Synthesis of stable dispersion of ZnO quantum dots in aqueous medium showing visible emission from bluish green to yellow

Aqueous dispersion of 4–8 nm size stable ZnO quantum dots (QDs) exhibiting luminescence in the visible region have been synthesized by a simple solution growth technique at room temperature. Silica has been used as capping agent to control the particle size as well as to achieve uniform dispersion o...

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Bibliographic Details
Published in:	Journal of luminescence Vol. 129; no. 3; pp. 320 - 324
Main Authors:	Patra, M.K., Manoth, M., Singh, V.K., Siddaramana Gowd, G., Choudhry, V.S., Vadera, S.R., Kumar, N.
Format:	Journal Article
Language:	English
Published:	Amsterdam Elsevier B.V 01-03-2009 Elsevier
Subjects:	Condensed matter: electronic structure, electrical, magnetic, and optical properties Exact sciences and technology Luminescence Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures Physics Quantum dots Semiconductor Quantum dots Semiconductor Luminescence Quantum confinement Atomic force microscopy Particle size Semiconductor materials Photoluminescence XRD Effective mass model Spectral line shift Defects Hexagonal lattices Energy gap Aqueous solutions Zinc oxide Spherical particle Absorption spectra
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Summary:	Aqueous dispersion of 4–8 nm size stable ZnO quantum dots (QDs) exhibiting luminescence in the visible region have been synthesized by a simple solution growth technique at room temperature. Silica has been used as capping agent to control the particle size as well as to achieve uniform dispersion of QDs in aqueous medium. X-ray diffractometer (XRD) analysis reveals formation phase pure ZnO particles having wurzite (hexagonal) structure. Atomic force microscope (AFM) images show that the particles are spherical in shape, having average crystalline sizes ∼4, 5.5 and 8 nm for samples prepared at pH values of 10, 12 and 14, respectively. From the optical absorption studies, the band gap energy of QDs is found to be blue shifted as compared to bulk ZnO (3.36 eV) due to the quantum confinement effect and is consistent with the band gap calculated by using effective-mass approximation model. The photoluminescence (PL) observed in these QDs has been attributed to the presence of defect centers.
ISSN:	0022-2313 1872-7883
DOI:	10.1016/j.jlumin.2008.10.014