用于包装防伪的稀土上转换发光材料

目的 从增强稀土离子发光的角度考察上转换发光调控及性能,综述稀土发光材料在光学防伪领域的应用,以期为上转换材料与包装材料的功能化研究提供参考。方法 检索近几年文献,介绍上转换发光纳米材料的发光机理、发光性能及调控、光学材料打印技术的研究进展。结果 稀土掺杂的上转换发光纳米材料表现出优异的发光性能,但随着粒径减小,纳米颗粒出现发光效率、量子产量低的问题。利用纳米颗粒表面钝化、表面等离子体耦合、与有机配体结合和外场调节等手段,可以使发光材料的发光效能显著增强。利用喷墨打印、丝网印刷、纳米压印光刻和气溶胶喷印等技术,可以使稀土掺杂的上转换发光纳米材料被打印成多样的防伪图案,在光学防伪、信息存储与标记等领域具有重大应用潜力,有望成为新型功能包装材料。结论 在光学材料合成技术、光学调控和打印技术的共同推动下,稀土掺杂上转换发光纳米材料因其特殊的光学特性,有望为功能化包装防伪技术作出贡献。     

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.     

凝胶网络模板法可控制备NaYF_4:Yb~(3+),Er~(3+)稀土上转换纳米颗粒

采用水凝胶空间网孔结构作为纳米级反应容器可控制备了NaYF4:Yb3+,Er3+稀土上转换发光纳米颗粒。通过控制交联剂密度可以改变网络凝胶网孔结构,用不同网孔结构的凝胶模板可以控制合成纳米颗粒。通过XRD、TEM、PL等方法研究了不同凝胶模板对颗粒的尺寸、发光性能的影响。结果表明,利用高分子交联后形成的凝胶网络,可以制得粒径在10 nm左右的NaYF4:Yb3+,Er3+纳米颗粒。随着交联剂浓度的升高,颗粒粒径及荧光强度都有所下降。本研究为稀土上转换发光纳米颗粒的制备提供了工艺简单、绿色环保的新方法。     

NaYF4：Yb,Er红色上转换发光纳米粒子的合成

利用热分解方法在油酸和十八胺的混合溶剂中合成了红色上转换发光的α-NaYF4：Yb,Er纳米粒子,通过X射线衍射（XRD）、透射电镜（TEM）以及980nm激发下的上转换发光光谱等方法进行表征,结果发现,在溶剂油酸和十八胺混合溶剂中,虽然反应时间和温度不同,但产物均为立方相结构且光学性能几乎呈现纯的红色发射光,说明可以在很广泛的范围内合成具有良好的红色上转换发光的NaYF4：Yb,Er纳米粒子。     

可控无机纳米颗粒制备与调变

近年来,纳米材料对各领域的影响、渗透引入注目,对纳米材料应用的呼声很高。国际国内已有许多纳米粉体上市,但纳米粉体在许多地方用不上,究其原因,是目前一些方法生产的纳米粉体的颗粒尺寸分布宽,尺寸分布不能任意调控,团聚再分散性差,结构也不可控,这些粉体的纳米特性和规格不能与各种应用相适应。当然,也有纳米粉体价格较贵,人们对纳米颗粒的认识不够的问题。纳米颗粒是纳米材料的基本构成单元,颗粒的性能不仅仅取决于颗粒的大小,还取决于它的形貌、结构。同时纳米颗粒只有均一、单分散,才能发挥纳米颗粒的本征特性,而且,各种需求需要不同…     

离子掺杂对纳米氧化钆发光强度及驰豫性能的影响

氧化钆纳米材料因其具备独特的光学性质与磁学性质,在发光材料、生物标记、生物成像和温度传感器等领域备受关注。为了进一步满足发光材料及生物医学领域对多功能纳米材料的需求,稀土离子及金属离子掺杂的钆基纳米材料应运而生,这种新型的纳米发光材料克服了传统荧光材料发光强度不稳定、检测灵敏度低、生物毒性高的缺点;基于近年来国内外稀土离子和金属离子掺杂纳米氧化钆的研究和现状,综述了不同离子掺杂的氧化钆纳米颗粒在发光材料及医学造影剂方面的应用,在此基础上介绍了提高氧化钆纳米颗粒发光强度、驰豫性能的途径。     

