Shiyong Bao

Structure regulation of silica nanotubes and their adsorption behaviors for heavy metal ions: pH effect, kinetics, isotherms and mechanism

Silica nanotubes (SNTs) with controlled nanotubular structure were synthesized via an electrospinning and calcination process. In this regard, SNTs were found to be ideal adsorbents for Pb(II) removal with a higher adsorption capacity, and surface modification of the SNTs by sym-diphenylcarbazide (SD-SNTs) markedly enhanced the adsorption ability due to the chelating interaction between imino groups and Pb(II). The pH effect, kinetics, isotherms and adsorption mechanism of SNTs and SD-SNTs on Pb(II) adsorption were investigated and discussed detailedly. The adsorption capacity for Pb(II) removal was found to be significantly improved with the decrease of pH value. The Langmuir adsorption model agreed well with the experimental data. As for kinetic study, the adsorption onto SNTs and SD-SNTs could be fitted to pseudo-first-order and pseudo-second-order model, respectively. In addition, the as-prepared SNTs and SD-SNTs also exhibit high adsorption ability for Cd(II) and Co(II). The experimental results demonstrate that the SNTs and SD-SNTs are potential adsorbents and can be used effectively for the treatment of heavy-metal-ions-containing wastewater.

Facile fabrication of AgNPs/(PVA/PEI) nanofibers: High electrochemical efficiency and durability for biosensors

A novel, facile and green approach for the fabrication of H2O2, glutathione (GSH) and glucose detection biosensor using water-stable PVA and PVA/PEI nanofibers decorated with AgNPs by combining an in situ reduction approach and electrospinning technique has been demonstrated. Small, uniform and well-dispersed AgNPs embedded in the PVA nanofibers and immobilized on functionalized PVA/PEI nanofibers indicate the highly sensitive detection of H2O2 with a detection limit of 5 μM and exhibit a fast response, broad linear range, low detection limit and excellent stability and reusability.

In situ growth of Rh nanoparticles with controlled sizes and dispersions on the cross-linked PVA–PEI nanofibers and their electrocatalytic properties towards H2O2

A facile approach for the synthesis of uniform, small size and well-dispersed rhodium nanoparticles (RhNPs) on cross-linked polyvinyl alcohol–polyethyleneimine (PVA–PEI) nanofibers has been demonstrated. Various methods were firstly employed to cross-link PVA nanofibers and the cross-linked PVA–PEI nanofibers exhibited good water stability and porous structures after immersing in water for 72 h. Because of the strong chelate effects among the amine groups, hydroxyl groups and Rh3+ ions, uniform RhNPs with an average diameter of about 2.5 ± 0.2 nm can evenly and densely grow throughout the PVA–PEI nanofibers via an in situ reduction. Meanwhile, the better dispersion and smaller size of the RhNPs grown on the nanofibers in comparison with the pre-synthesized RhNPs directly deposited on the nanofibers exhibit the advantages of in situ reduction for size and dispersion control. The successful fabrication of the RhNPs/(PVA–PEI) nanofibers with various densities of well-dispersed RhNPs demonstrates that the strong chelate effects and stabilization of the PVA–PEI nanofibers also play an essential role in the size and dispersion control of RhNPs. The crystal structures, chemical bonding and interactions of the prepared nanofibers were verified using XPS and FTIR spectra and XRD patterns. These novel nanomaterials were fabricated as non-enzymatic electrochemical sensors and exhibit highly electrocatalytic activity towards H2O2.

AgNPs/PVA and AgNPs/(PVA/PEI) hybrids: preparation, morphology and antibacterial activity

Two strategies are demonstrated to fabricate AgNPs/PVA and AgNPs/(PVA/PEI) nanofibre hybrids. In the first approach, we synthesized AgNPs in poly(vinylalcohol) (PVA) solution and then electrospun the AgNPs/PVA solution into the AgNPs/PVA nanofibres. In the other one, the polyethylenimine (PEI) was introduced to improve the water-stability of PVA and then the AgNPs were immobilized on electrospun PVA/PEI nanofibres to fabricate the AgNPs/(PVA/PEI) nanofibres. Field-emission scanning electron microscopy, transmission electron microscopy, ultraviolet–visible spectroscopy and x-ray photoelectron spectroscopy (XPS) were utilized to investigate the morphology and the growth mechanism of the hybrids. The investigations demonstrate that both of the obtained AgNPs/PVA hybrids and AgNPs/(PVA/PEI) hybrids exhibit good water-stability and good antibacterial activity against E. coli and S. aureus.

