Plasma catalysis has drawn attention from the plasma and chemical engineering communities in the past few decades as a possible alternative to the long-established Haber–Bosch process for ammonia ...production. The highly reactive electrons, ions, atoms, and radicals in the plasma significantly enhance the chemical kinetics, allowing ammonia to be produced at room temperature and atmospheric pressure. However, despite the promise of plasma catalysis, its performance is still well short of that of the Haber–Bosch process. This is at least in part due to the lack of understanding of the complex mechanisms underlying the plasma–catalyst interactions. Gaining such an understanding is a prerequisite for exploiting the potential of plasma catalysis for ammonia production. In this perspective, we discuss possible benefits and synergies of the combination of plasma and catalyst. The different regimes of plasma discharges and plasma reactor configurations are introduced and their characteristics in ammonia synthesis are compared. Based on detailed kinetic modeling work, practical ideas and suggestions to improve the energy efficiency and yield of ammonia production are presented, setting future research directions in plasma catalysis for efficient ammonia production.
Raman spectroscopy of diamond and doped diamond Prawer, Steven; Nemanich, Robert J.
Philosophical transactions of the Royal Society of London. Series A: Mathematical, physical, and engineering sciences,
11/2004, Letnik:
362, Številka:
1824
Journal Article
Recenzirano
The optimization of diamond films as valuable engineering materials for a wide variety of applications has required the development of robust methods for their characterization. Of the many methods ...used, Raman microscopy is perhaps the most valuable because it provides readily distinguishable signatures of each of the different forms of carbon (e.g. diamond, graphite, buckyballs). In addition it is non-destructive, requires little or no specimen preparation, is performed in air and can produce spatially resolved maps of the different forms of carbon within a specimen. This article begins by reviewing the strengths (and some of the pitfalls) of the Raman technique for the analysis of diamond and diamond films and surveys some of the latest developments (for example, surface-enhanced Raman and ultraviolet Raman spectroscopy) which hold the promise of providing a more profound understanding of the outstanding properties of these materials. The remainder of the article is devoted to the uses of Raman spectroscopy in diamond science and technology. Topics covered include using Raman spectroscopy to assess stress, crystalline perfection, phase purity, crystallite size, point defects and doping in diamond and diamond films.
Ammonia was synthesized from nitrogen and hydrogen in a dielectric-barrier discharge reactor packed with glass spheres and MgO pellets at atmospheric pressure. The addition of argon to nitrogen and ...hydrogen, and increasing the peak voltage, led to increases in discharge power and uniformity, gas temperature, and the fraction of hydrogen converted to ammonia.
Fast and reliable DNA sequencing is a long-standing target in biomedical research. Recent advances in graphene-based electrical sensors have demonstrated their unprecedented sensitivity to adsorbed ...molecules, which holds great promise for label-free DNA sequencing technology. To date, the proposed sequencing approaches rely on the ability of graphene electric devices to probe molecular-specific interactions with a graphene surface. Here we experimentally demonstrate the use of graphene field-effect transistors (GFETs) as probes of the presence of a layer of individual DNA nucleobases adsorbed on the graphene surface. We show that GFETs are able to measure distinct coverage-dependent conductance signatures upon adsorption of the four different DNA nucleobases; a result that can be attributed to the formation of an interface dipole field. Comparison between experimental GFET results and synchrotron-based material analysis allowed prediction of the ultimate device sensitivity, and assessment of the feasibility of single nucleobase sensing with graphene.
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•Annealing in oxygen gas increases the capacitance of nanocrystalline diamond films.•Oxygen replaces hydrogen species and etches the surface graphitic grain boundaries.•Diamond rich ...surface enables formation of sub-surface capacitance below surface.•Oxygen rich surface enables increases electrochemical capacitance above surface.•These results may assist in diamond based biological and electrochemical applications.
