Imparting biomimetic ion-gating recognition properties to electrodes with a hydrogen-bonding structured core-shell nanoparticle network

This paper presents findings of the creation of biomimetic ion-gating prope rties with core-shell nanoparticle network architectures. The architectures were formed by hydrogen-bonding linkages via an exchange-cross-linking-pre cipitation reaction pathway using gold nanoparticles capped with thiolate s hell and alkylthiols terminated with carboxylic groups as model building bl ocks. Such network assemblies have open frameworks in which void space is i n the form of a channel or chamber with the nanometer-sized cores defining its size, the geometric arrangement defining its shape, and the shell struc tures defining its chemical specificity, The formation of the network linka ges via head-to-head hydrogen-bonded carboxylic terminals and the reversibl e pH-tuned structural properties between neutral and ionic states were char acterized using infrared reflectance spectroscopic technique. The biomimeti c ion-gating properties were demonstrated by measuring the pH-tuned network "open-close" responses to charged redox probes. Such redox responses vr er e shown to depend on the degree of protonation-deprotonation of carboxylic groups at the interparticle linkages, core sizes of the nanoparticles, and charges of the redox probes. Differences in structural networking, pH-tunin g, and electrochemical gating properties were identified between the networ k films derived from nanoparticles of two different core sizes (2 and 5 nm) , The mechanistic correlation of these structural properties was discussed. These findings have added a new pathway to the current approaches to biomi metic molecular recognition via design of core-shell nanoparticle architect ures at both nanocrystal and molecular scales.