Novel heterometal-organic complexes as first single source precursors for up-converting NaY(Ln)F4 (Ln = Yb, Er, Tm) nanomaterials

First heterometal-organic single source precursors for NaYF(4) nanomaterials as a host matrix for up-conversion emission are reported. These novel heterobimetallic derivatives NaY(TFA)(4)(diglyme) (1), [Na(triglyme)(2)][Y(2)(TFA)(7)(THF)(2)] (2) and Na(2)Y(TFA)(5)(tetraglyme) (3) (TFA = trifluoroacetate), which were fully characterized by elemental analysis, FT-IR and (1)H NMR spectroscopy, TG-DTA data as well as single crystal X-ray structures, are advantageous in terms of being anhydrous and having lower decomposition temperatures in comparison to the homometallic precursor Y(TFA)(3)(H(2)O)(3). In addition, they also contain chelating glyme ligands, which act as capping reagents during decomposition to control the NaYF(4) particle size and render them monodisperse in organic solvents. On decomposition in 1-octadecene, the molecular derivatives 1 and 3 are converted, in the absence of any surfactant or capping reagent, to cubic NaYF(4) nanocrystals at significantly lower temperatures (below 250 °C). At higher temperature, a mixture of the cubic and hexagonal phases was obtained, the relative ratio of the two phases depending on the reaction temperature. A pure hexagonal phase, which is many folds more efficient for UC emission than the cubic phase, was obtained by calcining nanocrystals of mixed phase at 400 °C. In order to co-dope this host matrix with up-converting lanthanide cations, analogous complexes NaLn(TFA)(4)(diglyme) [Ln = Er (4), Tm (5), Yb (6)] and Na(2)Ln(TFA)(5)(tetraglyme) [Ln = Er (7), Yb (8)] were also prepared and characterized. The decomposition in 1-octadecene of suitable combinations and appropriate molar ratios of these yttrium, ytterbium and erbium/thulium derivatives gave cubic and/or hexagonal NaYF(4): Yb(3+), Er(3+)/Tm(3+) nanocrystals (NCs) capped by diglyme or tetraglyme ligands, which were characterized by IR, TG-DTA data, EDX analysis and TEM studies. Surface modification of these NCs by ligand exchange reactions with poly acrylic acid (PAA) and polyethyleneglycol (PEG) diacid 600 was also carried out to render them water soluble. The THF solutions of suitable combinations of the diglyme derivatives were also used to elaborate the thin films of NaYF(4):Yb(3+), Er(3+)/Tm(3+) on a glass or Si wafer substrate by spin coating. The multicolour up-conversion fluorescence was successfully realized in the Yb(3+)/Er(3+) (green/red) and Yb(3+)/Tm(3+) (blue/violet) co-doped NaYF(4) nanoparticles and thin films, which demonstrates that they are promising UC nanophosphors of immense practical interest. The up-conversion excitation pathways for the Er(3+)/Yb(3+) and Tm(3+)/Yb(3+) co-doped materials are discussed.     

Branched NaYF(4) nanocrystals with luminescent properties

In this article, branched NaYF(4) nanocrystals have been successfully synthesized via a simple hydrothermal method. On the basis of the analysis of HRTEM and TEM images, the growth modes of the branched structure and further branching behavior have been proposed. The up- and down-conversion luminescence of branched NaYF(4):Er(3+)/Yb(3+) and NaYF(4):Eu(3+) have been characterized. Multiarmed NaYF(4) phosphors can be introduced into polystyrene to form composite luminescent polymers because of its special geometrical shape. In conclusion, the luminescent branched particles should be of wide potential application as building blocks in the future nanoscience and nanotechnology.     

