| Water is the source of life and the precious resource of the earth.It is self-evident that high quality and pollution-free water resources are of great importance to animal,plant protection,human progress and social development.However,the problem of water pollution is still serious.Domestic sewage flows into rainwater pipelines,industrial wastewater is discharged directly without treatment,abuse of pesticides and fertilizers,Leakage accident in chemical industry enterprises all lead to water pollution.Among these water pollutants,there are many organic pollutants that are rare in content but are carcinogenic,teratogenic and mutagenic to human health.However,only chemical oxygen demand is used to measure the total amount of organic pollutants in water,which is not specific to the harmful organic pollutants.Therefore,in addition to the development of more stringent laws and regulations,a sensitive and quantitative trace detection method is needed to detect this kind of organic pollutants.Surface enhanced Raman scattering(SERS)is a highly sensitive and high resolution"fingerprint"spectroscopy technology that can provide specific chemical information of samples without adding reagents or destroying samples.This technology has been widely used in the identification and detection of chemical and biology.In this paper,nanosilver substrate,glass-based polydimethylsiloxane(PDMS)composite substrate and PDMS plasma cavity substrate were studied for SERS technology.SERS spectra of organic pollutants methylene blue,malachite green,methyl green and pigments represented by erythrocyte were measured.Quantitative analysis was carried out according to SERS spectra.The specific work is as follows:1.Preparation of nanosilver substrate,glass-based PDMS composite substrate,and PDMS plasma cavity substrate.The SERS properties of the substrates were investigated and compared using crystal violet as Raman probe,and the preparation conditions of the substrates were optimized to enhance the Raman probe significantly.2.Measure the SERS spectra of methylene blue,malachite green and methyl green in the water,and analyze the relationship between the concentration and intensity of Raman peak.With the increasing concentration of organic pollutants,the intensity of Raman characteristic peak increases rapidly at first,then slows down,and finally gradually weakens.This process of change is related to the adsorption process of organic pollutant molecules on the substrate.The adsorption process of organic pollutants on the surface of the substrate has undergone the process of unsaturated chemical adsorption,saturated chemical adsorption and physical adsorption,and multiple layers of physical adsorption.3.Based on PDMS plasma cavity substrate as SERS substrate,the relationship between Raman characteristic peak intensity and pollutant concentration of the three water pollutants was established.Based on this data,the back propagation artificial neural network algorithm was used to model the three water pollutants.The predicted results were compared with the actual measured data.The results showed that the measured coefficients R~2 of the data were greater than 0.99,and the prediction of the concentration of the three organic pollutants in water is realized.4.The nanosilver substrate with simple preparation,low cost and strong Raman enhancement effect is used as the SERS substrate,and the potassium thiocyanate is used as the internal standard to realize the trace detection of the etythrosine.In the concentration range of0.4mg/L to 20mg/L,a linear equation of the relative intensity of three Raman peaks and the concentration of erythrosine was established.The determination coefficients R~2 were 0.91,0.95and 0.95,respectively.The detection limit of erythromycin was as low as 0.2 mg/L.This method has advantages in detecting dyes in water.The research work in this paper enriches the field of SERS spectral detection to a certain extent,and provides a basis for the sensitive quantitative detection of trace organic pollutants in water. |
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