ORCID Profile
0000-0002-7280-4919
Current Organisation
Queensland University of Technology
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In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Functional Materials | Nanomaterials | Surfaces and Structural Properties of Condensed Matter | Macromolecular and Materials Chemistry | Plasma Physics; Fusion Plasmas; Electrical Discharges | Materials Engineering | Chemical Characterisation of Materials
Expanding Knowledge in the Physical Sciences | Consumer Electronic Equipment (excl. Communication Equipment) | Environmentally Sustainable Manufacturing not elsewhere classified | Expanding Knowledge in Technology |
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3SC50800E
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3CP50793A
Abstract: We have characterized the structural properties of submonolayer amounts of Zn on Pd(111) using scanning tunneling microscopy (STM) and spot-profile analysis low energy electron diffraction (SPA-LEED). Following room temperature deposition of ≈0.06 monolayers (ML) Zn onto Pd(111), we observe the substitution of Zn for Pd in the surface layer. At ≈0.20 ML of deposited Zn, STM reveals a locally ordered phase with a (2/√3 × 2/√3)R30° unit cell located near Zn substitutions SPA-LEED patterns reveal the same periodicity. We attribute this phase to the metastable bonding of atoms or clusters predominantly in hollow sites surrounding Zn substitutions in the surface layer. At ≈0.4 ML, STM images reveal local (√3 × √3)R30° and (2 × 1) ordering on surfaces annealed to 350 K. At coverages near 0.5 ML, both STM and SPA-LEED show the onset of the formation of the (2 × 1) ordering associated with the Zn : Pd 1 : 1 alloy phase. At all coverages, the surface is dominated by island growth the islands' size and density is shown to depend critically on annealing at temperatures as low as 350 K. These results provide insight into the structural features of a Zn/Pd(111) coverage regime that has been much debated in recent years.
Publisher: American Chemical Society (ACS)
Date: 24-11-2009
DOI: 10.1021/NN901504M
Abstract: The scanning tunneling microscope (STM) has evolved continually since its invention, as scientists have expanded its use to encompass atomic-scale manipulation, momentum-resolved electronic characterization, localized chemical reactions (bond breaking and bond making) in adsorbed molecules, and even chain reactions at surfaces. This burgeoning field has recently expanded to include the use of the STM to inject hot electrons into substrate surface states the injected electrons can travel laterally and induce changes in chemical structure in molecules located up to 100 nm from the STM tip. We describe several key demonstrations of this phenomenon, including one appearing in this issue of ACS Nano by Chen et al. Possible applications for this technique are also discussed, including characterizing the dispersion of molecule-substrate interface states and the controlled patterning of molecular overlayers.
Publisher: Springer Science and Business Media LLC
Date: 07-08-2009
DOI: 10.1007/S11103-009-9527-5
Abstract: Activation of E2F transcription factors at the G1-to-S phase boundary, with the resultant expression of genes needed for DNA synthesis and S-phase, is due to phosphorylation of the retinoblastoma-related (RBR) protein by cyclin D-dependent kinase (CYCD-CDK), particularly CYCD3-CDKA. Arabidopsis has three canonical E2F genes, of which E2Fa and E2Fb are proposed to encode transcriptional activators and E2Fc a repressor. Previous studies have identified genes regulated in response to high-level constitutive expression of E2Fa and of CYCD3 , but such plants display significant phenotypic abnormalities. We have sought to identify targets that show responses to lower level induced changes in abundance of these cell cycle regulators. Expression of E2Fa, E2Fc or CYCD3 was induced using dexamethasone and the effects analysed using microarrays in a time course allowing short and longer term effects to be observed. Overlap between CYCD3 and E2Fa modulated genes substantiates their action in a common pathway with a key role in controlling the G1/S transition, with additional targets for CYCD3 in chromatin modification and for E2Fa in cell wall biogenesis and development. E2Fc induction led primarily to gene downregulation, but did not antagonise E2Fa action and hence E2Fc appears to function outside the CYCD3-RBR pathway, does not have a direct effect on cell cycle genes, and promoter analysis suggests a distinct binding site preference.
Publisher: American Chemical Society (ACS)
Date: 03-06-2021
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9NR00672A
Abstract: Poly( para -phenylene) obtained by a three-step Ullmann coupling: two distinct 1D and 2D organometallic phases are reported.
