纳米晶钛酸钡粉体的相结构

采用溶剂热法一步合成了3~5nm单分散纳米晶钛酸钡(BaTiO3)粉体,利用原位变温Raman光谱研究了纳米晶BaTiO3粉体的微区结构特性。结果表明:纳米晶BaTiO3相变区间弥散,呈现多相共存的结构特性;即使晶粒尺寸小到5nm,仍然具有与大晶粒BaTiO3陶瓷类似的行为,即随温度升高经历从三方相→正交相→四方相→立方相的连续相变。     

ZnS∶Mn纳米晶的制备与荧光性能研究

本文采用胶体化学方法合成了无稳定剂修饰和巯基丙酸为稳定剂的单分散Zn S∶Mn掺杂纳米晶,研究了稳定剂对纳米晶荧光性能的影响。紫外吸收光谱说明了掺杂纳米晶具有明显的量子限域效应,与体相材料相比,紫外吸收带边蓝移了0.29 e V。荧光发射光谱研究表明,巯基丙酸稳定剂对纳米晶表面的修饰使得主体Zn S纳米晶的表面缺陷发射明显消失。掺杂纳米晶在575 nm处有一强的荧光发射峰,其归属于Mn的4T1-6A1跃迁产生的荧光发射。     

谷氨酰胺为稳定剂制备硒化镉纳米晶及光谱性质研究

以谷氨酰胺(Gln)为稳定剂合成了硒化镉纳米晶,利用X-射线粉末衍射(XRD)和透射电镜(TEM)对纳米晶结构进行了表征,粒径约为20 nm。通过紫外-可见吸收光谱、激发光谱与发射光谱研究了纳米晶光谱特性。实验结果表明,反应温度过高、反应时间过长都会破坏谷氨酰胺(Gln)的稳定作用,使CdSe聚集,影响其荧光性质。而聚乙二醇(PEG)的加入会使纳米晶的荧光发射明显加强,而且发射峰峰形尖锐。     

不同添加剂对铌酸钙掺铋纳米晶形貌和发光性能的影响

采用溶胶凝胶燃烧法合成了具有不同形貌和发光性能的纳米CaNb2O6:Bi3+和纳米CaNb2O6:1%Bi3+,1/2K+。通过调整不同添加剂的量,合成了一些有趣的纳米晶形,如球形、花状和棒状。在254nm紫外光激发下,该材料的发射光谱有两部分组成:一部分是弱的发射带,中心约在360nm;另一部分是410~650nm的较强发射区。在315nm紫外光激发下,该材料表现出350~650nm的宽带发射。透射电子显微镜和荧光光谱证实了纳米晶的形貌和尺寸对材料的发光行为有重大影响,并分析了产生这些影响的原因。     

氧化镓之字形纳米材料性能和结构研究

利用XRD、FESEM、SAED、EDS、HRTEM和PL分别时氧化镓之字形纳米材料的形貌和结构进行了分析.研究结果表明,之字形纳米氧化镓具有良好的结晶性,沿着[103]方向子自堆垛生长;光致发光光谱显示,氧化镓之字形纳米晶在370nm处有很强的发射峰,并有几十纳米的蓝移.     

光触媒纳米二氧化钛应用研究

将纳米TiO2制备戍含氟反相乳液，再利用超临界CO2流体技术将分散在乳液中的TiO2粒子注入纤维之中，制备戍具有光自洁功能的纤维制品，将其置于含有甲醛气体的密闭容器中，在不同功率的紫外光源照射下，测定密闭容器中甲醛气体随时间的变化率，以探讨纳米TiO2对有害气体的分解能力，对纳米TiO2微粒的乳化与分散、晶型、结构类型和添加剂等影响光催化效率的若干因素也进行了讨论。     

溶胶-凝胶法制备纳米晶γ-Al2O3：Tb^3＋粉末及其发光性能

以异丙醇铝为原料,聚乙二醇(PEG1000)为络合剂,采用溶胶-凝胶法制备了纳米晶γ-Al2O3:Tb3+发光粉;并采用DTA/TG、XRD、TEM及荧光光谱对其进行了一系列表征.研究结果表明:采用溶胶-凝胶制备工艺,经800℃煅烧4 h,可以得到发光强度高的纳米晶γ-Al2O3:Tb3+发光粉;发光粉的最佳激发波长为251 nm,对应于Tb3+4f-5d跃迁;最佳掺杂浓度为5%(物质的量浓度,下同),在251 nm光激发下,最强的发射峰位于544 nm,可以用作绿色发光材料.     

