Development of NIR Responsive Upconversion Nanosensor for Turn-on Detection of 4-Nonylphenol

4-Nonylphenol（NP）is a kind of estrogen belonging to the endocrine disrupter，widely used in various agricultural and industrial goods. However，extensive use of NP with direct release to environment poses high risks to both human health and ecosystems. Herein，for the first time，we developed near-infrared（NIR）responsive upconversion luminescence nanosensor for NP detection. The Förster resonance energy transfer based upconversion nanoparticles（UCNPs）-graphene oxide sensor offers highly selective and sensitive detection of NP in linear ranges of 5-200 ng/mL and 200-1 000 ng/mL under 980 nm and 808 nm excitation，respectively，with LOD at 4. 2 ng/mL. The sensors were successfully tested for NP detection in real liquid milk samples with excellent recovery results. The rare-earth fluoride based upconversion luminescence nanosensor with NIR excitation wavelength，holds promise for sensing food，environmental，and biological samples due to their high sensitivity，specific recognition，low LOD，negligible autofluorescence，along with the deep penetration of NIR excitation sources.