Sensitive and selective electrochemical detection of hydrocortisone using MoS₂-SiO₂ hybrid nanostructure modified...

Mesoporous silica (m-SiO₂) has been synthesized from rice husk ash (RHA) and was deployed as a template to grow MoS₂. The resulting MoS₂-SiO₂ hybrid nanostructures were subsequently utilized for the immobilization and signal amplification of the hydrocortisone (HC) on a glassy carbon electrode (GCE). Transmission electron microscopy (TEM) images revealed the successful formation of MoS₂-SiO₂ hybrid nanostructures consisting of thin MoS₂ nanosheets decorated with amorphous SiO₂ domains. Nitrogen adsorption-desorption studies revealed a 534 m²/g multipoint BET surface area of hybrid and well-defined interconnected channels. Moreover, Small-angle X-ray diffraction (SAXRD) revealed that m-SiO₂ possessed a disordered structure. Prior to the formation of the hybrid nanostructure, silica was amine-functionalized using APTES. X-ray photoelectron spectroscopy (XPS) confirmed the functionalization of silica and the formation of MoS₂-SiO₂ hybrid nanostructures. The electrochemical properties of the hybrid nanostructure were studied using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), anodic stripping differential pulse voltammetry (ASDPV), and amperometry. EIS and CV studies of the MoS₂-SiO₂ hybrid nanostructure-modified glassy carbon electrode (MoS₂-SiO₂/GCE) exhibited a lower charge transfer resistance (R_ct) as compared to m-SiO₂/GCE. The fabricated hybrid sensor was employed for the electrochemical detection of hydrocortisone (HC). The concentration of HC in healthy individuals typically ranges from 10 to 100 nM. The calibration plot obtained from ASDPV exhibited a linear relationship between the oxidation peak current and HC concentration ranging from 1 to 100 nM. The fabricated sensor exhibited a high sensitivity of 0.12 µA/nM and a low limit of detection (LOD) of 1 nM. Furthermore, Amperometry and ASDPV studies conveyed that minimal change in oxidation current of HC in the presence of common interfering molecules present in biofluid, confirming the suitability, excellent selectivity and anti-interference capability of the proposed sensor.