Eu3+掺杂铝硅酸钾发光材料的合成及性能研究

采用固相法在较温和的反应温度下合成了Eu3+掺杂铝硅酸钾发光材料,利用粉末X射线衍射仪(XRD)、扫描电子显微镜(SEM)、热分析仪(TG-DTA)、紫外-可见光谱、荧光光谱仪(PL)等手段对合成的样品进行表征。结果表明:在450,550,650,750℃下合成的KAlSiO4:Eu3+为无定形态,但其形貌受温度的影响较大,450℃下合成的样品分散性较好,其他温度下得到样品的形貌为块状团聚体;在394 nm的紫外光激发下,样品主要表现出掺杂Eu3+的特征发射(5D0→7F1和5D0→7F2跃迁),在650℃合成的样品的发射光谱强度最强,其荧光衰减曲线符合双指数衰减行为,经拟合平均荧光寿命为0.40 ms。     

绿色荧光粉Ba2-xB2O5:xTb3+的制备及发光性能研究

采用高温固相法合成了Ba2-xB2O5:xTb3+绿色荧光粉。XRD图谱表明合成物质为纯相的Ba2B2O5晶体。该样品在256 nm(4f8→4f75d1)处有最强激发;有4个发射峰,分别位于489 nm(5D4→7F6),545 nm(5D4→7F5),585 nm(5D4→7F4)和622 nm(5D4→7F3);其中在545 nm处有最强发射。随着Tb3+掺杂浓度的不同,激发峰与发射峰的强度先增大后减小,当x=0.7时最佳。研究了电荷补偿剂Na+对发光性能的影响,样品的发射光谱强度随Na+掺杂浓度的增大而增大,当掺杂浓度达到或超过Tb3+浓度后发射光谱强度下降。     

LED用Sr_((1-1.5x))Mo_(0.8)Si_(0.2)O_(3.8)∶Eu_x~(3+)红色荧光粉的制备及其荧光性能

通过高温固相法合成了LED用红色荧光粉Sr(1-1.5x)Mo0.8Si0.2O3.8∶Eu3x+(x=0.1,0.2,0.3,0.4,0.5)。通过XRD、激发光谱和发射光谱测试了材料的物相组成以及发光性能。x=0.1样品的XRD谱与JCPDS 08-0482(SrMoO4)的标准卡片相同。Eu3+代替晶格中Sr2+的位置成为发光中心。随着Eu3+含量x的增加,593 nm处的5D0-7F1跃迁和614 nm处的5D0-7F2跃迁发射强度会相互转换:当x≤0.4时,以磁偶极5D0-7F1跃迁为主,发射橙色光;而当x=0.5时,以电偶极5D0-7F2跃迁发射为主,发射红光。可能是过量掺杂的Eu3+离子,只能存在于晶格空位形成缺陷,无法占据SrMoO4中Sr2+的格位中,Eu3+在晶格中占据非对称中心的格位,导致电偶极跃迁变成允许跃迁,从而增加了5D0-7F2跃迁,减弱了5D0-7F1跃迁。因此,可以通过调节激活剂的含量获得不同发光色的荧光粉。Eu3+掺杂的硅钼酸锶体系,614 nm激发下,在368 nm处出现宽的基质吸收峰和467 nm处7 F0-5 D2的跃迁峰,且这2处的吸收峰在x=0.5时比x=0.4时...     

稀土Y_(2-x)SiO_5∶Eu_x~(3 )纳米发光材料结构对发光性能影响及发光机理研究

用溶胶凝胶法合成了Y2-xSiO5∶Eux纳米发光材料,使用XRD、FTIR和TEM对其结构进行了表征。讨论了相结构、煅烧温度和Eu3 掺杂浓度对材料发光性能的影响及规律。结果显示煅烧温度在900℃以下,材料主要呈非晶相结构,900℃以上材料主要呈晶态结构;颗粒随煅烧温度升高而增大,在非晶态时颗粒大小在15~45nm,在晶态时颗粒大小为60~80nm。激发光谱和荧光发射光谱受材料晶相结构以及Eu3 掺杂浓度的影响,在晶态结构中Y2-xSiO5∶Eux纳米材料呈现更精细的激发和发射光谱。在激发光谱中,电荷转移态吸收(CST)随煅烧温度升高呈现兰移现象,晶态时CST同非晶态相比明显红移;在发射光谱中,非晶态时5D0→7F2跃迁呈现强的发光峰,随材料制备温度升高而增强,在晶态时该发光峰强度减弱,在长波波段呈现两个新的发光尖峰,并随煅烧温度升高而增强;5D0→7F1发射峰从非晶态转变为晶态后,光谱裂分为三重尖峰;而5D0→7F0跃迁发光光谱受结构和颗粒大小影响较小。同时在60~80nm的Y2-xSiO5∶Eux晶体中,发现材料5D0→7F2和5D0→7F1跃迁发光强度,均受Eu3 掺杂浓度的影响,当掺杂浓度x=0.4时,材料发光强度最大。     

