Molecular Hydrogen Research Articles

Dissolution dynamics of partially protected poly(4-hydroxystyrene) in organic developers investigated by quartz crystal microbalance (QCM) method

Abstract Poly(4-hydroxystyrene) (PHS) molecules in solid films are connected each other through polar and nonpolar molecular interaction and hydrogen bonds. Although the dissociation of phenolic hydroxyl groups plays the major role in the dissolution of PHS films in tetramethylammonium hydroxide (TMAH) aqueous developer, it is important to clarify the effects of other interactions. In this study, we investigated the dissolution dynamics of partially protected PHS in organic developers by a quartz crystal microbalance method to deepen the fundamental understanding of the dissolution dynamics of chemically amplified resists. The dissolution dynamics in the solvents, in which the phenolic hydroxyl groups are hardly dissociated, was measured. In 50 vol% methanol aqueous developer, a large swelling was observed. By decreasing the polarity of developer, the dissolution dynamics was significantly changed. In the hexyl acetate, the dissolution kinetics of PHS films became similar to that in TMAH aqueous developer although the dissolution mechanism is different.

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Context. One of the main problems in astrochemistry is determining the amount of sulfur in volatiles and refractories in the interstellar medium. The detection of the main sulfur reservoirs (icy H2S and atomic gas) has been challenging, and estimates are based on the reliability of models to account for the abundances of species containing less than 1% of the total sulfur. The high sensitivity of the James Webb Space Telescope provides an unprecedented opportunity to estimate the sulfur abundance through the observation of the [S I] 25.249 µm line. Aims. Our aim is to determine the amount of sulfur in the ionized and warm molecular phases toward the Orion Bar as a template to investigate sulfur depletion in the transition between the ionized gas and the molecular cloud in HII regions. Methods. We used the [S III] 18.7 µm, [S IV] 10.5 µm, and [S l] 25.249 µm lines to estimate the amount of sulfur in the ionized and molecular gas along the Orion Bar. For the theoretical part, we used an upgraded version of the Meudon photodissociation region (PDR) code to model the observations. New inelastic collision rates of neutral atomic sulfur with ortho-and para- molecular hydrogen were calculated to predict the line intensities. Results. The [S III] 18.7 µm and [S IV] 10.5 µm lines are detected over the imaged region with a shallow increase (by a factor of 4) toward the HII region. This suggests that their emissions are partially coming from the Orion Veil. We estimate a moderate sulfur depletion, by a factor of ~2, in the ionized gas. The corrugated interface between the molecular and atomic phases gives rise to several edge-on dissociation fronts we refer to as DF1, DF2, and DF3. The [S l] 25.249 µm line is only detected toward DF2 and DF3, the dissociation fronts located farthest from the HII region. This is the first ever detection of the [S l] 25.249 µm line in a PDR. The detailed modeling of DF3 using the Meudon PDR code shows that the emission of the [S l] 25.249 µm line is coming from warm (>40 K) molecular gas located at AV ~1–5 mag from the ionization front. Moreover, the intensity of the [S l] 25.249 µm line is only accounted for if we assume the presence of undepleted sulfur. Conclusions. Our data show that sulfur remains undepleted along the ionic, atomic, and molecular gas in the Orion Bar. This is consistent with recent findings that suggest that sulfur depletion is low in massive star-forming regions because of the interaction of the UV photons coming from the newly formed stars with the interstellar matter.

A Density Functional Theory Study of Defective and Doped Structures of MgB2 and Their Interaction with Hydrogen

The LiBH4+MgH2 system exhibits promising potential for solid-state hydrogen storage, yet the sluggish rehydrogenation of MgB2 poses a significant challenge. In this study, we utilize density functional theory (DFT) simulations to investigate the energetics of hydrogen in pure, defective, and doped MgB2 in equilibrium with molecular hydrogen. Our findings reveal that the B-Frenkel defect process is the thermodynamically most favorable in MgB2. The calculated solution energy for hydrogen at the interstitial site indicates low hydrogen solubility, even at mild temperatures. Incorporating hydrogen into a pre-existing B vacancy enhances the process, facilitated by doping of O on the B site. Additionally, Li doping on the Mg site enhances incorporation by forming strong Li-H bonds, predicting lower activation barriers for hydrogen dissociation and diffusion. Doping MgB2 with O and F at the B site significantly enhances hydrogen solubility. These dopants make MgB2 a promising material for high-capacity and fast-kinetics hydrogen storage applications, and further research into these effects can lead to advancements in energy storage technology.

