Controllable Preparation And The SERS Activity Of Ordered Silver Nanostructure Using Templates

The ultra-thin alumina mask(UTAM) method has been considered as a promising technique for fabricating highly ordered nanostructured arrays because of its highly ordered hexagonal structure with close arrangement and ultrahigh density of the nanopore array structure of porous alumina template. The template can generate attractive advantages, such as its controllable parameters for ordered nanostructures, large area, high flexibility, high throughput and low equipment costs. So fabricating ordered surface nanostructures with tunable dimensions and properties have attracted considerable interest in surface nano-patterning researches via UTAM. A novel method utilizing aluminum pits array template not only inherits all the advantages of UTAM but also possesses unique advantages, such as easy handling and transfer.Surface-enhanced Raman scattering(SERS) is widely recognized as a powerful spectroscopic tool for detection and characterization of low concentration of molecules in the chemical and biological agents. This new technique has overcome the defects of low sensitivity of traditional Raman spectroscopy. Up to now, to fabricate SERS substrates which featured by large-scale, low cost, high uniformity, high sensitivity, great stability and reproducibility for quantitative detection of target molecules is still a challenge. In this thesis, it is the first time to investigate the SERS performance of different structure morphology of silver nanodots array fabricated with various thickness/diameter ratios of UTAM. Rhodamine 6G(R6G) was served as probe molecule. Besides, we present the fabrication of ordered embedded Ag particles array on periodic pit hexagonal pattern established on aluminum base after the first anodization. This well-ordered embedded Ag/Al nanodots array was firstly prepared for detecting R6 G. The SERS spectra of R6 G molecules on this nanodots array are obtained. We also studied how preparation parameters affect the structure and SERS properties of the embedded nanostructure. The major contents of this work are as follows:1. The ultrathin anodic alumina masks were fabricated by a two-step anodization method at 2 ℃ with 0.3 M oxalic acid solution as electrolyte. UTAMs with various diameters were obtained by changing the widening time, anodization voltage and secondary oxidation time. Scanning electron microscopy(SEM) was performed to characterize these UTAMs.2. A silver layer was deposited on the substrates by employing thermal evaporation in vacuum less than 8.0×10-4 Pa with UTAM as shadow mask. The structural parameter of metal nanoparticles array can be adjusted by changing thickness/diameter ratio of the ultra-thin alumina membrane. We got a series of Ag nanoparticle array substrates. Taking R6 G as the probing molecule we observed the SERS performance of these Ag nanoparticles array substrates.3. We successfully fabricated a new type of embedded Ag/Al nanodots array which possesses large-area and highly ordered specialty via using thermal evaporation on aluminum pits template. The SERS measurement resulting from the substrate with R6 G molecules as probe molecules showed a strong SERS performance with a huge enhancement factor and the very low detection limit to R6 G molecules. Enhancement factor is up to 1010 and the minimum concentration to detect R6 G molecules is 1×10-11 M. So it can be recognized as a powerful spectroscopic tool for detection and characterization of low concentration of molecules in the chemical and biological agents. At the same time, we investigated the preparation conditions(oxidation voltage, the thickness of evaporation, evaporation rate) on the embedded nanostructure and its SERS properties. Ultimately we got optimized conditions for preparing such embedded nanostructure.