Phase- and size-controllable synthesis of hexagonal upconversion rare-earth fluoride nanocrystals through an oleic acid/ionic liquid two-phase system

Herein, we introduce a facile, user- and environmentally friendly (n-octanol-induced) oleic acid (OA)/ionic liquid (IL) two-phase system for the phase- and size-controllable synthesis of water-soluble hexagonal rare earth (RE = La, Gd, and Y) fluoride nanocrystals with uniform morphologies (mainly spheres and elongated particles) and small sizes (<50?nm). The unique role of the IL 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF(6)) and n-octanol in modulating the phase structure and particle size are discussed in detail. More importantly, the mechanism of the (n-octanol-induced) OA/IL two-phase system, the formation of the RE fluoride nanocrystals, and the distinctive size- and morphology-controlling capacity of the system are presented. BmimPF(6) is versatile in term of crystal-phase manipulation, size and shape maintenance, and providing water solubility in a one-step reaction. The luminescent properties of Er(3+)-, Ho(3+)-, and Tm(3+)-doped LaF(3), NaGdF(4), and NaYF(4) nanocrystals were also studied. It is worth noting that the as-prepared products can be directly dispersed in water due to the hydrophilic property of Bmim(+) (cationic part of the IL) as a capping agent. This advantageous feature has made the IL-capped products favorable in facile surface modifications, such as the classic Stober method. Finally, the cytotoxicity evaluation of NaYF(4):Yb,Er nanocrystals before and after silica coating was conducted for further biological applications.     

Green upconversion nanocrystals for DNA detection

By combining magnetic-field-assisted bioseparation and concentration technology with magnetite nanoparticles, novel green upconversion (UC) fluorescence nanocrystals (NaYF4:Yb3+/Er3+) have been applied to the sensitive detection of DNA.     

Controlled hydrothermal growth and up-conversion emission of NaLnF(4) (Ln = Y, Dy-Yb)

The controlled hydrothermal preparation of NaYF(4) as both cubic and hexagonal phase types with specific associated morphologies, nanospheres and microtubes, respectively, has been achieved in the absence of organic solvents. The hexagonal NaYF(4) compound can be prepared in novel microtubular form and directly co-doped with Yb(3+)/Er(3+) ions. When excited by infrared light of 980 nm, these hexagonal NaYF(4) microtubes display strong green up-conversion emission, which was much more intense than that of cubic NaYF(4) or hexagonal NaYF(4) nanoparticles. Other related hexagonal-prismatic microtubes of NaLnF(4) (Ln = Dy-Yb) were also synthesized. A growth mechanism for the microtubes is proposed. In general, the diameter of the hexagonal NaLnF(4) microtubes is strongly dependent on the Ln(3+) size and increases as the rare-earth ionic radius decreases.     

Facile patterning of upconversion NaYF4:Yb,Er nanoparticles

Different kinds of highly ordered patterns of NaYF(4):Yb,Er nanoparticles on gold substrates were fabricated using a simple method combining micro-contact printing and "breath figures" techniques. Ordered arrays of water droplets were first formed in the hydrophilic regions of patterned self-assembled monolayers (SAMs). This was subsequently submerged in a chloroform solution of NaYF(4):Yb,Er nanoparticles. The particles were spontaneously assembled at the interface of chloroform/water droplet surface, leading to different kinds of uniform patterns after solvent evaporation. The structures of NaYF(4):Yb,Er particles patterns depended on the dimension of the substrate, the concentration of the NaYF(4):Yb,Er nanoparticles and the water condensation process.     

Facile and mass production synthesis of β-NaYF4:Yb3+, Er3+/Tm3+ 1D microstructures with multicolor up-conversion luminescence

Well defined, pure hexagonal-phased NaYF(4):Yb(3+),Er(3+)/Tm(3+) microtubes and microrods were first prepared by a facile and mass production molten salt method without using any surfactant, which offers a new alternative in synthesizing such materials and opens the possibility to meet the increasing commercial demand.     

Near‐Infrared‐Light‐Driven Artificial Photosynthesis by Nanobiocatalytic Assemblies

Artificial photosynthesis in nanobiocatalytic assemblies aims to reconstruct man‐made photosensitizers, electron mediators, electron donors, and redox enzymes for solar synthesis of valuable chemicals through photochemical cofactor regeneration. Herein, we report, for the first time, on nanobiocatalytic artificial photosynthesis in near‐infrared (NIR) light, which constitutes over 46% of the solar energy. For NIR‐light‐driven photoenzymatic synthesis, we synthesized silica‐coated upconversion nanoparticles, Si‐NaYF4:Yb,Er and Si‐NaYF4:Yb,Tm, for efficient photon‐conversion through Förster resonance energy transfer (FRET) with rose bengal (RB), a photosensitizer. We observed NIR‐induced electron transfer by using linear sweep voltammetric analysis; this indicates that photoexcited electrons of RB/Si‐NaYF4:Yb,Er are transferred to NAD+ through a Rh‐based electron mediator. RB/Si‐NaYF4:Yb,Er nanoparticles, which exhibit higher FRET efficiency due to more spectral overlap than RB/Si‐NaYF4:Yb,Tm, perform much better in the photoenzymatic conversion.     

