Bridge Bonds Research Articles

Tribological behavior of polycrystalline diamond based on photo-Fenton reaction

Polycrystalline diamonds (PCD) has high thermal conductivity and as heat sinks in semiconductor power devices. However, PCD exhibits high hardness and strong chemical inertness lead to lower processing efficiency and increase processing costs. Hence, achieving efficiently obtain high-quality PCD surfaces is crucial. In this study, we investigated the tribological behavior of PCD in different environments (deionized water, H2O2 + UV, Fenton, and photo-Fenton) and under different photo-Fenton conditions (pH, light intensity, Fe3O4 concentration, and H2O2 concentration) via Si3N4 ball-disk friction and wear experiments. The photo-Fenton reaction improved the material removal rate of PCD, which was the highest (285.4 μm3/min) under optimized conditions of pH = 3, 100 mW/cm2 light intensity, 2 wt% Fe3O4 concentration, and 10 wt% H2O2 concentration. Based on the friction and wear experimental results and X-ray photoelectron spectroscopy, we propose a material removal mechanism for PCD. The hydroxyl radical (·OH) produced by the photo-Fenton reaction oxidize the PCD surface to form CO, CO, and C–OH groups, which are converted into C–O–Si bridge bonds on the PCD surface, resulting in material removal. Our study findings provide theoretical support for the photo-Fenton reaction -assisted CMP of PCD.

TaBOX: A water-soluble tetraanionic rectangular molecular container for conjugated molecules and taste masking for berberine and palmatine

A water-soluble macrocycle that bears four carboxylate anions has been designed and prepared, which forms a rectangular cavity that can efficiently encapsulate discrete electron-deficient aromatic compounds, including berberine and palmatine. This macrocycle is revealed to be highly biocompatible and able to inhibit the bitter taste of the two drugs.

Condensation of residue during direct liquefaction of a high-vitrinite coal

To understand the formation of residues and its relation with the vitrinite structure and the products yield in direct coal liquefaction (DCL), a high vitrinite low-rank coal, Naomaohu (NMH), is studied at 380–460 °C in the presence of tetrahydronaphthalene and absence of a catalyst. The structures of coal and residues are characterized by the proximate and ultimate analyses, 13C nuclear magnetic resonance, and the electron spin resonance. Beside the frequently seen coal conversion and products yield at various temperatures and time, the products yield and the residues structure parameters are correlated with the residues yield (YRes) and the quantity of hydrogen donated from tetrahydronaphthalene (QH). It is found that the DCL can be roughly defined into two regions demarcated by 420 °C, with limited condensation at 380–400 °C and intensive condensation at 440–460 °C, for example. These two-region behaviors can be clearly evidenced by the different trends in products yield and the residues parameters, such as those relevant to the cleavage of bridge bonds (fal, Cn, δ-C and δ-O) and those relevant to the residues’ condensation (far, Xb, RD and H/C), against YRes and QH. The two-region behavior is important for optimization of DCL conditions and its processing scheme.

The competition between radical copolymerization and charge separation of cyclic ketene acetals and electron‐deficient olefins

AbstractCyclic ketene acetals (CKAs) possess unique features in two aspects. On one hand, after the addition of a radical on the alkene, CKAs can undergo ring‐opening via radical rearrangement, enabling polyester preparation based on chain‐growth polymerization. On the other hand, the alkene connected with two electron‐donating oxygens in a strained form exhibit unique reactivities, resulting in complex reactions in the presence of electron deficient compounds. In this investigation, fundamental studies on CKA radical ring‐opening polymerization and charge‐mediated reactions were performed. Alternating copolymers of CKA and maleimides, or maleates, were prepared and characterized. Quantum chemistry modeling from the perspectives of reaction kinetics and thermodynamics enabled an in‐depth mechanistic study on the side reactions between CKA and maleic anhydride or itaconic anhydride, inspiring the techniques to minimize those side reactions in competition with radical copolymerization. After purifying the anhydride monomers with sublimation, the copolymerization with CKA successfully occurred. The anhydride containing polyester structures with an alternating sequence were confirmed with comprehensive characterizations. Facile post‐functionalization with an alcohol was performed, resulting in carboxylate containing polyesters.

