Luyan Wang

A novel electrochemical aptasensor for ultrasensitive detection of kanamycin based on MWCNTs-HMIMPF6 and nanoporous PtTi alloy.

A novel aptasensor based on a novel composite film consisting of multi-walled carbon nanotubes (MWCNTs), ionic liquid (IL) of 1-hexyl-3-methylimidazolium hexafluorophosphate (HMIMPF6), and nanoporous PtTi (NP-PtTi) alloy was constructed for ultrasensitive detection of kanamycin. The NP-PtTi alloy was successfully fabricated by a simple dealloying of PtTiAl source alloy in HCl solution. The NP-PtTi alloy has uniform interconnected network structure with specific surface area and was used to immobilize aptamer. After modified with the composite material, current signal was amplified obviously, which attributed to the larger specific surface area and excellent electrical conductivity of NP-PtTi and MWCNTs. A number of factors affecting the activity of the aptasensor have been discussed and optimized. Under the optimized conditions, the proposed aptasensor provided a linear range of 0.05-100 ng mL(-1) with a low detection limit of 3.7 pg mL(-1). This aptasensor displayed high sensitivity, stability and reproducibility. In addition, the as-prepared aptasensor was successfully used for the determination of kanamycin in a real sample.

Hydrothermal and activated synthesis of adsorbent montmorillonite supported porous carbon nanospheres for removal of methylene blue from waste water

Novel adsorbent, montmorillonite supported porous carbon nanospheres (MMT-PCN) were conveniently synthesized by a hydrothermal carbonization and chemical activation treatment with ZnCl2. The as-prepared MMT-PCN material was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and N2 adsorption technology. The results indicated that the material possessed superior porosity with high surface area and large pore volume, which was utilized to remove methylene blue (MB) from an aqueous solution. The batch adsorption results implied that this novel MMT-PCN adsorbent exhibited greater performance (686.94 mg g−1) for the removal of MB than other adsorbents. Adsorption kinetics of MB onto the composite followed the pseudo-second-order kinetic model and the adsorption isotherm data were fitted well to the Langmuir isotherm. Thermodynamic parameters, such as ΔG°, ΔH° and ΔS° were also determined and evaluated. In addition, the MMT-PCN composite exhibited satisfactory reusability properties after five consecutive cycles.

High performance supercapacitors based on ternary graphene/Au/polyaniline (PANI) hierarchical nanocomposites

A ternary graphene/Au/PANI nanocomposite (GAP) is designed and fabricated via a facile two-step approach: Au nanoparticles dispersed on graphene sheets are achieved by a hydrothermal method, followed by coating with PANI through an in situ polymerization process. Electrochemical measurements demonstrate that the specific capacitance of the resulting ternary composite is 572 F g−1 at a current density of 0.1 A g−1 using a three-electrode system, which is significantly higher than that of pure PANI and the binary graphene-PANI composite. In addition, over 88.54% of the initial capacitance can be retained after repeating tests for 10u2006000 cycles, demonstrating a high cycling stability. The extraordinary electrochemical performance of the ternary GAP nanocomposite is attributed to its well-designed nanostructure and the synergistic effects among individual components.

A regular “signal attenuation” electrochemical aptasensor for highly sensitive detection of streptomycin

In this paper, a convenient electrochemical aptasensor for sensitive and selective determination of streptomycin antibiotic was constructed. Signal amplification strategy of the aptasensor was achieved by utilizing porous carbon nanorods, gold nanoparticles and copper oxide functionalized multiwalled carbon nanotube composites as biosensing substrates. Porous carbon nanorods were adopted in our strategy as the core conductive material for signal amplification. The multiwalled carbon nanotube–copper oxide–gold nanoparticle nanocomposites combined the advantages of their components, which not only promote electron transfer, but also provide abundant binding sites for the immobilization of biomolecules. The streptomycin aptamer was immobilized on the nanocomposites surface via the strong bonding interaction between the gold nanoparticles and the thiol group to generate a referenced differential pulse voltammetry signal, Iaptamer. Then, the streptomycin was immobilized on the aptasensor via the specific interaction between the aptamer and streptomycin to generate the attenuated signal, Istreptomycin. Under the optimized conditions, the changes in the signals were linear with the concentration of streptomycin in the range of 0.05–300 ng mL−1 with a low detection limit of 0.036 ng mL−1 when “ΔI = Iaptamer − Istreptomycin was used as the response signal for quantitative determination of streptomycin. In addition, the electrochemical aptasensor was also successfully applied to the determination of streptomycin in milk and honey samples. This highly sensitive electrochemical aptasensor is of great practical importance in food safety and could be widely extended to the detection of other antibiotics by replacing the sequence of the aptamer.

