Metal-supported cerium dioxide catalysts are widely used in industrial processes. This study investigates copper-cerium dioxide (Cu-CeO2) as a promising catalyst for CO oxidation, noted for its cost-effectiveness and low activation temperature. However, the reaction mechanism remains unclear. We examine the effects of copper ion doping into CeO2 nanoparticles at 0, 5, 15 at%, synthesized via precipitation. X-ray diffraction (XRD) analysis confirmed sample purity, revealing partial amorphization at a higher doping level. Lower Cu concentration in CeO2 facilitated CO oxidation at a lower temperature. X-ray absorption spectroscopy (XAS) investigated the electronic and atomic structures, showing that CeO2 with a lower Cu doping resulted in a higher lattice oxygen content and moderate Cu ion reduction. Increased Cu doping decreased Ce-O coordination numbers, while Cu-O radial distance was larger at lower doping. In situ XAS identified moderate reduction of Ce and Cu, elucidating CO oxidation via the Langmuir-Hinshelwood (LH) mechanism at lower Cu concentration. The superior low-temperature CO oxidation performance is attributed to moderate Ce and Cu ion reduction coupled with increased oxygen adsorption on the catalyst surface. These findings provide insights into the relationship between the dopant concentration, electronic structure, and catalytic activity for optimizing ceria-based catalysts for efficient CO oxidation.

High-quality two-dimensional Bi2WO6 nanolayers were synthesized via hydrothermal processes, with oxygen vacancies introduced through an ultrasound-assisted alkali etching treatment. Comprehensive characterization using Raman spectroscopy, X-ray absorption spectroscopy (XAS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and positron annihilation spectroscopy (PAS) confirmed the presence and effects of these vacancies on the structural and electronic properties of the nanolayers. Raman spectroscopy revealed shifts in vibrational modes, particularly a blue shift in the WO6 octahedral vibration modes, indicative of oxygen vacancy formation. XPS analysis showed a reduction in the binding energies of the Bi 4f and W 4f orbitals, confirming an altered electronic environment. TEM images demonstrated significant lattice distortions in the oxygen-vacancy-rich regions, particularly disordered WO6 octahedra and disrupted Bi-O bond lengths. These distortions are consistent with the structural disorder observed in XAS measurements, which highlighted a reduction in the coordination number of W atoms and a corresponding contraction of W-O bond lengths. This charge redistribution between Bi and W atoms due to oxygen vacancies leads to localized structural perturbations, as further evidenced by PAS, which showed increased positron lifetimes associated with vacancy clusters, particularly around the Bi and W atoms. These vacancies create defective sites that trap photogenerated electrons, preventing their recombination with holes, thereby significantly enhancing photocatalytic performance. The enhanced photocatalytic activity was demonstrated by the nearly 98 % degradation of Rhodamine B dye under visible-light irradiation, a substantial improvement over the 70 % degradation achieved by the untreated sample. This work presents an innovative approach for generating stable oxygen vacancies in Bi2WO6 nanolayers and offers an in-depth understanding of the mechanisms that enhance photocatalytic performance, providing valuable insights for advancing photocatalysts designed for environmental remediation.

This investigation explores the potential of co-incorporating nickel (Ni) and cobalt (Co) into copper oxide (CuO) nanostructures for bifunctional electrochemical charge storage and oxygen evolution reactions (OER). A facile wet chemical synthesis method is employed to co-incorporate Ni and Co into CuO, yielding diverse nanostructured morphologies, including rods, spheres, and flake. The X-ray diffraction (XRD) and Raman analyses confirmed the formation of NiCo-CuO nanostructure, with minor phases of nickel oxide (NiO) and cobalt tetraoxide (Co3O4). High-resolution Transmission Electron Microscope (HRTEM) also confirms the diverse morphologies and the minor phases of oxides. Synchrotron X-ray absorption spectroscopy revealed higher charge states of Cu, Ni, and Co in the NiCo-CuO nanostructure, enhancing its charge storage and OER. Site-selective X-ray absorption near edge structure analysis elucidated the spatial distribution of Cu, Ni, and Co in the nanostructure. Furthermore, extended X-ray absorption fine structure spectroscopy provided insights into the local atomic structures, revealing increased coordination numbers and interatomic distances in the NiCo-CuO nanostructure. In situ Raman analysis discloses the transformation of Co3O4 into cobalt hydroxide (Co(OH)2) and cobalt oxide (CoO) into cobalt oxyhydroxide (CoOOH) The NiCo-CuO nanostructures exhibited superior specific capacitance, favorable Tafel behavior, and low overpotential positioning as promising bifunctional materials for energy storage and conversion applications. This work contributes to the development of efficient CuO nanocatalysts.

