Complex Chemical Environment Research Articles

Chemical origins of β-Ti stabilization via B4C additions in metastable β-Ti alloys and composites

The aerospace industry relies on Ti alloys owing to their strength-to-weight ratio and corrosion resistance. In metastable β-Ti alloys, slow cooling from the β-transus leads to partial transformation into coarse α laths, which is detrimental to the mechanical properties. A refinement and decrease of α laths has been previously achieved in β-Ti alloys with B4C additions. In these materials, the ductility of β-Ti is preserved, and the TiB and TiC particles promote strengthening. However, the mechanism of the β-Ti stabilization remains unclear. Using atom probe tomography, we propose that Mo enrichment in the α-phase limits its growth by reducing the influx of Al from the β-phase. The complex chemical environment near eutectic TiB is enriched in Al and TiO, promoting heterogeneous nucleation of fine α-phase. Increased TiO concentration is observed with the introduction of B4C. A fundamental understanding of the α-refinement mechanism in Ti-alloys is critical for aerospace applications demanding high performance and reliability.

Probing Bioinorganic Electron Spin Decoherence Mechanisms with an Fe2S2 Metalloprotein.

Recent efforts have sought to develop paramagnetic molecular quantum bits (qubits) as a means to store and manipulate quantum information. Emerging structure-property relationships have shed light on electron spin decoherence mechanisms. While insights within molecular quantum information science have derived from synthetic systems, biomolecular platforms would allow for the study of decoherence phenomena in more complex chemical environments and further leverage molecular biology and protein engineering approaches. Here we have employed the exchange-coupled ST = 1/2 Fe2S2 active site of putidaredoxin, an electron transfer metalloprotein, as a platform for fundamental mechanistic studies of electron spin decoherence toward spin-based biological quantum sensing. At low temperatures, decoherence rates were anisotropic, reflecting a hyperfine-dominated decoherence mechanism, standing in contrast to the anisotropy of molecular systems observed previously. This mechanism provided a pathway for probing spatial effects on decoherence, such as protein vs solvent contributions. Furthermore, we demonstrated spatial sensitivity to single point mutations via site-directed mutagenesis and temporal sensitivity for monitoring solvent isotope exchange. Thus, this study demonstrates a step toward the design and construction of biomolecular quantum sensors.

Synthesis and Anion Recognition of Triangular Prism Quinoline Cage with Reduced Symmetry

AbstractOrganic molecular cages with low symmetry are promising to generate complex chemical environments for molecular recognition and catalysis. Herein, a new triangular prism cage with three rigid 8‐aminoquinoline‐2‐carboxylic acid derivatives as edges were synthesized. This molecular cage possesses reduced symmetry and contains both secondary amine and amide as hydrogen donating groups for molecular recognition. It could bind anions, such as NO3−, AcO−, and F− with moderate affinity.

Alloying effects on the microstructure and properties of laser additively manufactured tungsten materials

A large body of literature within the additive manufacturing (AM) community has focused on successfully creating stable tungsten (W) microstructures due to significant interest in their application for extreme environments. However, cracking and additional embrittling features at grain boundaries have resulted in poorly performing materials, stymying the application of AM as a manufacturing technique for W. Several alloying strategies, such as ceramic particles and ductile elements, have emerged with the promise to eliminate cracking while simultaneously enhancing stability against recrystallization. In this work, we provide new insights regarding the defects and microstructural features that result from the introduction of ZrC for grain refinement and NiFe as a ductile reinforcement phase – in addition to the resulting thermophysical and mechanical properties. ZrC is shown to promote microstructural stability with increased hardness due to the formation of ZrO2 dispersoids. Conversely, NiFe forms into micron-scale FCC phase regions within a BCC W matrix, producing enhanced toughness relative to pure AM W. A combination of these effects is realized in the WNiFe + ZrC system and demonstrates that complex chemical environments coupled with the tuning of AM microstructures provides an effective pathway for enabling laser AM W materials with enhanced stability and performance.

