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1.
The anisotropic shape transformation of gold nanorods (GNRs) with H2O2 was observed in the presence of “cethyl trimethylammonium bromide” (CTAB). The adequate oxidative dissolution of GNR is provided by the following autocatalytic scheme with H2O2: Au0 → Au+, Au0 + Aun+ → 2Au3+, n = 1 and 3. The shape transformation of the GNRs was investigated by UV-vis spectroscopy and transmission electron microscopy (TEM). As-synthesised GNRs exhibit transverse plasmon band (TPB) at 523 nm and longitudinal plasmon band (LPB) at 731 nm. Upon H2O2 oxidation, the LPB showed a systematic hypsochromic (blue) shift, while TPB stays at ca. 523 nm. In addition, a new emerging peak observed at ca. 390 nm due to Au(III)-CTAB complex formation during the oxidation. TEM analysis of as-synthesised GNRs with H2O2 confirmed the shape transformation to spherical particles with 10 nm size in 2 h, whereas centrifuged nanorod solution showed no changes in the aspect ratio under the same condition. Au3+ ions produced from oxidation, complex with excess free CTAB and approach the nanorods preferentially at the end, leading to spatially directed oxidation. This work provides some information to the crystal stability and the growth mechanism of GNRs, as both growth and shortening reactions occur preferentially at the edge of single-crystalline GNRs, all directed by Br ions.  相似文献   

2.
In this paper we report the combustion synthesis of trivalent rare-earth (RE3+ = Dy, Eu and Ce) activated Sr4Al2O7 phosphor. The prepared phosphors were characterized by the X-ray powder diffraction (XRD) and photoluminescence (PL) techniques. Photoluminescence emission peaks of Sr4Al2O7:Dy3+ phosphor at 474 nm and 578 nm in the blue and yellow region of the spectrum. The prepared Eu3+ doped phosphors were excited by 395 nm then we found that the characteristics emission of europium ions at 615 nm (5D0?7F2) and 592 nm (5D0?7F1). Photoluminescence (PL) peaks situated at wavelengths of 363 and 378 nm in the UV region under excitation at around 326 nm in the Sr4Al2O7:Ce3+ phosphor.  相似文献   

3.
钙钛矿型纳米BaFeO3的制备、结构表征及铁磁性研究   总被引:1,自引:0,他引:1       下载免费PDF全文
刘妍妍  刘发民  石霞  丁芃  周传仓 《物理学报》2008,57(11):7274-7278
采用溶胶-凝胶法制备出钙钛矿型纳米BaFeO3粉末,利用X射线衍射(XRD)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)分析研究了其微观结构及形貌,结果表明:胶体试样经800℃退火处理后,形成了20nm左右的钙钛矿型BaFeO3粉末,其(110)面晶面间距为0.280nm左右,(100)面晶面间距为0.401nm左右.利用振动样品磁强计(VSM)研究了纳米BaFeO3粉末的室温铁磁性能,测量结果表明:在室温条件下,纳米BaFeO关键词: 溶胶-凝胶法 3')" href="#">钙钛矿型纳米BaFeO3 铁磁性 氧空位  相似文献   

4.
Thin films of ZnWO4 and CdWO4 were prepared by spray pyrolysis and the structural, optical, and luminescence properties were investigated. Both ZnWO4 and CdWO4 thin films showed a broad blue-green emission band. The broad band of ZnWO4 films was centered at 495 nm (2.51 eV) consisted of three bands at 444 nm (2.80 eV), 495 nm (2.51 eV) and 540 nm (2.30 eV). The broad band of CdWO4 films at 495 nm (2.51 eV) could be decomposed to three bands at 444 nm (2.80 eV), 495 nm (2.51 eV) and 545 nm (2.28 eV). These results are consistent with emission from the WO66− molecular complex. The luminance and efficiency for ZnWO4 film at 5 kV and 57 μA/cm2 were 48 cd/m2 and 0.22 lm/w, respectively, and for CdWO4 film the values were 420 cd/m2 and 1.9 lm/w.  相似文献   

