Guoping Dong

Engineering and optimization of nano- and mesoporous silica fibers using sol―gel and electrospinning techniques for sorption of heavy metal ions

In this paper, we report on a novel design strategy of an efficient sorbent for removal of trace contaminants from water. This kind of sorbent is composed of a nonporous core of SiO(2) nanofiber and a mesoporous shell (denoted as nSiO(2)@mSiO(2) (n means nonporous and m means mesoporous)). The nSiO(2)@mSiO(2) fiber possesses a continuously long fibrous shape and mesoporous micromorphology, thus, showing both high sorption capacity and separability. The flexible nonporous SiO(2) nanofiber was prepared with electrospinning first, followed by covering a mesoporous SiO(2) shell based on a modified Stöber method using CTAB (cetyltrimethylammonium bromide) as the directing agent for formation of the mesopores. Also, functional thiol groups were grafted on the nSiO(2)@mSiO(2) to enhance its performance. With a large specific surface area and long fibrous morphology, the nSiO(2)@mSiO(2) fiber and its thiol-functionalized counterpart exhibit impressive performance on removal of Pb(2+) and Cd(2+) from water. Furthermore, the flexible texture and fibrous morphology of the nSiO(2)@mSiO(2) fiber also made the removal of metal ions and the separation process more convenient and efficient, implying that the nSiO(2)@mSiO(2) fiber could have great potential for industrial applications.

BCNO-Based Long-Persistent Phosphor

A BCNO-based long-persistent phosphor prepared by a low-temperature liquid-phase route is investigated. It shows a phosphorescence peak centered at 520 nm and its afterglow decay curve fits t -0.93 . Electron paramagnetic resonance confirms the presence of a paramagnetic center, the signal of which exhibits a synchronized decay with the afterglow intensity. We assume that the phosphorescence arises from electrons that are thermally released from nitrogen vacancies and then fall into the carbon-related defects, giving the greenish emission. The BCNO material is a competitive long-persistent phosphor because it is derived from cheap raw materials.

Fabrication and optical properties of Y2O3: Eu3+ nanofibers prepared by electrospinning

Y(2)O(3): Eu(3+) nanofibers with the average diameter of ~300 nm were in situ fabricated by electrospinning. X-ray diffraction (XRD) pattern confirmed that the Y(2)O(3): Eu(3+) nanofibers were composed of pure body-centered cubic (bcc) Y(2)O(3) phase. High-resolution transmission electron microscopy (HRTEM) results indicated that Y(2)O(3): Eu(3+) nanofibers were constituted of nonspherical crystalline grains, and these crystalline grains were orderly arranged along the axial direction of single nanofiber. These Y(2)O(3): Eu(3+) nanofibers showed a partially polarized photoluminescence (PL). The arrangement of crystalline grains and the mismatch of dielectric constant between Y(2)O(3): Eu(3+) nanofiber and its environment probably contributed together to the polarized PL from Y(2)O(3): Eu(3+) nanofiber.

Cooperative Quantum Cutting in Yb

Quantum cutting down-conversion (DC) with the emission of two near-infrared photons for each blue photon absorbed is realized in Yb -Tb codoped borosilicate glasses. With the excitation of Tb ion by a 484-nm monochromatic light, emission from the F F transition of Yb ions is observed and this emission is proved to originate from the DC between Tb ions and Yb ions. Results shows that maximum quantum efficiency reach as high as 153%, which is comparable with that in oxyfluoride glass ceramics in this system. With the advantages of excellent transparence, easy shaping, good stability, and low cost, Yb -Tb codoped borosilicate glasses are poten- tially used as down-converter layer in silicon-based solar cells. Index Terms—Optical glass, photovoltaic cells, quantum cutting (QC), Yb -Tb .

