Preparation Of Composite Nanostructured SERS Substrates And Their Application In Food Quantitative Detection

Surface enhanced Raman Scattering(SERS)is a prevailing technology of spectral analysis.This technique is comparable to the single molecule fluorescence technology.And it can enhance the Raman signal of molecules that attached to the surface of the nanoscale metal.The enhancement mechanism is mainly electromagnetic field enhancement and chemical enhancement.The materials with SERS activity are mainly gold,silver,coppers and other precious metals,as well as alkaline metals,such as alkaline metal lithium,sodium,potassium and other alkaline metals also can be used as an enhanced substrate for SERS.Since SERS being discovered by Fleischmann and others in 1974,it has been widely applied to detect harmful substances in food because of its high sensitivity.With the development of science and technology,single nanomaterials cannot reach the needs of the researchers.Therefore,composite nanomaterials have come into being.It not only has the advantages of single molecule materials but also can overcome some shortages of single molecule materials,which have become the hot spot of research.However,scholars and researchers find only a few precious metals have strong SERS spectra,and they also found that this enhancement effect depends not only on the properties of the metals,but also on the space,shape and size of the metal nanostructures.With the further research on SERS technique,scholars and researchers have realized that there are still many problems due to the interference of the Raman signal of some macromolecules s in food,so the technology cannot be widely used.In addition,the sensitivity and reproducibility of the SERS substrates and the quantitative detection of SERS have still faced many difficulties.The existence of these problems makes SERS technique not applicable to universal detection.The main research content of this dissertation is to develop a method to treat the detection material without preprocessing or simple preprocessing,and study the reappearance of SERS spectroscopy.First,we synthesized uniform gold nanoparticles and silver nanoparticles with large particle sizes.Secondly,the core-shell nanoparticles inlaid with probe molecules are synthesized,and the greatest advantage is to exclude the interference from the substrates,and effectively avoid the problem of the phase adsorption between the probe molecules and the molecules to be measured,and then apply it to the quantitative detection.The main contents of this dissertation can be summed up as follows:1.The gold seed sols with 15 nm and 45 nm diameters were prepared by the sodium citrate reduction method at 100? in the oil bath.The morphology and optical properties of gold seed sol were characterized by an ultraviolet visible absorption spectrometer and a field emission scanning electron microscope.2.The silver nanoparticles with different particle sizes(50nm,80 nm,100nm,125 nm and 150nm)were synthesized by the seed growth method.The gold nanoparticles with different sizes(50nm,80 nm,110nm,120 nm,150nm)are synthesized by the tromethamine seed growth method,respectively.The morphology and optical properties were characterized by the ultraviolet visible absorption spectrometer,the transmission electron microscope and the field emission scanning electron microscope.3.The gold nanoparticles and silver nanoparticles with uniform morphology were analyzed by SERS.First,the gold nanoparticles and silver nanoparticles were calculated by 3D-FDTD.The enhanced electromagnetic field of gold nanoparticles and silver nanoparticles with different particle sizes was analyzed,and the corresponding trend was obtained,and then malachite green was used as a probe,the silver nanoparticles were tested,and the particle size of the gold nanoparticles with the strongest SERS activity was chosen to be spread on a thin glass sheet,which was used as the SERS substrate to detect the malachite green on the fish surface.4.The core-shell nanoparticles inlaying probe molecules were synthesized,and they were characterized by Raman spectrometer,UV visible absorption spectrometer and transmission electron microscope,which verified the existence of probe molecules between the core and shell.The linear relationship between the peak intensity and the concentration of penicillin in milk was studied by using penicillin as an analyses to be measured.