共查询到20条相似文献,搜索用时 31 毫秒
1.
Fidelus JD Barczak M Michalak K Fekner Z Duzyńska A Jusza A Piramidowicz R Monty CJ Suchocki A 《Journal of nanoscience and nanotechnology》2012,12(5):3760-3765
Pure and ytterbium doped TiO2 nanopowders in anatase phase have been prepared by sol-gel method (SGM) and Solar Physical Vapour Deposition process (SPVD). The physico-chemical parameters of the nanopowders have been described based on the results of micro-structural characterization performed by X-ray diffractometry, scanning electron microscopy, atomic force microscopy, and nitrogen sorption measurements. Thus, final micro-structural properties of SGM and SPVD titania nanopowders have been compared in detail revealing significant changes in the structure and morphology of these two types of materials. Addition of ytterbium had no significant effect on above-mentioned properties, although it modifies significantly the optical properties of the investigated materials. The luminescent properties of developed material were found to be comparable to bulk oxide materials and better than these reported earlier for ytterbium doped titania. In particular it has been shown that the luminescence of SPVD nanopowders is significantly stronger than this of SGM samples. 相似文献
2.
Meng Wang 《Materials Letters》2009,63(2):325-327
The synthesis, characterization, and fluorescent spectra of rare-earth doped NaYF4 upconversion nanocrystals are introduced in this paper. The nanocrystals were synthesized in the water-ethanol-oleic acid system via a two-phase solvothermal approach, by using rare-earth stearate as the precursor. The as-prepared nanocrystals were of hexagonal phase, strong UC fluorescent intensity, with an average size of about 25 nm, which have been characterized by TEM, SAED, powder XRD, and luminescence spectroscopy. The possible mechanism of this synthesis that the nucleation and growth of nanocrystals occurred at the solid-liquid interface was also discussed. The nanocrystals are hydrophilic, and expected to fulfil the demand for biological applications via further modification. 相似文献
3.
Shilong Zhao Shiqing Xu Guohua Jia Degang Deng Lihui Huang Huanping Wang 《Materials Letters》2011,65(15-16):2407-2409
Transparent oxyfluoride borosilicate glass ceramic containing cubic NaYF4 nanocrystals were successfully fabricated. The cubic NaYF4 nanocrystals with average size of 30 nm were precipitated in the glass matrix, which was confirmed by the X-ray diffraction and TEM results. In comparison with the as-made glass, significant enhancement of upconversion luminescence is observed in the Er3+/Yb3+ codoped transparent glass ceramic, which may be due to the variation of coordination environment of Er3+ and Yb3+ ions after crystallization. The high transparency, intense upconversion luminescence and the simple, low-cost fabrication process make this material exhibiting potential applications in the fields of amorphous silicon solar cells. 相似文献
4.
Yb and Er codoped LaF3 nanocrystals were synthesized and studied. The upconversion luminescence properties of nanocrystals capped with different ligands are mainly dependent on the ligands, especially for the red emission which is sensitive to the nonradiative relaxation. The chelation between the ligands and rare earth ions can affect the morphology and fluorescent properties of samples. The chelating ligands will reduce the nonradiative quenching by isolating the RE ions from surrounding environment. So the upconversion luminescence properties of the samples vary correspondingly. 相似文献
5.
Water-soluble and amino-functionalized luminescent Dy3+-doped BaFCl nanocrystals have been synthesized for the first time via a facile one-step modified solvothermal method with polyethyleneimine (PEI) as capping agent. The obtained BaFCl:Dy3+ nanocrystals have a size of about 40 nm, remain stable in aqueous solutions under different pH, and exhibit intense visible luminescence of Dy3+. The synthesized nanocrystals featuring long-lived luminescence may have potential applications as time-resolved photoluminescent probes for bio-applications. 相似文献
6.
稀土上转换发光纳米材料的制备及生物医学应用研究进展 总被引:1,自引:0,他引:1
荧光探针技术已经被广泛应用于生物成像、生物标记、生物检测、免疫分析等生物医学领域。传统荧光标记材料,如有机荧光染料、荧光蛋白和半导体量子点,目前面临诸多应用局限,如发光强度不稳定、检测灵敏度低、生物毒性高、自荧光强等。有鉴于此,人们开发了La系金属离子掺杂的稀土上转换发光纳米材料作为新型生物标记材料,该材料受近红外光激发后发出近红外或可见光范围内的高能量光子。这种带有特殊光学性质及良好生物相容性的荧光标记材料克服了传统荧光标记材料的缺点,从而成为材料科学与生物医学交叉领域的研究热点。综述了稀土纳米材料上转换功能的特殊物理机制及其制备和表面修饰方法的研究进展。在此基础上介绍了稀土上转换纳米材料在生物成像、检测、载药、即时诊断器件开发等生物医学工程中的应用。 相似文献
7.