Multiplexed near-infrared in vivo imaging complementarily using quantum dots and upconverting NaYF4:Yb3+,Tm3+ nanoparticles

A new multiplexed NIR in vivo imaging is showcased by using quantum dots and NaYF(4):Yb(3+),Tm(3+) nanoparticles. The 'temporal' multiplexing is demonstrated by alternating the excitation wavelengths and unmixing the emissions of different probes. Multiplexed cellular imaging and the cellular trafficking in animal models are shown.     

An optical sensor for Cu(II) detection with upconverting luminescent nanoparticles as an excitation source

The first optical sensor for Cu(II) detection, with upconverting luminescent nanoparticles as an excitation source, showing high selectivity and good linear Stern-Volmer characteristics, has been achieved through a fluorescence resonance energy transfer (FRET) process between NaYF(4):Yb(3+)/Er(3+) and RB-hydrazide. The sensing mechanism is then discussed.     

NaYF4:Yb,Er/Tm上转换荧光纳米材料的合成、修饰及应用*

上转换荧光纳米材料NaYF4:Yb,Er/Tm因具有独特的上转换发光性能,在固体激光器、三维立体演示、红外成像等很多方面都有着重要的应用。近年来,NaYF4:Yb,Er/Tm上转换纳米颗粒作为荧光标记物用于生物标记引起了研究者的浓厚兴趣。合成出高质量、高荧光性能的NaYF4:Yb,Er/Tm上转换纳米颗粒是使之能够在生物医学等领域广泛应用的前提条件。本文针对NaYF4:Yb,Er/Tm上转换荧光纳米颗粒的合成方法、表面修饰以及生物应用等方面的研究进展进行综述。     

Preparation and up-conversion luminescence of hollow La2O3:Ln (Ln = Yb/Er, Yb/Ho) microspheres

Hollow La(2)O(3):Ln (Ln = Yb/Er, Yb/Ho) microspheres with up-conversion (UC) luminescence properties were successfully synthesized via a facile sacrificial template method by employing carbon spheres as hard templates followed by a subsequent heating process. The structure, morphology, formation process, and fluorescent properties are well investigated by various techniques. The results indicate that the hollow La(2)O(3):Ln microspheres can be well indexed to the hexagonal La(2)O(3) phase. The hollow La(2)O(3):Ln microspheres with uniform diameter of about 270 nm maintain the spherical morphology and good dispersion of the carbon spheres template. The shell of the hollow microspheres consists of numerous nanocrystals with the thickness of approximately 40 nm. Moreover, the possible formation mechanism of evolution from the carbon spheres to the amorphous precursor and to the final hollow La(2)O(3):Ln microspheres has also been proposed. The Yb/Er and Yb/Ho codoped La(2)O(3) hollow spheres exhibit bright up-conversion luminescence with different colors derived from different activators under the 980 nm NIR laser excitation. Furthermore, the doping concentration of the Yb(3+) is optimized under fixed concentration of Er(3+)/Ho(3+). This material may find potential applications in drug delivery, hydrogen and Li ion storage, and luminescent displays based on the uniform hollow structure, dimension, and UC luminescence properties.     

