Eu~(2+),Mn~(2+)共激活碱土镁硅酸盐基红色荧光粉的发光性能

制备了以R3MgSi2O8(R=Ba,Sr,Ca)为基,Eu2+,Mn2+共激活的红色荧光粉并研究了其荧光性质。分别以Ba3MgSi2O8,Sr3MgSi2O8,Ca3MgSi2O8为基质时,由于晶体场环境不同,发光强度、发射峰产生相应变化。研究了以(Ba,Sr)3MgSi2O8为基的荧光粉中Ba,Sr相对量,及Eu2+,Mn2+浓度对发光性质的影响并探讨了Eu2+,Mn2+在基质中所处格位;结果表明,红光是由基质中处于九配位的Eu2+将能量传递给八面体六配位的Mn2+,而由Mn2+所发射的。     

Ca10(Si2O7)3Cl2:Eu2+Mn2+单-基质白光荧光粉的发光性质

用高温固相法合成了颜色可调的Ca10(Si2O7)3Cl2:Eu2+Mn2+荧光粉.研究了它的发光性质和Eu2+与Mn2+之间的能量传递.Eu2+离子在Ca10(Si2O7)3Cl2晶体中形成了峰值为426 nm和523 nm的5d→4f跃迁发光,Eu2+中心向Mn2+中心传递能量,敏化Mn2+离子4T1(4G)-6A1(6S)跃迁而产生585 nm的黄光发射.黄绿蓝3个发射带叠加在单一基质中实现了白光发射.3个发射带的激发谱范围位于250-480 nm处,Ca10(Si2O7)3Cl2:Eu2+Mn2+在紫外-近紫外波段(350～410 nm)范围内有很强的激发,是一种适合InGaN管芯激发的单一基质白光LED荧光粉.     

新型WLED荧光粉Ca2MgSi2O7:Ce3+,Eu2+的能量传递和光色研究

用高温固相法制备了 Ca2 MgSi2O7:Ce3+,Eu2,并研究其发光特性.Ce3+的发射带峰值位于410 nm,对应于Ce3+的5d→4f跃迁;Eu2+的发射带峰值位于530 nm,对应于Eu2+的5d→4f跃迁.双掺样品的发射光谱表明两种离子间存在高效的电偶极-电偶极能量传递.当Ce3+和Eu2浓度分别为2％和0.125％时,样品发射光谱(λex=360 nm)色坐标为(0.221,0.312),落在白光区.以上研究说明Ca2 MgSi2O7:Ce3+,Eu2+是一种适用于近紫外芯片的新型WLED荧光粉,其光色可调谐.     

Eu^2＋，Mn^2＋共激活碱土镁硅酸盐基红色荧光粉的发光性能

制备了以R3MgSi2O8(R＝Ba，Sr，Ca)为基，Eu^2 ，Mn^2 共激活的红色荧光粉并研究了其荧光性质。分别以Ba3MgSi2O8，Sr3MgSi2O8，Ca3MgSi2O8为基质时，由于晶体场环境不同，发光强度、发射峰产生相应变化。研究了以(Ba，Sr)3MgSi2O8为基的荧光粉中Ba，Sr相对量，及Eu^2 ，Mn^2 浓度对发光性质的影响并探讨了Eu^2 ，Mn^2 在基质中所处格位；结果表明，红光是由基质中处于九配位的Eu^2 将能量传递给八面体六配位的Mn^2 ，而由Mn^2 所发射的。     

Ca掺杂的Ba2Al2Si10N14O4:Eu2+荧光粉发光性能

通过固相反应制备了系列Ca掺杂的Ba2Al2Si10M14O4:Eu2+色荧光粉,发现当半径较大的Ba被Ca取代后导致了晶格的收缩,通过X射线衍射(XRD)测量和Unitcell软件计算发现Ca的最大掺杂量在20％.Ca掺人Eu0.4Ba1.6Al2Si10N14O4荧光粉后,可有效地提高光转换性能,并使激发光谱发生一定程度的红移和宽化,从而被近紫外宽波段光有效激发,与近紫外LED的发射光谱匹配.同时Ca的掺杂也使发射光谱发生了可控的红移,可以由520 nm的绿光红移至548 nm的黄光区域.进一步发现Eu2+的淬灭浓度随着20％ Ca的掺入而降低,这是由于Ca掺入导致的晶格收缩使Eu2+离子间距离减小.最后在CIE色度图中对不同Ca,Eu浓度的荧光粉的色坐标位置进行比较,发现可通过Ca,Eu浓度的变化在很大范围内调制荧光粉的发光性能.     

