Dual signal AA detection based on fluorescence and local surface plasmon resonance absorption technology.

The core/shell Au@MnO nanoparticles (Au@MnO NPs) were prepared and characterized by UV-vis spectrum, transmission electron microscopy (TEM) and X-ray photoelectron spectrum (XPS). It was found that MnO in the shell of Au@MnO NPs could oxidize thiamine (VB) into blue fluorescent thiochrome (TC). The reduction of MnO in the shell layer could lead to a decrease of Au@MnO NPs size along with a blue shift of the localized surface plasmon resonance (LSPR) peak. Once ascorbic acid (AA) was introduced, MnO in the shell was rapidly reduced to Mn ions. Accordingly, the oxidation of VB was inhibited and the fluorescence of TC was weakened. Based on these phenomena, we have established a dual signal method for AA determination with the help of UV-vis and fluorescence spectrophotometer. Under the optimum conditions, the LSPR absorption peak shift (Δλ) of Au@MnO NPs and the decrease in fluorescence of TC correlated well with AA concentration ranging from 0.75 to 17.5 μM. The detection limits of LSPR absorption assay and fluorescence assay were 0.18 and 0.47 μM, respectively. More importantly, this dual-signal detection method has been used for the determination of AA in vitamin C tablets with high accuracy and precision, indicating its promising potential applications.