Sb Surface Research Articles

A DFT study on antimonene as a drug delivery vehicle for carmustine, lomustine and nitrosourea anticancer drugs

We used antimonene (Sb) as a delivery vehicle for transporting drugs like Carmustine (CMT), Lomustine (LOMU) and Nitrosourea (NU) in both gaseous and liquid states. The Sb nanosheet structure is stable, and its potential for drug adsorption has been investigated in both parallel and perpendicular directions. The parallel configuration is most stable with a higher adsorption energy of −1.18 eV, −0.63 eV and −1.14 eV for LOMU, CMT and NU respectively. We investigated structural parameters, electronic properties, work function and chemical reactivity. Only NU alters the Sb’s semiconductor behaviour to metallic and has the shortest recovery time in the parallel direction. Hirshfield charge analysis revealed that nanosheet displays electron accepting properties, whereas drugs act as electron donors. The decreased work function for CMT and LOMU enhances substrate activity, indicating stronger interactions that may improve drug delivery. We confirmed the drug’s effective interaction with amino acids without impairing proteins. Furthermore, calculated results predicted a minimal acidic environment of malignant growth, CM, NU and LOMU drugs could start to release from the Sb surface without significantly altering the structural properties. This study illustrates how Sb nanosheet holds promise as an effective carrier for drug delivery in biomedical applications.

Probing the Spin-Momentum Locking on Rashba Surfaces via Spin Current.

In this study, we investigate the spin-momentum locking phenomenon on Rashba states of antimony (Sb) films. Utilizing spin pumping in conjunction with an external charge current, we uncover the topological properties of Sb surface states. Our key finding is the precise manipulation of the direction and magnitude of the charge current generated by the inverse Rashba-Edelstein effect. This control is achieved through the dynamic interaction between out-of-equilibrium pumped spins and spin-momentum-locked flowing spins, which are perpendicular to the charge current. Our results highlight Sb as a promising material for both fundamental and applied spintronics research. The studied Sb nanostructures demonstrate potential for the development of low-power logic gates operating with currents in the microampere range, paving the way for advanced spintronic applications.

Formation and Manipulation of Diatomic Rotors at the Symmetry-Breaking Surfaces of a Kagome Superconductor.

Construction of diatomic rotors, which is crucial for artificial nanomachines, remains challenging due to surface constraints and limited chemical design. Here we report the construction of diatomic Cr-Cs and Fe-Cs rotors where a Cr or Fe atom switches around a Cs atom at the Sb surface of the newly discovered kagome superconductor CsV3Sb5. The switching rate is controlled by the bias voltage between the rotor and scanning tunneling microscope (STM) tip. The spatial distribution of rates exhibits C2 symmetry, possibly linked to the symmetry-breaking charge orders of CsV3Sb5. We have expanded the rotor construction to include different transition metals (Cr, Fe, V) and alkali metals (Cs, K). Remarkably, designed configurations of rotors are achieved through STM manipulation. Rotor orbits and quantum states are precisely controlled by tuning the inter-rotor distance. Our findings establish a novel platform for the controlled fabrication of atomic motors on symmetry-breaking quantum materials, paving the way for advanced nanoscale devices.

Effect of “black carbon” on antimony accumulation in traffic-loaded topsoil

Traffic-loaded areas have been of increasing concern due to the potential risk of carcinogenic pollutants, including antimony (Sb), which accumulates mostly in atmospheric particles (PM) and can interact with soil organic matter (Corg). The stability of Sb in topsoils was studied via the adsorption mechanism using standard soils and Corg-reach vehicle-produced particles as the unique source of “traffic” Sb. The mixed adsorbents were prepared from loamy sand and clay standard soils, and braking abrasion dust and diesel engine soot as Sb sources in atmospheric PM. Whereas the black carbon (BC), as part of Corg, disposes of exceptional adsorption properties compared to the other Corg, all adsorption experiments were performed identically on the adsorbents prepared from the original standard soils and Sb source materials and on the adsorbents prepared from the same materials annealed at 375 °C to ensure only BC participation in adsorption processes. The concentration of the Sb model solution corresponded to the average Sb content in rainwater from traffic-loaded localities. In addition to Sb, the Corg and iron (Fe) were monitored. The sorbability of Sb on the loamy sand soil mixtures increased up to 90% compared with the pure soil due to new active surface sites for Sb binding created due to the Corg added with the source material. The clay soil mixture containing 10 times more Corg compared with the loamy sand soil accumulated the Corg from the source material, which resulted in blocking active sites and a decline in Sb sorbability by up to 20%. The processes performed identically with original and annealed materials showed the same trends and confirmed the key role of BC and soil quality in the accumulation and stability of Sb in traffic-loaded topsoils. The participation of Fe in Sb surface interactions was not observed.

