Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ligand-Surface Interactions and Surface Oxidation of Colloidal PbSe
  Quantum Dots Revealed by Thin-film Positron Annihilation Methods   Positron Two Dimensional Angular Correlation of Annihilation Radiation
(2D-ACAR) measurements reveal modifications of the electronic structure and
composition at the surfaces of PbSe quantum dots (QDs), deposited as thin
films, produced by various ligands containing either oxygen or nitrogen atoms.
In particular, the 2D-ACAR measurements on thin films of colloidal PbSe QDs
capped with oleic acid ligands yield an increased intensity in the electron
momentum density (EMD) at high momenta compared to PbSe quantum dots capped
with oleylamine. Moreover, the EMD of PbSe QDs is strongly affected by the
small ethylediamine ligands, since these molecules lead to small distances
between QDs and favor neck formation between near neighbor QDs, inducing
electronic coupling between neighboring QDs. The high sensitivity to the
presence of oxygen atoms at the surface can be also exploited to monitor the
surface oxidation of PbSe QDs upon exposure to air. Our study clearly
demonstrates that positron annihilation spectroscopy applied to thin films can
probe surface transformations of colloidal semiconductor QDs embedded in
functional layers.

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The categories of this paper are: adap-org
28
The categories of this paper are: alg-geom
9
The categories of this paper are: nlin
36
The categories of this paper are: cmp-lg
33
The categories of this paper are: plasm-ph
0
The categories of this paper are: hep-ph
2
The categories of this paper are: math
26
The categories of this paper are: bayes-an
35
The categories of this paper are: mtrl-th
34
The categories of this paper are: chem-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: nucl-th
32
The categories of this paper are: atom-ph
10
The categories of this paper are: q-bio
8
The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas