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采用固相法在500℃下成功制备Zn 2+ 掺杂BiOCl:Eu 3+ 层状半导体, 并研究了Zn 2+ (0~20mol%)掺杂对Eu 3+ 激活BiOCl层状半导体发光性能的影响。利用X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电镜(SEM)、傅里叶变换红外光谱(FT-IR)、激发–发射光谱、荧光寿命衰减曲线对样品的结构和性能进行表征。研究发现, 随Zn 2+ 掺杂浓度增大, BiOCl晶体结构不变, Eu 3+ 荧光寿命延长, 但发光强度却出现先减后增的反常现象。综合分析表明这可能与BiOCl特殊的层状结构有关。通过XRD和XPS的表征可以推断: 当Zn 2+ 掺杂浓度≤10mol%, Zn 2+ 在BiOCl中掺杂方式以晶胞层间隙掺杂为主; 当Zn 2+ 掺杂浓度>10mol%后, 掺杂方式逐渐向取代掺杂转变。两种掺杂机制对Eu 3+ 荧光寿命的改变以及形成缺陷对基质能量传递效率的影响可能是形成上述反常现象的主要原因。研究结果有助于认识稀土掺杂层状半导体的发光性能及影响规律, 并对Eu 3+ 掺杂BiOCl这类新型发光材料的开发设计具有指导意义。

In this paper, Er3+/Eu3+ co-doped BiOCl phosphors are synthesized by the conventional solid state method at 500℃, which are characterized by XRD, SEM, absorption spectra, excitation spectra and emission spectra. XRD analysis indicates that the samples exhibit pure tetragonal phase BiOCl. In SEM pictures, the samples exhibit smooth plate-like particles. The absorption spectra indicate that Er3+/Eu3+ ion dopants result in an impurity energy level, and the excitation spectra show that the sample has excellent broadband near ultraviolet (NUV)-exciting ability, which is due to the electronic transitions of the BiOCl bandgap. Under at 380 nm excitation, the emission bands located at 410 nm (2H9/2→4I15/2), 525 nm (2H11/2→4I15/2), 554 nm (4S3/2→4I15/2), 673 nm (4F9/2→4I15/2) of Er3+ ions, and 581 nm (5D0→7F0), 594 nm (5D0→7F1), 622 nm (5D0→7F2), 653 nm (5D0→7F3), 699 nm (5D0→7F4) of Eu3+ ions can be observed, respectively. Moreover, contrary to most of the Er3+/Eu3+-activated phosphors, the Er3+/Eu3+ co-doped BiOCl phosphor shows the unique and effective emission of the violet (Er3+) and far-red (Eu3+), which results from the particular structure of BiOCl crystals. The tunability in color of emitted radiation has been visualized by using chromaticity diagram on changing the doping concentration. Results show that the Er3+/Eu3+ co-doped BiOCl is a promising phosphor for near UV white LEDs.

The green long-after-glow luminescence from Tb3+-doped Sr2SiO4 phosphors, which are synthesized by the high temperature solid state reaction in a reductive atmosphere, is observed in this paper. The results show that under ultraviolet excitation, the obtained phosphors produce an intense green-lighting-emission from the Tb3+, and the green-lighting long-after-glow luminescence related to Tb3+ can last half an hour after the irradiation source has been removed. Moreover, the effects of co-doping Li+, Dy3+, Er3+, Gd3+, and Yb3+ with Tb3+ on the decay properties and thermoluminescence properties are investigated to confirm the long-after-glow mechanism.

The Er3+/Yb3+ co-doped transparent oxyfluoride glass-ceramics containing CaF2 nano-crystals were successfully prepared. After heat treatments, transmission electron microscopy (TEM) images showed that CaF2 nano-crystals of 20–30 nm in diameter precipitated uniformly in the glass matrix. Comparing with the host glass, high efficiency upconversion luminescence of Er3+ at 540 nm and 658 nm was observed in the glass ceramics under the excitation of 980 nm. Moreover, the size of the precipitated nano-crystals can be controlled by heat-treatment temperature and time. With the increase of the nano-crystal size, the intensity of the red emission increased more rapidly than that of the green emission. The energy transfer process of Er3+ and Yb3+ was convinced and the possible mechanism of Er3+ up-conversion was discussed.

