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Item type:Publication, Access status: with files , Distinct electrification regimes at solid–liquid interfaces revealed by water isotope substitution(American Chemical Society (ACS), 2026-07-28); ; ; ; Solid–liquid contact electrification is widely studied using diverse experimental geometries that are often implicitly assumed to probe equivalent interfacial processes. Here, we directly test this assumption by comparing immersion–emersion, droplet-based contact, and pressure-driven intrusion–extrusion electrification using the same hydrophobic nanoporous silicon monolith and isotopically substituted liquids (H2O and D2O). Despite identical surface chemistry, isotopic substitution produces qualitatively different electrical responses depending on the wetting regime. Immersion–emersion experiments show polarity inversion between H2O and D2O, while droplet measurements reveal distinct charge evolution and periodic opposite-polarity events. In contrast, forced nanopore intrusion preserves polarity but strongly enhances electrical output for D2O. These results demonstrate that wetting of surface nanoroughness during droplet, vs immersion–emersion, vs complete nanopores wetting upon intrusion–extrusion correspond to fundamentally different electrification states. By using isotope substitution as a controlled probe, this work establishes a general framework for disentangling protocol-dependent effects in solid–liquid contact electrification and triboelectric energy conversion.Publicationtype: Journal Article10 15 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Open metal sites govern hydration kinetics and molecular fluctuations in metal–organic frameworks(American Chemical Society (ACS), 2026-07-01); ; ; ; Water under nanoscale confinement exhibits structural and dynamical states distinct from bulk behavior, yet the role of pore chemistry in governing these states remains insufficiently understood. Herein, the hydration kinetics and molecular-scale fluctuations of water confined within a comprehensive series of MOF-74 metal-organic frameworks incorporating Mg, Ni, Co, and mixed-metal compositions were investigated and compared with those observed in mesoporous MCM-41 silica. In situ impedance pectroscopy resolves a pronounced multistep hydration mechanism in MOF-74, initiated by rapid coordinative binding at open metal sites, followed by cluster formation and final capillary condensation. In contrast to MCM-41 silica, where capillary condensation dominates, the presence of coordinatively unsaturated metal centers fundamentally alters adsorption pathways. Mixedmetal MOF-74 exhibits accelerated and temporally broadened hydration, reflecting heterogeneous distributions of adsorption energies. Broadband dielectric spectroscopy reveals a distinct water-specific relaxation process (w-relaxation) attributed to fluctuations of water clusters interacting with metal nodes. Relaxation rates follow Arrhenius behavior with activation energies increasing in the order Mg < Ni < Co and further enhanced in mixed-metal systems. Remarkably, water confined within MOF-74 remains liquid-like down to 133 K without crystallization, whereas crystallization is observed in MCM-41 silica. All activation data of the MOF-74 systems obey a common Meyer−Neldel compensation relation, indicating cooperative molecular dynamics and suggesting a hindered glass-transition−like process of confined water clusters. These findings demonstrate that open metal sites and metal composition enable programmable control over hydration kinetics and collective water dynamics in microporous frameworks. MOF-74 thus provides a tunable model platform for engineering water-driven transport, catalysis, and energy-relevant processes at the nanoscale.Publicationtype: Journal Article48 50 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Energy-dependent chemical interface damping induced by 1-decanethiol self-assembled monolayer on Au(111)(Soc., 2026-02-11); ; ; ; The chemical interface damping (CID) effect increases the collision frequency of free electrons in metals by changes to the metal surface. We have now experimentally disentangled the two contributions to CID: induced roughness and direct charge transfer. The latter is an important area of research in photoelectrochemistry with potential applications in light-induced chemical reactions. We present a broadband investigation of the CID effect on Au(111) covered by a self-assembled monolayer of decanethiol. Spectroscopic ellipsometry measurements show a photon-energy-dependent increase of the collision frequency. We observe a constant, photon energy-independent contribution, which is attributed to induced roughness, and a contribution that linearly increases with photon energy from about 1 eV upward, which we attribute to direct charge transfer. The onset of the charge transfer mechanism corresponds to the occupied orbitals of thiols bound to the Au surface, as confirmed by density functional theory calculations.Publicationtype: Journal Article32 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Colossal effect of nanopore surface ionic charge on the dynamics of confined water(American Chemical Society (ACS), 2025-09-29); ; 31 