Yb Upconversion Research Articles

Tuning the emission color of SrLaAlO4:Er,Yb upconversion phosphors by decorating their surface with CsPbBr3-xIx quantum dots

In this work, SrLaAlO4:Er3+ (2 mol%),Yb3+ (4 mol%) upconversion phosphor was synthesized by using a combustion method. Later, CsPbBr3-xIx (x = 0, 1.5 and 0.75) perovskite quantum dots (QDs) were synthesized by using hot injection method. According the analysis by X-ray diffraction, the SrLaAlO4:Er,Yb (SL:Er,Yb) phosphors and QDs had tetragonal and cubic phases, respectively. Moreover, the analysis by microscopy revealed that the SL:Er,Yb phosphors are composed of micro-grains with irregular morphology, while the CsPbBr3-xIx QDs had a morphology of cubes. The surface of the SL:Er,Yb phosphors was decorated with CsPbBr3-xIx QDs and obtained three composite powders: CsPbBr3+SL:Er,Yb, CsPbBr1.5I1.5+SL:Er,Yb and CsPbBr2.25I0.75+SL:Er,Yb. Those composites were firstly excited with UV light (380 nm) and produced emissions in the green and orange-red regions by downconversion. Interestingly, the emission intensity of the composite powders was 45–75 % higher than that for the individual CsPbBr3-xIx QDs or SL:Er,Yb phosphors. Later, the same composite powders were excited with NIR light (980 nm), in consequence, intense green and yellow emissions were produced by upconversion. In particular, the CsPbBr1.5I1.5+ SL:Er,Yb composite produced strong red emission by upconversion because the presence of the QDs on the SL:Er,Yb surface promoted the following cross relaxation process: 4I11/2 (Er3+)+ 4F7/2 (Er3+)→4F9/2 (Er3+)+ 4F9/2 (Er3+). In general, the quantum dots deposited on the SL:Er,Yb surface not only enhanced the red upconversion emission, but also provoked a color tuning when they are excited with NIR or UV light. Those last effects have not been reported in the literature previously. Thus, the results of this investigation demonstrate that combining perovskite quantum dots and the SL:Er,Yb forms a luminescent material able to tune its emission by upconversion or downconversion. This last property can be utilized for the design of new LED based lamps, which are employed for general illumination in houses and buildings.

Construction of an upconversion luminescence composite nanoprobe for ratiometric single particle imaging detection of hydrogen peroxide in food

Hydrogen peroxide (H2O2) is associated with diseases and food safety. Thus, it is essential to achieve sensitive and efficient detection of H2O2. Herein, a ratiometric luminescence composite nanoprobe was designed for single particle imaging sensing of H2O2 by combining NaYbF4:Er@NaYbF4:Tm@NaGdF4:Yb upconversion nanoparticles (UCNPs) with cyanine dye IR-628. High brightness NaYbF4:Er@NaYbF4:Tm@NaGdF4:Yb UCNPs with double-peak emission (665 and 812 nm) were synthesised. Cyanine dye IR-628 with an absorption peak at 628 nm was synthesised and served as a recognition unit. More importantly, on the basis of the upconversion luminescence total internal reflection imaging technique, we developed a ratiometric single particle imaging quantitative analysis for sensing H2O2 with a limit of quantitation of 5 nM. This ratiometric single particle imaging method not only greatly eliminates the influence of the probe concentration and instrumental and environmental factors, but also reduces the dosage of the reagent used and improves the sensitivity of detection.

Investigating the effect of synthesis parameters on the structure and upconversion luminescent properties of NaYF4:Tm,Yb for anticounterfeiting printing ink

Introduction: In this study, NaYF4:Tm,Yb upconversion microparticles were prepared by a hydrothermal method. Methods: The effects of fabrication parameters such as rare earth concentration, reaction temperature and reaction time on the structure and luminescence properties of the materials were studied by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and photoluminescence spectroscopy (PL). Depending on the reaction temperature and time, the morphology of NaYF4:Tm,Yb is either a nanoparticle or a branched structure. Results: The crystallite size is approximately 70 nm and remains almost unchanged with increasing reaction temperature and time. These NaYF4:Tm,Yb powders strongly emit at 450 nm and 798 nm. In addition, the surface of the UCMPs was also modified with maleic anhydride to improve their dispersibility in solvents and binding to biological molecules. Conclusion: Printing ink based on UCMPs modified with maleic anhydride and polyamide for screen printing was prepared. The printed patterns on paper and polymer substrates glow blue light under LED excitation at 980 nm, and they are completely transparent in daylight.