Going beyond graphene and transition-metal dichalcogenides, group III-VI metal chalcogenides (GIIIMCs) with diverse crystallinities appear as new rising stars and have recently attracted numerous interesting physics for prospective optoelectronics, even though they face crucial challenges in their epitaxial technology. In this work, for the first time, large-compositional range In x Ga y Se z ternary alloys have been deposited on c-sapphire substrates by molecular beam epitaxy (MBE). We explored that MBE of In x Ga y Se z on c-sapphire substrates undergoes a two-dimensional (2D)-to-three-dimensional (3D) structural phase transition, resulting in mixed-dimensional alloy heterostructures of 2D hexagonal-In x Ga y Se z and 3D zinc-blende/wurtzite In x Ga y Se z . The 2D-to-3D transition supposedly originates from the indium segregation and depends strongly on the indium composition. We also found that modulating the growth parameters such as In/Ga ratio, deposition temperature, and deposition time could be an effective way to precisely control the 2D/3D crystal phases of the alloys. Overall, the results pave the way for phase/physical engineering of GIIIMC-based alloys through MBE and realizing mixed-dimensional alloy heterostructures for multifunctional applications.

Tungsten disulfide (WS2) quantum dots (QDs) dispersed in liquid crystal (LC) was studied for polarized photoluminescence (PL). Compared to diethylenetriamine-(DETA-) doped WS2 QDs, the DETA-doped WS2 QDs dispersed in LC molecules showed a red-shift in the PL peak and an enhanced PL intensity, which is explained by the electric dipole interaction between QDs and LC molecules. The linearly polarized PL was investigated in the LC-dispersed WS2 QDs under the applied voltages from 0 to 4.0 V. With increasing the applied voltages, the polarized PL intensity along to the rubbed polyimide direction decreases, leading to a decrease in the degree of linear polarization. The observed anisotropic changes of the polarized PL for the QDs in LC matrix can be accounted for by realignment between the LC molecules and QDs under the electric field.

We report the intriguing phenomena of evolution of color centers (F and F+) using time-dependent X-ray excited optical luminescence (XEOL) in c-plane Sapphire wafer, (3-Ga2O3/c-Sapphire and GaSe/(3-Ga2O3/c-Sapphire. The increasing emission intensity of F+ and F-color centers over time indicates the formation of new color centers by continuous exposure to X-ray irradiation. These oxygen vacancy defect states remained even after having layer of epitaxial thin film of (3-Ga2O3, and subsequent GaSe of sub mu m thickness on top due to high penetration depth of X-ray. Interestingly, defect states of (3-Ga2O3 decrease with time suggesting passivation of defect states induced by long term exposure to X-ray radiation. Also, we demonstrated the effect of long term X-ray irradiation using XEOL map, revealing spatial variation in defect state emission intensities. Time-resolved XEOL was used to measure dynamics of luminescence decay of F+ color center and defect state emission of Ga2O3.

