Generation Of Holes Research Articles

Carbon vacancies enriched carbon nitride nanotubes for Pd coordination environment optimization: Highly efficient photocatalytic hydrodechlorination and CO2 cycloaddition

The use of easily available solar energy to achieve pollutants efficient degradation and waste carbon resource CO2 utilization under mild conditions is highly desired. Herein, novel carbon vacancies enriched nanotubes graphitic carbon nitride (SCNT-500) has been successfully fabricated via melamine (MA) supramolecular hydrogen-bonded self-assembly in the presence of H2SO4. Pd NPs loaded carbon vacancies enriched carbon nitride nanotubes (Pd/SCNT-500) were used for photocatalytic chlorophenols hydrodechlorination and CO2 cycloaddition with styrene oxide. Up to 6.93 s-1 4-chlorophenol hydrodechlorination TOF and obviously improved CO2 cycloaddition efficiency could be realized with Pd/SCNT-500. The improved photocatalytic efficiency should be related to the morphology and carbon vacancies based Pd coordination environment optimization. Such as, the surface area increased nanotubes structure promoted light harvesting along with photoelectrons and holes generation; the carbon vacancies improved excited electrons capture, photoinduced carriers recombination inhibition along with substrates adsorption with electron rich Pd NPs. Mechanism studies not only demonstrated the important role of atomic hydrogen and Pd coordination environment optimization in the chlorophenols hydrodechlorination, but also confirmed the promotion ability of photogenerated electrons on CO2 cycloaddition.

Ultrafast modulation of a THz metamaterial/graphene array integrated device

We report on the ultrafast modulation of a graphene loaded artificial metasurface realized on a SiO2/Si substrate by near-IR laser pump, detected via terahertz probe at the resonant frequency of ∼0.8 THz. The results have been acquired by setting the Fermi energy of graphene at the Dirac point via electrostatic gating and illuminating the sample with 40 fs pump pulses at different fluences, ranging from 0.9 to 0.018 mJ/cm2. The sub-ps conductivity rising time was attributed to the combined effect of the ultrafast generation of hot carriers in graphene and electron–hole generation in silicon. In correspondence of the resonance, it was possible to clearly distinguish a partial recovery time of ∼2 ps mainly due to carrier-phonon relaxation in graphene, superimposed to the > 1 ns recovery time of silicon. The resonant metasurface yielded ∼6 dB modulation depth in E-field amplitude at 0.8 THz for the range of fluences considered. These measurements set an upper limit for the reconfiguration speed achievable by graphene-based terahertz devices. At the same time, this work represents a great progress toward the realization of an ultrafast THz optoelectronic platform for a plethora of applications, ranging from the investigation of the ultrastrong light-matter regime to the next generation wireless communications.

Embedding anatase TiO2 nanoparticles into holely carbon nanofibers for high-performance sodium/lithium ion batteries

Titanium dioxide (TiO2) has been considered as a promising anode material for alkaline ion batteries (AIBs), yet the low electrical conductivity and sluggish reaction kinetics have restricted its practical applications, while rational structure design can significantly overcome these drawbacks. Herein, we report a one-step fabrication of ultrafine anatase TiO2 nanoparticles within holely carbon nanofibers (denoted as A-TiO2 @HCNFs) via a facile electrospinning method and subsequent annealing treatment. The chemical reaction between TEOS (Si(OC2H5)4) and PVDF ((CH2CF2)n) in the precursor induces the generation of numerous holes (via 4HF + SiO2 = SiF4↑+ 2 H2O) during the carbonization process by annealing in Ar at 800 °C, leading to the formation of holely structure and the suppression of the anatase-to-rutile phase transformation. When employed as anode materials for AIBs, the A-TiO2 @HCNFs exhibit a high sodium storage capacity of 206.8 mAh g−1 at 1.0 A g−1 after 500 cycles and a superior rate performance of 188.4 mAh g−1 at 5.0 A g−1, and a lithium storage capacity is 354.0/233.9 mAh g−1 at 0.2/1.0 A g−1 after 100/500 cycles with an excellent rate performance of 145.6 mAh g−1 at 5.0 A g−1. The superior electrochemical performance is related to the unique structure with integration of ultrafine anatase TiO2 nanoparticles and holely carbon nanofibers, which bring many advantages including improved electrical conductivity, sufficient reaction sites and robust structure stability.

