Preparation And Sensing Mechanism Of Carbon Nanotubes/Silver Nanoparticles On SERS Substrates

Surface-Enhanced Raman Scattering（SERS）has a unique fingerprint spectrum,which can be used for rapid nondestructive detection without pretreatment of samples.And it has high sensitivity of detection.These advantages make SERS used as a powerful analytical technology.Its applications have gotten great attention in physics,chemistry,medicine,biology and other directions.In recent years,the preparation of SERS active substrate has become a hot topic in its research field.In addition to the commonly used metal substrate,there are more and more researches on the composite structure of metal and other materials as SERS substrate.The preparation of new SERS substrate is very important.There are many challenges in the sensitivity,stability and repeatability of detection.In this paper,a kind of SERS active substrate of carbon nanotubes and silver nanoparticles was prepared,and its sensing mechanism was explored.The main contents and research results are summarized as follows:1.Silver nanoparticles with uniform arrangement were grown on single-walled carbon nanotubes by hydrothermal synthesis method.Then it was dried to form a thin film and attached to the surface of silicon dioxide to obtain the composite structure of silicon dioxide/carbon nanotubes/silver nanoparticles（Si O₂/CNTs/Ag NPs）.By adjusting the size and spacing of silver nanoparticles,the enhanced performance of the substrate was optimized,and the SERS substrate with high sensitivity was obtained.2.Rhodamine 6G solution was used as a probe molecule to explore the enhancement performance of the SERS substrate.The detection limit is 10^-12M and the enhancement factor is 1.23×10⁸.In order to explore the sensing mechanism,the potentiation of single-walled carbon nanotubes’dispersion liquid and silver nanoparticles on the detection signal intensity was detected.The results show that the enhanced effect of Si O₂/CNTs/Ag NPs composite structure is much higher than that of single-walled carbon nanotubes’dispersion liquid and silver nanoparticles.This is mainly caused by electromagnetic enhancement.In addition,FDTD simulation was used to do a simple study on the interaction between molecules of the SERS substrate and the contribution of three-dimensional structure.3.Phenol red solution was used as the probe molecule to explore the relationship between the input signal and output signal of the SERS substrate as the sensor.The input variable is the concentration of phenol red solution,and the output variable is the corresponding Raman signal intensity.The signal stability and uniformity during the detection were good.Then the results obtained from multiple measurements were fitted by FDTD.The intensity of Raman signal is exponentially related to the concentration of phenol red solution.It realized the qualitative and quantitative detection.This kind of SERS substrate is easy to prepare and preserve.And its cost is low.What’s more,it has high sensitivity of detection.These make it have a good applied prospect.