Ultraviolet Upconversion Research Articles

Ultraviolet photon upconversion in Er–SiAlON under 1550 nm excitation

SiAlON ceramics are well known for their exceptional mechanical, thermal, and chemical stability, making them ideal for demanding industrial applications such as cutting tools, equipment for molten metal handling, extrusion molds, gas turbine engines, etc. Despite these applications, the potential for photonic applications such as photon upconversion (UC) in SiAlON ceramics remains less explored. This report demonstrates broad spectral photon UC properties in Er-doped SiAlON (Er–SiAlON) ceramics, covering the ultraviolet (UV) to near-infrared (NIR) range upon 1550 nm excitation. The Er–SiAlON ceramic was synthesized by hot press sintering. X-ray diffraction (XRD), transmission electron microscopy (TEM) and elemental mapping results confirmed the stabilization of the α-SiAlON phase by Er3+ ions. Optical spectra showed distinct transitions of Er³⁺ ions and high transparency of over 70 % in the mid-IR range for the sample thickness of 0.49 mm. Under 1550 nm excitation, UC emission spectra revealed UV, violet, blue, green, red, and NIR emissions. The Er³⁺ ions exhibited self-sensitization, acting both as sensitizers and activators for the UC luminescence. Decay curve analysis showed long excited state lifetimes, with ground state absorption (GSA), excited state absorption (ESA), and energy transfer UC (ETU) processes facilitating multi-photon absorption and diverse spectral emissions. Given the inherent mechanical properties of SiAlON ceramics, these findings highlight the potential of Er–SiAlON ceramics for advanced UC photonic devices operating in high-temperature and harsh environments.

Enhancement of ultraviolet upconversion photoluminescence of Y7O6F9:Pr, Gd induced by Li+ codoping☆

Ultraviolet upconversion photoluminescence materials have great potential in various fields, but the improvement of the upconversion efficiency is challenging. Codoping of Li+ is considered as an effective strategy and widely used to improve the photoluminescence properties of phosphors. In this paper, Li+ is introduced into a Y7O6F9:Pr3+,Gd3+ system. The effect of Li + codoping on the phase purity, crystal structure, microstructure, downshifting and upconversion photoluminescence as well as the decay dynamic of the phosphors was studied. It is revealed that the overall photoluminescence efficiency and the energy transfer efficiency from Pr3+ to Gd3+ are greatly promoted. The downshifting and upconversion photoluminescence increase by 2.58 and 10 times as 6 mol% of Li+ is codoped. The photoluminescence decay dynamic study shows that the 3P0 state decays slower in the Li + -containing phosphor than the Li+-free one. The improvement of the photoluminescence properties is due to the increase of the crystallinity and the reduce of the quenching center.

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.

Near-infrared to visible and ultraviolet upconversion in TiO2 thin films modified with Er and Yb.

Upconversion as a modification strategy to enhance the utilization of sunlight in titanium dioxide photoanodes with an internal upconverter was investigated. TiO2 thin films containing an Er activator and Yb sensitizer were deposited in the magnetron sputtering process on conducting glass, amorphous silica, and silicon. Scanning electron microscopy, energy dispersive spectroscopy, grazing incidence X-ray diffraction, and X-ray absorption spectroscopy allowed assessment of the thin film composition, structure, and microstructure. Optical and photoluminescence properties were measured by means of spectrophotometry and spectrofluorometry. Changing the content of Er3+ (1, 2, 10 at%) and Yb3+ (1, 10 at%) ions allowed us to achieve thin film upconverters with a crystallized and amorphous host. Upon 980 nm laser excitation Er3+ exhibits upconversion with the main emission in green (2H11/2 → 4I15/2, λ em ≈ 525 nm) and weak emission in red (4F9/2 → 4I15/2, λ em ≈ 660 nm). For a thin film with a higher ytterbium content (10 at%) a significant increase in red emission and upconversion from NIR to UV was observed. The average decay times of green emission for TiO2:Er and TiO2:Er,Yb thin films were calculated based on time-resolved emission measurements.

