Trapping Properties Research Articles

Supramolecular Modulation for Selective Mechanochemical Iron‐Catalyzed Olefin Oxidation

AbstractThe development of a mechanochemical Fe‐catalyzed Wacker oxidation of olefins with a sustainable and benign procedure holds significant promise for industrial applications. However, navigating the intricate interactions inherent in ball‐milling conditions to fine‐tune reaction selectivity remains a formidable challenge. Herein, leveraging the dispersive and/or trapping properties of cyclodextrins, an innovative mechanochemical approach is developed through the integration of cyclodextrins into a Fe‐catalyzed system, enabling a streamlined Wacker oxidation process from simple and/or commercially available alkenes. Our efforts have yielded optimized mechanochemical conditions demonstrating exceptional reactivity and selectivity in generating a diverse array of ketone products, markedly enhancing catalytic efficiency compared to conventional batch methods. Mechanistic investigations have revealed a predominantly Markovnikov‐selective catalytic cycle, effectively minimizing undesired alcohol formation, hydrogenation, and the other competing pathways, boosting both reaction yield and selectivity.

Supramolecular Modulation for Selective Mechanochemical Iron-Catalyzed Olefin Oxidation.

The development of a mechanochemical Fe-catalyzed Wacker oxidation of olefins with a sustainable and benign procedure holds significant promise for industrial applications. However, navigating the intricate interactions inherent in ball-milling conditions to fine-tune reaction selectivity remains a formidable challenge. Herein, leveraging the dispersive and/or trapping properties of cyclodextrins, an innovative mechanochemical approach is developed through the integration of cyclodextrins into a Fe-catalyzed system, enabling a streamlined Wacker oxidation process from simple and/or commercially available alkenes. Our efforts have yielded optimized mechanochemical conditions demonstrating exceptional reactivity and selectivity in generating a diverse array of ketone products, markedly enhancing catalytic efficiency compared to conventional batch methods. Mechanistic investigations have revealed a predominantly Markovnikov-selective catalytic cycle, effectively minimizing undesired alcohol formation, hydrogenation, and the other competing pathways, boosting both reaction yield and selectivity.

Water ice particles detected by SELENE's Spectral Profiler at lunar shadowed regions in various local times and latitudes

Processes of water (OH and H2O) migration on the Moon remain unclear, prompting active research. Understanding lunar water migration requires investigation of the trapping and diffusion properties of water at various latitudes and local times. This study analyzed visible to near-infrared spectral data obtained by the Spectral Profiler (SP) onboard SELENE for shadowed regions at various local times and latitudes, not limited to the polar permanently shadowed regions. We assessed SP data for shadowed regions in 60 areas, each spanning a 10° × 10° latitude–longitude grid. Of the 1,061,907 analyzed shadowed-region data, 41,385 at various latitudes exhibited significant absorption in the 1.25 and 1.5 µm bands, indicating water ice particles. Data with the two absorption features suggest the presence of a water ice frost layer covering the lunar surface or suspended water ice particles above the lunar surface, at various latitude shadowed regions. Our spectral simulations have quantified the ice particles as being 0.1–1 µm in diameter, with a column density of 10–4–10–3 kg/m2. The spectral parameters for band absorption at the 1.5 µm band show symmetry between morning and evening sides, which is potentially attributed to the absence of variations in ice grain size and quantity. The 1.5 µm band absorption shows an increasing trend toward terminator regions, indicating variation in the water ice distribution and likely reflecting temperature conditions for water retention. The latitudinal trend of ice grain size and quantity remains uncertain because of the observed noise levels. Observations of water ice particles in shadowed regions at various latitudes and local times can provide new constraints on trapping and diffusion processes of lunar water migration.

