Designation And Construction Of SERS Active Substrate And Its Performance In Pollutant Detection

Surface-Enhanced Raman Spectroscopy(SERS)with extremely high surface detection sensitivity that can forecast molecular structure characteristics and material composition.With the fingerprint characteristics,SERS has been widely applied in contaminant monitoring and even effective control of food and drug safety.The high sensitivity of SERS detection can be obtained only on the condition of the analyte with a large Raman scattering cross section and has a strong affinity with the the highly active Raman substrate.However,real samples are often having a small Raman scattering cross section and has a low affinity with the substrate.And they are always in complex environments with interference intensities thus making identification of chemical species a real challenge.These difficulties motivated the development towards the directions of designing functionalized substrate,assembling substrate and universality.From the perspective of designing functionalized substrate,assemble 3D substrate and semiconductor substrate,we constructed three different SERS substrates in view of the problems encountered in actual sample detection.The main work of this thesis includes the followings:(1)?-cyclodextrin(?-CD)stabilized AuNPs(AuNPs@?-CD)was synthesized by a simple hydrothermal reduction method.A SERS-UV dual-mode sensing system with the effective and specific detection of trace butyl benzyl phthalate(BBP,one of phthalate esters(PAEs))in liquor was demonstrated by constructing action between AuNPs@?-CD colloid and BBP.DFT calculations speculate the mechanism that the AuNPs@?-CD how to capture BBP.Herein,?-CD serving as a Raman capture probe and a stabilizer is anchored on the surface of AuNPs to capture BBP.Therefore,BBP acts as a binder as well as a controller to regulate the electromagnetic intensity and the metachromatic assembly process.AuNPs@?-CD assembled into nanoclusters with different shapes mediated by BBP.The AuNPs@?-CD 'aggregates' provides large-volume hot spots because of its larger specific surface and plentiful voids.BBP is quantified by combining a naked-eye observation of remarkable colorimetric response and LSPR of 'clusters'.DFT calculations speculate that the AuNPs@?-CD capture different hydrophobic groups of BBP.The obtained BBP-triggered AuNPs@?-CD clusters are able to amplify the corresponding SERS signals due to the abundant hot spots with a lowest detection limit of 0.01 ?M.In the colorimetric analysis of detecting BBP,the colorimetric distinguishable response can be accurately quantified via UV-vis spectroscopy with AuNPs@?-CD clusters act as naked-eye indicators and a detection limit as low as 14.9 nM.This research provides a fresh method for monitoring BBP as well as offers a novel inspiration for designing solvatochromic and SERS-based sensing system in field trial applications.(2)By taking the advantage of the large-area electromagnetic field "hotspots"and 3D reticular utilizes tellurium array,combing the template method with the LB assembly method,a Te-Au nano reticula sensor was designed with easily adjustable morphologies and used to detect melamine(MM)in milk samples.The excellent SERS intensity of 3D Te-Au nanowire reticular profit from its three-dimensional space providing much more high density uniform electromagnetic hotspots.Layers of ultrathin nanowires keep particles sequentially which ensure the repeatability and abundant hotspots at interparticle gaps guarantee the high SERS performance of the substrate.To theoretically explore the nanoparticle-enhanced localized surface plasmon resonance(LSPR)effects,the finite-difference time-domain(FDTD)analysis were employed.Ascribed to high-density hotspots,the 3D SERS substrate with superior SERS enhancement realized the ultramicro detection of water-soluble rhodamine 6G(R6G)with a detection limit of 1 pM.Furthermore,the nano reticula is exemplified by a real-life application of ultrasensitive SERS detection of MA with a fine linear relationship from 1 to 100 nM.Together with enduring repeatability,plentiful hot-spots and high sensitivity,these collective advantages empower 3D Te-Au nanowires reticular array been a practical tool to monitor relevant in industrial pollutants.(3)A kind of transition metal telluride HgTe tetrahedron nanoparticles was designed and developed as a highly sensitive SERS substrate.The abundant electron cloud density is calculated by the density functional theory of first principles,and the the distribution of electromagnetic field is calculated by the the finite-difference time-domain(FDTD).The strong interaction between the analyte and HgTe tetrahedral nanoparticles as well as the rich state density of the semi-metal HgTe tetrahedral nanoparticles near the Fermi level produced a good SERS effect to promote the charge transfer resonance of the analyte telluride complexes.which is helpful to produce local surface plasmon resonance(LSPR)effect.Moreover,the optical coupling between the tips of the special tetrahedral structure provide a larger scattering cross section.It also helps to generate a large number of hot spots to increase the Raman scattering effect.A Raman enhancement factor(EF)of 4.24×106 was obtained used the probe molecule R6G with the SERS substrate.Semi-metallic telluride HgTe nanoparticles can be used as SERS substrates to detect trace pollutants.