(Invited) Nanoarray Configured Monoliths for Self-Monitored Multi-Phase Reactive Processes

The incorporation of multiple functions synergistically into one device or platform can enable additions of application merits such as light weight, ease for system integration, reduced system complexity, cost-effectiveness, and programmability. This is especially true for usually complex energy, environmental, and biological systems with the integration need of many active or passive devices and components of various functionalities. In this work, we demonstrated a compact nanoarray configured monolith design with the ability to function as both a catalyst and a sensor to enable the self-monitoring of the complex multi-phase catalytic reaction processes during operation. A bimodular approach has been realized using both electrical and electrochemical interrogation modes for reactive gas and solid phase monitoring directly using the built-in catalysts. This new type of compact and built-in monolithic sensor configuration can lower the catalytic energetics and detect gas/solid composition semi-quantitatively at room temperature up to elevated temperature. Robust calibration curves of built-in sensor responses can be achieved with facile data processing and analyzing. The built-in monolith sensor shows good sensitivity and good selectivity sufficient for the self-monitoring of the reaction process. Besides, the nanoarray based monolith device has shown good environmental tolerance toward practical applications. Such compact monolithic device can serve as a self-monitored reactor, filter, and other function component that can potentially allow in-situ and real time monitoring and functional process control in complex and reactive physical and chemical environments. With further refining of the design and functional integration, this new type of smart monolithic device can provide necessary data and knowledge for future computation-driven situational awareness prediction and intelligent control of various complex dynamic processes and systems.

Highly Stable and Active RuO2/TiOx Electrode for Kolbe Electrolysis of Acetic Acid: An Investigation to Valorize the Pyroligneous Acid

The efficient utilization of renewable sources based on the simultaneous production of energy fuels and value-added chemicals is an essential tactic of achieving the targets of the circular economy as well as carbon neutrality. As an abundant by-product during the pyrolysis of biomass, pyroligneous acid is rich in acetic acid (AA, CH3COOH) that has been proven to be converted into valuable chemicals and fuels (e.g. methane, ethane, propane). Herein, we fabricate a highly stable and effective ruthenium oxide electrocatalyst (RuO2/TiOx) via using available titanium sheet as the substrate, to highly selectively transform AA to ethane by electrochemical conversion with ~82 (±5)% selectivity. The obtained results demonstrate that RuO2/TiOx exhibits an efficient electrochemical performance at low temperatures (5℃), and can convert AA at various pH, current density, and different concentrations. The catalytic ability of RuO2/TiOx could be maintained even after 200 hours of Kolbe electrolysis. Moreover, we mimicked the complex chemical environment of the pyroligneous acid by adding diverse hydrocarbons (e.g., phenols, aldehydes) in acid solution to evaluate the stability of RuO2/TiOx. The electrolysis was also conducted in original pyroligneous acid solution, in which the RuO2/TiOx exhibits a considerable performance to convert AA to ethane. This work, based on the selective production of ethane from AA by a RuO2/TiOx electrode as an alternative to bulk metals as anodes for oxidative upgrading of carboxylic acids, making it promise to directly turn biomass residual into fuel thus improve the biomass utilization.

Engineering a High Stable and Active RuO2 on Ti Sheet for Kolbe Electrolysis of Acetic Acid: An Investigation to Valorize the Pyroligneous Acid

The efficient utilization of renewable sources based on the simultaneous production of energy fuels and value-added chemicals is an essential to enable a biobased circular economy that benefits carbon neutrality. As an abundant by-product during the pyrolysis of biomass, pyroligneous acid is rich in acetic acid (CH3COOH) that is difficult to handle due to its highly acidic content. However, it is essential made up of renewable carbon that can be converted into valuable chemicals and fuels (e.g. methane, ethane, propane). Herein, we fabricate a highly stable and effective ruthenium oxide electrocatalyst (RuO2/TiOx) via using available titanium sheet as the substrate, to highly selectively transform AA to ethane by electrochemical conversion with ~82 (±5)% selectivity. The obtained results demonstrate that RuO2/TiOx exhibits an efficient electrochemical performance at low temperatures (5℃), and can convert AA at various pH, current density, and different concentrations. Moreover, we mimicked the complex chemical environment of the pyroligneous acid by adding diverse hydrocarbons (e.g., phenols, aldehydes) in acid solution to evaluate the stability of RuO2/TiOx. The electrolysis was also conducted in original pyroligneous acid solution, in which the RuO2/TiOx exhibits a considerable performance to convert AA to ethane. This work, based on the selective production of ethane from AA by a RuO2/TiOx electrode as an alternative to bulk metals as anodes for oxidative upgrading of carboxylic acids, making it promise to directly turn biomass residual into fuel thus improve the biomass utilization.

