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  • 1.
    Akhtar, Farid
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Rehman, Yaser
    Department of Metallurgical and Materials Engineering, University of Engineering and Technology Lahore, Pakistan.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    A study of the sintering of diatomaceous earth to produce porous ceramic monolithswith bimodal porosity and high strength2010In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 201, p. 253-257Article in journal (Refereed)
    Abstract [en]

    Diatomite powder, a naturally occurring porous raw material, was used to fabricate ceramic materials withbimodal porosity and high strength. The effect of the sintering temperature on the density and porosity ofdry pressed diatomite green bodies was evaluated using mercury porosimetry and water immersionmeasurements. It was found that the intrinsic porosity of the diatomite particles with a pore size around0.2 μm was lost at sintering temperatures above 1200 °C. Maintaining the sintering temperature at around1000 °C resulted in highly porous materials that also displayed a high compressive strength. Microstructuralstudies by scanning electron microscopy and energy-dispersive X-ray analysis suggested that the porecollapse was facilitated by the presence of low melting impurities like Na2O and K2O.

  • 2.
    Andersson, Linnéa
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Jones, Anthony C.
    Knackstedt, Mark A.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Permeability, pore connectivity and critical pore throat control of expandable polymeric sphere templated macroporous alumina2011In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 59, no 3, p. 1239-1248Article in journal (Refereed)
    Abstract [en]

    We have regulated the permeability in macroporous alumina materials by manipulating the connectivity of the pore phase and the sizes of the smallest constrictions between connected pores. Templating with particle-coated expandable polymeric spheres (EPS) significantly increased the fraction of isolated pore clusters, and reduced both the sizes and the number of connections with neighboring pores, as determined by three-dimensional evaluation with X-ray micro-computed tomography. The stable particle coating, applied onto the EPS surfaces using polyelectrolyte multilayers, reduced the volume expansion and the coalescence of the EPS at elevated temperatures, which reduced the simulated permeability by as much as two orders of magnitude compared to templating with uncoated EPS in materials of similar porosities. We show that the Katz-Thompson model accurately predicts the permeability for the macroporous alumina materials with porosities of 46-76%. This suggests that the permeability to fluid flow in these materials is governed by the smallest constrictions between connected pores: the critical pore throat diameter.

  • 3.
    Andersson, Linnéa
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Jones, Anthony C.
    Department of Applied Mathematics, Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 0200, Australia.
    Knackstedt, Mark A.
    Department of Applied Mathematics, Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 0200, Australia.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Three-dimensional structure analysis by X-ray micro-computed tomography of macroporous alumina templated with expandable microspheres2010In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 30, no 12, p. 2547-2554Article in journal (Refereed)
    Abstract [en]

    The three-dimensional (3D) structures of macroporous alumina, produced by a novel method that combines gel casting with expandable polymericmicrospheres as a sacrificial templating material, have been characterised by X-ray micro-computed tomography (µ-CT). The grey-scale intensitytomogram data produced by the X-ray µ-CT was segmented into porous and solid phases and the individual pores were identified. We comparedtwo-dimensional slices of the analysed data with the corresponding scanning electron microscopy images and showed that the structural featuresof the pores were well reproduced in the X-ray µ-CT images. 3D visualisations of the pore structure and the pore network were also shown. Theopen porosity obtained from X-ray µ-CT corresponded well with the porosity derived from mercury porosimetry for pores larger than the voxeldimension (3 µm). The quantitative analysis also yielded information on the spatial variations in porosity and the number of connected neighboursof pores. The 3D data was used to relate the calculated permeability to the open porosity.

  • 4.
    Apostolopoulou Kalkavoura, Varvara
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Fijoł, Natalia
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lombardo, Salvatore
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ruiz-Caldas, Maria-Ximena
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Mathew, Aji P.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Trash to treasure: 3D printing of waste-based polycotton composite for the production of water filters and commodity productsManuscript (preprint) (Other academic)
    Abstract [en]

    The recycling of polycotton without separating its constituents for high-performance applications has not yet been fully investigated. In this study, we propose a simple and efficient method involving one-pot, 2, 2, 6, 6 – tetramethylpiperdine-1-oxyl (TEMPO) - oxidation of post-consumer polycotton textile waste followed by lenient mechanical fibrillation. Successful chemical modification of the polycotton waste was confirmed by the Fourier-transform infrared (FT-IR) spectroscopy measurements, in which the presence of carboxyl groups introduced during the TEMPO-oxidation was observed. Moreover, the waste-based pellets were single-screw extruded into 3D printing filaments, which were further processed via desktop Fused Deposition Modelling (FDM) 3D printer.

    FDM processing was carried out without hindrance. The textile-based filament was used for the fabrication of a variety of high surface-finish quality models, which presented diverse geometries and porosity architectures. The versatility of the developed 3D printed models was demonstrated through both, their potential to be utilized as fashion accessories, and by evaluating their performance in water treatment applications. Taking advantage of the introduction of negatively charged carboxylic groups onto the polycotton-based materials, which was expected to facilitate the electrostatic interactions with positively charged species, the 3D printed filters were tested for removal of cationic dye methylene blue (MB) from water in a batch adsorption study. The adsorption followed Langmuir model, with a maximim adsorption capacity of 3 µmol/g. 

    Overall, this work presents a novel approach for the upcycling of polycotton waste into functional filament suitable for a variety of 3D printing, and further, engineering applications. The development of composite filaments and their mechanical and adsorption properties pave the way for future research within valorisation of textile-based waste.

  • 5.
    Apostolopoulou-Kalkavoura, Varvara
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Hu, Shiqian
    Lavoine, Nathalie
    Garg, Mohit
    Linares, Mathieu
    Munier, Pierre
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Zozoulenko, Igor
    Shiomi, Junichiro
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Humidity-Dependent Thermal Boundary Conductance Controls Heat Transport of Super-Insulating Nanofibrillar Foams2021In: Matter, ISSN 2590-2393, E-ISSN 2590-2385, Vol. 4, no 1, p. 276-289Article in journal (Refereed)
    Abstract [en]

    Cellulose nanomaterial (CNM)-based foams and aerogels with thermal conductivities substantially below the value for air attract significant interest as super-insulating materials in energy-efficient green buildings. However, the moisture dependence of the thermal conductivity of hygroscopic CNM-based materials is poorly understood, and the importance of phonon scattering in nanofibrillar foams remains unexplored. Here, we show that the thermal conductivity perpendicular to the aligned nanofibrils in super-insulating ice-templated nanocellulose foams is lower for thinner fibrils and depends strongly on relative humidity (RH), with the lowest thermal conductivity (14 mW m−1 K−1) attained at 35% RH. Molecular simulations show that the thermal boundary conductance is reduced by the moisture-uptake-controlled increase of the fibril-fibril separation distance and increased by the replacement of air with water in the foam walls. Controlling the heat transport of hygroscopic super-insulating nanofibrillar foams by moisture uptake and release is of potential interest in packaging and building applications.

