内嵌硫化镉与上转换纳米颗粒的二氧化钛复合纳米管用于近红外光驱动光催化（英文）

由于近红外光在太阳光谱中占44%,因此,近红外光驱动的光催化剂的研制具有十分重要的意义.上转换发光材料可将低能量的近红外光子转换为高能光子,这种高能光子可以通过构建荧光共振转移系统将能量转移并活化量子效率较高的半导体材料,对于太阳能的转化利用具有潜在的应用前景.在本文中,通过胶体化学的过程在电纺丝制备的内嵌CdS纳米颗粒以及上转换荧光纳米颗粒(UCNPs)的二氧化硅复合纳米纤维表面外延生长一层二氧化钛层,通过高温煅烧得到二氧化钛复合纳米管.我们通过二氧化硅结构将CdS纳米颗粒与上转换荧光纳米颗粒紧紧束缚在一起,实现较高的荧光共振能量转移.而且,选择β-NaYF_4:Yb(30%),Tm(0.5%)@NaYF_4:Yb(20%),Er(2%)作为纳米能量转换器,替代以前研究工作中使用的β-NaYF_4:Yb(30%),Tm(0.5%)或者β-NaYF_4:Yb(30%),Tm(0.5%)@NaYF_4纳米颗粒,来进一步提高近红外光的转换效率.通过透射电子显微镜照片很清楚的观察到制备的Ti O2复合纳米管内部内嵌有大量的CdS与上转换纳米颗粒.通过X-射线衍射以及X-射线光电子能谱能仪器对产物的物相以及表面的化学组成进行了细致的表征.结果显示,通过本实验方法已经成功获得了Ti O2复合纳米管.用稳态与瞬态荧光仪研究了最终样品的荧光性质.研究结果揭示,与上转换纳米颗粒以及二氧化硅复合纳米纤维相比,复合二氧化钛纳米管可以将上转换荧光纳米颗粒的(UV-Vis)部分荧光完全淬灭了.特别是,铒离子的荧光(650 nm)也被有效淬灭转移,说明本研究采用β-NaYF_4:Yb(30%),Tm(0.5%)@NaYF_4:Yb(20%),Er(2%)纳米能量转换器,可以提高近红外光的转换效率,紫外-可见吸收光谱证实,这种二氧化钛纳米管在紫外-可见光区中的吸收光谱与β-NaYF_4:Yb(30%),Tm(0.5%)@NaYF_4:Yb(20%),Er(2%)纳米颗粒的荧光光谱具有较大的重叠,使得上转换荧光纳米颗粒与CdS以及二氧化钛组分之间的荧光共振转移的效率大大提高,进而会显著提高光催化的效果.以罗丹明染料作为污染物为模型,我们研究了罗丹明染料在氙灯下或者近红外光光照下的光催化分解实验.研究结果表明,90%的罗丹明染料分子在20 min内就被降解掉,效率高于其它的近红外光催化剂.上转换荧光纳米颗粒的能量转换效率可以得到大幅度提高,本研究工作中制备的光催化剂利用太阳能的效率将会得到极大提高,在未来为能源危机以及环境保护提供一种可供选择的方法与技术.     

