红外上转换纳米发光材料的水热合成

利用稀土离子Y~(3+)、Yb~(3+)、Er~(3+)与乙二胺四乙酸形成的配合物,加入可溶性氟化物.控制溶液的pH值,利用配位-沉淀平衡体系制备了复合氟化物纳米粒子前驱物,在240℃下水热晶化前驱物,合成了红外上转换纳米发光材料.     

上转换发光材料的合成与应用

综述了目前国内外上转换发光材料的几种合成方法,包括传统的高温固相合成法、溶胶一凝胶法、水热合成法、共沉淀法等.总结了不同方法的优缺点,对上转换材料合成方法的发展进行了展望.并介绍了上转换技术的一些应用.     

Ho3+上转换发光在染料敏化太阳能电池中的应用

以水热和高温煅烧相结合的方法制备了掺Ho3+的TiO2上转换发光层,并将其组装在染料敏化太阳能电池中.通过XRD、荧光光谱仪、UV-vis和电池的光电性能测试,来分析上转换发光层的发光机理及其加入后对染料敏化太阳能电池性能的影响.结果表明,上转换发光层的引入有效地提高了DSSC的光电性能,在80mW/cm2红外光照射下最高光电转换效率达到了0.12‰,比未加上转换发光层的DSSC提高了360%.     

Silica shell-assisted synthetic route for mono-disperse persistent nanophosphors with enhanced in vivo recharged near-infrared persistent luminescence

Near-infrared (NIR) persistent-luminescence nanoparticles have emerged as a new class of background-free contrast agents that are promising for in vivo imaging.The next key roadblock is to establish a robust and controllable method for synthesizing monodisperse nanoparticles with high luminescence brightness and long persistent duration.Herein,we report a synthesis strategy involving the coating/etching of the SiO2 shell to obtain a new class of small NIR highly persistent luminescent ZnGa2O4∶Cr3+,Sn4+ (ZGOCS) nanoparticles.The optimized ZGOCS nanoparticles have an excellent size distribution of ～15 nm without any agglomeration and an NIR persistent luminescence that is enhanced by a factor of 13.5,owing to the key role of the SiO2 shell in preventing nanoparticle agglomeration after annealing.The ZGOCS nanoparticles have a signal-to-noise ratio ～3 times higher than that of previously reported ZnGa2O4∶Cr3+ (ZGC-1) nanoparticles as an NIR persistent-luminescence probe for in vivo bioimaging.Moreover,the persistent-luminescence signal from the ZGOCS nanoparticles can be repeatedly re-charged in situ with external excitation by a white lightemitting diode;thus,the nanoparticles are suitable for long-term in vivo imaging applications.Our study suggests an improved strategy for fabricating novel high-performance optical nanoparticles with good biocompatibility.     

CeO2∶Er3+纳米晶的合成及上转换发光特性研究

采用燃烧法制备得到CeO2∶Er3+纳米晶粉末.用X射线衍射仪(XRD)、高分辨透射电子显微镜(HRTEM)和荧光分光光度计等对CeO2∶Er3+纳米晶的结构、形貌和上转换发光特性进行了研究.结果表明:所得到的纳米晶粒度均匀、结晶完好,属于立方萤石结构.上转换发光光谱的研究表明:在980nm红外光激发下,可以发现上转换荧光,分别来自于Er3+离子的2H11/2,4S3/2→4 I15/2和4 F9/2→4I15/2跃迁.     

Two-dimensional infrared and mid-infrared imaging by single-photon frequency upconversion

Single-photon frequency upconversion is an effective method of infrared single-photon detection and imaging by converting the long-wavelength photons to shorter wavelengths to match the detector’s spectral response. We realized few-photon level 2D infrared imaging with a coincidence frequency upconversion system in a bulk periodically poled lithium niobate crystal. Moreover, the infrared photons carrying orbital angular momentum were converted to the visible regime with high efficiency, while the orbital angular momentum of the photons was well conserved during the frequency upconversion process. The single-photon frequency upconversion method was also used for mid-infrared imaging at 3.39 µm with high efficiency and low noise.     

Efficient infrared upconversion via a ladder-type atomic configuration

We have demonstrated experimentally that infrared light at 1529.4?nm can be converted into the visible at 780?nm with 54% efficiency through a ladder-type atomic configuration in ⁸⁵Rb. Specifically we theoretically analyze that high efficiency is due to the large nonlinear dispersion of the index of refraction from the off-resonant enhancement in a four-wave mixing (FWM) process. By using two perpendicular polarized pump fields, the coherence of two FWM processes in this configuration is verified.     

