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 Tb³⁺ ions over Er³⁺ ions and Tm³⁺ 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 Tb³⁺ emission in NaYbF₄:Tb@CaF₂ nanoparticles is prolonged extensively to ∼3.5 ms. Furthermore, NaYbF₄:Tb@CaF₂ was applied in <i>in vitro</i> and <i>in vivo</i> bioimaging. The presented luminescence enhancement strategy provides cooperative sensitization upconversion with new opportunities for bioapplication

Versatile Spectral and Lifetime Multiplexing Nanoplatform with Excitation Orthogonalized Upconversion Luminescence

Optical encoding together with color multiplexing benefits on-site detection, and enriching the components with narrow emissions from lanthanide could greatly increase the coding density. Here, we show a typical example to combine emission color and lifetime that are simultaneously integrated in a single lanthanide nanoparticle. With the multicompartment core/shell structure, the nanoparticles can activate different emitting pathways under varied excitation. This enables the nanoparticles to generate versatile excitation orthogonalized upconversion luminescence in both emission colors and lifetimes. As a typical example, green emission of Er³⁺ and blue emission of Tm³⁺ can be triggered with 808 and 980 nm lasers, respectively. Moreover, with incorporation of Tb³⁺, not only is emission from Tb³⁺ introduced but also the lifetime difference of 0.13 ms (Er³⁺) and 3.6 ms (Tb³⁺) is yielded for the green emission, respectively. Multiplexed fingerprint imaging and time-gated luminescence imaging were achieved in wavelength and lifetime dimensions. The spectral and lifetime encoding ability from lanthanide luminescence greatly broadens the scope of luminescent materials for optical multiplexing studies

Core–Shell–Shell NaYbF₄:Tm@CaF₂@NaDyF₄ Nanocomposites for Upconversion/T₂‑Weighted MRI/Computed Tomography Lymphatic Imaging

To circumvent the defects of different bioimaging techniques, the development of multifunctional probes for multimodality bioimaging is required. In the present study, a lanthanide-based core–shell–shell nanocomposite NaYbF₄:Tm@CaF₂@NaDyF₄ composed of an ∼9.5 nm NaYbF₄:Tm nanocrystal as the core, ∼2 nm CaF₂ as the middle layer, and 1–2 nm NaDyF₄ as the outermost shell was designed and synthesized. Following surface modification with the ligand, citrate acid, this nanocomposite was hydrophilic, emitted intense upconversion luminescence (UCL), and displayed a high X-ray computed tomography (CT) value of ∼490 Hounsfield units (HU) and excellent <i>r</i>₂ relaxivity of 41.1 mM^–1 s^–1. These results confirmed that the introduction of a middle CaF₂ layer was necessary as a barrier to reduce cross-relaxation and the surface quenching effect, thus enhancing the upconversion emission of Tm³⁺. This citrate-modified NaYbF₄:Tm@CaF₂@NaDyF₄ nanocomposite was used as a multifunctional contrast agent for trimodal lymphatic bioimaging with T₂-weighted magnetic resonance imaging (MRI), CT, and UCL imaging. The concept of fabricating a core–multishell nanostructure and the introduction of a Dy³⁺-based host as an outer layer is a useful strategy and can be used to develop a novel multifunctional nanoprobe for multimodality bioimaging

Additional file 1: Figure S1. of Agonist-induced activation of human FFA1 receptor signals to extracellular signal-regulated kinase 1 and 2 through Gq- and Gi-coupled signaling cascades

Forskolin did not mimic the effect of PTX. A. Serum-starved FFA1-HEK293 cells were pretreated with DMSO or Forskolin (10μM) for 1h, and the cells were then stimulated with 10μM LA for the indicated time. ERK1/2 phosphorylation was assessed by Western blot as described in the Experimental Procedures and corresponding immunoblots were quantified by Bio-Rad Quantity One Imaging system. B. FFA1-HEK293 and HEK293 cells were exposed to PTX(100ng/ml) for indicated time, and than cell viabilities were evaluated by CCK8 assay at OD450nm. Error bars represent the SEM for three replicates. The data shown are representative of at least three replicate independent experiments. Data were analyzed using Student’s t-test (* p<0.001). (DOC 2835 kb