Excellent field–trapping properties of large ring–shaped REBCO melt–textured bulks fabricated by the single–direction melt growth (SDMG) method

Abstract Ring-shaped homogeneous YBCO and DyBCO bulks were successfully fabricated using the Single-Direction Melt Growth (SDMG) method. The bulks were directly grown from ring-shaped compacted powder using ring-shaped molds with an outer diameter of 50 mm and inner diameters of 15, 20, and 25 mm. The ring-shaped bulks exhibited high trapped fields inside the rings up to 1.2 T at 77 K. Analyses of trapped field distributions revealed uniform current density distributions along the orbital direction. Stacked ring bulks demonstrated even higher trapped fields, reaching 2.0 T at 77 K. It was confirmed for the stacked bulks that time-independent uniform trapped fields can be achieved by magnetizing at lower fields than fully magnetizing conditions. Observed paramagnetic magnetization of the SDMG-processed YBCO bulk was negligibly small below the detection limit, which is considered to be more suitable for bulk NMR/MRI applications than DyBCO. Additionally, we proposed a method to quantitatively evaluate trapped fields of superconducting bulks with various diameters and thicknesses, where the estimated average current densities from the maximum trapped fields for all the obtained ring-shaped bulks were above 104 A/cm2 at 77 K. These results indicate that SDMG is an effective method for fabricating high-quality, large-scale ring-shaped bulks with superior field-trapping properties.

Electron trapping in HfO2 layer deposited over a HF last treated silicon substrate

Electron trapping in HfO2-based MOS structures was studied through pulsed capacitance-voltage (C-V) technique. 10 nm HfO2 layer was deposited by atomic layer deposition over a HF last treated Si substrate. The C-V curves were observed to shift to positive voltages driven by the positive applied voltage along the pulses, consistent with electron trapping due to tunneling transitions between the substrate and pre-existing defects within the oxide and the subsequent lattice relaxation through electron-phonon interaction. The dependences of the voltage shift for a given capacitance value (ΔVC) with stress bias and time, allowed to distinguish two mechanisms. An initial trapping process occurs for times shorter than the microsecond, probably associated with a thin non-stoichiometric SiOx interfacial layer, which is followed by a trapping process that starts after tens of μs and progressively slowed down, associated with traps within the HfO2 layer. Numerical simulations yield for the HfO2 traps an energy of 1.3 eV below the conduction band edge, decreasing exponentially with the distance from the Si interface with a characteristic length of 1.7 nm; and phonon and relaxation energies of 50 meV and 1 eV, respectively. These physical parameters are consistent with previous reports of electron trapping in HfO2 layers deposited on a controlled interfacial layer, suggesting that trapping properties of defects inside the HfO2 layer are insensitive to the treatment of the Si surface before HfO2 deposition. On the other hand, the observed large initial trapping suggests that the non-controlled SiOx interfacial region is more defective than a controlled one.

The surface electron transfer strategy promotes the hole of PDI release and enhances emerging organic pollutant degradation

In semiconductor photocatalysts, the easy recombination of photogenerated carriers seriously affects the application of photocatalytic materials in water treatment. To solve the serious problem of electron−hole pair recombination in perylene diimide (PDI) organic semiconductors, we loaded ferric hydroxyl oxide (FeOOH) on PDI materials, successfully prepared novel FeOOH@PDI photocatalytic materials, and constructed a photo-Fenton system. The system was able to achieve highly efficient degradation of BPA under visible light, with a degradation rate of 0.112 min−1 that was 20 times higher than the PDI system, and it also showed universal degradation performances for a variety of emerging organic pollutants and anti-interference ability. The mechanism research revealed that the FeOOH has the electron trapping property, which can capture the photogenerated electrons on the surface of PDI, effectively reducing the compounding rate of photogenerated carriers of PDI and accelerating the iron cycling and H2O2 activation on the surface of FeOOH at the same time. This work provides new insights and methods for solving the problem of easy recombination of carriers in semiconductor photocatalysts and degrading emerging organic pollutants.

Construction of Moiré-like TiO2/polypyrrole electrodes for high performance photo-assisted supercapacitors

There is currently a need for research into using external energy to increase the performance of the supercapacitor in energy storage systems because of their poor energy density. This paper reports the effective creation of photo-assisted supercapacitors with moiré-like morphology using polypyrrole (PPy) and titanium dioxide nano powder to replicate the surface of inexpensive and widely available CD discs. The composite material combines the moiré-like superstructure's strong light trapping property with titanium dioxide's high photo-sensitivity, achieving the aims of boosting light absorption, extending the optical route, and improving capacitor performance under light. By combining morphology construction and external energy interventions to improve capacitor performance, the specific capacitance under light is 509.0 F g−1 at 1 A g−1, 13.1 % higher than the same material without moiré-like morphology (449.9 F g−1). When assemble into a sandwich-structured symmetric supercapacitor, it has an area specific capacitance of 99.42 mF cm−2 and an energy density of 7.28 Wh kg−1 at a power density of 217.4 W kg−1, outperforming typical photo-assisted supercapacitors. The current work suggests a practical and straightforward method for increasing the light absorption efficiency and performance of photo-assisted supercapacitors.

