亚微米级Y3Al5O12:Ce3+荧光粉的共沉淀法合成、表征及光致发光

以金属硝酸盐为原料,使用NH3·H2O-NH4HCO3混合沉淀剂,开展了以反滴化学共沉淀方式和两步煅烧法合成掺铈的钇铝石榴石(Y3Al5O12Ce3+)黄色荧光粉研究.采用DTA-TGA和XRD研究共沉淀法制备的前驱体粉末热分解与钇铝石榴石晶相形成过程,通过荧光光谱和SEM研究荧光粉光致发光及添加剂对其发光和形貌影响规律.结果表明,采用化学共沉淀法合成温度比传统高温固相法降低300 ℃以上;荧光粉粒径0.3～1 μm,颗粒规则呈类球状;468 nm激发下荧光粉发射峰为532 nm;煅烧阶段添加氟化物,可使荧光粉的发射强度等发光特性明显提高,对控制Y3Al5O12Ce3+荧光粉的形貌有显著作用;与蓝光LED芯片封装后形成的白光LED色温Tc为5571 K,光效率为45 lm·W-1,显色指数Ra为79.9,色坐标为(0.3308,0.3476).     

亚微米级Y3Al5O12∶Ce3+荧光粉的共沉淀法合成、表征及光致发光

以金属硝酸盐为原料,使用NH3·H2O-NH4HCO3混合沉淀剂,开展了以反滴化学共沉淀方式和两步煅烧法合成掺铈的钇铝石榴石(Y3Al5O12∶Ce3 )黄色荧光粉研究。采用DTA-TGA和XRD研究共沉淀法制备的前驱体粉末热分解与钇铝石榴石晶相形成过程,通过荧光光谱和SEM研究荧光粉光致发光及添加剂对其发光和形貌影响规律。结果表明,采用化学共沉淀法合成温度比传统高温固相法降低300℃以上;荧光粉粒径0.3～1μm,颗粒规则呈类球状;468nm激发下荧光粉发射峰为532nm;煅烧阶段添加氟化物,可使荧光粉的发射强度等发光特性明显提高,对控制Y3Al5O12∶Ce3 荧光粉的形貌有显著作用;与蓝光LED芯片封装后形成的白光LED色温Tc为5571K,光效率为45lm·W-1,显色指数Ra为79.9,色坐标为(0.3308,0.3476)。     

Ce和Dy在Cd0.5Zn0.5B4O7中的发光特性及能量双向传递

采用高温固相法制备了白蓝光双发射为一体的Cd0.5Zn0.5B4O7∶Ce/Dy系列发光材料. 由XRD测得Cd0.41Zn0.5B4O7∶Ce0.04/Dy0.02的晶胞参数: a=1.3885 nm, b=0.8020 nm, c=0.8670 nm, 属于正交晶系, Pbca空间群. 在Ce/Dy双掺的体系中存在Ce3+和Dy3+两种发光中心, 254~350 nm激发主要是Dy3+的 4F9/2→6H15/2和4F9/2→6H13/2跃迁发射, 而355—390 nm激发主要为Ce3+的5d→4f跃迁发射. 340 nm激发Ce/Dy双掺发光体的发射强度是同浓度Dy3+单掺的31倍, Ce3+是Dy3+的高效敏化剂, 而355—390 nm激发Dy3+是Ce3+的敏化剂. 体系中存在少见的Ce3+→Dy3+与Dy3+→Ce3+的能量双向传递.     

LiAl_5O_8:Fe荧光粉的研究与应用

目前市售硼酸镉、钒酸钇和砷酸盐等灯用红色荧光粉,发射波长一般在610nm左右,呈桃红色。砷酸盐荧光粉掺红颜料,因而看到的是颜料的颜色,砷酸盐还有毒。因此,研制一种发射波长长,原料无毒的大红单色荧光粉有着重要的意义。关于金属离子Mn~(2+)、Cr~(3+)、Co~(2+)和Ni~(2+)在LiAl_5O_8中的发光特性已有研究。本文报导激活剂Fe~(3+)离子浓度和烧结温度对Fe~(3+)在LiAl_5O_8中发光性质的影响,并对该荧光粉的发光机制和效率等进行讨论。     

