ORCID Profile
0000-0002-2264-1760
Current Organisation
Queensland University of Technology
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Publisher: MDPI AG
Date: 04-07-2017
DOI: 10.3390/NANO7070170
Publisher: AIP Publishing
Date: 09-2010
DOI: 10.1063/1.3475728
Abstract: The possibility to discriminate between the relative importance of the fluxes of energy and matter in plasma-surface interaction is demonstrated by the energy flux measurements in low-temperature plasmas ignited by the radio frequency discharge (power and pressure ranges 50–250 W and 8–11.5 Pa) in Ar, Ar+H2, and Ar+H2+CH4 gas mixtures typically used in nanoscale synthesis and processing of silicon- and carbon-based nanostructures. It is shown that by varying the gas composition and pressure, the discharge power, and the surface bias one can effectively control the surface temperature and the matter supply rates. The experimental findings are explained in terms of the plasma-specific reactions in the plasma bulk and on the surface.
Publisher: Hindawi Limited
Date: 2015
DOI: 10.1155/2015/230987
Abstract: Vertical graphene nanosheets have advantages over their horizontal counterparts, primarily due to the larger surface area available in the vertical systems. Vertical sheets can accommodate more functional particles, and, due to the conduction and optical properties of thin graphene, these structures can find niche applications in the development of sensing and energy storage devices. This work is a combined experimental and theoretical study that reports on the synthesis and optical responses of vertical sheets decorated with gold nanoparticles. The findings help in interpreting optical responses of these hybrid graphene structures and are relevant to the development of future sensing platforms.
Publisher: American Society for Cell Biology (ASCB)
Date: 05-2014
Abstract: Atmospheric gas plasmas (AGPs) are able to selectively induce apoptosis in cancer cells, offering a promising alternative to conventional therapies that have unwanted side effects such as drug resistance and toxicity. However, the mechanism of AGP-induced cancer cell death is unknown. In this study, AGP is shown to up-regulate intracellular reactive oxygen species (ROS) levels and induce apoptosis in melanoma but not normal melanocyte cells. By screening genes involved in apoptosis, we identify tumor necrosis factor (TNF)–family members as the most differentially expressed cellular genes upon AGP treatment of melanoma cells. TNF receptor 1 (TNFR1) antagonist–neutralizing antibody specifically inhibits AGP-induced apoptosis signal, regulating apoptosis signal–regulating kinase 1 (ASK1) activity and subsequent ASK1-dependent apoptosis. Treatment of cells with intracellular ROS scavenger N-acetyl-l-cysteine also inhibits AGP-induced activation of ASK1, as well as apoptosis. Moreover, depletion of intracellular ASK1 reduces the level of AGP-induced oxidative stress and apoptosis. The evidence for TNF-signaling dependence of ASK1-mediated apoptosis suggests possible mechanisms for AGP activation and regulation of apoptosis-signaling pathways in tumor cells.
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C1NR10860C
Abstract: The possibility for the switch-over of the growth mode from a continuous network to unidirectional arrays of well-separated, self-organized, vertically oriented graphene nanosheets has been demonstrated using a unique, yet simple plasma-based approach. The process enables highly reproducible, catalyst-free synthesis of arrays of graphene nanosheets with reactive open graphitic edges facing upwards. Effective control over the nanosheet length, number density, and the degree of alignment along the electric field direction is achieved by a simple variation of the substrate bias. These results are of interest for environment-friendly fabrication of next-generation nanodevices based on three-dimensional, ordered self-organized nanoarrays of active nanostructures with very large surface areas and aspect ratios, highly reactive edges, and controlled density on the substrate. Our simple and versatile plasma-based approach paves the way for direct integration of such nanoarrays directly into the Si-based nanodevice platform.
