Mingda Sun

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.

Preparation of a durable superhydrophobic membrane by electrospinning poly (vinylidene fluoride) (PVDF) mixed with epoxy–siloxane modified SiO2 nanoparticles: A possible route to superhydrophobic surfaces with low water sliding angle and high water contact angle

A durable superhydrophobic surface with low water sliding angle (SA) and high water contact angle (CA) was obtained by electrospinning poly (vinylidene fluoride) (PVDF) which was mixed with epoxy-siloxane modified SiO(2) nanoparticles. To increase the roughness, modified SiO(2) nanoparticles were introduced into PVDF precursor solution. Then in the electrospinning process, nano-sized SiO(2) particles irregularly inlayed (it could also be regard as self-assembly) in the surface of the micro-sized PVDF mini-islands so as to form a dual-scale structure. This structure was responsible for the superhydrophobicity and self-cleaning property. In addition, epoxy-siloxane copolymer was used to modify the surface of SiO(2) nanoparticles so that the SiO(2) nanoparticles could stick to the surface of the micro-sized PVDF mini-islands. Through the underwater immersion test, the SiO(2) nanoparticles cannot be separated from PVDF easily so as to achieve the effect of durability. We chiefly explore the surface wettability and the relationship between the mass ratio of modified SiO(2) nanoparticles/PVDF and the CA, SA of electrospun mat. As the content of modified SiO(2) nanoparticles increased, the value of CA increased, ranging from 145.6° to 161.2°, and the water SA decreased to 2.17°, apparently indicating that the membrane we fabricated has a perfect effect of superhydrophobicity.

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.

A new fluorescent and colorimetric sensor for hydrazine and its application in biological systems

Hydrazine is a very important industrial chemical and exhibits high toxicity to human beings. Here we have constructed a novel ICT-based fluorescence sensor with a high selectivity and sensitivity, rapid detection, and huge color-change. We used the sensor for hydrazine determination in live cells and also in live fish, and manufactured dipsticks using our sensor. The sensing mechanism is well rationalized with the aid of TD-DFT (time-dependent density functional theory) calculations.

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.

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.

A new colorimetric fluorescent sensor for ratiometric detection of cyanide in solution, test strips, and in cells

A new high selective and sensitive fluorescent sensor for the detection of cyanide was developed based on the nucleophilic attack of CN− with a color change from purple to colourless. The chemosensor was used for fabrication of test strips that can detect cyanide in aqueous samples. The living animal fluorescence experiment demonstrated the practical value of the sensor in tracing the CN− in biological systems.

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.

Regenerable Fluorescent Nanosensors for Monitoring and Recovering Metal Ions Based on Photoactivatable Monolayer Self-Assembly and Host–Guest Interactions

Efficient detection, removal, and recovery of heavy metal ions from aqueous environments represents a technologically challenging and ecologically urgent question in the face of increasing metal-related pollution and poisoning across the globe. Although small-molecule and entrapment-based nanoparticle sensors have been extensively explored for metal detection, neither of these extant strategies satisfies the critical needs for high-performance sensors that are inexpensive, efficient, and recyclable. Here we first report the development of a regenerable fluorescent nanosensor system for the selective and sensitive detection of multiple heavy metal ions, based on light-switchable monolayer self-assembly and host-guest interactions. The system exploits photocontrolled inclusion and exclusion responses of an α-cyclodextrin (CD)-containing surface conjugated with photoisomerizable azobenzene as a supramolecular system that undergoes reversible assembly and disassembly. The metal nanosensors can be facilely fabricated and photochemically switched between three chemically distinct entities, each having an excellent capacity for selective detecting specific metal ions (namely, Cu(2+), Fe(3+), Hg(2+)) in a chemical system and in assays on actual water samples with interfering contaminants.