Peroxynitrite (ONOO⁻) is an important kind of reactive oxygen species (ROS), played an essential role in physiology and pathology. To date, various fluorescent probes for ONOO⁻ have been constructed successfully, but these probes exhibit turn-on fluorescence signal in single channel. While, ratiometric fluorescent probes, especially those probes with large emission shift, are suitable for bioimage in two channels. Herein, a hemicyanine-based fluorescent probe named Cy-NH₂ was designed and synthesized for ratiometric detection of ONOO⁻. The characteristics of Cy-NH₂ are as follows: (1) The probe possesses a simple structure, which can be obtained by easy synthetic steps; (2) The ratiometric fluorescent probe owns large emission shift (248 nm) due to the disruption of π-conjugation system caused by strong oxidizing ability of ONOO⁻; (3) The probe exhibits high sensitivity to ONOO⁻ with 1728-fold enhancement of fluorescence intensity ratio and superior selectivity for ONOO⁻ over various potentially interfering biological analytes; (4) The ratiometric fluorescent probe is applied for the image detection of exogenous and endogenous ONOO⁻ in living cells successfully.

过氧亚硝酸盐（ONOO ^- ）是一种重要的活性氧（ROS），在生理和病理方面发挥了重要作用。迄今为止，各种ONOO荧光探针^-已经成功地构建，但这些探针表现出导通在单一信道的荧光信号。同时，比例荧光探针，尤其是那些具有较大发射位移的探针，适合在两个通道中进行生物成像。在本文中，命名为CY-NH基于半花青荧光探针₂被设计和用于ONOO的比率检测合成^- 。Cy-NH _2的特征如下：（1）该探针结构简单，可以通过简单的合成步骤得到。（2）比率荧光探针拥有大的发射位移（248纳米）由于由ONOO的强氧化能力π共轭系统的破坏^- ; （3）ONOO的探针表现出高的灵敏度^-用的荧光强度比和ONOO优良的选择性1728倍的增强^-在各种潜在干扰生物分析物; （4）比率荧光探针被应用于外源性和内源性ONOO的图像检测^-在活细胞中成功。