由於表面電漿現象為一種強烈的侷域現象，可以將電子維持在小範圍內做集體共振，有辦法將電磁波原有的尺度限制到更小的範圍，達到奈米尺度或是次波長範圍；而石墨烯由於其特殊能帶結構，也被觀察到有表面電漿現象的發生，而另一方面，氧化石墨烯由於在氧化過程中受到氧化劑影響，會使得完整的蜂巢狀結構受到破壞，造成sp2團簇(cluster)減少，能隙產生變化，因此可以造成光致發光；
在本實驗中利用電化學剝離法(electrochemical exfoliation)製備石墨烯(G)，並嘗試以不同的參數去改變所製備的石墨稀品質，再以Hummers method法製備氧化石墨烯(GO)，在氧化過程中我們添加不同的氧化劑含量來改變氧化程度；在成功的製備了G與GO之後，我們使用噴塗系統來分別的噴塗上石墨烯與氧化石墨烯，之後再去做進一步的分析。
由電化學剝離實驗的結果，改變第一階段偏壓的時間，對於石墨烯尺寸可以達到小一點的碎片，但是拉曼上來看比值變化並不大，而在溶液中不同的位置的懸浮粉末，我們可以得到越上層的粉末所受到的破壞是越大的，而這結果是與拉曼光譜相符，當我們改變電解液濃度的時候，低濃度得到的是較小片的石墨烯片，而高濃度的得到較大片的結構，而在大片石墨烯上可以見到透明皺褶，但是在溶液狀態下我們無法控制到底如何精確的去剝離。
而氧化石墨烯的結果，可以看見隨著加入過錳酸鉀氧的量增加，氧化石墨烯的2D band逐漸的減少，而D band持續的上升，這表示了石墨片在氧化過程中受到了劇烈的破壞-石墨結構的破壞與氧官能基的生成，並造成了GO表面性質由疏水性轉為親水性；但是我們預計藉由改變過錳酸鉀的含量來改變氧的含量，從實驗結果來看，改變的幅度並沒有特別大，這原因是在製備GO的同時有兩種氧化劑加入-過錳酸鉀與硝酸鈉，其中硝酸鈉的作用是做為預氧化劑，目前對於GO的精確反應機制依然在討論之中，所以為了精確的控製氧化程度，未來將會嘗試只加入過錳酸鉀反應。
而最後我們使用噴塗系統來將G與GO耦合在一起，從光學顯微鏡的圖中來看，可以見到G的周圍圍繞著GO，只有在噴塗過厚的情況下，GO才會附著在石墨烯上，而我們原先假設GO可以直接噴塗在G的表面，由於兩著表面性質的不同，才造成了GO圍繞著G；我們也比較了G與GO還有混合後的光致發光性質，並藉由算式得到了耦合後的品質因子(Quality factor, Q factor)，其中Q factor最好的是自製G與GO-0.5的組合，可以達到10，但是跟其他材料的表面電漿雷射相比，數值是相對低的，也顯示出我們仍有相當大的進步空間。
從理論上來說，利用G的表面電漿現象，可以有效侷限電磁波到次波長範圍，且表面電漿共振可以當作一個百分之百反射的共振腔，對於雷射的應用是非常有前景的。

Summary
The surface plasma (SP) is a new way to break the diffraction limit and can help us to design more sensitive instruments. In our research, we use graphene (G) and graphene oxide(GO) to make a optic resonator. Because SP can occur on G surface and considered as 100% reflect resonator. In other hand, we use GO and change the oxygen concentration by different amount KMnO4. By changing the oxygen concentration, we expect GO will emit different wavelength light. To produce G, we use electrochemical exfoliation to produce G. GO use Hummers method to produce. In our result, although we change many parameter to affect the quality of G, the 2D/G ration still show it’s multi-layer graphene. The TEM also confirm this result. In GO, we change the amount of KMnO4 but the oxygen concentration difference is not obvious. The G and GO coupling result shows the low quality factor (Q factor) around 10. The Q factor is not high compare with other material system. We think we can improve by using single-layer G because SP in single-layer G is stronger. The SP is still a promising way to change the current observation method.
