Construction Of Homogeneous PA66 Nanofibers Shish-Kebabs Structure And Its Preliminary Application As A Template For SERS Substrate

Nanofibers shish-kebabs(NFSKs)structure is a hierarchical structure consisting of nanofibers and polymer crystal lamellae periodically decorated on the nanofibers along the length of the nanofibers.This structure has attracted the attention of many researchers due to its obvious advantages,such as,periodic three-dimensional morphology,large specific surface area,controllable morphology and good mechanical properties.Among them,NFSKs whose Shish part and kebab part are the same material is defined as homogeneous NFSK,sthe Shish part and the kebab part are homogenous NFSKs of the same material.Due to the difficulty of preparation,the homogenous NFSKs currently being studied are limited to polycaprolactone(PCL)and polyethylene oxide(PEO).Surface-enhanced Raman Spectroscopy(SERS)is a powerful and widely used non-destructive spectroscopy technique.The SERS substrate is the basis and key to realize the high-efficiency SERS detection process.Therefore,the SERS substrate with high sensitivity and good signal reproducibility has always been a research hotspot in the SERS field.In this research,we constructed homogenous PA66(Polyamide66)NFSKs structures with different morphologies,which broadens the scope of the existing research system of homogeneous NFSKs structure.In addition,we prepared a novel three-dimensional SERS substrate with excellent performance by using the prepared NFSKs structure film as a template.This is the first time that NFSKs structure was applied to the SERS field,NFSKs structure provides a new alternative template for the construction of three-dimensional SERS substrates.The specific content is as follows:1.The homogeneous PA66 NFSKs structure was constructed in pure ethylene glycol.Firstly,a PA66 NFs(Polyamide66 nanofibers)film with an average fiber diameter of 110nm was prepared by electrospinning.Then,it was added into hot pure EG after preheating and incubated for a period of time.In this way,the homogeneous PA66 NFSKs structure was constructed.The homogeneous PA66 NFSKs structure obtained by this method has a morphology that is quite different from the typical NFSKs structure,the size of kebab crystal lamellae is very small,and the kebab crystal lamellae are randomly growing on the surface of the nanofibers.The effects of the type of incubation solution,incubation temperature,incubation time,stirring speed during incubation and the amount of PA66 NFs film was added on the formation of homogeneous PA66 NFSKs were systematically explored.Based on the experimental results,a possible formation mechanism of the PA66 NFSKs structure in pure EG was proposed.This mechanism provides a good explanation for the formation process of the homogeneous PA66 NFSKs structure based on the theories of swelling and dissolution and solvent-induced crystallization.2.The homogeneous PA66 NFSKs structure was constructed in PA66(EG)solution.PA66 pellets were dissolved in EG at 190?to prepare PA66(EG)solution for use.The PA66electrospun nanofibers film with an average fiber diameter of 110nm was preheated and then added to the hot PA66(EG)solution for incubation.After separation,washing and drying,the homogeneous PA66 NFSKs structure was obtained.Compared with the homogenous PA66NFSKs structure obtained in pure EG,the homogenous PA66 NFSKs structure obtained in this way has a larger size of the kebab crystal lamella,exhibits obvious three-dimensional features and has a morphology similar to the structure of typical NFSKs.The influences of the concentration of PA66(EG)solution,the incubation temperature and the orientation degree of PA66 NFs on the morphology of the homogenous PA66 NFSKs were investigated.The influence of the formation of the homogenous PA66 NFSKs on the crystallization of PA66also was investigated.We believe that the formation mechanism of homogenous PA66 NFSKs in PA66(EG)solution follows the"soft epitaxial growth mechanism",and we compared it with the mechanism proposed in the first part of this work.3.A novel three-dimensional SERS substrate(Au NPs@PA66 NFSKs)based on the homogeneous PA66 NFSKs structure was prepared.We used the homogeneous PA66 NFSKs structure with obvious three-dimensional characteristics obtained in the second part of this work as a template,then Au nanoparticles was deposited on it by ion sputtering to form a novel three-dimensional SERS substrate(Au NPs@PA66 NFSKs).The influences of the ion sputtering time and the microstructure of the template on the Raman signal enhancement ability of the SERS substrate were explored.The novel three-dimensional SERS substrate based on the homogeneous PA66 NFSKs structure prepared under optimized conditions(Au NPs@PA66 NFSKs^0.01wt%-9min)has a high detection sensitivity of 10^-14mol/L for rhodamine6G(R6G)and shows good signal reproducibility.When used in the detection of melamine,it also achieved good results.