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Increasing interest has been noted in photosensitizer design. Currently, most small molecular photosensitizers have several drawbacks, including limited penetration depth and unsatisfying photostability. For addressing these limitations, Frequency upconversion luminescence (FUCL) small molecule was adopted as a photosensitizer design strategy for its deeper penetration, sensitive imaging, and better photostability. We developed a series of FUCL (NIR-NH 2 , NIR-NHEt, NIR-NEt 2) molecules with rigid structures. Equipped with the most powerful electron donor, NIR-NEt 2 exhibits the highest singlet oxygen generation, the strongest upconversion luminescence intensity under 808 nm irradiation and mitochondria-targeted ability. FUCL can be a superior molecular platform for image-guided photodynamic therapy of cancer cells. We developed a series of mitochondria-targeted small FUCL molecules (NIR-NH 2 , NIR-NHEt, and NIR-NEt 2) with different electron-donating segments and screened for the most outstanding one, NIR-NEt 2 , applied for the photodynamic therapy of cancer cells, which demonstrating a new molecular platform for deep-seated upconversion photodynamic therapy. [Display omitted] • FUCL is a one-photon process with advantages of deeper penetration, higher signal-to-noise ratio, and more excellent photostability over the traditional down-conversion luminescence. • NIR-NEt 2 was screened from a series of frequency upconversion luminescence molecules for the excellent photostability, best FUCL ability and ROS generation. • The tactic of heavy-atom free of FUCL PSs that modify strong donating groups on the electron-donating part of D-A structure was investigated. [ABSTRACT FROM AUTHOR]

Abstract: A series of hyperbranched polyimides were successfully synthesized by A2+B2B′+B2 copolymerization from 2,2-bis(3,4-dicarboxylphenyl) hexafluoropropane dianhydride (6FDA), 2,4,6-triaminopyrimidine (TAP) and 4,4′-oxydianiline (ODA). Self-standing polyimides membranes with sufficient mechanical properties were achieved by incorporation of difunctional B2 comonomer into the hyperbranched polymer structure. The degree of branching was estimated using 1H NMR spectroscopy. The morphology structure of the prepared polyimides was evaluated by wide-angle X-ray diffraction patterns, and the d-spacing values first increased gradually to the highest value 5.73Å with increasing the content of TAP, and then decreased. The densities of these films were tested and the difference in density is probably due to the different inter-macromolecular packing efficiency. Both the 5% weight loss at temperatures and the glass transition temperatures (Tg) of the obtained polyimides decreased with decreasing the content of ODA comonomer. Similar tendency was found for tensile strength and elongation at break. Gas transport measurements showed the prepared TAP–ODA–6FDA hyperbranched polyimides exhibited lower permeabilities compared with ODA–6FDA linear polyimides, but higher O2/N2 and CO2/N2 selectivities. So they are expected to apply in the field of gas separation. [Copyright &y& Elsevier]