Plasma-Induced Enhancement in Electronic Properties of Gold Nanoparticles: Application in Electrochemical Biosensing of Cortisol

Homogeneous distribution of nanoparticle (NP) deposition on electrode surfaces and fine-tuning of their electronic properties is essential for controlling the active surface area, which significantly influences a sensor’s sensitivity. This work demonstrates the enhancements in the distribution and improvements in the electronic properties of gold nanoparticles (AuNPs) through a room-temperature plasma-assisted technique. The plasma-assisted deposition induced size reduction of AuNPs and improved the uniformity of particle distribution on the electrode surface. The homogeneity in the AuNP distribution was studied using scanning electron microscopy. The plasma-induced electronic effects of AuNPs were evaluated for electrochemical sensing using cortisol as a model analyte. Analytical features of the proposed AuNP-based cortisol sensor were investigated with the help of electrochemical techniques such as cyclic voltammetry and electrochemical impedance spectroscopy. For comparison, cortisol sensors without the plasma treatment were also fabricated, and it was found that the electronic properties of AuNPs tuned by plasma treatment helped increase the sensor sensitivity toward electrochemical detection of cortisol.