Browsing by Author "Volkmann, Ulrich Georg"

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    AFM Study of Elastic Module of Physical-Vapor-Deposited Phospholipid Membranes
    (2018) Volkmann, Ulrich Georg; Catalán López, Rodrigo Esteban; Retamal Ponce, María José; Cisternas Fruns, Marcelo Andrés; Moraga Vent, Nicolás Andrés; Díaz Díaz, Diego Ignacio; Corrales, Tomás P.; Pérez-Acle, Tomás; Soto Arriaza, Marco Antonio; Huber, Patrick
    The physical study of artificial phospholipid membranes on solid substrates has become a relevant way to gain insights into the physical behavior of cell membranes. The study of mechanical properties of artificial membranes (lab-made) has become possible with the use of atomic force microscopy. Here, we analyze the Young's modulus and adhesion force of several phospholipidic membranes as a function of temperature using Scanning Force Spectroscopy (SFS). Phospholipids were deposited onto double-polished silicon substrates by physical vapor deposition (PVD), as we have recently reported [1, 2]. We have used Raman spectroscopy to show that the chemical structure of our deposited phospholipid remains unaltered after PVD. After PVD we performed AFM and SFS measurements on the following phospholipids: DPPC, DMPC and DSPC. Measurements using AFM in liquid confirm the self-assembly of the phospholipid bilayer. By using SFS of the deposited membrane in liquid, we observe 2 phase transitions, both in Younǵs Modulus, as well as adhesion channels. The measured phase transitions are consistent with the ripple-gel transition and the gel-liquid crystalline phases. Furthermore, we have studied the frequency dependence of these phase transitions by changing the tip velocity in SFS experiments. Supported by FONDECYT grant # 1141105 (UGV), FONDECYT INICIACION grant # 11160664 (TPC), CONICYT Fellowships (RC and MC), Postdoctoral Fellowship FONDECYT 3160803 (MJR) and CONICYT-PIA ACT 1409. [1] María J. Retamal, Marcelo A. Cisternas, Sebastian E. Gutierrez-Maldonado, Tomas Perez-Acle, Birger Seifert, Mark Busch, Patrick Huber and Ulrich G. Volkmann, J. Chem. Phys. 141, 104201 (2014). [2] María Jose Retamal, Tomas P. Corrales, Marcelo A. Cisternas, Nicolas H. Moraga, Diego I. Diaz, Rodrigo E. Catalan, Birger Seifert, Patrick Huber, and Ulrich G. Volkmann. Biomacromolecules 17 (3), 1142 (2016).
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    Tailoring of titanium dioxide thin film in dual radiofrequency plasma enhanced pulsed laser deposition
    (2025) Villegas Dissett, Rodrigo Benjamín; Tomlinson Cornejo, Matías Paul; Ureta De La Fuente, Valentina Isidora; Carrasco Navarro, Camilo Antonio; Miranda, Maximiliano; Fernández Adell, José Ignacio; Saavedra, Daniel; Retamal, María José; Inestrosa-Izurieta, Maria Jose; Singh, Dinesh Pratap; Angel Figueroa, Felipe Alfonso; Volkmann, Ulrich Georg; Takamura, Yayoi; Bhuyan, Heman
    Efficient and cost-effective methods to create photovoltaic materials are constantly being sought, with metal oxides like TiO2 playing a key role in this field. In this study, TiO2 thin films were grown on glass substrates using a dual radiofrequency (RF) plasma-enhanced pulsed laser deposition (PLD) system with a thermal budget that remained below 400 °C. The physical, chemical, and optical properties of the deposited thin films were studied as a function of low- and high-RF powers as well as deposition time. These parameters were found to impact the proportion of anatase and rutile phase and their crystallinity, as well as the oxygen vacancy concentration and band gap energy. These findings demonstrated the utility of dual RF plasma-enhanced PLD for precise modulation of TiO2 thin-films, offering promising applications in photovoltaics and photocatalysis
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    Wrinkled TiNAgNW Nanocomposites for High-Performance Flexible Electrodes on TEMPO-Oxidized Nanocellulose
    (2024) Gence Loik, Herve Patrick; Quero, Franck; Escalona Álvarez, Miguel Benito; Wheatley, Robert; Seifert, Birger; Díaz Droguett, Donovan Enrique; Retamal, María José; Wallentowitz, Sascha; Volkmann, Ulrich Georg; Bhuyan, Heman
    Flexible electrodes are essential for the development of future wearable such as implantable medicaldevices. While silver nanowire (AgNW) networks are promising candidates for transparent conductive electrodes (TCEs), they suffer from issues such as high roughness, low adhesion, and atmospheric corrosion sensitivity. Many flexible electrodes are made of a wrinkled conductive layer on top of a compliant s ubstrates. Wrinkles provide a way to maintain the integrity and conductivity of the electrode while it is being stretched or bent. In this study, we report on the characterization ofFE-SEMi-transparent electrodes produced by a novel plasma-enhanced pulsed laser deposition (PE-PLD) technique compatible with cellulose nanopaper (CNP) substrates. We combined AgNW with titanium nitride (TiN) layers to form wrinkled conducting nano-composite coatings with excellent electro-mechanical properties. Our results show that the incorporation of AgNW into TiN coatings improves the electrode’s electro-mechanical robustness. Additionally, our data show that CNP/TiNAgNW electrodesexhibit improved stability in air compared to bare AgNW coatings with improved adhesion. These findings have important implications for the development of bio-compatible flexible electronics and could pave the way for the creation of new wearable and implantable medical devices.