Introduction
Lasers are ideal for optical communication, accurate metrologies and sensitive spectroscopies. Lasers deliver coherent, powerful and directional high-frequency electromagnetic energy. The diffraction limits of light restrict the further application in smaller order scales. SPs show great promise for exciting new class of light source to break the diffraction limit. SPs have extremely strong confinement in one and two dimensions, enabling plasmon laser to deliver intense, coherent and directional energy below the diffraction barrier. Science single layer graphene has been produce, there are some people trying use graphene in plasmonic laser. SPs often observed in metal and also consider as the best material to study SPs, but there are some disadvantage like band gap is hardly tunable, large Ohmic losses. Graphene has extraordinary electro properties, eg. ultra-high carrier mobility, long mean free path, gate-tunable carrier density. Owing to the two dimensional nature of collective excitation, SPs in graphene confined much more strongly than noble metals. Graphene has low losses and the most important advantage is would be tunable. In our research, we use graphene coupling with GO. Graphene uses as substrate and we control different oxygen concentration of GO to couple. The SPs will happen between graphene and graphene oxide. When the boundary is broken, the sub-wavelength light will emit. It will be a promising application to generate plasmonic laser which whole material is carbon.

Experiment
We use electrochemical exfoliation method which is a fast, simple on step method and can produce G in short period. We adhered graphite flake to Pt plate and use as electrode. We first add low bias V1 for t1 minutes to let ions intercalate to graphite layer and add high bias V2 to exfoliated the layers. We use Hummers methods to produce GO. We used the graphite flakes as the source. Add 0.5g graphite flakes and 0.25g sodium nitrate in 4.14g sulfuric acid in ice-bath. The mixture was stirred with 300 rpm in all process. Then, slowly add 1.5g potassium permanganate into solution, the temperature cannot higher than 20℃. Remove ice-bath after all the potassium permanganate was added. The solution temperature will raised to 35℃ and stirred for one hour. Add 23g DI water slowly into solution, solution will reaction, appear white fume and accompanied by increase the temperature to 90℃. Use 20g hydrogen peroxide dilute in 200g DI water. Use this solution to wash GO solution, which remove remain oxidant. The washed GO solution was use 2000rpm to centrifuge and we will see the gel precipitation above the powder. Removed the gel precipitation and kept washing the GO solution until no gel precipitation appears. We will get the brown yellow GO solution and will not precipitate after centrifuge. Add exchange resin to GO solution and stirred 300 rpm for 24 hours. To collect the pure GO solution, filter with 75μm porous filter to remove resin and big particle. Up to here, we fabricate the graphene solution (in IPA) and GO solution (in water). We use the spray coating to coupling G-GO. The spray flow is 0.22ml/min and nozzle move speed is 25mm/sec. We use silicon substrate and keep heating during spray. We first spray commercial G and as-prepared G respectively, which the concentration is 0.1mg/ml and spray 6 times. Then spray different oxygen concentration of GO samples and spray 9 times.
We make the graphene solution to centrifuge and use the upper layer to coating on substrate. The graphene was analysis by SEM, Raman, TEM and photoluminescence (PL). SEM was to see the morphology and the size of our graphene. Raman spectrum was a powerful tool to analysis the carbon material. We use Raman to see the quality of our graphene. Use TEM to see high resolution TEM and see diffraction pattern. PL was use to analysis the graphene we made weather luminescence or not. The GO solution was analysis by SEM, Raman, XPS, optical microscope (OM) and PL. We used OM with dark field and irradiate 325nm light to see the luminescence. The graphene-GO coupling sample was analysis by OM, Raman and PL. Use Raman to see the peaks difference in graphene-GO sample. Use PL to see the intensity change and wavelength shift after coupling. We can further calculate the quality factor (Q) from the result.