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Electrosorption-induced deformation of nanoporous carbons: solvation pressure from molecular dynamics and continuum theory(American Chemical Society (ACS), 2025-04-07); ; ; Nanoporous carbons play an important role in different electrochemical applications, such as being utilized as electrodes in supercapacitors. Application of electric potential to a porous electrode in electrolyte solution stimulates the adsorption or desorption of ions on the electrode surface. Electrosorption causes the appearance of solvation pressure in the pores and results in electrode deformation. In this work, using molecular dynamics simulations and the continuum theory based on the modified Poisson–Boltzmann equation, we studied the structure of the electrical double layer in slit graphitic micropores filled with a NaCl aqueous solution and solvation pressure in these pores. We focused on the behavior of the solvation pressure as a function of the pore width and surface charge density. Within molecular dynamics simulations, two different water models were used: an explicit model based on SPC/E water molecules and an implicit model, i.e., a structureless background with fixed dielectric permittivity. The latter allows us to relate molecular dynamics simulations to continuum theory. Simulations with explicit water show a qualitatively different behavior of the solvation pressure in the 1 and 2 nm pores as a function of the surface charge density. We demonstrated that the value of the solvation pressure is defined by a delicate balance between van der Waals and electrostatic contributions. We demonstrated that the theory predicts the dependence of the solvation pressure on the pore width, which matches the results of simulations using the implicit water model. Finally, we adapted the continuum theory developed for adsorption-induced deformation to estimate the deformation of a carbon electrode due to electrosorption. Our results can be used in the further development of nanoporous actuators working based on electrosorption-induced deformation.Publicationtype: Journal Article12 16 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Chemical Interface Damping by Electrochemical Gold Oxidation(American Chemical Society (ACS), 2024-09-19); ; ; ; Chemical interface damping is a change in the effective collision frequency of conduction band electrons in metal originating from a chemical change in the metal interface. In this work, we present in situ ellipsometric measurements that reveal the chemical interface damping effect from the electrochemical oxidation of single-crystal and polycrystalline gold films. We observed an increase in collision frequency of up to 21 meV for single-crystalline gold. To compare with literature results obtained with thiols and metal oxides on gold nanoparticles, we normalize the collision frequency by the electron mean free path to the surface of the structure. We show that electrochemical gold oxidation provides a stronger effect on the collision frequency than these coatings. Similar ellipsometric experiments have previously been conducted to investigate the optical properties of gold oxide but without taking chemical interface damping into account. The change in reflection from the oxidation of gold was solely attributed to the oxide coating. We also show that the chemical interface damping effect saturates at a larger effective oxide thickness, which is attributed to the stabilization of the gold-oxide interface. Our results are important for the design of optoelectronic and photochemical experiments involving nanostructured gold. Electrochemical gold oxidation can be used to significantly change the optical response of such structures and to increase the efficiency of the light-matter interaction.Publicationtype: Journal Article33 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Size-dependent photoemission study by electrochemical coarsening of nanoporous gold(American Chemical Society (ACS), 2024-07-30); ; ; ; The generation and utilization of hot charge carriers in plasmonic materials have emerged as a topic of significant importance with profound implications across multiple disciplines, including optoelectronics, photovoltaics, photocatalysis, and sensing. In this study, we investigate the hot electron transfer from nanoporous gold (npAu) dependent on the structure size, utilizing both the nanoscale feature size and the interconnected nature of this material. We employed photoelectron injection from nanoporous gold into the electrolyte under UV illumination as a test electron transfer process. Nanoporous gold thin films with sub-10 nm initial ligament diameter are stepwise coarsened by potential cycles in a photoelectrochemical setup, thereby allowing us to precisely probe the influence of the ligament diameter on the photocurrent response. The resulting ligament diameter variations are confirmed by scanning electron microscopy (SEM) analysis. As the ligament diameter increased from 8 to 16 nm, there was a corresponding decrease in quantum efficiency proportional to the inverse ligament diameter squared. Such a dependency is expected for electrons excited by surface collisions. For the small ligament diameter of 10 nm, we estimate an emission efficiency of excited 