Ultraviolet Upconversion Luminescence Research Articles

Highly water-soluble and biocompatible hyaluronic acid functionalized upconversion nanoparticles as ratiometric nanoprobes for label-free detection of nitrofuran and doxorubicin

Antibiotic detection is crucial and challenging because the widespread consumption of antibiotics has shown extensive harmful effects on food, environment and human health. Here, we propose highly water-soluble and biocompatible hyaluronic acid (HYA) functionalized upconversion nanoparticles (UCNPs) for ratiometric detection of multiple antibiotics. The ultraviolet upconversion luminescence (UCL) from UCNPs was significantly quenched by nitrofurazone (NFZ)/nitrofurantoin (NFT), and blue UCL was quenched by doxorubicin (DOX), while red UCL remained unchanged for internal reference. The UCNPs-HYA nanoprobes exhibit excellently sensitive and selective NFZ, NFT and DOX detection in linear range of 2.5–100 μM, 2.5–80 μM, and 2.5–200 μM with the LOD at 0.28 μM (55 μg/kg), 0.20 μM (48 μg/kg) and 0.17 μM (97 μg/kg), respectively. The nanoprobes achieved detecting real samples of NFZ in lake water, liquid milk and chicken meat with satisfactory results, and UCL bioimaging of DOX in HeLa cells. The UCNPs-HYA ratiometric nanoprobes are promising for food samples detection and potential biosensing in the cellular environment.

Near-infrared light activated and hybridization chain reaction cascaded CRISPR/Cas12a system under the enhancement of Mn2+ for intracellular biosensing

While CRISPR/Cas12a system is a potent in vitro fluorescence biosensing toolbox, several difficulties including collective biological delivery, potential pre-activation and inadequate sensitivity make it challenging to further perform intracellular application. Herein, we raise a series of solving strategies. First, MnO2 nanoflower is used to conjointly carry the biomolecular modules comprising CRISPR/Cas12a system through a simple physisorption to actualize an efficient endocytosis, after which the MnO2 matrix will be reduced by the widespread intracellular biothiols to not only release the surface attached biomolecules but also produce abundant Mn2+ to enhance trans-cleavage activity. Besides, a light activation conception realized by inserting the biosensing frame with a facile photocleave group is applied to achieve a controllable spatiotemporal behavior, for which the target recognition process will be manually initiated by illuminating with an ultraviolet upconversion luminescence converted from 808 nm near-infrared photons. By making usage of hybridization chain reaction to construct a final cascaded CRISPR/Cas12a system, the additional signal amplification design renders this newly-raised CRISPR/Cas12a system-mediated fluorescent biosensor has an ultra-sensitive detection ability for microRNA-21. Moreover, this special CRISPR/Cas12a system is also equipped with a high-efficiency imaging performance in live cells and even bodies, impelling the development of CRISPR system based biosensing techniques.

Near-infrared upconversion photosensitizer enabling photodynamic production and in situ dynamic monitoring of hydroxyl radical in live mice

Upconversion photodynamic therapy (PDT), utilizing upconversion nanoparticles (UCNPs) to excite surface-anchored molecular photosensitizers, enables to treat deep-seated tumors using tissue-penetrating near-infrared (NIR) light. Yet, this technique was substantially limited by the O2 deficiency in solid tumors and the inability to visualize reactive oxygen species (ROS) for precise treatment. To address this challenge, we devised a neotype of multifunctional upconversion photosensitizer which not only efficiently generates hydroxyl radical (•OH) to induce cell apoptosis in hypoxic tumor, but also dynamically shows accumulated amount of radical •OH in situ in tumor. This photosensitizer consists of NaYbF4:Tm@NaYF4 upconversion nanoparticles (UCNPs) as the core, and mesoporous silica as the shell which was loaded with heterojunction Ag0-Ag2S quantum dots and IR 820 molecular probe on the surface. Under 980 nm NIR excitation, thulium ultraviolet and blue upconversion luminescence (UCL) excite spectrally overlapped Ag0-Ag2S, with metal-semiconductor heterojunction for enhanced electron-hole separation, to produce highly toxic •OH to induce cell death. While produced •OH can specifically degrade surface IR 820 dyes to remove luminescence resonant energy transfer from UCNPs to IR 820 dyes, this can turn on quenched UCL entailing dynamical observation of in situ generated •OH. Intravenous injection of the photosensitizers resulted in 8-fold tumor volume reduction as compared to control group, while dynamically showing accumulated production of •OH in hypoxic 4T1 tumor-bearing mice (Balb/c). These findings untap the use of upconversion photosensitizer for precise and visualized treatment of deep-seated hypoxic tumors in live mammals.