Sb surface terminated MnSb devices in the niccolite phase

The magneto-electronic properties of ferromagnetic MnSb grown by molecular beam epitaxy can be dominated by the presence of a surface state in the minority spin bandgap when the surface is Sb-terminated. The material resistivity is 120 µΩ.cm at 295 K, and although this is determined by the majority spin population, the anisotropic magnetoresistance, dependent on minority spins, is ∼0.24% for the Sb-terminated devices with Mn-terminated devices showing ∼0.02%. At 295 K, the extraordinary Hall constant is 0.5 Ω/T for the Sb-terminated surface and 1.5 Ω/T for the Mn-terminated surface with the extraordinary Hall constant and anisotropic magnetoresistance behaving with an anomalous temperature dependence between 295 and 1.5 K. The dominant MnSb structural phase on the GaAs (001) orientation is naturally doped p-type with a carrier density ∼1 × 1022 cm−3 determined by the normal Hall effect after the extraordinary Hall effect has saturated at higher fields than ∼2 T. Spintronic device possibilities are discussed, particularly the spin-light emitting diode and magnetic nano-structures. A natural p-type doping in MnSb limits the devices to dominant hole carrier effects although there is compatibility with both III–V and Si–Ge materials for hybrid device possibilities.

Investigation of milling performance and removal process mechanism of 3D SiCf/C-SiC composites using brazed diamond tools

The present paper evaluates the machinability of brazed diamond tools for milling 3D SiCf/C-SiC composites. Defined three milling modes of fiber orientation, transverse, longitudinal, and perpendicular, and surfaces, SA (transverse and longitudinal), SB (transverse and perpendicular), and SC (longitudinal and perpendicular), are chosen to reveal factors influencing milling force and surface integrity. Besides, the removal process mechanism is analyzed through high-speed cameras. The results show that combining fiber orientations influences milling force waveform, whereas surface quality is related to fiber orientation and damage types. The lower cutting speeds obtain better surface quality on SA surfaces, while superior surface quality on SB and SC surfaces is attained with higher cutting speeds. Dominant damage modes include direct fiber breakage and matrix fragmentation. Moreover, the removal process is sequentially matrix cracking and fiber/matrix debonding, fiber breakage, and ultimate failure. Toughening mechanisms of composites containing fiber bridging and fiber pullout are observed during milling.

Mass spectrometry and in situ x-ray photoelectron spectroscopy investigations of organometallic species induced by the etching of germanium, antimony and selenium in a methane-based plasma

Organometallic positive ions were identified in inductively coupled plasmas by means of mass spectrometry during the etching of Ge, Sb, Se materials. A preliminary study was focused on identifying M x H y + (M = Ge, Sb, Se) positive ion clusters during a H2/Ar etching process. The methane addition to the H2/Ar mixture generates CH x reactive neutral species. The latter react with the metalloids within gas phase to form M x C y H z + organometallic ions. In addition, the etching of Sb2Se3 and Ge19.5Sb17.8Se62.7 bulk targets forms mixed products via ion-molecule reactions as evidenced by the presence of SeSbC x H y + ion clusters. Changes in surface composition induced by the newly formed organometallic structures were investigated using in situ x-ray photoelectron spectroscopy. In the case of the Ge and Sb surfaces, (M)–M–C x environments broadened the Ge 2p3/2, Ge 3d, Sb 3d and Sb 4d spectra to higher values of binding energy. For the Se surface, only the hydrogen and methyl bonding could explain the important broadening of the Se 3d core level. It was found that the Ge39Se61 thin film presents an induced (Ge)–Ge–Se entity on the Ge 2p3/2 and Ge 3d core levels.

