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Abstract: The demand for rapid, field-deployable detection of hazardous substances has intensified the search for plasmonic sensors with both high sensitivity and fabrication simplicity. Conventional approaches to plasmonic substrates, however, often rely on lithographic precision or complex chemistries limiting scalability and reproducibility. Here, a facile, one-step synthesis of vertically aligned 2D nanosheets composed of intergrown Cu2O/CuO crystallites is presented, fabricated via oxygen plasma discharge on copper substrates. Decorated with a discontinuous Ag nanoparticle layer, the substrates serve as high-performance plasmonic metasurface exhibiting nanomolar sensitivity of explosive molecules, with detection limits as low as 4–5 nm for tetryl and 2–3 nm for HMX under 488 nm excitation. Importantly, the SERS (Surface enhanced Raman scattering) activity expands into a broad spectral range (488, 535, 633 nm), enabled by the formation of plasmonic “hotspots” network within nanoparticle gaps, crevices, that cumulatively boost SERS signal. A pronounced red-shift in the symmetric NO2 stretching mode of tetryl is further demonstrated, attributed to LUMO-mediated charge transfer from the Ag Fermi level—highlighting the need for laser- and substrate-sensitive interpretation of vibrational data. Together, these findings advance the rational design of low-cost, reproducible SERS substrates for trace chemical detection, with potential for integration into autonomous sensing platforms.
Keywords: plasmonic sensors, surface enhanced Raman scattering
Published in DiRROS: 16.09.2025; Views: 347; Downloads: 133
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Published in DiRROS: 15.09.2025; Views: 288; Downloads: 71
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Abstract: The recent discovery of ferroelectric nematic liquid crystalline phases marks a major breakthrough in soft matter research. An intermediate phase, often observed between the nonpolar and the ferroelectric nematic phase, shows a distinct antiferroelectric response to electric fields. However, its structure and formation mechanisms remain debated, with flexoelectric and electrostatics effects proposed as competing mechanisms. By controlling the magnitude of electrostatic forces through ion addition in two representative ferroelectric nematic materials, it is shown that the primary mechanism for the emergence of antiferroelectric order is the flexoelectric coupling between electric polarization and splay deformation of the nematic director. The addition of ions significantly expands the temperature range over which the antiferroelectric phase is observed, with this range increasing with increasing ion concentration. Polarizing optical microscopy studies and second harmonic generation (SHG) microscopy reveal the splayed structure modulated in 2D, while SHG interferometry confirms its antiferroelectric character. The model previously used to describe pretransitional behavior is extended by incorporating the electrostatic contribution of ions. The model shows qualitative agreement with the experiments, accurately reproducing the phase diagram and temperature-dependent evolution of the modulation period of the observed structure.
Keywords: ferroelectric nematic liquids, flexoelectricity, antiferroelectric order
Published in DiRROS: 15.09.2025; Views: 295; Downloads: 129
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Keywords: gozdne vlake, gozdne ceste, hudourniki, varstvo pred poplavami, gozdno gradbeništvo, odvodnjavanje
Published in DiRROS: 12.09.2025; Views: 418; Downloads: 139
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Abstract: Using scanning tunneling microscopy (STM) and inelastic tunneling spectroscopy, the low-frequency vibrational modes of a 7-atom wide armchair graphene nanoribbon (7-AGNR) is mapped. The inelastic tunneling channel is enhanced over the elastic one by a covalently bonded 7-AGNR to the apex of an STM tip. This setup has led to resonant inelastic tunneling between vibrational states of supported 7-GNR on Au(111) substrate and the states of the functionalized STM tip. The low-energy spectra reveal two localized peaks at the armchair edges with energies at ±14 and ±30 mV. The peaks are assigned to twice the energies of longitudinal compressive and shear-like modes of 7-AGNR, respectively. Remarkably, the well-separated peaks evolve rapidly into one broader peak toward the bulk of the ribbon due to scattering from substrate interactions. This suggests that edge state phonons are uniquely protected from the microenvironment and may have a profound effect on the transport properties of GNR devices.
Keywords: scanning tunneling microscopy, inelastic tunneling spectroscopy, armchair graphene nanoribbons
Published in DiRROS: 12.09.2025; Views: 262; Downloads: 119
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