Self-Assembly of an Anionic [Cu5I8]3- Supramolecular Cluster Driven by Ion-Pair Interaction and Catalytic Properties.

The rational design and controlling synthesis of an anionic cuprous iodide supramolecular cluster with high nuclearity through noncovalent interactions remains a significant challenge. Herein, a cationic organic ligand (L1)3+ was driven by anion-cation ion-pair electrostatic interaction to induce free cuprous iodide to aggregate into an anionic supramolecular cluster, [(Cu5I8)3-(L1)3+] (C1). Moreover, five copper(I) atoms bind with eight iodides through multiply bridged Cu-I bonds associated with intramolecular cuprophilic interactions in this butterfly-shaped cluster core. Supramolecular cluster C1 exhibited a solid-state emission at 380 nm and an emission at 405 nm in acetonitrile at room temperature, respectively. Interestingly, this unprecedented cuprous iodide cluster demonstrated a good catalytic performance for azide-alkyne cycloaddition reaction (CuAAC) and the catalytic yield can be up to 80% for eight different substrates at 80 °C. Furthermore, the density functional theory (DFT) calculation revealed that the thermodynamic-dependent cycloaddition reaction underwent a four-step pathway with an overall energy barrier of -43.6 kcal mol-1 on the basis of intermediates monitored by mass spectrum.

Phase evolution and mechanical-hydroscopic properties of alkali-silica reaction gels modified by magnesium nitrate

Alkali-silica reaction (ASR)'s destructiveness is governed by the compositions and properties of ASR products, while methods of converting these hygroscopic-expansive gel-like products into innocuous phases remain unexploited. In this study, the influence of magnesium nitrate on the evolutions of phase, molecular structure, hydroscopic and mechanical properties of ASR gels with varying Mg/Si ratios from 0.1 to 1.1 was investigated. The results indicate that the primary phases of ASR products, tobermorite-type calcium silicate hydrate (C–S–H) and alkali kanemites, can be suppressed into brucite and eventually converted into magnesium-silicate-hydrate (M-S-H) in the presence of increasing Mg/Si ratios and the consequent decreasing pH. The Si–O–Si bridging bonds and Si–O symmetric stretching in the Q3 sites of ASR products can be suppressed. The phase and structure modifications resulted in a 93.5% reduction in hydroscopic swelling, a 94.7% decrease in strength, and a 152.3% drop in modulus of elasticity rendering the ASR products less destructive.

New MCRs: Preparation of Novel Derivatives of Pyrazoloazepines in Ionic Liquid and Study of Biological Activity

In the present investigation, we have effectively synthesized innovative pyrazoloazepine derivatives with notable yields. The synthesis was successfully accomplished by means of a multicomponent reaction that was carried out in an ionic liquid at ambient temperature conditions. The constituents implicated in this procedure consisted of NH-acids such as isatins, α-halo ketones, electron deficient acetylenic compounds, hydrazine, and hydrazonoyl chlorides. Significantly, the inclusion of an NH group appeared as a crucial characteristic in the resultant compounds. Our investigation encompassed the examination of the antioxidant capabilities exhibited by these substances. The study utilized various assays, including ferric reduction capacity and diphenyl-picrylhydrazine (DPPH) radical trapping, to investigate the possible antioxidant benefits of the substances. The antioxidative capacity of the produced pyrazoloazepine compounds was evaluated by various evaluations. The synthetic approach we employ offers numerous advantages. To begin with, the prompt response time enables the expedited generation of complex compounds. Furthermore, the significant outputs of the specific items highlight the effectiveness of our approach. The ease with which the catalyst and products can be separated enhances the efficiency of the purification procedure.

Novel Isomer of Volleyballene Sc20C60.

