Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) was performed using a Varian 660 FTIR spectrometer (Agilent, Santa Clara, CA, United States) equipped with a Pike MIRacle single reflection ATR system (Pike Technologies, Madison, WI, United States). Suspensions of the supraparticles were dried on the crystal, and resulting films were measured with a resolution of 4 cm -1 by averaging 64 scans.