| Based on the interactions between noble metal nanoparticles to form one-,two-or three-dimensional advanced assemblies.Due to their multi-scale,multi-component and multi-level special structures,they exhibit richer aggregate and synergistic effects and thus have excellent catalytic,optical and electrical properties,making them valuable for a wide range of applications in catalysis,sensing,biomedicine and photonics.The liquid-liquid interface self-assembly method is widely used because of its simplicity,versatility and rapidity.By this method,gold nanoparticles with different morphologies are prepared into dense two-dimensional nanofilms with large structural surface area,strong coupling between particles and excellent interfacial properties between different components compared with unassembled gold nanoparticles,resulting in significantly enhanced surface-enhanced Raman scattering（SERS）,sensing and catalytic properties.Based on the above background,from the perspective of preparing uniform two-dimensional gold nanoparticle film structure,this study obtained different configurations of gold nanoarrays by liquid-liquid interface self-assembly method,and the homogeneous construction of dense two-dimensional monolayer films of spherical gold nanoparticles（2D MFGS）was achieved.The process does not require any template,organic ligand or biomolecule to induce assisted self-assembly.Further,2D MFGS materials with multilayer structures can also be prepared by layer-by-layer（Lb L）self-assembly.Then the SERS properties of several gold nanoparticle films synthesized and the electrical response of multilayer 2D MFGS materials are investigated using melamine（MA）as a probe molecule.This thesis focuses on the following three parts of work:（1）A liquid-liquid interface self-assembly method was used to form dense two-dimensional spherical gold nanoparticles（Au NPs）film with a particle size of about 16nm at the water/oil interface without any stabilizer modification by controlling the amount of methanol.Further,irregular-shaped gold nanoparticles（Au NIs）were prepared by controlling the reaction time to optimize the morphology of Au NPs and to construct 2D Au NIs films to enhance the SERS performance.The results of SERS Mapping scans and MA molecular Raman intensity analysis show that the large-size,irregularly shaped and unmodified two-dimensional gold nanoparticles obtained by this simple,rapid and universal self-assembly method have sensitive and uniform SERS response properties,which are have great potential for applications in sensing and catalysis.（2）This work used L-cysteine（L-Cys）and 2D MFGS to modify the Au electrodes to build uniform and stable multilayer films by Lb L self-assembly,denoted as Au/（L-Cys/2D MFGS）n（n=number of layers）.Electrochemical study showed that the specific surface area and current signal amplification capacity of the modified electrode increased with the increase of layers number.In addition,considering the orderliness inside the multilayer 2D MFGS assembly and experimental accessibility,we chose Au/（L-Cys/2D MFGS）n=4 as the working electrode and dopamine（DA）as the signal quantification molecule for the indirect detection of MA.The experimental results showed that the oxidation current of DA was inhibited due to the competitive adsorption behavior of MA on the working electrode.Under the optimal conditions,the decrease of the peak DA anode current is proportional to the MA concentration of 10-12-10-3 M,and the detection limit is 0.13 p M.These works reveal the great potential of 2D MFGS for applications in electrochemical food analysis.（3）High potential polymerization conditions of≥1.61 V can cause excessive oxidation of thiophene,leading to rapid degradation of the polymer structure and loss of electrical activity.Here,this research exploited the unique affinity of the sulfur-containing molecule 3-thiophene acetic acid（3-TAA）for gold atoms in multilayer 2D MFGS modified electrode in order to reach the goal of increasing the molecular concentration around the electrode and reducing the polymerization potential.The 3-TAA molecularly imprinted polymer（MIP）sensor was prepared using MA as a template molecule at 1.51V potential.The sensor performances were optimized,and the MIP showed a wide linear range of 10-13-10-6 M for MA detection with a low detection limit of 10-13 M under optimal conditions,and exhibited excellent selectivity,great reproducibility and stability.This work provides a feasible solution for the preparation of high-performance molecularly imprinted sensors by thiophene low potential electropolymerization. |
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