5.
In this paper, the Sr3Y2 (BO3)4:Eu3+ phosphor was synthesized by high temperature solid-state reaction method and the luminescence characteristics were investigated. The emission spectrum exhibits one strong red emission at 613nm corresponding to the electric dipole 5D0--7F2 transition of Eu3+ under 365nm excitation, this is because Eu3+ substituted for Y3+ occupied the non-centrosymmetric position in the crystal structure of Sr3Y2 (BO3)4. The excitation spectrum indicates that the phosphor can be effectively excited by ultraviolet (254nm, 365nm and 400nm) and blue (470nm) light. The effect of Eu3+ concentration on the red emission of Sr3Y2 (BO3)4:Eu3+ was measured, the result shows that the emission intensities increase with increasing Eu3+ concentration, then decrease. The Commission Internationale del'Eclairage chromaticity (x, y) of Sr3Y2(BO3)4:Eu3+ phosphor is (0.640,0.355) at 15 mol% Eu3+.  相似文献   

6.
Green emission at around 500 nm is observed in Gd2O3:Ce3+ nanoparticles and the intensity is highly dependent on the concentration of Ce3+ in the nanoparticles. The luminescence of this emission displays both picosecond (ps) and millisecond (ms) lifetimes. The ms lifetime is over four orders of magnitude longer than typical luminescence lifetimes (10-40 ns) of Ce3+ in traditional Ce3+ doped phosphors and therefore likely originates from defect states. The picosecond lifetime is shorter than the typical Ce3+ value and is also likely due to defect or surface states. When the samples are annealed at 700 °C, this emission disappears possibly due to changes in the defect moieties or concentration. In addition, a blue emission at around 430 nm is observed in freshly prepared Gd2O3 undoped nanoparticles, which is attributed to the stabilizer, polyethylene glycol biscarboxymethyl ether. On aging, the undoped particles show similar emission to the doped particles with similar luminescence lifetimes. When Eu3+ ions are co-doped in Gd2O3:Ce nanoparticles, both the green emission and the emission at 612 nm from Eu3+ are observed.  相似文献   

7.
An historic Strontianite-type specimen from Strontian, Scotland, UK, was characterized to broaden our knowledge on luminescence properties of common carbonates. These fibrous aggregates are Strontianite (SrxCa1−xCO3) with circa 6% of CaO, interfacial water, hydrosilicate anions and substitutional divalent cations, e.g., Ca2+, Mn2+, Fe2+ in structural Sr2+ positions. The specimen was analyzed by X-ray Fluorescence Spectrometry (XRF), Environmental Scanning Electron Microscopy coupled with an Energy Dispersive X-ray Spectroscopy (ESEM-EDS) probe, Spatially-resolved Cathodoluminescence under the Scanning Electron Microscope (SEM-CL), Differential-Thermal Analyses (DTA), Thermogravimetry (TG), Thermoluminescence (TL), Radioluminescence (RL) and High Resolution Spectra Thermoluminescence (3DTL), to gain an overview of the spectral emissions, the defect linkages were modified by heating from room temperature (RT) up to 500 °C. Substitutional transition elements are probably responsible for the spectral emission bands from 500 nm to 800 nm and hydrous molecules from 300 nm to 400 nm. DTA–TG analyses performed on little chips, to preserve the fiber interfaces coherence, exhibit minor endothermic peaks attributed to outflow of water groups in fiber interfaces. Both, CL and RL curves show common spectral positions but UV–blue and red emission intensities are counterbalanced since electron irradiation reduces the UV–blue emissions while X-irradiation increases them. The TL curves show a top thermal limit at 300 °C for the 300–400 nm TL emissions which become irreversibly destroyed, whereas the longer wavelength region emits at higher temperature. The non-reversible changes observed in the 320 nm and 360 nm bands during the spectra 3DTL emission could be linked with non-bridging oxygen defects, protons and hydroxyl groups and the red emissions to the 4G (4T1g)–6S Mn2+ ion transition. Following assignations and similar spectral CL patterns of Russian Strontianite samples, the emission-defect assignments: Dy3+ 480 nm; Tb3+ 540 nm; Dy3+ 580 nm and Sm3+ 640 nm cannot be disregarded.  相似文献   