Charge transfer effects in (HfNbTiVZr)C—Shown by ab initio calculations and X‐ray photoelectron spectroscopy

AbstractConsidering charge transfer effects and the variability of the bonding between elements with different electronegativity opens up a deeper understanding of the electronic structure and as a result many of the properties in high entropy‐related materials. This study investigates the importance of the diverse bonding and chemical environments when discussing multicomponent carbide materials. A combination of ab initio calculations and X‐ray photoelectron spectroscopy (XPS) was used to investigate the electronic structure of multicomponent thin films based on the (HfNbTiVZr)C system. The charge transfer was quantified theoretically using relaxed and nonrelaxed multicomponent as well as binary carbide reference structures, employing a fixed sphere model. High‐resolution XPS spectra from (HfNbTiVZr)C magnetron‐sputtered thin films displayed core‐level binding energy shifts and broadening effects as a result of the complex chemical environment. Charge transfer effects and a changed electronic structure in the multicomponent material, compared with the reference binary carbides, are observed both experimentally and in the density functional theory (DFT) simulations. The observed effects loosely follow electronegativity considerations, leading to a deviation from an ideal solid solution structure assuming nondistinguishable chemically equivalent environments.

Elucidating Factors Contributing to Dicamba Volatilization by Characterizing Chemical Speciation in Dried Dicamba-Amine Residues.

Dicamba is a semivolatile herbicide that has caused widespread unintentional damage to vegetation due to its volatilization from genetically engineered dicamba-tolerant crops. Strategies to reduce dicamba volatilization rely on the use of formulations containing amines, which deprotonate dicamba to generate a nonvolatile anion in aqueous solution. Dicamba volatilization in the field is also expected to occur after aqueous spray droplets dry to produce a residue; however, dicamba speciation in this phase is poorly understood. We applied Fourier transform infrared (FTIR) spectroscopy to evaluate dicamba protonation state in dried dicamba-amine residues. We first demonstrated that commercially relevant amines such as diglycolamine (DGA) and n,n-bis(3-aminopropyl)methylamine (BAPMA) fully deprotonated dicamba when applied at an equimolar molar ratio, while dimethylamine (DMA) allowed neutral dicamba to remain detectable, which corresponded to greater dicamba volatilization. Expanding the amines tested, we determined that dicamba speciation in the residues was unrelated to solution-phase amine pKa, but instead was affected by other amine characteristics (i.e., number of hydrogen bonding sites) that also correlated with greater dicamba volatilization. Finally, we characterized dicamba-amine residues containing an additional component (i.e., the herbicide S-metolachlor registered for use alongside dicamba) to investigate dicamba speciation in a more complex chemical environment encountered in field applications.

Direct Work Function Measurement Using in-situ Ambient Pressure X-ray Photoemission Spectroscopy and Its Application on Copper Oxidation Process.

The work function (WF) measurement plays a critical role in engineering energy materials and energy devices. However, the ultra-high vacuum (UHV) environments of photoemission method limit the practical application for absolute work function measurements of materials, especially under complex working conditions. To understand the energy level of materials under complex chemical environments, the in-situ measurements of work function is necessary in complex metal/semiconductor system for various application. In this paper, we describe the utilization of ambient pressure X-ray photoemission spectroscopy (APXPS) with utilization of low photon energy X-ray for absolute WF measurements at BL02B of the Shanghai Synchrotron Radiation Facility. We herein present the WF measurement during oxygen adsorption on Pt(111) and oxidation of Cu(111) in ambient oxygen environment as demonstration of the APXPS capability for WF measurement. After oxygen chemisorption on Pt and formation of Cu2O, the WF will increase. This is due to charge transfer from metal to chemisorbed oxygen atoms. After the formation of bulk Cu2O and CuO, the WF value almost remain at ~5.5 eV. We believe the direct measurement of absolute work function via APXPS could help bridge the gap between the physical properties and the surface chemical species for metal/semiconductor materials.

