A Long-term and Stable Surface Modification Method for Lanthanide Doped Upconversion Nanoparticles by Oxidized Alginate

Lanthanide doped upconversion luminescent nanoparticles (UCNPs) have drawn widely attention in biomedical research. The generally synthesized oleate capped UCNPs have no aqueous dispersibility so that surface modification is required to be water dispersible. Herein, we developed an easy-going but effective approach to prepare hydrophilic UCNPs based on oxidized alginate molecule (OAlg). After surface modification treatment, the OAlg modified UCNPs (UCNPs-OAlg) shows excellent dispersibility and longer stability in aqueous solution even after 180 days. After incubation with UCNPs-OAlg, the upconversion luminescent images of living Hela cells were clearly obtained. It indicated that oxidized alginate modified UCNPs can be candidate for excellent imaging probes in future.     

Lanthanide‐Doped LiLuF4 Upconversion Nanoprobes for the Detection of Disease Biomarkers

Lanthanide‐doped upconversion nanoparticles (UCNPs) have shown great promise in bioapplications. Exploring new host materials to realize efficient upconversion luminescence (UCL) output is a goal of general concern. Herein, we develop a unique strategy for the synthesis of novel LiLuF₄:Ln³⁺ core/shell UCNPs with typically high absolute upconversion quantum yields of 5.0 % and 7.6 % for Er³⁺ and Tm³⁺, respectively. Based on our customized UCL biodetection system, we demonstrate for the first time the application of LiLuF₄:Ln³⁺ core/shell UCNPs as sensitive UCL bioprobes for the detection of an important disease marker β subunit of human chorionic gonadotropin (β‐hCG) with a detection limit of 3.8 ng mL⁻¹, which is comparable to the β‐hCG level in the serum of normal humans. Furthermore, we use these UCNPs in proof‐of‐concept computed tomography imaging and UCL imaging of cancer cells, thus revealing the great potential of LiLuF₄:Ln³⁺ UCNPs as efficient nano‐bioprobes in disease diagnosis.     

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.     

A multifunctional upconversion nanoparticles probe for Cu2+ sensing and pattern recognition of biothiols

Lanthanide-doped upconversion nanoparticles (Ln-UCNPs) are a new type of nanomaterials with excellent fluorescence properties, which are well applied in fluorescent biosensing. Herein we developed a multifunctional probe based on the surface engineering of core-shell structure UCNPs with polyacrylic acid (PAA). The developed PAA/UCNPs probe could be highly selective to detect and respond to Cu²⁺ at different pH. Cu²⁺ could easily combine with the carboxylate anion of PAA to quench the fluorescence of UCNPs. Therefore, we creatively proposed a fluorescent array sensor (PAA/UCNPs-Cu²⁺), in which the same material acted as the sensing element by coupled with pH regulation for pattern recognition of 5 thiols. It could also easily identify the chiral enantiomer of cystine (l-Cys-and d-Cys), and distinguish their mixed samples with different concentrations, and more importantly, it could be combined with urine samples to detect actual level of homocysteine (Hcys) to provide a new solution for judging whether the human body suffers from homocystinuria.     

Upconversion nanoparticle-based fluorescence resonance energy transfer assay for Cr(III) ions in urine

A novel assay of chromium(III) ion based on upconversion fluorescence resonance energy transfer was designed and established. Lysine-capped NaYF₄:Yb/Er upconversion nanoparticles (UCNPs) and dimercaptosuccinic acid-capped gold nanoparticles (AuNPs) were used as the energy donor and acceptor, respectively. They were bound together via electrostatic interaction, resulting in the quenching of the fluorescence of UCNPs by AuNPs. Chromium(III) ions can specifically and strongly interact with dimercaptosuccinic acid that was modified on the surface of AuNPs, leading to the separation of AuNPs from UCNPs and the recovery of fluorescence of UCNPs. The fluorescence recovery of UCNPs showed a good linear response to Cr³⁺ concentration in the range of 2–500 nM with a detection limit of 0.8 nM. This method was further applied to determine the levels of Cr³⁺ in urine. Compared with other fluorescence methods, current method displayed very high sensitivity and signal-to-noise ratio because of the excitation of near-infrared that can eliminate autofluorescence, providing a promising examination of biological samples for the diagnostic purposes.     