Synthesis and Catalytic Properties of Polyaniline/Au Hybrid Nanostructure

Polyaniline (PANI)/Au hybrid nanostructure was synthesized by a simple two-step process without any other templates or additives. Transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) were employed to study the morphologies and structures of the hybrid. Results indicate that the AuNPs are evenly immobilized on the PANI nanofibers. Notably, the PANI/Au nanostructure exhibits extremely high catalytic activity toward the organic dyes, 4-nitro phenol (4-NP), and methylene blue (MB), which are attributed to stimulation effects of the AuNPs on the electrons transmission of NaBH4 to 4-NP or MB.

Facile Fabrication of Palladium Nanoparticles Immobilized on the Water-Stable Polyvinyl Alcohol/Polyehyleneimine Nanofibers Via In-Situ Reduction and Their High Electrochemical Activity

A facile strategy for the fabrication of electrochemical biosensors by immobilizing well-dispersed palladium nanoparticles (PdNPs) on the water-stable polyvinyl alcohol/polyethyleneimine (PVA/PEI) nanofibers through the combination of electrospinning technique and the process of in-situ reduction has been demonstrated. The synthesized PdNPs/(PVA/PEI) nanocomposites were characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The experimental results confirmed that the PdNPs immobilized on the electrospun PVA/PEI nanofibers with an average diameter of 3.4 nm were well-dispersed, which could be ascribed to the complexation between Pd(II) and the free amine groups of PEI. Further investigations suggested that the PdNPs/(PVA/PEI) nanocomposites with well-separated PdNPs and large surface area exhibited high performance as electrochemical biosensors to detect hydrogen peroxide (H2O2).

SYNTHESIS AND CHARACTERIZATION OF Au NANOPARTICLES/REDUCED GRAPHENE OXIDE NANOCOMPOSITE: A FACILE AND ECO-FRIENDLY APPROACH

In this paper, epigallocatechin gallate (EGCG) was used as a green reductant both for the fabrication of soluble reduced graphene oxide (rGO) and the synthesis of Au nanoparticles/rGO nanocomposite. Fourier transform infrared (FTIR) spectra confirmed the efficient removal of the oxygen-containing groups in graphene oxide (GO) through the reduction act of EGCG. Au nanoparticles (AuNPs) were anchored onto the rGO sheets by heating the mixed solution of rGO and chloroauric acid at 65°C using EGCG as reductant. Transmission electron microscopy (TEM), atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS) were employed to characterize the resulting nanocomposite. Due to the chelating effect of polyhydroxy EGCG, AuNPs with diameters of ~20–50 nm were stably decorated onto both sides of the rGO sheets. Because this reduction method avoids the use of toxic reagents, AuNPs/rGO nanocomposite would be eco-friendly, and it might be useful not only for electronic devices but also for biocompatible materials in the future applications.

TEMPLATE STRATEGY FOR THE SYNTHESIS OF Cu2O–Pt HIERARCHICAL HETEROSTRUCTURES FOR THE DEGRADATION OF METHYLENE BLUE

A facile and green route was introduced to synthesize Pt nanoparticles (PtNPs) immobilized on Cu2O octahedrons to form Cu2O–Pt hierarchical heterostructure. Transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) were employed to study their morphology, chemical and crystallographic properties of the Cu2O–Pt hierarchical heterostructure. These novel Cu2O–Pt hierarchical heterostructures show fascinating degradations of methylene blue (MB), due to the suppressed electron/hole recombination phenomena and the efficient ability to capture the light.