Nitrogen Bond Research Articles

Misfit accommodation in a single interface atomic layer at a highly lattice-mismatched InN/GaN

Heterostructures of covalent semiconductors provide an invaluable platform for synthesizing the distinct properties of materials, leading to unprecedented functions in electronic and optoelectronic devices. The main challenge has been to forge high-quality interfaces of the heterostructures that guarantee the designed properties. To date, high-quality interfaces have been attained in heterostructures with a lattice mismatch of less than a few percent. However, for highly lattice-mismatched interfaces, such as InN/GaN (0001) (11.1% mismatch), interfacial structures remain unknown. Here, we investigate the atomic structure of the InN/GaN interface using atomic-resolution transmission electron microscopy and large-scale density-functional calculations. Our findings show that an interface structure without any misfit dislocations is formed, where an InN single monolayer at the interface accommodates the entire misfit. We argue that the mechanism underlying the formation of this interface monolayer is the flexibility of the group III–nitrogen bond network.

Surface Modification of Additively Manufactured Ti6Al4V through In-Situ Nitrogen-Assisted Laser Surface Remelting

Abstract Laser surface remelting is a widely used method for surface modification of titanium and related alloys, particularly to enhance its workability in the biomedical industry through surface nitriding. The present work aims to develop the nitride surface over the LPBF-processed Ti6Al4V substrate by introducing the nitrogen environment in the build chamber during the remelting. The effects of different laser power and laser scan speeds were studied over the surface topography and elemental changes of the remelted surface. The result shows an increase in surface roughness with selective laser remelting, which could enhance cell proliferation or osseointegration, which is advantageous for biomedical applications.EDX results show a significant increase in nitrogen content in terms of weight percentage for the in-situ remelted surface. XRD phase analysis shows the presence of titanium(Ti) and aluminium(Al) nitride peaks, and X-ray Photon-electron Spectrometry (XPS) also indicates the formation of nitrogen bonds with Ti and Al, which were initially missing in the substrate. The results reported here confirm the nitride surface formation over the substrate due to the in-situ remelting under the nitrogen environment for the LPBF-processed Ti6Al4V, which could be used for improved biomedical applications.

Electrocatalytic and Photocatalytic N2 Fixation Using Carbon Catalysts.

Carbon catalysts have shown promise as an alternative to the currently available energy-intensive approaches for nitrogen fixation (NF) to urea, NH3, or related nitrogenous compounds. The primary challenges for NF are the natural inertia of nitrogenous molecules and the competitive hydrogen evolution reaction (HER). Recently, carbon-based materials have made significant progress due to their tunable electronic structure and ease of defect formation. These properties significantly enhance electrocatalytic and photocatalytic nitrogen reduction reaction (NRR) activity. While transition metal-based catalysts have solved the kinetic constraints to activate nitrogen bonds via the donation-back-π approach, there is a problem: the d-orbital electrons of these transition metal atoms tend to generate H-metal bonds, inadvertently amplifying unwanted HER. Because of this, a timely review of defective carbon-based electrocatalysts for NF is imperative. Such a review will succinctly capture recent developments in both experimental and theoretical fields. It will delve into multiple defective engineering approaches to advance the development of ideal carbon-based electrocatalysts and photocatalysts. Furthermore, this review will carefully explore the natural correlation between the structure of these defective carbon-based electrocatalysts and photocatalysts and their NF activity. Finally, novel carbon-based catalysts are introduced to obtain more efficient performance of NF, paving the way for a sustainable future.

Copper-catalyzed N–H bond chalcogenation of anilines

The chalcogen–nitrogen bond (X–N, where X = S, Se) is a key chemical motif in many structures, including inorganic and organic materials, catalysts, protein mimics, and pharmaceuticals.

