title: Upconversion nanoparticles for ratiometric fluorescence detection of nitrite.
abstract: We have developed a selective upconversion switching method for the ratiometric fluorescence detection of nitrite using upconversion nanoparticles (UCNPs) and an efficient nitrite reaction. The green emission (λ(em) = 539 nm) of NaYF4:Yb(3+),Er(3+) nanoparticles can be selectively quenched by the neutral red (NR) dye due to the spectral overlap between the emission at 539 nm and the absorption of NR, while its red emission (λ(em) = 654 nm) remains unchanged. Nitrite reacts specifically and strongly with NR to form diazonium salt and lose the diazonium group, which sharply decreases the absorption of NR. Thus, the green emission of NaYF4:Yb(3+),Er(3+) can be recovered by increasing the amount of nitrite, leading to visible color changes from red to orange-yellow and finally green under excitation at 980 nm. The increase in the ratio of emission intensities (I539/I654) is quantitatively correlated to the concentration of nitrite ions. Moreover, the developed method has been successfully applied to nitrite detection in real samples such as drinking water, natural water and meat foods. In particular, the upconversion sensors can efficiently avoid background optical interference and thus show potential for the detection of nitrite salts in complex samples.
authors.affiliation: Department of Chemistry, University of Science & Technology of China, Hefei, Anhui 230026, China.
authors.forename: Junfen
authors.initials: J
authors.lastname: Han
authors.forename: Cheng
authors.initials: C
authors.lastname: Zhang
authors.forename: Fei
authors.initials: F
authors.lastname: Liu
authors.forename: Bianhua
authors.initials: B
authors.lastname: Liu
authors.forename: Mingyong
authors.initials: M
authors.lastname: Han
authors.forename: Wensheng
authors.initials: W
authors.lastname: Zou
authors.forename: Liang
authors.initials: L
authors.lastname: Yang
authors.forename: Zhongping
authors.initials: Z
authors.lastname: Zhang
mesh_terms: D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles; D009573:Nitrites / Q000032:analysis*; D013050:Spectrometry, Fluorescence / Q000379:methods*
chemical_list: D009573:Nitrites