Polyethyleneimine-assisted one-pot synthesis of Au nanodendrites on carbon nanotube sheet as an efficient SERS substrate

A polyethyleneimine (PEI)-assisted simple and efficient one-pot hydrothermal reduction method is reported to prepare high-quality gold nanodendrites (AuNDs) on a carbon nanotube (CNT) sheet. We observed that the prepared AuNDs have a well-defined backbone-multiple branching structure. With the systematical investigation of the growth mechanism, it was found that the bromide (Br⁻) ion concentration has an essential effect on the formation of AuNDs. By evaluating the growth conditions of AuNDs, it was demonstrated that PEI attached on the surface of CNT sheet plays multiple crucial roles as a reducing agent, stabilizer, and structure director in the formation of AuNDs. The prepared CNT-AuNDs hybrid was employed as a flexible surface-enhanced Raman scattering (SERS) substrate to detect the analyte Congo red (CR). Due to the unique structure of AuNDs, such as 3-D branches, rough surface, and sharp edges, the analyte can be detected efficiently down to a concentration as low as 1 × 10⁻⁸ M with an enhancement factor as high as 5.6 × 10⁷.