| Abuse of food additives and excessive pesticide residues have seriously affected the human health and the threatened ecological balance,therefore,the trace detection of such substances has become a popular research in the field.Compared with limits of complicated operation for the traditional detection techniques,surface enhanced Raman scattering（SERS）spectroscopy has the advantages of high detection sensitivity and simple operation,while the high quality SERS substrate will play an important role in improving detection sensitivity.The preparation of periodic micro-nano structures to construct the surface plasmon coupling system has become one of the popular researches in preparation of high-quality SERS substrates.However,most of the existing technologies are highly dependent on materials,so it is necessary to develop universal micro-nano periodic structure preparation technology to improve the effective detection of trace residues such as food additives and pesticides.Combining the laser induced forward transfer technology with the advantages of high speed and universality of materials and the laser interference lithography technology with advantages of high positioning accuracy,no scanning and large area,the novel technology of laser interference-induced forward transfer technology（LIIFT）was proposed.The principle and system construction of LIIFT technology were explored,and periodic micro-nano stripes and lattice structures are prepared by double-beam and three-beam LIIFT.On this basis,typical food additives of Rh B was selected to verify the SERS characteristics of the transferred micro-structures,and the relationship between micro-nano structure and SERS characteristics was established,which will provide new ideas and methods for the preparation of SERS chips.The main researches were carried out as follows:1.Theoretical computation and analysis.Firstly,based on the basic principle of two-beam and three-beam laser interference,the distribution law of interference light field was discussed.Secondly,based on the mechanism of bubble-driven laser-induced forward transfer,taking the polyimide（PI）as an example,the LIIFT process and the factors were analyzed.Finally,the SERS characteristics of typical Ag nano-sphere substrates were simulated.The results showed that,the polarization mode,incident angle and azimuth angle of interference light were the main factors affecting the distribution of interference light field.In LIIFT process,after gasification,expansion and explosion of PI film,the remaining film would be delaminated and transferred to the receiving substrate.The transfer process would be affected by the incident laser fluence,PI film thickness and pulse number.Under the excitation of plane wave,the larger field strength of Ag nanospheres appeared in the gap between nanospheres,and the nanospheres with larger diameter and smaller spacing would be excited with larger field strength.2.Preparation of PI micro-stripes by LIIFT.On the basis of optimizing LIIFT system,periodic PI micro-stripes were prepared,and the effects of laser fluence,pulse number and PI film thickness on micro-stripes were systematically discussed.The results showed that,on the one hand,with the increase of the laser fluence,the larger micro-size would be transferred,while the excessive laser fluence would result in the disturbing between adjacent micro-stripes,which led to the destruction of micro-stripe structure.On the other hand,increasing the number of pulses properly could improve the integrity and height of micro-stripes.Finally,smaller PI film thickness tended to transfer the deformed micro-stripes,while the excessive thickness of PI film would affect the integrity and the regularity of micro-stripes.3.Preparation of metal micro-stripes by LIIFT.Based on two-beam and three-beam laser interference systems,the micro-structures of Au and Ag were transferred with the triazene polymer（TP）film and PI film mixed with carbon nanoparticles（CNPs@PI）as sacrificial layer.The results showed that the transfer of Ag micro-stripe had great selectivity with the CNPs@PI film as the sacrificial layer.The larger the thickness of Ag film,the larger the diameter of nanoparticles in Ag micro-stripes,and the smaller the density.The smaller the laser fluence,the smaller the density of Ag nanoparticles.Higher laser fluence would increase the probability of inter-particle clustering.With the increase of interference light field period,the density of nanoparticles in the transferred Ag microstructure would increase and the average particle size decrease.4.Research of the SERS characteristics on Ag micro-structure substrate.With rhodamine B（Rh B）as the analyte,the SERS characteristics of the transferred Ag micro-stripes and micro-dot substrates were tested,respectively.The results showed that the Ag micro-stripe substrate transferred under the laser fluence of 102 m J·cm-2showed the strong SERS characteristics,which could realize the minimum concentration with 10-10mol·L-1detection of the Rh B solution.With the increase of the interference light field period,the SERS characteristics of the transferred Ag micro-structure substrate would increase. |