Ce3+∶YAG闪烁晶体的真空紫外激发光谱特性

掺铈钇铝石榴石(Ce3+∶YAG)晶体是性能优良的闪烁材料. 以同步辐射光源为激发光源研究了单晶Ce3+∶YAG的真空紫外-紫外(VUV-UV)激发光谱和荧光谱. 同时也测量和分析了该晶体的吸收光谱、紫外-可见(UV-VIS)激发光谱和荧光谱.根据光谱测量的结果讨论了激发能在Ce3+∶YAG晶体中的传输过程和在Ce3+离子5d态的直接激发和YAG价带激发下Ce3+∶YAG单晶发光的差别.     

稀土氧化物前驱体的合成及其对YAG:Ce荧光粉影响的研究

分别用草酸和碳酸氢铵为沉淀剂通过沉淀法制备氧化钇及钇铈复合氧化物.并以其为原料,在高温下合成YAG:Ce黄色荧光粉.用XRD、SEM、粒度测试仪、光谱分析仪等表征了氧化物前驱体和YAG:Ce.SEM和比表面测试结果表明,碳酸氢铵沉淀法制备的氧化钇或钇铈复合氧化物的一次粒径约100nm,形貌规则,比表面积高.用该钇铈复合氧化物合成的YAG:Ce具有发光强度高、形貌规则、粒度小等优点.     

Ce3+-Yb3+共掺CaF2纳米粒子的近红外发光

采用简单的水热方法制备了一系列Ce3+ -Yb3+共掺的CaF2纳米粒子.XRD测试结果表明,Ce3+和Yb3+不同掺杂浓度下的CaF2纳米粒子结晶良好.SEM和TEM分析表明,纳米粒子的平均粒径为30 nm左右.系统地研究了各样品的发光性质包括激发谱、紫外-可见发射谱、近红外发射谱和荧光寿命.激发Ce3+的5d能级,在900 ～ 1050 nm波长范围得到很强的近红外发射.随着Yb3离子浓度的增加,Ce3的发射强度降低,Yb3+的发射强度先升高后降低,Ce3+的寿命减少,能量传递效率增加.作为一个下转换光转换器,这种材料应用于硅基太阳能电池前端,能够减少电池热损失,增加电池转换效率.     

紫外激发Sr1-x-yMgP2O7:xCe3+,yTb3+荧光粉的发光特性及能量传递

采用高温固相法合成了Sr1-x-yMgP2O7:xCe3+,yTb3+荧光粉.研究了荧光粉的晶体结构、发光特性、荧光寿命、能量传递机理和荧光粉的热稳定性.研究结果表明:在SrMgP2O7基质中,Ce3+的发射峰值为398nm,Tb3+的主发射峰值为545nm,它们分别属于5d-4f跃迁和5D4→7F5跃迁.Ce3+和Tb3+共掺时,Ce3+和Tb3+通过电偶极子-电偶极子相互作用发生能量传递,能量传递的临界距离为0.614nm.通过计算得到单掺杂Ce3+、Tb3+时热猝灭过程的激活能分别为0.122和0.111eV,Tb3+离子的发光热稳定性比Ce3+离子的好.     

Er3+,Sm3+掺杂纳米晶体NaNbO3的合成和上转换发光研究

首先用水热法合成了NaNbO3样品,然后用固相法分别合成了NaNbO3,NaNbO3:Er3+,NaNbO3:Sm3+样品,X射线衍射结果表明所制备的粉体NaNbO3(水热法200℃和固相法900℃退火),NaNbO3:Er3+(900℃退火),NaNbO3:Sm3+(900℃退火)为立方相结构,在退火温度800,950和1000℃时是正交晶系,长方体结构.该粉末在980 nm LD激发下,分别发射出中心波长约为526 nm绿色,547nm绿色和662 nm红色(掺Er3+)、526 nm绿色,550 nm绿色和660 nm红色(掺Sm3+)的上转换荧光.探讨了Er3+,Sm3+的上转换发光机制.研究了晶体的对称性和退火温度对NaNbO3:Er3+样品上转换发光强度的影响,结果表明,随着晶体的对称性降低和退火温度的提高,NaNbO3:Er3+样品的上转换发光强度增强.     

