Si 2p Research Articles

Qualitative surface characterization of Indian Permian coal using XPS and FTIR

ABSTRACT This paper reports on the surface properties associated with high-ash Indian Permian coal, which primarily depend on its geochemical compositions. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) techniques have been used to assess surface properties. The results confirm the presence of different elements, mineral phases, and organic functional groups in coal. The XPS survey confirms the presence of different elements on the surface of the coal. Some of them are C 1s (286.0 eV), O 1s (534.5 eV), N 1s (399.9 eV), S 2p (158.2 eV), such as SiO2 and Al2O3, which correspond to Si 2p (102.7 eV) and Al 2p (75.6 eV) with other clay minerals. XPS spectra of C 1s confirm the presence of aliphatic and aromatic carbon, which are hydrophobic compared to hydrophilic groups such as alcoholic, carboxylic, and phenolic. FTIR also validates the existence of hydrophobic functional groups as being higher than hydrophilic groups. Proximate and ultimate analysis results also confirm the presence of less moisture and a higher carbon percentage in the coal samples. Hence, the inherent hydrophobicity of the coal surface is excellent, and the surface hydrophobicity of coal can also be characterized using XPS and FTIR techniques. This information about the coal properties will be very beneficial for coal beneficiation and utilization.

Dual-Resistance of Ion Migration and Moisture Erosion via Hydrolytic Crosslinking of Siloxane Functionalized Poly(Ionic Liquids) for Efficient and Stable Perovskite Solar Cells

Dual-Resistance of Ion Migration and Moisture Erosion via Hydrolytic Crosslinking of Siloxane Functionalized Poly(Ionic Liquids) for Efficient and Stable Perovskite Solar Cells

Resonant inelastic soft x-ray scattering on LaPt2Si2

X-ray absorption and resonant inelastic x-ray scattering spectra of LaPt2Si2 single crystal at the Si 2p and La 4d edges are presented. The data are interpreted in terms of density functional theory, showing that the Si spectra can be described in terms of Si s and d local partial density of states (LPDOS), and the La spectra are due to quasi-atomic local 4f excitations. Calculations show that Pt d-LPDOS dominates the occupied states, and a sharp localized La f state is found in the unoccupied states, in line with the observations.

The Si + SO2 collision and an extended network of neutral–neutral reactions between silicon and sulphur bearing species

ABSTRACT The Si + SO2 reaction is investigated to verify its impact on the abundances of molecules with astrochemical interest, such as SiS, SiO, SO, and others. According to our results Si(3P) and SO2 react barrierlessly yielding only the monoxides SO and SiO as products. No favourable pathway has been found leading to other products, and this reaction should not contribute to SiS abundance. Furthermore, it is predicted that SiS is stable in collisions with O2, and that S(3P) + SiO2 and O(3P)+OSiS will also produce SO + SiO. Using these results and gathering further experimental and computational data from the literature, we provide an extended network of neutral–neutral reactions involving Si- and S-bearing molecules. The effects of these reactions were examined in a protostellar shock model, using the nautilus gas–grain code. This consisted in simulating the physicochemical conditions of a shocked gas evolving from (i) primeval cold core, (ii) the shock region itself, (iii) and finally the gas bulk conditions after the passage of the shock. Emphasizing on the cloud ages and including systematically these chemical reactions, we found that [SiS/H2] can be of the order of ∼10−8 in shocks that evolves from clouds of t = 1 × 106 yr, whose values are mostly affected by the SiS + O $\longrightarrow$SiO + S reaction. Perspectives on further models along with observations are discussed in the context of sources harbouring molecular outflows.

XPS characterization of ciprofloxacin tablet

Ciprofloxacin tablet was characterized by x-ray photoelectron spectroscopy. The sample was fixed to a stainless-steel sample holder with copper double-sided adhesive tape. Survey spectrum, C 1s, O 1s, N 1s, F 1s, Cl 2p, Mg 1s, and Si 2p core levels spectra were acquired. The results point out the presence of carbon, oxygen, nitrogen, and fluorine elements that constitute the ciprofloxacin; however, carbon and oxygen are also found in other ingredients (excipients). Additionally, chlorine, silicon, and magnesium were also detected, which are related with excipients.