Sandip DasKrishna C. Mandal 《Materials Letters》2012,66(1):46-49
CdS host nanocrystals (4.2-5.5 nm in diameter) have been prepared by a low-cost synthetic chemical route using air stable precursors and doped with rare earth (RE) ions, terbium (Tb3+) and ytterbium (Yb3+). The resulting RE3+-doped nanocrystals show a complete broadband absorption below their band edge (400-460 nm) to the deep UV region. CdS host nanocrystals act as an energy receptor and sensitizer for the RE3+-ions. A broadband emission in the visible region is observed for the RE3+-doped CdS nanocrystals by room temperature photoluminescence (PL) measurements. Our results show that these novel RE3+-doped nanocrystals can be used as an optical down-conversion material for solar spectral matching in solar cells or as a wavelength shifting down-converter for nanoscale optoelectronic applications. 相似文献
8.
稀土掺杂上转换发光玻璃陶瓷的制备及性能 总被引:1,自引:0,他引:1
实验制备了一类含有SrF2∶Yb3+,Tm3+及SrF2∶Yb3+,Er3+的透明发光玻璃和玻璃陶瓷,对比研究了热处理工艺对玻璃陶瓷相组成、微观结构和光谱性能的影响规律。研究表明,玻璃陶瓷具有立方SrF2纳米晶相均匀分布于玻璃基体的复相结构,利用HRTEM可观测到SrF2纳米晶相的(111)晶面,其晶粒尺度在10~30nm之间,且该析晶相中富集有Yb3+/Tm3+和Yb3+/Er3+。基于此,玻璃陶瓷在980nm LD激光激发下的上转换发光强度较玻璃样品有较大提高。其上转换发光机制分别主要为Yb3+-Yb3+之间的合作上转换,Yb3+-Tm3+和Tm3+-Tm3+之间的交叉弛豫能量传递过程,以及Yb3+-Er3+之间的能量传递上转换。 相似文献
9.
Pushpal Ghosh Suparna Sadhu Tapasi Sen Amitava Patra 《Bulletin of Materials Science》2008,31(3):461-465
Here, we report the dopant concentration and pump-power dependence upconversion emission properties of erbium doped BaTiO3 nanocrystals derived from sol-emulsion-gel method. Green (550 nm) and red (670 nm) upconversion emissions were observed at
room temperature from the 4
S
3/2 and 4
F
9/2 levels of Er3+: BaTiO3 nanocrystals. It is found that at 850 mW of cw excitation power (at 980 nm) the total luminescence was 17130 Cd/m2 for 1000°C heated 0.25 mol% Er-doped BaTiO3 nanocrystals. It is worthwhile to mention that the unusual power-dependent upconversion luminescence (saturation) is observed
at higher dopant concentration (2.5 mol%) and high pump power. Our analysis confirms that the depletion of the excited state
is responsible for the relevant fluorescence upconversion. We have again confirmed that a twophoton excited state absorption
process occurs for all samples. 相似文献
10.
11.
Achieving single‐band upconversion is a challenging but rewarding approach to attain optimal performance in diverse applications, such as multiplexed molecular imaging, security coding, and nonlinear photonic devices. Here, highly efficient single‐band upconversion luminescence in the green spectral regime (16.4 times increase in emission at 525 nm) accomplished by realizing minimal energy loss from two‐photon upconversion in a newly synthesized liquid‐quenched amorphous matrix is reported. In contrast to previously reported single‐band upconversion, this phenomenon originates from the elevated transition probability of the host sensitive transition via changes in the host matrix's microstructure. The elevated transition probability facilitates ultrafast decay of upconversion luminescence with decay times as short as 0.2 µs, the fastest decay ever reported. The material in this study therefore has strong potential for use in photonic devices demanding high upconversion efficiency with a fast response time, which to date has been inaccessible using upconversion materials. 相似文献
12.