基于CaBa_2(BO_3)_2中的Ce~(3+)→Tb~(3+)能量传递及光谱特性

采用高温固相法合成了Ce3+,Tb3+掺杂激活的CaBa2(BO3)2荧光粉,并对其发光特性进行了研究。观察到CaBa2(BO3)2中Ce3+对Tb3+发光的敏化现象。在367 nm紫外光激发下,单掺Tb3+时CaBa2(BO3)2不发光。当Ce3+和Tb3+共掺时,出现Tb3+的发射峰,样品发绿光,表明Ce3+对Tb3+的发光有很强的敏化作用。根据Forster-Dexter理论,分析Ce3+和Tb3+的能量传递过程,还证明在CaBa2(BO3)2:Ce3+,Tb3+中Ce3+对Tb3+的能量传递属于共振能量传递。     

Synthesis and electroluminescent properties of a phenothiazine‐based polymer for nondoped polymer light‐emitting diodes with a stable orange‐red emission

A novel phenothiazine‐based polymer was synthesized through the Heck reaction of 3,7‐divinyl‐N‐octyl‐phenothiazine with 4,7‐dibromo‐2‐octylbenzotriazole according to the alternating donor–acceptor strategy. The polymer was characterized with ¹H NMR, infrared spectroscopy, gel permeation chromatography, cyclic voltammetry, ultraviolet–visible spectroscopy, and fluorescence spectroscopy. With the polymer used as an active layer, three nondoped polymer light‐emitting diodes (PLEDs) with a double‐layer configuration were fabricated by the spin‐coating approach with different thermal annealing processes. The emission maximum in electroluminescent spectra was stabilized at 616 nm. The maximum luminance reached 2432 cd/m². The coordinate value of Commission International de l'Eclairage 1931 in the double‐layer PLEDs after the thermal treatment was nearly stabilized at (x, y) =(0.62, 0.38). Additionally, the luminous efficiency of device II reached a balanceable state with an increase in the current. Therefore, the polymer had an orange‐red emission with stable chromaticity coordinates under different driving voltages. Finally, a nondoped device with a stable luminous efficiency and chromaticity was obtained. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4867–4878, 2007     

内包碳化铁洋葱状富勒烯的合成和表征

自从Kr（ae）tschmer等发现宏观量制备富勒烯的方法以来,这种新型的球形碳质材料已经引起材料科学家愈来愈多的关注．特别是以洋葱状形态和包裹外来物质进入洋葱状富勒烯内部的碳质材料更是展现了这种新型碳材料的应用前景．     

Novel dimetal bridging carbene complexes derived from a terminal carbonyl dimetal compound. Syntheses, structures and reactivities of 7H-indene-coordinated diiron bridging carbene complexes

Pentacarbonyl-7H-indenediiron, [Fe2(CO)5(eta3,eta5-C9H8)] (1), reacts with aryllithium, ArLi (Ar = C6H5, p-C6H5C6H4), followed by alkylation with Et3OBF4 to give novel 7H-indene-coordinated diiron bridging alkoxycarbene complexes [Fe2{mu-C(OC2H5)Ar}(CO)4(eta4,eta4-C9H8)] (2, Ar = C6H5; 3, Ar = p-C6H5C6H4). Complexes 2 and 3 react with HBF4.Et2O at low temperature to yield cationic bridging carbyne complexes [Fe2(mu-CAr)(CO)4(eta4,eta4-C9H8)]BF4 (4, Ar = C6H5; 5, Ar = p-C6H5C6H4). Cationic 4 and 5 react with NaBH4 in THF at low temperature to afford diiron bridging arylcarbene complexes [Fe2{mu-C(H)Ar}(CO)4(eta4,eta4-C9H8)] (6, Ar = C6H5; 7, Ar = p-C6H5C6H4). The similar reactions of 4 and 5 with NaSC6H4CH3-p produce the bridging arylthiocarbene complexes [Fe2{mu-C(Ar)SC6H4CH3-p}(CO)4(eta4,eta4-C9H8)] (8, Ar = C6H5; 9, Ar = p-C6H5C6H4). Cationic 4 and 5 can also react with anionic carbonylmetal compounds Na[M(CO)5(CN)] (M = Cr, Mo, W) to give the diiron bridging aryl(pentacarbonylcyanometal)carbene complexes [Fe2{mu-C(Ar)NCM(CO)5}(CO)4(eta4,eta4-C9H8)] (10, Ar = C6H5, M = Cr; 11, Ar = p-C6H5C6H4, M = Cr; 12, Ar = C6H5, M = Mo; 13, Ar = p-C6H5C6H4, M = Mo; 14, Ar = C6H5, M = W; 15, Ar = p-C6H5C6H4, M = W). Interestingly, in CH2Cl2 solution at room temperature complexes 10-15 were transformed into the isomerized 7H-indene-coordinated monoiron complexes [Fe(CO)2(eta5-C9H8)C(Ar)NCM(CO)5] (16, Ar = C6H5, M = Cr; 17, Ar = p-C6H5C6H4, M = Cr; 18, Ar = C6H5, M = Mo; 19, Ar = p-C6H5C6H4, M = Mo; 20, Ar = C6H5, M = W; 21, Ar = p-C6H5C6H4, M = W), while complex 3 was converted into a novel ring addition product [Fe2{C(OC2H5)C6H4C6H5-p-(eta2,eta5-C9H8)}(CO)5] (22) under the same conditions. The structures of complexes 2, 6, 8, 14, 18 and 22 have been established by X-ray diffraction studies.     