钕掺杂钡铝硅透明玻璃陶瓷的制备和表征

采用熔融-晶化技术制备了含纳米微晶的Nd3+:BaO-Al2O3-SiO2透明玻璃陶瓷,用差热分析仪、X射线衍射分析仪、扫描电子显微镜和紫外-可见-近红外分光光度计和Fourier变换荧光光谱仪对样品的成核-晶化温度、晶相组成、微观形貌、光透过率和光谱性能进行了测试和表征.结果表明,钕掺杂钡铝硅系透明玻璃陶瓷的最佳成核温度为690℃,最佳成核时间为4 h,观测到钕掺杂钡铝硅玻璃陶瓷在808 nm激发下于1068nm处存在较强发射峰.     

纳米晶LaAlO_3掺Eu~(3+)的复合沉淀法制备及发光性质

以NH3·H2O-NH4HCO3混合溶液为复合沉淀剂,制备了LaAlO3∶Eu3+纳米晶体.通过X射线衍射、扫描电镜和透射电镜对产物进行了表征,用荧光光度计测试了样品的三维荧光光谱、激发光谱和发射光谱.结果表明:前驱沉淀物经800℃焙烧处理2h,制备出球型形貌,颗粒分散性好、尺寸约为40nm的立方相LaAlO3纳米晶.由三维荧光光谱确定了LaAlO3∶Eu3+的最佳监测波长和激发波长,在395nm波长光的激发下观察到纳米LaAlO3中Eu3+的591nm(5D0-7F1)和613nm(5D0-7F2)特征发射谱,磁偶极跃迁5D0-7F1的发射峰强度要比电偶极跃迁5D0-7F2更强,而且这种趋势随着焙烧温度的升高明显增强,说明由该法制备的纳米LaAlO3中Eu3+离子占据的位置具有高的对称性.     

稀土离子掺杂Ba0.65Zr0.35F2.70上转换纳米晶的制备与表征

采用水热法,以EDTA为络合剂制备了Ba0.65Zr0.35F2.70:Er3+,Yb3上转换纳米晶.采用XRD、TEM对样品进行物相、结构和形貌分析,确定了样品纳米晶的粒径尺寸,其粒径在20～ 40 nm之间.当Yb3:Er3+物质的量比为4:1时,上转换发光强度最强.根据泵浦功率与发光强度的关系曲线确定了523 nm、546 nm、650 nm的发射峰均属于双光子过程.     

CO2 laser-assisted preparation of transparent Eu2Ti2O7 thin films

We present a laser-assisted preparation of transparent europium-titanate Eu₂Ti₂O₇ thin films with tailored structural and optical properties. We have evaluated the effects of the irradiation time on the structural and the optical properties of the films. This approach allows the preparation of nanocrystalline crack-free films and micro patterns. The amorphous thin films were prepared by a sol-gel method. The films were annealed by a CO₂ laser beam for various time intervals. The laser irradiation induced a crystallization process that resulted in the formation of Eu₂Ti₂O₇ nanocrystals. The nanocrystals regularly grew with increasing irradiation time reaching the size from 25?nm to 45?nm. A film of a thickness 480?nm exhibited an optical transmission of 91.9% that is close to the maximal theoretical limit. The film's refractive index at 632?nm was 2.26. A micrometric pattern was prepared by a direct laser writing followed by a wet chemical etching. Feasibility of the demonstrated approach, together with the high film's quality, and europium-titanate chemical resistivity open up many opportunities for advanced applications. The approach can be used for a preparation of protective coatings and integrated photonic devices such as planar optical waveguides and couplers.     

