Upconversion Luminescence Nanomaterials Research Articles

Construction of active-inert core–shell structured nanocrystals for broad range multicolor upconversion luminescence

Rare earth doped up-conversion luminescent nano-materials exhibit abundant emission colors under suitable excitation condition. In this work, NaYF4:Er/Ho@NaYF4 and NaYbF4:Tm@NaYF4 nanoparticles were synthesized by co-precipitation method. The pure red emission can be realized by the designed NaYF4:Er/Ho@NaYF4 nanocrystals and the R/Gs reach 23.3 and 25 under excitations of 980 and 1550 nm lasers, respectively. The R/G declines as the power increasing with the emission color changing from red to yellow, which is due to the quick saturation of the energy levels, radiating red emissions. Meanwhile, the emission intensity of NaYbF4:Tm@NaYF4 nanocrystals increases by 58.3 folds after encasing the inert shell NaYF4 and the CIE color coordinate reaches (0.1646, 0.0602) under 980 nm laser excitation. Furthermore, broad range multicolor from blue to red and yellow up-conversion emissions is achieved by mixing NaYF4:Er/Ho@NaYF4 and NaYbF4:Tm@NaYF4 nanocrystals, which could be applied to colorful displaying, security anti-counterfeiting and information coding.

KHẢO SÁT TÍNH CHẤT CỦA VẬT LIỆU NANO PHÁT QUANG CHUYỂN ĐỔI NGƯỢC CHỨA Tm(III)/Yb(III) TRÊN NỀN NaYF4

This study aimed to investigate the properties of up-conversion luminescent nanomaterials containing Tm(III) and Yb(III) based on NaYF4 host. The materials were synthesized using the hydrothermal method. The morphology, structure and luminescent properties of the material were analyzed using field emission scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and photoluminescence spectroscopy. The results indicate that the synthesized nanomaterials were in the form of particles with a diameter ranging from 100-200 nm, had a hexagonal β-NaYF4 phase structure, and emitted blue light at a wavelength of 980 nm. These luminescent properties of the material indicate their potential application in biomedical fields.

A membrane biosensor based on colour differences encoded upconversion silica nanoparticles for multiplex nucleic acids detection

Upconversion luminescent nanomaterials provide a powerful tool for multiplex nucleic acids detection simultaneously. However, the conventional encoding methods based on emission spectrum or intensity have limitations due to spectral overlap and cross-relaxation quenching among various activators. Herein, we present a facile method for the preparation of high-capacity upconversion luminescent coding nanoparticles by multiple regulating the synthesis kinetics of lanthanide ions doped CaF2 nanocrystals in mesoporous silica nanotemplets (named C@S). The secondary growth of nanocrystals with different lanthanide ions inside mesopores has a similar performance to that of core/multi-shell-structured upconversion nanoparticles prepared through complicated processes. The textural properties and chemical conformations are maintained after repeated recombination, which is beneficial for reproducible multiplex bioassays. A membrane biosensor is constructed using various probe-modified C@S and a flexible graphene oxide-coated film to detect and identify multiple molecular species in one sample. The colour differences of encoded C@S derived from CIE-L*a*b* colour coordinate system are applied to quantify the divergence of upconversion luminescence for the first time, which allows the upconversion nanoparticles with similar spectra and luminescence colours to be used in the same multiplex detection platform and avoids subjective judgement. This work opens new opportunities for upconversion luminescent materials in the field of automatic high-throughput detection.