Plasma chemistry of NO in complex gas mixtures excited with a surfatron launcher

The plasma chemistry of NO has been investigated in gas mixtures with oxygen and/or hydrocarbon and Ar as carrier gas. Surface wave discharges operating at microwave frequencies have been used for this study. The different plasma reactions have been analyzed for a pressure range between 30 and 75 Torr. Differences in product concentration and/or reaction yields smaller than 10% were found as a function of this parameter. The following gas mixtures have been considered for investigation: Ar/NO, Ar/NO/O2, Ar/NO/CH4, Ar/CH4/O2, Ar/NO/CH4/O2. It is found that NO decomposes into N2 and O2, whereas other products such as CO, H2, and H2O are also formed when CH4 and O2 are present in the reaction mixture. Depending on the working conditions, other minority products such as HCN, CO2, and C2 or higher hydrocarbons have been also detected. The reaction of an Ar/NO plasma with deposits of solid carbon has also been studied. The experiments have provided useful information with respect to the possible removal of soot particles by this type of plasma. It has been shown that carbon deposits are progressively burned off by interaction with the plasma, and practically 100% decomposition of NO was found. Plasma intermediate species have been studied by optical emission spectroscopy (OES). Bands and/or peaks due to N2*, NO*, OH*, C2*, CN*, CH*, or H* were detected with different relative intensities depending on the gas mixture. From the analysis of both the reaction products and efficiency and the type of intermediate species detected by OES, different plasma reactions and processes are proposed to describe the plasma chemistry of NO in each particular mixture of gases. The results obtained provide interesting insights about the plasma removal of NO in real gas exhausts.     

Syntheses and reactions of hexavalent organotellurium compounds bearing five or six tellurium-carbon bonds

A variety of hexaorganotellurium compounds, Ar(6-n)(CH3)nTe [Ar=4-CF3C6H4, n=0 (1a), n=1 (3a), n=2 (trans-4a and cis-4a), n=3 (mer-5a), n=4 (trans-6a); Ph, n=0 (1b), n=1 (3b), n=2 (trans-4b); 4-CH3C6H4, n=0 (1c), n=1 (3c), n=2 (trans-4c), n=4 (trans-6c); 4-BrC6H4, n=0 (1d)] and Ar5(R)Te [Ar=4-CF3C6H4, R=4-CH3OC6H4 (8); Ar=4-CF3C6H4, R=vinyl (9), Ar=Ph, R=vinyl (10), Ar=4-CF3C6H4, R=PhSCH2 (11), Ar=Ph, R=PhSCH2 (12), Ar=4-CF3C6H4, R=nBu (13)] and pentaorganotellurium halides, Ar5TeX [Ar=4-CF3C6H4, X=Cl (2a-Cl), X=Br (2a-Br); Ar=Ph, X=Cl (2b-Cl), X=Br (2b-Br); Ar=4-CH3C6H4, X=Cl (2c-Cl), X=Br (2c-Br); Ar=4-BrC6H4, X=Br (2d-Br)] and (4-CF3C6H4)4(CH3)TeX [X=Cl (trans-7a-Cl) and X=Br (trans-7a-Br)] were synthesized by the following methods: 1) one-pot synthesis of 1 a, 2) the reaction of SO2Cl2 or Br2 with Ar5Te(-)Li+ generated from TeCl4 or TeBr4 with five equivalents of ArLi, 3) reductive cleavage of Ar(6-m)(CH3)(m)Te (m=0 or 2) with KC8 followed by treatment with CH3I, 4) valence expansion reaction from low-valent tellurium compounds by treatment with KC8 followed by reaction with CH3I, 5) nucleophilic substitution of Ar(6-y-z)(CH3)zTeX(y-z) (X=Cl, Br, OTf; z=0, 1; y=1, 2) with organolithium reagents. The scope and limitations and some details for each method are discussed and electrophilic halogenation of the hexaorganotellurium compounds is also described.     

