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1.
World J Urol ; 42(1): 360, 2024 May 29.
Artículo en Inglés | MEDLINE | ID: mdl-38811391

RESUMEN

PURPOSE: To estimate the incidences of left renal vein (LRV) entrapment by right renal artery (RRA), a phenomenon primarily reported as case reports. METHODS: The cross-sectional study consecutively screened renal vessel CT data of 38 (Renal) patients with nephropathy and 305 (Non-renal) patients with peripheral arterial diseases in a teaching hospital in northeast China between November 2018 and March 2023. The LRV compression by adjacent anatomical structures, including but not limited to RRA and multiple compression-related parameters, were investigated through multiplanar analysis of the CT data. RESULTS: The overall LRV entrapment rates by adjacent structures were 41.93% (12/31) and 24.00% (6/25), the rates of RRA-sourced LRV compression 22.58% (7/31) and 20.00% (5/25), and the rates of compression by superior mesenteric artery (SMA) 16.13% (5/31) and 4.00% (1/25) in the Renal and Non-renal groups, respectively, with no significance. The venous segments distal to the RRA-compressed site had a significantly larger transectional lumen area than those of the non-compressed veins in both groups (3.09 ± 1.29 vs. 1.82 ± 0.23, p < 0.001 and 4.30 ± 2.65 vs. 2.12 ± 0.55, p = 0.006; maximum-to-minimum area ratios in Renal and Non-renal groups, respectively). Nearly 80% of RRAs were found arising anteriorly rightwards instead of passing straight to the right. CONCLUSION: RRA-sourced LRV compression was not rare, and its incidence was higher than that of the compression by SMA in both patient cohorts. RRA could be a more common compression source than SMA concerning LRV entrapment. Further investigations involving different populations, including healthy individuals, are needed.


Asunto(s)
Arteria Renal , Venas Renales , Humanos , Estudios Transversales , Persona de Mediana Edad , Masculino , Femenino , Venas Renales/diagnóstico por imagen , Venas Renales/anomalías , Anciano , Arteria Renal/diagnóstico por imagen , Adulto , Tomografía Computarizada por Rayos X , Síndrome de Cascanueces Renal/complicaciones , Síndrome de Cascanueces Renal/diagnóstico por imagen , Incidencia
2.
Nano Lett ; 23(13): 6002-6009, 2023 Jul 12.
Artículo en Inglés | MEDLINE | ID: mdl-37342001

RESUMEN

Inorganic halide perovskite nanocrystals (NCs) are being widely explored as next-generation optoelectronic materials. Critical to understanding the optoelectronic properties and stability behavior of perovskite NCs is the material's surface structure, where the local atomic configuration deviates from that of the bulk. Through low-dose aberration-corrected scanning transmission electron microscopy and quantitative imaging analysis techniques, we directly observed the atomic structure at the surface of the CsPbBr3 NCs. CsPbBr3 NCs are terminated by a Cs-Br plane, and the surface Cs-Cs bond length decreases significantly (∼5.6%) relative to the bulk, imposing compressive strain and inducing polarization, which we also observed in CsPbI3 NCs. Density functional theory calculations suggest such a reconstructed surface contributes to the separation of holes and electrons. These findings enhance our fundamental understanding of the atomic-scale structure, strain, and polarity at the surface of inorganic halide perovskites and provide valuable insights into designing stable and efficient optoelectronic devices.

3.
Small ; 19(36): e2208253, 2023 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-37183297

RESUMEN

MXenes, a fast-growing family of two-dimensional (2D) transition metal carbides/nitrides, are promising for electronics and energy storage applications. Mo2 CTx MXene, in particular, has demonstrated a higher capacity than other MXenes as an anode for Li-ion batteries. Yet, such enhanced capacity is accompanied by slow kinetics and poor cycling stability. Herein, it is revealed that the unstable cycling performance of Mo2 CTx is attributed to the partial oxidation into MoOx with structural degradation. A laser-induced Mo2 CTx /Mo2 C (LS-Mo2 CTx ) hybrid anode has been developed, of which the Mo2 C nanodots boost redox kinetics, and the laser-reduced oxygen content prevents the structural degradation caused by oxidation. Meanwhile, the strong connections between the laser-induced Mo2 C nanodots and Mo2 CTx nanosheets enhance conductivity and stabilize the structure during charge-discharge cycling. The as-prepared LS-Mo2 CTx anode exhibits an enhanced capacity of 340 mAh g-1 vs 83 mAh g-1 (for pristine) and an improved cycling stability (capacity retention of 106.2% vs 80.6% for pristine) over 1000 cycles. The laser-induced synthesis approach underlines the potential of MXene-based hybrid materials for high-performance energy storage applications.