^{3+}

Sr(2)SiO(4):Eu electrospun nanofibers were in situ synthesized successfully by calcination in this work. X-ray diffraction results confirmed that the calcined nanofibers were composed of the orthorhombic alpha-Sr(2)SiO(4) phase. High resolution transmission electron microscopy and selected area electron diffraction indicated that the single Sr(2)SiO(4):xEu electrospun nanofiber was poly-crystalline with moderate orientation. Intense red and yellow emissions were observed in the calcined Sr(2)SiO(4):xEu(3+)(Eu(2+)) electrospun nanofibers. These nanofibers with intense visible emissions can be potentially applied in the fields of light-emitting-diode-based one-dimensional white light sources, displays, biological markers, etc

–Tb

In this paper, we report on a novel strategy for the preparation of silver nanoparticle-doped SiO(2) microspheres (Ag-SMSs) with an interesting strawberry-like morphology using a simple and efficient electrospraying method. SEM (scanning electron microscopy), TEM (transmission electron microscopy), XRD (x-ray diffraction), EDS (energy-dispersive spectroscopy) and UV-vis spectra (ultraviolet-visible spectra) were applied to investigate the morphology, structure, composition and optical properties of the hybrid microspheres, and E. coli (Escherichia coli) was used as a model microbe to evaluate their antibacterial ability. The results showed that the Ag-SMSs were environmentally stable and washing resistant. The Ag-SMSs exhibited effective inhibition against proliferation of E. coli, and their antibacterial ability could be well preserved for a long time. The environmental stability, washing resistance, efficient antibacterial ability and simple but productive preparation method endowed the Ag-SMSs with great potential for practical biomedical applications.

^{3+}

Eu 2+ -doped Ca(Sr)Al 2 Si 2 O 8 nanofibers with an average diameter of 500 nm were in situ synthesized by electrospinning and calcination in reduced ambience. X-ray diffraction results confirmed that the Ca(Sr)Al z Si 2 O 8 :Eu 2+ nanofibers were of the anorthite phase. An intense blue emission due to the 4f 6 5d 1 → 4f 7 transition of Eu 2+ ions was observed in the nanofibers. The emission band shifted to the blue region with the substitution of Ca by Sr due to the change in the crystal field surrounding Eu 2+ ions. The long afterglow decay curves of Ca(Sr)Al 2 Si 2 O 8 :Eu 2+ nanofibers contain rapid (∼ 13.86 s) and slow (∼ 157.12 s) components. By the co-doping of Dy 3+ ions, the emission and long afterglow duration of nanofibers were improved remarkably. These Ca(Sr)Al 2 Si 2 O 8 :Eu 2+ , Dy 3+ electrospun nanofibers with excellent emission and long afterglow properties were potentially applied in biological marker, disnlay, sensor, etc.

Codoped Borosilicate Glasses

In this paper, we propose a novel strategy for the preparation of flexible mesoporous SiO2 fibers containing silver nanoparticles (Ag-cSiO2@mSiO2) as an effective wound dressing. The Ag-cSiO2@mSiO2 was core–shell structured, composed of a condensed electrospun SiO2 nanofiber doped with Ag NPs (silver nanoparticles) and a mesoporous SiO2 shell. Due to a high specific surface area and large pore volume, the Ag-cSiO2@mSiO2 can substantially absorb exudates, the absorption capacity for water and SBF (simulated body fluid) reached 267 wt% and 254 wt% of the sample, respectively. Additionally, the mesopores can also act as hosts for the accommodation of drugs. The Loading capacity of IBU (ibuprofen) reached up to 18 wt% of the sample, and its release was relatively fast, more than 85% of the drug was released within 12 h. The condensed core of the SiO2 nanofiber not only endowed the sample with a high flexibility, but also slowly released silver to possess a sustained antibiotic effect. Considering its effective exudate-absorption ability, dual drug-release profiles (fast release of IBU and sustained release of silver), together with its chemical and physical stability, biocompatibility and high flexibility, Ag-cSiO2@mSiO2 could be a promising wound dressing material.

Intense Red and Yellow Emissions from Sr2SiO4 : Eu3 + ( Eu2 + ) Electrospun Nanofibers

We experimentally demonstrated a single-mode laser at 1056 nm with Nd-doped phosphate glass microstructured optical fiber (MOF), which was fabricated with conventional stack-and-draw method. The laser action was observed from a Fabry-Perot cavity formed by placing two dichroic mirrors of ∼100 and 85% reflectivity, to the two end facets of MOF. Pumped by CW laser diodes (LDs) at 808 nm, the MOF laser yielded a maximum output power of 8.5 mW and a slope efficiency of 2%.