Controllable Synthesis Based On Polydopamine Biomimetic Nanostructures And Its Highly Sensitive SERS Detection

Surface enhanced Raman spectroscopy（SERS）has many advantages such as high sensitivity,good repeatability and non-destructive detection,and has been widely used in the highly sensitive detection of trace samples in molecular science and material engineering fields.For SERS,to obtain highly sensitive,stable and reliable molecular Raman signals,the controlled preparation of SERS substrate was the most critical link.Therefore,using various physical or chemical methods to construct SERS substrate with high sensitivity and strong stability has always been a research hotspot in the field of analysis and detection.The surface of polydopamine（PDA）molecule contains a large number of functional groups,such as catechol groups,amino and imamino groups,so that it can form a strong interaction force with the host material,showing a strong adhesion characteristics similar to marine mussel foot protein-5.More importantly,these functional groups can be complexed with a variety of metal ions and reduced in situ at room temperature,providing an ideal platform for surface modification and functionalization of materials.This molecular structure property of PDA provides a new way for it to prepare highly sensitive SERS substrates on the surface of various materials and realize the highly sensitive detection.Based on the unique advantages of strong interface adhesion and surface metal functionalization of PDA molecules,this paper modified PDA on different material surfaces,and used the reducing power of PDA molecules to reduce silver ions in the silver ammonia solution（[Ag（NH₃）₂]⁺）in situ into silver nanoparticles（AgNPs）.A series of SERS substrates were prepared by adjusting the reaction conditions to realize the highly sensitive detection of the target molecules.The specific work of this paper is as follows:（1）The surface of filter paper（FP）was modified with PDA,and then reacted with[Ag（NH₃）₂]⁺to reduce in situ on the surface of FP to obtain AgNPs with uniform size and distribution.A series of FP@PDA@AgNPs flexible SERS substrates were prepared.Rhodamine 6G probe molecules were used to detect the enhancement effect of FP@PDA@AgNPs flexible SERS substrate,and the detection limit was as low as1.0×10^?10 M,and the substrate was measured to have high uniformity and storage stability.The malachite green on the surface of fish,crab and shrimp was collected and used for SERS detection by using the protrusion flexibility of FP@PDA@AgNPs substrate,and the minimum detection limits were 0.04635 pg/cm²,0.06952 pg/cm² and0.09270 pg/cm²,respectively,which effectively improved the detection sensitivity and detection efficiency.（2）A series of NF@PDA@AgNPs three-dimensional magnetic SERS substrates were prepared by modifying PDA molecules on the surface of nickel foam（NF）and reducing AgNPs in situ according to the strong adhesion and reducing ability of PDA molecules.The SERS enhanced effect of the three-dimensional magnetic substrate NF@PDA@AgNPs was detected by crystal violet probe molecules.The detection limit was as low as 1.0×10^?10 M,and it had good SERS stability.Based on the excellent magnetic response property of NF@PDA@AgNPs substrate,the rhodanine B residue in pepper powder can be extracted and detected rapidly by magnetic adsorption method,with the minimum detection amount of 10^?6 g/g.This kind of NF@PDA@AgNPs three-dimensional magnetic substrate can effectively improve the collection efficiency and detection sensitivity of the target analyte.（3）A series of highly sensitive flexible CS@PDA@AgNPs SERS substrates were designed and synthesized by modifying PDA molecules on the surface of cotton swab（CS）and in situ formation of AgNPs.Nile blue A（NBA）probe molecule was used to detect the SERS performance of CS@PDA@AgNPs substrate.The results showed that the CS@PDA@AgNPs substrates had good SERS sensitivity and stability,and its detection limit for NBA was as low as 1.0×10^?10 M.In view of the CS@PDA@AgNPs excellent flexibility,can effective collection and detection by the method of wiping thiram residues on the surface of the fruit,for its pears,grapes and peaches thiram residues on the surface of the detection limit were 0.12 ng/cm²,0.24 ng/cm² and 0.15ng/cm²,residual disinfectant in the field of environmental and biological science field tests show has great application potential.