Publisher: AIP Publishing
Date: 30-01-2012
DOI: 10.1063/1.3681782
Abstract: The formation of clearly separated vertical graphene nanosheets on silicon nanograss support is demonstrated. The plasma-enabled, two-stage mask-free process produced self-organized vertical graphenes of a few carbon layers (as confirmed by advanced microanalysis), prominently oriented in the substrate center–substrate edge direction. It is shown that the width of the alignment zone depends on the substrate conductivity, and thus the electric field in the vicinity of the growth surface is responsible for the graphene alignment. This finding is confirmed by the Monte Carlo simulations of the ion flux distribution in the silicon nanograss pattern.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2012
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5NR06365E
Abstract: Atomically thin graphene holds exceptional promise to enable new functionalities and drastically improve performance of electronic, energy, sensing, and bio-medical devices. One of the most promising approaches to device-compatible graphene synthesis is chemical vapour deposition on a copper catalyst this technique however is limited by very high temperatures (∼900 °C) and a lack of control as well as post-growth separation from the catalyst. We demonstrate and explain how, through the use of a plasma, a graphene film containing single layer graphene can be grown at temperature as low as 220 °C, the process can be controlled and an instant and water-mediated decoupling mechanism is realised. Potential use of our films in flexible transparent conductive films, electrical devices and magneto-electronics is demonstrated. Considering the benefits of catalyst reuse, energy efficiency, simplicity, and environmental friendliness, we present this versatile plasma process as a viable alternative to many existing graphene production approaches.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 11-2011
Publisher: Wiley
Date: 26-10-2012
Abstract: Low-temperature plasmas in direct contact with arbitrary, written linear features on a Si wafer enable catalyst-free integration of carbon nanotubes into a Si-based nanodevice platform and in situ resolution of in idual nucleation events. The graded nanotube arrays show reliable, reproducible, and competitive performance in electron field emission and biosensing nanodevices.
Publisher: Elsevier BV
Date: 11-2011
Publisher: AIP Publishing
Date: 05-2010
DOI: 10.1063/1.3431098
Abstract: Current-voltage characteristics of the planar magnetron are studied experimentally and by numerical simulation. Based on the measured current-voltage characteristics, a model of the planar magnetron discharge is developed with the background gas pressure and magnetic field used as parameters. The discharge pressure was varied in a range of 0.7–1.7 Pa, the magnetic field of the magnetron was of 0.033–0.12 T near the cathode surface, the discharge current was from 1 to 25 A, and the magnetic field lines were tangential to the substrate surface in the region of the magnetron discharge ignition. The discharge model describes the motion of energetic secondary electrons that gain energy by passing the cathode sheath across the magnetic field, and the power required to sustain the plasma generation in the bulk. The plasma electrons, in turn, are accelerated in the electric field and ionize effectively the background gas species. The model is based on the assumption about the prevailing Bohm mechanism of electron conductivity across the magnetic field. A criterion of the self-sustained discharge ignition is used to establish the dependence of the discharge voltage on the discharge current. The dependence of the background gas density on the current is also observed from the experiment. The model is consistent with the experimental results.
Publisher: Wiley
Date: 11-02-2015
Publisher: Wiley
Date: 19-08-2014
Publisher: Elsevier BV
Date: 12-2015
Publisher: Elsevier BV
Date: 11-2014
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3NR00550J
Abstract: We report on the comparative study of magnetotransport properties of large-area vertical few-layer graphene networks with different morphologies, measured in a strong (up to 10 T) magnetic field over a wide temperature range. The petal-like and tree-like graphene networks grown by a plasma enhanced CVD process on a thin (500 nm) silicon oxide layer supported by a silicon wafer demonstrate a significant difference in the resistance-magnetic field dependencies at temperatures ranging from 2 to 200 K. This behaviour is explained in terms of the effect of electron scattering at ultra-long reactive edges and ultra-dense boundaries of the graphene nanowalls. Our results pave a way towards three-dimensional vertical graphene-based magnetoelectronic nanodevices with morphology-tuneable anisotropic magnetic properties.
