Luminescent magnetic nanoparticles encapsulated in MOFs for highly selective and sensitive detection of ClO−/SCN− and anti-counterfeiting

Abstract

It is well-known that ClO⁻ and SCN⁻ can cause adverse effects on the environment and organisms; therefore, development of new strategies for detecting ClO⁻ and SCN⁻, especially in water, are highly desirable. Here, we present luminous Eu(III) complex-functionalized Fe₃O₄ nanoparticles encapsulated into zeolitic imidazolate framework materials (nano-ZIF-8) and successfully employ this nano-MOF as a fluorescence probe for selective and sensitive detection of ClO⁻ and SCN⁻. The introduction of ClO⁻ into nano-ZIF-8 solution induced a significant decrease in the characteristic fluorescence emission of Eu³⁺ at 613 nm. However, strong fluorescence emission was again observed when SCN⁻ was successively injected into the prepared nano-ZIF-8-ClO⁻. Thus, a novel fluorescence system for simultaneous detection of free ClO⁻ and SCN⁻ was established. On the basis of the superior adsorption performance of nano-MOF materials, free residual ClO⁻ and SCN⁻ in water was rapidly, sensitively and selectively detected with a detection limit of 0.133 nM and 0.204 nM, respectively. Moreover, nano-ZIF-8 was successfully used for monitoring the concentration levels of ClO⁻ and SCN⁻ in specimens of tap water and Yellow River water. Furthermore, the reversibility and regeneration of nano-ZIF-8 in sensing ClO⁻ and SCN⁻ is advantageous for applications of nano-ZIF-8 in solid-state sensing and anti-counterfeiting. As far as we know, this is the first time that nano-MOFs have been used as a selective fluorescence probe for ClO⁻/SCN⁻ detection and anti-counterfeiting.