Photo-Thermal Conversion and Raman Sensing Properties of Three-Dimensional Gold Nanostructure.

Three-dimensional plasma nanostructures with high light-thermal conversion efficiency show the prospect of industrialization in various fields and have become a research hotspot in areas of light-heat utilization, solar energy capture, and so on. In this paper, a simple chemical synthesis method is proposed to prepare gold nanoparticles, and the electrophoretic deposition method is used to assemble large-area three-dimensional gold nanostructures (3D-GNSs). The light-thermal water evaporation monitoring and surface-enhanced Raman scattering (SERS) measurements of 3D-GNSs were performed via theoretical simulation and experiments. We reveal the physical processes of local electric field optical enhancement and the light-thermal conversion of 3D-GNSs. The results show that with the help of the efficient optical trapping and super-hydrophilic surface properties of 3D-GNSs, they have a significant effect in accelerating water evaporation, which was increased by nearly eight times. At the same time, the three-dimensional SERS substrates based on gold nanosphere particles (GNSPs) and gold nanostar particles (GNSTs) had limited sensitivities of 10-10 M and 10-12 M to R6G molecules, respectively. Therefore, 3D-GNSs show strong competitiveness in the fields of solar-energy-induced water purification and the Raman trace detection of organic molecules.

A method to obtain the trapping energy and trapping range between hydrogen and defects at finite temperature

The binding energy between hydrogen (H) and defects in solid phase materials has been widely studied, which is of vital importance to understand the H retention effects and defect growth mechanisms. However, present studies of binding energy through density functional theory (DFT) or the molecular statics (MS) method were usually performed at 0 K, which could not take the influence of entropy into consideration. In this work, a thermodynamic method has been proposed to obtain the trapping energy between H and defects at finite temperatures. The method is based on the rate theory, which uses trapping energy (V) and trapping range (δ) to describe the trapping properties of defects. Ultimately, a parameterized H spatial cumulative distribution function at thermodynamic equilibrium state could be given. The trapping energy and trapping range parameters in the function can be determined by contrast with the results obtained from molecular dynamics or other methods. This method has been applied to calculate the trapping energies and trapping ranges of H to helium bubble and grain boundary, respectively. Further discussion has been made on the discrepancy between trapping energies obtained by this method and the conventional DFT/MS method.

A numerical approach to levitated superconductors and its application to a superconducting cylinder in a quadrupole field

Abstract Magnetically levitated superconductors in the Meissner state can be utilized as micro-mechanical oscillators with large mass, high quality factors and long coherence times. In previous works analytical solutions for the magnetic field distribution around a superconducting sphere in a quadrupole field have been found and used to derive the trap parameters, while non-spherical geometries have only been investigated in a few idealized cases. However, superconductors of almost arbitrary shape can be used as levitators in a magnetic trap and, as the trap’s properties depend strongly on the superconductor’s shape, allow for a wider parameter regime to be accessed. Finite element models are suitable to obtain the field distribution around arbitrarily shaped superconductors in arbitrary fields, but have not yet been used widely in the context of levitated superconductors. Here we present a simple numerical model for this purpose and use it to calculate the field distribution around cylindrical superconductors in a quadrupole field and to evaluate the trap parameters. We find that the cylindrical shape, compared to spherical levitators, allows for substantially higher trap frequencies and coupling strengths. This in turn reduces the demands on vibration isolation and significantly eases the requirements for feedback cooling to the ground state. The numerical model is provided in a file repository and can easily be adapted to various geometries and trap fields.