Molecular beam scattering from flat jets of liquid dodecane and water

AbstractMolecular beam experiments in which gas molecules are scattered from liquids provide detailed, microscopic perspectives on the gas–liquid interface. Extending these methods to volatile liquids while maintaining the ability to measure product energy and angular distributions presents a significant challenge. The incorporation of flat liquid jets into molecular beam scattering experiments in our laboratory has allowed us to demonstrate their utility in uncovering dynamics in this complex chemical environment. Here, we summarize recent work on the evaporation and scattering of Ne, CD4, ND3, and D2O from a dodecane flat liquid jet and present first results on the evaporation and scattering of Ar from a cold salty water jet. In the evaporation experiments, Maxwell–Boltzmann flux distributions with a cosθ angular distribution are observed. Scattering experiments reveal both impulsive scattering (IS) and trapping followed by thermal desorption (TD). Super‐specular scattering is observed for all four species scattered from dodecane and is attributed to anisotropic momentum transfer to the liquid surface. In the IS channel, rotational excitation of the polyatomic scatterers is a significant energy sink, and these species accommodate more readily on the dodecane surface compared to Ne. Our preliminary results on cold salty water jets suggest that Ar atoms undergo some vapor‐phase collisions when evaporating from the liquid surface. Initial scattering experiments characterize the mechanisms of Ar interacting with an aqueous jet, allowing for comparison to dodecane systems.Key Points Molecular beam scattering from flat liquid jets is a powerful technique to elucidate mechanistic detail at the gas–liquid interface. Previous dodecane scattering experiments have uncovered angularly‐resolved thermal desorption fractions and energy transfer at the interface for several small molecule scatterers. Preliminary results on scattering from cold salty water reveal mechanisms of interaction between argon and an aqueous jet.

Genomic identification and evolutionary analysis of chemosensory receptor gene families in two Phthorimaea pest species: insights into chemical ecology and host adaptation

BackgroundInsects rely on sophisticated sensitive chemosensory systems to sense their complex chemical environment. This sensory process involves a combination of odorant receptors (ORs), gustatory receptors (GRs) and ionotropic receptors (IRs) in the chemosensory system. This study focused on the identification and characterization of these three types of chemosensory receptor genes in two closely related Phthorimaea pest species, Phthorimaea operculella (potato tuber moth) and Phthorimaea absoluta (tomato leaf miner).ResultsBased on manual annotation of the genome, we identified a total of 349 chemoreceptor genes from the genome of P. operculella, including 93 OR, 206 GR and 50 IR genes, while for P. absoluta, we identified 72 OR, 122 GR and 46 IR genes. Through phylogenetic analysis, we observed minimal differences in the number and types of ORs and IRs between the potato tuber moth and tomato leaf miner. In addition, we found that compared with those of tomato leaf miners, the gustatory receptor branch of P. operculella has undergone a large expansion, which may be related to P. absoluta having a narrower host range than P. operculella. Through analysis of differentially expressed genes (DEGs) of male and female antennae, we uncovered 45 DEGs (including 32ORs, 9 GRs, and 4 IRs).ConclusionsOur research provides a foundation for exploring the chemical ecology of these two pests and offers new insights into the dietary differentiation of lepidopteran insects, while simultaneously providing molecular targets for developing environmentally friendly pest control methods based on insect chemoreception.

Neural network kinetics for exploring diffusion multiplicity and chemical ordering in compositionally complex materials

Diffusion involving atom transport from one location to another governs many important processes and behaviors such as precipitation and phase nucleation. The inherent chemical complexity in compositionally complex materials poses challenges for modeling atomic diffusion and the resulting formation of chemically ordered structures. Here, we introduce a neural network kinetics (NNK) scheme that predicts and simulates diffusion-induced chemical and structural evolution in complex concentrated chemical environments. The framework is grounded on efficient on-lattice structure and chemistry representation combined with artificial neural networks, enabling precise prediction of all path-dependent migration barriers and individual atom jumps. To demonstrate the method, we study the temperature-dependent local chemical ordering in a refractory NbMoTa alloy and reveal a critical temperature at which the B2 order reaches a maximum. The atomic jump randomness map exhibits the highest diffusion heterogeneity (multiplicity) in the vicinity of this characteristic temperature, which is closely related to chemical ordering and B2 structure formation. The scalable NNK framework provides a promising new avenue to exploring diffusion-related properties in the vast compositional space within which extraordinary properties are hidden.

