Fabrication of fluorescent SiO2@zeolitic imidazolate framework-8 nanosensor for Cu2+ detection

A simple strategy to fabricate a fluorescent SiO2@zeolitic imidazolate framework-8 (ZIF-8) core–shell nanosensor for Cu2+ detection was demonstrated in this work. The nanosensor was synthesized using carboxyl-functionalized SiO2 nanoparticles (SiO2 NPs) as a template to induce the growth of ZIF-8 on its surface. The porous SiO2@ZIF-8 exhibited extremely good adsorption properties and a large specific surface area to accumulate Cu2+, and the pyridyl nitrogen sites in imidazole played vital roles in the recognition of Cu2+. The fluorescent intensity decreased linearly with the increasing of Cu2+ concentration in the range of 10–500 nM and the detection limit was estimated to be 3.8 nM. The SiO2@ZIF-8 nanosensor could be further used to determine trace amounts of Cu2+ in real water samples, while some previous sensors had to be dispersed in organic solution for use, such as DMSO and MeCN. The core–shell nanostructures of SiO2@ZIF-8 made it possible for it to be dispersed directly in aqueous solution and prevented ZIF-8 from aggregation, which enhanced the sensing performance of the SiO2@ZIF-8 nanosensor.