Various nanostructures of ZnO grown by LP-PLA and chemical
methods
P. M. Aneesh, Arun Aravind, R. Reshmi and M. K. Jayaraj
Optoelectronic Devices Laboratory, Department of Physics,
Cochin University of Science and Technology, Kochi, India-682 022
Email: mkj@cusat.ac.in, aneeshpm@gmail.com
Zinc oxide (ZnO) is a wide band gap semiconductor that has become the
subject of investigation due to its unique optical, electrical and optoelectronic
properties. Liquid phase pulsed laser ablation (LP-PLA) has proven to be an
effective method for the preparation of many nanostructured materials. In the
present study, we discuss the growth and characterization of various surfactant
free ZnO nanostructures by LP-PLA, wet chemical and hydrothermal techniques.
By varying the laser fluence in LP-PLA method and concentration of the
precursors in wet chemical method, the morphology of the nanostructures can be
controlled. The structural and optical properties of these nanostructures were
characterized by studying transmission electron microscopy (TEM), x-ray
diffraction (XRD) and photoluminescence (PL) emission spectra. These ZnO
quantum dot (QD) colloidal solutions synthesized by LP- PLA and through
chemical routes were stable, transparent and luminescent. The luminescent
emission is visible to naked eye under UV illumination. The emission wavelength
could be varied (yellow to blue-violet) by varying the native defect chemistry of
ZnO quantum dots. The Yellow emission has been attributed to the oxygen
vacancy. This has been further supported by the experiments done with oxygen
bubbling during the LP- PLA, which resulted in the suppression of yellow peak
and the emergence of blue emission due to the zinc interstitials. These highly
luminescent nontoxic ZnO quantum dots have exciting application as florescent
probes in biomedical applications.
Fig (a) TEM image (b) SAED pattern (c) HRTEM image of ZnO QDs grown by
LP- PLA (d) TEM image of ZnO nanoribbons synthesized by LP-PLA method and
(e) SEM image of ZnO nanorods by hydrothermal method