Therapeutic Effect of Bone Marrow Mesenchymal Stem Cells on Rat Bladder Cancer

Objective: To analyze the effect of bone marrow mesenchymal stem cell therapy on rats with bladder cancer and provide a feasible direction for the treatment of human bladder cancer. Methods: An animal model was constructed, and Model 1 was used as an example. Two groups of rats were injected with anti-upconversion nanoparticles (UCNPs) (experimental group) and 0.9% normal saline (control group), respectively. In vivo imaging was performed to determine the accuracy of the anti-UCNPs method. Results: There were 15 rats in the experimental group with obvious bladder swelling. Among them, 11 rats had cauliflower-like and partially brown bladder tumors, whereas the other four rats had hard, nodular-like protrusions, with indistinct borders and adhesions to the anterior wall of the rectum. Small papillary masses were observed in two rats, local mucosal thickening without tumor formation was observed in two rats, and bladder stones were observed in six rats. The bladder specimens of 15 rats in the control group were pink and shiny, without any tumors. Fourteen rats in the experimental group and 12 rats in the control group had bladder cancer lesions, accounting for 93.33% and 80%, respectively. The detection accuracy of the experimental group was significantly better than that of the control group. Conclusion: Multimodal nanoprobes targeting bladder cancer stem cells in vivo were used to image the orthotopic tumor and lymph node metastasis models of animals by anti-UCNPs imaging to observe the distribution, migration, and differentiation process of bladder cancer stem cells in model mice. It is clear that rare earth upconversion luminescent nanomaterials, modified by BCMab1 and CD44 monoclonal antibodies, can be used as probes for the detection of bladder cancer, the tracking of lymph node metastasis in bladder cancer, and the comprehensive evaluation of the overall efficacy of nanoprobe-targeted therapy for bladder cancer stem cells.

Research Progress on Detection Methods of Contaminants in Food Based on Fluorescence Immunoassay

In recent years, there’s a trend that the maximum limit of food contaminant is decreasing. Therefore, the development of more rapid and sensitive methods for the detection of food contaminants is a great requirement. Fluorescence immunoassay is one of the current fastest developing detection methods, which has been widely applied in the detection of various food contaminants and other fields. It has the advantage of high sensitivity, fast detection speed, simple operation, satisfactory accuracy, etc. This review offers an overview of fluorescence-immunoassay-based methods for the detection of contaminants in food based on different fluorescent labeling materials. Three types of common fluorescent labeling materials (including ordinary fluorescent microspheres, quantum dots and time-resolved fluorescent materials) and three types of new fluorescent labeling materials (containing up-conversion luminescence nanomaterials, magnetic fluorescent nanomaterials and fluorescent proteins) are introduced with the comparison in their optical features and analytical performance. In additon, the detection methods of contaminants in food based on fluorescence immunoassay (FIA) are introduced, the latest progress of fluorescence immunoassay in food contaminants detection is also summarized.

A Novel Strategy to Obtain Hollow NaBiF₄:Yb3+/Er3+ Upconversion Nanospheres by One Step Coprecipitation.

Hollow upconversion luminescence nanomaterials have widespread applications in drug delivery, high efficiency catalysis, as well as energy storage owes to super-large specific surface area, cavity volume, and fluorescence properties. However, a series of complex processes and high temperature is required for the synthesis of these materials. Herein, a facile template-free coprecipitation route based on the Kirkendall diffusion process at room temperature had been developed to synthesize hollow NaBiF₄:Yb3+/Er3+ nanospheres with upconversion luminescence. X-ray diffraction (XRD), nitrogen adsoption/desorption isotherms, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and upconversion emission spectra demonstrated the successful preparation of NaBiF₄:Yb3+/Er3+ nanospheres with pervasive hollow morphology, relatively high specific surface area, and excellent upconversion luminescence properties. Moreover, the influence of some reaction parameters on the morphology and structure of the obtained samples were systematically explored. Additionally, the evolution mechanism of the hollow structure nanospheres was analyzed on account of the Kirkendall diffusion process related to the solid-liquid interfacial ion migration. It is expected that these hollow upconversion NaBiF₄:Yb3+/Er3+ nanospheres with upconversion luminescence prepared by this type of synthetic strategy will have widespread medical, environmental, and energy applications.