通过热场和电场实现镧系离子掺杂铁电纳米复合材料上转换发光的可逆增强（英文）

调节镧系离子发光特性在传感、多彩显示、信息传递、防伪等领域具有重要意义.发光调控通常采用调控化学组分来实现,然而化学调控法不利于发展多模式检测、多重信息防伪等.本研究以镧系离子掺杂铁电纳米复合材料为研究对象,在热场和电场两种外部环境刺激下实现增强发光.在热场激励下样品呈现反猝灭现象,升温有效地增强了镧系离子的上转换近红外发光.同时基质中的铁电微晶晶格具有机电软弹性;通过电场调节镧系离子周围的晶体场结构实现了显著的发光增强,这种调控具有优异的可逆性和非易失性.本研究表明,可以通过热场和电场调控镧系离子掺杂多功能无机铁电体纳米复合材料的发光性质,这为设计高度集成的发光传感器件和智能设备提供了重要参考,特别是发展先进的多模式检测材料.     

Plasmonic Au x Ag y bimetallic alloy nanoparticles enhanced photoluminescence upconversion of Er3+ ions in antimony glass hybrid nanocomposites

Er³⁺ ions and spherical (3–23?nm) Au _x Ag _y bimetallic alloy (where x?=?18–96 and y?=?4–82, atom %) nanoparticles incorporated novel antimony oxide based reducing dielectric (glass) matrix, K₂O–B₂O₃–Sb₂O₃ (KBS), has been synthesized by a new single step methodology involving selective thermochemical reduction. Their absorption spectra show a single tunable (536–679 nm) surface plasmon resonance band along with the typical absorption peaks of the Er³⁺ ion. X-ray and SAED indicate the formation of (111) and (200) planes of Au _x Ag _y alloy. The luminescence intensity of two prominent emission bands of Er³⁺ ions centered at 536 (green) and 645 (red) nm due to ⁴S_3/2 → ⁴I_15/2 and ⁴F_9/2 → ⁴I_15/2 transitions were observed to be strongly dependent on the Au _x Ag _y nanoparticle composition. Both the bands undergo a maximum of 1.5- and 4.5-fold intensity enhancement respectively in the presence of the Ag₅₆Au₄₄ alloy (atom %) due to plasmon induced local field enhancement.     

Aptamer-conjugated upconversion nanoprobes assisted by magnetic separation for effective isolation and sensitive detection of circulating tumor cells

Detection of circulating tumor cells （CTCs） plays an important role in cancer diagnosis and prognosis. In this study, aptamer-conjugated upconversion nano- particles （UCNPs） are used for the first time as nanoprobes to recognize tumor cells, which are then enriched by attaching with magnetic nanoparticles （MNPs） and placing in the presence of a magnetic field. Owing to the autofluorescence- free nature of upconversion luminescence imaging, as well as the use of magnetic separation to further reduce background signals, our technique allows for highly sensitive detection and collection of small numbers of tumor cells spiked into healthy blood samples, and shows promise for CTC detection in medical diagnostics.     

Monodisperse upconversion NaYF4 nanocrystals: Syntheses and bioapplications

A facile strategy using cheap and readily available precursors has been successfully developed for the synthesis of rare-earth doped hexagonal phase NaYF₄ nanocrystals with uniform shape and small particle size as well as strong photoluminescence. Due to their optical properties and good biocompatibility, these multicolor nanocrystals were successfully used as a bio-tag for cancer cell imaging. This novel synthetic method should also be capable of extension to the synthesis of other fluoride nanocrystals such as YF₃ and LaF₃.      

Recent progress in understanding the persistent luminescence in SrAl2O4:Eu,Dy

Ever since the discovery of SrAl₂O₄:Eu,Dy persistent afterglow material, that can intensively glow up to 20?h, the mechanism of long-lasting luminescence has been a popular area of research. The research is focused on discovering the mechanism of persistent luminescence in order to prolong the duration and intensity of afterglow in a controlled way. Although most researchers agree on the general things, there are still many unclarities and ambiguities to discuss upon. This review paper briefly sketches in the highlights of past research on the luminescence mechanism in SrAl₂O₄:Eu,Dy, mainly focusing on the research conducted in the past decade dedicated to clearing these ambiguities. This paper provides an overview of the latest persistent luminescence mechanisms offered by researchers.     

Design,Properties, and In Vivo Behavior of Super­paramagnetic Persistent Luminescence Nanohybrids

With the fast development of noninvasive diagnosis, the design of multimodal imaging probes has become a promising challenge. If many monofunctional nanocarriers have already proven their efficiency, only few multifunctional nanoprobes have been able to combine the advantages of diverse imaging modalities. An innovative nanoprobe called mesoporous persistent luminescence magnetic nanohybrids (MPNHs) is described that shows both optical and magnetic resonance imaging (MRI) properties intended for in vivo multimodal imaging in small animals. MPNHs are based on the assembly of chromium‐doped zinc gallate oxide and ultrasmall superparamagnetic iron oxide nanoparticles embedded in a mesoporous silica shell. MPNHs combine the optical advantages of persistent luminescence, such as real time imaging with highly sensitive and photostable detection, and MRI negative contrast properties that ensure in vivo imaging with rather high spatial resolution. In addition to their imaging capabilities, these MPNHs can be motioned in vitro with a magnet, which opens multiple perspectives in magnetic vectorization and cell therapy research.     

