Bimetallic AgNPs@dopamine modified-halloysite nanotubes-AuNPs for adenine determination using surface-enhanced Raman scattering.

A bimetallic nanoparticles modified halloysite nanotubes (HNTs) hybrid was prepared by embedding AgNPs and modifying AuNPs on the inner or outer wall of dopamine-modified HNTs (DHNTs) in sequence. The resulting bimetallic AgNPs@DHNTs-AuNPs hybrid as surface-enhanced Raman scattering (SERS) substrate exhibited improved enhancement ability over monometallic AgNPs@DHNTs, and DHNTs-AuNPs substrates, with intensity ratios of about 48:1:9 (crystal violet) and 11:1:2 (p-phenylenediamine). The giant SERS effect of AgNPs@DHNTs-AuNPs substrate is probably attributed to the synergetic enhancement of the electromagnetic field (Au/Ag), optical plasmon force, molecular enrichment (HNTs), and charge transfer (NPs-dopamine-molecules). The sensitive and reproductive AgNPs@DHNTs-AuNPs substrate was applied for SERS determination of adenine with a linear range of 0.010-0.50 mg·L-1 and a detection limit of 2.2 μg·L-1. The SERS method enables the rapid determination of adenine in fish, chicken kidney and heart, and serum samples, with recoveries of 83.5-121.6% and relative standard deviations of 2.5-7.9%. The SERS substrate has high value for rapid analysis of food and biomarker determinations. Schematic illustration of the preparation of AgNPs@HNTs-AuNPs for SERS analysis of adenine in complex sample.