下转换发光材料对钙钛矿本征性能的影响研究

利用太阳光的近红外和紫外部分实现全光谱响应无疑已成为提高钙钛矿太阳能电池功率转换效率的重要焦点。通过引入光致发光转换层将近红外或紫外光转换为可见光被钙钛矿光活性层利用,已被认为是一种非常有前景的途径。将两种经典的下转换发光材料(红粉和黄粉)引入钙钛矿本征层,采用一步旋涂法制备钙钛矿薄膜。利用缺陷评定高级显微系统、扫描电镜(SEM)、X射线衍射(XRD)、紫外可见吸收及荧光光谱分别探究了下转换发光材料对钙钛矿薄膜表面粗糙度、形貌、结构及光谱性能的影响。结果表明：下转换发光材料能够优化钙钛矿薄膜表面粗糙度、形貌,并未改变钙钛矿结构。紫外可见分光光度计和荧光光谱仪的结果证实了下转换发光材料确实能够拓宽钙钛矿薄膜的光谱响应范围,使整个吸收光谱范围向短波长方向移动,为有效利用全光谱提供了新思路。     

纳米铝颗粒强氧化反应发光特性研究

设计了利用电爆炸铝丝产生纳米铝颗粒强氧化反应发光的实验装置，对比了纳米铝颗粒在氧气和氮气环境下发光能量的大小，测量了铝氧反应发光光谱，并对电爆炸铝丝产生纳米铝颗粒强氧化反应发光的物理条件进行了研究，结果表明：发光能量随腔内氧气压力的减小而增加；随铝丝直径先增加而后减少；随电容器储能的增加而增加，且电容器储能对发光现象存在一个门槛值。     

纳米结构氧化锌的制备新方法

介绍了一种在纯水环境中水热法合成纳米结构ZnO的新方法,讨论了该方法制备纳米ZnO的生长机理和影响因素。通过扫描电镜检测可知,合成的纳米结构ZnO形貌均一,晶形规则。由荧光光谱可知,合成的纳米结构ZnO在370nm左右有典型的较窄的本征激发光峰,在500~550nm有宽泛的深能级激发光峰。     

水溶性NaYF4:Yb,Er纳米颗粒的溶剂热合成及其上转换发光性能

稀土上转换发光纳米材料具有极好的生物应用前景,但其应用的前提是能制备出水溶性、发光效率高的稀土纳米材料.以乙二醇为溶剂、稀土氯化物和NaP为反应物,采用简易的溶剂热法一步制备出水溶性的NaYF4:Yb,Er纳米颗粒.NaYF4:Yb,Er样品以粒径为25~40nm的球形颗粒为主,同时含有少量直径为25~40nm、长度为50～100nm的虫状纳米颗粒.该样品具有立方相结构,样品表面上的乙二醇配体使其能够很好地分散于水中.在980nm激光器激发下,NaYF4:Yb,Er纳米颗粒水溶液展现了强的黄绿色上转换发光.因此该样品拥有良好的生物应用潜力.     

Enhancing Optical Forces on Fluorescent Up‐Converting Nanoparticles by Surface Charge Tailoring

3D remote control of multifunctional fluorescent up‐converting nanoparticles (UCNPs) using optical forces is being required for a great variety of applications including single‐particle spectroscopy, single‐particle intracellular sensing, controlled and selective light‐activated drug delivery and light control at the nanoscale. Most of these potential applications find a serious limitation in the reduced value of optical forces (tens of fN) acting on these nanoparticles, due to their reduced dimensions (typically around 10 nm). In this work, this limitation is faced and it is demonstrated that the magnitude of optical forces acting on UCNPs can be enhanced by more than one order of magnitude by a controlled modification of the particle/medium interface. In particular, substitution of cationic species at the surface by other species with higher mobility could lead to UCNPs trapping with constants comparable to those of spherical metallic nanoparticles.     

Engineering of Lanthanide‐Doped Upconversion Nanoparticles for Optical Encoding

Lanthanide‐doped upconversion nanoparticles (UCNPs) are an emerging class of luminescent materials that emit UV or visible light under near infra‐red (NIR) excitations, thereby possessing a large anti‐Stokes shift property. Due to their sharp excitation and emission bands, excellent photo‐ and chemical stability, low autofluorescence, and high tissue penetration depth of the NIR light used for excitation, UCNPs have surpassed conventional fluorophores in many bioapplications. A better understanding of the mechanism of upconversion, as well as the development of better approaches to preparing UCNPs, have provided more opportunities to explore their use for optical encoding, which has the potential for applications in multiplex detection and imaging. With the current ability to precisely control the microstructure and properties of UCNPs to produce particles of tunable emission, excitation, luminescence lifetime, and size, various strategies for optical encoding based on UCNPs can now be developed. These optical properties of UCNPs (such as emission and excitation wavelengths, ratiometric intensity, luminescence lifetime, and multicolor patterns), and the strategies employed to engineer these properties for optical encoding of UCNPs through homogeneous ion doping, heterogeneous structure fabrication and microbead encapsulation are reviewed. The challenges and potential solutions faced by UCNP optical encoding are also discussed.     

