Study on Controllable Preparation and Surface-enhanced Raman Scattering Application of Ag Nanorod Hybrid Structure

Author:Chen Jian

Supervisor:wu xue zhong


Degree Year:2018





In recent years,the problems in medicine diagnosis,food safety and environmental monitoring had became increasingly prominent.An effective and accurate on-site biochemical detection can provide reliable support for subsequent treatment,saving people’s lives and property.However,the existing detection technology has the disadvantages such as low detection sensitivity,long detection time and large device size,which can not meet the requirement of rapid field detection.Therefore,there is demand for a detection technology,which has high sensitivity,better peculiarity,high automatic and low cost.Surface-enhanced Raman scattering(SERS)detection technology is a new kind of spectrum detection technology which has great potential of applications in rapid detection of biochemical substances on spot.However,one of the key technologies of SERS detection technology is controllable manufacturing process of high-performance SERS substrate.In view of the above problems,this thesis focused on two aspects of SERS,one is the improvement of the property of SERS substrate,the other is the integration of SERS detection system.It is proposed that the silver nanorods were prepared by the oblique deposition method,then,the Au@Ag core-shell nanoparticals were added into silver nanorods structure to fabricate hybrid structure with high performance of SERS.Lastly,microfluidic technology were used to achieve the detection system integration.In brief,this thesis focused on solving the key issues of the optimization design,electromagnetic simulation,controllable manufacturing process,performance characterization,system integration and applications of biochemical detection of silver nanorods and its hybrid structure.The main research contents are listed as following:1.An optimized design method of silver nanorods and its hybrid structure were established.The electromagnetic field enhancement characteristi cs of SERS substrate were analyzed and the structure of SERS substrate based on the finite difference time-domain method were optimized.To address the needs of improve the enhancement performance of the existing SERS substrates,proposed a scheme of silver nanorods structure optimization and performance enhancement was and designed the Silver nanorod hybrid SERS substrates based on metal nanoparticle.Based on the finite difference time-domain method,analyzed and calculated the electromagnetic field enhancement characteristics in 5 aspects which was the polarization direction of incident light,the material of underlying film,the thickness of the underlying film,the tilt angle and the length of the silver nanorod.By adding metal nano-particles into silver nanorod structure,fabricated the hybrid SERS substrate and studied the formation mechanism,distribution,intensity,density of the hybrid SERS substrate.The final results showed that due to add the metal nanoparticles,the new SERS hot spot were generated and coupled with the original hot spot of the structure,which not only increases the density of the SERS substrate but also increases the intensity of the SERS hot spot and effectively improves the SERS substrate enhancement performance,meanwhile,the optimal design of high-performance SERS substrate were achieved.2.A controllable manufacturing method of large area of silver nanorod structure was established.Aiming at the problems of complex preparation process and low controllability of high-performance SERS substrate,the controllability fabrication of wafer-level silver silver nanorod structures by the method of oblique angle deposition were achieved,and the SERS property and practical application ability of these substrates were tested.According to the parameters of silver nanorod structure that was optimized,the controllable manufacturing of the wafer-level silver nanorod structure was realized by adjusting the deposition angle and the thickness of deposited film based on the oblique angle deposition method,and the SERS substrate has ideal uniformity.The SERS enhancement properties of silver nanorods structure were analyzed with 1,2-bis(4-pyridyl)ethylene(BPE)as the probe molecule,with the lowest detection limit of10-6M.The label free method was used to evaluate the SERS substrate of this structure in the detection of methamphetamine,and the detection sensitivity is 10-6M,which has the potential of quantitative analysis of methamphetamine.3.The controllable manufacturing process method of hybrid structure was established.The optimization manufacturing process scheme was accomplished.The controllable manufacturing of the high-performance hybrid SERS substrate was realized.The SERS performance of the substrate was tested,and the high sensitive detection of methamphetamine was achieved.hrybrid methods of direct combination,in situ growth of polydopamine,and combination of two structures by using two kind of polymers linker were studied respectively to optimize the hybrid nanostructures based on silver nanorods in controllable.The results showed that the Ag NRs@P2VPy-Au@Ag NPs hybrid substrate fabricated by using P2VPy has shown the best SERS performance of all,because this kind of hybrid structrue has solves the problem of uniform dispersion of particles on the nanorods surface effectively,better process controllability,low cost and simple operation,which is suitable for large-area preparation.The SERS performance of the hybrid structure was studied by using BPE as the probe molecule.The minimum detection limit was 10-8M,which was 2 orders of magnitude higher than that of the silver nanorods.The hybrid SERS substrate showed better repeatability and stability.The label free method was used to detect the methamphetamine to evaluate the application ability of Ag NRs@P2VPy-Au@Ag NPs hybrid substrates,and the minimum detection limit was 10-8M and the detection time was less than 5min.4.The optimal design method of microfluidic SERS chip which was embedded the hybrid structure was established.The integration of microfluidic system of high performance SERS substrate was realized.The application capability of this integrated system in methamphetamine practical detection was tested.A microfluidic system integration solution for high performance SERS substrate and the influence law of the cross-sectional area of the microfluidic SERS chip on the flow velocity were studied.As a result,the shape of the detection area was determined to be an elliptical pattern with the width of 1400μm.The microfluidic SERS chip embedded with the nano structure were prepared by using MEMS technology.A microfluidic SERS detection system was set up to realize the microfluidic system integration of high performance SERS,and it was applied in methamphetamine detection.The characteristics of SERS signals of both microfluidic SERS chip embedded with the hybrid structure and opened hybrid structure were compared.The results showed that although the SERS intensity of the embedded SERS substrate decreased slightly,but the detection sensitivity of it remained the same order of magnitude(10-8M)as that of the open SERS substrate,which could still meet the needs of actual detection.Whats more,the embedded SERS chip has obvious advantages in the automation,integration,rapid detection,which are suitable for popularization and application.