Si Bond Research Articles

An Authentic Al=Si Double Bond

Aluminata‐silenes are the elusive heavier counterparts of the well‐known borataalkenes in which the B=C double bond is formally replaced by an Al=Si moiety. We report the isolation of a four‐membered anionic AlSi3 cycle with a bona fide Al=Si double bond, which is obtained by the reaction of 2 eq. of disilenide Tip2Si=SiTipLi with H2AlCl (Tip = 2,4,6‐triisopropylphenyl). X‐ray crystallography, UV‐vis spectroscopy and computational analysis confirm the double bond character with a very short Al‐Si bond of 2.283(1) Å and high Wiberg bond index (WBI) of 1.31. Intramolecular C‐H activation by the Al=Si bond and the reactions with sulfur sources confirm typical double bond reactivity.

An Authentic Al=Si Double Bond

Aluminata‐silenes are the elusive heavier counterparts of the well‐known borataalkenes in which the B=C double bond is formally replaced by an Al=Si moiety. We report the isolation of a four‐membered anionic AlSi3 cycle with a bona fide Al=Si double bond, which is obtained by the reaction of 2 eq. of disilenide Tip2Si=SiTipLi with H2AlCl (Tip = 2,4,6‐triisopropylphenyl). X‐ray crystallography, UV‐vis spectroscopy and computational analysis confirm the double bond character with a very short Al‐Si bond of 2.283(1) Å and high Wiberg bond index (WBI) of 1.31. Intramolecular C‐H activation by the Al=Si bond and the reactions with sulfur sources confirm typical double bond reactivity.

Sol–gel synthesis of silicon oxide (SiO2) nanoparticles: exploring gas sensing and photocatalytic applications

In this research, silicon oxide (SiO2) nanoparticles (NPs) were synthesized using the sol–gel method. The synthesized materials were characterized through various techniques. Fourier transform infrared spectroscopy (FTIR) revealed the absorption band corresponding to Si–O–Si bonds. Ultraviolet–visible (UV–Vis) spectroscopy analysis indicated a band gap energy of 5 eV. X-ray diffraction (XRD) analysis displayed a broad peak, confirming the amorphous nature of the material. Field emission scanning electron microscopy (FESEM) further demonstrated a spherical morphology of the SiO2 NPs. The photocatalytic degradation of MB dye using SiO2 NPs has been examined, revealing promising and improved degradation properties. Even a small amount of SiO2 NPs achieved around 69.20% degradation of MB within 240 min, with the rate constant for the material being 0.001 min−1. The gas sensing properties of the SiO2 NPs were tested on domestic gas sensor units for different gases, including ethanol, methanol, CO2, LPG, H2S, NH3, O2, and Cl2, at temperatures ranging from room temperature to 300 °C. Among these materials, SiO₂ NPs displayed the strongest response to H₂S gas, showing outstanding gas-sensing performance at a concentration of 100 ppm. The response time was 18 S, with a quick recovery time of approximately 22 S.Graphical

Cobalt-based Photocatalysis: From Fundamental Principles to Applications in the Generation of C-X (X=C, O, N, H, Si) Bond.

Over the past few decades, the merger of photocatalysis and transition metal-based catalysis or self-photoexcitation of transition metals has emerged as a useful tool in organic transformations. In this context, cobalt-based systems have attracted significant attention as sustainable alternatives to the widely explored platinum group heavy metals (iridium, rhodium, ruthenium) for photocatalytic chemical transformations. This review encompasses the basic types of cobalt-based homogeneous photocatalytic systems, their working principles, and the recent developments (2018-2024) in C-X (X=C, N, O, H, Si) bond formations. Noteworthy to mention that cobalt-based heterogeneous photocatalysis is beyond the scope of the present review. An elaborate presentation on the mechanistic intricacies of cobalt-based photocatalysis, without any external photocatalyst, and cobalt-based dual organophotoredox catalysis have been provided in this comprehensive review, excluding the dual-metal photoredox catalysis. To the best of our knowledge, this is the only contemporary review encompassing the aforementioned two major types of cobalt-based photocatalysis, in general synthetic chemistry, covering all types of C-X bond formations spanning a range of the last six years.