Smart NIR light-gated CRISPR/Cas12a fluorescent biosensor with boosted biological delivery and trans-cleavage activity for high-performance in vivo operation

Despite the in vitro usage of CRISPR/Cas12a system in fluorescent biosensors has made remarkable achievements, many challenges such as poor biological delivery, insufficient sensitivity, and uncontrollable initiation compel them hard to conduct in vivo analysis. Thus, we propose here some fruitful sensing concepts. First, the multiple biomolecular components of CRISPR/Cas12a system are collectively carried by MnO2 nanosheets via a simple physical absorption to achieve a highly-efficient biological uptake. Under the reduction of widespread biothiols, not only the sensing frame is easily released but also sufficient Mn2+ is produced to serve as an effective trans-cleavage accelerator. Furthermore, a photocleavge-linker induced smart near-infrared (NIR) light-gated manner is designed to offer a spatiotemporal target recognition, for which a 808 nm NIR light transduced ultraviolet upconversion luminescence with weak thermal effect is employed to completely prevent the sensing flow from pre-initiating during the biological delivery. As a conceptual validation, this biosensor has satisfactory sensitivity and specificity to survivn messenger RNA (a broad-spectrum cancer biomarker). More importantly, it can work as a reliable imaging platform for differentiating cancers in live cellular level and also presents a high-performance operation ability for analyzing live mice, greatly promoting the CRISPR technology in biosensing field.

Multifunctional α-NaYbF4:Tm3+ nanocrystals with intense ultraviolet self-sensitized upconversion luminescence and highly efficient optical heating

Lanthanide-doped upconversion photoluminescent nanoparticles with unique anti-Stokes spectroscopic properties excel in many fields of application. Ytterbium-based self-sensitized fluorides with rich Yb3+ possess higher absorption efficiency of incident near infrared laser, and are more favorable for photoluminescence or optical heating applications. In this work, α-NaYbF4:Tm3+ crystalline nanoparticles are synthesized, which exhibit intense ultraviolet self-sensitized upconversion photoluminescence and highly efficient optical heating capability under 980 nm laser excitation. NaYbF4:Tm3+ nanocrystals emit multi-band luminescence with emission peaks located in the ultraviolet, blue and red spectral regions. The energy transfer mechanism and electronic transition pathways for the Upconversion luminescence are investigated based on the energy level scheme, and are further confirmed by luminescent dynamic analysis. Due to cross-relaxations between Tm3+ and energy back transfer from Tm3+ to Yb3+ processes, the NaYbF4: 1 mol% Tm3+ nanoparticles possess the highest luminescence intensity. The luminescent dynamic characteristics, such as decay time and rise time, vary with Tm3+ doping concentrations. Highly efficient optical heating effect is observed in the NaYbF4:Tm3+ nanoparticles with slope efficiency of photothermal conversion for 10 s laser irradiation is as high as 100.48 °C/W.

Up-Conversion Luminescence Processes in NaLaF4 Doped with Tm3+ and Yb3+ and Dependence on Tm3+ Concentration and Temperature.

