1-Amino 2-Naphthol Modified Solvent Filled Carbon Nanotubes for Enhanced Electrochemical Sensing of Bioanalytes

Abstract

Our research interest is mainly on developing cost-effective electrochemical sensors for bioanalytes sensing. For example, bioanlytes such as ascorbic acid, dopamine, and uric acid present together in human body poses challenge for selective sensing of one over other. As these molecules play a vital role in controlling the body’s metabolism, it is paramount to develop a sensor tool with high sensitivity towards these bioanlytes for diagnosing diseases, including AIDS, Parkinsonism, etc. Development of fast and reliable methods for sensing these biomolecules is of considerable importance in offering rapid diagnosis.1–3 In the present experimental work, it is shown for the first time that liquid-filled multi-walled carbon nanotubes (MWCNTs) exhibit remarkably enhanced characteristics for sensor applications, the detection threshold being lowered by as much as an order of magnitude, while detection sensitivity is doubled for a number of molecules including ascorbic acid, dopamine, and uric acid. 1H NMR relaxometry at a moderately low field, i.e., 14.6 MHz (0.34 T), confirms that the improved sensor characteristics are correlated with the filling of MWCNTs with solvents such as acetonitrile, dimethyl sulfoxide, etc. The molecular motions are slowed down when solvent molecules fill MWCNTs, thus increasing motional correlation times, and hence, longitudinal relaxation rate increases under extreme narrowing conditions. The filling of MWCNTs appears to relate to solvent-CNT interactions that are in line with the principle of hard and soft acids and bases, and also correlates with solvent dipole moments.4 We have further enhanced the detection limit and selectivity towards ascorbic acid by modifying the MWCNTs surface with amino naphthol.