In this paper, AlInN nanowire ultraviolet light-emitting diodes (LEDs) with emission at ∼299 nm have been successfully demonstrated. We have further studied the light extraction properties of these ...nanowire LEDs using photonic crystal structures with square and hexagonal lattices of nanowires. The light extraction efficiency (LEE) of the periodic nanowire LED arrays was found to be significantly increased as compared to random nanowire LEDs. The LEEs reach ∼ 56%, and ∼ 63% for the square and hexagonal photonic crystal-based nanowire structures, respectively. Moreover, highly transverse-magnetic polarized emission was observed with dominant vertical light emission for the AlInN nanowire ultraviolet LEDs.
O-doped g-C3N4 (denoted as x-OCN, where x is the volume of 30% H2O2 for a given amount of urea) materials were prepared by calcining dried the mixtures of urea impregnated with H2O2 at 550 °C. The ...characterization shows that the x-OCN materials are formed by replacing N in g-C3N4 by O atoms, which is further supported by density functional theory calculations. The rhodamine B photodegradation performance on the x-OCN materials is higher than the pure g-C3N4. Among the x-OCN samples, 40-OCN shows the strongest photocatalytic activity, which could be attributed to the largest content of doped-O in the matrix of g-C3N4, leading to a reduced bandgap energy and a lower recombination rate of photogenerated electrons and holes, therefore enhancing the photocatalytic performance. The mechanism for the photocatalytic degradation of RhB was proposed based on the investigation on the role of active species and the pathway of RhB degradation.
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•O-doped g-C3N4 materials were prepared.•The photocatalytic performance for the materials was investigated.•The doping O in g-C3N4 lead to an improvement in its photocatalytic performance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this research, WO
3
, g-C
3
N
4
, and g-C
3
N
4
@WO
3
nanocomposites were synthesized from Na
2
WO
4
.2H
2
O and urea precusors via the hydrothermal method in a strong acid medium. ...Physico-chemical characteristics of WO
3
, g-C
3
N
4
, and g-C
3
N
4
@WO
3
nanocomposites were examined by means of XRD, Raman, FTIR, FE-SEM, BET, and UV-Vis spectroscopy. The produced materials were then applied for studying adsorptive removal of methylene blue (MB) as a model pollutant from aqueous solutions. The results showed that g-C
3
N
4
@WO
3
nanocomposites were successfully synthesized, with a hexagonal shape and an average crystal size of in the range of 15.4-20.7 nm. The surface area (68.3 m
2
/g) of g-C
3
N
4
@WO
3
nanocomposites was 2.37 times higher compared to sole WO
3
, and g-C
3
N
4
@WO
3
composites were mesoporous materials with a typical average pore diameter of 4.5 nm. It was revealed that the MB adsorption process occurred extremely quickly, reaching equilibrium after only about 20 min, with a maximum uptake of MB of 190 mg/g which was significantly higher than other adsorbents. The adsorption process was followed the first-order-kinetics model and the adsorbent showed high durability in adsorbing MB, with a slight decline in adsorption efficiency after 4 cycles (from 98.7% to 95.9%). This research provides an easy method for producing high adsorption capacity nanocomposite which can be applied for efficient removal of MB from water.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
We study the application of the receding horizon optimal control (RHOC) for hydraulic pipeline systems described by the so-called water hammer equations. Sufficient conditions to guarantee an ...asymptotic stability to an equilibrium state are first introduced and then integrated in the RHOC scheme. For the implementation, calculus of variations is employed to characterize the optimal solution in terms of the adjoint state and the recently proposed Lattice Boltzmann method is used to solve both direct and adjoint partial differential equations. This approach is finally validated in simulation.
Understanding the interaction of water and graphene is crucial for various applications such as water purification, desalination, and electrocatalysis. Experimental and theoretical studies have ...already investigated water adsorption on N- and B-doped graphene. However, there are no reports available that elucidate the influences of the N and B doping content in graphene on the microscopic geometrical structure and the electronic properties of the adsorbed water. Thus, this work is devoted to solving this problem using self-consistent van der Waals density functional theory calculations. The N and B doping contents of 0.0, 3.1, 6.3, and 9.4% were considered. The results showed that the binding energy of water increases almost linearly as a function of doping content at all concentrations for N-doped graphene but below 6.3% for B-doped graphene. In the linear range, the binding energy increases by approximately 30 meV for each increment of the doping ratio. Analyses of the geometric and electronic structures explained the enhancement of the water-graphene interaction with the variation in doping percentage.
N and B doping content in graphene alters the microscopic geometrical structure and electronic properties of adsorbed water.
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IJS, KILJ, NUK, UL, UM, UPUK
Understanding the genetic diversity in endangered species that occur inforest remnants is necessary to establish efficient strategies for the species conservation, restoration and management. Panax ...vietnamensis Ha et Grushv. is medicinally important, endemic and endangered species of Vietnam. However, genetic diversity and structure of population are unknown due to lack of efficient molecular markers.
