Optical and Electrical Properties of Graphene Oxide Quantum Dots with Amino Acid

• Main Authors: Yun-Syuan Chou, 周芸瑄
• Other Authors: Ji-Lin Shen
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/z9amcj

碩士 === 中原大學 === 物理研究所 === 106 === In this research, pulsed laser ablation was used to synthesize graphene oxide quantum dots (GOQDs) doped with different amino acids. When exposed to Ultraviolet (UV)light, amino acid doped-GOQDs display blue photoluminescence (PL) with high-intensity. UV-vis absorption, PL, time-resolved PL (TRPL), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were used to investigate the effect of amino acid doping on the structure and optical properties of GOQDs. The average particle size of the histidine-doped GOQDs is 4.6 ± 0.04 nm with a PL intensity of about 110 times stronger than that of the undoped GOQDs, mainly due to the increase of the pyrrolic-nitrogen configuration within GOQDs structure after doping. In addition, the electrical properties of amino acid doped-GOQDs were also studied. It is found that GOQDs doped with lysine showed highest conductivity compared to other amino-acid doped GOQDs in this research. In addition, electrical property of amino acid-doped GOQDs was observed. Here, the electrical response of the amino acid-doped GOQDs versus environment and illumination were observed. On the basis of environmental effects on electrical response, the amino acid-doped GOQDs were subjected in vacuum and air as well as in nitrogen and oxygen. The use of laser excitation of different wavelengths as the light source was utilized for investigation of effect of illumination wavelength versus electrical response. Photoelectric flow measurement was performed using a violet laser (405 nm) and demonstrated a negative photoconductivity (NPC) for amino acid doped-GOQDs. The responsivity and photoresponse time were also measured. It was found that the lysine-doped GOQDs has a photoresponsivity of 6833.3 nA·W-1 with a photoresponse time of 49.5 s. The curves of the gate voltage and the drain current reveal that the lysine-doped GOQDs are p-type semiconductors with carrier mobility of 3.29 × 10-2 cm2·V-1·s-1. With regards, we propose that the mechanism of NPC is mainly due to the fact that water molecules in the air will adsorb on the surface of the GOQDs and de-absorb after irradiation.