Miniaturized nanohole array based plasmonic sensor for the detection of acetone and ethanol with insights into the kinetics of adsorptive plasmonic sensing

Abstract

The present work demonstrates development of a miniaturized plasmonic platform comprised of a Au nanohole array (NHA) on a Si/Si₃N₄ substrate. Plasmonic responses of the NHA platform, which is coated with Cu-benzenetricarboxylate metal organic framework (MOF), are found to be promising even towards 500 nmol mol⁻¹ (ppb) of acetone or ethanol vapors at room temperature. The sensing characteristics are further investigated by varying the operating temperature (296 K to 318 K) of the sensor and the concentrations of vapors (500 nmol mol⁻¹ to 320 μmol mol⁻¹). The plasmonic responses for the sensors are correlated with the adsorption of vapors on the MOF surface and modeled in accordance to Langmuir-type adsorption. Kinetic parameters are estimated for the adsorption of fixed concentrations of acetone and ethanol vapors within the studied operating temperature range. The linear variation of characteristic response time constants with the operating temperature provides Arrhenius activation energies for the adsorption of acetone and ethanol vapors. The comparatively lower activation energy estimated for the adsorption of ethanol results in faster and more sensitive response of the sensor towards that analyte. The plasmonic sensor for the detection of nmol mol⁻¹ level acetone and ethanol vapors at room temperature along with the kinetic correlation on plasmonic response with the adsorption of the analytes described herein offer new insights to existing reports on surface modification and plasmonic detection.