Construction Of Repairable Catalystic Substrate Based On Multivalent Host-guest Interactions

For the prominent catalystic activity, size dependent optical properties,good biocompatibility and high extinction coefficient, gold nanoparticles(AuNPs) were extensively researched. Its catalystic property has involve in the field of industry. As precious mental, the reuse of AuNPs was popularly concerned. Therefore, more and more reuse methods were propersed in recent years. But most of them are transferred or cyclic dispersion and aggregation,which is not a real recovery. So there are a lot of scientists focus on the recovery of AuNPs now and many kinds of schemes were presened, including magnetic recovery, centrifugal separation and so on. No matter which scheme,it is necessary to combine with other substrates and the complex can't be separated after application or recovery. In particular, the substrates need to be clearned and dried before reused. So it's a waste of time, power and cost with such a batch mode. In consideration of the requirements of efficiency and economy of industry, it's worth noteing that AuNPs could be immobized on porous substrates or filamentous material, which was used to contruct continued-catalyze mode by filtering way. But the unrepariable limited its application. In view of the above problems, AuNPs functionalized catalytic substrates were prepared based on the high strength and photoresponse properties of multivalent host-guest interaction between ?-cyclodextrin (?-CD)and azobenzene (Azo).In previous expriments, the fixed AuNPs can't be separated from the substrate, which limits the function of AuNPs to some extent. In the first part of the experiment, the AuNPs with diameter of 17.27 nm were synthesized on the one hand. Afterwards, the AuNPs were coated with Azo through S-Au bond. On the other hand, modified ?-CD was combined to the nickel foam(PNi) by a layer-by-layer functionalization and the obtained substrates allowed the immobilization of Azo coated AuNPs with multivalent host-guest interactions. When exposed to UV light, the host-guest interactions between Azo and ?-CD failed, which caused the release of AuNPs. On the contraty,AuNPs would be recombined to PNi under visible light irradiation. The AuNPs can be released and recoveried on demand with such a switching process.For the steric hindrance effects, limited number of Azo can exist on the surface of AuNPs, which affect the immobilization of heavy AuNPs just through multivalent host-guest interactions. In the second part of the experiment, ?-CD coated AuNPs with diameter of 3.27 nm were prepared and immobilized to the suface of Azo functionalized PNi through multivalent host-guest interactions. The obtained substrate can be used as solid catalyst for the reduction of 4-nitrophenol and the catalytic efficiency higher than 96%. In addition, when AuNPs modified substrates were cut into small pieces and packed into a 2 mL syringe, a "catalytic bed" with catalytic efficiency close to 95% was constructed. What's more, the deactivated AuNPs could be removed and the "catalystic bed" was repaired in-situ according to the release mechanism of the first part, which meets the demand of industry to a great extent.