Spray Deposition Synthesis of Locally Ordered Mesoporous Polycrystalline Titania Films at Low Temperature Gunnar Símonarson, Antiope Lotsari, Anders E. C. Palmqvist Molecules, 2022 A low-temperature spray deposition synthesis was developed to prepare locally hexagonally ordered mesoporous titania films with polycrystalline anatase pore walls in an evaporation-induced self-assembly process. The titania film preparation procedure is conducted completely at temperatures below 50 °C. The effects of spray time, film thickness, synthesis time prior to spray deposition, and aging time at high relative humidity after deposition on the atomic arrangement and the mesoorder of the mesoporous titania were studied. We find the crystallite size to depend on both the synthesis time and aging time of the films, where longer times result in larger crystallites. Using the photocatalytic activity of titania, the structure-directing agent is removed with UV radiation at 43–46 °C. The capability of the prepared films to remove the polymer template increased with longer synthesis and aging times due to the increased crystallinity, which increases the photocatalytic efficiency of the titania films. However, with increasingly longer times, the crystallites grow too large for the mesoorder of the pores to be maintained. This work shows that a scalable spray coating method can be used to prepare locally ordered mesoporous polycrystalline titania films by judiciously tuning the synthesis parameters.
Fast charging negative electrodes based on anatase titanium dioxide beads for highly stable Li-ion capacitors G. Calcagno, A. Lotsari, A. Dang, S. Lindberg, A.E.C. Palmqvist, et al. Materials Today Energy, 2020 Hybrid energy storage systems aim to achieve both high power and energy densities by combining supercapacitor-type and battery-type electrodes in tandem. The challenge is to find sustainable materials as fast charging negative electrodes, which are characterized by high capacity retention. In this study, mesoporous anatase beads are synthetized with tailored morphology to exploit fast surface redox reactions. The TiO2-based electrodes are properly paired with a commercial activated carbon cathode to form a Li-ion capacitor. The titania electrode exhibits high capacity and rate performance. The device shows extremely stable performance with an energy density of 27 mWh g-1 at a specific current of 2.5 A g−1 for 10,000 cycles. The remarkable stability is associated with a gradual shift of the potential during cycling as result of the formation of cubic LiTiO2 on the surface of the beads. This phenomenon renews the interest in using TiO2 as negative electrode for Li-ion capacitors.
An imidazolium ionic liquid as effective structure-directing agent for the fabrication of silica thin films with vertically aligned nanochannels Szilvia Vavra, Neus Vilà, Antiope Lotsari, Alain Walcarius, Anna Martinelli Microporous and Mesoporous Materials, 2020 In parallel to the increasing variety of ionic liquids that show different kinds of nanometer-scale structuration in their pure and solved forms, there is a raising interest in exploring the possibility of using ionic liquids as soft-templates for the synthesis of mesoporous materials. We report the case of 1-hexadecyl-3-methylimidazolium chloride (C16MIMCl), a surface active ionic liquid (SAIL), here used as an excellent soft-template for the formation of vertically aligned, uniform mesochannels, with a well defined pore width of 2.5 nm in silica thin films deposited with the electrochemically assisted self-assembly (EASA) method. The obtained mesochannels run through the entire thickness of the films and after removal of the ionic liquid the emptied mesochannels ensure a thorough mass transport to the substrate, here monitored by the redox-active electrochemical probe Ru(II)/Ru(III) during cyclic voltammetry (CV). Moreover, the mechanism of pore formation is explained; unlike the mechanisms reported for short chain imidazolium ionic liquid silica templates, in the case of C16MIMCl the dominating so-called cooperative interaction is the electrostatic attraction between the C16MIM+ and the network-forming negatively charged silicate oligomers. Therefore, this study provides a better understanding of the templating behavior of long chain imidazolium ionic liquids and motivates further research on the synthesis of ionic liquid-based functional hybrid materials.
