Mixed Surfactant-Mediated Synthesis of Hierarchical PANI Nanorods for an Enzymatic Glucose Biosensor

The hierarchical nanoscale structure plays a crucial role in achieving excellent property, which can successfully be used in preparing tailor-made materials for sensing applications. These hierarchical nanostructures can successfully be prepared with the help of structure directing agents (SDAs). In the present work, we report the preparation of polyaniline (PANI) nanorods in the presence of anionic (sodium dodecyl sulfate, SDS) and nonionic surfactant (pluronic F127) as the SDAs. We prepare a series of ternary composites with a varying ratio of PANI and F127 for a given amount of SDS. The SDS and F127 play a pivotal role as structure directing agents (SDAs) in delivering a hierarchical nanostructure of PANI. Detailed characterization reveals that the in situ polymerization of PANI ensures the formation of the well-dispersed composite. The amphiphilic character of F127 facilitates the formation of a core-shell micellar structure, which in turn facilitates the polymerization of PANI in the core region. We have observed a composition-dependent structure formation of the ternary composites. With increasing the amount of F127, the composite shows higher crystallinity (viz. less porosity) as measured by XRD and microscopy imaging. Among all the prepared composites, the one with an 1:1 ratio of PANI and F127 exhibits less porosity (viz., high crystallinity) as measured by the BET surface area measurement. The XRD analysis does not show a sharp peak, which signifies that the material possesses a polycrystalline structure, as revealed by HRTEM analysis. The polycrystalline nature of the nanorods provides the highest thermal stability, contributes significantly toward the enhanced electrochemical activity, and thus, can successfully be used in sensing applications. The 1:1 material exhibits remarkably high glucose sensitivity (∼486 μA/cm2 mM) over the other ternary composites under amperometric measurements. The sensor shows an excellent electrochemical performance within a range of 5-50 mM with a lower detection limit of ∼4 μM.