空气中合成固溶体荧光粉Ba_2(Zn,Mg)Si_2O_7∶Eu~(2+),Eu~(3+),Ce~(3+)及其发光特性

采用高温固相法在空气中合成了Ba1.97-yZn1-xMgxSi2O7∶0.03Eu,y Ce3+系列荧光粉。分别采用X-射线衍射和荧光光谱对所合成荧光粉的物相和发光性质进行了表征。在紫外光330~360 nm激发下,固溶体荧光粉Ba1.97-yZn1-xMgxSi2O7∶0.03Eu的发射光谱在350~725 nm范围内呈现多谱峰发射,360和500 nm处有强的宽带发射属于Eu2+离子的4f 65d1-4f 7跃迁,590~725 nm红光区窄带谱源于Eu3+的5D0-7FJ(J=1,2,3,4)跃迁,这表明,在空气气氛中,部分Eu3+在Ba1.97-yZn1-xMgxSi2O7基质中被还原成了Eu2+;当x=0.1时,荧光粉Ba1.97Zn0.9Mg0.1Si2O7∶0.03Eu的绿色发光最强,表明Eu3+被还原成Eu2+离子的程度最大。当共掺入Ce3+离子后,形成Ba1.97-yZn0.9Mg0.1Si2O7∶0.03Eu,y Ce3+荧光粉体系,其发光随着Ce3+离子浓度的增大由蓝绿区经白光区到达橙红区;发现名义组成为Ba1.96Zn0.9Mg0.1Si2O7∶0.03Eu,0.01Ce3+的荧光粉的色坐标为(0.323,0.311),接近理想白光,是一种有潜在应用价值的白光荧光粉。讨论了稀土离子在Ba2Zn0.9Mg0.1Si2O7基质中的能量传递与发光机理。     

碱土金属离子(Mg2+,Ca2+,Ba2+)掺杂对长余辉荧光粉SrAl2O4:Eu2+,Dy3+发光性能的影响

采用高温固相法制备了碱土金属离子(Mg2 ,Ca2 ,Ba2 )掺杂的SrAl2O4:Eu2 ,Dy3 长余辉荧光粉.XRD谱分析表明,随着基质中掺人的碱土金属离子(Mg2 ,Ca2 ,Ba2 )浓度增加,基质晶格常数也随之发生变化.Mg2 ,Ca2 和Ba2 3种碱土离子在SrAl2O4中的固溶范围分别为40%,15%和30%.光谱分析则表明在固溶范围内随着掺杂Mg3 ,Ca2 和Ba2 浓度的增大,样品的发射峰值会在480～530 nm范围出现规律性移动.适当浓度的Mg2 ,Ba2 掺杂会不同程度地提高样品的发光强度,而Ca2 的掺杂则会降低发光强度.但是碱土金属离子(Mg2 ,Ca2 ,Ba2 )的掺杂并不能延长SrAl2O4:Eu2 ,Dy3 荧光粉的余辉时间.     

钨钼酸盐荧光粉基质组成及其退火过程对荧光性能的影响

采用高温固相法合成了一系列Eu3+掺杂的钨钼酸盐红色荧光粉CaxSr0.88-x(WO4)y(MoO4)1-y:0.08Eu3+。对其晶体结构和荧光性能进行了X射线衍射(XRD)、荧光光谱(PL)的表征,研究了不同Sr/Ca和WO4/MoO4比例对荧光粉光谱性能的影响,初步研究了不同退火过程对其发光性能的影响。所合成的Ca0.70Sr0.18(MoO4)0.5(WO4)0.5:0.08Eu3+荧光粉发光强度较好,可以被近紫外光(395 nm)和蓝光(465nm)有效激发,发射峰位于616 nm(Eu3+的5 D0→7 F2跃迁)。     

