β-NaYF4:Yb,Er upconversion nanophosphor (UCNP) is known as one of the most efficient NIR-to-visible upconversion materials, which shows great potential in bioanalytical chemistry and bioimaging. However, its applications are greatly limited due to its low water dispersibility and thus poor biocompatibility. In this paper, poly(acrylic acid) (PAA)-based ligand exchange strategies are carried out to modify oleic acid-capped hydrophobic β-NaYF4:Yb,Er UCNPs into hydrophilic ones. After efficient surface modification, the presence of free carboxylic acid groups on the surfaces of UCNPs results in high solubility in water, and also allows further conjugation with NH2-containing biomolecules. Facilitated by the covalent linkage between the–COOH groups on UCNPs surfaces and –NH2 groups in antigen/antibody, a sensitive immunosensor is constructed by using PAA-functionalized β-NaYF4:Yb,Er UCNPs as biolabels. Through monitoring the upconversion fluorescence intensity or fluorescent imaging of the final immunocomplexes, high sensitivity is achieved for the proposed immunoassay and as low as 0.1 ng/mL goat anti-human immunoglobulin G (IgG) can be detected, which suggests that PAA-modified UCNPs may serve as an ideal candidate for use as bioanalysis and bioimaging probes.

采用高温固相法在1 350 ℃弱还原气氛下制备了Sr1-xBaxAl2O4:Eu2+ ,Dy3+ (x=0,0.2,0.4,0.6,0.8,1.0)长余辉材料,并对其微观结构和发光特性进行了分析.X射线衍射结果表明,当钡的掺杂摩尔分数x＜0.4时,样品晶体结构为SrAl2O4单斜晶系结构;当x≥0.4时,样品晶体结构为BaAl2O4六角晶系结构;而且随着钡对锶的取代,两种晶体结构的晶格常数都发生了一定程度的膨胀.光致发光测试结果表明,当x从0增大到1.0时,样品发射波长峰值也相应由515 nm逐渐蓝移到494 nm.通过热释光谱测试表明, SrAl2O4结构的样品的热释光峰所对应的温度比BaAl2O4 结构的要高,且对应SrAl2O4结构的样品的余辉时间更长,初始亮度更高.

采用高温固相法在1350℃弱还原气氛下制备了Sr1-xBaxAl2O4∶Eu^2＋,Dy^3＋（x=0,0.2,0.4,0.6,0.8,1.0）长余辉材料,并对其微观结构和发光特性进行了分析。X射线衍射结果表明,当钡的掺杂摩尔分数x〈0.4时,样品晶体结构为SrAl2O4单斜晶系结构;当x≥0.4时,样品晶体结构为BaAl2O4六角晶系结构;而且随着钡对锶的取代,两种晶体结构的晶格常数都发生了一定程度的膨胀。光致发光测试结果表明,当x从0增大到1.0时,样品发射波长峰值也相应由515nm逐渐蓝移到494nm。通过热释光谱测试表明,SrAl2O4结构的样品的热释光峰所对应的温度比BaAl2O4结构的要高,且对应SrAl2O4结构的样品的余辉时间更长,初始亮度更高。

As novel functional materials,long afterglow phosphors have drawn more and more attention in recent years because of a constantly growing market for their applications in traffic signs,emergency signage,watches and clocks,textile printing,among others.Amid the newly developed long afterglow materials which have already found commercial use,green-emitting SrAl2O4:Eu2+,Dy3+ is of special interest because of its high quantum efficiency,good stability and excellent persistent luminescence combined with an easy proces-sability.However the mechanism of afterglow phosphors is still unclear,even the effect of the reductive using on the producing process on the luminescence is not well studied.In this paper,compounds of SrAl2O4:Eu,Dy were prepared in air atmosphere by high temperature solid state reaction firstly,and then were treated in weak reductive atmosphere(95%N2+5%H2).Thirdly,in air atmosphere again,and finally,in weak reductive atmosphere(95%N2+5%H2).The effect of this process on the structure,luminescent properties,and themoluminescent spectra of the samples were studied by X-ray diffraction(XRD),fluorescent spectrophoto-meter and thermoluminescence dosimeter(TLD) respectively.The monoclinic structure remains the same irrespective of the process,and is in good agreement with that of the powder diffraction file(JCPDS) 34-0379(SrAl2O4).The reduction of Eu3+→Eu2+ was firstly observed in the aluminate phosphor of SrAl2O4:Eu,Dy synthesized in air condition and the reductive mechanism was also discussed in this paper.Eu3+ shows completely different luminescent properties with Eu2+ in SrAl2O4.Eu3+ has two narrow,intense spectra peaking at 592 nm and 612 nm,which resulted from the 5D0→7F1 transition and 5D0→7F4 transition respectively,implied that the Eu3+ may occupy two different lattice sites in the host crystal lattice;while Eu2+ has only one broad band spectra peaking at 513 nm,which resulted from the 4f65d→4f7 transition.The emission of Dy3+ was not found in all the four samples,indicated that the Dy3+ ions play a roll as trap centre in the phosphor,but not the luminescence centre.The concentration of Eu2+ in the samples treated in weak reductive atmosphere greatly increased whereas the concentration of Eu3+greatly decreased when compared to the samples treated in air atmosphere.The samples treated in weak reductive atmosphere have much higher thermoluminescent peak than that of the samples treated in air atmosphere.But all the samples,irrespective being treated in air atmosphere or reductive atmosphere,have the same trap depth(about 0.65 eV),which derived from Dy3+.All these phenomena indicated that,for the long after-glow phosphor material of SrAl2O4:Eu,Dy prepared in air atmosphere,the process of being treated in weak reductive atmosphere,air atmosphere and weak reductive atmosphere orderly,changes the valence of Eu ion and luminescence intensity,but doesn't change the trap depth in the material.