  • 6. Atluri, Rambabu
    et al.
    Iqbal, Muhammad Naeem
    Bacsik, Zoltan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Villaescusa, Luis Angel
    Garcia-Bennett, Alfonso E.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry. alfonso@mmk.su.se.
    Self-Assembly Mechanism of Folate-Templated Mesoporous Silica2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 38, p. 12003-12012Article in journal (Refereed)
    Abstract [en]

    A method to form ordered mesoporous silica based on the use of folate supramolecular templates has been developed. Evidence based on in situ small-angle X-ray scattering (SAXS), electron microscopy, infrared spectroscopy, and in situ conductivity measurements are used to investigate the organic inorganic interactions and synthesis mechanism. The behavior of folate molecules in solution differs distinctively from that of surfactants commonly used for the preparation of ordered mesoporous silica phases, notably with the absence of a critical micellar concentration. In situ SAXS studies reveal fluctuations in X-ray scattering intensities consistent with the condensation of the silica precursor surrounding the folate template and the growth of the silica mesostructure in the initial stages. High-angle X-ray diffraction shows that the folate template is well-ordered within the pores even after a few minutes of synthesis. Direct structural data for the self-assembly of folates into chiral tetramers within the pores of mesoporous silica provide evidence for the in register stacking of folate tetramers, resulting in a chiral surface of rotated tetramers, with a rotation angle of 30 degrees. Additionally, the self-assembled folates within pores were capable of adsorbing a considerable amount of CO2 gas through the cavity space of the tetramers. The study demonstrates the validity of using a naturally occurring template to produce relevant and functional mesoporous materials.

  • 7.
    Aziz, Baroz
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Bacsik, Zoltán
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Quantification of chemisorption and physisorption of carbon dioxide on porous silica modified by propylamines: Effect of amine density2012In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 159, p. 42-49Article in journal (Refereed)
    Abstract [en]

    Detailed molecular aspects of carbon dioxide sorption on porous silica with different amounts of tethered and cross-linked n-propylamine groups were investigated. Infrared spectroscopy was applied to directly quantify physisorbed and chemisorbed CO2 on the amine modified silicas. The fractions of physisorbed CO2 and various chemisorbed species were determined as functions of CO2 pressure and the amine density on the modified silica. Physisorbed CO2 was a minor portion of the total CO2 uptake at low pressures, but it’s contribution increased to ∼35% at 1 bar of CO2 when the propylamine surface density was low or medium (0.87-1.67 NH2/nm2). Chemisorption of CO2 dominated when the propylamine content was high (2.74 NH2/nm2). The quantities of propylammonium propylcarbamate ion pairs increased with increasing propylamine content. At low or medium amine surface densities (0.87-1.67 NH2/nm2) this increase was approximately proportional to the amine density, but the quantity of ion pairs increased very significantly when the propylamine content was high (2.74 NH2/nm2). This dependency on amine density is consistent with the idea that a sufficiently close proximity of propylamine groups allows a formation of ion pairs. The relative fractions of carbamic acid and silylpropylcarbamate were significant for materials on which ion pairs could not form. Furthermore, the quantities of carbamic acid increased with increasing amine densities suggesting that the ion pairs have a role to stabilize the labile carbamic acid through hydrogen bonds.

  • 8. Cavalcante, Larissa Lopes
    et al.
    Barbolini, Natasha
    Stockholm University, Faculty of Science, The Bolin Centre for Climate Research (together with KTH & SMHI). University of Bergen and Bjerknes Centre for Climate Research, Norway.
    Bacsik, Zoltán
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Vajda, Vivi
    Analysis of fossil plant cuticles using vibrational spectroscopy: A new preparation protocol2023In: Review of Palaeobotany and Palynology, ISSN 0034-6667, E-ISSN 1879-0615, Vol. 316, article id 104944Article in journal (Refereed)
    Abstract [en]

    Analyses for organic fingerprints on fossilized plant cuticles and pollen hold valuable chemotaxonomic and palaeoclimatic information, and are thus becoming more utilized by palaeobotanists. Plant cuticle and pollen composition are generally analyzed after standard treatments with several chemical reagents for mineral and mesophyll removal. However, the potential alterations on the fossil composition caused by the different cleaning reagents used are still poorly understood. We tested the effects of commonly used palaeobotanical processing methods on the spectra of fossilized cuticles from successions of Late Triassic to Early Jurassic age, including the gymnosperms Lepidopteris , Ginkgoites , Podozamites , Ptilozamites and Pterophyllum astartense. Our study shows that standard chemical processing caused chemical alterations that might lead to erroneous interpretation of the infrared (IR) spectra. The difference in pH caused by HCl induces changes in the proportion between the two bands at similar to 1720 and 1600 cm(-1) (carboxylate and C-C stretch of aromatic compounds) indicating that the band at similar to 1610 cm(-1) at least partially corresponds to carboxylate instead of C-C stretch of aromatic compounds. Interestingly, despite being used in high concentration, HF did not cause changes in the chemical composition of the cuticles. The most alarming changes were caused by the use of Schulze's solution, which resulted in the addition of both NO2 and (O)NO2 compounds in the cuticle. Consequently, a new protocol using H2CO3 , HF, and H2O2 for preparing fossil plant cuticles aimed for chemical analyses is proposed, which provides an effective substitute to the conventional methods. In particular, a less aggressive and more sustainable alternative to Schulze's solution is shown to be hydrogen peroxide, which causes only minor alteration of the fossil cuticle's chemical composition. Future work should carefully follow protocols, having in mind the impacts of different solutions used to treat leaves and other palaeobotanical material such as palynomorphs with aims to enable the direct comparison of spectra obtained in different studies.

  • 9.
    Cheung, Ocean
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Bacsik, Zoltán
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Krokidas, Panagiotis
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Mace, Amber
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
    Laaksonen, Aatto
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    K+ Exchanged Zeolite ZK-4 as a Highly Selective Sorbent for CO22014In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, no 32, p. 9682-9690Article in journal (Refereed)
    Abstract [en]

    Adsorbents with high capacity and selectivity for adsorption of CO2 are currently being investigated for applications in adsorption-driven separation of CO2 from flue gas. An adsorbent with a particularly high CO2-over-N-2 selectivity and high capacity was tested here. Zeolite ZK-4 (Si:Al similar to 1.3:1), which had the same structure as zeolite A (LTA), showed a high CO2 capacity of 4.85 mmol/g (273 K, 101 kPa) in its Na+ form. When approximately 26 at % of the extraframework cations were exchanged for K+ (NaK-ZK-4), the material still adsorbed a large amount of CO2 (4.35 mmol/g, 273 K, 101 kPa), but the N-2 uptake became negligible (<0.03 mmol/g, 273 K, 101 kPa). The majority of the CO2 was physisorbed on zeolite ZK-4 as quantified by consecutive volumetric adsorption measurements. The rate of physisorption of CO2 was fast, even for the highly selective sample. The molecular details of the sorption of CO2 were revealed as well. Computer modeling (Monte Carlo, molecular dynamics simulations, and quantum chemical calculations) allowed us to partly predict the behavior of fully K+ exchanged zeolite K-ZK-4 upon adsorption of CO2 and N-2 for Si:Al ratios up to 4:1. Zeolite K-ZK-4 with Si:Al ratios below 23:1 restricted the diffusion of CO2 and N-2 across the cages. These simulations could not probe the delicate details of the molecular sieving of CO2 over N-2. Still, this study indicates that zeolites NaK-ZK-4 and K-ZK-4 could be appealing adsorbents with high CO2 uptake (similar to 4 mmol/g, 101 kPa, 273 K) and a kinetically enhanced CO2-over-N-2 selectivity.