Ca_2Y_8(SiO_4)_6O_2∶RE(RE=Eu,Tb)发光薄膜的制备及发光性能的研究

采用溶胶 凝胶法制备了稀土离子掺杂 (Eu3 ,Tb3 )的氧磷灰石三元稀土硅酸盐Ca2 Y8(SiO4 ) 6 O2 发光薄膜。通过X射线衍射 (XRD) ,红外光谱 (IR) ,扫描电镜 (SEM)等方法对薄膜的组成、结构、颗粒尺寸、形貌及厚度进行了研究 ,通过发光光谱对薄膜的发光性质进行了分析。XRD结果表明 70 0℃时薄膜尚处于非晶态 ,80 0℃时已开始有Ca2 Y8(SiO4 ) 6 O2 的物相形成 ,10 0 0℃时结晶已完全。这一点和红外光谱的结果相符。发光光谱测试表明Ca2 Y8(SiO4 ) 6 O2 ∶Eu3 薄膜显示了很强的红光发射 ,并以Eu3 的5D0 -7F2 (616nm)超灵敏跃迁为最强一组。Ca2 Y8(SiO4 ) 6 O2 ∶Tb3 的发射光谱由蓝光发射和绿光发射两部分组成 ,前者对应于5D3-7FJ,后者对应于5D4 -7FJ(J =6,5 ,4,3 ) ,且以5D4 -7F5(5 44nm)绿光发射为最强。     

Ce3+,Tb3+,Eu3+共掺杂Sr2MgSi2O7体系的白色发光和能量传递机理

通过正交试验,采用高温固相法制备了Sr2-x-y-zMgSi2O7∶xCe3+,yTb3+,zEu3+系列样品.使用X射线衍射仪和荧光光谱仪表征了样品的物相和发光性质,并讨论了Ce3+-Tb3+-Eu3+共掺杂Sr2MgSi2O7体系中的能量传递过程.实验结果表明,在327 nm波长激发下,所合成荧光粉的发射峰主要位于387 nm(蓝紫)、542nm(绿)和611 nm(红)处;分别以387,542和611 nm为监控波长,所得激发光谱显示荧光粉在327 nm处有最好的激发.在327 nm光激发下,系列样品发光进入白光区.最优化的荧光粉为Sr1.91MgSi2O7∶0.01Ce3+,0.05Tb3+,0.03Eu3+,其色坐标为(0.337,0.313),是一种潜在的发光二极管(LED)用白色荧光粉.     

Ti-48Al-2M~1-2M~2(M~1=Nb,V;M~2=Mn,Cr,V)合金电子结构

用紧束缚能带计算方法(EHT)研究了标题多元合金的能带及电子结构。发现少量的多种元素在γ-TiAl中掺杂,对合金中电荷分布的影响,具有单种元素掺杂的叠加性;选择适当的合金元素就能达到多种掺杂的性能互补。多种元素掺杂能更有效地使成键电子云趋势于球形化,Peierls力均称为化,有利于增加γ-TiAl合金的塑性和变形性。     

Investigation of the formation of new bimetallic clusters of the type (η-C5Me5)2M2M′2(μ3-S)4(CO)2 (M  Cr,Mo; M′  Co), containing the M2M′2S4 core

The reaction of the sulfur rich pentamethylcyclopentadiene complexes (C₅Me₅)₂Cr₂S₅ and (C₅Me₅)₂Mo₂S₄ with Co₂(CO)₈ results in the formation of new bimetallic clusters of composition (C₅Me₅)₂M₂Co₂(μ₃-S)₄(CO)₂ (M  Cr, Mo), containing the M₂Co₂S₄ core.     

SiO_2负载的Pt－M、Rh－M异双核络合物催化剂催化CO_2氢化反应

考察了ＳｉＯ２负载的（ＰＰｈ３）２ＨＰｔ（μ－ＣＯ）（μ－ＰＰｈ２）Ｍ（ＣＯ）４和（ｄｐｐｅ）Ｒｈ（μ－ＣＯ）２Ｍ（ＣＯ）３（Ｍ＝Ｃｒ、Ｍｏ、Ｗ；ｄｐｐｅ＝Ｐｈ２Ｐ（ＣＨ２）２ＰＰｈ２）异双核络合物催化剂催化ＣＯ２氢化反应的活性和选择性．两者皆表现出较高的催化活性和含氧化合物选择性，而前者比后者更好．     

Synthesis, Characterization and Thermal Decomposition of M1[M2(C2O4)2]xH2O (x=5 for M1=Co and x=4 for M1=Cd; M2=Ni)

Cobalt bis(oxalato)nickelate pentahydrate, Co[Ni(C₂O₄)₂]5H₂O and cadmium bis(oxalato)nickelate tetrahydrate, Cd[Ni(C₂O₄)2]4H₂O have been synthesized and characterized by elemental analysis, reflectance and IR spectral studies. Thermal decomposition studies (TG, DTG and DTA ) in air showed that both the compound of cobalt and cadmium produced the oxide, MNiO_x (x=3 for M=Co; x=2 for M=Cd ) at 325 and 360°C respectively. DSC studies in nitrogen attributed only the mixture of both the metal at the end. This revised version was published online in July 2006 with corrections to the Cover Date.     