Controllable structural and optical properties of NaYF4:Tm, Yb microparticles by Yb3+ doping for anti-counterfeiting.

Hexagonal NaYF4:Tm, Yb upconversion (UC) phosphors with excellent UC luminescence quantum efficiency and chemical stability meet demands for applications in bioimaging and anti-counterfeiting printing. In this work, a series of NaYF4:Tm, Yb upconversion microparticles (UCMPs) with different concentrations of Yb were synthesized by a hydrothermal method. Then, the UCMPs become hydrophilic through surface oxidation of the oleic acid (C-18) ligand to azelaic acid (C-9) using the Lemieux-von Rodloff reagent. The structure and morphology of UCMPs were investigated by X-ray diffraction and scanning electron microscopy. The optical properties were studied using diffusion reflectance spectroscopy and photoluminescent spectroscopy under 980 nm laser irradiation. The emission peaks of the Tm3+ ions are 450, 474, 650, 690, and 800 nm, attributed to the transitions from the excited state to ground state 3H6. These emissions are the results of two or three photon absorption through multi-step resonance energy transfer from excited Yb3+, confirmed via a power-dependent luminescence study. The results show that the crystal phases and luminescence properties of the NaYF4:Tm, Yb UCMPs are controlled by changing the Yb doping concentration. The printed patterns are readable under the excitation of a 980 nm LED. Moreover, the zeta potential analysis shows that the UCMPs after surface oxidation are water dispersible. In particular, the naked eye can observe the enormous upconversion emissions in UCMPs. These findings indicated that this fluorescent material is an ideal candidate for anti-counterfeiting and biological applications.

Retracted: Facile Synthesis of NaYF4:Yb Up-Conversion Nanoparticles Modified with Photosensitizer and Targeting Antibody for In Vitro Photodynamic Therapy of Hepatocellular Carcinoma.

[This retracts the article DOI: 10.1155/2022/4470510.].

Facile Synthesis of NaYF4:Yb Up-Conversion Nanoparticles Modified with Photosensitizer and Targeting Antibody for In Vitro Photodynamic Therapy of Hepatocellular Carcinoma.

Rare Earth up-conversion nanoparticles NaYF4:20%Yb,2%Er@PEI (UCNPs) were generated via a one-step hydrothermal technique at relatively reduced temperatures. Photosensitizer Ce6 and anti-EpCAM, a highly expressed monoclonal antibody in cancer stem cells of hepatocellular carcinoma, were linked to UCNP surfaces via the formation of amide linkage between carboxyl from Ce6 or anti-EpCAM and abundant amino from PEI, leading to the formation of Ps-Ce6 and anti-EpCAM-UCNPs-Ce6 nanoparticles. The synthesized nanoparticles characterized by XRD, TEM, and IR, and their zeta potential, ROS generation ability, Ce6 loading rate, and up-conversion fluorescence properties were investigated. It has been revealed that all the products were uniformly dispersed nanoparticles (25–32 nm), which crystallized primarily as hexagonal structures, and their up-conversion fluorescence spectra were similar to that of NaYF4:20%Yb,2%Er. The Ce6 loading rate in the anti-EpCAM-UCNPs-Ce6 nanoparticles was about 2.9%, thereby resulting in good ROS generation ability. For anti-EpCAM-UCNPs-Ce6, the biosafety, targeting effect, and PDT effect exposed under near-infrared (NIR) laser (980 nm) were evaluated using human liver cancer cells (BEL-7404). The results showed that it has good biocompatibility and biosafety as well as high targeting and PDT treatment efficiencies, which renders it a potential experimental material for the near-infrared PDT study.

