Joining Two Switches in One Nano‐Object: Photoacidity and Photoisomerization in Electrostatic Self‐Assembly

Abstract

Multi‐switchable supramolecular nano‐objects that respond to irradiation of different wavelengths with changes in size and shape have been built from two different water‐soluble molecular switches, joined by attachment to the same polyelectrolyte. Accordingly, two wavelength‐specific reactions, namely the excited‐state proton dissociation of a photoacid and the cis–trans isomerization of an azo dye, are combined in one supramolecular nano‐object that is stable in aqueous solution. The concept has potential in the fields of sensors, molecular motors, and transport.

Scanning tunneling microscopy study of [1,1:3,1′′-terphenyl]-4,4′′-dicarboxylic acid on HOPG

“…2 Two-dimensional molecular self-assembly has potential advantages in constructing heterojunction materials, and the construction of highly complex surface supramolecular structures is important for realizing surface molecular devices. A series of new materials obtained from self-assembly techniques can be applied in various fields such as sensing, 3,4 optoelectronics, 5 medicine, 6 etc , thus they have attracted the attention of many researchers in recent years. Theoretically, we can rationally design simple molecular building blocks from the bottom up to obtain the desired complex functional nanostructures and characterized materials through the technique of self-assembly.…”

Comparative study of the co-assembly behaviour of 3-chloro-4-hydroxy-phenylazo dyes with DTAB

“…18 Due to the interest in lightswitchability, the interaction between dye molecules and polyelectrolytes has been studied for a long time, revealing that such systems form well-defined supramolecular nanoparticles of adjustable size, based on electrostatic assembly with various azo dyes. 19 Furthermore, the assembly morphology was shown to not only depend on structural features of the dye, but also on its self-assembly behaviour. 20 The use of polymeric building blocks does, however, come along with some drawbacks.…”

Controlling the Morphology in Electrostatic Self-Assembly via Light

“…Diverse structures such as cell membranes [ 1 , 2 ], supramolecules [ 3 , 4 , 5 ], and protein complexes [ 6 , 7 , 8 , 9 , 10 ] are formed via multiple non-covalent interactions between adjacent molecules that occur due to their chemical nature. Recently, electrostatic self-assembly has emerged as one of the most facile approaches for fabricating such synthetic particles in aqueous solution [ 11 , 12 , 13 , 14 ]. This process is mainly driven by thermodynamics [ 15 , 16 ]; however, kinetics is also found to be an essential factor in structural manipulation [ 17 ].…”

“…Due to their relatively weak nature, these non-covalent interactions can be altered using various parameters, including pH, concentration, preparation method, charge ratio, and counterions. The precise manipulation of the nano-objects with external stimuli is critical to multiple applications ranging from nanoelectronics [ 11 , 13 , 18 , 19 , 20 , 21 ] to controlled drug delivery [ 22 , 23 , 24 ]. Light responsiveness as a non-invasive trigger attracted the most attention in this respect [ 14 , 25 , 26 ].…”

“…Previously, electrostatic assemblies have been formed using AY38 dye and G4 PAMAM dendrimer by Willerich et al [ 14 ], where the pH control and light irradiation caused reproducible nano assemblies. Later, Zika et al [ 13 ] introduced the effect of photoacids in this type of system and created multi-switchable electrostatic assemblies with defined sizes and shapes.…”