An ethanol-induced on-paper perovskite nanocrystal crystallization mechanism for expiratory alcohol screening and information encryption

Perovskite nanocrystals (PNCs) are promising fluorescent nanomaterials that have been employed in a wide range of areas. However, their applications in some specific fields, such as chem-/biosensing remain hampered due to their inherent instability to different external stimuli. Herein, we discover a novel mechanism that ethanol, a chemical that is generally thought to be detrimental to PNCs, could specifically initiate the in-situ crystallization of the precursor salts absorbed by paper fiber to yield standard CsPbBr3 fluorescent PNCs. Based on systematical experimental verification, it is revealed that ethanol could mediate the interfacial inter-action of the PNC precursor salts on the paper fiber to allow for this exceptional in-situ PNC crystallization process. Accordingly, a fluorescence turn-on mode paper sensor for rapid and high-sensitive expiratory alcohol detection is designed, which could fulfill the on-site visualized drink-driving screening requirement. Further-more, the application of this new mechanism in multidimensional information encryption is also demonstrated. This work not only discovers a new mechanism for PNC crystallization but also expands the sensing application toolbox of PNCs.