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C8SC05267K
Abstract: Temperature mapping of the different molecular phases of tribromoterthienobenzene on (111) coinage metals.
Publisher: Proceedings of the National Academy of Sciences
Date: 02-06-2010
Abstract: One of the great challenges in surface chemistry is to assemble aromatic building blocks into ordered structures that are mechanically robust and electronically interlinked—i.e., are held together by covalent bonds. We demonstrate the surface-confined growth of ordered arrays of poly(3,4-ethylenedioxythiophene) (PEDOT) chains, by using the substrate (the 110 facet of copper) simultaneously as template and catalyst for polymerization. Copper acts as promoter for the Ullmann coupling reaction, whereas the inherent anisotropy of the fcc 110 facet confines growth to a single dimension. High resolution scanning tunneling microscopy performed under ultrahigh vacuum conditions allows us to simultaneously image PEDOT oligomers and the copper lattice with atomic resolution. Density functional theory calculations confirm an unexpected adsorption geometry of the PEDOT oligomers, which stand on the sulfur atom of the thiophene ring rather than lying flat. This polymerization approach can be extended to many other halogen-terminated molecules to produce epitaxially aligned conjugated polymers. Such systems might be of central importance to develop future electronic and optoelectronic devices with high quality active materials, besides representing model systems for basic science investigations.
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C3NR05710K
Abstract: We present an STM and XPS study on the synthesis of organometallic and covalent polymeric networks and elucidate the role of the substrate on their thermal stability.
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C3CP54782E
Abstract: We have performed a high-resolution synchrotron radiation photoelectron spectroscopy study of the initial growth stages of the ZnPd near-surface alloy on Pd(111), complemented by scanning tunnelling microscopy data. We show that the chemical environment for surfaces containing less than half of one monolayer of Zn is chemically distinct from subsequent layers. Surfaces where the deposition is performed at room temperature contain ZnPd islands surrounded by a substrate with dilute Zn substitutions. Annealing these surfaces drives the Zn towards the substrate top-layer, and favours the completion of the first 1 : 1 monolayer before the onset of growth in the next layer.
Publisher: American Physical Society (APS)
Date: 21-03-2008
Publisher: IOP Publishing
Date: 15-01-2005
Publisher: American Chemical Society (ACS)
Date: 05-02-2020
Publisher: American Chemical Society (ACS)
Date: 22-07-2020
Publisher: American Chemical Society (ACS)
Date: 09-09-2013
DOI: 10.1021/NN4035684
Abstract: We provide insight into surface-catalyzed dehalogenative polymerization, analyzing the organometallic intermediate and its evolution into planar polymeric structures. A combined study using scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED), near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and first-principles calculations unveils the structural conformation of substrate-bound phenylene intermediates generated from 1,4-dibromobenzene precursors on Cu(110), showing the stabilizing role of the halogen. The appearance of covalently bonded conjugated structures is followed in real time by fast-XPS measurements (with an acquisition time of 2 s per spectrum and heating rate of 2 K/s), showing that the detaching of phenylene units from the copper substrate and subsequent polymerization occur upon annealing above 460 ± 10 K.
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C4CC03719G
Abstract: The tip of a scanning tunneling microscope (STM) can be used to dehydrogenate freely-diffusing tetrathienoanthracene (TTA) molecules on Cu(111), trapping the molecules into metal-coordinated oligomeric structures.
Publisher: American Chemical Society (ACS)
Date: 14-09-2015
Publisher: American Chemical Society (ACS)
Date: 03-02-2015
DOI: 10.1021/LA5048886
Abstract: The behavior of small molecules on a surface depends critically on both molecule-substrate and intermolecular interactions. We present here a detailed comparative investigation of 1,3,5-benzene tricarboxylic acid (trimesic acid, TMA) on two different surfaces: highly oriented pyrolytic graphite (HOPG) and single-layer graphene (SLG) grown on a polycrystalline Cu foil. On the basis of high-resolution scanning tunnelling microscopy (STM) images, we show that the epitaxy matrix for the hexagonal TMA chicken wire phase is identical on these two surfaces, and, using density functional theory (DFT) with a non-local van der Waals correlation contribution, we identify the most energetically favorable adsorption geometries. Simulated STM images based on these calculations suggest that the TMA lattice can stably adsorb on sites other than those identified to maximize binding interactions with the substrate. This is consistent with our net energy calculations that suggest that intermolecular interactions (TMA-TMA dimer bonding) are dominant over TMA-substrate interactions in stabilizing the system. STM images demonstrate the robustness of the TMA films on SLG, where the molecular network extends across the variable topography of the SLG substrates and remains intact after rinsing and drying the films. These results help to elucidate molecular behavior on SLG and suggest significant similarities between adsorption on HOPG and SLG.
