Synthesis and characterization of thermosensitive and polarity-sensitive fluorescent PNIPAM-coated gold nanoparticles

Thermosensitive PNIPAM-coated Au nanoparticles (AuNPs@P(NIPAM-co-MADMAC)) were synthesized by the radical grafting through copolymerization of 4-methacryloyloxy-4'-dimethylaminochalcone (MADMAC), MAEL-capped AuNPs and N-isopropylacrylamide (NIPAM) using azobisisobutyronitrile (AIBN) as the initiator. AuNPs@P(NIPAM-co-MADMAC) were characterized by transmission electron microscopy (TEM), ultraviolet-visible (UV-Vis) spectroscopy, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), H-1 nuclear magnetic resonance (NMR), and Fourier transform infrared (FTIR) spectroscopy. AuNPs@P(NIPAM-co-MADMAC) exhibited thermo-sensitivity from poly(NIPAM-co-MADMAC) chains and sensitive fluorescence from the MADMAC group. AuNPs@P(NIPAM-co-MADMAC) showed weak fluorescence after the temperature increased from 25 degrees C to 45 degrees C, or after beta-cyclodextrin (beta-CD) was added. Furthermore, it exhibited strong fluorescence when the solvent was changed to ethanol or chloroform.