  • 10.
    Cheung, Ocean
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Jie, Su
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zoltán, Bacsik
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Jing, Li
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Samain, Louise
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Xiaodong, Zou
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Niklas, Hedin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    CO2 selective NaMg-CTS-1 and its structural formation from the titanium silicate based molecule sieve NaMg-ETS-4 upon dehydration2014In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 198, p. 63-73Article in journal (Other academic)
    Abstract [en]

    A range of titanium silicates (ETS-4 and CTS-1) with interesting gas separation properties were studied as CO2 adsorbents. Some of these adsorbents, in particular NaMg-CTS-1, showed the ability to selectively adsorb CO2-over-N2. Partially exchanged NaM-ETS-4 (M = Mg, Ca, Sr and Ba) were synthesised in the Na+ form and ion exchanged with group 2 cations. All but NaBa-ETS-4 transformed into their CTS-1 counterparts, when these partially exchanged Na-ETS-4 were dehydrated. The transformation from ETS-4 to CTS-1 was monitored and studied extensively using diffraction and spectroscopic techniques. Powder X-ray diffraction allowed us to follow the changes of the unit cell parameters occurred at different temperatures. We combined high energy X-ray total scattering (analysed by pair distribution functions – PDF analysis), electron diffraction, infrared, Raman and Nuclear Magnetic Resonance (NMR) spectroscopy to study the transformation of ETS-4 to CTS-1. We understood that under dehydration steps, there was significant disruption to the Ti–O–Ti chain along the b-axis, which occurred concurrently with the distortion of the double 3-rings alongside of these chains. These changes were partly responsible for the contraction of the ETS-4 framework (and successive transformation to CTS-1). The new information allowed us to understand the interesting structures and sorption properties of these adsorbents

  • 11.
    Cheung, Ocean
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Zoltán, Bacsik
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Panagiotis, Krokidas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Niklas, Hedin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    CO2 separation properties of high silicon zeolite NaK-ZK-4 with Si:Al up to 2.8:1Manuscript (preprint) (Other academic)
  • 12.
    Cheung, Ocean
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Zoltán, Bacsik
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Petr, Vasiliev
    Niklas, Hedin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Carbon dioxide separation from methane on highly selective ion exchanged zeolite NaKCsA – a possible sorbent for biogas upgradingManuscript (preprint) (Other academic)
  • 13.
    Di, Andi
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Xu, Jipeng
    Zinn, Thomas
    Sztucki, Michael
    Deng, Wentao
    Ashok, Anumol
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lian, Cheng
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Tunable Ordered Nanostructured Phases by Co-assembly of Amphiphilic Polyoxometalates and Pluronic Block Copolymers2023In: Nano Letters, ISSN 1530-6984, E-ISSN 1530-6992, Vol. 23, no 5, p. 1645-1651Article in journal (Refereed)
    Abstract [en]

    The assembly of polyoxometalate (POM) metal–oxygen clusters into ordered nanostructures is attracting a growing interest for catalytic and sensing applications. However, assembly of ordered nanostructured POMs from solution can be impaired by aggregation, and the structural diversity is poorly understood. Here, we present a time-resolved small-angle X-ray scattering (SAXS) study of the co-assembly in aqueous solutions of amphiphilic organo-functionalized Wells-Dawson-type POMs with a Pluronic block copolymer over a wide concentration range in levitating droplets. SAXS analysis revealed the formation and subsequent transformation with increasing concentration of large vesicles, a lamellar phase, a mixture of two cubic phases that evolved into one dominating cubic phase, and eventually a hexagonal phase formed at concentrations above 110 mM. The structural versatility of co-assembled amphiphilic POMs and Pluronic block copolymers was supported by dissipative particle dynamics simulations and cryo-TEM. 

  • 14.
    Eden, Mattias
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Physical Chemistry.
    Grins, Jekabs
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Inorganic Chemistry.
    Jansson, Kjell
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Al and O substitutions in BaS-phases, Ba2AlxSi12-xN16-xO2+x: A TEM, XRD and solid-state NMR study2008In: Solid State Sciences, ISSN 1293-2558, E-ISSN 1873-3085, Vol. 10, no 1, p. 50-60Article in journal (Refereed)
    Abstract [en]

    In a series of Ba-based oxonitrido-silicate S-phases (Ba2AlxSi12-xN16-xO2+x) spanning a compositional range up to x approximate to 3, we examine the incorporation of Al and O by Si-29 and Al-27 magic-angle spinning (MAS) solid state nuclear magnetic resonance (NMR) and Al-27 triple-quantum MAS (3QMAS). The 3QMAS spectra reveal Al-27 signals from two distinct structural environments, assigned to AlN4 or AlN3O tetrahedra, respectively, and with their relative amounts depending on the S-phase substitution parameter x. Si-29 NMR show variable fractions of SiN4 and SiN3O environments. The NMR results accord overall with a structural substitution model for which O enters at one crystallographic position (occupied according to N4-xOx), in conjunction with a random Al for Si substitution at two distinct crystallographic positions. This leads to S-phase frameworks built from SiN4, SiN3O, AlN4 and AlN3O tetrahedra.

  • 15. Enrico, Alessandro
    et al.
    Buchmann, Sebastian
    De Ferrari, Fabio
    Lin, Yunfan
    Wang, Yazhou
    Yue, Wan
    Martensson, Gustaf
    Stemme, Göran
    Hamedi, Mahiar Max
    Niklaus, Frank
    Herland, Anna
    Zeglio, Erica
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Cleanroom-Free Direct Laser Micropatterning of Polymers for Organic Electrochemical Transistors in Logic Circuits and Glucose Biosensors2024In: Advanced Science, E-ISSN 2198-3844Article in journal (Refereed)
    Abstract [en]

    Organic electrochemical transistors (OECTs) are promising devices for bioelectronics, such as biosensors. However, current cleanroom-based microfabrication of OECTs hinders fast prototyping and widespread adoption of this technology for low-volume, low-cost applications. To address this limitation, a versatile and scalable approach for ultrafast laser microfabrication of OECTs is herein reported, where a femtosecond laser to pattern insulating polymers (such as parylene C or polyimide) is first used, exposing the underlying metal electrodes serving as transistor terminals (source, drain, or gate). After the first patterning step, conducting polymers, such as poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), or semiconducting polymers, are spin-coated on the device surface. Another femtosecond laser patterning step subsequently defines the active polymer area contributing to the OECT performance by disconnecting the channel and gate from the surrounding spin-coated film. The effective OECT width can be defined with high resolution (down to 2 mu m) in less than a second of exposure. Micropatterning the OECT channel area significantly improved the transistor switching performance in the case of PEDOT:PSS-based transistors, speeding up the devices by two orders of magnitude. The utility of this OECT manufacturing approach is demonstrated by fabricating complementary logic (inverters) and glucose biosensors, thereby showing its potential to accelerate OECT research. Ultrafast focused femtosecond laser has been introduced for the direct micropatterning of organic electrochemical transistors (OECTs), providing high resolution (2 mu m), selective cleanroom-free patterning of insulating and conjugated polymer layers while preserving device operation, and high flexibility in device design. The approach has been validated in the fabrication of complementary inverters and glucose biosensors.image

