Fabrication Of The Nano-Caped SERS-Active Chips And Its Application In Medical Diagnosis

Surface-enhanced Raman scattering?SERS?effect possesses high sensitivity and selectivity,which has widely applied in surface sciences,elechemical,biotechnology and so on.This paperstudies the SERS performance of Ag/Fe?SiO₂?/Agsandwich nano-caped composite structure,combining theory and actual applied detection,we obtained a series of innovative results.The main research content and achievement are included tothe following three parts:1.In this paper,the ordered arrays of Ag and Ag/SiO₂/Ag films were prepared byself-assembled polystyrene?PS?templates and multi-layer sputtering deposition technique.The isolated or adjacent nanoparticles can be optimized by the thickness of the sputtering film and the size of the polystyrene microspheres.Isolated nano-bowl arrays show high local surface plasmon resonance?LSPR?and surface plasmon resonance?SPR?,which can lead to the enhancement of SERS signals.In contrast with Ag nanoparticles array,the insulating layer SiO₂ was used as an insulating layer in the Ag/SiO₂/Ag sandwich nanobowl array to improve the SERS signal.In view of the Ag/SiO₂/Ag sandwich bowl array,the outermost Ag film also can produce new plasma coupling phenomenon,in addition to the contribution of adjacent bowls and nanogap between the nano-bowls of the sharp edges.The finite time-domain difference?FDTD?method results show that the main contribution of electromagnetic field enhancement is the LSPR of the Ag-SiO₂ interface and SPR of the outermost Ag surface.The simulation results and experimental analysis show that the SERS signals of the Ag/SiO₂/Ag sandwich nano-bowl arrayswith the SiO₂ insulator layer have a better enhancement effect.2.We have designed a new type of SERS active chip used to detect liver cancer biomarkers?Lens culinaris agglutinin-reactive Alpha-fetoprotein,AFP-L3?,usingthe Ag/SiO₂/Ag layes coated onthe two-dimensional?2D?non-closed packing of PS array,forming different sizes of PS@Ag/SiO₂/Ag composite structure is used as a SERS active chip,modification of the surface of the Ag/SiO₂/Ag with antibody5,5-Dithiobis?succinimidyl-2-nitrobenzoate??DSNB?used as SERS probe molecules.The correlation coefficient between the concentration of AFP-L3 and the DSNB molecule was better than that of the Raman peak at 1440 cm^-1.A good linear relationship between the concentration of AFP-L3 and Raman intensity ratio I₁₃₉₀/I₁₀₇₄of DSNB was obtained,with the correlation coefficient R²=0.997.The SERS-active chip was detected in a wide range?0-8 ng/mL?,and the detection limit?3??was 0.078 ng/mL.This method was used to detect serum samples of three patientscollected from patients diagnosed with liver disease,the results showed that this method had potential applicationsof the developed method in clinical diagnosis.3.The sandwich cap-shapedAg/Fe/Ag thin filmswere prepared on the PS templatesby LBL depositing method.The influence of Fe film thickness on SERS was studied by magnetron sputtering time to control the thickness of the film.With the gradual increasing of Fe layer thickness,SERS signal increases firstly and then decreases due to the charge transfer between metal Ag and Fe Fermi energy level.The introduction of Fe magnetic layer has a good effect on the contribution of SERS,which promotes the understanding of surface plasmon resonance and charge transfer.The results show that the substrate has good SERS performance and extends the application field of Fe in SERS.In addition,we also used this substrate to design the SERS active chip,and qualitatively and quantitatively detect the Ag/Fe/Ag SERS-active substrate as theimmunoassay chip for quantitative determination of AFP-L3 which is the biomarkerof hepatocellular carcinoma?HCC?.This study indicates that the SERS-active substrate of Ag/Fe/Ag sandwich cap-shaped arrays has a high sensitivity to biological analysis.Based on the physicaldepositionsystem and chemical modification methods,we preparedthesandwichnano-capedSERSactivechip,itshighenhancement factorandhigh sensitivity,which is helpful for further application in biomedical diagnosis.