NaYF_4：Yb,Er上转换荧光纳米粒子的表面修饰及其在免疫分析中的应用

稀土掺杂上转换荧光纳米材料因其近红外区激发,可见光区发射的特殊发光性能,在生物标记方面具有独特优势,可大幅度降低荧光背景.β-NaYF4：Yb,Er是目前已知的发光效率最高的上转换荧光纳米材料之一,已在生命分析及生物成像分析领域展现出了广阔的应用前景.然而,由于现有β-NaYF4：Yb,Er制备工艺多是在高温条件下于高沸点有机溶剂中反应制得,所得产品在水溶液中的分散性差,限制了其在生命分析中的广泛应用.本文采用聚丙烯酸（PAA）配体交换反应,对表面包覆油酸基团的疏水β-NaYF4：Yb,Er纳米粒子进行了有效的表面修饰.表面修饰后,上转换荧光纳米粒子表面的PAA具有众多游离羧基,使其在水溶液中具有良好的分散性.同时,由于羧基的存在,使得带有氨基的生物分子能够通过化学交联反应结合到纳米粒子表面.本文以PAA表面修饰后的β-NaYF4：Yb,Er纳米粒子为荧光探针,以磁珠作为免疫反应的载体,成功构建了一种新型免疫传感器,对模型靶标分子羊抗人IgG进行了灵敏检测.磁珠表面固定兔抗羊IgG,PAA修饰的β-NaYF4：Yb,Er纳米粒子表面连接人IgG,当样品中存在羊抗人IgG时,便会在磁珠表面形成（兔抗羊IgG-羊抗人IgG-上转换荧光纳米粒子标记的人IgG）三明治式免疫复合体,通过磁分离除去未反应的组分,在980nm激光激发下测定免疫复合体的上转换荧光强度,即可实现靶标分子的高灵敏分析,可检测到低至0.1ng/mL的羊抗人IgG.同时,以磁珠为载体的免疫复合体也可通过激光扫描共聚焦荧光显微镜进行荧光成像分析,背景荧光信号低,成像质量高.实验结果表明,PAA修饰的β-NaYF4：Yb,Er上转换荧光纳米粒子是一种理想的生物标记材料,有望在生物传感及生物成像分析领域获得广泛应用.     

β-NaYF4：Yb,Er纳米晶与四甲基异氰酸罗丹明染料分子间的发光共振能量转移研究

Yb^3＋和Er^3＋离子掺杂的NaYF4纳米晶在近红外光（980nm）激发下可产生中心位于539和655nm的上转换发光,其中位于539nm的发光与四甲基异氰酸罗丹明（tetrametrylrhodarnine isothiocyante,TRITC）染料分子的吸收光谱部分重叠.本文基于上述光谱重叠特性,构筑了以β-NaYF4：Yb,Er为能量给体、TRITC为能量受体的发光共振能量转移（LRET）体系.TRITC分子通过静电作用紧密吸附于纳米晶表面,其较近距离的相互作用利于提高LRET效率和体系的稳定性.在980nm近红外光激发下,LRET过程使NaYF4：Yb,Er位于539nm的上转换发光减弱,同时可观察到TRITC染料分子的发光.对发光寿命的研究也证实了β-NaYF4：Yb,Er到TRITC的能量传递.     

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。     

近红外光驱动的UCNPs/ZnxCd1-xS纳米复合结构的化学合成并用于光化学还原六价铬

近红外光约占入射太阳能的 44% 以上, 为实现太阳能量的最大化利用, 近红外光 (NIR) 驱动的光催化技术成为科学研究的热点. 由于上转换荧光纳米材料 (UCNPs) 是优良的红外能量转换器, 合金半导体 ZnxCd1-xS 具有较好的化学稳定性以及生物相容性, 本文发展了一种简易的水热法, 将 UCNPs 和 ZnxCd1-xS 合金结合, 成功构建了 NIR 与可见光响应的核壳纳米结构. 由于这两种材料的晶格失配度较高, 很难直接外延生长, 我们通过引入非晶 TiO2将形成的催化剂纳米颗粒ZnxCd1-xS 紧紧束缚在 UCNPs 外面形成蛋黄-蛋壳结构, 在 NIR 光照下获得了较高的能量转换效率.首先, 在 UCNPs 外面外延生长一层 AA-Zn[(OH)4]2–复合物, 形成 UCNPs@AA-Zn[(OH)4]2–复合纳米结构, 然后在其核壳结构外面外延生长薄层的非晶 TiO2, 以稳定后续要制备的合金半导体 ZnxCd1-xS; 在水热条件下, UCNPs@AA-Zn[(OH)4]2–/TiO2与醋酸镉和硫脲反应, 形成 UCNPs@ZnxCd1-xS/TiO2复合材料. 在此, 我们选择β-NaYF4:Yb(30%),Tm(0.5%)@NaYF4:Yb(20%),Er(2%) 作为 NIR 的能量转换器. 样品的形貌、物相及化学组成分别采用场发射扫描电子显微镜、透射电子显微镜、X 射线衍射和原子吸收光谱法进行表征.研究表明, 我们成功制备了具有蛋黄-蛋壳结构的 UCNPs@ZnxCd1-xS/TiO2纳米颗粒. 此外, 非晶态 TiO2将 UCNPs 与ZnxCd1-xS 紧密结合, 对最终样品 UCNPs@ZnxCd1-xS 核壳纳米粒子的形成起到重要作用. 而且, 合金 ZnxCd1-xS 的化学组成可通过调整镉源和锌源的用量进行调节. 所制备的 UCNPs@ZnxCd1-xS 核壳纳米粒子在 NIR 光线或模拟太阳光照射下显示出高效的光化学还原 Cr(VI) 性能. 溶液中 70% 以上的 Cr(VI) 在 NIR 光照射 30 min 后被还原为 Cr(III). 本研究将为环境污水处理和太阳能利用提供一种可供选择的策略, 且所制的复合纳米结构在肿瘤治疗、药物释放和能量转换等领域也有着潜在的应用价值.     