High-energy x-ray photoelectron spectroscopy on Si3N4 with Ga Kα photons

Silicon nitride (Si3N4) grown by metalorganic chemical vapor deposition on Si was analyzed using high-resolution high-energy x-ray photoelectron spectroscopy (HAXPES). The HAXPES spectra of Si3N4 obtained using monochromatic Ga Kα radiation at 9252.13 eV include a survey scan and high-resolution spectra of Si 1s, Si 2p, N 1s, and O 1s.

High-energy x-ray photoelectron spectroscopy spectra of SiO2 measured by Cr Kα

Silicon oxide (SiO2) grown by rapid thermal oxidation on Si was analyzed using high-resolution high-energy x-ray photoelectron spectroscopy (HAXPES). The HAXPES spectra of SiO2 obtained using monochromatic Cr Kα radiation at 5414.8 eV include two survey scans (Al Kα and Cr Kα) and high-resolution spectra of Si 2p, Si 2s, Si 1s, and O 1s.

High energy x-ray photoelectron spectroscopy spectra of Si3N4 measured by Cr Kα

Silicon nitride (Si3N4) grown by metalorganic chemical vapor deposition on Si was analyzed using high-resolution high-energy x-ray photoelectron spectroscopy (HAXPES). The HAXPES spectra of Si3N4 obtained using monochromatic Cr Kα radiation at 5414.8 eV include two survey scans (Al Kα and Cr Kα) and high-resolution spectra of Si 2p, Si 2s, Si 1s, and N 1s.

HAXPES on SiO2 with Ga Kα photons

Silicon oxide (SiO2) grown by rapid thermal oxidation (RTO) was analyzed using high-resolution high-energy x-ray photoelectron spectroscopy (HAXPES). The HAXPES spectra of SiO2 obtained using monochromatic Ga Kα radiation at 9252.13 eV include a survey scan and high-resolution spectra of Si 1s, Si 2p, O 1s, and C 1s.

A Synchrotron Radiation Photoemission Study of SiGe(001)-2×1 Grown on Ge and Si Substrates: The Surface Electronic Structure for Various Ge Concentrations.

Beyond the macroscopic perspective, this study microscopically investigates Si1−xGex(001)-2×1 samples that were grown on the epi Ge(001) and epi Si(001) substrates via molecular-beam epitaxy, using the high-resolution synchrotron radiation photoelectron spectroscopy (SRPES) as a probe. The low-energy electron diffraction equipped in the SRPES chamber showed 2×1 double-domain reconstruction. Analyses of the Ge 3d core-level spectra acquired using different photon energies and emission angles consistently reveal the ordered spots to be in a Ge–Ge tilted configuration, which is similar to that in epi Ge(001)-2×1. It was further found that the subsurface layer was actually dominated by Ge, which supported the buckled configuration. The Si atoms were first found in the third surface layer. These Si atoms were further divided into two parts, one underneath the Ge–Ge dimer and one between the dimer row. The distinct energy positions of the Si 2p core-level spectrum were caused by stresses, not by charge alternations.

Effect of chromium and boron incorporation methods on structural and catalytic properties of hierarchical ZSM-5 in the methanol-to-propylene process

We introduced chromium and boron into the hierarchical structure of ZSM-5 by following an incipient wet impregnation and hydrothermal synthesis approach to enhance the performance of the catalysts in the methanol-to-propylene process. Crystal structure, preferred orientation, and crystal symmetry of synthesized zeolites were discussed using Rietveld refinement and revealed that all synthesized zeolites crystallized in a monoclinic structure, whereas the boron-incorporated sample exhibited an orthorhombic symmetry. Large-scale defect-free single-crystalline structures of hierarchical zeolite created by CTAB and F127 mesoporogens are confirmed by electron microscopy and magic angle spinning nuclear magnetic resonance (MAS NMR). The formation of surface metal oxides and extra-framework metal oxides caused changes in the electronic structure of the components as visible in Si 2p and O 1s spectra. The predominant presence of OH groups and the higher Cr (VI) /Cr (III) ratio account for the better performance of impregnated chromium-ZSM-5 especially in the production of light olefins. The introduction of boron by impregnation further preserved the preferred growth orientation, hierarchical structure with high crystallinity and caused surface acidity changes in favor of increasing propylene selectivity to 67% with a propylene/ethylene ratio of close to 8.

