The construction of silver aggregate with inbuilt Raman molecule and gold nanowire forest in SERS-based immunoassay for cancer biomarker detection

Heterostructures of one-dimensional gold nanowires supported silver aggregates with a large amount of hotspots are promising for future SERS-based immunoassay. In this paper, silver aggregates with various coordination numbers were first obtained through adjusting the ligand incubation time and encapsulated by polystyrene-block-poly(acrylic acid). The SERS intensity of inbuilt Raman molecule (2-naphthalenethiol) in silver aggregates increased gradually with the increase of coordination number and the largest SERS enhancement ratio of the aggregates to single nanoparticles finally reached to 10. After decorating the silver aggregates onto the vertically aligned ultrathin gold nanowire forest, much more intensive SERS signals were observed compared with those on bare silica wafer. This promising result can be attributed to the strong surface plasmon coupling at the interface regions of the two materials that introduced multiple co-enhanced hotspots in the heterostructures. Then, the silver aggregates were modified with antibody and employed in immunoassay with immune gold nanowire forest as substrate. This SERS immunosensor exhibited a wide linear range (1 mu g mL(-1) to 1 fg mL(-1)) and an ultra-low detection limitation of 1 fg mL(-1) for PSA. (c) 2017 Elsevier B.V. All rights reserved.