Metal nanoparticles as labels for heterogeneous, chip-based DNA detection

The last decade has witnessed the development of a variety of metal nanoparticle-based techniques for DNA detection. High sensitivity and specificity, miniaturization, and cost-efficient detection are problems addressed by the use of nanoparticle labels in heterogeneous DNA detection schemes. The small label size, established bioconjugation chemistry, and the unusual optical and electrical properties of metal nanoparticles make them unique tools for DNA detection. This paper reviews the different physical characteristics of metal nanoparticles and their implementation in assays. It covers various optical as well as gravimetric, electrochemical and electrical methods for analysing nanoparticle-labelled analytes, and particularly DNA, at sensing surfaces.     

Tip-enhanced Raman detection of antibody conjugated nanoparticles on cellular membranes

Tip enhanced Raman scattering (TERS) microscopy is used to image antibody conjugated nanoparticles on intact cellular membranes. The combination of plasmonic coupling and the resultant electric field obtained from intermediate focusing of a radially polarized source gives rise to Raman images with spatial resolution below 50 nm. Finite element method calculations are used to explain the origins of the observed image resolution and spectroscopic signals. The observed Raman scattering provides information about the biomolecules present near the nanoparticle probes. The results show that aggregates of nanoparticles produce spectroscopic results similar to those reported from other surface enhanced Raman spectroscopies, e.g., shell isolated nanoparticle enhanced Raman spectroscopy (SHINERS) and aggregated nanoparticles; however, TERS enables the detection of isolated nanoparticles on cell membranes where the observed spectra provide information about the interaction of the specific biomolecule conjugated to the nanoparticle probe. These measurements present a new technique for exploring biomolecular interactions on the surface of cells and tissue.     

NIR Biosensing of Neurotransmitters in Stem Cell‐Derived Neural Interface Using Advanced Core–Shell Upconversion Nanoparticles

Nondestructive neurotransmitter detection and real‐time monitoring of stem cell differentiation are both of great significance in the field of neurodegenerative disease and regenerative medicine. Although luminescent biosensing nanoprobes have been developed to address this need, they have intrinsic limitations such as autofluorescence, scattering, and phototoxicity. Upconversion nanoparticles (UCNPs) have gained increasing attention for various biomedical applications due to their high photostability, low auto‐fluorescent background, and deep tissue penetration; however, UCNPs also suffer from low emission intensities due to undesirable energy migration pathways. To address the aforementioned issue, a single‐crystal core–shell–shell “sandwich” structured UCNP is developed that is designed to minimize deleterious energy back‐transfer to yield bright visible emissions using low power density excitations. These UCNPs show a remarkable enhancement of luminescent output relative to conventional β‐NaYF4:Yb,Er codoped UCNPs and β‐NaYF4:Yb,Er@NaYF4:Yb “active shell” alike. Moreover, this advanced core–shell–shell UCNP is subsequently used to develop a highly sensitive biosensor for the ultrasensitive detection of dopamine released from stem cell‐derived dopaminergic‐neurons. Given the challenges of in situ detection of neurotransmitters, the developed NIR‐based biosensing of neurotransmitters in stem cell‐derived neural interfaces present a unique tool for investigating single‐cell mechanisms associated with dopamine, or other neurotransmitters, and their roles in neurological processes.     

Biosensing with plasmonic nanosensors

Recent developments have greatly improved the sensitivity of optical sensors based on metal nanoparticle arrays and single nanoparticles. We introduce the localized surface plasmon resonance (LSPR) sensor and describe how its exquisite sensitivity to size, shape and environment can be harnessed to detect molecular binding events and changes in molecular conformation. We then describe recent progress in three areas representing the most significant challenges: pushing sensitivity towards the single-molecule detection limit, combining LSPR with complementary molecular identification techniques such as surface-enhanced Raman spectroscopy, and practical development of sensors and instrumentation for routine use and high-throughput detection. This review highlights several exceptionally promising research directions and discusses how diverse applications of plasmonic nanoparticles can be integrated in the near future.     

