Liquid Research Articles

High temperature melting of dense molecular hydrogen from machine-learning interatomic potentials trained on quantum Monte Carlo.

We present results and discuss methods for computing the melting temperature of dense molecular hydrogen using a machine learned model trained on quantum Monte Carlo data. In this newly trained model, we emphasize the importance of accurate total energies in the training. We integrate a two phase method for estimating the melting temperature with estimates from the Clausius-Clapeyron relation to provide a more accurate melting curve from the model. We make detailed predictions of the melting temperature, solid and liquid volumes, latent heat, and internal energy from 50 to 180GPa for both classical hydrogen and quantum hydrogen. At pressures of roughly 173GPa and 1635K, we observe molecular dissociation in the liquid phase. We compare with previous simulations and experimental measurements.

Identification of the immune infiltration and biomarkers in ulcerative colitis based on liquid–liquid phase separation-related genes

Identification of the immune infiltration and biomarkers in ulcerative colitis based on liquid–liquid phase separation-related genes

Electrolyte Design Using "Porous Water” for High‐purity Carbon Monoxide Electrosynthesis from Dilute Carbon Dioxide

Electrosynthesis of high‐purity carbon monoxide (CO) from captured carbon dioxide (CO₂) remains energy‐intensive due to the unavoidable CO₂ regeneration and post‐purification stages. Here, we propose a direct high‐purity CO electrosynthesis strategy employing an innovative electrolyte, termed porous electrolyte (PE), based on "porous water". Zeolite nanocrystals within PE provide permanent pores in the liquid phase, enabling physical CO₂ adsorption through an intraparticle diffusion model, as demonstrated by molecular dynamics simulations and in‐situ spectral analysis. Captured CO₂ spontaneously desorbs under applied reductive potential, driven by the interfacial CO₂ concentration gradient, and is subsequently reduced electrochemically. The high CO₂ concentration in PE enhances mass transfer, and surface ion exchange between Si–OH groups and K⁺ ions on the zeolite surface generates a stronger interfacial electric field, promoting electron transfer steps. This optimized kinetics for mass and electron transfer confers heightened intrinsic activity toward CO₂ electroreduction. The PE‐based electrolysis system demonstrated superior CO Faradaic efficiency and partial current density compared to the conventional CO₂‐fed system. A circular system using PE and a Ni‐N/C cathode realized continuous production of high‐purity CO (97.0 wt%) from dilute CO2 (15%) and maintained > 90.0 wt% under 150 mA cm‐2, with significantly reduced energy consumption and costs.

Electrolyte Design Using "Porous Water" for High-purity Carbon Monoxide Electrosynthesis from Dilute Carbon Dioxide.

Electrosynthesis of high-purity carbon monoxide (CO) from captured carbon dioxide (CO₂) remains energy-intensive due to the unavoidable CO₂ regeneration and post-purification stages. Here, we propose a direct high-purity CO electrosynthesis strategy employing an innovative electrolyte, termed porous electrolyte (PE), based on "porous water". Zeolite nanocrystals within PE provide permanent pores in the liquid phase, enabling physical CO₂ adsorption through an intraparticle diffusion model, as demonstrated by molecular dynamics simulations and in-situ spectral analysis. Captured CO₂ spontaneously desorbs under applied reductive potential, driven by the interfacial CO₂ concentration gradient, and is subsequently reduced electrochemically. The high CO₂ concentration in PE enhances mass transfer, and surface ion exchange between Si-OH groups and K⁺ ions on the zeolite surface generates a stronger interfacial electric field, promoting electron transfer steps. This optimized kinetics for mass and electron transfer confers heightened intrinsic activity toward CO₂ electroreduction. The PE-based electrolysis system demonstrated superior CO Faradaic efficiency and partial current density compared to the conventional CO₂-fed system. A circular system using PE and a Ni-N/C cathode realized continuous production of high-purity CO (97.0 wt%) from dilute CO2 (15%) and maintained > 90.0 wt% under 150 mA cm-2, with significantly reduced energy consumption and costs.

An atomically economical and environmentally benign approach for the scalable synthesis of rare‐earth metal‐organic framework catalysts

AbstractMetal–organic frameworks (MOFs), as an emerging class of porous materials, demonstrated substantial potential for applications in chemical engineering processes. However, their production often generates significant waste including ionic residues and organic solvents, posing considerable environmental concerns. Herein, we report the environmentally benign MOF synthesis with metal oxides precursors, yielding water as the exclusive by‐product. This approach not only enhances atom economy but also promotes solvent recycling by preventing anion accumulation, significantly reducing waste generation. The synthesis can be easily scaled up in a 10‐L reactor with an impressive space–time yield of 608 kg·m−3·day−1. Furthermore, MOF‐76(Y) was implemented in a reactor for catalytic cycloaddition reaction at kg‐scale. Through optimization of the interfacial contact between CO2 and the reaction liquid phase, a yield of 96.7% was achieved under mild conditions. This work demonstrates a rare example of scalable and sustainable synthesis of MOF materials coupled with catalysis implementation at kilogram scale.