4.
Drug Dev Ind Pharm ; 48(12): 708-716, 2022 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-36630569

RESUMEN

OBJECTIVE: To compare the consistency between the decoction of Paeonia rubra hort dispensing granules from different manufacturers and traditional decoction (TD), and to provide a reference for the clinical application of Paeonia rubra hort dispensing granules. METHODS: Nine batches of Paeonia rubra hort dispensing granules (from three manufacturers, A, B, and C) and 20 batches of Paeonia rubra hort decoction pieces were collected. The contents of four active components in vivo and in vitro were determined by HPLC and UPLC-MS/MS, respectively. The consistency of the Paeonia rubra hort decoction pieces and dispensing granules were compared based on the Criteria Importance Though Intercrieria Correlation (CRITIC) weighting method and the equivalent correction suggestions (1 g of dispensing granule equals the same amount of Chinese herbal samples) were put forward for the dispensing granules. RESULTS: The total content of active ingredients in vivo and in vitro of manufacturer A was significantly lower than that of TD (p < 0.05), and the total content of active ingredients in vivo of manufacturer C was significantly lower than that of TD (p < 0.05); The equivalent of manufacturer A and manufacturer C should be corrected from 1:11 and 1:5 to 1:5 and 1:4, respectively. CONCLUSION: The quality of Paeonia rubra hort dispensing granule decoction from some manufacturers aligns that of TD, but the other is slightly inferior to that of TD. After appropriate equivalent correction, quality consistency can be achieved with TD.


Asunto(s)
Medicamentos Herbarios Chinos , Paeonia , Cromatografía Liquida , Espectrometría de Masas en Tándem , Cromatografía Líquida de Alta Presión/métodos
5.
J Am Chem Soc ; 143(7): 2660-2664, 2021 02 24.
Artículo en Inglés | MEDLINE | ID: mdl-33502185

RESUMEN

While nanoscale mimics of peroxidase have been extensively developed over the past decade or so, their catalytic efficiency as a key parameter has not been substantially improved in recent years. Herein, we report a class of highly efficient peroxidase mimic-nickel-platinum nanoparticles (Ni-Pt NPs) that consist of nickel-rich cores and platinum-rich shells. The Ni-Pt NPs exhibit a record high catalytic efficiency with a catalytic constant (Kcat) as high as 4.5 × 107 s-1, which is ∼46- and 104-fold greater than the Kcat values of conventional Pt nanoparticles and natural peroxidases, respectively. Density functional theory calculations reveal that the unique surface structure of Ni-Pt NPs weakens the adsorption of key intermediates during catalysis, which boosts the catalytic efficiency. The Ni-Pt NPs were applied to an immunoassay of a carcinoembryonic antigen that achieved an ultralow detection limit of 1.1 pg/mL, hundreds of times lower than that of the conventional enzyme-based assay.

6.
Electrophoresis ; 42(7-8): 991-1002, 2021 04.
Artículo en Inglés | MEDLINE | ID: mdl-33570197

RESUMEN

Accomplishing slow translocation speed with high sensitivity has been the most critical mission for solid-state nanopore (SSN) device to electrically detect nucleobases in ssDNA. In this study, a method to detect nucleobases of ssDNA using a 2D SSN is introduced by considerably reducing the translocation speed and effectively increasing its sensitivity. The ultra-thin titanium dioxide coated hexagonal boron nitride nanopore was fabricated, along with an ionic-liquid 1-butyl-3-methylimidazolium hexafluorophosphate/2.0 M KCl aqueous (cis/trans) interface, for increasing both the spatial and the temporal resolutions. As the ssDNA molecules entered the nanopore, a brief surge of electrical conductivity occurred, which was followed by multiple resistive pulses from nucleobases during the translocation of ssDNA and another brief current surge flagging the exit of the molecule. The continuous detection of nucleobases using a 2D SSN device is a novel achievement: the water molecules bound to ssDNA increased the molecular conductivity and amplified electrical signals during the translocation. Along with the experiment, computational simulations using COMSOL Multiphysics are presented to explain the pivotal role of water molecules bound to ssDNA to detect nucleobases using a 2D SSN.


