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

Journal Article · Thu Apr 14 00:00:00 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), Vol. 98:15; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

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