Accurate reference spectra of HD in an H2–He bath for planetary applications

Context. The hydrogen deuteride (HD) molecule is an important deuterium tracer in astrophysical studies. The atmospheres of gas giants are dominated by molecular hydrogen, and the simultaneous observation of H2 and HD lines provides reliable information on the D/H ratios on these planets. The reference spectroscopic parameters play a crucial role in such studies. Under the thermodynamic conditions encountered in these atmospheres, spectroscopic studies of HD require not only the knowledge of line intensities and positions but also accurate reference data on pressure-induced line shapes and shifts. Aims. Our aim is to provide accurate collision-induced line-shape parameters for HD lines that cover any thermodynamic conditions relevant to the atmospheres of giant planets, namely any relevant temperature, pressure, and perturbing gas composition (the H2–He mixture). Methods. We performed quantum-scattering calculations on our new, highly accurate ab initio potential energy surface (PES), and we used scattering S matrices obtained in this way to determine the collision-induced line-shape parameters. We used cavity ring-down spectroscopy to validate our theoretical methodology. Results. We report accurate collision-induced line-shape parameters for the pure rotational R(0), R(1), and R(2) lines, the most relevant HD lines for investigations of the atmospheres of the giant planets. Besides the basic Voigt-profile collisional parameters (i.e., the broadening and shift parameters), we also report their speed dependences and the complex Dicke parameter, which can influence the effective width and height of the HD lines up to almost a factor of 2 for giant planet conditions. The sub-percent-level accuracy reached in this work is a considerable improvement over previously available data. All the reported parameters (and their temperature dependences) are consistent with the HITRAN database format, hence allowing for the use of the HITRAN Application Programming Interface (HAPI) for generating the beyond-Voigt spectra of HD.

Unveiling the Antimicrobial, Anti-Biofilm, and Anti-Quorum-Sensing Potential of Paederia foetida Linn. Leaf Extract against Staphylococcus aureus: An Integrated In Vitro–In Silico Investigation

Antimicrobial resistance poses a global health threat, with Staphylococcus aureus emerging as a notorious pathogen capable of forming stubborn biofilms and regulating virulence through quorum sensing (QS). In the quest for novel therapeutic strategies, this groundbreaking study unveils the therapeutic potential of Paederia foetida Linn., an Asian medicinal plant containing various bioactive compounds, contributing to its antimicrobial activities, in the battle against S. aureus. Through a comprehensive approach, we investigated the effect of ethanolic P. foetida leaf extract on S. aureus biofilms, QS, and antimicrobial activity. The extract exhibited promising inhibitory effects against S. aureus including the biofilm-forming strain and MRSA. Real-time PCR analysis revealed significant downregulation of key virulence and biofilm genes, suggesting interference with QS. Biofilm assays quantified the extract’s ability to disrupt and prevent biofilm formation. LC-MS/MS analysis identified quercetin and kaempferol glycosides as potential bioactive constituents, while molecular docking studies explored their binding to the QS transcriptional regulator SarA. Computational ADMET predictions highlighted favorable intestinal absorption but potential P-glycoprotein interactions limiting oral bioavailability. While promising anti-virulence effects were demonstrated, the high molecular weights and excessive hydrogen bond donors/acceptors of the flavonoid glycosides raise concerns regarding drug-likeness and permeability. This integrated study offers valuable insights for developing novel anti-virulence strategies to combat antimicrobial resistance.

Stacking Fault-Enriched MoNi4/MoO2 Enables High-Performance Hydrogen Evolution.