Eu2+-Doped Glass Ceramics Containing BaF2 Nanocrystals as a Potential Blue Phosphor for UV-LED

The Eu²⁺-doped glass ceramics containing BaF₂ nanocrystals were prepared and their luminescence properties were investigated. The excitation spectra of Eu²⁺-doped glass ceramics showed an excellent overlap with the main emission region of an ultraviolet light-emitting diode (UV-LED) centered at 380 nm. The 450 nm emission of Eu²⁺ in glass ceramics under the 385 nm excitation was much stronger than that in glass. The Eu²⁺-doped glass ceramics containing BaF₂ nanocrystals may be used as a potential blue-emitting phosphor for UV-LED.     

Enhanced upconversion study of Er3+-Yb3+ codoped NaYF4 phosphors synthesized by the reverse microemulsion method

Herein, nanocrystals of Er³⁺ and Er³⁺, Yb³⁺ co-doped NaYF₄ upconversion (UC) phosphor were prepared via the reverse-microemulsion method. The impact of different concentrations of Er³⁺ ions on the UC emission intensity after 980?nm diode laser excitation is discussed. The structure, morphology and composition of the nanophosphors were confirmed by X-ray diffraction, transmission electron microscopy, scanning electron microscopy and the results showed the presence of NaYF₄ nanocrystals with hexagonal phases of NaYF₄. The UC spectra revealed two emission bands including a green and a red emission band and the CIE coordinate for the samples were estimated. The present research revealed that the reverse-microemulsion approach will be suitable for the synthesis of efficient upconversion nanophosphors.     

Synthesis and Photoluminescence Properties of Eu3+-Doped Calcium Phosphates

Eu³⁺-doped (1–12 mol%) calcium hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) powders were synthesized by a precipitation method and their photoluminescence (PL) properties were investigated. Eu has a limited solubility in HA and Eu₂O₃ was detected by X-ray diffraction above 3% doping, whereas a nearly single β-phase was obtained up to 6% doping in TCP but EuPO₄ appeared in the 12% Eu-doped specimen. Electron spin resonance measurement confirmed that europium ions exist as Eu³⁺ in both samples. Eu³⁺-doped HA exhibited a strong emission at 575 nm with several minor peaks at 610–640 nm and Eu³⁺-doped TCP had an intense emission at 613 nm with secondary peaks at 590–600 nm, which were consistent with the earlier reports determined at low temperatures. In Eu-doped TCP, the PL intensity increased with increasing calcination temperature without phase transformation. The more the Eu added, the higher the PL intensity obtained in both cases.     

Y掺杂BaZrO3纳米管阵列的制备和光致发光性能

以阳极氧化制备的ZrO2纳米管阵列为模板,采用水热法合成了不同量Y掺杂的BaZrO3纳米管阵列薄膜。通过TEM、XRD和SEM等方法对样品进行了表征。结果表明,样品薄膜均由纳米管组成,管壁光滑均匀。Y3+掺杂进入BaZrO3晶格中,产物具有立方钙钛矿型结构。不同掺杂量的纳米管阵列在400 nm光激发下发出波长为454 nm的蓝光和530 nm的绿光,并且在Y掺杂量小于5 mol%范围内,随着Y掺杂量的增加发光强度逐渐增强。     

Al掺杂对甲醇醇解法合成ZnO纳米粉体的影响

采用醇解法,在130℃的甲醇溶液中分别合成纯的和Al掺杂纳米氧化锌(ZnO)晶体.使用X射线衍射仪,透射电子显微镜,Fourier红外光谱和偏振稳态荧光光谱对其晶体结构和光学性能进行了表征.结果表明:在甲醇溶液中,在较低的温度(130℃)下,成功制备出纳米ZnO晶体.Fourier红外吸收光谱表明醇解法合成的ZnO纳米晶体含有较少的有机物杂质.荧光光谱结果可以看出,纯ZnO和Al掺杂的ZnO纳米晶体在可见光范围(400nm～700nm)内有一个高的蓝光发光带(峰位为440nm)和一个绿光发光带(纯的和Al掺杂的峰位分别为520nm和530nm).通过对比发现掺杂Al可以有效的改变ZnO纳米粉体的可见光发光特性.     

