Synthesis, characterization, and antibacterial activity of copper oxide nanosheets
The investigation on nanoparticles, which includes fabrication and characterization of the structural, physical, and chemical properties and their functions in various field of technology, is a fundamental cornerstone of nanotechnology and nanoscience. The applications of nanoparticles are kno...
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| Format: | Thesis |
| Language: | English |
| Published: |
2013
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| Online Access: | http://psasir.upm.edu.my/id/eprint/67354/1/FS%202013%2065%20IR.pdf http://psasir.upm.edu.my/id/eprint/67354/ |
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| Summary: | The investigation on nanoparticles, which includes fabrication and characterization of
the structural, physical, and chemical properties and their functions in various field of
technology, is a fundamental cornerstone of nanotechnology and nanoscience. The
applications of nanoparticles are known in many fields, such as catalysis, coating,
semiconductors, and electronics. Among all practical matters that are produced at the
nanometer scale, metal oxides are mainly attractive candidates from a technological and
scientific point of view. Amongst all metal oxide nanoparticles, copper oxide (CuO) has
gained the most interest because of its wide applications. During the past decades
different methods have been proposed to synthesis CuO nanoparticles. Some of these
methods have limitations due to requirements for high temperature, expensive
instruments and special catalysis. In this study fabrication of CuO nanosheets in
polyvinylpyrrolidone (PVP) by the quick precipitation method was investigated. The
main advantages of this method compared to other methods are environmentally friendly, cost-effectiveness, producing pure materials and simplicity of operation.
Synthesis parameters include pH, concentration of stabilizer, and molar ratio of Cu2+ and
OH- were varied and their influences on the properties of CuO were investigated.
Copper nitrate trihydrate Cu(NO3)2.3H2O, polyvinylpyrrolidone (PVP) and sodium
hydroxide (NaOH) were utilized as copper precursor, stabilizer and reducing agent,
respectively. As evidenced by XRD analysis, all the products synthesized at pH 10 and
12 were CuO with monoclinic structure and all the products obtained under acidic pH
were copper hydroxyl nitrate (Cu2(OH)3NO3). Electron microscopy analysis illustrated
that nanocrystals have a sheet-like geometry. By careful observation of electron
microscopy revealed that oriented attachment mechanism was responsible for formation
nanosheets from nanosized subunits. EDAX clearly confirmed the existence of Cu and O
with an atomic ratio of 1:1 in all samples synthesized at pH 10 and 12. Diffuse
reflectance spectroscopy studies revealed that the band gap of CuO nanosheets was
found to be size-dependant. FT-IR spectroscopy was applied in this work to study the
bonding at the surface of the synthesized CuO nanosheets. The result of FT-IR indicated
that C=O in PVP Coordinated with CuO nanosheets and formed a protection layer.
Investigation of effect of molar ratios of Cu2+ and OH- on CuO indicated that when the
molar ratio of Cu2+ and OH- is 1:1, the final product is not pure. The pure monoclinic
CuO were formed at the molar ratio of 1:3 and 1:4. From electron microscopy studies,
sheet-like CuO at the molar ratio of 1:3 and 1:4 and ellipsoid-shape at a molar ratio of
1:1 were formed. The as synthesized CuO nanosheets were examined for antibacterial
activity against four human pathogens, including two Gram-positive (Staphylococcus.
areas and Bacillus. subtilis) and two Gram-negative (Salmonella and Klebsiella
pneumonia). The antibacterial activity of CuO nanosheets was found to be size dependent. The zone of inhibition increased as particle size decreased. The main
observation was that CuO nanosheets indicated greater antimicrobial activity against
Gram-positive bacteria. The inhibition zone for all microorganisms reached the
maximum using CuO nanosheets fabricated in PVP 5% wt at pH 10. |
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