An electrochemical aptasensor based on the amplification of two kinds of gold nanocrystals for the assay of L-histidine with picomolar detection limit

Au nanocrystals (NCs) enclosed by higher-index facets have high surface chemical activity. They attract much attention because of their excellent biocompatibility. In this work, well-defined elongated tetrahexahedral (ETHH) Au NCs and end-truncated ETHH with high-index facets are successfully prepared by using a single surfactant system of didodecyldimethylammonium bromide (DDAB) and a binary system of cetyltrimethylammoniumbromide and DDAB in two-step seed-mediated growth. The characteristics of high-index facet Au NC modified electronic aptamer-based sensors are presented and they are applicable to a wide range of aptamers. Herein, we only take L-histidine as the representative sensing target. With modification of the Au NCs, a very low detection limit (sub-picomolar) is obtained. In particular, a detailed sensitivity comparison between the modification of end-truncated ETHH and ETHH Au NCs is presented to demonstrate the slight difference in the chemical activities of Au NCs with different high-index facets. Our work sheds light on the large scale fabrication of Au/metallic NCs with high-index facets and also provides a new eye-opening example of engineering ultra-sensitive DNA sensors based on Au NCs.