Chemistry methods : new approaches to solving problems in chemistry最新文献

Understanding the reactivity of hydrated electron, especially the role of solvent dynamics, remains a key challenge. Its reaction with dimethyl disulfide, a system whose known highly exothermicity contrasts with its low electron affinity, using density functional theory-based molecular dynamics simulations is investigated. This work reveals a mechanism gated by a critical S···H hydrogen bond, which enables a kinetically challenging electron transfer step. The overall exothermicity is not driven by electron transfer itself but by a large release of solvation energy that stabilizes the nascent radical anion of dimethyl disulfide. Following the electron transfer, the system undergoes a complex solvent reorganization driven by dynamic hydrogen bonding, where a relaxation of the initial hydrated electron cavity competes with the stabilization of the resulting radical anion. These findings suggest that insufficient solvation can either kinetically hinder the initial electron transfer or by subsequently failing to stabilize the anion, promote SS bond cleavage.

The Cover Feature shows a customized DRIFTS cell based on the Harrick reaction chamber for operando FTIR spectroscopic studies of plasma-assisted heterogeneous catalyzed reactions; it is connected to a mass spectrometer for online quantitative product gas analysis. The nonthermal plasma ignites in the immediate vicinity of the catalyst surface. The performance of the plasma DRIFTS cell has been demonstrated by investigating the plasma-assisted CO₂ splitting reaction with CeO₂. More information can be found in the Research Article by D. Peña Fuentes, R. Brandenburg, C. Kubis and co-workers (DOI: 10.1002/cmtd.202500057).

The Front Cover features a liquid-phase hydrogenation reactor, employing attenuated total reflectance-infrared (ATR-IR), Raman, and fluorescence spectroscopy under industrially relevant conditions. Specifically, it highlights the use of inline ATR-IR spectroscopy and partial least-squares regression to determine the concentrations of two bio-derived lactones from the acquired spectra. In the Research Article by B. M. Weckhuysen and co-workers (DOI: 10.1002/cmtd.202500054), the reactor design is clarified, and changes in the spectra not induced by concentration changes are pinpointed, shedding light on the challenges associated with performing spectroscopy under reaction conditions.

The article presents bleaching with emission and absorption monitoring (BEAM), a cost-effective and customizable optical setup designed for real-time monitoring of photochemical reactions through simultaneous measurement of absorption and emission spectra. BEAM utilizes readily available optical components such as lamp or laser diodes for excitation, cuvettes for sample containment, and spectrometers for spectral acquisition. Its modular architecture enables precise control over excitation wavelength, sample volume, temperature, and stirring conditions, making it highly adaptable to various experimental needs. The article also proposes a detailed protocol for measuring the effective photon flux density and irradiance across different optical configurations. The system's capabilities are demonstrated through the study of Citrine's photobleaching, a widely used but poorly photostable fluorescent protein (FP). BEAM enables continuous monitoring of Citrine's spectral evolution under different conditions, including excitation laser powers, solution volumes, and protein concentrations. The results revealed complex changes in both absorption and emission spectra during the bleaching process. Nevertheless, the fluorescence intensity of Citrine follows a first-order decay profile, facilitating straightforward kinetic modeling. This allowed determination of key photophysical parameters, such as the photobleaching molar cross section and quantum yield. These findings underscore BEAM's utility for characterizing fluorescent proteins and open pathways for comparative studies with other FPs.

The shift to energy-efficient near-infrared (NIR) diode lasers in polymer powder bed fusion (PBF-LB/P) challenges standard polymer powders due to insufficient NIR absorption and necessitates tailored feedstock modifications. This study explores the potential of surface modification (s-mod) of polyamide 12 (PA12) with LaB₆ nanoparticles (NP) as a scalable alternative to conventional volume modification (v-mod) with carbon black (CB). Despite a tenfold lower overall NIR absorbance, s-mod PA12 achieves comparable melting behavior with only a 1.5-fold increase in laser energy. Combined differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyses reveal that surface-localized absorption enables partial retention of α-domains at intermediate energy densities, consistent with a heterogeneous, surface-dominated melting mechanism. At higher energies, s-mod and v-mod converge to fully γ-phase materials with comparable crystallinity. Mechanical testing demonstrates that intermediate s-mod parts exhibit higher crystallinity, whereas fully molten s-mod parts outperform v-mod counterparts in tensile strength while maintaining ductility. Our findings indicate that s-mod PA12 not only matches the processability of industrial v-mod powders but also introduces new degrees of freedom for tailoring mechanical properties via controlled melting. Decoupling energy absorption from volumetric filler loading expands the material design space for NIR-based additive manufacturing and paving the way for next-generation, high-performance polymer components.

The authors report a combination of multimodal scanning three-dimensional X-ray diffraction (S3DXRD), X-ray diffraction computed tomography (XRD-CT), and X-ray fluorescence computed tomography (XRF-CT) used for the first time to provide multiscale (spanning the size regime 0.15–500 µm) insight into the aging of a CeO₂ZrO₂ solid solution known to exhibit outstanding reversible oxygen storage capacity (OSC). The authors show that using nanobeams is necessary to map in detail the distribution of elements and crystalline phases. In particular, the latter information is derived from two imaging methodologies to capture the diffraction signal originating from single crystals and powder-averaged crystallites, respectively. Ultimately, a decrease in relative OSC by 25% in the aged material could be correlated with a transformation of the cation-ordered pyrochlore Ce₂Zr₂O₇ phase to the cation-disordered CeO₂ZrO₂ fluorite structure. This is manifested as a loss in homogeneity of Ce and Zr distribution of the cation-ordered pyrochlore seen by nanoXRF-CT. The diffraction signal in both the S3DXRD and XRD-CT provides evidence that the solid-state transformation between the phases preferentially takes place at the periphery of the catalyst particle, resulting in a pyrochlore-rich core and fluorite on the surface and accompanied by significant sintering.