LED用Sr(1-1.5x)Mo0.8Si0.2O3.8:Eu3+x红色荧光粉的制备及其荧光性能

通过高温固相法合成了LED用红色荧光粉Sr(1-1.5x)Mo0.8Si0.2O3.8∶Eu3+x（x=0.1,0.2,0.3,0.4,0.5）。 通过XRD、激发光谱和发射光谱测试了材料的物相组成以及发光性能。 x=0.1样品的XRD谱与JCPDS 08-0482(SrMoO4)的标准卡片相同。 Eu3+代替晶格中Sr2+的位置成为发光中心。 随着Eu3+含量x的增加,593 nm处的5D0-7F1跃迁和614 nm处的5D0-7F2跃迁发射强度会相互转换：当x≤0.4时,以磁偶极5D0-7F1跃迁为主,发射橙色光;而当x=0.5时,以电偶极5D0-7F2跃迁发射为主,发射红光。 可能是过量掺杂的Eu3+离子,只能存在于晶格空位形成缺陷,无法占据SrMoO4中Sr2+的格位中,Eu3+在晶格中占据非对称中心的格位,导致电偶极跃迁变成允许跃迁,从而增加了5D0-7F2跃迁,减弱了5D0-7F1跃迁。 因此,可以通过调节激活剂的含量获得不同发光色的荧光粉。 Eu3+掺杂的硅钼酸锶体系,614 nm激发下,在368 nm处出现宽的基质吸收峰和467 nm处7F0-5D2的跃迁峰,且这2处的吸收峰在x=0.5时比x=0.4时强3倍左右。 材料能非常好的吸收368 nm波长的光,产生颜色可调的橙红色。 与近紫外光LED芯片匹配良好。     

Sr2CeO4:Eu,Gd的微波合成与荧光性质

用微波法合成了Gd3 和Eu3 共掺杂的Sr2CeO4荧光体.Gd3 对Sr2CeO4:Eu的发光起不同的作用:当Eu3 浓度较低(掺杂浓度为1 mol%)时,Gd3 离子起猝灭作用;当Eu3 浓度较高(掺杂浓度为8 mol%)时,Gd3 离子起敏化作用,尤其是Gd3 离子掺杂浓度为3 mol%时,Eu3 的5D0→7F2(614 nm)跃迁发射增强为Sr2CeO4:Eu荧光强度的145%.     

Eu3+和Tb3+在LnBaB9O16中的紫外和真空紫外发光性质

研究了Tb3+和Eu3+在LnBaB9O16(Ln=La,Gd,Y,Lu)中的紫外和真空紫外光谱性质.X射线粉末衍射数据指标化结果表明,LnBaB9O16(Ln=La,Gd,Y,Lu)系列化合物属于三方晶系.Eu3+的荧光光谱结果表明,LaBaB9O16和GdBaB9O16中稀土离子占据非中心对称的格位,Eu3+在其中的特征发射以5D0→7F2电偶极跃迁为主;而在YBaB9O16和LuBaB9~O16中稀土离子占据中心对称性的格位,Eu3+在其中的特征发射以5D0→7F1磁偶极跃迁为主.Tb3+在LaBaB9O16和GdBaB9O16中的发射为5D3→7F0和5D4→7F1(J=0～6)辐射跃迁,在YBaB9O16和LuBaB9O16中只能观察到5D4→7F1(J=3～6)辐射跃迁.与Eu3+的发光性质相反,Tb3+占据非中心对称的格位时的发射强度比占据中心对称的格位时要弱得多.Eu3+和Tb3+掺杂的样品在真空紫外波段的吸收弱.     

Gd_3Al_5O_(12)∶Eu~(3+)柠檬酸盐硝酸盐燃烧法合成及其发光性能研究

采用柠檬酸盐硝酸盐燃烧法,在较低的温度(900℃)下成功地合成单一晶相Gd3Al5O12∶Eu3+发光粉体,紫外激发荧光光谱分析表明,粉体615 nm和593 nm荧光发射源于Eu3+的5D0-7F2和5D0-7F1跃迁.该方法中各工艺条件(如pH值、柠檬酸/金属离子比、煅烧温度)对Gd3Al5O12∶Eu3+发光性能均有影响,通过试验得出了获得最佳发光性能荧光粉体的工艺参数.     

Al2O3/蒙脱土:Eu2+架状结构发光材料的制备及发光性能研究

采用高温固相法,在还原气氛下制备出Al2O3/蒙脱土:Eu2+光致发光材料。研究了原料配比、烧结温度、保温时间以及激活剂Eu2+的含量对发光性能的影响。实验结果表明:加入蒙脱土后,所制备的样品仍保持Al2O3的架状结构,晶格常数发生变化,晶体产生畸变,使得Eu2+更容易进入到晶格中。荧光光谱分析显示,发射光谱是两个宽峰组成,对应于Eu2+的4f65d→4f7(8S7/2)宽带允许跃迁。发光机制分析认为,宽峰结构由Eu0.92[Al1.76Si2.24O8]新相产生,生成的新相增加了Eu2+的取代格位,形成新的发光中心。因此Eu2+不仅取代了Al2O3八面体中Al的格位,而且取代了蒙脱土层间所吸附的阳离子格位,使样品发光强度提高了220%。     

一种可用于白光LED的硅酸盐红光荧光粉发光特性的研究

采用固相合成法制备了成分为M1-xSiO3:xEu3+(M=Mg,Ca,Sr,Ba)的红光荧光粉.测量了它们的激发光谱和发射光谱.它们均发射红光,可用于近紫外和蓝光LED芯片,与其他荧光粉一起封装白光LED 以调节显示指数和色温等参数.BaSiO3:Eu3+在室温下发射的主峰波长是613 nm的红光,激发峰值在393和464 nm,可用于调节基于近紫外或者蓝光芯片的白光LED的显色指数.用高斯曲线对它的发射光谱进行了拟合,分析了它的能级跃迁的情况.结果发现,BaSiO3:Eu3+的发射峰是由5D0→7F0(583.04 nm),5D0→7F1(592 nm),5D0→7F2(612.15和620.79 nm),5D0→7F3(650.55 nm)和5D0→7F4(688.5和701.5 nm)跃迁得到的.用两个高斯函数拟合5D0→7F2和5D0→47的发射峰可以得到更合理的结果,并且5D0→70和5D0→7F1这两个能级跃迁的发射峰叠加在一起只能观察到一个峰值.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.