Highly selective and sensitive sensing of 2,4,6-trinitrophenol in beverages based on guanidine functionalized upconversion fluorescent nanoparticles

Abstract

In this study, a highly selective and sensitive fluorescent sensing method based on guanidine functionalized upconversion nanoparticles (UCNPs@GDN) for the detection of 2,4,6-trinitrophenol (TNP) has been developed. The oil-soluble UCNPs (NaYF4: Yb3+, Er3+) with the diameter of 80nm, which were synthesized by solvo-thermal method, were modified with 3-aminopropyltrimethoxysilane to obtain amine functionalized UCNPs (UCNPs@NH2). The aqueous dispersed UCNPs@GDN was obtained by changing the amine groups of UCNPs@NH2 into guanidine groups with s-ethylisothiourea hydrobromide. When excited by 980nm wavelength, UCNPs@GDN displayed three emission peaks at 365nm, 479nm and 550nm, respectively. The UCNPs@GDN exhibited strongly fluorescent quenching effect at 365nm in the presence of TNP, which can be applied to detect TNP based on fluorescence resonance energy transfer (FRET). When the concentration of TNP was in the range of 1×10−8–1×10−12M, the quenching intensity of fluorescent signal at 365nm was linear with the concentration of TNP. The detection limit of 7.78×10−13M for TNP was achieved. The present method showed high selectivity to TNP. Finally, six kinds of beverage samples containing the target were analyzed, which indicated that this method could be applied to the rapid and sensitive detection of TNP in beverages.