Effect of calcium magnesium aluminate on microstructural distribution of SiO2 impurity in magnesia

AbstractThe effect of calcium magnesium aluminate (hereinafter referred to as CMA) on the microstructural distribution of the main impurity SiO2 in magnesia was investigated in this research. The XRD, SEM, and EDS analyses were used in this work. It can be seen from the result that SiO2 in low‐grade sintered magnesia diffused into CMA area at high temperature and the distribution of SiO2 in sintered magnesia was significantly reduced. The main mineral phase of sintered magnesia was periclase and monticellite, and impurities in sintered magnesia mainly existed in the form of monticellite, which was completely decomposed into liquid phase and periclase above 1400°C, SiO2 in the liquid phase in the sintered magnesia migrated into the liquid phase that formed in the CMA. Furthermore, the adsorption energy of CaO on SiO2 is stronger than that of MgO on SiO2, so the SiO2 in sintered magnesia diffused into CMA due to its relatively higher CaO content compared with the sintered magnesia. The SiO2 content in fused magnesia was lower than that of sintered magnesia and the dicalcium silicate (C2S) content in fused magnesia was higher than that of sintered magnesia, so the influence of CMA on microstructural distribution of SiO2 in fused magnesia was obviously different than that with low grade sintered magnesia.

Controlling Electrostatics To Enhance Conductivity in Structured Electrolytes.

Solid-state electrolytes are currently being explored as a safe material capable of addressing consumer energy-storage demands. Solid polymer electrolytes, in particular, offer a high energy density and improved safety when compared to liquid-based electrolytes, but tend to have a significantly lower ionic conductivity. We hypothesize structured ionic liquids can enhance conductivity compared to polymer electrolytes. Here, we explore the performance of these materials through coarse-grained molecular dynamics simulation. While we observe similar phase behavior (incorporating solid, smectic, and liquid phases) to that seen in experiments, we also observe significantly more mobility in the cationic species compared to the anionic species before the system reaches an arrest transition. We further discuss how the general results within this paper can guide further studies and target the design of new highly conductive solid electrolytes with the potential to enable the use of multivalent ionic species as ion conductors.

Anisotropy Factor Spectra for Weakly Allowed Electronic Transitions in Chiral Ketones.

Quantum chemical calculations of one-photon absorption, electronic circular dichroism and anisotropy factor spectra for the A-band transition of fenchone, camphor and 3-methylcyclopentanone (3MCP) are reported. While the only weakly allowed nature of the transition leads to comparatively large anisotropies, a proper theoretical description of the absorption for such a transition requires to account for non-Condon effects. We present experimental data for the anisotropy of 3MCP in the liquid phase and show that corresponding Herzberg-Teller corrections are critical to reproduce the main experimental features. The results obtained with our comprehensive theoretical model highlight the importance of the vibrational degree of freedom, paving the way for a deeper understanding of the dynamics in electronic circular dichroism.

Highly sensitive and selective carbon dot sensor for hydrogen sulfide based on dual quenching effect

Due to the serious impact of hydrogen sulfide (H2S) on the environment and human health, a series of sensors have been increasingly used in industrial production and daily life. In this work, we introduce a novel, to the best of our knowledge, detection method for trace H2S in the liquid and gaseous phases based on the dual-quenching mechanism (DQE) of silver ion-doped nitrogen-sulfur co-doped carbon dots (N, S-CDs@Ag+). Ag+ could significantly enhance the fluorescence intensity and detection sensitivity. In the linear detection range of 10–120 nM H2S solution, the N, S-CDs@Ag+ sensor has a limit of detection (LoD) of 0.83 nM and a response time of 1 min. An enhanced fluorescent sensing film is prepared by assembling N, S-CDs@Ag+ on a silica microsphere (SM) microstructured substrate (N, S-CDs@Ag+/SM@PVA) using the layer-by-layer method. In the linear detection range of 1–50 ppm, the film sensor has the advantages of low detection limit (0.41 ppm), fast response time (5 min), stable performance, electromagnetic interference resistance, ease of integration, and in-field detection. It is expected to develop into a compact portable on-site H2S trace sensor.

