New Dihexadecyldithiophosphate
SAMs on Gold Provide
Insight into the Unusual Dependence of Adsorbate Chelation on Substrate
Morphology in SAMs of Dialkyldithiophosphinic Acids
Ronan
R. San Juan
Christopher J. Allan
Muhammad Iqbal
S. Holger Eichhorn
Charles L. B. Macdonald
Tricia Breen Carmichael
10.1021/ja404798q.s001
https://acs.figshare.com/articles/journal_contribution/New_Dihexadecyldithiophosphate_SAMs_on_Gold_Provide_Insight_into_the_Unusual_Dependence_of_Adsorbate_Chelation_on_Substrate_Morphology_in_SAMs_of_Dialkyldithiophosphinic_Acids/2363446
We
report the formation and characterization of new self-assembled
monolayers (SAMs) formed from dihexadecyldithiophosphate (C<sub>16</sub>)<sub>2</sub>DDP and compare their properties with those of SAMs
formed from the structurally similar adsorbate dihexadecyldithiophosphinic
acid (C<sub>16</sub>)<sub>2</sub>DTPA. The new (C<sub>16</sub>)<sub>2</sub>DDP SAMs were characterized using X-ray photoelectron spectroscopy,
reflection–absorption infrared spectroscopy, contact angle
measurements, and electrochemical impedance spectroscopy. The data
indicate that (C<sub>16</sub>)<sub>2</sub>DDP forms SAMs on gold films
formed by e-beam evaporation in which all adsorbates chelate to gold,
in contrast to (C<sub>16</sub>)<sub>2</sub>DTPA SAMs, in which 40%
of the adsorbates are monodentate. The alkyl chains of the (C<sub>16</sub>)<sub>2</sub>DDP SAM are also less densely packed and ordered
than those of the (C<sub>16</sub>)<sub>2</sub>DTPA SAM. To understand
these differences, we present density functional theory calculations
that show that there are only minimal differences between the geometric
and electronic structures of the two adsorbates and that the energetic
difference between monodentate and bidentate binding of a goldÂ(I)
ion are surprisingly small for both adsorbates. This study leads to
the conclusion that differences in intermolecular interactions within
the SAM are the driving force for the difference in chelation between
the two adsorbates.
2013-10-23 00:00:00
gold films
Dialkyldithiophosphinic AcidsWe report
electrochemical impedance spectroscopy
Adsorbate Chelation
Substrate Morphology
theory calculations
contact angle measurements
New Dihexadecyldithiophosphate SAMs
bidentate binding
adsorbate dihexadecyldithiophosphinic acid
Unusual Dependence
adsorbates chelate
alkyl chains