The Stone-Wales defect is a well-known and significant defective structure in carbon materials, impacting their mechanical, chemical, and electronic properties. Recently, a novel metal-carbon nanomaterial named Volleyballene was discovered, characterized by a C-C bond bridging two carbon pentagons. Using first-principles calculations, a stable Stone-Wales-defective counterpart of Volleyballene, exhibiting Th symmetry, has been proposed by rotating the C-C bond by 90°. Although its binding energy per atom is slightly higher than that of Volleyballene (ΔEb = 0.009 eV/atom), implying marginally lower structural stability, it can maintain its bond structure until the effective temperature reaches about 1500 K, indicating greater thermodynamic stability. Additionally, its highest vibration frequency is 1346.2 cm-1, indicating a strong chemical bond strength. A theoretical analysis of the Sc20C60 + Sc20C60 binary systems highlights that the stable building block may be applied in potential nanoassemblies.

Green Synthesis and Biological Study of New Imidazothiazines Using New MCRs: A Combined Experimental and Theoretical Investigation

For the performing this research multicomponent reaction of isatin, electron-deficient acetylenic compounds, α-haloketones, ammonium acetate, isothiocyanates and methyl aziridine in aqueous at room temperature was investigated for the production of novel derivatives of azepinothiazine in excellent yields. The synthesized azepinothiazines have OH, NH2 and NH functional groups that have acidic hydrogen and show high antioxidant activity. These synthesized compounds also displayed antimicrobial activity by using the disk diffusion procedure and two Gram-positive and Gram-negative bacteria. Also, to better understanding reaction mechanism density functional theory-based quantum chemical methods have been applied. The employed process for the production of azepinothiazine has some benefits such as short time of reactions, excellent efficiency of the product, easy separation of products.

A novel zinc‐chelating peptide identified from rapeseed (Brassica napus) protein hydrolysate: insights into its zinc‐binding sites by density functional theory

SummaryThe binding sites between zinc chelating peptide (ZCP) and zinc have not been clearly understood at the quantum chemistry level. Ala‐Ser‐His (ASH), a new ZCP located in the cruciferin precursor, was identified from in vitro digestion hydrolysate of rapeseed (Brassica napus) protein. Also, ASH exerted the concentration value of 114.09 ± 0.98 mM showing 50% zinc chelating activity. The prepared ASH–Zn (ZCP‐zinc chelate), displayed varying characteristics from ASH on surface microstructures, X‐ray photon energies, and infrared spectrum. The geometric structure of ASH–Zn with minimum free energy was obtained using density functional theory, producing a bridge bond of O21–Zn41–O32 between Ser and His residues. Based on the basic set of 6–311++G (d, p), O21–Zn 41 and O32–Zn41, respectively, had bond lengths of 1.96503 Å and 1.94515 Å, while O21–Zn41–O32 displayed a bond angle of 136.41069°. These findings further promote research on rapeseed proteins providing new possibilities for studying peptide‐metal chelates.

A preliminary study on the quality evaluation of coking coal from its structure thermal transformation: Applications of fluidity and swelling indices

Evaluating the coking coal quality from coal structure thermal transformation was crucial to control the coking process. The coal quality indices of ash composition, volatile matter, element distribution and caking indices were redefined based on the coal structural characteristics. Five structure parameters derived from volatile matter and element distribution, including carbon aromaticity (fa), average number of condensation rings (NCR), ring condensation index (2(NCR −1)/C), aliphatic hydrogen content (AlH) and number of bridge bonds (AlB), were proposed to evaluate the comprehensive structure properties of coals. The rationality of these parameters was verified through 13C NMR analysis. The superiority of fluidity and swelling indices in reflecting the structure transformation of individual and blended coals was clarified. In addition, a novel mothed for measuring swelling pressure was developed, taking into account the impact of heat and mass transfer on the coking process. The results show that the bridge bonds content (AlB) affects the coal particle softening which attributes to the thermal cleavage of Cal-Cal/O and Car-O. The high aliphatic hydrogen content (AlH) relating to the stabilization of pyrolytic fragments decreases maximum fluidity temperature. The formula of F(MD) captures the relevance among maximum dilatation, volatile matter, caking and plastic layer indices, which aids in comprehending the swelling mechanism based on the balance between gas release and permeability evolution. The fluidity and swelling indices serve as indicators of the structural transformation during individual coal coking, contributing to the quality evaluation of blended coals with similar coke performance. The self-designed device provides a more accurate prediction of pushing current based on the maximum swelling pressure, compared to the Audibert-Arnu dilatation. This work contributes to the scientific evaluation of coking coals and the precise control of the coking process.

