Optimized Potassium Ion Detection Using Angular Interrogation SPR Enhanced by Multiwalled Carbon Nanotube-Nanocrystalline Cellulose

Abstract This study presented the enhancement of a plasmonic optical sensor utilizing the surface plasmon resonance (SPR) to detect potassium ions (K + ). The sensor performance was improved by integrating a nanocomposite carbon-based material, i.e., multiwalled carbon nanotubes-nanocrystalline cellulose (MWCNT-NCC), as the sensing layer. The SPR curve analysis was carried out by the evaluation of critical parameters, including the detection range, binding affinity, sensitivity, full width at half maximum (FWHM), data accuracy (DA), and signal-to-noise ratio (SNR). The results showed that the sensor detection range was between 0.08 ppm and 0.6 ppm before reaching saturation. The sensor also had a good sensitivity value of 0.595 6 °·ppm −1 . The Langmuir and Sips isotherm models were used for the binding affinity, and the calculated binding affinity constants were 1.586 6×10 5 M −1 and 1.644 1×10 5 M −1 , respectively, much higher than the previously reported binding affinity constant for metal ion detection. Based on the Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis, it was demonstrated that the MWCNT-NCC thin film contained COOH functional groups that might bind with K + through the electrostatic interaction, leading to improved sensing capabilities of the sensor.