Dynamic Nanocellulose Networks for Thermoset-like yet Recyclable Plastics with a High Melt Stiffness and Creep Resistance Anna Peterson, Ida Östergren, Antiope Lotsari, Abhijit Venkatesh, Johannes Thunberg, et al. Biomacromolecules, 2019 Many polymers, including polyethylene, feature a relatively low melting point and hence must be cross-linked to make them viable for applications that demand a high stiffness and creep resistance at elevated temperatures. The resulting thermoset plastics cannot be recycled, and therefore alternative materials with a reconfigurable internal network structure are in high demand. Here, we establish that such a thermoset-like yet recyclable material can be realized through the addition of a nanocellulose reinforcing agent. A network consisting of cellulose nanocrystals, nano- or microfibrils imparts many of the characteristics that are usually achieved through chemical cross-linking. For instance, the addition of only 7.5 wt % of either nanocellulose material significantly enhances the melt stiffness of an otherwise molten ethylene-acrylate copolymer by at least 1 order of magnitude. At the same time, the nanocellulose network reduces the melt creep elongation to less than 10%, whereas the neat molten matrix would rupture. At high shear rates, however, the molten composites do not display a significantly higher viscosity than the copolymer matrix, and therefore retain the processability of a thermoplastic material. Repeated re-extrusion at 140 °C does not compromise the thermomechanical properties, which indicates a high degree of recyclability. The versatility of dynamic nanocellulose networks is illustrated by 3D printing of a cellulose composite, where the high melt stiffness improves the printability of the resin.
Silica-based diffusion probes for use in FRAP and NMR-diffusometry Maria Pihl, Krzysztof Kolman, Antiope Lotsari, Marie Ivarsson, Erich Schüster, et al. Journal of Dispersion Science and Technology, 2019 Development of multi-purpose probes for mass transport measurements is of importance to gain knowledge in diffusional behaviour in heterogeneous structures such as food, hygiene or pharamceuticals. By combining different techniques, such as Fluorescence Recovery After Photobleaching (FRAP) and Nuclear Magnetic Resonance Diffusometry (NMR-d), information of both local and global diffusion can be collected and used to gain insights on for example material heterogeneities and probe-material interactions. To obtain a FRAP-responsive probe, fluorescent silica particles were produced using fluorescent preconjugates added in a modified Stöber process. A NMR-d responsive moiety was introduced by derivatizing the fluorescent silica particles with polyethylene glycol. The particle size distributions were determined by dynamic light scattering and transmission electron microscopy and these measurements were compared to value extrapolated from diffusion measurements using FRAP and NMR-d. The good agreement between the FRAP and NMR-d measurements demonstrates the potential of multi-purpose probes for future applications concerning mass transport at local and global scale simultaneously. GRAPHICAL ABSTRACT
Evolution of the Polymorph Selectivity of Titania Formation under Acidic and Low-Temperature Conditions Gunnar Símonarson, Sanna Sommer, Antiope Lotsari, Björn Elgh, Bo B. Iversen, et al. ACS Omega, 2019 Evolution of the polymorph selectivity of titanium dioxide was studied under acidic and low-temperature synthesis conditions. Short synthesis times resulted in high relative amounts of the rutile phase, and long synthesis times resulted in high relative amounts of the brookite and anatase phases. The effect of titania precursor concentration was investigated and found to have a large impact on the polymorph selectivity. As the reaction proceeds with time, changes in the chemical environment, caused in particular by the gradually decreasing titania precursor concentration, are therefore likely the cause of the change in polymorph selectivity observed.