Effects of N2O plasma treatment on the performance and stability of high indium content InGaZnO thin-film transistors

Abstract This study investigates the effects of N2O plasma treatment on the electrical performance and stability of In(2%)GaZnO thin-film transistors (TFTs). The experimental results show that with increasing N2O plasma treatment time, the electrical performance of In(2%)GaZnO TFTs deteriorated, and the threshold voltage (V th) is positively shifted. Moreover, the optimized In(2%)GaZnO:N2O (4 min) TFTs exhibited the best electrical performance, which include a μ FE of 22.5 cm2 Vs−1, a small SS value of 0.31 V decade−1, a small V th of 0.3 V, a low D it value of 8.5 × 1011 cm−2 eV−1, and a high I on/I off of 107. Moreover, a small V th shift (0.4, 0.6, −0.5 and −0.7 V) in In(2%)GaZnO:N2O (4 min) TFT was observed under the gate bias and light illumination test. X-ray photoelectron spectroscopy and low-frequency noise analysis indicate that this enhanced performance is attributed to the appropriate N2O plasma treatment that can reduce the oxygen vacancy, interface trap density, and other bulk/surface defects due to the formation of metal–nitrogen bonds (especially Ga–N) and N–O bonds. Over all, the N2O plasma treatment simple method has provided a novel approach to achieve high performance and highly stable oxide In(2%)GaZnO TFTs for applications in flat panel displays.

Effect of nitrogen partial pressure on the structural and mechanical properties of (MoNbTaW)N thin films deposited by DC magnetron sputtering

This study investigates the influence of nitrogen partial pressure on the microstructure, crystal structure, chemical bonding, and mechanical properties of (MoNbTaW)N films deposited on silicon substrates via DC reactive sputtering. The depositions were carried out at room temperature from a MoNbTaW alloy target at 0.6 Pa by varying nitrogen partial pressure between 0% and 50%. The surface morphology, crystal structure, bonding characteristics, and mechanical properties were studied using scanning electron microscopy (SEM), atomic force microscopy (AFM), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and nanoindentation. SEM and AFM findings reveal significant morphological changes from lenticularlike structures to fine-grain structures as nitrogen partial pressure increases from 0% to 50%, with feature size decreasing from 12 to 8 nm. XRD analysis confirms a crystalline structure in all films, transforming from body-centred cubic to face-centred cubic, occurring between 16% and 33% nitrogen partial pressure. XPS analysis confirms the formation of metal–nitrogen (Me–N) bonds through binding energy shifts. Despite these structural changes, no significant variations in hardness and film modulus were observed with changes in nitrogen partial pressure, which can be attributed to weaker p(N)-d(TM) interactions. The study underscores nitrogen's crucial role in altering microstructure and crystal structure, while the strength of the Me–N bond limits its effect on mechanical properties.

2-Dimensional Palladium Organometallic Framework Generated Via C-H Activation for Electrochemical Syngas Production from CO2

