Upconversion luminescence of Y_2O_3:Er^(3+), Yb^(3+) nanoparticles prepared by a homogeneous precipitation method

Y2O3： Er^3＋, Yb^3＋ nanoparticles were synthesized by a homogeneous precipitation method without and with different concentrations of EDTA 2Na. Upconversion luminescence spectra of the samples were studied under 980 nm laser excitation. The results of XRD showed that the obtained Y2O3：Er^3＋,Yb^3＋ nanoparticles were of a cubic structure. The average crystallite sizes calculated were in the range of 28-40 nm. Green and red upconversion emission were observed, and attributed to ^2H11/2,^4S3/2→^4I15/2 and ^4F9/2→^4I15/2 transitions of the ion, respectively. The ratio of the intensity of green emission to that of red emission drastically changed with a change in the EDTA 2Na concentration. In the sample synthesized without EDTA, the relative intensity of the green emission was weaker than that of the red emission. The relative intensities of green emission increased with the increased amount of EDTA 2Na used. The possible upconversion luminescence mechanisms were discussed.

Preparation and upconversion luminescence of YAG(Y_3Al_5O_(12)):Yb^(3+),Ho^(3+) nanocrystals

Cubic YAG：Yb3＋, Ho3＋ pure phase nanocrystals were synthesized by using coprecipition nitrate and ammonium hydrogen carbonate as raw materials.After calcining the precipitates at 800 °C, the resultant YAG：Yb3＋, Ho3＋ nanocrystals were nearly spheric and the particle size was about 40 nm.Intense upconversion spectra were observed on the powder compact pumped by a 980 nm continuous wave diode laser, and green emission centered at 549 nm, red emission centered at 667 nm, and NIR centered at 760 nm were all due to two photons process, which originated from 5S2（5F4）→5I8, 5F5→5I8, and 5S2（5F4）→5I7 transitions, respectively.

Controlled Assembly of Gold and Rare-Earth Upconversion Nanoparticles for Ratiometric Sensing Applications

In this paper, the Au nanoparticles and rare-earth （RE） upconversion nanoparticles （NPs） were respectively synthesized by using polyelectrolyte as the capping agents. Since the synthesized Au NPs and RE NPs had the similar size and surface conditions, Their mixture were employed in a pH sensing application. Benefited from the good spectral overlap between the RE upconversion emission bands and pH-tunable surface plasmon bands of the Au NPs, the pH-induced manipulation of green-to-red emission intensity ratio of the upconversion fluorescence was achieved in the Au-RE mixture. The results demonstrate a rapid ratiometric approach for pH sensing, which is more efficient than traditional sensing methods that depend on single intensity-based responses to analytes.

稀土掺杂上转换纳米材料在金属离子检测领域中的应用

重点综述了基于稀土掺杂上转换纳米材料(REEs-UCNPs)构建荧光共振能量转移(FRET)体系或发光共振能量转移(LRET)体系来实现对金属离子定量分析检测的研究进展,并对REEs-UCNPs在生物医学、卫生分析和环境检测等领域应用的未来发展趋势进行了展望。

基于稀土掺杂上转换纳米材料NaYF_(4):Yb,Er@TGA直接对金属离子进行定量分析的方法探究

目的:基于荧光猝灭或增强机制,构建稀土掺杂上转换纳米材料NaYF_(4):Yb,Er@TGA直接对金属离子进行定量分析的方法,实现对金属离子快速、准确、灵敏检测。方法:通过溶剂热法制备出性能优良的稀土掺杂上转换纳米材料NaYF_(4):Yb,Er@TGA,并对其进行表征;通过测量14种常见的金属离子对NaYF_(4):Yb,Er@TGA荧光强度的影响,筛选能够引起NaYF_(4):Yb,Er@TGA荧光强度增强或下降,且与金属离子浓度呈线性关系的金属离子类型,进而建立检测新方法。结果:金属离子Mg^(2+)、Fe^(3+)分别在浓度范围为0~7.00μg/mL、0~6.00μg/mL与NaYF_(4):Yb,Er@TGA的荧光强度呈现良好的线性关系,其标准曲线方程的线性系数分别为0.9924、0.9982,检出限分别为1.79μg/mL、1.30μg/mL,加标回收率分别为95.5%~98.8%、92.5%~97.8%,方法相对标准偏差分别为4.05%、8.18%。结论:该方法检测限低、准确度较高、精密度较好,有望用于实际样品中Mg^(2+)、Fe^(3+)定量分析。

