Boron-Made N2 : Realization of a B≡B Triple Bond in the B2 Al3 - Cluster.

Until now, all B≡B triple bonds have been achieved by adopting two ligands in the L→B≡B←L manner. Herein, we report an alternative route of designing the B≡B bonds based on the assumption that by acquiring two extra electrons, an element with the atomic number Z can have properties similar to those of the element with the atomic number Z+2. Specifically, we show that due to the electron donation from Al to B, the negatively charged B≡B kernel in the B2 Al3 - cluster mimics a triple N≡N bond. Comprehensive computational searches reveal that the global minimum structure of B2 Al3 - exhibits a direct B-B distance of 1.553 Å, and its calculated electron vertical detachment energies are in excellent agreement with the corresponding values of the experimental photoelectron spectrum. Chemical bonding analysis revealed one σ and two π bonds between the two B atoms, thus confirming a classical textbook B≡B triple bond, similar to that of N2 .

Probe-Free Direct Identification of Type†I and Type†II Photosensitized Oxidation Using Field-Induced Droplet Ionization Mass Spectrometry.

While Type I and Type II photosensitizers are often carefully tailored to achieve their respective advantages in treating different cancers, the identifications of the Type I and II mechanisms as such, the key reaction intermediates, and the consequent oxidation products of the substrates have never been easy. Using our unique home-built field-induced droplet ionization mass spectrometry (FIDI-MS) method that selectively samples molecules at the air-water interface, here we show the facile determination of both Type I and II mechanisms of a poster-child photosensitizer, temoporfin, without the addition of any probes. The unstable doublet radical resulting from the hydrogen abstraction by the triplet temoporfin through the Type I mechanism is captured, manifesting the in situ advantage of FIDI-MS. We anticipate that the method developed in this study can be widely utilized in the future designs of novel photosensitizers and the screening of their photosensitization mechanisms.

Mass Spectrometric Study of Acoustically Levitated Droplets Illuminates Molecular-Level Mechanism of Photodynamic Therapy for Cancer involving Lipid Oxidation.

Even though the general mechanism of photodynamic cancer therapy is known, the details and consequences of the reactions between the photosensitizer-generated singlet oxygen and substrate molecules remain elusive at the molecular level. Using temoporfin as the photosensitizer, here we combine field-induced droplet ionization mass spectrometry and acoustic levitation techniques to study the "wall-less" oxidation reactions of 18:1 cardiolipin and 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (POPG) mediated by singlet oxygen at the air-water interface of levitated water droplets. For both cardiolipin and POPG, every unsaturated oleyl chain is oxidized to an allyl hydroperoxide, which surprisingly is immune to further oxidation. This is attributed to the increased hydrophilicity of the oxidized chain, which attracts it toward the water phase, thereby increasing membrane permeability and eventually triggering cell death.

A Porous Network of Bismuth Used as the Anode Material for High-Energy-Density Potassium-Ion Batteries.

Potassium-ion batteries (KIBs) are plagued by a lack of materials for reversible accommodation of the large-sized K+ ion. Herein we present, the Bi anode in combination with the dimethoxyethane-(DME) based electrolyte to deliver a remarkable capacity of ca. 400 mAh g-1 and long cycle stability with three distinct two-phase reactions of Bi↔ KBi2 ↔K3 Bi2 ↔K3 Bi. These are ascribed to the gradually developed three-dimensional (3D) porous networks of Bi, which realizes fast kinetics and tolerance of its volume change during potassiation and depotassiation. The porosity is linked to the unprecedented movement of the surface Bi atoms interacting with DME molecules, as suggested by DFT calculations. A full KIB of Bi//DME-based electrolyte//Prussian blue of K0.72 Fe[Fe(CN)6 ] is demonstrated to present large energy density of 108.1 Wh kg-1 with average discharge voltage of 2.8 V and capacity retention of 86.5 % after 350 cycles.

