Type

Journal Article

Authors

Jonathan N Coleman
Valeria Nicolosi
Mervyn Shannon
Aleksey Shmeliov
Giovanni Costantini
Cerianne Partridge
Thomas W White
Ben Moreton
Klaus Müllen
Lukas Doessel
and 3 others

Subjects

Chemistry

Topics
hildebrand solubility parameter dispersions self assembled transmission electron microscopy tem highly oriented pyrolytic graphite structures materials organic solvents

High quality dispersions of hexabenzocoronene in organic solvents. (2012)

Abstract We have studied the exfoliation and dispersion of hexabenzocoronene (HBC) in 28 different solvents. We see a wide range of dispersed concentrations and aggregation states, all of which can be related to the solvent properties. To a first approximation, the dispersed concentration is maximized for solvents with Hildebrand solubility parameter close to 21 MPa(1/2), similar to graphitic materials such as nanotubes and graphene. We have also studied the concentration dependence of the absorbance and photoluminescence of HBC for both a good solvent, cyclohexyl pyrrolidone (CHP), and a poor solvent, tetrahydrofuran (THF). In both cases, we observe features that can be associated with either individual molecules or aggregates, allowing us to establish metrics both for aggregate and individual molecule content. While the aggregate content always increases with concentration, good solvents disperse individual molecules at relatively high concentrations while poor solvents display aggregation even at low concentrations. Using these metrics, we determine that large populations of individual molecules are present at low concentrations in certain solvents with Hildebrand solubility parameters close to 21 MPa(1/2). However, the aggregation state of HBC is considerably more sensitive to solvent Hildebrand parameter for halogenated solvents than for amide solvents. We find a combination of high overall concentrations and large populations of individual molecules in four solvents: cyclohexyl pyrrolidone, 1-chloronaphthalene, 1-bromonaphthalene, and 1,2,4-trichlorobenzene. Scanning tunnelling microscopy (STM) measurements show the formation of self-assembled monolayers at the interface between a HBC-solvent dispersion and a highly oriented pyrolytic graphite (HOPG) substrate. Similar structures were observed on ultrathin supports by aberration-corrected transmission electron microscopy (TEM). Also observed were graphitic objects of size ~1 nm consistent with monomers or aggregated stacks of very few monomers. We believe this is strong evidence of the presence of individual molecules in dispersions prepared with appropriate solvents.
Collections Ireland -> Trinity College Dublin -> PubMed

Full list of authors on original publication

Jonathan N Coleman, Valeria Nicolosi, Mervyn Shannon, Aleksey Shmeliov, Giovanni Costantini, Cerianne Partridge, Thomas W White, Ben Moreton, Klaus Müllen, Lukas Doessel and 3 others

Experts in our system

1
Jonathan Coleman
Trinity College Dublin
Total Publications: 217
 
2
Valeria Nicolosi
Trinity College Dublin
Total Publications: 67
 
3
Aleksey Shmeliov
Trinity College Dublin
Total Publications: 7