Lead-free double perovskites (DPs) with excellent moisture, light, and heat stability have been explored as alternatives to toxic lead halide perovskite (APbX 3 ) (A for monovalent cation and X for Cl, Br, or I). However, the bandgaps of the current DPs are generally larger and either indirect or direct forbidden, which leads to weak visible light absorption and limitation for photovoltaic and other optoelectronic applications. Herein, we demonstrate the first synthesis of Cu 2+ -doped Cs 2 AgInCl 6 double perovskite nanocrystals via a facile hot-injection solution approach. The electronic bandgap can be dramatically tuned from ∼3.60 eV (Cs 2 AgInCl 6 , parent) to ∼2.19 eV (Cu 2+ -doped Cs 2 AgInCl 6 ) by varying the Cu 2+ doping amount. We conclude that the decrease of bandgap is attributed to the overlap of the Agd/In-p/Cl-p orbitals and the Cu-3d orbitals in the valence band. The wide tunability of the optical and electronic properties makes Cu 2+ -Doped Cs 2 AgInCl 6 DP NCs promising candidates for future optoelectronic device applications.

Combinations of immune checkpoint therapies show encouraging results in the treatment of many human cancers. However, the higher costs and greater side effects of such combinations compared with single-agent immunotherapies limit their further applications. In this work, a novel smart agent, KN046@ 19 F-ZIF-8, is developed to overcome these limitations. KN046 is a novel recombinant humanized PD-L1/CTLA-4 bispecific single-domain antibody-Fc fusion protein, which can bind to both PD-L1 and CTLA-4 effectively. ZIF-8 is a smart delivery system, which can safely and effectively deliver KN406 to a tumor. In vitro and in vivo results demonstrate that the smart agent KN046@ 19 F-ZIF-8 not only improves the immune response rate of the antibody drug in treatment of tumors but also reduces its toxic side effects, thereby achieving excellent antitumor efficacy. This study provides an engineering strategy for clinical applications of a more effective immunotherapy.

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