  • 16.
    Eriksson, Mirva
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Department of Materials Chemistry.
    Liu, Yi
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Department of Materials Chemistry.
    Hu, Jiangfeng
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Department of Materials Chemistry.
    Gao, Lian
    State Key Lab of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai.
    Nygren, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Department of Materials Chemistry.
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Department of Materials Chemistry.
    Transparent hydroxyapatite nanoceramics by high pressure spark plasma sintering at the minimized sintering temperatureManuscript (preprint) (Other academic)
    Abstract [en]

    For direct observation of the bio-interfacial reactions with improved spatial and temporal resolution by confocal microscopy transparent hydroxyapatite nanoceramics are demanded. The aim of the present study was to, through detailed kinetics study and micostructural characterization, define a processing window within which transparent HAp nanoceramics can be produced by spark plasma sintering of dry powders.  A lab-made hydrothermally processed bulky powder composed of loosely aggregated nanorods and a commercial granulated-powder composed of irregular shaped nanorods were tested.  The use of a high pressure cell allows the application of pressure up to 500 MPa. It was found that applying of high pressure is beneficial for widen up the processing window for attaining dense HAp ceramics with nano grained microstructure. The high transparency of HAp nanoceramics obtained in this study is ascribed to the high density and homogeneous nano-structure achieved besides the unique intrinsic optical properties of the HAp crystal, i.e. its low refractive index and very small birefringence. Achieving full densification at the minimized sintering temperature allows for the first time the preparation of transparent HAp nanoceramics with stoichiometric composition, i.e. avoiding the loss of water that commonly encountered  during the conventional ways of sintering.

  • 17.
    Eriksson, Mirva
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Department of Materials Chemistry.
    Salamon, David
    Nygren, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Department of Materials Chemistry.
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Department of Materials Chemistry.
    Spark plasma sintering and deformation of Ti-TiB2 composites.2008In: Materials Science & Engineering, A: Structural Materials: Properties, Microstructure and Processing, ISSN 0921-5093, Vol. 1-2, no A475, p. 101-104Article in journal (Refereed)
    Abstract [en]

    Spark plasma sintering (SPS) was used to investigate the densification and deformation behaviour of Ti–TiB2 composites. Fully densified samples were prepared with Ti addition larger than 5%. The prepared composites can be deformed under compression at 1700 °C to achieve a strain of 50% without cracking. At lower temperatures, cracks were initiated due to low ductility of TiB2 and low content of Ti. During the sintering and deformation, TiB is formed via a reaction between Ti and TiB2. To elucidate the formation mechanism of TiB in the SPS process, reactive sintering of TiB using element precursors was also performed. Fully dense samples were prepared but it was not possible to prepare pure uniphase TiB. The reactive sintering resulted in the formation of TiB and TiB2 mixtures at low temperatures and a mixture of TiB2 and Ti3B4 at high temperature

  • 18.
    Eriksson, Mirva
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Yan, Haixue
    School of Engineering and Materials Science, Queen Mary University of London,.
    Nygren, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Reece, Mike J
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Low temperature consolidated lead-free ferroelectric niobateceramics with improved electrical properties2010In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 25, no 2, p. 240-247Article in journal (Refereed)
    Abstract [en]

    There is a concerted effort to develop lead-free piezoelectric ceramics. ((Na0.5K0.5)NbO3 based ceramics have good electrical properties, and are a potential replacement material for lead zirconate titanate piezoelectric ceramics. In this work a commercial powder based on (Na0.5K0.5)NbO3 with an initial particle size of 260 nm was consolidated by plasma sintering (SPS). To avoid volatilization, high mechanical pressures were used to minimize the densification temperature. It was found that under a uniaxial pressure of 100 MPa, fully densified compacts can be prepared at 850. Ceramics densified at such a low temperature demonstrate an unusually high remanent polarization (30 mC/cm2) and high d33 (146 pC/N). The improved ferroelectric properties are ascribed to the homogeneous, dense, and submicron grained microstructure achieved.

  • 19.
    Eriksson, Mirva
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Department of Materials Chemistry.
    Yan, Haixue
    School of Engineering and Materials Science and Nanoforce Technology Ltd, Queen Mary University of London, London, United Kingdom.
    Viola, Giuseppe
    School of Engineering and Materials Science and Nanoforce Technology Ltd, Queen Mary University of London, London, United Kingdom.
    Ning, Huanpo
    School of Engineering and Materials Science and Nanoforce Technology Ltd, Queen Mary University of London, London, United Kingdom.
    Gruner, Daniel
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Department of Materials Chemistry.
    Nygren, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Department of Materials Chemistry.
    Reece, Mike
    School of Engineering and Materials Science and Nanoforce Technology Ltd, Queen Mary University of London, London, United Kingdom.
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Department of Materials Chemistry.
    Effect of grain size on ferroelectric domain and electrical properties of submicron sized sodium potassium niobate ceramicsManuscript (preprint) (Other (popular science, discussion, etc.))
    Abstract [en]

    Piezoelectric ceramics of the composition Na0.5K0.5NbO3 (NKN) with grain sizes in the range of 0.2 - 1 mm were fabricated by Spark Plasma Sintering using normal pressure dies and a high pressure cell designed for pressures up to 500 MPa  with the purpose of investigating the effect of grain size on domain structures and electrical properties. Optimized processing conditions enabled ceramics of high densities (>99.5%TD) to be made at T≥850°C. It was found that domain size decreases with decreasing grain size and that non-180° ferroelectric domains walls were still visible in 200 nm sized grains. The room temperature dielectric constant firstly increased with decreasing grain size and then decreased in the low grain size regime. The materials with finer grain size displayed a broad ferro-paraelectric phase transition and a depression of the dielectric maximum at the Curie point. They also displayed an increase in the coercive field and approximately unchanged remnant polarization. The material sintered at 850°C represents a very good candidate for lead-free piezoelectric applications, because of its high piezoelectric constant (d33 = 160±2 pC/N).

  • 20.
    Faure, Bertrand
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Sæderup Lindeløv, Jesper
    Wahlberg, Michael
    Adkins, Nicholas
    Jackson, Phil
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Spray drying of TiO2 nanoparticles into redispersible granules2010In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 203, no 2, p. 384-388Article in journal (Refereed)
    Abstract [en]

    We have demonstrated how titania nanoparticles can be spray-dried to produce redispersible granules. Theevaluation of different dispersants using rheology, particle size and electrokinetic measurements showedthat an anionic carboxylated polyelectrolyte, Dispex N40, was able to stabilize the primary aggregates of thetitania nanoparticles with a size of about 180 nm at an addition of 2.4% dry-weight basis over a relativelylarge pH-range. Transmission electron microscopy showed that the commercial P-25 titania nanopowdercould not be deagglomerated down to the individual crystallite size of 15–40 nm. Spherical granules with asize between 20 and 50 μm and a minimum amount of dusty fines could be produced by spray drying theaqueous titania dispersions in a configuration with internal bag filters. The granules could be completelydisintegrated and redispersed in water by ultrasonication into a stable suspension with a size distributionthat is identical to the as-received powder. The possibility to prepare redispersible nanoparticle granules byspray drying is a route to minimize the risk of airborne exposure and facilitate the handling of nanopowders.

