We have clearly discriminated the single-, bilayer-, and multiple-layer graphene (<10 layers) on Si substrate with a 285 nm SiO2 capping layer by using contrast spectra, which were generated from the ...reflection light of a white light source. Calculations based on Fresnel's law are in excellent agreement with the experimental results (deviation 2%). The contrast image shows the reliability and efficiency of this new technique. The contrast spectrum is a fast, nondestructive, easy to be carried out, and unambiguous way to identify the numbers of layers of graphene sheet. We provide two easy-to-use methods to determine the number of graphene layers based on contrast spectra: a graphic method and an analytical method. We also show that the refractive index of graphene is different from that of graphite. The results are compared with those obtained using Raman spectroscopy.
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IJS, KILJ, NUK, PNG, UL, UM
The development of rotary nanomotors is an essential step towards intelligent nanomachines and nanorobots. In this article, we review the concept, design, working mechanisms, and applications of ...state-of-the-art rotary nanomotors made from synthetic nanoentities. The rotary nanomotors are categorized according to the energy sources employed to drive the rotary motion, including biochemical, optical, magnetic, and electric fields. The unique advantages and limitations for each type of rotary nanomachines are discussed. The advances of rotary nanomotors is pivotal for realizing dream nanomachines for myriad applications including microfluidics, biodiagnosis, nano-surgery, and biosubstance delivery.
This article reviews the concepts, designs, working mechanisms, and applications of the state-of-the-art rotary nanomotors made from synthetic nanomaterials.
•A novel convection-enhanced flow field is designed for redox flow batteries.•Energy efficiency and electrolyte utilization are improved significantly.•The concept of critical flow rate is firstly ...proposed for redox flow batteries.
In this work, we propose and fabricate a convection-enhanced flow field for aqueous redox flow batteries. Similar to the conventional single serpentine flow field, the new flow field here has an inlet and outlet, but the repatterned flow path induces higher pressure differences between adjacent flow channels over the entire electrode surface, thereby enhancing the under-rib convection between adjacent flow channels. The application of the new flow field to a vanadium redox flow battery enables substantial performance improvements. At 1.67 mL min−1 cm−2, which is a typical flow rate for a kilowatt-class VRFB stack, the energy efficiency, and electrolyte utilization reach 75.3% and 49.6% at a current density of 250 mA cm−2, increasing by 10.0% and 33.3% as opposed to the use of the conventional serpentine flow field, respectively. Three-dimensional numerical modelling shows that the improved performance is ascribed to the more uniform in-plane distribution of reactants and current with the new flow field. Another important finding of this work is that there is a critical flow rate above which energy efficiency tends to stabilize for a given current density.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The interaction between graphene and a SiO2 surface has been analyzed with first-principles DFT calculations by constructing the different configurations based on α-quartz and cristobalite ...structures. The fact that single-layer graphene can stay stably on a SiO2 surface is explained based on a general consideration of the configuration structures of the SiO2 surface. It is found that the oxygen defect in a SiO2 surface can shift the Fermi level of graphene down which opens up the mechanism of the hole-doping effect of graphene adsorbed on a SiO2 surface observed in a lot of experiments.
The flower perianth has various, non‐mutually exclusive functions, such as visual signalling to pollinators and protecting the reproductive organs from the elements and from florivores, but how ...different perianth structures and their different sides play a role in these functions is unclear. Intriguingly, in many species there is a clear colour difference between the different sides of the perianth, with colour patterns or pigmentation present on only one side. Any adaptive benefit from such colour asymmetry is unclear, as is how the asymmetry evolved. In this viewpoint paper, we address the phenomenon of flowers with differently coloured inner and outer perianth sides, focusing on petals of erect flowers. Guided by existing literature and our own observations, we delineate three non‐mutually exclusive evolutionary hypotheses that may explain the factors underlying differently coloured perianth sides. The pollen‐protection hypothesis predicts that the outer side of petals contributes to protect pollen against UV radiation, especially during the bud stage. The herbivore‐avoidance hypothesis predicts that the outer side of petals reduces the flower's visibility to herbivores. The signalling‐to‐pollinators hypothesis predicts that flower colours evolve to increase conspicuousness to pollinators. The pollen‐protection hypothesis, the herbivore‐avoidance hypothesis, and the signalling‐to‐pollinators hypothesis generate largely but not entirely overlapping predictions about the colour of the inner and outer side of the petals. Field and laboratory research is necessary to disentangle the main drivers and adaptive significance of inner–outer petal side colour asymmetry.
