Research On Formation Mechanism Of Bundle Structure Using AFM And SERS Application

Nowadays,three-dimensional?3D?nanostructures fabricated on the polymer surface have significant applications,such as gratings for sensors,the surface nanostructure of the binary optics and SERS substrate.Due to the significant applications,many approaches are thus utilized to fabricate 3D nanostructure,which includes focused ion beam?FIB?,electron beam lithography?EBL?,and conventional photolithography.AFM tip-based nanofabrication method,which possesses the advantages of precise spatial resolution,in-situ imaging and inexpensive device,has been widely used by scholars to fabricate nanostructures.The bundle structures,which belong to quasi-sinusoidal nanostructure,can be formed on the surface of polycarbonate sheet when conduct scratching on the sample surface using AFM tip However,the formation mechanism of bundle structures is still unclear,in addition,the relationship between the fabricating parameters and the structure size of bundle needs to be investigated further.Raman detection approach,which belongs to one of the lable-free detection methods,is employed to detect biomolecule by the specific interactive position and has an immense application potential in the field of biomolecule detection.At present,the Raman detection of protein is mainly based on the colloidal system?Au or Ag?.However,the molecular-structure sensitivity and SERS signal reproducibility are poor due to the uneasy control of the colloidal system.The troubles can be resolved by using a specific micro/nano structures as the SERS substrate.Based on the aforesaid reasons,a polycarbonate sheet with superior properties such as high strength and impact resistance was selected as the experimental sample in this study.The bundles and dots structures were fabricated on the sample surface using AFM system.The formation mechanism of bundle structures and the effect of machining parameters on the bundle/nanodots structures were investigated,furthermore,the Raman detection of rhodamine 6G and lysozyme were performed on the SERS substrate which transferred from the bundle/nanodot structures.The specific research contents are as follows:The formation mechanism of bundle structures was studied first.The torsion angle of tip cantilever was calculated based on the proposed theoretical model,the friction signal exerted on the tip was recorded from the AFM system.The structure size difference between the bundles that fabricated by two tips with different torsional rigidity were compared.The formation mechanism of bundle was explained based on the friction force and the material properties.The bundle structures were fabricated on the sample surface using single scratching approach.The effect of machining parameters such as scratching direction,normal load,machining velocity,feed value on the bundle structures size were studied.In addition,the nanodots were fabricated using two times scratching with different included angles.The influences of included angle and the sample rotation on the nanodots structures were investigated.The Raman detection experiment for rhodamine 6G and lysozyme was performed using the bundle and nanodots structures.For detection of R6G,the effect of substrate structures,thickness of Au film and the solution concentration on the Raman intensity was studied.For detection of lysozyme and the binary protein,the adsorption mechanism of lysozyme and NaNO₃ on the silver substrate was investigated.In addition,the influence of insulin content between the binary protein on the intensity was studied,which provided the reference for the detection of cells or tissues using Raman approach.