Transparent Tm3+/Er3+/Yb3+ co-doped oxyfluorogermanate glass ceramics containing BaF2 nanocrystals are prepared. Under excitation of a 980-nm laser diode (LD), compared with the glass before heat treatment, the Tm3+/Er3+/Yb3+co-doped oxyfluorogermanate glass ceramics can emit intense blue, green and red up-conversion luminescence and Stark-split peaks; X-ray diffraction (XRD) and transmission electron microscope (TEM) results show that BaF2 nanocrystals with an average diameter of 20 nm are precipitated from the glass matrix. Stark splitting of the up-conversion luminescence peaks in the glass ceramics indicates that Tm3+, Er3+ and (or) Yb3+ ions are incorporated into the BaF2 nanocrystals. The up-conversion luminescence intensities of Tm3+, Er3+ and the splitting degree of luminescence peaks in the glass ceramics increase significantly with the increase of heat treat temperature and heat treat time extension. In addition, the possible energy transfer process between rare earth ions and the up-conversion luminescence mechanism are also proposed.

We report the effects of self-reduction of glass matrix on the broadband near infrared (NIR) emissions from Bi-doped alkali earth aluminoborosilicate glasses. Bi2O3 -doped as well as Eu2O3, -doped as a comparison, 35SiO2-25AlPO4-12.5Al2O3-12.5B2O3-15RO (R=Ca,Sr,Ba) glasses were prepared in air. Results show that the self-reduction process of Eu3+→Eu2+ occurs in this glass matrix. Meanwhile the intensity of NIR emission peaked at about 1300nm increases with the increase in the radius of alkali earth ions, while the intensity of both NIR emission peaked at about 1100nm and the red emission from Bi2+decreases. Then the origins of infrared-emitting bismuth centers were discussed according to the correlation of the conversion of Bi ions with the size of alkali earth ions. The results of this work is helpful for understanding the nature of Bi-NIR-emission and may be a guide for the selection of composition of high performance Bi-doped glass.

Influences of alkaline earth oxides on super broadband near infrared luminescence properties from Bi-doped RO-Al2O3-SiO2 (R=Ca, Sr, Ba) aluminosilicate glasses are investigated. The results show that under different pumping sources, the near infrared (NIR) luminescence shows different behaviors. Under 808 nm excitation, the infrared emission located at 1300 nm with lifetime more than 600 ms is observed, whose intensity increases with the increase of ionic radius. However, under 690 nm excitation, the luminescence at 1100 nm with a full width at half maximum of 400 nm decreases with the increase of ionic radius. According to the above results, it is suggested that infrared emissions may originate from Bi+ and BiO.

usc Photonic crystals (PCs) with periodic dielectric structures are capable to control the propagation of photons when photon energy is in the region of photonic bandgap. The upconversion luminescence (UCL) of nanocrystals coated on the PCs surface can be enhanced by the PCs effects. While surface plasmon resonance(SPR) of noble metal nanoparticles (NPs) is being extensively applied to enhance the UCL properties of nanocrystals. However, the PCs or SPR effect are developed separately for the UCL enhancement. In this work, we present a facile preparation method of the Au NPs embedded inverse opals, which was used as substrates to improve the UCL properties of NaYF₄:Yb³⁺,Er³⁺NPs. The significant luminescence enhancement of NaYF₄:Yb3⁺,Er³⁺ up converting NPs was obtained by the coupling between the SPR of Au NPs and PCs effects from AuNPs embedded inverse opals substrates. The finding demonstrated that the AuNPs embedded inverse opals as substrates may be useful for the enhanced UCLof other phosphors, producing novel photonic devices. Refereed/Peer-reviewed

