RESUMEN
Excessive fluoride ion (F-) in the environment can affect health and even endanger life when ingested by the human body. However, most fluoride probes have the disadvantages of low sensitivity and long detection time. Herein, fluorescent probe 3a is successfully synthesized by linking two acetylenyltrimethylsilyl groups at both ends of the fluorinated benzothiadiazole core. After the addition of F- to 3a, the emission at 436 nm is significantly quenched and slightly blue-shifted. It is confirmed by electrospray ionization high-resolution mass spectrometry (ESI-HRMS) and density functional theory calculations (DFT) that these changes are due to the F- triggered Si-C bond cleavage and the subsequent inactivation of intramolecular charge transfer (ICT). The detection limit and response time of probe 3a for F- are 10-8 mol/L and 25 s, respectively. Importantly, fluorescent material 3a can be processed into portable test tools for the visual detection of fluoride ion.
RESUMEN
Microplastic-derived dissolved organic matter(MPDOM) during the aging process could be complexed with organic pollutants, heavy metals, and other contaminants and thus affect their migration and transformation. In this study, two types of microplastics, polyethylene terephthalate(PET) and polystyrene(PS), were selected to investigate the spectral properties of MPDOM and their effect on the complexation between MPDOM and sulfadiazine(SDZ)/copper ion(Cu2+) using the fluorescence quenching method, various spectroscopic analysis techniques, and the Ryan-Weber quenching model. The results of UV-vis absorption spectroscopy analysis showed that the molecular weight of the two MPDOMs decreased; the aromaticity and humification increased; and the carboxyl, carbonyl, hydroxyl, and ester substituents on aromatic rings increased after aging. The fluorescence quenching process between MPDOM and SDZ/Cu2+ was static quenching. After quenching, the aromaticity and humification of the two MPDOMs were similar, and the molecular weights were comparable. Combined with three-dimensional fluorescence spectra and parallel factor analysis, two humic-like components and one protein-like component were identified. In addition, the protein-like components of MPDOM reacted preferentially with SDZ and were more sensitive to Cu2+. The results of the Ryan-Weber quenching model revealed that the binding ability of humic-like components to PET-DOM was higher in both SDZ and Cu2+ quenching systems, but the binding ability of MPDOM in the SDZ quenching system was generally stronger than that in the Cu2+ system.
RESUMEN
In this study, montmorillonite-supported nanoscaled zero-valent iron (Mt-nZVI) composites were fabricated using a facile liquid-phase reduction method to avoid serious agglomeration of nZVI particles in suspensions due to magnetic effect. The morphology, crystal structure, functional groups, and magnetic properties of as-prepared composites were explored using scanning and transmission electron microscope, X-ray diffractometer, Fourier transform infrared spectroscope, X-ray photoelectron spectroscope, zeta potential analyzer, and superconducting quantum interference device. The fabricated composites were then applied to remove antibiotic oxytetracycline from water. The optimal weight ratio of the Mt particles (mean size, 25 µm) to the nZVI particles (size, 60-100 nm) was first determined to be 2:1 (simply denoted as 2Mt-nZVI). Experimental results showed that 99% of 100 mg/L oxytetracycline at pH 5.0 was removed using 0.6 g/L of the 2Mt-nZVI composite and the mineralization reached 70% after 20 min of reaction. Finally, the transformation products and intermediates were detected and identified by a high-resolution liquid chromatography mass spectrometry (LC-MS) and the pathways were proposed during the degradation of oxytetracycline over the 2Mt-nZVI composite.