Asunto(s)
Líquidos Iónicos , Nanoporos , ADN de Cadena Simple , Nucleótidos , Agua
7.
J Am Chem Soc ; 142(16): 7480-7486, 2020 Apr 22.
Artículo en Inglés | MEDLINE | ID: mdl-32239925

RESUMEN

To discover the nonlinear optical (NLO) materials with strong second harmonic generation (SHG), the design of NLO-active molecular units with large polarization is considered as a common strategy. Herein, we propose that the local structural distortion induced with vacancies, apart from the NLO-active units, can be employed to improve the NLO effect in solids as well. Accordingly, a new tungsten bronze (TB) oxide, Pb2(Pb0.15Li0.7□0.15)Nb5O15 (□ representing vacancies), is successfully designed and prepared, which exhibits a strong SHG response of 39 times that of KH2PO4. The detailed analysis reveals that the local structural distortions enhanced by the vacancies in PLN strengthen the local dipole moments of neighboring NbO6 octahedra, and thus significantly prompt the SHG effect. Moreover, a series of new TB compounds with large NLO effects are discovered by this molecular design strategy, which are perspectives for new NLO materials synthesis.

8.
Electrophoresis ; 41(7-8): 630-637, 2020 04.
Artículo en Inglés | MEDLINE | ID: mdl-31709550

RESUMEN

In this work, we present a step-by-step workflow for the fabrication of 2D hexagonal boron nitride (h-BN) nanopores which are then used to sense holo-human serum transferrin (hSTf) protein at pH ∼8 under applied voltages ranging from +100 mV to +800 mV. 2D nanopores are often used for DNA, however, there is a great void in the literature for single-molecule protein sensing and this, to the best of our knowledge, is the first time where h-BN-a material with large band-gap, low dielectric constant, reduced parasitic capacitance and minimal charge transfer induced noise-is used for protein profiling. The corresponding ΔG (change in pore conductance due to analyte translocation) profiles showed a bimodal Gaussian distribution where the lower and higher ΔG distributions were attributed to (pseudo-) folded and unfolded conformations respectively. With increasing voltage, the voltage induced unfolding increased (evident by decrease in ΔG) and plateaued after ∼400 mV of applied voltage. From the ΔG versus voltage profile corresponding to the pseudo-folded state, we calculated the molecular radius of hSTf, and was found to be ∼3.1 nm which is in close concordance with the literature reported value of ∼3.25 nm.


Asunto(s)
Compuestos de Boro/química , Técnicas Electroquímicas/métodos , Nanoporos , Transferrina/química , Diseño de Equipo , Humanos , Conformación Proteica , Termodinámica , Titanio , Transferrina/análisis
9.
Appl Surf Sci ; 4992020 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-32863496

RESUMEN

Marking colon tumors for surgery is normally done with the use of India ink. However, non-fluorescent dyes such as India ink cannot be imaged below the tissue surface and there is evidence for physiological complications such as abscess, intestinal perforation and inconsistency of dye injection. A novel infrared marker was developed using FDA approved indocyanine green (ICG) dye and ultrathin hollow silica nanoshells (ICG/HSS). Using a positively charged amine linker, ICG was non-covalently adsorbed onto the nanoparticle surface. For ultra-thin wall 100 nm diameter silica shells, a bimodal ICG layer of < 3 nm is was formed. Conversely, for thicker walls on 2 µm diameter silica shells, the ICG layer was only bound to the outer surface and was 6 nm thick. In vitro testing of fluorescent emission showed the particles with the thinner coating were considerably more efficient, which is consistent with self-quenching reducing emission shown in the thicker ICG coatings. Ex-vivo testing showed that ICG bound to the 100 nm hollow silica shells was visible even under 1.5 cm of tissue. In vivo experiments showed that there was no diffusion of the ICG/nanoparticle marker in tissue and it remained imageable for as long as 12 days.

10.
Electrophoresis ; 40(9): 1337-1344, 2019 05.
Artículo en Inglés | MEDLINE | ID: mdl-30667089

RESUMEN

This paper describes a method to gauge the stiffness of nanosized liposomes - a nanoscale vesicle - using a custom-made recapture platform coupled to a solid-state nanopore sensor. The recapture platform electrically profiles a given liposome vesicle multiple times through automated reversal of the voltage polarity immediately following a translocation instance to re-translocate the same analyte through the nanopore - provides better statistical insight at the molecular level by analyzing the same particle multiple times compared to conventional nanopore platforms. The capture frequency depends on the applied voltage with lower voltages (i.e., 100 mV) permitting higher recapture instances than at higher voltages (>200 mV) since the probability of particles exiting the nanopore capture radius increases with voltage. The shape deformation was inferred by comparing the normalized relative current blockade ( ΔI/I0̂) at the two voltage polarities to that of a rigid particle, i.e., polystyrene beads. We found that liposomes deform to adopt a prolate shape at higher voltages. This platform can be further applied to investigate the stiffness of other types of soft matters, e.g., virus, exosomes, endosomes, and accelerate the potential studies in pharmaceutics for increasing the drug packing and unpacking mechanism by controlling the stiffness of the drug vesicles.


