Inherent Inertness Research Articles

Energy transfer-mediated multiphoton synergistic excitation for selective C(sp3)–H functionalization with coordination polymer

Activation and selective oxidation of inert C(sp3)–H bonds remain one of the most challenging tasks in current synthetic chemistry due to the inherent inertness of C(sp3)–H bonds. In this study, inspired by natural monooxygenases, we developed a coordination polymer with naphthalenediimide (NDI)-based ligands and binuclear iron nodes. The mixed-valence FeIIIFeII species and chlorine radicals (Cl•) are generated via ligand-to-metal charge transfer (LMCT) between FeIII and chlorine ions. These Cl• radicals abstract a hydrogen atom from the inert C(sp3)–H bond of alkanes via hydrogen atom transfer (HAT). In addition, NDI converts oxygen to 1O2 via energy transfer (EnT), which then coordinates to FeII, forming an FeIV = O intermediate for the selective oxidation of C(sp3)–H bonds. This synthetic platform, which combines photoinduced EnT, LMCT and HAT, provides a EnT-mediated parallel multiphoton excitation strategy with kinetic synergy effect for selective C(sp3)–H oxidation under mild conditions and a blueprint for designing coordination polymer-based photocatalysts for C(sp3)–H bond oxidation.

Visible-Light Photoredox-Catalyzed Direct Carboxylation of Tertiary C(sp3)-H Bonds with CO2: Facile Synthesis of All-Carbon Quaternary Carboxylic Acids.

Direct carboxylation of C-H bonds with CO2 represents an attractive strategy to synthesize valuable carboxylic acids with high atom, step, and redox economy. Although great progress has been achieved in this field, catalytic carboxylation of tertiary C(sp3)-H bonds still remains challenging due to their inherent inertness and significant steric hindrance. Herein, we report a direct carboxylation of tertiary benzylic C(sp3)-H bonds with CO2 via visible-light photoredox catalysis. Various all-carbon quaternary carboxylic acids, which are of significant importance in medicinal chemistry, are successfully obtained with high yields. This direct carboxylation is characterized by good functional group tolerance, broad substrate scope, and mild operational conditions. Furthermore, our methodology enables the efficient and rapid synthesis of key drug or bioactive molecules, such as carbetapentane, caramiphen, and PRE-084 (σ1 receptor agonist), and facilitates various functionalizations of C(sp2)-H bonds using the directing ability of target carboxylic acids, thus highlighting its practical applications. Mechanistic studies indicate that a carbanion, which serves as the key intermediate to react with CO2, is catalytically generated via a single electron reduction of a benzylic radical through a consecutive photoinduced electron transfer process.

Noble metal-modified copper surfaces for alkaline condition hydrogen evolution reaction

Cu-based materials would be attractive candidates for cost-effective alkaline hydrogen evolution reaction (HER) electrocatalysts due to high abundance, excellent conductivity, and excellent stability in alkaline environments, if not for the inherent inertness of Cu in HER. This inertness has led to a relative lack of research on Cu-based HER catalysts in both experimental and theoretical domains. Here, We report engineered Cu(111) surfaces that can significantly improve the poor activity of H2O dissociation on pure Cu(111) surface. We do this by introducing noble metal atoms (M = Ru, Rh, Pd, Ag, Os, Ir, Pt) through surface doping. These modified surfaces exhibit excellent thermodynamic and electrochemical stability, with the exception of Cu(111)-Ag. Notably, the H2O dissociation energy barrier on Cu(111)-Os (Eb) is only 0.74 eV, which is much smaller than that (1.31 eV) of pure Cu(111), and is even lower than that of Pt (Eb = 0.92 eV), which is commercially used for electrodes. The low Eb and resulting expected excellent performance of Cu(111)-Os for water splitting is related to the particular local electronic properties of doped Os atoms, specifically the electronic structure of the Os d-orbitals, which have a d-band center near Fermi level (EF) and a high density of states around EF, including just above EF. These results are expected to stimulate the investigation of surface alloyed Cu, leading to a new direction for the design of high-performance and low-cost electrocatalysts.

