Preparation And Application Of Paper-Based SERS Substrate

Raman spectroscopy has the advantage of non-invasive and enables precise analysis of the material structure.Surface-Enhanced Raman Scattering(SERS)can substantially enhance the intensity of conventional Raman signal.Recent years,SERS technology has shown great potential in the field of analytical science,surface science and medicine.However,the preparation of SERS substrates often requires expensive equipment and complicated preparation process,in addition,the sensitivity and reproducibility of SERS substrates cannot be effectively guaranteed.There are still great challenges in the application of SERS technology in practical detection.To improve the sensitivity and convenience of SERS technology in practical application,we prepared SERS substrates with high sensitivity and good reproducibility using common materials in the laboratory and demonstrated its potential in the detection of agricultural residues.1.In this paper,SERS enhanced principle of different Ag Nano-particles(Ag NPs)was analyzed.Different shapes and sizes of Ag NPs were prepared by varying the heating time of the microwave method.The experiment found that with the increase of heating time,the particle size of Ag NPs increased,the homogeneity became worse,and the SERS enhancement effect on rhodamine 6G(R6G)was parabolic with the first enhancement and then became weak.To explore the principle,the electric field distribution of Ag NPs(three kinds of heating time)was numerically simulated by the Time-Domain Finite-Difference method.Simulations revealed that the factors affecting the electric field intensity between dimeric Ag NPs are particle size,particle spacing and particle type.The combination of nanospheres and nanowires generated the strongest interparticle electric field intensity.However,the combination of nanospheres with multiple nanowires substantially reduces the intensity of interparticle electric field.The numerical simulation results are in good agreement with the experimental results,which provides a basis for optimizing microwave heating time.This provids theoretical support for preparing SERS substrates with high sensitivity and good uniformity.Finally,We selected Ag NPs with the heating time of 5 minutes to prepare the SERS substrates.2.In this paper,a nano-silver glue pen was designed and used to prepare paper-based SERS substrate.The pen facilitated the long-term storage and convenient application of Ag NPs.The air-laid paper was used as the paper-based material to prepare SERS substrates by experimental comparison.Taking R6 G as the probe molecule,the factors affecting the Raman enhancement effect on paper-based SERS substrates were analyzed,such as drying time,soaking time and water content.Based on this,we proposed the method to ensure the substrate exerts the SERS effect normally.As tested,the relative standard deviation of the Raman peak at 612 cm-1 of R6 G was 11.13% and the enhancement factor was 7.84? 1012.In addition,high-precision SERS arrays were fabricated in combination with 3D printers.The high precision SERS array is beneficial to improve the reproducibility of the SERS signal,and the preparation cost is very low.In terms of pesticide residue detection,the substrate was able to detect 1×10-8 mol/L thiram residue on the apple peel,which was lower than both the national standard of 2.44×10-6 mol/L and the EU Standard of 0.97×10-6 mol/L.The test results for malachite green were also in line with the national standard and the EU standard.These experiments demonstrated the feasibility of the proposed substrate in practical detection.High sensitivity and convenience of paper-based SERS substrates facilitate the rapid detection of pesticide residues in the field.