Realization of an Al≡Al Triple Bond in the Gas-Phase Na3 Al2 - Cluster via Double Electronic Transmutation.

The discovery of homodinuclear multiple bonds composed of Group 13 elements represents one of the most challenging frontiers in modern chemistry. A classical triple bond such as N≡N and HC≡CH contains one σ bond and two π bonds constructed from the p orbitals perpendicular to the σ bond. However, the traditional textbook triple bond between two Al atoms has remained elusive. Here we report an Al≡Al triple bond in the designer Na3 Al2 - cluster predicted in silico, which was subsequently generated by pulsed arc discharge followed by mass spectrometry and photoelectron spectroscopy characterizations. Being effectively Al2- due to the electron donation from Na, the Al atoms in Na3 Al2 - undergo a double electronic transmutation into Group 15 elements, thus the Al2- ≡Al2- kernel mimics the P≡P and N≡N molecules. We anticipate this work will stimulate more endeavors in discovering materials using Al2- ≡Al2- as a building block in the gas phase and in the solid state.

Pb nanospheres encapsulated in metal-organic frameworks-derived porous carbon as anode for high-performance sodium-ion batteries.

Alloying-type anode materials are considered promising candidates for sodium-ion batteries (SIBs) due to their high theoretical capacities. However, their application is limited by the severe capacity decay stemming from dramatic volume changes during Na+ insertion/extraction processes. Here, Pb nanospheres encapsulated in a carbon skeleton (Pb@C) were successfully synthesized via a facile metal-organic frameworks (MOFs)-derived method and used as anodes for SIBs. The nanosized Pb particles are uniformly incorporated into the porous carbon framework, effectively mitigating volume changes and enhancing Na+ ion transport during discharging/charging. Benefiting from this unique architecture, a reversible capacity of 334.2 mAh g-1 at 2 A g-1 is achieved after 6000 cycles corresponding to an impressive 88.2 % capacity retention and a minimal capacity loss of 0.00748 % per cycle. Furthermore, a high-performance full sodium-ion battery of Pb@C//NVPF was constructed, demonstrating a high energy density of 291 Wh kg-1 and power density of 175 W kg-1. This facile MOFs-derived method offers insights into the design of high-capacity alloy-type anode materials using Pb sources, opening up new possibilities for innovative approaches to Pb recycling and pollution prevention.

Mass Spectrometry and Cryogenic Electron Microscopy Illuminate Molecular-Level Mechanisms of the Oxidative and Structural Damage to Lipid Membranes by Radical-Bearing Graphene Oxide.

Biomedical applications of graphene in tumor and bacterial treatment have become cutting-edge fields due to its unique physical and chemical properties. However, a mechanistic understanding of the interactions and reactions between graphene-based material and biological systems such as lipid membranes remains elusive, especially at the molecular level. By using the unique field-induced droplet ionization mass spectrometry and cryogenic electron microscopy methodologies, we reveal the oxidation products of monolayer lipid membranes at the air-water interface and the change in the morphology of bilayer lipid membranes in an aqueous solution caused by the incorporation of graphene oxide bearing π-conjugated carbon radicals [hydrated graphene oxide (hGO)]. We discovered that hGO is an efficient source of hydroxyl radicals and that it is not only the incorporation of the hGO sheets but also the irregular packing of the lipid oxides from the hydroxyl radical oxidation that causes the structural distortions of the liposomes.

Beyond lipid peroxidation: Distinct mechanisms observed for POPC and POPG oxidation initiated by UV-enhanced Fenton reactions at the air-water interface.