8.
OH and Cl doped Bi4Ge3O12 (BGO) single crystals had been grown by Vertical Bridgman (VB) method. The structure of these crystals was determined by XRD, the transmittance and emission spectra in near infrared region (NIR) were measured at room temperature. 5% OH doped BGO shows a significant emission band peaking around 1181 nm under 808 nm laser diodes (LDs) excitation, and the 5% Cl doped BGO exhibits a relatively weak emission band as well. 100% and 5% OH doped BGO show noticeable emission band centered at about 1346 nm under 980 nm LDs excitation.  相似文献   

9.
OH doped and Bi-rich Bi4Ge3O12 (BGO) single crystals were grown by Vertical Bridgman (VB) method. The structure of these crystals was determined by XRD, and the emission spectra in visible and near infrared region (NIR) were measured at room temperature. The emission spectrum of Bi-rich BGO has extra peaks at 385, 367 and 357 nm, Bi-rich BGO after annealing in Ar at 500 °C for 5 h shows a significant emission band peaking around 1170 nm under 808 nm laser diodes (LDs) excitation, and OH doped BGO shows a noticeable emission band centered at about 1346 nm under 980 nm LDs excitation. A brief discussion is presented.  相似文献   

10.
采用高温固相法制备了Ca2SiO4:Dy3+发光材料.在365nm紫外光激发下,测得Ca2SiO4:Dy3+材料的发射光谱为一多峰宽谱,主峰分别位于486nm,575nm和665nm处;监测575nm发射峰,测得材料的激发光谱为一多峰宽谱,主峰分别位于331nm,361nm,371nm,397nm,435nm,461nm和478nm处.研究了Dy3+掺杂浓度对Ca2SiO4:Dy3+材料发射光谱及发光强度的影响,结果显示,随Dy3+浓度的增大,黄、蓝发射峰强度比(Y/B)逐渐增大,利用Judd-Ofelt理论解释了其原因;随Dy3+浓度的增大,Ca2SiO4:Dy3+材料发光强度先增大,在Dy3+浓度为4 mol%时到达峰值,而后减小,根据Dexter理论其浓度猝灭机理为电偶极-电偶极相互作用.研究了电荷补偿剂Li+,Na+和K+对Ca2SiO4:Dy3+材料发射光谱的影响,结果显示,不同电荷补偿剂下,随电荷补偿剂掺杂浓度的增大,Ca2SiO4:Dy3+材料发射光谱强度的演化趋势相同,即Ca2SiO4:Dy3+材料发射峰强度先增大后减小,但不同电荷补偿剂下,材料发射峰强度最大处对应的补偿剂浓度不同,对应Li+,Na+和K+时,浓度分别为4mol%,4mol%和3mol%. 关键词: 白光LED 2SiO4:Dy3+')" href="#">Ca2SiO4:Dy3+ 发光特性 电荷补偿  相似文献   

11.
Luminescence channels of manganese-doped spinel   总被引:1,自引:0,他引:1  
Two independent luminescence channels are observed from manganese-doped spinel Mn:MgAl2O4. The luminescence around 520 nm is assigned to transition from the lowest electronic excited state 4T1 to the ground state 6A1 of Mn2+ (3d)5 ion by analyzing the excitation spectrum and electron spin resonance measurement. The emission at 650 nm is triggered by the band edge excitation and is assigned similarly to the charge-transfer process associated with the manganese ion.  相似文献   