In this work, luminescence processes in polycrystalline NaLaF4:Tm3+ and NaLaF4:Tm3+,Yb3+ materials were studied. Luminescence spectra and decay kinetics measurements were performed for NaLaF4 doped with various Tm3+ concentrations (0.01, 0.1, 0.5, 1, and 2 mol%) under direct excitation to 3P0, 1D2, 1G4, and 3H4 states. It was found that some of the Tm3+ excited states are more affected by Tm3+ concentration than other states. Under infrared excitation of Yb3+, energy transfer to Tm3+ occurred and intensive ultraviolet and blue up-conversion luminescence was observed. Possible up-conversion mechanisms are discussed. Spectroscopic measurements show that long-duration excitation radiation reduces ultraviolet up-conversion luminescence intensity, and this intensity reduction is related to sample heating due to high excitation radiation density and a poor heat sink from samples. It was found that sample configuration for spectroscopic measurements is crucial to correctly describe measured up-conversion luminescence spectra.

Optical study of SrLaGa3O7 ceramic samples doped with Er3+ and Yb3+

We present a preliminary study concerning the luminescence properties of polycrystalline ceramics with stoichiometric formula Sr(ErxYbyLa1-x-y)Ga3O7 (x = 0.005, 0.01; y = 0.03, 0.04) obtained by solid-state reaction and normal sintering method. Spectroscopic characteristics were investigated in order to assess the potential of this material as phosphor for visible domain. Red (660 nm, 4F9/2 → 4I15/2), green (550 nm, (2H11/2,4S3/2) → 4I15/2), violet (408 nm, 2H9/2 → 4I15/2) and ultraviolet (380 nm, 4G11/2 → 4I15/2) upconversion luminescence were obtained for the first time in Sr(ErxYbyLa1-x-y)Ga3O7 ceramic samples, by pumping at 973 nm.

Visible and ultraviolet upconversion and near infrared downconversion luminescence from lanthanide doped La2Zr2O7 nanoparticles

Single materials which have a multitude of photophysical processes by selective doping are in high demand in the community of material science due to their multifunctional applications. Upconversion (UC) and downconversion (DC) luminescence properties of lanthanide doped nanoparticles (NPs) are imperative for their broad application potentials. Here, we describe two series of either doubly or triply doped La2Zr2O7 NPs synthesized by a molten salt method. For the former, La2Zr2O7:Yb,Er NPs display bright red and moderate green UC (VUC) and NIR-B DC (NDC) at around 1550 nm, which are highly desirable for in-vivo bioimaging applications. For the latter, La2Zr2O7:Gd,Yb,Tm NPs demonstrate ultraviolet UC (UVUC) which can be exploited for water purification. In addition, we systematically investigated the effects of sensitizer doping level on the morphology, crystal structure and UC and DC emission intensity of these NPs. The processes involved in the VUC, NDC and UVUC emissions are evaluated in detail by pump power dependence studies which reveal that the VUC emissions are two-photon processes whereas the UVUC emission is a five-photon absorption process. The mechanisms of all these three luminescence processes have been extensively explained based on energy transfer and f-f transition processes. The idea provided in this work extends the knowledge on doping induced UC and DC luminescence in pyrochlore NPs which show multifunctionalities in light emission properties.

Intense ultraviolet upconversion luminescence from YF3: Yb/Tm submicrorice

It is still a challenge to design and synthesize fluoride particles with novel morphology and superior ultraviolet (UV) upconversion (UC) emissions using simple strategy. Here, we report the preparation of water-soluble and morphology tunable YF3: Yb/Tm submicrorices (SMRs) with high UV UC efficiency. The morphology and size of the SMRs were controlled by tuning the added amount of fluorine source and organic modifier. All these SMRs presented excellent UV UC photoluminescence under 980-nm irradiation. Particularly, the intensities of the 5-photon UC emissions from the 1I6 level of Tm ions were much stronger than those of the 4-photon UC emissions from the 1D2 level and the 3-photon UC emissions from the 1G4 level. In addition, the UC mechanisms of these samples were investigated in detail.

