低温凝胶燃烧法合成Y2O3∶Er3+，Yb3+纳米晶上转换发光材料

分别以柠檬酸和甘氨酸为燃烧剂,采用低温凝胶燃烧法合成了Er³⁺、Yb³⁺共掺Y₂O₃纳米晶粉体。通过TG-DSC、XRD、SEM等分析手段对两种燃烧剂所对应的反应过程及纳米晶粉体的物理性能进行了分析,结果表明甘氨酸法具有更高的反应效率、更好的粉体分散性及粒径均匀性。在980 nm激光二极管(LD)激发下,对甘氨酸法所得样品的上转换发光性能分析表明,绿光和红光发射谱带分别来自于Er³⁺的⁴S_3/2/ ²H_11/2→ ⁴I_15/2和⁴F_9/2→ ⁴I_15/2跃迁。此外,对Er³⁺和Yb³⁺掺杂浓度、粉体煅烧温度对纳米晶样品上转换发光性能的影响进行了讨论。     

Fura-2探针对希土Y3+跨PC12细胞膜行为研究

使用AR-MIC-CM阳离子测定系统,发展Fura-2荧光测定技术,将其应用于测定细胞内游离希土离子Y³⁺,并以此研究了Y³⁺跨PC12细胞(大鼠嗜铬细胞瘤细胞)膜的行为。结果表明：在模拟细胞内各离子组分,pH=7.05的溶液中,测得表观解离常数为4.5p mol·L^-1。对于PC12细胞,静息条件下Y³⁺不能跨越细胞膜进入胞内。与钙离子通道相关的KCl和去甲肾上腺素均不能刺激希土Y³⁺过膜。用Ouabain(哇巴因)使胞内Na⁺超载后,Y³⁺可过膜进入细胞内,且过膜量与胞外Y³⁺浓度和胞内Na⁺超载程度有一定的浓度依赖关系,提示Y³⁺可以经由Na⁺/Y³⁺交换机制过膜而进入细胞内。     

Yb3+/Tm3+共掺杂的钨酸镉纳米晶发光性能的研究

本文采用水热法制备了稀土离子Yb³⁺/Tm³⁺共掺杂的钨酸镉纳米晶。运用X-射线粉末衍射、场发射环境扫描电子显微镜和光谱分析对制备的样品的结构和发光性能进行了表征。根据XRD图谱可知, 钨酸镉为单斜晶系, 晶粒平均尺寸在28 nm左右。从ESEM图片可明显看出, 钨酸镉呈纳米棒结构, 直径在30 nm左右, 长径比在5~8之间。利用980 nm半导体激光器激发钨酸镉纳米晶得到样品的发射光谱, 存在一个较强的蓝光发射, 发光峰位于481 nm,对应于Tm³⁺的¹G₄→³H₆能级的跃迁, 分析了Tm³⁺/Yb³⁺离子共掺体系的发光机制。讨论了发光强度随稀土离子浓度的变化, 当Tm³⁺离子的掺杂浓度在2%, Yb³⁺/Tm³⁺物质的量浓度比为10:1时钨酸镉纳米晶的发光强度最强。根据泵浦功率与发光强度之间的关系, 可知处于481 nm的蓝光发射属于三光子过程, 由发光强度与掺杂浓度之间的双对数衰减曲线可知, 引起蓝光发射源于Tm³⁺的电偶极跃迁。     

试验优化设计Er3+-Yb3+共掺杂Gd2Ti2O7上转换发光特性

采用溶胶-凝胶（Sol-gel）法制备了Er³⁺-Yb³⁺共掺杂Gd₂Ti₂O₇纳米晶粉末,通过试验优化设计的理论建立了Er³⁺-Yb³⁺掺杂浓度与发光强度的回归方程,利用遗传算法优化计算出方程的最优解Er³⁺、Yb³⁺掺杂浓度分别为5.60%（物质的量分数）和13.43%。Er³⁺-Yb³⁺共掺杂Gd₂Ti₂O₇纳米晶粉末为单一面心立方Gd₂Ti₂O₇相结构,随Yb³⁺共掺杂浓度增加,X射线衍射峰逐渐向高角偏移。在976 nm激光激发下,Er³⁺-Yb³⁺共掺杂Gd₂Ti₂O₇获得了分别对应于Er³⁺的²H_11/2/⁴S_3/2→⁴I_15/2和⁴F_9/2→⁴I_15/2跃迁的绿色和红色上转换发光,且绿色和红色发光均为双光子吸收过程。研究了最优样品上转换发光与温度之间的关系,发现绿色上转换发光具有优良的温度传感特性,对红色上转换发光的温度猝灭进行了解释。     

