| Summary: | 碩士 === 國立臺灣科技大學 === 化學工程系 === 103 === Nanoparticles have wide applications on medicine, material engineering, and environment, since they have high specific surface area. Zinc oxide has wide ban gap, large exciton binding energy, and mechanical stability, and therefore it has wide variety of potential applications in catalysts, solar cells and antibacterials. However, the characteristics of Zinc oxide strongly depends on its structure like shape and size.
Since the structure of zinc oxide nanoparticles is affected by difference parameters on crystallization process, the effects of precursor, protector , and solvent on the fabrication of zinc oxide nanoparticles are investigated in Part A of this thesis: Nanoparticles of zinc oxide were prepared at different precursor (zinc ion and hydroxide ion) concentrations and different precursor ratios. The observation on TEM indicated that with different ratios (1:1, 1:2 and 1:4) of zinc ion and hydroxide ion, the morphology of particles changed from nano-sphere, nano-bicone to flower-like structure. Particle size of zinc oxide was proportional to precursor concentration. High concentration of protector effectively regulated particle growth. The sizes of particles synthesized in ethylene glycol were smallest among all particles in this experiment. The energy band gap of these particles was 3.3 eV to be zinc oxide particle, and crystal structure by XRD indicated a wurtzite hexagonal lattice of zinc oxide.
Formaldehyde is one of pollutants and carcinogen, which can be degradated on photo-catalyst. Among zinc oxide nanoparticles with different sizes and shapes synthesized in Part A, three kinds of particle size (>micrometer, 100-600 nm, and 6-25 nm) and two kinds of particle shape (flower-like shape and nano-sphere) were chosen as photo-catalysts on oxidation of formaldehyde in Part B. The detection of formaldehyde is based on the Hantzsch reaction. This reaction involves the cyclization of 2,4-pentanedione and the formation of 3,5-diacetyl-1,4-dihydrolutidine (DDL), which can be detected by UV-vis absorption spectra. The relationship between absorbance of DDL at 412 nm and concentration of formaldehyde were determined on calibration curve, which was followed Beer–Lambert law. On oxidation, small particles had good efficacy on degradation and flower-like shape had higher efficacy than nano-sphere with similar size.
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