Metaheuristic optimization algorithms-based prediction modeling for titanium dioxide-Assisted photocatalytic degradation of air contaminants

Airborne contaminants pose significant environmental and health challenges. Titanium dioxide (TiO2) has emerged as a leading photocatalyst in the degradation of air contaminants compared to other photocatalysts due to its inherent inertness, cost-effectiveness, and photostability. To assess its effectiveness, laboratory examinations are frequently employed to measure the photocatalytic degradation rate of TiO2. However, this approach involves time-consuming requirements, labor-intensive tasks, and high costs. In literature, ensemble or standalone models are commonly used for assessing the performance of TiO2 photocatalytic degradation of water and air contaminants. Nonetheless, the application of metaheuristic hybrid models has the potential to be more effective in predictive accuracy and efficiency. Accordingly, this research utilized hybrid machine learning (ML) algorithms to estimate the photo-degradation rate constants of organic air pollutants using TiO2 nanoparticles and exposure to ultraviolet light. Six metaheuristics optimization algorithms, namely, nuclear reaction optimization (NRO), differential evolution algorithm (DEA), human felicity algorithm (HFA), lightning search algorithm (LSA), Harris hawks algorithm (HHA), and tunicate swarm algorithm (TSA) were combined with random forest (RF) technique to establish the hybrid models. A database of 200 data points was acquired from experimental studies for model training and testing. Furthermore, multiple statistical indicators and 10-fold cross-validation were employed to examine the established hybrid model's accuracy and robustness. The TSA-RF model demonstrated superior prediction accuracy among the six suggested models, achieving an impressive correlation (R) of 0.90 and a lower root mean square error (RMSE) of 0.25. In contrast, the HFA-RF, HHA-RF, and NRO-RF models exhibited a slightly lower R-value of 0.88, with RMSE scores of 0.32. The DEA-RF and LSA-RF models, while effective, showed a marginally lower R-value of 0.85, with RMSE values of 0.45 and 0.44, respectively. Moreover, the SHapley Additive exPlanation (SHAP) results indicated that the degradation rates of air contaminants through photocatalysis were most notably influenced by factors such as the reactor sizes, photocatalyst dosage, humidity, and intensity.

Computation of differential and integral operators using [formula omitted]-polynomials of gold crystal

Gold is generally considered a noble metal since it is inherently inert in its bulk state. However, gold demonstrates reactivity when it is in its ionic state. The inherent inertness of bulk gold has resulted in its widespread recognition as a vital raw material in various biomedical processes. The applications of these technologies include drug delivery microchips, dental prostheses, reconstructive surgery, culinary additives, and cardiovascular stents. Gold can also exist in molecules or ions, particularly gold ions, which facilitates the production of gold nanomaterials. In this paper, we have computed differential and integral operators by using the M-Polynomial of gold crystals and by utilizing this polynomial, we have also computed eleven topological indices like 1st Zagreb, 2nd Zagreb, Hyper, Sigma, Second Modified, General Randic, General Reciprocal Randic, 3rd Redefined Zagreb, Symmetric Division Degree, Harmonic, Inverse Sum indices for the structure of Gold crystal.

Investigation of reduced reverse degree based polynomials & indices of gold crystals

Gold is widely recognized as a noble metal due to its inherent inertness in its bulk form. Nevertheless, gold exhibits reactivity in its ionic form. The inert qualities of bulk gold have led to its extensive recognition as a fundamental raw ingredient in several biomedical processes. These applications encompass drug delivery microchips, dental prostheses, reconstructive surgery, food additives, and endovascular stents. Gold in large amounts can be thought of as safe. Gold can also exist as molecules or ions, specifically gold ions, making it easier to make gold nanomaterials. The distinctive characteristics of gold set it apart from its molecular or bulk states, making its execution a very efficient instrument in the field of nanomedicine. Some of these traits are ease of synthesis, a higher ratio of surface area to volume, more reactive particles, the ability to withstand changes to the surface, and strong optical properties. The reduced reverse degree-based polynomials and topological descriptors of the molecular structure of the gold crystal are investigated in this manuscript. The numerical and graphical analysis of outcomes this study are also described.