Producing green hydrogen in a cost-competitive manner via water electrolysis will make the long-held dream of hydrogen economy a reality. Although platinum (Pt)-based catalysts show good performance toward hydrogen evolution reaction (HER), the high cost and scarce abundance challenge their economic viability and sustainability. Here, a non-Pt, high-performance electrocatalyst for HER achieved by engineering high fractions of stacking fault (SF) defects for MoNi4/MoO2 nanosheets (d-MoNi) through a combined chemical and thermal reduction strategy is shown. The d-MoNi catalyst offers ultralow overpotentials of 78 and 121mV for HER at current densities of 500 and 1000mA cm-2 in 1M KOH, respectively. The defect-rich d-MoNi exhibits four times higher turnover frequency than the benchmark 20% Pt/C, together with its excellent durability (> 100 h), making it one of the best-performing non-Pt catalysts for HER. The experimental and theoretical results reveal that the abundant SFs in d-MoNi induce a compressive strain, decreasing the proton adsorption energy and promoting the associated combination of *H into hydrogen and molecular hydrogen desorption, enhancing the HER performance. This work provides a new synthetic route to engineer defective metal and metal alloy electrocatalysts for emerging electrochemical energy conversion and storage applications.

Modulated bandgap and gas adsorption behavior on two-dimensional SrAl2S4 monolayer: Potential applications for photovoltaic and energy storage

The structure of a novel two-dimensional layered material SrAl2S4 monolayer has been proposed, and its kinetic and thermodynamic stability has been confirmed. Researches have shown that SrAl2S4 monolayer is a semiconductor material with a bandgap of 1.630 eV for PBE and 2.798 eV for HSE06 at the ground state. Under biaxial strain, SrAl2S4 monolayer can complete the transition from a direct bandgap semiconductor to an indirect bandgap semiconductor, and its bandgap can vary between 0.187 eV and 1.712 eV. In addition, We have considered the adsorption behavior of SrAl2S4 monolayer for hydrogen and oxygen molecules, and the results show that SrAl2S4 monolayer adsorbed H2 molecules remains a direct bandgap semiconductor, whereas SrAl2S4 monolayer adsorbed O2 molecules show indirect bandgap semiconductor properties. At the same time, the adsorption of O2 molecules causes a flat band near the Fermi level, which increases the electrical conductivity. The few charges transfer observed between the SrAl2S4 monolayer and gas molecules confirms that the adsorption process of gas molecules on SrAl2S4 monolayer is physical adsorption. The tunable bandgap characteristics and good adsorption behavior of hydrogen and oxygen exhibited by SrAl2S4 monolayer make it a promising candidate material in the fields of photovoltaics and energy storage.

Hydrogen storage in M(BDC)(TED)0.5 metal-organic framework: physical insights and capacities.

Finding renewable energy sources to replace fossil energy has been an essential demand in recent years. Hydrogen gas has been becoming a research hotspot for its clean and free-carbon energy. However, hydrogen storage technology is challenging for mobile and automotive applications. Metal-organic frameworks (MOFs) have emerged as one of the most advanced materials for hydrogen storage due to their exceptionally high surface area, ultra-large and tuneable pore size. Recently, computer simulations allowed the designing of new MOF structures with significant hydrogen storage capacity. However, no studies are available to elucidate the hydrogen storage in M(BDC)(TED)0.5, where M = metal, BDC = 1,4-benzene dicarboxylate, and TED = triethylenediamine. In this report, we used van der Waals-dispersion corrected density functional theory and grand canonical Monte Carlo methods to explore the electronic structure properties, adsorption energies, and gravimetric and volumetric hydrogen loadings in M(BDC)(TED)0.5 (M = Mg, V, Co, Ni, and Cu). Our results showed that the most favourable adsorption site of H2 in M(BDC)(TED)0.5 is the metal cluster-TED intersection region, in which Ni offers the strongest binding strength with the adsorption energy of -16.9 kJ mol-1. Besides, the H2@M(BDC)(TED)0.5 interaction is physisorption, which mainly stems from the contribution of the d orbitals of the metal atoms for M = Ni, V, Cu, and Co and the p orbitals of the O, C, N atoms for M = Mg interacting with the σ* state of the adsorbed hydrogen molecule. Noticeably, the alkaline-earth metal Mg strongly enhanced the specific surface area and pore size of the M(BDC)(TED)0.5 MOF, leading to an enormous increase in hydrogen storage with the highest absolute (excess) gravimetric and volumetric uptakes of 1.05 (0.36) wt% and 7.47 (2.59) g L-1 at 298 K and 7.42 (5.80) wt% and 52.77 (41.26) g L-1 at 77 K, respectively. The results are comparable to the other MOFs found in the literature.