  • 21. Fischer, Christian E.
    et al.
    Mink, Janos
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Hajba, Laszlo
    Bacsik, Zoltan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Nemeth, Csaba
    Mihaly, Judith
    Raith, Alexander
    Cokoja, Mirza
    Kuehn, Fritz E.
    Vibrational spectroscopic study of SiO2-based nanotubes2013In: Vibrational Spectroscopy, ISSN 0924-2031, E-ISSN 1873-3697, Vol. 66, p. 104-118Article in journal (Refereed)
    Abstract [en]

    Novel organic-inorganic hybrid nanotubes containing silica and ethane (EtSNT), ethylene (ESNT) and acetylene (ASNT) units, as well as brominated ESNT (Br-ESNT) and glycine-modified Br-ESNT (Gly-ESNT) have been studied by IR and Raman spectroscopy. The results are compared with the spectral features for conventional silica nanotubes (SNT) and amorphous silica. Bands peculiar to organic moieties have been detected and assigned. Assignment of the silicate backbone vibrations was based on the results of normal coordinate calculations. Furthermore, characteristic silicate, so-called 'nanotube' vibrations have been identified and their band positions have been summarized to serve as a future reference for such compounds. SiOSi antisymmetric stretchings were observed in the range 1000-1110 cm(-1), while the symmetric stretchings appeared between 760 and 960 cm(-1) for EtSNT, ESNT and Br-ESNT. Force constants have been refined for models of the repeating structure units: O3SiOSi(OSi)(3) for SNT and SiCHnCHnSi(OSi)(3) for organosilica nanotubes (n = 2, EtSNT: n = 1, ESNT and n = 0, ASNT). The calculated SiO stretching force constants were increased from 4.79 to 4.88 and 5.11 N cm(-1) for EtSNT, ESNT and ASNT, respectively. The force constants have been compared with those for several silicates and SiO bond length are predicted and discussed.

  • 22.
    García Mayo, Susana
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Synthesis of gold nanoparticles for rapid genotyping of M. tuberculosis using rolling circle amplification and nanoflare technology2017Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
    Abstract [en]

    Tuberculosis (TB) is an airborne disease caused by Mycobacterium tuberculosis, with an incidence in a quarter of the world population. Despite the scientific and technological advances, an effective diagnostic method has not yet been found that allows an early diagnosis and, also, to detect the strain present in the patient. The combination of nanotechnology with molecular diagnostics has shown promising advances offering new possibilities, such as the development of nanoflares. 

    Nanoflares represent a new class of molecular probes, composed of gold nanoparticles functionalized with a recognition sequence that can be amplified by rolling circle amplification (RCA) technique, producing a fluorescence signal. 

    This thesis focuses in the synthesis of gold nanoparticles, with different coatings and sizes, as well as their subsequent application in the preparation and optimization of nanoflares for the genotyping of synthetic M. tuberculosis targets using RCA technique. The different preparations of nanoflares have an impact in the assay sensitivity, showing two times increase in sensitivity for citrate-coated nanoparticles with respect to those coated with PEG. Furthermore, it was observed that the sensitivity is directly related to the synthesized particle size. 

    Sensitivity is also affected by the application of a purification post-treatment of the synthesis product. This post-treatment reduces the sensitivity of nanoflares by up to 37% but, by contrast, extends its useful life. 

    The results obtained are shown as a proof of concept for a future cost-effective, rapid and robust in situ diagnostic method that identifies the strain of tuberculosis present in the patient. 

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  • 23.
    Gebauer, Denis
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Gunawidjaja, Philips N.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
    Ko, J. Y. Peter
    Bacsik, Zoltan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Aziz, Baroz
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Liu, Lijia
    Hu, Yongfeng
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Sham, Tsun-Kong
    Edén, Mattias
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Proto-Calcite and Proto-Vaterite in Amorphous Calcium Carbonates2010In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 49, no 47, p. 8889-8891Article in journal (Refereed)
    Abstract [en]

    Amorphous order: Amorphous calcium carbonates (ACC) have an intrinsic structure relating to the crystalline polymorphs of calcite and vaterite. The proto-crystalline structures of calcite and vaterite (pc-ACC and pv-ACC) are analyzed by NMR (see picture), IR, and EXAFS spectroscopy, which shows that the structuring of ACC relates to the underlying pH-dependent equilibria.

  • 24.
    Gebauer, Denis
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Liu, Xingmin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Aziz, Baroz
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zhao, Zhe
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Porous tablets of crystalline calcium carbonate via sintering of amorphous nanoparticles2013In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 15, no 6, p. 1257-1263Article in journal (Refereed)
    Abstract [en]

    Porous tablets of crystalline calcium carbonate were formed upon sintering of a precursor powder of amorphous calcium carbonate (ACC) under compressive stress (20 MPa) at relatively low temperatures (120-400 degrees C), induced by pulsed direct currents. Infrared spectroscopy ascertained the amorphous nature of the precursor powders. At temperatures of 120-350 degrees C and rates of temperature increase of 20-100 degrees C min(-1), the nanoparticles of ACC transformed into crystallites of mainly aragonite, which is generally difficult to achieve using wet-chemicals under kinetic control. The amorphous precursor particles (similar to 10 nm) transformed into crystallites (similar to 30-50 nm) during sintering. Consistently, the specific surface areas of 140-160 m(2) g(-1) for the precursor particles were reduced to 10-20 m(2) g(-1) for the porous tablets. The porous network within the tablets consisted of fused aragonite and vaterite particles in a ratio of similar to 80 : 20. The fraction of aragonite to vaterite was invariant to the temperature and rate of temperature change used. The particle size increased only to a small amount on an increased rate of temperature change. At temperatures above 400 degrees C, porous tablets of calcite formed. The later transformation was under thermodynamic control, and led to a minor reduction of the specific surface area. The size of the crystallites remained small and the transformation to calcite appeared to be a solid-state transformation. Porous, template-and binder-free tablets of calcium carbonate could find applications in for example, biology or water treatment.

  • 25.
    Gebauer, Denis
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Oliynyk, Vitaliy
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Salajkova, Michaela
    Sort, Jordi
    Zhou, Qi
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Salazar-Alvarez, German
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    A transparent hybrid of nanocrystalline cellulose and amorphous calcium carbonate nanoparticles2011In: NANOSCALE, ISSN 2040-3364, Vol. 3, no 9, p. 3563-3566Article in journal (Refereed)
    Abstract [en]

    Nanocellulose hybrids are promising candidates for biodegradable multifunctional materials. Hybrids of nanocrystalline cellulose (NCC) and amorphous calcium carbonate (ACC) nanoparticles were obtained through a facile chemical approach over a wide range of compositions. Controlling the interactions between NCC and ACC results in hard, transparent structures with tunable composition, homogeneity and anisotropy.

