Ratiometric 1,8-naphthalimide/1,2,4-triazole conjugates as highly sensitive and self-regenerating solid-state “naked eye” probes for ammonia and low molecular weight volatile amines

Abstract

The development of reliable low-cost fluorescent probes for real-time detection of toxic volatile organic amines, especially predominant ammonia, entails a significant social effect related to food safety and protection of public health and the environment. However, traditional organic fluorophores are usually effective only in dilute solutions, which is why extending the principles of molecular sensors from solution to solid phase is currently becoming a top priority. That is why, herein we focused on the synthesis and photophysical study in solution and solid-state of two 1,8-naphthalimide/1,2,4-triazole conjugates possessing unusually high for the 4-amino-1,8-naphthalimides acidity of the C-4 nitrogen atom. Due to their unusually high acidity, the new compounds easily deprotonate their C-4 nitrogen not only in solution, but also in the solid state (thin film and strip paper) in the presence of volatile amines. Furthermore, it is worth emphasizing that the formed in the presence of basic vapors non-fluorescent anions are rapidly neutralized in a neutral atmosphere without the need for additional acidification of the medium. The results obtained clearly showed the high potential of the synthesized compounds as self-regenerating solid-state ratiometric probes for colorimetric and fluorescent detection of volatile low molecular biogenic amines and they can be considered as an effective platform for rapid detecting toxic gaseous species in our surrounding environment.