UVB upconversion of LiYO2:Ho3+,Gd3+ for application in luminescence thermometry.

Development of novel ultraviolet (UV) upconversion materials has been emerging as a hot research topic for application in tunable UV lasers, photocatalysis, sterilization, tagging, and most recently luminescence thermometry. We readily synthesized a series of Ho3+/Gd3+ co-doped LiYO2 upconversion phosphors by a traditional high-temperature reaction. Under excitation from a blue ∼445 nm laser, LiYO2:Ho3+,Gd3+ polycrystalline powders yield intense sharp ultraviolet B (UVB) upconversion luminescence from Gd3+ 6Pj (j = 7/2, 5/2, 3/2) excited states. By means of steady and dynamic photoluminescence spectra, we systematically investigated the involved two-photon absorption upconversion as well as the accompanying energy transfer processes between Ho3+ and Gd3+ ions in the LiYO2 host lattice. Interestingly, the distinguishable UVB luminescence constituents from Gd3+ 6Pj excited states exhibit sensitive temperature dependence in a 353-673 K range. Shedding light on thermal equilibria between Gd3+ 6Pj UV-emitting levels, their luminescence intensity ratios follow Boltzmann statistics for the application of new luminescence thermometry. For the scheme of 6P7/2-6P3/2 thermally coupled levels, it works over a temperature range of 373-673 K with a maximum relative sensitivity (Sr) of about 1.07% K-1 at 373 K, and its 6P7/2-6P5/2 counterpart works over 353-533 K with a maximum Sr of about 0.83% K-1 at 353 K. Overall, our study provides a new pathway to develop UV upconversion materials, and promotes the application of Gd3+-related UV luminescence constituents in sensitive temperature sensing over a wide temperature range.

Near-infrared light responsive intensified multiphoton ultraviolet upconversion in nanostructures towards efficient reactive oxygen species generation.

Near-infrared-to-ultraviolet (NIR-to-UV) multiphoton upconversion has recently received increasing attention owing to its promising frontier applications in the fields of biomedicine and nanophotonics. However, the realization of high-efficiency NIR-to-UV upconversion remains a dispiriting challenge due to weak excitation light harvesting and photo-conversion efficiency. Herein, we propose a mechanistic strategy to achieve intensified UV upconversion by manipulating the injected excitation energy flux. A simple LiYbF4:Tm@LiYF4 host-sensitized sublattice core-shell nanostructure was initially proposed to compete with the concentration quenching effect and increase energy transfer efficiency. Then, the organic dye ICG was further coated to introduce the antenna sensitization effect to highly increase the absorption ability of nanocrystals. After optimizing the ICG number loaded on the surface and separation distance, up to 167-fold UV upconversion emission enhancement was achieved under low-power excitation of 808 nm. More importantly, the efficient UV upconversion exhibits enhanced reactive oxygen species (ROS) generation activity by fabricating a TiO2-modified upconversion nanocomposite, revealing great application potential in frontier fields such as in vivo photodynamic therapy and bioimaging-guided therapeutics. Our results can provide versatile designs to achieve efficient UV upconversion, overcome conventional limitations, and offer exciting opportunities for potential applications in biomedical fields.

Amplified Fenton-Based Oxidative Stress Utilizing Ultraviolet Upconversion Luminescence-Fueled Nanoreactors for Apoptosis-Strengthened Ferroptosis Anticancer Therapy