Metal-organic frameworks with optimal pore cages for high Xe adsorption and efficient Xe/Kr separation

Separation of Xe/Kr mixtures obtained from the by-products of air separation is a paramount industrial process but still a formidable challenge due to the inherent inertness and close physicochemical properties of Xe and Kr. Herein we present two isostructural metal–organic frameworks (MOF), MIL-88B-tpt and MIL-88B-tpt-F, which were found to have high Xe uptake capacities and efficient Xe/Kr separation resulted from the suitable pore caged structures and pore sizes. Remarkably, MIL-88B-tpt exhibits a record-high Xe sorption capacity of 210.2 cm3 g−1 at 273 K and 1 bar. The highest Xe uptake and moderate Xe/Kr separation selectivity endow MIL-88B-tpt with high-performance Xe/Kr separation, ranking it among the best-performing MOF. The comparable Xe/Kr separation performance observed for the fluorinated version of MIL-88B-tpt-F and MIL-88B-tpt indicates the fluorine groups have a negligible effect on the Xe/Kr separation. Thus the efficient Xe/Kr separation for both MOF is mainly resulted from the optimal pore cages for Xe trapping and the well-matched pore sizes for Xe atom. The extensive Xe···framework interactions unveiled by computational simulations facilitate a strong binding affinity to Xe, thus leading to the highest Xe uptakes and efficient separation ability for both MOF.

Control of Zeolite Local Polarity toward Efficient Xenon/Krypton Separation.

The inherent inertness and striking physicochemical similarities of krypton and xenon pose significant challenges to their separation. Reported herein is the efficient xenon capture and xenon/krypton adsorptive separation by transition metal-free zeolites under ambient conditions. The polarized environment of zeolite, denoted as local polarity, can be tuned by changing the topology, framework composition, and counter-cations, which in turn correlates with the guest-host interaction and separation performance. Chabazite zeolite with a framework Si/Al ratio of 2.5 and Ca2+ as the counter-cations, namely, Ca-CHA-2.5, is developed as a state-of-the-art zeolite adsorbent, showing remarkable performance, i.e., high dynamic xenon uptake, high xenon/krypton separation selectivity, and good recyclability, in the adsorptive separation of the xenon/krypton mixture. Grand Canonical Monte Carlo simulation reveals that extraframework Ca2+ cations act as the primary binding sites for xenon and can stabilize xenon molecules together with the chabazite framework, whereas krypton molecules are stabilized by weak guest-host interaction with the zeolite framework.

Insights into charge transfer dynamics of Li batteries through temperature-dependent electrochemical impedance spectroscopy (EIS) utilizing symmetric cell configuration

Studying charge transfer processes in Li batteries poses a challenge due to their complicated nature and the battery's inherent inertness. While electrochemical impedance spectroscopy (EIS) offers a promising approach to investigating these processes, its effectiveness is hindered by the complexity of the data generated and the ambiguity in the analyses. Here, we demonstrate that the assignment process is not straightforward for complex secondary Li batteries, and it necessitates additional measurements and in-depth analysis. We first performed simplification of the impedance data by employing symmetric cell configurations to obtain charge transfer resistance values for each electrode. We second took advantage of altering three parameters during the EIS measurement: electrolyte composition, measurement temperature, and the state of health to extract important parameters related to both the anodic and cathodic charge transfer mechanisms. The analysis enabled the correlation of the observed charge transfer resistances to the corresponding electrochemical process and to obtain the kinetic parameters of the studied process. Our work illustrates how EIS can be used to study and understand the intricate electrochemical charge transfer processes in Li batteries, which are difficult to explore using alternative techniques.

Synergistic effect of K and Zn on Fe-based catalysts for efficient CO2 hydrogenation.

Excessive emission of CO2 into the atmosphere has severely impacted the global ecological environment. Converting CO2 into valuable chemicals and fuels is of great significance for sustainable development. However, low activity and undesirable selectivity often result from the inherent inertness of CO2. Herein, K- or/and Zn-modified Fe-based catalysts were prepared by an incipient-wetness impregnation method for CO2 hydrogenation via a cascade reaction. The results indicate that K species exist as K2O while Zn species exist as ZnFe2O4. In the CO2 hydrogenation pathway, K2O facilitates the adsorption of CO2 and restrains the adsorption of H2, accelerating the transformation of CO2 into C2-C4 olefins rather than paraffins while Zn species promote the dispersion of Fe species, leading to improved activity. Synergistically, a K- and Zn-modified Fe-based catalyst (2Zn-10K-Fe/Al) shows excellent catalytic CO2 hydrogenation activity, achieving a CO2 conversion of 77% which is 1.8 times that (42%) of the unmodified Fe-based catalyst (Fe/Al). Our catalyst also shows a significantly promoted selectivity to C2-C4 olefins of 17% in comparison with the Fe/Al catalyst (0%). It is envisioned that such a binary effect of elements might contribute to the low-cost and industrial production of Fe-based catalysts for selective CO2 conversion.