Importance of valence-band anharmonicity and carrier distribution for third- and fifth-harmonic generation in Si:B pumped with intense terahertz pulses

We observe third-harmonic generation (THG) and fifth-harmonic generation (FHG) of free holes in the valence band of bulk Si:B at cryogenic temperature upon irradiation with intense terahertz pulses from a free-electron laser, polarized along the $\mathrm{\ensuremath{\Gamma}}\text{\ensuremath{-}}X$ direction. The intensities of both signals increase as a function of pulse energy following power laws with respective exponents of 4.2 and 6.2, larger than the exponents of 3 and 5 expected for ${\ensuremath{\chi}}^{(3)}$ and ${\ensuremath{\chi}}^{(5)}$ processes with constant susceptibilities and a fixed number of holes. The larger values are attributed to the increase in the density of mobile holes, which results from impact ionization of boron dopants by thermally activated holes in the electric field of the terahertz pulses as already observed in our studies of THG in Si:B reported in Phys. Rev. B 102, 075205 (2020). We apply Monte Carlo simulations of the nonlinear heavy- and light-hole field response, coupled with a finite-difference time-domain treatment of the pump-pulse propagation in the sample, which reproduce the experimental THG:FHG intensity ratio reasonably well. An analysis of the local response demonstrates that, in our pump regime, the harmonic generation is dominated by the band anharmonicity as opposed to the energy-dependent momentum scattering rates or interband scattering. Comparison with the results of a simple one-dimensional model and scrutiny of the three-dimensional band structure shows that one must account for the extent of the carrier distribution transverse to the $\mathrm{\ensuremath{\Gamma}}\text{\ensuremath{-}}X$ axis as the anharmonicity grows rapidly away from this axis.

Effects of non-standard interaction on microscopic black holes from ultra-high energy neutrinos

If the universe has more than 4-dimensions, the TeV scale gravity theories predict formation of microscopic black holes due to interaction of ultra high energy neutrinos coming from some extragalactic origin with the nucleons present in the Earth’s atmosphere. The decay of these black holes can generate high multiplicity events which can be detected through neutrino telescopes. Ultra high energy neutrinos can also produce events without the formation of black holes which can be distinguished from the black hole events depending on their topological structure. In this work we study the effects of non-standard interaction on the production of these shower events. We find that new physics has inconsequential impact on the number of events produced through the generation of black holes. For events produced without the formation of black holes, new physics can only provide a marginal deviation. Therefore a large enhancement in the number of shower events over the standard model prediction can provide unambiguous signatures of TeV scale gravity in the form of microscopic black hole production.

Static and fatigue testing of open-hole and assembled composites based on long carbon fiber and a nylon matrix developed using fused deposition modelling: Multiscale characterization of printed holes and machined holes

The three-dimensional printing of long fiber composites was developed in recent years, and the mechanical behavior of the printed composites requires further investigation. The joining of this type of material requires a hole; and with reference to the available literature, the bearing strength requires investigation. In this context, three manufacturing processes were used for hole generation: direct printing, conventional drilling, and abrasive waterjet drilling (AWJ). The holes obtained by these manufacturing processes were characterized using X-ray tomography and a roughness system. Open-hole quasi-static and fatigue tests were used to assess the mechanical behavior of hole manufacturing on the tensile sections. Single-shear bearing tests yielded the same trend as that observed with open holes, where conventional drilling demonstrated higher performance than the printed and AWJ specimens. The absence of delamination and higher drilling temperature sealed the surface, thus limiting the influence of voids.

