Hengguo Wang

Layer-by-Layer Assembled Fe3O4@C@CdTe Core/Shell Microspheres as Separable Luminescent Probe for Sensitive Sensing of Cu2+ Ions

A novel multifunctional microsphere with a fluorescent CdTe quantum dots (QDs) shell and a magnetic core (Fe(3)O(4)) has been successfully developed and prepared by a combination of the hydrothermal method and layer-by-layer (LBL) self-assembly technique. The resulting fluorescent Fe(3)O(4)@C@CdTe core/shell microspheres are utilized as a chemosensor for ultrasensitive Cu(2+) ion detection. The fluorescence of the obtained chemosensor could be quenched effectively by Cu(2+) ions. The quenching mechanism was studied and the results showed the existence of both static and dynamic quenching processes. However, static quenching is the more prominent of the two. The modified Stern-Volmer equation showed a good linear response (R(2) = 0.9957) in the range 1-10 μM with a quenching constant (K(sv)) of 4.9 × 10(4) M(-1). Most importantly, magnetic measurements showed that the Fe(3)O(4)@C@CdTe core/shell microspheres were superparamagnetic and they could be separated and collected easily using a commercial magnet in 10 s. These results obtained not only provide a way to solve the embarrassments in practical sensing applications of QDs, but also enable the fabrication of other multifunctional nanostructure-based hybrid nanomaterials.

Porphyrin-functionalized Fe3O4@SiO2 core/shell magnetic colorimetric material for detection, adsorption and removal of Hg2+ in aqueous solution

A fluorimetric/colorimetric mercury(II) sensor based on porphyrin-functionalized Fe3O4@SiO2 core/shell magnetic microspheres has been developed and demonstrated by sol–gel grafting reaction. These multifunctional microspheres show excellent fluorescence sensitivity and selectivity towards Hg2+ over other metal ions (K+, Na+, Ba2+, Mn2+, Ca2+, Co2+, Cu2+, Ag+, Mn2+, Ni2+ and Pb2+). Upon addition of Hg2+, the color of porphyrin-functionalized Fe3O4@SiO2 microspheres changes from red to green within 1 min and the fluorescence of microspheres becomes obviously weak. Conversely, no significant changes in fluorescence emission or color are observed in the parallel experiment with other metal ions. Regarding the reversibility of the microspheres, the color and fluorescence of the porphyrin-functionalized Fe3O4@SiO2 microspheres in the presence of Hg2+ ion are found to be almost reversible when the microspheres are treated with EDTA solution. Furthermore, the used microspheres can efficiently remove Hg2+ ions in aqueous solution and easily separated from the mixture by adding an external magnetic field. Theses results suggest that functionalized Fe3O4@SiO2 core/shell magnetic microspheres are potentially useful materials for simultaneously detecting and removing environmental pollutants.

Electrospun novel bifunctional magnetic–photoluminescent nanofibers based on Fe2O3 nanoparticles and europium complex

Novel bifunctional magnetic-photoluminescent nanofibers based on Fe(2)O(3) nanoparticles and europium complex Eu(DBM)(3)(Bath) (DBM=dibenzoylmethanate, Bath=bathophenanthroline) have been prepared by electrospinning. Extensive characterizations of the resulting bifunctional nanofibers have been performed using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM). The influence on photoluminescence properties of bifunctional nanofibers of the addition of Fe(2)O(3) nanoparticles has also been studied. The results indicate that due to decreased symmetry in the composite nanofibers the excitation bands of the composite nanofibers are split into two different components. Furthermore, the existence of the Fe(2)O(3) and polymer hybrid matrixes can improve the thermal and photo stability of the europium complex and elongate the fluorescence lifetime of the europium complex.