Gd3+掺杂TiO2纳米复合材料的可见光响应性能

采用溶胶-凝胶技术,在钛酸四丁酯(TBOT)的水解过程中,加入硝酸钆(Gd(NO₃)₃),得到具有可见光响应活性的Gd³⁺/TiO₂复合材料。应用TEM、XRD、TG-DTA和UV-Vis等手段对纳米TiO₂复合材料进行了表征。当Gd³⁺的掺杂量为0.5%时,Gd³⁺/TiO₂复合材料在550 nm附近产生宽强吸收带。Gd³⁺进入TiO₂晶格中,形成了新的掺杂能级(E_g=1.27 eV)。适量Gd³⁺掺杂的纳米TiO₂复合材料的光催化性能优于纯TiO₂粉体材料。     

静电纺丝技术制备Y2O3∶Eu3+纳米带及其发光性质

采用静电纺丝技术制备了PVP/[Y(NO₃)₃+Eu(NO₃)₃]复合纳米带,将其进行热处理,获得了Y₂O₃∶Eu³⁺纳米带。采用XRD、FTIR、SEM、TEM、荧光光谱等技术对焙烧后的样品进行了表征。结果表明：600 ℃焙烧即可获得Y₂O₃∶Eu³⁺纳米带,800 ℃时结晶更为良好,产物属于立方晶系。纳米带表面光滑,由平均直径为30 nm的小颗粒紧密排列而成,为多晶结构。随着温度升高,纳米带宽度减小。焙烧800 ℃获得的Y₂O₃∶Eu³⁺纳米带的发光性质优于焙烧600 ℃的Y₂O₃∶Eu³⁺纳米带。与体材料相比,该纳米带的激发光谱Eu³⁺-O^2-电荷迁移态(CTB)发生红移,发射光谱发生蓝移。     

CaWO4:xEu3+,ySm3+,zLi+红色荧光粉的制备及光学性能

采用微波固相法制备了CaWO₄：xEu³⁺,ySm³⁺,zLi⁺红色荧光粉。测量样品的XRD图、激发谱、发射谱及发光衰减曲线,研究并分析了Eu³⁺、Sm³⁺、Li⁺的掺杂浓度,对样品微结构、光致发光特性、能量传递及能级寿命的影响。结果表明,Eu³⁺、Sm³⁺、Li⁺掺杂并未引起合成粉体改变晶相,仍为CaWO₄单一四方晶系结构。Eu³⁺、Sm³⁺共掺样品中,Sm³⁺掺杂为3%时,Sm³⁺对Eu³⁺的能量传递最有效。Li⁺掺杂起到了助熔剂和敏化剂的作用,使样品发光更强。在394 nm激发下,与CaWO₄：3%Eu³⁺样品比较,3%Eu³⁺、3%Sm³⁺共掺CaWO₄及3%Eu³⁺、3%Sm³⁺、1%Li⁺共掺CaWO₄样品的发光分别增强2倍及2.4倍。同一激发波长下,单掺Eu³⁺样品寿命最短,Sm³⁺、Eu³⁺共掺样品随Sm³⁺浓度增加,寿命先减小后增加,且掺杂了Li⁺的样品比不掺Li⁺的样品⁵D₀能级寿命有所增加。     

稀土Y2-xSiO5∶Eux3+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Y_2-xSiO₅∶Eu_x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15～45 nm，在晶态时颗粒大小为60～80 nm。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Y_2-xSiO₅∶Eu_x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60～80 nm的Y_2-xSiO₅∶Eu_x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。     

共沉淀法合成Yb3+∶Y2O3纳米粉及透明陶瓷的性能

以Y₂O₃为基质材料,掺杂不同含量的Yb³⁺,采用共沉淀法制备出性能良好的Yb³⁺∶Y₂O₃纳米粉,将粉体在1 700 ℃和真空度为1×10^-3 Pa下烧结5 h得到Yb³⁺∶Y₂O₃透明陶瓷。用XRD、TEM、UV-Vis、FL分别对样品的结构、形貌和发光性能进行了研究。结果表明：Yb³⁺完全固溶于Y₂O₃的立方晶格中,Yb³⁺∶Y₂O₃粉体大小均匀,近似球形,尺寸约40～60 nm。Yb³⁺∶Y₂O₃透明陶瓷相对密度为99.7%,在波长600～800 nm范围内其透光率达到80%。Yb³⁺∶Y₂O₃透明陶瓷在950 nm处吸收线宽达到26 nm,在1 031 nm和1 076 nm处的发射线宽分别为13 nm和17 nm。     

