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Item type:Publication, Access status: without files , Directed self-assembly of the organic semiconductor C8-BTBT-C8 in anodic aluminum oxide nanopores(American Chemical Society (ACS), 2025-12-24); ; ; ; Controlling the self-assembly of organic semiconductors at the nanoscale is critical for advancing high-performance electronic and photonic devices, yet it remains challenging due to their intrinsic anisotropic crystallization and sensitivity to processing conditions. Here, we demonstrate that cylindrical nanoconfinement within anodic aluminum oxide membranes provides a versatile platform to precisely tune the molecular orientation and phase behavior of the prototypical organic semiconductor 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT-C8). Combining temperature-dependent high-resolution synchrotron X-ray scattering with optical birefringence measurements, we uncover that confinement geometries (pore diameters 25–180 nm) and surface chemistry govern the emergence of distinct smectic A textures, featuring molecular layers either parallel or perpendicular to the pore axis. The competition between axial and radial smectic layering is modulated by pore size, surface hydrophilicity, and thermal history, enabling reversible control over domain orientations and transitions between liquid crystalline and crystalline states. Notably, nanoconfinement stabilizes the smectic phase over an expanded temperature range compared to bulk, while inducing complex multidomain configurations owing to geometric constraints and anchoring conditions. Our results elucidate fundamental mechanisms by which anisotropic nanoscale confinement directs the self-organization of highly conjugated organic molecules, with implications for optimizing directional charge transport and anisotropic optical responses in organic–inorganic hybrid nanoarchitectures. This study establishes nanoconfinement as a powerful strategy to engineer morphology and functional properties in organic semiconducting materials with nanoscale precision.Publicationtype: Journal Article45 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Water imbibition in nanoporous Vycor glass : X-ray tomography-based Lattice-Boltzmann simulations and their validation by optical and gravimetric experiments(InterPore2023, 2023-05); ; ; ; Capillary rise dynamics of molecular liquids in nanoporous solid is governed by the interplay of liquid’s viscosity, the liquid-solid interaction and permeability of the porous medium. Classical hydrodynamics provides a square-root-of-time dependent law to describe the liquid front advancement during imbibition, also known as Lucas-Washburn law (L-W). Although the validity of the L-W law down to the single digit nm scale has been proven [1], complex dynamics and broadening of the imbibition front arise in connection to the pore size distribution of the solid and its tortuosity. To address this problem we present Lattice-Boltzmann computer simulations (L-B) of water imbibition in nanoporous Vycor glass. X-ray-based tomography of a 400 porous Vycor reveals the geometry of the pore space from the single-pore up to the Darcy scale. The scale invariant spinodal demixing-based pore formation in controlled pore glass allows us to re-scale such geometry 100 times down. Thus we complement the L-B simulations with optical imaging experiment for water imbibition in Vycor with poresizes of 4 . At this scale, changes in the refractive index of the solid upon filling provide for direct observation of the rise dynamics and the broadening of the filling front. The latter is visible via intense light scattering at this region induced by the coexistence of liquid-gas phases at length scales comparable to the light characteristic wavelengths.Publicationtype: Conference Poster35 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Capillary rise of water in nanoporous glass as revealed by X-ray tomography-based Lattice-Boltzmann simulations(Springer, 2023); ; 21 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , On the issue of textured crystallization of Ba(NO₃)₂ in mesoporous SiO₂: Raman spectroscopy and lattice dynamics analysis(Elsevier, 2022-07-05); ; ; ; The lattice dynamics of preferentially aligned nanocrystals formed upon drying of aqueous Ba(NO3)2 solutions in a mesoporous silica glass traversed by tubular pores of approximately 12 nm are explored by Raman scattering. To interpret the experiments on the confined nanocrystals polarized Raman spectra of bulk single crystals and X-ray diffraction experiments are also performed. Since a cubic symmetry is inherent to Ba(NO3)2, a special Raman scattering geometry was utilized to separate the phonon modes of Ag and Eg species. Combining group-theory analysis and ab initio lattice dynamics calculations a full interpretation of all Raman lines of the bulk single crystal is achieved. Apart from a small confinement-induced line broadening, the peak positions and normalized peak intensities of the Raman spectra of the nanoconfined and macroscopic crystals are identical. Interestingly, the Raman scattering experiment indicates the existence of comparatively large, ∼10–20 μm, single-crystalline regions of Ba(NO3)2 embedded in the porous host, near three orders of magnitude larger than the average size of single nanopores. This is contrast to the initial assumption of non-interconnected pores. It rather indicates an inter-pore propagation of the crystallization front, presumably via microporosity in the pore walls.Publicationtype: Journal Article37 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Paraelectric KH₂PO₄ nanocrystals in monolithic mesoporous silica: Structure and lattice dynamicsCombining dielectric crystals with mesoporous solids allows a versatile design of functional nanomaterials, where the porous host provides a mechanical rigid scaffold structure and the molecular filling adds the functionalization. Here, we report a study of the complex lattice dynamics of a SiO₂:KH₂PO₄ nanocomposite consisting of a monolithic, mesoporous silica glass host with KH₂PO₄ nanocrystals embedded in its tubular channels ~12 nm across. A micro-Raman investigation performed in the spectral