RESULTS AND DISCUSSION
In the result, when we prolong the t1 from 5 min to 45 min, which means the ions accumulate at graphite boundary, the I2D/IG still around 0.4. The I2D/IG shows the graphene we made is still multi-layer graphene. In 圖 三十一(b) has low I2D/IG and higher wavenumber which means the graphene is more than other, also can see the morphology is different to other samples. We observed the graphene powder in the solution stratified to three layers and we named it as top, middle and bottom. From the Raman result, we can see there are very different. 圖 三十二shows the D band is increase gradually from bottom to top, represent the top layer powder has more damage during electrochemical exfoliation. We also change the V2, the result in 圖 三十三also shows higher V2 leads to higher D band and accompany by 2D band vanish. prolong t1 didn’t make obviously change, the morphology still like flakes, but we can get larger size with t1 increase. From 圖 三十五(a), there are many bubbles on the surface, when we focus on those bubbles, it depressed and like a film cover on a cave. Those bubbles make the D-band increased. In 圖 三十五(b), there are many small flakes with sequence arrange on big flakes. We think that small flakes are few layer graphene, when we centrifuge the solution, it attach to big flake again. In 圖 三十五(c) we also can see there is very thin graphene cover on the particle. With the different electrolyte concentration, lower concentration leads to small lateral size. High concentration leads to big flakes and can see semitransparent wrinkle layer on particle. The semitransparent wrinkle layer represents the layer is distract but not enough to separate, in wet chemistry we can’t effectively control the ions to distract the graphite layer. 圖 三十七(c)(d), the HRTEM shows larger spacing at boundary(0.37nm) than inside the flake(0.34nm), which means ions are intercalate to the boundary. From 圖 三十七(b) SADP pattern, we can get clearly hexagonal diffraction pattern and the d-spacing is 0.214nm which is (11 ̅00) planes. We also can calculate the layer is 3-10 layers.
In GO result, we can see 2D peak is gradually decreased while the KMnO4 increase. That means the graphite layers is become heavily damage. For our sample, the different amount of KMnO4 didn’t make distinguish oxygen concentration, but it still can see more KMnO4 has more oxygen concentration. In our XPS result (表格 四), Peak1 to peak5 is sp2carbons in aromatic rings (284.5 eV), hydroxyl (C-OH, 285.86 eV), epoxide (C-O-C, 286.55 eV), carbonyl (>C=O, 287.5 eV), carboxyl groups (COOH, 289.2 eV) respectively. For different GO samples, the oxygen concentration is similar but the oxygen function group is different for GO-0.1 and GO-4. From GO-0.1, the sp2 carbon is less than other sample. For GO-4, there almost no hydroxyl group in sample. Both of GO-0.1 and GO-4 have higher epoxide group.
In G-GO coupling result, Raman spectrum is very different to neither G nor GO. The spectrum has abnormally background increase from 1100cm-1 - 3000cm-1. The main reason is that when we do the spray coating, the spray wet the powder and makes powder aggregate. The aggregation powder makes the scatter increase and leads to the Raman background increase. From表格 五, we can see the D and G peaks have blue shift is due to the surface plasma oscillation makes the electron localized and the electron transfer is limit, which makes the spectrum blue shift.
Because we consider the G -GO as a resonator, we do the PL to check the intensity change before and after coupling. In our experiment, we choose 325nm to excite sample and change the incident beam slit to change the beam intensity. Graphene has no luminescence and GO can see a board peak around 420nm in 圖 四十七. The GO PL peak is so broaden due to the defect in graphene structure and functional group. Those defects open the graphene band gap and introduce different energy state. Owing to the G-GO are consider as a resonator, we want to know the quality factor (Q). As we mention before, the SP resonant can use as a optical resonator with 100% reflectivity. So we use the optical resonator relate to Finesses to calculate the Q factor. Q=mF=F(Finesse)=(π√R)/(1-R), where m= coefficient and R=reflectively. In our case, we consider m=1 for simplest situation for no other material or structure. The reflectivity is1-Ic/Io, Ic is the intensity after coupling and Io is original GO intensity. So the equation is 1-Ic/Io means the light reflect between G-GO, or can consider light is trapped.
In the calculate result, the Q factor of commercial graphene with GO-0.5, GO-1, GO-2 are 8.6, 3.8, 6.9 respectively. The as-prepared graphene with GO-0.5, GO-1, GO-2 are 10, 0.9, 2.4. Compare to other plasmonic laser resonator, our Q factor is not outstanding. But in our experiment has many point can be improve.

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