In this study, we employed Illumina HiSeq™ 4000 sequencing to analyze the transcriptomes of P. vietnamensis (roots, leaves and stems). Raw reads total of 23,741,783 was obtained and then assembled, from which the generated unigenes were 89,271 (average length = 598.3191 nt). The 31,686 unigenes were annotated in different databases i.e. Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, Nucleotide Collection (NR/NT) and Swiss-Prot for functional annotation. Further, 11,343 EST-SSRs were detected. From 7774 primer pairs, 101 were selected for polymorphism validation, in which; 20 primer pairs were successfully amplified to DNA fragments and significant amounts of polymorphism was observed within population. The nine polymorphic microsatellite loci were used for population structure and diversity analyses. The obtained results revealed high levels of genetic diversity in populations, the average observed and expected heterozygosity were H
= 0.422 and H
= 0.479, respectively. During the Bottleneck analysis using TPM and SMM models (p < 0.01) shows that targeted population is significantly heterozygote deficient. This suggests sign of the bottleneck in all populations. Genetic differentiation between populations was moderate (F
= 0.133) and indicating slightly high level of gene flow (Nm = 1.63). Analysis of molecular variance (AMOVA) showed 63.17% of variation within individuals and 12.45% among populations. Our results shows two genetic clusters related to geographical distances.
Our study will assist conservators in future conservation management, breeding, production and habitats restoration of the species.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In this work, we investigate a single projection method with double inertial extrapolation steps and self-adaptive step sizes for solving pseudomonotone variational inequality problems in a real ...Hilbert space. Weak and linear convergence are presented under suitable conditions. Some simple numerical examples are given to illustrate the performance of the proposed algorithm.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract
Removal of divalent metal ions (Mg and Ca) by graphene membrane has a great implication for manufacturing chitin and chitosan in filtration process. Despite its importance, influences of the ...doping and vacancy in graphene on the adsorption of those metal ions remain unclear. Here, we study the adsorption of those metal ions on several graphene surfaces, namely pristine graphene (Gra), graphitic N- and B- doped graphene (N- and B-Gra), monovacancy graphene (MV-Gra), monovacancy graphene functionalized by an epoxy (O-MV-Gra), and monovacancy graphene functionalized by an hydroxyl group (OH-MV-Gra) by van der Waals density functional (vdW-DF) method. It was found all considered graphene surfaces have strong interactions with Ca, whereas Mg only chemisorbs on MV-Gra and B-Gra. Energetically, comparing with Ca adosprtion on pristine graphene, both B doping and vacancy creation strengthen the Ca adsorption, while N doping slight decreases it. The electronic structure analysis uncovers enhancement of the Cagraphene interaction by B doping and vacancy formation. Because of the results that have been observed, the removal of Ca ions from aqueous solution can be enhanced by the creation of nanopore or B doping in graphene, in which Ca atom are strongly captured by graphene.
In situ g-C3N4@ZnO nanocomposites (with 0, 1, 3, 5, and 7 wt.% of g-C3N4 in nanocomposite) were synthesized via a one-pot hydrothermal method using precursors of urea, zinc nitrate hexahydrate, and ...hexamethylenetetramine. The g-C3N4@ZnO nanocomposites were characterized by X-ray diffraction, scanning electron microscope, diffuse reflectance spectroscopy, and photoluminescence spectroscopy. The photocatalyst activity of g-C3N4@ZnO nanocomposites was evaluated via methylene blue degradation experiment under visible light irradiation. The g-C3N4@ZnO nanocomposites showed an enhancement in photocatalytic activity in comparison to pure ZnO which increased with the g-C3N4 content (1, 3, 5, and 7 wt.%) in nanocomposites. The photocatalytic activity reached the highest efficiency of 96.8% when the content of g-C3N4 was 7.0 wt.%. Nanocomposite having 7.0 wt.% of g-C3N4 also showed good recyclability with degradation efficiency higher than 90% even in the 4th use. The improvement of photocatalytic activity could be attributed to the adsorption ability and effective separation of electron-hole pairs between g-C3N4 and ZnO. This work implies a simple method to in situ prepare the nanocomposite material of g-C3N4 and semiconductors oxide for photocatalyst applications with high efficiency and good recyclability.
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FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
We report on the illustration of the first electron blocking layer (EBL) free AlInN nanowire light-emitting diodes (LEDs) operating in the deep ultraviolet (DUV) wavelength region (sub-250 nm). We ...have systematically analyzed the results using APSYS software and compared with simulated AlGaN nanowire DUV LEDs. From the simulation results, significant efficiency droop was observed in AlGaN based devices, attributed to the significant electron leakage. However, compared to AlGaN nanowire DUV LEDs at similar emission wavelength, the proposed single quantum well (SQW) AlInN based light-emitters offer higher internal quantum efficiency without droop up to current density of 1500 A/cm 2 and high output optical power. Moreover, we find that transverse magnetic polarized emission is ∼ 5 orders stronger than transverse electric polarized emission at 238 nm wavelength. Further research shows that the performance of the AlInN DUV nanowire LEDs decreases with multiple QWs in the active region due to the presence of the non-uniform carrier distribution in the active region. This study provides important insights on the design of new type of high performance AlInN nanowire DUV LEDs, by replacing currently used AlGaN semiconductors.
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