Chemical bonding and facet modulating of p-n heterojunction enable vectorial charge transfer for enhanced photocatalysis

Heterojunctions have been proved to be the promising photocatalysts for hazardous contaminants removal, but the inferior interfacial contact, low carrier mobility and random carrier diffusion seriously hamper the photoactivity improvement of the conventional heterojunctions. Herein, SO chemically bonded p-n oriented heterostructure is fabricated via selectively anchoring of p-type Ag2S nanoparticles on the lateral facet of n-type Bi4TaO8Cl nanosheet. Such a p-n heterojunction engineering on specific facet of Bi4TaO8Cl semiconductor derives ingenious double internal electric field (IEF), which not only effectively creates the spatially separated oxidation and reduction sites, but also delivers the powerful driving forces for impactful spatial directed photocarrier transfer along the cascade path. Additionally, our experimental and theoretical analyses jointly signify that the interfacial SO bond could serve as an efficient atomic-level interfacial channel, which is conducive to encouraging the vectorial charge separation and migration kinetic. As a result, the Ag2S/Bi4TaO8Cl oriented heterojunction exhibits significantly enhanced visible light driven photocatalytic redox ability for tetracycline oxidation and hexavalent chromium reduction than those of single component and the traditional random/mixed heterojunctions. This study could provide a deeper insight into the synergistic effects of multi-IEF modulation and interfacial chemical bond bridging on optimizing the photogenerated carrier behaviors.

Glycerol-based H3PO4-activated carbon as a versatile adsorbent for removal of pollutants from wastewater: A novel synthesis protocol

Aiming at revaluing oversupplied glycerol as a result of biodiesel production, this approach introduces an authentic synthesis protocol for producing glycerol-based activated carbons holding suitable textural/surface properties for an efficient application in the methylene blue and Pb2+ adsorption processes. Typically, glycerol and phosphoric acid were submitted to a polycondensation reaction in order to insert manipulable fractions of C-O-P bridge bonds throughout the whole polymer chain in the form of mono, di and triesters before the traditional carbonization and activation steps. The physicochemical and surface chemistry properties of the ACPs were characterized by means of N2 adsorption/desorption isotherms, thermal analysis, elemental analysis, surface functional groups titration and pHpzc, X-rays diffraction, FTIR spectroscopy and scanning electron microscopy. Indeed, such strategy gave rise to a set of micro/mesoporous activated carbons (ACP) with surface area of up to 1056 m2/g and total acidity, constituted by thermally insensitive carbonyls-/phosphorus-containing functional groups, ranging from 1.63 to 2.32 mmol g−1. Adsorptive features of the obtained series of activated carbons were validated in the methylene blue and Pb2+ removal processes reaching out adsorption capacity of up to 543.3 and 26.5 mg g−1 at 298 K, respectively. Additionally, after confronting experimental data with several isothermal and kinetic theoretical models, it was demonstrated that the adsorption mechanism of both pollutants onto the ACPs is driven by chemisorption up to the monolayer coverage. The thermodynamic study indicated spontaneity of the adsorption processes and suggested a relation between the textural properties and surface functionalities of the ACPs with the enthalpic nature of the adsorbent-adsorbate interactions.

