Advances in the controlled assembly of nanoscale building blocks have resulted in functional devices which can find applications in electronics, biomedical imaging, drug delivery etc. In this study, novel covalent nanohybrid materials based upon [Ru(bpy)3](2+)-doped silica nanoparticles (SiNPs) and gold nanoparticles (AuNPs), which could be conditioned as OFF-ON probes for glutathione (GSH) detection, were designed and assembled in sequence, with the disulfide bonds as the bridging elements. The structural and optical properties of the nanohybrid architectures were characterized using transmission electron microscopy, UV-vis spectroscopy and fluorescence spectroscopy, respectively. Zeta potential measurements, x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were employed to monitor the reaction processes of the SiNPs-S-S-COOH and SiNPs-S-S-AuNPs synthesis. It was found that the covalent nanohybrid architectures were fluorescently dark (OFF state), indicating that SiNPs were effectively quenched by AuNPs. The fluorescence of the OFF-ON probe was resumed (ON state) when the bridge of the disulfide bond was cleaved by reducing reagents such as GSH. This work provides a new platform and strategy for GSH detection using covalent nanohybrid materials.
In this study, a highly sensitive and reliable method for the determination of 20 polyfluoroalkane substances (PFASs) in milk was established using the QuEChERS approach and an online interference trapping LC-MS/MS analysis. By a calibration with stable-isotope-labeled internal standards, we showed that the method displayed excellent linear dynamic ranges for 20 PFASs (correlation coefficients ≥0.997). The LOQs for the two types of PFASs, perfluorinated carboxylic acids (PFCAs) and perfluorinated sulfonic acids (PFSAs), were 0.010 and 0.050 μg/L, respectively. At the three spiking levels, the average recoveries for PFCAs ranged from 78.5 to 111% with the RSD (n = 6) within 1.20-13.1%, and those for PFSAs ranged from 72.8 to 105% with the RSD (n = 6) within 3.53-14.9%. By the developed method, 16 PFASs were found to be positive in 46 milk samples, and the levels for the PFASs with longer chains were significantly higher than those reported from other known regions.
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