Extracting hot holes from plasmonic semiconductors for photocatalysis

We achieved efficient hot hole collection via interfacing plasmonic CuS nanoplatelets with a suitable p-type semiconductor for the first time. The approach we applied was to rationally select a semiconductor (herein, BiOCl) such that it has a suitable band structure to prevent the hole loss from CuS in the dark, while allowing the hot hole injection from the plasmon-excited CuS under illumination. The resultant, efficient hot hole injection was then verified by our systematic measurements along with theoretical modelling. We showed that the transversal mode dominates the hot hole generation and has a greater contribution to photocatalysis than the longitudinal mode. We then elaborated on an optimal CuS/BiOCl composite configuration allowing for efficient hot hole collection in near-infrared photocatalysis. This work demonstrates the feasibility of harvesting hot holes from plasmonic semiconductors and opens a new route for the rational design of broadband and cost-effective plasmonic photocatalysts.

Optimization of growth parameters of AlN thin films and investigation of electrical and electroluminescence characteristics from Au/i-AlN/n-GaN UV light-emitting diode

Aluminum nitride (AlN) film has a wide range of applications optoelectronic devices. In this paper, AlN thin films were prepared by magnetron sputtering method, the influence of substrate temperature and nitrogen-argon ratio on the structure, morphology and optical properties of AlN films were evaluated by X-ray diffractometer, scanning electron microscope and ultraviolet–visible spectrophotometer. The analysis showed that the AlN film exhibited better crystallization quality under the substrate temperature of 350 °C with a nitrogen-argon ratio of 5:40. In addition, an Au/i-AlN/n-GaN metal–insulator-semiconductor (MIS) structure device was fabricated based on high-quality AlN films. The current–voltage and electroluminescence characteristics of the device under different temperatures were studied in detail. The results showed that the device exhibited excellent rectification behavior at all operating temperatures, producing an intense UV emission (∼372 nm). This paper proposes a hole generation model and a carrier transport and recombination mechanism. The research results provide a new reference for the practical application of AlN films.

Sonocatalytic degradation of ciprofloxacin by BiOBr/BiFeO3

A novel BiOBr/BiFeO3 heterojunction sonocatalyst was prepared and characterized. The sonocatalytic activity of BiOBr/BiFeO3 composite was evaluated by the catalytic degradation of ciprofloxacin. BiOBr/BiFeO3 composite combined with persulfate had excellent sonocatalytic activity for ciprofloxacin degradation under ultrasonic irradiation, and the degradation rate was 73.64% ± 7.96%. The formation of Z-type heterojunction of BiOBr/BiFeO3 and the generation of hydroxyl radical, superoxide anion and hole were the key to the catalytic activity of BiOBr/BiFeO3. Free radicals will attack the positions of piperazine ring, cyclopropyl, C-F bond, carboxyl group and ethylenic linkage in ciprofloxacin structure, and gradually degrade ciprofloxacin through multiple paths. After the sonocatalytic degradation, the bacteriostatic effect of the solution decreased significantly and the environmental pollution decreased significantly. As a sonocatalyst, BiOBr/BiFeO3 composite has good degradation and removal effect on ciprofloxacin and has practical application potential. Meanwhile, it lays a foundation for the further practical application of sonocatalytic degradation technology.

A Newly Developed Inverted Rotating Disk Electrode (IRDE) Setup for the Investigation of Photoelectrochemical Reactions