  • 26.
    Gordeyeva, Korneliya
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Design, processing and properties of lightweight foams from cellulose nanofibers2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Foams are applied in many areas including thermal insulation of buildings, flotation devices, packaging, filters for water purification, CO2 sorbents and for biomedical devices. Today, the market is dominated by foams produced from synthetic, non-renewable polymers, which raises serious concerns for the sustainable and ecological development of our society. This thesis will demonstrate how lightweight foams based on nanocellulose can be processed and how the properties in both the wet and dry state can be optimized.

    Lightweight and highly porous foams were successfully prepared using a commercially available surface-active polyoxamer, Pluronic P123TM, cellulose nanofibers (CNFs), and soluble CaCO3 nanoparticles. The stability of wet and dry composite foams was significantly improved by delayed aggregation of the CNF matrix by gluconic acid-triggered dissolution of the CaCO3 nanoparticles, which generated a strong and dense CNF network in the foam walls. Drying the Ca2+-reinforced foam at 60 °C resulted in moderate shrinkage but the overall microstructure and pore/foam bubble size distribution were preserved after drying. The elastic modulus of Ca2+-reinforced composite foams with a density of 9 – 15 kg/m3 was significantly higher than fossil-based polyurethane foams.

    Lightweight hybrid foams have been prepared from aqueous dispersions of a surface-active aminosilane (AS) and CNF for a pH range of 10.4 – 10.8. Evaporative drying at a mild temperature (60 °C) resulted in dry foams with low densities (25 – 50 kg/m3) and high porosities (96 – 99%). The evaporation of water catalyzed the condensation of the AS to form low-molecular linear polymers, which contributed to the increase in the stiffness and strength of the CNF-containing foam lamella.

    Strong wet foams suitable for 3D printing were produced using methylcellulose (MC), CNFs and montmorillonite clay (MMT) as a filler and tannic acid and glyoxal as cross-linkers. The air-water interface of the foams was stabilized by the co-adsorption of MC, CNF and MMT. Complexation of the polysaccharides with tannic acid improved the foam stability and the viscoelastic properties of the wet foam for direct ink writing of robust cellular architectures. Glyoxal improved the water resistance and stiffened the lightweight material that had been dried at ambient pressure and elevated temperatures with minimum shrinkage. The highly porous foams displayed a specific Young’s modulus and yield strength that outperformed other bio-based foams and commercially available expanded polystyrene.

    Unidirectional freezing, freeze-casting, of nanocellulose dispersions produced cellular foams with high alignment of the rod-like nanoparticles in the freezing direction. Quantification of the alignment with X-ray diffraction showed high orientation of CNF and short and stiff cellulose nanocrystals (CNC).

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  • 27.
    Grüner, Daniel
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Shen, Zhijian James
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Ordered coalescence of nano-crystals during rapid solidification of ceramic melts2011In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 13, no 17, p. 5303-5305Article in journal (Refereed)
    Abstract [en]

    Rapid cooling of an aluminosilicate-zirconia melt after laser sintering results in the formation of zirconia nano-crystals and dendritic zirconia crystals embedded in a glass matrix. The nano-crystals act as building blocks for the formation of non-faceted secondary crystals. Several secondary crystals built from two or a few nano-crystals with perfect structural coherence across the interface have been observed. Thus, the earliest states of these secondary crystals have been preserved by rapid cooling. Crystal growth can be described by a mechanism, ordered coalescence, which is characterized by self-assembly of nano-crystals combined with atom-by-atom growth and links classical and non-classical crystallization.

  • 28.
    Hadi, Seyed Ehsan
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Davoodi, Saeed
    Oliaei, Erfan
    Morsali, Mohammad
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Åhl, Agnes
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nocerino, Elisabetta
    Wang, Fengyang
    Andersson, Matilda
    Luehder, Malwine
    Conceição, André L. C
    Sipponen, Mika H.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Berglund, Lars
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry. Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Lundell, Fredrik
    Comparing the production energy, structure and properties of TEMPO-Oxidized Lignocellulose and Cellulose Nanofibers FoamsManuscript (preprint) (Other (popular science, discussion, etc.))
  • 29.
    Hadi, Seyed Ehsan
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Möller, Elias
    Nolte, Sina
    Åhl, Agnes
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Donzel-Gargand, Olivier
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry. Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Holm, Alexander
    Hierarchical Incorporation of Reduced Graphene Oxide into Anisotropic Cellulose Nanofiber Foams reduces their Radial Thermal ConductivityManuscript (preprint) (Other (popular science, discussion, etc.))
  • 30. Hodgkins, Robert P.
    et al.
    Ahniyaz, Anwar
    Parekh, Kinnari
    Belova, Lyubov M.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Maghemite nanocrystal impregnation by hydrophobic surface modification of mesoporous silica2007In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, no 17, p. 8838-8844Article in journal (Refereed)
    Abstract [en]

    Here, we report the design of a hybrid inorganic/organic mesoporous material through simultaneous pore engineering and hydrophobic surface modification of the intramesochannels to improve the uptake of superparamagnetic maghemite nanocrystals via impregnation techniques. The mesoporous material of the SBA-15 type was functionalized in situ with thiol organo-siloxane groups. Restricting the addition of the thiol organo-siloxane to 2 mol % yielded an inorganic/organic hybrid material characterized by large pores and a well-ordered hexagonal p6mm mesophase. The hydrophobic surface modification promoted the incorporation of 7.5 nm maghemite (gamma-Fe2O3) nanocrystals, prepared through temperature-control led decomposition of iron pentacarbonyl in organic solvents. The hydrophobic, oleic acid capped superparamagnetic maghemite nanocrystals were incorporated into the porous network via wet impregnation from organic suspensions. Combining diffraction, microscopy, and adsorption data confirmed the uptake of the nanocrystals within the intramesochannels of the silica host. Magnetization dependencies on magnetic field at different temperatures show a constriction in the loop around the origin, which indicates immobilization of maghemite nanocrystals inside the thiol-functionalized silica host.

  • 31.
    Iqbal, Muhammad Naeem
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Robert-Nicoud, Ghislaine
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ciurans-Oset, Marina
    Akhtar, Farid
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Bengtsson, Tore
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Mesoporous Silica Particles Retain Their Structure and Function while Passing through the Gastrointestinal Tracts of Mice and Humans2023In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, , p. 12Article in journal (Refereed)
    Abstract [en]

    Mesoporous silica particles (MSPs) can be used as food additives, clinically for therapeutic applications, or as oral delivery vehicles. It has also been discussed to be used for a number of novel applications including treatment for diabetes and obesity. However, a major question for their possible usage has been if these particles persist structurally and retain their effect when passing through the gastrointestinal tract (GIT). A substantial breaking down of the particles could reduce function and be clinically problematic for safety issues. Hence, we investigated the biostability of MSPs of the SBA-15 kind prepared at large scales (100 and 1000 L). The MSPs were orally administered in a murine model and clinically in humans. A joint extraction and calcination method was developed to recover the MSPs from fecal mass, and the MSPs were characterized physically, structurally, morphologically, and functionally before and after GIT passage. Analyses with N2 adsorption, X-ray diffraction, electron microscopy, and as a proxy for general function, adsorption of the enzyme α-amylase, were conducted. The adsorption capacity of α-amylase on extracted MSPs was not reduced as compared to the pristine and control MSPs, and adsorption of up to 17% (w/w) was measured. It was demonstrated that the particles did not break down to any substantial degree and retained their function after passing through the GITs of the murine model and in humans. The fact the particles were not absorbed into the body was ascribed to that they were micron-sized and ingested as agglomerates and too big to pass the intestinal barrier. The results strongly suggest that orally ingested MSPs can be used for a number of clinical applications. 