Distinctive 3D heterostructures of partial sulfidation with FeCo LDH: A potent electrocatalyst for synergistic alkaline overall water splitting

The reasonable surface engineering allows effective modification of the adsorption energy of reactive hydrogen molecules, resulting in the improvement of the effectiveness of water separation. Herein, we fabricated MoS2-FeCoS2-FeCo LDH/NF (defined as: MS-FCS-FCL/NF) sea urchin-like nanospike sphere catalysts with heterogeneous interfaces by a simple two-step hydrothermal method and simultaneous sulfurisation of FeCo LDH for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), which optimised the electronic structure and exposed more active sites, thus revealing excellent electrocatalytic performance. As predicted, the synthesized 3D "sea urchin-like" structure MS-FCS-FCL/NF has excellent HER (η10 = 176 mV) and OER (η10 = 149 mV) properties. Remarkably, when used as a bifunctional catalyst to perform overall water decomposition, it requires just a low cell voltage (1.53 V for 10 mA cm−2) and has outstanding stability (48 h). Density functional theory (DFT) calculations have proven that tuning electron dissipation and aggregation at heterogeneous interfaces can optimize the electron transfer rate in the active sites and D-band centers near the Fermi level and enhance the inherent catalytic activity. This work provides both an elegant method for building hierarchical heterostructures and a multiscale strategy for water separation electrocatalyst.

Electron beam irradiation-induced atomically thin domes of two-dimensional materials: Graphene and MoS[formula omitted]

The local strain-induced indirect-to-direct band gap transition in bulk transition metal dichalcogenides (TMDCs) holds great potential for optoelectronic applications. The formation of domes on the topmost layer of a multilayered flake through hydrogen ion H+ irradiation is an effective technique for tuning the band gap locally via molecular hydrogen (H2) confinement. In this work, we present an alternative robust, simpler, and faster technique for concurrently forming and visualizing dome-like structures of two-dimensional (2D) materials through low-energy electron beam irradiation. We investigated the growth mechanism and dynamics of the domes under exposure to electron beams at different energy levels. The simultaneous production and imaging of atomically thin domes of 2D materials has several practical and fundamental applications, such as mass storage and transport, single photon emission, nano/micro-electromechanical sensors, strain engineering, etc.

Hydrogen Nanobubbles and Oxidative Windows: Investigating How Varying Hydrogen Concentrations Influence Seed Germination and Stress Defense

The hydrogen molecule can effectively regulate plant growth and development, improving plant resistance to abiotic stresses. However, studies regarding the optimal concentration of hydrogen and the associated mechanisms of action in organisms are lacking. This study showed that the maximum germination rate of radish seeds decreased from 90% to 50% under the stress of cadmium ions (Cd2+), and hydrogen nanobubble (NB) water significantly alleviated the stress effect of Cd2+ on radish seed germination. A hydrogen concentration of 0.8 ppm had the best effect, reducing Cd2+ accumulation in radish seeds by 63.23% and increasing the maximum germination rate from 50% to 65%. At concentrations exceeding 1.2 ppm, the beneficial effect of hydrogen was weakened or even reversed. Consequently, we integrated the concept of the oxidative window into a REDOX balance model and demonstrated that an appropriate hydrogen concentration can effectively maintain the REDOX state within organisms. Transcriptome sequencing analysis revealed that hydrogen NB water modulated Cd2+ absorption and accumulation in seeds by regulating cell wall components, alleviating oxidative stress through oxidoreductase activity, and enhancing nutrient synthesis and metabolism. This collectively alleviated the inhibitory effect of Cd2+ on seed germination. This study is helpful for further understanding the effect of hydrogen concentration on the REDOX balance of seed germination, providing a theoretical basis for selecting hydrogen concentration to improve its effectiveness in agricultural fields.Environmental ImplicationCadmium is one of the most common heavy metal pollutants. It is more easily absorbed by plants and has great biological toxicity. If the cadmium concentration in soil is too high, it will cause significant inhibitory effects or serious damage to plant cell growth and division, photosynthesis, plant enzyme activity and nucleic acid metabolism, thereby inhibiting plant growth and development. Research indicates that hydrogen nanobubble water effectively alleviates the toxic effects of heavy metal stress on plants and aquatic organisms, offering new insights into addressing heavy metal pollution. This discovery holds significant importance for environmental restoration and maintaining ecological balance.

