Plasma break-down and re-build : same functional vertical graphenes from diverse natural precursors

Plasmas, the 4th state of matter, uniformly transform natural precursors with different chemical composition in solid, liquid, and gas states into the same functional vertical graphenes in a single-step process within a few minutes. Functional vertical graphenes show reliable biosensing properties, strong binding with proteins, and improved adhesion to substrates.

Vertical graphene gas- and bio-sensors via catalyst-free, reactive plasma reforming of natural honey

A rapid reforming of natural honey exposed to reactive low-temperature Ar + H2 plasmas produced high-quality, ultra-thin vertical graphenes, without any metal catalyst or external heating. This transformation is only possible in the plasma and fails in similar thermal processes. The process is energy-efficient, environmentally benign, and is much cheaper than common synthesis methods based on purified hydrocarbon precursors. The graphenes retain the essential minerals of natural honey, feature reactive open edges and reliable gas- and bio-sensing performance.

Tuning of magnetization in vertical graphenes by plasma-enabled chemical conversion of organic precursors with different oxygen content

Different magnetization in vertical graphenes fabricated by plasma-enabled chemical conversion of organic precursors with various oxygen atom contents and bonding energies was achieved. The graphenes grown from fat-like precursors exhibit magnetization up to 8 emu g−1, whereas the use of sugar-containing precursors results in much lower numbers. A relatively high Curie temperature exceeding 600 K was also demonstrated.

Structure-controlled, vertical graphene-based, binder-free electrodes from plasma-reformed butter enhance supercapacitor performance

Vertical graphene nanosheets (VGNS) hold great promise for high-performance supercapacitors owing to their excellent electrical transport property, large surface area and in particular, an inherent three-dimensional, open network structure. However, it remains challenging to materialise the VGNS-based supercapacitors due to their poor specific capacitance, high temperature processing, poor binding to electrode support materials, uncontrollable microstructure, and non-cost effective way of fabrication. Here we use a single-step, fast, scalable, and environmentally-benign plasma-enabled method to fabricate VGNS using cheap and spreadable natural fatty precursor butter, and demonstrate the controllability over the degree of graphitization and the density of VGNS edge planes. Our VGNS employed as binder-free supercapacitor electrodes exhibit high specific capacitance up to 230 F g−1 at a scan rate of 10 mV s−1 and >99% capacitance retention after 1,500 charge-discharge cycles at a high current density, when the optimum combination of graphitic structure and edge plane effects is utilised. The energy storage performance can be further enhanced by forming stable hybrid MnO2/VGNS nano-architectures which synergistically combine the advantages from both VGNS and MnO2. This deterministic and plasma-unique way of fabricating VGNS may open a new avenue for producing functional nanomaterials for advanced energy storage devices.

Deterministic control of structural and optical properties of plasma-grown vertical graphene nanosheet networks via nitrogen gas variation

The effect of nitrogen on the growth of vertically oriented graphene nanosheets on catalyst-free silicon and glass substrates in a plasma-assisted process is studied. Different concentrations of nitrogen were found to act as versatile control knobs that could be used to tailor the length, number density and structural properties of the nanosheets. Nanosheets with different structural characteristics exhibit markedly different optical properties. The nanosheet samples were treated with a bovine serum albumin protein solution to investigate the effects of this variation on the optical properties for biosensing through confocal micro-Raman spectroscopy and UV-Vis spectrophotometry. © 2012 Optical Society of America.

Self-organized Au nanoarrays on vertical graphenes : an advanced three-dimensional sensing platform

A three-dimensional surface enhanced Raman scattering (SERS)/plasmonic sensing platform based on plasma-enabled, catalyst-free, few-layer vertical graphenes decorated with self-organized Au nanoparticle arrays is demonstrated. This platform is viable for multiple species detection and overcomes several limitations of two-dimensional sensors.

Thinning vertical graphenes, tuning electrical response : from semiconducting to metallic

A simple, uniquely plasma-enabled and environment-friendly process to reduce the thickness of vertically standing graphenes to only 4–5 graphene layers and arranging them in dense, ultra-large surface area, ultra-open-edge-length, self-organized and interconnected networks is demonstrated. The approach for the ultimate thickness reduction to 1–2 graphene layers is also proposed. The vertical graphene networks are optically transparent and show tunable electric properties from semiconducting to semi-metallic and metallic at room and near-room temperature, thus recovering semi-metallic properties of a single-layer graphene.

Vertical graphene nanosheets coated with gold nanoparticle arrays: Effect of inter-particle spacing on optical response

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.

