dna detection based on localized surface plasmon resonance spectroscopy of ag@au biocomposite nanoparticles

Noble metal nanoparticles (nps) have attracted much attention due to their unique physical and chemical properties such as tunable surface plasmonics, high-efficiency electrochemical sensing, and enhanced fluorescence. we produced two biosensor chips consisting of ag@au bimetallic nanoparticles (bnps) on a carbon thin film by simple rf-sputtering and rf-plasma-enhanced chemical vapor co-deposition. we deposited au nps with average size of 4 nm (au1 nps) or 11 nm (au2 nps) on a sensor chip consisting of ag nps with mean size of 15 nm, and we investigated the effect of shell size (au nps) on the chemical activities of the resulting ag@au1 bnps and ag@au2 bnps. we estimated the average size and morphology of ag@au bnps by scanning electron microscopy (sem) and atomic force microscopy (afm) images. x-ray diffraction (xrd) patterns revealed that ag nps and au nps had face-centered cubic (fcc) structure. we studied aging of the biosensor chips consisting of ag@au bnps by localized surface plasmon resonance (lspr) spectroscopy for up to 3 months. uv–visible aging of the prepared samples indicated that ag@au1 bnps, which corresponded to ag nps covered with smaller au nps, were more chemically active than ag@au2 bnps. furthermore, we evaluated changes in the lspr absorption peaks of ag@au1 bnps and bare ag nps in the presence of a dna primer decamer at fm concentrations, to find that ag@au1 bnps were more sensitive biosensor chips within a short response time as compared to bare ag nps.