Publisher: IOP Publishing
Date: 14-04-2011
DOI: 10.1088/0022-3727/44/17/174019
Abstract: The fast advances in nanotechnology have raised increasing concerns related to the safety of nanomaterials when exposed to humans, animals and the environment. However, despite several years of research, the nanomaterials safety field is still in its infancy owing to the complexities of structural and surface properties of these nanomaterials and organism-specific responses to them. Recently, plasma-based technology has been demonstrated as a versatile and effective way for nanofabrication, yet its health and environment-benign nature has not been widely recognized. Here we address the environmental and occupational health and safety effects of various zero- and one-dimensional nanomaterials and elaborate the advantages of using plasmas as a safe nanofabrication tool. These advantages include but are not limited to the production of substrate-bound nanomaterials, the isolation of humans from harmful nanomaterials, and the effective reforming of toxic and flammable gases. It is concluded that plasma nanofabrication can minimize the hazards in the workplace and represents a safe way for future nanofabrication technologies.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2014
Publisher: American Chemical Society (ACS)
Date: 24-05-2007
DOI: 10.1021/CM070767R
Publisher: Wiley
Date: 03-07-2013
Publisher: American Physical Society (APS)
Date: 05-02-2013
Publisher: AIP Publishing
Date: 15-03-2011
DOI: 10.1063/1.3553853
Abstract: Characteristics of electrical breakdown of a planar magnetron enhanced with an electromagnet and a hollow-cathode structure, are studied experimentally and numerically. At lower pressures the breakdown voltage shows a dependence on the applied magnetic field, and the voltage necessary to achieve the self-sustained discharge regime can be significantly reduced. At higher pressures, the dependence is less sensitive to the magnetic field magnitude and shows a tendency of increased breakdown voltage at the stronger magnetic fields. A model of the magnetron discharge breakdown is developed with the background gas pressure and the magnetic field used as parameters. The model describes the motion of electrons, which gain energy by passing the electric field across the magnetic field and undergo collisions with neutrals, thus generating new bulk electrons. The electrons are in turn accelerated in the electric field and effectively ionize a sufficient amount of neutrals to enable the discharge self-sustainment regime. The model is based on the assumption about the combined classical and near-wall mechanisms of electron conductivity across the magnetic field, and is consistent with the experimental results. The obtained results represent a significant advance toward energy-efficient multipurpose magnetron discharges.
Publisher: AIP Publishing
Date: 11-10-2010
DOI: 10.1063/1.3502562
Abstract: The formation of vertically aligned, clearly separated, copper-capped carbon nanocones with a length of up to 500 nm and base diameter of about 150 nm via three-stage process involving magnetron sputtering, N2 plasma treatment, and CH4+N2 plasma growth is studied. The width of gaps between the nanocones can be controlled by the gas composition. The nanocone formation mechanism is explained in terms of strong passivation of carbon in narrow gaps, where the access of plasma ions is hindered and the formation of large CnH2n+2 molecules is possible. This plasma-enabled approach can be used to fabricate nanoelectronic, nanofluidic, and optoelectronic components and devices.
Publisher: Wiley
Date: 22-05-2013
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2013
Publisher: American Chemical Society (ACS)
Date: 31-10-2012
DOI: 10.1021/AM301680A
Abstract: Controlled self-organized growth of vertically aligned carbon nanocone arrays in a radio frequency inductively coupled plasma-based process is studied. The experiments have demonstrated that the gaps between the nanocones, density of the nanocone array, and the shape of the nanocones can be effectively controlled by the process parameters such as gas composition (hydrogen content) and electrical bias applied to the substrate. Optical measurements have demonstrated lower reflectance of the nanocone array as compared with a bare Si wafer, thus evidencing their potential for the use in optical devices. The nanocone formation mechanism is explained in terms of redistribution of surface and volumetric fluxes of plasma-generated species in a developing nanocone array and passivation of carbon in narrow gaps where the access of plasma ions is hindered. Extensive numerical simulations were used to support the proposed growth mechanism.