Asymmetric price range effects on vertical extensions

Vertical line extensions, both step-up and step-down, are common occurrence in consumer products. For example, Timex recently launched its luxury high-end Valentino line. On the other hand, many companies use downscale extensions to increase the overall sales volume. For instance, a number of luxury watch brands recently introduced watch collections with lower price points, like TAG Heur’s affordable watch the Aquaracer Calibre 5. Previous literature on vertical extensions has investigated how number of products in the line (Dacin and Smith 1994), the direction of the extension, brand concept (Kim, Lavack, and Smith 2001), and perceived risk (Lei, de Ruyter, and Wetzels 2008) affect extensions’ evaluation. Common to this literature is the use of models based on adaptation-level theory, which states that all relevant price information is integrated into a single prototype value and used in consumer judgments of price (Helson 1947; Mazumdar, Raj, and Sinha 2005). In the current research we argue that, while adaptation-level theory can be viewed as a useful simplification to understanding consumers’ evaluations, it misses out important contextual influences caused by a brand’s price range. Drawing on research on range-frequency theory (Mellers and Cooke 1994; Parducci 1965) we investigate the effects of price point distance and parent brand’s price range on evaluations of vertical extensions. Our reasoning leads to two important predictions that we test in a series of three experiments...

Diminishing effects of perceived fit on vertical extensions

A common finding in brand extension literature is that extension’s favorability is a function of the perceived fit between the parent brand and its extension (Aaker and Keller 1990; Park, Milberg, and Lawson 1991; Volckner and Sattler 2006) that is partially mediated by perceptions of risk (Milberg, Sinn, and Goodstein 2010; Smith and Andrews 1995). In other words, as fit between the parent brand and its extension increases, parent brand beliefs become more readily available, thus increasing consumer certainty and confidence about the new extension, which results in more positive evaluations. On the other hand, as perceived fit decreases, consumer certainty about the parent brand’s ability to introduce the extension is reduced, leading to more negative evaluations. Building on the notion that perceived fit of vertical line extensions is a function of the price/quality distance between parent brand and its extension (Lei, de Ruyter, and Wetzels 2008), traditional brand extension knowledge predicts a directionally consistent impact of perceived fit on evaluations of vertical extensions. Hence, vertical (upscale or downscale) extensions that are placed closer to the parent brand in the price/quality spectrum should lead to higher favorability ratings compared to more distant ones.

Methods for the illumination of multilevel buildings with vertical light pipes

This paper examines the feasibility of using vertical light pipes to naturally illuminate the central core of a multilevel building not reached by window light. The challenges addressed were finding a method to extract and distribute equal amounts of light at each level and designing collectors to improve the effectiveness of vertical light pipes in delivering low elevation sunlight to the interior. Extraction was achieved by inserting partially reflecting cones within transparent sections of the pipes at each floor level. Theory was formulated to estimate the partial reflectance necessary to provide equal light extraction at each level. Designs for daylight collectors formed from laser cut panels tilted above the light pipe were developed and the benefits and limitations of static collectors as opposed to collectors that follow the sun azimuth investigated. Performance was assessed with both basic and detailed mathematical simulation and by observations made with a five level model building under clear sky conditions.

The path less travelled: Vertical circulation spaces in apartment buildings in the subtropics

This paper presents data on residents’ use of common stairways and lifts (vertical circulation spaces) in multi-storey apartment buildings (MSABs) in Brisbane, Australia. Vertical movement is a defining aspect of multi-storey living and the energy consumed by lifts contributes significantly to the energy budget of the typical MSAB. The purpose is to investigate whether a reappraisal of vertical circulation design, through the lens of residents’ requirements, might contribute to energy reductions in this building type. Data was gathered on a theoretical sample of MSAB ranging from five decades old to very recent schemes. 90 residents were surveyed about their day-to-day experiences of circulation and access systems. The results showed that residents mainly chose to use the stairs for convenience and exercise. Building management regimes that limited residents’ access to collective spaces were the main impediment to discretionary stair use. Only two buildings did not have fully enclosed stairwells and these had the highest stair usage, suggesting that stair design, and building governance are two areas that might be worthy of attention. The more that circulation design is focussed on limiting access, the less opportunities there are for personal choice, incidental social interaction and casual surveillance of collective spaces. The more that design of vertical circulation spaces in MSAB meets residents’ needs the less likely they are to be reliant on continuous energy supply for normal functioning.

Synergistic fusion of vertical graphene nanosheets and carbon nanotubes for high-performance supercapacitor electrodes

Graphene and carbon nanotubes (CNTs) are attractive electrode materials for supercapacitors. However, challenges such as the substrate-limited growth of CNTs, nanotube bundling in liquid electrolytes, under-utilized basal planes, and stacking of graphene sheets have so far impeded their widespread application. Here we present a hybrid structure formed by the direct growth of CNTs onto vertical graphene nanosheets (VGNS). VGNS are fabricated by a green plasma-assisted method to break down and reconstruct a natural precursor into an ordered graphitic structure. The synergistic combination of CNTs and VGNS overcomes the challenges intrinsic to both materials. The resulting VGNS/CNTs hybrids show a high specific capacitance with good cycling stability. The charge storage is based mainly on the non-Faradaic mechanism. In addition, a series of optimization experiments were conducted to reveal the critical factors that are required to achieve the demonstrated high supercapacitor performance.

Mixed convection in non-Newtonian fluids along a vertical plate in a porous medium

The problem of mixed convection from vertical surfaces in a porous medium saturated with a power-law type non-Newtonian fluid is investigated. The transformed conservation laws are solved numerically for the case of variable wall temperature conditions. Results for the details of the velocity and temperature fields as well as the Nusselt number have been presented. The viscosity index ranged from 0.5-2.0.