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At least 217 records · Page 12

Dissolution of poorly soluble uranyl phosphate phases in the Metaautunite Subgroup under uranyl peroxide cage cluster forming conditions

Uranyl phosphate minerals are widespread in uranium deposits and usually exhibit very low solubility in aqueous systems. Uranyl phosphates of the autunite group and metaautunite subgroup impact the mobility of uranium in the environment and have inspired groundwater remediation strategies that emphasize their low solubility. The importance of soluble uranium-bearing macro-anions, including nanoscale uranyl peroxide cage clusters, is largely unexplored relative to solubilization of normally low-solubility uranium minerals. Eight synthetic analogs of metaautunite subgroup minerals have been prepared and placed in various alkaline aqueous solutions containing hydrogen peroxide and tetraethylammonium hydroxide. Each uranyl phosphate studied has a topologically identical anionic sheet of uranyl square bipyramids and phosphate tetrahedra combined with various cations (Li + , Na + , K + , Rb + , Cs + , Mg 2+ , Ca 2+ , Ba 2+ ) and water in the interlayer. Uranyl peroxides formed under many of the experimental conditions examined, including solid studtite [(UO 2 )(O 2 )(H 2 O) 2 ](H 2 O) 2 and soluble uranyl peroxide cage clusters containing as many as 28 uranyl ions. Uranyl phosphate solids in contact with solutions in which uranyl peroxide cage clusters formed dissolved extensively or completely. The greatest dissolution of uranyl phosphates occurred in systems that contained cations with larger hydrated radii, Li + and Na + . The details of the uranium speciation in solution depended on the pH and counter cations provided from the interlayers of the uranyl phosphate solids.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NiAl–MoO 2 S 2 Nanoparticles: Structural Evolution and Mechanistic Insights into High-Performance Selenium Oxyanion Removal across Diverse pH Conditions

Advancing sorbent materials for the selective removal of toxic oxyanions from water requires synthetic control, tunable chemistry, and an atomic-level understanding of structure–function relationships. Here, we report the synthesis and detailed characterization of NiAl–MoO 2 S 2 , a novel layered double hydroxide (LDH) nanomaterial designed for the efficient sequestration of selenium oxoanions (SeO 3 2– and SeO 4 2– ) from complex aqueous environments. The material is synthesized through a room-temperature ion-exchange process, wherein interlayer NO 3 – anions in NiAl–LDH are replaced with MoO 2 S 2 2– clusters, forming high-surface-area, flower-like nanoparticles. Comprehensive structural analysis using the synchrotron X-ray pair distribution function, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy reveals a distinct chemical transformation of intercalated [MoO 2 S 2 ] 2– into [Mo 2 O 2 S 6 ] 2– -like clusters, generating redox-active interlayers that drive selenium capture. This tailored interfacial chemistry underpins the material’s exceptional sorption performance, achieving distribution coefficients (K d ) ≥ 10 6 mL/g and maximum capacities of 343 mg/g for SeO 4 2– and 514 mg/g for SeO 3 2– , outperforming state-of-the-art inorganic sorbents. Importantly, NiAl–MoO 2 S 2 maintains high selectivity and capacity across acidic, neutral, and alkaline pH, efficiently removing selenium from ppm to sub-10 ppb trace levels, even in the presence of competing ions typical of natural and industrial waters. The selenium uptake proceeds via reductive precipitation coupled with the oxidation of molybdenum and sulfide within the LDH framework. This study highlights the power of strategic synthetic modification and interlayer functionalization in LDHs to unlock new structural motifs and redox chemistries, offering a scalable route to advanced materials for environmental remediation.

Adsorption↗

Improvements in the utilization of calcium carbonate in promoting sustainability and environmental health

Calcium carbonate (CaCO 3 ) is an incredibly abundant mineral on Earth, with over 90% of it being found in the lithosphere. To address the CO 2 crisis and combat ocean acidification, it is essential to produce more CaCO 3 using various synthetic methods. Additionally, this approach can serve as a substitute for energy-intensive processes like cement production. By doing so, we have the potential to not only reverse the damage caused by climate change but also protect biological ecosystems and the overall environment. The key lies in maximizing the utilization of CaCO 3 in various human activities, paving the way for a more sustainable future for our planet.

