Direct visualization of swollen microgels by scanning electron microscopy using ionic liquids

We developed a simple and versatile method for the visualization of swollen microgels using standard scanning electron microscopy (SEM) that does not require the conventional sample pretreatment steps of sputtering. Specifically, microgels were swollen using ionic liquids (ILs), which remained nonvolatile even under high vacuum conditions. Two types of widely studied stimuli-responsive microgels and their hybrids with Au nanoparticles were visualized via SEM to demonstrate the versatility of the method. In particular, we observed the dispersion of embedded Au nanoparticles within the microgels because of the swelling caused by the ILs, confirming that the approach is versatile and useful for the evaluation of nanocomposite materials, such as hybrid microgels.