NIR to VIS frequency upconversion luminescence properties of Er-doped YPO4 phosphors

Different concentrations of Er³⁺-doped YPO₄:Er powder phosphors have been synthesized by the conventional solid state reaction method and are characterized by X-ray diffraction (XRD), field emission scanning electronic microscopy (FESEM), and upconversion emission measurements. An intense red emission band and a weak green emission band are observed under NIR excitation at 975 nm in case of samples with high dopant concentration while no upconversion emission was observed at lower Er³⁺ ion concentrations. The possible mechanisms involved in the upconversion process have been discussed in comparison to results with similar reported works.     

Yb3+-Tm3+共掺BiOBr纳米晶的近红外上转换发光特性研究

采用水热法合成了Yb³⁺-Tm³⁺共掺BiOBr纳米晶, 研究了其上转换发光性能。在980 nm光激发下, 样品中Tm³⁺离子实现了³H₄→³H₆、¹G₄→³F₄和¹G₄→³H₆跃迁, 进而发出强烈的近红外光(801 nm)和较弱的红光(655 nm)与蓝光(485 nm)。探讨了样品的上转换发光机理, 上转换发光强度与激发功率的关系表明在980 nm激发下Tm³⁺的蓝光和红光发射为三光子过程, 而近红外发光为双光子过程。随着Yb³⁺浓度增加, 近红外发光显著增强, 近红外光与蓝光(I_{801 nm}/I_{485 nm})的发光强度比高达71.4。研究结果表明, Yb³⁺-Tm³⁺共掺BiOBr纳米晶在生物荧光标记领域具有潜在的应用前景。     

Local thermal effect at luminescent spot on upconversion luminescence in Y2O3:Er,Yb nanoparticles

Y₂O₃:Er³⁺,Yb³⁺ nanoparticles were synthesized using Pechini type sol-gel method and then characterized by XRD, TEM, SEM, Raman spectroscopy, and fluorescence spectrophotometer. Local temperature effect on upconversion luminescence intensities was theoretically analyzed and experimentally tested. These results indicate that a competition process between local temperature at luminescent spot and laser pump power density decides the development trend of upconversion luminescence intensity. Therefore, it can be concluded that the most intensive upconversion luminescence in Y₂O₃:Er³⁺,Yb³⁺ nanoparticles can be achieved at a certain pump power density, which should be slightly below a given constant value (the corresponding threshold of temperature).     

Preparation and upconversion property of TeO2:Er/Yb nanoparticles

Different crystal structure of TeO₂ nanoparticles were used as the host materials to prepare the Er³⁺/Yb³⁺ ions co-doped upconversion luminescent materials. The TeO₂ nanoparticles mainly kept the original morphology and phase after having been co-doped the Er³⁺/Yb³⁺ ions. All the as-prepared TeO₂:Er³⁺/Yb³⁺ nanoparticles showed the green emissions (525 nm, 545 nm) and red emission (667 nm) under 980 nm excitation. The green emissions at 525 nm, 545 nm and red emission at 667 nm were attributed to the ²H_11/2 → ⁴I_15/2, ⁴S_3/2 → ⁴I_15/2 and ⁴F_9/2 → ⁴I_15/2 transitions of the Er³⁺ ions, respectively. For the α-TeO₂:Er³⁺/Yb³⁺ (3/10 mol%) nanoparticles, three-photon process involved in the green (²H_11/2 → ⁴I_15/2) emission, while two-photon process involved in the green (⁴S_3/2→⁴I_15/2) and red (⁴F_9/2 → ⁴I_15/2) emissions. For the β-TeO₂:Er³⁺/Yb³⁺ (3/10 mol%) nanoparticles, two-photon process involved in the green (²H_11/2 → ⁴I_15/2), green (⁴S_3/2 → ⁴I_15/2) and red (⁴F_9/2 → ⁴I_15/2) emissions. It suggested that the crystal structure of TeO₂ nanoparticles had an effect on transition processes of the Er³⁺/Yb³⁺ ions. The emission intensities of the α-TeO₂:Er³⁺/Yb³⁺ (3/10 mol%) nanoparticles and β-TeO₂:Er³⁺/Yb³⁺ (3/10 mol%) nanoparticles were much stronger than those of the (α + β)-TeO₂:Er³⁺/Yb³⁺ (3/10 mol%) nanoparticles.     

Role of organic molecules on upconversion luminescence of LaF3 nanoparticles

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.