Chemistry↗

Topological controls on aluminosilicate glass dissolution: Complexities induced in hyperalkaline aqueous environments

Abstract Fly ash, an aluminosilicate composite consisting of disordered (major) and crystalline (minor) compounds, is a low‐carbon alternative that can partially replace ordinary portland cement (OPC) in the binder fraction of concrete. Therefore, understanding the reactivity of fly ash in the hyperalkaline conditions prevalent in concrete is critical to predicting concrete's performance; including setting and strength gain. Herein, temporal measurements of the solution composition (using inductively coupled plasma‐optical emission spectrometry: ICP‐OES) are used to assess the aqueous dissolution rate of monophasic synthetic aluminosilicate glasses analogous to those present in technical fly ashes, under hyperalkaline conditions (10 ≤ pH ≤ 13) across a range of temperatures (25°C ≤ T≤45°C). The dissolution rate is shown to depend on the average number of topological constraints per atom within the glass network (n c , unitless), but this dependence weakens with increasing pH (>10). This is postulated to be on account of: (a) time‐dependent changes in the glass’ surface structure, that is, the number of topological constraints; and/or (b) a change in the dissolution mechanism (eg from network hydrolysis to transport control). The results indicate that the topological description of glass dissolution is most rigorously valid only at very short reaction times (ie at high undersaturations), especially under conditions of hyperalkalinity. These findings provide an improved basis to understand the underlying factors that affect the initial and ongoing reactivity of aluminosilicate glasses such as fly ash in changing chemical environments, for example, when such materials are utilized in cementitious composites.

Oey, Tandré↗

Enhanced ZIF-8-enabled colorimetric CO 2 sensing through dye-precursor synthesis

The accumulation of carbon dioxide (CO 2 ) within enclosed spaces, along with volatile organic compounds, under certain humidity, temperature, and ventilation conditions is associated with detrimental human health symptoms such as fatigue. Color-based chemical sensing is a promising approach to detect CO 2 levels relevant to indoor air quality through producing fast, quantifiable output visible to the naked eye. In a prior work, a colorimetric gas sensor was fabricated through synthesizing the metal-organic framework, ZIF-8, as the adsorbent, followed by post-synthetic mixing with a dye, phenol red (PSP), and primary amine, ethylenediamine (ED). While this sensor (termed PSP-ED/ZIF-8) maintained its structural integrity in atmospheric conditions and exhibited an increasing fuchsia-to-yellow color change with increasing CO 2 levels in dry environment, the colorimetric response greatly suffered in the presence of humid CO 2 . Here in this work, a significantly improved colorimetric CO 2 sensor (referred to as ED/PSP:ZIF-8) is accomplished through directly incorporating phenol red in the ZIF-8 metal and linker precursor solutions and then blending with ethylenediamine. MATLAB-generated color distributions and in-situ ultraviolet-visible (UV-Vis) spectroscopic studies quantitatively demonstrate an enhanced colorimetric gas response of ED/PSP:ZIF-8 compared to that of PSP-ED/ZIF-8 across an important range of CO 2 for indoor air quality monitoring (500 – 3500 ppm) and across a range of humidity. The new sensor also exhibits high selectivity to CO 2 compared to select volatile organic compounds, such as acetone and ethanol, which contribute to human health symptoms experienced indoors. The enhanced performance is attributed to the proposed incorporation of phenol red within ZIF-8, while maintaining the chemical stability of the MOF.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

An integrated in vivo/in vitro framework to enhance cell-free biosynthesis with metabolically rewired yeast extracts

Cell-free systems using crude cell extracts present appealing opportunities for designing biosynthetic pathways and enabling sustainable chemical synthesis. However, the lack of tools to effectively manipulate the underlying host metabolism in vitro limits the potential of these systems. Here, we create an integrated framework to address this gap that leverages cell extracts from host strains genetically rewired by multiplexed CRISPR-dCas9 modulation and other metabolic engineering techniques. As a model, we explore conversion of glucose to 2,3-butanediol in extracts from flux-enhanced Saccharomyces cerevisiae strains. We show that cellular flux rewiring in several strains of S. cerevisiae combined with systematic optimization of the cell-free reaction environment significantly increases 2,3-butanediol titers and volumetric productivities, reaching productivities greater than 0.9 g/L-h. We then show the generalizability of the framework by improving cell-free itaconic acid and glycerol biosynthesis. Our coupled in vivo/in vitro metabolic engineering approach opens opportunities for synthetic biology prototyping efforts and cell-free biomanufacturing.