Asymptotic Behavior of the Rydberg States of Molecular Hydrogen in the Limit of a United Atom

Asymptotic Behavior of the Rydberg States of Molecular Hydrogen in the Limit of a United Atom

A hydrogen generator composed of poly (lactic-co-glycolic acid) nanofibre membrane loaded iron nanoparticles for infectious diabetic wound repair

Diabetic wound, which is chronic skin disease, poses a significant challenge in clinical practice because of persistent inflammation and impaired angiogenesis. Recently, hydrogen has emerged as a novel therapeutic agent due to its superior antioxidant and anti-inflammatory properties. In this study, we engineered a poly (lactic-co-glycolic acid) (PLGA) electrospun nanofibre membrane loaded with citric acid (CA) and iron (Fe) nanoparticles, referred to as Fe@PLGA + CA. Our in vitro assays demonstrated that the Fe@PLGA + CA membrane continuously generated and released hydrogen molecules via a chemical reaction between Fe and CA in an acidic microenvironment created by CA. We also discovered that hydrogen can ameliorate fibroblast migration disorders by reducing the levels of matrix metalloproteinase 9 (MMP9). Furthermore, we confirmed that hydrogen can scavenge or biochemically neutralise accumulated reactive oxygen species (ROS), inhibit pro-inflammatory responses, and induce anti-inflammatory reactions. This, in turn, promotes vessel formation, wound-healing and accelerates skin regeneration. These findings open new possibilities for using elemental iron in skin dressings and bring us one step closer to implementing hydrogen-releasing biomedical materials in clinical practice.

Desymmetric Hydrogenation of meso-Dicarboxylic Acids.

Efficient transformation of platform chemicals into key intermediates has been increasingly important for the pharmaceutical industry. The development of the catalytic reduction of abundant carboxylic acids with molecular hydrogen has been of both practical and theoretical value. We herein report the homogeneous hydrogenation of dicarboxylic acids with the strategy of desymmetrization. Using a rhodium/bisphosphine catalyst, one carboxyl group of meso-diacids was selectively reduced to yield chiral lactones with satisfactory enantioselectivity. This method provides a straightforward approach to produce chiral lactone intermediates for the manufacture of biotin, telaprevir, and other antivirus drugs. Both experimental and computational investigations were carried out, revealing a novel neighboring group coordination mechanism in the catalytic cycle.

Retracted] Molecular hydrogen improves type 2 diabetes through inhibiting oxidative stress.

[This retracts the article DOI: 10.3892/etm.2020.8708.].

Superconductivity in Dilute Hydrides of Ammonia under Pressure.

The past decade has witnessed great progress in predicting and synthesizing polyhydrides that exhibit superconductivity under pressure. Dopants allow these compounds to become metals at pressures lower than those required to metallize elemental hydrogen. Here, we show that by combining the fundamental planetary building blocks of molecular hydrogen and ammonia, conventional superconducting compounds can be formed at high pressure. Through extensive theoretical calculations, we predict metallic metastable structures with NHn (n = 10, 11, 24) stoichiometries that are based on NH4+ superalkali cations and complex hydrogenic lattices. The hydrogen atoms in the molecular cation contribute to the superconducting mechanism, and the estimated superconducting critical temperatures, Tc's, are comparable to the highest values computed for the alkali metal polyhydrides. The largest calculated (isotropic Eliashberg) Tc is ∼180 K for Pnma-NH10 at 300 GPa. Our results suggest that other molecular cations can be mixed with hydrogen under pressure, yielding superconducting compounds.