Asunto(s)
Elasticidad , Liposomas/ultraestructura , Nanotecnología/métodos , Automatización/métodos , Electricidad , Microesferas , Nanoporos , Poliestirenos/normas
11.
Zhongguo Zhong Yao Za Zhi ; 44(23): 5134-5142, 2019 Dec.
Artículo en Zh | MEDLINE | ID: mdl-32237350

RESUMEN

Traditional Chinese medicine( TCM) decoction contains complex bitterness. In this paper,the simple mixing of TCM monomer bitter substances is used as the entry point to study the law of bitterness superposition. With berberine hydrochloride( alkaloids),geniposide( terpenoids),and arbutin( glycosides) as mother liquor,sophoridine( alkaloids),gentiopicroside( terpenoids),and puerarin( glycosides) as additive substances,these different additive substances were mixed with different mother liquor according to concentration gradients to form different liquid mixtures. The bitterness of the additive solution and the mixtures was evaluated by traditional human taste panel method( THTPM) and electronic tongue; the bitterness-concentration fitting model of the additive solution and the liquid mixtures was established by Weibull and logarithmic curves. By comparing and analyzing the bitterness-concentration model and the bitterness difference( ΔI_0/ΔI_e) of the additive solution and the mixture,the influence of mother liquor on the bitterness of the mixture was investigated. The results showed that both the additive solution bitterness model and the liquid mixture bitterness model were consistent with the Weibull model and the logarithmic model( THTPM: R~2≥0. 887 0,P<0. 01; electronic tongue test:R~2≥0. 753 2,P<0. 05). The fitting degree of the Weibull model was generally higher than that of the logarithmic model; the bitterness difference( ΔI_0) was monotonously decreasing; the fitting equation of tongue bitterness and electronic tongue bitterness: R~2≥0. 874 2,P<0. 01. In this article,through the superposition of different kinds of TCM bitter substances,THTPM and electronic tongue test was combined. It was found that the bitterness after superposition was still in Weibull or logarithmic relationship with the concentration of additive substances; THTPM showed that the effect of bitter mother liquor on the bitterness of the mixture decreased with the increase of the concentration of the additive; the bitterness of the electronic tongue was obviously related to the bitterness of THTPM. However,further verification is needed later by optimizing the concentration gradient and expanding the sample size.


Asunto(s)
Nariz Electrónica , Medicina Tradicional China , Gusto , Alcaloides/análisis , Glicósidos/análisis , Humanos , Terpenos/análisis
12.
Nano Lett ; 17(6): 3919-3925, 2017 06 14.
Artículo en Inglés | MEDLINE | ID: mdl-28557462

RESUMEN

We demonstrate gate-tunable resonant tunneling and negative differential resistance between two rotationally aligned bilayer graphene sheets separated by bilayer WSe2. We observe large interlayer current densities of 2 and 2.5 µA/µm2 and peak-to-valley ratios approaching 4 and 6 at room temperature and 1.5 K, respectively, values that are comparable to epitaxially grown resonant tunneling heterostructures. An excellent agreement between theoretical calculations using a Lorentzian spectral function for the two-dimensional (2D) quasiparticle states, and the experimental data indicates that the interlayer current stems primarily from energy and in-plane momentum conserving 2D-2D tunneling, with minimal contributions from inelastic or non-momentum-conserving tunneling. We demonstrate narrow tunneling resonances with intrinsic half-widths of 4 and 6 meV at 1.5 and 300 K, respectively.

13.
Nano Lett ; 16(4): 2812-7, 2016 Apr 13.
Artículo en Inglés | MEDLINE | ID: mdl-26999499

RESUMEN

Noble-metal nanoframes are of great interest to many applications due to their unique open structures. Among various noble metals, Ru has never been made into nanoframes. In this study, we report for the first time an effective method based on seeded growth and chemical etching for the facile synthesis of Ru nanoframes with high purity. The essence of this approach is to induce the preferential growth of Ru on the corners and edges of Pd truncated octahedra as the seeds by kinetic control. The resultant Pd-Ru core-frame octahedra could be easily converted to Ru octahedral nanoframes of ∼2 nm in thickness by selectively removing the Pd cores through chemical etching. Most importantly, in this approach the face-centered cubic (fcc) crystal structure of Pd seeds was faithfully replicated by Ru that usually takes an hcp structure. The fcc Ru nanoframes showed higher catalytic activities toward the reduction of p-nitrophenol by NaBH4 and the dehydrogenation of ammonia borane compared with hcp Ru nanowires with roughly the same thickness.

