Uniformity Interface Assisted Self-assembly Optimization Of Preparation And Application Of 3D SERS Substrate

SERS is a molecular fingerprint that has no special treatment or nondestructive characteristics in sample analysis.Together with its fast detection speed and high sensitivity characteristics,so as to be widely used in biosafety,chemical detection and medicine.At present,precious metal materials mainly composed of gold,silver and copper have better SERS effect,while nano silver has the best SERS enhancement effect.However,for quite some time,silver materials have been destructive to their SERS enhancement due to their susceptibility to oxidation and vulcanization,and so far,there has not been a substrate with uniform distribution of hot spots to enhance the uniform effect,resulting in reproducibility of sample detection signals.Not good,especially for trace detection,signal uniformity is very necessary.This paper starts with the SERS substrate,using a single crystal silicon wafer or a glass slide as a solid substrate carrier layer.Using a self-assembly method at the air-liquid interface,it can be transferred to any solid substrate after film formation.The morphology uniformity and substrate stability,SERS sensitivity and signal reproducibility of the substrate were investigated.The main works are as follows:(1)Synthesis and optimization of different lengths of Ag NRs and 3D Ag NRs SERS substrate preparation and molecular detection.Gold nanoparticles with a five-fold twin structure(nanodecahedron)were used as seeds,and Ag NRs were grown in the CTAC system by adding Ag NO3 and AA.By adjusting the amount of Ag NO3,a series of lengths of Ag NRs are obtained,which are all purified nanorods after purification.The Ag NRs synthesized by this method have a length of 53 nm-245 nm,not only having the high degree of monodispersity but also having the uniform particle size,both of which are 22 ± 1 nm.Taking Ag NRs with length of 200 nm as an example,the Ag NRs were assembled into a film at the air-liquid interface,and the SERS activity of the substrates(NL=1-20)obtained by the layer transfer method was evaluated by threeexcitation light(532 nm,633 nm and 785 nm).The RSD of average SERS intensity at three wavelengths(532 nm,633 nm and 785 nm)was within 10%(except for single-layer assembly),and an optimized 3D SERS substrate(NL=6)was found.Under the confirmation of optimized NL,different lengths of Ag NRs were studied.The SERS activity of the 3D Ag NRs substrate(NL=6)assembly confirmed the final optimized 3D SERS substrate.Finally,the optimized 3D SERS substrate was used to quantitatively detect the four biomolecules(urea,Phe,Trp and melamine)with low detection concentration,which proved the substrate has excellent detection sensitivity and is useful for biological applications.(2)Synthesis and optimization of Au NRs@Ag NC core-shell nanocuboids.Preparation and molecular detection of 3D Au NRs@Ag NC SERS substrate.Au NRs were used as seeds to grow into Au NRs@Ag NC by adding Ag NO3 and AA in the CTAC system.Seed-mediated growth of Au NRs@Ag NC is highly monodispersed,with a uniform cuboid size,an average length of 95 ± 6 nm,and an average width of 33 ± 1 nm.The Au NRs@Ag NC is assembled into a film at the air-liquid interface and transferred to any clean solid substrate in a pull-up manner to obtain a series of different layer and thickness substrates through three excitation wavelengths(532 nm,633 nm and 785 nm).The SERS activity of these assembled substrates was studied by 4-MBA as a probe under the laser.The RSD of these substrates was less than 10%.The optimized 3D SERS substrate(NL=4)was found by comparison.Quantitative analysis of the two molecules(pesticide TMTD and fluorescent dye RB)with the optimized 3D SERS substrate showed a good linear relationship in the detection concentration.At the same time,the two molecules(pesticide TMTD and dye MG)were added to the internal standard Au NRs@p MBA@Ag NC)performed quantitative detection.For the TMTD in which the characteristic peak of the internal standard does not coincide with the characteristic peak of the detection molecule,the linearity after correction is improved,and the MG with the coincident peak has no good effect.The detection of these molecules also further demonstrates the potential advantages of 3D SERS substrates.