Arylzinc alkoxides: [ArZnOCHPr(i)2]2 and Ar2Zn3(OCHPr(i)2)4 when Ar = C6H5, p-CF3C6H4, 2,4,6-Me3C6H2, and C6F5

From the reactions between diarylzinc compounds (Ar2Zn) and the alcohol (Pr(i)2CHOH) in toluene, the compounds [ArZn(OCHPr(i)2)]2 (Ar = C6H5, C6F5, p-CF3C6H4, and 2,4,6-Me3C6H2) have been isolated and shown to exist in equilibra with the trinuclear complexes Ar2Zn3(OCHPr(i)2)4 and Ar2Zn when Ar = C6H5, C6F5, and p-CF3C6H4. The trinuclear complexes have also been prepared from reactions of the Ar2Zn compounds with the alcohol, which reveals that the ease of Zn-C(aryl) bond cleavage is sensitive to the nature of the Ar group: C6H5 > 4-CF3C6H4 > C6F5. The molecular structures of Ar2Zn3(OCHPr(i)2)4 where Ar = p-CF3C6H4 and C6F5 and [ArZn(OCHPr(i)2)]2 where Ar = C6F5, p-CF3C6H4, and 2,4,6-Me3C6H2 are reported based on single-crystal X-ray diffraction studies. The X-ray structure of Zn(p-CF3C6H4)2 is also reported. The reactivity of these new compounds toward the polymerization of propylene oxide (PO) and the copolymerization of PO and CO2 have been investigated along with related reactions involving the partial hydrolysis of the Ar2Zn and R2Zn compounds, where R = t-Bu, n-Bu, and n-Oct. These results are compared with the previous studies employing Et2Zn as an organozinc precursor.     

Photochemical E-Z isomerization of meta-terphenyl-protected phosphaalkenes and structural characterizations

A series of phosphaalkenes, E-ArP=C(H)Ar' (Ar = 2,6-Mes2C6H3, Ar' = Ph (1a); Ar = 2,6-Mes2C6H3, Ar' = p-C6H4Br (2a); Ar = 4-Br-2,6-Mes2C6H2, Ar' = Ph (3a); Ar = 4-Br-2,6-Mes2C6H2, Ar' = p-C6H4Br (4a)) have been prepared by phospha-Wittig reactions and characterized. Exposure of these materials either to room light over an extended period of time (days) or to UV light (hours) produced equilibrium mixtures of the E and Z isomers (1b-4b) as indicated by 1H and 31P NMR spectroscopy. The structures of compounds 4a and 4b were determined by single-crystal X-ray diffraction methods. Variable-temperature (1)H NMR studies of 4b indicate hindered rotation about the P-CAr bond, with DeltaH(double dagger) = 13.8 kcal/mol and DeltaS(double dagger) = 1.3 eu. The electronic structures of E- and Z-PhP=C(H)Ph have been examined using density functional theory.     