Surface plasmon effects of Ag nanostructures are being extensively applied to enhance upconversion (UC) luminescence properties of rare-earth-ion-doped nanoparticles. However, the plasmonic absorption bands from various Ag nanostructures are generally located at a visible region that cannot couple effectively with the 980 nm near infrared excitation light, resulting in a smaller UC emission enhancement factor. In this paper, we present a facile method to fabricate the porous Ag films with tunable and ultra-broad surface plasmonic absorption by using a polystyrene microsphere as a hard template, and then investigate the influence of tunable surface plasmonic absorption (SPA) on the UC emission. About 10 and 60-fold UC emission enhancement of NaYF4: Yb3+, Er3+ nanoparticles was obtained on the Ag films with narrow and ultra-broad SPA ranging from 350 to 1400 nm, respectively. The UC emission increases 60 fold at the surface of porous Ag film with the ultra-broad plasmonic absorption, which is attributed to efficient coupling between the ultra-broad SPA and the 980 nm near infrared excitation light and UC emission. The results demonstrate Ag film with ultra-broad plasmonic absorption is more appropriate as a substrate for the enhancement of UC emission in comparison with the narrow plasmonic absorption Ag film usc Refereed/Peer-reviewed

The upconversion luminescence (UCL) of rare earth ion-doped nanoparticles excited at 808 nm is more suitable for biological applications than those excited at 980 nm, as the former avoids overheating of biological tissues caused by 980 nm excitation light. However, one of the major challenges limiting the application of UCL of rare earth ion-doped nanoparticles excited at 808 nm is their low UCL efficiency. Inthis work, tunable plasmonic Au films were used to improve the UCL of Nd³⁺sensitized NaYF₄:Yb³⁺,Er³⁺nanoparticles. The results show that the enhancement factors and mechanisms of the UCL of Nd³⁺-sensitized nanoparticles are associated with the tunable plasmonic properties of Au films. The maximum enhancement factors of green and red UCL of NaYF₄:Nd³⁺,Yb³⁺,Er3³⁺ nanoparticles excited at 808 nmare 6 and 5.8 on the Au film with ultra-broad plasmonic absorption band, respectively. A differentiation of UCL-enhanced mechanisms of NaYF₄:Nd³⁺,Yb³⁺,Er³⁺ nanoparticles on tunable plasmonic Au films was observed. The enhanced UCL of NaYF4:Nd³⁺,Yb³⁺,Er³⁺ nanoparticles on the Au film with a narrow plasmonic absorption peak was due to the enhanced excitation field. The enhanced excitation field and energy-transfer enhancement was responsible for the UCL enhancement of NaYF₄:Nd³⁺,Yb³⁺,Er³⁺ nanoparticles on the Au film with ultra-broad plasmonic absorption. usc

The SiO2:Yb3 +, Tb3 + inverse opal photonic crystals containing gold nanoparticles were prepared by the self-assembly technique combined with a sol-gel method, and their up-conversion luminescence properties have been investigated under the excitation of 980 nm. The upconversion emission bands from the Tb3 + ions were located at 489, 544, 585 and 622 nm in the SiO2:Yb3 +, Tb3 + inverse opals. The influence of Au nanoparticles on the upconversion emission was observed in the SiO2:Yb3 +, Tb3 + inverse opals. The upconversion emission of SiO2:Yb3 +, Tb3 + inverse opals was enhanced, which is from the population increasing of 5D4 luminescent level of Tb3 + ions induced by surface plasmon effects of Au nanoparticles usc Refereed/Peer-reviewed