Na(Y1.5Na0.5)F6:Yb3+/Er3+纳米棒的制备及其上转换发光特性

采用水热合成法,使用油酸作为乳化剂制备了Yb3+/Er3+共掺杂六角相Na(Y1.5Na0.5)F6纳米棒。通过X射线衍射(XRD)、扫描电子显微镜(SEM)以及荧光光谱等测试手段对所制备的样品进行表征。测试结果表明,Na(Y1.5Na0.5)F6纳米晶的晶格常数为a=b=0.600 nm,c=0.352 nm。在980 nm红外光激发下,Yb3+/Er3+共掺杂Na(Y1.5Na0.5)F6纳米棒发出从红光到近紫外的上转换荧光,其中红光、绿光和近紫外光分别对应于Er3+离子4F9/2→4I15/2,(2H11/2,4S3/2)→4I15/2和(2G11/2/2H9/2)→4I15/2的能级跃迁。详细讨论和分析了各荧光波段的上转换发射过程。     

Li+掺杂对TeO2:Tm3+/Er3+/Yb3+纳米材料上转换发光的增强作用

采用水热法制备了发白光的Li+掺杂α-TeO2∶Tm3+/Er3+/Yb3+和β-TeO2∶Tm3+/Er3+/Yb3+纳米上转换发光材料。采用X射线衍射、透射电镜和上转换发光光谱对制备的TeO2∶Tm3+/Er3+/Yb3+/Li+纳米材料进行表征,结果显示:Li+的掺入基本不改变纳米材料的晶型和结构;在980 nm近红外光的激发下,纳米材料发射出中心波长476 nm的蓝光,525 nm及545 nm的绿光和659 nm及675nm的红光,分别对应于Tm3+的1G4→3H6能级跃迁,Er3+的2H11/2→4I15/2和4S3/2→4I15/2能级跃迁,Er3+的4F9/2→4I15/2能级跃迁和Tm3+的3F2→3H6能级跃迁;Li+的掺入能够增大白光体系的发光强度,基本不改变纳米材料的白光颜色。此外,探讨了纳米材料的上转换发光机理。     

β-Na（Y_（1.5-x-y）Na_（0.5））F_6：Yb_xTm_y纳米颗粒的合成及其上转换发光性质

本文采用水热合成法制备了β-Na（Y1.5-x-yNa0.5）F6：YbxTmy（x=0.2~1.0,y=0.001~0.008）纳米颗粒,并利用X射线粉末衍射仪、透射电子显微镜和F-4600荧光分光光度计表征了其样品的物相、形貌和发光性质.结果表明样品物相为六角相,颗粒平均直径约22nm,并探讨了Yb3＋和Tm3＋掺杂浓度对样品的上转换发光性质的影响,结果表明敏化剂Yb3＋的最佳掺杂浓度为60%,而激活剂Tm3＋的最佳掺杂浓度为0.6%.     

