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Displacement Processes of Octylamine Monolayers by Alkanethiols and Steric Effects on the Formation of Alkanethiol Monolayers on Au(111)

Title
Displacement Processes of Octylamine Monolayers by Alkanethiols and Steric Effects on the Formation of Alkanethiol Monolayers on Au(111)
Author
양태호
Alternative Author(s)
양태호
Advisor(s)
노재근
Issue Date
2022. 2
Publisher
한양대학교
Degree
Master
Abstract
Displacement processes of pre-covered octylamine (OA) self-assembled monolayers (SAMs) by dodecanethiol (DDT) on Au(111) were examined as a function of displacement time by scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV) , and contact angle (CA) measuremetns. STM measurements clearly revealed that the OA SAMs with a disordered phase was changed to an ordered phase as a result of displacement by DDT. It was also confirmed that the intensity of reductive desorption peak of OA SAMs at -960 mV decreased, whereas that of DDT SAMs at -1100 mV increased as a function of displacement time. In addition, XPS measurements revealed that the intensity of S 2p XPS peak at 162 eV corresponding to DDT monolayers increased as a function of displacement time, while the intensity of N 1s peak at 399.5 eV corresponding to OA monolayers decreased, suggesting that pre-covered OA SAMs were displaced by DDT molecules. In this study, we clearly demonstrated that OA SAMs on Au(111) can be easily displaced by DDT. On the other hand, to understand the steric effects on the formation of alkanethiol SAMs on Au(111), we compared the surface structures of 2-octanethiol (2-OT) SAMs with those of OT. STM measurements showed that 2-OT SAMs had loosely packed ordered phase with a (8  3) packing structures (areal density: 28.6 Å2/molecule), which is comparable to a c( 4  2) packing structures for OT SAMs (areal density: 21.6 Å2/molecule). Reductive desorption peak for of 2-OT SAMs was observed at less negative potential of -984 mV compared with OT SAMs observed at -1050 mV. This result is attributed to weak van der Waals interactions of 2-OT SAMs resulting from lower packing density as demonstrated by STM results. From this work, a methyl group attached to -carbon position in 2-OT molecules significantly affects the formation and surface structures of alkanethiol SAMs on Au(111).
URI
http://hanyang.dcollection.net/common/orgView/200000592270https://repository.hanyang.ac.kr/handle/20.500.11754/167569
Appears in Collections:
GRADUATE SCHOOL[S](대학원) > CHEMISTRY(화학과) > Theses (Master)
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