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|Issue Date: ||2016-10-13 12:43:32 (UTC+8)|
|Abstract: ||首先本研究以聚4乙烯吡啶(poly(4-vinylpyridine), P4VP)經熱燒結後製備出富含氮碳材，將其應用於作為表面拉曼光譜訊號增強(surface-enhanced Raman scattering, SERS)基材後，觀察到其增強訊號的能力良好。探討聚4乙烯吡啶經一系列熱燒結溫度下製備樣品的氮摻雜組態後，發現氮組態中的四級氮(graphitic-N)比例隨燒結溫度升高而增加，此時最高占據分子軌域和最低未占據分子軌域間能隙(HOMO-LUMO gap)降低，電荷傳遞能力(charge transfer)提升，此時四級氮周圍的碳上有很高的區域電子雲密度(charge density)使富含氮碳材帶有更高的極性，則富含氮碳材與分子間的偶極-偶極力(dipole-dipole interaction)也會提升，最終作為表面拉曼光譜訊號增強基材的能力也跟著提升。|
接下來由於聚4乙烯吡啶(P4VP)的熱燒結溫度已達臨界點，為了更進一步製備出具更高表面拉曼光譜訊號增強能力的基材，即以聚苯乙烯－聚4乙烯吡啶(poly(styrene-block-4-vinylpyridine), PS-b-P4VP)製備微胞薄膜後，經熱燒結製備一系列富含氮中孔碳材。期望藉由表面積提升，製備出具更高表面拉曼光譜訊號增強能力的基材。藉由低掠角小角度X光散射儀(grazing-incidence small-angle X-ray scattering, GISAXS)量測平面上X光散射 (1D in-plane)強度，再配合Igor Pro軟體以相對應的X光散射關係式進行擬合後，發現具有更高表面積的富含氮中孔碳材由於吸附表面的分子越多且進行分子與基材間電荷傳遞的表面積越大，表面拉曼光譜訊號增強能力也隨之增強，最終得到具有明顯表面積提升的富含氮中孔碳材其表面拉曼光譜訊號增強能力明顯較富含氮碳材為好的結果。
;Nitrogen-enriched carbon materials could be fabricated by thermal pyrolysis of poly(4-vinylpyridine) thin layers. By using the nitrogen-enriched carbon materials as surface-enhanced Raman scattering substrates, the excellent enhancement of Raman signal is observed. From the analysis of nitrogen configurations for nitrogen species for nitrogen-enriched carbon materials, the proportion of graphitic-N depends on pyrolysis temperature. Due to the fact that the presence of graphitic-N could reduce the band gap, graphitic-N could favor charge transfer between the substrate and the molecule. Due to different electronegativity between carbon and nitrogen, positive high charge densities could be present on the carbons neighboring to graphitic-N, which may result in dipole-dipole interactions between the substrate and the molecule. As a result, the ability of surface-enhanced Raman scattering substrate can be finely determined by pyrolysis temperature.
Considering that porous carbon nanomaterials have high surface areas, nitrogen-enriched porous carbon nanomaterials were fabricated through thermal pyrolysis of poly(styrene-block-4-vinylpyridine) diblock copolymers. With grazing-incidence small-angle X-ray scattering characterizations and model simulations for nitrogen-enriched porous carbon nanomaterials templated by PS-b-P4VP, the surface area of hierachical pores within nitrogen-enriched porous carbon nanomaterials was estimated. The increased surface area of copolymer templated nitrogen-enriched porous carbon could increase the capacity of molecular adsorption. More surface area equals to higher charge transfer ability. As a result, more surface area equals to higher ability of surface-enhanced Raman scattering substrate.
In the last part, iodine doping was applied to improve the ability of surface-enhanced Raman scattering substrate. Iodine-doped nitrogen-enriched porous carbon nanomaterials were fabricated by two approaches. The first approach is that nitrogen-enriched and iodine-doped porous carbon nanomaterials were fabricated by pyrolyzing poly(styrene-block-2-vinylpyridine) followed by iodine doping. The second approach is that the two processes were switched; iodine doping was first imposed on PS-b-P2VP block copolymers and then thermal pyrolysis was carried out. Both approaches could successfully generate nitrogen-enriched and iodine-doped porous carbon nanomaterials, which show improved Raman scattering intensity enhancement. From the analysis of nitrogen configurations, iodine-nitrogen bonds were found. The iodine-nitrogen bonds could induce more positive charges on carbons that promote the charge transfer ability between substrate and molecule. The polarity of iodine promotes dipole-dipole interactions between substrate and molecule. As a result, iodine doping indeed improves the ability of surface-enhanced Raman scattering substrate. Besides, for the second approach, carbonization could generate nanomaterials with high crystallinity. As a result such carbon nanomaterials show improvement of Raman scattering intensity of adsorbed dye molecules.
|Appears in Collections:||[化學工程與材料工程研究所] 博碩士論文|
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