| Surface-enhanced Raman scattering?SERS?detection technology is an ultra-sensitive optical detection technology.The sensitivity of this detection technique can reach the level of single molecule,so since it was discovered in 1974,it has attracted wide attention of people and been applied in various fields.The huge electromagnetic field near metal surface is the dominated enhanced factor in SERS.The huge electromagnetic field comes from the surface plasmon,which is the collective oscillation of free electrons generated by light excitation.As a result,the obtained strong molecular Raman signals are mainly derived from those molecules which are located in the nano-gaps or clefts,so-called hot-spots.In the actual detection,people generally deposited silver or gold nanoparticles with different morphologies on silicon wafers or glass wafers to prepare SERS base.Unfortunately,because common substrates such as glass and silicon wafers are hydrophilic,the nanoparticles dispersed in the solvent evaporate would disperse freely on the substrates,making the distance between the nanoparticles too large to create a huge electromagnetic field.Given the diffusion of the solute,it is hoped that a method can be used to successfully concentrate the solute in a very small area,so that the nanoparticles are tightly packed together and the molecules to be detected can easily enter the hot spots,thus enhancing the molecular Raman signal.Based on this idea,people prepared various kinds of hydrophobic or superhydrophobic base as SERS substrate.However,many superhydrophobic materials may lose solutes due to their inherent nano/micro structures.Moreover,the preparation of general super hydrophobic SERS bases are complex and expensive,so its wide application in industry is a barrier.In order to improve the practical application of superhydrophobic SERS substrate,we proposed a method using laser engraving technology to prepare SERS substrate on Teflon.Laser engraving can change the hydrophobicity of Teflon to reduce the contact area between droplets and substrate.A kind of superhydrophobic Teflon substrate with microarrays structure was obtained by designing appropriate laser engraving patterns and appropriate engraving parameters.SEM images of the engraved area show that the micro/nano structure generated during the engraving process is crucial to its superhydrophobicity.The microarray circles are hydrophobic throughout the substrate and are surrounded by superhydrophobic surfaces produced by laser engraving.Due to the superhydrophobic structure next to the small circle,during the evaporation process,the contact area between the droplets and the substrate would gradually shrink,and eventually all the solutes would gather on the small circle.Due to the special superhydrophobic structure of the microarray,the solute dissolved in water can be successfully collected into the hydrophobic small circle in only 10 minutes after evaporation at high temperature.Our microarray structures are similar to that of the24-well plate in the biological laboratory.The fabricated superhydrophobic substrate has virtual walls which can detect different molecules conveniently on the same substrate.We studied the minimum detection limit of methylene blue and rhodamine 6G(the limited of detection is 1×10-14 M)on the prepared substrate,and used biomolecules?bovine serum albumin?to demonstrate their advantages in biological applications.Raman spectral intensity measured on the laser-engraved Teflon indicated its potential value as SERS substrate.In addition,the SERS substrate cost obtained was only 20 yuan,and the whole manufacturing process only took 20 minutes.In conclusion,this paper prepared a kind of SERS 6substrate with low cost,reliability,practicality and strong activity,and it was able to achieve rapid evaporation without affecting the detection result.This kind of simple,cheap and sensitive SERS substrate developed by us has high commercial value and wide application prospects. |
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