Publisher: Wiley
Date: 29-10-2021
Abstract: Melt electrowriting (MEW) has been widely used to process polycaprolactone (PCL) into highly ordered microfiber scaffolds with controllable architecture and geometry. However, the integrity of PCL during specific processes involved in routine MEW scaffold development has not yet been thoroughly investigated. This study investigates the impact of MEW processing on PCL following exposure to high temperatures required for melt extrusion as well as atmospheric plasma, a widely used surface treatment for improving MEW scaffold hydrophilicity. The change in polymer molecular weight and melt temperature is characterized, in comparing unprocessed and processed s les, in addition to analysis of the mechanical and surface properties of the scaffolds. No significant difference in the molecular weight or mechanical properties of the PCL scaffolds is evident following 5 days of cyclic heating to 90 °C. Exposure to plasma for up to 5 min significantly increased hydrophilicity and surface adhesion force, characterized via contact angle and atomic force microscope, however, significant polymer degradation occurred evidenced by increased brittleness of the scaffolds. This study demonstrates the degradation of PCL following fabrication via MEW and surface treatment to guide the optimization of scaffold development for subsequent applications in tissue engineering and biofabrication.
Publisher: American Chemical Society (ACS)
Date: 26-09-2012
DOI: 10.1021/LA303010P
Abstract: Upon adsorption on the (111) facet of Ag, 4-[trans-2-(pyrid-4-yl-vinyl)] benzoic acid (PVBA) self-assembles into a highly ordered, chiral twin chain structure at submonolayer coverages with domains that can extend for micrometers in one dimension. Using polarization-dependent measurements of C and N K-shell excitations in near-edge X-ray absorption fine structure (NEXAFS) spectra, we determine the binding geometry of single PVBA molecules within this unique ensemble for both low and high coverage regimes. At submonolayer coverage, the molecule is twisted to facilitate the formation of hydrogen bonds. The gas-phase planarity is gradually recovered as the coverage is increased, with complete planarity coinciding with loss of order in the overlayer. Thermal treatment of the PVBA film results in deprotonation of the carboxyl tail of the molecule, but despite the suppression of the stabilizing hydrogen-bonds, the overlayer remains ordered.
Publisher: IOP Publishing
Date: 08-2011
Abstract: We review recent new avenues for controlling two-dimensional (2D) self-assembly stabilized by non-covalent interactions. The use of host–guest architectures has opened new pathways for supramolecular self-assembly in two dimensions by immobilizing molecules of interest in 2D nano-porous networks. We also describe how a judicious choice of guest molecule can induce effective changes in host templates. These transformations could enable full control of 2D self-assembly with nanoscale precision, by tuning parameters such as stoichiometry, geometry and non-covalent interactions. This approach is of paramount importance for understanding changes of dimensionality and subsequently the formation of 2D and 3D supramolecular networks and ordered films that can be used as active materials for applications (e.g., electronic devices).
Publisher: Wiley
Date: 13-10-2021
Abstract: Layered molybdenum disulphide (MoS 2 ) crystals in combination with graphene create the opportunity for the development of heterostructures with tailored surface and structural properties for energy storage applications. Herein, 2D heterostructures are developed by growing MoS 2 on epitaxial and self‐standing nanoporous graphene (NPG) using chemical vapor deposition (CVD). The effect of substrate as well as different CVD growth parameters such as temperature, amount of sulfur and MoO 3 precursors, and argon flow on the growth of MoS 2 is systematically investigated. Interestingly, various structures of MoS 2 such as monolayer triangular islands, spirals, standing sheets, and irregular stacked multilayered MoS 2 are successfully developed. The growth mechanism is proposed using different advanced characterization techniques. The formation of a continuous wetting layer with grain boundaries over the surface prior to formation of any other structures is detected. As a proof of principle, MoS 2 /NPG is employed for the first time as anode material in potassium ion battery. The electrode delivers a specific capacity of 389 mAh g −1 with over 98% stability after 200 cycles. The porous structures clearly facilitate the ion transport which is beneficial for the ion battery. These encouraging results open new opportunities to develop hierarchical heterostructures of 2D‐materials for next‐generation energy storage technologies.