Fenton or Fenton-like reactions are ubiquitous in nature, and the hydroxyl radicals (·OH) generated in these reactions are accountable for a plethora of oxidation processes both in the environment and in vivo. Among these oxidation reactions, lipid oxidation initiated by ·OH radicals has long been oversimplified as a peroxidation mechanism, but in reality, it is a highly complicated process that can result in a large variety of products. Using the unique field-induced droplet ionization mass spectrometry (FIDI-MS) methodology that is capable of selective sampling of amphiphilic molecules that reside at the air-water interface, here, we show distinct mechanisms from the ultraviolet (UV)-enhanced Fenton oxidations of two phospholipids, POPC and POPG, even though these two lipids possess the same functional groups that are vulnerable to ·OH attack. We postulate that it is the different packing densities that determine the permeability of ambient NO molecules into the monolayers, resulting in highly distinct reaction pathways and products. We anticipate that this work will be a wake-up call that the lipid peroxidation mechanism is sometimes taken for granted and that lipid oxidation can be subtly affected by various factors that deserves deeper investigations.

Investigation of the Acid-Mediated Photosensitized Reactions of Amphiphilic α-Keto Acids at the Air-Water Interface Using Field-Induced Droplet Ionization Mass Spectrometry.

The photochemistry of α-keto acids has been of great interest due to its implications in atmospheric and prebiotic chemistries. α-Keto acids with long alkyl chains are amphiphilic in nature, and they tend to partition at the air-water interface of atmospheric water droplets and add to the complexity of the chemistries therein. The air-water interface is a unique environment that plays a vital role in overall atmospheric processes. However, existing studies mostly focus on the photochemistry of α-keto acids in the bulk solution and neglect the reactions that occur at the interface. In this study, using the field-induced droplet ionization mass spectrometry methodology that is capable of selectively sampling amphiphilic molecules that reside at the air-water interface, we show that the acid-mediated photochemistry of 2-oxooctanoic acid and 2-oxoheptoic acid is highly different from those of previously reported reactions in the bulk and contributes to the formation of humic-like substances (HULIS). This work emphasizes the uniqueness of the photochemistry at the air-water interface. We anticipate that studies of atmosphere-relevant photochemistry at the air-water interface will be an avenue rich with opportunities.

Intramolecular electron-induced proton transfer and its correlation with excited-state intramolecular proton transfer.

Electron-induced proton transfer depicts the proton motion coupled with the attachment of a low-energy electron to a molecule, which helps to understand copious fundamental chemical processes. Intramolecular electron-induced proton transfer is a similar process that occurs within a single molecule. To date, there is only one known intramolecular example, to the best of our knowledge. By studying the 10-hydroxybenzo[h]quinoline and 8-hydroxyquinoline molecules using anion photoelectron spectroscopy and density functional theory, and by theoretical screening of six other molecules, here we show the intramolecular electron-induced proton transfer capability of a long list of molecules that meanwhile have the excited-state intramolecular proton transfer property. Careful examination of the intrinsic electronic signatures of these molecules reveals that these two distinct processes should occur to the same category of molecules. Intramolecular electron-induced proton transfer could have potential applications such as molecular devices that are responsive to electrons or current.

Low-Cost K4 Fe(CN)6 as a High-Voltage Cathode for Potassium-Ion Batteries.

Potassium-ion batteries (KIBs) are of interest for large-scale electrical energy storage, owing to the abundance of K resources and potential high energy density. Low-cost cathodes with high performance are crucial for KIBs. Herein, K4 Fe(CN)6 is shown to be a low-cost and high-voltage cathode for KIBs. It can deliver a high voltage of approximately 3.6 V and a discharge capacity of 65.5 mAh g-1 with a lifespan of 400 cycles of discharge and charge. This is attributed to the strong σ bonds between C atoms and Fe and to the reduced particle size and good contact with conductive carbon brought about by ball milling, which benefit both the K+ ion and the electronic conduction. The [Fe(CN)6 ]3-/4- redox couple is found to be responsible for charge compensation upon reversible extraction/insertion of K+ from/into K4 Fe(CN)6 . The high voltage and stability of K4 Fe(CN)6 will make it a promising low-cost cathode for KIBs and encourage more investigations into high-performance cathode materials.