Synthesis of magnetic and fluorescent multifunctional hollow silica nanocomposites for live cell imaging

In this paper, we report a synthesis of multifunctional core/shell silica nanocomposites in mixed water-ethanol solvents at room temperature. Water-soluble CTAB-stabilized nanoparticles (Fe(3)O(4) and quantum dots) are used as templates and tetraethoxysilane (TEOS) is used as a precursor to fabricate multifunctional hollow silica nanocomposites. Owing to the high abundance of folate receptors in many cancer cells, folic acid is used as the targeting ligand. By coupling with folic acids, the multifunctional silica nanocomposites conjugates are successfully used for tumor cell imaging. In vitro cellular uptakes of such SiO(2) nanocomposites are investigated with fluorescence microscope, which demonstrate much higher internalization of the folate-decorated SiO(2) nanocomposites by Hela cancer cells which are of over-expression of folate receptors than the cellular uptake by NIH 3T3 fibroblast cells which are of low expression of folate receptors. Magnetic manipulation, fluorescence imaging, hollow structure, and cell targeting are simultaneously possible using a multifunctional silica nanocomposite. Our results demonstrate a robust hydrophobic nanoparticles-based approach for preparing multifunctional and biocompatible hollow silica composites, which could be also suitable for silica coating of other kinds of nanoparticles.

A novel multinozzle electrospinning process for preparing superhydrophobic PS films with controllable bead-on-string/microfiber morphology

Superhydrophobic polystyrene (PS) surfaces with mechanical integrity were manufactured by electrospinning in this work. We first report a novel strategy here to combine bead-on-string fibers from 4% PS solution and micro-sized fibers from 20% PS solution homogeneously in one electrospinning step by multinozzle electrospinning. The superhydrophobicity of electrospun sheet can be achieved by the presence of bead-on-string fibers, while micro-sized PS fibers are responsible for the improvement of mechanical property of electrospun mat due to their elastic and flexible behavior. The distinctive design of our multinozzle electrospinning setup places two nozzles in separate electrical fields which guarantee that fibers with different structures are mixed homogeneously. We investigate the relationship between the mass ratio of fibers from two types of solutions and the CA of electrospun mat, the effect of mass ratio to the mechanical property of electrospun mat can also be observed. The result shows that CA value of PS surface merely comprised of bead-on-string fibers could reach up to 154.65°. As the content of microfibers increased, the value of CA decreased, ranging from 153.66° to 145.94°, but the tensile strength of composite mat was enhanced from 0.50 MPa to 1.22 MPa correspondingly which is beneficial to put the mats into practice.

Preparation of fluorescent nanofibrous film as a sensing material and adsorbent for Cu2+ in aqueous solution via copolymerization and electrospinning.

Novel naphthalimide-functionalized nanofibrous film was prepared by copolymerization and electrospinning. Vinyl naphthalimide monomer was synthesized and then copolymerized with methyl methacrylate via solution polymerization. This prepared copolymer was electrospun into nanofibrous film, which is an excellent sensing material and adsorbent for Cu(2+). When the nanofibrous film was added into acetonitrile/aqueous solution, the presence of Cu(2+) induces the formation of a 1:1 metal-ligand complex, which exhibits a 48 nm blue-shifted from 487 nm to 439 nm in fluorescence spectra. The fluorescent film shows high sensitivities due to the high surface area-to-volume ratio of the nanofibrous film structures. The detection limit for Cu(2+) is 20 × 10(-6)M. Furthermore, the prepared materials could be utilized as an adsorbent to remove Cu(2+) in aqueous solution efficiently, the adsorption capacity was 10.39 mg of Cu(2+) ions per gram of nanofibrous film. All of the results in this paper show that the naphthalimide-functionalized nanofibrous film made by electrospun technique has excellent sensitivities and adsorbent properties toward Cu(2+) over other metal ions.