Understanding of single-layer and bilayer thin films of WO3 and Ta2O5 for electrochromic applications remains elusive. In this study, single layers of WO3 and Ta2O5 and bilayer thin films of WO3/Ta2O5 and Ta2O5/WO3 were prepared by the sol–gel method followed by spin coating. X-ray diffraction (XRD) analysis revealed the semicrystalline nature of WO3 and the absence of significant crystalline planes in Ta2O5. Raman spectroscopy confirmed the characteristic vibrational modes of WO3 and Ta2O5 in both single-layer and bilayer thin films. Enhancement in cyclic voltammetry (CV) was observed in Ta2O5/WO3 compared to other thin films. Additionally, Ta2O5/WO3 exhibited a greater change in transmittance (ΔT) relative to other configurations. The impact of proton irradiation on the thin films was further investigated, revealing modifications in their structural and phonon vibrational properties. Notably, the CV performance of the irradiated thin films was drastically reduced. X-ray absorption spectroscopy (XAS) provided insights into the modulation of hybridization of O with W/Ta and the charge states of W and Ta in the thin films. This study provides a comprehensive understanding of single-layer and bilayer electrochromic thin films and their response to proton irradiation, paving the way for the development of space-applicable electrochromic bilayer thin films with improved performance and stability.

Abstract Integrating two-dimensional (2D) layered materials with wide bandgap β-Ga2O3 has unveiled impressive opportunities for exploring novel physics and device concepts. This study presents the epitaxial growth of 2D β-In2Se3/3D β-Ga2O3 heterostructures on c-Sapphire substrates by plasma-assisted molecular beam epitaxy. Firstly, we employed a temperature-dependent two-step growth process to deposit Ga2O3 and obtained a phase-pure $$(\overline{2 }01)$$ ( 2 ¯ 01 ) β-Ga2O3 film on c-Sapphire. Interestingly, the in-situ reflective high-energy electron diffraction (RHEED) patterns observed from this heterostructure revealed the in-plane ‘b’ lattice constant of β-Ga2O3 ~ 3.038Å. In the next stage, for the first time, 2D In2Se3 layers were epitaxially realized on 3D β-Ga2O3 under varying substrate temperatures (Tsub) and Se/In flux ratios (RVI/III). The deposited layers exhibited (00l) oriented β-In2Se3 on $$(\overline{2 }01)$$ ( 2 ¯ 01 ) β-Ga2O3/c-Sapphire with the epitaxial relationship of $$[11\overline{2 }0]$$ [ 11 2 ¯ 0 ] β-In2Se3 || [010] β-Ga2O3 and $$[10\overline{1 }0]$$ [ 10 1 ¯ 0 ] β-In2Se3 || [102] β-Ga2O3 as observed from the RHEED patterns. Also, the in-plane ‘a’ lattice constant of β-In2Se3 was determined to be ~ 4.027Å. The single-phase β-In2Se3 layers with improved structural and surface quality were achieved at a Tsub ~ 280 °C and RVI/III ~ 18. The microstructural and detailed elemental analysis further confirmed the epitaxy of 2D layered β-In2Se3 on 3D β-Ga2O3, a consequence of the quasi-van der Waals epitaxy. Furthermore, the β-Ga2O3 with an optical bandgap (Eg) of ~ 5.04 eV (deep ultraviolet) when integrated with 2D β-In2Se3, Eg ~ 1.43eV (near infra-red) can reveal potential applications in the optoelectronic field.

In this work, vanadium pentoxide (V2O5) and titanium-modified V2O5 thin films were synthesized using the sol-gel spin coating route. The effect of Ti-doping concentration on the electrochromic optical properties and atomic/electronic structures of V2O5 smart thin films is examined. As the doping concentration of Ti increases, the surface roughness of the films is reduced. The structure of the films is analyzed using X-ray diffraction (XRD) and Raman spectroscopy, while the electrochromic modulation of atomic and electronic structures is elucidated through Raman and X-ray absorption spectroscopy (XAS) conducted during lithiation and delithiation. The XRD patterns demonstrate that an increase in Ti concentration leads to a more amorphous structure of the films and a shift of the main diffraction peak to a lower angle, attributable to the enlarged spacing between the stacking layers resulting from the incorporation of Ti ions. Soft X-ray absorption spectroscopy (XAS) and in situ hard XAS of the V L-edge, the O K-edge, and the V K-edge revealed a reduction in the charge state of V and local atomic structural symmetry modification upon lithated coloration and delithiated bleaching process. The critical insights provided by in situ XAS provides reveal that a small amount of Ti has the ability to modify the interlayer distance and local atomic structure of V2O5, thereby improving its electrochromic switching rate and stability when utilized in smart windows.

