Anisotropic Gold Nanorod Arrays for Plasmon-Enhanced Electrochemical Sensing

Electrochemical (bio)sensors are widely employed as point-of-care devices for the detection of diverse analytes for health and environmental purposes as they can offer high sensitivity, rapid response, and applicability to miniaturization. However, the recorded electrochemical signals usually have a low signal-to-noise ratio, especially when nanoscaled tags are used for labeling in sensor architectures. This increases the effects of interference, which would eventually lead to poorer reproducibility and limited sensor performance. Plasmon-enhanced electrochemistry (PEEC) is a recently growing field, which is based on the relationship between plasmonic nanostructures and their electrocatalytic function under the localized surface plasmon resonance (LSPR) region for analytical-based applications. The integration of plasmonic nanostructured materials with electrochemical sensor platforms can exhibit enhanced catalytic activity and sensitivity when surface plasmons are created under light irradiation. Herein, we demonstrate the first-time use of anisotropic gold nanorod arrays (AuNRs) as the source of plasmonic enhancement in the electrochemical detection of doxorubicin (DOX), a chemotherapeutic agent. To achieve this, AuNRs were deposited onto carbon screen-printed electrodes (cSPEs) at a deposition angle of 10° by the oblique angle deposition (OAD) technique. Based on the excitation of the surface using an 808 nm near-infrared (NIR) laser, the plasmon-based catalytic enhancement on the electrochemical response of AuNRs-deposited cSPEs was investigated using a redox mediator in comparison to bare cSPEs. The effect of laser excitation time (0–120 s) and power (0.2–1.8 W) on PEEC was optimized to clarify the plasmonic effect. Utilizing the oriented surface alignment of nanorods, the effect of isotropy was also investigated by directional laser excitation and found to be an effective parameter due to possible plasmon trapping effects. This plasmon-induced electrocatalytic enhancement enabled increased sensitivity for DOX detection, which shows its applicability as a proof-of-concept design in practical real-world sensor applications.