In this paper, we have presented a novel graphene quantum dots based upconversion fluorescent sensor for detection of phosphate. The upconversion fluorescence of graphene quantum dots with emission wavelength at 407 nm was quenched by rare earth ion, Eu 3+ in proper concentration. The quenching constant is calculated from Stern-Volmer equation. Importantly, quenched fluorescence of graphene quantum dots-Eu 3+ could be recovered with the addition of phosphate based on a competition mechanism, which provides a turn-on sensing strategy for phosphate assay. The recovered fluorescence is proportional to the concentration of phosphate. The linear range for the detection of phosphate was 1 to 12 μM with a detection limit of 100 nM. The proposed sensing system has been successfully used for the assay of phosphate in real river water samples, indicating the practical potential.
Iridium nanoparticles (IrNPs) have shown intriguing enzyme-like activities, however, the mechanism behind their versatile enzymatic behaviors is still elusive. A new kind of IrNPs stabilized with β-cyclodextrin (CD) was prepared...
Selective removal of an organic compound in the coexistence of other constituents is a great challenge in separation and purification processes. In this work, bovine serum albumin (BSA) stabilized iridium...
A weaker solvent was constantly added at the middle of
the two
columns to set up a two-step solvent gradient in twin-column recycling
chromatography so that the eluotropic strength of the downstream liquid
was reduced. Therefore, the back edge of the band moved faster than
the front edge during the circulation of the solute band, initiating
special gradient compression to effectively counteract the band spreading.
Herein, modified recycling chromatography was applied to the simultaneous
purification and concentration of minor impurities in the bulk drug.
Taking orlistat as an example, the target impurity with only 0.7%
content in orlistat bulk drug was isolated, giving a purity of 96%.
Its concentration was enhanced by 9.4 times. Investigations on operating
conditions verified that decreasing the eluent eluotropic strength,
increasing the solvent gradient, extending the column switching interval,
and enhancing the number of switches within proper ranges were beneficial
to the improvement of separation.
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