Noble metal catalysts have been recognized for their exceptional catalytic activity and efficiency, sparking extensive research efforts. Recently, there has been a notable shift towards utilizing noble metal catalysts supported on stable materials, particularly within the realm of heterogeneous catalysts. Metal-Organic Frameworks (MOFs) have emerged as promising candidates in this regard, offering versatile platforms that serve as porous substrates for dispersing external noble metal species. Various methodologies have been developed to fabricate MOF-based noble metal catalysts, including the introduction of metal nanoparticles, the anchorage of metalloligands, and the utilization of desired metal clusters within the framework. However, because MOFs require metals to form their structures, the introduction of metal nanoparticles and the use of metalloligands necessarily entails the use of undesired metals. Therefore, while it is attractive to synthesize MOFs composed only of desired noble metals, direct synthesis of noble metal-based MOFs has been rarely reported due to significant synthetic challenges arising from the self-assembly of noble metal nanoparticles during solvothermal reactions.Considering the chemical softness of noble metals, expanding the range of metal–ligand bonds to include chemical soft bonds is crucial for diversifying linkages and incorporating metal atoms as low-valent metal ions and noble metals. Beyond traditional metal–oxygen and metal–nitrogen bonds with carboxylates and azolates, organometallic metal–carbon (M–C) bond connecting crystalline frameworks has gained attention. However, due to the scarcity of multivalent ligands for the M–C bond, generating organometallic frameworks with a single organic linker presents synthetic challenges.Herein, we found a new synthetic strategy applying organometallic chemistry. We successfully synthesized a Pd organometallic framework, PdOF-1, with a terephthalic acid (H2bdc), one of the most common ligands used for MOFs. PdOF-1 crystals were obtained through a one-pot solvothermal reaction of Pd acetate and H2bdc in dimethyl sulfoxide. Via Pd-catalyzed ortho C–H activation directed by carboxylic acid, Pd–C bonds were formed which directly connected bdc and Pd atoms. The framework comprises atomically dispersed Pd atoms forming organometallic Pd–C bonds, constituting a 2D network with the C2/c space group. As a result, PdOF-1 showed electrochemical CO2 reduction to produce syngas (H2/CO = 0.98) at a low potential of −0.33 V vs. RHE. This work not only presents a rare Pd organometallic framework, but also suggests a synthetic strategy to synthesize noble metal networks with M–C bonds and atomically dispersed noble metals.

Overtone Excitation of Nitrogen Molecules via Stimulated Raman Pumping.

Nitrogen bond activation is a pivotal process in chemistry, with bond excitation being fundamental to understanding the underlying mechanisms, making the preparation of molecules in specific quantum states crucial. Here we report the first overtone excitation of the N2 molecule from X1Σg+(v = 0, j = 0, 1, and 2) to X1Σg+(v = 2, j = 0, 1, 2, and 3) using the stimulated Raman pumping (SRP) method in a pulsed molecular beam. N2 was detected using 2+1 resonance-enhanced multiphoton ionization through the a″1Σg+ state. An excitation efficiency of 4% was achieved within the excitation region in which the SRP laser intensity was saturated, indicating the low cross-sectional nature of the process. The SRP detuning spectra for different branches were measured, and the excited N2 [X1Σg+(v = 2)] was further used to access various vibrational states of a″1Σg+, enabling the determination of its vibrational constants. This research opens up new opportunities for studying the specific high vibrational excitation of nitrogen in reactions and scattering experiments and contributes additional precise spectral data for the N2 molecule.

Chemical changes from N-doped graphene and Metal-Organic Frameworks to N-G/MOF composites for improved electrocatalytic activity

Integrating N-doped graphene (N-G) with Metal-Organic Frameworks (MOFs) enhances catalytic activity for oxygen reduction reaction (ORR), often exceeding both the performances of their precursors and, in some cases, even Platinum group metal (PGM)-based catalysts. However, the factors driving this improved catalytic activity in N-G/MOF composites remain unexplored, particularly from the perspective of the chemical changes. To investigate the chemical changes in N-G and MOF upon their integration and the implications of these changes on ORR catalytic activity, an N-G/MOF was synthesized from N-G with a MOF (ZIF-8) following a mechanochemical wet ball milling process. The N-G, ZIF-8, and N-G/MOF samples were examined for changes in elemental composition, chemical state of carbon, different nitrogen and carbon bonds, and other chemical interactions. In the N-G/MOF catalyst, compared to its N-G and ZIF-8 precursors, the relative oxygen content increased, indicating the formation of additional oxygen-containing groups. The C 1s peak shifted to a lower binding energy in N-G/MOF, suggesting changes in the overall chemical or oxidation state of the carbon atoms. Besides, the increase in pyridinic-N functional groups in N-G/MOF points to the formation of additional active sites. Furthermore, the formation of C–Zn bonds in N-G/MOF suggests the probable emergence of single-atom Zn sites, while the increase in CO bonds points to the formation of carboxyl or carbonyl groups. These chemical changes could be linked to the enhanced electrocatalytic activity of the N-G/MOF composite for ORR. This study may also be beneficial for other research focused on developing composite catalysts involving various N-G and MOFs-based materials.

