Ultra-selective and real-time detection of dopamine using molybdenum disulphide decorated graphene-based electrochemical biosensor

Abstract

In this work, a graphene-molybdenum disulphide nanocomposite (pGr-MoS2) was synthesized by a hydrothermal method using pulverized graphite (pGr) as the source of graphene, which exhibited ultra-selective electrochemical (EC) sensing towards dopamine (DA) by exhibiting current response only for DA in the presence of biomolecules such as ascorbic acid (AA), uric acid (UA), epinephrine, norepinephrine, folic acid, glucose, nicotine, caffeine, serotonin acetylcholine, glutathione, cysteine, and histidine. A recent work by our group has demonstrated a simultaneous EC sensing of DA, AA, and UA by pGr with selectivity towards DA and was attributed to the less oxidized and intact aromatic structure of pGr, which interacts with the aromatic ring structure of DA. Intriguingly, pGr-MoS2 surpassed the selectivity property of pGr and all the other reported non-enzymatic DA sensors by exhibiting peak only for DA. The limit of detection value (LOD) obtained for DA using pGr-MoS2 was 0.01 nM (i.e., 10 pM) with a linear dynamic range (LDR) from 0.00001 to 10 μM. Thus, the LDR and LOD values satisfactorily meet the sensitivity requirement for detecting DA, which is 1000 magnitudes lower than the normal physiological concentration of DA. A possible mechanism for this superior selectivity of pGr-MoS2 towards DA was proposed and discussed with evidence. Further, the EC sensing was successfully extended to human blood samples spiked with DA, suggesting the efficiency of the sensor to work in real samples.