to their absorbed more photons and reduced electron hole pair recombination.