负载金纳米粒子的表面凹凸型聚合物微球的制备及其催化性能

Preparation and Catalytic Property of Au Nanoparticle Dispersed Polymeric Microspheres with Special Morphology

通过链转移自由基聚合和端基置换反应合成了聚N-异丙基丙烯酰胺(PNIPAAm)大分子单体,使其与丙烯腈和苯乙烯进行三元分散共聚,制得了表面具有凹凸形态的PNIPAAm接枝聚丙烯腈/聚苯乙烯聚合物(PNAS)微球。以四氯金酸为Au源,分别在50℃下进行醇热还原和室温紫外光还原,将与PNIPAAm酰胺基配位的Au3+原位还原成Au纳米粒子,负载在PNAS微球的表面。采用透射电子显微镜、X射线衍射、傅里叶变换红外光谱和紫外-可见光吸收光谱等方法对PNAS微球负载Au纳米粒子(Au-PNAS)进行了表征。表征结果显示,Au纳米粒子较均匀地负载在PNAS微球表面;采用醇热还原法,当c(Au3+)=0.0025mmol/L时有70%的Au纳米粒子的粒径小于10nm;采用紫外光还原法得到的Au纳米粒子的粒径相对较大,Au纳米粒子呈现多种形态;Au-PNAS微球具有良好的催化活性,在30min内可基本上将对硝基苯酚催化还原为对氨基苯酚。

Poly （N-isopropylacrylamide） （PNIPAAm） macromonomer with a vinyl end group was obtained by chain transferring radical polymerization and end capping reaction. PNIPAAm- polyacrylonitrile-polystyrene（PNAS） trimer microspheres with embossed morphology were prepared by dispersion copolymerization with PNIPAAm as stabilizer. Diameters of PNAS microspheres were in range of sub-micron. Au nanoparticles were dispersed evenly onto surfaces of PNAS microspheres by in situ reduction of Au3＋ water solution at 50 ℃ using ethanol as reducing agent or by UV irradiation reduction at room temperature. The properties of PNAS microspheres with dispersed Au nanoparticles （Au-PNAS） were studied by means of TEM, XRD, FTIR and UV-Vis spectrometry. Size of Au nanoparticles could be adjusted by changing Au^3＋ concentration of starting solution. By using 0.002 5 mmol/L HAuCl4 solution, the diameter of 70% of obtained Au nanoparticles were smaller than 10 nm. But by UV irradiation reduction, Au nanoparticles with larger diameters were obtained and showed different morphology. 4-Nitrophenol basically converted to 4-aminophenol in water medium in presence of Au-PNAS catalyst and sodium borohydride at ambient temperature after reaction 30 min.