The Preparation And Application Of Cellulose-based Composite In SERS Sensing

Surface-enhanced Raman scattering(SERS)spectroscopy is an advanced analytical technique due to the high sensitivity and excellent selectivity,which has been widely used in detection of chemical and biological molecules.The performance of SERS is highly relied on the feature of the active substrate.Compared with the traditional rigid SERS substrate,the flexible SERS substrate has many advantages,such as good mechanical property,flexible and easy to bend,can be cut to any size and shape,and can fully contact with the actual sample,which improves the detection effect of SERS on irregular surface.In this thesis,cellulose-based metal nanoparticle composites were prepared by loading metal nanoparticles on cellulose surface by in-situ synthesis,electrostatic self-assembly and seed-mediated method.The existence and structure of metal nanoparticles were characterized by UV,IR,SEM,TEM,XRD,and surface enhanced Raman spectroscopy,which were applied to the detection of pesticide residues on fruits and vegetables in real life.The main work of this paper is as follows:1.Regenerated cellulose fiber from waste paper was used as solid carrier,and after surface modification,nano-gold and nano-silver particles were loaded on cellulose surface by electrostatic self-assembly,so as to prepare regenerated cellulose fiber-nano-gold/silver composite materials.The standard mean square deviations of spectral uniformity of fiber/gold and fiber/silver SERS substrates are 3.5%and 5.8%,respectively.Two kinds of flexible SERS substrates were used for SERS detection of environmental pollutants nillan molecules and bisphenol A in beverages,and their sensitivities were 10^-9M and 0.01 ppm respectively.The SERS activity of flexible SERS substrate is proved by theoretical simulation.2.The traditional self-assembly method is difficult to deposit high-density silver nanoparticles on the fiber surface due to diffusion limitation.In this chapter,medical defatted cotton was used as flexible carrier to prepare cotton-silver composite as SERS substrate.High density silver nanoparticles were deposited on the surface of defatted cotton by in-situ growth method.Scanning electron microscope,electron microscope imaging and so on proved that high-density silver nanoparticles were deposited on cotton surface.SERS activity was optimized by adjusting preparation conditions.And that prepare SERS substrate has good SERS activity and spectral uniformity.The substrate was applied to the detection of pesticide residues on the surface of apples and fish,and the lowest sensitivity was 0.1 ppm,and the multi-channel detection of pyrimethanil and thiram could be realized.3.In this chapter,silver nanoparticles(Ag-NPs)were loaded on the surface of cotton gauze by in-situ synthesis method to prepare multifunctional flexible SERS substrates.Silver nanoparticles were labeled with multi-molecules,and the precise regulation of spectral information was realized by controlling the species and proportion of Raman probe molecules on the surface of silver nanoparticles.The optical information stored in the device can be flexibly regulated,and it can be used as an information modulation SERS substrate for packaging applications.The substrate can also be used as a flexible substrate for SERS detection of pesticide residues on fruit surfaces.