Functionalization and performance of hybrid nanocellulose from plant-based/metal oxide nanocomposites for sustainable energy applications

Abstract Growing concerns over our dependence on finite, non-renewable resources like petroleum and metals have driven the development of eco-friendly technologies centered on advanced hybrid nanomaterials. Among these, the use of renewable nanocellulose – ranging in size from 1 to 100 nm – has gained significant attention in nanotechnology research. Derived from sustainable sources, nanocellulose offers notable advantages; however, challenges persist when integrating it with metal oxide nanoparticles (MONPs). These challenges include high reactivity in cellular environments, elevated production costs, and a tendency to aggregate, leading to instability in both liquid and dry states. Aggregation can impair uniform dispersion and result in sediment formation in certain applications. A promising solution to these challenges is hybridizing MONPs with functionalized nanocellulose, a method widely adopted by researchers. This approach is cost-effective, environmentally sustainable, and produces a renewable material with low density, excellent stability, superior mechanical properties, and biocompatibility. However, several questions remain unresolved, such as the most commonly used functionalization techniques for MONPs hybridization, the underlying mechanisms, and the specific benefits of this hybridization. Based on current findings, oxidation and carboxymethylation emerge as the most frequently used functionalization techniques for hybridizing MONPs with nanocellulose. These processes introduce carboxylic acid and carboxymethyl groups, respectively, which act as capping agents that readily bond with MONPs. This results in high degrees of substitution (DS) and improved nanoparticle dispersion. Furthermore, hybridization enhances properties such as thermal stability, UV protection, antibacterial activity, adsorption capacity, and mechanical performance, underscoring its potential for diverse applications.

Dynamic Behavior of the Glassy and Supercooled Liquid States of Aceclofenac Assessed by Dielectric and Calorimetric Techniques

Aceclofenac (ACF), a non-steroidal anti-inflammatory drug, was obtained in its amorphous state by cooling from melt. The glass transition was investigated using dielectric and calorimetric techniques, namely, dielectric relaxation spectroscopy (DRS), thermally stimulated depolarization currents (TSDC), and conventional and temperature-modulated differential scanning calorimetry (DSC and TM-DSC). The dynamic behavior in both the glassy and supercooled liquid states revealed multiple relaxation processes. Well below the glass transition, DRS was able to resolve two secondary relaxations, γ and β, the latter of which was also detectable by TSDC. The kinetic parameters indicated that both processes are associated with localized motions within the molecule. The main (α) relaxation was clearly observed by DRS and TSDC, and results from both techniques confirmed a non-Arrhenian temperature dependence of the relaxation times. However, the glass transition temperature (Tg) extrapolated from DRS data significantly differed from that obtained via TSDC, which in turn showed reasonable agreement with the calorimetric Tg (Tg-DSC = 9.2 °C). The values of the fragility index calculated by the three experimental techniques converged in attributing the character of a moderately fragile glass former to ACF. Above the α relaxation, TSDC showed a well-defined peak. In DRS, after “removing” the high-conductivity contribution using ε’ derivative analysis, a peak with shape parameters αHN = βHN = 1 was also detected. The origin of these peaks, found in the full supercooled liquid state, has been discussed in the context of structural and dynamic heterogeneity. This is supported by significant differences observed between the FTIR spectra of the amorphous and crystalline samples, which are likely related to aggregation differences resulting from variations in the hydrogen bonds between the two phases. Additionally, the pronounced decoupling between translational and relaxational motions, as deduced from the low value of the fractional exponent x = 0.72, derived from the fractional Debye–Stokes–Einstein (FDSE) relationship, further supports this interpretation.

Theoretical study of the structure and vibrational sum frequency generation spectroscopy of liquid-vapor interface of aqueous acetic acid.

We have investigated the liquid-vapor interface of aqueous acetic acid solution through calculations of the structure and vibrational sum frequency generation (VSFG) spectra of the interfaces for varying concentrations of the acetic acid (AA). Our findings reveal the surface propensity of the AA molecules. As the concentration of AA increases, more AA molecules are found to be present in the interfacial region. The AA molecules at the interface are found to be oriented in a manner where the hydrophobic part (methyl chain) is oriented toward the vapor phase and the hydrophilic part is pointed toward the liquid phase. The total VSFG spectrum reveals that the intensity of the peak of dangling OH groups of water around 3750 cm-1 decreases when the concentration of AA increases, while the intensity of the peak around 3550 cm-1 due to OH groups having hydrogen bonds between water and AA molecules increases. Furthermore, the latter peak is redshifted as the AA concentration increases, which is due to the partial cancellation between the positive response of water OH modes and the negative response of the OH modes of AA molecules. It is also noted that the AA molecules make the interfacial water more structured by making hydrogen bonds with its otherwise dangling OH modes at the surface.

