Detection Of Micro Plastic Contamination By Infrared And Raman Spectroscopy

In recent years,as a new type of global environmental pollutants,microplastics have attracted extensive attention.It is of great significance to study the pollution of microplastics in water environment and soil environment,and the influence of microplastics on the growth and survival of organisms.In this dissertation,Fourier transform infrared spectroscopy(FTIR)and surface enhanced Raman spectroscopy(SERS)were used to study micro plastics in order to explore an effective method for the identification micro plastics pollution in the water of Dianchi Lake.The influence of micro plastics on seed germination was also studied.The main works are as follows:1.SERS substrate for micro plastic detection was fabricated.We used sodium citrate as a protective agent and reducing agent to prepare AuNPs.By changing the amount of sodium citrate,four kinds of AuNPs with different sizes were obtained.The differences of morphology,UV Vis,SERS activity,reproducibility and stability of four kinds of AuNPs were investigated.The Raman enhancement effect of 45 nm AuNPs was the best.The effect of p H conditions on SERS enhancement of AuNPs was explored.The R6 G probe molecule experiment showed that the R6 G probe molecule changed from protonation in the form of open loop to deprotonation in the form of closed loop in the process of p H increasing from small to large angle between the surface of NPs increases gradually,which interferes with the stretching vibration of C-N bond and C-C bond of aromatic ring.There is a linear relationship between the stretching vibration and C-C and C-N frequency under acidic condition.2.Using NaCl as the polymerizing agent,AuNPs as the enhancement substrate,SERS can effectively detect micro plastics,which has a certain enhancement effect on Raman signal and good suppression of fluorescence.It was found that the ratio of sample to polymerizing agent 1:1 could effectively detect low concentration of micro plastics in water environment.The intensity of characteristic peak of SERS spectra showed a linear change with the concentration of micro plastics in a certain range.This provides more possibilities for the rapid detection of low concentration micro plastics and nano plastics in the future.The abundance of microplastics in Dianchi Lake is about 1.88 ± 0.27 n/L.the microplastics in Dianchi Lake water mainly show the characteristics of particles,fragments,transparency and small size.Polyethylene and polypropylene are the main pollution components of microplastics.The results show that the microplastics in water do adsorb many substances,and the granular and fibrous microplastics have stronger adsorption capacity than the film.3.The effect of micro plastics on the growth of corn seeds was studied.The micro plastics polyethylene(m PE)and polystyrene(m PS)were characterized by FTIR and the seeds after the composite micro plastics were studied.The mobilization of storage materials was analyzed by curve fitting and principal component analysis.The results showed that the germination rate,inhibition rate and bud length of corn seeds under PE and PS exposure showed a trend of "low concentration promotion and high concentration inhibition".m PE had stronger inhibition on the activity index of corn seeds.Infrared spectroscopy showed that the main storage materials of corn seeds were starch,protein and fat.2D-IR studies showed that different micro plastics were recovered the number,location and intensity of the automatic and cross peaks of the seeds after the combined pollution were significantly different,which indicated that the different nutrient substance calls were different during germination.By fitting the spectral range of polysaccharides and proteins,it was found that glycogen,amylose and amylopectin were the main factors affecting seed germination.The effects of high concentration of micro plastics and m PE on these storage substances were significant,while the β-fold structure of nutrient protein played a leading role in the growth.By PCA,the preliminary identification could be made Identify germination seeds exposed to different types and concentrations of micro plastics.