Hydrogen Bonded Nanostructures on Surfaces: STM, XPS and Electrospray Deposition

Swarbrick, Janine Cathy (2006) Hydrogen Bonded Nanostructures on Surfaces: STM, XPS and Electrospray Deposition. PhD thesis, University of Nottingham.

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Molecules adsorbed on surfaces can show fascinating characteristics and properties. In particular the assembly of molecules into ordered arrays on surfaces is of great interest, whether one considers possible commercial applications or fundamental physical interactions. Specifically, the mediation of ordered molecular arrangements via hydrogen bonding yields many interesting structures.

This thesis focusses primarily on the importance of hydrogen bonding between molecules on surfaces in ultra high vacuum (UHV), and how these interactions govern ordered phase formation. Scanning tunnelling microscopy is used to investigate the planar perylene derivative PTCDA on the hexagonal Ag-Si(111) (sqrt 3) * (sqrt 3)R30^o surface alone,

with C_{60}, and with melamine. Interesting molecular architectures are observed including a square PTCDA arrangement, and a PTCDA-melamine hexagonal network which contains both stabilising hydrogen bonds and potentially repulsive interactions. Hydrogen bonding systems of pyridinecarboxylic acids on rutile TiO_2 have been studied using photoemission spectroscopy. Ordered films of isonicotinic acid were investigated using valence band photoemission, and an angular dependence is observed in valence band spectra as the angle between the sample and the incoming light is changed. Biisonicotinic acid was also studied on TiO_2 and on gold using core level photoemission to determine how it bonds to these surfaces; it is thought to chemisorb to both TiO_2 and gold through its carboxylic acid groups in an upright orientation.

Some large or fragile molecules cannot be sublimed in vacuum for deposition as they fragment. Another research focus has been the development of a technique for depositing non-volatile molecules in vacuum directly from solution. Concepts of electrospray ionisation have been used in the development of a vacuum electrospray deposition system. The molecule is dissolved or suspended in solution and electrosprayed directly into a vacuum environment, with the result that molecules of interest are deposited on a sample without fragmentation or corruption. The samples may then be investigated with vacuum based techniques such as scanning tunnelling microscopy and photoemission spectroscopy.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: O'Shea, James
Beton, Peter
Keywords: hydrogen bonding, hydrogen bonded nanostructures, nanoscience, nanostructures, scanning tunneling microscopy, scanning tunnelling microscopy, STM, photoemission spectroscopy, XPS, electrospray deposition, supramolecular nanostructures, TiO_2, TiO2, Si 7 * 7, Si 7 x 7, Si, silver terminated silicon, biisonicotinic acid, valence band photoemission, PTCDA, PTCDA-melamine
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Faculties/Schools: UK Campuses > Faculty of Science > School of Physics and Astronomy
Item ID: 10245
Depositing User: EP, Services
Date Deposited: 26 Apr 2007
Last Modified: 13 Sep 2016 20:53
URI: http://eprints.nottingham.ac.uk/id/eprint/10245

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