Construction Of Ordered Micro/Nano Structures Based On Si For Applications In Detection

Nowdays,nanoscale material atracts more and more interests of researchers compared with other types of material,and is widely used in the detection of gas,water pollutants and biological molecules because of its unique properties.Nanostructures can provide unique properties,such as enhancing the Raman scattering,capturing tumor cell,and so on.Herein,we applied a variety of technology of micro-nano material processing,and successfully fabricated several ordered micro/nano structures on the surface.After that,we studied their applications in surface enhanced Raman scattering and biological detection,respectively.The thesis mainly includes three parts:Firstly,we propose an efficient method to make more analyte molecules in hotspots by fabricating bowtie nanostructures with supporting bridges.At first,free-standing bowtie nano-structure array is fabricatied at the silicon substrate.Then the technology of vapor evaporation is used to form silver nanoparticles.The gaps between the silver bowties can be regulated by the dissolving time of silver.While the bridges between the polystyrene(PS)have been reserved after dissolving process.Eventually the bridge serve as a platform to carry Raman probe molecules,which is beneficial for locating more Raman probe molecules at hot spots and making full use of the hot spots.The structure exhibits good Raman detection performance.This method can greatly enhance the Raman intensity.Moreover,the relative standard deviation(RSD)is lowered to 5.91% for the integrated band area at 1095 cm-1.This concept of locating molecules in the hot spots can also be used for the preparation of other structures,which provides a new approach for preparating detective substrate(not only Raman substrate).Secondly,to increase the reproducibility of SERS measurement,we propose an efficient method to prepare a substrate by using the electroless deposition of silver nanoparticles(Ag NPs).The Ag NPs are uniformly formed on the tops of the Si nanopillars by taking droplet-confined electroless deposition on the hydrophobic Si nanopillar arrays.The Ag NPs present an excellent reproducibility in Raman measurement,the RSD is down to 3.40%.Meanwhile,the hydrophobicity of the substrate results in an enrichment of the probe molecules,which leads to a higher detection sensitivity.There exists a great linear correlation between the concentration of Rhodamine 6G and the Raman intensity in the log-log plot,the R2 is 0.998,which is up to the standard for the quantitative analysis.Thirdly,the hole array with diameter of 10 μm on silicon wafers is obtained through photolithography by the template with the holes diameter of 10 μm as mask.By controlling the conditions,silver nanoparticles are deposited in the holes uniformly.After a metal assisted chemical etching,we remove part of the silicon nanowires by taking ultrasonic bath.Finally the micro-nano hierarchical PDMS structures are obtained by duplication.We found that the structure can capture the circulating tumor cell with 94 percent after bonding antibodies.PDMS is a soft biocompatible material,avoiding breaking circulating tumor cell.