Light-fueled transient supramolecular assemblies in water as fluorescence modulators

Abstract

Dissipative self-assembly, which requires a continuous supply of fuel to maintain the assembled states far from equilibrium, is the foundation of biological systems. Among a variety of fuels, light, the original fuel of natural dissipative self-assembly, is fundamentally important but remains a challenge to introduce into artificial dissipative self-assemblies. Here, we report an artificial dissipative self-assembly system that is constructed from light-induced amphiphiles. Such dissipative supramolecular assembly is easily performed using protonated sulfonato-merocyanine and chitosan based molecular and macromolecular components in water. Light irradiation induces the assembly of supramolecular nanoparticles, which spontaneously disassemble in the dark due to thermal back relaxation of the molecular switch. Owing to the presence of light-induced amphiphiles and the thermal dissociation mechanism, the lifetimes of these transient supramolecular nanoparticles are highly sensitive to temperature and light power and range from several minutes to hours. By incorporating various fluorophores into transient supramolecular nanoparticles, the processes of aggregation-induced emission and aggregation-caused quenching, along with periodic variations in fluorescent color over time, have been demonstrated. Transient supramolecular assemblies, which act as fluorescence modulators, can also function in human hepatocellular cancer cells.

Reversible photo control of proton chemistry

“…24–27 The positive charge may also allow the proton acceptor to attract other anionic species including the deprotonated mPAH. 28 The mPAH becomes an anionic molecule after it releases its proton, and can attract other cations, e.g. Ca 2+ .…”

“…In fact, some recent studies have shown this trend. 24,28,33 Another example would be CO 2 capture, which is an extremely important task. Although using mPAHs for releasing captured CO 2 with solar light is a promising approach, little has been done in this direction.…”

“…This energy conversion mechanism has been utilized to fuel dissipative assemblies with photoenergy. 25–28,32,33,35–37 No chemical waste is generated during the dissipative process and spatial, temporal and intensity control can be easily achieved. Such systems may also be used to mimic the dissipative assemblies sustained by chemical energy as those in living systems because the energy form that directly interacts with the assembly is chemical energy of a high proton concentration.…”

“…50 Yang, Chen, Li and coworkers developed a functional nanoassembly of chitosan and an mPAH. 28 The mPAH was noncovalently incorporated into the assembly instead of only in the medium. The group further incorporated fluorophores into the assembly.…”

Dynamic Timing Control over Multicolor Molecular Emission by Temporal Chemical Locking

“…[3] However, it is still highly challenging to explore dynamic molecular systems capable of showing time-dependent multicolor emission (i.e., dynamic timing emission). Although some successful examples [15][16][17][18][19] have been realized by combining kinetic supramolecular self-assembly with emissive assemblies, dynamic timing control over the inherent multicolor emission of individual molecules, to the best of our knowledge, remains unrealized.…”