Modification of Optical Properties of SrAl_2O_4：Eu~（2＋）,Dy~（3＋） Phosphor by Terbium Doping

以尿素为燃料,采用快速燃烧法在650℃合成了Tb3＋掺杂的SrAl2O4：Eu2＋,Dy3＋新型长余辉光致发光材料。研究了Tb3＋掺杂对Eu2＋,Dy3＋共激活的铝酸盐长余辉发光材料的发光特性的影响。X射线衍射分析结果表明：当Tb3＋的掺杂量x=0.17%时,合成的样品结构为单相SrAl2O4单斜晶系。光致发光测试结果表明：样品的激发光谱为峰值位于345nm附近的连续宽带谱,发射光谱为峰值位于510nm左右的连续宽带谱。余辉衰减曲线结果表明：Tb3＋的适量掺杂可以提高铝酸锶的余辉性能。与SrAl2O4：Eu2＋,Dy3＋相比,掺杂Tb3＋有利于形成结晶度良好的固溶体,样品中的晶体细密紧凑,颗粒粒径约为100nm。     

Optical characterisation of silicon nanocrystals embedded in SiO2/Si3N4 hybrid matrix for third generation photovoltaics

ABSTRACT: Silicon nanocrystals with an average size of approximately 4 nm dispersed in SiO2/Si3N4 hybrid matrix have been synthesised by magnetron sputtering followed by a high-temperature anneal. To gain understanding of the photon absorption and emission mechanisms of this material, several samples are characterised optically via spectroscopy and photoluminescence measurements. The values of optical band gap are extracted from interference-minimised absorption and luminescence spectra. Measurement results suggest that these nanocrystals exhibit transitions of both direct and indirect types. Possible mechanisms of absorption and emission as well as an estimation of exciton binding energy are also discussed.     

Upconversion emission of ZrO2 nanoparticles doped with erbium (Er3+) and ytterbium (Yb3+), synthesized by hydrothermal route

This paper reports the luminescent response upconversion of zirconium oxide (ZrO₂) nanoparticles doped with erbium (Er³⁺) and ytterbium (Yb³⁺) ions, synthesized by hydrothermal route. X ray diffraction (DRX) showed that the synthesized material presents the face centered cubic (FCC) structure. High resolution transmission electron microscopy (HRTEM) showed the presence of crystals size smaller than 10 nm. The photoluminescent analysis allowed to observe an intense upconversion luminescence emission of the samples doped with both ions Er³⁺ and Yb³⁺, when these are excited with 910 nm laser source, showing the electronic transitions ⁴F_9/2 → ⁴I_5/2; ²H_11/2 → ⁴I_5/2; ⁴S_3/2 → ⁴I_15/2 of Er³⁺. Two decay times were observed, whose behavior can be associated to the average distance between erbium ions within the nanocrystals.     

Al2O3 Colloidal Nanocrystals with Strong UV Emission

A facile sol–gel procedure has been developed for the synthesis of colloidal alumina nanocrystals. For the first time, optical characterization procedures were employed to study the quantum confinement effects in optical properties of the prepared Al₂O₃ sol. Accordingly, the hyperbolic band model was used to determine the optical band gap of colloidal alumina nanocrystals. X‐Ray diffraction pattern was used to study the crystallographic phase of the dried gel. Morphological characterization was performed using scanning electron microscopy (SEM). Inductively Coupled Plasma (ICP) emission spectroscopy was used to determination purity of the Al₂O₃ powder. High‐resolution TEM showed that the diameter of colloidal nanocrystals is about 10 nm. Photoluminescence spectroscopy demonstrated that quantum yields for colloidal nanocrystals are 68% with 300 nm excitation wavelength. The experimental observations confirm that highly stable alumina sol with strong UV emission was synthesized. The mentioned optical properties have not been reported before.