59 BASIC BIOLOGICAL SCIENCES↗

Aminopolycarboxylates in trivalent f-element separations

Aminopolycarboxylate reagents strongly bind a variety of metal ions. Trivalent f-elements are no exception. The formed complexes are very stable, especially when aminopolycarboxylate structure contains multiple aminoacetate groups. The efficient coordination of trivalent f-elements by these reagents prompted decades of research and development efforts devoted to separation and purification of f-block metal ions. This chapter overviews the fundamental and applied aspects of aminopolycarboxylate use in trivalent f-element separations. First, a brief synopsis on how the chemical properties of 4f and 5f metal ions determine their similar solution behavior is followed by a discussion of aqueous complexation as means to perturb it. The synthetic methodologies for preparation of aminopolycarboxylate complexants are discussed next. Fundamental features of trivalent f-element complexation by aminopolycarboxylates are summarized, focusing on a variety of structure-function relationships demonstrated for this class of chelators and theoretical efforts to accurately describe such coordination environments. Finally, historical accounts of aminopolycarboxylate use in 4f and 5f element separations are supplemented by recent advances in those research fields.

Jansone-Popova, Santa↗

Concerted proton–electron transfer reactions of manganese–hydroxo and manganese–oxo complexes

The enzymes manganese superoxide dismutase and manganese lipoxygenase use MnIII–hydroxo centres to mediate proton-coupled electron transfer (PCET) reactions with substrate. As manganese is earth-abundant and inexpensive, manganese catalysts are of interest for synthetic applications. Recent years have seen exciting reports of enantioselective C–H bond oxidation by Mn catalysts supported by aminopyridyl ligands. Such catalysts offer economic and environmentally-friendly alternatives to conventional reagents and catalysts. Mechanistic studies of synthetic catalysts highlight the role of Mn–oxo motifs in attacking substrate C–H bonds, presumably by a concerted proton–electron transfer (CPET) step. (CPET is a sub-class of PCET, where the proton and electron are transferred in the same step.) Knowledge of geometric and electronic influences for CPET reactions of Mn–hydroxo and Mn–oxo adducts enhances our understanding of biological and synthetic manganese centers and informs the design of new catalysts. In this Feature article, we describe kinetic, spectroscopic, and computational studies of MnIII–hydroxo and MnIV–oxo complexes that provide insight into the basis for the CPET reactivity of these species. Systematic perturbations of the ligand environment around MnIII–hydroxo and MnIV–oxo motifs permit elucidation of structure–activity relationships. For MnIII–hydroxo centers, electron-deficient ligands enhance oxidative reactivity. However, ligand perturbations have competing consequences, as changes in the MnIII/II potential, which represents the electron-transfer component for CPET, is offset by compensating changes in the pKa of the MnII–aqua product, which represents the proton-transfer component for CPET. For MnIV–oxo systems, a multi-state reactivity model inspired the development of significantly more reactive complexes. Weakened equatorial donation to the MnIV–oxo unit results in large rate enhancements for C–H bond oxidation and oxygen-atom transfer reactions. These results demonstrate that the local coordination environment can be rationally changed to enhance reactivity of MnIII–hydroxo and MnIV–oxo adducts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Comparative evaluation of antimicrobial activity of human granulysin, bovine and porcine NK-lysins against Shiga toxin-producing Escherichia coli O157:H7

