Construction And Application Of Optical Intelligent SERS Sensing Platform Based On New Three-dimensional Multi-stage Composite Porous Materials

In this paper,the construction and application of a new type of three-dimensional composite porous material SERS sensing platform are studied.First,on basis of the principle of building more SERS"hot spots"and combining the electromagnetic and chemical enhancement advantages of foam copper,silver(Ag)nanomaterials and transition metal compounds,the aim was to design a new SERS substrate with high detection sensitivity,versatility,good repeatability and uniformity.Several new three-dimensional multistage composites of Cu@Co₃O₄@Ag have been successfully constructed by physical and chemical methods.Two simple and efficient ways have been explored:One is the in-situ hydrothermal assembly of Ag(NH₃)₂OH solution to synthesize three-dimensional foam-cobalt oxide nanowires and silver nanoparticles Cu@Co₃O₄@Ag-H composites;The other is the synthesis of 3D foamed copper-cobalt oxide nanowires-silver nanoparticles(Cu@Co₃O₄@Ag-S)composites by physical sputtering deposition of silver nanoparticles.Chemical hydrothermal method is used to grow in the basal material above silver nanoparticles,by adjusting the concentration of hydrothermal precursor solution to implement the regulation of silver nanoparticles size implementation controllable adjustment and optimization of the precious metal coupling spacing and the effective construction of three-dimensional multi-level space"hot spots",for the preparation of new type of three dimensional composite porous materials used in the SERS sensor platform,the optimal scheme.On the basis of the successful preparation of 3D foam copper-based cobalt oxide nanowire substrate material,in order to explore the influence of the morphology of silver nanoparticles on the SERS activity performance of the composite material,a comparative experiment was designed for the deposition of silver nanoparticles by physical sputtering method.The morphology of silver nanoparticles was controlled by controlling the deposition time.The SERS activity of Cu@Co₃O₄@Ag-S was further evaluated.It was found that the spherical silver nanoparticles generated by hydrothermal method significantly increased the hot spot content between the silver nanoparticles compared with the silver particles deposited by physical sputtering method,so they had stronger SERS activity.Therefore,we selected the 3D foam-based cobalt oxide nanowires supported by hydrothermal generation of silver nanoparticles composite material to explore the construction and application of its optical intelligent SERS sensing platform finally.Secondly,by using 4-NBT molecule and R6G molecule as Raman probe molecule,the advantages of ultra-trace SERS detection platform of Cu@Co₃O₄@Ag-H and Cu@Co₃O₄@Ag-S as well as superhydrophobic modified Cu@Co₃O₄@Ag-S composite materials were studied by SERS respectively.The SERS sensitivity of Cu,Cu@Co₃O₄,Cu@Co₃O₄@Ag-H and Cu@Co₃O₄@Ag-S were compared through parallel contrast experiments.Through the comparison of characteristic peaks intensity,it was found that the Cu@Co₃O₄@Ag-H composite substrate optimized by hydrothermal method had the best SERS sensitivity.The best optimized Cu@Co₃O₄@Ag-H substrate can be used as an excellent SERS sensor.The enhancement factor of 4-NBT is up to 8×10⁷,and the minimum concentration of 1×10^-10 mol L^-1 can be detected,which proves that this substrate has a high SERS sensitivity.In addition,the influence of superhydrophobic modification on the properties of the material was further explored.The results showed that the material after superhydrophobic modification had stronger SERS signal for the probe molecular solution with the same concentration,and it also had the advantages of repeated utilization.The comprehensive results show that Cu@Co₃O₄@Ag-H composite material has great adaptability and application potential in SERS detection,and its excellent performance makes it possible to be used as a fast real-time detection method to detect pesticide residues in food.Finally,on this basis,in view of the development trend of the detection speed and limit of pesticide residues on the surface of fruits and vegetables at present,the designed,synthesized and finally optimized material Cu@Co₃O₄@Ag-H was used as an efficient SERS substrate.In view of the SERS detection performance of pesticide residues,thiram(tetramethylthiuram disulfide)was used as the probe molecule for the high sensitivity detection of thiram residues.The minimum detection concentration of thiram was up to0.1 ppb and the homogeneity of thiram was excellent(RSD=9.26%).The SERS signal intensity corresponding to the thiram droplets with different concentration gradients presented a linear change rule.Moreover,as a new SERS sensing platform,the composite material had uniform hot spot distribution,excellent SERS activity and stability.Aiming at the concentration detection limit of thiram solution,ultra-trace detection of 600 ppt concentration can be realized,which is enough to meet the current requirements of thiram detection limit.In addition,the 3D material as a sensing platform also has the advantages of fast and convenient.This paper also studied the SERS activity after the surface modification of the substrate material reached the superhydrophobic effect and the practical application effect in pesticide residue detection.The results showed that the addition of superhydrophobic surface modification improved the SERS activity of three-dimensional substrate materials,and the ability of detecting pesticide residues with ultra-trace droplets was achieved.Meanwhile,it changed that the SERS sensing platform could only be used once under ordinary detection conditions,and repeated utilization increased the detection times of the same platform,and reduced the cost of materials.