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• A mitochondria-targetable "naked-eye" fluorescent probe RosPO(OH) 2 was obtained. • The first dual-function probe for simultaneous determination of HOCl and pH is reported. • Probe have rapid response, low detection limit and a wide range of pH application. • The fluorescent imaging demonstrated its value of practical application. A series of rosamine dyes were designed and synthesized through one-step reaction. Among them, bifunctional fluorescent probe RosPO(OH) 2 showed excellent water solubility and large molar extinction coefficient. RosPO(OH) 2 underwent a two-step ionization process as the pH value of the HEPES buffer increased, accompanied a blue shift of UV absorption and an enhancement of fluorescence intensity. This means it can be used as a pH sensor. After the addition of HOCl, the fluorescence of RosPO(OH) 2 was quenched and the color of the solution changed from pink to colorless which permitted "naked eye" detection. RosPO(OH) 2 could be used as a sensor for detecting HOCl with high selectivity, rapid response, low detection limit (52 nM) and a wide range of pH application (pH 1–10). Colocalization results showed that RosPO(OH) 2 could specifically stain in mitochondria. Due to the low toxicity and the excellent water solubility of RosPO(OH) 2 , it had been successfully applied to image pH and HOCl in living cells. [ABSTRACT FROM AUTHOR]

• It is the first QM-based AIE fluorescent probe for ONOO−. • QM-ONOO− showed bigger Stokes shift (190 nm) than the reported. • QM-ONOO− possessed rapid response, and low detection limit (27.5 nM). • The exogenous and endogenous ONOO− imaging in MCF-7 cells demonstrated its value of practical tool. Peroxynitrite (ONOO−), as one type of reactive nitrogen species (RNS) , is closely related to multiple pathophysiological processes. Visualization of ONOO− in living system is essential for further study of its physiological functions. However, most existing ONOO− fluorescent probes continuously display the aggregation-caused quenching (ACQ). In present research, a new activatable AIEgen fluorescent probe QM-ONOO− for ONOO− recognition and imaging was proposed. Activation of the probe by ONOO−, induced aggregation of QM−OH. This sensor showed fast response time (<4 min) and high sensitivity (DL, 27.5 nM), large Stock's shift (190 nm), long emission wavelength. Furthermore, the outcomes indicate that QM-ONOO− as an activatable AIEgen fluorescent sensor was robust chemical tool to detect endogenous peroxynitrite in living biological system. [ABSTRACT FROM AUTHOR]

• A new two-photon fluorescent probe for HNO was developed. • The probe showed faster response time (2 min), lower detection limit (32 nm) and strong anti-interference ability. • The probe can target the ER and visualization of NO and H 2 S cross-talk on the ER for the first time. Nitroxyl (HNO) is a one-electron reduction product of nitric oxide (NO), which mainly exists in protonated form during physiological processes. As a kind of reactive nitrogen species (RNS), HNO has significant correlations with many physiological and pathological pathways. In this study, we report a two-photon fluorescent probe R2, which can detect HNO based on the reaction with a triarylphosphine group. Upon exposure to HNO, the probe R2 holds "naked eye" recognition, high selectivity and fast response (2 min). These excellent spectral properties promoted the detection of exogenous and endogenous HNO in MCF-7 cells. Furthermore, the probe could be selectively located in the endoplasmic reticulum (ER) with high biocompatibility and successfully apply to visualize NO/H 2 S cross-talk to generate HNO. These results support that R2 will provide a powerful tool to elucidate the physiological and pathological functions of HNO in the ER. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A new N-oxide based and turn on fluorescent probe for Fe2+ was developed. • The probe possessed a high selectivity for Fe2+ among various biologically relevant species and fast rapid response. • Monitoring Fe2+ with TPM fluorescence imaging for the first time. Abstract Iron is an essential element for human body, involved in important biochemical processes in the body, especially in biological oxidation. Misregulation of iron levels in the cell is concerned with serious diseases. Here, a novel two photon and turn on NIR-fluorescent probe based ICT for detection of Fe2+ is first reported. The probe exhibited brilliant selectivity and excellent sensitivity (DL = 4.5 μM), rapid response (15 min) and "naked-eye colorimetric sensor" for monitoring of Fe2+. More importantly, the probe was successfully applied to real-time monitor Fe2+ in living cell through two-photon microscopy fluorescence imaging with excitation 680 nm. [ABSTRACT FROM AUTHOR]