The surface plasmon resonance of Ag nanoparticles (NPs) and SiO2 coating had been extensively employed to improve the photoluminescence (PL) intensity of nanomaterials. In the article, the LaPO4:Eu3+ inverse opal photonic crystals were fabricated via combining a self-assembly process with a sol–gel method. The SiO2 shells were formed on the skeleton surface of LaPO4:Eu3+ inverse opals and the Ag NPs were added into the voids of LaPO4:Eu3+ inverse opals with the SiO2 shells. The influence of the SiO2 shells and Ag NPs on the PL of the LaPO4:Eu3+ inverse opals were investigated. About sevenfold luminescence enhancement of LaPO4:Eu3+ inverse opals was obtained by the coordination action of surface plasmon absorption effects of Ag nanoparticle and silica-coating effects. The luminescence enhancement mechanisms of LaPO4:Eu3+ inverse opals were discussed usc Refereed/Peer-reviewed

usc Rare earth ions doped upconversion nanoparticles have broad applications ranging from biological imaging to solar energy conversion. However, the application of upconversion nanoparticles has been limited due to their low upconversion efficiencies. In this paper, two kinds of Au films with tunable and broad surface plasmonic absorptions were used to enhance the upconversion emission of NaYF4:Yb3+, Er3+ nanoparticles, respectively. The results demonstrated that the upconversion enhancement is highly dependent on the topography of Au films. About 77 and 40-fold enhancement were obtained for the green and red UC emissions of NaYF4:Yb3+, Er3+ nanoparticles on the irregular and random Au particles. About 121 and 78-fold enhancement were obtained for the green and red UC emissions of NaYF4:Yb3+, Er3+ nanoparticles on continuous Au films with papilla Au nanoparticles, respectively. In contrast to that of NaYF4:Yb3+, Er3+ nanoparticles deposited on quartz substrate, and the corresponding UC efficiency of NaYF4:Yb3+, Er3+ nanoparticles on irregular and random Au particles and continuous Au films with papilla Au nanoparticles increased by 50% and 100%, respectively. The enhancement of UC emission may be attributed to the increase of radiative decay rate and the enhancement of excitation field Refereed/Peer-reviewed

Energy transfer has attracted extensive attention due to its widespread applications in medical diagnostics, DNA analysis and lighting devices. There are few reports on the energy transfer from rare earth ions to dyes. In the present work, the SiO2:Tb inverse opals with and without Au nanoparticles were prepared, and the organic rhodamine-B (RhB) dyes were filled into the voids of SiO2:Tb inverse opals. Non-radiative and radiative energy transfer processes from the SiO2:Tb inverse opals to the RhB were observed. The influence of Au nanoparticles and photonic band gap on the energy transfer from SiO2:Tb inverse opals to the RhB was investigated. The Au nanoparticles enhanced energy transfer was observed due to the surface plasmon resonance effects of the Au nanoparticles. When the emission peaks from the SiO2:Tb inverse opal is overlapped with the photonic band gap, the emission suppression of the SiO2:Tb inverse opal as well the emission enhancement of the RhB dyes were obtained, which is attributed to improved energy transfer caused by the photonic band gap. The steady state rate equations were used to explain enhancement of energy transfer caused by the photonic band gap usc Refereed/Peer-reviewed

LaPO4:Eu3+ three dimensional ordered macroporous (3DOM) films co-doped with Li+ ions were prepared via a sol-gel method combined with template-assisted process, and their photoluminescence (PL) properties and decay behaviours have been investigated. The emission peaks locat at 593 (5D0 7F1), 615 (5D0 7F2), 653 (5D0 7F3) and 698 nm (5D0 7F4) from Eu3+ were observed in the LaPO4:Eu3+ 3DOM films. The Li+ co-doping exhibited various influences on the 593, 615, 653 and 698 nm photoluminescence. The 593, 653 and 698 nm emission of Eu3+ increased by a factor of 6 by co-doping of Li+ ions, while the 615 nm emission corresponding to the 5D0 7F2 transition of Eu3+ increased by nearly 17-fold. The significant enhancement of 615 nm emission corresponding to the 5D0 7F2 transition of Eu3+ is attributed to its increased radiative decay rate. usc Refereed/Peer-reviewed