Publisher: American Scientific Publishers
Date: 07-2009
DOI: 10.1166/JNN.2009.M82
Abstract: We report the growth of vertically oriented carbon micro-cones without using any foreign catalyst on silicon (100) substrate by microwave plasma assisted chemical vapour deposition method. The average height and bottom diameter of the carbon micro-cones are approximately 20 microm and approximately 1.4 microm, respectively. The diameters of the carbon micro-cones decrease gradually from bottom to tip, terminating in a nanotube structure. Mechanical damage of micro-cones resulted in the breaking and partial removal of the carbon micro-cones to show the structures possessed a nanotube core. Outside the micro-cone, the nanotubes showed a flattened ribbon structure. Electron microscopy and micro-Raman spectroscopy shows the nanotubes are multi walled and highly graphitic, with low structural disorder. The advanced vacuum electron emission devices could be fabricated with the carbon micro-cones grown directly on silicon substrate without using any catalyst.
Publisher: Informa UK Limited
Date: 10-2014
Publisher: Oxford University Press (OUP)
Date: 13-10-2014
DOI: 10.1093/CRJ/CLU019
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3CC46218H
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C1JM13835A
Publisher: Elsevier
Date: 2014
Publisher: Springer Science and Business Media LLC
Date: 03-11-2016
DOI: 10.1038/SREP36168
Abstract: Deterministic band gap in quasi-one-dimensional nanoribbons is prerequisite for their integrated functionalities in high performance molecular-electronics based devices. However, multiple band gaps commonly observed in graphene nanoribbons of the same width, fabricated in same slot of experiments, remain unresolved, and raise a critical concern over scalable production of pristine and/or hetero-structure nanoribbons with deterministic properties and functionalities for plethora of applications. Here, we show that a modification in the depth of potential wells in the periodic direction of a supercell on relative shifting of passivating atoms at the edges is the origin of multiple band gap values in nanoribbons of the same width in a crystallographic orientation, although they carry practically the same ground state energy. The results are similar when calculations are extended from planar graphene to buckled silicene nanoribbons. Thus, the findings facilitate tuning of the electronic properties of quasi-one-dimensional materials such as bio-molecular chains, organic and inorganic nanoribbons by performing edge engineering.
Publisher: Elsevier BV
Date: 2012
Publisher: Elsevier BV
Date: 09-2009
Publisher: Hindawi Limited
Date: 2012
DOI: 10.1155/2012/891318
Abstract: Nanoparticle contrast agents offer the potential to significantly improve existing methods of cancer diagnosis and treatment. Advantages include biocompatibility, selective accumulation in tumor cells, and reduced toxicity. Considerable research is underway into the use of nanoparticles as enhancement agents for radiation therapy and photodynamic therapy, where they may be used to deliver treatment agents, produce localized enhancements in radiation dose and selectively target tumor cells for localized damage. This paper reviews the current status of nanoparticles for cancer treatment and presents preliminary results of a pilot study investigating titanium dioxide nanoparticles for dual-mode enhancement of computed tomography (CT) imaging and kilovoltage radiation therapy. Although titanium dioxide produced noticeable image contrast enhancement in the CT scans, more sensitive detectors are needed to determine whether the nanoparticles can also produce localized dose enhancement for targeted radiation therapy.
Publisher: Springer Science and Business Media LLC
Date: 05-02-2013
DOI: 10.1038/SREP01221
Publisher: Elsevier BV
Date: 11-2014
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2014
Location: No location found
Location: Australia
Start Date: 2011
End Date: 2013
Funder: Commonwealth Scientific and Industrial Research Organisation
View Funded ActivityStart Date: 2016
End Date: 2019
Funder: Australian Research Council
View Funded Activity