As an emerging anticancer strategy, ferroptosis has recently been developed in combination with current therapeutic modalities to overcome the existing limitations of conventional therapies. Herein, an ultraviolet (UV) upconversion luminescence-fueled nanoreactor is explored to combine ferroptosis and apoptosis through the UV-catalyzed Fenton reaction of an iron supplement (ferric ammonium citrate) loaded in a mesoporous silica layer in addition to the support of a chemotherapeutic agent (cisplatin) attached on the functionalized silica surface for the treatment of triple negative breast cancer (TNBC). The nanoplatform can circumvent the low penetration depth typical of UV light by upconverting near-infrared irradiation and emitting UV photons that convert Fe3+ to Fe2+ to boost the generation of hydroxyl radicals (·OH), causing devastating lipid peroxidation. Apart from DNA damage-induced apoptosis, cisplatin can also catalyze Fenton-based therapy by its abundant production of hydrogen peroxide (H2O2). As a bioinspired lipid membrane, the folate receptor-targeted liposome as the coating layer offers high biocompatibility and colloidal stability for the upconversion nanoparticles, in addition to prevention of the premature release of encapsulated hydrophilic compounds, before driving the nanoformulation to the target tumor site. As a result, superior antitumor efficacy has been observed in a 4T1 tumor-bearing mouse model with negligible side effects, suggesting that such a nanoformulation could play a pivotal role in effective apoptosis-strengthened ferroptosis TNBC therapy.

Intense blue-emitting Yb/Tm-CaSiO3 wollastonite upconversion phosphors

Wollastonite is a naturally occurring mineral with a chemical formula of CaSiO3. Owing to outstanding mechanical, chemical, and thermal stabilities, wollastonites have become one of the most versatile industry minerals for applications in construction materials, cement, plastics, paints and coatings, friction, automobile brakes, ceramic and metallurgical applications to name a few. Despite technological importance, research on functional properties such as photon upconversion in wollastonites is still lacking. In this report, an initiative has been taken to demonstrate ultra-violet, blue, and near-infrared photon upconversion in CaSiO3 wollastonite via Yb and Tm doping. The wollastonite ceramics are synthesized via microwave hydrothermal technique followed up by heat-treatment in air. β-wollastonite (2M) phase in the synthesized samples has been confirmed by X-ray diffraction and a successful doping of Yb3+ and Tm3+ ions in the CaSiO3 lattice has been confirmed by X-ray photoelectron spectroscopy. The most intense phonon band has been observed at 872 cm−1. Upon 980 nm excitation, ultraviolet, intense blue, and near-infrared upconversion emissions as well as downshifting infrared emissions are observed from Tm3+ ions as a result of sensitization by Yb3+. The temporal evolution of the emitting states is studied to understand the emission mechanism. An absolute upconversion quantum yield of the 20Yb/0.5Tm–CaSiO3 sample in the 400–850 nm range is 0.79%.

Ultraviolet and visible upconversion in Yb/Er-CaSiO3 β-wollastonite phosphors

Wollastonite (CaSiO3) is a well-known rock-forming mineral and an important constituent in ceramics and cement industries due to its outstanding mechanical, chemical, and thermal stabilities. Despite technological importance, functional properties such as photon upconversion in CaSiO3 wollastonite ceramics have not been studied. In this contribution, Yb- and Er-doped CaSiO3 (Yb/Er–CaSiO3) wollastonite ceramics were synthesized via microwave hydrothermal technique followed up by heat-treatment in an air environment. X-ray diffraction and transmission electron microscopy studies confirmed the β-wollastonite (2M) phase in the synthesized samples heat-treated at 1050 °C. X-ray photoelectron spectroscopy analysis has shown that the binding energy of Ca 2p orbitals decreases after doping, indicating a change in the crystal environment of Ca in the CaSiO3 and hence a successful incorporation of Yb3+ and Er3+ ions in the lattice. The 980 nm excitation resulted in ultraviolet, violet and strong green and red upconversion emissions as well as downshifting infrared emissions due to the energy transfer between Yb3+ and Er3+ ions. An absolute upconversion quantum yield in the 400–800 nm range is 0.04%. The most intense phonon band was observed at 969 cm−1 in the Yb/Er–CaSiO3 system. This study demonstrates that the β-wollastonite can be developed as a new kind of efficient upconversion phosphor material.

