Adsorption–desorption oscillations of nanoparticles on a honeycomb-patterned pH-responsive hydrogel surface in a closed reaction system

A new type of pH-responsive hydrogel surface with varying nanoparticle adsorptivities was fabricated to form a micro-patterned film. To increase its responsivity to environmental pH changes, we incorporated graphene oxide (GO) into a poly(methacrylic acid)–polyethylene glycol copolymer. Incorporating GO in the pH-responsive hydrogel significantly increased the adsorption–desorption responsivity of Ag nanoparticles on the gel surface. A pH oscillator in a closed reaction system composed of BrO3−–Fe(CN)64−–SO32− facilitated the self-oscillating adsorption–desorption of Ag nanoparticles on the GO-incorporated gel surface. The reversible adsorption–desorption of Ag nanoparticles on the patterned hydrogel surface in response to pH oscillations was determined using UV–visible spectroscopy in aqueous solution. The observed heterogeneous oscillations indicated that the adsorptivity of the gel surface can be reversibly changed on the patterned pH-responsive gel. This phenomenon is similar to various natural biological systems.