Simultaneous improvement in emission intensity and spectral purity of red photon upconversion in Gd2O3:Yb3+/Er3+ phosphors under 1550 nm excitation

Upconversion luminescent nano-materials with both excitation and emission peaks in the “optical window” is of significant importance for application in deeper bio-imaging, due to the weak effects of light absorption, light scattering, and auto-fluorescence. This paper reports an Er3+ self-sensitized red up-converting nanophosphors with improved emission intensity and spectral purity. The influence of Yb3+ concentration on upconversion luminescence properties is investigated comprehensively. Compared with the sample without Yb3+ doping, the luminescence intensity in the sample with 10% Yb3+ is increased by 12.9 times. Moreover, the dominant wavelength at 1550 nm excitation is about 60 nm larger than that excited at 980 nm. It has been demonstrated that Yb3+ co-doping can not only improve the photon absorption at 1550 nm and the probability of red emission, but also suppress other light emissions and phonon emission through the selective population of red-emitting level.

Recent progress in upconversion luminescence nanomaterials for biomedical applications.

Upconversion nanoparticles (UCNPs) are one kind of luminescence nanomaterials that convert low energy photons to high energy emissions. These nanomaterials have recently attracted enormous attention due to their unique photophysical properties, such as resistance to photobleaching and photoblinking, low background autofluorescence, and long luminescence lifetime. Owing to these unique advantages, UCNPs have been widely examined for biomedical applications, including biosensing, imaging, and theranostics. In this review, we have first summarized the mechanisms for three generally accepted upconversion luminescence processes, i.e., lanthanide (Ln) doped upconversion luminescence, dye-sensitized upconversion, and triplet-triplet annihilation upconversion, and then discussed recent advancements on the preparation, functionalization, and biomedical applications of each type of UCNPs. The review article finally concludes with our perspectives on UCNPs' emerging and potential biomedical applications in the near future.

Clean synthesis of YOF:Er3+, Yb3+ upconversion colloidal nanoparticles in water through liquid phase pulsed laser ablation for imaging applications

Upconversion luminescent nanomaterials have great outlook towards imaging applications. These materials have high chemical and thermal stability, low auto fluorescence, high photo stability and IR excitation does not cause photo damage to living cells and penetrate deeply into tissue. Most of the reported nanoparticles are synthesized through chemical methods in which surface modification is needed for dispersing nanoparticles in water. In this paper we report clean and simple synthesis of upconversion luminescent yttrium oxyfluoride (YOF) nanoparticles through laser ablation in deionized water. YOF:Er3+, Yb3+ pellets were used for ablation. Er3+ is the emission centre Yb3+ is the sensitizer. Obtained colloidal solution is transparent to day light and showing red emission on exciting with 980 nm IR laser. By controlling ablation parameters particles of size less than 10 nm dispersed uniformly in water can be obtained through this surfactant free method. The synthesized nanoparticles can be used for cell imaging.

Highly Enhanced Cooperative Upconversion Luminescence through Energy Transfer Optimization and Quenching Protection.

Upconversion luminescence nanomaterials have shown great potential in biological and physical applications because of their unique properties. However, limited research exists on the cooperative sensitization upconversion emission in Tb(3+) ions over Er(3+) ions and Tm(3+) ions because of its low efficiency. Herein, by optimizing the doping ratio of sensitizer and activator to maximize the utilization of the photon energy and introducing the CaF2 inert shell to shield sensitizer from quenchers, we synthesize ultrasmall NaYbF4:Tb@CaF2 nanoparticles with a significant enhancement (690-fold) in cooperative sensitization upconversion emission intensity, compared with the parent NaYbF4:Tb. The lifetime of Tb(3+) emission in NaYbF4:Tb@CaF2 nanoparticles is prolonged extensively to ∼3.5 ms. Furthermore, NaYbF4:Tb@CaF2 was applied in in vitro and in vivo bioimaging. The presented luminescence enhancement strategy provides cooperative sensitization upconversion with new opportunities for bioapplication.

Stimuli responsive upconversion luminescence nanomaterials and films for various applications.