usc Refereed/Peer-reviewed The silica-coated LaPO₄:Eu³⁺ three dimensional ordered macroporous (3DOM) materials were prepared via a template-assisted process. The influence of SiO₂ shell on photoluminescence of LaPO₄:Eu³⁺ 3DOM materials was investigated. The photoluminescence intensity of LaPO₄:Eu³⁺ 3DOM materials was strongly enhanced due to the suppression of surface quenching effect caused by the formation of SiO₂ shells. The luminescence lifetime change of LaPO₄:Eu³⁺ 3DOM material after and before SiO₂ shell was observed, which is attributed to the medium refractive index variety of the LaPO₄Eu³⁺ 3DOM material caused by formation of SiO₂ shells.

usc Refereed/Peer-reviewed The YbPO₄:Er³⁺ three dimensional ordered macroporous (3DOM) materials with upconversion luminescence and Ag nanoparticles were fabricated via template-assisted process and sodium citrate reduction method, respectively. The upconversion emission bands centered at 545 (⁴S₃/₂ -> ⁴I₁₅⁄₂), 650 (⁴F₉⁄₂ -> ⁴I₁₅⁄₂), and 526 nm (2H₁₁⁄₂ -> ⁴I₁₅⁄₂) from Er³⁺ were obtained in the YbPO₄:Er³⁺ three dimensional ordered macroporous (3DOM) materials. The influence of the Ag nanoparticles on upconversion luminescence of YbPO₄:Er³⁺ 3DOM materials were investigated by directly adding the Ag nanoparticles into the voids of YbPO₄:Er³⁺ 3DOM materials. The results show that the upconversion luminescence of YbPO₄:Er³⁺ 3DOM materials were enhanced after the addition of Ag nanoparticles, and the biggest 6-fold enhancement is obtained. The upconversion luminescence enhancement is attributed to the located surface plasmon effect of the Ag nanoparticles.

usc Refereed/Peer-reviewed In this paper, a simple effective approach has been developed to enhance upconversion emission of three-dimensionally ordered macroporous materials, which is attributed to formation of silica shell around surface of three-dimensionally ordered macroporous materials. This approach involves the preparation of Bi₂Ti₂O₇:Er³⁺, Yb³⁺ three-dimensionally ordered macroporous materials and the formation of amorphous SiO₂ shell on the macroporous surfaces of three-dimensionally ordered macroporous materials. The influence of silica shell on the upconversion emission of Er³⁺ ions was investigated, and the enhanced upconversion emission was observed in the Bi₂Ti₂O₇:Er³⁺, Yb³⁺ three-dimensionally ordered macroporous materials owing to the suppression of surface quenching effect caused by the formation of silica shells.

Rare-earth-ion-doped upconversion (UC) nanoparticles have generated considerable interest because of their potential application in solar cells, biological labeling, therapeutics, and imaging. However, the applications of UC nanoparticles were still limited because of their low emission efficiency. Photonic crystals and noble metal nanoparticles are applied extensively to enhance the UC emission of rare earth ions. In the present work, a novel substrate consisting of inverse opal photonic crystals and Ag nanoparticles was prepared by the template-assisted method, which was used to enhance the UC emission of NaYF₄: Yb³⁺, Er³⁺ nanoparticles. The red or green UC emissions of NaYF₄: Yb³⁺, Er³⁺ nanoparticles were selectively enhanced on the inverse opal substrates because of the Bragg reflection of the photonic band gap. Additionally, the UC emission enhancement of NaYF₄: Yb³⁺, Er³⁺ nanoparticles induced by the coupling of metal nanoparticle plasmons and photonic crystal effects was realized on the Ag nanoparticles included in the inverse opal substrate. The present results demonstrated that coupling of Ag nanoparticle with inverse opal photonic crystals provides a useful strategy to enhance UC emission of rare-earth-ion-doped nanoparticles. usc Refereed/Peer-reviewed