Au-decorated NaYF4:Yb,Tm@NaGdF4:Yb@TiO2 nanophotosensitizers for photodynamic therapy and MR/PET imaging

A near-infrared (NIR) light triggered photosensitizer (PS) was synthesized by deposition of Au on TiO2-coated NaYF4:Yb,Tm@NaGdF4:Yb upconversion nanoparticles (UCNPs). Au can improve the PS’s in vitro photodynamic therapy (PDT) efficiency by enhancing reactive oxygen species (ROS) generation. It is proved that a new surface modification method via gold-thiol interaction confers desirable propertiestothePS. With the satisfying longitudinal relaxivity and facile 18F-labeling process, the PS exhibits a promising application prospect in magnetic resonance (MR) and positron emission tomography (PET) imaging-guided PDT for tumor therapy.

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.

Fluorescence sensing of cyanide anions based on Au-modified upconversion nanoassemblies.

Cyanides have been recognized as one of the most toxic chemicals and are harmful to the environment and human beings. Herein, fluorescence resonance energy transfer (FRET)-based upconversion nanoprobes for cyanide anions have been designed and prepared by assembling Au nanoparticles (NPs) on core-shell-structured NaYF4:Yb,Er@NaYF4:Yb upconversion NPs (csUCNPs), where csUCNPs act as the energy donor and Au NPs act as the energy acceptor. The Au content was optimized in order to have a large quenching efficiency in upconversion luminescence (UCL). The cyanide-mediated redox reaction leads to the consumption of Au NPs, resulting in UCL recovery by the inhibition of the FRET process. On the basis of these features, csUCNP/Au nanoassemblies can serve as sensitive nanoprobes for cyanide ions with a detection limit of 1.53 μM. Moreover, no significant UCL variation was observed upon the addition of other interfering ions, showing the excellent selectivity of nanoprobes toward cyanide ion sensing. The easy preparation of such upconversion-based nanoprobes provides a promising platform for sensitive and selective sensing of other hazardous species.

Harvesting the lost photon by plasmonic enhanced hematite-upconversion nanocomposite for water splitting.

Converting solar energy to chemical energy in the form of hydrogen via water splitting is one of the promising strategies to solve the global energy crisis. Hematite, a traditional semiconducting oxide photoelectrode, can only absorb UV and visible parts of the solar spectrum, losing 40% infrared energy. In this paper, we report a novel plasmonic enhanced water splitting photoanode based on hematite-lanthanide upconversion nanocomposites to harvest lost photons below the bandgap of hematite. NaYF4:Er, Yb upconversion nanoparticles can upconvert photons from 980 nm to 510 nm-570 nm within the bandgap of hematite. More importantly, a gold nanodisk array with a plasmonic peak centered ∼1000 nm can further boost the photocurrent by 93-fold. It is demonstrated that the excitation process of lanthanide upconversion nanoparticles can be significantly enhanced by plasmonic nanostructures and can thus improve the water oxidation activity via plasmonic enhanced upconversion and hot electron injection, respectively. This new promising strategy will pave the way for plasmonic enhanced lost photon harvesting for applications in solar energy conversion.

Влияние температуры апконверсионных частиц NaYF4:Er,Yb на формирование люминесценции

The intensity of upconversion luminescence depends nonlinearly on the excitation intensity. The aim of this work is to study the effect of the temperature of NaYF4:Er,Yb upconversion particles on the dependence of the luminescence intensity on the excitation intensity. The synthesized particles were observed to have the shape of a hexagonal prism with a width of about 440 nm and a height of 445 nm. The upconversion luminescence spectra were obtained in the temperature range of 22–55° C with the excitation intensity in the range of 1.5–9.4 W/cm2. The obtained results show the green-band luminescence photons can be generated by means of two-step and three-step mechanisms: the contribution of these mechanisms depends on the temperature of the particles. As the temperature increases, the contribution of the three-stage mechanism of green luminescence excitation is enhanced.

