Two-step sequential energy transfer in sodium carboxymethyl cellulose-based gels for information encryption.

Sodium carboxymethyl cellulose (NaCMC)-based gels have been widely explored for various applications; however, innovative preparation methods are still required to further extend their potential. In this study, we introduced a low-molecular-weight gelator, 3,3',3″-[1,3,5-benzenetriyltris(carbonylimino)]trisbenzoic acid (HL), to induce gelation in NaCMC. The resulting NaCMC/HL gel was further developed into an information-encryption material with misleading functionality. This approach employs a two-step sequential energy transfer platform, with 4,7-di(2-thienyl)-2,1,3-benzothiadiazole and sulforhodamine101 serving as the first and second energy transfer acceptors, respectively, to construct gels that exhibit blue, yellow, and red fluorescence. Upon the addition of NaOH, these gels' fluorescence either is quenched, shifts red or remains unaffected, whereas the addition of HCl can restore their fluorescence. This acid-base responsiveness forms the basis for a unique information-encryption system in which the correct information can only be accessed through a specific processing method; otherwise, the incorrect result would be obtained. This study not only broadens the preparation methods for NaCMC-based gels but also establishes a new paradigm for their application in information encryption.