Upconversion Fluorescence Detection Of Cr(?)and Glyphosate Contents In Instant Green Tea

Instant tea is popular with consumers because of its simple eating way and rich nutrition.However,with getting the higher concentration of nutrients in instant tea,harmful substances,such as heavy metals and pesticides,will also be enriched.There are many detection methods of these substances.But conventional detection methods usually need expensive detection instruments,complex sample processing or hard-operated micro derivative processing;as for rapid detection methods,they mainly rely on fragile and sensitive enzymes,antibodies,aptamers or other biological reagents.Therefore,we researched upconversion nanoparticles?UCNPs?synthesis and adopt its specific optical properties to develop the upconversion fluorometric detection system,and it realized the rapid and label free fluorescence detection of heavy metals and pesticides.The key accomplishments and results are outlined as follows:?1?A label-free fluorometric method for sensitive and selective detection of Cr?III?was developed by utilizing Na Y/Gd F₄:Yb,Er upconversion nanoparticles?UCNPs?and citrate-modified silver nanoparticles?CIT-Ag NPs?.The fluorescence of amino-modified UCNPs?NH₂-UCNPs?can be quenched due to aggregation of CIT-Ag NPs induced by Cr?III?via inner filter effect.The observed quenching in the fluorescence intensity of the UCNPs is found to be dependent on the concentration of Cr?III?.The fluorescence decreases linearly within the investigated concentration of 0.5?40?M Cr?III?with a limit of detection 34 n M.The practical applicability of the present sensing method is ascertained by detecting Cr?III?in spiked tap water and instant tea samples.?2?A dual?colorimetric and fluorometric?method was described for sensitive and selective determination of the herbicide glyphosate.It is based on a system composed of polyethylenimine-capped Na Gd F₄:Yb,Er upconversion nanoparticles?PEI-UCNPs?,copper?II?ions,hydrogen peroxide and 3,3?,5,5?-tetramethylbenzidine.The fluorescence of PEI-UCNPs?with emission peaks at 545 and 660 nm under 980 nm excitation?can be reduced in the presence of Cu?II?,because Cu?II?show its peroxidase mimicking activity to produce a blue oxidation product of 3,3?,5,5?-tetramethylbenzidine.In the presence of glyphosate,its strong affinity for Cu?II?leads to the formation of N-?phosphonomethyl?glycine copper?II?complexes.This inhibits the quenching ability and catalysis activity of Cu?II?.Hence,fluorescence is increasingly less reduced.Fluorescence at 660 nm increases linearly in the 0.05 to 125?g/m L glyphosate concentration range and the detection limit is found 9.8 ng/m L.The colorimetric assay has a detection ranges from5 to 125?g/m L,and the limit of detection is 1?g/m L.The developed upconversion detection method was used for specificity test and detection assay in real instant green tea samples,showing significant specificity and excellent practical application.