Quantitative SERS Techniques Based On Core-shell Nanoparticles And An Advanced Calibration Theory

Compared with other spectroscopic techniques,surface-enhanced Raman spectroscopy(SERS)has the advantages of exquisite sensitivity,fast measuring speed and simple sample preparation,and hence has great application potential in many fields.However,at the present stage,SERS is still a qualitative and semi-quantitative technique,due to the fact that the SERS signals of the analytes of interest depend not only on their concentrations but also the physical properties of SERS enhancing substrates,such as the size and shape of nanoparticles as well as their degree of aglomeration.In this thesis,the spectral deformation quantitative theory(SSD)was combined with core-shell composite nanoparticles embedded with internal standard to effectively eliminate the effects on SERS signals caused by variations in the physical properties of the enhancing substrate,and hence to realize accurate quantiative SERS detection of the analytes of interest.The main contents of this thesis are as follows:In chapter 2,Au core-Ag shell composite nanoparticles embedded with different internal standards(IS)was synthesized by the sequential reduction method.The composite nanoparticles Au@IS@Ag were characterized by UV-vis sepctrsocpy,TEM and SERS technique.Experimental results demonstrated that the composite nanoparticles sythesized were of core-shell structures,and had good stability and high SERS activity.In chapter 3,core-shell composite nanoparticle embedded with internal standard4-MBA(Au@4-MBA@Ag)combined with the SSD model was applied to the quantative SERS detection of methimazole in plasma and tablets.The proposed method effectively mitigated the effects on the SERS signals of methimazole caused by heterogeneity of enhancing substrate,and successfully gained satisfactory quantitative detection results of methimazole in plasma and tablets.The experimental results showed that the recovery rates of the proposed method for methimazole in both plasma and tablet samples were within the ranges of 91.3%~102.1% and99.6%~105.7%,respectively.The limit of detection was estimated to be 23 nmol/L.In chapter 4,core-shell nanoparticles embedded with internal standards 2-MB and PATP(Au@2-MB+PATP@Ag)were combined with the SSD model for the quantitative SERS detection of phosmet residues on apple skin.Its quantitative results were compared with those obtained by using core-shell nanoparticles embedded witheither 2-MB or PATP(i.e.,Au@2-MB@Ag or Au@PATP@Ag).Since the SSD model can make full use of the SERS spectral information of multiple internal standards,the combination of the SSD model and Au@2-MB+PATP@Ag obtained more accurate and precise concentration predictions than both univariate ratiometric calibration models and traditional multivariate calibration models in combination with Au@2-MB@Ag,Au@PATP@Ag or Au@2-MB+PATP@Ag.The accuracy and precision of the quantitatvie results obtained by the proposed method were comparable with those of LC-MS/MS.