核酸适配体功能化的稀土上转换纳米材料在生物检测中的应用

稀土上转换纳米材料可以吸收近红外光并发射出可见光或紫外光,在生物传感领域得到了广泛研究。核酸适配体能高特异性和高亲和性地与靶标物结合,被广泛应用于生物传感、疾病诊断等领域。将稀土上转换纳米材料与核酸适配体结合构建的检测体系,可实现对目标物灵敏、高选择性的检测。本文介绍了近几年核酸适配体功能化的稀土上转换纳米材料在生物小分子、蛋白质、核酸、病原微生物、细胞等方面的应用,并展望了其在分析检测领域的发展前景。     

Boosting Luminance Energy Transfer Efficiency in Upconversion Nanoparticles with an Energy‐Concentrating Zone

Despite the successful application of upconversion nanoparticles (UCNPs), their low energy transfer efficiency is still a bottleneck to further applications. Here we design UCNPs with a multilayer structure, including an inert NaYF₄:Gd core and an energy‐concentrating zone (ECZ), for efficient energy concentration. The ECZ is composed of an emitting layer of NaYF₄:Yb,Er and an absorption layer of NaYF₄:Nd,Yb with antenna IRDye 800CW to manipulate the energy transfer. The stable and tight packing of 800CW linked originally with a bisphosphonate ligand improves greatly the transfer efficiency. The proximity of the emitting layer to both surface antenna and accepter also decreases energy depletion. Compared to classical UCNPs, the ECZ UCNPs show 3600 times higher luminescence intensity with an energy transfer efficiency near 60 %. In proof‐of‐concept applications, this type of structure was employed for Hg²⁺ detection and for photodynamic therapy under hypoxic conditions.     

Enhanced red emission from GdF3:Yb3+,Er3+ upconversion nanocrystals by Li+ doping and their application for bioimaging

Under 980?nm near-infrared (NIR) excitation, upconversion luminescent (UCL) emission of GdF(3):Yb,Er upconversion nanoparticles (UCNPs) synthesized by a simple and green hydrothermal process can be tuned from yellow to red by varying the concentration of dopant Li(+) ions. A possible mechanism for enhanced red upconverted radiation is proposed. A layer of silica was coated onto the surface of GdF(3):Yb,Er,Li UCNPs to improve their biocompatibility. The silica-coated GdF(3):Yb,Er,Li UCNPs show great advantages in cell labeling and in vivo optical imaging. Moreover, GdF(3) UCNPs also exhibited a positive contrast effect in T(1)-weighted magnetic resonance imaging (MRI). These results suggest that the GdF(3) UCNPs could act as dual-modality biolabels for optical imaging and MRI.     

优化稀土上转换纳米材料发光的方法

稀土上转换纳米材料(Upconversion Nanoparticles,UCNPs)可将近红外光转换为可见光,其发光性能优异、化学性质稳定、激发光能有效避免自荧光,因此在生物医学领域应用广泛。但UCNPs的低发光效率限制了其进一步发展。本文综述了近年来研究较多的几种优化稀土上转换纳米材料发光的方法,主要包括调整基质材料和掺杂离子、过渡金属离子与镧系离子共掺杂、引入协同敏化剂减少热效应、有机染料与UCNPs协同作用以及金属表面等离子体共振增强法等。文中分别论述了上述方法的最新研究进展,并总结了这些方法目前存在的问题,指出上转换发光领域的研发重点:一是着重分析各种优化发光方法的作用机理,提出更加完备清晰的理论体系;二是探索更容易被生物体降解的UCNPs,使其副作用降到最低。     

Multicolor output and shape controlled synthesis of lanthanide-ion doped fluorides upconversion nanoparticles

A general and facile approach for tailoring the multicolor output and shapes of lanthanide-ion doped fluoride upconversion nanoparticles (UCNPs) within a given composition is presented. By adjusting the temperature and time in the thermolysis procedure, the color output and shapes of NaYF(4):20%Yb, 2%Er UCNPs can be readily manipulated. The nanoparticles were characterized through the use of transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and upconversion luminescence spectroscopy. It is shown that the relative intensities of green emissions gradually increased with the rise of temperature and prolongation of growth time under excitation of 980 nm, which resulted in multicolor output of NaYF(4):20%Yb, 2%Er UCNPs. Simultaneously, the shapes for UCNPs can also be controlled. TEM images, estimated micro-stress by Williamson-Hall methodology and a series of control experiments and analyses reveal that crystallinity is mainly responsible for the multicolor output of UCNPs. Based on the above method, the tailoring of color output is also successfully realized in Ho(3+) and Tm(3+) ions. It is expected that this method may be used to tune the physical properties of other nanoparticles, and these multicolored UCNPs are promising for applications in multiplexed bioimaging, biodetection, display, other optical technologies, etc.     