6sp electrons as 3.14%, reaching 23% for the surface-excited electrons.Publicationtype: Journal Article20 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Quantitative chemical mapping of Pt/Rh gauze catalysts for ammonia oxidation using resonant X-ray tomography(American Chemical Society (ACS), 2024-03-18); ; The loss of platinum group metals during the industrial Ostwald process for catalytic ammonia oxidation is a century-old concern. Understanding catalyst degradation requires knowledge of physicochemical changes occurring on stream, particularly on technical Pt/Rh gauze catalysts. However, such catalysts are mainly studied with surface-sensitive methods or as model systems since their composition of noble metals (e.g., 95/5 wt % Pt/Rh) makes it challenging to characterize the bulk catalyst. Here, we exploit the high-resolution and elemental sensitivity of synchrotron-based hard X-ray resonant tomography to quantify the 3D distribution of Rh and Pt in technical gauze catalysts. Resonant tomography performed above and below the Rh K-edge (23.300 and 23.208 keV, respectively) allowed computation of elemental distribution. Absorption contrast tomography was successful despite beam transmission of <0.1%. This was achieved using a single-photon counting detector. Rh segregation, Pt loss, and bulk material degradation leading to redistribution of elements were visualized and quantified within intact ∼76 μm diameter wires, with 2 μm resolution, and up to 50 days on stream. The estimated local Pt and Rh wt % changes showed significant material loss from the wire exterior and characteristic protrusions. However, the wire core was unaffected by the reaction conditions even after 50 days on stream. No volume diffusion from the wire center to the exterior was observed to mitigate material loss from the latter. This flexible and high-throughput quantitative imaging approach is uniquely possible with synchrotron hard X-ray tomography, opening further routes of study for compositionally challenging industrial catalysts.Publicationtype: Journal Article51 129 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Thermal with Electronic Excitation for the Unidirectional Rotation of a Molecule on a Surface(2023-08-21); ; ; ; Exploring the limits of the microscopic reversibility principle, we investigated the interplay between thermal and electron tunneling excitations for the unidirectional rotation of a molecule-rotor on the Au(111) surface. We identified a range of moderate voltages and temperatures where heating the surface enhances the unidirectional rotational rate of a chemisorbed DMNI-P rotor. At higher voltage, inelastic tunneling effects dominate, while at higher temperature, the process becomes stochastic. At each electron transfer event during tunneling, the quantum mixing of ground and excited electronic states brings part of the surface thermal energy in the excited electronic states of the molecule-rotor. Thermal energy contributes therefore to the semiclassical unidirectional rotation without contradicting the microscopic reversibility principle.Publicationtype: Journal Article28 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Straight versus Spongy: Effect of Tortuosity on Polymer Imbibition into Nanoporous Matrices Assessed by Segmentation-Free Analysis of 3D Sample ReconstructionsWe comparatively analyzed imbibition of polystyrene (PS) into two complementary pore models having pore diameters of ∼380 nm and hydroxyl-terminated inorganic-oxidic pore walls, controlled porous glass (CPG) and self-ordered porous alumina (AAO), by X-ray computed tomography and EDX spectroscopy. CPG contains continuous spongy-tortuous pore systems. AAO containing arrays of isolated straight cylindrical pores is a reference pore model with a tortuosity close to 1. Comparative evaluation of the spatiotemporal imbibition front evolution yields important information on the pore morphology of a probed tortuous matrix like CPG and on the imbibition mechanism. To this end, pixel brightness dispersions in tomographic 3D reconstructions and 2D EDX maps of infiltrated AAO and CPG samples were condensed into 1D brightness dispersion profiles normal to the membrane surfaces. Their statistical analysis yielded positions and widths of the imbibition fronts without segmentation or determination of pore positions. The retardation of the imbibition front movement with respect to AAO reference samples may be used as a descriptor for the tortuosity of a tested porous matrix. The velocity of the imbibition front movements in CPG equaled two-thirds of the velocity of the imbibition front movements in AAO. Moreover, the dynamics of the imbibition front broadening discloses whether porous matrices are dominated by cylindrical neck-like pore segments or by nodes. Independent single-meniscus movements in cylindrical AAO pores result in faster imbibition front broadening than in CPG, in which a morphology dominated by nodes results in slower cooperative imbibition front movements involving several menisci. The results presented here may be relevant to applications including printing and adhesive bonding, as well as to the optimization of production and properties of engineering, construction, and hybrid materials.Publicationtype: Journal Article33