Transformation of amorphous calcium phosphate to bone-like apatite Antiope Lotsari, Anand K. Rajasekharan, Mats Halvarsson, Martin Andersson Nature Communications, 2018 Mineralisation of calcium phosphates in bone has been proposed to proceed via an initial amorphous precursor phase which transforms into nanocrystalline, carbonated hydroxyapatite. While calcium phosphates have been under intense investigation, the exact steps during the crystallisation of spherical amorphous particles to platelet-like bone apatite are unclear. Herein, we demonstrate a detailed transformation mechanism of amorphous calcium phosphate spherical particles to apatite platelet-like crystals, within the confined nanodomains of a bone-inspired nanocomposite. The transformation is initiated under the presence of humidity, where nanocrystalline areas are formed and crystallisation advances via migration of nanometre sized clusters by forming steps at the growth front. We propose that such transformation is a possible crystallisation mechanism and is characteristic of calcium phosphates from a thermodynamic perspective and might be unrelated to the environment. Our observations provide insight into a crucial but unclear stage in bone mineralisation, the origins of the nanostructured, platelet-like bone apatite crystals.The growth of apatite crystals from amorphous calcium phosphate is an area of intense study. Here, the authors report on the use of high resolution TEM imaging to provide evidence of nucleation clusters in the transformation process
Bioinspired Structural Hierarchy within Macroscopic Volumes of Synthetic Composites Anand K. Rajasekharan, Antiope Lotsari, Viviane Lutz-Bueno, Marianne Liebi, Martin Andersson Advanced Healthcare Materials, 2018 A key challenge in developing bioinspired composites is the fabrication of well-defined 3D hierarchical structures ranging from nano to the macroscale. Herein, the development of a synthetic polymer-apatite composite realized by integrating bottom-up self-assembly and additive manufacturing (AM) is described. The resulting composite exhibits a bioinspired hierarchical structure over its 3D macroscopic volume. The composite is assembled in a bottom-up manner, where periodic nanoscale assemblies of organic micellar fibrils and inorganic apatite nanocrystals are organized as bundles of mineralized microstructures. These microstructural bundles are preferentially oriented throughout the macroscopic volume of the material via extrusion based AM. The obtained structural hierarchy is investigated in 3D using electron microscopy and small angle X-ray scattering tensor tomography and correlated to the structural hierarchy and anisotropy observed in biological tissues such as bone and the bone-cartilage interface. This work demonstrates the possibility to form polymer-apatite composites with a well-defined hierarchical structure throughout its macroscopic volume, which is crucial for the development of mechanically optimized materials for applications such as bone and osteochondral implants.
Spray Deposition Synthesis of Locally Ordered Mesoporous Polycrystalline Titania Films at Low Temperature G Símonarson, A Lotsari, AEC Palmqvist Molecules 27 (1), 303 , 2022 2022 Citations: 2
Growth model for high-Al containing CVD TiAlN coatings on cemented carbides using intermediate layers of TiN MB Hassine, HO Andrén, AHS Iyer, A Lotsari, O Bäcke, D Stiens, ... Surface and Coatings Technology 421, 127361 , 2021 2021 Citations: 38
An imidazolium ionic liquid as effective structure-directing agent for the fabrication of silica thin films with vertically aligned nanochannels S Vavra, N Vilà, A Lotsari, A Walcarius, A Martinelli Microporous and Mesoporous Materials, 110407 , 2020 2020 Citations: 12
Fast charging negative electrodes based on anatase titanium dioxide beads for highly stable Li-ion capacitors G Calcagno, A Lotsari, A Dang, S Lindberg, AEC Palmqvist, A Matic, ... Materials Today Energy 16, 100424 , 2020 2020 Citations: 27
