Multifunctionalized PEG derivatives-based inverse opal photonic microspheres with a broad thermo operating window and pH responsiveness

In the last decade, photonic structures based on responsive poly(ethylene glycol) (PEG)-analogues have drawn considerable attention. Nevertheless, the majority of reports concentrate on building 2D-like film-based photonic structures and lack multifunctionality. In this work, we report the construction of multifunctionalized PEG-analogues hydrogel-based photonic microspheres with an inverse opal structure. Opal-structured photonic microspheres (OSPMs) were firstly created using microfluidics-produced droplets of an aqueous dispersion of SiO 2 colloidal particles (CPs) as templates. The OSPMs were sequentially subjected to monomer infiltration, UV-induced polymerization and crosslinking, and wet etching of the SiO 2 CP building blocks, ultimately producing inverse opal photonic microspheres (IOPMs) with pH- and thermoresponsiveness. The IOPMs have a broad thermal operating window and can detect temperatures as high as 75 °C. The carboxylic acid groups in the skeleton of the IOPMs were further utilized to bind with positively charged compounds, such as ruthenium-functionalized polymers with fluorescence. The photonic microspheres are expected to show promising prospects in advanced sensing, visual temperature detection, anti-counterfeiting, and other related fields.