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[Display omitted] • The first pH fluorescent sensor with two pKa values. • This sensor enables monitoring of pH with the dual-color response. • The portable paper strips can be facilely fabricated based on the sensor. • The paper strips can be successfully employed for the real food analysis. Tracking pH fluctuations in food samples is important for ensuring food freshness. Fluorescent probes have been widely applied as promising tools for the on-site detection of pH changes; however, most of them can be applied only at either lower or higher pH ranges because their response structures commonly have a single acid dissociation constant (pKa). To address this problem, we designed a fluorescent sensor, called HMB, containing a methylpiperazine group with two pKa values, which exhibited a unique dual-color response to pH changes over a wide pH range. Furthermore, the HMB-based test strips are easily prepared and used as portable labels for the visual monitoring of food spoilage that results in microbial and anaerobic glycolytic pathways in real food (such as cheese and shrimp). To the best of our knowledge, this is the first fluorescent pH sensor with two pKa values, and we expect that this work will inspire more sensor designs for food quality control. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel red-emissive ESIPT-based quinolone probe enables ratiometric detection of phosgene. • This probe exhibits the rapid response (in 10 s), stable signal output (last for 10 min), high sensitivity (LOD ∼ 6.7 nM), and distinct emission color change (red to green) towards phosgene. • The sensing mechanism have been investigated by using 1H NMR, HRMS and fluorescence lifetime techniques, confirming that amidation reaction effectively suppressed the ESIPT process. • The probe-embedded nanofibers were facilely prepared by electrospinning and successfully employed to monitor gaseous phosgene with high specificity. Phosgene is a highly toxic gas that poses a serious threat to human health and public safety. Therefore, it is of great importance to develop an available detection method enabling on-the-spot measurement of phosgene. In this paper, we report a novel ESIPT fluorescent probe for phosgene detection based on quinolone fluorophore. This probe exhibits rapid response (in 10 s), stable signal output (last for 10 min), high sensitivity (LOD ∼ 6.7 nM), and distinct emission color change (red to green) towards phosgene. The sensing mechanism was investigated by using 1H NMR, HRMS and fluorescence lifetime techniques, confirming that the amidation reaction between phosgene and quinolone effectively suppressed the ESIPT process of probe. Eventually, this probe was fabricated into polymer nanofibers by electrospinning and successfully employed to monitor gaseous phosgene with high specificity. This work provided a promising analytical tool for rapid and ratiometric detection of phosgene both in solution and in the gas phase. [ABSTRACT FROM AUTHOR]

[Display omitted] • A surfactant-assisted fluorescent method is reported for sensitive detection of benfluralin herbicide in water with a LOD of 80 nM. • The role of surfactant on signal amplification has been carefully studied by the polarity-dependent DFT calculation. • The sensing properties including response time, sensitivity, selectivity, and anti-interference ability, have been fully studied. • This surfactant-assisted method enables the fluorescent monitoring of benfluralin in living plants. Developing an effective detection method for benfluralin (BFA) is of great significance, since BFA as most widely used herbicides can be bioaccumulated by aquatic organisms in environment, possessing potential risks to human health. Owing to aggregation-caused quenching effect, most fluorescent detection methods based on donor–acceptor organic fluorophores suffered from very low sensitivity towards BFA in water system, hampering the bioimaging application in plants. In this work, we reported a novel surfactant-assisted fluorescent probe enabling detection of BFA in water with a high sensitivity. The involvement of specific surfactant Triton X100 (TX100) could amplify the response signal of probe more than 100-fold. The detection limit for BFA was determined to be 80 nM, satisfying the environmental protection requirements. Moreover, we demonstrated applications of this strategy for the fluorescent imaging of BFA in plant. The absorbance of BFA into roots of Arabidopsis thaliana and castor seedlings was successfully observed based on this method. [ABSTRACT FROM AUTHOR]

[Display omitted] • A dicyanoisophorone-based fluorescent probe DCO2 with twisted N,N-diethylamino as donor is reported for the discrimination of HSA from BSA. • DCO2 could selectively bind with HSA compared to previous probe DCO1. • Experimental results indicated that specific spectral response to HSA was ascribed to the rigid donor structure and steric hindrance of DCO2. • DCO2 could accurately and sensitively detect HSA in the biological fluids. Despite the rapid development of fluorescent probe techniques for the detection of human serum albumin (HSA), a probe that discriminates between HSA and bovine serum albumin (BSA) is still a challenging task, since their similar chemical structures. As a continuation of our work, herein, a dicyanoisophorone-based fluorescent probe DCO2 is systematically studied for discrimination of HSA from BSA. The photophysical and sensing performances of DCO2 , including basic spectroscopic properties, sensing sensitivity, and selectivity, exhibits that DCO2 could selectively bind with HSA and display remarkable fluorescence enhancement (∼254-fold) at 685 nm. The gap of the fluorescent response of DCO2 between HSA and BSA is an obvious increase from 21% to 73% compared to the previous probe DCO1. The sensing mechanism was elucidated by Job's plot, displacement experiment, and molecular docking, suggesting that the specific response to HSA originated from the rigid donor structure and steric hindrance. DCO2 could be buried in the DS1 pocket of HSA, and only partly wedged into the DS1 pocket of BSA with exposing twisted N,N-diethylamino group outside. Application studies indicated that DCO2 has well detective behavior for HSA in the biological fluids. This work could provide a new approach to design HSA-specific near-infrared fluorescence probes. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new series of dicyanoisophorone fluorophores with different donor groups have been synthesized and their photophysical properties have been studied. • The fluorescent probe with p -dimethylamine and o -hydroxyl group exhibited the best sensing ability to human serum albumin. • The sensing mechanism was studied by Job's plot, replacement experiment, and molecular docking. • The fluorescent probe is capable of determination of albumin in real serum and urine samples. It is urgently needed to develop NIR-fluorescent probe for detection of human serum albumin (HSA) since the interference of short-wavelength-fluorescence from endogenous species in real serum and urine. However, most previous reports were located in the short-wavelength region (<600 nm). In this work, a series of dicyanoisophorone (DCO)-based fluorophores 1 – 4 with different donor groups have been designed and investigated. A systematic study of their photophysical properties has been carried out. Among these probes, 4 exhibited NIR emission with the highest fluorescence brightness and the most sensitive signal response to HSA. Further studies demonstrated that 4 could strongly bind into the DS1 pocket of HSA with a 1:1 ratio. Importantly, the method based on 4 has been proven to be capable of sensing HSA in real serum and urine samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel flavonoid probe is reported for fluorescence discrimination of HSA from BSA. • The sensing mechanism was studied by Job's plot, site-displacement experiment, and molecular docking. • The specific response to HSA was attributed to the albumin-induced restricted intramolecular rotation of flavonoid probe. Discrimination of human serum albumin (HSA) from bovine serum albumin (BSA) based on the fluorescence probe technique is still challenging due to similar chemical structures. In this work, a novel flavonoid-based fluorescent probe AF is reported for successful discrimination of HSA from BSA. The sensing performances of probe, including sensing dynamic, sensitivity and selectivity, have been carefully studied. Moreover, sensing mechanism was elucidated by Job's plot, displacement experiment, and molecular docking, suggesting that the specific response to HSA originated from the albumin-induced restricted intramolecular rotation (RIR) of probe. This work may provide a simple way for designing of novel probes for HSA with high selectivity. [ABSTRACT FROM AUTHOR]