Indirect Fluorescent Probes Based On Noble Metal Nanoclusters

As a type of novel fluorescent nanomaterials,noble metal nanoclusters have ultra-small size in structure.And they have attracted widely attention with advantageous characteristics,such as good stability,excellent optical properties,good biocompatibility and easy synthesis and so on.The fluorescence probe is mainly used to detect the target analyte based on the change of the fluorescence signal.In this dessertation,gold nanoclusters and silver nanoclusters were synthesized,which developed highly sensitive detections of nitrite ion,hydrogen peroxide and glucose using the indirect interaction between the target analyte and the nanoclusters.Nitrite plays an important role in the biology and food industries.However,intake of unusually high amount of nitrite will endanger human health,so the content of nitrite should be strictly monitored in various fields.In the first part of this paper,gold nanoclusters coated with bovine serum albumin(BSA-AuNCs)were synthesized and used as the fluorescence material.We found that nitrite could catalyze the redox reaction between bromate and iodide ions,and generate a large amount of iodine element,which could etch gold nanoclusters quenching the fluorescence.Therefore,we established a highly sensitive means for nitrite detection based on this catalytic fluorescence reaction.Fluorescence intensity linearly decreased in the 10 nM to 0.8μM nitrite concentration range.The limit of detection is 1.1 nM.The probe was successfully applied for water samples detection.As an important reactive oxygen species regulating biological process,hydrogen peroxide has become a health index in clinical diagnosis.In the second part of this paper,silver nanoclusters with polyethylenimine(PEI-AgNCs)as stabilizer were used as fluorescence materials.The fluorescence from these nanoclusters was efficiently quenched by reduced glutathione(GSH)through interaction from its thiol group.As an oxidant,hydrogen peroxide inhibited the effect of PEI-AgNCs-GSH,thus obtaining the recovery of fluorescence.This response was adopted for a turn-on fluorescence analysis of hydrogen peroxide,which presented a linear in the range of 0.1-20 μM with a detection limit at 35 nM.The scheme was further coupled with glucose oxidase for a glucose measurement down to 0.11 μM.This method was selective and was successfully applied for blood glucose measurement in human serum samples.