Although polycrystalline hexagonal boron nitride (PC-hBN) has been realized, defects and grain boundaries still cause charge scatterings and trap sites, impeding high-performance electronics. Here, ...we report a method of synthesizing wafer-scale single-crystalline hBN (SC-hBN) monolayer films by chemical vapor deposition. The limited solubility of boron (B) and nitrogen (N) atoms in liquid gold promotes high diffusion of adatoms on the surface of liquid at high temperature to provoke the circular hBN grains. These further evolve into closely packed unimodal grains by means of self-collimation of B and N edges inherited by electrostatic interaction between grains, eventually forming an SC-hBN film on a wafer scale. This SC-hBN film also allows for the synthesis of wafer-scale graphene/hBN heterostructure and single-crystalline tungsten disulfide.
Edible unclonable functions Leem, Jung Woo; Kim, Min Seok; Choi, Seung Ho ...
Nature communications,
01/2020, Letnik:
11, Številka:
1
Journal Article
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Counterfeit medicines are a fundamental security problem. Counterfeiting medication poses a tremendous threat to patient safety, public health, and the economy in developed and less developed ...countries. Current solutions are often vulnerable due to the limited security levels. We propose that the highest protection against counterfeit medicines would be a combination of a physically unclonable function (PUF) with on-dose authentication. A PUF can provide a digital fingerprint with multiple pairs of input challenges and output responses. On-dose authentication can verify every individual pill without removing the identification tag. Here, we report on-dose PUFs that can be directly attached onto the surface of medicines, be swallowed, and digested. Fluorescent proteins and silk proteins serve as edible photonic biomaterials and the photoluminescent properties provide parametric support of challenge-response pairs. Such edible cryptographic primitives can play an important role in pharmaceutical anti-counterfeiting and other security applications requiring immediate destruction or vanishing features.
Growth of 2D van der Waals layered single‐crystal (SC) films is highly desired not only to manifest the intrinsic physical and chemical properties of materials, but also to enable the development of ...unprecedented devices for industrial applications. While wafer‐scale SC hexagonal boron nitride film has been successfully grown, an ideal growth platform for diatomic transition metal dichalcogenide (TMdC) films has not been established to date. Here, the SC growth of TMdC monolayers on a centimeter scale via the atomic sawtooth gold surface as a universal growth template is reported. The atomic tooth‐gullet surface is constructed by the one‐step solidification of liquid gold, evidenced by transmission electron microscopy. The anisotropic adsorption energy of the TMdC cluster, confirmed by density‐functional calculations, prevails at the periodic atomic‐step edge to yield unidirectional epitaxial growth of triangular TMdC grains, eventually forming the SC film, regardless of the Miller indices. Growth using the atomic sawtooth gold surface as a universal growth template is demonstrated for several TMdC monolayer films, including WS2, WSe2, MoS2, the MoSe2/WSe2 heterostructure, and W1−xMoxS2 alloys. This strategy provides a general avenue for the SC growth of diatomic van der Waals heterostructures on a wafer scale, to further facilitate the applications of TMdCs in post‐silicon technology.
The atomic sawtooth Au surface allows the anisotropic adsorption energy of transition metal dichalcogenide (TMdC) clusters to yield unidirectional epitaxial growth of triangular TMdC grains, eventually forming a single‐crystal TMdC film, regardless of the Miller indices. Growth using the atomic sawtooth gold surface as a universal growth template is further demonstrated for several TMdC monolayer films, including WS2, WSe2, MoS2, the MoSe2/WSe2 heterostructure, and W1−xMoxS2 alloys.
Color of Copper/Copper Oxide Kim, Su Jae; Kim, Seonghoon; Lee, Jegon ...