First Extragalactic Detection of Thermal Hydroxyl (OH) 18 cm Emission in M31 Reveals Abundant CO-faint Molecular Gas

The most abundant interstellar molecule, molecular hydrogen (H2), is practically invisible in cold molecular clouds. Astronomers typically use carbon monoxide (CO) to trace the bulk distribution and mass of H2 in our galaxy and many others. CO observations alone fail to trace a significant component of molecular gas known as “CO-dark” molecular gas, which can be probed with molecules such as OH and CH. We present an extremely sensitive pilot search for the 18 cm hydroxyl (OH) lines in the Andromeda galaxy (M31) with the 100 m Robert C. Byrd Green Bank Telescope. We successfully detected the 1665 and 1667 MHz OH lines in faint emission. The 1665/1667 MHz line ratio displays the characteristic 5:9 ratio predicted under conditions of local thermodynamic equilibrium. To our knowledge, this is the first detection of nonmaser 18 cm OH emission in another galaxy. We compare our OH and H i observations with archival CO (1–0) observations. Our OH detection position overlaps with the previously discovered Arp Outer Arm in CO. Our best estimates show that the amount of H2 traced by OH is 100%–140% higher than the amount traced by CO in this sight line. The amount of dark molecular gas implied by dust data supports this conclusion. We conclude that the 18 cm OH lines hold promise as a valuable tool for mapping of the “CO-dark” and “CO-faint” molecular gas phase in nearby galaxies, especially with upcoming multibeam, phased-array feed receivers on radio telescopes, which will allow for drastically improved mapping speeds of faint signals.

Assessing the global natural orbital functional approximation on model systems with strong correlation.

In the past decade, natural orbital functional (NOF) approximations have emerged as prominent tools for characterizing electron correlation. Despite their effectiveness, these approaches, which rely on natural orbitals and their associated occupation numbers, often require hybridization with other methods to fully account for all correlation effects. Recently, a global NOF (GNOF) has been proposed [Piris, Phys. Rev. Lett. 127, 233001 (2021)] to comprehensively address both dynamic and static correlations. This study evaluates the performance of GNOF on strongly correlated model systems, including comparisons with highly accurate Full Configuration Interaction calculations for hydrogen atom clusters in one, two, and three dimensions. Additionally, the investigation extends to a BeH2 reaction, involving the insertion of a beryllium atom into a hydrogen molecule along a C2v pathway. According to the results obtained using GNOF, consistent behavior is observed across various correlation regions, encompassing a range of occupations and orbital schemes. Furthermore, distinctive features are identified when varying the dimensionality of the system.

Terahertz spectroscopic study of the dehydration process and hydrogen bonding network of DL-glutamic acid and its monohydrate

The dehydration process involves the dissociation and reorganization of hydrogen bonds, and for the characterization of the dehydration process of amino acid-based hydrates, the analysis of their molecular vibrational modes and hydrogen bonds is still challenging nowadays. In this paper, the dynamic process of the dehydration of DL-glutamic acid monohydrate was monitored using terahertz spectroscopy. Quantitative simulations were performed on DL-glutamic acid and its monohydrate, with vibrational mode assignments and hydrogen bonding network analysis based on Density Functional Theory (DFT) for terahertz absorption peaks. The results show that the hydrogen bond stretching vibration is intermixed with atomic vibration. Specifically, the intermolecular hydrogen bond O4-H9···O2 of DL-glutamic acid exhibits a stronger vibration at 2.43 THz. Furthermore, the intramolecular hydrogen bond O5-H11···O4 in DL-glutamic acid monohydrate shows significant changes in bond length and bond angle at 1.85 THz. These findings validate the effectiveness of terahertz spectroscopy in monitoring the transformation process of the hydrate and the analysis of the hydrogen bond.

Electronic, rashba and photocatalytic properties of janus XMoYZ2 (X= S, Se, Te ; Y=Si, Ge and Z=N, P) monolayers

In this work, the electronic, photocatalytic, and spin properties of 2D Janus XMoYZ2 (X= S, Se, Te; Y=Si, Ge and Z=N, P) monolayers are studied. The electronic properties are investigated and the results indicate that all of them are semiconductor with a suitable bandgap. The band structures with spin–orbit consideration indicate Rashba spin-splitting at the Γ-valley in the valence band. The spin-splitting at the K-point in the valence band is also significant, whereas the conduction band has negligible spin-splitting. Due to the mirror asymmetry of these compounds, their potential distribution and the corresponding dipole moments are investigated. Finally, by studying the photocatalytic properties, it is found that the redox happened on both sides of SMoSiN2 and SMoGeN2 monolayers. However, in the cases of SMoSiP2 and TeMoGeN2 monolayers, each photocatalytic half-reaction occurs on one side where the generated hydrogen and oxygen molecules are separated.