Laser-ablated core-shell nanostructures of MWCNT@Ta2O5 as plasmonic framework for implementation of highly sensitive refractive index sensor

Abstract

Refractive index is a crucial physical parameter to be estimated in myriad analytical procedures, biological and physico-chemical processes, and a variety of industrial operations. This work describes a nanomaterial-assisted strategy for highly sensitive investigation of refractive index variations utilizing core-shell nanostructures having multi-walled carbon nanotubes as core surrounded by tantalum (v) oxide shell (MWCNT@Ta2O5). Pulsed laser ablation technique using Q-switched Nd:YAG laser is used to synthesize MWCNT@Ta2O5 core-shell nanostructures in liquid phase. Their refractive index sensing attributes are probed by measuring absorption spectra corresponding to core-shell nanostructures prepared using glucose solutions of varying refractive index values spanned in range 1.33–1.39 as solvent. A red shift equaling ∼8 nm in peak absorption wavelength is attained with an increase in solvent refractive index. The operating parameters including the laser fluence and ablation duration are optimized to fine tune the sensing performance. Morphologically characterized by SEM, TEM and EDS, MWCNT@Ta2O5 core-shell nanostructures exhibit sensitivity and limit of detection of 240 nm/RIU (at refractive index 1.33) and 1.62×10−3 RIU, respectively. Further, the sensitivity follows a linear declining trend in the considered refractive index range of 1.33–1.39. The distinguished analytical features furnished by the nanostructured material in a wide refractive index range project it as an efficient scaffold for refractive index measurements for various applications in different disciplines.