Preparation Of 2D SERS Substrate And Its Application In The Detection Of Trace Components In Sweat And Cosmetics

Sweat is secreted by the sweat glands of the skin and is one of the important components of human body fluids.There are quite a lot of chemical components in sweat,which play important roles in human health.Various physiologically active substances in sweat often represent different human health conditions.By analyzing the concentration of certain physiologically active substances in sweat,we can even judge the diseases that may exist in the human body.At the same time,with the rapid development of today’s era,the continuous progress of social economy and the enrichment of material life,more and more people are using skin care products in their daily life.Otherwise,profits in the cosmetics industry have soared because of their widespread use,leading illegal manufacturers to produce low-quality products.Therefore,it is of great significance to develop the detection technology of physiologically active substances in human sweat and to study the method of rapid detection of prohibited substances in cosmetics.Surface-Enhanced Raman Scattering（SERS）refers to the phenomenon that when some molecules are adsorbed on the surface of some special materials,the signal intensity of Raman scattering is greatly enhanced than that of ordinary Raman scattering.SERS technology has many advantages,such as non-invasive,high sensitivity,strong specificity,fast detection speed,little interference by water,less required samples,large amount of information,simple operation,etc.,so it has attracted the attention of researchers in various fields.It has been proved to be an effective method to detect physiological active substances in sweat and prohibited substances in cosmetics through the preparation of highly sensitive SERS substrate.However,part of the SERS substrate developed at present still has some shortcomings,such as inaccurate quantitative analysis and easy to be interfered by environment and experimental conditions.Therefore,three different kinds of 2D SERS substrates were constructed in this paper,and different detection methods were used for quantitative detection and analysis of uric acid,urea and tyrosine in sweat and nitrite in cosmetics.The main research contents of this paper include the following three aspects:1.In the second chapter,a kind of 2D glass-Si O₂-Ag NPs SERS substrate was designed.Two kinds of silane coupling agents with amino group and epoxy group,namely3-Triethoxysilylpropylamine（KH550）andγ-（2,3-epoxypropoxy）propytrimethoxysilane（KH560）,were used to construct SERS substrate by ring-opening reaction between amino group and epoxy group.KH560 was grafted on the glass sheet,meanwhile KH550 was grafted on the silica nanoparticles.Then through the ring-opening reaction of amino and epoxy groups,the silica nanoparticles were loaded on the glass sheet in the form of a single layer.At the same time,the electrostatic adsorption between amino and silver nanoparticles was used to load silver nanoparticles on the silicon dioxide.As for the larger silver nanoparticles loaded on the relatively small silica nanoparticles,several silica nanoparticles supported one silver nanoparticles,resulting in rough surface and"hot spots",which enhanced the SERS performance of the substrate.The 2D SERS substrate combined with Griess reaction was used to detect the nitrite in cosmetics and food.2.In the third chapter,according to the characteristics of4-Aminothiophenol（p-ATP）,p-ATP was used as internal standard molecule and linking molecule.Similar to the previous chapter,we firstly modified piranha solution treated glass sheet with KH560,and then successfully combined p-ATP and KH560 to form new compounds through ring-opening reaction between the amino group on p-ATP and the epoxy group on KH560 under acidic conditions.The p-ATP is tightly decorated on the glass,the external sulfhydryl group could easily combine with the silver nanoparticles to form Ag-S bond,so as to construct the glass/p-ATP/Ag NPs SERS substrate.The p-ATP Raman characteristic peak of 1076 cm^-1was used as the calibration peak,the ratio of the intensity of the two characteristic peaks of uric acid(493 cm^-1and 693 cm^-1)to the intensity of 1076 cm^-1was analyzed linearly with the logarithm of the concentration of uric acid to achieve the quantitative analysis of uric acid.3.In the experiment of chapter 2,it was found that if the silver nanoparticles on one side of glass-Si O₂-Ag NPs SERS substrate were removed,and then the SERS detection was conducted by laser through the side on which the silver nanoparticles were removed,better SERS performance could be obtained.Therefore,in the fourth chapter,a kind of glass-Si O₂-Au@Ag NPs SERS probe was designed.The laser passed through the glass layer,and then the microlens effect of Si O₂nanospheres was used to focus the laser on the silver nanoparticles to enhance the SERS signal.A SERS probe similar to an endoscope was formed to detect tyrosine and urea.At the same time,using Au@MBN@Ag NPs core-shell structure and MBN as internal standard molecule,the quantitative detection of tyrosine and urea was realized by internal standard correction method.