12.
Photoluminescence properties of thenardite activated with Eu   总被引:1,自引:0,他引:1  
Na2SO4:Eu phosphors were prepared by heating pure natural thenardite with EuF3 at 900 °C for 20 min in air. The photoluminescence (PL) and excitation spectra of as-prepared and γ-ray-irradiated phosphors were observed at 300 K. The PL spectrum under 394 nm excitation consisted of strong narrow bands with peaks at 579, 592, 616, 652, 697 and 741 nm, assigned to the 5D07FJ (J=0, 1, 2, …, 5) transitions, respectively, within Eu3+. The PL spectrum under 340 nm excitation consisted of a broad Eu2+ band with a peak at 435 nm. The excitation spectrum obtained by monitoring the violet luminescence consisted of a weak band with a peak at approximately 261 nm and a broad Eu2+ band with a peak at approximately 338 nm. The relative efficiency of the violet luminescence of the γ-ray-irradiated phosphor at the exposure of 46 kGy increased up to 3.0 times that of the unirradiated phosphor. The enhancement of violet luminescence by γ-ray irradiation was ascribed to the conversion of Eu3+ to Eu2+ in Na2SO4.  相似文献   

13.
李堂刚  刘素文  王恩华  宋灵君 《物理学报》2011,60(7):73201-073201
通过燃烧法制备了Yb3+-Tm3+共掺的Y2O3纳米粉体,并对样品在980 nm激光照射下的上转换发光特性进行了研究.实验发现,样品在可见光区域能够产生强烈的蓝色发光(476 nm和487 nm)和较弱的红色发光(约650 nm),而且同时观察到了两个紫外发光峰1I63H6 (~297 nm)和1关键词: 2O3:Yb3+')" href="#">Y2O3:Yb3+ 3+')" href="#">Tm3+ 上转换光谱 敏化 紫外发光  相似文献   

14.
The luminescence properties of BaZr(BO3)2:5% Eu were investigated under ultraviolet (UV) and vacuum ultraviolet (VUV) excitation and different luminescence behaviors were observed by different excitation energies. After the analyses of the luminescence spectra, the result indicates that Eu3+ occupying non-centrosymmetric sites Ba2+ can be excited preferentially under 254 nm excitation, while Eu3+ occupying centrosymmetric sites Zr4+ can be excited preferentially under 147 nm excitation.  相似文献   

15.
SrAl_2B_2O_7:Dy~(3+)材料的制备及其发光性能   总被引:1,自引:0,他引:1       下载免费PDF全文
杨志平  马欣  赵盼盼  宋兆丰 《物理学报》2010,59(8):5387-5391
采用高温固相法制备了SrAl2B2O7:Dy3+发光材料.在350nm紫外光激发下,测得SrAl2B2O7:Dy3+材料的发射光谱为一个多峰宽谱,主峰分别为480,573和678nm;分别和Dy3+的4F9/2→6H15/2,4F9/2→6H13/2,4F9/2→6H11/2的跃迁发射相对应;监测573nm的发射峰,得到材料的激发光谱为一个多峰宽谱,主峰分别为295,325,350,365,400nm.研究了Dy3+掺杂浓度对SrAl2B2O7:Dy3+材料发射光谱的影响,随着Dy3+掺杂浓度的增大,SrAl2B2O7:Dy3+材料的Iy/Ib逐渐增大,根据Judd-Ofelt理论解释了其原因.随着Dy3+掺杂浓度的增大,Dy3+的4F9/2→6H13/2跃迁产生的573nm发射峰强度先增大,在4%时达到最大值,之后减小,其自身的浓度猝灭机理为电偶极-电偶极相互作用.不同的电荷补偿剂Li+,Na+,K+的引入均使发光强度得到提高,尤其以Li+最佳,发光强度提高了大约33%.  相似文献   