A new setup for an inverted rotating disk electrode (IRDE) was developed for the investigation of photoassisted or photoelectrochemical processes involving mass transfer reactions, as in electrodeposition or etching processes. In this setup, rotation of the disk electrode is achieved by magnetic coupling between a driver magnet (i.e. a magnetic stirrer) and the follower magnet included in the sample holder. For photoelectrochemical experiments, the cell allows a homogeneous illumination and removal of gaseous reaction products, while still providing leak tightness. In this way, controlled flow conditions are provided with the possibility to simultaneously illuminate the sample surface from a distance as small as 20 mm. At the same time gases formed during the reaction can easily ascend through the electrolyte.The light source is placed on top of the cell and illumination is done through the electrolyte. A low liquid level (≥ 15 mm) allows a small distance between the sample and the light source and therefore a high light intensity on the sample surface. Illumination is done using a high-power LED. Due to the high power, thermal effects need to be taken into consideration and especially an effective cooling of the LED is essential.As a wide band gap semiconductor, silicon carbide (SiC) has gained large interest due to its high chemical and physical stability. Since photoassisted anodic etching of n-type 4H silicon carbide in potassium hydroxide solutions [1] requires both UV illumination and the removal of gaseous reaction products, this reaction is investigated in the newly developed IRDE setup. Possible applications for such a process are defect decoration [2], trench etching, and dicing.Photoassisted anodic etching of n-type SiC occurs in three steps: (1) hole generation in the material through illumination with light with an energy higher than the bandgap of the semiconductor (2) oxidation of silicon and carbon through the holes driven to the semiconductor-electrolyte interface by an external potential and (3) dissolution of the oxidation products in the electrolyte. In accordance with the three steps of the reaction, different processes can be limiting: For low light intensities (either through a large distance between the sample and the LED or through low driving currents through the LED) the number of photon-induced holes is limiting. At low electrolyte concentrations, the transport of hydroxyl ions and the dissolution of the oxidation products determine the etch rate. For high light intensities and high electrolyte concentrations, the external potential and thereby the oxidation reaction are limiting for the overall current flow. These different reaction regimes can be distinguished in cyclic voltammetry measurements in the newly developed IRDE cell.[1] D. H. van Dorp und J. J. Kelly, „Photoelectrochemistry of 4H–SiC in KOH solutions,“ Journal of Electroanalytical Chemistry, Bd. 599, Nr. 2, pp. 260-266, 2007.[2] J. L. Weyher, S. Lazar, J. Borysiuk und J. Pernot, „Defect-selective etching of SiC,“ physica status solidi, Bd. 202, Nr. 4, pp. 578-583, 2005. Figure 1

(Digital Presentation) Finite Element Modeling of Thermoelectric Effects in Phase Change Memory Cells

Phase change memory (PCM) is a high-speed high-endurance non-volatile electronic memory technology which utilizes the electrical resistivity difference between the amorphous and the crystalline phases of phase change materials, such as Ge2Sb2Te5 (GST), to store information [1]. PCM cells are switched by short duration electrical pulses by melting a small volume to transition to dielectric amorphous phase (reset) or heating above glass-transition temperature to crystallize (set). The cells experience extremely large thermal gradients (~ 50 K/nm) and high current densities (~50 MA/cm2) during reset. Hence thermoelectric (TE) contributions are very significant both in bulk and at the material and solid-liquid interfaces [2]. In this work, we performed finite element simulations of mushroom PCM cells and analyzed contributions of Joule heating (symmetric) and thermoelectric heat (asymmetric) during reset and set operations using COMSOL Multiphysics. A field effect transistor (FET), modeled using a circuit model, is used as an access device. We self-consistently solve for current continuity, heat transport (Fig. 1) and phase changes in the materials, including temperature, electric-field and phase-dependent electrical and thermal conductivity, thermal boundary resistances and latent heat of fusion, along with temperature dependent stochastic nucleation, growth and grain-boundary amorphization, accounting for all energy exchanges [3-6].Thermoelectric heat exchanges are due to generation and recombination of electrons and holes as well as the kinetic energy absorbed or released by the transported free charge carriers [7]. These energy exchanges can take place at material interfaces (Peltier heat) or in bulk material (Thomson heat). Discontinuity of Seebeck coefficient and temperature (due to thermal boundary resistances) make TE contributions very significant in PCM devices.Our simulation results show the significance of the TE contributions on the reset behavior of PCM devices (Fig. 2). Self-heating at the bottom TiN-GST interface is substantially higher for one of the current polarities, giving rise to an over-sized mushroom in the case of negative polarity, for the same reset pulse amplitude. The negative polarity case (over-reset cell) cannot be set with the same set pulse as the positive polarity case. From the power consumption and peak current requirement point of view, it is advantageous to have higher TE heating inside the mushroom and its interfaces. TE cooling away from the mushroom interfaces is advantageous for reduced thermal cross-talk and write-disturb on the neighboring cells. However, thermal gradients also need to be kept under consideration for reliability perspective.Acknowledgement: Md Tashfiq Bin Kashem acknowledges support from General Electric through a Graduate Fellowship for Innovation. This work is supported through US National Science Foundation (NSF) award # 1710468.