On determining the surface segregation kinetics of Sb in binary and ternary Fe alloys during continuous annealing

In the present research, Sb surface segregation kinetics for Fe-(0.01/0.03)Sb and Fe-2Mn-(0.01/0.03)Sb at.% alloys were determined based on the modified Darken model and linear heating followed by isothermal annealing. The modified Darken model was used to evaluate the measured Sb segregation profile during continuous galvanizing heat treatments. Based on the kinetic analysis, increasing temperatures and isothermal holding times led to an increase in Sb surface segregation. Sb segregation was observed at the surface for both the Fe-xSb and Fe-2Mn-xSb alloys after annealing. It was found that Sb surface diffusion in the Fe-Sb alloys was faster than in the Fe-2Mn-Sb alloys, which was attributed to the crystal structure and the defect density in the matrix. The segregation rate was determined from the Darken curves and a higher segregation rate was observed in Fe-xSb alloys. The activation energy of Sb diffusion for the Fe-Sb and Fe-2Mn-xSb alloys was determined to be ∼ 193±18 kJ/mol, which is close to the activation energy of bulk Sb diffusion in α-Fe.

Synergistic role of Sb doping and surface modification in high performance ultrahigh-nickel layered oxides cathode materials

Before the ultrahigh-nickel LiNixCoyMnzO2 (NCM, x + y + z = 1, x ≥ 0.9) layered oxides are able to be used as a commercial electrode material for Li+ batteries, problems such as structural instability and capacity degradation due to repeated cycling need to be overcome. In this essay, we designed and prepared the Sb-modified LiNi0.92Co0.04Mn0.04O2 (Sb-NCM) materials, which simultaneously realize synergistic role of Sb doping and surface modification. The discharge capacity of the Sb-NCM materials is 206.0 mA h g−1 at 0.5 C between 2.7 V and 4.3 V. The capacity maintenance is 82.9 % after 125 cycles at 5 C, compared with 50.1 % of the pristine sample. It also demonstrates excellent rate performance, exhibiting the capacity at 5 C equal to 88.5 % at 0.1 C, while the pristine sample is only 83.7 %. According to the in situ X-ray diffractometer (XRD) test, the higher stability of Sb-NCM materials is mainly manifested in the strain mitigation induced by the absorption of anisotropic lattice shrinkage / extraction, which inhibits the formation of microcracks during charge-discharge test. Therefore, simultaneous Sb doping and Sb oxides coating layer are positive solution to stabilize layered structure and improve electrochemical properties.

A molecular level understanding of antimony immobilization mechanism on goethite by the combination of X-ray absorption spectroscopy and density functional theory calculations

A molecular level understanding of antimony (Sb) immobilization mechanism on Fe oxides is required to clarify the fate of Sb in the soil. In this study, macroscopic sorption experiments, combined with extended X-ray absorption fine structure (EXAFS) spectroscopy and density functional theory (DFT), were utilized to explore the interaction between Sb and goethite. The ion strength has no effect on Sb sorption on goethite, indicating the inner-sphere complex Sb formed on goethite. Goethite has the higher sorption potential to Sb(III) than Sb(V), consistent with the higher thermodynamic stability of the geometry for Sb(III) formed on goethite than Sb(V) revealed by DFT calculations. By comparing the Sb-Fe distances obtained by EXAFS spectroscopy and DFT, eight kinds of Sb(III) surface complexes and nine kinds of Sb(V) surface complexes were considered to be the possible geometries Sb formed on different crystal planes of goethite, including monodentate mononuclear, bidentate mononuclear, bidentate binuclear, tridentate mononuclear, tridentate binuclear, tridentate four-nuclear complexes. The structural and energetic details of these filtered geometries provide comprehensive information on Sb immobilization mechanism on goethite, helpful in clarifying the fate of Sb in soils.

