Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Molecular-Scale Hydrophilicity Induced by Solute: Molecular-thick
  Charged Pancakes of Aqueous Salt Solution on Hydrophobic Carbon-based
  Surfaces   We directly observed molecular-thick aqueous salt-solution pancakes on a
hydrophobic graphite surface under ambient conditions employing atomic force
microscopy. This observation indicates the unexpected molecular-scale
hydrophilicity of the salt solution on graphite surfaces, which is different
from the macroscopic wetting property of a droplet standing on the graphite
surface. Interestingly, the pancakes spontaneously displayed strong positively
charged behavior. Theoretical studies showed that the formation of such
positively charged pancakes is attributed to cation-{\pi} interactions between
Na+ ions in the aqueous solution and aromatic rings on the graphite surface,
promoting the adsorption of water molecules together with cations onto the
graphite surface; i.e., Na+ ions as a medium adsorbed to the graphite surface
through cation-{\pi} interactions on one side while at the same time bonding to
water molecules through hydration interaction on the other side at a molecular
scale. These findings suggest that actual interactions regarding carbon-based
graphitic surfaces including those of graphene, carbon nanotubes, and biochar
may be significantly different from existing theory and they provide new
insight into the control of surface wettability, interactions and related
physical, chemical and biological processes.

20
The categories of this paper are: acc-phys
6
The categories of this paper are: astro-ph
14
The categories of this paper are: math-ph
16
The categories of this paper are: stat
33
The categories of this paper are: plasm-ph
21
The categories of this paper are: adap-org
9
The categories of this paper are: nlin
5
The categories of this paper are: gr-qc
27
The categories of this paper are: comp-gas
0
The categories of this paper are: hep-ph
30
The categories of this paper are: q-alg
18
The categories of this paper are: econ
29
The categories of this paper are: funct-an
28
The categories of this paper are: alg-geom
1
The categories of this paper are: cs
13
The categories of this paper are: quant-ph