Light-induced reversible hydrophobization of cationic gold nanoparticles via electrostatic adsorption of a photoacid

Abstract

Photo-switching between the zwitterionic and anionic forms of a photoacid allows reversible hydrophobization and assembly of cationic gold nanoparticles.

Light‐Responsive Dynamic DNA‐Origami‐Based Plasmonic Assemblies

“…Previously demonstrated pH‐responsive DNA‐origami‐based CPMs utilized DNA triplexes with TAT content varying between 50 % and 80 %, which could be operated at pH values between 6 and 9 [24, 48] . On the other hand, MCH + has been typically used to modulate the pH of aqueous solutions at pH values below 6 [38, 42, 49] . To achieve compatibility between the light‐regulated pH modulation and the switching of pH‐responsive locks, we utilized DNA triplexes with a TAT content of 40 % (Figure 1 B and Table S4).…”

The Many Ways to Assemble Nanoparticles Using Light

“…Unfortunately, the SP/MC switch in water undergoes gradual hydrolysis, which decreased the number of cycles that could be performed to 30–40 . The hydrolysis can be suppressed by working in more acidic solutions, whereby, however, the photoinduced pH drop is less pronounced.…”

“…It is also possible to induce NP assembly via less specific supramolecular interactions. Ikkala and co‐workers have recently reported the reversible, light‐induced hydrophobization of charged NPs in water . They worked with a mixture of positively charged (decorated with tetraalkylammonium groups) gold NPs and photoacid 3 .…”

“…The lifetimes of these transient aggregates ranged from ≈100 min at 15 °C to >1 min at 50 °C. Remarkably, when the process was carried out in water in the presence of a toluene phase, it entailed a near‐quantitative—yet reversible—transfer of the NPs from water to the organic phase …”

“…b) TEM images of gold NPs decorated with tetraalkylammonium groups before (left) and after (right) exposure to blue light in the presence of 3 . b) Reproduced with permission . Copyright 2019, The Royal Society of Chemistry.…”