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Abstract
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The electrochemical determination of 2,4,6-trinitrotoluene (TNT) is a critical analytical task due to its wide spread use in explosives and environmental concerns. However, a significant challenge in this process is the interference caused by other nitroaromatic compounds (NACs) with similar electrochemical behavior and structural properties. The distinguishing feature of NACs in the TNT family, such as dinitrotoluene (DNT) and nitrotoluene (NT), is the number of nitro groups in them, which can affect the acidity of these compounds and the degree of hardness of these acids. This research investigates the synthesis and application of doped carbon ni trides (CNs) for the electrochemical detection of nitroaromatic compounds, based on the hard-soft acid-base (HSAB) theory. CNs were doped with varying dopants (Se, S, and P) to modulate their hardness/softness. The study reveals a correlation between the hardness/softness of the dopants and the nitroaromatic analytes, where harder dopants exhibit a higher affinity towards harder NACs (e.g., TNT). Calibration slopes for nitroaromatic detection varied depending on the dopant, with P and S (relatively harder dopants) yielding the highest sensi tivity for TNT as a relatively harder analyte. In contrast, Se (a softer dopant) showed the best performance for NT as a softer analyte. The dopants’ electrocatalytic effects also influenced the NACs reduction peak potentials, shifting them towards less negative potentials, with the greatest shift observed when the dopant hardness was matched to the analyte hardness. The addition of gold nanoparticles (AuNPs) further increased the sensitivity by increasing the peak currents in all cases and allowed the measurement of TNT in the range of 0.2–200 nM with a detection limit of 0.06 nM. These findings demonstrate that tailoring the CN dopant based on HSAB principles and matching the hardness/softness of the dopant to the analyte can significantly improve the sensitivity and selectivity of electrochemical nitroaromatic detection
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