Construction of high-efficiency fixing structure of waterborne paint on silicate-modified poplar surfaces by bridging with silane coupling agents

To improve the wettability, the surface free energy, and film adhesion performance of silicate-modified poplar wood (SMPW) surfaces, different silane coupling agents (KH550, KH560, KH570, and KH580) were applied to SMPW surfaces. The properties including film adhesion, functional groups, wettability, penetration depth, and surface free energy were analyzed and characterized by film adhesion tests, FT-IR, XPS, SEM, contact angle measurements, optical magnifying microscope test, and surface free energy calculations. The results showed that the film adhesion of poplar wood, SMPW, and the silane coupling agents KH550, KH560, KH570 and KH580 treated SMPW surfaces were grade 1, grade 3, grade 1, grade 0, grade 1, and grade 0, respectively. The SEM test results were consistent with results of the paint film adhesion. According to the XPS results, there were two binding energies peaks at 99–104 eV and 151–155 eV, corresponding to Si 2p and Si 2s, respectively, indicating that the form of Si had changed. In the FITR spectra, the SiOSi stretching and bending vibrations on the surface of the modified material treated with silane coupling agents were significantly stronger than that of the SMPW, indicating that silane coupling agents chemically bonded to the surface of the SMPW. The contact angles of the WBSV on the surface of poplar material, SMPW and silane coupling agent KH550, KH560, KH570, and KH580 were 50.60°, 77.17°, 52°, 45.92°, 52.83°, and 47.20°, respectively. The wettability of the surface after silicate modification was lower than that of the poplar material. After silane coupling agent treatment, the wettability of the surface to the WBSV was improved to varying degrees. The surface free energy of poplar and SMPW were 46.88 and 37.72 (10−3 J·m−2), respectively, illustrating that SMPW reduced the surface free energy. The surface free energy of SMPW treated with silane coupling agents KH550, KH560, KH570, and KH580 was 45.10, 50.93, 44.06, and 49.49 (10−3 J·m−2), respectively, which showed that the surface free energy of SMPW treated with different silane coupling agents was higher than that of SMPW.

Chirality Transfer from Chiral Mesoporous Silica to Perovskite CsPbBr 3 Nanocrystals: The Role of Chiral Confinement

Chirality Transfer from Chiral Mesoporous Silica to Perovskite CsPbBr ₃ Nanocrystals: The Role of Chiral Confinement

High-energy photoelectron spectroscopy of Si3N4 thin film on Si with Cr Kα excitation

Si3N4 thin film grown by low-pressure chemical vapor deposition was measured by high-energy photoelectron spectroscopy using monochromatic Cr Kα (5414.8 eV) radiation. A survey scan and high-resolution spectra of Si 1s, Si 2s, Si 2p, and N 1s are reported.

High-energy photoelectron spectroscopy of 6H-SiC wafer with Cr Kα excitation

A C-terminated SiC wafer was analyzed by high-energy photoelectron spectroscopy using monochromatic Cr Kα (5414.8 eV) radiation. The data include a survey scan and high-resolution spectra of Si 1s, Si 2s, Si 2p, C 1s, and O 1s core levels.

High-energy photoelectron spectroscopy of Si(100) with Cr Kα excitation

Si (100) wafer was analyzed by high-energy photoelectron spectroscopy (HAXPES) using monochromatic Cr Kα radiation (5414.8 eV). The HAXPES spectra reported here include a survey scan and high-resolution spectra of Si 1s, Si 2s, and Si 2p core-levels.

Orange-reddish photoluminescence enhancement and wollastonite nanocrystals formation induced by CaO in Sm3+-doped calcium sodium borosilicate glasses

The influence of CaO content on the structural, chemical, and optical properties of Sm3+-doped calcium sodium borosilicate glasses is presented. Different undoped and Sm3+-doped borosilicate glasses with varying CaO (0–30 mol%) and Sm2O3 (0–4 mol%) contents were synthesized using the melt-quenching technique at 1300–1400 °C. Although XRD results showed the amorphous nature of all the glasses, HRTEM analysis revealed the formation of small wollastonite nanocrystals with sizes in the range of 10–25 nm for 30 mol% of CaO. FTIR and XPS analyses indicated the occurrence of the boric anomaly in glasses with 0–10 mol% CaO contents, causing an increase in the [BO4]- units and a decrease in [BO3] units. The high-resolution O 1s and Si 2p XPS spectra, studied as a function of increased CaO content, revealed the continuous formation of non-bridging oxygens that increased the glass structure's asymmetry and promoted the formation of interstitials used as host for Sm3+ ions. Consequently, PL intensity of Sm3+-doped borosilicate glasses increased with the addition of CaO, reaching a maximum at 30 mol%. Besides, the optimization of Sm2O3 doping concentration produced the highest intensity at 0.25 mol% with orange-reddish emission (CIE coordinates: x = 0.60, y = 0.40). These glasses have potential applications as n-UV and blue-excited LED-driven orange-reddish phosphors in white solid-state lighting devices and color displays.

