Enhanced electrochemical sensing of nitroaromatic compounds based on hydroxyl modified carbon submicroparticles

• Carbon submicrospheres prepared from glucose own high density of hydroxyl groups.
• HCSs exhibit high sensitivity to NB with a favorably low background current.
• The H-bonding and electron donor-acceptor complex between HCSs and NB are crucial.
• HCSs exhibit well-defined peaks for sensing of NB, DNB and TNB, respectively.

To explore the active sites for detection of nitroaromatic compounds and improve the sensing performance of carbon based materials, the commercial carbon nanoparticles (CNPs), nitric acid pre-oxidized carbon nanoparticles (OCNPs) and hydroxyl-rich carbon submicrospheres (HCSs) were systematically investigated by transmission electron microscopy, infrared spectroscopy, X-ray photoelectron spectra and electrochemical tests. OCNPs, prepared from CNPs by HNO3 oxidation, contain amounts of oxygen functional groups (OFG) including –COOH, –OH, CO and so on. HCSs, prepared by the green and facile hydrothermal carbonization of glucose, possess the highest loading of hydroxyl groups (approximately 80% of total surface oxygen-containing groups) among these carbon materials. The HCSs modified electrode exhibits the highest current response to nitrobenzene (NB), accompanied by a favorably low background current which is only 30% of that for OCNPs. The excellent sensing performance is attributed to the abundant hydroxyl groups, which facilitate the formation of H-bonding and charge-transfer interaction between electron-donating hydroxyl groups on HCSs and electron-deficiency nitroaromatic molecules. The further investigation by square wave voltammetry indicates that the HCSs modified electrode exhibits a series of well-defined current peaks for NB, dinitrobenzene (DNB) and trinitrobenzene (TNB) with high sensitivity (>6 nA μg−1 L) and low detection limit (0.88 ∼ 1.8 μg L−1). Moreover, the proposed sensor exhibits high reproducibility, satisfactory storage stability and good anti-interference ability.

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