Multiwalled carbon nanotubes bearing 'terminal monomeric unit' for the fabrication of epinephrine imprinted polymer-based electrochemical sensor

摘要

Carbon-nanotubes play a pivotal role in molecularly imprinted polymer technology for inculcating conducting property, high surface to volume ratio, and maximum porosity in the film texture. Contrary to the non-covalent heterogeneous dispersion of pure (unmodified) multiwalled carbon nanotubes in the imprinted polymer film, the homogeneous distribution of their functionalized derivative was found more effective to augment the sensitivity of the measurement. This could be made feasible using multiwalled carbon nanotubes bearing terminal monomeric unit (termed as "CNT-mer") for the polymerization (one CNT-mer in each repeating unit). In this work, the CNT-mer entails a N-hydroxyphenyl maleimide functionality to be utilized in the chain propagation with simultaneous imprinting of epinephrine in the polymeric network. This system, when casted on the tip of a pencil graphite electrode, responded a highly sensitive and selective response for epinephrine, prevalent in aqueous and real samples at ultratrace level (linear range 0.09-5.90ngmL~(-1), limit of detection 0.02ngmL~(-1), S/N=3), without any cross-reactivity and matrix effects. The proposed sensor is advantageous in obtaining enhanced differential pulse anodic stripping voltammetric current vis-a-vis the corresponding imprinted sensor modified with randomly dispersed flocculated multiwalled carbon nanotubes bundles. While the latter might restrict the interlayer diffusion of analyte in the film, the former sensor facilitated high diffusivity with the channelized electron transport to respond higher current. The CNT-mer dispersed sensor was found to be stable and rugged against mechanical stress and can be used, after regeneration, for more than hundred consecutive experiments in clinical settings.