Research On The Interaction Between Functionalized SiO₂ Nanoparticles And Self-assembled Membrane Electrodes And The Electroanalytical Characteristics Of MicroRNA

Due to the characteristics of high coverage,few defects,thermodynamic stability and ordered molecular arrangement,self-assembled film technology is still the focus of research in the design and preparation of functional nanomaterials and analytical sensing interfaces.Self-assembled film have shown great advantages in the field of electroanalysis,such as,pre-designing film structures at the molecular level to obtain special properties and functions.More importantly,the specific interaction of films with the target can be achieved by pre-designing and modifying the film.In addition,the ordered regular monomolecular film provides a uniform electrode surface,and can effectively avoid the diffusion of electroactive substances onto the electrode surface.According to these features,many researchers have studied the interaction of self-assembled film with different nanoparticles in the field of electroanalytical chemistry and obtained better electroanalytical chemistry characteristics.Although SiO2 nanoparticles were widely used in optical methods because they were easy to functionalize,non-toxic,biocompatible,uniform in particle size,and controllable,few researchers combined self-assembled film with functionalized SiO2 nanoparticles to explore their electroanalytical chemistry characteristics.In this thesis,the focus herein is to combine the self-assembled film with functionalized SiO2 nanoparticles and further study their electrochemical and electrochemiluminescence properties.This thesis includes two parts,the first was the review section and the other was the research section.The review section,the definition and characteristics of self-assembled film were introduced,and focus on the new developments in the application of self-assembled film in electroanalytical chemistry.The research section was mainly composed of the following two aspects:1.Interaction of Chitosan/SiO2 nanoparticles with gold naoparticles on the surface of self-assembled film and electrochemical detecting microRNA.In this work,the 1,9-nonanedithiol self-assembled film modified gold electrode was used to immobilize the gold nanoparticles on electrode surface through the Au-S bond.Then the electrostatic interaction of gold nanoparticles with Chitosan/SiO2 nanoparticles was further used to self-assebly Chitosan/SiO2 nanoparticles on gold nanoparticles surface.Thereafter,the modified electrode was being electropolymerized in luminol solution to form a polyluminol film on partly gold nanoparticles surface.Finally,the Chitosan/SiO2 nanoparticles on the modified electrode were etched by HF solution to obtain a resulting electrode.Based on the discrimination effect of the electrode on the bare Chitosan/SiO2 nanoparticles and the single-stranded DNA protected state of the nanoparticles,a sensitive electrochemical method for the determination of microRNA electroanalytical chemistry was developed with the preconcnetration effect of bare Chitosan/SiO2 nanoparticles on resulting electrode.Under the optimal experimental conditions,the concentration of let-7a and the DPV current signal showed a good linear relationship in the range of 1.O×10-12-9.O×10-12 mol/L.The detection limit of the method was 3.0 ×10-13 mol/L.2.Interaction of Cu2+/Chitosan/CMC/SiO2 composite nano particles with 1,6-hexanedithiol self-assembled film and electrochemiluminescence analysis of microRNA.In this work,it was found that the Cu2+/Chitosan/CMC/SiO2 composite nanoparticles could greatly decrease the electrochemiluminescence signal of luminol on 1,6-hexanedithiol self-assembled film modified gold electrode.Then,based on the discrimination effect of Cu2+/Chitosan/CMC/SiO2 towards ssDNA probe and ssDN A/micro RN A complex as well as the pre-concentration effect of Cu2+/Chitosan/CMC/SiO2 nanoparticles on 1,6-hexanedithiol self-assembled film modified gold electrode,a sensitive electrochemiluminescence method for the quantitative determination of microRNA was developed.Under the optimal experimental conditions,the let-7a concentration has a good linear relationship with the electrochemical luminescence signal in the range of 1.0×10-13-9.0×10-12 mol/L,and the detection limit of the method was 3.0 × 10-14 mol/L.