Study On Fabrication Of Mechanically Assembled Highly-Sensitive Surface-Enhanced Raman Substrates And Their Performance

Surface-enhanced Raman scattering（SERS）technology can provide important information such as chemical structure and chemical bonding for the object to be tested by largely enhancing the signal intensity of probe molecules on the metal surface.It has the advantages of high sensitivity,fingerprint specificity and nondestructive detection,and thus has a wide range of applications in many fields such as spectral sensing,surface analysis,environmental detection,food safety and biomedicine.For an enhanced detection signal of the analyte on the substrate surface and a SERS substrate with excellent detection ability,it is a key to construct"hot spots"with surface plasmon resonance phenomenon.At present,there are many methods to fabricate metal nanostructured substrates with different sizes and shapes,but how to fabricate large-area SERS substrates with low cost and excellent detection ability in large quantities is still an important research direction.In this thesis,SERS substrates with excellent performance are fabricated by combining nanoimprinting,depositing process,peel-off process and mechanical assembly.And the influence of substrate topography on Raman spectra of probe molecules is studied.The main research contents of this paper are as follows:（1）A low-cost and highly-sensitive SERS substrate was prepared.Crystal violet and rhodamine were used as the probe molecules for the characterization of the prepared SERS substrate,and their detection limits were up to 10^-7 M and 10^-9 M,respectively.And it was calculated that when the concentration of probe molecules were 10^-5 M,the crystal violet molecule had a relative standard deviation（RSD）of13.1%at the characteristic peak of 1175 cm^-1 and the R6G molecule had a RSD value of 8.6%at the characteristic peak of 1650 cm^-1,exhibiting good sensitivity,reproducibility,uniformity and universality of the prepared SERS substrate.At the same time,the finite difference time domain（FDTD）method was used to conduct simulation calculations and the results showed that the metal nanogap structure provided an enhancement for the SERS signal.（2）Metal nanodisc arrays were fabricated based on the samples with metal array structures prepared by nanoimprinting and thermal evaporation,and the peel-off process.In order to transfer the metal disk array on the surface of the cylindrical array,a variety of peel-off and transfer schemes were designed.Finally,through the exploration of the processes,an excellent scheme in which a fluorosilane anti-adhesion layer was formed on the surface of the sample by using trichloro（1H,1H,2H,2H-tridecafluoro-n-octyl）silane modification was obtained to make the metal structure on the sample surface easy to be transferred.（3）Based on the above peel-off and transfer scheme and mechanical assembly method,a flexible SERS substrate was fabricated and the effects of metal adhesion layer,pre-stretching ratio,stretching method and metal deposition thickness on the SERS signal of the fabricated flexible SERS substrate were also explored.The experimental results showed that the metal adhesion layer would cause the attenuation of the electric field strength,which would lead to the weakening of the SERS signal;the signal enhancement was best when the biaxial pre-stretching ratio was 20%;meanwhile,the influence of the metal deposition thickness on the SERS signal was closely related to the surface topography of the substrate.