Long persistent phosphors SrxCa1−xAl2O4: Eu2+, Dy3+ (x=0, 0.2, 0.4, 0.6, 0.8, 1.0) were prepared through a solution-combustion method at 600°C. The phase structures of the phosphors were characterized by X-ray diffraction. The major phase was CaAl2O4 when x<0.8 with SrAl2O4 phase as a minor phase, whereas the major phase was SrAl2O4 when x≥0.8. The results indicated that the phase structure of the samples changed from CaAl2O4 to SrAl2O4 when x changed from 0 to 1.0. The emission colors changed accordingly from blue to green-blue and then to green in visible range, as evidenced from the emission spectra. The decay characteristics showed that the life times also varied with the value of x. These results revealed that the emission colors and life times can be adjusted by the value of x. Furthermore, the reason that the emission colors and decay times varied with x has been ascribed to the distortion of crystal lattice.

The modification effect of the doping of Yb3+ ions, as an auxiliary activator, onto the luminescent properties of SrAl2O4:Eu2+, Dy3+ phosphor was studied for the first time. The phosphorescent nanoparticles were prepared by the combustion method. The experimental results indicate that the appropriate doping of Yb3+ ions largely improves phosphorescence of the phosphors with more intense luminescence, higher brightness, and no change in emission spectrum peaked at 513nm. Meanwhile the decay speed of the phosphor nanoparticles rises increasingly with the doping ratio of Yb3+ ions, whereas an excessive Yb3+ ions doping leads to the disappearance of the pure monoclinic phase of SrAl2O4 and the appearance of the weak diffraction lines of the YbAlO3 phase. The phosphorescent mechanism of the phosphors could be well understood based on the hole, thermally released from the trap levels of Dy3+ and Yb3+.

Rare-Earth doped strontium aluminate phosphors were synthesized through combustion method.XRD results indicate that the dominant host phase is SrAl2O4 when n(Al)∶n(Sr)=2.With the increasing of Al∶Sr ratios,the new crystalline phase of Sr4Al14O25 was initially formed.The phase SrAl12O19 was formed when Al∶Sr ratios increased to 4,and this phase was the dominate phase when Al∶Sr ratios increased to 12.The emission spectra show that the peaks of SrAl2O4∶Eu2+,Dy3+ and SrAl12O19∶Eu2+,Dy3+ lied round 519 and 512nm,respectively.The decay curves show that the decay process of all the samples with different crystalline phases consist of the initial fast process and the latter slow process.Intensity and decay lifetimes of the samples vary with the different crystalline phases.

采用燃烧合成方法，在600℃温度条件下，首次合成镱／钕掺杂的SrxCa1-xAl2O4：Eu^2＋，Dy^3＋长余辉光致发光材料。通过X射线衍射和发射光谱分析，结果表明镱或钕的掺杂几乎没有改变材料的晶体结构以及Eu^2＋发光中心电子的4f^65d→4f^7的跃迁环境。余辉衰减特性曲线显示，与SrAl2O4：Eu^2＋，Dy^3＋相比较，SrAl2O4：Eu^2＋，Dy^3＋，Yb^3＋的初始发光亮度有明显提高，余辉时间略微减小，而SrAl2O4：Eu^2＋，Dy^3＋，Nd^3＋的初始亮度却大幅度的降低，同时余辉时间也降低。热释发光实验的进一步研究发现，不同的发光体存在不同深度的陷阱能级，而且陷阱能级的深度与余辉时间相对应。

以高纯度的硝酸锶、硝酸钙、硝酸铝和稀土氧化物为原料，以硼酸为助溶剂，采用燃烧法在600℃的低温条件下合成SrxCa1-xAl2O4：Eu^2＋，Dy^3＋（x=0、0．6、1．0）长余辉发光材料。光致发光光谱分析表明样品发光光谱均为宽带谱，样品CaAl2O4：Eu^2＋，Dy^3＋和样品SrAl2O4：Eu^2＋，Dy^3＋的发射谱峰值分别位于442和511nm左右，样品Sr0.6Ca0.4Al2O4：Eu^2＋，Dy^3＋有两个发射峰，分别位于442和507nm左右。余辉检测结果表明：样品余辉衰减都是由初始的快衰减过程和其后的慢衰减过程组成，但不同样品衰减快慢不同。利用热释光检测结果对样品中存在的陷阱能级进行了计算，讨论了样品的余辉衰战机制。通过对锶钙配比（X值）不同的样品余辉发光性能的比较分析，研究锶钙配比对余辉发光性能的影响。研究表明：通过调节锶钙配比（X值）的方法，能有效调控余辉发光颜色和衰减快慢。