Preparation Of Polymer-coated Gold Nanoparticles And Its Sensor Investigation

Gold nanoparticles (GNPs) have attracted continuous interest owing to theirunusual properties and potential applications in optics, catalysts, electrical and sensors.The polymer is the ideal carrier of the nanocomposites because of its good thermal andchemical stability. The hydrophilic polymer protected GNPs were widely believed toenhance the long-term stability in solution due to the abundant ionization groups.Based on the above background and new development tendence, the contents of thecorresponding four research works are shown as follows:(1) Selective detection of Cr3+using poly (methylacrylic acid) monolayer-protected gold nanoparticles. The GNPs with uniform size and distribution were firstlysynthesized by the citrate reduction method. The PMAA-@-GNPs was prepared by thestrong binding of the GNPs and the thiol ends groups of the PMAA. The monolayerstructure was proved by the dynamic light scattering, UV-visible spectra andtransmission electron microscopy. In the presence of Cr3+, the color of the solutionchanged from wine red to purple and could be measured by visual inspection. TEMresults demonstrated the induced aggregation of GNPs by Cr3+crosslinking carboxylgroups. The selectivity of Cr3+has also been investigated by comparing the colorchanges of solution with other metal ions. After-treatment by EDTA, the aggregatedPMMA-@-GNPs could be renewable and recycled detecting Cr3+.(2) Aggregation behavior of pH-and thermo-responsive block copolymerprotected gold nanoparticles. Two distinctive block copolymers protected GNPs wereprepared with SH-PMAA-b-PNIPAM and SH-PNIPAM-b-PMAA through strong gold-sulfur bonding. The hybrid NPs have a pH-responsive inner shell (or corona) and athermo-responsive corona (or inner shell) due to different location relations of thePNIPAM and PMAA on the surface of GNPs. Then, the aggregation behaviors, as wellas the changes of optical properties, of two hybrid NPs were compared in response toboth stimuli. The results showed the obvious inter-particles aggregation caused by the phase transition for hydrophobic coronal polymer. However, the particles ofhydrophilic corona layer retained good dispersion and the pH-responsive or thermo-responsive characteristics of shell layer made relatively minor changes.(3) Synthesis and temperature-anion responsiveness by self-assembly of ionicliquid block copolymers. The double-hydrophilic ionic liquid block copolymers(ILBCs), PNIPAM-b-PMMPImB was synthesized through two-step reversibleaddition-fragmentation chain transfer (RAFT) polymerization. It was observed thatincreasing the concentration of the (CF3SO2)2N-induced the micellization of PNIPAM-b-PMMPImB to form a core-shell structure containing the core with hydrophilicPMMPImB-(CF3SO2)2N-surrounded by the shell of PNIPAM. In addition, thethermally induced phase separation behavior of PNIPAM-b-PMMPImB caused themicelles with the shell of PMMPImB block around the core. The ionic liquid segmentwith strong hydrophilic property enhanced the hydrogen bonding interaction whichexpanded the temperature range of phase transition and increased the lower criticalsolution temperature (LCST) of the system.(4) Preparation of poly (reverse-ionic liquid) hydrogel containing goldnanoparticle and its anion responsiveness. Poly (ionic liquid) hydrogel wassynthesized by radical polymerization of N-vinly-N’-Ethylimidazolebromize anddivinylbenzene, then the hydrogel loading GNPs was obtained by one step in situreduction. We study the dispersion of GNPs in the poly (ionic liquid) hydrogel andthose anion responsive aggregate by UV-vis specture and TEM. It was found that theGNPs was well dispersed in the net of poly(ionic liquid) hydrogel with a spherica (2-5nm) and the SPR absorption peaks for527nm, due to the steric hindrance andelectrostatic interactions. Through the anion exchange between PF6-with Br-, the SPRabsorption peaks change of532nm, under the action of PF6-, the hydrogel turn fromhydrophilic to hydrophobic, and the gel contraction induced the aggregate of GNPsinside gel. The results show the effect of anion responsiveness initially.