Yanfeng Bi

Synergistic effect of upconversion and plasmons in NaYF4:Yb3+, Er3+, Tm3+@TiO2–Ag composites for MO photodegradation

Structure-based rational design of photocatalysts to enable combination of nanocomponents of radically different properties for enhanced solar energy utilization is a very challenging task. Herein, we integrated up-conversion material NaYF4:Yb3+, Er3+, Tm3+ with TiO2 shells and Ag nanoparticles to synthesise a new class of materials with good stability, broadband absorption from ultraviolet to near infrared, and excellent photocatalytic activity. Structure analysis proved that intimate contact between the NaYF4:Yb3+, Er3+, Tm3+ core and the TiO2 shell and between the TiO2 shell and Ag NPs is the reason for the enhanced photocatalytic activity. Furthermore, the materials also showed exceptionally high stability and reusability under similar experimental conditions. All these results reveal that hierarchical core–shell microspheres exhibit great prospects for developing efficient solar photocatalysts.

Synthesis and up-conversion photoluminescence properties of uniform monodisperse YbPO4:Ln3+ (Ln3+ = Er3+, Tm3+, Ho3+) hollow microspheres

Uniform monodisperse YbPO4 hollow microspheres have been successfully synthesized via the combination of a facile homogeneous precipitation approach, an ion-exchange process, and a calcination process for the first time. The crystal structure, morphology, and luminescence properties of the as-obtained samples have been characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and up-conversion (UC) luminescence spectroscopy. It is noted that the polystyrene (PS) microspheres essentially determine the shape and structure of the final products. Furthermore, the UC luminescence properties as well as the emission mechanisms of the YbPO4:Ln3+ (Ln3+ = Er3+, Tm3+, Ho3+) hollow microspheres were systematically investigated, which show green (Er3+, 4S3/2, 2H11/2–4I15/2), blue (Tm3+, 1G4–3H6) and red (Ho3+, 5F5–5I8) luminescence under 980 nm NIR excitation, which provides potential applications in bioanalysis, optoelectronic and nanoscale devices, future color displays and light-emitting devices, and so on.

Synthesis and luminescent properties of uniform monodisperse LuPO4:Eu3+/Tb3+ hollow microspheres

Uniform monodisperse LuPO4:Eu3+/Tb3+ hollow microspheres with diameters of about 2.4 µm have been successfully synthesized by the combination of a facile homogeneous precipitation approach, an ion-exchange process and a calcination process. The possible formation mechanism for the hollow microspheres was presented. Furthermore, the luminescence properties revealed that the LuPO4:Eu3+ and LuPO4:Tb3+ phosphors show strong orange-red and green emissions under ultraviolet excitation, respectively, which endows this material with potential application in many fields, such as light display systems and optoelectronic devices. Since the synthetic process can be carried out at mild conditions, it should be straightforward to scale up the entire process for large-scale production of the LuPO4 hollow microspheres. Furthermore, this general and simple method may be of much significance in the synthesis of many other inorganic materials.

Large-scale fabrication of porous YBO 3 hollow microspheres with tunable photoluminescence

Hollow lanthanide-doped compounds are some of the most popular materials for high-performance luminescent devices. However, it is challenging to find an approach that can fabricate large-scale and well-crystallized lanthanide-doped hollow structures and that is facile, efficient and of low cost. In this study, YBO3: Eu3+/Tb3+ hollow microspheres were fabricated by using a novel multi-step transformation synthetic route for the first time with polystyrene spheres as the template, followed by the combination of a facile homogeneous precipitation method, an ion-exchange process and a calcination process. The results show that the as-obtained YBO3: Eu3+/Tb3+ hollow spheres have a uniform morphology with an average diameter of 1.65 µm and shell thickness of about 160 nm. When used as luminescent materials, the emission colours of YBO3: Eu3+/Tb3+ samples can be tuned from red, through orange, yellow and green-yellow, to green by simply adjusting the relative doping concentrations of the activator ions under the excitation of ultraviolet light, which might have potential applications in fields such as light display systems and optoelectronic devices.

Large-scale synthesis and luminescence of GdPO4 hollow microspheres

GdPO4 hollow microspheres were synthesized by using a novel multi-step transformation synthetic route for the first time with polystyrene (PS) spheres as the template, followed by the combination of a facile homogeneous precipitation method, an ion-exchange process, and a calcination process. The XRD results indicated that the GdPO4 hollow microspheres have a pure hexagonal phase. The SEM and TEM images confirmed that the as-obtained GdPO4 hollow spheres have a uniform morphology with an average diameter of 2.7 μm and shell thickness of about 150 nm. The up-conversion luminescence properties as well as the emission mechanisms of the GdPO4:Yb3+, Ln3+ (Ln3+ = Tm3+, Er3+ and Ho3+) hollow microspheres were systematically investigated, which show blue (Tm3+, 1G4 → 3H6), green (Er3+, 4S3/2, 2H11/2 → 4I15/2), and red (Ho3+, 5F5 → 5I8) luminescence under 980 nm NIR excitation, providing potential applications in bioanalysis, optoelectronic and nanoscale devices, future color displays and light-emitting devices, and so on.

