Chao Yao

Preparation of polyaniline/graphene composites with excellent anti-corrosion properties and their application in waterborne polyurethane anticorrosive coatings

Polyaniline, a novel conductive polymer, has been widely used as an anti-corrosive filler. In order to further improve the anti-corrosion performance, polyaniline/graphene (PANI/RGO) composites were prepared by in situ polymerization. And PANI/RGO composite anti-corrosion coatings were also prepared using PANI/RGO as anti-corrosive filler and waterborne polyurethane (WPU) as matrix. The anti-corrosion properties were proven by potentiodynamic polarization curves (Tafel polarization curves), electrochemical impedance spectroscopy and salt spray test analysis of the WPU anti-corrosive coatings. The results showed that the obtained composite coatings reinforced by 0.75 wt% of PANI/RGO composites possessed superior anti-corrosive performance when the graphene content of the filler was 4 wt%.

A voltammetric sensor based on electrochemically activated glassy carbon electrode for simultaneous determination of hydroquinone and catechol

A simple and reliable voltammetric sensor for simultaneous determination of hydroquinone (HQ) and catechol (CC) was developed on an electrochemically activated glassy carbon electrode (GCE). The cyclic voltammograms in a mixed solution of HQ and CC have shown that the oxidation peaks become well resolved and were separated by 108 mV, although the bare GCE gave a single broad oxidation peak. Moreover, the oxidation peak currents of both HQ and CC were remarkably increased at the electrochemically activated GCE, which makes it suitable for simultaneous determination of these isomers. In the presence of 5.0 × 10−5 mol L−1 isomer, the oxidation peak currents of square wave voltammograms are proportional to the concentration of HQ in the range of 1.0 × 10−6 to 1.0 × 10−4 mol L−1, and to that of CC in the range of 2.0 × 10−6 to 1.0 × 10−4 mol L−1. The corresponding detection limits for HQ and CC are as low as 1.8 × 10−8 and 3.2 × 10−8 mol L−1 (S/N = 3), respectively.

Restructuring of silica-pillared clay (SPC) through posthydrothermal treatment and application as phosphotungstic acid supports for cyclohexene oxidation.

A facile posthydrothermal treated process has been successfully established for restructuring of silica-pillared clay. This approach involves the hydrothermal treated process utilizing octadecylamine as structural agency followed by calcination at high temperatures. The formation of expanded interlayered mesopores is a result of treatment with octadecylamine hydrothermal conditions. The following calcination at higher temperatures gives silica-pillared clay larger pore volume and conserved high surface area. The kind of pore expansion process has been confirmed by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption-desorption isotherms and transmission electron microscopy (TEM). The pore expansion mechanism of silica-pillared clay is proposed. The pore expanded silica-pillared clay has been used as the catalytic supports for H3PW12O40 loading as high as 26.9%, 35.8% and 48.2% for oxidation reaction of cyclohexene using H2O2 as oxidant. The stable charge force between H3PW12O40 and negative charged clay layers, together with big and open porous structure, large pore volume, and high loading of H3PW12O40 contributes to the efficiency conversion, high selectivity toward cyclohexene epoxide and brilliant reusability.

Spectroscopic Studies on the Interaction Between Troxerutin and Bovine Hemoglobin

The interaction of bovine hemoglobin (BHb) with troxerutin was investigated by UV–Vis absorption spectra and fluorescence spectra methods, circular dichroism spectra, and the freeze-fractured TEM methods. Results showed that troxerutin causes the fluorescence quenching of BHb through a static quenching mechanism. The binding constant KA and number of binding sites n of troxerutin with BHb were obtained. Positive values of the thermodynamic parameters enthalpy change and entropy change indicate that the interaction between troxerutin and BHb is driven mainly by electrostatic interactions. This shows that the binding is spontaneous at the standard state since the change in the standard Gibbs energy value is negative. The average binding distance between the donor (BHb) and the acceptor (troxerutin) was assessed from the Förster theory. The present study suggests that the thermal stability of BHb is enhanced upon binding with troxerutin.

Synthesis of magnetic FexOy@silica-pillared clay (SPC) composites via a novel sol–gel route for controlled drug release and targeting

Novel magnetic silica-pillared clay (SPC) materials with an ordered interlayered mesopore structure were synthesized via a two-step method including gallery molecular self-assembly and sol-gel magnetic functionalization, resulting in the formation of FexOy@SPC composites. Small-angle XRD, TEM and N2 adsorption-desorption isotherms results show that these composites conserved a regular layered and ordered mesoporous structure after the formation of FexOy nanoparticles. Wide-angle XRD and XPS analyses confirmed that the FexOy generated in these mesoporous silica-pillared clay hosts is mainly composed of γ-Fe2O3. Magnetic measurements reveal that these composites with different γ-Fe2O3 loading amounts possess super-paramagnetic properties at 300K, and the saturation magnetization increases with increasing Fe ratio loaded. Compared to the pure SPC, the in vitro drug release rate of the FexOy@SPC composites was enhanced due to the fact that the intensities of the SiOH bands on the pore surface of SPC decrease after the generation of FexOy. However, under an external magnetic field of 0.15T, the drug release rate of the FexOy@SPC composites decreases dramatically owing to the aggregation of the magnetic FexOy@SPC particles triggered by non-contact magnetic force. The obtained FexOy@SPC composites imply the possibility of application in magnetic drug targeting.

