Fluorinated organic ammonium salt passivation for high-efficiency and stable inverted CsPbI2Br perovskite solar cells.

All-inorganic CsPbI2Br inverted perovskite solar cells (PSCs) have drawn increasing attention because of their outstanding thermal stability and compatible process with tandem cells. However, relatively low open circuit voltage (Voc) has lagged their progress far behind theoretical limits. Herein, we introduce phenylmethylammonium iodide and 4-trifluoromethyl phenylmethylammonium iodide (CFPMAI) on the surface of a CsPbI2Br perovskite film and investigate their passivation effects. It is found that CFPMAI with a -CF3 substituent significantly decreases the trap density of the perovskite film by forming interactions with the under-coordinated Pb2+ ions and effectively suppresses the non-radiative recombination in the resulting PSC. In addition, CFPMAI surface passivation facilitates the optimization of energy-level alignment at the CsPbI2Br perovskite/[6,6]-phenyl C61 butyric acid methyl ester interface, resulting in improved charge extraction from the perovskite to the charge transport layer. Consequently, the optimized inverted CsPbI2Br device exhibits a markedly improved champion efficiency of 14.43% with a Voc of 1.12 V, a Jsc of 16.31 mA/cm2, and a fill factor of 79.02%, compared to the 10.92% (Voc of 0.95 V) efficiency of the control device. This study confirms the importance of substituent groups on surface passivation molecules for effective passivation of defects and optimization of energy levels, particularly for Voc improvement.

Nanometer-Resolved Mapping of Organic Cation Migration Behavior in Methylammonium Lead Halide Perovskites.

The performance and stability of organic metal halide perovskite (OMHP) optoelectronic devices have been associated with ion migration. Understanding of nanoscale resolved organic cation migration mechanism would facilitate structure engineering and commercialization of OMHP. Here, we report a three-dimensional approach for in situ nanoscale infrared imaging of organic ion migration behavior in OMHPs, enabling to distinguish migrations along grain boundary and in crystal lattice. Our results reveal that organic cation migration along OMHP film surface and grain boundaries (GBs) occurs at lower biases than in crystal lattice. We visualize the transition of organic cation migration channels from GBs to volume upon increasing electric field. The temporal resolved results demonstrate the fast MA+ migration kinetics at GBs, which is comparable to diffusivity of halide ions. Our findings help understand the role of organic cations in the performance of OMHP devices, and the proposed approach holds broad applicability for revealing migration mechanisms of organic ions in OMHPs based optoelectronic devices.

Progress and Prospects in Metallic FexGeTe2 (3 ≤ x ≤ 7) Ferromagnets.

Thermal fluctuations in two-dimensional (2D) isotropy systems at non-zero finite temperatures can destroy the long-range (LR) magnetic order due to the mechanisms addressed in the Mermin-Wanger theory. However, the magnetic anisotropy related to spin-orbit coupling (SOC) may stabilize magnetic order in 2D systems. Very recently, 2D FexGeTe2 (3 ≤ x ≤ 7) with a high Curie temperature (TC) has not only undergone significant developments in terms of synthetic methods and the control of ferromagnetism (FM), but is also being actively explored for applications in various devices. In this review, we introduce six experimental methods, ten ferromagnetic modulation strategies, and four spintronic devices for 2D FexGeTe2 materials. In summary, we outline the challenges and potential research directions in this field.

Enhanced saturation magnetization in buckypaper-films of thin walled carbon nanostructures filled with Fe3C, FeCo, FeNi, CoNi, Co and Ni crystals: the key role of Cl.

We report an advanced chemical vapour deposition approach which allows the direct in situ synthesis of cm-length ultrathin buckypapers comprising carbon nanostructures filled with Fe3C, FeCo, FeNi, CoNi, Co and Ni by sublimation and pyrolysis of single or combined metallocenes with very low quantities of dichlorobenzene. As a result, extremely high saturation magnetizations of 117 emu g(-1), 90 emu g(-1) and 80 emu g(-1) are obtained for the specific cases of Fe3C, FeCo and FeNi, respectively, while variable saturation magnetizations of 70 emu g(-1), 58 emu g(-1) and 6.7 emu g(-1) are obtained for Co, CoNi and Ni respectively.

TaF4: A Novel Two-Dimensional Antiferromagnetic Material with a High Néel Temperature Investigated Using First-Principles Calculations.