Shiga toxin-producing Escherichia coli (STEC) O157:H7 (O157) is a foodborne pathogen causing human disease ranging from hemorrhagic colitis and hemolytic uremic syndrome to kidney failure, while remaining harmless to cattle, its primary reservoir. The severity of the human disease associated mainly with Shiga toxin production and a global emergence of antibiotic resistant STEC highlights the need for effective non-antibiotic, pre-harvest strategies to reduce O157 in cattle, the principal source of human infection. Towards this goal three synthetic antimicrobial peptides (AMPs): human granulysin (hGRNL), bovine NK-lysin (bNK2A), and porcine NK-lysin (pNKL), were tested in vitro against O157 isolates. As expected, circular dichroism spectroscopy findings were consistent with a predominantly α-helical conformation for all three AMPs in an environment mimicking bacterial outer surface or liposaccharides. The minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations of hGRNL (200 μM), bNK2A (12.5 μM against strain 86–24 and 25 μM against EDL933), and pNKL (6.25 μM) were determined using the Clinical and Laboratory Standards Institute broth microdilution method in Müeller-Hinton broth (cation-adjusted). The bNK2A and pNKL AMPs did not induce Shiga toxin expression in O157 at MIC, as there was a significant decrease or no change in toxin expression following 4- or 20 h incubation with the AMPs; bNK2A p <0.0001 (4 h) and p = 0.4831 (20 h); pNKL p <0.0001 (4 h) and p = 0.0001 (20 h). Propidium iodide uptake assay revealed faster O157 membrane damage or killing kinetics with bNK2A and pNKL compared to hGRNL. Nonetheless, transmission electron microscopy demonstrated that all three AMPs mediated damage to O157 membranes. In contrast, the three AMPs showed minimal cytotoxicity (<2%) against cattle red blood cells at tested concentrations (0.39–50 μM). Overall, our results demonstrate the potential for bNK2A and pNKL to be further developed into novel non-antibiotic agents to reduce O157 shedding in cattle.

59 BASIC BIOLOGICAL SCIENCES↗

WISP: Watching grid Infrastructure Stealthily through Proxies (Final Technical Report)

The complex interdependencies of cyber systems (sensors and communications), physical grids and associated electricity market operations make protecting electric power grids a significant challenge. The energy sector is constantly under new, targeted, advanced and dangerous cyber-attacks that have the potential to result in the loss of human life. These threats are further exacerbated by our need to modernize the grid. One focus of cyber security research in smart grids is the securing of the SCADA system through advanced intrusion detection systems (IDS) and bad data detection algorithms in state estimation. These methods either require full knowledge of the system topology and parameters or fail to understand the physical behaviors under attack. WISP (Watching grid Infrastructure Stealthily through Proxies) is designed to provide additional protection to the power grid using only publicly available data. In particular, WISP exploits the spatio-temporal nature of the real time locational marginal prices (LMPs), in conjunction with other information such as bids, weather, outages and load data to analyze anomalous power pricing behaviors and then correlate those observations to localize regions of interest and identify potential cyber events. WISP is non-intrusive as the tool is deployed as a service in the Cloud or on premise and provides reliable information to system operators for enhanced situational awareness, without impeding energy delivery functions. The WISP technology comprises three modules: the data-driven anomaly detection core, the vulnerability and risk analysis and the root cause analysis. The data-driven anomaly detection core performs the tasks of feature selection, anomaly detection and attack region localization. The vulnerability and risk analysis module provides system level information of the vulnerable variables and times, assisting the operators in selecting monitoring and protection nodes. The root cause analysis module takes the detection results and identifies potential operational conditions that contribute to the detected anomalies. In Phase I, we have demonstrated the feasibility and effectiveness of WISP. We developed a realistic electricity market simulator capable of generating normal and attack market data under various operational conditions. We developed a series of cyber-attack detection and analysis algorithms and evaluated them under multiple data sources. Finally, we integrated all modules into an end-to-end software, providing functions for data management, data analytics and visualization. Specifically, we have achieved: (i) real-time data acceptance from external utility interfaces with >99% acceptance rate; (ii) high performance anomaly detection algorithms with >98% detection accuracy and <0.1% false alarm rate; and (iii) ultra-low computing delay <50 milliseconds. Additionally, our team developed algorithms to identify the vulnerable variables in electricity market operations and root cause analysis functions to identify major contributors to the price spikes. These ancillary modules are necessary when deploying WISP in real world industry environment. In Phase II, we have demonstrated the effectiveness of WISP software on realistic largescale power systems. We performed red team testing for the Phase I WISP software and identified software vulnerabilities and implemented corresponding mitigation solutions. We adapted the electricity market simulator for the Texas synthetic 2000-bus system and generated datasets for the false data injection attacks. We created database and visualization interfaces for the Texas system and the ISO New England system. We performed software optimization in terms of operation efficiency, computing speed and detection accuracy. Finally, we tested the software on the Texas system and the ISO New England system and evaluated the detection performance. Overall, we achieved above 89% detection rate, below 3% false alarm rate and below 37 seconds of end-to-end detection delay.

