Evolution of the size and shape of 2D nanosheets during ultrasonic fragmentation

Abstract

2-dimensional (2D) nanosheets such as graphene, graphene oxide, boron nitride or transition metal dichalcogenides can be produced on a large scale by exfoliation techniques. The lateral shape of these 2D materials is typically considered random and irregular, and their average size is often estimated using techniques characterized by strong approximations or poor statistical significance. Here we measure in a quantitative, objective way the size and shape of 2D monoatomic nanosheets using a combination of optical, electronic and scanning probe techniques. We measure, one by one, the size and shape of thousands of sheets of graphene oxide as they undergo a standard ultrasonication treatment. Using automatic image processing and statistical modelling we identify two different fragmentation processes in 2D at the nanoscale, related to two populations of nanosheets described by gamma and exponential size distributions respectively. The two populations of sheets coexist during the fragmentation process, each one retaining its average size and shape. Our results explain the size reduction commonly observed in nanosheets upon sonication as an effect of changes in the respective weights of the two populations of nanosheets present in the material.

Degradation behaviors and mechanisms of MoS2 crystals relevant to bioabsorbable electronics

“…In addition, the formation of MoO 3 groups leads to the addition of oxygen atoms at the broken edge, continuing the oxidation and degradation process 48 . In some respects, imperfections, such as dislocations and point defects, in CVD-grown monolayer MoS 2 crystals strongly influence the degradation process, which could potentially be further controlled by defect or domain size engineering in the future 42,50 . For instance, vacancies can be created or healed to modulate the defect density and degradation speed of monolayer MoS 2 via synthetic or postprocessing technologies.…”

Improved Biocompatibility of Amino‐Functionalized Graphene Oxide in Caenorhabditis elegans

“…Images were acquired with a commercial microscope Multimode 8 (Bruker) operated in the tapping mode under ambient conditions. The average size of GO flakes was measured by automatic image processing …”

Topochemical Synthesis of Two‐Dimensional Transition‐Metal Phosphides Using Phosphorene Templates

“…As depicted in Figure c, exfoliated BP flakes present mean diameters of (2.8±1.5) μm and thicknesses of (3.2±1.1) nm. This polydispersed size/thickness distribution is associated with a fragmentation‐exfoliation mechanism, well‐known for top‐down exfoliation methods. Based on energy‐dispersive X‐ray spectroscopy (EDX; Figures S3 and S4), the cobalt and nickel phosphides comprise atomic ratios of 2.1:1.0 (Co/P) and 2.3:1.0 (Ni/P), almost identical to their theoretical stoichiometry (i.e.…”