Low-dimensional Nanomaterials Synthesis, Application And Theoretical Research

In this thesis, we use gold nanoparticles as the catalyst, indium metal clusters and oxygen as the precursors to synthesize In2O3 nanowires via vapor-liquid-solid (VLS) method. We achieve good In2O3 nanowire morphology at the temperature of 500℃for the substrate region and 800℃for the source region. The diameter of the wires could be controlled between 20-100 nn. We applied XRD, SEM and TEM analysis for material characterizations. Moreover, we use indium and tin metal clusters for the synthesis of ITO nanowires. The XRD results show that the doping mechanisms for ITO nanowires on different substrates are not the same. Tin would perform as substitutional dopants in ITO nanowires on SiO2 substrate and interstitial dopants in its counterparts on FTO substrates. The STEM analysis shows that the doping rate is around 5%.Further, we constructed microbial fuel cells (MFC) to realize energy conversion from chemical energy to electrical one. We use pseudomonas aeruginosa as the microbe, glucose solution as fuel, and oxygen as electron acceptor to measure the performance of MFCs with a variety of electrodes. We applied plane ITO glass, carbon cloth and high density ITO nanowire array as the anode part, as well as carbon cloth with Pt loading and multi-wall carbon nanotube array with Pt/Ru nanoparticles as the cathode part. Our results show that the application of nanostructures into electrodes will greatly enhance the performance of MFCs. We achieve 64.46 mW/m2 power density and a 4 kΩinternal resistance by ITO nanowire array anode and carbon nanotube array with Pt/Ru nanoparticles as cathode.In addition, we performed first-principles calculation based on density functional theory to investigate the interface between single layer graphene and metal oxides. Our study reveals that by single crystal SiO2 and Al2O3 contact, graphene lost its degeneracy around the conical point and comes to be semiconducting. Compared to the free-standing single layer graphene which performs as a semi-metal, oxides contact expands its energy gap to-0.9 and-1.8 eV, respectively. We find the gap originated from the breakage ofπbond integrity, whose extent is related to the interface atom configuration. We believe that our results highlight a promising direction for the feasibility to apply large scale graphene layer as building blocks in future electronics devices.