Multiphonon resonant Raman scattering (MRRS) of semiconductor nanomaterials for biodetection

Robust, rapid and sensitive detection of specific molecules at ultra low concentrations is becoming increasing important, especially for medical diagnosis, food safety and environmental protection. Various spectroscopic techniques have been developed to apply in analysis and assay fields, including fluorescent spectroscopy, infrared spectroscopy and surface-enhanced Raman spectroscopy (SERS), etc. Multiphonon resonant Raman scattering (MRRS) technique is usually used to investigate optical lattice vibrations and the interaction between phonon and electron in semiconductor nanomaterials. Recently, it exhibits fascinating prospects in biodetection due to its significant specific spectroscopic and material advantages. The multiple-order phonon lines are material intrinsic and thus can be used as a characteristic fingerprint signal to label the biomolecules. The strong anti-interference capacity to external environment allows an accurate detection. Narrow bandwidth makes the technique suitable for multiplexed analysis. Proper choice of nontoxic inorganic semiconductor materials facilitates in-vivo detection. This review focuses on the current theoretical and technical developments in MRRS of semiconductor nanomaterials and highlights their applications in bioanalysis. The basic principle, merits, challenges and future perspectives of MRRS detection technique are discussed.     

Size dependent ferromagnetism in dodecyl amine capped ZnO nanoparticles

We investigated the size dependent ferromagnetism in dodecyl amine capped zinc oxide nanoparticle. X-ray diffraction and X-ray photoelectron spectroscopy analysis demonstrated that density of oxygen vacancies was enhanced due to an increase in compressive strain concomitant with the decrease in particle size. Magnetic measurements showed increased ferromagnetic ordering in ZnO nanoparticles with reduced particle size. It was also found that the increase in coercive field, saturation magnetization and magnetic hysteresis loop area were invariably associated with increased oxygen defect population. The observed ferromagnetism in organic capped zinc oxide nanocrystals has therefore been assigned to defect induced phenomena. Results of sample characterization using optical absorption spectroscopy, photo luminescence spectroscopy and high resolution transmission electron microscope have also been presented.     

Near-infrared light activated persistent luminescence nanoparticles via upconversion

Persistent luminescence nanoparticles (PLNPs) and upconversion nanoparticles (UCNPs) are two special optical imaging nanoprobes.In this study,efficient upconverted persistent luminescence (UCPL) is realized by combining their unique features into polymethyl methacrylate,forming a film composed of both PLNPs and UCNPs.The red persistent luminescence (～640 nm) of the PLNPs (CaS∶Eu,Tm,Ce) can be activated by upconverted green emission of UCNPs (β-NaYF4∶Yb,Er@NaYF4) excited by near-infrared light (NIR).Using this strategy,both the unique optical properties of PLNPs and UCNPs can be optimally synergized,thus generating efficient upconversion,photoluminescence,and UCPL simultaneously.The UCPL system has potential applications in in vivo bioimaging by simply monitoring the biocompatible low power density of NIR-light-excited persistent luminescence.Due to its simplicity,we anticipate that this method for the preparation of UCPL composite can be easily adjusted using other available upconversion and persistent phosphor pairs for a number of biophotonic and photonic applications.     

Temperature Determination of Resonantly Excited Plasmonic Branched Gold Nanoparticles by X‐ray Absorption Spectroscopy

The fields of bioscience and nanomedicine demand precise thermometry for nanoparticle heat characterization down to the nanoscale regime. Since current methods often use indirect and less accurate techniques to determine the nanoparticle temperature, there is a pressing need for a direct and reliable element‐specific method. In‐situ extended X‐ray absorption fine structure (EXAFS) spectroscopy is used to determine the thermo‐optical properties of plasmonic branched gold nanoparticles upon resonant laser illumination. With EXAFS, the direct determination of the nanoparticle temperature increase upon laser illumination is possible via the thermal influence on the gold lattice parameters. More specifically, using the change of the Debye–Waller term representing the lattice disorder, the temperature increase is selectively measured within the plasmonic branched nanoparticles upon resonant laser illumination. In addition, the signal intensity shows that the nanoparticle concentration in the beam more than doubles during laser illumination, thereby demonstrating that photothermal heating is a dynamic process. A comparable temperature increase is measured in the nanoparticle suspension using a thermocouple. This good correspondence between the temperature at the level of the nanoparticle and at the level of the suspension points to an efficient heat transfer between the nanoparticle and the surrounding medium, thus confirming the potential of branched gold nanoparticles for hyperthermia applications. This work demonstrates that X‐ray absorption spectroscopy‐based nanothermometry could be a valuable tool in the fast‐growing number of applications of plasmonic nanoparticles, particularly in life sciences and medicine.