Effect of extracts of petroleum ether, dichloromethane and methanol on thiophenic sulfur release during coal pyrolysis

The existing forms and thermal transformation of sulfur in high sulfur coal directly influence the efficiency of coal clean utilization by the staged pyrolysis conversion. Low molecular compounds distributed in coal are very different from the macromolecular structure of coal and play an important role during coal pyrolysis. In order to investigate the effects of low molecular compounds on the release of typical thiophenic sulfur species during coal pyrolysis by Py-GC/MS, petroleum ether, dichloromethane, and methanol were used for sequential ultrasonic extraction of Linfen coal (LFC). The compositions of extracts were detected by GC×GC/MS. Results show that three primary kinds of thiophenic sulfur species (2-methyl thiophene, benzothiophene, and dibenzothiophene) were released during coal pyrolysis and they are mainly derived from the cracking of macromolecular skeleton containing thiophenic sulfur in coal. The amounts of thiophenic sulfur released during raw coal and residues pyrolysis both increase with temperature. Besides, extracts with different compositions have different effects on the release of thiophenic sulfur during pyrolysis. In detail, the cyclization of aliphatic compounds could provide active hydrogen. On the one hand, the active hydrogen promotes the break of bridge bonds around thiophenic sulfur. On the other hand, active hydrogen may attack sulfur atoms of thiophenic sulfur, reducing the energy barriers of thiophenic sulfur decomposition. Aromatic compounds polymerize with sulfur-containing groups converting to benzothiophene and dibenzothiophene with larger molecular weight. In addition, thiophenic sulfur may be oxidized by esters to sulfones or sulfoxides, which further decompose, resulting in the inhibition effect on thiophenic sulfur formation during coal pyrolysis.

Effect of SrTiO3 amount and ultrasonic disperse on the thickness of Bi2O3 nanosheets and the photocatalytic performance of the composite α-Bi2O3/SrTiO3

Due to the correlation between structure and activity, even the photoelectric performance of simple materials can be improved by designing component structures reasonably. Taking α-Bi2O3/SrTiO3 as an example, this article reports a novel ultrasound assisted synthesis method for adjusting the thickness of α-Bi2O3 nanosheets (NSs) in heterojunctions. The continuous variation from ∼200 to ∼10 nm confirms that the thickness of NSs is limited by the amount of SrTiO3 added, and ultrasonic dispersion before calcination is a key initiative. Systematic tests indicate that the opto-electronic properties of the heterojunctions are highly thickness-dependent. The heterojunction with a thickness of ∼20 nm α-Bi2O3 NSs has a wider light absorption range (>550 nm), higher photocurrent response (52.8 μA cm−2), lower charge transfer resistance, and efficient catalytic ability for organic degradation (0.071 min−1 for 0.1 g·L−1 RhB). Various spectroscopic evidences display that Bi-O-Ti oxygen bridge bonds provides an efficient transport channel for photogenerated carriers. Furthermore, large specific surface area, and the built-in electric field of heterojunctions jointly accelerate the oxidation degree of pollutants. As high as 98.9% (0.1 g·L−1) and 55.9% (0.5 g·L−1) degradation efficiencies in 1 h, importantly, documented that the α-Bi2O3/SrTiO3 heterojunctions was competitive for the dispose of high-concentration [RhB] outlet water.

Re‐establishing the Lost Covalency of the Inverted Bond in [1.1.1]Propellane

AbstractThe nature of the bridging C−C bond in [1.1.1]propellane has been a topic of much debate, and finally it has been established to be a charge‐shift bond. But the question remains: Can we restore the “lost” covalency of this charge shift bond? Herein we have attempted to investigate the nature of the bridging C−C bond, by replacing the CH2 groups at the wing positions with NH, O, and S. Detailed analyses using atoms in molecules (AIM) and electron localization function (ELF) reveal that the bridging bond emerges as a covalent bond upon substitution with S.

Higher energy density of MoSe2/polyaniline capsule nanospheres for enhanced performance supercapacitor

It is very important to develop novel nanocomposites as electrode materials for supercapacitors (SCs). MoSe2 porous nanospheres were prepared by one-step hydrothermal method, and polyaniline (PANI) nanosheets were grown in situ to obtain MoSe2/PANI capsule nanospheres (CNs). By changing the amount of aniline, it was found that MoSe2/PANI-16 CNs had the best electrochemical performance, and a high specific capacitance of 753.2 F g−1 was obtained at a current density of 1 A g−1. In addition, the interface electron transport path was clarified that a C–Mo–Se bridge bonds may be formed for rapid electron transfer. The reaction kinetics was also explored. The large specific surface areas of MoSe2/PANI CNs provided more reactive sites, so that the contribution of pseudocapacitance was much larger than diffusion capacitance. The assembled MoSe2/PANI//activated carbon asymmetric supercapacitor has a energy density of 20.1 Wh kg−1 at a power density of 650 W kg−1. These results indicate that the MoSe2/PANI CNs are a promising electrode material.