NaYF4:Yb,Tm上转换发光纳米材料的合成及在手印显现中的应用研究

采用溶剂热法合成了NaYF_4:Yb, Tm上转换发光纳米材料,并对纳米材料的微观形貌、物相组成、近红外吸收性能、上转换发光性能进行了表征。将制得的NaYF_4:Yb, Tm上转换发光纳米粉末用于潜在手印的显现技术中,分别获得了蓝色可见光显现信号和近红外光显现信号,通过光谱表征手段详细考察了手印显现的对比度。实验结果表明,基于NaYF_4:Yb, Tm的手印纳米荧光显现方法具有对比度强、灵敏度高、选择性好等优势,对于颜色复杂及荧光强烈客体表面潜在手印的显现是一种较为理想的方法。     

Surface modification of hydrophobic NaYF_4:Yb,Er upconversion nanophosphors and their applications for immunoassay

β-NaYF4:Yb,Er upconversion nanophosphor (UCNP) is known as one of the most efficient NIR-to-visible upconversion materials, which shows great potential in bioanalytical chemistry and bioimaging. However, its applications are greatly limited due to its low water dispersibility and thus poor biocompatibility. In this paper, poly(acrylic acid) (PAA)-based ligand exchange strategies are carried out to modify oleic acid-capped hydrophobic β-NaYF4:Yb,Er UCNPs into hydrophilic ones. After efficient surface modific...     

Monodisperse Dual‐Functional Upconversion Nanoparticles Enabled Near‐Infrared Organolead Halide Perovskite Solar Cells

Extending the spectral absorption of organolead halide perovskite solar cells from visible into near‐infrared (NIR) range renders the minimization of non‐absorption loss of solar photons with improved energy alignment. Herein, we report on, for the first time, a viable strategy of capitalizing on judiciously synthesized monodisperse NaYF₄:Yb/Er upconversion nanoparticles (UCNPs) as the mesoporous electrode for CH₃NH₃PbI₃ perovskite solar cells and more importantly confer perovskite solar cells to be operative under NIR light. Uniform NaYF₄:Yb/Er UCNPs are first crafted by employing rationally designed double hydrophilic star‐like poly(acrylic acid)‐block‐poly(ethylene oxide) (PAA‐b‐PEO) diblock copolymer as nanoreactor, imparting the solubility of UCNPs and the tunability of film porosity during the manufacturing process. The subsequent incorporation of NaYF₄:Yb/Er UCNPs as the mesoporous electrode led to a high efficiency of 17.8 %, which was further increased to 18.1 % upon NIR irradiation. The in situ integration of upconversion materials as functional components of perovskite solar cells offers the expanded flexibility for engineering the device architecture and broadening the solar spectral use.     

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.     

Phase control of upconversion nanocrystals and new rare earth fluorides though a diffusion-controlled strategy in a hydrothermal system

Here we report a general hydrothermal technology to obtain well-known rare earth fluorides involving β-NaYF(4):Yb, Er/Tm and β-NaGdF(4):Yb, Er/Tm upconversion nanocrystals, one new polymorph of γ-REF(3) (RE = Eu-Tm, Y) and hexagonal LiREF(4) (RE = Nd-Lu, Y) colloidal nanocrystals.     

Recent Advances in Controlled Synthesis of Upconversion Nanoparticles and Semiconductor Heterostructures

It's of great importance for construction of upconversion nanoparticles (UCNPs)/semiconductor heterostructures activated by near infrared light, which have gained worldwide research interests owing to important applications in photocatalysis, solar cells, nanomedicine, and etc. In this review, we highlight the synthetic strategies developed to fabricate upconversion nanoparticles based heterostructures, such as chemical epitaxial growth method, electrospinning technique, self‐assembly method, hydrothermal method, and etc. Numerous examples are given concerning the use of the strategies to fabricate various microstructures/nanostructures incorporated with UCNPs and semiconductors materials. The latest advances and perspectives in the synthetic strategies and preparation of this kind of composite nanostructures are made.     