Adsorption of Orange II dye from aqueous solutions using phosphoric-acid modified clam shell powder

AbstractIn this study, the clam shell, a waste biomaterial, was modified with phosphoric acid to improve the adsorption amount of Orange II dye. The effects of initial concentration, contact time, and temperature on the adsorption were studied. The equilibrium adsorption data of Orange II on the phosphoric acid-modified clam shell powder (PCSP) were adequately represented by Langmuir isotherm with an adsorption capacity of 1,017.13 mg/g, which is higher than that obtained using raw clam shell powder. Adsorption kinetics followed the pseudo-second-order rate expression. Thermodynamic parameters show that the process is exothermal, feasible, and spontaneous. The effect of temperature inferred that the type of adsorption in the study is a physical adsorption. Therefore, PCSP is an efficient and economical adsorbent for dye removal.

A novel amperometric sensor based on intercalated montmorillonite modified carbon paste electrode for hydroquinone determination

A simple and reliable amperometric sensor for hydroquinone (HQ) determination is developed based on an intercalated montmorillonite (MMT) modified carbon paste electrode (CPE). The modified CPE significantly enhances the peak current of HQ on cyclic voltammograms and differential pulse voltammograms. The electro-catalytic properties of the intercalated MMT can be attributed to the remarkably increased specific surface area of MMT after the intercalation process, which leads to a higher accumulation efficiency for HQ at this modified CPE. The modified CPE shows a linear range between 5 and 2000 μM HQ with a correlation coefficient of 0.9997, and the detection limit is as low as 0.57 μM (S/N = 3).

Black phosphorus quantum dots/attapulgite nanocomposite with enhanced photocatalytic performance

Novel black phosphorus quantum dots/attapulgite (BPQDs/ATP) nanocomposites were prepared via a facile hydrothermal-deposition method. TEM showed that BPQDs dispersed evenly on the surface of ATP with uniform particle size about 5nm. UV-Vis revealed that the BPQDs/ATP composite showed wider visible light absorption range as compared with pure ATP. The photocatalytic activity was evaluated by degradation of bisphenol A (BPA). Results showed that BPQDs/ATP reached 90% degradation rate under solar light irradiation for 180min. The coherent heterostructure formed by BPQDs and ATP was responsible for the enhanced photocatalytic performance, due to the sensitization effect of BPQDs and the facilitation of charges separation.

One-Pot Preparation of Graphene-Based Polyaniline Conductive Nanocomposites for Anticorrosion Coatings

Graphene-based polyaniline (PANI/RGO), used as conductive filler, was synthesized through a new one-pot emulsion polymerization technology. Graphene dispersion (RGO) was obtained by ultrasonically reducing graphene oxide (GO) in a hot sodium hydroxide solution in the absence of any toxic reductant, such as hydrazine hydrate. Sodium dodecyl benzene sulfonate (SDBS), in which RGO sheets were dispersed, was synthesized using dodecyl benzenesulfonic acid (DBSA) and NaOH. In this RGO/SDBS mixture, polyaniline (PANI), doped with multiple acids (HCl-DBSA), was then uniformly polymerized on the surface of the RGO sheets. The experimental results showed that this reaction improved the dispersion of the RGO in the PANI system, and increased the homogeneous distribution of the formed PANI particles on the RGO surface. The synthesized composite material (PANI/RGO) had good thermal stability, electrical conductivity (about 11.71S⋅cm−1) and water dispersibility. Based on its excellent properties, the PANI/RGO was combined with waterborne epoxy resin to prepare anticorrosion coatings. The corrosion resistance of these coatings was studied using Tafel plots, along with other critical properties tested by the national standards. The results suggested that the surface resistivity of the coatings could be as high as 2.48×108Ω with the addition around 3wt.% of the PANI/RGO meeting good antistatic standards. In addition, the antistatic coatings had outstanding corrosion resistance, as well as tremendous physical and chemical properties.

Preparation and Characterization of Magnetic Chitosan Nanocomposites for Removal of Cu2+ from Aqueous Solution

ABSTRACT In this article, highly efficient magnetic chitosan nanoparticles were prepared by the glutaraldehyde cross-linking method and then chemically-modified with amino groups through reaction between triethylenetramine and glycidyl methacrylate. The adsorption kinetics and isotherms of these novel adsorbents fit the pseudo-second-order model and the Langmuir model. The maximum adsorption capacities were 293 mg/g at pH = 4.3 and t = 1.4 hours. The rate-limiting step was the chemical adsorption. Further recycling experiments showed that the adsorbent provided the potential regeneration and reuse after adsorbing Cu2+. All the experimental results demonstrated that the adsorbent had a potential application in Cu2+ removal from wastewater. GRAPHICAL ABSTRACT