以表面電漿共振技術探討電化學法之石墨烯氧化物去氧還原過程

Abstract

表面電漿共振(surface plasmon resonance，SPR)技術利用表面電漿波(surface plasmon wave，SPW)可偵測固體表面物質的些微變化。本論文利用電化學循環伏安法(cyclic voltammetry，CV)還原石墨烯氧化物(graphene oxide，GO)並搭配SPR技術即時檢測GO的還原現象，其還原態則稱為「還原石墨烯氧化物(reduced graphene oxide，rGO)」。在去氧還原的過程中因為GO的折射率變化使得SPR角度產生位移現象。因此可藉由位移角度的變化量推測rGO的還原程度。 實驗流程首先在在金膜表面連結十八烷基硫醇(1-Octadecanethiol，ODT)，作為GO的連結層。然後將金膜浸泡於GO水溶液裡，使GO連結在金膜表面。使用電化學CV還原GO以得到rGO，還原過程中同時記錄SPR角位移。除了1層GO，本實驗另外製作多層GO，比較層數對於電化學還原法與SPR角變化的影響。最後以X光光電子能譜儀(X-ray photoelectron spectroscopy，XPS)驗證經CV不同掃描圈數所得之rGO的碳含量。 當GO層數越來越多時，介電層的整體折射率以及厚度造成SPR角往大角度移動，降低漸逝波與表面電漿波的耦合效率。經過電化學法還原GO後，rGO的SPR角將會往小角度移動，且SPR曲線也會因此變得比較窄以及SPR耦合效率提升。Surface plasmon resonance (SPR) technology can detect the slight variation of materials near the solid surface by surface plasmon wave (SPW). This paper used cyclic voltammetry (CV) of electrochemistry to restore graphene oxide (GO), and used SPR technology to detect the phenomenon of reduction of GO, simultaneously. The electrochemically reduced GO, referred to as rGO herein. The SPR angle shifted in the process of deoxidization since the refractive index of GO changed, so we could presume the extent of reduction of GO by SPR angle shift. In the beginning of this experiment, we used 1-Octadecanethiol (ODT) to be a linker for GO. Then immersed the Au in the GO aqueous solution to make the GO sheet on the surface of Au. We used CV to restore GO and got rGO sheet, and recorded the SPR angle in the meantime. In addition to monolayer GO, we made multilayer GO to observe the number of layer influence the CV curve and SPR angle. In the last we used X-ray photoelectron spectroscopy (XPS) to proof the carbon level of rGO after different CV scan number of reduction. While the layer of GO become much more, the whole refractive index of dielectric layer and thickness will make the SPR angle shift to bigger angle, which decrease the coupling efficiency of SPW and evanescent wave. After electrochemical reduction, the SPR angle will shift to small angle and the SPR curve will become narrower and increase coupling efficiency.