Surface Functionalization Of Molybdenum Disulfide Nanosheet And Its Application In Disease Diagnosis And Treatment

Molybdenum disulfide（MoS₂）is a typical transition metal sulfide,which has received extensive attention due to its ultra-thin structure and unique physical and chemical properties.Single-layer or few-layer MoS₂ nanosheets are considered to be the semiconductor analogues of graphene.Because of their high specific surface area,excellent light-to-heat conversion performance,and easy functionalization,they have been used in many applications such as catalysis,drug loading,and disease treatment.Application in the field.However,unmodified MoS₂ cannot meet the current application requirements in many aspects,so it is particularly important to develop multifunctional nanomaterials based on MoS₂.In this paper,MoS₂ nanosheets were prepared by an improved liquid phase exfoliation method,and surface functionalization was carried out with different methods,and applied research on two aspects of disease detection and treatment was launched.Firstly,we successfully prepared MoS₂ nanosheets in aqueous solution by using the surfactant sodium cholate combined with ultrasonication.X-ray diffraction,X-ray electron spectroscopy,UV-Vis absorption spectrum,Raman spectroscopy and other characterization methods prove that the nanosheet is few or single-layered,and TEM images show that the diameter of the nanosheet is about 200 nm.According to the feature that that MoS₂ nanosheets are easily modified with precious metal nanoparticles,MoS₂ nanosheets functionalized with gold nanoparticles were synthesized by the reduction method and used as electrode modification materials to construct electrochemical sensors for dopamine and ascorbic acid.XRD,FTIR,XPS,and Raman results all proved that gold nanoparticles modified MoS₂ nanosheets were successfully synthesized.TEM images showed that the gold nanoparticles are uniform in size and distributed on the surface of the MoS₂ nanosheets.Electrochemical test results show that the sensor has good electrocatalytic activity for dopamine and ascorbic acid.The linear ranges are 0.5-350 μM and 5-900 μM,respectively,and the detection sensitivity is 0.2 μM and 1.5 μM.The chemical sensor has a satisfactory wide range and sensitivity.In addition,the impedance data also proves that MoS₂ nanosheets functionalized with gold particles have higher diffusion efficiency and excellent electrical conductivity.The modification of gold nanoparticles bridges the gap between MoS₂ nanosheets and conductors such as metals and graphene to a certain extent,and improves the conductivity and catalytic activity of the MoS₂ sensing system.The experiments in this chapter have important application value for the application of biosensors in the fields of small biomolecule detection and clinical medical diagnosis.In addition,we have carried out disease treatment applications on MoS₂ nanosheets.Although MoS₂ nanosheets have a high specific surface area,the stability of MoS₂ under physiological conditions is very poor.Therefore,it is necessary to modify the surface to improve its stability.We modified the nanosheets through sulfur chemistry.The use of polyethylene glycol and polyethyleneimine polymers with lipoic acid as the end group improved the stability and biocompatibility of the material and made it responsive to the slightly acidic biological environment.In order to further improve the biocompatibility of the material and make it targeted,we attached bovine serum albumin modified with biotin to the surface of the obtained material.FTIR spectrum indicated that the above-mentioned substances have been successfully modified on the surface of MoS₂ nanosheets.Next,we found through photothermal experiments that the multifunctional MoS₂ nanocomposite had a photothermal efficiency of 21%,showing good photothermal performance.In addition,we used doxorubicin hydrochloride as a model drug to analyze the drug loading of the multifunctional nanocomposite and found that the prepared material has a drug loading rate of about 11%,which had a good drug loading capacity.In addition,the TEM images showed that the diameters of the synthesized nanocomposite materials before and after drug loading were all around 400 nm,with no obvious change,and were consistent with the results of DLS images.Finally,we analyzed the cytotoxicity of the multifunctional MoS₂ nanocomposite.The results of cell experiments showed that the multifunctional MoS₂ nanocomposite was a kind of biocompatible material,and when the material was loaded with doxorubicin,it could efffectively kill cancer cells.The above exploration on the application of MoS₂ nanosheets in the treatment of diseases has laid foundation for the realization of photothermal and drug combination therapy.