Superstrong Lightweight Aerogel with Supercontinuous Layer by Surface Reaction.

Breaking the thermal, mechanical and lightweight performance limit of aerogels has pivotal significance on thermal protection, new energy utilization, high-temperature catalysis, structural engineering, and physics, but is severely limited by the serious discrete characteristics between grain boundary and nano-units interfaces. Herein, a thermodynamically driven surface reaction and confined crystallization process is reported to synthesize a centimeter-scale supercontinuous ZrO2 nanolayer on ZrO2-SiO2 fiber aerogel surface, which significantly improved its thermal and mechanical properties with density almost unchanged (≈26 mgcm-3). Systematic structure analysis confirms that the supercontinuous layer achieves a close connection between grains and fibers through Zr─O─Si bonds. The as-prepared aerogel exhibits record-breaking specific strength (≈84615 Nmkg-1, can support up to ≈227272 times aerogel mass) and dynamic impact resistance (withstanding impacts up to 500 times aerogel mass and up to 200 cycling stability at 80% strain). Besides, its temperature resistance has also been greatly optimized (400°C enhancement, stability at 1500°C). This work will provide a new perspective for exploring the limits of lightweight, high strength, and thermal properties of solid materials.

Molecular Dynamics Study of Fretting Wear Characteristics of Silicon Nitride Bearings

AbstractTo study fretting wear characteristics of silicon nitride bearing. Atomic model of surface fretting wear of silicon nitride bearing is constructed by molecular dynamics method and deep learning self‐fitting potential function. First principles are used to match silicon nitride crystal parameters; Dynamic analysis of fretting wear process of nanoscale silicon nitride bearing is realized. Experiment shows that friction force in the Z direction is a maximum of 3.5 nN. The output potential energy 2.31 × 107 eV is 1.63 times that of the y‐axis, which is main factor causing the fretting wear. The force perpendicular to the direction of roller and the collar of silicon nitride bearings should be avoided in the process of using or transporting the bearings. Silicon nitride bearing fretting wear process is non‐transient elastic stress‐strain, along the rolling plane extension, in the roller rolling direction to form a sharp angle shape high strain linear region. Bearing Z direction damage degree increased; Silicon nitride bearing surface layer has 22.47% of the N─Si bond fracture. The study of the fretting wear characteristics of silicon nitride ceramic bearings has a reference value for reducing the surface friction of silicon nitride bearings and improving the life of silicon nitride bearings.

Modulation of electron distribution and intermediate adsorption by C–O–Si sites for efficient oxygen reduction and lithium storage

Porous Si-doped banana-peel biomass-derived carbon is successfully fabricated. The charge distribution of the carbon can be regulated by abundant C–O–Si bonds, leading to enhanced ORR activity/selectivity and a modulated ORR reaction pathway.

Titanium-Catalyzed Reaction of Silacyclobutanes with Alkenes: Mimicking the Reactivity and Reversing the Selectivity Towards Late Transition Metals.

Transition metal-catalyzed ring opening and expansion reactions of silacyclobutanes (SCBs) constitute an atom- and step-economical strategy to construct value-added silicon-containing chemicals. Despite extensive studies, the reaction of SCBs with simple alkenes has only one precedent. Moreover, most reported reactions of SCBs use late transition metals (Pd, Ni, Rh) as catalysts. By contrast, there are no reports of using early transition metals. Herein, we report the first example, to our knowledge, of early-transition-metal-catalyzed reactions of SCBs using earth's second abundant titanium as a catalyst. Notably, orthogonal selectivity was observed. Selective activation of the relatively inert C(sp3)-Si bond was achieved in the case of benzosilacyclobutenes, a selectivity that has rarely been achieved using other metals. Even for silacyclobutanes with C(sp3)-Si bonds only, our titanium system also shows complementary selectivity towards late transition metals to give distinct products. Thus, structurally varied SCBs and alkenes were reacted in our system to afford structurally diverse silicon-containing products that are otherwise difficult to obtain using other transition metals.