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  • 32. Jiang, Q. H.
    et al.
    Liu, F. T.
    Nan, Ce-Wen
    Lin, Yuan-Hua
    Reece, M. J.
    Yan, H. X.
    Ning, H. P.
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    High-temperature ferroelectric phase transition observed in multiferroic Bi0.91La0.05Tb0.04FeO32009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 95, no 1, p. 12909-Article in journal (Refereed)
    Abstract [en]

    A single-phase Bi0.91La0.05Tb0.04FeO3 polycrystalline ceramic was fabricated by spark-plasma-sintering the precursor powder prepared by a sol-gel method. Temperature-dependent properties of polycrystalline Bi0.91La0.05Tb0.04FeO3 were characterized by x-ray diffraction, dielectric, and piezoelectric measurement. The x-ray diffraction results revealed a phase transition near 700 degrees C. Especially, temperature-dependent dielectric behavior demonstrated that there was a dielectric abnormal peak at about 697 degrees C, in addition to those two well-known dielectric abnormal peaks at 337 degrees C (Neel temperature) and 831 degrees C (Curie temperature). The observations, together with thermal depoled behavior, suggest a ferroelectric-ferroelectric phase transition from R(3)c to Pbnm at around 700 degrees C.

  • 33. Jiang, Qing-Hui
    et al.
    Mei, Ao
    Lin, Yuan-Hua
    Nan, Ce-Wen
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Ferroic properties of highly dense multiferroic Bi1-xLa0.05TbxFeO3 ceramics via sheltered spark plasma sintering2008In: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 91, no 7, p. 2189-2194Article in journal (Refereed)
    Abstract [en]

    Multiferroic Bi0.95-xLa0.05TbxFeO3 (BLTFO) ceramics were prepared by spark plasma sintering. The protection of CeO2 powders in the spark plasma sintering process can effectively restrain the valence fluctuation of iron ions and high-dense BLTFO ceramics with good dielectric and ferroelectric properties are fabricated. The BLTFO ceramics have low loss (tan delta similar to 5%) between 10(2) and 10(6) Hz. The doping of Tb can increase the dielectric and ferromagnetic properties, but decrease the ferroelectricity of BLTFO ceramics.

  • 34. Kamba, S.
    et al.
    Nuzhnyy, D.
    Vanek, P.
    Savinov, M.
    Knizek, K.
    Shen, Z.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Santava, E.
    Maca, K.
    Sadowski, M.
    Petzelt, J.
    Magnetodielectric effect and optic soft mode behaviour in quantum paraelectric EuTiO3 ceramics2007In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 80, no 2, p. 27002-Article in journal (Refereed)
    Abstract [en]

    Infrared reflectivity and time-domain terahertz transmission spectra of EuTiO3 ceramics revealed a polar optic phonon at 6-300K whose softening is fully responsible for the recently observed quantum paraelectric behaviour. Even if our EuTiO3 ceramics show lower permittivity than the single crystal due to a reduced density and/ or small amount of secondary pyrochlore Eu2Ti2O7 phase, we confirmed a magnetic field dependence of the permittivity, also slightly smaller than in single crystal. An attempt to reveal the soft phonon dependence at 1.8K on the magnetic field up to 13T remained below the accuracy of our infrared reflectivity experiment.

  • 35.
    Kocjan, Andraz
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry. Stockholm Univ, Berzelii Ctr EXSELENT Porous Mat, Stockholm.
    Dakskobler, Ales
    Budic, Bojan
    Kosmac, Tomaz
    Suppressed Reactivity of AlN Powder in Water at 5 degrees C2013In: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 96, no 4, p. 1032-1034Article in journal (Refereed)
    Abstract [en]

    The hydrolysis behavior of AlN powder suspensions (525wt%) at 5 degrees C has been investigated to explore the impact of low temperatures on the hydrolysis behavior. Throughout the 312-h long experiment, the pH value of the suspensions was below 9, where the hydrolysis remained in the induction period and was eventually suppressed due to the formation of a few-nanometers-thick film of amorphous aluminum hydroxide gel around the AlN particles, acting as a passivation layer. Moreover, the aqueous part of the suspension possessed a remarkably high value of dissolved [Al(III)]aq, being an order of magnitude higher at a given pH value than the aqueous AlCl3 solution.

  • 36. Krycka, K. L.
    et al.
    Borchers, J. A.
    Laver, M.
    Salazar Alvarez, German
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Lopez-Ortega, A.
    Estrader, M.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Surinach, S.
    Baro, M. D.
    Sort, J.
    Nogues, J.
    Correlating material-specific layers and magnetic distributions within onion-like Fe3O4/MnO/gamma-Mn2O3 core/shell nanoparticles2013In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, no 17, p. 17B531-Article in journal (Refereed)
    Abstract [en]

    The magnetic responses of two nanoparticle systems comprised of Fe3O4/gamma-Mn2O3 (soft ferrimagnetic, FM/hard FM) and Fe3O4/MnO/gamma-Mn2O3 (soft FM/antiferromagnetic, AFM/hard FM) are compared, where the MnO serves to physically decouple the FM layers. Variation in the temperature and applied field allows for Small Angle Neutron Scattering (SANS) measurements of the magnetic moments both parallel and perpendicular to an applied field. Data for the bilayer particle indicate that the graded ferrimagnetic layers are coupled and respond to the field as a single unit. For the trilayer nanoparticles, magnetometry suggests a Curie temperature (T-C) approximate to 40 K for the outer gamma-Mn2O3 component, yet SANS reveals an increase in the magnetization associated with outer layer that is perpendicular to the applied field above T-C during magnetic reversal. This result suggests that the gamma-Mn2O3 magnetically reorients relative to the applied field as the temperature is increased above 40 K.

  • 37.
    Lin, C.
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Xiao, Changhong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Shen, Zhijian James
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Nano Pores Evolution in Hydroxyapatite Microsphere during Spark Plasma Sintering2011In: Science of Sintering, ISSN 0350-820X, Vol. 43, no 1, p. 39-46Article in journal (Refereed)
    Abstract [en]

    Micron-spherical granules of hydroxyapatite (HAp) nanoparticles were prepared by powder granulation methods. Through subsequent sintering, porous HAp microspheres with tailored pore and grain framework structures were obtained. Detailed microstructure investigation by SEM and TEM revealed the correlation of the pore structure and the necking strength with the sintering profiles that determine the coalescence features of the nanoparticles. The partially sintered porous HAp microspheres containing more than 50% porosity consisting of pores and grains both in nano-scale are active in inducing the precipitation of HAp in simulated body fluid. The nano-porous HAp microspheres with an extensive surface and interconnecting pores thus demonstrate the potential of stimulating the formation of collagen and bone and the integration with the newly formed bones during physiological bone remodeling.