Publisher: American Chemical Society (ACS)
Date: 22-05-2019
DOI: 10.1021/ACS.LANGMUIR.8B04233
Abstract: The surface-assisted reaction of rationally designed organic precursors is an emerging approach toward fabricating atomically precise nanostructures. Recently, on-surface decarboxylation has attracted attention due to its volatile by-products, which tend to leave the surface during the reaction means only the desired products are retained on the surface. However, in addition to acting as the reactive site, the carboxylic acid groups play a vital role in the adsorption configuration of small-molecule molecular precursors and therefore in the reaction pathways. Here, scanning tunnelling microscopy (STM), synchrotron radiation photoelectron spectroscopy (SRPES), and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy have been employed to characterize the monodeprotonated, fully deprotonated, and decarboxylated products of isophthalic acid (IPA) on Cu(111). IPA is partially reacted (monodeprotonated) upon adsorption on Cu(111) at room temperature. Angular-dependent X-ray photoelectron spectroscopy reveals that IPA initially anchors to the surface via the carboxylate group. After annealing, the molecule fully deprotonates and reorients so that it anchors to the surface via both carboxylate groups in a bipodal configuration. NEXAFS confirms that the molecule is tilted upon adsorption and after full deprotonation. Following decarboxylation, the flat-lying molecule forms into oligomeric motifs on the surface. This work demonstrates the importance of molecular adsorption geometry for on-surface reactions.
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7CP01058C
Abstract: Hydrogen bonding controls the intermolecular distances in supramolecular networks – a platform to design molecular patterns at surfaces/interfaces.
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C4NR07057G
Abstract: We investigate, by using scanning tunnelling microscopy, the adsorption of pentacene on Ni(111) at room temperature, and the on-surface conversion of these monolayer films to graphene at temperatures as low as 220 °C.
Publisher: American Chemical Society (ACS)
Date: 14-06-2008
DOI: 10.1021/JP802762Q
Publisher: American Chemical Society (ACS)
Date: 25-03-2014
DOI: 10.1021/NN500322R
Publisher: American Chemical Society (ACS)
Date: 24-01-2013
DOI: 10.1021/NN305572S
Abstract: The imaging and characterization of single-molecule reaction events is essential to both extending our basic understanding of chemistry and applying this understanding to challenges at the frontiers of technology, for ex le, in nanoelectronics. Specifically, understanding the behavior of in idual molecules can elucidate processes critical to the controlled synthesis of materials for applications in multiple nanoscale technologies. Here, we report the synthesis of an important semiconducting organic molecule through an unprecedented reaction observed with submolecular resolution by scanning tunneling microscopy (STM) under ultrahigh vacuum (UHV) conditions. Our images reveal a sulfur abstraction and cyclization reaction that converts tetrathienoanthracene precursors into pentacene on the Ni(111) surface. The identity of the final reaction product was confirmed by time-of-flight secondary ion mass spectrometry (TOF-SIMS). This reaction has no known literature analogue, and highlights the power of local-probe techniques for exploring new chemical pathways.
Publisher: IOP Publishing
Date: 30-01-2005
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7FD00099E
Abstract: Ullmann coupling is the most common approach to form surface-confined one- and two-dimensional conjugated structures from haloaryl derivatives. The dimensions of the formed nanostructures can be controlled by the number and location of halogens within the molecular precursors. Our study illustrates that the type of halogen plays an essential role in the design, orientation, and extent of the surface-confined organometallic and polymeric nanostructures. We performed a comparative analysis of five 1,4-dihalobenzene molecules containing chlorine, bromine, and iodine on Cu(110) using scanning tunneling microscopy, fast-X-ray photoelectron and near edge X-ray absorption fine structure spectroscopies. Our experimental data identify different molecular structures, reaction temperatures and kinetics depending on the halogen type. Climbing image nudged elastic band simulations further clarify these observations by providing distinct diffusion paths for each halogen species. We show that in addition to the structure of the building blocks, the halogen type has a direct influence on the morphology of surface-confined polymeric structures based on Ullmann coupling.
