Rapid Detection Of Benzo(a)pyrene Based On Surface-enhanced Raman Spectroscopy Technique

Benzo[a]pyrene(BaP)is a kind of polycyclic aromatic hydrocarbons,with highly carcinogenicity and chemical stability.Water or foods are vulnerable to BaP pollution,and food safety issues related to BaP have caused increasing attention in recent years.At present,conventional methods,which widely used to detect BaP,include fluorescence spectroscopy,high-performance liquid chromatography-fluorescence method,and gas chromatography-mass spectrometry method.Most of these traditional methods are time-consuming,and require expensive equipment,complicated pre-processing,and large amount of chemical reagents.Therefore,it is significantly important to develop a fast and highly sensitive method for BaP detection.Surface enhanced Raman spectroscopy(SERS)is a rapid and sensitive detection method,which has been extensively applied for identification of different chemical and biological analytes in recent years.The main purpose of this paper is to detect BaP in water and edible oil based on SERS technique.Firstly,highly-ordered Ag nanodot arrays were fabricated by anodic aluminum oxide(AAO)template method.Then,detection of BaP in water based on mercaptan-functionized Ag nanodot arrays was realized.Finally,SERS coupled with molecular imprinting technique was used for analysis of BaP in edible oils.The main contents and conclusions are as follows:(1)Preparation and characterization of SERS-active Ag nanodot arrays substrate.The Ag nanodot arrays with different heights and diameters were prepared by AAO template method,and were then characterized by scanning electron microscopy(SEM),transmission spectroscopy,FDTD simulation,and Raman probe molecule.The results show that Ag nanodot arrays with larger diameter can cause stronger local surface plasmon resonance(LSPR)effect,therefore can obtain better SERS effect.Ag nanodot arrays with diameter of 80 nm and height of 50 nm can obtain best SERS effect,with an enhancement factors(EFs)reaching 1.6×106.In addition,the reproducibility and life of use of the substrate were also investigated.The relative standard deviation of the characteristic peak intensity of the rhodamine probe ranged from 13% to 19%.The substrates were still effective after the storage of 60 days,with EFs of 1.5×105.(2)Detection of BaP in water based on mercaptan-functionized Ag nanodot arrays.Firstly,density functional theory(DFT)was used to calculate theoretical Raman spectra of BaP.The calculated results were in accordance with the Raman spectra of standard BaP solid,and characteristic peaks of BaP were then attributed.Then,BaP was detected by Ag nanodot arrays modified with three mercaptans(hexanethiol,decanethiol and octadecanethiol).The results showed that SERS substrates modified by mercaptans with shorter chain can obtain stronger Raman intensity of BaP.Hence,the BaP was qualitatively and quantitatively analyzed using hexanethiol-modified substrates.The detection limit of BaP was 1.0 ppb,and the relative standard deviation of the quantitative characteristic peak was 9.7%,which meet the criteria of highly-reproducible SERS substrates.In addition,owing to powerful whole-organism fingerprinting ability of Raman spectroscopy,identification of four polycyclic aromatic hydrocarbons(pyrene,anthracene,benzanthracene,BaP)using the modified substrate was realized.(3)Rapid detection of BaP in edible oil using SERS coupled with molecular imprinting technique.First,molecular imprinted polymers(MIPs)with BaP as templates were successfully prepared by noncovalent bulk polymerization.The maximum adsorption capacity of BaP was 34.6 ?g/g.Then,edible oil samples was preprocessed by solid phase extraction with MIPs as packing,and subsequently detected by SERS methods.The results show that the separation of BaP in edible oil could be achieved by molecular imprinting solid phase extraction,and the SERS detection of isolated BaP was not influenced by the category of edible oil.This method can be used to detect BaP in edible oil with detection limit of 5.0 ng/m L,which meet the national standard(10 ng/g),and recovery rate from 93% to 100%.