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Research On Preparation Of SERS Structured Substrates And High Sensitivity Detection

Posted on:2014-01-19Degree:DoctorType:Dissertation
Country:ChinaCandidate:W Y ZhangFull Text:PDF
GTID:1228330395996372Subject:Microelectronics and Solid State Electronics
Abstract/Summary:PDF Full Text Request
This paper aims to develop a kind of SERS substrate which is widespread,high efficient, low cost, highly sensitive. Surface Enhanced RamanScattering (SERS) technology is an important technology in modern testingfield. SERS technique is widely applied in chemical industrial analysis,biological analysis, medical detection and many other areas for its highsensitivity, low background fluorescence and nondestructive testing ofsamples. At present, the commonly used SERS substrate preparation processis relatively complex, difficult. All these disadvantages hinder theapplication of this technology. This thesis aims to develop multi-levelSERS substrates via laser micro-nano processing, electrostatic spinningtechnology and physical vapor deposition (PVD) technology. The substrateis not only surface morphology designed, high detection sensitivity andlow cost, but also can realize rapid preparation in large area. The keyinnovation work is summarized as followed:(1)Rapid SERS-active substrate preparation which has two-dimensional grating structure via laser interference technology and PVDmethod. In this part, we use the NOA-63photoresist to prepare gratingstructure rapidly via laser interference system, and then evaporate themetal nanoparticles onto the grating structure via PVD technology. So weget a metal covered double-level SERS substrate. We can determine thefirst level phase of grating structure through adjusting the angle of twobeams of coherent light, which enhances surface plasmon resonance. In thisway, the Raman scattering is increased. We use R6G and p-ATP as the probemolecules to test the SERS substrate we got,and the Raman scatteringenhancement factor can reach. Based on the method of laserinterference technology, we can rapidly prepare substrate in large area,and our SERS substrate process is relatively simple, so it is a kind of ideal SERS substrate preparation.(2)Metal covered nano fiber grating periodic three levels SERSsubstrate preparation via electrostatic spinning technology incombination with UV light lithography and PVD. First, we use SU-8toprepare the nano fiber film with a range of surface roughness viaelectrostatic spinning technology.Electrostatic spinning technology isrelatively simple.The fibre diameter is uniform,and porosity is high.Then Electrospun SU-8nanofiber films is patterned into gratings withperiods of100,200,300and400, respectively. Finally,deposition ofa silver nanolayer on these interlaced nanofiber films would lead to theformation of various plasmonic nanostructures.So this kind of SERSsubstrate has three levels structure——grating period,nanofiber andmetal silver nanoparticles.For the further study,which showed that theSERS substrate has a super hydrophobic properties due to its surfaceroughness,thus roughness can make the solution gathered in the surfaceof the SERS substrate and finally realize high molecular density to makea high SPR. We use rhodamine6G(R6G) as a probe molecule to test theperformance of the SERS substrates and the enhancement factor can reach.The SERS substrate preparation method above is relatively simplerand lower cost in technological process compared with the preparationmethods currently. In addition, the process parameters can be controlled.The resultant SERS substrates show both high sensitivity and goodreproducibility.(3)SERS test paper based on the natural surface via physical vapordeposition technology which can be used in production.The main idea isto seek a certain natural surface which have some roughness,and preparehigh sensitive and easy to long-term preserved SERS test paper. First,we studied the morphology of a variety of paper surface,and finally determined to use filter paper as a SERS test paper based material.Themorphology of the filter paper including the micron scale fiber,micro-nano fold on the fiber and the nanoscale fibers on the fold,whichcan form uniform Raman enhancement "hot spots" and effectively improvethe surface enhanced Raman scattering effect. We can use the multilevelstructure of filter paper as the template to get the SERS test paper viaphysical vapor deposition evaporate silver nanoparticles on it. It stillcan get stronger Raman signal,when R6G solution reduced to M. At thesame time, the substrate can keep the SERS activity when it is exposedin the air9hours.We adopt the method that to seal and nitrogenenvironment to save activity,and there is not obviously change aftera month, the test index is stable. The second approach is to choose driedrose petals as the base,and use PVD to evaporate silver film on it, thenget a high SERS effect substrate.Rose petals have micro concave and convexsurface topography,and it has a good super hydrophobic properties due tosuch a surface morphology.We deposite silver nanoparticles on it to makebetter surface roughness,and the SERS substrates show excellent SERSproperties. When R6G concentration is as low as M,the SERS substratealso has strong Raman signal, and the repeatability is very good, theenhancement factor can reach.Both method mentioned above are idealSERS substrate preparation and hold great promise for the applications.
Keywords/Search Tags:SERS, double-beam interference, grating structure, electrostatic spinning, high sensitivity, super hydrophobic, nanometerfiber, SPR
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