Electrochemical Sensor Based on N–Doped Carbon Nanodots Derived from the Agro-Waste Cotton Boll Peel Extracts for Nano Molar Determination of an Anti-Cancer Drug, Pemetrexed

Abstract

A green and facile one-step synthetic route was proposed for the synthesis of nitrogen-doped carbon nanodots (N-CDs) from agro-waste cotton boll peel extract as a natural carbon source and glycine as a nitrogen source. The prepared N-CDs were utilized further in the fabrication of an electrochemical sensor for the nanomolar determination of an anti-cancer drug, pemetrexed (PMT). The electrode material was characterized by XRD, FTIR, TEM, Raman, EDX, UV–vis, fluorescence, cyclic voltammetric and electrochemical impedance spectroscopic studies. The N-CDs drop-casted on the surface of glassy carbon electrode (GCE) served as a good sensing material and exhibited electrocatalytic activity as evident from ∼20-fold enhancement in the oxidation peak current of PMT at N-CDs/GCE with 130 mV lesser positive oxidation peak potential than that at bare GCE. This was attributed to excellent conductivity, higher electroactive surface area, graphitic cores of N-CDs besides the interactions between PMT and N-CDs via hydrogen bonding and π–π stacking. The sensing performance of the demonstrated electrode was optimized by varying the peak current dependant parameters and also by investigating the influence of interfering substances in the determination of PMT. The electrochemical behaviour of PMT at different pH revealed the adsorption controlled electrode process with the involvement of protons. Under optimized conditions, differential pulse voltammetric (DPV), square wave voltammetric (SWV) and adsorptive differential pulse voltammetric (AdSDPV) methods were developed for sensitive determination of PMT at nano molar level. Further, these developed analytical methods were applied successfully for the determination of PMT in analyte fortified human urine samples and pharmaceutical formulations.