Titanium‐Catalyzed Reaction of Silacyclobutanes with Alkenes: Mimicking the Reactivity and Reversing the Selectivity Towards Late Transition Metals

AbstractTransition metal‐catalyzed ring opening and expansion reactions of silacyclobutanes (SCBs) constitute an atom‐ and step‐economical strategy to construct value‐added silicon‐containing chemicals. Despite extensive studies, the reaction of SCBs with simple alkenes has only one precedent. Moreover, most reported reactions of SCBs use late transition metals (Pd, Ni, Rh) as catalysts. By contrast, there are no reports of using early transition metals. Herein, we report the first example, to our knowledge, of early‐transition‐metal‐catalyzed reactions of SCBs using earth's second abundant titanium as a catalyst. Notably, orthogonal selectivity was observed. Selective activation of the relatively inert C(sp3)−Si bond was achieved in the case of benzosilacyclobutenes, a selectivity that has rarely been achieved using other metals. Even for silacyclobutanes with C(sp3)−Si bonds only, our titanium system also shows complementary selectivity towards late transition metals to give distinct products. Thus, structurally varied SCBs and alkenes were reacted in our system to afford structurally diverse silicon‐containing products that are otherwise difficult to obtain using other transition metals.

Charge transport mechanism in [GeOx](z)[SiO2](1-z) based MIS structures

The mechanisms of conductivity in metal–insulator–semiconductor (MIS) structures based on [GeOx](z)[SiO2](1-z) films (0.25 ≤ z ≤ 1) fabricated by co-evaporation of germanium oxide and silicon oxide powders in vacuum and deposition on a p+-type silicon substrate are studied. Indium tin oxide deposited by magnetron method is used as the top electrode. According to IR spectroscopy, Ge–O, Si–O, and Ge–O–Si bonds are detected in the films, while no features related to the presence of germanium clusters are found in the Raman spectra. The current–voltage characteristics (I–V curves) are measured at different temperatures and analyzed by applying the eight most common models of charge transport in MIS structures. It is found that the experimental I–V curves are most accurately approximated in the space charge limited current model, and the parameters of the charge traps are determined within this model.

Thermal Properties of Polysiloxane/Ag Nanocomposites with Different Network Structures and Distributions of Si-H Groups.

Polysiloxanes with silver nanoparticles (Ag NPs) have garnered attention for their distinctive physicochemical properties, which make them promising candidates for advanced material applications. This study presents a systematic investigation into the thermal properties and degradation mechanisms of polysiloxane/Ag nanocomposites, emphasising the innovative incorporation of Ag NPs directly into polysiloxane networks via in situ reduction of Ag⁺ ions by Si-H groups. Six polysiloxane matrices were synthesised by hydrosilylation of poly(methylhydrosiloxane) (PMHS) or poly(vinylsiloxane) (polymer V3) with three cross-linking agents of varying molecular structures and functionality. Thermogravimetric analysis combined with mass spectrometry revealed that the introduction of Ag NPs alters the thermal properties of polysiloxane networks, primarily affecting the redistribution of Si bonds that occurs during the pyrolysis of these systems. Monitoring the pyrolysis process using FTIR spectroscopy allowed us to investigate the effect of the presence of Ag NPs on the degradation mechanism of the studied nanocomposites. The presence of the free-carbon phase and metallic silver phase in the Ag-containing silicon oxycarbide materials obtained was confirmed by Raman spectroscopy and XRD analyses, respectively. These findings demonstrate the possibility of fabricating Ag/SiOC materials with ceramic residues in the range of 43 to 84%. This work provides new insights into the thermal behaviour of polysiloxane/Ag nanocomposites and underscores their potential for high-performance applications in thermally demanding environments.

