Near-Edge X-ray Absorption Fine Structure Spectroscopy of Diamondoid Thiol Monolayers on Gold
Diamondoids, hydrocarbon molecules with cubic-diamond-cage structures, have unique properties with potential value for nanotechnology. The availability and ability to selectively functionalize this special class of nanodiamond materials opens new possibilities for surface-modification, for high-efficiency field emitters in molecular electronics, as seed crystals for diamond growth, or as robust mechanical coatings. The properties of self-assembled monolayers (SAMs) of diamondoids are thus of fundamental interest for a variety of emerging applications. This paper presents the effects of thiol substitution position and polymantane order on diamondoid SAMs on gold using near-edge X-ray absorption fine structure spectroscopy (NEXAFS) and X-ray photoelectron spectroscopy (XPS). A framework to determine both molecular tilt and twist through NEXAFS is presented and reveals highly ordered diamondoid SAMs, with the molecular orientation controlled by the thiol location. C 1s and S 2p binding energies are lower in adamantane thiol than alkane thiols on gold by 0.67 {+-} 0.05 eV and 0.16 {+-} 0.04 eV respectively. These binding energies vary with diamondoid monolayer structure and thiol substitution position, consistent with different amounts of steric strain and electronic interaction with the substrate. This work demonstrates control over the assembly, in particular the orientational and electronic structure, providing a flexible design of surface properties with this exciting new class of diamond clusters.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 944318
- Report Number(s):
- UCRL-JRNL-236817; JACSAT; TRN: US200902%%680
- Journal Information:
- Journal of the American Chemical Society, Vol. 130, Issue 32; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ABSORPTION
ALKANES
COATINGS
CYCLOALKANES
DIAMONDS
ELECTRONIC STRUCTURE
FINE STRUCTURE
GOLD
HYDROCARBONS
ORIENTATION
SEEDS
SPECTROSCOPY
STRAINS
SURFACE PROPERTIES
THIOLS
X-RAY PHOTOELECTRON SPECTROSCOPY