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Soft X-ray induced oxidation on acrylic acid grafted luminescent silicon quantum dots in ultrahigh vacuum

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Author

Summary, in English

Water soluble acrylic acid grafted luminescent silicon quantum dots (Si-QDs) were prepared by a simplified method. The resulting Si-QDs dissolved in water and showed stable strong luminescence with peaks at 436 and 604 nm. X-ray photoelectron spectroscopy (XPS) was employed to examine the surface electronic states after the synthesis. The co-existence of the Si2p and C1s core levels infers that the acrylic acid has been successfully grafted on the surface of silicon quantum dots. To fit the Si2p spectrum, four components were needed at 99.45, 100.28, 102.21 and 103.24 eV. The first component at 99.45 eV (I) was assigned to Si-Si within the silicon core of the Si-QDs. The second component at 100.28 eV (II) was from Si-C. The third at 102.21 eV (III) was a sub-oxide state and the fourth at 103.24 eV (IV) was from SiO2 at Si-QDs surface. With an increase in exposure to soft X-ray photons, the intensity ratio of the two peaks within the Si2p region A and B increased from 0.5 to 1.4 while the peak A intensity decreased, and eventually a steady state was reached. This observation is explained in terms of photon-induced oxidation taking place within the surface dangling bonds. As the PL profile for Si-QDs is influenced by the degree of oxidation within the nanocrystal structure, the inducement of oxidation by soft X-rays will play a role in the range of potential applications where such materials could be used - especially within biomedical labelling. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Department/s

Publishing year

2011

Language

English

Pages

2424-2429

Publication/Series

Physica Status Solidi. A: Applications and Materials Science

Volume

208

Issue

10

Document type

Journal article

Publisher

Wiley-Blackwell

Topic

  • Physical Sciences
  • Natural Sciences

Keywords

  • core levels
  • quantum dots
  • silicon
  • XPS

Status

Published

ISBN/ISSN/Other

  • ISSN: 1862-6300