Preparation and characterization of organic ligands utilized in the synthesis of zinc oxide precursors

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Preparation and characterization of organic
ligands utilized in the synthesis of zinc oxide
precursors

• Felicia A. McClary
• Howard University, Graduate School
• Advisor Jason S. Matthews, PhD
• Department of Chemistry
• July 26, 2007

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Outline

• Objective
• What is Zinc Oxide?
• Synthesis/Characterization
• Future work

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Objective

• Synthesize novel ligands for use in the
  fabrication of Zinc Oxide nanowires
• Improve the purity of synthesized ZnO materials
  by reducing carbon contamination.

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Zinc Oxide

• Molecular Formula, ZnO
• Environmentally friendly
• Multiple forms
• Found in
• Paints
• Cosmetics
• Lotions/Sunscreens
• Semiconductor
• Piezoelectric properties

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Piezoelectric Effect

• The ability of a crystalline structure to
  generate an electrical current with applied
  stress through flexing
• Crystalline structure is capable of flexing when
  placed in an electrical field (current applied)

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Nanogenerator

• Aligned zinc oxide nanowires on a substrate
• provide a continuous electric current with
  applied
• stress
• Convenient/portable alternative to battery packs
• Provides power to nanodevices
• Portable electronics
• Implantable medical devices
• Biosensors

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Nanogenerator
Zhong Lin Wang."Nanogenerator Provides Continuous
Electrical Power." Georgia Institute of
Technology. April 5, 2007.
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Steps for zinc oxide preparation
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Ligand synthesis
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Purification

• Vacuum Distillation (Reduced Pressure)
• Why?
• High molecular weight compoundhigh boiling point
• Prevents decomposition of product before
  distillation
• Removes unreacted starting material

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Characterization

• FT-IR Fourier Transform Infrared Spectroscopy
• Determines functional groups present in a
  compound
• Deduce relative structure

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Characterization

• GC/MS Gas Chromatography/Mass Spectrometry
• Determine if product is pure
• Provides molecular weights of parent compound and
  ions formed

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Characterization

• ¹H-NMR Proton Nuclear Magnetic Resonance
• Determine arrangement of each unique proton
  (H atoms)
• Deduce structure of product

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Precursor Formation

• Ligand central atom (Zinc), used to create the
  final compound
• Common precursors
• Metal alkoxides
• Metal diketonoates
• What makes a suitable precursor
• Volatile
• Deposit with minimal to no Carbon Contamination
• Thermal stability

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Preparation of Zinc Oxide nanowires

• Sol-gel
• Sol-solid particles suspended in a liquid phase
  (precursor)
• Deposited onto a substrate
• Particles condense to the gel phase.
• Removal of solvent yields crystalline coating
• Metal-Organic Chemical Vapor Deposition
• uses a metal-organic gas source (Zn Precursor)
• Precursor is heated to its gas phase
• Carried to a heated substrate by a carrier gas
• React with the substrate to deposit the solid
  product

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MOCVD-Metal-Organic Chemical Vapor Deposition

• Why preferred?
• High purity
• Large area growth
• Control of film thickness
• High growth rates
• Preferred structural orientation

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Future Work

• Synthesize metal complexes (Precursors)
• Deposit Zinc oxide
• Eliminate Carbon Contaminationincrease purity
• Outcome
• Biosafe Nanogenerator
• Economical
• Replace battery packs

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Acknowledgements

• Alliance for Graduate Education and the
  Professoriate (AGEP)
• Jason S. Matthews, PhD
• Joshua Halpern, PhD
• Partnership for Research and Education in
  Materials (PREM)
• Howard University, Department of Chemistry