The structural, electronic, and magnetic properties of a novel two-dimensional monolayer material, TaF4, are investigated using first-principles calculations. The dynamical and thermal stabilities of two-dimensional monolayer TaF4 were confirmed using its phonon dispersion spectrum and molecular dynamics calculations. The band structure obtained via the high-accuracy HSE06 (Heyd-Scuseria-Ernzerhof 2006) functional theory revealed that monolayer two-dimensional TaF4 is an indirect bandgap semiconductor with a bandgap width of 2.58 eV. By extracting the exchange interaction intensities and magnetocrystalline anisotropy energy in a J1-J2-J3-K Heisenberg model, it was found that two-dimensional monolayer TaF4 possesses a Néel-type antiferromagnetic ground state and has a relatively high Néel temperature (208 K) and strong magnetocrystalline anisotropy energy (2.06 meV). These results are verified via the magnon spectrum.

Stable room-temperature ferromagnetism and gate-tunable quantum anomalous Hall effect of two-dimensional 5d transition-metal trihalide OsX3 (X = Cl, Br, I) monolayers.

5d transition-metal compounds are usually not expected to exhibit distinct magnetic ordering owing to their substantial binding energy associated with 5d electrons. In this study, we demonstrate that two-dimensional (2D) 5d transition-metal Os trihalide OsX3 monolayers can exhibit room-temperature ferromagnetism and quantum anomalous Hall effect (QAHE) by utilizing density functional theory and Monte Carlo simulation. Our calculation results of coexisting Raman and infrared activities of lattice vibration reveal the structural stability of 2D OsX3 (X = Cl, Br, I) and structural instability of 2D OsX3 (X = F). Furthermore, all 2D OsX3 trihalides (X = Cl, Br, I) are half-metals, and their ferromagnetism remains stable under ambient temperature, where 2D OsCl3 and OsBr3 have an in-plane easy axis while 2D OsI3 has an out-of-plane easy axis. Notably, when spin-orbit coupling is included, the gate-tunable QAHE could emerge in ferromagnetic 2D OsI3, while 2D OsCl3 and OsBr3 are topologically trivial. Additionally, the magnon bands of 2D OsX3 (X = Cl, Br, I) possess two spin-wave branches with dispersion similar to that of the Dirac cone in the electronic structure of graphene, which are attributed to the unique ferromagnetic honeycomb sublattice of osmium atoms.

Atomic Force Microscopy-Based Nanoscale Infrared Techniques for Catalysis.

Atomic force microscopy (AFM)-based nanoscale infrared (nano-IR) techniques have found extensive application in the fields of chemistry, physics, and materials science, enabling the visualization of nanoscale features that surpass the optical diffraction limit. More recently, tentative investigations have been conducted into the use of these techniques in the field of catalysis, particularly in studying interfacial processes involving molecular monolayer samples. IR nanoimaging and nanospectroscopy offer unique perspectives on catalytic processes. Considering the specific characteristics of catalytic processes, this Perspective highlights the need for and reviews the current status of AFM-based nano-IR techniques for catalysis investigations, which aims to contribute to a deeper understanding of the nanoscale mechanisms underlying the catalytic processes.

Large-scale fabrication and Mo vacancy-induced robust room-temperature ferromagnetism of MoSe2 thin films.

Molybdenum selenide (MoSe2) has recently attracted particular attention due to its room-temperature ferromagnetism (RTFM) and related spintronic applications. However, not only does the FM mechanism of MoSe2 remain controversial, but also the synthesis of MoSe2 thin films with robust RTFM is still an unmet challenge. Here it is shown that using polymer-assisted deposition under appropriate growth conditions, large-scale (4 cm × 4 cm) synthesis of MoSe2 thin films with robust RTFM and a smooth surface (roughness average ∼0.22 nm) is possible. A new record-high saturation magnetization (6.69 emu g-1) is achieved in the prepared MoSe2 thin films, about 5 times the previously reported record (1.39 emu g-1) obtained in 2H-MoSe2 nanoflakes. Meanwhile, the coercivity of the MoSe2 films can be tuned down to a new record-low value (5.0 Oe), one-tenth of the previously reported record. Notably, detailed analysis combining the experimental findings and calculation results shows that the robust RTFM mainly comes from the Ruderman-Kittel-Kasuya-Yoshida (RKKY) interaction between the magnetic moments induced by abundant Mo vacancies (VMos) in the MoSe2 films. Our results give insights into the large-scale production and robust RTFM of MoSe2 thin films and may provide a platform for designing and fabricating spintronic materials and devices based on transition-metal dichalcogenides.

