Mechanisms of 1s Double-Core-Hole Excitation and Decay in Neon

The formation and decay of double-core-hole (DCH) states of the neon ion irradiated by an intense electromagnetic x-ray field are studied theoretically. In the present research DCH formation is the result of sequential absorption of two photons with the creation of an intermediate ion. Detailed calculations of the partial decays and probabilities of shake-ups at the atomic and ionic ionization stages are presented. The angular distribution of photoelectrons corresponding to various residual ionic states are calculated. Specifically, we predict the lack of any photoelectrons corresponding to the residual ionic state 1s12s22pnmpn′2Sf+1D in the direction of the electric field polarization. Dynamical competition between single-core-hole state decay and excitation is analyzed and pulse parameters corresponding to various dynamical regimes are found.

The synthesis of ReS2 flakes and its application in photodetectors

ReS2 is attracting much attention because of its stable trion state. This kind of stable trion state arises on account of weak interlayer coupling as well as anisotropic crystal structure. In this research, we have synthesized ReS2 flakes successfully by using chemical vapor deposition (CVD) method. Stable ionic states in hexagonal wafers are observed by photoluminescence spectroscopy (PL). This substance is stable at room temperature. The HRTEM image from the single ReS2 hexagon reveals that the individual hexagon is single crystal. EDS spectroscopy indicates the purity of the synthesized product. We find that the Re and S atoms ratio in pure ReS2 is 1:2. Then we fabricate a photo detector on individual ReS2 flakes and test its performance. We compare the photocurrent in dark current and under a 500 nm incident light for two media (air and 100 ppm H2). Emission current increases from 1.15 μA to 1.67 μA (forward) and from 7.9 μA to 13.8 μA (reverse). Therefore, the ReS2 hexagonal wafer is an ideal choice for stable and reliable room temperature optical gas sensor. And the material can also be used for fast switch.

Benchmark PhotoIonization Cross-Sections of Neutral Scandium from the Ground and Excited States

The B-spline R-matrix method has been used to investigate cross-sections for photoionization of neutral scandium from the ground and excited states in the energy region from the 3d and 4s valence electron ionization thresholds to 25 eV. The initial bound states of Sc and the final residual Sc+ ionic states have been accurately calculated by combining the multiconfiguration Hartree-Fock method with the frozen-core close-coupling approach. The lowest 20 bound states of Sc I belonging to the ground 3d4s2 and excited 3d24s, 3d24p, 3d4s4p, 4s24p, and 3d3 configurations have been considered as initial states. The 81 LS final ionic states of Sc+ belonging to the terms of 3p63d2, 3p63d4l (l = 0–3), 3p63d5l (l = 0–3), 3p63d6s, 3p64s2, 3p64s4l (l = 0–3), 3p64s5l (l = 0–1), and 3p64p2 configurations have been included in the final-state close-coupling expansion. The cross-sections are dominated by complicated resonance structures in the low energy region converging to several Sc+ ionic thresholds. The inclusion of all these final ionic states has been noted to significantly impact the near-threshold resonance structures and background cross-sections. The important scattering channels for leaving the residual ion in various final states have been identified, and the 3d electron ionization channels have been noted to dominate the cross-sections at higher photon energies.

Plant-Derived Nanobiomaterials as a Potential Next Generation Dental Implant Surface Modifier

Dental implants resemble synthetic materials, mainly designed as teeth-mimics to replace the damaged or irregular teeth. Specifically, they are demarcated as a surgical fixture of artificial implant materials, which are placed into the jawbone, and are allowed to be fused with the bone, similar to natural teeth. Dental implants may be categorized into endosteal, subperiosteal, and zygomatic classes, based on the placement of the implant “in the bone” or on top of the jawbone, under the gum tissue. In general, titanium and its alloys have found everyday applications as common, successful dental implant materials. However, these materials may also undergo corrosion and wear, which can lead to degradation into their ionic states, deposition in the surrounding tissues, as well as inflammation. Consequently, nanomaterials are recently introduced as a potential alternative to replace the conventional titanium-based dental implants. However, nanomaterials synthesized via physical and chemical approaches are either costly, non/less biocompatible, or toxic to the bone cells. Hence, biosynthesized nanomaterials, or bionanomaterials, are proposed in recent studies as potential non-toxic dental implant candidates. Further, nanobiomaterials with plant origins, such as nanocelluloses, nanometals, nanopolymers, and nanocarbon materials, are identified to possess enhanced biocompatibility, bioavailability and no/less cytotoxicity with antimicrobial efficacy at low costs and ease of fabrication. In this minireview, we present an outline of recent nanobiomaterials that are extensively investigated for dental implant applications. Additionally, we discuss their action mechanisms, applicability, and significance as dental implants, shortcomings, and future perspectives.