Density Functional Theory Study of Metallic Silicon (111) Plane Structures.

The band structure on the surface might be influenced by the abruptly ended periodic structure and change the physical properties of the semiconductor. By using the density functional theory, this research also demonstrates that the Si unit cell has the calculated room-temperature electrical conductivity as 4.01 × 10–6 (Ω–1 cm–1), similar to the experimental result. Thus, the Si(111) plane structures are calculated, and we found out that the one-layer and two-layer plane structures have the theoretical room-temperature electrical conductivities as 129.68 (Ω–1 cm–1) and 547.80 (Ω–1 cm–1), respectively. In addition, the results reveal that the conduction band and valance band of the Si(111) one-layer and two-layer structures will connect on the ⟨111⟩ direction, mainly contributed by Si 3p orbitals. Thus, the band structure at the ⟨111⟩ direction on the Si(111) surface has variation and increases the electrical conductivity to 7 to 8 orders compared to the intrinsic Si and offers new surface science and surface engineering concepts for future applications.

Effects of electronegativities and charge delocalization on Q2 Raman shifts of alkaline- and alkaline earth-bearing glasses and metasilicate crystals

Abstract Raman shifts of the symmetric stretch of silicate Q2 species vary over a range of ~90 cm−1 in crystals and glasses containing alkali and alkaline earth oxides. The shifts display a striking, sympathetic relationship with the electronegativity of the alkali and alkaline earth metals (M), with the highest frequency observed for Mg-silicate glasses and crystals and the lowest frequency for Cs-bearing glasses. Frequencies are determined primarily by the electron density on constituent Si and O atoms of the Q2 tetrahedra, as measured by Si 2p and O 1s X-ray photoelectron spectra (XPS). The electron density is, in turn, determined by the extent to which electronic charge is transferred from the modifier metal “M” to the NBO of the Q2 tetrahedron. The charge transferred to NBO is redistributed (delocalized) over all atoms of the tetrahedron by the four equivalent Si sp3 orbitals. Although negative charge accumulates on all atoms of the tetrahedron, it accumulates preferentially on Si. Coulombic interactions among Si and all O atoms are thus weakened, resulting in decreased force constants and lowered symmetric stretch frequencies of Q2 species. Density functional theoretical (DFT) calculations on six staggered and eclipsed M6Si2O7 (M = Li, Na, K) molecules corroborate the findings. Charge is transferred from the metal atoms to NBO and delocalized over tetrahedra in accordance with Li, Na, and K electronegativities. Calculated Si-O force constants and Raman shifts decrease with decreasing electronegativity of the cation but surprisingly, calculated Si-NBO bond lengths are largely unaffected, with all being similar at 1.665 ± 0.003 Å.

An accurate many-body expansion potential energy surface for SiH2 (11 A') using a switching function formalism.

An accurate many-body expansion potential energy surface for the ground state of SiH2 is reported. To warrant the correct behavior at the Si (1D) + H2 (X1Σ+g) dissociation channels involving silicon in the first excited Si (1D) and ground Si (3P) states, a switching function formalism has been utilized. A great deal of ab initio points based on aug-cc-pV(Q+d)Z and aug-cc-pV(5+d)Z basis sets are utilized at the multi-reference configuration interaction level using the full-valence-complete-active-space wave function as the reference. Subsequently the calculated energies are corrected via a many-body expansion method to extrapolate to the complete basis set limit. The topographic features of the novel many-body expansion global potential energy surface are studied in detail, showing a good agreement with the theoretical and experimental results in the literature. Moreover, the integral cross-section of the Si (1D) + H2 (X1Σ+g) → H (2S) + SiH (X2Π) reaction has been calculated using the time-dependent wave packet method, which provides support for the reliability of the title potential energy surface. This work can serve as the foundation for the study of Si (1D) + H2 (X1Σ+g) reaction kinetics, and for the construction of the larger multibody expansion potential energy surface of silicon/hydrogen containing systems.