24 POWER TRANSMISSION AND DISTRIBUTION↗

Energetics of hydroxylbastnäsite solid solutions, La 1-$\chi$ Nd $\chi$ CO 3 OH

Bastnäsites (LnCO 3 (F,OH)) are a group of common rare earth elements (REE)-bearing minerals and are one of the primary global sources of REE. Due to the chemical similarities among REE, bastnӓsites tend to occur as solid solutions instead of end members in REE containing ores. To better understand the processes and the mechanisms of formation of such deposits, it is essential to determine the thermodynamic properties of bastnӓsites, including hydroxylbastnӓsite (LnCO 3 OH) solid solutions. In this work, we performed detailed structural and calorimetric investigations on synthetic hexagonal La–Nd hydroxylbastnӓsite (La 1-$\chi$ NdCO 3 OH, $\chi$ = 0, 0.25, 0.5, 0.75, 1) solid solutions. X-ray diffraction confirms the crystal structure of the solid solution series in the $\ P$6 space group, and pair distribution function (PDF) analysis reveals local bonding environments characterized by three different types of 9-coordinated metal-oxygen polyhedra. Unit cell parameters of La1–xNdxCO3OH exhibit a nearly linear relation with the Nd content x, suggesting a random distribution of La and Nd in the structure. Their standard enthalpies of formation (Δ$\ H$° f ) were determined by high temperature oxide melt drop solution calorimetry, from which the enthalpies of mixing (Δ$\ H$ mix ) were derived. The Δ$\ H$ mix can be fitted by a regular solution model with an interaction parameter of 12.58 ± 0.16 kJ/mol, suggesting enthalpic metastability of La1–xNdxCO3OH relative to the two endmembers. Combining entropy and enthalpy, we further estimated the Gibbs free energies of mixing (Δ$\ G$ mix ) at relevant temperatures, revealing favorable temperatures under which the intermediate La 1-$\chi$ NdCO 3 OH phases can be stabilized. Such entropy-driven stabilization, as is consistent with our geochemical modeling results, may explain the enhancement of thermal stability of the solid solutions in nature. Additionally, the temperature range constrained from this study may be used to estimate the thermal history of REE bastnӓsite deposit.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

The Impact of Nonzenith Elevation Angles on Ground-Based Infrared Thermodynamic Retrievals

Observing thermodynamic profiles within the planetary boundary layer is essential to understanding and predicting atmospheric phenomena because of the significant exchange of sensible and latent heat between the land and atmosphere within that layer. The Atmospheric Emitted Radiance Interferometer (AERI) is a ground-based infrared spectrometer used to obtain the vertical profiles of temperature and water vapor mixing ratio. Most AERIs are only capable of zenith views, although the Marine AERI (M-AERI) has a design that allows it to view various elevation angles. In this study, we quantify the improvement in the information content and accuracy of the retrieved profiles when nonzenith angles are included, as is common with microwave radiometer profilers. The impacts of the additional scan angles are quantified through both a synthetic study and with M-AERI observations from the ARM Cloud Aerosol Precipitation Experiment (ACAPEX) campaign. Furthermore, the simulation study shows that low elevation angles contain more information content for temperature whereas high elevation angles have more information content for water vapor. Outside of very humid environments, the addition of low elevation angles also results in lower root-mean-square errors when compared with high angles for both temperature and water vapor mixing ratio, although this is primarily a result of averaging multiple observations together to reduce instrument noise. Real-world results from the ACAPEX dataset indicate similar results as were found for the simulation study, although not all predicted benefits are realized because of the small sample size and observational uncertainties.

