Preparation and self-assembly of NaYF4:Eu3+ nanocrystals-PNIPAm complex nanogels

Abstract In this work, NaYF4: Eu3+ nanocrystals were prepared by hydrothermal method, and then they were decorated by 3-butenylamine hydrochloride to obtain functionalized nanocrystals. After that, by a “graft-to” route of free radical polymerization of N-isopropylacrylamide (NIPAm), a complex nanogels of NaYF4:Eu3+-PNIPAm were synthesized. Finally, 3D self-assembled colloidal crystals (CCs) were fabricated by centrifugation. The microstructure of the nanogels was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and their thermo-sensitive performance was investigated by differential scanning calorimeter (DSC) and dynamic light scattering (DLS). Moreover, the self-assembly behavior of the nanogels was studied by Ultraviolet–visible absorption spectrum (UV–Vis) and photoluminescence (PL) respectively. The results indicated that concentration of the nanogels and environmental temperatures have significant effect on their self-assembly, due to volume variation of the 3D assemblies induced by environmental temperatures, its PL emission intensity changed drastically.