Profiting from spatial confinement of macrocyclic compounds, supramolecular cascade meeting to induce or improve the luminescence of natural chromophore by noncovalent interactions akin to hydrogen bonding[1], [2], [3], [4], host-guest inclusion[5], [6], [7], [8], metal-ligand coordination[9], [10], [11], [12], and in situ polymerization [13] has turn out to be one of many analysis hotspots and quite a lot of stimulus-response methods have been efficiently developed for utility in info encryption[14], [15], [16], [17], biosensing[18], [19], [20], [21], [22], power switch[23], [24], [25], [26], molecular recognition[27], [28], and hydrogels[29], [30], [31]. Sometimes, cascade supramolecular methods include two or extra supramolecular macrocycles assembled with luminescent visitor molecules to attain stimulus response by luminescence pushed by gentle gasoline, temperature, pH, and mechanical drive[32], [33], [34], [35], [36], [37], [38]. Among the many varied macrocycles, cucurbit[n]urils (CB[n]s, n = 7, 8) with inflexible cavities can induce molecular folding[39], [40] and molecular dimerization[41], [42] by host-guest interplay, which might successfully and considerably enhance the luminescent habits of visitor molecules. For instance, Ni and colleagues achieved multicolor luminescence, particularly white gentle emission, in a single resolution by merely adjusting the quantity of CB[8] added, reaching the white gentle emission by a balanced combination of the visitor’s intrinsic blue luminescence and the meeting’s yellow luminescence. Furthermore, the system exhibited a protracted fluorescence lifetime and excessive quantum yield, sustaining environment friendly luminescent efficiency throughout varied concentrations, which supplied novel insights for the event of clever and tunable luminescent supplies, significantly within the fields of optoelectronic units and fluorescence sensors[43]. Multiply charged macrocycles, akin to sulfobutylether-β-cyclodextrin (SBE-βCD)[44] or sulfonatocalix[4]arene[45] have been used as secondary constructing blocks because of their potential to additional assemble with the host-guest complicated by hydrophobic cavities and electrostatic interplay, which cannot solely keep away from the quenching of the fluorophores but in addition change the luminescence habits of the fluorophores. Our group reported the SBE-βCD induced directional aggregation of cyanovinylene derivatives into nanorods, reaching UV-vis absorption and near-infrared fluorescence red-shift. Below alkaline circumstances, the system confirmed reversible fluorescence blue-shift and 90-fold depth enhancement, demonstrating reversible acid-base accountability, which supplied a brand new technique for setting up clever fluorescent sensor units[46]. Past pH-responsive methods, light-responsive supramolecular assemblies have additionally superior quickly lately[47], [48], [49]. Our group developed a light-responsive supramolecular hydrogel through cascade meeting of Laponite (LP) with CB[7]-encapsulated dicyanostilbene derivatives, which exhibited fluorescence enhancement and a 3D gel community at excessive LP concentrations. Additional integration of fluorophores enabled reversible crimson/inexperienced chromatic switching, permitting self-erasing info encryption and anti-counterfeiting[50]. Nonetheless, macrocyclic hosts regulated supramolecular topological morphology rework, particularly pseudorotaxane in situ polymerization to assemble supramolecular reversible multicolor luminescent hydrogel utilizing cascade meeting methods are uncommon stories to the very best of our information.
Herein, we reported the development of multicolored fluorescence emission supramolecular polyrotaxane hydrogel based mostly on alkenyl-alkyl modified pyrenyl pyridine salts (PPD), CB[n]s, acrylamide (AM), and double bond-modified spiropyran (SP) (Scheme 1). CB[7] confined PPD enhanced the fluorescence, and emission was blue-shifted from 526 nm to 500 nm, which the quantum yield elevated from 54.65 % to 74.86 %. Nonetheless, the fluorescence emission was red-shifted from 526 nm to 534 nm whereas encapsulated by CB[8], and the quantum yield was as much as 64.43 %, and nanoparticles and nanofibers have been shaped, respectively. Subsequently, when the cascade assembled with SBE-βCD, not solely was the emission of PPD⊂CB[7]/CB[8] meeting additional red-shifted, but in addition topological architectures underwent secondary variation to type nanosheets and nanorods, respectively. Moreover, by copolymerizing CB[7]/PPD with SP and AM, the place SP was used as an power receptor, a multi-color fluorescence emission hydrogel was efficiently constructed spanning blue, inexperienced, yellow, orange, and crimson, which was utilized in multicolor info encryption and erasable ink.