Advanced materials,
04/2021, Letnik:
33, Številka:
15
Journal Article
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Stochastic inhomogeneous oxidation is an inherent characteristic of copper (Cu), often hindering color tuning and bandgap engineering of oxides. Coherent control of the interface between metal and ...metal oxide remains unresolved. Coherent propagation of an oxidation front in single‐crystal Cu thin film is demonstrated to achieve a full‐color spectrum for Cu by precisely controlling its oxide‐layer thickness. Grain‐boundary‐free and atomically flat films prepared by atomic‐sputtering epitaxy allow tailoring of the oxide layer with an abrupt interface via heat treatment with a suppressed temperature gradient. Color tuning of nearly full‐color red/green/blue indices is realized by precise control of the oxide‐layer thickness; the samples cover ≈50.4% of the standard red/green/blue color space. The color of copper/copper oxide is realized by the reconstruction of the quantitative yield color from the oxide “pigment” (complex dielectric functions of Cu2O) and light‐layer interference (reflectance spectra obtained from the Fresnel equations) to produce structural color. Furthermore, laser‐oxide lithography is demonstrated with micrometer‐scale linewidth and depth through local phase transformation to oxides embedded in the metal, providing spacing necessary for semiconducting transport and optoelectronics functionality.
Atomically flat perfect single‐crystal Cu films prepared by the atomic‐sputtering epitaxy method realize the coherent propagation of an oxidation front and display full‐color by controlling the oxide‐layer thickness. More than 50% of the standard red/green/blue color space is covered. Laser‐oxide lithography forming a microscale local oxide embedded in metal is introduced.
Copper surfaces that exhibit a wide range of achromatic colors while still metallic have not been studied, despite advancements in antireflection coatings. A series of achromatic copper films grown ...with 111 preferred orientation by depositing 3D porous nanostructures is introduced via coherent/incoherent atomic sputtering epitaxy. The porous copper nanostructures self‐regulate the giant oxidation resistance by constructing a curved surface that generates a series of monoatomic steps, followed by shrinkage of the lattice spacing of one or two surface layers. First‐principles calculations confirm that these structural components cooperatively increase the energy barrier against oxygen penetration. The achromaticity of the single‐crystalline porous copper films is systematically tuned by geometrical parameters such as pore size distribution and 3D linkage. The optimized achromatic copper films with high oxidation resistance show an unusual switching effect between superhydrophilicity and superhydrophobicity. The tailored 3D porous nanostructures can be a candidate material for numerous applications, such as antireflection coatings, microfluidic devices, droplet tweezers, and reversible wettability switches.
A series of achromatic Cu films with semi‐permanent stability and switchable superhydrophobic and superhydrophilic states on rough or curved surfaces is realized by an innovative strategy. Comprehensive atomic‐resolution microscopy reveals that their surfaces are of a series of monoatomic steps and have a counterintuitive lattice contraction, which demonstrates the self‐oxidation resistance of copper.
BACKGROUND—Modern treatments have improved the survival rate following cardiac arrest, but prognostication remains a challenge. We examined the prognostic value of continuous electroencephalography ...according to time by performing amplitude-integrated electroencephalography on patients with cardiac arrest receiving therapeutic hypothermia.
METHODS AND RESULTS—We prospectively studied 130 comatose patients treated with hypothermia from September 2010 to April 2013. We evaluated the time to normal trace (TTNT) as a neurological outcome predictor and determined the prognostic value of burst suppression and status epilepticus, with a particular focus on their time of occurrence. Fifty-five patients exhibited a cerebral performance category score of 1 to 2. The area under the curve for TTNT was 0.97 (95% confidence interval, 0.92–0.99), and the sensitivity and specificity of TTNT<24 hours after resuscitation as a threshold for predicting good neurological outcome were 94.6% (95% confidence interval, 84.9%–98.9%) and 90.7% (95% confidence interval, 81.7%–96.2%), respectively. The threshold displaying 100% specificity for predicting poor neurological outcome was TTNT>36 hours. Burst suppression and status epilepticus predicted poor neurological outcome (positive predictive value of 98.3% and 96.4%, respectively). The combination of these factors predicted a negative outcome at a median of 6.2 hours after resuscitation (sensitivity and specificity of 92.0% and 96.4%, respectively).