Near-infrared rechargeable glass-based composites for green persistent luminescence

The fabrication of Yb3+, Tm3+ co-doped oxyfluorophosphate glass-based composites, with green persistent luminescence after being charged with near-infrared light, is demonstrated. The mechanism responsible for the green afterglow after near-infrared illumination is unveiled. The composite is prepared using a modified melting process to limit the evaporation of fluorine during melting. Intense (blue and ultraviolet) up-conversion emission is obtained by optimizing the Yb2O3 and Tm2O3 concentrations. A heat treatment promotes volume precipitation of Yb3+, Tm3+ co-doped CaF2 crystals. Although the intensity of the blue up-conversion emission from the Tm3+1G4 level is lower in the highly Yb3+-concentrated glass-ceramic due to reverse energy transfer from Tm3+ to Yb3+, the heat treatment leads to an increase of the intensity of the emissions around 346 nm, 361 nm nm and 450 nm coming from the Tm3+1I6 and 1D2 levels. By combining the Yb3+ and Tm3+ ions with SrAl2O4:Eu2+,Dy3+crystals, green afterglow can be obtained after charging with near-infrared light.

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.

Simultaneous ultraviolet, visible, and near-infrared continuous-wave lasing in a rare-earth-doped microcavity

Microlaser with multiple lasing bands is critical in various applications, such as full-color display, optical communications, and computing. Here, we propose a simple and efficient method for homogeneously doping rare earth elements into a silica whispering-gallery microcavity. By this method, an Er-Yb co-doped silica microsphere cavity with the highest quality (Q) factor (exceeding 108) among the rare-earth-doped microcavities is fabricated to demonstrate simultaneous and stable lasing covering ultraviolet, visible, and near-infrared bands under room temperature and a continuous-wave pump. The thresholds of all the lasing bands are estimated to be at the submilliwatt level, where both the ultraviolet and violet continuous wave upconversion lasing from rare earth elements has not been separately demonstrated under room temperature until this work. This ultrahigh-Q doped microcavity is an excellent platform for high-performance multiband microlasers, ultrahigh-precision sensors, optical memories, and cavity-enhanced light–matter interaction studies.

Intensifying Upconverted Ultraviolet Emission towards Efficient Reactive Oxygen Species Generation.

Multiphoton upconversion that can convert near-infrared irradiation into ultraviolet emission offers many unique opportunities for photocatalysis and phototherapy. However, the high-lying excited states of lanthanide emitters are often quenched by the interior lattice defects and deleterious interactions among different lanthanides, resulting in weak ultraviolet emission. Here, we describe a novel excitation energy lock-in approach to boost ultraviolet upconversion emission in a new class of multilayer core-shell nanoparticles with a gadolinium-rich core domain. Remarkably, we observe more than 70-fold enhancements in Gd3+ emission from the designed nanoparticles compared with the conventional nanoparticles. Our mechanistic investigation reveals that the combination of energy migration over the core domain and optically inert NaYF4 interlayer can effectively confine the excitation energy and thus lead to intense multiphoton ultraviolet emission in upconversion nanostructures. We further achieve a 35.6% increase in photocatalytic reactivity and 26.5% in reactive oxygen species production yield in ZnO-coated upconversion nanocomposites under 808-nm excitation. This study provides a new insight to energy transfer mechanism in lanthanide-doped nanoparticles and offers an exciting avenue for exploring novel near-infrared photocatalysts.

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.

Upconversion Luminescence-Initiated and GSH-Responsive Self-Driven DNA Motor for Automatic Operation in Living Cells and In Vivo.

In light of the worthy design flexibility and the good signal amplification capacity, the recently developed DNA motor (especially the DNA walker)-based fluorescent biosensors can offer an admirable choice for realizing bioimaging. However, this attractive biosensing strategy not only has the disadvantage of uncontrollable initiation but also usually demands the supplement of exogenous driving forces. To handle the above obstacles, some rewarding solutions are proposed here. First, on the surface of an 808 nm near-infrared light-excited low-heat upconversion nanoparticle, a special ultraviolet upconversion luminescence-initiated three-dimensional (3D) walking behavior is performed by embedding a photocleavage linker into the sensing elements, and such light-controlled target recognition can perfectly overcome the pre-triggering of the biosensor during the biological delivery to significantly boost the sensing precision. After that, a peculiar self-driven walking pattern is constructed by employing MnO2 nanosheets as an additional nanovector to physically absorb the sensing frame, for which the reduction of the widespread glutathione in the biological medium can bring about sufficient self-supplied Mn2+ to guarantee the walking efficiency. By selecting an underlying next-generation broad-spectrum cancer biomarker (survivin messenger RNA) as the model target, we obtain that the newly formed autonomous 3D DNA motor shows a commendable sensitivity (where the limit of detection is down to 0.51 pM) and even an outstanding specificity for distinguishing single-base mismatching. Beyond this sound assay performance, our sensing approach is capable of working as a powerful imaging platform for accurately operating in various living specimens such as cells and bodies, showing a favorable diagnostic ability for cancer care.

