LSPR optical fibre sensors based on hollow gold nanostructures

Compared to solid gold nanoparticles (AuNPs) which have been widely used for the construction of localized surface plasmon resonance (LSPR) sensors, hollow gold nanoparticles have attracted greater attention recently due to the stronger plasmonic effect that they demonstrate. Combining this with the known advantages of the use of fibre optic technology, a portable, reliable and highly sensitive sensor system has been developed and reported in this study and evaluated for various potential sensing applications. In this work, hollow gold nanocages have been designed and the synthesized specifically for the development of a LSPR-based optical fibre sensor, in this case for Refractive Index (RI) measurement. In doing so, different hollow structures of nanogold have been synthesized and characterized and the experimental results obtained show that the sensitivity of the hollow nanostructure-based LSPR sensor, in response to known RI variations, is closely related to the hollowness of the gold nanocages. It was observed that with the decrease of the wall thickness of the nanocages, the sensitivity of the LSPR sensor created increases dramatically and this is due to the strong plasmonic coupling seen between the interior and exterior fields. Compared to the LSPR sensors based on solid-nanoparticles reported earlier by the authors, the nanocage-based sensor created in this work has demonstrated an excellent sensitivity of 1933 nm/RIU, thus showing a significant improvement of at least 3 fold in sensitivity from that prior work.