Hole Trapping in Halide Perovskites Induces Phase Segregation

ConspectusMetal halide perovskites have garnered a great deal of attention for their applications in photovoltaics, LEDs, and radiation detection. The ease of solution processing high-quality perovskite semiconductors with large absorption coefficients and tolerance to native defects is decidedly attractive. Additionally, the ability to precisely tune the band gap of halide perovskites through compositional alloying of the halide ion is of particular interest for a range of applications, especially for tandem solar cells. However, under steady state light irradiation, an initially homogeneous mixed halide perovskite (MHP) will form local domains that are rich in one halide ion (e.g., Br or I). This light-induced phase segregation in MHPs forms iodide-rich domains that act as charge carrier traps and lowers the efficiency of perovskite-based devices. Thus, phase segregation poses a serious challenge to the implementation of MHPs in real-world device settings. Interestingly, when a phase segregated MHP film is placed in the dark, entropic driving forces become dominant and the segregated perovskite remixes and returns to its initially homogeneous state. Several key mechanistic details of phase segregation have been elucidated over the years. However, there are still aspects of halide segregation that are not clear, and there is ongoing debate in the literature as to what are the key factors that contribute to the mechanism.This Account discusses recent results that point to the specific role of hole trapping in phase segregation. Interestingly, generation of holes through above-band-gap excitation or through electrochemical injection increases ion migration and leads to phase segregation. The thermodynamic and redox properties of halide perovskites provide a strong driving force for hole trapping and oxidation of iodide species in MHPs. However, mobile halide species within the perovskite lattice take time to migrate and generate halide-rich domains. When in contact with a nonpolar solvent, the migration of iodine species is further extended to expulsion of iodine from the perovskite film. Thus, the mobility of halides and their susceptibility to hole-induced oxidation play a crucial role in determining the long-term stability of metal halide perovskites. Strategies to gain kinetic control over ion migration to slow phase segregation are needed to overcome these hurdles and achieve stable mixed halide perovskites. Modification of the perovskite composition through introduction of different cations or halide ions, or introduction of low-dimensional perovskite phases may suppress phase segregation. Thus, in achieving stability and improving the efficiency of perovskite solar cells and light emitting devices with minimal impacts, suppression of segregation remains the key factor.

One-Step Fabrication of Flower-Like ZnWO4/BiOBr Nanospheres with Enhanced Photocatalytic Degradation Efficiency

Flower-like zinc tungstate/bismuth bromate (ZnWO4/BiOBr) nanospheres were synthesized by a one-step hydrothermal method. The photocatalytic activity of the ZnWO4/BiOBr heterojunction was evaluated by the photocatalytic degradation of 30[Formula: see text]mg/L of rhodamine B (RhB). It was found that 10% of ZnWO4/BiOBr had the best degradation ability toward RhB. The degradation rate of RhB reached 97.7% (5 times and 358 times those of BiOBr and ZnWO4, respectively) after light-emitting diode (LED) visible light irradiation for 30[Formula: see text]min. The ZnWO4/BiOBr heterojunction had excellent photocatalytic activity because of its higher specific surface area and enhanced spectral response range. Moreover, the ZnWO4/BiOBr heterojunction improved the charge separation efficiency and promoted the generation of more holes, [Formula: see text] O[Formula: see text] and [Formula: see text] OH radicals under light irradiation; thus, improving the degradation efficiency. Finally, a possible photocatalytic degradation mechanism was proposed. This study provides a good reference for the preparation of bismuth-based composite photocatalysts for the degradation and purification of organic pollutants.

