Wenjuan Guo

A novel signal amplification strategy of an electrochemical aptasensor for kanamycin, based on thionine functionalized graphene and hierarchical nanoporous PtCu.

An ultrasensitive electrochemical aptasensor for the quantitative detection of kanamycin antibiotic was fabricated based on a novel signal amplification strategy. This aptasensor was developed using thionine functionalized graphene (GR-TH) and hierarchical nanoporous (HNP) PtCu alloy as biosensing substrates for the first time. HNP-PtCu alloy with controllable bimodal ligament/pore distributions was successfully prepared by two-step dealloying of a well-designed PtCuAl precursor alloy combined with an annealing operation. GR-TH composite was synthesized by one-step reduction of graphene oxide (GO) in TH solution. Greatly amplified sensitivity was achieved by using GR-TH/HNP-PtCu composite owing to its large specific surface and good electron-transfer ability. Under the optimized conditions, the proposed aptasensor exhibited a high sensitivity and a wider linearity to kanamycin in the range 5 × 10(-7)-5 × 10(-2) μgmL(-1) with a low detection limit of 0.42 pgmL(-1). This aptasensor also displayed a satisfying electrochemical performance with good stability, selectivity and reproducibility. The as-prepared aptasensor was successfully used for the determination of kanamycin in animal derived food.

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.

A novel electrochemical aptasensor based on MWCNTs–BMIMPF6 and amino functionalized graphene nanocomposite films for determination of kanamycin

A simple electrochemical sensor based on a novel composite film consisting of multi-walled carbon nanotubes (MWCNTs), a room temperature ionic liquid (RTIL) of 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6), and amino functionalized graphene (GR–CO–NH–CH2–CH2–NH2) was constructed for the detection of kanamycin. Firstly, MWCNTs–BMIMPF6 composites were fabricated on the surface of a glass carbon electrode (GCE). The synergy mechanism between the MWCNTs and RTIL has been discussed. Secondly, GR–CO–NH–CH2–CH2–NH2 was modified on the first film, which could greatly improve the conductivity of the electrode. The structure of the resultant graphene oxide (GO) was confirmed by FTIR and SEM. The properties of the aptasensor were characterized by electrochemical methods. Under the optimum conditions, the electrochemical aptasensor exhibited a wide linear range for kanamycin from 0.001 to 100 μM with a low limit of detection of 0.87 nM (S/N = 3). The as-prepared aptasensor showed high sensitivity, reproducibility and stability. Finally, the proposed electrochemical aptasensor was successfully applied for the detection 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.

A novel signal amplification strategy of an electrochemical immunosensor for human chorionic gonadotropin, based on nanocomposites of multi-walled carbon nanotubes–ionic liquid and nanoporous Pd

A sensitive label-free immunosensor adopting a novel signal amplification strategy was proposed for the electrochemical detection of human chorionic gonadotropin (hCG). Firstly, a novel composite film consisting of multi-walled carbon nanotubes (MWCNTs) and a room temperature ionic liquid (RTIL) of 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6), which combined the advantages of MWCNTs and RTILs, was fabricated on a glassy carbon electrode surface. The mechanism of the synergy between the MWCNTs and RTIL has been discussed. Secondly, the first film was modified with nanoporous Pd (NP-Pd) prepared by a simple dealloying method. The structure of NP-Pd has been confirmed by EDS, XRD, SEM, TEM and BET analysis. Due to the large specific surface area and excellent electrical conductivity of NP-Pd, electron transfer was promoted and the amount of hCG antibody was enhanced significantly. The results showed that MWCNTs–BMIMPF6/NP-Pd composites were successfully designed as a sensitive immunosensor platform for hCG determination. Under the optimum conditions, the immunosensor exhibited high sensitivity and a wide linear range for hCG from 0.05 to 50 ng mL−1 with a detection limit of 3.2 pg mL−1. The prepared immunosensor showed high sensitivity, reproducibility and stability. This immunosensor preparation strategy presents a promising platform for clinical application.

Preparation, characterization and application of magnetic Fe3O4-CS for the adsorption of orange I from aqueous solutions.

