Construction And Application Of Colorimetric/Fluorescent-SERS Dual-Mode Detection Sensor

Colorimetric and fluorescence methods have gradually become research hotspots of the field of rapidly scene detection due to the advantages of simplicity,visualization and portability.Although the colorimetric method has low detection cost,simple operation process and intuitive results.The result has certain inaccuracy because the concentration of elemental substances has a linear relationship with the color depth.Hence,the method is not suitable for the analysis of trace substances.Fluorescence analysis technology is widely used in analytical detection due to the high sensitivity,small sample size and low cost.However,most fluorescent probes are difficult to distinguish some substances with similar structure.Surface enhanced Raman spectroscopy（SERS）is highly sensitive because it amplifies the Raman signal of the molecule by adsorbing the target molecule onto the nanoparticle with SERS activity.Due to the different molecules have different Raman spectra signal,the Raman peak position,peak intensity,line shape,line width and number of spectral lines could be analyzed to achieve qualitative and quantitative analysis of samples from the molecular level.SERS has become a powerful and highly sensitive fingerprint technology.However,the reproducibility of the SERS substrate is poor,and the detection results are susceptible to interference.Therefore,the establishment of a dual-mode detection method to achieve complementarity between two detection technologies and ensure more accurate detection results,which has practical significance for the rapid,simple and highly sensitive detection of target substances.In this study,a dual-mode sensor was constructed based on nanomaterials with enzyme catalytic activity and surface Raman enhancement properties,combined with colorimetric/fluorescence-Raman detection methods to achieve the high selectivity and rapid detection of target molecules.The specific research is as follows:（1）Based on the specific binding between gold nanoparticles（AuNPs）and histamine derivatives,a fluorescence-SERS dual-mode detection method for histamine was established.Biogenic amines is influence for the detection of histamine due to the similar chemical structure and properties.To achieve specific detection of histamine,the Schiff product have fluorescence and SERS activity was formed that the product generate from the reaction of the amino group of histamine（-NH₃）and the aldehyde group of o-phthalaldehyde（-CHO）.Meanwhile,AuNPs exhibit a dual effect with enhanced Raman signal intensity and fluorescence quenching.Under the optimized analytical conditions,the linear ranges of the fluorescence and SERS modes were0.05～4.5 mg/L and 1～20 mg/L,respectively,and the detection limits were 0.04 mg/L and 0.32 mg/L,respectively.The fluorescence-SERS dual-mode histamine detection technology successfully detected histamine in seafood.（2）A colorimetric-SERS dual-mode detection technique was designed for the detection of the pesticide thiram based on the enzymatic activity and SERS properties of the AuNPs.The AuNPs with good nano-size and shape possess excellent mimetic oxidase（OXD）properties and plasmon resonance properties by modifing thiol-β-cyclodextrin（SH-β-CD）.AuNPs@SH-β-CD was used to oxidize 3,3’5,5’-tetramethylbenzidine（TMB）to highly Raman-active oxidation product（ox TMB）based on OXD and Raman enhancement effect.The addition of thiram inhibited the OXD of AuNPs@SH-β-CD,which reduced the absorbance of ox TMB and the intensity of SERS signal.Therefore,a colorimetric-SERS dual-mode detection method for thiram was established.The linear ranges of the colorimetric and SERS modes were0.5～80μg/m L and 0.05～5μg/m L,respectively,with detection limits of 0.3μg/m L and0.04μg/m L.The developed method was successfully used for the determination of thiram in tobacco samples.（3）Based on the enzyme activity and SERS activity of glucose carbon dots gold nanoparticles（Glu-CDs/AuNPs）,a colorimetric-SERS dual-mode detection technology for heparin and raloxifene was established.Glu-CDs/AuNPs were successfully prepared by using glucose carbon dots（Glu-CDs）as reducing agent and stabilizer.The peroxidase activity（POD）of Glu-CDs/AuNPs is enhanced by heparin or raloxifene.A colorimetric detection method of heparin and raloxifene was established by the oxidase reaction of TMB.In parallel,the leucomalachite green（LMG）was oxidized to malachite green（MG）with high SERS activity by using the POD activity of Glu-CDs/AuNPs,and a SERS detection method for heparin and raloxifene was established.The mechanism of heparin and raloxifene enhancing POD activity was studied by particle size and Zeta potential.These methods were successful used to the determination of heparin in blood and aloxifene in pharmaceutical tablets.The results demonstrated the good selectivity and sensitivity of the assay for heparin and raloxifene.It provided an idea for the development of a dual-mode colorimetric-SERS assay technique.