Publisher: Elsevier BV
Date: 02-1998
DOI: 10.1016/S0031-9422(97)00577-3
Abstract: The identity of a new gibberellin (GA) in spinach and oil palm sap has been confirmed as 2 beta-hydroxy-GA12 (GA110) by comparisons of GC-mass spectral data obtained for the trimethylsilyl ether methyl ester derivatives with those of a synthetic s le prepared by means of a 24 step sequence from gibberellic acid 2 beta-hydroxy-GA24 was also prepared. Experimental details for the latter part of the syntheses are described.
Publisher: American Chemical Society (ACS)
Date: 31-07-2018
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C4NR02512A
Abstract: We describe a new method for the growth of reduced graphene oxide rGO on the 316L alloy of stainless steel 316L. Cell viability studies reveal that these rGO coatings do not have toxic effects on mammalian cells.
Publisher: Springer Science and Business Media LLC
Date: 04-01-2016
DOI: 10.1038/NCOMMS10235
Abstract: On-surface covalent self-assembly of organic molecules is a very promising bottom–up approach for producing atomically controlled nanostructures. Due to their highly tuneable properties, these structures may be used as building blocks in electronic carbon-based molecular devices. Following this idea, here we report on the electronic structure of an ordered array of poly(para-phenylene) nanowires produced by surface-catalysed dehalogenative reaction. By scanning tunnelling spectroscopy we follow the quantization of unoccupied molecular states as a function of oligomer length, with Fermi level crossing observed for long chains. Angle-resolved photoelectron spectroscopy reveals a quasi-1D valence band as well as a direct gap of 1.15 eV, as the conduction band is partially filled through adsorption on the surface. Tight-binding modelling and ab initio density functional theory calculations lead to a full description of the band structure, including the gap size and charge transfer mechanisms, highlighting a strong substrate–molecule interaction that drives the system into a metallic behaviour.
Publisher: American Chemical Society (ACS)
Date: 27-10-2014
DOI: 10.1021/JP507729W
Publisher: American Chemical Society (ACS)
Date: 20-09-2019
Publisher: American Chemical Society (ACS)
Date: 02-04-2021
Publisher: IOP Publishing
Date: 25-09-2008
DOI: 10.1088/0957-4484/19/42/424021
Abstract: We performed an ultra-high vacuum scanning tunneling microscopy (STM) investigation of the self-assembly of rubrene at room temperature on Cu(111), a metal surface with threefold symmetry. Rubrene self-assembles into two different structures called row and trimer. Both are different than the structures already observed on Cu(110) and Cu(100). Row and trimer structures have comparable molecular packing densities and are equally distributed across the surface. In the row structure the molecules are oriented with their backbone along the same high symmetry directions of the surface: [[Formula: see text]], [[Formula: see text]] or [[Formula: see text]]. The trimer structure is composed of units of three rubrene molecules, oriented along the high symmetry surface directions. These units are chiral, as revealed by height profile measurements by STM, and self-assemble in domains containing only one type of enantiomer.
Publisher: AIP Publishing
Date: 22-08-2002
DOI: 10.1063/1.1499536
Abstract: We demonstrate that a Geiger–Müller-type bandpass photon detector, suitable for inverse photoemission experiments, can be constructed from a MgF2 entrance window that has a high-energy transmission threshold of 10.97 eV, and ethanol, a detection gas with an ionization potential of 10.48 eV. The photon detector has a mean detection energy of ℏωd=(10.89±0.07) eV and a bandpass of Δℏωd=(0.37±0.05) eV. A photon detector can also be constructed from n-propanol/MgF2 with a mean detection energy of ℏωd=(10.76±0.07) eV and a bandpass Δℏωd=(0.41±0.05) eV. These two new detection gas/window combinations have a higher detection energy and a narrower bandpass than the dimethylether/MgF2 detector [Δℏωd=(0.71±0.04) eV and ℏωd=10.60 eV]. Since all three detectors utilize a MgF2 entrance window, the photon bandpass can be changed straightforwardly by changing the detection gas. For systems that can be easily damaged by electron beams, having the freedom to open up the detector bandpass is an advantage because it can reduce the total electron exposure time.