Pulsed-laser deposition was utilized to fabricate Eu-doped ZnO epitaxial films on c-plane sapphire substrates with Eu concentrations ranging from 0.5 to 4.0 at. %. The structural properties were analyzed using x-ray diffraction surface normal radial scans and azimuthal cone scans, which confirmed the epitaxy of the film samples. Reciprocal space mapping was performed on ZnO(101̄1) to visualize the effect of Eu incorporation. X-ray fluorescence mapping confirmed the homogeneous distribution of Zn and Eu, and x-ray absorption near-edge structure spectra directly confirmed the trivalent state of Eu ions. The optical properties were assessed using temperature-dependent photoluminescence (PL). Various defects were identified. With increasing Eu dopant concentration, PL emissions from defects and the Eu 4f-intraband transitions gradually became the predominant features in the PL spectra at low temperatures. Furthermore, PL analysis suggested that Eu ions substituted Zn, occupying sites with lower C3v symmetry due to the distortion caused by Eu incorporation.

In this work, we investigated the polarization characteristics of nanoscale undoped hafnium oxide (HfO2) ferroelectric film. The nanoscale domain switching behavior of undoped HfO2 is mainly dominated by mixed ferroelectric/nonferroelectric crystalline phases and interface domain pinning by oxygen vacancies or defect traps. Our experimental results confirm that these issues can be improved by film thickness scaling and well-controlled mechanical stress. We demonstrated a 4-nm-thick undoped HfO2 negative capacitance thin film transistor (NCFET) with an energy-efficient switch characteristic of a low overdrive voltage of -0.6 V, a steep subthreshold swing of sub-60 mV/dec and a uniform hysteresis distribution of sub-60 mV.

The development of an excellent multifunctional electrocatalyst that is based on non-precious metal is critical for improving the electrochemical processes of the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER), and the urea oxidation reaction (UOR) in alkaline media. This study demonstrates that incorporating Mo into Co3O4 facilitated the formation of rich oxygen vacancies (Vo), which promotes effective nitrate adsorption and activation in urea electrolysis. Subsequently, in situ/operando X-ray absorption spectroscopy is used to explore the active sites in Mo-Co3O4-3 under OER, indicating the oxygen vacancies are first filled with OH• in Mo-Co3O4; facilitated the pre-oxidation of low-valence Co, and promoted the reconstruction/deprotonation of intermediate Co-OOH•. Mo-Co3O4-3 electrocatalysts show impressive HER, OER, and UOR with low overpotentials of 141 mV, 220 mV, and 1.32 V, respectively, at 10 mA cm-2 in an alkaline medium. Furthermore, in situ/Operando Raman spectroscopy results reveal the importance of CoOOH active sites for enhanced electrochemical performance in Mo-Co3O4-3 compared to the pure Co3O4. The urea electrolyzer with Mo-Co3O4 electrocatalysts acts as an anode and the cathode delivers 1.42 V at 10 mA cm-2. A viable approach to creating effective UOR electrocatalysts involves synergistic engineering exploiting doping and oxygen vacancies.

