Preparation And Properties Of PNIPAM/AuNPs Organometallic Hybrid Particles

Gold nanoparticles(AuNPs)have excellent optical and catalytic properties,making them widely used in catalysts,biomedicine,new materials and other fields.Due to its high surface energy,and it is prone to irreversible aggregation.The smart responsive polymer composite with AuNPs can not only improve the stability of AuNPs,but also give the hybrid particle smart responsive characteristics.In this thesis,a temperature responsive polymer poly(N-isopropylacrylamide)(PNIPAM)and citrate-stabilized AuNPs are combined to construct the PNIPAM/AuNPs temperature responsive system by using the "Au-S" covalent bond and electrostatic interaction.The multi-functional organometallic hybrid particles with two different configurations(core-shell and surface-covered)and dual applications(colorimetric temperature-sensor and temperature-switchable smart catalysis)are successfully obtained.The main works of this thesis are as follows:(1)PNIPAM with thiol end group(PNIPAM-SH)was prepared by RAFT polymerization and reduction reaction,and then PNIPAM-SH was grafted onto the surface of AuNPs by the "grafting to" method to construct core-shell hybrid nanoparticles.PNIPAM-SH with a number-average molecular weight of 6900 g/mol are immobilized on the surface of AuNPs with a particle size of 14.8 nm,the thickness of PNIPAM shell of the core-shell hybrid nanoparticles is about 2.6 nm by TEM.(2)The core-shell PNIPAMs-AuNP hybrid nanoparticles have temperature-responsive in water or salt solution at 25-50?,and the stability of AuNPs grafted with PNIPAM in salt solution is improved.The color of PNIPAMs-AuNP hybrid nanoparticle dispersion change under the action of temperature and salt,and it can be used as a colorimetric temperature sensor.Increasing the salt concentration and adding different type of salt,it can aggravate the color change of the dispersion,and improve the sensitivity of the sensor.The degree of changes is followed MgCl2>KCl>NaCl.(3)The reduction reaction of 4-nitrophenol is used as a catalytic model to investigate the effect of reaction temperature on the catalytic rate of the hybrid nanoparticles.The results show that the PNIPAMs-AuNP hybrid nanoparticles have temperature-switchable catalytic performance and can be recycled.The catalytic rate first increases and then decreases with the increase of the reaction temperature.(4)PNIPAM microgel with positive surface charge is prepared by soap-free emulsion polymerization,and then combined with citrate-stabilized AuNPs to prepare surface-covered PNIPAM-AuNPs hybrid particles by electrostatic interaction.The effect of the AuNPs contents,mixing method and PNIPAM crosslinking degree on the temperature responsive of the PNIPAM-AuNPs hybrid particles are investigated.The hybrid particles prepared by standing at 25? for 1 h have the best stability.The temperature responsive of the hybrid particles prepared by using PNIPAM microgel with a low cross-linking degree is more obvious,and can be directly used as a colorimetric temperature-sensor when dispersed in pure water.(5)The catalytic activity of the surface-covered hybrid particles is higher than that of the core-shell hybrid nanoparticles,and they also have temperature-controllable catalytic performance.As the reaction temperature increases,the catalytic rate first decreases and then increases.