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Research Of Structural Designs And Applications Of Surface Plasmon Resonance Sensors

Posted on:2022-11-22Degree:DoctorType:Dissertation
Country:ChinaCandidate:S Y CuiFull Text:PDF
GTID:1488306764460194Subject:Physics
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Surface plasmon resonance sensors,as one of the most potential optochemical sensors,have the advantages of label-free,non-destructive,and point-of-care testing.The optical field energy of surface plasmon poloritons waves can be focused to the micro-and nano-scale with breaking the diffraction limit due to the near-field optical properties of localized surface plasmon resonance(LSPR).This nanoscale optical field phenomenon can produce a strong local electromagnetic field enhancement effect,which is broadly used in near-field optical imaging,surface-enhanced Raman scattering(SERS),biochemical sensing and other fields.However,the commercial applications of SPR sensors ae still limited by many chanllenges.Since the traditional incident light source cannot provide the light source within the nanometer scale size.Thus,the detection resolution and the sensing signal is low,and the sensitivity needs to be further improved.In this dissertation,the sensitization mechanism based on the LSPR principle is firstly studied.By designing and optimizing,the gold microarray structures with high aspect ratio of different particle shapes to improve the sensitivity of the LSPR sensors.Secondly,the finite difference time domain method is used to optimize the design of the structures,so as to obtain the optimal resonance effect of the sensors,which solves the problem that the traditional LSPR sensors cannot provide a nanometer-scale excitation light source.Finally,the applications of LSPR sensors are proposed,which can be used as biochemical sensors based on optical signals such as LSPR absorption spectroscopy,SERS spectroscopy,and fluorescence spectroscopy.The main content and research are as follows:1.Design a gold micro-pillar array structure-based biochemical sensor.According to the requirements of high sensitivity and high precision of LSPR sensors,the structures of LSPR sensors are designed.Their optical and physical distribution are researched by using the characteristics of low loss of gold material,not easy to oxidize,resistant to chemical corrosion,good ductility,and high density.A large-area,uniformly distributed gold micropillar array structure was fabricated by heavy ion tracking technology,which can realize nanoscale LSPR phenomenon and serve as a biochemical sensor based on optical signals.First,from numerical simulation to experimental verification,it is proved that the micro-nano structure with high aspect ratio can produce strong absorption and confinement effect on photon energy.The surface of the structure was observed by a near-field scanning optical microscope.A strong electromagnetic“hot spot”with a full width at half maximum of about 100 nm is generated.Secondly,based on this optical property,the sensing of refractive index and molecules is realized through optical signals.Therefore,this structure provides a research idea for biochemical sensors with switchable functions.2.Research the LSPR sensitivity optimization mechanism of gold microcone array structure-based sensor.In order to improve the sensing sensitivity,calculational simulation based on the finite difference time domain method was carried out to optimize the sensitivity,and the LSPR effect was selected by improving the structural design,particle spacing,period number,light source type,etc.A gold microcone array structure with 26.7 aspect ratio was designed and fabricated,which can generate nanometer-scale electromagnetic“hot spots”under the excitation of incident light at 532 nm.It can be used as a tiny excitation light source in the sensing process,which not only improves the detection resolution,but also improves the detection sensitivity.Verified by near-field experiments,a high-energy electromagnetic“hot spot”with full width at half maxima of about 86 nm is generated at the tip of the structure.3.Design a highly sensitive gold micro-cone structure-based LSPR sensor for temperature and incident angle testing.Since the gold microcone array structure can generate high-energy electromagnetic field“hot spots”,it can be used as a nanometer-scale excitation light source,thereby improving the temperature and incident angle sensing sensitivity.For the temperature change,since the LSPR absorption spectrum is very sensitive to the change of the surrounding medium environment,through the spectral experiment,it is obtained that when the ambient temperature is between 308.15 K?318.15 K(35°C?45°C),the optimal sensitivity of the absorption wavelength shift at the peak of the LSPR absorption spectrum is about 5.80 nm/K,and the absorption The optimal sensitivity of the rate is about5.58×10-3 K-1.At the same time,an approximate numerical model is proposed based on the experimental results.For the incident angle of the light source,when the incident light angle is between 10°?20°,the maximum sensitivity of the absorption wavelength shift is about 22.37 nm/deg,and the maximum sensitivity of the absorption rate is about 2.24×10-2 deg-1.It can be seen that the sensor can realize the detection of temperature and incident angle.4.Apply gold microcone array structure based on LSPR sensitization mechanism to improve SERS perfoemance.In order to verify the extensive applications scenarios of the LSPR structures,a strong LSPR phenomenon can be generated based on the gold microcone array.This optical physics serves as a kind of electromagnetic field enhancement of SERS.It is proposed that this structure can be used as a SERS substrate to detect local changes in dielectric constant or refractive index caused by the adsorption of molecules to the sensor surface,which can be used to improve the sensitivity and signal intensity of SERS.Using thiophenol as the target molecule,compared with the commonly used SERS substrates,the analytical enhancement factor of the gold microcone array is 102 that of the gold film substrate and silver film substrate.In addition,the detection limit test was carried out,and the structure has a more obvious enhancement effect due to the LSPR enhancement effect.The thiophenol solution with a concentration of 10-8 mol/L can be detected,and the analytical enhancement factor can reach 109.Through the design and optimization of the high aspect ratio gold microstructures,the absorption and convergence of electromagnetic energy can be effectively improved based on the LSPR principle,thereby improving the detection sensitivity.From numerical simulations to experimental discussions,the influence of electromagnetic“hotspots”on sensing sensitivity.The optical properties,LSPR absorption spectrum,fluorescence spectrum and SERS were investigated by spectroscopic experiments.Based on this special optical phenomenon,they were applied to the fields of biochemical sensing and bioimaging.
Keywords/Search Tags:localized surface plasmon resonance, surface plasmon poloritons, gold micro-nano structures, sensitivity
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