Enhancing the thermal properties of foam concrete with pumice-encapsulated soy wax phase change material: a novel approach.

This study explored an innovative technique for improving the thermal characteristics of foam concrete by incorporating soy wax phase change material (PCM) encapsulated within pumice. The core of this research is the development of PCM-pumice aggregates through the macro encapsulation of soy wax. This process involves direct impregnation, where melted soy wax is uniformly distributed within the porous structure of lightweight pumice aggregates. The thermal properties of the resulting foam concrete, notably its thermal conductivity, were rigorously evaluated. This evaluation entailed measuring the conductivity using a heat flow meter and subjecting the concrete samples to controlled temperature cycles, with a focus on the 25°C and 55°C marks. These specific temperatures were chosen to assess the impact of the PCM phase change on the thermal behavior of the concrete. Key findings indicate that the incorporation of PCM-pumice aggregates markedly improves thermal conductivity and heat retention in the solid state while simultaneously reducing fluidity, density, and compressive strength as a result of increased cohesion and porosity. Thermal conductivity significantly increased by up to 37% in the solid state relative to the control mix, due to the phase change material occupying air gaps within the concrete. Conversely, the thermal conductivity decreased in the liquid state, utilizing the PCM's latent heat capacity to lower heat transfer rates.

Behavior of water at lipid/water interfaces upon phase transition of the lipid bilayer: Insights from 1D- and 2D-vibrational sum frequency generation spectral calculations from molecular dynamics simulations.

We have investigated the structural and dynamical changes of the interfacial water near [1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine] (DMPC) lipid bilayer across various temperatures, ranging from 285K (gel phase of lipid) to 320K (liquid phase of lipid), through calculations of one-dimensional (1D) and two-dimensional (2D) vibrational sum frequency generation (VSFG) spectra from molecular dynamics simulations. The 1D-VSFG spectra show a broad positive peak in the hydrogen-bonded region, which means that water molecules are oriented upward toward the lipid bilayer. Although DMPC is a zwitterionic lipid, the negatively charged phosphate group primarily influences the orientation of the water molecules. The absence of a dangling peak in the 1D- and 2D-VSFG spectra shows that the water molecules form hydrogen bonds with the lipid headgroup atoms. The spectral diffusion timescales obtained from the 2D-VSFG metrics of the slope of the nodal line clearly reveal a dynamical crossover and exhibit Arrhenius behavior with different activation energies before and after the melting of the lipid bilayer. Apart from 2D-VSFG, the frequency fluctuation time correlation function also exhibits a dynamical crossover upon melting of the lipid bilayer.

Investigation of gas-liquid flow hydrodynamics in the industrial-scale stirred tank with inclined impeller

Abstract The inclined-axis stirring system is widely employed in industrial processes due to its exceptional mixing capabilities, ease of industrial retrofitting, and commendable safety and stability features. This study numerically investigates the multiphase flow characteristics within an industrial-scale inclined-axis stirring tank, utilizing the realizable k-ε model and the volume of fluid model. With the validated model, the impact of impeller rotational speed on the flow characteristics in the stirred tank is explored. The findings reveal several noteworthy observations: As the stirring speed increases, liquid level fluctuations intensify. At excessively high stirring speeds, a large number of bubbles are entrained and dispersed into the stirring tank. Multi-scale vortices are observed within the inclined-axis stirred tank. Notably, two relatively large-scale vortices manifest on either side of the rotating blade. Comparatively, the tilted arrangement of the stirring shaft disrupts the symmetry of the flow field. Regions beneath the blades and at the bottom of the stirred tank exhibit elevated liquid phase velocities, radial velocities, and axial velocities. The rising area of the fluid in the stirred tank is near the wall, forming a ring shape, while the center of the ring is characterized by descending fluid. These findings provide valuable theoretical insights for the structural configuration and considerations related to energy conservation in industrial agitation equipment.

Gel-Based Electrolytes for Organic Electrochemical Transistors: Mechanisms, Applications, and Perspectives.

