Design And Preparation Of SERS Composite Substrate With High Performance And Application For Hexachlorocyclohexane Pesticide Residues Detection

Hexachlorocyclohexane(HCH)is a typical environmental pollutant with high toxicity and structural stability.It is prone to long-term existence in stable media such as soil and water.The environmental problems brought by historical use of HCH have been one of people's focuses,therefore,the rapid,efficient identification and trace,portable detection is particularly important.However,the detection method for HCH(chromatography,bioanalysis,electrochemical sensing,etc.)at present could not achieve this goal.Surface-enhanced Raman scattering(SERS)spectroscopy,due to its high sensitivity and fingerprint recognition,has unique advantages in the detection and application in highly toxic molecules,and will be an effective way to achieve the goal of HCH detection.However,due to the weak interaction between HCH molecules and noble metal SERS substrates,it is difficult to achieve effective capture and high sensitivity detection.In view of this,we proceeded from the efficient enrichment and specific selection of HCH molecules,and carried out the design and preparation of SERS composite substrates with high performance.Then,we studied the SERS response of substrates for HCH,and explored ways for high efficiency and trace detection.The main research work and innovative results are as follows:(1)A strategy based on low temperature regulation to control nanocrystal growth has been developed.By adjusting the temperature of the growth solution to control the relative growth rates of<110>and<111>directions,the shape' regulation of Au nanocrystal and the structural optimization of SERS substrate were realized.Films constructed by concave trisoctahedron and calyptriform Au nanocrystals exhibited strong SERS activity due to high density sharp corners/edges.For the SERS-based lindane molecular detection,the enhancement factor(EF)was as high as 107 and the detection limit was 30 ppb.This strategy provided a variety of novel SERS substrates for trace detection of HCH pesticides.(2)A seed growth method based on kinetic control was proposed.The chestnut-like Au nanostructure with high density tips was constructed by adjusting the addition rate of the Au seed solution to the growth solution.The formation of this configuration was attributed to the preferential growth of the seeds along<111>direction and the formation of nanoneedles.The films made by Au nanocrystals with high density tips show strong SERS performance.When it was used for SERS-based detection of ?-HCH molecular,the detection limit was as low as 10 ppb.This structure provided an efficient SERS substrate for the identification and detection of trace HCH pesticides.(3)A porous ZIF-8 shell wrapped urchin-like Au-Ag alloy nanoparticles(UAAN)core-shell configuration was designed and prepared.This structure was used as SERS substrate for the detection of trace ?-HCH and a-HCH molecules,and it was found that a suitable thickness of the ZIF-8 shell could significantly improve the SERS performance of trace HCH detection.Especially in low concentration solution,it exhibited an increasing enrichment effect,and the detection limit was about 1.5 ppb.This work successfully achieved efficient enrichment and SERS detection for trace HCH molecules.(4)A new route to capture HCH pesticides actively was found.The HCH molecules were actively captured by Suzuki cross-coupling reaction between HCH and 4-mercaptophenylboronic acid(4-MPBA)by modifying 4-MPBA on the surface of Au nanosheets-built hollow sub-microcubes(ANHCs).The SERS results demonstrated that ultra-sensitive detection of HCH could be achieved with a detection limit of 0.3 ppb.In addition,4-MPBA modified substrates exhibited higher reproducibility and sensitivity than unmodified substrates.This strategy could be used for the detection and differentiation of HCH isomers in mixtures samples.