The electrochemical capacitance of nitrogen-doped ultrananocrystalline diamond (N-UNCD) can be dramatically increased by treating the surface with an RF-oxygen plasma. Such treated surfaces display excellent properties for use as electrodes in neural stimulation and recording. In the present work, we elucidate the origins of this phenomenon by investigating the effects of different methods of oxygen termination. We found that the increase in electrochemical capacitance is dependent on the details of the method used for oxygen termination. Whilst N-UNCD subjected to UV/ozone treatment, oxygen plasma treatment, and furnace annealing in oxygen gas all displayed increased surface capacitance, the highest capacitance was exhibited by the oxygen annealed sample, with which we achieved ~ 3 orders of magnitude increase in the electrochemical capacitance as compared to the as-grown sample. The maximum recorded capacitance was 3746 ± 132 µF cm−2, which is substantially greater than previously reported N-UNCD electrodes’ electrochemical capacitance (1070 µF cm−2, W. Tong. et al, 2016). Our findings point to the presence of sub-surface solid state capacitance which contributes significantly to the observed electrochemical capacitance of the oxygen terminated N-UNCD electrodes. When combined with the favourable biocompatibility and inertness of the N-UNCD, our approach may provide a route towards the development of advanced neural sensing and stimulating electrodes.
Coherent coupling between single quantum objects is at the very heart of modern quantum physics. When the coupling is strong enough to prevail over decoherence, it can be used to engineer quantum ...entangled states. Entangled states have attracted widespread attention because of applications to quantum computing and long-distance quantum communication. For such applications, solid-state hosts are preferred for scalability reasons, and spins are the preferred quantum system in solids because they offer long coherence times. Here we show that a single pair of strongly coupled spins in diamond, associated with a nitrogen-vacancy defect and a nitrogen atom, respectively, can be optically initialized and read out at room temperature. To effect this strong coupling, close proximity of the two spins is required, but large distances from other spins are needed to avoid deleterious decoherence. These requirements were reconciled by implanting molecular nitrogen into high-purity diamond. PUBLICATION ABSTRACT
Durable and safe energy storage is required for the next generation of miniature bioelectronic devices, in which aqueous electrolytes are preferred due to the advantages in safety, low cost, and high ...conductivity. While rechargeable aqueous batteries are among the primary choices with relatively low power requirements, their lifetime is generally limited to a few thousand charging/discharging cycles as the electrode material can degrade due to electrochemical reactions. Electrical double layer capacitors (EDLCs) possess increased cycling stability and power density, although with as-yet lower energy density, due to quick electrical adsorption and desorption of ions without involving chemical reactions. However, in aqueous solution, chemical reactions which cause electrode degradation and produce hazardous species can occur when the voltage is increased beyond its operation window to improve the energy density. Diamond is a durable and biocompatible electrode material for supercapacitors, while at the same time provides a larger voltage window in biological environments. For applications requiring higher energy density, diamond-based pseudocapacitors (PCs) have also been developed, which combine EDLCs with fast electrochemical reactions. Here we inspect the properties of diamond-related materials and discuss their advantages and disadvantages when used as EDLC and PC materials. We argue that further optimization of the diamond surface chemistry and morphology, guided by computational modelling of the interface, can lead to supercapacitors with enhanced performance. We envisage that such diamond-based supercapacitors could be used in a wide range of applications and in particular those requiring high performance in biomedical applications.
The study of neurons is fundamental for basic neuroscience research and treatment of neurological disorders. In recent years ultrasound has been increasingly recognized as a viable method to ...stimulate neurons. However, traditional ultrasound transducers are limited in the scope of their application by self-heating effects, limited frequency range and cavitation effects during neuromodulation. In contrast, surface acoustic wave (SAW) devices, which are producing wavemodes with increasing application in biomedical devices, generate less self-heating, are smaller and create less cavitation. SAW devices thus have the potential to address some of the drawbacks of traditional ultrasound transducers and could be implemented as miniaturized wearable or implantable devices. In this mini review, we discuss the potential mechanisms of SAW-based neuromodulation, including mechanical displacement, electromagnetic fields, thermal effects, and acoustic streaming. We also review the application of SAW actuation for neuronal stimulation, including growth and neuromodulation. Finally, we propose future directions for SAW-based neuromodulation.
The fabrication of stable ultrabright single photon sources operating at room temperature is reported. The emitter is based on a color center within a diamond nanocrystal grown on a sapphire ...substrate by chemical vapor deposition method and exhibits a two-level electronic behavior with a maximum measured count rate of 3.2 × 106 counts/s at saturation. The emission is centered at ∼756 nm with a full width at half-maximum ∼11 nm and an excited state lifetime of 3.7 ns. These unique properties make it a leading candidate for quantum photonics and communication applications as well as for cellular biomarking.
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