稀土掺杂上转换发光材料的研究进展

上转换发光,一种呈现反斯托克斯位移特性的发光现象,主要通过稀土元素制备的材料来实现。本文深入探讨了稀土掺杂上转换材料的发光机理,概述了常用的制备技术,并全面评述了其在生物医学、防伪技术、信息存储等多个领域的现有应用,同时展望了其在工程领域的潜在应用前景。尽管上转换发光纳米材料在功能多样性方面表现出远超块状材料的显著优势,但其合成产率和发光效率仍存在挑战,处于相对较低水平。逐步攻克这些难题,将有助于进一步拓宽上转换发光材料的应用领域。

Dual excitable upconversion nanoparticle@polydopamine nanocomposite with intense red emission and efficient photothermal generation

Integration of strong upconversion emission with deep tissue penetration and stable photothermal generation is of great significance for imaging-guided photothermal therapy under infrared excitation.Herein,the NaYF_(4):Yb^(3+),Ho^(3+),Ce^(3+)@NaGdF_(4):Yb^(3+),Nd^(3+)@NaGdF_(4)core-shell-shell upconversion nanoparticles(UCNPs) with increasing Ce^(3+)doping concentration were firstly synthesized,in which the size manipulation,enhanced red to green emission intensity ratio(IR/IG),980 and 808 nm dual-modal excitations,as well as improved total upco nversion emission intensity can be achieved.After the coating of polydopamine(PDA) through dopamine spontaneous polymerization on the UCNPs surface under alkaline condition,the obtained UCNP@PDA nanocomposites show efficient photothermal effect under 808 nm excitation,while the thickness variation of PDA can be indicated by the upconversion spectra under 980 nm excitation.Interestingly,the photothermal effect of the UCNP@PDA nanocomposites with high IR/IGratio is mo re stable with PDA thickness variation,which bene fits from the structure design that allows PDA to simultaneously absorb the visible emission from inside UCNPs and the external 808 nm infrared light.Further in vitro cytotoxicity assay and photothermal therapy demonstrate that the UCNP@PDA nanocomposite has good biocompatibility and ability to kill tumor cells by photothermal effect under 808 nm excitation.This research may provide a nanoplatform for integrating deep bioimaging with highly stable photothermal therapy without the sacrifice of radiative transitions of rare earth ions.

Recent progress of energy transfer and luminescence intensity boosting mechanism in Nd3+-sensitized upconversion nanoparticles

Rare earth doped upconversion nanoparticles can be considered as the spice of research in the field of luminescence nanomaterials due to their unique optical properties such as near-infrared excitation.Enormous works have been reported about biomedical applications of 980 nm excited and Yb^3+-sensitized upconversion nanoparticles.However,980 nm excitation wavelength overlaps with the absorption band of water molecules in the biological environment,leading to overheating effect that can induce thermal damages of normal cells and tissues.Recently,Nd^3+-sensitized upconversion nanoparticles which can be excited with 808 nm has been widely investigated as alternative nanoparticles that can surmount this issue of overheating effect.Even though Nd^3+-sensitized upconversion nanoparticles can reduce the overheating effect by 20 fold as compared to Yb^3+-sensitized counterpart,there are several factors that reduce the upconversion luminescence intensity.In this review article,photon energy harvesting and transferring mechanisms in Nd^3+,Yb^3+and emitter ions co-doped upconversion nanoparticles under 808 nm excitation are briefly discussed.Factors that affect upconversion luminescence intensity and quantum yield of Nd^3+-sensitized upconversion nanoparticles are also addressed.Besides,some of the important strategies that have been recently utilized to boost upconversion luminescence intensity of Nd^3+sensitized upco nversion nanoparticles are tho roughly summarized.Lastly,the future challenges in the area and our perspectives are in sight.