Synthesis, characterization, and biological potential of 2-thiophene carbaldehyde o-phenylenediamine Schiff base and its Cr(II), Mn(II), and Fe(II) Complexes

A Schiff base was produced through the chemical reaction of 2-thiophene carbaldehyde with o-phenylenediamine. The corresponding metal (II) chlorides were refluxed with the Schiff base to produce the complexes of Cr (II), Mn (II), and Fe (II). These complexes were then characterized by elemental analysis, FT-IR, atomic absorption spectroscopy, solubility, melting/decomposition temperature, and magnetic susceptibility. The vibrational peak at 1622 cm̄1 in the FT-IR spectral data of the Schiff base was ascribed to the vibration frequencies of azomethine u(C=N). But in the complexes, it was discovered that the azomethine band shifted between 1614 and 1659 cm̄1 , suggesting that they were involved in the complexes’ creation. The complexes’ measured absorption bands in the range of 713–769 cm1 were attributed to the M–N bond, indicating the occurrence of metal–nitrogen bonds. The complexes exhibit non-electrolyte properties attributed to their low molar conductance values ranging from 8.00 to 29 Ohm̄1 cm̄ ²mol̄¹. The determination of the melting point of the Schiff base yielded 120 °C, while the decomposition temperature fell within the range of 149–160 °C for the complexes, indicating their thermal stability. Analysis of magnetic susceptibility indicated an octahedral geometry for all the complexes, with values ranging from 2.24 to 3.12 BM. The elemental should analysis of both the Schiff base and its metal (II) complexes for C, H, and N indicated a close agreement between observed and calculated percentages, suggesting a consistent 1:2 metal-Schiff base ratio across all complexes. The qualitative analysis of the compounds confirmed the presence of chloride, which was quantified and determined to range from 4.62% to 7.90%. The prepared Schiff base and its metal (II) complexes underwent evaluation for their antibacterial efficacy against Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, and Pseudomonas aeruginosa, as well as their antifungal properties against Candida albicans and Aspergillus niger. The results of the experiments indicated that the metal complexes displayed notable antimicrobial effects.

Nanoarchitectonics of Nickel Nitride‐V2CTX Mxene: An Efficient Bifunctional Catalyst for Alkaline Water/Seawater Applications

AbstractSeawater, being the most plentiful natural water source worldwide, is a highly abundant and cost‐efficient medium for producing hydrogen by alkaline water electrolysis. However, the advancement of seawater electrolysis is hindered by notable impediments caused by chloride corrosion at the anode and the simultaneous chlorine evolution process. Only a limited number of non‐noble electrocatalysts demonstrate noteworthy bifunctional catalytic efficacy and long‐term durability. In this regard, Nickel Nitride tailored V2CTX Mxene nanostructures is reported as a bifunctional catalyst for overall water/seawater applications. The optimized sample Ni3N@3000‐V2CTx exhibits low overpotential values of 90 and 300 mV in acidic and alkaline + seawater solutions respectively at 10 mA cm−2 for hydrogen evolution reaction. Similarly, this catalyst shows 70 and 240 mV overpotential values in alkaline water and alkaline + seawater solutions respectively at the same current density for oxygen evolution reaction. Synergetic effects of Multiple Vanadium and Nickel valency along with compelling nitrogen bonds creates elevated density of exposed functional sites for electrocatalytic activity. Furthermore, the notable electrochemical active surface area and mass activity suggest an enhanced and significant presence of abundant active sites. Additionally, the high stability and significantly decreased charge transfer resistance expedited the overall water/seawater‐splitting reaction rate.

Cascade Synthesis of Fe-N2-Fe Dual-Atom Catalysts for Superior Oxygen Catalysis.