Electrochemical and structural characterization of lithiation in spray deposited ordered mesoporous titania as an anode for Li ion batteries G Simonarson, G Calcagno, A Lotsari, AEC Palmqvist RSC advances 10 (34), 20279-20287 , 2020 2020 Citations: 3
Dynamic nanocellulose networks for thermoset-like yet recyclable plastics with a high melt stiffness and creep resistance A Peterson, I Ostergren, A Lotsari, A Venkatesh, J Thunberg, A Strom, ... Biomacromolecules 20 (10), 3924-3932 , 2019 2019 Citations: 23
Silica-based diffusion probes for use in FRAP and NMR-diffusometry M Pihl, K Kolman, A Lotsari, M Ivarsson, E Schüster, N Lorén, R Bordes Journal of Dispersion Science and Technology 40 (4), 555-562 , 2019 2019 Citations: 10
Evolution of the polymorph selectivity of titania formation under acidic and low-temperature conditions G Símonarson, S Sommer, A Lotsari, B Elgh, BB Iversen, AEC Palmqvist ACS omega 4 (3), 5750-5757 , 2019 2019 Citations: 11
Transformation of amorphous calcium phosphate to bone-like apatite A Lotsari, AK Rajasekharan, M Halvarsson, M Andersson Nature communications 9 (1), 4170 , 2018 2018 Citations: 454
Bioinspired structural hierarchy within macroscopic volumes of synthetic composites AK Rajasekharan, A Lotsari, V Lutz‐Bueno, M Liebi, M Andersson Advanced healthcare materials 7 (18), 1800466 , 2018 2018 Citations: 15
Effect of compositional interlayers on the vertical electrical conductivity of Si-doped AlN/GaN distributed Bragg reflectors grown on SiC E Hashemi, F Hjort, M Stattin, T Ive, O Bäcke, A Lotsari, M Halvarsson, ... Applied Physics Express 10 (5), 055501 , 2017 2017 Citations: 7
Publications in journals OC Haenssler, MF Wieghaus, A Kostopoulos, G Doundoulakis, ... JOURNAL OF APPLIED PHYSICS 119, 224305 , 2016 2016 Citations: 22
A study of the piezoelectric properties of semipolar GaN/AlN quantum dots TD Young, G Jurczak, A Lotsari, GP Dimitrakopulos, P Komninou, ... physica status solidi (b) 252 (10), 2296-2303 , 2015 2015 Citations: 5
Direct spontaneous growth and interfacial structural properties of inclined GaN nanopillars on r-plane sapphire A Adikimenakis, A Lotsari, GP Dimitrakopulos, T Kehagias, KE Aretouli, ... Journal of Applied Physics 117 (24) , 2015 2015 Citations: 3
Angular-dependent Raman study of a-and s-plane InN K Filintoglou, M Katsikini, J Arvanitidis, D Christofilos, A Lotsari, ... Journal of Applied Physics 117 (7) , 2015 2015 Citations: 4
Structural anisotropic properties of a-plane GaN epilayers grown on r-plane sapphire by molecular beam epitaxy A Lotsari, T Kehagias, G Tsiakatouras, K Tsagaraki, M Katsikini, ... Journal of Applied Physics 115 (21) , 2014 2014 Citations: 18
Influence of defect characteristics on the nanoindentation response of a ‐plane GaN thin films P Kavouras, A Lotsari, T Kehagias, A Georgakilas, P Komninou, ... physica status solidi (a) 210 (1), 213-217 , 2013 2013 Citations: 3
Structure and interfacial properties of semipolar s ‐plane (1‐101) InN grown on r ‐plane sapphire GP Dimitrakopulos, A Lotsari, T Kehagias, A Ajagunna, A Georgakilas, ... physica status solidi (a) 210 (1), 199-203 , 2013 2013 Citations: 2
Structure and strain state of polar and semipolar InGaN quantum dots T Koukoula, A Lotsari, T Kehagias, GP Dimitrakopulos, I Häusler, A Das, ... Applied surface science 260, 7-12 , 2012 2012 Citations: 9
Structural characterization of InN epilayers grown on r ‐plane sapphire by plasma‐assisted MBE A Lotsari, GP Dimitrakopulos, T Kehagias, AO Ajagunna, E Iliopoulos, ... physica status solidi c 9 (3‐4), 534-537 , 2012 2012 Citations: 4
MOST CITED SCHOLAR PUBLICATIONS
Transformation of amorphous calcium phosphate to bone-like apatite A Lotsari, AK Rajasekharan, M Halvarsson, M Andersson Nature communications 9 (1), 4170 , 2018 2018.0 Citations: 454
Growth model for high-Al containing CVD TiAlN coatings on cemented carbides using intermediate layers of TiN MB Hassine, HO Andrén, AHS Iyer, A Lotsari, O Bäcke, D Stiens, ... Surface and Coatings Technology 421, 127361 , 2021 2021.0 Citations: 38
