Core–Shell Lanthanide Upconversion Nanophosphors as Four-Modal Probes for Tumor Angiogenesis Imaging

Multimodality imaging overcomes the shortage and incorporates the advantages of different imaging tools. Lanthanide-based nanoprobes are unique and have rich optical, magnetic, radioactive, and X-ray attenuation properties; however, simple doping of different lanthanide cations into one host can result in a material with multifunction but not the optimized properties. In this study, using NaLuF₄:Yb,Tm as the core and 4 nm of ¹⁵³Sm³⁺-doped NaGdF₄ (half-life of ¹⁵³Sm = 46.3 h) as the shell, we developed a lanthanide-based core–shell nanocomposite as an optimized multimodal imaging probe with enhanced imaging ability. The lifetime of upconversion luminescence (UCL) at 800 nm and relaxation rate (1/<i>T</i>₁) were at 1044 μs and 18.15 s^–1·mM^–1, respectively; however, no significant decrease in the attenuation coefficient was observed, which preserved the excellent X-ray imaging ability. The nanomaterial NaLuF₄:Yb,Tm@NaGdF₄(¹⁵³Sm) was confirmed to be effective and applicable for UCL imaging, X-ray computed tomography (CT), magnetic resonance imaging, and single-photon emission computed tomography (SPECT) <i>in vivo</i>. Furthermore, the NaLuF₄:Yb,Tm@NaGdF₄(¹⁵³Sm) nanoparticles were applied in tumor angiogenesis analysis by combining multimodality imaging of CT, SPECT, and confocal UCL imaging, which shows its value of multifunctional nanoparticles NaLuF₄:Yb,Tm@NaGdF₄(¹⁵³Sm) in tumor angiogenesis imaging

Red-Light-Controllable Liquid-Crystal Soft Actuators via Low-Power Excited Upconversion Based on Triplet–Triplet Annihilation

A red-light-controllable soft actuator has been achieved, driven by low-power excited triplet–triplet annihilation-based upconversion luminescence (TTA-UCL). First, a red-to-blue TTA-based upconversion system with a high absolute quantum yield of 9.3 ± 0.5% was prepared by utilizing platinum­(II) tetra­phenyl­tetra­benzo­porphyrin (PtTPBP) as the sensitizer and 9,10-bis­(di­phenyl­phosphoryl)­anthracene (BDPPA) as the annihilator. In order to be employed as a highly effective phototrigger of photodeformable cross-linked liquid-crystal polymers (CLCPs), the PtTPBP&BDPPA system was incorporated into a rubbery polyurethane film and then assembled with an azotolane-containing CLCP film. The generating assembly film bent toward the light source when irradiated with a 635 nm laser at low power density of 200 mW cm^–2 because the TTA-UCL was effectively utilized by the azotolane moieties in the CLCP film, inducing their <i>trans</i>–<i>cis</i> photo­isomerization and an alignment change of the mesogens via an emission–reabsorption process. It is the first example of a soft actuator in which the TTA-UCL is trapped and utilized to create photomechanical effect. Such advantages of using this novel red-light-controllable soft actuator in potential biological applications have also been demonstrated as negligible thermal effect and its excellent penetration ability into tissues. This work not only provides a novel photo­manipulated soft actuation material system based on the TTA-UCL technology but also introduces a new technological application of the TTA-based upconversion system in photonic devices

3D Long-Range Triplet Migration in a Water-Stable Metal–Organic Framework for Upconversion-Based Ultralow-Power <i>in Vivo</i> Imaging

Triplet–triplet annihilation upconversion (TTA-UC) has gained increasing attention because it allows for harvesting of low-energy photons in the solar spectrum with high efficiency in relevant applications including solar cells and bioimaging. However, the utilization of conventional TTA-UC systems for low-power bioapplications is significantly hampered by their general incompatibility and low efficiency in aqueous media. Herein we report a metal–organic framework (MOF) as a biocompatible nanoplatform for TTA-UC to realize low-power <i>in vivo</i> imaging. Our MOF consists of a porphyrinic sensitizer in an anthracene-based Zr-MOF as a TTA-UC platform. In particular, closely aligned chromophores in the MOF facilitate a long-range 3D triplet diffusion of 1.6 μm allowing efficient energy migration in water. The tunable ratio between sensitizer and annihilator by our synthetic method also allows an optimization of the system for maximized TTA-UC efficiency in water at a very low excitation power density. Consequently, the low-power imaging of lymph node in a live mouse was successfully demonstrated with an excellent signal-to-noise ratio (SNR > 30 at 5 mW cm^–2)

