| In recent years,near-infrared fluorescent molecular switches have been well developed,and have broad prospects in optical information storage,electronic devices and biological imaging.Terrylenediimide(TDI)as one of near-infrared fluorescent materials show high fluorescence quantum yield,near infrared absorption and fluorescence emission.A nearinfrared fluorescent molecular switch with excellent optical properties can be obtained by connecting TDI with dithienylethene(DTE).However,the conventional near-infrared molecular switches have the common problem of fluorescence weakened or even aggregation-induced quenching in the aggregated or solid state,which can be solved by introducing aggregation-induced emission(AIE)groups.Therefore,in this paper,a series of AIE groups were selected,which were conjugated with photochromic DTE,and then several of these conjugated groups were covalently coupled with a single TDI to form a donor-receptor-donor triplet to construct a series of TDI near-infrared fluorescent molecular switches.To study their optical properties such as solid-state emission,photochromism,fluorescence switch.Their applications in optical memory and super-resolution fluorescence imaging are explored,and the main research content is as follows:(1)In order to overcome the problem of ACQ,a near-infrared fluorescent molecular switch modified with triphenylacrylcyanide(TPCN)AIE group is designed and synthesized,named TDI-4(DTE-TPCN).Its solid powder has the largest emission peak at 810 nm and fluorescence intensity than the TDI powder increased 9.5 times.The molecular switch has460-770 nm red light absorption,750-850 nm near-infrared fluorescence emission and the closed-form reaction can occur in the wavelength range of 302-405 nm.Fluorescence quenching of the closed-form reaction can be achieved by means of fluorescence resonance energy transfer(FRET)and photoinduced electron transfer(PET).Upon 302 nm light irradiation in THF solution after 5 s,its fluorescence quenching nearly 99%,the maximum switch ratio up to 3467:1,which shows excellent photochromic rate and high fluorescence switching ratio.As a probe dyed block copolymers,the overall resolution of 30 nm is obtained in super resolution fluorescence imaging,which is 10 times higher than that of conventional fluorescence imaging.(2)In order to further study the influence of the electron-donating properties of AIE groups on the photochromism and fluorescent switch properties,two dimethylamine groups are added to the TPCN to obtain near-infrared fluorescent molecular switch,named TDI-4(DTE-DNTPCN).Its solid powder has the maximum emission peak at 830 nm and fluorescence intensity than the TDI powder increased 7.2 times.The molecular switch has530-770 nm red light absorption,750-850 nm near-infrared fluorescence emission and the closed-form reaction can occur in the wavelength range of 302-385 nm.Fluorescence quenching of the closed-form reaction can be achieved by means of FRET and PET.Upon302 nm light irradiation in THF solution after 20 s,the fluorescence quenching 90%,the maximum switch ratio up to 411:1 which shows good photochromic rate and high fluorescence switching ratio.Compared with TPCN,adding two dimethylamine groups resulted in the degradation of photochromic and fluorescent switch properties.TDI-4(DTEDNTPCN)has protonization capability can be applied in biosensors.And it can be used as an optical storage material to demonstrate macro/micro information storage.(3)In order to improve the dependence of near-infrared fluorescent molecular switches on ultraviolet light,TPCN was replaced with triphenylamine(TPA)group to form TDI-4(DTE-TPA).TPA is not only a good visible light sensitive group,but also easy to form compounds with AIE effect.Its solid powder has maximum fluorescence peak at the 830 nm and fluorescence intensity than the TDI powder increased 1.8 times.The molecular switch has 510-770 nm red light absorption,750-850 nm near-infrared fluorescence emission and the closed-form reaction can occur in the wavelength range of 302-420 nm.Fluorescence quenching of the closed-form reaction can be achieved by means of FRET and PET.Under 405 nm visible light irradiation in THF solution after 20 s,the fluorescence quenching almost 100%,the maximum switch ratio up to 355:1,which shows good photochromic rate and high fluorescence switching ratio.As a probe dyed block copolymers,the overall resolution of 27 nm is obtained in super resolution fluorescence imaging. |
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