X-ray photoelectron spectroscopy of CdSe nanocrystals with applications to studies of the nanocrystal surface

Journal Article · Thu Apr 14 04:00:00 EDT 1994 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100066a034· OSTI ID:7267852

Katari, J E.B. ^[1]; Colvin, V L; Alivisatos, A P ^[2]

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1. Univ of California, Berkeley, CA (United States)
2. Lawrence Berkeley Lab., CA (United States) Univ. of California, Berkeley CA (United States)

We report the use of X-ray photoelectron spectroscopy (XPS) to determine the surface composition of semiconductor nanocrystals. Crystalline, nearly monodisperse CdSe nanocrystals ranging in radius from 9 to 30 A were chemically synthesized and covalently bound to Au and Si surfaces for study. XPS core level peak positions for Cd and Se were in agreement with those of bulk CdSe. We have determined that the majority of Se atoms on the surface are unbonded as prepared and that Cd atoms are bonded to the surface ligand, tri-n-octylphosphine oxide, to the extent that such bonding is sterically allowed. We have determined that the total ligand saturation of the nanocrystal surface varies from 60% in the smaller nanocrystals to 30% in the larger nanocrystals. In addition, we have determined that upon exposure of the nanocrystals to air Se surface sites are oxidized, forming a SeO[sub 2] surface film which causes the nanocrystals to degrade over time. The nanocrystal surface can be modified by dispersing the crystals in pyridine. Nearly all of the P ligands are removed in this case, leaving behind primarily unsaturated Cd and Se surface atoms. In this case, both Cd and Se oxidize upon exposure to air. 35 refs., 17 figs., 1 tab.

• OSTI ID: 7267852
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 98:15; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360602* -- Other Materials-- Structure & Phase Studies
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102 -- Chemical & Spectral Procedures
400201 -- Chemical & Physicochemical Properties
AZINES
CADMIUM COMPOUNDS
CADMIUM SELENIDES
CHALCOGENIDES
CHEMICAL BONDS
CHEMICAL REACTIONS
COVALENCE
CRYSTALS
ELECTRON SPECTROSCOPY
ELEMENTS
GOLD
HETEROCYCLIC COMPOUNDS
LIGANDS
MATERIALS
METALS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDATION
OXYGEN COMPOUNDS
PHOSPHINE OXIDES
PHOSPHINES
PHOSPHORUS COMPOUNDS
PHOTOELECTRON SPECTROSCOPY
PYRIDINE
PYRIDINES
SELENIDES
SELENIUM COMPOUNDS
SEMICONDUCTOR MATERIALS
SEMIMETALS
SILICON
SPECTRA
SPECTROSCOPY
SURFACE PROPERTIES
SYNTHESIS
TRANSITION ELEMENTS
X-RAY SPECTRA