From lithium to potassium: Comparison of cations in poly(ethylene oxide)-based block copolymer electrolytes for solid-state alkali metal batteries

Liquid electrolytes (LEs) commonly show severe side reactions at the electrode-electrolyte interface, especially with alkali metal anodes, leading to rapid capacity fade of metal-ion batteries. Solid polymer electrolytes (SPEs), however, contribute to the suppression of side reactions due to their inherent inertness and high mechanical strength, providing long-term stable battery operation. Herein, we investigated physical and electrochemical properties of SPEs based on our previously reported microphase-separated poly(vinyl benzyl methoxy poly(ethylene oxide) ether)-block-polystyrene block copolymer (PVBmPEO-b-PS) with different alkali metal ions (A+ = Li+, Na+ or K+) and their use in the respective metal batteries, showing the potential for the transition from lithium to post-lithium batteries. Rheological and thermal properties as well as ion transport in the SPEs with different bis(trifluoromethanesulfonyl)imide (TFSI) salts concentrations revealed similar shear storage moduli (G’) for the investigated SPEs, while the lowest glass transition temperatures (Tg) were found for KTFSI-based films. By contrast, the highest total ionic conductivity was found for the LiTFSI-based SPEs. To quantify the A+ transference numbers (TA+), the Bruce-Vincent method and pulsed-field gradient (PFG) NMR were conducted, revealing significant challenges for TA+ determination of post-Li systems. Further, the examination of the interfacial stability of SPE/A interfaces by conducting plating/stripping experiments revealed significantly higher resistances for sodium- and potassium-based systems in comparison to their lithium-based counterpart. Nonetheless, A-metal/SPE/cathode cells with PVBmPEO-b-PS-based Na- and K-SPEs with the Prussian Blue analogues (PBAs, Na2-xFe[Fe(CN)6] and K2-xFe[Fe(CN)6]) positive electrodes and the respective alkali metal negative electrodes enabled cycling at elevated temperature of 55 °C. Herein, both sodium and potassium metal batteries exhibited stable cycling with capacity retentions of 73% over 100 cycles for the Na-cell, and 94% over the same cycle number for the K-cell, (and a high coulombic efficiency (CE) of 98% at the 100th cycle).

Poly(ethylene oxide)-Based Electrolytes for Solid-State Potassium Metal Batteries

Most conventional batteries today employ organic liquid electrolytes (LEs) that are not only flammable, but also serve as a medium for irreversible side reactions at the electrode interfaces, especially when metal is used as electrode. In post-lithium systems, such as potassium batteries, this issue is even more pronounced due to a higher reactivity of the metal as compared to lithium, and typically results in electrochemical instability leading to a rapid capacity fade of the battery.[1] When switching from LEs to solid polymer electrolytes (SPEs) that typically show better electrochemical stability at low (< 0.5 V vs. K+/K) and high (> 4 V vs. K+/K) potentials due to polymers inherent inertness, enhanced cycle life of the battery is expected.[2] Moreover, well-known disadvantage of SPEs in Li-based batteries, i.e., poor ionic conductivity at ambient temperature, could be overcome in systems with larger cation size, e.g. K+ [3,4], potentially removing some of the bottlenecks previously encountered in the case of Li-transport.In this presentation, a series of poly(ethylene oxide) - potassium bis(trifluoromethane sulfonyl)imide (PEO-KTFSI) compositions with different salt concentration was investigated for their potential application as SPEs in potassium metal batteries. To identify the most promising candidate in terms of ion transport and mechanical integrity, the effect of KTFSI concentration on thermal, rheological and electrochemical properties was studied. Several electrolyte compositions were examined in solid-state potassium batteries with a potassium metal negative electrode, and a positive electrode from Prussian blue analogue family. Our results reveal the advantages of solid-state systems with respect to improved capacity retention and Coulombic efficiency as compared to the reference system with carbonate-based LE, as demonstrated in Figure 1, thus paving the way for a new generation of potassium batteries with significantly improved key performance parameters. Figure 1. Comparison of potassium half-cells employing different electrolyte systems: carbonate-based liquid electrolyte (LE) vs. PEO-based solid polymer electrolyte (SPE) (a) capacity retention and (b) corresponding Coulombic efficiencies.[1] H. Wang, D. Zhai, F. Kang, Energy Environ. Sci. 2020, 13, 4583–4608.[2] J. Mindemark, M. J. Lacey, T. Bowden, D. Brandell, Prog. Polym. Sci. 2018, 81, 114–143.[3] M. Perrier, S. Besner, C. Paquette, A. Vallée, S. Lascaud, J. Prud’homme, Electrochim. Acta 1995, 40, 2123–2129.[4] U. Oteo, M. Martinez-Ibañez, I. Aldalur, E. Sanchez-Diez, J. Carrasco, M. Armand, H. Zhang, ChemElectroChem 2019, 6, 1019–1022. Figure 1

