The Design And Fabrication Of Porous Aluminum Oxide Photonic Crystals For Application Of Surface Enhanced Raman Scattering

In recent years,photonic crystals?PCs?have attracted widespread attentions from researchers due to their unique ordered structures and photon regulating capabilities.For instance,using Bragg reflection from the photonic band gap?PBG?of PCs,and slow photon effects from the edges of PBGs,many important results have been obtained in applications of the surface enhanced Raman scattering?SERS?and the semiconductor photocatalysis fields.In this master dissertation,the author mainly introduces some new progresses on PCs in the application of the SERS,and points some difficulties and problems that cannot be ignored,and then proposes several feasible research ideas and strategies,such as,to design and fabricate porous anodized aluminum oxide defective photonic crystals?AAO DPCs?and anodized aluminum oxide heterostructure photonic crystals?AAO HPCs?with large areas by using anodization method for application of the SERS signal enhancement.On this basis,the author systematically summarized his research work carried out during the time of pursuing the master's degree under the title of“The design and fabrication of porous anodic aluminum oxide photonic crystals for application of surface enhanced Raman scattering”.The main contents are divided into the following two aspects:1.High quality anodized aluminum oxide defective photonic crystals?AAO DPCs?are successfully prepared by using of the improved pulsed anodization process,and the positions of their defect state spectral peaks are adjustable in a certain wavelength range by anodic voltage waveform parameters.Then Ag nanoparticles are loaded on the surfaces of the obtained AAO DPCs by vacuum evaporation method,to form the Ag@AAO DPCs films that have ordered distributed nanopore surface,high-quality defect state and tunable photonic band gap?PBG?,which are ideally suited for the SERS substrates.The results show that the Ag@AAO DPCs substrates exhibit excellent SERS performance for testing rhodamine B?rhB?molecules with high sensitivity and reproducibility.The detection limitation can reach to the order of 10^-10 mol/L,and the enhancement factor can increase to the order of 10⁵,especially when the defect state energy level position matches with the incident light wavelength?at 633nm?.Analysis believes that the main reasons for the SERS signal enhancement of the Ag@AAO DPCs would be attributed to the synergistic effect between the enhanced local electric field strengthened by the Bragg reflection of PCs'structure and electron transfer induced by the defect state resonance with the incident light.2.Grounded on the work above,new anodized aluminum oxide heterostructure photonic crystals?AAO HPCs?films are successfully designed and prepared by using of the improved pulsed anodization process.In this special heterostructure more photonic band gaps?PBGs?will appear,and their positions can be regulated to the range of Ag surface plasmon resonance absorption by adjusting anodic voltage waveform parameters.Then similarly,Ag nanoparticles are loaded on the surfaces of the obtained AAO HPCs by vacuum evaporation method,to form the Ag@AAO HPCs films that have ordered distributed nanopore surface,high-quality tunable PBGs,which are ideally suited for the SERS substrates.The results show that the Ag@AAO HPCs substrates present excellent SERS performance for testing rhodamine B?rhB?molecules with better reusability and uniformity.When the more PBG edges are located in Ag surface plasmon resonance absorption region,the detection limitation can reach to the order of 10^-11 mol/L,and the enhancement factor can increase to the order of 10⁶,about 20.3times higher than that of the sample with a single PBG.Analysis believes that the main reasons for the SERS signal enhancement of the Ag@AAO HPCs would be attributed to the synergistic effects among the high-density hot spots distributed on the AAO surface,the Bragg reflection from the PBGs in specified band of Ag surface plasmon resonance absorption,and the slow photon effect from the edges of PBGs.The interesting results mentioned above would have potential application prospect on special trace detection for the biomedical.