Enhanced ultraviolet upconversion emission in Ho3+/Yb3+-codoped NaYF4 microcrystals induced by tridoping with Gd3+ ions

NaY(0.78-x)GdxHo0.02Yb0.2F4 (x = 0, 0.2, 0.4) microcrystals are synthesized by hydrothermal process. Ultraviolet upconversion emissions centered at 340 and 360 nm in Ho3+/Yb3+/NaYF4 microcrystals, which are stimulated by 976 nm lasers, can be enhanced by tridoping with Gd3+ ions. The ultraviolet upconversion radiations are enhanced more than fourfold for Gd3+ ions concentrations of 20 mol%. The X-ray diffraction (XRD) data mean that the enhancement is not come from expanding structural. Excitation and down emission spectra and decay lifetimes results demonstrate that the enhancement due to an energy back transfer process (PJ6(Gd3+)→(F5, F3, G5)2 (Ho3+)). The UV UC mechanisms are supported by decay lifetime and pump power dependence.

Dye-Sensitized Rare Earth Nanoparticles with Up/Down Conversion Luminescence for On-Demand Gas Therapy of Glioblastoma Guided by NIR-II Fluorescence Imaging.

As the primary malignant tumor in the brain, glioblastoma exhibits a high mortality due to the challenges for complete treatment by conventional therapeutic methods. It is of great importance to develop innovative therapeutic agents and methods for treatment of glioblastoma. In this work, the imaging and therapy of glioblastoma are reported by using dye sensitized core-shell NaYF4 :Yb/Tm@NaYF4 :Nd nanoparticles with strong up/down-conversion luminescence, of which the ultraviolet up-conversion emissions at 348 and 365nm are significantly enhanced by nearly 28 times and used to control the release of SO2 from 5-Amino-1,3-dihydrobenzo[c]thiophene 2,2-dioxide prodrug for gas therapy, and the second near-infrared (NIR-II) down conversion emission at 1340nm is increased five times and applied for imaging. It is revealed that the released SO2 molecules not only cause oxidative stress damage of tumor cells, but also induce their pro-death autophagy by down-regulating the expression of p62 and up-regulating the ratio of LC3-II/LC3-I, ultimately inhibiting tumor growth. The work demonstrates the great potential of rare earth nano-platform with functions of NIR-II imaging and photo-controlled gas therapy in the diagnosis and treatment of orthotopic glioblastoma.

Dye Sensitization for Ultraviolet Upconversion Enhancement.

Upconversion nanocrystals that converted near-infrared radiation into emission in the ultraviolet spectral region offer many exciting opportunities for drug release, photocatalysis, photodynamic therapy, and solid-state lasing. However, a key challenge is the development of lanthanide-doped nanocrystals with efficient ultraviolet emission, due to low conversion efficiency. Here, we develop a dye-sensitized, heterogeneous core–multishelled lanthanide nanoparticle for ultraviolet upconversion enhancement. We systematically study the main influencing factors on ultraviolet upconversion emission, including dye concentration, excitation wavelength, and dye-sensitizer distance. Interestingly, our experimental results demonstrate a largely promoted multiphoton upconversion. The underlying mechanism and detailed energy transfer pathway are illustrated. These findings offer insights into future developments of highly ultraviolet-emissive nanohybrids and provide more opportunities for applications in photo-catalysis, biomedicine, and environmental science.