Direct amperometric detection of glucose on a multiple-branching carbon nanotube forest

Abstract

We show here that a re-structured carbon nanotube (CNT) forest can be used ‘as-received’ for high selectivity, non-enzymatic glucose detection without the need to incorporate catalytic metal nanoparticles or an exclusion polymeric membrane. Direct amperometric sensing of glucose has been achieved by using multiply-branched CNTs prepared by growing secondary or tertiary ‘offshoot’ CNTs on top of the existing CNT layer. The increased roughness factor on these re-structured CNTs enhances the amperometric detection sensitivity for glucose by a factor of 20× over that of interfering species like ascorbic acid or uric acid. A sensitivity of 60 µA mM⁻¹ cm⁻² and a detection limit of 1 µM, with a linear detection range of 1–11 mM (R² = 0.999), could be attained on the re-grown CNTs. When the re-grown CNTs were subjected to further anodization in acid to introduce a highly-charged interface, the sensitivity to glucose was enhanced to 157 µA mM⁻¹ cm⁻².