Study on strengthening of sulfide tailings high-efficiency solid-liquid separation using water reducing admixtures

The global focus on refined mineral processing and environmental protection has led to stricter requirements for tailings disposal processes. The complex composition and chemical environment of tailings pose challenges in sedimentation and pipeline transportation. This research developed a new additive that is suitable for disposing of copper-lead-zinc sulfide tailings. This additive not only improves sedimentation efficiency and concentration, but also enhances the flowability of high-concentration slurry. This study investigated the effects of four typical water reducing admixtures on the settling and rheological properties of tailings. However, the combination of lignin/PCE and NPAM had a synergistic effect, further improving settling and rheological performance. The addition of PCE increased settling rate by over 2 times, increased sediment concentration by 6.71%, and significantly reduced slurry viscosity and yield stress. The study also used FBRM to analyze the changes in particle/floc size distribution over time. The results showed that the addition of PCE captured more fine particles during flocculation and formed larger flocs. These findings can be used as a reference for the use and optimization of additives in tailings disposal engineering.

Molecular mechanisms of differentiation and class choice of olfactory sensory neurons.

The sense of smell is intricately linked to essential animal behaviors necessary for individual survival and species preservation. During vertebrate evolution, odorant receptors (ORs), responsible for detecting odor molecules, have evolved to adapt to changing environments, transitioning from aquatic to terrestrial habitats and accommodating increasing complex chemical environments. These evolutionary pressures have given rise to the largest gene family in vertebrate genomes. Vertebrate ORs are phylogenetically divided into two major classes; class I and class II. Class I OR genes, initially identified in fish and frog, have persisted across vertebrate species. On the other hand, class II OR genes are unique to terrestrial animals, accounting for ~90% of mammalian OR genes. In mice, each olfactory sensory neuron (OSN) expresses a single functional allele of a single OR gene from either the class I or class II OR repertoire. This one neuron-one receptor rule is established through two sequential steps: specification of OR class and subsequent exclusive OR expression from the corresponding OR class. Consequently, OSNs acquire diverse neuronal identities during the process of OSN differentiation, enabling animals to detect a wide array of odor molecules. This review provides an overview of the OSN differentiation process through which OSN diversity is achieved, primarily using the mouse as a model animal.

Clustering of chemically propelled nanomotors in chemically active environments.

Synthetic nanomotors powered by chemical reactions have been designed to act as vehicles for active cargo transport, drug delivery, and a variety of other uses. Collections of such motors, acting in consort, can self-assemble to form swarms or clusters, providing opportunities for applications on various length scales. While such collective behavior has been studied when the motors move in a chemically inactive fluid environment, when the medium in which they move is a chemical network that supports complex spatial and temporal patterns, through simulation and theoretical analysis we show that collective behavior changes. Spatial patterns in the environment can guide and control motor collective states, and interactions of the motors with their environment can give rise to distinctive spatiotemporal motor patterns. The results are illustrated by studies of the motor dynamics in systems that support Turing patterns and spiral waves. This work is relevant for potential applications that involve many active nanomotors moving in complex chemical or biological environments.

Feature-rich electronic properties of three-dimensional ternary compound: Li7P3S11

PurposeThe theoretical findings serve as a foundation for further research into understanding sulfide-based solid-state electrolytes, ultimately advancing the progress of all-solid-state batteries.Design/methodology/approachThe electronic properties of Li7P3S11 are thoroughly explored through first-principles calculations.FindingsThis investigation encompasses the intricate atom-dominated valence and conduction bands, spatial charge density distribution and the breakdown of atom and orbital contributions to van Hove singularities. Additionally, the compound’s wide and discrete energy spectra reflect the substantial variations in bond lengths and its highly anisotropic geometric structure. The complex and nonuniform chemical environment indicates the presence of intricate hopping integrals.Originality/valueThis study provides valuable insights into the critical multiorbital hybridizations occurring in the Li-S and P-S chemical bonds. To validate the theoretical predictions, experimental techniques can be employed. By combining theoretical predictions with experimental data, a comprehensive understanding of the geometric and electronic characteristics of Li7P3S11 can be achieved.

Intrinsic and environmental modulation of stereoselective aldol organocatalyzed reactions by proline-containing lipopeptides.

