Plasma- and anneal-assisted hybridization of SWCNT-Au network for rapid and high-sensitive electrical detection of antibody-antigen interactions

Abstract

A novel strategy is proposed to facilely hybridize the single-walled carbon nanotubes (SWCNTs) and gold nanoparticles (Au NPs) with the assistance of a mild O₂-plasma process and annealing at 500 °C in air. An immunosensor was constructed by the SWCNT-Au network bridging an interdigital electrode. The O₂-plasma-oxidized SWCNTs can easily assemble positively charged Au NPs with a high-density and uniform morphology. The annealing leads to surface melting and aggregation of the Au NPs and makes the survival of the SWCNTs much less likely, moreover, it helps to remove any impurities adsorbed on the SWCNT-Au and to form a good contact between the network and the electrode. The annealing-induced alterations result in an interesting power-law current–voltage behavior because of the Au NPs cotunneling effects and its energy-band modulation of the SWCNTs, and greatly amplify the sensitivity on antibody-antigen interactions. The sensor realized high-sensitive, rapid, and selective detections of Salmonella enteritidis flagellin (SEF) and Staphylococcus aureus enterotoxins A (SEA), which was functionalized with the SEF antibody (anti-SEF) and the SEA antibody (anti-SEA), respectively. The results demonstrate a detection limit of at least 2 ng mL⁻¹ in 5 min incubation for the antibody–antigen reaction. The proposed strategy represents a novel, robust, and simple way to establish immunosensor chips.