聚多巴胺在强负电型微球表面的形貌调控

多巴胺(DA)已被证实可在多种材料的表面进行氧化自聚而形成聚多巴胺(PDA),但其在带强负电荷的表面上的聚合机理和所形成的形貌却还不太明确。 为考察材料表面的电负性、氧化条件等对DA氧化自聚速度和聚多巴胺层形貌的影响,本文通过无皂乳液聚合制备了以聚苯乙烯(PS)为核、聚丙烯酸(PAA)为壳的纳米粒子(PS/PAA NPs),探究其表面的阴离子在不同pH缓冲液、反应时间下与DA的加入量对聚合过程及其形貌的影响。 通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)和Zeta电势对所得纳米粒子的结构、形貌与尺寸等进行分析。 结果发现,在pH值为8.5的三羟甲基氨基甲烷(Tris)缓冲溶液中,当DA与PS/PAA NPs的质量比为1∶1时,在反应24 h后,PDA以纳米颗粒的形式存在于PS/PAA NPs的表面,即所形成的PS/PAA/PDA NPs为明显的树莓状结构。 随着DA含量的增加和反应时间的延长,所形成的树莓状粒子粒径增大;当DA远远过量时,PDA最终在微球表面形成致密、均匀的壳层。 Zeta电势结果表明树莓状结构是由于DA在PAA表面聚合过程中受到静电相互作用和电荷排斥作用间的竞争而形成的,随着DA量的增大和反应时间的延长,形成的静电作用增大,使较多的PDA粘附至PAA表面而形成较致密的均匀壳层。 同时,DA在电负性较小的PS/SDS微球和非离子的PS微球表面聚合时,均形成致密的PDA壳层。 因而,材料表面的电负性大小可以调控DA在其表面的沉积,以制备不同形貌的PDA复合材料。     

Tunable red-green upconversion luminescence in novel transparent glass ceramics containing Er: NaYF4 nanocrystals

To develop NaYF(4) as bulk luminescence material, transparent glass ceramics containing Er(3+): NaYF(4) nanocrystals were fabricated for the first time, and the influences of heat-treatment temperature and Er(3+) doping level on their upconversion luminescence were investigated. With increasing heating temperature, the upconversion intensity enhanced accordingly, attributing to the incorporation of more Er(3+) into the grown NaYF(4). Notably, when the heating temperature reached 650 degrees C, the upconversion intensity augmented drastically due to the occurrence of phase transition from the cubic NaYF(4) to the hexagonal one. Interestingly, for the samples heat-treated at 620 degrees C, when the Er(3+) doping level was increased from 0.05 to 2.0 mol %, the upconversion emission was whole-range tunable from monochromatic green to approximately monochromatic red, which could be mainly attributed to the cross-relaxation between Er(3+) ions. The excellent optical properties and its convenient, low-cost synthesis of the present glass ceramic imply that it is an excellent substitution material for the unobtainable bulk NaYF(4) crystal, potentially applicable in many fields.     

Hydrophilic, Upconverting, Multicolor, Lanthanide-Doped NaGdF(4) Nanocrystals as Potential Multifunctional Bioprobes

Monodisperse water-soluble hexagonal phase Ln(3+) -doped NaGdF(4) upconverting nanocrystals (UCNCs) have been successfully fabricated by means of a fast, facile, and environmentally friendly microwave-assisted route with polyethylenimine as the surfactant. Fine-tuning of the UC emission from visible to near-IR and finally to white light has been achieved. Furthermore, studies of the magnetic resonance imaging as well as the magnetization (magnetization-magnetic field curves) and the targeted recognition properties of FA-coupled amine-functionalized NaGdF(4) @SiO(2) UCNCs indicate that the obtained NaGdF(4) UCNCs can be potential candidates for dual-mode optical/magnetic bioapplications.     

局域结构依赖的稀土上转换发光

稀土掺杂上转换发光纳米材料作为一种新型的荧光材料,因其发光性能优异、化学性质稳定以及自发荧光干扰小等优点受到国内外研究者的广泛关注。如何实现稀土上转换发光性能的可控调节一直是稀土纳米发光材料研究中的一个热点问题。简要总结了近年来关于局域结构依赖的稀土上转换发光性能的研究进展,分别从结构设计和晶体结构调节两个方面展开,主要内容包括核壳结构、复合结构和孔洞结构的设计对稀土上转换发光性能的影响及晶体结构对稀土上转换发光强度和上转换发光红绿比的影响,以期为制备高质量、可定制上转换发光性质的稀土掺杂纳米发光材料提供参考。     

Synthesis of hollow CaCO3 nanospheres templated by micelles of poly(styrene-b-acrylic acid-b-ethylene glycol) in aqueous solutions