14.
Nano Lett ; 16(2): 1328-34, 2016 Feb 10.
Artículo en Inglés | MEDLINE | ID: mdl-26694227

RESUMEN

Lattice-polarity-driven epitaxy of hexagonal semiconductor nanowires (NWs) is demonstrated on InN NWs. In-polarity InN NWs form typical hexagonal structure with pyramidal growth front, whereas N-polarity InN NWs slowly turn to the shape of hexagonal pyramid and then convert to an inverted pyramid growth, forming diagonal pyramids with flat surfaces and finally coalescence with each other. This contrary growth behavior driven by lattice-polarity is most likely due to the relatively lower growth rate of the (0001̅) plane, which results from the fact that the diffusion barriers of In and N adatoms on the (0001) plane (0.18 and 1.0 eV, respectively) are about 2-fold larger in magnitude than those on the (0001̅) plane (0.07 and 0.52 eV), as calculated by first-principles density functional theory (DFT). The formation of diagonal pyramids for the N-polarity hexagonal NWs affords a novel way to locate quantum dot in the kink position, suggesting a new recipe for the fabrication of dot-based devices.

15.
Nano Lett ; 16(9): 5437-43, 2016 09 14.
Artículo en Inglés | MEDLINE | ID: mdl-27494551

RESUMEN

Controllable doping of two-dimensional materials is highly desired for ideal device performance in both hetero- and p-n homojunctions. Herein, we propose an effective strategy for doping of MoS2 with nitrogen through a remote N2 plasma surface treatment. By monitoring the surface chemistry of MoS2 upon N2 plasma exposure using in situ X-ray photoelectron spectroscopy, we identified the presence of covalently bonded nitrogen in MoS2, where substitution of the chalcogen sulfur by nitrogen is determined as the doping mechanism. Furthermore, the electrical characterization demonstrates that p-type doping of MoS2 is achieved by nitrogen doping, which is in agreement with theoretical predictions. Notably, we found that the presence of nitrogen can induce compressive strain in the MoS2 structure, which represents the first evidence of strain induced by substitutional doping in a transition metal dichalcogenide material. Finally, our first principle calculations support the experimental demonstration of such strain, and a correlation between nitrogen doping concentration and compressive strain in MoS2 is elucidated.

16.
Angew Chem Int Ed Engl ; 55(52): 16039-16043, 2016 12 23.
Artículo en Inglés | MEDLINE | ID: mdl-27882633

RESUMEN

Identifying key factors that govern the in vivo behavior of nanomaterials is critical to the clinical translation of nanomedicines. Overshadowed by size-, shape-, and surface-chemistry effects, the impact of the particle core density on clearance and tumor targeting of inorganic nanoparticles (NPs) remains largely unknown. By utilizing a class of ultrasmall metal NPs with the same size and surface chemistry but different densities, we found that the renal-clearance efficiency exponentially increased in the early elimination phase while passive tumor targeting linearly decreased with a decrease in particle density. Moreover, lower-density NPs are more easily distributed in the body and have shorter retention times in highly permeable organs than higher-density NPs. The density-dependent in vivo behavior of metal NPs likely results from their distinct margination in laminar blood flow, which opens up a new path for precise control of nanomedicines in vivo.


Asunto(s)
Riñón/metabolismo , Nanopartículas del Metal/química , Neoplasias/química , Glutatión/química , Glutatión/metabolismo , Oro/química , Oro/metabolismo , Humanos , Neoplasias/metabolismo , Tamaño de la Partícula , Plata/química , Plata/metabolismo , Propiedades de Superficie
17.
Nanotechnology ; 26(12): 125404, 2015 Mar 27.
Artículo en Inglés | MEDLINE | ID: mdl-25742426