Dual-atom catalysts (DACs) have been proposed to break the limitation of single-atom catalysts (SACs) in the synergistic activation of multiple molecules and intermediates, offering an additional degree of freedom for catalytic regulation. However, it remains a challenge to synthesize DACs with high uniformity, atomic accuracy, and satisfactory loadings. Herein, we report a facile cascade synthetic strategy for DAC via precise electrostatic interaction control and neighboring vacancy construction. We synthesized well-defined, uniformly dispersed dual Fe sites which were connected by two nitrogen bonds (denoted as Fe-N2-Fe). The as-synthesized DAC exhibited superior catalytic performances towards oxygen reduction reaction, including good half-wave potential (0.91 V), high kinetic current density (21.66 mA cm-2), and perfect durability. Theoretical calculation revealed that the DAC structure effectively tunes the oxygen adsorption configuration and decreases the cleavage barrier, thereby improving the catalytic kinetics. The DAC-based zinc-air batteries exhibited impressive power densities of 169.8 and 52.18 mW cm-2 at 25 °C and -40 °C, which is 1.7 and 2.0 times higher than those based on Pt/C+Ir/C, respectively. We also demonstrated the universality of our strategy in synthesizing other M-N2-M DACs (M=Co, Cu, Ru, Pd, Pt, and Au), facilitating the construction of a DAC library for different catalytic applications.

Cascade Synthesis of Fe‐N2‐Fe Dual‐Atom Catalysts for Superior Oxygen Catalysis

AbstractDual‐atom catalysts (DACs) have been proposed to break the limitation of single‐atom catalysts (SACs) in the synergistic activation of multiple molecules and intermediates, offering an additional degree of freedom for catalytic regulation. However, it remains a challenge to synthesize DACs with high uniformity, atomic accuracy, and satisfactory loadings. Herein, we report a facile cascade synthetic strategy for DAC via precise electrostatic interaction control and neighboring vacancy construction. We synthesized well‐defined, uniformly dispersed dual Fe sites which were connected by two nitrogen bonds (denoted as Fe‐N2‐Fe). The as‐synthesized DAC exhibited superior catalytic performances towards oxygen reduction reaction, including good half‐wave potential (0.91 V), high kinetic current density (21.66 mA cm−2), and perfect durability. Theoretical calculation revealed that the DAC structure effectively tunes the oxygen adsorption configuration and decreases the cleavage barrier, thereby improving the catalytic kinetics. The DAC‐based zinc‐air batteries exhibited impressive power densities of 169.8 and 52.18 mW cm−2 at 25 °C and −40 °C, which is 1.7 and 2.0 times higher than those based on Pt/C+Ir/C, respectively. We also demonstrated the universality of our strategy in synthesizing other M‐N2‐M DACs (M=Co, Cu, Ru, Pd, Pt, and Au), facilitating the construction of a DAC library for different catalytic applications.

A Covalent Organic Nanoribbon: Preparation, Single‐Crystal Structure with Chinese Luban Lock Configuration, and Photocatalytic Behavior

AbstractThe multiple mortise‐and‐tenon joint parts are the core factors to provide the structural stability and diversity of Chinese Luban locks; however, constructing such structures is very challenging. Herein, single crystals of a covalent organic nanoribbon (named CityU‐27) are prepared through the assembly of hexahydroxytriphenylene (HHTP), 4,4′‐vinylenedipyridine (BYE), and phenylboronic acid (BA) together through dative boron←nitrogen (B←N) bonds. The single‐crystal X‐ray diffraction analysis indicates that CityU‐27 has a covalent organic nanoribbon structure, where each nanoribbon forms multiple and tight π–π interactions with four neighboring others to generate a Luban lock‐like configuration. CityU‐27 has been demonstrated to be an efficient photocatalyst in a one‐pot tandem reaction of hydrogen evolution reaction (HER) and semi‐hydrogenation reaction of alkynes in series to produce olefins without any additional photosensitizers and co‐catalysts (metal‐free).

