Preparation Of Functionalized SERS Substrates And Their Application In Analysis Detection And Biosensing

As a powerful analytical tool,surface-enhanced Raman scattering(SERS)spectroscopy has gained extensive attention due to its high sensitivity,in-situ and nondestructive testing.SERS can provide the chemical structure information of molecules and even enable the detection of single molecule.The main problem in the current SERS quantification is to prepare SERS substrates with highly dense“hot spot”areas,and to make the molecules enter the effective“hot spot”areas.Since the single noble metal nanoparticles are difficult to realize functionalization,an increasing of research focuses on the preparation of composite functionalized SERS substrates.In this paper,two raspberry-shaped core-satellite SERS substrates were prepared.One is a SERS substrate COFs-Au NPs with covalent organic frameworks(COFs)as the core and gold nanoparticles(Au NPs)self-assembled on its surface.The other is a dual-mode SERS subatrate F-Si O₂-Au/Ag composed of a dye encapsulated silica nanosphere core and an immuno-SERS tag decorated shell.The main studies are as follows:1.A three-dimensional(3D)self-assembly SERS substrate COFs-Au NPs with better SERS performance was fabricated via electrostatic interaction between COFs with positive charges on its surface and Au NPs with negative charges,and it actually successfully applied for analysis of malachite green(MG)residue in different seafood products as well as thiram residue in several kinds of fruit juice.The spherical-like structure SERS substrate with larger surface area can provide more active adsorption sites in detection and improve the efficiency of sample enrichment on the COFs-Au NPs substrate.The linearity range is 1.0×10^-9 mol·L^-1-1.0×10^-6 mol·L^-1 for MG and 5.0×10^-8 mol·L^-1-1.0×10^-5 mol·L-1 for thiram,covering three orders of magnitude,and both of them show good linearity(R~2?0.995).The detection limit is6.2×10^-10 mol·L^-1 for MG solution and 1.7×10^-8 mol·L^-1 for thiram solution.The COFs-Au NPs substrate was actually applied for analysis of MG in seafood products and thiram in different fruit juice with the recoveries in the range of 94.67%-108.99%for MG and in the range of 95.00%-107.58%for thiram,and both of the relative standard deviation(RSD)are no more than 5.88%.This work indicates that the developed COFs-Au NPs substrate is promising for SERS analysis and detection of residues in foods.2.Metformin hydrochloride(MH)and rosiglitazone hydrochloride(RH)are two different anti-diabetic drugs,which depend on different routes to reduce blood sugar levels.For diabetic patients who suffer from breast cancer,whether hypoglycemic drugs bring side effects is a question that needs to be answered.Herein,we proposed a SERS/fluorescence dual-mode nanoprobe to assess anti-diabetic drug actions from the expression level of the epidermal growth factor receptor(EGFR)that is a significant biomarker for cancers.The nanoprobe is a raspberry-shaped core-shell nanosphere(about 340±10 nm)with a dye encapsulated silica nanosphere core and an immuno-SERS tag decorated shell,which features fluorescence performance and SERS activity.The quantitative and in-situ analysis for EGFR on the cell membrane surfaces was achieved by real-time fluorescence imaging and SERS measurements,which were also employed to track the EGFR expression after drug actions.Our study suggests that RH may be a potential drug for diabetic patients who have breast cancer,while MH may be improper for the above patients since it can accelerate the EGFR expression of MCF-7 cells.Meanwhile,the successful dual-mode sensing platform endows more feasibility for highly sensitive and accurate identification of cancer cells markers.In summary,these two functionalized substrates expand the application of SERS in analysis detection and biosensing,and it also provides reference for the diversification of SERS application scenarios.