Modulating trap properties by Cr3+-doping in Zn2SiO4: Mn2+ nano phosphor for optical information storage

Photo-stimulated luminescent materials are one of the most attractive alternatives for next-generation optical information storage technologies. However, there are still some challenges in regulating appropriate energy levels of traps in luminescent materials for optical information storage. Herein, a green emission nanophosphor Zn2SiO4: Mn2+, Cr3+ with the trap depth of 1.05 eV, fulfilling the requirements for optical information storage, was fabricated for the first time through the solution combustion method and subsequent heat treatment at 1000 °C for 2 h. The crystal structure, micromorphology, photoluminescence (PL), photoluminescence excitation (PLE), and afterglow properties of Zn2SiO4: Mn2+, Cr3+ were studied systematically. By applying the strategy of trap depth engineering, high trap density with proper trap depth was observed when Cr3+ ions were introduced into Zn2SiO4: Mn2+. Thermoluminescence (TL) glow-curve analysis through the initial rise (IR) method was conducted to gain some insights into the information of traps. As proof of application, optical information storage was experimentally achieved by choosing 275 nm illumination for “information writing” and 980 nm NIR excitation for “information reading”. The results indicate that Zn2SiO4: Mn2+, Cr3+ phosphor holds promise for potential applications in the field of optical information storage.

Investigating the role of palladium electrical contacts in interactions with carbyne nanomaterial solid matter

Introduction: Traps at the interface between carbyne and palladium nanocoatings, produced at different growth conditions, are explored by current-voltage characteristics, scanning electron microscopy and thermal stimulation of charges for evaluation of their nature. It was found that the Pd films can form an Ohmic contact with the carbyne at certain deposition conditions and such deviated from the Ohmic behavior according to the RF sputtering voltage. This growth parameter was found to affect the interfacial traps formation on the carbyne surface, which is important feature for the charge trapping and releasing properties for hydrogen isotopes in the context of the energy release applications.Methods, Results and Discussion: The sputtering voltages of 0.5 kV and 0.7 kV were found unsuitable for controlled trap formation. Based on the currentvoltage and thermally stimulated current (TSC) measurements, a sputtering voltage of 0.9 kV appeared to be more favorable compared to 0.5 kV and 0.7 kV. At 0.9 kV thermal activation of charge carriers are enabled at lower thermal energies, showing a distinct change in TSC behavior correlated to trap activation.

Effect of pore structure regulation on the properties of 3D cellulose nanofiber electret filtration materials

The properties, electret property and purification performance, of electret filter materials are closely associated with its pore structure, but the effect mechanism of pore structure on its electret property has not been clarified. Herein, the pore structure of 3D electret fiber materials which were prepared by freeze-drying technology and corona polarization technology based on dialdehyde cellulose nanofibers (DAMCC) and ethyl cellulose nanofibers (EC) was regulated by changing the DAMCC/EC mass ratio, solvent system, pre-freezing temperature and fiber concentration to explore the influence of pore structure on its electret properties and purification performance. The results show that the charge trapping and storage properties can be altered by the regulation of pore structure, and the 3D fiber material, prepared under the conditions of DAMCC/EC nanofiber mass ratio of 1/2, TBA content of 10 %, pre-freezing temperature of −40 °C and fiber concentration of 1.5 w/v%, presents a cellular porous structure with a complete fiber mesh wall. This structure is not only beneficial to the migration of space charge to the interior of the fiber material, but also can effectively prevent the escape behavior of space charge inside the material by extending the tortuous pore channel length, thereby improving the initial and stable surface potentials from 0.72 kV and 0.02 kV to 1.19 kV and 0.47 kV respectively. Moreover, the purification time of 3D electret fiber materials can be reduced from 51 min to 13 min owe to the improvement of electret property and pore structure. These will provide guidance for the investigation of pore structure regulation to alter the properties of electret fiber material for air purification.