1532 nm sensitized luminescence and up-conversion in Yb,Er:YAG transparent ceramics

Luminescent properties of Yb,Er:YAG transparent ceramics containing 5 at% Yb3+ and 0.5, 1 and 1.5 at%, respectively, Er3+ ions have been studied. It has been found that increasing of erbium ions concentration increases both efficiency of nonradiative energy transfer Yb3+→Er3+ (which reaches 72% for 1.5 at% Er3+) and the luminescence in the range of 650–700 nm associated with 4F9/2, 11/2 → 4I15/2 transitions of Er3+ ions. It was also determined that the concentration quenching of sensitized luminescence of Er3+ ions at 1532 nm is associated with secondary excitation of metastable energy level of Er3+ followed by up-conversion emission.

Efficient up-conversion in Yb:Er:NaT(XO4)2 thermal nanoprobes. Imaging of their distribution in a perfused mouse.

Yb and Er codoped NaT(XO4)2 (T = Y, La, Gd, Lu and X = Mo, W) disordered oxides show a green (Er3+ related) up-conversion (UC) efficiency comparable to that of Yb:Er:β-NaYF4 compound and unless 3 times larger UC ratiometric thermal sensitivity. The similar UC efficiency of Yb:Er doped NaT(XO4)2 and β-NaYF4 compounds allowed testing equal subcutaneous depths of ex-vivo chicken tissue in both cases. This extraordinary behavior for NaT(XO4)2 oxides with large cutoff phonon energy (ħω≈ 920 cm-1) is ascribed to 4F9/2 electron population recycling to higher energy 4G11/2 level by a phonon assisted transition. Crystalline nanoparticles of Yb:Er:NaLu(MoO4)2 have been synthesized by sol-gel with sizes most commonly in the 50–80 nm range, showing a relatively small reduction of the UC efficiency with regards to bulk materials. Fluorescence lifetime and multiphoton imaging microscopies show that these nanoparticles can be efficiently distributed to all body organs of a perfused mouse.

Rich stochastic dynamics of co-doped Er:Yb fluorescence upconversion nanoparticles in the presence of thermal, non-conservative, harmonic and optical forces

The stochastic dynamics of individual co-doped Er:Yb upconversion nanoparticles (UCNP) were investigated from experiments and simulations. The UCNP were characterized by high-resolution scanning electron microscopy, dynamic light scattering, and zeta potential measurements. Single UCNP measurements were performed by fluorescence upconversion micro-spectroscopy and optical trapping. The mean-square displacement (MSD) from single UCNP exhibited a time-dependent diffusion coefficient which was compared with Brownian dynamics simulations of a viscoelastic model of harmonically bound spheres. Experimental time-dependent two-dimensional trajectories of individual UCNP revealed correlated two-dimensional nanoparticle motion. The measurements were compared with stochastic trajectories calculated in the presence of a non-conservative rotational force field. Overall, the complex interplay of UCNP adhesion, thermal fluctuations and optical forces led to a rich stochastic behavior of these nanoparticles.

A Multifunctional Nanocrystalline CaF2:Tm,Yb@mSiO2 System for Dual-Triggered and Optically Monitored Doxorubicin Delivery.

Daunting challenges in investigating the controlled release of drugs in complicated intracellular microenvironments demand the development of stimuli-responsive drug delivery systems. Here, a nanoparticle system, CaF2:Tm,Yb@mSiO2, made of a mesoporous silica (mSiO2) nanosphere with CaF2:Tm,Yb upconversion nanoparticles (UCNPs) is developed, filling its mesopores and with its surface-modified with polyacrylic acid for binding the anticancer drug molecules (doxorubicin, DOX). The unique design of CaF2:Tm,Yb@mSiO2 enables us to trigger the drug release by two mechanisms. One is the pH-triggered mechanism, where drug molecules are preferentially released from the nanoparticles at acidic conditions unique for the intracellular environment of cancer cells compared to normal cells. Another is the 808 nm near infrared (NIR)-triggered mechanism, where 808 nm NIR induces the heating of the nanoparticles to weaken the electrostatic interaction between drug molecules and nanoparticles. In addition, luminescence resonance energy transfer occurs from the UCNPs (the energy donor) to the DOX drug (the energy acceptor) in the presence of 980 nm NIR irradiation, allowing us to monitor the drug release by detecting the vanishing blue emission from the UCNPs. This study demonstrates a new multifunctional nanosystem for dual-triggered and optically monitored drug delivery, which will facilitate the rational design of personalized cancer therapy.

