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Hydrazine (N2H4) is a potent organic amine known for its extreme toxicity and risk of spontaneous combustion or explosion in the presence of strong oxidizers, air, or elevated temperatures. Regulatory bodies including the U.S. Environmental Protection Agency, the World Health Organization, and the International Agency for Research on Cancer classify hydrazine as a Class B2 hazardous substance, emphasizing the urgent need for reliable detection techniques.
Fluorescence turn-on probes that employ the excited-state intramolecular proton transfer (ESIPT) mechanism are noted for their high sensitivity and minimal background noise, making them promising tools for identifying harmful substances. Nonetheless, existing designs often face challenges regarding specificity, especially for similar analytes, and research on the impact of substituent modifications on sensing performance remains limited. Thus, enhancing the effectiveness of ESIPT-based probes through careful adjustment of substituent characteristics is an ongoing challenge.
To address this challenge, a research team spearheaded by Prof. Dou Xincun from the Xinjiang Technical Institute of Physics and Chemistry, part of the Chinese Academy of Sciences, has innovated a design strategy for a zero-background fluorescence probe specifically aimed at achieving ultra-sensitive and precise detection of hydrazine.
Their research findings, published in Analytical Chemistry, highlight the modulation of the electron-accepting strength of the para-substituent at the recognition site, along with carefully positioning the proton donor in relation to the recognition element, to heighten the probe’s reactivity towards N2H4 and bolster the ESIPT process.
In their study, the researchers formulated a range of zero-background fluorescent probes, including m-Br-OH-BDMN, m-CH3-OH-BDMN, OH-BDMN, Br-BDMN, and p-Br-OH-BDMN, utilizing dicyanoethylene as the recognition site. They manipulated the electron-accepting capability of the para-substituent (-Br > -H > -CH3) on the dicyanoethylene and the relative positioning (either para or ortho) of the hydroxyl proton donor.
The team observed that enhancing the electron-accepting ability substantially boosted the recognition site’s reactivity. The probe only generated a hydrazone in the presence of N2H4 when the hydroxyl group was positioned ortho to the recognition site, which subsequently activated the ESIPT process and produced blue-green fluorescence.
Specifically, the probe m-Br-OH-BDMN, featuring bromine as the electron-accepting group, showcased outstanding detection capabilities for N2H4, achieving a limit of detection (LOD) of 0.46 nM (14.72 ng/L), a rapid response time of one second, and exceptional selectivity, even amidst 18 other interfering substances, including varying structural analogs of primary amines.
Additionally, the researchers introduced a silicon-based porous sensing material design that effectively adsorbs and concentrates target substances, thereby enhancing molecular collision frequency. This method successfully differentiates N2H4 from ethylenediamine solutions and vapors within five seconds, without interference from other volatile compounds. This novel non-fluorescent probe design offers valuable perspectives for the strategic development of functional probes and advanced sensing techniques.
More information: Fang Xiao et al, Zero-Fluorescence Probe for Ultrasensitive and Specific Detection of Hydrazine by Regulating the Electron-Accepting Strength, Analytical Chemistry (2025). DOI: 10.1021/acs.analchem.5c00343
Citation: Zero-background fluorescence probe enables precise detection of hazardous hydrazine (2025, April 28).
Source
phys.org