Bednarkiewicz A Wawrzynczyk D Gagor A Kepinski L Kurnatowska M Krajczyk L Nyk M Samoc M Strek W 《Nanotechnology》2012,23(14):145705
Most of the synthesis routes of lanthanide-doped phosphors involve thermal processing which results in nanocrystallite growth, stabilization of the crystal structure and augmentation of luminescence intensity. It is of great interest to be able to transform the sample in a spatially localized manner, which may lead to many applications like 2D and 3D data storage, anti-counterfeiting protection, novel design bio-sensors and, potentially, to fabrication of metamaterials, 3D photonic crystals or plasmonic devices. Here we demonstrate irreversible spatially confined infrared-laser-induced annealing (LIA) achieved in a thin layer of dried colloidal solution of ultra-small ~8 nm NaYF? nanocrystals (NCs) co-doped with 2% Er3? and 20% Yb3? ions under a localized tightly focused beam from a continuous wave 976 nm medium power laser diode excitation. The LIA results from self-heating due to non-radiative relaxation accompanying the NIR laser energy upconversion in lanthanide ions. We notice that localized LIA appears at optical power densities as low as 15.5 kW cm?2 (~354 ± 29 mW) threshold in spots of 54 ± 3 μm diameter obtained with a 10 × microscope objective. In the course of detailed studies, a complete recrystallization to different phases and giant 2-3 order enhancement in luminescence yield is found. Our results are highly encouraging and let us conclude that the upconverting ultra-small lanthanide-doped nanophosphors are particularly promising for direct laser writing applications. 相似文献
13.
Zhaohui Shen Suling Zhao Dandan Song Zheng Xu Bo Qiao Pengjie Song Qiongyu Bai Jingyue Cao Gaoqian Zhang Wageh Swelm 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(26)
Lead halide perovskites and their applications in the optoelectronic field have garnered intensive interest over the years. Inorganic perovskites (IHP), though a novel class of material, are considered as one of the most promising optoelectronic materials. These materials are widely used in detectors, solar cells, and other devices, owing to their excellent charge‐transport properties, high defect tolerance, composition‐ and size‐dependent luminescence, narrow emission, and high photoluminescence quantum yield. In recent years, numerous encouraging achievements have been realized, especially in the research of CsPbX3 (X = Cl, Br, I) nanocrystals (NCs) and surface engineering. Therefore, it is necessary to summarize the principles and effects of these surface engineering optimization methods. It is also important to scientifically guide the applications and promote the development of perovskites more efficiently. Herein, the principles of surface ligands are reviewed, and various surface treatment methods used in CsPbX3 NCs as well as quantum‐dot light‐emitting diodes are presented. Finally, a brief outlook on CsPbX3 NC surface engineering is offered, illustrating the present challenges and the direction in which future investigations are intended to obtain high‐quality CsPbX3 NCs that can be utilized in more applications. 相似文献
14.
15.
Suárez G Borodianska H Sakka Y Aglietti EF Vasylkiv O 《Journal of nanoscience and nanotechnology》2010,10(10):6634-6640
A 2.7 mol% yttria stabilizing tetragonal zirconia (2.7Y-TZP) nanopowder was synthesized and stored for five years. Humidity and unsatisfactory storage conditions gradually caused heavy agglomeration. Within a few months, 2.7Y-TZP nanopowder became useless for any technological application. A bead-milling deagglomeration technique was applied to recover the heavily agglomerated yttria-stabilized zirconia nanopowder. Low-temperature sintering and spark plasma sintering (SPS) were performed, resulting in fully dense nanostructured ceramics. Compacts formed with heavily agglomerated powder present low sinterability and poor mechanical properties. Bead-milling suspension formed compacts exhibit mechanical properties in the range of the values reported for nanostructured zirconia. This observation confirms the effectiveness of bead-milling in the deagglomeration of highly agglomerated nanopowders. The high value of Vickers hardness of 13.6 GPa demonstrates the success of the processing technique for recovering long-time-stored oxide nanopowders. 相似文献
16.
Luo W Fu C Li R Liu Y Zhu H Chen X 《Small (Weinheim an der Bergstrasse, Germany)》2011,7(21):3046-3056
A comprehensive survey of electronic structure and optical properties of rare-earth ions embedded in semiconductor nanocrystals (NCs) is of vital importance for their potential applications in areas as diverse as luminescent bioprobes, lighting, and displays. Er3+ -doped anatase TiO2 NCs, synthesized via a facile sol-gel solvothermal method, exhibit intense and well-resolved intra-4f emissions of Er3+ . Crystal-field (CF) spectra of Er3+ in TiO2 NCs are systematically studied by means of high-resolution emission and excitation spectra at 10-300 K. The CF analysis of Er3+ assuming a site symmetry of C(2v) yields a small root-mean-square deviation of 25.1 cm(-1) and reveals the relatively large CF strength (549 cm(-1) ) of Er3+, thus verifying the rationality of the C(2v) symmetry assignment of Er3+ in anatase TiO2 NCs. Based on a simplified thermalization model for the temperature-dependent photoluminescence (PL) dynamics from (4) S(3/2) , the intrinsic radiative luminescence lifetimes of (4) S(3/2) and (2) H(11/2) are experimentally determined to be 3.70 and 1.73 μs, respectively. Green and red upconversion (UC) luminescence of Er3+ can be achieved upon laser excitation at 974.5 nm. The UC intensity of Er3+ in Yb/Er-codoped NCs is found to be about five times higher than that of Er-singly-doped counterparts as a result of efficient Yb3+ sensitization and energy transfer upconversion (ETU) evidenced by its distinct UC luminescence dynamics. Furthermore, the origin of defect luminescence is revealed based on the temperature-dependent PL spectra upon excitation above the TiO2 bandgap at 325 nm. 相似文献
17.