Tunable plasmonic tweezers based on nanocavity array structure for multi-site nanoscale particles trapping

The ability of plasmonic optical tweezers based on metal nanostructure to stably trap and dynamically manipulate nanoscale objects at low laser power has been widely used in the fields of nanotechnology and life sciences. In particular, their plasmonic nanocavity structure can improve the local field intensity and trap depth by confining electromagnetic fields to subwavelength volumes. In this paper, the R6G dye molecules with 10−6 M were successfully trapped by using the Ag@Polydimethylsiloxane nanocavity array structure, and a R6G micro-ring was formed under the combined action of plasmonic optical force and thermophoresis. Subsequently, the theoretical investigation revealed that the trapping performance can be flexibly adjusted by changing the structural parameters of the conical nanocavity unit, and it can provide a stable potential well for polystyrene particles of RNP = 14 nm when the cavity depth is 140 nm. In addition, it is found that multiple trapping sites can be activated simultaneously in the laser irradiation area by investigating the trapping properties of the hexagonal conical nanocavity array structure. This multi-site stable trapping platform makes it possible to analyze multiple target particles contemporaneously.

Modelling neutron damage effects on tritium transport in tungsten

A damage-induced hydrogen trap creation model is proposed, and parameters for tungsten are identified using experimental data. The methodology for obtaining these parameters using thermo-desorption analysis spectra data is outlined. Self-damaged and optionally annealed tungsten samples have undergone TDS analysis, which has been analysed to identify the properties of extrinsic traps induced by the damage and to determine how they evolve with damage and annealing temperature. A parametric study investigated the impact of the damage rate and temperature on tritium inventories in tungsten. Tritium transport simulations have been performed with FESTIM considering a 1D model of a 2 mm sample of tungsten with damage rates and temperatures varying from 0– 102 dpa/fpy and 600–1300 K, respectively. The results show that after 24 h simultaneous exposure to neutron damage at 102 dpa/FPY and tritium implantation at 700 K, tritium inventories can increase by up to four orders of magnitude when damaged at a rate of 102 dpa/FPY compared to undamaged, defect-free tungsten, increasing further to five orders of magnitude after one full power year. The time taken to reach retention saturation shows the need for kinetic models of trapping properties on time scales relevant to reactor operation. The trap-creation model parameterisation procedure can be used to investigate neutron damage effects on other fusion-relevant materials such as EUROFER, Inconel and more.

Microfluidic Platform with Precisely Controlled Hydrodynamic Parameters and Integrated Features for Generation of Microvortices to Accurately Form and Monitor Biofilms in Flow.

Microorganisms often live in habitats characterized by fluid flow, and their adhesion to surfaces in industrial systems or clinical settings may lead to pipe clogging, microbially influenced corrosion, material deterioration, food spoilage, infections, and human illness. Here, a novel microfluidic platform was developed to investigate biofilm formation under precisely controlled (i) cell concentration, (ii) temperature, and (iii) flow conditions. The developed platform central unit is a single-channel microfluidic flow cell designed to ensure ultrahomogeneous flow and condition in its central area, where features, e.g., with trapping properties, can be incorporated. In comparison to static and macroflow chamber assays for biofilm studies, microfluidic chips allow in situ monitoring of biofilm formation under various flow regimes and have better environment control and smaller sample requirements. Flow simulations and experiments with fluorescent particles were used to simulate bacteria flow in the platform cell for calculating flow velocity and direction at the microscale level. The combination of flow analysis and fluorescent strain injection in the cell showed that microtraps placed at the center of the channel were efficient in capturing bacteria at determined positions and to study how flow conditions, especially microvortices, can affect biofilm formation. The microfluidic platform exhibited improved performances in terms of homogeneity and robustness for in vitro biofilm formation. We anticipate the presented platform to be suitable for broad, versatile, and high-throughput biofilm studies at the microscale level.

Enhanced trapping properties of coupled plasmonic tweezers via plasmon-exciton interaction.

Excited plasmonic nanoantennas enable the manipulation of photons coupled with quantum emitters or the trapping of particles as plasmonic tweezers, leveraging the strong evanescent gradient fields at the nanoscale. However, the ohmic loss of metals presents a significant challenge for the stable and high-precision manipulation of nanoparticles without causing damage. In this study, we investigated the enhanced trapping properties induced by plasmon-exciton interaction for coupled plasmonic tweezers. Through the coupling between plasmons and excitons, dynamic particle trapping is achievable under low excitation power conditions of 0.45 mW, with the trapping stiffness increasing by nearly 20 times. Furthermore, the trapping stiffness can be fine-tuned by modulating the quantity of excitons to regulate the coupling strength. Coupled plasmonic tweezers offer an effective strategy to mitigate the influence of ohmic loss on trapping performance, by manipulating particles with minimal laser power. These findings provide insights into enhancing trapping performance through plasmon-exciton coupling, with potential applications in biomedicine and quantum information science.