掺杂比例和光敏剂对上转换纳米材料性能的影响

以NaYF_4材料为基质的上转换纳米颗粒(UCNPs)是最早报道的、应用范围最广的上转换材料之一。掺杂了稀土离子的颗粒不但可以在不同激发条件下发射出不同波长和强度的荧光,而且可以与多种光敏分子搭配使用,通过荧光共振能量转移产生单线态氧,实现生物医学成像或诊疗方面的应用。但是其形貌和荧光性能均受制备方法和工艺条件的影响较大。本文通过水热法合成了两类掺杂不同稀土离子的十种NaYF_4 UCNPs,在保持掺杂离子的终浓度不变的条件下,探究离子类型与比例对纳米材料的结构和上转换发光性能的影响。在此基础上,探索了多种卟啉类光敏剂分子与NaYF_4 UCNPs发生能量转换及单线态氧的产生能力。本工作可为基于NaYF_4材料的上转换颗粒的规模化制备和工艺升级提供数据支撑和理论参考。     

Aqueous-phase synthesis of upconversion metal-organic frameworks for ATP-responsive in situ imaging and targeted combinational cancer therapy

Herein, the nanoscaled ATP-responsive upconversion metal-organic frameworks（UCMOFs） are aqueousphase synthesized for co-delivery of therapeutic protein cytochrome c（Cyt c） and chemodrugs doxorubicin（DOX）, achieving targeted combinational therapy of human cervical cancer. The UCMOFs are rationally fabricated by growing ZIF-90 on mesoporous silica-coated upconversion nanoparticles（UCNPs）,in which the ZIF-90 layer attenuates the upconversion luminescence（UCL） and the rigid frameworks increase the s...     

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.     

DNA-mediated coordinative assembly of upconversion hetero-nanostructures for targeted dual-modality imaging of cancer cells

We reported a simple and universal strategy for DNA-mediated assembly of CdTe quantum dots (QDs) and lanthanide-doped upconversion nanoparticles (UCNPs). Such DNA-QD/UCNPs heterostructures not only maintains both fluorescent properties of QDs and upconversion luminescence behaviors of UCNPs, but also offers a polyvalent DNA surface, allowing for targeted dual-modality imaging of cancer cells using an aptamer     

基于上转换荧光共振能量转移的Hg~(2+)侧流检测模型的设计和应用

本工作利用荧光共振能量转移(FRET)过程,以上转换荧光纳米材料(UCNPs)作为能量供体,以金纳米粒子(AuNPs)作为能量受体,通过适配体识别Hg~(2+),在硝化纤维素膜(NC)上制备侧流检测试纸条。Hg2+的参与会拉近能量供受体距离,引起检测区UCNPs的荧光猝灭。通过检测区的荧光猝灭效率,可判断样品中的Hg~(2+)浓度。该传感器在缓冲溶液中的检测线性范围为0.1~100nmol/L;检出限为0.1nmol/L。本研究成功证实了上转换荧光共振能量转移体系在侧流模型应用的可行性。     

Upconversion nanophosphors for small-animal imaging

Rare-earth upconversion nanophosphors (UCNPs), when excited by continuous-wave near-infrared light, exhibit a unique narrow photoluminescence with higher energy. Such special upconversion luminescence makes UCNPs promising as bioimaging probes with attractive features, such as no auto-fluorescence from biological samples and a large penetration depth. As a result, UCNPs have emerged as novel imaging agents for small animals. In this critical review, recent reports regarding the synthesis of water-soluble UCNPs and their surface modification and bioconjugation chemistry are summarized. The applications of UCNPs for small-animal imaging, including tumor-targeted imaging, lymphatic imaging, vascular imaging and cell tracking are reviewed in detail. The exploration of UCNPs as multifunctional nanoscale carriers for integrated imaging and therapy is also presented. The biodistribution and toxicology of UCNPs are further described. Finally, we discuss the challenges and opportunities in the development of UCNP-based nanoplatforms for small-animal imaging (276 references).     

