Haiquan Su

A synthesis and up-conversional photoluminescence study of hexagonal phase NaYF4:Yb,Er nanoparticles

In this article, hexagonal phase NaYF4:Yb,Er (β-NaYF4:Yb,Er) nanoparticles with a controlled size and morphology were synthesized via a simple and environmentally friendly method under relatively mild conditions. The different F−/Y3+ molar ratios were used in the synthesis of hexagonal Yb3+,Er3+ codoped NaYF4 nanocrystals as a means of controlling the size and morphology of the nanocrystals. Subsequently, the morphology and structure of the products were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The effect of the F−/Y3+ molar ratio on the size and morphology of the products was examined. When the F−/Y3+ molar ratio was gradually increased, the products transformed from spherical hexagonal nanocrystals to regular hexagonal nanocrystals and the size of the products changed from 8 to 400 nm. That is to say, excessive F− ions were capable of accelerating for the formation of larger β-NaYF4:Yb,Er nanoparticles in our synthesis procedure. Meanwhile the upconversion photoluminescence of the nanocrystals was investigated in detail by fluorescent spectroscopy to reveal the relationship between the optical properties and the morphology and size of the products. As a consequence, the upconversion photoluminescence of the nanocrystals demonstrated a morphology and size dependence. Thus the fabrication of β-NaYF4:Yb,Er nanoparticles with different sizes and morphologies would satisfy the diverse requirements in various fields.

Fabrication and characterization of novel magnetic/luminescent multifunctional nanocomposites for controlled drug release

In this study, a new kind of multifunctional drug-release system combined with the interesting properties of up-conversion fluorescence, magnetism and controlled drug release was successfully prepared by encapsulation of NaYF4:Yb,Er nanocrystals, Fe3O4 functionalized α-ZrP nanocomposites and gentamicin sulfate (GS) with chitosan (CHI). In this system, the NaYF4:Yb,Er nanocrystals were adsorbed on the surface of zirconium bis-(monohydrogen orthophosphate) monohydrate (α-ZrP), while GS and Fe3O4 nanoparticles were intercalated into the interlayer of α-ZrP. Additionally, a thin layer of chitosan enwrapped the above nanocomposites. The resultant nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis, photoluminescence spectra (PL), magnetometry and other characterization methods. The results revealed that the as-prepared multifunctional nanocomposites exhibited efficient upconversion luminescence and magnetism that had potential in magnetic separation and bioimaging. Meanwhile, in vitro drug release tests using the obtained nanocomposites (pH 7.4 buffer solution at 37 °C) indicated that the nanocomposites exhibited a prolonged drug release rate. Further, the antibacterial activity of GS released from the system on Gram-negative Escherichia coli was tested. Our results suggested that the obtained multifunctionalized nanomaterials could take full advantage of each component, and might be very attractive for a variety of biomedical applications, such as bioimaging, drug targeting and bioseparation.

Preparations and characterizations of γ-Ce2S3@SiO2 pigments from precoated CeO2 with improved thermal and acid stabilities

A series of γ-Ce2S3@SiO2 pigments are prepared successfully by sulfurizing their corresponding precoated CeO2 with different thicknesses of SiO2 shell. Properties of the samples are investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric (TG) analysis and a spectrophotometer. The results show that when a well controlled thickness of SiO2 coated CeO2 is used as a precursor, γ-Ce2S3 nanoparticles with excellent properties are obtained. With the shell thickness increasing, the colours of the samples are expanded from red to orange to yellow. At the same time, the thermal and acid stabilities are also improved gradually.

Synthesis of Cobalt–Based Catalyst Supported on TiO2 Nanotubes and its Fischer–Tropsch Reaction

The cobalt–based Fischer–Tropsch (F–T) catalysts, in which Co3O4 nanocrystals, supported on TiO2 nanotubes were prepared and charactered. The structure of the catalysts was characterized by X–ray diffraction, Transmission electron microscope and energy–dispersive X–ray spectroscopy. And the catalytic activity in F–T reaction was also investigated. In the CO hydrogenation reaction, the cobalt species dispersed on the TiO2 nanotubes have higher selectivity and activity compare to sample in which Co3O4 nanocrystals supported on TiO2 bulk materials. According to the data of product selectivity, it can be concluded that cobalt–based F–T catalysts had higher selectivity and activity.

Bifunctional dual-modal luminescence nanocomposites: grafting down luminescence onto core–shell, up-conversional silica nanoarchitecture

Dual-modal luminescence nanocomposites (NCs) were successfully prepared via a facile and versatile strategy by coating the down-shifting emission (DS) ZnO quantum dots (QDs) onto core–shell NCs, in which up-conversion (UC) luminescence NaYF4:Yb3+, Er3+/Tm3+ nanoparticles (NPs) were coated by SiO2. The as-prepared NCs were characterized by X-ray powder diffraction (XRD), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray (EDX) analysis, nitrogen adsorption–desorption isotherms and other characterization methods. Due to both their strong NIR-to-visible upconversion luminescence under 980 nm excitation and bright visible emission under UV irradiation, the dual-mode luminescent NCs are potentially useful in highly sensitive fluorescent labeling, which may attract wide attention from the fields of chemistry, materials, nanotechnology, nanobiotechnology and nanomedicine.