Y1-xCaxBaCo2O5+δ的制备和性能表征

利用固相反应法合成了层状钙钛矿钴氧化物Y_1-xCa_xBaCo₂O_5+δ(x=0,0.1,0.15,0.2)材料,系统研究了材料的氧吸附性能和电输运性质。XRD结果表明Ca²⁺掺杂的样品具有母相YBaCo₂O_5+δ层状钙钛矿结构,随着Ca²⁺掺杂量的增加,样品的晶格参数增大。TG结果显示：从室温到1 273 K,所有样品经历了两次吸氧和脱氧的过程,Ca²⁺掺杂增强了样品的氧脱附性能。在中低温下,约650 K附近,吸氧量达到最大,同时,样品发生了半导体金属转变。Ca²⁺掺杂量的增加,半导体金属转变温度增大,电导率下降。半导体金属转变与氧变化量δ有关而电导率下降与Ca²⁺掺杂引起Co³⁺离子的增加有关。     

Sol–gel preparation and properties of hydroxypropylcellulose–titania hybrid thin films

Hydroxypropylcellulose (HPC)–titania hybrid thin films were prepared by sol–gel method where titanium tetraisopropoxide Ti(OC₃H₇ ⁱ )₄ was hydrolyzed under acidic conditions in the presence of HPC, followed by dip-coating and drying at 120 °C for 24 h. The viscosity average molecular weight of HPC was 55,000–70,000 or 110,000–150,000, and the TiO₂/(HPC + TiO₂) mass ratio ranged from 0 to 1, which was calculated on the assumption that all Ti(OC₃H₇ ⁱ )₄ is converted into TiO₂. The films were 0.35–1.0 μm thick, transparent in visible region and opaque in ultraviolet (UV) region, where the optical absorption coefficient in UV region increased with increasing titania content. The refractive index increased with increasing titania content, ranging from 1.6 to 1.8 for the hybrid thin films. The pencil hardness increased from 6B to 5H, the durability in hot water significantly increased and the contact angle of water on films increased from 35° to 89° with increasing titania content. Crack-free films could be deposited on organic polymer substrates irrespective of titania or HPC contents, where cracking did not occur at higher HPC contents even when the substrate was bent.     

Role of yttrium loading in the physico-chemical properties and soot combustion activity of ceria and ceria–zirconia catalysts

Ce_1−xY_xO₂ and Ce_0.85−xZr_0.15Y_xO₂ mixed oxides have been prepared by 1000 °C-nitrates calcination to ensure thermally stable catalysts. The physico-chemical properties of the mixed oxides have been studied by N₂ adsorption at −196 °C, XPS, XRD, Raman spectroscopy and H₂-TPR, and the catalytic activity for soot oxidation in air has been studied by TG in the loose and tight contact modes. Yttrium is accumulated at the surface of Ce_1−xY_xO₂ and Ce_0.85−xZr_0.15Y_xO₂, and this accumulation is more pronounced for the former formulation than for the latter, because the deformation of the lattice due to zirconium doping favours yttrium incorporation. Yttrium and zirconium exhibit opposite effects on the surface concentration of cerium; while zirconium promotes the formation of cerium-rich surfaces, yttrium hinders the accumulation of cerium on the surface. For experiments in tight contact between soot and catalyst, all the Ce_1−xY_xO₂ catalysts are more active than bare CeO₂, and Ce_0.99Y_0.01O₂ is the most active catalyst. The benefit of yttrium doping in catalytic activity of ceria can be related to two facts: (i) the Y³⁺ surface enrichment hinders crystallite growth; (ii) the surface segregation of Y³⁺ promotes oxygen vacancies creation. High yttrium loading (x = 0.12) is less effective than low dosage (x = 0.01) because yttrium is mainly accumulated at the surface of the particles and hinders the participation of cerium in the soot oxidation reaction, which is the active component. For the mixed oxides with formulation Ce_0.85−xZr_0.15Y_xO₂ (operating in tight contact) the effect of zirconium on the catalytic activity prevails with respect to that of yttrium. For experiments in loose contact between soot and catalyst, the catalytic activity depends on their BET surface area, and the catalysts Ce_0.85−xZr_0.15Y_xO₂ (BET = 10–13 m²/g) are more active than the catalysts Ce_1−xY_xO₂ (BET = 2–3 m²/g). In the loose contact mode, the yttrium doping and loading have a minor or null affect on the activity, and the stabilising effect of the BET area due to zirconium doping prevails.     

