Fabrication Of High-density Metal Nano-array For SERS Detection

Surface-enhanced Raman scattering?SERS?refers to the phenomenon that the intensity of Raman signal increases significantly by 10⁵-10⁶orders of magnitude at the sharp edges of rough metal surfaces or at the gaps between metal nanostructures?namely,"hot spots"?.SERS has the advantages of high detection sensitivity,narrow Raman characteristic peak spectrum,fast detection,and non-invasiveness.It can be used as molecular fingerprints and has wide applications in food safety,environmental monitoring and biomedicine.For surface-enhanced Raman scattering,the surface structure and morphology of the SERS substrate are the key factors that determine the enhanced performance,so how to prepare a high-performance SERS substrate becomes the primary issue in SERS detection.According to the change in particle size before and after preparation,the methods for preparing SERS substrates can be divided into top-down methods and bottom-up methods.The bottom-up methods generally have the characteristics of simple operation and low production cost.But due to the uneven structure of the substrate,the detection repeatability and reproducibility are poor.While the substrate with Top-down methods generally has the feature of highly ordered substrate structure,high detection repeatability and reproducibility.But the procedure is time-consuming and expensive as well as large area preparation is difficult.Nano-imprinting technology as a top-down method for preparing nanostructures,besides ensuring high sensitivity,uniformity and reproducibility of the substrate,has the advantages of simple process,low cost,and large-scale industrial production capacity,making it have great development potential in the preparation of SERS substrates.In this paper,we used single-pass anodized aluminum as a template and prepared a highly ordered and dense gold nanopillar array on a flexible PC substrate with nano-imprinting technology and the coating process.Then we used it as a SERS substrate and calculated its enhancement factor relative to a flat gold film surface.A factor of 10⁶ proved the effectiveness of high-density nanoarray structures for SERS enhancement.In order to improve the service life of the template,we made a flexible nickel template on the surface of the PC nanopillar array by electroplating.In the process of anti-sticking treatment on the surface of the nickel template,we innovatively used titanium that can react with the anti-sticking agent fluorochlorosilane to replace the traditional nickel as the seed layer material,without changing the original shape of the substrate,and obtained a nano-imprint template with good flexibility and low surface energy.Based on the prepared SERS substrate,we designed a“harpin”structure nucleic acid detection SERS sensor and used this sensor to detect the p53 gene,an important tumor suppressor gene in the human body,and testified the sensitivity,specificity and reproducibility of the sensor for p53 gene detection with the detection limit reaching1p M,the signal intensity of the probe molecule located in the p53 solution at the characteristic peak of 1358cm^-1 1.5 times higher than the signal intensity in the mutant solution of the single-base mismatch of the p53 gene,and the relative standard deviation of 8.8%on five samples.The test results proved that the prepared SERS sensor has high sensitivity,specificity and reproducibility.Finally,we designed and successfully prepared a micro-nano composite structure array with nano-pillars nested in micro-pores through nano-imprinting process combined with photolithography process.Then we used the prepared composite structure to reproduce nickel template.Afterwards,we used the nickel template to thermally imprint the PC sheet and obtained the micro-nano composite structure at one time,without the need for photolithography and other steps.This preparation method has the advantages of simplicity,high efficiency and low cost.Compared with the nano-pillar structure,the composite structure can make full use of the capillary force between the liquids and improve the uniformity of the distribution of molecules on the SERS substrate,and thus improve the detection reproducibility.