新型三嗪桥连的双1,8-萘酰亚胺衍生物的合成及其光物理行为

以1,8-萘酰亚胺和三聚氯氰为主要原料, 合成了两种由三嗪环桥连的双1,8-萘酰亚胺化合物3 和5. 采用紫外-可见光谱和荧光光谱等手段考察了两种化合物在不同溶剂中的光物理行为. 与参比化合物N-丁基-1,8-萘酰亚胺相比, 在二氯甲烷、三氯甲烷和甲醇等极性溶剂中, 化合物3和5除了在短波区(λ<400 nm)存在1,8-萘酰亚胺的特征荧光发射峰外, 在长波区(>450 nm)均产生一个较强的新荧光发射峰, 表现出分子内激基缔合物的光物理行为. 与化合物5相比, 由于化合物3特殊的构象异构, 其荧光强度发生严重的猝灭. 在非极性溶剂甲基环己烷中, 化合物5 由于存在较强的分子间氢键作用而聚集, 受激后形成了较稳定的分子间激基缔合物, 但未观察到明显的分子内激基缔合物的形成. 在甲苯溶剂中, 化合物3和5与甲苯分子形成了激基复合物, 并未形成分子内激基缔合物. 进一步研究3和5的固态激发态性质, 发现化合物3和5的固体薄膜受激后分别在465和469 nm处出现激基缔合物的特征荧光发射峰.     

微乳液法合成白光LED NaLu(MO_4)_2:Eu~(3+)/Eu~(3+),Tb~(3+)(M=W,Mo)荧光粉

采用微乳液法制备Na Lu(WO4)2-x(Mo O4)x∶8%Eu3+(x=0,0.5,1.0,1.5,2.0)/y%Eu3+,5%Tb3+(y=1,3,5,7,9)系列荧光粉。通过X射线衍射(XRD)表征,所制样品的X射线衍射峰与标准卡片PDF#27-0729基本吻合,表明所制的样品为白钨矿结构,属于四方晶系。扫描电镜(SEM)显示制备的纳米粒子是梭子状的,粒径大约是110 nm。激发发射光谱显示,在Eu3+离子掺杂物质的量分数为8%时,Na Lu(WO4)(Mo O4)∶Eu3+发光强度最大。Na Lu(WO4)2-x(Mo O4)x∶8%Eu3+(x=0,0.5,1.0,1.5,2.0)荧光粉在nMo/nW比达到1∶1(x=1)时发光强度最大,强烈的红光发射表明该材料可用于白光LED材料。该荧光粉在268、394和466 nm波长光激发下分别发出橙红色、黄色和淡黄色光,可以满足不同光色需要。Na Lu(WO4)(Mo O4)∶y%Eu3+,5%Tb3+(y=1,3,5,7,9)荧光粉,随着y值增大,从绿光区(x=0.278,y=0.514)进入白光区(x=0.356,y=0.373),(x=0.278,y=0.313),同时观察到Tb3+到Eu3+有效能量传递。     

基于油酸辅助水热法制备NaLuF4:Ln3+及光谱性质

采用油酸辅助水热法合成了具有上下转换发光性能的NaLuF_4∶Ce~(3+)、NaLuF_4∶Ce~(3+),Tb~(3+)、NaLuF_4∶Yb~(3+),Tm~(3+)、NaLuF_4∶Yb~(3+),Er~(3+)以及NaLuF_4∶Yb~(3+),Er~(3+),Tm~(3+)荧光粉材料。X射线衍射(XRD)表征结果表明产物各个衍射峰与标准卡片PDF#27-0726较好的吻合,得到六方相NaLuF_4晶体。扫描电镜(SEM)显示产物形貌为六棱柱,由粒径分布图可知属于微米级材料。NaLuF_4基质中单掺Ce~(3+)时,研究掺杂浓度对样品发光性能的影响表明NaLuF_4∶0.09Ce~(3+)的发光强度最大。双掺Ce~(3+)、Tb~(3+)时,详细讨论了NaLuF_4基质中Ce~(3+)→Tb~(3+)的能量传递机制,可认为是偶极-四极作用。在980 nm激光激发下,增大Yb~(3+)的掺杂浓度可以使Er~(3+)的红(~4F_(9/2)→~4I_(15/2))/绿(~2H_(11/2)→~4I_(15/2),~4S_(3/2)→~4I_(15/2))光发射比例增大,Er~(3+)的红光和绿光发射过程均属于双光子发射,Tm~(3+)的蓝光发射过程属于三光子发射,并且NaLuF_4∶0.20Yb~(3+),0.005Er~(3+),0.005Tm~(3+)样品实现了白光发射(x=0.335,y=0.385)。     

航天探测器CO2两相主动热控系统试验及分析

本文设计了一种以机械泵驱动的CO2两相散热系统,用于高热流密度航天探测器的高精度温度控制.分别对其稳态特性包括散热热流密度、流动阻力特性和动态性能包括启动特性、控温特性试验研究发现:机械泵CO2两相控温系统控温精度不低于1.5℃,启动性能和控温实时性能良好.     

Synchronization in a Mutualism Ecosystem Induced by Noise Correlation

Understanding the cause of the synchronization of population evolution is an important issue for ecological improvement. Here we present a Lotka-Volterra-type model driven by two correlated environmental noises and show, via theoretical analysis and direct simulation, that noise correlation can induce a synchronization of the mutualists. The time series of mutual species exhibit a chaotic-like fluctuation, which is independent of the noise correlation, however, the chaotic fluctuation of mutual species ratio decreases with the noise correlation. A quantitative parameter defined for characterizing chaotic fluctuation provides a good approach to measure when the complete synchronization happens.     