Luminescent Chemodosimeters for Bioimaging

Luminescent Chemodosimeters for Bioimagin

Upconversion Luminescent Materials: Advances and Applications

Upconversion Luminescent Materials: Advances and Application

Nd³⁺-Sensitized Upconversion Nanostructure as a Dual-Channel Emitting Optical Probe for Near Infrared-to-Near Infrared Fingerprint Imaging

Lanthanide upconversion nanophosphors (Ln-UCNPs) have attracted great attention in a variety of fields, benefiting from low background fluorescence interference and a high signal-to-noise ratio of upconversion luminescence. However, the establishment of Ln-UCNPs with dual near-infrared (NIR) emission channels still remains challenging. Herein, we report the design and synthesis of Nd³⁺-sensitized NaYbF₄:Tm@NaYF₄:Yb@NaNdF₄:Yb hierarchical-structured nanoparticles that emit NIR luminescence at 696 and 980 nm under excitation at 808 nm. The sensitizer-rich NaYbF₄ core promotes efficient energy transfer to Tm³⁺. The interlayer of NaYF₄:Yb effectively prevents the cross-relaxation process from Tm³⁺ to Nd³⁺ and thus enhances the luminescence emission. The introduction of Nd³⁺ ion as the sensitizer transforms the excitation wavelength from 980 to 808 nm, which subtly averts the laser-induced thermal effect and offers a new pathway for the NIR emission channel at 980 nm. The as-prepared nanoparticles were further applied in developing latent and blood fingerprint images, which exhibited high signal-to-noise ratio and distinguishable details under 808 nm excitation with negligible thermal damage to the sample. Our work provides a promising strategy to realize NIR-to-NIR dual-channel emissions in Ln-UCNPs. With further functionalization, such nanoparticles are expected to have great potential in forensic and biological sciences

Sub-10 nm Hexagonal Lanthanide-Doped NaLuF₄ Upconversion Nanocrystals for Sensitive Bioimaging in Vivo

By thermal decomposition in the presence only of oleylamine, sub-10 nm hexagonal NaLuF₄-based nanocrystals codoped with Gd³⁺, Yb³⁺, and Er³⁺ (or Tm³⁺) have been successfully synthesized. Sub-10 nm β-NaLuF₄: 24 mol % Gd³⁺, 20 mol % Yb³⁺, 1 mol % Tm³⁺ nanocrystals display bright upconversion luminescence (UCL) with a quantum yield of 0.47 ± 0.06% under continuous-wave excitation at 980 nm. Furthermore, through the use of β-NaLuF₄:Gd³⁺,Yb³⁺,Tm³⁺ nanocrystals as a luminescent label, the detection limit of <50 nanocrystal-labeled cells was achieved for whole-body photoluminescent imaging of a small animal (mouse), and high-contrast UCL imaging of a whole-body black mouse with a penetration depth of ∼2 cm was achieved

Highly Photostable Near-IR-Excitation Upconversion Nanocapsules Based on Triplet–Triplet Annihilation for in Vivo Bioimaging Application

Triplet–triplet-annihilation-based upconversion (TTA-UC) imaging boasts a low-excitation irradiance and an uncanny lack of autofluorescence interference. Because of these promising features, this approach has been the subject of intensifying investigation. Despite the ideal features, the classical approach of TTA-UC imaging suffers from some crucial drawbacks. A major deficiency of the system lies within its poor photostability, especially for a near-IR-excitation system. Here we report a reduction strategy to improve the TTA-UC photostability. The poor photostability of TTA-UC can be attributed to singlet oxygen generation by the sensitizer under irradiation. We control the singlet oxygen by including a reductive solvent, which consumes the singlet oxygen, thereby improving the TTA-UC photostability. We also prepared TTA-UC nanocapsules with reductive solvent soybean oil inside. In comparison to nonreductive solvents such as toluene, our system shows a significant enhancement to the TTA-UC photostability. The prepared TTA-UC nanocapsules were then used for whole-animal deep imaging with a high signal-to-noise ratio