Interface Engineering of Cu(In,Ga)Se2 Solar Cells by Optimizing Cd- and Zn-Chalcogenide Alloys as the Buffer Layer.

The optimization of band alignment at the buffer/absorber interface is realized by tuning compositions of Cd and Zn chalcogenides as the buffer layer toward high-efficiency Cu(In,Ga)Se2 (CIGS) solar cells. Using the special quasi-random structure (SQS) approach, we construct randomly disordered ZnxCd1-xSySe1-y alloys and ZnSxO1-x alloys as alternatives to the traditional CdS buffer layer. The compositional dependence of formation energies, lattice parameters, band-gap energies, and band alignments of ZnxCd1-xSySe1-y and ZnSxO1-x alloys is investigated by first-principles density functional theory calculations. For quaternary ZnxCd1-xSySe1-y alloys, we find that the miscibility temperatures and the bandgap bowing coefficients are proportional to the lattice mismatch between the mixing elements. The linear dependence of lattice parameters, trinomial dependence of band-gap energies and band-edge positions on the alloy-composition of ZnxCd1-xSySe1-y alloys are established. For ZnSxO1-x alloys, we find the lattice parameters also exhibit a linear dependence on its composition. Because of the large lattice mismatch and the chemical disparity between ZnO and ZnS, the bowing coefficient for the bandgap energies of ZnSxO1-x alloys is composition dependent, and is larger for dilute ZnSxO1-x alloys. With the optimization criteria of moderate spike-like conduction band offset, large valance band offset, sufficiently wide bandgap, and lattice match with respect to the CIGS absorber, we illustrate the optimal composition range of both ZnxCd1-xSySe1-y alloys and ZnSxO1-x alloys as the buffer layer of the CIGS solar cells. Our work demonstrates that ZnxCd1-xSySe1-y alloys and ZnSxO1-x alloys are promising buffer layers for high-efficiency CIGS solar cells.

Defect Dynamic Model of the Synergistic Effect in Neutron- and γ-Ray-Irradiated Silicon NPN Transistors.

A defect dynamic model is proposed for the positive synergistic effect of neutron- and γ-ray-irradiated silicon NPN transistors. The model considers a γ-ray-induced transformation and annihilation of the neutron-induced divacancy defects in the p-type base region of the transistor. The derived model of the base current predicts a growth function of the γ-ray dose that approaches exponentially an asymptotic value, which depends linearly on the neutron-induced initial displacement damage (DD) and a linear decay function of the dose whose slope depends quadratically on the initial DD. Variable fluence and dose neutron-γ-ray irradiation experiments are carried out, and we find all of the novel dose and fluence dependence predicted by the proposed model are confirmed by the measured data. Our work, hence, identifies that the defect evolution under γ-ray irradiation, rather than the widely believed interface Coulomb interaction, is the dominating mechanism of the synergistic effect. Our work also paves the way for the modification of displacement defects in silicon by γ-ray irradiation.

Mn(ii) chelate-coated superparamagnetic iron oxide nanocrystals as high-efficiency magnetic resonance imaging contrast agents.

In this communication, a paramagnetic bifunctional manganese(ii) chelate ([Mn(Dopa-EDTA)]2-) containing a catechol group is designed and synthesized. The catechol can bind iron ions on the surface of superparamagnetic iron oxide (SPIO) nanocrystals to form core-shell nanoparticles. Both 4 and 7 nm SPIO@[Mn(Dopa-EDTA)]2- show good water solubility, single-crystal dispersion, and low cytotoxicity. The study of the interplay between the longitudinal and transverse relaxation revealed that 4 nm SPIO@[Mn(Dopa-EDTA)]2- with lower r 2/r 1 = 1.75 at 0.5 T tends to be a perfect T 1 contrast agent while 7 nm SPIO@[Mn(Dopa-EDTA)]2- with a higher r 2/r 1 = 15.0 at 3.0 T tends to be a T 2 contrast agent. Interestingly, 4 nm SPIO@[Mn(Dopa-EDTA)]2- with an intermediate value of r 2/r 1 = 5.26 at 3.0 T could act as T 1-T 2 dual-modal contrast agent. In vivo imaging with the 4 nm SPIO@[Mn(Dopa-EDTA)]2- nanoparticle shows unique imaging features: (1) long-acting vascular imaging and different signal intensity changes between the liver parenchyma and blood vessels with the CEMRA sequence; (2) the synergistic contrast enhancement of hepatic imaging with the T 1WI and T 2WI sequence. In summary, these Fe/Mn hybrid core-shell nanoparticles, with their ease of synthesis, good biocompatibility, and synergistic contrast enhancement ability, may provide a useful method for tissue and vascular MR imaging.