One-step synthesis of hollow PEI-NaBiF4:Yb^3+/Er^3+upconversion nanoparticles for water-responsive luminescent probe

Novel PEI-modified NaBiF4:Yb3+/Er3+upconversion nanoparticles(UCNPs)with hollow structure were prepared by a surface modification free one-step solvothermal method and applied as a luminescent probe to determinate water content in organic solvents.XRD,SEM and HRTEM results demonstrate that the obtained PEI-NaBiF4:Yb3+/Er3+UCNPs are pure hexagonal phase with uniform size.The successful modification of PEI on the UCNPs surface was evidenced byζ-potential test,XPS and TG analysis.These synthesized UCNPs are disintegrated into smaller nanoparticles in the presence of water and thus result in a surface quenching effect,which show the features of 0-100%wide range water response in various organic solvents.The sensing performance towards real samples was validated by the water content determination in beer,rum and white spirit.Furthermore,the luminescence intensity variation of the PEI-modified NaBiF4:Yb3+/Er3+enable the test visualization and ease of portability.

Ultra-high sensitivity of rhodamine B sensing based on NaGdF_4:Yb^(3+),Er^(3+)@NaGdF_4 core-shell upconversion nanoparticles

A series of mono-dispersed hexagon NaGdF_4:Yb^(3+),Er^(3+)@NaGdF_4 core-shell nanoparticles with different shell thickness were synthesized via a co-precipitation method. Nanoparticles with high upconversion fluorescent emissions result in large signal-to-noise ratio, which guarantees the accuracy of the sensitivity. Besides, the maximum sensitivity of these NPs as detection film increases first and then decreases with the shell thickness increasing. When the shell thickness is 2.3 nm(NaGdF_4-2), the maximum sensitivity(0.69959 ppm^(-1)) is reached. A large degree of overlap between the rhodamine B absorption band and the Er^(3+) green emission bands ensures that the NaGdF_4:Yb^(3+),Er^(3+)@NaGdF_4 nanoparticles can be used as fluorescent probe to detect the concentration of rhodamine B based on fluorescent intensity ratio technology. The linear relationship between the rhodamine B concentration and the intensity ratio(R) of green and red emission intensity(I_(S+H) and I_F) were studied systematically. The result shows that the maximum sensitivity can be obtained in low concentration rhodamine B(<4 ppm), which is lower than the reported minimum detection concentration. Thus, the ultra-high sensitivity detection by NaGdF_4:Yb^(3+),Er^(3+)@NaGdF_4 core-shell upconversion nanoparticles in low concentration can be realized,which provides promising applications in bio-detection filed.

Preparation and upconversion luminescence of monodisperse Y_2O_2S:Yb/ Ho-silica/aminosilane core-shell nanoparticles

Y2O2S:Yb/Ho-silica/aminosilane core-shell nanoparticles were prepared by a solid-gas method in combination with polyvinylpyr-rolidone assisted one-step ammoniating method. The core was a single Y2O2S:Yb/Ho with 80 nm in diameter and the shell was silica/aminosilane with around 5 nm in thickness. The results of sedimentation experiment indicated that the nanoparticles could be well-dispersed in ethanol and water to form stable colloids. Since the coating weakened lattice vibration energies of the Y2O2S:Yb/Ho...

Recent development in upconversion nanoparticles and their application in optogenetics:A review

Ion channels present in the plasma membrane are responsible for integration and propagation of electric signals,which transmit information in nerve cells.Malfunction of these ion channels leads to many neurological diseases.Recently,optogenetic technology has gained a lot of attention for the manipulation of neuronal circuits.Optogenetics is a neuromodulation approach that has been developed to control neuronal functions and activities using light.The lanthanide-doped upconversion nanoparticles(UCNPs)absorb low energy photons in near-infrared(NIR) window and emit high energy photons in the visible spectrum region via nonlinear processes.In the last few decades,UCNPs have gained great attention in various bio-medical applications such as bio-imaging,drug delivery and optogenetics.The near-infrared illumination is considered more suitable for optogenetics application,due to its lower degree of light attenuation and higher tissue penetration compared to visible light.Therefore,UCNPs have been considered as the new promising candidates for optogenetics applications.Upconversion nanoparticlemediated optogenetic systems provide a great opportunity to manipulate the ion channel in deep tissue.Herein,we summarize the upconversion photoluminescence in lanthanide doped nanomaterials and its mechanisms and several approaches adopted to tune emission color or enhance upconversion efficiency.Recent advances of lanthanide-doped UCNPs design strategy and their mechanism are reviewed.Then,we discuss the neural circuitry modulation using upconversion nanoparticles mediated optogenetics.Moreover,the future perspectives towards optogenetics are also included.

