Optical Temperature Sensing and Bioimaging of Aquatic Invertebrates with Nd3+- Sensitized Core@Shell Nanoparticles

In biomedical and optical applications, multifunctional upconverting nanoparticles (UCNPs) play an essential role where non-invasive temperature sensing and imaging are necessary. UCNPs smaller than 20 nm, which can be excited under an 808 nm wavelength, are particularly promising in this area and can be implemented in humans or other mammals. However, new versatile nanoprobes are still needed for biology, especially for challenging studies of small aquatic invertebrates. Such tools allow better monitoring and understanding of their physiology, biochemistry and ecological responses, which is crucial due to the growing pollution of water reservoirs and climate change. Herein, multifunctional NaYF4:Yb3+, Er3+@NaNdF4:Yb3+ core@shell NPs (15 nm), forming stable aqueous colloids, exhibiting intense emissions under excitation in the first biological window (808 nm), and presenting high thermal sensitivity and resolution related to the thermally coupled energy levels of Er3+ ions, are designed and synthesized. Such properties of UCNPs are further utilized for optical imaging of aquatic invertebrates (Daphnia magna) and temperature detection inside their bodies under an 808 nm excitation. This pioneering application of NaYF4:Yb3+, Er3+@NaNdF4:Yb3+ demonstrates the high potential of developed UCNPs for multifunctional applications, especially for bioimaging and temperature sensing within whole organisms.在生物医学与光学应用中，多功能上转换纳米颗粒（upconverting nanoparticles, UCNPs）在需要无创温度传感与成像的场景中发挥着关键作用。尺寸小于20 nm、可在808 nm波长下激发的UCNPs在该领域极具应用前景，且可应用于人体或其他哺乳动物体内。然而，生物学领域仍亟需新型多功能纳米探针，尤其是针对小型水生无脊椎动物的挑战性研究场景。这类工具可助力更精准地监测与解析这类生物的生理学、生物化学及生态响应，而鉴于当前水库污染日益严峻与气候变化问题，此类研究的重要性愈发凸显。本文设计并合成了多功能NaYF₄:Yb³⁺, Er³⁺@NaNdF₄:Yb³⁺核壳纳米颗粒（nanoparticles, NPs，尺寸为15 nm）：该颗粒可形成稳定的水相胶体，在第一生物窗口（808 nm）激发下可产生强烈发射信号，且基于Er³⁺离子的热耦合能级具备优异的热灵敏度与温度分辨率。依托上述特性，研究团队进一步将该UCNPs应用于水生无脊椎动物——大型溞（Daphnia magna）的光学成像，以及808 nm激发条件下其体内的温度检测。此项针对NaYF₄:Yb³⁺, Er³⁺@NaNdF₄:Yb³⁺的开创性应用，证实了所开发的UCNPs在多功能场景中具备极高应用潜力，尤其适用于完整生物体的生物成像与温度传感。