54 ENVIRONMENTAL SCIENCES↗

Heterologous synthesis of the complex homometallic cores of nitrogenase P- and M-clusters in Escherichia coli

Nitrogenase is an active target of heterologous expression because of its importance for areas related to agronomy, energy, and environment. One major hurdle for expressing an active Mo-nitrogenase in Escherichia coli is to generate the complex metalloclusters (P- and M-clusters) within this enzyme, which involves some highly unique bioinorganic chemistry/metalloenzyme biochemistry that is not generally dealt with in the heterologous expression of proteins via synthetic biology; in particular, the heterologous synthesis of the homometallic P-cluster ([Fe 8 S 7 ]) and M-cluster core (or L-cluster; [Fe 8 S 9 C]) on their respective protein scaffolds, which represents two crucial checkpoints along the biosynthetic pathway of a complete nitrogenase, has yet to be demonstrated by biochemical and spectroscopic analyses of purified metalloproteins. Here, we report the heterologous formation of a P-cluster-containing NifDK protein upon coexpression of Azotobacter vinelandii nifD, nifK, nifH, nifM, and nifZ genes, and that of an L-cluster-containing NifB protein upon coexpression of Methanosarcina acetivorans nifB, nifS, and nifU genes alongside the A. vinelandii fdxN gene, in E. coli. Our metal content, activity, EPR, and XAS/EXAFS data provide conclusive evidence for the successful synthesis of P- and L-clusters in a nondiazotrophic host, thereby highlighting the effectiveness of our metallocentric, divide-and-conquer approach that individually tackles the key events of nitrogenase biosynthesis prior to piecing them together into a complete pathway for the heterologous expression of nitrogenase. As such, this work paves the way for the transgenic expression of an active nitrogenase while providing an effective tool for further tackling the biosynthetic mechanism of this important metalloenzyme.

59 BASIC BIOLOGICAL SCIENCES↗

High-energy X-ray phase analysis of CMAS-infiltrated 7YSZ thermal barrier coatings: Effect of time and temperature

Calcium–magnesium–alumino-silicate (CMAS) particulates enter the aero-engine in a sandy environment, melt and infiltrate into 7 wt% yttria-stabilized zirconia (7YSZ) thermal barrier coatings (TBCs), reducing their lifetime. This leads to chemical degradation in 7YSZ accompanied by tetragonal to monoclinic phase transformation upon cooling. In this work, electron-beam physical vapor deposition coatings were infiltrated with a synthetic CMAS. Here, synchrotron X-ray diffraction measurements show that CMAS infiltration at 1250 °C has about 43% higher monoclinic phase volume fraction (PVF) at the coating surface compared to 1225 °C and remains consistently higher throughout the coating depth. Additionally, the increase in annealing time from 1 to 10 h results in a 31% higher monoclinic phase at the surface. Scanning electron microscopy revealed the presence of globular monoclinic phases corresponding spatially with the above findings. These results resolve the impact of time and temperature on CMAS infiltration kinetics which is important for mitigation.

36 MATERIALS SCIENCE↗

Thermal and photoinduced chemistry of the aromatic Criegee intermediate, benzaldehyde oxide: Implications for indoor air quality

Essential oils contain a complex mixture of volatile organic compounds, ranging from terpenes to aromatics. When released into the indoor air environment or into the atmosphere, they may undergo oxidation to generate complex reactive intermediates that affect indoor air quality. Cinnamaldehyde is one such aromatic molecule that is abundant in essential oils. When released into the indoor air environment, it may undergo oxidation to form a carbonyl oxide (Criegee intermediate) with an aromatic substituent: benzaldehyde oxide. In this manuscript, we present a high-level quantum chemical study that shows that, unlike smaller atmospherically relevant Criegee intermediates, benzaldehyde oxide is expected to undergo solar photolysis on timescales that are competitive with its ground state unimolecular and bimolecular chemistry. We show that aromatic substitution leads to a drastic bathochromic shift in the spectroscopically relevant excited states, revealing that photolysis in the indoor or outdoor environment should not be neglected when modeling the climate and air quality implications of Criegee intermediates with extended conjugation. Here, we predict a range of products that may be important for forming lower volatility compounds via tropospherically relevant photochemistry. To motivate future experimental validation of our results, we propose a viable synthetic procedure of the relevant precursor for generating and stabilizing benzaldehyde oxide.

atmospheric photochemistry↗

Effect of Charged Block Length Mismatch on Double Diblock Polyelectrolyte Complex Micelle Cores

