Spectrofluorometric determination of berberine using a novel Au nanocluster with large Stokes shift.

Berberine hydrochloride (BHC), a natural isoquinoline alkaloid, is widely applied as a an agent in traditional Chinese medicine. Almost all the traditional methods for BHC detection require complicated preprocessing steps or expensive instruments. In this article, we report a simple, rapid, sensitive, and selective method for BHC detection using fluorescent gold nanoclusters (F-AuNCs) as the fluorescent probe with a large Stokes shift of 237 nm. The F-AuNCs prepared with citrate-stabilized stannous chloride and hydrogen tetrachloroaurate(III) as raw materials in an aqueous medium display strong and stable fluorescence at 566 nm. When F-AuNCs are mixed with BHC, the fluorescence of F-AuNCs is effectively quenched. Under optimized conditions, this method allows sensitive and selective measurements of BHC in a concentration ranging from 1.0 × 10-6 to 1.0 × 10-4 mol L-1 with a detection limit of 7.5 × 10-8 mol L-1, which is relatively low among reported spectral methods. This method provides excellent selectivity for the detection of BHC against inorganic anions and natural amino acids. In addition, the BHC content in two different types of berberine tablets was successfully determined by this method and the results showed high accuracy. Graphical Abstract ᅟ.

Hydrothermal carbons/ferrihydrite heterogeneous Fenton catalysts with low H2O2 consumption and the effect of graphitization degrees.

As the heterogeneous Fenton reactions are always restricted by the unsatisfied reduction efficiency of Fe(III) and ineffective consumption of H2O2, many strategies have been developed. In this work, we prepared hydrothermal carbons (HTC) with different graphitization degrees using glucose under different hydrothermal times, and then they were combined with ferrihydrite (Fh). Interestingly, although 30%HTC/Fh has much better BPA degradation efficiency than Fh (26 times larger of calculated degradation rate constants), the decomposition rate of H2O2 in the former system is lower. The generated Fe(II) of HTC/Fh is much higher than that of Fh during the heterogeneous Fenton reactions, and the degradation of BPA is almost unaffected by p-benzoquinone (scavenger of superoxide radicals (O2•-)) while greatly inhibited by isopropanol (scavenger of hydroxyl radicals (HO•)). These results indicate that HTC act as electron donors due to the abundant carbon-centered persistent free radicals (PFRs) to directly reduce Fe(III) to Fe(II) and therefore decrease the H2O2 consumption by Fe(III), which subsequently inhibits the generation of less active O2•- and promote the utilization efficiency of H2O2. HTC with a low graphitization degree contain more PFRs for Fe(III) reducing, significantly enhancing the Fenton catalytic activity of Fh.