Construction And Properties Of Novel Fluorescent Switching With CdSe Quantum Dot And Diarylethene

Quantum dots（QDs）has grown exponentially over the past few decades due to their excellent intrinsic properties such as wide excitation,narrow emission,optical stability,high brightness,et al.As an important semiconductor material,CdSe quantum dots（CdSe-QDs）have been extensively studied due to the mature preparation method,the strong luminescence and photostability,the low band gap energy,and the ability to regulate its emission within the visible range by changing its crystal size.Theses advantages can be used as optical switch material is studied,including reversible photoluminescent modulation of CdSe-QDs is very attractive.However,the photo responsive switching materials are required to construct reversible photocontrolled fluorescence switching systems with CdSe-QDs.Photochromic compounds,as a typical of photo responsive materials have attracted great attention,due to their wide application in photo-thermal switching.Among various photochromic compounds,diarylethenes have been regarded as the most promising optical switching materials in many fields,due to their fast light response,high fatigue resistance,and excellent thermal stability.Therefore,the research on the combination of various photo-controlled fluorescent switching systems such as diarylethenes and fluorophore,nanoparticles,carbon dots and QDs has aroused a great enthusiasm.This paper,a series of light controlled and reversible fluorescent switching systems have been constructed with CdSe-QDs and five photochromic diarylethene molecules with different functional groups.Morover,all the five fluorescent switches can be reversible under ultraviolet of 365nm and visible light irradiation.In addition,the switching properties,fluorescence modulation efficiency,and fatigue resistance of the five systems were studied systematically by CdSe-QDs solution mixed with diarylethene solution according to a certain amount.The main research contents of this paper are as follows:1.CdSe-QDs was prepared,and the fluorescence switching system was constructed by mixing the CdSe-QDs solution with diarylethene compound 1o.Under the irradiation of ultraviolet light,Due to the energy transfer between them,diarylethene compound 1o successfully modulated the fluorescence of CdSe-QDs,the fluorescence intensity of CdSe-QDs weakened,and the color of the mixed solution changed from light yellow to blue.At the same time,the"on"and"off"fluorescence states of CdSe-QDS can be switched between ultraviolet and visible light irradiation.Under the irradiation of visible light,the fluorescence of CdSe-QDs and the color of the solution returned to the initial state.The fluorescence switching effect was best when the concentration of CdSe-QDs was 0.8 mg m L^-1 and the concentration of diarylethene compound 1o was 1.75×10^-4 mol L^-1.Under these conditions,the modulation efficiency was 76.9%and the cycle could be repeated 19 times.2.CdSe quantum dot-2o and CdSe quantum dot-3o fluorescence switch systems were successfully constructed by using the prepared 0.8 mg m L^-1 CdSe-QDs solution and the diarylethene compound with aldehyde group（2o）and carboxyl group（3o）at the terminal.The fluorescence switching effect was best when the concentration of CdSe-QDs was 0.8 mg m L^-1 and the concentration of diarylethene compound both were 2.0×10^-4 mol L^-1.Under these conditions,the modulation efficiency of the two switching systems is 89.5%and 59.0%,and can be repeated for9 times and 3 times respectively.The CdSe-QDs-3o switch can be applied to the design of logic gates.It is obvious that the diarylethene with a formyl group has the maximum fluorescence modulation efficiency,and the symmetrical diarylethene with a phenyl group at the end has the best resistance to fatigue.3.CdSe-QDs-4o and CdSe-QDs-5o fluorescence switch systems were successfully constructed.Mixing 0.8 mg m L^-1 CdSe-QDs solution with 4o(c=1.75×10^-4 mol L^-1)and 5o(c=2.0×10^-4 mol L^-1)has the best modulation effect,with the modulation efficiency of 72.5%and 73.9%,respectively.The"on"and"off"states of CDSE-QDS fluorescence can also switch between UV and visible light to form a reversible fluorescence switch system.The CdSe-QDs-4o and CdSe-QDs-5o fluorescence switch systems can be repeated 11 times and 10 times respectively.It was found that both the diarylethene with hydrazide terminal group and the fluorescence switch constructed by CdSe-QDs had good fatigue resistance.