Novel one-dimensional/two-dimensional composite films: Ag nanowires/ZnO nanowalls

We synthesized novel Ag nanowires/ZnO nanowalls composite films successfully, which integrated the beneficial characteristics of one-dimensional Ag nanowires and two-dimensional ZnO nanowalls. And the resulting Ag nanowires/ZnO nanowalls composite films exhibited outstanding photoelectric properties and enhanced light trapping abilities. The evenly distributed and interlaced Ag nanowires/ZnO nanowalls composite structures were clearly observed. By measuring the total transmittance (TT), diffuse transmittance (DT) and sheet resistance of the composite films, it can be seen that the haze value at 550 nm is 0.26, and the sheet resistance value is 42.5 Ω/sq. These indicated that the photoelectric and light trapping properties of the Ag nanowires/ZnO nanowalls composite films were enhanced significantly compared with those of the simplex films.

Sub-bandgap photo-response of black silicon fabricated by femtosecond laser irradiation under water

Here we propose a method to fabricate black Si without the need for any chalcogenide doping, accomplished by femtosecond (fs) laser irradiation in a liquid environment, aiming to fabricate the infrared detector and investigating their optoelectronic performance. Multi-scale laser-induced periodical surface structures (LIPSSs), containing micron sized grooves decorated with low spatial frequency ripples on the surface, can be clearly observed by SEM and 3D confocal microscope. The generated black Si demonstrates superior absorption capabilities across a broad wavelength range of 200-2500 nm, achieving an average absorptance of up to 71%. This represents a notable enhancement in comparison to untreated Si, which exhibits an average absorption rate of no more than 20% across the entire detectable spectrum. A metal-semiconductor-metal (MSM) type photodetector was fabricated based on this black Si, demonstrating remarkable optoelectronic properties, specifically, it attains a responsivity of 50.2 mA/W@10 V and an external quantum efficiency (EQE) of 4.02% at a wavelength of 1550 nm, significantly outperforming the unprocessed Si by more than five orders of magnitude. The great enhancement in infrared absorption as well as the optoelectronic performance can be ascribed to the synergistic effect of the multi-scale LIPSSs and the generated intermediate energy levels. On one hand, the multi-scale structures contribute to an anti-reflection and light trapping property; on the other hand, the defects levels generated through fs laser ablation process under water may narrow the band gap of the Si. The results therefore underscore the remarkable potential of black Si processed by fs laser under water for the application of photodetection, especially in the near-infrared band.

Red Persistent Luminescence and Trap Properties of Mg2SiO4: Mn2+, M3+ (M3+ = B3+; Al3+; Ga3+; In3+) Material

Abstract Persistent luminescence (PersL), also called long-lasting phosphorescence or simply afterglow, is a luminescence characterised by the emission of radiation from a few seconds to several days after the excitation source has been switched off. Over the past two decades, research on PersL materials, both in fundamental and applied physics, has developed rapidly; however, the explanation for the physical processes that cause afterglow still needs to be clarified. Today, PersL materials are used mainly for luminescent paints, safety signs and decorations. At the same time, research into using such materials in medicine, information storage, anti-counterfeiting technology, etc., is underway. Currently, information on the long persistent luminescence materials with emission in the blue and green spectral range is widely available. In contrast, the number of publications on the afterglow in the red and near-infrared spectral range is considerably lower. Within the framework of this research, Mg2SiO4: Mn2+; M3+ (M3+ = B3+; Al3+; Ga3+; In3+) materials were synthesised using solid state reaction synthesis. When excited with X-rays, the materials exhibited a broad Mn2+ PersL band with two maxima at approximately 625 nm and 730 nm. After cessation of irradiation, an afterglow of at least 6 hours could be observed. The research focuses on the trap properties of the materials. It was concluded that at least three discrete trap levels with activation energies approximately between 0.4–1.6 eV were present in the samples. Additionally, co-doping with Al3+; Ga3+; In3+ ions improved PersL longevity of the Mg2SiO4: Mn2+ material.