Shear stress mediated scrolling of graphene oxide

© 2018 Elsevier. This manuscript version is made available under the CC-BY-NC-ND 4.0 license: http://creativecommons.org/licenses/by-nc-nd/4.0/ This author accepted manuscript is made available following 24 month embargo from date of publication (May 2018) in accordance with the publisher’s archiving policyGraphene oxide scrolls (GOS) are fabricated in high yield from a colloidal suspension of graphene oxide (GO) sheets under shear stress in a vortex fluidic device (VFD) while irradiated with a pulsed laser operating at 1064 nm and 250 mJ. This is in the absence of any other reagents with the structure of the GOS established using powder X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, X-ray photoelectron spectroscopy, Raman spectroscopy, transmission electron microscopy, atomic force microscopy and scanning electron microscopy

Sub-micron moulding topological mass transport regimes in angled vortex fluidic flow

Shear stress in dynamic thin films, as in vortex fluidics, can be harnessed for generating non-equilibrium conditions, but the nature of the fluid flow is not understood. A rapidly rotating inclined tube in the vortex fluidic device (VFD) imparts shear stress (mechanical energy) into a thin film of liquid, depending on the physical characteristics of the liquid and rotational speed,ω, tilt angle,θ, and diameter of the tube. Through understanding that the fluid exhibits resonance behaviours from the confining boundaries of the glass surface and the meniscus that determines the liquid film thickness, we have established specific topological mass transport regimes. These topologies have been established through materials processing, as spinning top flow normal to the surface of the tube, double-helical flow across the thin film, and spicular flow, a transitional region where both effects contribute. The manifestation of mass transport patterns within the film have been observed by monitoring the mixing time, temperature profile, and film thickness against increasing rotational speed,ω. In addition, these flow patterns have unique signatures that enable the morphology of nanomaterials processed in the VFD to be predicted, for example in reversible scrolling and crumbling graphene oxide sheets. Shear-stress induced recrystallisation, crystallisation and polymerisation, at different rotational speeds, provide moulds of high-shear topologies, as ‘positive’ and ‘negative’ spicular flow behaviour. ‘Molecular drilling’ of holes in a thin film of polysulfone demonstrate spatial arrangement of double-helices. The grand sum of the different behavioural regimes is a general fluid flow model that accounts for all processing in the VFD at an optimal tilt angle of 45°, and provides a new concept in the fabrication of novel nanomaterials and controlling the organisation of matter

Highly Uniform Nanodiamond-Graphene Composites Microspheres for Electrocatalytic Hydrogen Evolution

To progress the clean hydrogen-gas-based energy economy, there is a demand for cost-effective, highly efficient catalysts to facilitate the hydrogen evolution reaction process (HER). Due to the amazing catalytic capabilities of two-dimensional materials, extensive research has been done on these structures. However, most of the described syntheses take a lot of time, are challenging, and are ineffective. The present work demonstrates the performance of the recently reported nanodiamond/graphene composite microsphere ND-GCSs as a catalyst for HER. These spheres were produced via the microwave-irradiation approach. A modified process was adopted to improve the particle size uniformity and yield. The prepared composite spheres showed very interesting catalytic activity for the HER when assembled on a screen-printed carbon electrode. The prepared ND-GCSs@SPCE showed a significant shift of the onset potential to ca. −450 mV and a small Tafel slope value of ca. 85 mV/decade. The electron transfer was drastically enhanced with a tremendous decrease in charge transfer resistance to ca. 265 Ω. The electrocatalyst showed excellent long-term stability for the HER application. Additionally, this novel composite structure might be beneficial for diverse applications including batteries, supercapacitors, catalyst supports, and more

Sub-Micron Moulding Topological Mass Transport Regimes in Angled Vortex Fluidic Flow

Induced mechanical energy in a thin film of liquid in an inclined rapidly rotating tube in the vortex fluidic device (VFD) can be harnessed for generating non-equilibrium conditions, which are optimal at 45o tilt angle, but the nature of the fluid flow is not understood. Through understanding that the fluid exhibits resonance behaviours from the confining boundaries of the glass surface and the meniscus that determines the liquid film thickness, we have established specific topological mass transport regimes. These topologies have been established through materials processing, as circular flow normal to the surface of the tube, double-helical flow across the thin film, and spicular flow, a transitional region where both effects contribute. This includes new phenomenological shear stressed crystallization and molecular drilling. The manifestation of these patterns has been observed by monitoring mixing times, temperature profiles, and film thickness against rotational speed of liquids in the tube. The grand sum of the different behavioural regimes is a general fluid flow model that accounts for all processing in the VFD at an optimal tilt angle of 45o, and provides a new concept in the fabrication of novel nanomaterials and controlling the organisation of matter.</b