Indirect Voltammetry Detection of Non-Electroactive Neurotransmitters Using Glassy Carbon Microelectrodes: The Case of Glutamate

Glassy carbon (GC) microelectrodes have been successfully used for the detection of electroactive neurotransmitters such as dopamine and serotonin through voltammetry. However, non-electroactive neurotransmitters such as glutamate, lactate, and gamma-aminobutyric acid (GABA) are inherently unsuitable for detection through voltammetry techniques without functionalizing the surface of the microelectrodes. To this end, we present here the immobilization of the L-glutamate oxidase (GluOx) enzyme on the surface of GC microelectrodes to enable the catalysis of a chemical reaction between L-glutamate, oxygen, and water to produce H2O2, an electroactive byproduct that is readily detectable through voltammetry. This immobilization of GluOx on the surface of bare GC microelectrodes and the subsequent catalytic reduction in H2O2 through fast-scan cyclic voltammetry (FSCV) helped demonstrate the indirect in vitro detection of glutamate, a non-electroactive molecule, at concentrations as low as 10 nM. The functionalized microelectrodes formed part of a four-channel array of microelectrodes (30 μm × 60 μm) on a 1.6 cm long neural probe that was supported on a flexible polymer, with potential for in vivo applications. The types and strengths of the bond between the GC microelectrode surface and its functional groups, on one hand, and glutamate and the immobilized functionalization matrix, on the other hand, were investigated through molecular dynamic (MD) modeling and Fourier transform infrared spectroscopy (FTIR). Both MD modeling and FTIR demonstrated the presence of several covalent bonds in the form of C-O (carbon–oxygen polar covalent bond), C=O (carbonyl), C-H (alkenyl), N-H (hydrogen bond), C-N (carbon–nitrogen single bond), and C≡N (triple carbon–nitrogen bond). Further, penetration tests on an agarose hydrogel model confirmed that the probes are mechanically robust, with their penetrating forces being much lower than the fracture force of the probe material.

Electronic and structural insights into boron nitride counterparts of Net-(Y,W)

Computational materials play a crucial role in comprehending various material classes and their properties, offering valuable insights for predicting novel structures and complementing experimental approaches. Net-(C,Y,W) has emerged as stable two-dimensional carbon allotropes of 4-6-8 carbon rings within this framework. This study uses density functional theory calculations and ab initio molecular dynamics simulations to explore the structural, electronic, optical, and mechanical properties of their boron nitride counterparts, named NetBN-W and NetBN-Y, with NetBN-C already investigated. The electronic analysis reveals an insulating characteristic for NetBN-W and a potential wide band gap semiconducting nature for NetBN-Y, with values of 5.12 eV and 3.71 eV, respectively. Optical properties examination indicates UV activity for these materials, accompanied by optical anisotropy between the x and y directions. Evaluation of mechanical properties also uncovers significant anisotropy in both materials, with Young’s moduli reaching 417.58 GPa for NetBN-W and 433.31 GPa for NetBN-Y when stretched in the y-direction of the basal plane. The nearly zero Young’s modulus for NetBN-Y in the x-direction signifies its substantial instability under tension due to nitrogen bonds parallel to the strain direction. These findings offer valuable insights into the fundamental properties of NetBN-W and NetBN-Y and their potential applications.

A Covalent Organic Nanoribbon: Preparation, Single-Crystal Structure with Chinese Luban Lock Configuration, and Photocatalytic Behavior.

The multiple mortise-and-tenon joint parts are the core factors to provide the structural stability and diversity of Chinese Luban locks; however, constructing such structures is very challenging. Herein, single crystals of a covalent organic nanoribbon (named CityU-27) are prepared through the assembly of hexahydroxytriphenylene (HHTP), 4,4'-vinylenedipyridine (BYE), and phenylboronic acid (BA) together through dative boron←nitrogen (B←N) bonds. The single-crystal X-ray diffraction analysis indicates that CityU-27 has a covalent organic nanoribbon structure, where each nanoribbon forms multiple and tight π-π interactions with four neighboring others to generate a Luban lock-like configuration. CityU-27 has been demonstrated to be an efficient photocatalyst in a one-pot tandem reaction of hydrogen evolution reaction (HER) and semi-hydrogenation reaction of alkynes in series to produce olefins without any additional photosensitizers and co-catalysts (metal-free).

