Characterization of cocrystals formed by grinding amino acids through terahertz time-domain spectroscopy

In this paper, we used terahertz time-domain spectroscopy (THz-TDS) over a range of 0.3–2.5 THz to investigate the formation of solid-state cocrystals of amino acids, formed by grinding mixtures of two different kinds of amino acids. For comparison, we prepared dual-layer samples, combined by pressing two single-component pellets together without grinding. In the ground-mixture samples, some extra absorption peaks appeared, different from the characteristic peaks of the pure components, but these peaks did not appear in the dual-layer samples. Thus, these extra absorption peaks in the THz range are unique features of cocrystals. From our results, we believe that THz-TDS is a promising technique to characterize cocrystals.