The detection of trace water (H 2 O) content is important and challenging in food and food-related industries. Herein, highly crystalline two-dimensional covalent organic frameworks (TAPT-BTCA-COF) with yellow-green fluorescence were prepared by using 1,3,5-tris(4-aminophenyl)triazine (TAPT) and 1,3,5-benzenetricarboxaldehyde (BTCA) as precursors. The fluorescence of TAPT-BTCA-COF is sensitive to the solvent polarity due to the intermolecular charge transfer (ICT) effect and can be quenched by trace H 2 O due to the block of ICT effect by H 2 O. On this base, TAPT-BTCA-COF is applied for sensing of trace H 2 O in common organic solvents such as DMF, acetonitrile , THF and acetone with fast response and high sensitivity. The limits of detection for H 2 O in DMF, acetonitrile, THF and acetone are 0.082 wt%, 0.0053 wt%, 0.0091 wt% and 0.0061 wt%, respectively. Furthermore, a ratiometric fluorescent sensor is proposed by using TAPT-BTCA-COF as the signal probe and red fluorescent tris(2,2′-bipyridyl)ruthenium(II) dichloride as the reference and successfully applied for quantitatively and semi-quantitatively sensing of trace H 2 O in honey sample and the moisture in N 2 gas.
Reducing the dissolution of Mn from LiMn 2 O 4 (LMO) and enhancing the stability of film electrodes are critical and challenging for Li + ions selective extraction via electrochemically switched ion exchange technology. In this work, we prepared a nitrogen-doped carbon cladding LMO (C-N@LMO) by polymerization of polypyrrole and high-temperature annealing in the N 2 gas to achieve the above purpose. The modified C-N@LMO film electrode exhibited lower Mn dissolution and better cyclic stability than the LMO film electrode. The dissolution ratio of Mn from the C-N@LMO film electrode decreased by 42% compared to the LMO film electrode after 10 cycles. The cladding layer not only acted as a protective layer but also functioned as a conductive shell, accelerating the migration rate of Li + ions. The intercalation equilibrium time of the C-N@LMO film electrode reached within an hour during the extraction of Li + ions, which was 33% less compared to the pure LMO film electrode. Meanwhile, the C-N@LMO film electrode retained evident selectivity toward Li + ions, and the separation factor was 118.38 for Li + toward Mg 2+ in simulated brine. Therefore, the C-N@LMO film electrode would be a promising candidate for the recovery of Li + ions from salt lakes.
危险品化学品经营许可证（带存储）