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Photonic Crystal Fiber Based Surface Plasmon Sensing Technology

Posted on:2014-06-18Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y T ZhangFull Text:PDF
GTID:1268330398485702Subject:Physical Electronics
Abstract/Summary:PDF Full Text Request
Surface plasmon (SP) based sensing technology is a powerful tool for biomolecular analysis. Owing to the unique advantages of label-free and noninvasive measurement, ultra-high sensitivity, and capability of real-time detection, the technique has been attracting world-wide research interests for decades and has accommodated diverse sensing demands, such as biomedicine, drug screening, environmental monitoring, food safety and national defense. Moreover, its combination with fiber technology, especially photonic crystal fibers (PCFs), has accelerated the pace of miniaturization and integration of SP sensing devices, which emerged as a hot spot of research recently. Supported by the international cooperation project between China and Singapore (No.2009DFA12640), a systematic study of two key sensing techniques, which are surface plasmon resonance (SPR) and surface enhanced Raman scattering (SERS), has been carried out, with PCF as a compact and robust sensing platform. The research work is summarized as follows.(1) To address two problems of fiber based SPR sensors, which are nonlinearity of the sensing response to refractive index variation and the instability of measurement accuracy over a large range of refractive index, a novel PCF based SPR sensor with an analyte channel introduced in the core region has been designed. It has been demonstrated that the central analyte channel plays a role of tuning the propagation constant of the core-guided mode. In this way the sensing response has been linearized and the sensor performance has been balanced and optimized.(2) Based on the future developing trend of high-throughput and miniaturized sensing devices, a PCF based multichannel plasmonic sensor has been proposed for the first time. The sensor with wagon-wheel cladding structure is able to achieve simultaneous detection of two different analytes. The sensitivities for parallel channels are1535nm/RIU and1550nm/RIU over a refractive index range of1.33to1.36.(3) Multilayered silanization self-assembly for deposition of gold nanoparticles (AuNPs) on the inner surface of air holes in a solid-core PCF has been studied. Sensing performance of the probe developed with this deposition technique has been examined using two different launching methods, which are launching from the center of the core and the offset launching. The experimental results show that by using the offset launch method SERS efficiency of the probe has been enhanced. The detection limit of the probe has been lowered to1OOnM in concentration.(4) A novel SERS configuration based on a defect-core PCF has been proposed. By using monolayer silanization self-assembly process, SERS substrates with equal AuNP coverage density have been deposited within two PCF templates, which are defect-core PCF and solid-core PCF respectively. The influence of fiber structure on SERS performance is quantificationally studied. The experimental result shows the defect-core PCF, with evanescent field stronger than the solid-core PCF, is able to enhance SERS intensity by32times.(5) The impact of self-assembly procedure on the AuNP coverage density has been investigated. By adjusting the coverage density of AuNPs to an appropriate value, enhancement factor of the optimized SERS probe was pushed up to121. The capability of the probe for ultra-low concentration molecular analysis has been examined. It has been demonstrated that the probe has achieved a concentration limit of1pM, implying that the probing is at a single-molecule level. The detection limit is two orders lower than the lowest concentration achieved by the existing PCF based SERS sensors. Additionally a remote SERS experiment with a long section of defect-core PCF has been carried out. In remote operation, the probe reaches a high sensitivity for DNA identification and pollutant detection at a low concentration, showing the SERS probe is a robust platform for biochemical and environmental applications.
Keywords/Search Tags:surface plasmon, surface enhanced Raman scattering, photonic crystal fiber, gold nanoparticle, self-assemblysensitivity, limit of detection
PDF Full Text Request
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