Water-soluble red afterglow imaging agents based on ecofriendly nanomaterials have potential application in time-gated afterglow bioimaging due to their larger penetration depth and nondurable excitation. Herein, red afterglow imaging agents consisted of Rhodamine B (RhB) and carbon nanodots (CNDs) have been designed and demonstrated. In these agents, CNDs act as energy donors, and RhB acts as an energy acceptor. Both of them are confined into a hydrophilic silica shell to form a CNDs-RhB@silica nanocomposite. The phosphorescence emission spectrum of the CNDs and the absorption spectrum of the RhB match well, and efficient energy transfer from the CNDs to the RhB via Förster resonant energy transfer process can be achieved, with a transfer efficiency can reach 99.2%. Thus, the as-prepared nanocomposite can emit a red afterglow in aqueous solution, and the afterglow spectrum of CNDs-RhB@silica nanocomposite can extend to the first near-infrared window (NIR-I). The luminescence lifetime and afterglow quantum yield (QY) of the CNDs-RhB@silica can reach 0.91 s and 3.56%, respectively, which are the best results in red afterglow region. Time-gated in vivo afterglow imaging has been demonstrated by using the CNDs-RhB@silica as afterglow agents.

中文翻译：

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用于在水溶液中实现红色余辉的磷光碳纳米点辅助 Förster 共振能量转移

基于环保纳米材料的水溶性红色余辉成像剂由于其较大的穿透深度和非持久激发，在时间门控余辉生物成像中具有潜在的应用价值。在此，设计并展示了由罗丹明 B (RhB) 和碳纳米点 (CND) 组成的红色余辉成像剂。在这些药物中，CNDs 作为能量供体，RhB 作为能量受体。它们都被限制在亲水性二氧化硅壳中以形成 CNDs-RhB@silica 纳米复合材料。CNDs的磷光发射光谱与RhB的吸收光谱匹配良好，可以通过Förster共振能量转移过程实现从CNDs到RhB的高效能量转移，转移效率可达99.2%。因此，所制备的纳米复合材料可以在水溶液中发出红色余辉，CNDs-RhB@silica纳米复合材料的余辉光谱可以扩展到第一近红外窗口（NIR-I）。CNDs-RhB@silica 的发光寿命和余辉量子产率（QY）分别达到 0.91 s 和 3.56%，是红色余辉区域的最佳结果。时间门控已经通过使用 CNDs-RhB@silica 作为余辉剂证明了体内余辉成像。