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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: with files , Transition-metal azo Schiff base complexes: nonlinear optics across solutions, thin films and nanocomposites(Wiley, 2025-10-24); ; ; ; This paper investigates the nonlinear optical (NLO) properties of azo-based Schiff base ligand and its corresponding complexes incorporating Cu(II) and Zn(II) metal cations, designed upon the previous synthesis work. Both 2nd and 3rd order NLO properties are examined, with a particular focus on their potential for optoelectronic and photonic applications. The Z-scan technique is employed to analyze NLO refraction and NLO absorption in solution. All samples exhibit positive NLO phenomena, with Zn(L)2 showing the highest values (𝝌(3) = 27.95 × 10−22 m2 V−2, 𝜸 = 54.44 × 10−47 m5 V−2), attributed to enhanced ligand-to-metal charge transfer (LMCT). Additionally, thin films deposited via the spin coating method undergo 3rd order NLO analysis through the Maker fringe technique. THG analysis further confirms superior 3rd order NLO performance in Zn(L)2, exceeding several benchmark transition-metal complexes. 2nd order NLO properties are also explored in hybrid nanocomposites designed from Zn(L)2 embedded in nanoporous pSiO2 membrane. This structure exhibits anisotropic SHG behavior, with 𝝌 (2) = 0.11 pm V−1 under s-p polarization, suggesting polarization confinement within nanochannels. The results clearly demonstrate that transition-metal azo Schiff base complexes, particularly Zn(L)2, exhibit strong NLO responses, positioning them as potential candidates for applications in all-optical switching and frequency conversion.Publicationtype: Journal Article22 17 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Controlling organic semiconductor self-assembly through cylindrical nanoconfinement(American Chemical Society (ACS), 2025-09-30); ; ; ; Controlling the self-assembly of organic semiconductors at the nanoscale is critical for advancing high-performance electronic and photonic devices, yet 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 multi-domain 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: Preprint45 18 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Self-assembly of bent-core nematics in nanopores(American Chemical Society (ACS), 2025-06-17); ; ; ; Bent-core nematic liquid crystals exhibit unique properties, including giant flexoelectricity and polar electro-optic responses, making them ideal for energy conversion and electro-optic applications. When confined in nanopores, they can stabilize chiral nanostructures, enhance polar order, and enable defect-driven switching -- offering potential in nanofluidics, sensing, and adaptive optics. Here we examine the thermotropic ordering of the bent-core dimer CB7CB confined in anodic aluminum oxide (AAO) and silica membranes with precisely engineered cylindrical nanochannels -- ranging from just a few nanometers to several hundred nanometers. These well-aligned nanochannels enable high-resolution polarimetry studies of optical anisotropy, revealing how geometric confinement affects molecular organization and phase behavior. Under weak confinement, CB7CB forms a layered heterophase structure, with nematic, splay-bent, and twist-bent heliconical phases likely arranged concentrically. As confinement increases, a Landau-de Gennes analysis shows that ordered phases are suppressed, leaving only a paranematic phase under strong spatial constraints. Remarkably, temperature-dependent changes in optical birefringence under confinement closely resemble those seen under applied electric fields, revealing a parallel between geometric and electro-optic effects. Overall, our work demonstrates how nanoconfinement allows one to systematically tailor the self-assembly and optical behavior of bent-core nematics, enabling novel functionalities in responsive and anisotropic materials.Publicationtype: Preprint18 13 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Self-assembly of bent-core nematics in nanopores(Wiley, 2025); ; ; Bent-core nematic liquid crystals exhibit unique properties, including giant flexoelectricity and polar electro-optic responses, making them ideal for energy conversion and electro-optic applications. When confined in nanopores, they can stabilize chiral nanostructures, enhance polar order, and enable defect-driven switching – offering potential in nanofluidics, sensing, and adaptive optics. The thermotropic ordering of the bent-core dimer CB7CB confined in anodic aluminum oxide (AAO) and silica membranes with precisely engineered cylindrical nanochannels – ranging from just a few nanometers to several hundred nanometers–is examined. These well-aligned nanochannels enable high-resolution polarimetry studies of optical anisotropy, revealing how geometric confinement affects molecular organization and phase behavior. Under weak confinement, CB7CB forms a layered heterophase structure, with nematic, splay-bent, and twist-bent heliconical phases likely arranged concentrically. As confinement increases, a Landau-de Gennes analysis shows that ordered phases are suppressed, leaving only a paranematic phase under strong spatial constraints. Remarkably, temperature-dependent changes in optical birefringence under confinement closely resemble those seen under applied electric fields, revealing a parallel between geometric and electro-optic effects. Overall, this work demonstrates