The highly sensitive detection of improvised explosives is of great significance for ensuring national security and public safety, yet remains a major challenge in analytical detection. Xinjiang Key Laboratory of Trace Chemical Substances Sensing, Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, has dedicated extensive research to enhancing on-site trace explosives detection performance through fundamental mechanism studies. The laboratory has pioneered a series of solutions to boost the detection sensitivity and anti-interference capabilities in aspects such as modulating fluorescent probe structure, tuning amorphous nanomaterial, and constructing multimodal sensing materials (Angew. Chem. Int. Ed. 2022, 61, e202203358; Adv. Mater. 2023, 35, 2300526; Adv. Mater. 2020, 32, 1907043; Adv. Sci. 2024, 11, 2309182; JACS Au, 2024, 4, 545; Aggregate 2022, 3, e260).

Hydrogen peroxide (H₂O₂), the primary precursor for representative improvised explosives—including triacetone-triperoxide (TATP), diacetone diperoxide (DADP), and hexamethylene triperoxide diamine (HMTD)—demands ultrasensitive detection performance to meet the requirement in practical scenarios. To address this challenge, Xinjiang Key Laboratory of Trace Chemical Substances Sensing has proposed a synergistic strategy to improve the detection sensitivity towards H₂O₂ via π conjugated bridge regulation and nanocellulose signal enrichment. Firstly, thiophene, benzene ring and furan were successfully introduced as the bridge, and three naphthalimide-based probes (MOHB-IMTP, MOHB-IMP, and MOHB-IMF) featuring boric acid as the recognition site were designed and synthesized. Among these, the MOHB-IMTP probe demonstrated the strongest reactivity, while H₂O₂ detection triggers the oxidation of its boric acid and the cleavage of the π-conjugated bridge’s C=N bond, resulting in a ratiometric fluorescent change from light blue to yellow-green. This MOHB-IMTP probe showed superior sensing performance toward H₂O₂, including a lower LOD (38.5 nM) and an excellent selectivity even in the existence of 22 interferents. Secondly, further signal enrichment for an even better LOD of 4.0 nM was realized through a MOHB-IMTP/cellulose colloidal probe, which enabled successful integration into a portable device for automated monitoring. The synergistic π conjugated bridge regulation and nanocellulose signal enrichment strategies are expected to provide new ideas for the design of highly sensitive sensing materials against trace chemical substances.

This progress was published in Analytical Chemistry entitled as "Precise Modulation of the π-Conjugated Bridge of Naphthalimide-Based Probes for High-Performance Fluorescent Sensing of H₂O₂". This work was supported by the National Natural Science Foundation of China, the Natural Science Foundation of Xinjiang, the Tianshan Innovation Team Plan, and the Youth Innovation Promotion Association of the Chinese Academy of Sciences.

Figure: Schematic Diagram of π Conjugated Bridge Regulation Strategy for Naphthalimide-Based Fluorescent Probes