RESUMEN

Transition metal oxides have attracted great interest as alternative anode materials for rechargeable lithium-ion batteries. Among them, ruthenium dioxide is considered to be a prototype material that reacts with the Li ions in the conversion type. In situ transmission electron microscopy reveals a two-step process during the initial lithiation of the RuO2 nanowire anode at atomic resolution. The first step is characterized by the formation of the intermediate phase LixRuO2 due to the Li-ion intercalation. The following step is manifested by the solid-state amorphization reaction driven by advancing the reaction front. The crystalline/amorphous interface is consisted of {011} atomic terraces, revealing the orientation-dependent mobility. In the crystalline matrix, lattice disturbance and dislocation are identified to be two major stress-induced distortions. The latter can be effective diffusion channels, facilitating transportation of the Li ions inside the bulk RuO2 crystal and further resulting in non-uniform Li-ion distribution. It is expected that the local enrichment of the Li ions may account for the homogeneous nucleation of dislocations in the bulk RuO2 crystal and the special island-like structures. These results elucidate the structural evolution and the phase transformation during electrochemical cycling, which sheds light on engineering RuO2 anode materials.

18.
Angew Chem Int Ed Engl ; 54(19): 5672-6, 2015 May 04.
Artículo en Inglés | MEDLINE | ID: mdl-25783453

RESUMEN

The synthesis of ultrathin face-centered-cubic (fcc) Au@Pt rhombic nanoplates is reported through the epitaxial growth of Pt on hexagonal-close-packed (hcp) Au square sheets (AuSSs). The Pt-layer growth results in a hcp-to-fcc phase transformation of the AuSSs under ambient conditions. Interestingly, the obtained fcc Au@Pt rhombic nanoplates demonstrate a unique (101)f orientation with the same atomic arrangement extending from the Au core to the Pt shell. Importantly, this method can be extended to the epitaxial growth of Pd on hcp AuSSs, resulting in the unprecedented formation of fcc Au@Pd rhombic nanoplates with (101)f orientation. Additionally, a small amount of fcc (100)f -oriented Au@Pt and Au@Pd square nanoplates are obtained with the Au@Pt and Au@Pd rhombic nanoplates, respectively. We believe that these findings will shed new light on the synthesis of novel noble bimetallic nanostructures.

19.
Nat Commun ; 15(1): 8589, 2024 Oct 04.
Artículo en Inglés | MEDLINE | ID: mdl-39366956

RESUMEN

Hexagonal boron nitride (hBN), as one of the few two-dimensional insulators, holds strategic importance for advancing post-silicon electronic devices and circuits. Achieving wafer-scale, high-quality monolayer hBN is essential for its integration into the semiconductor industry. However, the physical mechanisms behind the chemical vapor deposition (CVD) synthesis of hBN are not yet well understood. Investigating morphology engineering is critical for developing scalable synthetic techniques for the large-scale production of high-quality hBN. In this study, we explored the underlying mechanisms of the CVD growth process of hBN and found that the involvement of a small amount of oxygen effectively modulates the shape of the single-crystal hBN islands. By tuning the oxygen content in the CVD system, we synthesized well-aligned hexagonal hBN islands and achieved a continuous, high-quality single-crystal monolayer hBN film through the merging of these hexagonal islands on conventional single-crystal metal-foil substrates. Density functional theory was used to study the edges of hBN monolayers grown in an oxygen-assisted environment, providing insights into the formation mechanism. This study opens new pathways for controlling the island shape of 2D materials and establishes a foundation for the industrial-scale production of high-quality, large-area, single-crystal hBN.

20.
Adv Mater ; : e2406944, 2024 Sep 02.
Artículo en Inglés | MEDLINE | ID: mdl-39221655

RESUMEN

Diamond-type silicon has a work function of ≈4.8 eV, and conventional n- or p-type doping modifies the value only between 4.6 and 5.05 eV. Here, it is shown that the alkali clathrates AxSi46 have substantially lower work functions approaching 2.6 eV, with clear trends between alkali electropositivity and clathrate cage size. The low work function enables alkali clathrates such as K8Si46 to be effective Haber-Bosch catalyst supports for NH3 synthesis. The catalytic properties of Si, Ge, and Sn-based clathrates are investigated while supporting Fe and Ru on the surface. The activity largely scales with the work function, and low activation energies below 60 kJ mol-1 are observed due to strong electron donation effects from the support. Ru metal and Sn clathrates seem to be unsuitable for stability issues. Compared to other similar hydride/electride catalysts, the simple structure and composition combined with stability in air/water make a systematic study of these clathrates possible and open the door to other electron-rich Zintl phases and related intermetallics as low-work function materials suitable for catalysis. The observed low work function may also have implications for other existing electronic applications.

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