Nitrogen, sulfur-doped carbon quantum dots with large Stokes shift for real-time monitoring of pH in living cells

Self-assembly of S,N-codoped Ce/Cu bimetallic nanoparticles for fluorescence and visual detection of hexavalent chromium

Ce2(SO4)3 was doped into 4,6-diamino-2-mercaptopyrimidine (DAMP)-encapsulated copper nanoclusters (CuNCs) via a facile, rapid, low-temperature, and green self-assembly synthesis method to obtain fluorescent S,N-codoped Cu/Ce-DAMP nanoparticles (S,N-codoped Cu/CeNPs) for the detection of Cr(VI). The prepared Cu/CeNPs exhibit double emission peaks at 470 nm and 610 nm. The fluorescence emission at 610 nm is significantly enhanced due to the aggregation-induced emission (AIE) effect, and the quantum yield is as high as 20.19%. The fluorescence emission at 610 nm can be selectively quenched by Cr(VI) due to the internal filter effect (IFE) and dynamic quenching, whereas the weak fluorescence at 470 nm remains almost stable. On this basis, a fluorescence assay method for Cr(VI) was established, with good linearity in the concentration range 0.5-120 µM and a detection limit (LOD) of 134 nM. Using a smartphone to take photos of the fluorescence signals changes caused by Cr(VI) rapid visual detection is achieved with a linear range of 10-130 μM and a LOD of 2.35 μM. The proposed method was successfully applied to the detection of Cr(VI) in actual water samples.

A novel ratiometric fluorescent sensor from modified coumarin-grafted cellulose for precise pH detection in strongly alkaline conditions

Accurate and convenient monitoring of pH under extreme alkaline conditions is still a challenge. In this work, 4-(3-(7-hydroxy-2-oxo-2H-chromen-3-yl)-3-oxoprop-1-en-1-yl)benzamide (HCB), a coumarin derivative, was grafted onto dialdehyde cellulose (DAC) to obtain a sensor DAC-HCB, which exhibited a ratiometric fluorescent response to the pH of alkaline solutions, resulting in a significant fluorescent color change from yellow to blue (FI459 nm/FI577 nm) at pH 7.5-14. The structure of DAC-HCB was characterized through FT-IR, XRD, XPS, SEM. The pKa of sensor DAC-HCB was 13.16, and the fluorescent intensity ratio FI459 nm/FI577 nm possessed an excellent linear characteristic with pH in the scope of 9.0-13.0. Meanwhile, sensor DAC-HCB showed good selectivity, anti-interference, and fast response time to basic pH, which is an effective fluorescent sensor for examination of pH in alkali circumstance. The recognition mechanism of DAC-HCB to OH- was elucidated with HRMS and density-functional theory (DFT) computational analyses. Sensor DAC-HCB was successfully used for precise detection of environmental water samples pH. This work furnished a new protocol for test strips as a convenient and highly efficient pH detection tool for the high pH environment, and it has great potential for application in environmental monitoring.