Polyelectrolyte complex micelles are hydrophilic nanoparticles that self-assemble in aqueous environments due to associative microphase separation between oppositely charged blocky polyelectrolytes. In this work, we employ a suite of physical characterization tools to examine the effect of charged block length mismatch on the equilibrium structure of double diblock polyelectrolyte complex micelles (D-PCMs) by mixing a diverse library of peptide and synthetic charged-neutral block polyelectrolytes with a wide range of charged block lengths (25–200 units) and chemistries. Early work on D-PCMs suggested that this class of micelles can only be formed from blocky polyelectrolytes with identical charged block lengths, a phenomenon referred to as chain length recognition. Here, we use salt annealing to create PCMs at equilibrium, which shows that chain length recognition, a longstanding hurdle to repeatable self-assembly from mismatched polyelectrolytes, can be overcome. Interestingly, D-PCM structure–property relationships display a range of values that vary systematically with the charged block lengths and chemical identity of constituent polyelectrolyte pairings and cannot be described by generalizable scaling laws. We discuss the interdependent growth behavior of the radius, ionic pair aggregation number, and density in the micelle core for three chemically distinct diblock pairings and suggest a potential physical mechanism that leads to this unique behavior. By comparing the results of these D-PCMs to the scaling laws recently developed for single diblock polyelectrolyte complex micelles (S-PCMs: diblock + homopolymer), we observe that D-PCM design schemes reduce the size and aggregation number and restrict their growth to a function of charged block length relative to S-PCMs. Understanding these favorable attributes enables more predictive use of a wider array of charged molecular building blocks to anticipate and control macroscopic properties of micelles spanning countless storage and delivery applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Reduction‐induced metal/oxide interfacial sites for selective CO 2 hydrogenation

Abstract The interfacial structures of bimetallic‐derived catalysts play an important role in promoting the activation of reactants such as CO 2 . In particular, both the physical property (e.g., local bonding environment) and the electronic property (e.g., oxidation state) can evolve from their native states under different environments, such as upon reduction and during the catalytic reaction. Hence, taking the CO 2 hydrogenation reaction over Rh‐based catalysts as a case study, the present work compares the interfacial structures in tuning the selectivity toward CH 4 or CO. The combination of ex situ and in situ characterization reveals two representative interfacial structures: the Rh/CeO x interface formed over Rh/CeO 2 is active and selective to produce CH 4 (~95%) by following a formate‐mediated pathway; in comparison, the InO x /Rh interface derived after reduction is active for CO 2 activation and enables a redox mechanism for the exclusive formation of CO (~100%). This work provides insights into the environment‐induced structural evolution at the metal−oxide interfaces, as well as the role of distinct interfacial active sites in tuning the selectivity of CO 2 hydrogenation.

10 SYNTHETIC FUELS↗

Rational design of heterogeneous single-site catalysts via surface organometallic chemistry

Single-site heterogeneous catalysts offer an attractive route to unite the molecular precision of homogeneous catalysis with the durability and practical advantages of solids. Surface organometallic chemistry (SOMC) provides a particularly powerful strategy for this purpose by grafting molecular precursors onto tailored surfaces and converting support functionalities into ligand environments for isolated metal centers. As a result, SOMC brings the language and logic of coordination chemistry to heterogeneous catalysis, where the support becomes an integral part of the active site coordination sphere. This Review surveys recent progress in the rational design of SOMC-derived single-site catalysts, with emphasis on synthetic routes, post synthetic transformations, and the deliberate tuning of catalytic behavior through metal-support interactions. Discussions are made on how support identity, hydroxyl topology, acidity, and redox activity shape the geometry, electronic structure, and oxidation state of supported metal sites, as well as how these factors determine activity, selectivity, and stability. We also examine a central limitation of these systems: despite their molecularly informed design, supported single sites often exist as structurally distributed ensembles rather than uniform species, particularly on amorphous supports. This site heterogeneity, along with catalyst dynamics under operating conditions, remains a major barrier to definitive structure-activity relationships. Therefore, emerging approaches that combine advanced characterization, first-principles modeling, ensemble kinetics, and machine learning to resolve active-site structure and guide catalyst development are highlighted. Together, these advances position SOMC as a versatile coordination chemistry framework for the predictive design of heterogeneous catalysts with well-defined molecularly tailored active sites.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