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31 January 2012 Optofluidic surface-enhanced Raman spectroscopy with nanoparticle-functionalized flow-through multihole capillary
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Surface-enhanced Raman scattering (SERS) has emerged as a powerful analytical technique for direct detection of chemical and biological analytes because of high sensitivity, selectivity, and rapid response. Here we propose and develop a novel optofluidic SERS structure, i.e., nanoparticle-functionalized flow-through multihole capillary. This unique platform provides many advantages. First, its 3-dimensional (3-D) structure, similar to nanoporous aluminum membranes, nanoporous polymer monoliths, and photonic crystal fibers (PCFs), provides large surface area for the deposition of noble nanoparticles or nanoclusters to achieve high SERS intensity. Second, it has well-defined flow-through channels. It provides robust and controllable nanoparticle immobilization like PCFs, but much higher nanoparticle density thus large SERS-active sites due to large surface within the detection volume, and also enables fast and convenient analyte delivery for real-time, online detection. Third, the well-defined multihole capillary can also confine and transmit light along the longitudinal direction, accumulating large SERS signal like PCFs. Fourth, it is easy to integrate with other sensing platforms, such as label-free biosensors, to provide comprehensive information on molecular interaction. Moreover, the multihole capillary can be mass-produced easily and cost effectively using the fiber drawing method. In this report, using a capillary consisting of thousands of micrometer-sized holes adsorbed with gold nanoparticles, we investigated the proposed optofluidic SERS system using the transverse and longitudinal detection methods, where the SERS excitation and collection were perpendicular to and along the capillary, respectively. A detection limit better than 100 fM for rhodamine 6G was achieved with an enhancement factor exceeding 108.
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Yunbo Guo, Maung Kyaw Khaing Oo, Karthik Reddy, and Xudong Fan "Optofluidic surface-enhanced Raman spectroscopy with nanoparticle-functionalized flow-through multihole capillary", Proc. SPIE 8212, Frontiers in Biological Detection: From Nanosensors to Systems IV, 82120F (31 January 2012);


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