Photocatalyzed (3+2) Cycloaddition for the Dearomatization of Electron-Poor Arenes under Flow Conditions.

The photocatalyzed dearomative reaction between various electron-deficient aromatic compounds and a non-stabilized azomethine ylide is successfully performed in a flow system. Whereas the use of supported eosin as organic photocatalyst exhibits limited efficiency, turning to the soluble Rose Bengal allows to transform a broad range of substrates from hetarenes (indole, benzofuran, quinoline, pyridine) to naphthalenes and benzenes. This photocatalyzed (3+2) dearomative cycloaddition under green light irradiation provides a simple and efficient access to tridimensional pyrrolidino scaffolds with a tetrasubstituted carbon center at ring junction and can be performed in the friendly ethyl acetate. Computational studies support the mechanism involving azomethine ylide as reactive species toward the electron-poor arene.

Investigation on the catalytic performance of magnetic copper ferrite nanoparticles in the catalytic hydroconversion of Hanglaiwan long flame coal

Magnetic copper ferrite (CuFe2O4) was prepared by hydrothermal synthesis method and used for the catalytic hydroconversion (CHC) of Hanglaiwan long flame coal (HLFC) in cyclohexane under 1 MPa of initial hydrogen pressure (IHP) at 300 °C for 4 h. The total yield of soluble portion (SP) from the CHC is 33.7 wt%, significantly being higher than that (10.5 wt%) from the non-CHC (NCHC) under the same conditions. The main compounds detected in SPCHC (for CHC) are arenes and oxygen-containing organic compounds (OCOCs). Benzyloxybenzene (BOB), 2-(benzyloxy)naphthalene (BON), oxybis(methylene)dibenzene (OBMDB), oxydibenzene (ODB), and 2,2′-oxydinaphthalene (ODN) were used as HLFC-related model compounds to investigate the catalytic activity of CuFe2O4 and understand the CHC mechanism of HLFC. According to the model reactions, CuFe2O4 activates H2 to biatomic active hydrogen (H…H) and splits H…H to mobile H+ and immobile H-. H+ addition to oxygen atoms (OAs) in >C-O- bridged bonds (BBs) cleaves the BBs and releases SP during the CHC of HLFC.

Experimental Investigation on the Thermal Management for Lithium-Ion Batteries Based on the Novel Flame Retardant Composite Phase Change Materials

Thermal management systems are critical to the maintenance of lithium-ion battery performance in new energy vehicles. While phase change materials are frequently employed in battery thermal management systems, it’s important to address the concerns related to their leakage and flammability, as they can pose hazards to the safety performance of batteries. This paper proposes a novel flame retardant composite phase change material (CPCM) consisting of paraffin, high-density polyethylene, expanded graphite, ammonium polyphosphate, red phosphorus, and zinc oxide. The performance of CPCMs containing different ratios of flame retardants is investigated, and their effects when applied to battery thermal management systems are compared. The results demonstrate that the leakage rate of the flame retardant CPCMs is maintained within 1%, indicating excellent flame retardant performance and thermal management efficiency. The combination of ammonium polyphosphate and red phosphorus in the flame retardant exhibits effective synergistic effects, while zinc oxide may help phosphate compounds create their bridging bonds, which would then make it possible to construct a char layer that would separate heat and oxygen. Under a 2C discharge rate, the maximum temperature of the battery pack remains below 50 °C, and the temperature difference can be controlled within 5 °C. Even under a 3C discharge rate, the maximum temperature and temperature difference are reduced by 30.31% and 29.53%, respectively.