| Surface enhanced Raman scattering (SERS) as a high senstentive, specificity, nov-invasive technique has been widely attention in recently years. The work about optimizing and creating more better SERS material has been reported, the key impact to SERS effect is the "hot-spot", which related technique and different microstructure of materials were developed. In our work, we synthesized the specific siliver nanoparticle probe which has prefect SERS effect, and constructed dense packed ring-like substrate which has a lot number of hot spots via to the coffee ring effect. β-cyclodextrins (P-CD) were absorbed physically on the surface of the silver nanoparticles as capturing layers of aromatic compounds for enriching the analytes on the interface of the silver nanoparticles in solution. After analyte was captured, the mixture of silver nanoparticles and aromatic compounds were dropped on silicon wafer to form the coffee ring, a dense packed silver nanoparticles loaded with the analyte on the interface of silicon wafer, In light of this, analytes were able to enrich twice in the process. Furthermore, dense-packed substrate produced a large number of "hot-spots" to improve the SERS effect. The combination of the pre-concentration of β-CD and the SERS effect of the coffee-ring enhanced the detection ability of SERS on aromatic compounds. Moreover, we developed the two-scale interface enrichment technique and fabricated a 3D SERS substrate, and achieved high sensitive detection of aromatic compounds.The details are as follows:1. Siliver nanoparticles modified with β-cyclodextrins (AgNP@β-CD) were synthesized, and the average size of AgNP@β-CD was 30 nm. We study the optical property, the stability of material, micro-structure using UV-Vis spectrophotometer and scanning electron microscope (SEM). The solution presenting transparent bright yellow indicated that the AgNP@β-CD is monodisperse in solution and the surface of AgNP was successfully modified with 2 nm thick β-CD. The results of Fourier transform infrared spectrum (FITR) proved the surface of siliver nanoparticles succeed modified with β-CD. We successfully synathesized good mono-dispersed, surface modified P-CD and uniform size siliver nanoparticles, which provides good foundation for the subsequent experiment.2. Based on the principle of the coffee ring effect form, we select the optimize hydrophocity silicon wafer as the silid substrate through palfilm film, Teflon, silicon, glass, which is benefit to the coffee ring effect form under laboratory condition. We optimize the conditions of AgNP@β-CD assembled ring-like substrate containing the concentration of AgNP@β-CD, the volume of droplet, environmental temperature, time. AgNP and AgNP@β-CD respentivly deposited via the coffee-ring effect and uniform deposited, it is concluded that the AgNP @ beta CD material formed by coffee ring used basal results have better specificity and SERS enhancement effect. Furthermore, under the coffee-ring effect, the signal was greater than the pattern which uniformly deposited on the silicon wafer. In the end, the AgNP@β-CD assmbelly facibracied 3D SERS substrate which contains a lot number of hot spots.3. We select several typical aromatic compounds which containing OPD,2,3-Diaminonaphthalene,2, 4-dihydroxybenzoic acid as the detection represent and achieve the detection of low concentration. The detection limit of this platform is variant for different analytes(OPD:100 pM; 2, 3-Diaminonaphthalene:lnM; 2,4-Dihydroxybenzoic acid:100nM;) under the optimized conditions, the calibration curves clearly show that the intensity of characteristic peak was influenced by the concentration of solution(OPD:0.1 -10 μM; 2,3-Diaminonaphthalene:10-100 nM; 2, 4-Dihydroxybenzoic acid:1-10 nM;). and prove that the two-scale interface enrichment technique greatly improve the SERS effect. Moreover, the technique also can be applied in the ditection of other trace analytes (biological molecules, heavy metal ion, organic contaminant). |
PDF Full Text Request