本實驗使用醋酸纖維素取代傳統化學氣相沉積法製備石墨烯的甲烷或乙炔等烃類氣體,來當作固態碳源。藉由快速熱退火機制將醋酸纖維素汽化並斷鍵,使其中碳原子沉積於鎳網並在表面析出生長石墨烯,然後在PMMA薄膜的保護下蝕刻掉鎳基底,最後搭配熱解法來移除樣品表面的PMMA,我們可以得到獨立的管狀石墨烯結構(tubular graphene,TG)。比起其他製備石墨烯的方法,本實驗的製程擁有快速的製備時間、較低的生長溫度、避免處理易爆氣體或毒化學物品等優點。 而藉由調控生長溫度、固態碳源的多寡、熱退火時間等製備參數,我們可製備不同管壁厚度的管狀石墨烯,並利用掃瞄式電子顯微鏡、高分辨率穿透式電子顯微鏡、原子力顯微鏡等儀器來檢測管狀石墨烯之整體生長均勻度與管壁厚度(石墨烯層數)。我們也發現樣品的拉曼光譜中之D-band、G-band和2D-band會隨製程參數而改變,證明了不同的製備參數,確實影響管狀石墨烯的結晶優劣性和生長層數。而樣品的四點電阻值,也是用於檢測樣品層數變化的性質。
Graphene, a rapidly rising star on the horizon of materials science and condensed-matter physics, has received significant attention from both fundamental research and applied sciences. But most important of all, manipulation of individual graphene sheets/films into novel macroscopic architectures is highly important for practical uses and opening/exploring their new functions. In this study, macroscopic, freestanding, and tubular graphene (TG) architectures were fabricated via a versatile and robust method based on annealing of cellulose acetate (CA) on nickel templates and thermo-assisted removal of poly(methyl methacrylate) (PMMA). Specially, the TG architectures with a diameter of ~ 50 µm can be obtained as individual and woven tubes, and various configurations via manipulation of Ni templates into predetermined shapes. The effect of experimental parameters such as annealing temperatures, annealing time, and amount of carbon precursors (cellulose acetate) on the graphitic crystallinity, number of graphene layers, and graphene surface has been investigated and characterized by Raman spectroscopy, SEM, HRTEM etc. Some intriguing properties of TG like ultra-thin-walled hollow structural, high electrical conductivity, high transparency, flexibility, show great promise for numerous potential applications such as flexible and lightweight electronics, electron emitters, X-ray tube sources, and microscopic cavities for storing and filling with expedient materials toward multifunctional composites, and high surface area catalyst/supports.
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