Upconversion nanoparticles:Recent strategies and mechanism based applications

Upconversion nanoparticles(UCNPs)doped with lanthanides can convert near-infrared excitation into UV and visible emissions.Because of their relatively high emission efficiency,UCNPs are appealing materials for use in a variety of sectors.UCNPs are known for low auto-fluorescence,excellent chemical and thermal photo-stability,deep tissue penetration,exceptional biocompatibility,low toxicity,color purity,and ease of surface functionalization.In this review,we explain a few recent strategies to boost the efficiency and luminescence of upconversion nanoparticles and minimize quenching by fabricating them as core/shell,nanofibers,or heavily doped lanthanides.Applications of UCNPs in drug delivery,Photodynamic therapy(PDT),biosensors,bioimaging,and optogenetics are also discussed along with their mechanism of action.Our motivation for this review is to understand the working mechanism of UCNPs and their applications in various fields.

Enhancement of red upconversion emission intensity of Ho^(3+) ions in NaLuF4:Yb^(3+)/Ho^(3+)/Ce^(3+)@NaLuF_(4) core-shell nanoparticles

The red upconversion emission of Ho^(3+)ions,in the optical window of biological tissue,exhibits excellent prospects in biological applications.This study aims to enhance the red upconversion emission intensity of Ho^(3+)ions in NaLuF_(4):20%Yb^(3+)/2%Ho^(3+)/12%Ce^(3+) nanoparticles through building different core–shell structures with different excitation wavelengths.A significantly enhanced red upconversion emission with a higher red-to-green ratio was successfully obtained in NaLuF_(4):20%Yb^(3+)/2%Ho^(3+)/12%Ce^(3+)@NaLuF_(4) core–shell nanoparticles by introducing the Yb^(3+)and Yb^(3+)/Nd^(3+)ions into the NaLuF_(4) shell,with enhancement of the red emission occurring when Yb^(3+)and Nd^(3+)ions in the shell transfer more excitation energy to the Ho^(3+)ions.Investigation of the red emission enhancement mechanism is based on spectral characteristics and lifetimes.We examined the synergistic effect of dual-wavelength co-excitation NaLuF_(4):20%Yb^(3+)/2%Ho^(3+)/12%Ce^(3+)@NaLuF_(4):10%Yb^(3+)/15%Nd^(3+)core–shell nanoparticles to establish optimal excitation conditions.It is hoped that this method,using red upconversion emission core–shell nanoparticles with multi-mode excitation,can provide new ways to expand the applications of rare-earth luminescent materials in biomedicine and anti-counterfeiting.

Improving acceptor efficacy rather than energy transfer efficiency:Dominant contribution of monomers of acceptors modified on upconversion nanoparticles

Upconversion nanosensitizers have been widely considered to have important applications in the treatment of major diseases such as tumors and the utilization of solar energy.Majority of the efforts so far have been focused on improving the efficiency of energy transfer(ET)between upconversion nanoparticles(UCNPs)and the anchored sensitizers with premise that high ET efficiency will lead to high acceptor efficacy.This premise is,however,proved by our current work to be invalid for commonly used load.Interaction between adjacent sensitizing molecules was found to be critical which undermines the amount of excited monomer sensitizers and thus fades the efficacy.Here NaYF_(4):Yb^(3+),Er^(3+)UCNPs and rose bengal(RB)photosensitizer molecules were used as the model energy donors and acceptors,respectively.Contrary to monotonous increase of the ET efficiency from UCNPs to RB species with increasing RB loading,acceptor efficacy characterized by the reactive oxygen species,as well as the RB fluorescence,exhibits bizarre dependence on the RB loading.The underlying mechanism was well studied by the steady-state and time-resolved spectroscopy of a series of samples.RB aggregates are believed to be responsible for the severe deviation between the ET efficiency and acceptor efficacy.The conclusion was validated by in vitro test where the photodynamic therapy with the most monomer RB in UCNPs-RB nanosensitizers kills 35.8%more cells than that with the highest RB loading.This understanding sheds light on construction of new ET based nanosystems for broad applications,such as medicine,solar energy utilization and optical storage.

