Films of Graphene Nanomaterials Formed by Ultrasonic Spraying of Their Stable Suspensions

Figures & data

FIG. 1. TEM images of typical graphene nanomaterials. (a) GNF; the inset shows several GNFs on a TEM grid. (b) A MLG flake with some GNFs attached to its surface.

FIG. 2. (a) Ultrasonic spraying system used for film deposition experiments (front view) and (b) description of droplet formation on the surface of the ultrasonic atomizer.

FIG. 3. Size distribution of GNFs and MLG flakes suspended in (a) DMF, (b) ethanol, and (c) NMP.

TABLE 1 Zeta potential of GNFs and MLG flakes in sprayable suspensions

Material	Concentration (wt%)	Solvent (1:19 v/v)	Zeta potential (mV)	Electrical conductivity (μS/cm)
GNF	0.0011	DMF:Ethanol	−44.5	22
MLG	0.0118	DMF:Ethanol	−38.4	8.8
GNF	0.0021	NMP:Ethanol	−46.0	8.9
MLG	0.0026	NMP:Ethanol	−42.8	18.9

FIG. 4. Optical microscopy images of droplet footprints from GNF suspensions (a, on glass; b, on MA-glass) and MLG suspensions (c, on glass; d, on MA-glass).

FIG. 5. SEM images of graphene nanomaterial films on glass. GNF films at spraying time, t_s, of (a) 7 min and (b) 14 min. MLG films at t_s of 7 min for varying suspension concentrations of (c) 0.2 wt%, (d) 0.1 wt%, and (e) 0.05 wt%. (f) Image of a 0.1 wt% MLG suspension sprayed for 14 min.

FIG. 6. SEM images of graphene nanomaterial films on MA-glass. GNFs at t_s of (a) 7 min and (b) 14 min. MLG flakes at t_s of (c) 7 min and (d) 14 min; inset scale bar indicates is 1 μm. Low-magnification images of (e) GNFs and (f) MLGs sprayed for 14 min.

FIG. 7. Cross-sectional SEM images of MLG on glass (a, 14 min) and MA-glass (b, 14 min; c, 7 min); and GNF on glass (d, 14 min) and MA-glass (e, 14 min; f, 7 min). Insets show MLG flakes buried in the films; scale bar: 200 nm.