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Now showing 1 - 5 of 12
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    Multi-Wavelength Angle-Resolved Scattering of Randomly Rough Surfaces Based on the Scalar Diffraction Theory
    (MDPI, 2023-10-27) Šulc, Václav; Vohánka, Jíří; Ohlídal, Ivan; Klapetek, Petr; Ohlídal, Miloslav; Kaur, Nupinder Jeet; Vižďa, František
    Angle-resolved scattering was measured for four samples of silicon exhibiting different surface roughnesses. The measurements were performed for three wavelengths: 457.9 nm, 514.5 nm, and 647.1 nm. Three approaches were used to evaluate the experimental data. The first approach corresponds to the exact formula derived using the scalar diffraction theory. This formula is quite complicated, and numerical methods must be used for its evaluation. For this reason, another two approaches representing approximations by much simpler formulae were considered. The use of several wavelengths allowed us not only to recover the power spectral density function in a limited interval of spatial frequencies but also to determine the total rms values of the heights, which represent the quantity of roughness for all spatial frequencies. The possibility of recovering the total rms values of the heights using the multi-wavelength approach is the most important result of this work. The results obtained from the scattering experiment and atomic force microscopy are compared.
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    Enhanced Adhesion of Electrospun Polycaprolactone Nanofibers to Plasma-Modified Polypropylene Fabric
    (MDPI, 2023-03-28) Janů, Lucie; Dvořáková, Eva; Polášková, Kateřina; Buchtelová, Martina; Ryšánek, Petr; Chlup, Zdeněk; Kruml, Tomáš; Galmiz, Oleksandr; Nečas, David; Zajíčková, Lenka
    Excellent adhesion of electrospun nanofiber (NF) to textile support is crucial for a broad range of their bioapplications, e.g., wound dressing development. We compared the effect of several low- and atmospheric pressure plasma modifications on the adhesion between two parts of composite-polycaprolactone (PCL) nanofibrous mat (functional part) and polypropylene (PP) spunbond fabric (support). The support fabrics were modified before electrospinning by low-pressure plasma oxygen treatment or amine plasma polymer thin film or treated by atmospheric pressure plasma slit jet (PSJ) in argon or argon/nitrogen. The adhesion was evaluated by tensile test and loop test adapted for thin NF mat measurement and the trends obtained by both tests largely agreed. Although all modifications improved the adhesion significantly (at least twice for PSJ treatments), low-pressure oxygen treatment showed to be the most effective as it strengthened adhesion by a factor of six. The adhesion improvement was ascribed to the synergic effect of high treatment homogeneity with the right ratio of surface functional groups and sufficient wettability. The low-pressure modified fabric also stayed long-term hydrophilic (ten months), even though surfaces usually return to a non-wettable state (hydrophobic recovery). In contrast to XPS, highly surface-sensitive water contact angle measurement proved suitable for monitoring subtle surface changes.
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    Interplay between multipole expansion of exchange interaction and Coulomb correlation of exciton in colloidal II-VI quantum dots
    (IOP Publishing Ltd, 2022-03-01) Klenovský, Petr; Valdhans, Jakub; Krejčí, Lucie; Valtr, Miroslav; Klapetek, Petr; Fedotova, Olga
    We study the effect of Coulomb correlation on the emission properties of the ground state exciton in zincblende CdSe/ZnS core-shell and in wurtzite ZnO quantum dots (QDs). We validate our theory model by comparing results of computed exciton energies of CdSe/ZnS QDs to photoluminescence and scanning near-field optical microscopy measurements. We use that to estimate the diameter of the QDs using a simple model based on infinitely deep quantum well and compare the results with the statistics of the atomic force microscopy scans of CdSe/ZnS dots, obtaining excellent agreement. Thereafter, we compute the energy fine structure of exciton, finding striking difference between properties of zincblende CdSe/ZnS and wurtzite ZnO dots. While in the former the fine structure is dominated by the dipole terms of the multipole expansion of the exchange interaction, in the latter system that is mostly influenced by Coulomb correlation. Furthermore, the correlation sizeably influences also the exciton binding energy and emission radiative rate in ZnO dots.
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    Optical characterization of inhomogeneous thin films with randomly rough boundaries
    (Optica Publishing Group, 2022-01-17) Vohánka, Jíří; Ohlídal, Ivan; Buršíková, Vilma; Klapetek, Petr; Kaur, Nupinder Jeet
    An inhomogeneous polymer-like thin film was deposited by the plasma enhanced chemical vapor deposition onto silicon single-crystal substrate whose surface was roughened by anodic oxidation. The inhomogeneous thin film with randomly rough boundaries was created as a result. This sample was studied using the variable-angle spectroscopic ellipsometry and spectroscopic reflectometry. The structural model including the inhomogeneous thin film, transition layer, and identically rough boundaries was used to process the experimental data. The scalar diffraction theory was used to describe the influence of roughness. The influence of the scattered light registered by the spectrophotometer due to its finite acceptance angle was also taken into account. The thicknesses and optical constants of the inhomogeneous thin film and the transition layer were determined in the optical characterization together with the roughness parameters. The determined rms value of the heights of roughness was found to be in good agreement with values obtained using AFM. The results of the optical characterization of the studied inhomogeneous thin film with rough boundaries were also verified by comparing them with the results of the optical characterization of the inhomogeneous thin film prepared using the same deposition conditions but onto the substrate with a smooth surface. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
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    Amine modification of calcium phosphate by low-pressure plasma for bone regeneration
    (Nature Portfolio, 2021-09-01) Kodama, Joe; Harumningtyas, Anjar Anggraini; Ito, Tomoko; Michlíček, Miroslav; Sugimoto, Satoshi; Kita, Hidekazu; Chijimatsu, Ryota; Ukon, Yuichiro; Kushioka, Junichi; Okada, Rintaro; Kamatani, Takashi; Hashimoto, Kunihiko; Tateiwa, Daisuke; Tsukazaki, Hiroyuki; Nakagawa, Shinichi; Takenaka, Shota; Makino, Takahiro; Sakai, Yusuke; Nečas, David; Zajíčková, Lenka; Hamaguchi, Satoshi; Kaito, Takashi
    Regeneration of large bone defects caused by trauma or tumor resection remains one of the biggest challenges in orthopedic surgery. Because of the limited availability of autograft material, the use of artificial bone is prevalent; however, the primary role of currently available artificial bone is restricted to acting as a bone graft extender owing to the lack of osteogenic ability. To explore whether surface modification might enhance artificial bone functionality, in this study we applied low-pressure plasma technology as next-generation surface treatment and processing strategy to chemically (amine) modify the surface of beta-tricalcium phosphate (beta-TCP) artificial bone using a CH4/N-2/He gas mixture. Plasma-treated beta-TCP exhibited significantly enhanced hydrophilicity, facilitating the deep infiltration of cells into interconnected porous beta-TCP. Additionally, cell adhesion and osteogenic differentiation on the plasma-treated artificial bone surfaces were also enhanced. Furthermore, in a rat calvarial defect model, the plasma treatment afforded high bone regeneration capacity. Together, these results suggest that amine modification of artificial bone by plasma technology can provide a high osteogenic ability and represents a promising strategy for resolving current clinical limitations regarding the use of artificial bone.