In situ synthesis of polymer-modified boron nitride nanosheets via anionic polymerization

Owing to their inherent inertness, covalent functionalization of hexagonal boron nitride nanosheets (BNNSs) proves very difficult, greatly limiting their potential applications. Herein, we report an one-pot in-situ synthesis of polymer-modified boron nitride nanosheets via reductive functionalization. Negatively charged boron nitride nanosheets, generated by a smooth reductive treatment in an electron-rich environment, are directly employed as an initiator to trigger in situ anionic polymerization of methyl methacrylate (MMA) monomers, avoiding the use of complex initiators. The successful grafting of polymethyl methacrylate (PMMA) chains onto BNNS surfaces is evidenced by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The functionalized boron nitride nanosheets formed via B-C bonding through this facile “grafting from” method exhibit excellent dispersibility in acetone. When used as a filler, the material shows remarkable mechanical reinforcement for polymeric composites. The reductive charge provides a simple and scalable route for versatile chemical modifications of BNNSs to tailor surface properties of BNNSs, which will find important applications in sensors, catalysis, composite coating, bioimaging and drug delivery etc.

Ambient Ammonia Electrosynthesis: Current Status, Challenges, and Perspectives.

Ammonia (NH3 ) electrosynthesis from atmospheric nitrogen (N2 ) and water is emerging as a promising alternative to the energy-intensive Haber-Bosch process; however, such a process is difficult to perform due to the inherent inertness of N2 molecules together with low solubility in aqueous solutions. Although many active electrocatalysts have been used to electrocatalyze the N2 reduction reaction (NRR), unsatisfactory NH3 yields and lower Faraday efficiency are still far from practical industrial production, and thus, considerable research efforts are being devoted to address these problems. Nevertheless, most reports still mainly focus on the preparation of electrocatalysts and largely ignore a summary of optimization-modification strategies for the NRR. In this review, a general introduction to the NRR mechanism is presented to provide a reasonable guide for the design of highly active catalysts. Then, four categories of NRR electrocatalysts, according to chemical compositions, are surveyed, as well as several strategies for promoting the catalytic activity and efficiency. Later, strategies for developing efficient N2 fixation systems are discussed. Finally, current challenges and future perspectives in the context of the NRR are highlighted. This review sheds some light on the development of highly efficient catalytic systems for NH3 synthesis and stimulates research interests in the unexplored, but promising, research field of the NRR.

