Surface-Enhanced Raman Spectroscopy Detection Of Polycyclic Aromatic Hydrocarbonsbased On Au@organic Core-shell Nanoparticles

Polycyclic Aromatic Hydrocarbons?PAHs?are a class of hydrocarbons including two or more benzene rings in the form of fused ring connection,which has strong toxicity,carcinogenicity and teratogenicity.Due to the food chain and the biological cumulative effect,PAHs brings great harm to the ecological environment and human health.Currently the widely used detection methods of PAHs have high sensitivity,but they are expensive,operation-complicated,time-consuming,and without real-time in situ monitoring.Surface-Enhanced Raman Scattering spectroscopy?SERS?is a kind of optical enhancement phenomenon of nanoscale rough surface or particle system.With the advantages of rich information content,high sensitivity,less-sample pretreatment and operating easily,SERS is considered to be a very promising analytical technique.With the help of SERS,it is expected to achieve real-time and rapid detection of PAHs.This thesis is focused on the SERS detection of PAHs.The main research work is described as follows:1.Self-assembled monolayer film of gold nanoparticles?Au@DDT core-shell nanoparticles?at the air/water interface as SERS sensor for PAHs detection.In this work,n-dodecanethiol?DDT?was employed in the functionalization of Au nanoparticles surface so that the Au nanoparticles could self-assemble large-scale Au@DDT core-shell nanoparticles monolayer film at the air/water interface,and this Au@DDT core-shell nanoparticles film was used as the SERS substrate for PAHs detection.What's more,DDT could preconcentrate PAHs close to the substrate surface and arrive to electromagnetic enhancement field through the hydrophobic interaction between PAHs and DDT's hydrophobic alkyl chain,which makes the SERS detection of PAHs possible.Research shows qualitative and quantitative detection of PAHs have been achieved by using Au@DDT core-shell nanoparticles,which prepared by self-assembled monolayer film of gold nanoparticles at the air/water interface.Quantitative analysis of PAHs is further realized based on the prepared SERS substrate,as the SERS intensity of PAHs versus its logarithmic concentrations exhibits a good linear relationship and the correlation coefficients?R²?can arrive to 0.9977.The recovery rates measured with five different concentration Benzo[a]pyrene?B[a]P?range from 89.9%to 104.3%and its RSD range from 2.34%to 15.36%.In addition,the SERS substrate prepared by Au@DDT core-shell nanoparticles has good reproducibility and uniformity for PAHs detection.2.Preparation and characterization of Au@ZrPP core-shell nanoparticles,and its application in SERS detection of PAHs.HF,TGA,heating temperature,reaction time and the ratio of liquid ZrPP have some effect on the synthesis of Au@ZrPP core-shell nanoparticles.Though characterization of TEM and improving synthesis method,we successfully synthesized Au@ZrPP core-shell nanoparticles with the 2 nm shell thickness.Au@ZrPP core-shell nanoparticles mainly contained five elements C,P,O,Zr and Au by Energy Dispersive Spectrometer analysis.For the FT-IR spectrum of Au@ZrPP core-shell nanoparticles,the presence of bands at 692 cm^-1,728 cm^-1,748 cm^-1,1046 cm^-1,1157 cm^-1,1384 cm^-1 and 1437cm^-1 are similar to ZrPP.For the UV-vis spectrum of Au@ZrPP core-shell nanoparticles,it is found that the solution of Au@2 nm ZrPP core-shell nanoparticles has a maximum absorption peak at 539 nm,which shifts 4 nm to long wavelength direction compared to the maximum absorption peak of gold nanoparticles.At the same time,it appears some small B band absorption peak of benzene ring in the 250-270 nm.Due to the shell of zirconium phenyl phosphonic acid?ZrPP?containing a large number of benzene ring,PAHs molecules can be captured to the Au@ZrPP core-shell nanoparticles surface though?-?stacking interaction between ZrPP and PAHs.And it can be realized the SERS detection of PAHs with the help of electromagnetic enhancement of Au core.SERS qualitative and semi-quantitative for PAHs detection was realized by using concentrated Au@2 nm ZrPP core-shell nanoparticles solution.It can be obtained high quality SERS spectra and successfully detected 10^-7 M B[a]P.At the same time,a preliminary exploration the preparation of Au@ZrPP core-shell nanoparticles monolayer SERS substrate was carried out.3.Preparation and characterization of Au@PVP core-shell nanoparticles,and its application in SERS detection of PAHs.PVP can covalently combine on the Au atoms of gold nanoparticles through the nitrogen and oxygen atom heterocyclic ring,and then form Au@PVP core-shell nanoparticles.Au@PVP core-shell nanoparticles have 2-nm PVP shell synthesis in different temperature.At the same time,the synthesised Au@?PVP&TGA?core-shell nanoparticles also have 2-nm shell,but its shell is more uniform and dense compared to Au@PVP core-shell nanoparticles.However,SERS detection of B[a]P isn't realized by using Au@PVP core-shell nanoparticles.