The effect of gold nanorod dimensions on the electrochemical performance of an enzymatic glucose biosensor

Abstract

The nanostructuring of electrode surfaces is commonly employed to enhance the electrochemical performance of enzymatic glucose biosensors. However, the optimisation of nanostructure morphology and dimensions remains an incompletely explored area. In this work, three colloidal solutions of gold nanorods (AuNR), different in size, were synthesised. SEM analysis revealed that nanorods exhibited distinct lengths: 32.8 ± 3.4 nm for AuNRI, 35.0 ± 3.5 nm for AuNRII and 90.0 ± 6.7 nm for AuNRIII. Glucose biosensors based on graphite rod electrodes modified with AuNR and glucose oxidase showed enhanced electrochemical performance. Notably, biosensors fabricated with AuNRI and AuNRIII achieved similar maximal current changes during the enzymatic reaction (∆Imax = 49.31 ± 2.64 and 48.45 ± 2.35 µA, respectively), despite the pronounced difference in the electroactive surface area obtained after AuNR deposition (0.082 ± 0.009 and 0.194 ± 0.005 cm2, respectively). Moreover, the fabricated glucose biosensor based on AuNRI exhibited a linear range of practical relevance (0.1–8 mM), a low limit of detection (4.6 µM), and is suitable for glucose detection in the diluted blood serum. Overall, the results indicate that morphological characteristics, including size, aspect ratio, and spatial organisation, play a crucial role in optimising the design and performance of enzymatic glucose biosensors.