Figure 1

(a),(b) Histograms of the diameter-distribution of rounded and faceted particles, suggesting that ice particles with larger diameter tend to be faceted. (inset) Typical corresponding low-magnification TEM images of the particles.Reuse & Permissions

Figure 2

(a) HRTEM and corresponding FFT pattern of an ice nanoparticle with ice ${\mathrm{I}}_h$ structure. The image shows the hexagonal network shown as bright dots, which are separated by $\sim 0.25\mathrm{nm}$. (b) Simulated TEM image viewed from the [0001] zone axis of ice ${\mathrm{I}}_h$ using the following parameters: convergence angle of 0.5 mrad, $C_S$ value of $3\mu \mathrm{m}$, defocus spread of 9 nm, sample thickness of 42 nm, defocus value of $+33\mathrm{nm}$ (overfocus), and objective aperture radius of $7{\mathrm{nm}}^{-1}$. The simulation image shows bright dots, which corresponds to the position of the oxygen columns. Models of water molecules are superimposed. (c) A crystal model of the [0001] zone axis of ice ${\mathrm{I}}_h$. Hydrogen atoms (white circles) are located between the oxygen columns (red circles), but are invisible in experiment. (d) Schematic model of a water molecule.Reuse & Permissions

Figure 3

(a) Core-level EELS from an individual ice nanoparticle, showing the oxygen $K$-edge ($\sim 540\mathrm{eV}$). Note that no carbon $K$ edge can be detected. (inset) TEM image of the corresponding ice nanoparticle (indicated by an arrow) (b) EELS valence analysis of a hexagonal ice nanoparticle. The interband transitions are quite visible and specific to crystalline ice particles. The peak at 21 eV is a bulk plasmon. (c) Oxygen $K$-edge fine structure of the experimental and simulated spectra. The prepeak ($\sim 542\mathrm{eV}$) just before the main peak (546 eV) of the experimental spectrum cannot be reproduced by simulations for ice ${\mathrm{I}}_h$ or ${\mathrm{I}}_c$. A smallest selected area aperture (200 nm in diameter) was used.Reuse & Permissions

Figure 4

Sequential TED patterns of an isolated ice nanoparticle recorded at a constant dose rate with $4.8\times {10}^3\mathrm{\text{electrons}}/{\mathrm{nm}}^2\mathrm{s}$. (a)–(f) 3, 19, 20, 5, 36, and 42 s, respectively.Reuse & Permissions