Synthesis and Optimization of CVD Graphene Films for Smart Applications

Abstract

Many researchers have paid attention to various applications using graphene, a one-atom-thick planar sheet of sp2-bonded carbon atoms, due to its exceptional mechanical, electronical and chemical properties. Here, we discuss interesting applications of graphene films grown by chemical vapor deposition (CVD) method from the point of physical and material chemistry. A brief overview of the chapters 1, 2 and 3 in this dissertation are shown below. In chapter 1, we researched graphene barrier to prevent the decolorization of ink dye such as crystal violet (CV) under oxygen-rich condition. A quartz substrate coated with CV was placed under sunlight and the changes of absorbance in time-dependence were monitored for 7 days by Ultraviolet-visible spectroscopy, resulting from blue-violet to colorless. To analyze the effect of graphene films under harsh condition, the absorbance changes of CV films covered with several stacking layer under UV/ozone were calculated. The absorbance ratio (A/A0) of CV covered with 4-layer graphene is as low as 0.54 after 64 minutes under UV/O3, which corresponds to 13 times compared to bare CV substrates. The graphene-passivated CV films exhibit attractive a prolong lifetime as well as environmental stability compared to the non-passivated the pigment film. We strongly confirm that graphene barriers not only prevent the oxidation of the dye but also decrease color change compared to no graphene on a pigment. In chapter 2, we applied graphene heaters for real life through two heating mechanisms. First, to evaluate the powerful heating protocols and determine the more effective body region for heating, 4-layer graphene heaters were utilized in a cold environment, which conserved electrical power about 71% compared to continuous heating as well as achieved efficient the upper back heating. Secondly, the other heater was conducted in microwave condition because the electrons on graphene absorbed electromagnetic (EM) waves and released thermal energy. From this unique mechanism, graphene film was applied on a bottle glass using the smart defogging system through EM absorption. In chapter 3, we controlled Fermi level of graphene by self-assembly monolayers with functional groups (-NH2, -CH3). We supposed that the electron donating property of amine group (-NH2) promoted the reactivity than natural and p-doped graphene due to a mount of electrons on graphene. Interestingly, n-doped graphene enhanced the electrochemical reactivity of the surface functionalization and the synthesis of gold nanoparticles compared to other substrates. As the results, we expect to be able to use it for biosensors if we can functionalize and synthesize other attractive materials on graphene.