Chiroptical Signal Amplification in Amorphous Siloxane Network by Asymmetric Ring Distortion

Understanding the polymorphs and amorphous structures of silicon oxide is an essential issue not only for fundamental science but also for energy and environmental science. In particular, the amplification mechanism of chiroptical signals in amorphous silicon oxide has drawn significant attention. Here, we explore how the chiroptical signal can be amplified in amorphous silicon oxide (silica) having nanoscale helical structures. Our findings reveal that the observed vibrational circular dichroism (VCD) signals originate from the formation of symmetry-broken siloxane ring structures. Furthermore, we demonstrate that the amplification of siloxane VCD signals is driven by an enthalpy-driven asymmetric ring distortion during volumetric shrinkage.