Publisher: Wiley
Date: 11-06-2013
Abstract: The supramolecular self-assembly of brominated molecules was investigated and compared on Cu(110) and Cu(110)-O(2×1) surfaces under ultrahigh vacuum. By using scanning tunnelling microscopy, we show that brominated molecules form a disordered structure on Cu(110), whereas a well-ordered supramolecular network is observed on the Cu(110)-O(2×1) surface. The different adsorption behaviors of these two surfaces are described in terms of weakened molecule-substrate interactions on Cu(110)-O(2×1) as opposed to bare Cu(110). The effect of oxygen-passivation is to suppress debromination and it can be a convenient approach for investigating other self-assembly processes on copper-based substrates.
Publisher: Inderscience Publishers
Date: 2008
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8CC04380A
Abstract: Surface-catalyzed reactions provide a versatile route to synthesizing new 2D materials. Here, we show that the statistical nature of an activated reaction can lead to a ersity of intermolecular bonding motifs through partially-reacted molecules. With increasing annealing, we observe different periodic, well-defined phases of 1,3,5-benzenetricarboxylic acid on Ag(111), where the surface structure in each case is defined by the degree of deprotonation of the carboxylic groups. Over a wide range of deprotonation levels (∼50% to near 100%), we observe a granular alloy comprising two distinct phases in a continuous network. This ordered phase lacks well-defined translational symmetry, is stabilized through both intermolecular interactions and epitaxy, and demonstrates a design approach to creating non-crystalline phases by capitalizing on the chemical ersity of partially reacted molecules on a surface.
Publisher: AIP Publishing
Date: 09-03-2009
DOI: 10.1063/1.3093674
Abstract: Ge islands with areas up to hundreds of μm2 were grown on Si(111). These islands, grown above 750 °C and at a deposition rate of 1 monolayer/min, become decreasingly compact with increasing size and can have nonuniform cross sections with heights reaching over 500 nm. The largest islands are ramified, often comprising multiple discrete parts. X-ray photoemission electron microscopy absorption maps show that the islands have a higher concentration of Ge at their centers, with more Si near the edges. We propose that the shape transformation is driven by strain relief at the island perimeters.
Publisher: American Physical Society (APS)
Date: 19-06-2006
Publisher: American Chemical Society (ACS)
Date: 10-07-2019
Abstract: Ullmann coupling is one of the most frequently employed methodologies for producing π-conjugated surface-confined polymers. One unfortunate side product of the reaction is the creation of metal halide islands formed from liberated halogen atoms. Following the coupling reaction, these halide islands can account for a large proportion of the substrate surface area and thus inhibit domain growth and effectively poison the catalyst. Here, we describe an efficient and reliable methodology for removing the halogen byproduct at room temperature by exposure to a beam of atomic hydrogen this action removes the halogen atoms in a matter of minutes, with minimal impact to the polymer structure. We also find that it is possible under certain circumstances to preserve the pre-exposure epitaxy after removal of the halogen. This finding provides a convenient and straightforward technique for addressing the most often-cited drawback of the on-surface Ullman coupling methodology and provides access to a previously inaccessible parameter space for these types of experiments.
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8CC01465E
Abstract: On-surface synthesis of conjugated polymers is made challenging by the need to promote the desired reaction while preventing or minimizing unwanted ancillary reactions that compromise the product integrity.
Publisher: American Chemical Society (ACS)
Date: 07-06-2022
Publisher: AIP Publishing
Date: 24-02-2015
DOI: 10.1063/1.4908143
Abstract: Model systems are critical to our understanding of self-assembly processes. As such, we have studied the surface self-assembly of a small and simple molecule, indole-2-carboxylic acid (I2CA). We combine density functional theory gas-phase (DFT) calculations with scanning tunneling microscopy to reveal details of I2CA assembly in two different solvents at the solution/solid interface, and on Au(111) in ultrahigh vacuum (UHV). In UHV and at the trichlorobenzene/highly oriented pyrolytic graphite (HOPG) interface, I2CA forms epitaxial lamellar structures based on cyclic OH⋯O carboxylic dimers. The structure formed at the heptanoic acid/HOPG interface is different and can be interpreted in a model where heptanoic acid molecules co-adsorb on the substrate with the I2CA, forming a bicomponent commensurate unit cell. DFT calculations of dimer energetics elucidate the basic building blocks of these structures, whereas calculations of periodic two-dimensional assemblies reveal the epitaxial effects introduced by the different substrates.