Kinetic simulations are efficient tools for supporting the development of technologies. However, in radiation-based technologies, as many intermediates are involved in the chemistry, simulations can be challenging to implement. To address these challenges, a versatile, nonselective automated method for the implementation of radiolysis kinetic simulations is developed. The approach uses curated various open-access databases and the FACSIMILE software and is accompanied by diagnostic tools. For validation, the simulation results are compared to experimental data from the literature for a CO₂/O₂/CO mixture and comparable results are found. This method is then used to evaluate a more complex system: an original nuclear-to-chemical concept for flue gas (N₂/CO₂/H₂O/O₂/CO/NO₂/SO₂) valorization. A parametric study that includes varying the initial pressure, temperature, and composition to identify regimes of interest is performed. The conversion of CO₂ is found to improve by a factor of five with the addition of 90(vol.%) NH₃, and the production of energetic molecules is evidenced with the addition of H₂S, with some promising yield maxima like an H₂ production > 900 molecules·100 eV⁻¹. This shows the potential of the developed method for kinetic studies and identification of regimes of interest. Overall, this study could open the path toward rapid and rigorous concept testing for various chemistry applications.

Coupling Raman spectroscopy with X-ray diffraction (XRD) provides complementary structural information on solid materials such as heterogeneous catalysts. A laboratory-based operando 532 nm Raman-XRD setup combining structural analysis is presented with simultaneous quantitative gas-phase analysis using infrared (IR) spectroscopy. To avoid the effect of sample heating by laser irradiation and for better statistics in the XRD patterns, the sample is constantly rotated during experiments. The potential of the setup is illustrated for the depth-dependent structural analysis of iron molybdate (Fe₂(MoO₄)₃) catalyst during the oxidative dehydrogenation of ethanol, the latter monitored by IR spectroscopic analysis of the gas phase. When applying reductive conditions to Fe₂(MoO₄)₃, structural dynamics are observed, accompanied by changes in the catalytic performance. The reduction of Fe₂(MoO₄)₃ to β-FeMoO₄ is quantified by Rietveld analysis (XRD) and the (sub)surface structure of Fe₂(MoO₄)₃ is probed via molybdate stretching vibrations (Raman). Temporal analysis reveals different timescales of catalyst reduction attributed to a faster (sub)surface contribution (Raman) and a slower bulk response (XRD), enabling depth-dependent analysis. The presented coupled Raman-XRD setup offers high versatility for detailed laboratory-based structural analysis under in situ and operando conditions, providing complementary information on the catalyst's structure and structural dynamics.

The electrolyte/solid interface is ubiquitous in nature and for many applications. In particular, the double-layer properties are essential for predicting adsorption and transport behavior. While for small colloidal particles, electrophoretic mobility has developed into a routine technique, there is currently a lack of analogously established techniques for particles with diameters larger than 10 microns. Such particles are often encountered in natural soils, industrial formulations, and as contaminants in the form of microplastics. Herein, a systematic method development using the streaming potential technique of particle plugs composed of large particles is presented. This approach revives an analytical method that was first introduced nearly 75 years ago, which has rarely been used for particulate systems. Comparing the zeta-potential versus pH of polystyrene particles with varying surface functionalization demonstrated that streaming potential measurements can distinguish these surface groups. In agreement with theoretical predictions, no dependence on the particle dimensions and shape is observed. Moreover, the particle arrangement within the particle plugs has been characterized by X-ray microtomography. The viability of this technique is tested by monitoring the artificial weathering of artificially fragmented microplastic particles of non-spherical shape. This technique opens new possibilities for characterizing the interfacial properties of environmentally relevant microplastics.

Expanded porphyrins offer a unique platform for probing how (anti)aromaticity influences molecular properties. These macrocycles are remarkably flexible, capable of adopting diverse π-conjugation topologies, including Möbius strip-like and twisted Hückel structures, which are difficult to realize with regular porphyrins. Their rich redox chemistry facilitates the formation of congeneric macrocycles with (4n + 2) and (4n) π-electrons, making them ideal systems for testing the practical limits of Hückel, Möbius, and Baird aromaticity rules. Spectroscopic properties are commonly employed to experimentally probe the ground- and excited-state aromaticity of expanded porphyrins. Nevertheless, quantifying aromaticity remains challenging from both experimental and theoretical standpoints due to the intricate interplay between local and macrocyclic ring currents, which often leads to discrepancies between descriptors based on different criteria. This review summarizes our efforts to unravel the aromaticity fingerprint on the photophysical and nonlinear optical properties of expanded porphyrins. A multidimensional framework to quantify Hückel and Möbius aromaticity is first introduced, integrating global and local descriptors derived from the energetic, reactivity, magnetic, electronic, and structural criteria. The complex structure–property relationships between aromaticity and spectroscopic features across redox- and topology-controlled expanded porphyrins are examined. Lastly, innovative approaches to uncover the driving forces governing the spectroscopic properties of diverse hexaphyrin databases are introduced.