range of 70–1600 cm−1 reveals the complex lattice dynamics of the confined crystals. Their Raman spectrum resembles the one taken from bulk KH₂PO₄ crystals and thus, along with X-ray diffraction experiments, corroborates the successful solution-based synthesis of KH₂PO₄ nanocrystals with a structure analogous to the bulk material. We succeeded in observing not only the high-frequency internal modes (~900–1200 cm−1), typical of internal vibrations of the PO₄ tetrahedra, but, more importantly, also the lowest frequency modes typical of bulk KH₂PO₄ crystals. The experimental Raman spectrum was interpreted with a group theory analysis and first-principle lattice dynamics calculations. The calculated phonon spectrum reveals a lattice instability against two optical modes probably related to an intrinsic anharmonicity of the vibrational dynamics of KH₂PO₄ crystals originating from the uncertainty of proton localization within the network of hydrogen bonds. The analysis of calculated eigen-vectors indicates the involvement of hydrogen atoms in most phonon modes corroborating the substantial significance of the hydrogen subsystem in the lattice dynamics of paraelectric bulk and of KH₂PO₄ crystals in extreme spatial confinement. A marginal redistribution of relative Raman intensities of the confined compared to unconfined crystals presumably originates in slightly changed crystal fields and interatomic interactions, in particular for the parts of the nanocrystals in close proximity to the silica pore surfaces.Publicationtype: Journal Article60 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Adaptive photonic metamaterials by self-assembly of liquid crystals in nanoporous solidsSelf-organized multiscale porosity in terms of precise pore size, shape, and orientation has been achieved in many base materials. Here we exemplify that in combination with self-assembly of liquid crystals in pore space this provides particularly versatile pathways for the engineering of photonic metamaterials. We present temperature-dependent structuralcharacterizations of the thermodynamic and structural self-assembly behavior of the liquid crystals confined in nanoporous silicon, silica and alumina in combination with experiments on the resulting effective optics of the hybrid materials.Publicationtype: Conference Paper27 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Adsorption from binary liquid solutions into mesoporous silica: a capacitance isotherm on 5CB nematogen/cyclohexane mixtures(2021); ; We present a capacitance method to measure the adsorption of rod-like nematogens (4-cyano- (Formula presented.) -pentylbiphenyl, 5CB) from a binary liquid 5CB/cyclohexane solution into a monolithic mesoporous silica membrane traversed by tubular pores with radii of 5.4 nm at room temperature. The resulting adsorption isotherm is reminiscent of classical type II isotherms of gas adsorption in mesoporous media. Its analysis by a model for adsorption from binary solutions, as inspired by the Brunauer–Emmett–Teller (BET) approach for gas adsorption on solid surfaces, indicates that the first adsorbed monolayer consists of flat-lying (homogeneously anchored) 5CB molecules at the pore walls. An underestimation of the adsorbed 5CB amount by the adsorption model compared to the measured isotherm for high 5CB concentrations hint towards a capillary filling transition in the mesopores similar to capillary condensation, i.e. film-growth at the pore walls is replaced by filling of the pore centres by the liquid crystal. The experimental method and thermodynamic analysis presented here can easily be adapted to other binary liquid solutions and thus allows a controlled filling of mesoporous materials with non-volatile molecular systems.Publicationtype: Journal Article56 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Liquid crystals confined in nanoporous solids : from fundamentals to functionalities of integrated material systems(World Scientific Publishing (WSPC), 2020-08); ; ; Publicationtype: Book Part145 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Mesoporous alumina- and silica-based crystalline nanocomposites with tailored anisotropy: Methodology, structure and propertiesWe present several recently synthesized nanocomposites consisting of liquid crystals as well as an organic molecular crystal embedded into the nanochannels of mesoporous alumina and silica. As liquid-crystalline mesogens achiral, nematogen and chiral cholesteric guest molecules infiltrated into nanochannels by spontaneous imbibition were chosen. The molecular ordering inside the nanochannels, which can be tailored by modifying the surface anchoring, was characterized by optical polarimetry (linear and/or circular birefringence) in combination with X-ray diffraction. For the synthesis of the solid crystalline nanocomposites ferroelectric triglycine sulfate (TGS) nanocrystals were deposited into the nanochannels by slow evaporation of saturated water solutions imbibed into the porous hosts. Their textural and physicochemical properties were explored by x-ray diffraction, scanning electron microscopy and dielectric techniques.Publicationtype: Conference Paper147 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , KH2PO4+ host matrix (Alumina / SiO2) nanocomposite: Raman scattering insight(2019-07); ; ; ; Adamiv, V. T.We report on the synthesis and Raman scattering characterization of composite materials based on the hostnanoporous matrices filled with nanostructured KH2PO4 (KDP) crystal. Silica (SiO2) and anodized aluminium oxide (AAO) were used as host matrices with various pore diameters, inter-pore spacing and morphology. The structure of the nanocomposites was investigated by X-ray diffraction and scanning electron microscopy. Raman scattering reveals the creation of one-dimensional nanostructured KDP inside the SiO2 matrix. We clearly observed the stretching ν1, ν3, and bending ν2 vibrations of PO4 tetrahedral groups in the Raman spectrum of SiO2 + KDP. In Raman scattering spectra of AAO + KDP nanocomposite, the broad fluorescence background of AAO matrix dominates to a great extent, hindering thus the detecting of the KDP compound spectral response.Publicationtype: Conference Paper113