Solvent-dependent assembly of terphenyl- and quaterphenyldithiol on gold and gallium arsenide.
The assembly of terphenyldithiol (TPDT) and quaterphenyldithiol (QPDT) on gold and gallium arsenide from ethanol (EtOH), tetrahydrofuran (THF), and solutions consisting of both solvents has been characterized by near-edge X-ray absorption fine structure spectroscopy. The surface coverage and the average orientation of both TPDT and QPDT on gold are solvent-independent. These molecules readily form monolayers on gold with an ensemble-average backbone tilt of 30 degrees +/- 3 degrees from the substrate normal. In sharp contrast, the assembly of TPDT and QPDT on gallium arsenide is extremely solvent-sensitive. At high ethanol fractions, both molecules form monolayers with an ensemble-average orientation that is indistinguishable from those on gold substrates. At low ethanol fractions and in pure THF, however, these molecules are disordered on gallium arsenide and the surface coverage is poor.
Krapchetov
Dmitry A
DA
Chemical Engineering Department and Center for Nano- and Molecular Science and Technology, University of Texas at Austin, Austin, Texas 78712, USA.
Ma
Hong
H
Jen
Alex K Y
AK
Fischer
Daniel A
DA
Loo
Yueh-Lin
YL