Proline, along with its derivatives, has been employed as an efficient organocatalyst for aldol reactions, with the ability to promote the creation of stereoselective C-C bonds. Even though the Houk-List transition state model is able to explain the stereoselectivity observed when proline is used as a catalyst, few studies investigate the role of microheterogeneous media in modulating the reaction outcome. In this work, molecular dynamics and electronic structure calculations were used to investigate the aldol reaction in the condensed phase. Our research focused on a lipopeptide compound incorporating the proline residue within the sequence PRWG-(C18H37), where P represents l-proline, R stands for l-arginine, W for l-tryptophan, and G for l-glycine. This sequence is covalently bonded to a hydrophobic segment formed by a long aliphatic chain, acting as an organocatalyst in an aqueous solution. This catalytic phase utilizes the complex chemical environment of the solution to achieve high selectivity. Our findings indicate a Houk-List-like mechanism, in which the amide acts as an H-bond donor, complemented by a mechanism in which the counter ion, trifluoracetic acid (TFA), acts as a proton shuttle. Both mechanisms demonstrated low energy barriers-12.23 and 1.42 kcal mol-1 for the (S,R) stereoisomer formation, computed using DLPNO-CCSD with def2-TZVPP basis set. Further, to explore the catalytic effect of the PRWG-(C18H37) lipopeptide in water, molecular dynamics simulations were conducted. It was observed that the micellar phase significantly enhances stereospecific encounters, favouring the experimentally observed ratio of (SR/SS) isomers, in contrast to reactions in a pure cyclohexanone medium. By quantifying the effects enabled by the supramolecular assembly, we were able to shed light on the factors that modify and enhance the stereoslectivity of the reaction.

Confined PbO2 nanoparticles in carbon nanotubes on boron-doped diamond substrate for highly efficient chlortetracycline degradation

Realizing highly efficient catalysis with high stability in complex chemical environments remains a major challenge for advanced oxidation processes. Here, confined lead dioxide (PbO2) nanoparticles in carbon nanotubes (CNTs) on boron-doped diamond (BDD) substrate is designed and fabricated as a heterogeneous catalyst for antibiotic treatment, achieving ultra-efficient degradation of chlortetracycline (CTC) with high reaction rate and stability. The maximum degradation rate of CTC reaches 98.8 % in 120 min, and it remains 91.0 % after ten cycles, which are significantly higher than that proposed by the contrast catalysts. The excellent degradation performance of this heterogeneous catalyst is mainly attributed to three factors: (i) the prepared PbO2 nanoparticles with an average size of 5 nm are confined in CNTs, providing more active sites and higher electron transfer rate; (ii) secondary pollution and catalyst deactivation of PbO2 are avoided by protecting CNTs; (iii) BDD shows strong capacity for mineralizing organic compounds related to the high oxygen evolution reaction potential. This finding provides a novel strategy for advanced oxidation processes in environmental remediation.

Spatial Distribution of Glycine and Aspartic Acid in Rapidly Frozen Brines Relevant to Enceladus

Saturn’s moon Enceladus harbors a global, subsurface liquid ocean beneath an icy crust that actively erupts water jets from fissures in its south pole. Data returned from the Cassini mission have identified salts and organic matter within these ejected plume particles. Such combinations of water, organics, and salts present rather complex chemical environments that may hold direct implications for habitability. The fundamental behavior of organics in frozen brine systems upon exposure to relevant Enceladus surface conditions is an important aspect that has not been explored to date (e.g., how they organize and partition relative to the salt minerals within the ice matrix). The present work investigates this topic by characterizing the spatial distribution of two amino acids with different side chains (glycine and aspartic acid) in a putative frozen Enceladus brine, containing sodium, chloride, and carbonate ions, via micro-Raman imaging. The results show that both organic–salt solutions likely undergo some degree of vitrification upon flash freezing, especially for the chloride-bearing species. The subsequent annealing of the vitreous samples reveals a preferential association of the amino acids with crystalline salt hydrates, while minimal negative to no correlation is found between them and water ice. In particular, both amino acids exhibit stronger affinities for natron (Na2CO3•10H2O) than hydrohalite (NaCl•2H2O). This suggests that solute–solute interaction likely dominates in these frozen systems, especially when charged species are present. The results imply that salt-rich ice particles can serve as concentrators of organic biomarkers, enhancing their potential for detection from remote sensing or in situ analysis.