基于NaYF_4∶Yb~(3+),Er~(3+)上转换发光纳米晶的复合微球组装及其光动力活性

采用微乳液法,以NaYF4∶Yb3+,Er3+纳米晶为发光基元,肽菁锌(Zn Pc)光敏分子与十八碳烯-马来酸酐共聚物(PMAO)为功能分子,一步组装获得了NaYF4-Zn Pc-PMAO复合微球,此微球同时具备成像与光动力活性功能,NaYF4可作为低生物背景的荧光成像剂,同时其上转换发光可以敏化Zn Pc用于光动力活性研究,PMAO分子经过简单的水解反应即可实现表面羧基功能化。TEM,Zeta电位与PL测试证实了微球的结构与性能。利用荧光共聚焦成像技术实现了对Hela细胞的发光成像;进一步通过单线态氧监测及980 nm光照下的MTT法细胞活性测试表明微球具有光动力活性功能。     

基于NaYF4:Yb3+,Er3+上转换发光纳米晶的复合微球组装及其光动力活性研究

采用微乳液法,以NaYF₄:Yb³⁺,Er³⁺纳米晶为发光基元,肽菁锌(ZnPc)光敏分子与十八碳烯-马来酸酐共聚物(PMAO)为功能分子,一步组装获得了NaYF₄-ZnPc-PMAO复合微球,此微球同时具备成像与光动力活性功能,NaYF₄可作为低生物背景的荧光成像剂,同时其上转换发光可以敏化ZnPc用于光动力活性研究,PMAO分子经过简单的水解反应即可实现表面羧基功能化。TEM,Zeta电位与PL测试证实了微球的结构与性能。利用荧光共聚焦成像技术实现了对Hela细胞的发光成像;进一步通过单线态氧监测及980 nm光照下的MTT法细胞活性测试表明微球具有光动力活性功能。     

Synthesis and surface modification of ultrasmall monodisperse NaYF4:Yb3+/Tm3+ upconversion nanoparticles

The emerging upconversion nanoparticles (UCNP) have gained substantial consideration in the field of bioanalytical as well as diagnostic applications. Therefore, great progress has been made in the synthesis and surface modification of luminescent UCNPs over the last two decades. In this paper, we have reported monodispersed and high luminescent upconversion nanoparticles NaYF₄: 20%Yb³⁺, 2%Tm³⁺ have been synthesized using a solvothermal method, followed by a coating of the NaYF₄ shell with a thin layer of SiO₂ on the surface to afford the core-shell NaYF₄:Yb³⁺, Tm³⁺@SiO₂ nanoparticles (NP@SiO₂). The prepared nanoparticles were of strong upconversion fluorescent emission intensity, hexagonal phase, and with an average size of about 8 ± 1 nm, which have been characterized by luminescence spectroscopy, powder X-ray diffraction (P-XRD), Dynamic light scattering (DLS), and Transmission electron microscopy (TEM). The results indicate that the NP@SiO₂ can be used for the conjugation of fluorescent probes for various biomolecules and can find applications in cancer cell imaging and disease diagnosis.     

Luminescent Ink Based on Upconversion of NaYF4:Er,Yb@MA Nanoparticles: Environmental Friendly Synthesis and Structural and Spectroscopic Assessment

NaYF₄:Er,Yb upconversion luminescent nanoparticles (UCNPs) were prepared by hydrothermal methods at 180 °C for 24 h. The X-ray diffraction (XRD) and TEM (transmission electron microscopy) images show that the resulting 60 nm UCNPs possess a hexagonal structure. In this work, maleic anhydride (MA) was grafted on the surface of UCNPs to induce hydrophilic properties. The photoluminescence spectra (PL) show upconversion emissions centered around 545 nm and 660 nm under excitation at 980 nm. The luminescent inks, including UCNPs@MA, polyvinyl alcohol (PVA), deionized water (DI), and ethylene glycol (EG), exhibit suitable properties for screen printing, such as high stability, emission intensity, and tunable dynamic viscosity. The printed patterns with a height of 5 mm and a width of 1.5 mm were clearly observed under the irradiation of a 980 nm laser. Our strategy provides a new route for the controlled synthesis of hydrophilic UCNPs, and shows that the UCNPs@MAs have great potential in applications of anti-counterfeiting packing.