| The advancement of nanotechnology and the trend of device miniaturization have prompted us to discover more sophisticated orderly nanostructures,and to further explore interesting physical and chemical phenomena that exist in these nanostructures.In many methods for constructing ordered nanostructures,AAO(AAO,Anodic Aluminum Oxide)is one of the most important template because of its large-area ordered pore structure and three-dimensionally adjustable structural parameters(including the period,pore size,and length of pore).In addition,alumina itself has high temperature resistance,chemical stability,and is suitable for assembly of various materials.These excellent characteristics make AAO can be widely used in photoelectric conversion,catalysis,plasma optics,biomedicine,and surface enhancement spectroscopy.In this thesis,we solve two problems based on AAO template.On the one hand,traditional AAO template has a variety of morphologies in the longitudinal direction(corresponding to Z-axis),but the selectable periodic patterns in X-Y plane is lacking,which result in a shortage in the preparation of large-area sophisticated nanostructures and limited application field of AAO template.On the other hand,surface-enhanced Raman scattering(SERS)has become one of the most sensitive spectroscopic methods due to its rapid detection,high-characteristic and real-time monitoring,which play an important role in detection of pesticide residues,biological analysis and art appreciation.Therefore,how to conveniently prepare high-sensitivity and reproducibility SERS substrates and simultaneously solve the problems in application process of SERS substrates are the key points in SERS.Based on the advantages of AAO templates in constructing SERS substrates,our focus is on the exploration of the hierarchical structure of AAO templates and its application in late-model SERS substrates.The main research contents and achievements are as follows: 1.Enriched the hierarchical structure of AAO template based on the under-voltage oxidation method and explored the growth mechanism of its pore structure.In the second part of the thesis,by using the self-ordered attribute of AAO,five hierarchical structures have been developed under the condition of under-voltage oxidation,including two arrangements of hexagonal and tetragonal,which greatly enriches the hierarchical pattern of AAO.Providing more options for the preparation of sophisticated ordered nanostructures in large areas.An empirical formula for under-voltage oxidation is proposed,and the growth mechanism of the hierarchical pore is discussed which is attributed to the synergistic effect of the preset pattern,oxidation voltage,pore interaction force and average electric field.This research further improved the hierarchical periodic system of AAO template.2.Proposed a backward detection mode in SERS detection.In the third section of this thesis,a three-dimensional(3D)ultrasensitive SERS substrate with a backward detection mode is designed for the problem of less detection mode of planar SERS substrate.According to the 3D nanostructure of the substrate,the excitation and collection mode of signals are optimized.At the same time,the structure of this SERS substrate perfectly replicates the pattern of hierarchically structural AAO,greatly increasing the hot spot position within the periodic cell,and allowing the hot spot structure to be distributed on the substrate surface with high density and controllability.In the backward detection mode,the detection limit for the pesticide thiram can be 10 fM.3.Realized a diamond stamp that can be easily used to prepare high-performance SERS substrates.Based on the advantages of the hierarchically ultrasensitive SERS substrates in the second section,a structured diamond stamp was prepared for rapid acquisition of ultrasensitive 3D SERS substrates.Transfer technique of ultra-thin alumina membrane(UTAM)and reactive ion etching technology were used to replicate the hierarchical structure on the surface of the single crystal diamond,and a diamond stamp with a special periodic pattern was obtained.This efficient and stable stamp has a long lifespan,spare the use of the release agent,which greatly simplifies the preparation process of the ultra-sensitive SERS substrate.This technology enables hierarchical periodic structures to be applied to more materials or substrates,laying the foundation for extending the application field of hierarchical structures.4.Developed a dynamic response mechanism to modulate nanostructures with plasmons effect.In the fifth section,laser in SERS detection is used as the external driving force to stimulate the plasmon polariton and realize the dynamic regulation of the hierarchical periodic array structure.Nanorods in one period are as a unit,the oedered “closed” motions change the nanorod spacing from 40 nm to less than 10 nm(hot sopt),and dynamically exhibit two structural parameters on the same substrate.In addition,FDTD simulations illuminate that the superhydrophobic surface of the substrate makes the molecules accurately coincide with the “hot spot” after the nanorods are aggregated,which solves the problem in most SERS substrate that the molecules cannot access the “hot spot” structure.The realization of the controllable aggregation on nanometer scale not only brings the ultra-sensitive performance of SERS,but also enriches the research model of plasma optics. |
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