G-C3N4 Coated Upconversion Nanoparticles for 808 nm Near-Infrared Light Triggered Phototherapy and Multiple Imaging

Exploring novel photosensitizer (PS) with good stability and high light converting efficiency and designing novel structure to integrate deep penetrating near-infrared (NIR) light excitable up-conversion nanoparticles (UCNPs) and PS into one system are highly fascinating in the photodynamic therapy (PDT) field. In this study, a novel core–shell structured platform (UCNPs@g-C3N4–PEG) with all-in-one “smart” functions for simultaneous photodynamic therapy, photothermal therapy (PTT), and trimodal imaging properties has been rationally designed and fabricated. This system is composed of a core–shell–shell structured NaGdF4:Yb/Tm@NaGdF4:Yb@NaNdF4:Yb up-conversion luminescence (UCL) core and photoactive graphitic-phase carbon nitride (g-C3N4) mesoporous shell closely coated on individual core. This designed structure allows large specific surface area, high loading amount, close proximity to the UCL core, and almost no leakage of g-C3N4 PS, thus ensuring sufficient reactive oxygen species (ROS) to damage tumor...

Photon upconversion in Yb3+–Tb3+ and Yb3+–Eu3+ activated core/shell nanoparticles with dual-band excitation

Photon upconversion emission in a series of Yb3+–Tb3+ and Yb3+–Eu3+ activated nanoparticles were investigated in this study.

Nd3+ sensitized dumbbell-like upconversion nanoparticles for photodynamic therapy application.

Better tissue penetration and lower overheating problems mean 808 nm near-infrared laser excited upconversion nanoparticles (UCNPs) have potential in bioapplications. Dumbbell-like structured NaYF4:Yb/Er@NaNdF4:Yb nanoparticles are fabricated in this work and applied in photodynamic therapy (PDT). The epitaxial growth along the c axis attributed to the large structure mismatch of NaNdF4versus NaYF4 has been demonstrated to play a key role in the growth of the dumbbell structure. Due to better space separation in this structure, energy back-transfer from Er3+ to Nd3+ is prohibited partially, and the optimized Nd3+ doping concentration is up to 90% for a high UC emission intensity. PDT effects of these dumbbell-like structured UCNPs upon 808 nm laser irradiation were examined and compared with isotropic NaYF4:Yb/Er@NaYF4:Nd0.2 core-shell and NaYF4:Yb/Er@NaYF4:Nd0.2@NaYF4 core-shell-shell UCNPs. The results show that the dumbbell-like UCNPs are most effective in generating singlet oxygen (1O2) and killing cancer cells in PDT though their UC emission intensity is lower than that of the core-shell-shell UCNPs. This research presents a simple yet valid strategy to balance the UCL efficiency and FRET efficiency, which may lead to better PDT therapeutic effect for cancer therapy.

Surface modification of Y2O3:Er,Yb upconversion nanoparticles prepared by laser ablation in water

Y2O3:Er,Yb upconversion nanoparticles were prepared by laser ablation in liquid and capped with poly(ethylene glycol) (PEG). A Nd:YAG green laser with nanosecond pulse duration was used. Capping was carried out by a two-step process. The first step is surface modification using a silane coupling agent, (3-aminopropyl)triethoxysilane (APTES), to aminate the surface of nanoparticles. The second step was the conjugation of PEG chains to the surface by amido binding reaction between the surface amino groups and activated esters connected to PEG. The prepared upconversion nanoparticles were highly crystalline polycrystals, the particle size of which was approximately 20 nm. Dopants in phosphor nanoparticles were not removed by laser irradiation. The spectra of PEG-capped nanoparticles were almost the same as those of uncapped nanoparticles. The capped nanoparticles would be useful for biomedical applications.

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