Structure and morphology control of amorphous Mn-doped Fe oxide composite using soft-templates for efficient Sb(V) removal in textile wastewater: Mechanism of solid-liquid interface regulation and Sb(V) adsorption

To achieve high removal rate and efficacy of Sb(V) from textile wastewater and simultaneously realize cyclic Sb(V) recovery, the structure and surface property of amorphous Mn-doped Fe oxide composite (MFOC) were regulated via the combination of facile soft-template synthesis and sintering treatment. Characterization and adsorption results indicated MFOC structure was greatly changed from aggregated large sphere to dispersive small sphere after adjusted by the optimal Brij-58 (SMFO-B). Because of the generated fasciculate micelle, long carbon chain feature and the lowest residual amount of Brij-58, abundant mesopores were generated and the aggregation of unit particles was apparently decreased for SMFO-B. Surface area and total pore volume of SMFO-B became 10 and 6 times of MFOC and more functional hydroxyl groups were generated and exposed on the interface between SMFO-B and water solution. Additionally, the surface positive potential of SMFO-B under neutral condition was also greatly increased. Thus, the maximum adsorption capacity and rate of SMFO-B towards Sb(V) reached to 147 mg/g and 0.1067 mg/(g·min), 2 and 5 times of MFOC. SMFO-B also possessed better selective adsorption ability, exhibited stronger static and dynamic adsorption performance in real textile wastewater and realized the cyclic desorption and enrichment of Sb(V) due to its better phase stability. X-ray absorption spectroscopy showed two main specific forms, such as bidentate edge-(E2) and corner-sharing (C2) complexes, for the inner-sphere complexation during Sb(V) adsorption and E2 complex was proved to play the most important role through the analysis of CD-MUSIC model. This study supplied an excellent adsorbent for Sb(V) removal from textile wastewater and a deeper insight about Sb(V) adsorption onto amorphous Fe oxide.

Structural and mechanistic study of antimonite complexation with organic ligands at the goethite-water interface

Antimony is a re-emerging contaminant, and its complexation with natural organic matter is rising to ever-increasing levels due to global climate change, which has far-reaching impacts on its environmental fate and mobility. A molecular-level understanding of the interactions between Sb(III) and organic ligands at the solid-liquid interface is of paramount importance in deciphering the effect of these organic ligands. Herein, we identified and characterized Sb(III)-organic ligand complexes in solution and at the goethite-water interface using complementary techniques. The FT-ICR MS, XANES, and DFT calculations show that organic ligands bind Sb(III) through nucleophilic functional groups, such as -COO-, -OH and -HS. The formation of surface ternary Sb(III)-bridging complexes retarded the Sb(III) surface precipitation starting from 3.8mg-Sb/L to a much higher level at 8.3-13.5mg-Sb/L. The strong bond between Sb(III) and organic ligands is the key factor to inhibit Sb(III) adsorption, surface precipitation and oxidation under sunlight irradiation. Our results showed the chemical basis for the multifaceted functions of organic ligands in stabilizing trace metalloids such as Sb(III) in the environment.

Connection between coherent phonons and electron-phonon coupling in Sb (111)

We report time- and angle-resolved photoemission spectroscopy (trARPES) measurements on the Sb(111) surface. We observe band- and momentum-dependent binding-energy oscillations in the bulk and surface bands driven by ${A}_{1g}$ and ${E}_{g}$ coherent phonons. While the bulk band shows simultaneous ${A}_{1g}$ and ${E}_{g}$ oscillations, the surface bands show either ${A}_{1g}$ or ${E}_{g}$ oscillations. The observed behavior is reproduced by frozen-phonon calculations based on density functional theory. This evidences the connection between electron-phonon coupling and coherent binding-energy dynamics tied to lattice vibration and confirms that band-, momentum-, and mode-dependent electron-phonon coupling can indeed be probed by trARPES in the low fluence limit.

Borophene and Pristine Graphene 2D Sheets as Potential Surfaces for the Adsorption of Electron-Rich and Electron-Deficient π-Systems: A Comparative DFT Study.