16.
Vacuum ultraviolet luminescence of Er3+ ions in LiYF4 and BaY2F8 crystals has been investigated. It is revealed that under excitation by 193 nm radiation from an ArF excimer laser the interconfigurational 5d–4f radiative transitions in Er3+ ions are observed. It is shown that from the LiYF4:Er crystal only the spin-forbidden luminescence (λ = 165 nm) is detected, whereas both the spin-forbidden (λ = 169 nm) and spin-allowed (λ = 160.5 nm) components are observed from the BaY2F8:Er crystal.  相似文献   

17.
许秀来  徐征  侯延冰  苏艳梅  徐叙 《物理学报》2000,49(7):1390-1393
研究了Gd3Ga5O12:Ag材料的制备及其发光性质.Gd3Ga5O12:Ag材料通过固相反应法制得,采用X射线衍射法分 析了材料的结晶度及成分.用电子束蒸发将该材料制备成交流的薄膜电致发光器件,得到了 较好的蓝紫色发光,发光峰分别位于397和467nm.通过对材料的光致发光和激发光谱的研究 和比较,得出397和467nm分别来自于氧空位和Ag+的发光.  相似文献   

18.
The calcium aluminates doped with Eu ions, Ca5Al8O14: Eu, phosphors are prepared by the combustion method. The formation of crystalline aluminates was confirmed by X-ray diffraction pattern. The prepared phosphors were characterized by SEM, TGA, DTA, particle size analyzer and Photoluminescence (PL) techniques. From the UV-excited luminescence spectra it was found that the Eu ions acts as a luminescent centre with luminescence at the blue (λ max = 470 nm) region due to 4f 65d 1 → 4f 7 transition. The excitation spectra show the broad band at 355 nm wavelength (λ em = 470 nm). The excitation 355 nm is a mercury free excitation and therefore Ca5Al8O14: Eu may be useful for the solid state lighting phosphor in lamp industry.   相似文献   

19.
甘平  辜敏  卿胜兰  鲜晓东 《物理学报》2013,62(7):78101-078101
应用分光光度计测量Te/TeO2-SiO2复合薄膜的透射光谱和吸收光谱, 在480nm附近观察到Te颗粒引起的等离子体共振吸收峰; 采用Z扫描技术研究了共振(激发波长为532 nm)和非共振情况下(激发波长1064 nm) 不同电位制备薄膜的Te颗粒状态与复合薄膜的三阶非线性极化率的关系. 基于有效介质理论对复合薄膜的三阶非线性效应进行分析, 研究Te颗粒大小对Te/TeO2-SiO2复合薄膜的非线性光学性质的影响及其产生机理. 结果表明薄膜制备过电位增大, Te的粒径减小, 颗粒数量多, 颗粒分布趋于均匀, 使得金属颗粒的表面等离子体共振峰红移, 吸收强度增强, 导致三阶非线性光学效应增强, χ(3)由1064 nm的5.12×10-7 esu增大为532 nm的8.11×10-7 esu. 关键词: 碲 二氧化碲 复合薄膜 三阶非线性  相似文献   

20.
Single-phased Sr3B2SiO8:Eu3+ phosphor was prepared by a solid-state method at 1020 °C. The luminescence spectra showed that Sr3B2SiO8:Eu3+ phosphor can be effectively excited by near ultraviolet light (393 nm) and blue light (464 nm). When excited at 393 or 464 nm Sr3B2SiO8:Eu3+ exhibited the main emission peaks at 611 and 620 nm, which resulted from the supersensitive 5D07F2 transition of Eu3+. The luminescence intensity of Sr3B2SiO8:Eu3+ at 611 and 620 nm reached the maximum when the doping content of Eu3+ was 4.5 mol%. Its chromaticity coordinates (0.646, 0.354) were very close to the NTSC standard values (0.67, 0.33). Thus, Sr3B2SiO8:Eu3+ is considered to be an efficient red-emitting phosphor for long-UV InGaN-based light-emitting diodes.  相似文献   

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