A highly efficient adsorbent adapting to low pH condition for Pb(II) sequestration from aqueous solution − marine diatom: Laboratory and pilot scale tests

Highly efficient, economically feasible and environmentally friendly adsorbents have been a research hotspot for heavy metal sequestration. In the present study, dried marine diatom biomass (mainly composed of Chaetoceros sp.), which possessed high suface area and cumulative pore volume of 5.72 m2/g and 0.028 cm3/g, respectivly, were used to adsorb Pb(II) from aqueous solution. The immoblized marine diatom beads and an adsorption reactor filled with the beads were further investigated for continuous Pb(II) removal. The removal efficiency was evaluated as a function of contact time, initial concentration, pH and co-existing cations. Results indicated that the dried diatom biomass and the immobilized diatom beads effectively adsorbed Pb(II) under pH > 3.0 and pH > 4 0.0 conditions, respectively. The optimal conditions for the immobilized diatom beads preparation were: diatom powder dosage of 5.0 g / 100 mL sodium alginate solution, sodium alginate concentration of 20 g/L, CaCl2 concentration of 2 %, and cross linking time of 1 h. The Pb(II) adsorption on the marine diatom biomass and the immobilized beads were both well described by pseudo-second-order kinetic and Langmuir model. The maximumPb(II) adsorption capacities of the immobilized beads were 919.1 mg/g, which were much higher than that of the most of adsorbents reported elsewhere. Adsorption mechanism analysis demonstrated that Pb(II) was adsorbed onto the diatom biomass mainly through interaction with nitrogen bonds (mainly with pyrrolic nitrogen) and carboxylic groups, and ion exchange with light metals and hydrogen ions in quaternary nitrogen bonds. The diatom beads were used as adsorbents in a continuous Pb(II) treatment reactor, and the Pb(II) removal efficiency of the reactor reached to almost 100 % from the initial concentration of Pb(II) = 50 mg/L.

Cobalt–Nitrogen Bonding for Triggering the Low-Power Dual Detection of NO2 and NH3 by Mixed-Valence Co2+ and Co3+

Cobalt–Nitrogen Bonding for Triggering the Low-Power Dual Detection of NO₂ and NH₃ by Mixed-Valence Co²⁺ and Co³⁺

Water Microdroplets in Air: A Hitherto Unnoticed Natural Source of Nitrogen Oxides.

Water microdroplets are widespread in the atmosphere. We report a striking observation that micron-sized water droplets obtained from zero-volt spray sources (sonic spray, humidifier, spray bottle, steamer, etc.) spontaneously generate nitrogen oxides. The mechanistic investigation through the development of custom-designed sampling sources combined with mass spectrometry and isotope labeling experiments confirmed that air nitrogen reacts with the water at the air-water interface, fixing molecular nitrogen to its oxides (NO, NO2, and N2O) and acids (HNO2 and HNO3) at trace levels without any catalyst. These reactions are attributed to the consequence of an experimentally detected feeble corona discharge (breakdown of air) at the air-water interface, likely driven by the high intrinsic electric field at the surface of water microdroplets. The extent of this corona discharge effect varies depending on the pH, salinity/impurity, size, speed, and lifetime of microdroplets in the air. Thus, this study discloses that the air-water interface of microdroplets breaks the strong chemical bond of nitrogen (N2), producing nitrogen oxides in the environment, while lightning strikes and microbial processes in soil are considered their dominant natural sources. As nitrogen oxides are toxic air pollutants, their spontaneous formation at the air-water interface should have important implications in atmospheric reactions, requiring further investigations.