The photoluminescence emission behavior of carboxymethyl β-cyclodextrin powder and tablet is explained in detail from a new perspective of cluster formation and emission, which provides strong evidence that pressing powder into tablet can effectively enhance the photoluminescence quantum yield and persistent room-temperature phosphorescence emission.

Nonconventional luminogens have great potential applications in fields like cell imaging and anti-counterfeiting encryption. But so far, the photoluminescence quantum yield (PLQY) of most these solids is still relatively low and the persistent room-temperature phosphorescence (p-RTP) emission is relatively weak. To improve their PLQY and p-RTP, pressing the powder into tablets is preliminarily proven to be an effective method, but the specific mechanism has not been fully elucidated yet. Herein, carboxymethyl β-cyclodextrin (CM-β-CD) is chosen as the representative to solve the problem. The results show that the PLQY and p-RTP lifetimes of the tablet of CM-β-CD are improved compared to the powder. By the mechanism of clustering-triggered emission and average packing density-promoted emission mechanism, it is demonstrated that the enhanced molecular interactions after compression is the key reason, resulting in the formation of cluster emission centers with stronger emission capabilities. CM-β-CD is proven to have excellent cell imaging and anti-counterfeiting functions.