Mechanism of ultraviolet upconversion luminescence of Gd3+ ions sensitized by Yb3+-clusters in CaF2:Yb3+, Gd3+

Ultraviolet (UV) luminescence under the near infrared (NIR) excitation is very important for the photodynamic therapy and NIR photocatalysis. In this paper, UV emission of Gd3+ ions in CaF2:Yb3+, Gd3+ excited by 980nm laser is studied theoretically on the basis of the cooperative energy transfer from excited lanthanide tetramers. The main mechanism for the cooperative energy transfer from an excited Yb3+-tetramer to a Gd3+ ion is dq-dq-qq (d means an electric dipole and q means an electric quadrupole) and the energy transfer rate is calculated to be 1.7 × 10−6s−1, which is well comparable with the previous calculated cooperative luminescence rate of 1.8 × 10−6s−1 from an Yb3+-trimer. This is reasonably agreed with our previous experimental result that showed UV luminescence of Gd3+ ions and Yb3+-trimers within the same order of magnitude in CaF2:Yb3+, Gd3+ under the excitation of 980nm laser. The present paper suggests that CaF2:Yb3+, Gd3+ is a potential up-conversion luminescent material for UV, and stimulates the design and development of new UV luminescent phosphors sensitized by lanthanide ion clusters.

Near infrared ray to ultraviolet up-conversion luminescence of Tm3+–Yb3+ co-doped (CaY)F2 nanocrystals

Near Infrared Ray (NIR)-ultraviolet (UV) up-conversion luminescence (UCL) materials have potential application in many fields of biological science, including cells and tissue labeling for bio-imaging, bio-detection, therapy or multiplexed analysis. Tm3+/Yb3+ co-doped (CaY)F2 nanocrystals have been successfully synthetized through the hydrothermal method, and the effect of different synthesis conditions on the morphology and luminescence property of (CaY)F2 phosphors have been discussed. When the molar concentration of Tm3+ and Yb3+ were 0.4 and 20%, respectively, the obtained (CaY)F2 nanocrystals have excellence density, crystallinity, single particle dispersion, uniform particle size (55.5 nm), and high up-conversion luminescence efficiency with the hydrothermal conditions of 180° C and 12 h and calcined temperature of 500° C. Specifically, the synthesized nanocrystals could be stably excited by a 980 nm pump light, converted to 360 nm UV. In addition, the cytotoxicity of (CaY)F2 nanocrystals has also be explored, which shows low cytotoxicity examined by the L929 murine fibroblast cells. With this biocompatibility and excellent up-conversion luminescence properties, the obtained (CaY)F2 nanocrystals have a high potential as biomaterials for photodynamic therapy assisted by TiO2.

Enhanced high-order ultraviolet upconversion luminescence in sub-20 nm β-NaYbF4:0.5% Tm nanoparticles via Fe3+doping

Despite showing great promise in bioapplications, lanthanide-doped upconversion nanoparticles (UCNPs) are still restricted by low upconversion efficiency. In this work, ultra-small, monodisperse and uniform β-NaYbF4:0.5% Tm NPs were successfully prepared through a solvothermal route, and remarkably enhanced ultraviolet upconversion luminescence (UV UCL) had been achieved via Fe3+ doping. The UV UCL enhancement in NaYbF4:0.5% Tm NPs was investigated in detail. It was found that the UCL intensities of the UV and blue emissions of NPs doped with 5 mol% Fe3+ ions were enhanced by 10 and 6 times, respectively, compared to that of the Fe3+-free sample. The enhancement of UV UCL is mainly ascribed to the high population density of excited Yb3+ and the energy transfer from |2F7/2, 4T1g > (Yb3+–Fe3+ dimer) to 3F2,3 (Tm3+) states. Moreover, through dynamic analysis, we further demonstrate the proposed mechanisms of UC processes. The results suggest that ultra-small UCNPs with enhanced UV UCL may have potential applications in the biomedical field.