The versatility of striped borophene (sB), β12 borophene (β12), and pristine graphene (GN) to adsorb π-systems was comparatively assessed using benzene (BNZ) and hexafluorobenzene (HFB) as electron-rich and electron-deficient aromatic π-systems, respectively. Using the density functional theory (DFT) method, the adsorption process of the π-systems on the investigated 2D sheets in the parallel configuration was observed to have proceeded more favorably than those in the vertical configuration. According to the observations of the Bader charge transfer analysis, the π-system∙∙∙sB complexes were generally recorded with the largest contributions of charge transfer, followed by the π-system∙∙∙β12 and ∙∙∙GN complexes. The band structures of the pure sheets signaled the metallic and semiconductor characters of the sB/β12 and GN surfaces, respectively. In the parallel configuration, the adsorption of both BNZ and HFB showed more valence and conduction bands compared to the adsorption in the vertical configuration, revealing the prominent preferentiality of the anterior configuration. The density-of-states (DOSs) results also affirmed that the adsorption process of the BNZ and HFB on the surface of the investigated 2D sheets increased their electrical properties. In all instances, the sB and β12 surfaces demonstrated higher adsorptivity towards the BNZ and HFB than the GN analog. The findings of this work could make a significant contribution to the deep understanding of the adsorption behavior of aromatic π-systems toward 2D nanomaterials, leading, in turn, to their development of a wide range of applications.

Robustness of the unidirectional stripe order in the kagome superconductor CsV3Sb5

V-based kagome materials AV3Sb5 (A = K, Rb, Cs) have attracted much attention due to their novel properties such as unconventional superconductivity, giant anomalous Hall effect, charge density wave (CDW) and pair density wave. Except for the 2a 0 × 2a 0 CDW (charge density wave with in-plane 2 × 2 superlattice modulation) in AV3Sb5, an additional 1 × 4 (4a 0) unidirectional stripe order has been observed at the Sb surface of RbV3Sb5 and CsV3Sb5. However, the stability and electronic nature of the 4a 0 stripe order remain controversial and unclear. Here, by using low-temperature scanning tunneling microscopy/spectroscopy (STM/S), we systematically study the 4a 0 stripe order on the Sb-terminated surface of CsV3Sb5. We find that the 4a 0 stripe order is visible in a large energy range. The STM images with positive and negative bias show contrast inversion, which is the hallmark for the Peierls-type CDW. In addition, below the critical temperature about 60 K, the 4a 0 stripe order keeps unaffected against the topmost Cs atoms, point defects, step edges and magnetic field up to 8 T. Our results provide experimental evidences on the existence of unidirectional CDW in CsV3Sb5.

Geometry of tellurene adsorbed on the Si(111)-R30°-Sb surface from first principles calculations.

The 2D form of tellurium, named tellurene, is one of the latest discoveries in the family of 2D mono-elemental materials. In a trilayer configuration, free-standing tellurene was predicted theoretically to acquire two crystallographic forms, the α and β phases, corresponding to either a 1T-MoS2-like geometry or a trilayer slab exposing the Te(101̄0) surface of bulk Te with helical chains lying in-plane and further reconstructed due to the formation of interchain bonds. Either one or the other of the two phases was observed experimentally to prevail depending on the substrate they were grown onto. In the perspective to integrate tellurene on silicon, we here report an ab initio study of the adsorption of tellurene on the Si(111)-R30° surface passivated by antinomy. According to the literature, this substrate is chosen for the growth of several tellurides by molecular beam epitaxy. The calculations reveal that on this substrate the adsorption energy mostly compensates the energy difference between the α and β phases in the free-standing configuration which suggests that the prevalence of one phase over the other might in this case strongly depend on the kinetics effects and deposition conditions.

Multiband Superconductivity with Sign-Preserving Order Parameter in Kagome Superconductor CsV_{3}Sb_{5}.

The superconductivity of a kagome superconductor CsV_{3}Sb_{5} is studied by scanning tunneling microscopy and spectroscopy at ultralow temperature with high resolution. Two kinds of superconducting gaps with multiple sets of coherent peaks and residual zero-energy density of states (DOS) are observed on both half-Cs and Sb surfaces, implying multiband superconductivity. In addition, in-gap states can be induced by magnetic impurities but not by nonmagnetic impurities, suggesting a sign-preserving or s-wave superconducting order parameter. Moreover, the interplay between charge density waves (CDW) and superconductivity differs on various bands, resulting in different density-of-states distributions. Our results suggest that the superconducting gap is likely isotropic on the sections of Fermi surface that play little roles in CDW, and the superconducting gaps on the sections of Fermi surface with anisotropic CDW gaps are likely anisotropic as well. The residual spectral weights at zero energy are attributed to the extremely small superconducting gap on the tiny oval Fermi pockets. Our study provides critical clues for further understanding the superconductivity and its relation to CDW in CsV_{3}Sb_{5}.