Publisher: AIP Publishing
Date: 29-01-2004
DOI: 10.1063/1.1637435
Abstract: A high-brightness, low energy electron source and dual Geiger–Müller-type isochromat photon detectors are combined to create a versatile new inverse photoemission system. The bandpass of the photon detector can be set to one of the following discrete values: 0.37±0.02, 0.43±0.02, 0.56±0.02, or 0.73±0.04 eV by using ethanol, 1-propanol, 1-butanol, or a dimethyl ether/ethanol mixture, respectively, as the detection gas(es). All of the alcohols are self-quenching and do not require the addition of a quench gas. The design of the photon detectors, the electron gun, and the circuits that perform the dead time gating are described in detail. The capabilities of the new system are illustrated using spectra from both metal (Cu) and semiconductor (Si) surfaces.
Publisher: IOP Publishing
Date: 06-03-2023
Abstract: The surface science-based approach to synthesising new organic materials on surfaces has gained considerable attention in recent years, owing to its success in facilitating the formation of novel 0D, 1D and 2D architectures. The primary mechanism used to date has been the catalytic transformation of small organic molecules through substrate-enabled reactions. In this Topical Review, we provide an overview of alternate approaches to controlling molecular reactions on surfaces. These approaches include light, electron and ion-initiated reactions, electrospray ionisation deposition-based techniques, collisions of neutral atoms and molecules, and superhydrogenation. We focus on the opportunities afforded by these alternative approaches, in particular where they may offer advantages in terms of selectivity, spatial control or scalability.
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9NR08901B
Abstract: The rapid development of smart wearable electronics is driving the engineering of novel miniaturized sensing materials that can rapidly respond to very small changes in the concentration of biomarkers at room temperature. Carbon-based nanomaterials offer numerous attractive properties such as low resistivity, good mechanical robustness and integration potential, but lack a strong detection and transduction mechanism for the measurement of chemical molecules or photons. Here, we present a three-dimensional nanostructured architecture comprising optimally integrated graphene oxide (GO)-ZnO heterojunctions for the room temperature sensing of volatile biomarkers. We show that this layout also provides excellent response to UV light showcasing its applicability as a visible-blind photodetector. Notably, the optimal integration of well-dispersed GO nanodomains in a 3D ZnO network significantly enhances the room-temperature chemical sensitivity and light responsivity, while higher GO contents drastically worsen the material performance. This is attributed to the different roles of GO at low and high contents. Small amounts of GO lead to the formation of electron depleted nano-heterojunctions with excellent electron-hole separation efficiency. In contrast, large amounts of GO form a percolating electrical network that inhibits the light and chemical-sensing properties of the ZnO nanoparticles. Our optimal GO-ZnO demonstrates 33 A W
Publisher: American Chemical Society (ACS)
Date: 09-09-2015
Publisher: Wiley
Date: 06-03-2009
Abstract: The surface-mediated synthesis of epitaxially aligned and separated polyphenylene lines on Cu(110) by exploiting the Ullmann dehalogenation reaction is reported. Scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) show that the C-I bonds of 1,4-diiodobenzene and 1,3-diiodobenzene (C(6)H(4)I(2)) are catalytically cleaved when dosed onto the surface. Subsequent annealing transforms the copper-bound phenylene intermediates into covalent conjugated structures: linear chains of poly(p-phenylene) for 1,4-diiodobenzene and zigzag chains of poly(m-phenylene) as well as macrocyclic oligomers in the case of 1,3-diiodobenzene. The chains are strongly bound to the surface (likely through C--Cu bonds at the chain-ends) while the macrocycles are very mobile and can only be imaged by STM at low temperature. The detached halogens adsorb on the surface and separate the polymer chains from each other.
Location: Canada
Start Date: 05-2016
End Date: 06-2020
Amount: $430,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 03-2019
End Date: 03-2020
Amount: $844,947.00
Funder: Australian Research Council
View Funded Activity