Reduction of supported noble-metal ions using glow discharge plasma

A novel plasma reduction method has been developed to reduce supported noble-metal ions without the use of any reducing chemicals. H2PtCl6, PdCl2, AgNO3, and HAuCl4 supported on nonporous TiO2 and porous gamma-Al2O3 and HZSM-5 were reduced using an Ar glow discharge plasma. Optical absorption spectra and X-ray photoelectron spectroscopy show that the supported metal ions are completely reduced to metallic species. Transmission electron microscopy shows that the prepared metals are amorphous clusters and homogeneously distributed with nanoscale sizes. X-ray diffraction also confirms that the plasma-reduced metals exist as small crystallites or amorphous clusters. Thermal annealing of plasma-reduced samples at elevated temperature transforms the clusters into crystals with a slight increase in particle sizes, but the sizes are still smaller than those of H2-reduced metals. O2 glow discharge plasma can also reduce noble-metal ions, accompanied by production of a small amount of oxides. Plasma reduction is very promising for the preparation of metal nanoparticles and supported metal catalysts.     

Dimethylaluminium iminophosphoranylenamides and iminophosphoranylanilides: synthesis, characterisation, and their controlled ring-opening polymerisation of ε-caprolactone

A series of aluminium iminophosphoranylenamide complexes, [Me(2)Al{N(Ar)C(Ph)=CHP(Ph(2))=N-Ar(1)}] (Ar = Ph, Ar(1) = p-MeC(6)H(4) (9); Ar = Ph, Ar(1) = o-ClC(6)H(4) (10); Ar = Ph, Ar(1) = o-FC(6)H(4) (11); Ar = p-MeC(6)H(4), Ar(1) = o-FC(6)H(4) (12)), were synthesised by the reactions of ArN=C(Ph)CH(2)P(Ph(2))=NAr(1) (5-8) with AlMe(3) in toluene. Similar reactions between o-{ArN=P(Ph(2))}C(6)H(4)NHC(Ph)=CHP(Ph(2))=NAr (Ar = p-MeC(6)H(4), 13), and AlMe(3) in toluene generates aluminium iminophosphoranylanilide, 14. All new compounds were characterised by NMR spectroscopy and elemental analysis. The molecular structures of complexes 9 and 14 were further characterised by single-crystal X-ray structure determination. In the presence of benzyl alcohol (BnOH) each of the complexes is catalytically active for the ring-opening polymerisation (ROP) of ε-caprolactone (ε-CL), and complex 14 has the highest activity among them.     

Activation of nanoparticle Pt-Ru fuel cell catalysts by heat treatment: a 195Pt NMR and electrochemical study

(195)Pt NMR spectroscopic and electrochemical measurements were carried out on commercial Pt-Ru alloy nanoparticle samples to investigate the effect of high-temperature annealing in different vacuum/gas-phase environments. Samples annealed at 220 degrees C in Ar gas, or in a vacuum, did not show any demonstrable change in catalytic activity vs electrochemically reduced, room-temperature samples. In contrast, annealing at 220 degrees C in H(2) gas led to a 3-fold increase in reactivity toward methanol oxidation (per surface site). NMR experiments show that annealing at 220 degrees C (in both Ar and H(2)) leads to a slight reduction in the Fermi level local density of states (E(F)-LDOS) at the Pt sites, which we attribute to surface enrichment of Ru. This electronic effect alone, however, appears to be too small to account for the increase in the catalytic activity observed for the H-treated catalyst. By comparing the electrochemical and NMR data of the H- and Ar-treated samples, we conclude that annealing at 220 degrees C in the hydrogen atmosphere reduces surface Ru oxides into metallic Ru, and consequently, the presence of metallic Ru and its enrichment on the surface are essential for the enhanced catalytic activity. In contrast, heat treatment at 600 degrees C in both vacuum and argon atmosphere increases the particle size and reduces the amount of platinum on the nanoparticle surface, thereby increasing the surface Ru content beyond the optimum surface composition values. This causes a large reduction in catalytic activity. Our results suggest that optimizing the amount of surface Ru by heat treatment at temperatures near 200 degrees C, in a hydrogen atmosphere, can be utilized to produce Pt-Ru alloy nanoparticles with high methanol oxidation activity. Finally, our NMR and electrochemical data, taken together with the lattice parameter measurements, lead to a novel model of Pt-Ru alloy nanoparticles having a Ru-rich core and a Pt-Ru alloy overlayer.