A Blocked Mercapto Silane Functionalized Silica Decorated‐Aramid Nanofiber to Evolve Elastomer/Silica Composite for Energy‐Efficient Tire

ABSTRACTIn situ generated nanosilica particles were grafted onto aramid nanofibers while modified with a blocked mercapto silane (3‐Octanoylthio‐1‐propyltriethoxysilane). Nanofibers were derived from macro aramid fibers (poly (p‐phenylene terephthalamide)). Fourier‐transform infrared spectroscopy and x‐ray photoelectron spectroscopy revealed that the direct condensation reaction between the silane's ethoxy groups and the nanofiber's hydroxyl or carboxylic groups forms SiO‐C bonds. Morphological analysis of nanofibers revealed the formation of nanosilica from unreacted residual silane on the modified nanofiber (A‐NM) surface. In situ silica formation caused SiOSi bond formation, according to the spectroscopic analysis. Styrene butadiene rubber‐silica composites with modified nanofiber additive were prepared. The bound rubber content and filler flocculation rate displayed an improvement in nanofiber dispersion and rubber‐nanofiber interaction after silane modification. Mechanical characteristics of the composites improved after rubber and modified nanofiber interaction, dispersion, and strengthening. The nanofibers evenly distributed during mixing, as proven by morphological analysis of composites. Incorporation of 1 phr of A‐NM increased tensile strength by 16% and abrasion resistance by 3.1%. Composite's rolling resistance indicator (6.2%) and winter traction indicator increased at high temperatures with 1 phr of A‐NM loading. This specialized filler decorated nanofibers could be used as energy‐efficient tire additives as an alternative to other trendy commercial materials.

Low-Temperature Ozone Atomic-Level Trimming on Ge Interfused Channel with Subthreshold Characterization Enhancement for Gate-All-Around Si Nsstransistors

Recently, stacked nanowire/nanosheet GAAFETs have been under intensive investigation owing to their excellent electrostatics and short-channel control, which can fulfill the requirement of the 5-nm technology node and beyond. However，GAAFETs are affected by the overall thermal budget of the integration process, and after channel release removes the SiGe stack, the presence of Ge residues on the Si channel surface increases the interfacial trap charge, leading to increased defects on the channel surface, which affects the subthreshold characteristics of the device and increases the SS. Due to the tendency to overcorrode during the channel release process and the effect of Ge diffusion, the NS surface roughness becomes larger, leading to enhanced surface scattering and resulting in a decrease in the effective mobility of the carriers, in which the surface roughness change mainly affects the surface roughness scattering and Coulomb scattering of the carriers. Conventional interface treatment methods cannot accomplish the reduction of SS and surface roughness at the same time, so in this paper, we propose a low-temperature ozone atomic-level stripping process method to thin the trench of the gate-all-around NS device. Removing Ge diffused into the trench due to the thermal budget, reducing the trench surface roughness and the surface state, and repairing the free Si and Ge bonds caused by the high thermal budget and the diffusion of Ge. Finally, the device subthreshold characteristics are optimized.In this paper, the verification is first carried out on capacitor wafers by using low temperature ozone atomic level stripping treatment on silicon wafers with simulated channel surfaces for 1/2/5 times, respectively. After O3 treatment, the interface state density is significantly reduced, the interface optimization results results are shown in Fig1. At the same time the above operation makes the thickness of the oxide layer reduce significantly, the EOT is reduced, resulting in a lower K value. So two O3 treatments are applied to the channel surface after channel release in the actual device. The result SS is reduced from 67.5 to 64.3 mV/dec for PFET and reduced from 67.8 to 64.8 mV/dec for NFET (Fig. 2), the device characteristics are significantly improved.N-type MOSCAPs were fabricated with the standard high-k/metal-gate (HK/MG) on a Si0.7Ge0.3 epitaxy layer on p-type bulk-Si (100) wafers. The process flows and key process-step techniques are shown. To reflect the channel interface issues of GAA NSFETs, the capacitors were fabricated on the epitaxy substrate with at a rapid thermal annealing (RTA) and a simulated channel release process. Firstly, 12 nm Si and 18 nm Si0.7Ge0.3 were epitaxially grown on the substrate as the channel surface, and an RTA of 850 ℃ for 75s was performed based on the general thermal budget requirement of the front-end process. Next, the SiGe layer was removed by channel release solution. Afterwards, the substrate was processed by O3 for 2 second after wet-etch SiGe 20s, and then rinsed in DHF for 20s to remove the oxidation. Figure 1