Constructing a high-efficiency iron-based catalyst for carbon dioxide oxidative dehydrogenation of 1-butene: The role of oxygen mobility and proposed reaction mechanism

The utilization of CO2 as a soft oxidant for the synthesis of 1,3-butadiene (BD) through the oxidative dehydrogenation (ODH) of 1-butene is emerging as a potential technology not only because it can reduce the environmental problems caused by CO2 but also because of the abundant availability, low cost and mild oxidizing properties of CO2. However, this technology suffers from low catalytic activities due to the inherent inertness of CO2. Herein, a high-efficiency iron-based catalyst for the ODH of 1-butene with CO2 was designed and prepared from the perspective of improving the catalyst oxygen mobility, and the turnover frequency (TOF) has been improved to thrice that of the traditional Fe2O3/γ-Al2O3 catalyst. Furthermore, the effect of the oxygen mobility in the catalysts on their catalytic activity was determined. The oxygen mobility of the catalysts played a key role in CO2 activation, which in turn facilitated the ODH reaction. The TOFs of the catalysts increased linearly with increasing oxygen mobility. In addition, the γ-Al2O3 support, especially the Lewis acid sites on its surface, was proved to be necessary for the reaction. Both the carrier and active component were required for the reaction to proceed. Based on the above results, the mechanism of the ODH of 1-butene with CO2 was proposed.

Biomimetic coating of cross-linked gelatin to improve mechanical and biological properties of electrospun PET: A promising approach for small caliber vascular graft applications.

Electrospun PET (ePET) is a promising material for small caliber vascular graft applications owing to its tunable mechanical properties, biocompatibility, and nanofibrous structure that mimic the morphology of natural extracellular matrix. However, the inherent inertness of PET impairs the adhesion and proliferation of endothelial cells on the inner surface of ePET tubular grafts, hindering the formation of a functional endothelium. Gelatin coatings, owing to their ability to promote endothelialization, are a valuable approach to overcome the limitations of ePET. Herein, a novel process for the deposition of stable biomimetic coatings of gelatin on ePET tubular grafts is proposed. Electrospun PET was first aminated by plasma treatment and then coated with a gelatin hydrogel cross-linked in situ by a Michael-type addition reaction. Amination provided a superhydrophilic behavior to the ePET surface, allowing easy gelatin interpenetration along the wall thickness of the tubular structure, and the obtainment of thin coatings that maintained the morphology of ePET fibers. Gelatin coating was stable at long term in a physiological-like environment, noncytotoxic and promoted in vitro cell adhesion and proliferation. Noteworthy, the mechanical properties of gelatin-coated ePET tubular grafts were improved in terms of elastic modulus, compliance, and elastic recoil, finally better matching the characteristics of native blood vessels. Altogether, the proposed coating technique successfully combines the advantages of ePET nanofibrous structure with cross-linked gelatin biological cues and mechanical reinforcement, and emerges as a promising strategy for the development of biocompatible small caliber vascular grafts with superior biomimetic and mechanical properties. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2405-2415, 2017.

Catalyst-free N-methylation of amines using CO2.

Recently, utilizing CO2 as a methylation reagent to construct functional chemicals has attracted significant attention. However, the conversion of CO2 is still a challenge due to its inherent inertness. In this study, we have developed a catalyst-free N-methylation of amines to prepare numerous methylamines using CO2 as a methyl source. By utilizing 2 eq. PhSiH3 as the reductant, amines could undergo N-methylation under 1 atm of CO2 in DMF at 90 °C. Aliphatic and aromatic amines were compatible, generating the desired products in up to 95% yield.

Palladium-catalyzed decarboxylative, decarbonylative and dehydrogenative C(sp2)-H acylation at room temperature.

Over the past few decades, an impressive array of C-H activation methodology has been developed for organic synthesis. However, due to the inherent inertness of the C-H bonds (e.g. ∼110 kcal mol-1 for the cleavage of C(aryl)-H bonds) harsh reaction conditions have been realized to overcome high energetic transition states resulting in a limited substrate scope and functional group tolerance. Therefore, the development of mild C-H functionalization protocols is in high demand to exploit the full potential of the C-H activation strategy in the synthesis of a complex molecular framework. Although, electron-rich substrates undergo electrophilic metalation under relatively mild conditions, electron-deficient substrates proceed through a rate-limiting C-H insertion under forcing conditions at high temperature. In addition, a stoichiometric amount of toxic silver salt is frequently used in palladium catalysis to facilitate the C-H activation process which is not acceptable from the environmental and industrial standpoint. We report herein, a Pd(ii)-catalyzed decarboxylative C-H acylation of 2-arylpyridines with α-ketocarboxylic acids under mild conditions. The present protocol does not require stoichiometric silver(i) salts as additives and proceeds smoothly at ambient temperature. A novel decarbonylative C-H acylation reaction has also been accomplished using aryl glyoxals as acyl surrogates. Finally, a practical C-H acylation via a dehydrogenative pathway has been demonstrated using commercially available benzaldehydes and aqueous hydroperoxides. We also disclose that acetonitrile solvent is optimal for the acylation reaction at room temperature and has a prominent role in the reaction outcome. Control experiments suggest that the acylation reaction via decarboxylative, decarbonylative and dehydrogenative proceeds through a radical pathway. Thus we disclose a practical protocol for the sp2 C-H acylation reaction.