Ultraviolet upconversion enhancement in triply doped NaYF4:Tm3+, Yb3+ particles: The role of Nd3+ or Gd3+ Co-doping

Upconversion (UC) particles are currently under intensive investigation, normally for their visible instead of ultraviolet (UV) light luminescence under near-infrared (NIR) irradiation. As a commonly studied host, NaYF4 in particular is known to have low phonon energy and high UC efficiency. Here, we present our work on enhancing UC luminescence in the UV region by adding a third dopant into a binary-doped NaYF4:Yb3+,Tm3+ host. More specifically, neodymium (Nd3+) or gadolinium (Gd3+) ions was co-doped into parent NaYF4:20mol%Yb3+,0.5mol%Tm3+ UC particles to enhance their UV UC luminescence. Experimental results demonstrated that these particles exhibited the highest degree of UV UC enhancements when co-doped with 0.05mol% Nd3+ or 2.0mol% Gd3+, expanding the potential of this type of materials into many possible applications by directly converting NIR irradiation into UV light. Fundamentally, the UV UC emission dependence of these triply doped NaYF4:Yb3+,Tm3+ particles with different Nd3+ and Gd3+ doping concentrations was investigated in terms of ground state absorption, excited state absorption and energy transfer UC mechanisms.

Synthesis and intense ultraviolet to visible upconversion luminescence of YF3:Ho3+ nanoparticles

Abstract Ho 3+ single-doped YF 3 nanoparticles were successfully synthesized by a hydrothermal method. Ultraviolet upconversion luminescence around 288 nm was observed clearly in YF 3 :Ho 3+ nanoparticles under excitation at 450 nm. The structure, composition and upconversion emission properties of the as-prepared products were characterized by X-ray crystallography, scanning electron spectrophotometry, energy-dispersive X-ray analysis, and fluorescence spectrophotometry. Hydrothermal temperature had a significant influence on the size and morphology of YF 3 :Ho 3+ nanoparticles, but the molar ratio of Y 3+ /Ho 3+ had little effect on these characteristics. Upconversion emission spectra demonstrated that the upconversion luminescence properties of the synthesized products were closely related to hydrothermal temperature and the molar ratio of Y 3+ /Ho 3+ . The YF 3 :Ho 3+ @TiO 2 photocatalyst was prepared via a sol-gel process and gave higher photocatalytic activity in degraded Rhodamine B (RhB) than did P25 under Xe lamp irradiation.

Ultraviolet and visible upconversion luminescence in Y_2O_3:Er^3+, Gd^3+ microcrystals by 155 μm excitation

Upconversion (UC) emission spectra of Y2O3:Er3+ (3 mol. %), Gd3+ (0, 10, 20, and 40 mol. %) microcrystals were studied under 1.55 μm excitation. Ultraviolet (UV) UC from the L15/22, H9/22, D1/24, D3/24, D7/24, D5/24, D5/22, P1/22, P3/22, G11/24, and G9/22 levels in Er3+ and from the D1/26 and P7/26 levels in Gd3+ were obtained. Enhancements of UV UC emissions of Er3+ were observed in Y2O3:Er3+, Gd3+. The cooperative energy transfer from Er3+ to Gd3+ and the energy transfer from Gd3+ to Er3+ ions were thought to be the possible mechanisms for these enhancements. This phenomenon provides a new idea for investigating the enhancement of UC radiations in rare-earth ion doped materials. The dependencies of UC emissions on pump power and dopant concentration were also studied for understanding possible UC mechanisms.

Controllable synthesis and crystal structure determined upconversion luminescence properties of Tm3+ (Er3+) ions doped YbF3 and NaYbF4 crystals

The synthesis of YbF3 and NaYbF4 crystals was successfully fulfilled by a facial hydrothermal method. The phase and morphology of the products were adjusted by changing the surfactant additive and fluorine source and tuning the pH value of the initial solution. The products with various morphologies range from octahedral nanoparticles, corn-like nanobundles, nanospheres, microrods, and hollow microprisms were prepared at different conditions. The growth mechanism of these products has been systematically studied. Impressively, relatively enhanced high order ultraviolet (UV) upconversion (UC) luminescence was observed in Tm3+ (Er3+) ions doped YbF3 nanocrystals (NCs) compared with NaYbF4 microcrystals under the excitation of 980nm infrared laser. The investigation results reveal that the crystal symmetry of matrix has significant effect on the spectra and lifetimes of the doping lanthanide ions. The simply synthesized water soluble YbF3 NCs with efficient UV UC luminescence may find potential application in biochemistry.

