Construction And Application Of Electroactive Molecule-Molybdenum Disulfide Electrochemical Sensing Platform

Molybdenum disulfide?MoS₂?is a member of the two-dimensional?2D?layered nanomaterial family.It has a large specific surface area,high electron mobility,tunable band gap,many defect sites,easy functionalization and excellent biocompatibility,which has been successfully applied in many fields such as catalysis,energy,sensing,drug delivery and therapy.In order to expand the application of MoS₂ and improve the application performance of MoS₂,various MoS₂nanocomposites have emerged.Electrochemical sensors are favored by many researchers because of their simple operation,fast detection,sensitive responsiveness and low cost.In view of the unique structure of MoS₂ and superior optoelectronic properties,this paper focuses on the application prospects of MoS₂ nanocomposites in the construction of electrochemical sensors.In this paper,the electroactive molecules were functionalized on the surface of MoS₂,forming electroactive molecule-molybdenum disulfide nanocomposites.The electrochemical properties of these nanocomposites were investigated and electrochemical sensing platforms based on these nanocomposites was constructed for highly sensitive detection of biomolecules.The main content of this paper is divided into the following two parts:?1?In this chapter,we reported an electrochemical sensing platform based on methylene blue?MB?functionalized molybdenum disulfide?MoS₂?nanocomposites.We successfully adsorbed MB on the surface of MoS₂ to synthesize MoS₂@MB nanocomposites by electrostatically interacting and?-?stacking.Based on the systematic study of the adsorption behavior of MB on the surface of MoS₂,the atomic force microscopy?AFM?was used to characterize the MoS₂@MB nanocomposites.The results showed that the adsorption isotherms of MB on the surface of MoS₂conform to the Temkin model rather than the Langmuir model.Electrochemical characterization showed that MoS₂@MB nanocomposites have superior electrochemical properties and can be used to construct electrochemical sensors for highly sensitive detection of microRNAs and neurotransmitters.Under optimal conditions,the MoS₂@MB sensing platform can detect microRNA-21?miRNA-21?as low as 68.0 fM with good selectivity without labeling.Meanwhile,the same sensing platform can individually and simultaneously determine dopamine?DA?and uric acid?UA?.The above results confirm that MoS₂@MB nanocomposites can be used as a highly efficient electrochemical sensing platform for highly sensitive detection of biological or chemical target molecules.?2?In this chapter,we successfully prepared poly?L-cysteine??PL-Cys?functionalized molybdenum disulfide?MoS₂?nanocomposites by electrodeposition method.We used MoS₂modified glassy carbon electrode?MoS₂/GCE?as the working electrode to prepare MoS₂@PL-Cys nanocomposites by changing the electrochemical deposition conditions.Since the polymerized PL-Cys still had good electrochemical behavior,we constructed an electrochemical sensing platform based on MoS₂@PL-Cys nanocomposite for the highly sensitive detection of miRNA-21.The surface of the electropolymerized MoS₂@PL-Cys/GCE was positively charged,which can load the negatively charged probe DNA by electrostatic adsorption.When the target miRNA-21 was added,the DNA hybridized with miRNA-21 to form a double strand.Since the DNA-miRNA-21double strand was still adsorbed on the surface of the electrode,which hindered electron transfer and made the electrochemical signal of PL-Cys lower.Therefore,a"signal-off"detection strategy was designed for miRNA-21 detection.It should be noted that we also designed a“signal-on”detection strategy using the same sensing platform.The reason was ascribed to the MoS₂@PL-Cys nanocomposite possessed amino group?NH₂?,which could efficiently bind carboxyl?COOH?-labeled probe DNA by a carboxamide reaction.With the addition of target miRNA-21,the DNA-miRNA double-strand structure was erected on the surface of the modified electrode due to its high rigidity,which promoted the transfer of electrons and,enhancing the electrochemical signal utilizing two sensing strategies,this MoS₂@PL-Cys-based can achieve 100 fM miRNA-21detection with high selectivity.