Tapered Micro-nano Hierarchical Flexible SERS Substrate For High Sensitivity Explosive Detection

With the acceleration of China's urbanization process,the problem of population densification is becoming increasingly prominent,and the resulting security risks are very serious.In recent years,there are more or less safety detection problems of high-energy explosive TNT in densely populated areas such as airports and stations.In addition,long-term existence of TNT powder in the air can cause anemia and liver function damage.Under such an environmental background,we used a flexible material PET film as a substrate,and successfully designed a tapered micro-nano graded flexible SERS substrate through a series of micro-nano processing methods,and used the flexible SERS substrate to perform trace TNT Ultra-sensitive detection.The main research works of this paper are as follows:1.A flexible enhanced Raman scattering substrate is designed and processed.Theoretical research shows that the smaller the nanometer gap between the micronano structures on the substrate surface,the better the enhancement effect.On this basis,a nanocone array with a minimum gap of about 50 nm was fabricated in this paper by means of nanosphere etching and RIE reactive ion beam etching.2.In order to process the nanocone structure with ideal morphology,the parameters of the spinning machine for spinning monolayer polystyrene(PS)pellets on the surface of clean PET film were determined by SEM.When determining the optimal RIE etching time,we used a series of etching time parameters,selected the corresponding etching time of the SEM image with the smallest nanometer gap through the SEM image taken,and finally used the substrate processed in this time as the standard substrate for subsequent experiments.3.The repeatability and homogeneity of the signal prepared by the substrate were verified by using the R6 G molecule as the reporter molecule.The substrate was immersed in R6 G ethanol solution and incubated for 2 hours.During Raman detection,20 Raman spectral lines were obtained by randomly selecting 20 points on the substrate.The homogeneity of the substrate signals was verified by waterfall diagram.Then randomly select 5 bases and sample 6 points on each base to verify the repeatability of the base signal.4.In order to determine the theoretical electromagnetic enhancement effect of the prepared substrate,we carried out electromagnetic simulation on the substrate,and the simulation result is the same as our assumption.The maximum area of plasma resonance on the substrate is found by electromagnetic simulation,and the maximum enhancement value of the theory is obtained.5.Considering that the Raman scattering cross section of TNT is relatively small and not easy to detect directly,we adopted the method of indirect detection and successfully obtained the Raman signal of TNT dissolved in ethanol solution with low concentration by forming the complex structure of meisenheimer with 4-atp molecule.Then,we took it a step further,dropping TNT solution on the computer backpack,and successfully simulated the feasibility of the substrate in the actual test by wiping the surface directly with the modified substrate.