The intrinsic mechanism of packing-regulated photoluminescence in raffinose.

Nonconventional luminophores, with their unique luminescent properties, excellent water solubility, low biotoxicity, and environmental friendliness, hold great potential for diverse applications. To date, however, the photoluminescence quantum yield (PLQY) of most nonconventional luminophores remains relatively low, and their persistent room-temperature phosphorescence (p-RTP) emission is also rather weak. In this work, raffinose powder was found to exhibit remarkable nonconventional luminescence characteristics, including aggregation-induced emission, excitation-dependent photoluminescence (PL), and widespread phosphorescence. Upon compression into a tablet, the nonconventional luminescence features of raffinose were well preserved, accompanied by enhanced PLQY and prolonged p-RTP lifetimes. Combined with the clustering-triggered emission (CTE) mechanism and theoretical calculations, this study indicates that upon tableting, the intrinsically diversified emissive clusters of raffinose undergo further aggregation, leading to the formation of a stronger noncovalent interaction network, including hydrogen bonds and short contacts between oxygen atoms. This work advances the understanding of the CTE mechanism and provides new insights into the rational regulation of the PL properties of nonconventional luminophores.