59 research outputs found
Reversible Surface Wettability by Silanization
The chemistry and wettability of oxygen containing surfaces can be conveniently modified by silanization with various organosilanes which form SiO bonds on the surface. This work shows that a superhydrophobic nanoporous polymer coating can be reverted to its previous hydrophilic state by removing the fluoroalkyl silane with fluoride anions using tetrabutyl ammonium fluoride. This leads to a completely reversible process of silanization and desilanization which can be performed in less than 2 min for each step as proven by droplet shape analysis and secondary ion mass spectrometry. Additionally, the desilanization solution can be applied spatially by an automated liquid dispenser or manually by a brush, leading to patterns with different wettability, such as droplet microarrays or liquid channels
Ozonation-Based Decolorization of Food Dyes for Recovery of Fruit Leather Wastes
Commercial manufacture of fruit leathers (FL) usually results in a portion of the product that is out of specification. The disposition of this material poses special challenges in the food industry. Because the material remains edible and contains valuable ingredients (fruit pulp, sugars, acidulates, etc.), an ideal solution would be to recover this material for product rework. A key practical obstacle to such recovery is that compositing of differently colored wastes results in an unsalable gray product. Therefore, a safe and scalable method for decolorization of FL prior to product rework is needed. This research introduces a novel approach utilizing ozonation for color removal.
To explore the use of ozonation as a decolorization step, we first applied it to simple solutions of the commonly used food colorants 2-naphthalenesulfonic acid (Red 40), tartrazine (Yellow 5), and erioglaucine (Blue 1). Decolorization was measured by UV/vis spectrometry at visible wavelengths and with a Hunter colorimeter. Volatile and semivolatile byproducts from ozone-based colorant decomposition were identified and quantified with solid phase microextraction coupled with gas chromatographyâmass spectrometry (SPME-GC-MS). Removal of Yellow 5, Red 40 and Blue 1 of about 65%, 80%, and 90%, respectively, was accomplished with 70 g of ozone applied per 1 kg of redissolved and resuspended FL. Carbonyl compounds were identified as major byproducts from ozone-induced decomposition of the food colorants. A conservative risk assessment based on quantification results and published toxicity information of potentially toxic byproducts, determined that ozone-based decolorization of FL before recycling is acceptable from a safety standpoint. A preliminary cost estimate based on recycling of 1000 tons of FL annually suggests a potential of $275,000 annual profit from this practice at one production facility alone
Non-volatile leaky integrate-and-fire neurons with domain walls in antiferromagnetic insulators
Despite the rapid development of powerful supercomputers in recent years, the human brain still has some abilities that outperform modern computers which are based on the von Neumann architecture. The human brain is much more energy efficient than state-of-the-art digital computers and can at the same time perform complex tasks such as pattern recognition. The brain-inspired neuromorphic computing paradigm is a promising path towards next generation analogue computers with fundamentally different architecture. The building blocks of the human brain are neurons with leaky integrate-and-fire mechanisms. In this work, using the advantage of antiferromagnetic insulators, we propose a non-volatile spintronic-based neuron. In our proposal, an antiferromagnetic domain wall in the presence of a magnetic anisotropy gradient mimics a biological neuron with leaky and integrative properties. This single neuron is controlled by polarized antiferromagnetic magnons, activated by either a magnetic field pulse or a spin transfer torque mechanism. We propose that this single neuron, based on antiferromagnetic insulators, is faster and more energy efficient than other metallic ferromagnetic-based neurons
Copper Thiophosphate (Cu3PS4) as Electrode for Sodium-Ion Batteries with Ether Electrolyte
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Abstract
Lithium and sodium thiophosphates (and related compounds) have recently attracted attention because of their potential use as solid electrolytes in solidâstate batteries. These compounds, however, exhibit only limited stability in practice as they react with the electrodes. The decomposition products partially remain redox active hence leading to excess capacity. The redox activity of thiophosphates is explicitly used to act as electrode for sodiumâion batteries. Copper thiophosphate (Cu3PS4) is used as a model system. The storage behavior between 0.01 and 2.5 V versus Na+/Na is studied in half cells using different electrolytes with 1 m NaPF6 in diglyme showing the best result. Cu3PS4 shows highly reversible charge storage with capacities of about 580 mAh gâ1 for more than 200 cycles @120 mA gâ1 and about 450 mAh gâ1 for 1400 cycles @1 A gâ1. The redox behavior is studied by operando Xâray diffraction and Xâray photoelectron spectroscopy. During initial sodiation, Cu3PS4 undergoes a conversion reaction including the formation of Cu and Na2S. During cycling, the redox activity seems dominated by sulfur. Interestingly, the capacity of Cu3PS4 for lithium storage is smaller, leading to about 170 mAh gâ1 after 200 cycles. The results demonstrate that thiophosphates can lead to reversible charge storage over several hundred cycles without any notable capacity decay.Peer Reviewe
Single SiGe Quantum Dot Emission Deterministically Enhanced in a High-Q Photonic Crystal Resonator
We report the resonantly enhanced radiative emission from a single SiGe
quantum dot (QD), which is deterministically embedded into a bichromatic
photonic crystal resonator (PhCR) at the position of its largest modal electric
field by a scalable method. By optimizing our molecular beam epitaxy (MBE)
growth technique, we were able to reduce the amount of Ge within the whole
resonator to obtain an absolute minimum of exactly one QD, accurately
positioned by lithographic methods relative to the PhCR, and an otherwise flat,
a few monolayer thin, Ge wetting layer (WL). With this method, record quality
(Q) factors for QD-loaded PhCRs up to are achieved. A comparison
with control PhCRs on samples containing a WL but no QDs is presented, as well
as a detailed analysis of the dependence of the resonator-coupled emission on
temperature, excitation intensity, and emission decay after pulsed excitation.
Our findings undoubtedly confirm a single QD in the center of the resonator as
a potentially novel photon source in the telecom spectral range
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