Continuous synthesis of ultrasmall core-shell upconversion nanoparticles via a flow chemistry method

A continuous synthesis method for the less than 10 nm core-shell upconversion nanoparticles was developed via coiled tube embedded flask reactors and a flow solvothermal co-participation reaction up to 300℃.Fast nucleation of hexagonal nanocrystals in less than 9 min residence time was achieved owing to the excellent heating ability of the reactors,and a two-step reaction strategy was created for the synthesis of β-NaYF4:Gd,Yb,Er/Ho/Tm@NaYF_(4) particles without intermediate purification.

Upconversion luminescence turning of NaREF4(RE=0.4Y＋0.4La＋0.2(Yb, Er, Tm))nanoparticles and their applications for detecting Rhodamine B in shrimp

Biocompatible NaREF_4（RE=0.4Y＋0.4La＋0.2（Yb,Er,Tm）（molar ratio）） upconversion nanoparticles（UCNPs） with strong visible fluorescence were synthesized by a solvothermal method and subsequent surface modification. Modulated upconversion luminescence emission spectra were obtained via changing the doping. In vitro and in vivo bioimagings were carried out with shrimps. The upconversion nanoprobes with an acidic/PEG hybrid ligand could quickly capture the basic Rhodamine-B（RB） in shrimp cells and formed a close UCNPs@RB system. The residual organic dye RB in shrimps could be detected on the basis of luminescent resonance energy transfer（LRET）. It could be rapidly addressed based on LRET detection that RB residue existed in the shrimps after incubating in the aqueous solution of RB higher than 3 μg/m L for 12 h.

综合化学实验——NaGdF_(4):Ln的粒子间能量传递上转换性能研究

本实验围绕稀土上转换发光材料的上转换发光过程,设计了一个NaGdF_(4):Ln纳米粒子及其粒子间能量传递上转换性能研究的综合性实验。该实验在锻炼学生基础实验操作等实验能力与荧光分光光度计等的熟练操作之余,也使学生接触了解稀土上转换发光材料在当前科学研究的前沿热点的实际应用,帮助学生开拓视野、拓展思路,激发对科研的兴趣。

稀土掺杂上转换纳米材料在农药残留检测中的应用

随着农药应用的日益广泛,农药残留对人群健康和环境污染带来的潜在危害日益凸显出来。由于农药残留具有残留量低,样品基底成分复杂等特点,因此,构建对农药残留进行灵敏、准确、稳定、简便、快速的微量甚至痕量检测方法已成为一个热点研究领域。稀土掺杂上转换纳米材料(REEs-UCNPs)作为一种非常重要的具备反斯托克斯发光的稀土发光材料,化学稳定性和光稳定性好,具有发射峰窄、毒性低、量子产率高等显著优势。近些年来,用REEs-UCNPs作为荧光探针在分析检测领域备受关注。重点综述了基于REEs-UCNPs的免疫分析法和荧光分析法对农药残留进行检测的研究进展。以期为后续建立和发展灵敏、简单、快速以及低成本的农药残留检测方法提供思路,从而为人类健康、农业生产以及生态文明建设保驾护航。

反向能量传递增强Er^(3+)上转换发光

提高上转换发光效率是促进上转换发光材料实际应用的关键。在NaErF_(4)@NaYF_(4)体系中,惰性NaYF_(4)壳层可以抑制高组分Er^(3+)掺杂下的发光浓度猝灭,其上转换发光主要来源于Er^(3+)-Er^(3+)的能量传递上转换。本文利用共沉淀法制备了Er^(3+)和Yb^(3+)分区掺杂的NaErF_(4)@NaYbF_(4)@NaYF_(4)核壳结构的纳米颗粒,通过包覆惰性壳层研究Er^(3+)-Yb^(3+)-Er^(3+)之间的能量传递和反向能量传递过程。由于808 nm波长只能激发Er^(3+)而不能激发Yb^(3+),因此在808 nm波长激发下,Er^(3+)在惰性壳层的保护作用下将激发态能量传递给Yb^(3+),随后通过反向能量传递回Er^(3+),使得Er^(3+)的上转换发光增强。实验结果发现,当中间层Yb^(3+)掺杂浓度为100%时,绿色和红色上转换发光最大增强倍数为24.9和9.79。