Jeffrey Yue

Solvothermal synthesis of ZnO-decorated α-Fe2O3 nanorods with highly enhanced gas-sensing performance toward n-butanol

This paper reports a newly developed solvothermal strategy for the synthesis of ZnO-decorated α-Fe2O3 nanorods based on the reaction of α-Fe2O3 nanorods with zinc sulfate and urea in autoclaves at 180 °C. The resulting nanocomposites consist of porous α-Fe2O3 nanorods with diameters of 100–200 nm and a surface decorated with small ZnO nanoparticles (10–20 nm). The ZnO NPs are found to grow epitaxially on {110} planes of α-Fe2O3, forming an interfacial orientation relationship of (100)ZnO/(110)α-Fe2O3. The addition of ZnO is found to shift the Fe 2p peak position in the α-Fe2O3/ZnO nanocomposites to higher binding energies due to the formation of the α-Fe2O3/ZnO heterojunction interface. The gas-sensing results show that the ZnO-decorated α-Fe2O3 nanorods exhibit excellent sensitivity, selectivity, and stability toward n-butanol gas at a low optimum temperature of 225 °C. In particular, they show higher sensitivity compared to pure α-Fe2O3 (4 times higher) and ZnO nanorods (2.5 times higher), respectively, along with faster response times. The significant enhancement in sensitivity may be attributed to the chemical and electronic sensitization induced by the ZnO nanoparticles deposited on the surfaces of the α-Fe2O3 nanorods. The findings reported in this study will be useful for the design and construction of surface modified-metal oxide nanostructures with enhanced gas-sensing performance.

Deposition of gold nanoparticles on β-FeOOH nanorods for detecting melamine in aqueous solution

This study demonstrates a facile but efficient approach to deposit metallic (gold) nanoparticles on β-FeOOH nanorods to obtain Au/β-FeOOH nanocomposites without the assistance of any polymers or surfactants at ambient conditions. In this method, a strong reducing agent (NaBH(4)) can be used to extensively produce Au nanoparticles, converting β-FeOOH into Fe(3)O(4) and depositing gold particles onto magnetic Fe(3)O(4) simultaneously. The microstructure, composition, and chemical properties of the obtained nanocomposites are characterized by various advanced techniques, including transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV-vis spectroscopy. Moreover, the Au/β-FeOOH nanocomposite can be used to detect trace melamine using UV spectrum in the ultraviolet wavelength range (190-260 nm), in which the nanocomposites show a higher sensitivity toward melamine due to the promotion of symmetry-forbidden bands (n→π(*)) of melamine molecules and also avoid the disturbance of commercial products containing solid colloids or food colorings that distort visual spectrum during the detection of chemical sensing. The deposition mechanisms and their sensing detection toward melamine are discussed.

Theoretical Study of Growth Mechanism of Goethite in the Presence of Surfactants

Goethite (α-FeOOH) nanorods could be prepared by a surfactant directed approach in aqueous solution at ambient conditions. In this approach, it is observed that the surfactants (e.g, cetyltrimethylammonium bromide (CTAB) and tetraethylamine chloride (TEAC)) play a key role in the growth of goethite nanorods under the reported conditions. The molecular dynamics (MD) method is used to understand the underlying principle governing particle formation and growth through the analysis of the interaction energies between the crystal surfaces and the surfactant molecules. The findings will be useful for understanding the growth mechanism of anisotropic particles and their surface coatings with heterogeneous materials for desired functional properties.

Experimental and Theoretical Study of Low-Dimensional Iron Oxide Nanostructures

Iron oxide has many phases, including 16 pure phases (e.g., FeO, Fe3O4), 5 polymorphs of FeOOH (e.g., -FeOOH, -FeOOH) and 4 kinds of Fe2O3 (e.g., -Fe2O3, -Fe2O3). Because of their unique properties (optical, electronic, magnetic), they have found many applications in the areas of catalysts, magnetic recording, sorbents, pigments, flocculants, coatings, gas sensors, lubrications, and biomedical applications (e.g., magnetic resonance imaging, drug delivery and therapy).