Magnetically separable iron oxide nanostructures-TiO2 nanofibers hierarchical heterostructures: controlled fabrication and photocatalytic activity

Novel hierarchical heterostructures of TiO2 nanofibers separately decorated with hematite (α-Fe2O3) or magnetite (Fe3O4) were prepared by combining the electrospinning technique and the hydrothermal method. Extensive characterizations of the resulting hierarchical heterostructures revealed that the secondary α-Fe2O3 or Fe3O4 nanostructures successfully grew on the surface of the primary TiO2 nanofibers substrates, thus integrating the magnetic and photocatalytic properties into the α-Fe2O3/TiO2 and Fe3O4/TiO2 hierarchical heterostructures. The component as well as morphology of the secondary α-Fe2O3 or Fe3O4 nanostructures could be further controlled by simply tuning the experimental parameters. Moreover, the magnetic properties and photocatalytic activities of the hierarchical heterostructures were systematically investigated. Electronic interactions between two semiconductors are the major contributing factor for the changed photoactivity. Most importantly, magnetic measurements showed that the Fe3O4/TiO2 hierarchical heterostructures were ferromagnetic and they could be separated and collected easily using a commercial magnet.

Preparation of quantum dots encoded microspheres by electrospray for the detection of biomolecules.

In this paper, a novel method based on the electrospray technique has been developed for preparation of quantum dot (QD)-encoded microspheres for the fist time. By electrospraying the mixture of polymer solution and quantum dots solution (single-color QDs or multi-color QDs), it is accessible to obtain a series of composite microspheres containing the functional nanoparticle. Poly(styrene-acrylate) was utilized as the electrospray polymer materials in order to obtain the microsphere modified with carboxyl group on the surface. Moreover, to test the performance of the QD-encoded microsphere in bioapplication, it is carried out that immunofluorescence analysis between antigens of mouse IgG immobilized on the functional microsphere and FITC labeled antibodies of goat-anti-mouse IgG in experiment. To the best of our knowledge, this is the first report of QD-encoded microspheres prepared by electrospray technology. This technology can carry out the one-pot preparation of different color QD-encoded microspheres with multiple intensities. This technology could be also suitable for encapsulating other optical nanocrystals and magnetic nanoparticles for obtaining multifunctional microspheres. All of the results in this paper show that the fluorescence beads made by electrospray technique can be well applied in multiplex analysis. These works provide a good foundation to accelerate application of preparing microspheres by electrospray technique in practice.

Aggregation states of rhodamine 6G in electrospun nanofibrous films.

Novel fluorescent composite nanofibrous films of rhodamine 6G (Rh6G) and polyacrylonitrile (PAN) are first prepared by electrospinning. The aggregation states of Rh6G in electruspun nanofibrous films are studied as a function of concentrations and characterized by UV-vis absorption spectroscopy and emission and excitation fluorescence spectroscopy. We have also used casting films as reference material to compare the effect of incorporation of Rh6G in electrospun nanofibrous films and casting films. The large specific surface area of the nanofibers and fast evaporation of the solvents in the electrospinning process reduced the aggregation of Rh6G. The appearance of fluorescent J-type dimers, even at higher dye concentration in elctrospun films, demonstrates that the electrospun films are an ideal material for incorporation of fluorescent dyes.

Synthesis and characterization of multifunctional CdTe/Fe2O3@SiO2 core/shell nanosensors for Hg2+ ions detection

Novel multifunctional magnetic-photoluminescent Hg2+ ion sensing nanocomposites were developed by applying SiO2 as the encapsulation agent to package Fe2O3 NRs and CdTe QDs, resulting in CdTe/Fe2O3@SiO2 core/shell nanostructures. The core/shell structural nanocomposites were confirmed by field-emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDXA), X-ray diffraction (XRD) patterns, high-resolution transmission electron microscopy (HRTEM) and selective-area electron diffraction (SAED) patterns. Photoluminescence (PL) spectroscopy and superconducting quantum interference device (SQUID) were used to investigate the optical and magnetic properties of the core/shell structural nanocomposites, respectively. The fluorescence of the obtained nanocomposites could be quenched effectively by Hg2+ ions without obvious changes of spectral widths and optical shift of PL emission. The quenching mechanism was studied and the results showed the existence of both static and dynamic quenching processes. The modified Stern–Volmer equation showed a linear response in the range of 1 to 10 μM with a quenching constant (Ksv) of 3.5 × 104 M−1. This hydrophilic, biocompatible, multifunctional, easy to separate and sensitive fluorescence nanosensor may find applications in Hg2+ ion determination in the biological and environmental areas.