Boosting the Efficiency of Dye-Sensitized Solar Cells by a Multifunctional Composite Photoanode to 14.13 %

We report a new strategy to fabricate a multifunctional composite photoanode containing TiO₂ hollow spheres (TiO₂-HSs), Au nanoparticles (AuNPs) and novel NaYF₄ : Yb,Er@NaLuF₄ : Eu@SiO₂ upconversion nanoparticles (UCNPs). The AuNPs are grown on the photoanode film including TiO₂-HSs and UCNPs by a simple in situ plasmonic treatment. As a result, an impressive power conversion efficiency of 14.13 % is obtained, which is a record for N719 dye-based dye-sensitized solar cells, demonstrating great potential for the solar cells toward commercialization. This obvious enhancement is ascribed to a collaborative mechanism of the TiO₂-HSs exhibiting excellent light-scattering ability, of the UCNPs converting near-infrared photons into visible photons and of the AuNPs presenting outstanding surface plasmon resonance effect. Notably, a steady-state experiment further reveals that the champion cell exhibits 95.33 % retainment in efficiency even after 180 h of measurements, showing good device stability.     

Multifunctional Core–Shell Upconverting Nanoparticles for Imaging and Photodynamic Therapy of Liver Cancer Cells

Lanthanide‐doped upconversion nanoparticles (UCNPs) have attracted considerable attention for their application in biomedicine. Here, silica‐coated NaGdF₄:Yb,Er/NaGdF₄ nanoparticles with a tetrasubstituted carboxy aluminum phthalocyanine (AlC₄Pc) photosensitizer covalently incorporated inside the silica shells were prepared and applied in the photodynamic therapy (PDT) and magnetic resonance imaging (MRI) of cancer cells. These UCNP@SiO₂(AlC₄Pc) nanoparticles were uniform in size, stable against photosensitizer leaching, and highly efficient in photogenerating cytotoxic singlet oxygen under near‐infrared (NIR) light. In vitro studies indicated that these nanoparticles could effectively kill cancer cells upon NIR irradiation. Moreover, the nanoparticles also demonstrated good MR contrast, both in aqueous solution and inside cells. This is the first time that NaGdF₄:Yb,Er/NaGdF₄ upconversion‐nanocrystal‐based multifunctional nanomaterials have been synthesized and applied in PDT. Our results show that these multifunctional nanoparticles are very promising for applications in versatile imaging diagnosis and as a therapy tool in biomedical engineering.     

Highly plasmon-enhanced upconversion emissions from Au@β-NaYF4:Yb,Tm hybrid nanostructures

Unselectively enhanced multicolour upconversion (UC) emissions and low pumping threshold were achieved in Au@β-NaYF(4):Yb,Tm hybrid nanostructures. This demonstrates that the plasmon field enhancement effect is the main reason for the improved UC emission efficiency.     

Synthesis and characterization of ternary nanocomposites of TiO2/rGO/CdS as an efficient catalyst for photo-degradation of methyl orange

Novel ternary composite photocatalysts have been successfully prepared by TiO₂ nanofibers, reduced graphene oxide, and CdS nanoparticles (TiO₂/rGO/CdS) by using electrospinning technique with easy chemical methods. The structures and their properties are examined by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and field-emission scanning electron microscope (FESEM). The structural characterization of the composite reveals that pure TiO₂ NFs and CdS NPs crystalline very well and the reduced graphene oxide is tightly composed with TiO₂ NFs and CdS Nps. The photodegradation of methyl orange (MO) under UV light illumination is significantly enhanced compared with that of bare materials. This ternary composite degrades methyl orange within 75 min. The enhanced photocatalytic degradation performance resulted from effective separation of e–h pairs with rGO sheets and also contributed for high rate degradation efficiency. This novel ternary composite has a potential application of wastewater purification and utilization for energy conversions.     

Stabilization of High Oxidation State Upconversion Nanoparticles by N‐Heterocyclic Carbenes

The stabilization of high oxidation state nanoparticles by N‐heterocyclic carbenes is reported. Such nanoparticles represent an important subset in the field of nanoparticles, with different and more challenging requirements for suitable ligands compared to elemental metal nanoparticles. N‐Heterocyclic carbene coated NaYF₄:Yb,Tm upconversion nanoparticles were synthesized by a ligand‐exchange reaction from a well‐defined precursor. This new photoactive material was characterized in detail and employed in the activation of photoresponsive molecules by low‐intensity near‐infrared light (λ =980 nm).