Relativistic-consistent electron densities of the coinage metal clusters M2, M4, M4(2-), and M4Na2 (M = Cu, Ag, Au): a QTAIM study

We employ second-order M?ller-Plesset perturbation theory level in combination with recently developed pseudopotential-based correlation consistent basis sets to obtain accurate relativistic-consistent electron densities for small coinage metal clusters. Using calculated electron densities, we employ Bader's quantum theory of atoms in molecules (QTAIM) to gain insights into the nature of metal-metal bonding in the clusters M(2), M(4), M(4)(2-), and M(4)Na(2) (M = Cu, Ag, Au). For the simplest case of the metal dimer, M(2), we correlate the strength of the metal-metal bond with the value of the electron density at the bond critical point, the total energy density at the bond critical point, the sharing (delocalization) index, and the values of the two principle negative curvatures. We then consider changes to the metal-metal bonding and charge density distribution upon the addition of two metal atoms to form the metal tetramer, M(4), and then followed by the addition of an electron pair to form M(4)(2-) and finally followed by the addition of two alkali metal (sodium) ions to form M(4)Na(2). Using topological properties of the electron density, we present evidence for the existence of σ-aromaticity in Au(4)(2-). We also report the existence of two non-nuclear attractors in the molecular graph of Cu(4)(2-) and large negative charge accumulation in the nonbonded Cu basins of this cluster.     

A study of the reaction NO3 + NO2 + M → N2O5 + M(M = N2, O2)

The gas-phase reaction of the NO₃ radical with NO₂ was investigated, using a flash photolysis-visible absorption technique, over the total pressure range 25–400 Torr of nitrogen or oxygen diluent at 298 ± 2 K. The absolute rate constants determined (in units of 10^?13 cm³ molecule^?1 s^?1) at 25, 100, and 400 Torr total pressure were, respectively, (4.0 ± 0.5), (7.0 ± 0.7), and (10 ± 2) for M = N₂ and (4.5 ± 0.5), (8.0 ± 0.4), and (8.8 ± 2.0) for M = O₂. These data show that the third-body efficiencies of N₂ and O₂ are identical, within the error limits, and that previous evaluations for M = N₂ are applicable to the atmosphere. In addition, upper limits were determined for the rate constants of the reactions of the NO₃ radical with methanol, ethanol, and propan-2-ol of ?6 × 10^?16, ?9 × 10^?16, and ?2.3 × 10^?15 cm³ molecule^?1 s^?1, respectively, at 298 ± 2 K.     

An Air-Stable Heterobimetallic Si2M2 Tetrahedral Cluster

Air- and moisture-stable heterobimetallic tetrahedral clusters [Cp(CO)₂MSiR]₂ (M=Mo or W; R=SitBu₃) were isolated from the reaction of N-heterocyclic carbene (NHC) stabilized silyl(silylidene) metal complexes Cp(CO)₂M=Si(SitBu₃)NHC with a mild Lewis acid (BPh₃). Alternatively, treatment of the NHC-stabilized silylidene complex Cp(CO)₂W=Si(SitBu₃)NHC with stronger Lewis acids such as AlCl₃ or B(C₆F₅)₃ resulted in the reversible coordination of the Lewis acid to one of the carbonyl ligands. Computational investigations revealed that the dimerization of the intermediate metal silylidyne (M≡Si) complex to a tetrahedral cluster instead of a planar four-membered ring is due to steric bulk.     

Kinetics of the reactions Br + NO2 + M and I + NO2+ M

The reactions Br + NO₂ + M → BrNO₂ + M (1) and I + NO₂ + M → INO₂ + M (2) have been studied at low pressure (0.6-2.2 torr) at room temperature and with helium as the third body by the discharge-flow technique with EPR and mass spectrometric analysis of the species. The following third order rate constants were found k₁₍₀₎ = (3.7 ± 0.7) × 10^?31 and k₂₍₀₎ = (0.95 ± 0.35) × 10^?31 (units are cm⁶ molecule^?2 s^?1). The secondary reactions X + XNO₂ → X₂ + NO₂ (X = Br, I) have been studied by mass spectrometry and their rate constants have been estimated from product analysis and computer modeling.