Tuning the electronic structure, bandgap energy and photoluminescence properties of hexagonal boron nitride nanosheets via a controllable Ce3+ ions doping

The modification of electronic structure, bandgap energy and photoluminescence properties of hexagonal boron nitride (h-BN) nanosheets has been challenging due to the inherent inertness and chemical stability of h-BN. In the present work, we realized tuning the electronic structure and bandgap energy properties of h-BN nanosheets via a controllable Ce3+ ions doping through a one-step facile thermal chemical reaction route using HBO3, C3H6N6 and Ce(Ac)3·nH2O as reactant precursors. As the Ce3+ ions incorporating content is lower than the critical threshold saturation value of 1.25%, the Ce-doped BN samples show an obvious band gap monotonically narrowing trend from 4.42 eV of pure BN to 3.31 eV for 1.25% Ce-doped BN nanosheets. With incorporation of Ce3+ ions into the lattice of h-BN, the intensity of electron paramagnetic resonance (EPR) signals closely associated with the nitrogen vacancies in Ce-doped BN samples, displays a decline trend with increasing the concentration of the incorporated Ce3+ ions, suggesting a decrease in the concentration of paramagnetic centers. The introduction of Ce3+ ions can result in the formation of a doping energy level between the conduction and valence bands of BN, and thus shifts the absorption band to the large-wavelength region, corresponding to the bandgap energy narrowing of Ce-doped BN, resulting in a red shift of the absorption edge of the Ce-doped BN samples. The B–N–O–Ce bonding due to the Ce3+ ion doping is responsible for bandgap energy narrowing in the Ce-doped BN materials. As the concentration of the incorporated Ce3+ ions reaches the critical threshold value of 1.25%, no more nitrogen vacancies are available, so the bandgap energy narrowing effect from the Ce3+ ion doping is reduced.

Photo-lability of deep ocean dissolved black carbon

Abstract. Dissolved black carbon (DBC), defined here as condensed aromatics isolated from seawater via PPL solid phase extraction and quantified as benzenepolycarboxylic acid (BPCA) oxidation products, is a significant component of the oceanic dissolved organic carbon (DOC) pool. These condensed aromatics are widely distributed in the open ocean and appear to be tens of thousands of years old. As such DBC is regarded as highly refractory. In the current study, the photo-lability of DBC, DOC and coloured dissolved organic matter (CDOM; ultraviolet-visible absorbance) were determined over the course of a 28 day irradiation of North Atlantic Deep Water under a solar simulator. During the irradiation DBC fell from 1044 ± 164 nM-C to 55 ± 15 nM-C, a 20-fold decrease in concentration. Dissolved black carbon photo-degradation was more rapid and more extensive than for bulk CDOM and DOC. The concentration of DBC correlated with CDOM absorbance and the quality of DBC indicated by the ratios of different BPCAs correlated with CDOM absorbance spectral slope, suggesting the optical properties of CDOM may provide a proxy for both DBC concentrations and quality in natural waters. Further, the photo-lability of components of the DBC pool increased with their degree of aromatic condensation. These trends indicate that a continuum of compounds of varying photo-lability exists within the marine DOC pool. In this continuum, photo-lability scales with aromatic character, specifically the degree of condensation. Scaling the rapid photo-degradation of DBC to rates of DOC photo-mineralisation for the global ocean leads to an estimated photo-chemical half-life for oceanic DBC of less than 800 years. This is more than an order of magnitude shorter than the apparent age of DBC in the ocean. Consequently, photo-degradation is posited as the primary sink for oceanic DBC and the apparent survival of DBC molecules in the oceans for millennia appears to be facilitated not by their inherent inertness but by the rate at which they are cycled through the surface ocean's photic zone.