Rhodium-Catalyzed (Asymmetric) Annulation of Silacyclobutanes with Bicyclic Olefins via C–Si Bond Activation

Rhodium-Catalyzed (Asymmetric) Annulation of Silacyclobutanes with Bicyclic Olefins via C–Si Bond Activation

Experimental Charge Density Study of Hypersilyl Sulfur Diimide

AbstractIn here three newly synthesized silyl substituted sulfur diimides S(NSi(SiMe3)3)2 (2), S(NSi(NMe2)3)2 (3) and S(NSiHiPr2)2 (4) are presented. 2 is characterised by experimental charge density investigations and compared to the di‐tert‐butyl sulfur diimide S(NtBu)2 (1). While the silylation seems not to have much impact on the sulfur‐nitrogen bonding the increase of negative charge at the nitrogen atoms is obvious. Hence, the silylated molecules should be better donors in metal chelation, provided the change from the genuine E/Z conformation to E/E is facilitated. Indeed, their calculated free energy gaps between initial and transition states, related to the rotation of the silyl substituted derivatives 2–4, interestingly found via different rearrangements, turned out to be only a third of that of 1, despite of changing the substituents linked to the Si atoms. This is due to the longer and more polar N−Si bonds compared to the N−C bonds.

Supramolecular Structure of Sulfonamide-Substituted Silatranes: Quantum Chemical DFT Calculations.

The supramolecular structure of the crystal products-N-[2-chloro-2-(silatranyl)ethyl]-4-nitro-benzenesulfonamide 4d and N-chloro-N-[2-chloro-1-(silatran-1-yl-methyl)ethyl]benzene-sulfonamide 5a was established by X-ray diffraction analysis data, FTIR spectroscopy and DFT quantum chemical calculations. Their crystal lattice is formed by cyclic dimers with intermolecular hydrogen NH∙∙∙O-Si bonds and CH∙∙∙O=S short contacts. The distribution of electron density in the monomers was determined using quantum chemical calculations of their molecular electrostatic potential (MESP) in an isolated state (in gas) and in a polar medium. The transition from covalent N-Si bonds in crystal compounds and polar medium to non-covalent N∙∙∙Si bonds happened while performing the calculations on the monomer molecules and their dimers in gas. The effect of intermolecular interactions on the strength of the N-Si and N∙∙∙Si bonds in molecules was evaluated through calculations of their complexes with H2O and DMSO.

Disilicon‐Mediated Carbon Monoxide Activation: From a 1,2,3‐Trisila‐ to 1,3‐Disilacyclopentadienes with Hypercoordinate λ4Si‐λ3C Double Bonds

AbstractThe facile reaction of the SiPh2‐bridged bis‐silylene (LSi:)2SiPh2 (L=PhC(NBut)2) with diphenylacetylene affords the unprecedented 1,2,3‐trisilacyclopentadiene (LSi)2(PhC)2SiPh2 1 with a hypercoordinate λ4Si−λ3Si double bond. Compound 1 is very oxophilic and consumes three molar equivalents of inert N2O to form the bicyclic oxygenation product 2 through O‐atom insertion in the Si=Si and Si−Si bonds. Strikingly, 1 can completely split the C≡O bonds of carbon monoxide under ambient conditions (1 atm, room temperature), yielding the 1,3‐disilacyclopentadiene 3, representing the first hypercoordinate example of a cyclosilene with a λ4Si‐λ3C double bond. Likewise, reaction of Xyl‐NC (Xyl=2,6‐dimethylphenyl), an isocyanide isoelectronic with CO, with 1 furnishes the related 1,3‐disilacyclopentadiene 4 but with an amidinato silylene pendent attached to the Si=C carbon ring atom.

