Highly Stable 11-MUA Capped Gold Nanobipyramid for Refractive Index Sensing

Gold nanobipyramids (Au NBPs) are nanostructures with narrow plasmon resonances, which make them suitable for sensing applications. In the present work, Au NBPs of different aspect ratios were synthesized using a seed-mediated growth method by tuning the seed volume. The usual capping molecule CTAB was replaced by 11-mercaptoundecanoic acid (11-MUA), and the nanoparticle stability was studied. The 11-MUA capped NBPs were found to be more stable compared to the CTAB capped NBPs. The bulk refractive index sensitivities of all Au NBPs of CTAB and 11-MUA capped NBPs were measured using sucrose solutions of different weight percentages (0–30%). 11-MUA capped Au NBPs showed better refractive index sensitivity than CTAB capped Au NBPs. The NBPs of aspect ratio 3 showed maximum sensitivity of 353 nm/RIU.