The defect character of GaN growth on r-plane sapphire J Smalc-Koziorowska, G Tsiakatouras, A Lotsari, A Georgakilas, ... Journal of Applied Physics 107 (7) , 2010 2010.0 Citations: 35
Fast charging negative electrodes based on anatase titanium dioxide beads for highly stable Li-ion capacitors G Calcagno, A Lotsari, A Dang, S Lindberg, AEC Palmqvist, A Matic, ... Materials Today Energy 16, 100424 , 2020 2020.0 Citations: 27
Morphology and strain of self-assembled semipolar GaN quantum dots in (112¯ 2) AlN GP Dimitrakopulos, E Kalesaki, J Kioseoglou, T Kehagias, A Lotsari, ... Journal of Applied Physics 108 (10) , 2010 2010.0 Citations: 26
Improved luminescence and thermal stability of semipolar (11-22) InGaN quantum dots A Das, GP Dimitrakopulos, Y Kotsar, A Lotsari, T Kehagias, P Komninou, ... Applied Physics Letters 98 (20) , 2011 2011.0 Citations: 24
Dynamic nanocellulose networks for thermoset-like yet recyclable plastics with a high melt stiffness and creep resistance A Peterson, I Ostergren, A Lotsari, A Venkatesh, J Thunberg, A Strom, ... Biomacromolecules 20 (10), 3924-3932 , 2019 2019.0 Citations: 23
Publications in journals OC Haenssler, MF Wieghaus, A Kostopoulos, G Doundoulakis, ... JOURNAL OF APPLIED PHYSICS 119, 224305 , 2016 2016.0 Citations: 22
Metal-containing amorphous carbon (aC: Ag) and AlN (AlN: Ag) metallo-dielectric nanocomposites GM Matenoglou, H Zoubos, A Lotsari, CE Lekka, P Komninou, ... Thin Solid Films 518 (5), 1508-1511 , 2009 2009.0 Citations: 21
Structural anisotropic properties of a-plane GaN epilayers grown on r-plane sapphire by molecular beam epitaxy A Lotsari, T Kehagias, G Tsiakatouras, K Tsagaraki, M Katsikini, ... Journal of Applied Physics 115 (21) , 2014 2014.0 Citations: 18
Interfacial structure of semipolar AlN grown on m ‐plane sapphire by MBE T Kehagias, L Lahourcade, A Lotsari, E Monroy, GP Dimitrakopulos, ... physica status solidi (b) 247 (7), 1637-1640 , 2010 2010.0 Citations: 16
Bioinspired structural hierarchy within macroscopic volumes of synthetic composites AK Rajasekharan, A Lotsari, V Lutz‐Bueno, M Liebi, M Andersson Advanced healthcare materials 7 (18), 1800466 , 2018 2018.0 Citations: 15
Morphology and origin of V-defects in semipolar (11–22) InGaN A Lotsari, A Das, T Kehagias, Y Kotsar, E Monroy, T Karakostas, ... Journal of crystal growth 339 (1), 1-7 , 2012 2012.0 Citations: 14
An imidazolium ionic liquid as effective structure-directing agent for the fabrication of silica thin films with vertically aligned nanochannels S Vavra, N Vilà, A Lotsari, A Walcarius, A Martinelli Microporous and Mesoporous Materials, 110407 , 2020 2020.0 Citations: 12
Evolution of the polymorph selectivity of titania formation under acidic and low-temperature conditions G Símonarson, S Sommer, A Lotsari, B Elgh, BB Iversen, AEC Palmqvist ACS omega 4 (3), 5750-5757 , 2019 2019.0 Citations: 11
Silica-based diffusion probes for use in FRAP and NMR-diffusometry M Pihl, K Kolman, A Lotsari, M Ivarsson, E Schüster, N Lorén, R Bordes Journal of Dispersion Science and Technology 40 (4), 555-562 , 2019 2019.0 Citations: 10
Structure and strain state of polar and semipolar InGaN quantum dots T Koukoula, A Lotsari, T Kehagias, GP Dimitrakopulos, I Häusler, A Das, ... Applied surface science 260, 7-12 , 2012 2012.0 Citations: 9
Structural properties of semipolar InGaN/GaN quantum dot superlattices grown by plasma-assisted MBE A Lotsari, GP Dimitrakopulos, T Kehagias, A Das, E Monroy, P Komninou Microelectronic engineering 90, 108-111 , 2012 2012.0 Citations: 9
Structure, stability and mechanical performance of AlN: Ag nanocomposite films A Lotsari, GP Dimitrakopulos, T Kehagias, P Kavouras, H Zoubos, ... Surface and Coatings Technology 204 (12-13), 1937-1941 , 2010 2010.0 Citations: 9
Transformation of amorphous calcium phosphate to bone-like apatite, Nat. Commun. 9 (2018) 4170 A Lotsari, AK Rajasekharan, M Halvarsson, M Andersson Citations: 9