Disilicon-Mediated Carbon Monoxide Activation: From a 1,2,3-Trisila- to 1,3-Disilacyclopentadienes with Hypercoordinate λ4Si-λ3C Double Bonds.

The facile reaction of the SiPh2-bridged bis-silylene (LSi:)2SiPh2 (L=PhC(NBut)2) with diphenylacetylene affords the unprecedented 1,2,3-trisilacyclopentadiene (LSi)2(PhC)2SiPh2 1 with a hypercoordinate λ4Si-λ3Si double bond. Compound 1 is very oxophilic and consumes three molar equivalents of inert N2O to form the bicyclic oxygenation product 2 through O-atom insertion in the Si=Si and Si-Si bonds. Strikingly, 1 can completely split the C≡O bonds of carbon monoxide under ambient conditions (1 atm, room temperature), yielding the 1,3-disilacyclopentadiene 3, representing the first hypercoordinate example of a cyclosilene with a λ4Si-λ3C double bond. Likewise, reaction of Xyl-NC (Xyl=2,6-dimethylphenyl), an isocyanide isoelectronic with CO, with 1 furnishes the related 1,3-disilacyclopentadiene 4 but with an amidinato silylene pendent attached to the Si=C carbon ring atom.

Comparative Study of Si−O−Al and Si−O−Si Bond Stability in HZSM‐5 Zeolite Under Steam and Hot Liquid Water Environments

AbstractUnderstanding the changes in the zeolite framework and catalytic active sites during zeolite‐based vapor‐phase and aqueous catalytic processes is crucial. Herein, the evolution of framework T atoms (Si and Al) in ammonium hexafluorosilicate (AHFS)‐treated HZSM‐5 zeolite under steam and hot liquid water (HLW) environments was inverstigated using various characterization techniques. In HLW, Si−O−Si bonds exhibit poorer hydrothermal stability than Si−O−Al bonds, in contrast to steam. Significant Si atom leaching occurs regardless of whether the framework tetrahedral Al atoms (Al(IV)‐1) are removed. Similar to steam, Al(IV)‐1 species in HLW sequentially evolve into partially coordinated framework Al species and then into extra‐framework Al (EFAL) species through partial and complete hydrolysis. The generated EFAL species act as Lewis acid sites, but their local structures or chemical environments may differ. These findings reveal the difference in the T−O−T bonds attacked by water molecules: the Si−O−Al bonds are primarily attacked in steam, whereas the Si−O−Si bond are primarily attacked in HLW.

Structure and Electronic Properties of the A‐center in Si1−xGex Alloys: Insight from the Heyd–Scuseria–Ernzerhof Hybrid Functional Calculations

This study investigates the structure and electronic properties of the A‐center in Si1−xGex alloys (x = 0, 0.25, 0.50, 0.75, and 1), using the Heyd–Scuseria–Ernzerhof hybrid functional. It is found that the most stable structures form SiOSi bonds, with the other two atoms surrounding the A‐center being Ge atoms, which form a long bond between them. The behavior of the O atoms is significantly influenced by the Ge content. As it increases, the position of the O atom shifts relative to the surrounding atoms, thereby affecting the bond lengths and angles. The formation energy of the A‐center first decreases with increasing Ge content up to 0.75, which enhances the defect production; however, then it decreases from 0.75 to 1, thus suppressing defect production. The calculations are consistent with the experimental data, showing that the distance of the defect level from the conduction band minimum increases with Ge content, supporting the observed enthalpy changes in electron ionization.