Upconversion luminescence (UCL) refers to nonlinear optical processes, which can convert near-infrared photons to short-wavelength emission. Recent advances in nanotechnology have contributed to the development of photon upconversion materials as promising new generation candidates of fluorescent bioprobes and spectral converters for biomedical and optoelectronic applications. Apart from the remarkable photoluminescence of the materials under photon excitation, some UCL materials may exhibit intrinsic magnetic, ferroelectric, X-ray absorption properties, and so on. These interesting characteristics provide an opportunity for us to couple a single stimulus or multiple stimuli (electric field, magnetic field, X-ray, electron beam, temperature and pH, etc.) to various types of UCL materials. In this review, we will primarily focus on the stimuli responsive properties of UCL materials beyond light-matter interaction, which can aid both fundamental research and widespread applications of the materials. The mechanisms of the response to various stimuli in the UCL materials are discussed. This article will also highlight recent advances in the development of these materials in response to various stimuli and their applications in multimodal bioimaging, drug delivery and release, electro-optical devices, magnetic, temperature and pH sensors and multiple anti-counterfeiting inks. Lastly, we will present potential directions of future research and challenging issues which arise in expanding the applications of stimuli responsive UCL materials.

A feasible strategy to synthesize LaOI:Yb3+/Ho3+ upconversion luminescence nanostructures via succeeding to the morphologies of precursors

In order to develop new-typed up-conversion luminescent nanomaterials with peculiar morphology, LaOI:Yb3+/Ho3+ nanostructures, including nanofibers and nanobelts, were synthesized by electrospinning combined with a double-crucible iodination technique using NH4I as iodine source for the first time. X-ray powder diffraction (XRD) analysis indicates that LaOI:Yb3+/Ho3+ nanostructures are tetragonal phase with space group of P4/nmm. Scanning electron microscope (SEM) analysis and histograms reveal that diameter of LaOI:Yb3+/Ho3+ nanofibers and the width of LaOI:Yb3+/Ho3+ nanobelts are respectively 147.48±17.50nm and 3.54±0.22μm, and the thickness of the nanobelts is 186nm. Under the excitation of a 980-nm diode laser (DL), LaOI:Yb3+/Ho3+ nanostructures emit strong green and red up-conversion emissions centering at 541nm and 655nm, respectively attributed to 5F4/5S2→5I8 and 5F5→5I8 energy levels transitions of Ho3+. The up-conversion luminescent mechanism and the formation mechanism of LaOI:Yb3+/Ho3+ nanostructures are also proposed.

Hydrothermal synthesis and upconversion properties of CaF2:Er3+/Yb3+ nanocrystals.

A series of rare-earth ions (Er3+ and Yb3+) Co-doped CaF2 upconversion luminescent nanomaterials have been successfully prepared via a facile hydrothermal method using pluronic p123 (p123), pluronic F127 (F127) and sodium citrate as surfactants at 180 degrees C with different reaction time. The crystallographic phase, size and morphology can be controlled by simply tuning the reaction parameters such as the types of surfactants and the reaction time. It is found that reaction time and surfactant play a key role in forming the nanocrystals with different morphologies. X-ray diffraction, field-emission scanning electron microscopy FE-SEM, and photoluminescence spectra were used to characterize the structure, morphology and upconversion luminescence properties of CaF2:Er3+/Yb3+ upconversion nanomaterials, respectively. The experimental results indicate that three monodispersive and highly uniform CaF2:Er3+/Yb3+ nanocrystals with mean size of 200 nm, 3 um, and 700 nm have cubic and sphere shapes, respectively. While the possible mechanisms of upconversion luminescence are analyzed by the diagram of proposed energy transfer mechanisms, the schematic energy level diagrams showing typical upconversion processes for Er3+ also reveals that the as-synthesized CaF2:Er3+/Yb3 nanomaterials may be in the cubic structure with space group Fm-3m, in which Ln3+ cations occupy crystal lattice positions with lower point symmetry, leading to a high upconversion efficiency under the excitation of a 980 nm diode laser.