Curved fronts in the Belousov–Zhabotinskii reaction–diffusion systems in R2

In this paper we consider a diffusion system with the Belousov–Zhabotinskii (BZ for short) chemical reaction. Following Brazhnik and Tyson [4] and Pérez-Muñuzuri et al. [45], who predicted V-shaped fronts theoretically and discovered V-shaped fronts by experiments respectively, we give a rigorous mathematical proof of their results. We establish the existence of V-shaped traveling fronts in ${\mathbb{R}}^2$ by constructing a proper supersolution and a subsolution. Furthermore, we establish the stability of the V-shaped front in ${\mathbb{R}}^2$.     

Intercalation and photophysical properties of the tetra-(8-hydroxyquinolinato) boron complex and 3,3',4,4'-benzophenone tetracarboxylic anion into Mg-Al layered double hydroxides

The tetra-(8-hydroxyquinolinato) boron complex (Bq) and 3,3',4,4'-benzophenone tetracarboxylic anion (BPTC) were successfully intercalated into layered double hydroxides with an ion-exchange method. Elemental analyses, powder X-ray diffraction, FTIR spectra, and thermogravimetric analyses indicated that the hydrothermal treatment could efficiently improve the reaction process, the purity and crystallinity of products, and that Bq and BPTC molecules steadily arranged with C2 axis perpendicular to the layer plane, and the J-type aggregate in the host interlayer, respectively. The fluorescence studies showed that, compared with those observed in the dilute solutions of the guests, the spectra of Mg3Al-Bq and Mg3Al-BPTC evolved to the high-energy side and the low-energy side with increasing their loading, respectively, which were attributed to various arrangements of guests and the increased intermolecular interaction. Furthermore, their fluorescence intensity gradually decreased with increasing the intercalated guest content due to the concentration quenching, and Mg3Al-Bq exhibits enhanced solid-state blue luminescence due to a more rigid and constrained environment of the host.     

微乳液法合成白光LED NaLu(MO4)2:Eu3+/Eu3+,Tb3+(M=W, Mo)荧光粉

采用微乳液法制备NaLu(WO₄)_2-x(MoO₄)x:8%Eu³⁺(x=0, 0.5, 1.0, 1.5, 2.0)/y%Eu³⁺,5%Tb³⁺(y=1, 3, 5, 7, 9)系列荧光粉.通过X射线衍射(XRD)表征,所制样品的X射线衍射峰与标准卡片PDF#27-0729基本吻合,表明所制的样品为白钨矿结构,属于四方晶系.扫描电镜SEM显示制备的纳米粒子是梭子状的,粒径大约是110 nm.激发发射光谱显示,在Eu³⁺离子掺杂浓度为8%时,NaLu(WO₄)(MoO₄):Eu³⁺发光强度最大.NaLu(WO₄)_2-x(MoO)x :8%Eu³⁺(x=0, 0.5, 1.0, 1.5, 2.0)荧光粉在Mo/W比达到1:1(x=1)时发光强度最大,强烈的红光发射表明该材料可用于白光LED材料.该荧光粉在268、394和466 nm波长光激发下分别发出橙红色、黄色和淡黄色光,可以满足不同光色需要.NaLu(WO)(MoO):y%Eu³⁺,5%Tb³⁺(y=1, 3, 5, 7, 9)荧光粉,随着y值增大,从绿光区(x=0.278, y=0.514)进入白光区(x=0.356, y=0.373), (x=0.278, y=0.313),同时观察到Tb³⁺到Eu³⁺有效能量传递.     

GdVO4:Ln3+(Ln=Eu,Tm,Dy)荧光粉的水热法制备及其发光性能

以EDTA为矿化剂,采用水热法制备了Gd VO4∶Dy~(3+)、Gd VO4∶Dy~(3+),Eu~(3+)和Gd VO4∶Dy~(3+),Eu~(3+),Tm~(3+)荧光粉,研究了所制备样品的相结构、形貌、荧光性质、Dy~(3+)到Eu~(3+)的能量传递及Dy~(3+)的4F9/2→6H15/2跃迁的衰减曲线。X射线衍射(XRD)确定了所合成的Gd VO4∶0.03Dy~(3+)、Gd VO4∶0.03Dy~(3+),0.07Eu~(3+)和Gd VO4∶0.03Dy~(3+),0.07Eu~(3+),0.07Tm~(3+)样品均为四方晶系;扫描电镜(SEM)显示Gd VO4∶0.03Dy~(3+),0.07Eu~(3+)和Gd VO4∶0.03Dy~(3+),0.07Eu~(3+),0.07Tm~(3+)均为棒状结构,平均长度分别约为0.458和0.491μm;通过研究Gd VO4∶Dy~(3+),Eu~(3+)的发射光谱和衰减曲线,佐证了Dy~(3+)到Eu~(3+)的能量传递过程,并确定了其能量传递的机制为偶极-偶极相互作用。通过调节Gd VO4∶0.03Dy~(3+),x Eu~(3+)荧光粉中Eu~(3+)的掺杂浓度实现了准白光输出(0.424,0.350);调节Gd VO4∶0.03Dy~(3+),0.07Eu~(3+),y Tm~(3+)荧光粉中Tm~(3+)的掺杂浓度,也实现了白光输出(0.346,0.301)。     

Chemical Constituents of Ampelopsis japonica

Chemistry of Natural Compounds -