Carbon Spherical\nShells Functionalized with Nitrogen\nas Sustainable Electrochemical Materials for Rapid Detection of Diclofenac\nin Saliva, Urine, Water, and Tablets

We introduce a facile\nstrategy to obtain nitrogen-functionalized\ncarbon spherical shells (N-CSSs). These N-CSS were prepared using\nan eco-friendly hydrothermal synthesis with urea and an aqueous dispersion\nof carbon spherical shells (CSSs) produced with water and glucose\ngreen precursors. The urea/CSS mass ratio was varied to evaluate the\neffects of the urea amount on N-CSS functionalization and sensitivity.\nThe N-CSS was used as a sustainable electrochemical material for rapid\ndetection of diclofenac in saliva, urine, water, and tablets. The\nsensitive, selective, and ultralow cost (2 g<sup>–1</sup>) with a sensitivity of 0.12 A M<sup>–1</sup> and limit of detection 0.358 μM (3.58 × 10<sup>–7</sup> M). The disposable sensor detects diclofenac in a linear working\nrange from 0.5 to 5 μM with high reproducibility, selectivity,\nand stability. Detection of diclofenac was also performed in real\nsamples consisting of saliva, urine, and water and in solutions prepared\nwith commercial tablets with satisfactory recoveries. The environmental\nimpact of N-CSS was evaluated through a life cycle assessment, which\nindicated that N-CSS is a sustainable choice as an electrochemical\nsensing material. The high sensitivity, versatility, fast detection,\ncost-effectiveness, and easy operation of the disposable electrochemical\nsensor represent significant potentials for on-site, real-time, decentralized\nanalysis, and monitoring of anti-inflammatory contaminants in biological\nand environmental samples.