Drilling parameter optimization of cenosphere/HDPE syntactic foam using CO2 laser

High-density polyethylene is a high-strength, and low-weight material system. Besides numerous applications in a variety of fields and products, its machining for generation of holes is rather difficult with traditional methods such as drilling as the process is not very conducive for composites due to associated damage. Hence, a non-contact material removal process such as laser machining provides an appealing, cost-effective, accurate, and fast alternative. For this study, the effect of the laser process controls key parameters such as laser power and laser speed on the cut surface integrity defined by surface roughness, kerf taper angle, and heat-affected zone of neat HDPE and HDPE with 60 wt% cenosphere was investigated and optimized using response surface methodology. Also, the machining operation was visualized using a Photron FASTCAM SA 1.1 high-speed camera to observe the effects of the high-intensity laser beam on specimens and to investigate the mechanism of laser machining. The optimum values for a defect-free cut surface (minimum surface roughness and low kerf taper angle) in neat HDPE comes out to be as laser power of 97.5 W and laser speed of 5 mm/s, with corresponding surface roughness and kerf taper angle of 54.304 μm and 0.152 degrees respectively and the optimum input values for HDPE with 60 wt% cenosphere are 102.126 W laser power and 5 mm/s laser speed, with corresponding surface roughness and kerf taper angle of 26.574 μm and 0.253 degrees. This study finds importance for the industrial and medical application to creates small size holes for mechanical joints such as rivets, bolts, and screws in assembly as low surface roughness and kerf width are always preferred as quality parameters in creating holes for industrial applications.

Plasmon-induced super-semiconductor at room temperature in nanostructured bimetallic arrays

Solid-state electrical conducting materials can be roughly categorized as superconductors, conductors, and semiconductors, depending on their conducting carriers, resistance, and band structures. This research reports the discovery of super-semiconductors, whose resistivity is 3–10 orders of magnitude lower than conventional semiconductors at room temperature. In addition, there is a transition from a metal state to a super-semiconducting state at near room temperatures, which is accompanied by an increase in hole carrier density and the mobility increase in electrons. For the first time, a hole-dominated carrier metal is observed in nanostructured bimetallic arrays near room temperature, and no other special conditions are required. Such a behavior is due to the generation of hot electrons and holes induced by metal plasmon resonance in the infrared range in the nanostructured bimetallic arrays. Our research empowers metals with semiconductor features and paves the way to realize ultra-low-power metal-based semiconductor devices.

Study on practical application for in-process blowholes detection technology

For the development of in-process blowholes detection and prediction technology, a welding system with an infrared camera and welding robot was integrated and the authors verified the detection of welding phenomena directly associated with the occurrence of blowholes. In addition, an image analysis index for welding defect detection and prediction was considered. It was clarified that it is possible to observe the bubbling phenomena just under the arc due to the blow hole generation by the welding system. In addition, it was considered possible to detect and predict the occurrence of blowholes with high accuracy by analyzing the observation frequency of the bubble generation phenomenon directly under the arc with an appropriate index.

Negative Gate Bias Induced Dynamic ON-Resistance Degradation in Schottky-Type p-Gan Gate HEMTs

In this article, the impacts of the <small>off</small>-state gate bias (<i>V</i>_GS,OFF) on dynamic <small>on</small>-resistance (<i>R</i>_ON) are systematically investigated in commercial Schottky-type <i>p</i>-GaN Gate high-electron-mobility transistors. Double-pulse tester and pulsed <i>I</i>&#x2013;<i>V</i> system are adopted to evaluate the dynamic <i>R</i>_ON with various <small>off</small>-state gate and drain bias (<i>V</i>_DS,OFF) under hard- and soft-switching conditions. More negative <i>V</i>_GS,OFF can aggravate the dynamic <i>R</i>_ON degradation under both soft- and hard-switching, especially when switching with a high <i>V</i>_DS,OFF. The impacts of <i>V</i>_GS,OFF on switching transients and <small>off</small>-state stress are investigated separately to reveal the underlying mechanisms, which are found to be associated with the generation and movements of holes. The <small>off</small>-state gate bias of the voltage-driving scheme needs to be carefully considered according to the identified mechanisms in terms of dynamic <small>on</small>-resistance degradation.