Epitaxial growth of GeTe/Sb2Te3 superlattices

In the quest for superlattices with engineered interfaces for disruptive applications such as neuromorphic computing, we present a dedicated study on the epitaxial growth of nominal GeTe/Sb2Te3 chalcogenide superlattices (CSL) on the Sb passivated Si(111) − (√3 × √3)R30°− Sb surface. Intermixing at the GeTe and Sb2Te3 interface is assessed by X-Ray diffraction and reflectivity. A new growth procedure with element flux interruptions is proposed to engineer the degree of intermixing and the tailoring of the GeSbTe layers into Sb-rich compositions.

Biohybrid Bovine Bone Matrix for Controlled Release of Mesenchymal Stem/Stromal Cell Lyosecretome: A Device for Bone Regeneration.

SmartBone® (SB) is a biohybrid bone substitute advantageously proposed as a class III medical device for bone regeneration in reconstructive surgeries (oral, maxillofacial, orthopedic, and oncology). In the present study, a new strategy to improve SB osteoinductivity was developed. SB scaffolds were loaded with lyosecretome, a freeze-dried formulation of mesenchymal stem cell (MSC)-secretome, containing proteins and extracellular vesicles (EVs). Lyosecretome-loaded SB scaffolds (SBlyo) were prepared using an absorption method. A burst release of proteins and EVs (38% and 50% after 30 min, respectively) was observed, and then proteins were released more slowly with respect to EVs, most likely because they more strongly adsorbed onto the SB surface. In vitro tests were conducted using adipose tissue-derived stromal vascular fraction (SVF) plated on SB or SBlyo. After 14 days, significant cell proliferation improvement was observed on SBlyo with respect to SB, where cells filled the cavities between the native trabeculae. On SB, on the other hand, the process was still present, but tissue formation was less organized at 60 days. On both scaffolds, cells differentiated into osteoblasts and were able to mineralize after 60 days. Nonetheless, SBlyo showed a higher expression of osteoblast markers and a higher quantity of newly formed trabeculae than SB alone. The quantification analysis of the newly formed mineralized tissue and the immunohistochemical studies demonstrated that SBlyo induces bone formation more effectively. This osteoinductive effect is likely due to the osteogenic factors present in the lyosecretome, such as fibronectin, alpha-2-macroglobulin, apolipoprotein A, and TGF-β.

Mechanisms of antimony ageing in soils: An XAS study

Antimony (Sb) retention in soils increases in the long term, resulting in lower soluble Sb concentrations and thus a decreased environmental risk of Sb. However, the mechanisms responsible for Sb ageing in soils are not clear, although this is necessary to understand, describe and predict Sb ageing processes in soils. To do so, the long-term retention of added Sb(V) to nine soil samples with contrasting soil properties and to a model iron (Fe; hydrous ferric oxide or HFO) and aluminium (Al; hydrous aluminium oxide or HAO) hydroxide under aerobic conditions was studied with X-ray absorption spectroscopy (XAS). The solid-liquid distribution coefficients (KD) of the soils increased by a factor of 2–4 between 2 weeks and 6 months. In addition, ageing of Sb was more pronounced in the Sb(V)-spiked HFO than in the soils, while no ageing of Sb(V) in the HAO was noted. The added Sb(V) did not change redox speciation throughout six months of aerobic incubation and no indications of antimonate precipitates with Fe or calcium (Ca) were found. Conversely, it was found that with time, Sb(V) was increasingly retained by the HFO and by the soils, likely through micropore diffusion and/or through substitution of Sb(V) into surface Fe octahedra in ferrihydrite. In addition, in the soils, the Sb(V) surface speciation on Fe hydroxides changed with time leading to higher proportion of edge-sharing bidentate Sb⋯Fe complexes. These results suggest that Sb(V) ageing in soils is controlled by different mechanisms simultaneously, i.e., by slow micropore diffusion and/or substitution processes that remove Sb(V) from the reactive surface of the Fe hydroxides and by slow surface processes, with slow sorption reactions more prevalent for edge-sharing bidentate Sb(V) than for corner-sharing bidentate Sb(V) surface complexes.