Different dynamics of ultraviolet upconversion in Tm3+:ZBLAN glass under blue laser excitation

Ultraviolet upconversion luminescence around 292nm, 350nm and 363nm in Tm3+:ZBLAN glass was observed clearly by pulsed excitation at 464nm. Upconversion dynamics was discussed in detail by an analysis of the measured intensity dependence, decay curves and excitation spectra of upconversion luminescence, from which it was clarified that upconversion luminescence around 292nm and 350nm from 1I6 level was attributed to excited state absorption, while that around 363nm from 1D2 level was attributed to energy transfer process.

Ultraviolet and visible up-conversion luminescence of Er3+/Yb3+ co-doped CaF2 nanocrystals in sol–gel derived glass-ceramics

Glass-ceramics containing Er3+/Yb3+ codoped CaF2 nanocrystals have been prepared by using the controlled crystallization above 650°C of the (Yb3+/Er3+) codoped CaF2–SiO2 xerogels. X-ray diffraction and scanning electron microscopy data have revealed the formation of CaF2 nanocrystals of about 16nm size. For pumping at 973nm, this glass-ceramics shows, besides green and red up-conversion luminescence, violet (at ∼408nm) and near-ultraviolet emission (at ∼380nm). The mechanisms responsible for the upconversion luminescence are presented and discussed. The fluorescence lifetimes of the metastable levels responsible for violet, green and red luminescence are measured and their quantum efficiencies are estimated.

Temperature sensor based on the UV upconversion luminescence of Gd3+ in Yb3+–Tm3+–Gd3+ codoped NaLuF4 microcrystals

Optical temperature sensing characteristics based on the ultraviolet (UV) upconversion luminescence (UCL) of Gd3+ ions are reported here for the first time. Under 980 nm excitation, the temperature dependence five-photon UV UCL from the 6PJ and 6IJ levels of Gd3+ ions in NaLuF4:Yb3+, Tm3+, Gd3+ microcrystals were investigated systematically. The fluorescence intensity ratios (FIR) of two pairs of thermally coupled levels (6P5/2, 6P7/2 and 6I9/2, 6I7/2) were studied as a function of temperature in a range of 298–523 K. The maximum sensor sensitivities were found to be about 0.0004 K−1 (333 K) and 0.0029 K−1 (298 K) by exploiting the UC emissions from the 6PJ and 6IJ levels, respectively. This suggests that the Gd3+-based UCL materials are promising prototypes for application as multi-mode probes for use in bio-separation, MRI imaging, optical thermometers, etc.

Upconversion emission enhancement of Gd3+ ions induced by surface plasmon field in Au@NaYF4 nanostructures codoped with Gd3+–Yb3+–Tm3+ ions

Au nanoparticles (NPs) attached β-NaYF4 nanocrystals codoped with Gd3+–Yb3+–Tm3+ were synthesized by a facial solution method. The UV–vis-near-infrared absorption spectrum shows typical surface plasmon resonance band of Au NPs in addition to the characteristic absorption peaks of Yb3+ ion. X-ray diffraction and selected area electron diffraction results indicate the existence of Au NPs. The transmission electron microscopic image reveals the formation of Au@NaYF4 nanostructures. Enhanced ultraviolet (UV) upconversion luminescence (UCL) was observed in the nanostructures under the excitation of 980-nm infrared laser. The largest enhancement factor was obtained as 76 for the 6IJ→8S7/2 emission of Gd3+ ions, which was much larger than those emission enhancement factors of Tm3+. It is for the first time to our knowledge that the emission enhancement of Gd3+ ions was obtained. Local field enhancement induced by Au NPs was found to be responsible for the UCL enhancement, which is the further experimental evidence of local field enhancement theory. Magnetic measurements of the Au@NaYF4 nanostructure indicated it would have potential application in magnetic resonance imaging.