IntroductionMyelodysplastic syndrome (MDS) is a heterogeneous constellation of myeloid neoplasms originating from the clonal proliferation of aberrant hematopoietic stem cells (HSC). The human kinome, which comprises over five hundred kinases, plays a critical role in regulating numerous cellular functions. Although the dysregulation of kinases has been observed in various human cancers, the characterization and clinical implications of kinase expressions in MDS have not been investigated before.MethodsOverall, 341 patients diagnosed with primary MDS according to the 2016 WHO classification, who had adequate cryopreserved diagnostic unsorted bone marrow (BM) samples for DNA and RNA sequencing, were recruited. The normalized gene expressions of a total of 517 kinase gene were studied. We first identified those kinases whose expressions were higher in MDS patients than in healthy controls, and then used LASSO-regularized Cox proportional hazards regression to identify prognostically significant kinases to construct the KInase Stratification Score (KISS).ResultsWe discovered that the expression levels of seven kinases (PTK7, KIT, MAST4, NTRK1, PAK6, CAMK1D, PRKCZ) could predict patient outcome, and we used these kinases to construct the KISS; we further validated its prognostic significance in two external MDS cohorts. A higher KISS was associated with older age, higher BM blast percentage, higher IPSS-R risk, complex karyotype, and mutations in several adverse-risk genes in MDS. In the multivariate analysis, a higher KISS was proved to be an independent unfavorable risk factor.ConclusionsAltogether, our findings suggest that KISS holds the potential to improve the current prognostic scheme of MDS, and inform novel therapeutic opportunities.

Molecular beam epitaxy (MBE) is demonstrated as an excellent growth technique for growing a low-defect GaN channel layer, which is crucial for controlling vertical leakage current and improving breakdown voltage (BV) in GaN-based high-electron mobility transistors (HEMTs). The 3D islands to 2D growth mode transition approach was induced by modulating substrate growth temperature (Tsub), displaying an overall improvement in film quality. A comprehensive investigation was conducted into the effects of Tsub on surface morphologies, crystal quality, and the optical and electrical properties of GaN films. Optimal results were achieved with a strain-relaxed GaN film grown at 690 °C, exhibiting significantly improved surface characteristics (root-mean-square roughness, Rq = 0.3 nm) and impressively reduced edge dislocations. However, the film with the smoothest surface roughness, attributed to the effect of the Ga-rich condition, possessed a high surface pit density, negatively affecting optical and electrical properties. A reduction in defect-related yellow emission further confirmed the enhanced crystalline quality of MBE GaN films. The optimized GaN film demonstrated outstanding electrical properties with a BV of ~1450 V, surpassing that of MOCVD GaN (~1180 V). This research significantly contributes to the advancement of MBE GaN-based high electron mobility transistor (HEMT) applications by ensuring outstanding reliability.

In this study, by combining the tight-binding description with the gradient approximation, we investigated the impacts of electric gating and divacancies on the optical characteristics of zigzag buckling silicene nanoribbons. Our results show that the back-gate electric potential tends to shift the peak structure to higher frequencies in the free-defective structures, while the side-gate electric potentials intensify the intensity of the excitation channels obeying the selection rule Delta J = even. In particular, applying the potentials in a suitable range can improve the optical absorption efficiency at a certain frequency with the back gate or widen the threshold absorption intensity from Jv = 1 to Jc =1 with the side gates. Besides, the defective structures' absorption spectra exhibit richer features than the perfect one, with the appearance of new optical excitations due to the transitions between the local minimum or maximum in the low-energy bands around the Fermi level. Moreover, applying electric gating in defective structures can also tune the absorption spectra with additional features.