Synthesis of sodium polyacrylate–bentonite using in situ polymerization for Pb2+ removal from aqueous solutions

Polymer/clay composites have attracted a great deal of interest because of their wide applications in environmental protection. In this study, a sodium polyacrylate–bentonite material (PAANa–Bent), as an adsorbent for heavy metal ions, is synthesized for the first time using in situ polymerization. A series of analytical methods including FTIR, zeta potential measurements, SEM, TG/DTA, DSC, a N2 adsorption–desorption isotherm study and XRD were used to characterize PAANa–Bent. Furthermore, to evaluate the heavy metal ion adsorption capability of PAANa–Bent, batch experiments were conducted using Pb2+ as an adsorbate. The results demonstrate that PAANa–Bent was prepared successfully and the layered structure of bentonite was protected during polymerization. PAANa–Bent has more negative surface charges and a better dispersity than the original bentonite (O-Bent). The maximum adsorption capacity of PAANa–Bent is 70.41 mg g−1 at pH = 6, t = 300 min and T = 25 °C, an increase of 113% compared with O-Bent. A kinetic study shows that the adsorption process of PAANa–Bent obeys a pseudo-second-order model and the best-fit adsorption isotherm is a Freundlich isotherm, indicating the heterogeneous nature of PAANa–Bent. Besides, desorption experiments suggest that the PAANa–Bent can be regenerated easily with 0.1 M HCl as a stripping agent and the desorption ratio was still more than 91% after four cycles. Overall, the results indicate the potential of PAANa–Bent as a low-cost and highly efficient adsorbent for Pb2+ removal from aqueous solutions.

Preparation and characterization of sodium polyacrylate-grafted bentonite and its performance removing Pb2+ from aqueous solutions

A new adsorbent, sodium polyacrylate (PAANa) grafted onto the surface of bentonite (Bent), was successfully synthesized by a facile and green Ce(IV)-redox process, for the removal of Pb2+ from aqueous solutions. The results indicate that by this method the original layered structure of the clay can be protected along with its cation exchange capability (CEC), leading to an improved adsorption capacity. The adsorbent (Bent–PAANa) was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and N2 adsorption–desorption isotherm studies. Subsequently the effects of pH, initial concentration and contact time on the adsorption of Pb2+ from aqueous solutions were investigated. The results of the batch experiments specifically indicate that a high adsorption capacity (149.62 mg g−1) of Bent–PAANa for the removal of Pb2+ was obtained at pH = 5, C0 = 1100 mg L−1 and 25 °C. Furthermore, the adsorption kinetics of Pb2+ onto the composite followed a pseudo-second-order kinetic model. The adsorption data fitted better to a Freundlich adsorption isotherm than a Langmuir adsorption isotherm hence confirming multilayer adsorption.

Electrochemical synthesis of poly(3-thiophene acetic acid) nanowires with water-soluble macromolecule templates

Poly(3-thiophene acetic acid) (PTAA) nanowires are synthesized in a high yield by electrochemical polymerization, with diameters of about 200 nm and lengths of tens of micrometres. In the reaction systems, the water soluble macromolecules hydroxyethylcellulose (HEC), chitosan (Cs) and polyacrylamide (PAM) are added respectively as templates through a dip-coating process, where the macromolecules are spread on an indium tin oxide glass which is used as the working electrode. However, when polyethylene glycol (PEG) is used, only a PTAA film can be obtained. Therefore the interactions between template macromolecules and TAA monomers play a key role in the formation of PTAA nanowires and the dip-coating process presents an effective way to produce 1D conductive polymer materials with controllable shape. The optical, electrochemical and surface properties are also studied respectively to compare the performances of PTAA film and nanowires, where the latter indicates good electrochemical responsiveness and evidently increased hydrophobicity.

Cationic Polymer Grafted-Bentonite by Ce(IV)-Redox System for Adsorption of the Anionic Dye

Modified bentonite was prepared by grafting poly(2-(acryloyloxy)ethyl)trimethyl ammonium chloride by a Ce(IV)-redox process to remove an anionic dye, brilliant yellow (BY). The BY removal efficiency changed with pH, temperature and reaction time. The adsorption capacity for BY decreased slightly with value of pH enhanced from 2.0 to 10.0 in solution. Kinetics models and isotherms models were used to match the adsorption behavior. Adsorption kinetics showed the adsorption was a fast course, achieving balance within 180xa0min and could be described well by the pseudo-second-order model. The thermodynamic equilibrium data showed that the adsorption isotherm matched with Langmuir model. Results represented that the adsorption capacity increased greatly by grafting PDAC on bentonite and the maximum adsorption capacity could reach to 302.9xa0mg/g.

Effects of the Chemical Structure of Polycarboxy-Ether Superplasticizer on Its Performance in Sulphoaluminate Cement

A series of polycarboxy-ether (PCE) surfactants were prepared with different lengths and densities of polyethylene oxide (PEO) side chains. The effects of the chemical structure of PCE surfactant on its performances in sulphoaluminate cement (SAC) were investigated. The results show that better initial paste flow, worse flow retention, and retardation effect are obtained with the increase of PEO side chains length. Initial paste flow and flow retention perform well at first and become poor later with the growing density of PEO side chains. The optimal initial paste flow and flow retention were attained at the molar percentage of 30% of allyl polyethylene glycol (APEG).

Preparation of polyamine grafted bentonite by surface-initiated atom transfer radical polymerization for efficient adsorption of Orange I from aqueous solution

A poly(glycidyl methacrylate) (PGMA) grafted bentonite (Bent) was prepared by surface-initiated atom transfer radical polymerization (SI-ATRP), followed by modification with tetraethylenepentamine (TEPA) through a ring-opening reaction of the epoxy groups in PGMA to form polyamine grafted bentonite (Bent–PGMA–TEPA). The as-prepared novel material was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA). The ability of Bent–PGMA–TEPA to adsorb Orange I (OI), a negatively charged dye, was tested. The effects of pH, initial concentration, contact time and temperature were investigated. The equilibrium adsorption isotherm and adsorption kinetics fitted well with the Langmuir model and the pseudo-second-order kinetic model respectively.