  Transmission electron microscopy has undergone a revolution in recent years
with the possibility to perform routine cryo-imaging of biological materials
and (bio)chemical systems, as well as the possibility to image liquids via
dedicated reaction cells or graphene-sandwiching. These approaches however
typically require imaging a large number of specimens and reconstructing an
average representation and often lack analytical capabilities. Here, using atom
probe tomography we provide atom-by-atom analyses of frozen liquids and
analytical sub-nanometre three dimensional reconstructions. The analyzed ice is
in contact with, and embedded within, nanoporous gold (NPG). We report the
first such data on 2-3 microns thick layers of ice formed from both high purity
deuterated water and a solution of 50mM NaCl in high purity deuterated water.
We present a specimen preparation strategy that uses a NPG film and,
additionally, we report on an analysis of the interface between nanoporous gold
and frozen salt water solution with an apparent trend in the Na and Cl
concentrations across the interface. We explore a range of experimental
parameters to show that the atom probe analyses of bulk aqueous specimens come
with their own special challenges and discuss physical processes that may
produce the observed phenomena. Our study demonstrates the viability of using
frozen water as a carrier for near-atomic scale analysis of objects in solution
by atom probe tomography.
