Two-dimensional SERS Substrates For Onsite Detection Aided By Fast Pretreatment

Surface-enhanced Raman scattering（SERS）technology can enhance the Raman spectrum signal of the analyte by 10⁴-10¹⁴ times,greatly improving the detection sensitivity,and has been widely used in environmental detection,reaction monitoring,and biochemical analysis in recent years.And biological imaging.As we all know,the localized surface plasmon resonance（LSPR）effect of precious metal nanoparticles greatly increases the electromagnetic field intensity near the surface of the nanoparticles,which is the main reason for the enhancement of the Raman scattering of the molecules near the surface of the metal nanoparticles.It is worth noting that the areas of high curvature on the nanoparticles and the gaps between the nanoparticles have stronger electromagnetic field strength than other sites,commonly known as SERS"hot spot".Therefore,the introduction of the target into the SERS"hot spot"in practical applications is critical to the sensitivity of detection.For a long time,researchers have devoted to the development of various anisotropically structured precious metal nanoparticles as highly sensitive SERS substrates,such as nanocubes and nanoflowers.However,the morphological uniformity of the nano-sol particles is not good,the yield is not high,and they are in random movement all the time,and the detection reproducibility is not good.The solid-phase substrate has good uniformity,high reproducibility,and strong stability,so people are paying more attention to the solid-phase substrate.However,most of the existing solid-phase substrate preparation technologies are expensive and complex to prepare.Therefore,there is an urgent need to develop a simple and low-cost preparation method for preparing highly sensitive and highly reproducible SERS solid-phase substrates.It cannot be ignored that there are often many interfering substances in the actual application system,and the Raman spectrum signal of the target object is easily covered/annihilated in the background.Not only that,the mass transfer efficiency of the solid-liquid two-phase interface is low,especially when the target lacks affinity with the SERS substrate,it is difficult for the target to enter the hot spot area,which makes the detection difficult to achieve the expected sensitivity.In view of the above-mentioned factors that restrict the practical application of SERS,this thesis has developed a simple and reproducible method for preparing a two-dimensional SERS substrate,and designed two fast and convenient pretreatment strategies based on different sample objects.The work and results are as follows:1.Using self-assembled small-diameter gold nanoparticles as a template,a dense and gapped gold nanoparticle two-dimensional cluster structure was prepared by the cyclic growth method.The density of SERS"hot spot"can be adjusted by optimizing growth parameters.Synthesized reticulated colloidal lignin particles（CLPs）are used for the rapid enrichment and phase transfer of benzotriazole（BTA）in transformer oil,so that BTA can easily enter the"hot spot"area of the substrate.The detection limit can be down to 0.12 mg/L,and the linear range is 1-300 mg/L.2.Using self-assembled hollow copper sulfide nanoparticles as a template,a dense and gapped gold-coated copper sulfide nanoparticle two-dimensional cluster structure is prepared by the cyclic growth method.The plasmon coupling effect between the copper sulfide core and the gold shell,and adjacent gold shell endows this two-dimensional heterogeneous substrate with two superior properties:Electromagnetic field enhances the SERS"hot spot",that is,"electromagnetic hot spot".Photothermal effect promotes mass transfer at the solid-liquid interface and induces micro-region enrichment of matter,namely"photothermal hot spot".The enrichment time of the"dual-hot"two-dimensional heterogeneous substrate only takes 10 minutes,the detection limit of crystal violet（CV）molecules is 8.55 n M,and the linear range is 10-300 n M.