Electrospinning preparation and up-conversion luminescence properties of LaOBr:Er3+ nanofibers and nanoribbons

Abstract LaOBr:Er3+ nanofibers and nanoribbons were synthesized for the first time via calcinating the respective electrospun PVP/[La(NO3)3 + Er(NO3)3 + NH4Br] composites. The morphology, structure and luminescent properties of the final products were investigated in detail by field emission scanning electron microscopy (FESEM), energy dispersion spectroscopy (EDS), X-ray diffractometry (XRD) and fluorescence spectroscopy. The diameter of the LaOBr:Er3+ nanofibers with the pure tetragonal crystal phase are ca. 144.36 nm. The width and the thickness of LaOBr:Er3+ nanoribbons with the pure tetragonal in structure are ca. 5.66 μm and 151 nm, respectively. Under the excitation of a 980-nm diode laser, LaOBr:Er3+ nanofibers and nanoribbons exhibit the characteristic up-conversion emissions of Er3+ ions, and the optimum doping concentration of Er3+ ions in the LaOBr:Er3+ nanofibers and nanoribbons is 3.0%. Interestingly, the luminescence intensity of LaOBr:Er3+ nanoribbons is obviously stronger than that of LaOBr:Er3+nanofibers under the same measuring conditions. The color emissions of LaOBr:Er3+ nanostructures can be tuned from green emission to yellow emission by changing the concentration of doping Er3+ ions and the morphologies of nanostructures. Moreover, the predominant near-infrared emission at 1.50 μm of LaOBr:Er3+ nanostructures are obtained under the excitation of a 532-nm laser. The formation mechanisms of LaOBr:Er3+ nanofibers and nanoribbons are also proposed. Electrospinning is a simple and efficient method for the synthesis of luminescent LaOBr:Er3+ nanostructures, which would be promising up-conversion luminescent nanomaterials.

Preparation of Ag@SiO2@GdF3：Er,Yb Core-shell Structure Nanomaterials and Enhanced Up-conversion Luminescence

Noble metal nanoparticles such as Ag or Au and rare earth ions doped-up-conversion luminescence materials are all potential in the fields of biological labeling and sensing, diagnosis and biotherapy. When coupling with them together to form core-shell structure composites, noble metal nanostructures will present the strong surface plasmon resonances (SPRs), they can act as the function of "antenna", that is they can transfer the absorption energy to the luminescence particles and enhance their luminescence intensities. Moreover, when positioned in close proximity to metal surfaces, the luminescence materials can exhibit optical property changes (quenching or enhancement of luminescence), likely a result of the changed near-field electro-dynamical environment around the metal that arises from the collective oscillation of conduction electrons. This is a perfect model for studing the effects on luminescence properies of metal and luminescence materials. In this article, Ag nanoparticles were prepared by a glycol reduction method, and SiO2 spacers were coating on the surface of Ag nanoparti- cles by modified Stober method, at last, the core-shell structure Ag@SiO2@GdF3:Er,Yb up-conversion luminescent nanopar- ticles were successfully synthesized by direct precipitation method. The structure and luminescence property of the samples were characterized by XRD, TEM, FTIR, UV-Vis and fluorescence spectra. XRD patterns show that the orthogonal phase GdF3:Er,Yb nanocrystals are coated on the surface of Ag cores. TEM images present that the obtained composites have ob- vious spherical core-shell structure, the diameter of the Ag core is 50 nm, the size of the Ag@SiO2@GdF3:Er,Yb composites is about 80~120 nm, the surface is smooth and the coating is complete, GdF3:Er,Yb nanoparticles are found obviously in the shell. UV-Vis spectra indicate that GdF3:Er,Yb and SiO2 are coated successfully on the surface of Ag, which increased the refractive index of local area around Ag nanoparticles, and the surface plasma absorption peaks of Ag have red shift. The up-conversion luminescent spectra also indicate that the core-shell structure composite particles have the same red and green up-conversion emissions as the pure GdF3:Er,Yb, their strong peaks are all near 655 nm corresponding to the 4 F9/2→ 4 I15/2 transition of Er 3 + . The fluorescent intensity of the core-shell structure composites is stronger than that of the pure GdF3:Er,Yb when the SiO2 as spacers, which indicates that Ag cores realize the up-conversion fluorescent enhancement of GdF3:Er,Yb. The luminescence intensity is enhanced with the increasing of silica thickness and the amount of GdF3:Er,Yb. This core-shell structure has a certain reference value for preparation of highly efficient rare earth up-conversion luminescent nanomaterials. Keywords GdF 3:Yb,Er; core-shell structure; up-conversion luminescence