Du Sifan, Zhu Xuefeng, Zhang Li, Liu Minghua
Beijing National Laboratory for Molecular Science (BNLMS), CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China.
University of Chinese Academy of Sciences, Beijing 100049, P. R. China.
ACS Appl Mater Interfaces. 2021 Apr 7;13(13):15501-15508. doi: 10.1021/acsami.1c00181. Epub 2021 Mar 25.
While the tremendous deal of efforts has been dedicated to the design and fabrication of materials with circularly polarized luminescence (CPL), the development of the chiroptical switch between different CPL signals is one of the important routes toward its application. Here, we prepared a supramolecular gel from the coassemblies containing a chiral gelator (9-fluoren-methoxycarbonyl-functionalized glutamate derivatives, FLG), a fluorescent molecule [(rhodamine B, RhB) or (2',7'-dichlorofluorescein sodium salt, DCF)], and a photochromic molecule [1,2-bis(2,4-dimethyl-5-phenyl-3-thienyl)-3,3,4,4,5,5-hexafluoro-1-cyclopentene, DAE], thus constructing photomodulated switchable CPL soft materials. It was found that FLG could form supramolecular gel in ethanol and self-assemble into left-handed twisted nanostructures. During the formation of a co-gel with RhB (or DCF) and DAE, the chirality of FLG could be effectively transferred to both the fluorescent and photochromic components, which induced them with chiroptical properties including CPL and circular dichroism (CD). DAE undergoes a reversible transition between the achromatous open state and the dark purple closed state in the co-gel under alternating irradiation with UV and visible light. During such a process, an intermolecular Förster resonance energy transfer (FRET) behavior from fluorescent RhB to ring-closed DAE caused the emission quenching of RhB, which led to CPL silence of RhB in the co-gel. Subsequent irradiation with visible light caused the restoration of the emission and CPL activity with the restored open state. These changes could be repeated many times upon alternate UV and visible irradiation. Therefore, a reversible CPL switch was fabricated in supramolecular gels through the photomodulated FRET process.
尽管人们在设计和制备具有圆偏振发光（CPL）的材料方面付出了巨大努力，但开发不同CPL信号之间的手性光学开关是其应用的重要途径之一。在此，我们通过包含手性凝胶剂（9-芴甲氧羰基官能化谷氨酸衍生物，FLG）、荧光分子[罗丹明B（RhB）或2',7'-二氯荧光素钠盐（DCF）]和光致变色分子[1,2-双（2,4-二甲基-5-苯基-3-噻吩基）-3,3,4,4,5,5-六氟-1-环戊烯，DAE]的共组装制备了一种超分子凝胶，从而构建了光调制的可切换CPL软材料。研究发现，FLG能在乙醇中形成超分子凝胶并自组装成左手扭曲纳米结构。在与RhB（或DCF）和DAE形成共凝胶的过程中，FLG的手性能够有效地传递给荧光和光致变色组分，从而赋予它们包括CPL和圆二色性（CD）在内的手性光学性质。在共凝胶中，DAE在紫外光和可见光交替照射下会在无色开放态和深紫色关闭态之间发生可逆转变。在此过程中，从荧光RhB到闭环DAE的分子间Förster共振能量转移（FRET）行为导致RhB的发射猝灭，进而使共凝胶中RhB的CPL沉默。随后用可见光照射会随着开放态的恢复导致发射和CPL活性的恢复。这些变化在紫外光和可见光交替照射下可以重复多次。因此，通过光调制FRET过程在超分子凝胶中制备了一种可逆CPL开关。