Structure, morphology and luminescence properties of nanocrystalline samples of YAl3(BO3)4 (YAB) undoped and doped with neodymium, ytterbium and chromium obtained by the sol-gel method are presented. The best results of synthesis are obtained for mannitol as polymerizing agent. Single phase of nanopowder is obtained for pure YAB. Dopants destroy the compound structure; two other compounds, namely Al18B4O33 and YBO3, were revealed by X-ray investigation. Nanopowders show isometric and needles forms, the calculated size of crystallites is about 60 nm. Their optical properties are determined and results are compared to data obtained for single crystal counterparts. It is shown that the influence of rare earth ions incorporated into YBO3 phase on luminescent spectra and excited state relaxation dynamics of the nanopowders is negligibly small when the YBO3 content is of the order of several wt%. Residual impurity phases do not affect significantly spectroscopic properties of YAB nanopowders. 相似文献
18.
Chan EM Han G Goldberg JD Gargas DJ Ostrowski AD Schuck PJ Cohen BE Milliron DJ 《Nano letters》2012,12(7):3839-3845
Nanoparticles doped with lanthanide ions exhibit stable and visible luminescence under near-infrared excitation via a process known as upconversion, enabling long-duration, low-background biological imaging. However, the complex, overlapping emission spectra of lanthanide ions can hinder the quantitative imaging of samples labeled with multiple upconverting probes. Here, we use combinatorial screening of multiply doped NaYF(4) nanocrystals to identify a series of doubly and triply doped upconverting nanoparticles that exhibit narrow, spectrally pure emission spectra at various visible wavelengths. We then developed a comprehensive kinetic model validated by our extensive experimental data set. Applying this model, we elucidated the energy transfer mechanisms giving rise to spectrally pure emission. These mechanisms suggest design rules for electronic level structures that yield robust color tuning in lanthanide-doped upconverting nanoparticles. The resulting materials will be useful for background-free multicolor imaging and tracking of biological processes. 相似文献
19.
Yttria stabilised zirconia (YSZ) nanocrystals, with a mean size between 5 and 10 nm, were prepared by microwave flash synthesis. Flash synthesis was performed in alcoholic solutions of yttrium, zirconium chloride and sodium ethoxide (EtONa) using a microwave autoclave (RAMO system) specially designed by authors. Energy dispersive X-ray analysis (EDX), X-ray powder diffraction (XRD), BET adsorption technique, photon correlation spectroscopy (PCS) transmission and scanning electron microscopy (TEM and SEM) are used to characterized these nanoparticles. Compared with conventional synthesis, nanopowders can be produced in a short period (e.g. 10 s), both high purity and stoechiometric control are obtained. Nevertheless, this mean of production is more cheaper and much faster than the ones commonly used to produce yttria stabilized zirconia (YSZ) by conventional sol-gel techniques. 相似文献
20.
Bezdorozhev O Borodianska H Sakka Y Vasylkiv O 《Journal of nanoscience and nanotechnology》2011,11(9):7901-7909
Weakly agglomerated 1.75 and 3 mol% yttria stabilized zirconia nanopowders were used in this study after six years of storage in vacuum-processed plastic containers. The proper storage conditions of the Y-TZP nanopowders avoided the hard agglomeration. Untreated and bead-milled nanopowders were used to obtain dense ceramics by slip casting and subsequent low-temperature sintering. Fully dense nanostructured 1.75Y-TZP and 3Y-YZP ceramics with and without doping of 1 wt% Al2O3 were produced by an optimized spark plasma sintering (SPS) technique at the temperatures of 1050-1150 degrees C at a pressure of 100 MPa. The SPS has revealed the clear advantage of consolidation of the weakly agglomerated nanopowders without preliminary deagglomeration. The Vickers hardness of both the low-temperature and spark plasma sintered samples was found to lie in the range of 10.98-13.71 GPa. A maximum fracture toughness of 15.7 MPa m(1/2) (average 14.23 MPa m(1/2)) was achieved by SPS of the 1.75Y-TZP ceramic doped with 1 wt% Al2O3 whereas the toughness of the 3Y-TZP ceramics with and without alumina doping was found to vary between 3.55 and 5.5 MPa m(1/2). 相似文献