Facile Synthesis of GdF3:Yb3+, Er3+, Tm3+@TiO2–Ag Core–Shell Ellipsoids Photocatalysts for Photodegradation of Methyl Orange Under UV, Visible, and NIR Light Irradiation

To enhance solar energy utilization efficiency, goal-directed design of architectures by combining nanocomponents of radically different properties, such as plasmonic, upconversion, and photocatalytic properties may provide a promising method to utilize the most energy in sunlight. In this work, a new strategy was adopted to fabricate a series of plasmonic Ag nanoparticles decorated GdF3:Yb3+, Er3+, Tm3+-core@porous-TiO2-shell ellipsoids, which exhibit high surface area, good stability, broadband absorption from ultraviolet to near infrared, and excellent photocatalytic activity. The results showed that photocatalytic activities of the as-obtained photocatalysts was higher than that of pure GdF3:Yb3+, Er3+, Tm3+ and GdF3:Yb3+, Er3+, Tm3+@TiO2 samples through the comparison of photodegradation rates of methyl orange under UV, visible, and NIR irradiation. The possible photocatalytic mechanism indicates that hydroxyl radicals and superoxide radical play a pivotal role in the photodegradation. Furthermore, the materials also showed exceptionally high stability and reusability under UV, visible, and NIR irradiation. All these results reveal that core-shell hierarchical ellipsoids exhibit great prospects for developing efficient solar photocatalysts.

Facile Synthesis and Down-Conversion Emission of RE3+-Doped Lutetium Oxide Nanoparticles

Lu2O3:RE3+ (RE3+ = Eu3+, Tb3+, Ho3+) nanoparticles have been successfully synthesized by a facile homogeneous precipitation method with subsequent sintering process. The crystal structure, morphology and luminescence properties of the as-prepared samples have been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), photoluminescence (PL) and cathodoluminescence (CL) spectra. Upon ultraviolet (UV) and low-voltage electron beam excitation, Lu2O3:RE3+ (RE3+ = Eu3+, Tb3+, Ho3+) nanoparticles show strong red (Eu3+,5D0 → 7F2), green (Tb3+,5D4 → 7F5), and green (Ho3+,5S2 → 5I8) emissions. They exhibit a good advantage of multicolor emissions in the visible region, and endow these kinds of materials with potential application in many fields, such as light display systems, optoelectronic devices and biological imaging.

Highly Uniform Hollow GdF3 Ellipsoids: Controllable Synthesis, Characterization and Up-Conversion Luminescence Properties

In this paper, the hollow GdF3 ellipsoids were successfully synthesized through a facile hydrothermal approach. The results indicated that the as-obtained GdF3 sample has an orthorhombic structure and the average length and diameter of the hollow ellipsoids are 750 nm and 350 nm, respectively. The possible formation mechanism of the hollow GdF3 ellipsoids has been presented. The upconversion (UC) luminescence properties of the hollow GdF3: Yb3+/Ln3+ (Ln3+ = Er3+, Tm3+, Ho3+) ellipsoids were systematically investigated, which showed green (Er3+, 4S3/2, 2H11/2 → 4I15/2), blue (Tm3+, 1G4 → 3H6), and green (Ho3+, 5S2 → 5I8) luminescence under 980 nm NIR excitation, respectively. Furthermore, the UC white light was successfully obtained in the GdF3: Yb3+/Er3+/Tm3+ sample through adjusting relative doping concentration of Yb3+, Er3+ and Tm3+ ions. These findings may reveal potential applications in the fields of laser, bioanalysis, optoelectronic and nanoscale devices due to multicolor emissions in the visible region.

Uniform and Well-Dispersed LuBO3 Hollow Microspheres: Synthesis, Formation and Photoluminescence Properties

A hard template strategy is developed to fabricate the LuBO3: Eu3+/Tb3+ hollow microspheres using a novel multi-step transformation synthetic route for the first time with polystyrene (PS) spheres as the template, followed by the combination of a facile homogeneous precipitation method, an ion-exchange process, and a calcination process. The results show that the as-obtained LuBO3: Eu3+/Tb3+ hollow spheres have a uniform morphology with an average diameter of 1.8 μm and shell thickness of about 80 nm. When used as luminescent materials, the emission colors of LuBO3: Eu3+/Tb3+ samples can be tuned from red, through orange, yellow and green-yellow, to green by simply adjusting the relative doping concentrations of the activator ions under the excitation of ultraviolet (UV) light, which might have potential applications in the field such as light display systems and optoelectronic devices.