Controllable Catalytic And Fluorescence Properties Of Gold Nanoparticles/Coumarin Embedded Multi-responsive Polymer Hybrids

Gold nanoparticles(Au NPs)are widely employed as catalysts because of their distinctive optoelectronic properties.However,the high surface energy entails effortless agglomeration and stern preservation which triggers the introduction of matrix to load and stabilize Au NPs.Among them,amphiphilic block copolymers with special functional groups could not only effectively stabilize Au NPs but also achieve high efficiency or multi-functional capabilities due to the imparted capability from the special groups to polymers.For example,coumarins are often embedded in the side chains to bring light-controlled encapsulation and release owing to the reversible crosslinking/de-crosslinking upon various UV light.In addition,the hydrophilic N-isopropylacrylamide(NIPAAm)may facilitate the self-assembling of amphiphilic polymers and bring thermal sensitivity.At various temperatures,the self-assembled aggregates will have different diastolic states.Ultimately,the copolymer could be multi-responsive if those two functional groups are employed simultaneously.Herein,an amphiphilic block copolymer P(NIPAAm-r-CA)-b-PMMA was synthesized by RAFT polymerization with coumarin units embeded in the side chain.Followed by a reduction of the therminal group to-SH,a relatively stable polymer aggregate after self-assembling could be prepared and it could be employed as a carrier of Au NPs through covalent bond between-SH and Au.Owing to the introduction of photoresponsive coumarin units and thermoresponsive PNIPAAm segments,the aggregate with Au NPs decorated onto the surface was provided with the reversible catalytic property by adjusting termpertrure and UV irradiation.The catalytic performance could be retained and reused even after 3 cycles of photo-or thermo-responsive regulation.Importantly,the fluorescence characteristics under different pH values were studied to clarify the mechanism of fluorescence emission,laying a necessary foundation for further visualization of the catalytic process.