| Summary: | 碩士 === 國立中山大學 === 材料與光電科學學系研究所 === 103 === In the first part, predominant C-Si-H doped Co1-xO particulates/nanocondensates and minor turbostratic graphene, faceted graphite and Co(OH)2 tubes/belts, were formed by pulsed laser ablation (PLA) of Co plate in TEOS without appreciable transformation into Co3O4 which would otherwise be stable below ca. 900oC under open air condition. The C-Si-H doped Co1-xO particles are ~(100) and {111} faceted for (hkl)-specific coalescence and contain paracrystalline distribution of defect clusters with interspacing ca. 2.5 times that of the host lattice parameter as well as abundant planar defects, i.e. 1-D 3x and 5x{111} commensurate superstructures occasionally mixed with alternating Co close packed interlayer. UV-visible absorbance spectrum of the resultant colloidal suspension indicates the particles and nanocondensates have multiple absorptions in UV-visible range corresponding to a minimum band gap of 3.1 to 3.7 eV.
In the second part, PLA of Co plate in aqueous solution of ammonium hydroxide (0.25 M NH4OH) caused the predominant formation of N-H-doped Co3-δO4 particulates and nanocondensates with paracrystalline distribution of defect clusters and larger lattice parameter than the ambient value of undoped bulk Co3-δO4, indicating that N enters the interstitial site in the spinel-type structure. The 3x3x3 spinel-type derived superstructure, due to tramp Co3+, N and H+ doping, along with Co3-δO4 and Co1-xO domains were also found in the rapidly solidified particulates. The co-existing Co layer-double hydroxide ribbons are optically birefringent and vulnerable to electron irradiation; whereas the hexagonal Co2O3 and triclinic cobalt nitrate were not favored by the present PLA process in aqueous ammonia. The N-H doped cobalt oxide particulates/nanocondensates showed characteristic bonding states of the constituent elements in the XPS as well as a significant violet absorbance corresponding to a minimum band gap of 2.9 eV for potential optocatalytic applications.
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