Upconversion nanosensitizers have been widely considered to have important applications in the treatment of major diseases such as tumors and the utilization of solar energy.Majority of the efforts so far have been focused on improving the efficiency of energy transfer(ET)between upconversion nanoparticles(UCNPs)and the anchored sensitizers with premise that high ET efficiency will lead to high acceptor efficacy.This premise is,however,proved by our current work to be invalid for commonly used load.Interaction between adjacent sensitizing molecules was found to be critical which undermines the amount of excited monomer sensitizers and thus fades the efficacy.Here NaYF4∶Yb3+,Er3+UCNPs and rose bengal(RB)photosensitizer molecules were used as the model energy donors and acceptors,respectively.Contrary to monotonous increase of the ET efficiency from UCNPs to RB species with increasing RB loading,acceptor efficacy characterized by the reactive oxygen species,as well as the RB fluorescence,exhibits bizarre dependence on the RB loading.The underlying mechanism was well studied by the steady-state and time-resolved spectroscopy of a series of samples.RB aggregates are believed to be responsible for the severe deviation between the ET efficiency and acceptor efficacy.The conclusion was validated by in vitro test where the photodynamic therapy with the most monomer RB in UCNPs-RB nanosensitizers kills 35.8％more cells than that with the highest RB loading.This under-standing sheds light on construction of new ET based nanosystems for broad applications,such as medicine,solar energy utilization and optical storage.

Jie Ren;Yadan Ding;Hancheng Zhu;Zhipeng Li;Xia Hong;Huiying Zhao;Hong Zhang

Key Laboratory of UV-Emitting Materials and Technology(Northeast Normal University),Ministry of Education,Changchun 130024,China;Department of Basic Medicine,Gerontology Department of First Bethune Hospital,University of Jilin,Changchun 130021,China;Van't Hoff Institute for Molecular Sciences,University of Amsterdam,Science Park 904,1098,XH,Amsterdam,the Netherlands

稀土学报（英文版）

[1]Jie Ren;Yadan Ding;Hancheng Zhu;Zhipeng Li;Xia Hong;Huiying Zhao;Hong Zhang-.Improving acceptor efficacy rather than energy transfer efficiency:Dominant contribution of monomers of acceptors modified on upconversion nanoparticles)[J].稀土学报（英文版）,2022(05):702-708

nanosensitizers,undermines,Er3+UCNPs

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