A Clinical Case of Breast Reconstruction with Greater Omentum Flap for Treatment of Upper Extremity Lymphedema.

Patients presenting with complications regarding breast cancer surgery require individualized surgical protocol for correction and reconstruction. This clinical case summarizes our clinical experience in the application of the free greater omentum flap for treatment of upper extremity lymphedema and breast reconstruction. This method combines aesthetic reconstruction of the breast with functional correction. The presented clinical vignette features a patient with post-biquadrantectomy upper extremity lymphedema. A free greater omentum flap was chosen for the purpose of breast reconstruction and vascularized lymph node transfer to treat upper extremity lymphedema. Upper extremity circumferences were monitored before and after surgical correction. The revascularized flap survived well after the operation and the reconstructed breast had a natural appearance. Six months after the operation, the patient's upper extremity circumferences decreased significantly, and the pain and swelling were also alleviated. The patient was satisfied with the results. The use of the free greater omentum flap for breast reconstruction and treatment of upper extremity lymphedema provides both aesthetic and functional patient rehabilitation. The application of this technique requires proper patient selection and thorough surgical planning.

[Influence of Different Straws Returning with Landfill on Soil Microbial Community Structure Under Dry and Water Farming].

Based on rice, wheat, corn straw and rape, broad bean green stalk as the research object, using phospholipid fatty acid (PLFA) method, combining principal component analysis method to study the soil microbial quantity, distribution of flora, community structure characteristics under dry and water farming as two different cultivated land use types. The PLFA analysis results showed that: under dry farming, total PLFA quantity ranged 8.35-25.15 nmol x g(-1), showed rape > broad bean > corn > rice > wheat, rape and broad bean significantly increased total PLFA quantity by 1.18 and 1.08 times compared to the treatment without straw; PLFA quantity of bacterial flora in treatments with straws was higher than that without straw, and fungal biomass was significantly increased, so was the species richness of microbial community. Under water faming, the treatments of different straws returning with landfill have improved the PLFA quantity of total soil microbial and flora comparing with the treatment without straw, fungi significantly increased, and species richness of microbial communities value also increased significantly. Total PLFA quantity ranged 4.04-22.19 nmol x g(-1), showed rice > corn > wheat > broad bean > rape, which in rape and broad bean treatments were lower than the treatment without straw; fungal PLFA amount in 5 kinds of straw except broad bean treatment was significantly higher than that of the treatment without straw, bacteria and total PLFA quantity in broad bean processing were significantly lower than those of other treatments, actinomycetes, G+, G- had no significant difference between all treatments; rice, wheat, corn, rape could significantly increase the soil microbial species richness index and dominance index under water faming. The results of principal component analysis showed that broad bean green stalk had the greatest impact on the microbial community structure in the dry soil, rape green stalk and wheat straw had the biggest influence on soil microbial community structure in water soil.

Improvement of Endurance Based on Muscle Fiber-Type Composition by Treatment with Dietary Apple Polyphenols in Rats.

A recent study demonstrated a positive effect of apple polyphenol (APP) intake on muscle endurance of young-adult animals. While an enhancement of lipid metabolism may be responsible, in part, for the improvement, the contributing mechanisms still need clarification. Here we show that an 8-week intake of 5% (w/w) APP in the diet, up-regulates two features related to fiber type: the ratio of myosin heavy chain (MyHC) type IIx/IIb and myoglobin protein expression in plantaris muscle of 9-week-old male Fischer F344 rats compared to pair-fed controls (P < 0.05). Results were demonstrated by our SDS-PAGE system specialized for MyHC isoform separation and western blotting of whole muscles. Animal-growth profiles (food intake, body-weight gain, and internal-organ weights) did not differ between the control and 5% APP-fed animals (n = 9/group). Findings may account for the increase in fatigue resistance of lower hind limb muscles, as evidenced by a slower decline in the maximum isometric planter-flexion torque generated by a 100-s train of electrical stimulation of the tibial nerve. Additionally, the fatigue resistance was lower after 8 weeks of a 0.5% APP diet than after 5% APP, supporting an APP-dose dependency of the shift in fiber-type composition. Therefore, the present study highlights a promising contribution of dietary APP intake to increasing endurance based on fiber-type composition in rat muscle. Results may help in developing a novel strategy for application in animal sciences, and human sports and age-related health sciences.