Theoretical modelling of Au and Ag hollow cylinders for high resolution refractive index sensing of bio-analytes and gases

Abstract

A highly sensitive yet simple plasmonic refractive index (RI) sensor consisting of Au trimer hollow nanocylinders surrounded by an Ag hollow nanocylinder is proposed with a wide range of applications in the near IR range. The plasmonic behaviour of the structure is studied by analysing the absorption cross-section on illumination by electromagnetic (EM) wave using the finite element method (FEM). Nanoscale detections can be realized by using the shift in resonance wavelength of localized surface plasmon resonance (LSPR) in response to the change in RI. The optimized RI sensor gives a maximum sensitivity of 2545.4 nm/RIU, figure of merit (FOM) of 43.90 RIU−1 and sensor resolution of the order of 10−5 RIU. The proposed sensor can detect even small variations in RI of the order of 10−5 RIU with a sensitivity of 1998 nm/RIU. With the observed high sensitivity, resolution and quality, the sensor can contribute a lot to health-care applications and is found highly suitable for multiple detections covering broad range of RI including bio-analytes, chemicals, and gases.