Controlled Experiments and Optimized Theory of Absorption Spectra of Li Metal and Salts

<b><u>Abstract:</u></b> Investigations of Li metal and ionic compounds through experimental and theoretical spectroscopy has been of tremendous interest due to their prospective applications in Li-metal and Li-ion batteries. Li <i>K</i>-edge soft X-ray absorption spectroscopy (sXAS) provides the most direct spectroscopic characterization; unfortunately, due to the low core-level energy and the highly reactive surface, Li<i>-K</i> sXAS of Li metal has been extremely challenging, as evidenced by many controversial reports. Here, through controlled and ultra-high energy resolution experiments of two kinds of <i>in-situ</i> prepared samples, we report the intrinsic Li<i>-K</i> sXAS of Li-metal that displays a prominent leading peak, which has never been revealed before. Furthermore, theoretical simulations show that the Li<i>-K</i> sXAS is strongly affected by the response of the valence electrons to the core-hole due to the low number of valence electrons in Li. We successfully reproduce the Li<i>-K</i> sXAS by state-of-the-art calculations with considerations of a number of relevant parameters such as temperature, resolution, and especially contributions from transitions which are forbidden in the so-called single-particle treatment. Such a comparative experimental and theoretical investigation is further extended to a series of Li ionic compounds, which highlight the importance of considering the total and single-particle energies for obtaining an accurate alignment of the spectra. Our work provides the first reliable Li<i>-K</i> sXAS of Li metal surface with advanced theoretical calculations. The experimental and theoretical results provide a critical benchmark for studying Li surface chemistry in both metallic and ionic states.

Controlled Experiments and Optimized Theory of Absorption Spectra of Li Metal and Salts

<b><u>Abstract:</u></b> Investigations of Li metal and ionic compounds through experimental and theoretical spectroscopy has been of tremendous interest due to their prospective applications in Li-metal and Li-ion batteries. Li <i>K</i>-edge soft X-ray absorption spectroscopy (sXAS) provides the most direct spectroscopic characterization; unfortunately, due to the low core-level energy and the highly reactive surface, Li<i>-K</i> sXAS of Li metal has been extremely challenging, as evidenced by many controversial reports. Here, through controlled and ultra-high energy resolution experiments of two kinds of <i>in-situ</i> prepared samples, we report the intrinsic Li<i>-K</i> sXAS of Li-metal that displays a prominent leading peak, which has never been revealed before. Furthermore, theoretical simulations show that the Li<i>-K</i> sXAS is strongly affected by the response of the valence electrons to the core-hole due to the low number of valence electrons in Li. We successfully reproduce the Li<i>-K</i> sXAS by state-of-the-art calculations with considerations of a number of relevant parameters such as temperature, resolution, and especially contributions from transitions which are forbidden in the so-called single-particle treatment. Such a comparative experimental and theoretical investigation is further extended to a series of Li ionic compounds, which highlight the importance of considering the total and single-particle energies for obtaining an accurate alignment of the spectra. Our work provides the first reliable Li<i>-K</i> sXAS of Li metal surface with advanced theoretical calculations. The experimental and theoretical results provide a critical benchmark for studying Li surface chemistry in both metallic and ionic states.

Enhancement of Efficiency of Pd/Al2O3Catalysts in Selective Hydrogenation of Sec-Butylbenzene by Modification with H2SO4 or H2WO4

Hydrogenation of bulky aromatic hydrocarbons is an important problem to be solved in order to improve the quality of fuels. Pd-containing catalysts modified by strong acids have been prepared and studied by diffuse-reflectance IR spectroscopy, and the catalytic activity of the materials has been determined. In studying the selective liquid-phase hydrogenation of sec-butylbenzene as a model substrate, it was shown that modification of Pd/Al2O3 catalysts with acid additives (H2SO4 or H2WO4) results in a significant increase in the hydrogenation activity and selectivity. IR spectroscopy of adsorbed CO and d3-acetonitrile revealed that larger palladium metal particles are formed on the Pd-H2SO4(H2WO4)/Al2O3 catalysts, with ionic states of palladium being present even in the samples reduced in H2.