Fe3O4 (Fe3O4-CS) coated with magnetic chitosan was prepared as an adsorbent for the removal of Orange I from aqueous solutions and characterized by FTIR, XRD, SEM, TEM and TGA measurements. The effects of pH, initial concentration and contact time on the adsorption of Orange I from aqueous solutions were investigated. The decoloration rate was higher than 94% in the initial concentration range of 50–150 mg L−1 at pH 2.0. The maximum adsorption amount was 183.2 mg g−1 and was obtained at an initial concentration of 400 mg L−1 at pH 2.0. The adsorption equilibrium was reached in 30 minutes, demonstrating that the obtained adsorbent has the potential for practical application. The equilibrium adsorption isotherm was analyzed by the Freundlich and Langmuir models, and the adsorption kinetics were analyzed by the pseudo-first-order and pseudo-second-order kinetic models. The higher linear correlation coefficients showed that the Langmuir model (R2 = 0.9995) and pseudo-second-order model (R2 = 0.9561) offered the better fits.

A facile procedure to fabricate nano calcium carbonate–polymer-based superhydrophobic surfaces

A facile procedure to fabricate superhydrophobic surfaces based on nano calcium carbonate–polymer composites has been described. The hydrophobicity of the resulting surfaces can be tuned by varying the weight ratio of nano calcium carbonate–polymer composites. The simple and robust strategy can facilitate the fabrication of superhydrophobic surfaces on general substrates.

Sensitive sandwich electrochemical immunosensor for human chorionic gonadotropin using nanoporous Pd as a label

A novel sandwich-type electrochemical immunosensor for sensitive detection of human chorionic gonadotropin (hCG) was designed. The nanoporous Pd (NP-Pd) was prepared by a dealloying method and used as an electrochemical label due to its wonderful conductivity, good biocompatibility and strong electrocatalytic activity toward antigen–antibody reaction. Results proved that the immunosensor fabricated using the label based on NP-Pd loaded with horseradish peroxidase (HRP) and secondary anti-hCG antibody (Ab2) (NP-Pd–HRP–Ab2) had high sensitivity, and the sensitivity of the label NP-Pd–HRP–Ab2 was much higher than that of HRP–Ab2. Gold nanoparticles (GNPs), Prussian blue (PB) and GNPs as immobilization matrix were not only used to immobilize anti-hCG (Ab1) but also took part in the signal amplification. Under optimized conditions, the amperometric signal increased linearly with hCG concentration in the range of 0.5 ng mL−1 to 200 ng mL−1 (γ = 0.9986) with a low detection limit (3σ) of 9.2 pg mL−1 (0.093 mIU mL−1). The immunosensor displayed good sensitivity and selectivity. In addition, the immunosensor was successfully used for the determination of hCG in human serum.

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 10 000 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.

Thermo-sensitive zwitterionic block copolymers via ATRP

Novel thermo-sensitive zwitterionic ABC-type triblock copolymers poly(ethylene glycol)-block-[2-(methacryloyloxy)ethyl]dimethyl(3-sulfopropyl)-ammonium hydroxide-block-poly[2-(dimethylamino)ethyl methacrylate] (MPEG-b-PSBMA-b-PDMAEMA) were synthesized by atom transfer radical polymerization (ATRP). The bromide-terminated diblock copolymers poly(ethylene oxide)-block-[2-(methacryloyloxy)ethyl]dimethyl(3-sulfopropyl)-ammonium hydroxide (MPEG-b-PSBMA-Br) were prepared by the ATRP of methacryloxyethyl sulfobetaine initiated by the macroinitiator MPEG-Br, which was obtained by the esterification of poly(ethylene glycol) monomethyl ether (MPEG) with 2-bromoisobutyryl bromide. Then, poly(2-(diethylamino)ethyl methacrylate) (PDMAEMA) was introduced by a sequential ATRP process to obtain the triblock copolymers. These copolymers with varied compositions, molecular weights and polydispersities were characterized by 1H NMR and GPC. Variable temperature ultraviolet analysis was employed to test their stimuli-sensitive properties. These block copolymers exhibited distinct thermo-sensitivity under different molecular compositions or solution conditions. The resistance to the non-specific protein adsorption of the triblock copolymers was evaluated, and excellent antifouling property occurred. This can be attributed to surface hydration via hydrogen bonds between PEG and water molecules and the surface hydration via ionic-induction between PSBMA and water molecules. The synergistic effect resulted in an effective reduction of protein adsorption. These copolymers have potential applications as antifouling and antibacterial agents.