Microstructures and photocatalytic properties of Ag and La surface codoped TiO2 films prepared by sol–gel method

Ag⁺ and La³⁺ surface codoped TiO₂ films were successfully prepared by the improved sol–gel and doping processes. The as-prepared specimens were characterized using differential thermal analysis-thermogravimetry (DTA–TG), X-ray diffraction (XRD), high-resolution field emission scanning electron microscopy (FE-SEM), X-ray energy dispersive spectroscopy (EDS), Brunauer–Emmett–Teller (BET) surface area, Photoluminescence spectrum (PL) and UV–vis diffuse reflectance spectroscopy. The photocatalytic activities of the films were evaluated by degradation of an organic dye in aqueous solution. The results of XRD, FE-SEM and BET analyses indicated that the TiO₂ films were composed of nano-particles or aggregates with a size of less than 10 nm. With the codoping of Ag⁺ and La³⁺, TiO₂ films with high photocatalytic activity and clearly responsive to the visible light were obtained. The improvement mechanism by ions doping was also discussed.     

Vacuum Ultraviolet Excited Photoluminescence Properties of Y2O2S：Eu^3＋,Bi^3＋ Phosphor

As an Hg-free lamp using phosphor, the Bi^3＋ and EH^3＋ co-doped Y2O2S phosphors were prepared and their luminescence properties under vacuum ultraviolet（VUV） excitation were investigated. The VUV photoluminescent intensity of Y2O2S：Eu^3＋ was weak, however, considerably stronger red emission at 626 nm with good color purity was observed in Y2O2S：Eu^3＋,Bi^3＋ systems. Investigation on the photoluminescence reveals that the strong VUV luminescence of Y2O2S：Eu^3＋,Bi^3＋ at 147 nm is mainly because the Bi^3＋ acts as a medium and effectively performs the energy transfer process： Y^3＋-O^2-→Bi^3＋→Eu^3＋, while the intense emission band at 172 nm is attributed to the absorption of the characteristic ^1So-^1P1 transition of Bi^3＋ and the direct energy transfer from Bi^3＋ to Eu^3＋. The Y2O2S：Eu^3＋,Bi^3＋ shows excellent VUV optical properties compared with the commercial （Y,Gd）BO3：Eu^3＋. Thus, the Y2O2S：Eu^3＋,Bi^3＋ can be a potential red VUV-excited candidate applied in Hg-free lamps for backlight of liquid crystal display.     

Fabrication,patterning and luminescence properties of X2–Y2SiO5:A (A=Eu3+, Tb3+, Ce3+) phosphor films via sol–gel soft lithography

X₂–Y₂SiO₅:A (A=Eu³⁺, Tb³⁺, Ce³⁺) phosphor films and their patterning were fabricated by a sol–gel process combined with a soft lithography. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM), scanning electron microscopy (SEM) optical microscopy and photoluminescence (PL) were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 900 °C with X₁–Y₂SiO₅, which transformed completely to X₂–Y₂SiO₅ at 1250 °C. Patterned thin films with different band widths (5 μm spaced by 5 μm and 16 μm spaced by 24 μm) were obtained by a soft lithography technique (micromoulding in capillaries, MIMIC). The SEM and AFM study revealed that the nonpatterned phosphor films were uniform and crack free, and the films mainly consisted of closely packed grains with an average size of 350 nm. The doped rare earth ions (A) showed their characteristic emissions in X₂–Y₂SiO₅ phosphor films, i.e., ⁵D₀–⁷F_J (J=0,1,2,3,4) for Eu³⁺, ⁵D_{3, 4}–⁷F_J (J=6,5,4,3) for Tb³⁺ and 5d (²D)–4f (²F_{2/5, 2/7}) for Ce³⁺, respectively. The optimum doping concentrations for Eu³⁺, Tb³⁺ were determined to be 13 and 8 mol% of Y³⁺ in X₂–Y₂SiO₅ films, respectively.     