Implications of stochastic effects for primordial black hole production in ultra-slow-roll inflation

We study the impact of stochastic noise on the generation of primordial black hole (PBH) seeds in ultra-slow-roll (USR) inflation with numerical simulations. We consider the non-linearity of the system by consistently taking into account the noise dependence on the inflaton perturbations, while evolving the perturbations on the coarse-grained background affected by the noise. We capture in this way the non-Markovian nature of the dynamics, and demonstrate that non-Markovian effects are subleading. Using the ΔN formalism, we find the probability distribution P(ℛ) of the comoving curvature perturbation ℛ. We consider inflationary potentials that fit the CMB and lead to PBH dark matter with i) asteroid, ii) solar, or iii) Planck mass, as well as iv) PBHs that form the seeds of supermassive black holes. We find that stochastic effects enhance the PBH abundance by a factor of \U0001d4aa(10)–\U0001d4aa(108), depending on the PBH mass. We also show that the usual approximation, where stochastic kicks depend only on the Hubble rate, either underestimates or overestimates the abundance by orders of magnitude, depending on the potential. We evaluate the gauge dependence of the results, discuss the quantum-to-classical transition, and highlight open issues of the application of the stochastic formalism to USR inflation.

Optical black hole characteristics using microring space‐time distortion circuit

AbstractAn optical black hole circuit designing and modeling using microring Kerr effect within the microring resonator system is proposed. An InGaAsP/InP material other than metamaterials are employed for optical black hole generation. The input sources are the space‐time function modulations, where the resonant space‐time distortion of the electric field propagation through the circuit can be arranged to meet the balanced optical path differences. The nonlinearr Kerr effect can be generated by the two side rings and induced into the center ring. The optical black hole circuit characteristics are investigated from the event horizon to the singularity area, where the potential for a high‐performance light absorber can be envisaged. In applications, the device can be employed in photovoltaics and quantum technology.

Highly amidoxime utilization ratio of porous poly(cyclic imide dioxime) nanofiber for effective uranium extraction from seawater

Fibrous adsorption material with amidoxime (AO) group is widely considered as the most prospect of industrial application in uranium (U) extraction from seawater. However, the challenge of the AO-based adsorbents is that the utilization of AO has encountered bottle-neck of less than 1/100, which is far from saturated for decades. Herein, we construct porous structure in raspberry-like nanofibers (NFs) with rearranged AO groups cyclic imide dioxime (CID) nanoparticles (CID NFs) to improve the AO utilization ratio during U adsorption. By adjusting the size of the CID nanoparticles in NF, the area of the functional groups can be maximum exposed, which resulted in a breakthrough of the AO utilization ratio with high adsorption capacity. In simulated seawater with a U concentration of 330 ppb, the highest AO utilization ratio can reach 1/31. After adsorption in natural seawater for 87 days, the adsorption capacity of U was determined to be 11.39 mg-U/g-ads with AO utilization ratio of 1/74. Furthermore, extended X-ray absorption fine structure (EXAFS) fits and nuclear magnetic resonance (NMR) spectra suggested that the mechanism of AO bind uranyl ion was a tridentate binding model with CID. Density functional theory (DFT) computational studies proved that the tridentate binding model was the most stable combination. Positron annihilation lifetime spectroscopy (PALS) found that the generation of smaller free-volume holes in CID NFs have a certain cooperative binding in space on U adsorption. The CID NFs with unique nano morphology, and special CID chemical structure provide a new idea and potentiality for a novel design of U adsorbents in future U extraction from seawater.