Flexible Electrochemical Sensor with Graphene and Gold Nanoparticles to Detect Dopamine and Uric Acid

Electrochemical sensor is a promising platform in diagnosing the disorders of nervous and metabolic systems for its feasibility of detecting dopamine (DA) and uric acid (UA). Nevertheless, the reported electrochemical sensors still suffer from unfavorable selectivity and the high limit of detection (LOD). To address these problems, this paper introduced a heterogeneous electrode interface to improve the sensor's selectivity with differently charged regions. The electrode was prepared on a flexible polyolefin substrate and modified with negatively charged graphene (GP) and electroneutral gold nanoparticles (Au NPs). Experimental results show that the optimal electrode with five layers GP and Au NPs (GP5AuNPs5) was capable of detecting DA and UA in the ascorbic acid (AA)-coexisted solution with minimum interference. The GP5AuNPs5 sensor manifests low LODs ( $3 {\sigma } /\text{S}$ ) of 10 nM and $1.47 {\mu } \text{M}$ for DA and UA, respectively, confirming its feasibility to detect the lowest concentration of the human body. Moreover, the introduction of the Au NPs makes a better separation for current peaks, which might be from the existence of a concentration gradient by electrostatic force difference and an enhanced diffusion from Au NPs. The high-performance sensor with well-separated current peaks is meaningful for detecting DA and UA electrochemically.