掺杂Zr4+对纳米Au/TiO2催化剂结构和性能的影响

采用氨水反滴加沉淀法合成了Zr4+掺杂的系列TiO2载体,以尿素溶液为沉淀剂,用沉积-沉淀法制备负载金催化剂。运用N2吸附-脱附(BET)、X射线衍射(XRD)、X射线荧光(XRF)、高分辨电镜(HR-TEM)和氨吸附红外光谱(NH3-IR)等技术对催化剂的结构与形貌进行了表征,并在色谱-微反应装置上考察了催化剂对CO氧化反应的活性。结果表明:(1)少量的Zr4+掺杂可形成锐钛矿型固溶体,且载体的比表面积增大;随着Zr4+掺杂量增加至10%以上,载体逐渐向无定形转变,同时比表面积急剧增大。(2)保持规整锐钛矿晶相的Zr4+掺杂载体,其表面Lewis酸位占有率较高,且具备结构缺陷,而无定形载体表面的Lewis酸位占有率大幅度降低。(3)载体表面的Lewis酸位以及结构缺陷有利于增强载体对Au颗粒的锚定作用,从而减弱焙烧过程中的颗粒聚集。(4)少量Zr4+掺杂入TiO2载体中,可以提高Au颗粒的抗烧结能力,焙烧所得的Au颗粒尺寸较小(3.63 nm),且表现出优异的催化活性,在常温下就可以将CO完全氧化。     

Photocatalytic degradation of methylene blue on Fe3+-doped TiO2 nanoparticles under visible light irradiation

Fe³⁺-doped TiO₂ composite nanoparticles with different doping amounts were successfully synthesized using sol-gel method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and ultravioletvisible spectroscopy (UV-Vis) diffuse reflectance spectra (DRS). The photocatalytic degradation of methylene blue was used as a model reaction to evaluate the photocatalytic activity of Fe³⁺/TiO₂ nanoparticles under visible light irradiation. The influence of doping amount of Fe³⁺ (ω: 0.00%–3.00%) on photocatalytic activities of TiO₂ was investigated. Results show that the size of Fe³⁺/TiO₂ particles decreases with the increase of the amount of Fe³⁺ and their absorption spectra are broaden and absorption intensities are also increased. Doping Fe³⁺ can control the conversion of TiO₂ from anatase to rutile. The doping amount of Fe³⁺ remarkably affects the activity of the catalyst, and the optimum efficiency occurs at about the doping amount of 0.3%. The appropriate doping of Fe³⁺ can markedly increase the catalytic activity of TiO₂ under visible light irradiation. __________ Translated from Journal of Northwest Normal University (Natural Science), 2006, 42(6): 55–56 [译自: 西北师范大学学报(自然科学版)]     

Ru–bis(pyridine)pyrazolate (bpp)‐Based Water‐Oxidation Catalysts Anchored on TiO2: The Importance of the Nature and Position of the Anchoring Group

Three distinct functionalisation strategies have been applied to the in,in‐[{Ru^II(trpy)}₂(μ‐bpp)(H₂O)₂]³⁺ (trpy=2,2′:6′,2′′‐terpyridine, bpp=bis(pyridine)pyrazolate) water‐oxidation catalyst framework to form new derivatives that can adsorb onto titania substrates. Modifications included the addition of sulfonate, carboxylate, and phosphonate anchoring groups to the terpyridine and bis(pyridyl)pyrazolate ligands. The complexes were characterised in solution by using 1D NMR, 2D NMR, and UV/Vis spectroscopic analysis and electrochemical techniques. The complexes were then anchored on TiO₂‐coated fluorinated tin oxide (FTO) films, and the reactivity of these new materials as water‐oxidation catalysts was tested electrochemically through controlled‐potential electrolysis (CPE) with oxygen evolution detected by headspace analysis with a Clark electrode. The results obtained highlight the importance of the catalyst orientation with respect to the titania surface in regard to its capacity to catalytically oxidize water to dioxygen.     

Visible and near-IR luminescence via energy transfer in rare earth doped mesoporous titania thin films with nanocrystalline walls

Selected photoluminescence in the wavelength range of 600-1540 nm is generated by energy transfer from a light-gathering mesostructured host lattice to an appropriate rare earth ion. The mesoporous titania thin films, which have a well-ordered pore structure and two-phase walls made of amorphous titania and TiO₂ nanocrystallites, were doped with up to 8 mol% lanthanide ions, and the ordered structure of the material was preserved. Exciting the titania in its band gap results in energy transfer and it is possible to observe photoluminescence from the crystal field states of the rare earth ions. This process is successful for certain rare earth ions (Sm³⁺, Eu³⁺, Yb³⁺, Nd³⁺, Er³⁺) and not for others (Tb³⁺, Tm³⁺). A mechanism has been proposed to explain this phenomenon, which involves energy transfer through surface states on titania nanocrystals to matching electronic states on the rare earth ions.