Thermosensitive polymer stabilized core-shell AuNR@Ag nanostructures as "smart" recyclable catalyst

Core-shell AuNR@Ag nanostructures were synthesized and surface-grafted with thermosensitive poly(N-isopropylacrylamide) to enhance stability and endow stimuli-responsive property. The AuNR cores showed average dimensions of 8-nm diameter and 33-nm length, while the anisotropic silver shells displayed 1-2 nm thin side and maximal 8 nm fat side. The obtained polymer-stabilized AuNR@Ag nanostructures as catalysts showed normal Arrhenius change of apparent rate constant, k(app), in catalyzed reaction between 20 and 30 degrees C, but displayed a decrease of k(app) with respect to the temperature increasing between 32.5-40 degrees C, showing self-inhibition of the observed catalytic activity. Such "smart" self-inhibition of catalytic activity at enhanced temperature can be attributed to the thermosensitive response of the grafted polymer molecules and should be significant to control the reaction rate and avoid superheat for exothermic reactions. Such polymer-stabilized nanocatalyst also could be recovered and reused in the catalytic system.