An asymmetric triblock copolymer, poly(styrene-b-acrylic acid-b-ethylene glycol) (PS-b-PAA-b-PEG), was synthesized via reversible addition-fragmentation chain transfer controlled radical polymerization. Micelles of PS-b-PAA-b-PEG with PS core, PAA shell, and PEG corona were then prepared in aqueous solutions, followed by extensive characterization based on dynamic light scattering, zeta-potential, and transmission electron microscopy (TEM) measurements. The well-characterized micelles were used to fabricate hollow nanospheres of CaCO(3) as a template. It was elucidated from TEM measurements that the hollow nanospheres have a uniform size with cavity diameters of ca. 20 nm. The X-ray diffraction analysis revealed a high purity and crystallinity of the hollow nanospheres. The hollow CaCO(3) nanospheres thus obtained have been used for the controlled release of an anti-inflammatory drug, naproxen. The significance of this study is that we have overcome a previous difficulty in the synthesis of hollow CaCO(3) nanospheres. After mixing of Ca(2+) and CO(3)(2-) ions, the growth of CaCO(3) is generally quite rapid to induce large crystal, which prevented us from obtaining hollow CaCO(3) nanospheres with controlled structure. However, we could solve this issue by using micelles of PS-b-PAA-b-PEG as a template. The PS core acts as a template that can be removed to form a cavity of hollow CaCO(3) nanospheres, the PAA shell is beneficial for arresting Ca(2+) ions to produce CaCO(3), and the PEG corona stabilizes the CaCO(3)/micelle nanocomposite to prevent secondary aggregate formation.     

Controlled synthesis of uniform and monodisperse upconversion core/mesoporous silica shell nanocomposites for bimodal imaging

Here we report the design and controlled synthesis of monodisperse and precisely size-controllable UCNP@mSiO(2) nanocomposites smaller than 50?nm by directly coating a mesoporous silica shell (mSiO(2)) on upconversion nanocrystals NaYF(4):Tm/Yb/Gd (UCNPs), which can be used as near-infrared fluorescence and magnetic resonance imaging (MRI) agents and a platform for drug delivery as well. Some key steps such as transferring hydrophobic UCNPs to the water phase by using cetyltrimethylammonium bromide (CTAB), removal of the excess amount of CTAB, and temperature-controlled ultrasonication treatment should be adopted and carefully monitored to obtain uniform upconversion core/mesoporous silica shell nanocomposites. The excellent performance of the core-shell-structured nanocomposite in near-infrared fluorescence and magnetic resonance imaging was also demonstrated.     

NaYF_4:Yb/Er-碳纳米管功能纳米材料的制备、表征及其在肿瘤细胞的靶向检测和治疗中的应用

将叶酸分子(FA)和2,3-二巯基丁二酸(DMSA)修饰的稀土上转换发光纳米粒子NaYF4:Yb/Er通过酰胺键偶联在多壁碳纳米管(MWCNT)的表面,得到NaYF4:Yb/Er-MWCNT-FA功能化复合纳米材料,并通过透射电子显微镜(TEM)、X射线衍射(XRD)、紫外-可见吸收光谱(UV-vis)、荧光光谱(PL)和共聚焦激光扫描显微镜等手段表征了其形貌、结构、发光性能和靶向成像性能.共聚焦激光扫描显微镜结果表明,相对于正常的HLF细胞,所制备的复合材料能够靶向检测叶酸受体高表达的宫颈癌Hela细胞.此外,将阿霉素进一步通过ππ堆垛吸附在此复合材料后,该载药体系具有明显的抗肿瘤活性,能够实现对肿瘤细胞的一步检测和治疗.     

NaYF4∶Er3＋, Yb3＋纳米晶的液相合成

采用丙三醇液相结晶法制备了NaYF4∶Er3＋, Yb3＋上转换纳米晶, 合成步骤被简化. 常温下, 用980 nm的红外激光激发可以观察到很强的绿光、红光发射, 用荧光光谱仪记录了该上转换光谱. X射线粉末衍射(XRD)结果表明, 该方法制备NaYF4∶Er3＋, Yb3＋纳米晶属于立方混合六方晶系. 研究了纳米晶的上转换发光机理, 根据晶体场理论对Er3＋的两个上转换能级进行了Stark分裂计算, 对两个能级之间的谱线进行了归属, 进一步证实了980 nm光子激发Er3＋离子的上转换机理, 一个是连续吸收两个980 nm光子的过程(激发态吸收), 另一个是吸收980 nm光子后, 电子转移到亚稳态能级, 然后再吸收980 nm光子过程(能量转移上转换).