Organic electrochemical transistors (OECTs) have emerged as the core component of specialized bioelectronic technologies due to their high signal amplification capability, low operating voltage (<1 V), and biocompatibility. Under a gate bias, OECTs modulate device operation via ionic drift between the electrolyte and the channel. Compared to common electrolytes with a fluid nature (including salt aqueous solutions and ion liquids), gel electrolytes, with an intriguing structure consisting of a physically and/or chemically crosslinked polymer network where the interstitial spaces between polymers are filled with liquid electrolytes or mobile ion species, are promising candidates for quasi-solid electrolytes. Due to relatively high ionic conductivity, the potential for large-scale integration, and the capability to suppress channel swelling, gel electrolytes have been a research highlight in OECTs in recent years. This review summarizes recent progress on OECTs with gel electrolytes that demonstrate good mechanical as well as physical and chemical stabilities. Moreover, various components in forming gel electrolytes, including different mobile liquid phases and polymer components, are introduced. Furthermore, applications of these OECTs in the areas of sensors, neuromorphics, and organic circuits, are discussed. Last, future perspectives of OECTs based on gel electrolytes are discussed along with possible solutions for existing challenges.

Titanium oxide covers graphite felt as negative electrode for vanadium redox flow battery by liquid phase deposition

Titanium oxide covers graphite felt as negative electrode for vanadium redox flow battery by liquid phase deposition

Impact of vanadium (V) content on in-situ oxidation, high temperature mechanical strength and tribological properties of Al0.5CrFeNiVx high entropy alloys

In this study, four vanadium (V) containing high entropy alloys (HEAs) Al0.5CrFeNiVx (x=0.25, 0.5, 0.75, 1.0) were developed and investigated, in terms of examining the influence of V content on their microstructure, in-situ oxidation behavior, high temperature mechanical strength, and high temperature tribological performances. An increase in the V content causes precipitation of the Laves phase (VAl2) in the body-centered cubic (BCC) matrix. This structural transition increases the alloy hardness and compressive strength through solid solution strengthening, precipitation strengthening and grain refinement strengthening. When x is increased from 0.25 to 1, the maximum compressive strength increases from about 2476 to 3241MPa at room temperature and from about 521 to 797MPa at 700oC, respectively. In-situ oxidation investigation reveals that a higher V content accelerates the oxidation and provides a direct evidence of vanadium oxides melting at 700oC and thus forming the liquid oxide phases on the surface of HEAs. During high temperature tribological contact, the liquid oxide phases minimize the friction, allowing thicker and more complex oxide layers to form on the worn surface to improve the HEAs’ wear resistance. The findings in this work contribute to the development of novel HEAs with superior properties for potential applications that need outstanding mechanical strength, wear resistance, and thermal stability.

From brushite to hydroxylapatite: A study on phosphate mineral transformation and the fate of oxytetracycline.

Livestock manure, a common fertilizer in Chinese agriculture, can lead to environmental contamination and potential health risks due to elevated antibiotic and phosphorus levels. Importantly, the high phosphorus levels initiates transformations of phosphate minerals in soils, especially calcareous soils. These variations in phosphate mineralogy can significantly impact the migration and fate of antibiotics within the soil. However, the impact of the transformation process, particularly involving the metastable phase brushite (DCPD), on the fate of antibiotics remains unclear. In this study, we synthesized DCPD and hydroxylapatite (HAP) and examined their transformation process to assess their removal capacity and investigate the migration and fate of oxytetracycline (OTC). The findings reveal that HAP exhibits a maximum immobilization capacity for OTC of 20.10mg/g, surpassing that of DCPD by 2.56 times (7.86mg/g). This disparity in immobilization capacity between DCPD and HAP leads to a redistribution of OTC between the solid and liquid phases during the transformation process. Notably, the introduction of OTC also inhibits the transformation process, potentially impacting the fate of other potentially harmful elements. The study highlights that the transformation process of calcium phosphorus minerals has a significant impact on the mobility and fate of antibiotics in soil, which aids in better management and mitigation of the environmental risks associated with fertilizer application.

Oxygen Driving Hydrogen Into the Inner Core: Implications for the Earth's Core Composition

AbstractEarth's core should contain light elements to account for the density deficit relative to pure iron as inferred from seismic observations. Of particular interest is hydrogen, as planetary accretion models predict the delivery of water possibly sequestered in the core. In this study, we investigate the partitioning of hydrogen across the inner‐core boundary using extensive atomistic simulations with machine learning potentials. While showing the tendency of hydrogen to dominantly remain in the liquid phase during inner core solidification, we find that the presence of oxygen would drive more hydrogen into the inner core, where 7 mol% oxygen even reverses the partitioning of hydrogen. By considering such mutual influences of partitioning among light elements in the core, we propose that the inner core can be an important reservoir of primordial hydrogen along with its growth.