Phosphates have emerged as promising materials for electrochemical charge storage applications. However, a comprehensive understanding of their storage mechanism remains elusive. The present work reports the impact of nickel ion doping on hydroxyapatite (PH) prepared by a wet-chemical route. X-ray diffraction (XRD) reveals the formation of NiO and Raman and Fourier-transform infrared (FTIR) analyses demonstrate the suppression of phosphate modes on doping. The incorporation of Ni ions induces nanoneedles morphology, effectively engineering the surface area and volume of the material. Notably, specific capacitance significantly improves to 415.35 Fg-1 at 10 mAg-1 for Ni-incorporated PH (0.1 M of Ni) (0.1NH), a remarkable enhancement compared to 166.77 Fg-1 at 10 mAg-1 for pristine (PH). X-ray photoelectron spectroscopy (XPS) confirms the mixed valence state of Ni2+/3+ and the presence of Ni-O bonding on Ni incorporation. Moreover, X-ray absorption spectroscopy (XAS) reveals the formation of Ni-O-Ni clusters, enhanced charge transfer by Ni ions, and optimized coordination of Ni-O bonds. The comprehensive correlation established between the phase, morphology, and electronic and local atomic structures elucidates the excellent electrochemical charge storage performance. This investigation sheds light on the potential of Ni-doped hydroxyapatite as a promising material for electrochemical applications, contributing valuable insights for the design and optimization of advanced energy storage systems.

The structural features and nanomechanical properties of ZnO and Sb-doped (1.0 at%) ZnO (SbZO) thin films deposited on a-plane sapphire substrates by radio-frequency (RF) magnetron sputtering are comparatively investigated in this study. The X-ray diffraction and atomic force microscopy analyses indicated that both ZnO and SbZO thin films were highly (002)-oriented albeit with somewhat different grain structure and surface morphologies. Nanoindentation results of both films exhibited apparent discontinuities (so-called pop-ins) in the load-displacement curves (P-h curves), while no discontinuity was observed in the unloading segment of the P-h curves. By using a Berkovich nanoindenter operating with the continuous contact stiffness measurement mode, the obtained hardness and Young's modulus of ZnO (SbZO) thin films are 7.3 +/- 0.2 (8.5 +/- 0.4) GPa and 259.6 +/- 17.8 (327.4 +/- 13.9) GPa, respectively. Furthermore, the facture toughness and fracture energy of ZnO and SbZO thin films obtained by Vickers indentation were also compared.

Molecular beam epitaxy (MBE) of InGaSe/2D-GaSe/sapphire hybrid structures has been reported in this study. We explore that MBE of the InGaSe layer on 2D-GaSe/sapphire results in a mixed dimensional alloy, comprising two-dimensional (2D) hexagonal-InxGa1-xSe and three-dimensional (3D) zinc blende (InGa)(2)Se-3, in which the 3D one is more favorable. It is also revealed that the surface morphology of the underneath 2D-GaSe layer grown under different modes, i.e., screw-dislocation-driven (SDD-GaSe) and layer-by-layer (LBL-GaSe), significantly governs the epitaxial behavior of the InGaSe top layer. Indeed, in the case of the InGaSe alloy grown on 2D LBL-GaSe, it is more and more preferable to nucleate from the edges of GaSe triangular flakes with increasing deposition temperature, thus promoting lateral growth. On the other hand, the surface morphology of InGaSe alloy on 2D SDD-GaSe appears to have a high density of nanoclusters. Moreover, a structural transition from 2D-to-3D has been recognized from in-situ RHEED observation, in which its on-set point is likely accelerated at lower growth temperatures. The gain from this study benefits our understanding of the mixed dimensional GaSe-based heterostructures by MBE, in terms of exploring semiconductor physics and widening potential applications of group-III metal chalcogenides.

MoSSe is a semiconducting material with a layered structure similar to MoS(2 )and MoSe2, which shows potential applications in optoelectronics, solar cells, sensing, and catalysis. Synthesis of this material with a controllable structure and chemical composition represents a great challenge. Herein, we report a new method for the synthesis of MoSSe by employing an [Et4N](2)[Mo3S4Se3Br6] complex as the sole precursor. Thermal annealing of this complex under an Ar atmosphere at moderate temperatures ranging from 350 degrees C to 650 degrees C resulted in the formation of pure MoSSe. The morphology and structure of MoSSe were characterized using SEM, HRTEM, XRD, Raman spectroscopy, X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). The effects of annealing temperature on the structure of MoSSe were also examined.