Evolutionary hypotheses aimed at explaining why inner and outer sides of petals are often differently coloured.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Growth of high-quality single-crystalline InSb layers remains challenging in material science. Such layered InSb materials are highly desired for searching for and manipulation of Majorana Fermions ...in solid state, a fundamental research task in physics today, and for development of novel high-speed nanoelectronic and infrared optoelectronic devices. Here, we report on a new route toward growth of single-crystalline, layered InSb materials. We demonstrate the successful growth of free-standing, two-dimensional InSb nanosheets on one-dimensional InAs nanowires by molecular-beam epitaxy. The grown InSb nanosheets are pure zinc-blende single crystals. The length and width of the InSb nanosheets are up to several micrometers and the thickness is down to ∼10 nm. The InSb nanosheets show a clear ambipolar behavior and a high electron mobility. Our work will open up new technology routes toward the development of InSb-based devices for applications in nanoelectronics, optoelectronics, and quantum electronics and for the study of fundamental physical phenomena.
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IJS, KILJ, NUK, PNG, UL, UM
Nafion membranes are extensively used in aqueous redox flow batteries due to their high proton conductivity and excellent chemical stability, but their low ion selectivity and high cost restrict the ...further development of flow batteries. Here we demonstrate a composite membrane consisting of electrospun Nafion nanofibers embedded in a polybenzimidazole (PBI) matrix. The interconnected Nafion nanofibers act as consecutive proton-conducting pathways, allowing a high proton conductivity with low Nafion content, while the highly selective PBI matrix suppresses the crossover of redox species, ensuring a high ion selectivity. Moreover, the acid-base interactions between the Nafion and PBI along with the rigid nature of PBI offer excellent mechanical stability. The resultant membrane with only 40 wt% Nafion exhibits 58-fold improvement in blocking vanadium permeation and a nearly 60% retention in proton conductivity compared with the Nafion 212 membrane. More notably, the optimal membrane enables a vanadium redox flow battery to obtain a coulombic efficiency of 99.8% and an energy efficiency (EE) of 80.0% at a high current density of 210 mA cm
−2
, exceeding that with the Nafion 212 membrane (EE ∼ 77.2%). This work presents a new approach for developing efficient and affordable membranes for aqueous redox flow batteries.
A composite membrane with consecutive proton-conducting pathways is designed for aqueous redox flow batteries. The high proton conductivity and ion selectivity are endowed respectively by the interconnected Nafion nanofibers and PBI matrix.
With the increase of communication frequency, terahertz (THz) communication technology has been an important research field; particularly the terahertz modulator is becoming one of the core devices ...in THz communication system. The modulation performance of a THz communication system depends on the characterization of THz modulator. THz modulators based on different principles and materials have been studied and developed. However, they are still on the way to practical application due to low modulation speed, narrow bandwidth, and insufficient modulation depth. Therefore, we review the research progress of THz modulator in recent years and evaluate devices critically and comprehensively. We focus on the working principles such as electric, optical, optoelectrical, thermal, magnetic, programmable metamaterials and nonlinear modulation methods for THz wave with semiconductors, metamaterials, and 2D materials (such as graphene, molybdenum disulfide, and tungsten disulfide). Furthermore, we propose a guiding rule to select appropriate materials and modulation methods for specific applications in THz communication.
Summary
Background
Icariin is a major flavonoid isolated from Epimedium spp. leaves (Epimedium Herba), and has multiple pharmacological functions, including anti‐angiogenesis, anti‐oxidant, ...anti‐inflammatory and immunoprotective effects.
Aim
To investigate whether icariin can stimulate growth of hair follicles in mice and the underlying mechanism.
Methods
In vitro, the effect of icariin on hair growth was assessed by using a vibrissae hair follicle (VHF) organ‐culture model. The proliferation of hair matrix keratinocytes and the expression of insulin‐like growth factor (IGF)‐1 in follicles were examined by double immunostaining for 5‐bromo‐2′‐deoxyuridine and IGF‐1, in the presence or absence of icariin. Dermal papilla cells (DPCs) were cultured and IGF‐1 level was measured by reverse transcription‐PCR and ELISA after icariin treatment. In vivo, the effect of icariin on hair growth was examined by gavage feeding of icariin to mice whose backs had been depilated, and the conversion of telogen to anagen hair was observed.
Results
Treatment with icariin promoted hair shaft elongation, prolonged the hair cycle growth phase (anagen) in cultured VHFs, and accelerated transition of hair cycle from telogen to anagen phase in the dorsal skin of mice. There was significant proliferation of matrix keratinocytes and an increased level of IGF‐1 in cultured VHFs. Moreover, icariin treatment upregulated IGF‐1 mRNA expression in DPCs and increased IGF‐1 protein content in the conditioned medium of DPCs.
Conclusions
These results suggest that icariin can promote mouse hair follicle growth via stimulation of IGF‐1 expression in DPCs.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
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