how nanoconfinement allows one to systematically tailor the self-assembly and optical behavior of bent-core nematics, enabling novel functionalities in responsive and anisotropic materials.Publicationtype: Journal Article24 13 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Synthesis, nanocrystalline morphology, lattice dynamics and nonlinear optics of mesoporous SiO2&LiNbO3 nanocomposite(Springer, 2024-10-16); ; ; ; We demonstrate a hybrid nanocomposite combining mesoporous silica, pSiO2, as a host medium and guest lithium niobate LiNbO3 nanocrystals embedded into tubular silica nanochannels by calcination of the precursor mixed solution of lithium and niobium salts. High-resolution transmission electron microscopy, X-ray diffraction and Raman scattering techniques reveal trigonal LiNbO3 nanocrystals within the pSiO2 nanochannels, indicating their random texture morphology. Annealing at high temperatures (950∘C) during calcination also leads to partial crystallization of the pSiO2 matrix with the formation of trigonal α-SiO2 nanocrystals. The Raman microscopy analysis of the pSiO2:LiNbO3 nanocomposite reveals three structural crystalline phases, α-SiO2, LiNbO3 and a mixed phase which involves the α-SiO2 phase of host membrane and LiNbO3 nanocrystals embedded into the membrane. The finite size of the LiNbO3 nanocrystals results in specific features of the LO-TO phonon frequency splitting, which are investigated by Raman microscopy. In the transmission geometry, the second harmonic generation emission exhibits no Maker fringes and is characterized by a broad angular diagram of diffusely scattered light. The second harmonic generation response is independent of the polarization direction of the incident pump light, thus indicating a spatial isotropy of the nonlinear optical conversion in the pSiO2:LiNbO3 composite, consistent with the randomly oriented textural morphology of the deposited LiNbO3 nanocrystals. The contribution of the guest LiNbO3 nanocrystals to the second harmonic generation effect was found to be strongly dominant compared to the partially crystallized host pSiO2 matrix. The nanocomposite pSiO2:LiNbO3 membrane, set in the 90∘ nonlinear optical geometry, shows unusually high diffusely transmitted second harmonic generation light (back-reflected emission), apparently supported by internal light reflection from the tubular nanochannel network. Despite the fundamental interest, the revealed anomalous back-reflected second harmonic generation emission from pSiO2:LiNbO3 nanocomposite membranes expands the prospects for their photonic and nonlinear optical applications.Publicationtype: Journal Article19 21 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Self-assembly of ionic superdiscs in nanopores(American Chemical Society (ACS), 2024-06-04); ; ; ; Discotic ionic liquid crystals (DILCs) consist of self-assembled superdiscs of cations and anions that spontaneously stack in linear columns with high one-dimensional ionic and electronic charge mobility, making them prominent model systems for functional soft matter. Compared to classical nonionic discotic liquid crystals, many liquid crystalline structures with a combination of electronic and ionic conductivity have been reported, which are of interest for separation membranes, artificial ion/proton conducting membranes, and optoelectronics. Unfortunately, a homogeneous alignment of the DILCs on the macroscale is often not achievable, which significantly limits the applicability of DILCs. Infiltration into nanoporous solid scaffolds can, in principle, overcome this drawback. However, due to the experimental challenges to scrutinize liquid crystalline order in extreme spatial confinement, little is known about the structures of DILCs in nanopores. Here, we present temperature-dependent high-resolution optical birefringence measurement and 3D reciprocal space mapping based on synchrotron X-ray scattering to investigate the thermotropic phase behavior of dopamine-based ionic liquid crystals confined in cylindrical channels of 180 nm diameter in macroscopic anodic aluminum oxide membranes. As a function of the membranes’ hydrophilicity and thus the molecular anchoring to the pore walls (edge-on or face-on) and the variation of the hydrophilic-hydrophobic balance between the aromatic cores and the alkyl side chain motifs of the superdiscs by tailored chemical synthesis, we find a particularly rich phase behavior, which is not present in the bulk state. It is governed by a complex interplay of liquid crystalline elastic energies (bending and splay deformations), polar interactions, and pure geometric confinement and includes textural transitions between radial and axial alignment of the columns with respect to the long nanochannel axis. Furthermore, confinement-induced continuous order formation is observed in contrast to discontinuous first-order phase transitions, which can be quantitatively described by Landau-de Gennes free energy models for liquid crystalline order transitions in confinement. Our observations suggest that the infiltration of DILCs into nanoporous solids allows tailoring their nanoscale texture and ion channel formation and thus their electrical and optical functionalities over an even wider range than in the bulk state in a homogeneous manner on the centimeter scale as controlled by the monolithic nanoporous scaffolds.Publicationtype: Journal Article17 18 - 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