Facile and large scale in situ synthesis of the thermal responsive fluorescent SiNPs/PNIPAM hydrogels

We herein report the synthesis of fluorescent silicon nanoparticles (F-SiNPs) with uniformly small sizes and stable fluorescence, and further preparation of F-SiNPs/poly(N-isopropylacrylamide) (F-SiNPs/PNIPAM) composite hydrogels by in situ polymerization. This type of hydrogel displayed visible thermal-sensitive phase transition properties. Upon heating, the fluorescence intensity of the hydrogels decreased sharply beyond the lower critical solution temperature (LCST) of PNIPAM. The process of fluorescence quenching and recovery was reversible after repeated heating and cooling cycles. This result suggests that the present organic/inorganic hybrid F-SiNPs/PNIPAM hydrogels will have potential applications in visual detection as fluorescence-based temperature sensors.