CONCLUSIONS—A TTNT<24 hours was associated with good neurological outcome. The lack of normal trace development within 36 hours, status epilepticus, and burst suppression were predictors of poor outcome. The combination of these negative predictors may improve their prognostic performance at an earlier stage.
Ion enhanced polarizationHafnium oxide is an exciting material because it has ferroelectric behavior that makes it attractive for various device applications. Kang et al. found that the ferroelectric ...properties improve by bombarding films of hafnium oxide with a beam of helium ions. The ion bombardment creates oxygen vacancies and strain changes from helium implantation that push more of the polycrystalline samples into the ferroelectric orthorhombic phase. This method may become an important tool for stabilizing the ferroelectric phase for the next generation of electronic devices. —BG
The issues over increases in energy demand and environmental pollution attributed to excessive use of fossil fuel have been the driving forces of the exploration for eco-friendly resource. ...Lignocellulosic biomass consisting of carbohydrates and lignin can be a renewable feedstock for replacing fossil fuels in the future because it is a plentiful and carbon neutral material. Especially, lignin, cross-linked phenolic polymers, is a topic of interest owing to its abundant production from pulp/paper industries as well as lignocellulose based biorefinery. The large potential of platform chemicals and biofuels from lignin has opened up an extensive range of opportunities to develop thermal and catalytic conversion technology. Over a few decades, several lignin conversion processes including catalytic pyrolysis, catalytic depolymerization, and catalytic oxidation have been developed to improve target products yields and to suppress side reactions. More recently, lignin-first approaches which maintain carbohydrates intact by selective extraction of lignin as valuable phenolics from whole biomass has been suggested. This review introduces recent ten years progress on thermal and catalytic conversion technology in terms of process type, catalyst development, and target products. This review is expected to offer an influential information for future research into the thermal and catalytic conversion of lignin as well as lignocellulosic feedstock.
•Recent discoveries in thermal and catalytic lignin conversion are introduced.•A proper conversion process should be considered depending on the lignin type.•Catalyst plays a decisive role in product distribution and selectivity in process.•The challenges and future perspective of each process is discussed.
1,3-propanediol (1,3-PDO) is the most widely studied value-added product that can be produced by feeding glycerol to bacteria, including Lactobacillus sp. However, previous research reported that L. ...reuteri only produced small amounts and had low productivity of 1,3-PDO. It is urgent to develop procedures that improve the production and productivity of 1,3-PDO.
We identified a novel L. reuteri CH53 isolate that efficiently converted glycerol into 1,3-PDO, and performed batch co-fermentation with glycerol and glucose to evaluate its production of 1,3-PDO and other products. We optimized the fermentation conditions and nitrogen sources to increase the productivity. Fed-batch fermentation using corn steep liquor (CSL) as a replacement for beef extract led to 1,3-PDO production (68.32 ± 0.84 g/L) and productivity (1.27 ± 0.02 g/L/h) at optimized conditions (unaerated and 100 rpm). When CSL was used as an alternative nitrogen source, the activity of the vitamin B12-dependent glycerol dehydratase (dhaB) and 1,3-propanediol oxidoreductase (dhaT) increased. Also, the productivity and yield of 1,3-PDO increased as well. These results showed the highest productivity in Lactobacillus species. In addition, hurdle to 1,3-PDO production in this strain were identified via analysis of the half-maximal inhibitory concentration for growth (IC50) of numerous substrates and metabolites.
We used CSL as a low-cost nitrogen source to replace beef extract for 1,3-PDO production in L. reuteri CH53. These cells efficiently utilized crude glycerol and CSL to produce 1,3-PDO. This strain has great promise for the production of 1,3-PDO because it is generally recognized as safe (GRAS) and non-pathogenic. Also, this strain has high productivity and high conversion yield.
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