  • 38.
    Liu, Jinrong
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Thalakkale Veettil, Unnimaya
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Huertas Alonso, Alberto José
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Plivelic, Tomás S.
    Sipponen, Mika H.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    High-yield production of lignin photonic crystals with ethanol and waterManuscript (preprint) (Other academic)
    Abstract [en]

    Structural colors in nature have inspired research into engineered photonic materials starting from renewable resources such as lignin extracted from wood and agricultural residues. A notable obstacle in developing lignin-based photonic crystals lies in the use of hazardous organic solvents, giving rise to safety and environmental concerns. Additionally, low product yields hinder scalable production of lignin photonics. Here, we report a highly efficient method for the fabrication of colloidal lignin particles of predicable size for producing photonic crystals using ethanol and water as the sole solvents. We achieved a 78% mass yield of photonic crystals starting from a crude soda lignin, resulting in vibrant colors spanning the entire visible spectrum. Controlling the particle size can be achieved by varying the dilution rate of a lignin ethanol solution with water, enabling the direct generation of colloidal crystals of preferred colors. The new method paves the way for large-scale development of lignin photonics.

  • 39.
    Ma, Jing
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Zhang, Junzhan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Liu, Wei
    Shen, Zhijian James
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Suppressing pore-boundary separation during spark plasma sintering of tungsten2013In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 438, no 1-3, p. 199-203Article in journal (Refereed)
    Abstract [en]

    A tungsten powder with bimodal particle size distribution is consolidated by spark plasma sintering (SPS). Effects are made for understanding the densification and grain growth mechanisms and their relations to the SPS processing parameters. By holding the sample at an intermediate temperature, i.e., 1200 degrees C for 5 min, where the densification is enhanced by particle close packing, the pore-boundary separation that yields the formation of entrapped pores inside individual grains at final stage of sintering is suppressed. This optimization of the SPS process is beneficial for preparing fine grained bulk tungsten with homogeneous microstructure from the powders produced in industrial-scale. The prepared tungsten with minimized porosity appears a potential candidate for plasma-facing materials in the divertor region in the International Thermonuclear Experimental Reactor (ITER).

  • 40.
    Mathew, Renny
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
    Turdean-Ionescu, Claudia
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Stevensson, Baltzar
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
    Izquierdo-Barba, Isabel
    Garcia, Ana
    Arcos, Daniel
    Vallet-Regi, Maria
    Eden, Mattias
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
    Direct Probing of the Phosphate-Ion Distribution in Bioactive Silicate Glasses by Solid-State NMR: Evidence for Transitions between Random/Clustered Scenarios2013In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 25, no 9, p. 1877-1885Article in journal (Refereed)
    Abstract [en]

    By employing P-31 multiple-quantum coherence-based solid-state nuclear magnetic resonance spectroscopy, we present the first comprehensive experimental assessment of the nature of the orthophosphate ion distributions in silicate based bioactive glasses (BGs). Results are provided both from melt prepared BG and evaporation-induced self-assembly-derived mesoporous bioactive glass (MEBG) structures of distinct compositions. The phosphate species are randomly dispersed in melt-derived BGs (comprising 44-55 mol % SiO2) of the Na2O-CaO-SiO2-P2O5 system, whereas a Si-rich (86 mol % SiO2) and Ca-poor ordered MBG structure exhibits nanometer-sized amorphous calcium phosphate clusters, conservatively estimated to comprise at least nine orthophosphate groups. A Ca-richer MBG (58 mol % SiO2) reveals a less pronounced phosphate clustering. We rationalize the variable structural role of P in these amorphous biomatetials.

  • 41. Mayerhoefer, Thomas G.
    et al.
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    SUBLeonova, Ekaterina
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Physical Chemistry.
    Eden, Mattias
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Physical Chemistry.
    Kriltz, Antje
    Popp, Juergen
    Consolidated silica glass from nanoparticles2008In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 181, no 9, p. 2442-2447Article in journal (Refereed)
    Abstract [en]

    A dense silica glass was prepared by consolidating a highly dispersed silicic acid powder (particle size < 10 nm) with the Spark Plasma Sintering (SPS) technique. The glass was characterized by ellipsometry, transmission electron microscopy (TEM), infrared reflectance and transmittance spectroscopy, as well as by Raman, UV-Vis-NIR and solid-state nuclear magnetic resonance (NMR) spectroscopy. The prototypic sample showed a transmittance of about 63% compared to silica glass in the UV-Vis spectral range. Based on the results of infrared transmittance spectroscopy this lower transparency is due to the comparably high water content, which is about 40 times higher than that in silica glass. H-1 magic-angle spinning (MAS) NMR confirmed an increase in hydroxyl groups in tie sample prepared by SPS relative to that of the conventional SiO2 reference glass. Aside from the comparably high water content, we conclude from the similarity of the IR-reflectance and the Si-29 MAS NMR spectra of the SPS sample and the corresponding spectra of the conventionally prepared silica glass, that the short- and medium-range order is virtually the same in both materials. Raman spectroscopy, however, Suggests that the number of three- and four-membered rings is significantly smaller in the SPS sample compared to the conventionally prepared sample. Based on these results we conclude that it is possible to prepare glasses by compacting amorphous powders by the SPS process. The SPS process may therefore enable the preparation of glasses with compositions inaccessible by conventional methods. 

  • 42.
    Mille, Christian
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Corkery, Robert W.
    KTH Royal Inst Technol, Div Phys Chem, Dept Chem, Stockholm.
    A structural and thermal conductivity study of highly porous, hierarchical polyhedral nanofoam shells made by condensing silica in microemulsion films on the surface of emulsified oil drops2013In: Journall of Material Chemistry A, ISSN 2050-7488, Vol. 1, no 5, p. 1849-1859Article in journal (Refereed)
    Abstract [en]

    Light-weight solid foams are utilized in applications such as packaging and insulation mainly due to their intrinsically high porosity, low relative density and associated mechanical and transport properties. Here hollow core spherical shells are prepared with walls made of a polyhedral silica nanofoam with open cells. A microemulsion film at the oil-water interface of oil droplets is used as a soft structural template for the condensation of soluble silica species. The microemulsion sets the length scale of the monodisperse silica nanofoam cells, and the emulsion droplets set the micron-scale dimensions of the polydisperse spherical shells. Porosity is achieved by removing the templates and oils, leaving pure low-density silica. This results in a hierarchically structured, highly porous shell foam material that packs into beds with a measured porosity of approximately 97.3%, well into the range of silica aerogels. Using a combination of electron microscopy, small-angle synchrotron X-ray diffraction and nitrogen physisorption, an accurate structural model for the nanofoam shells is constructed. The material is shown to be comprised of open-cell foams that are structurally analogous to dry polyhedral soap froths having minimal surface partitions, and Plateau boundaries. The primary polyhedral nanofoam cells are 30 nm in diameter connected by 7 nm cylindrical windows. These nanofoams form spherical monolithic shells with volume average mean diameter of 41 microns and shell thickness of 0.7 microns. Simple models for the thermal conductivity of these nanofoam shell materials are constructed that include accounting for the nanoscale effects on gaseous and solid thermal conductivity. These are compared to the measured value of 0.041 W m(-1) K-1. These materials represent new structures in the family of self-assembled, highly porous silica materials and are potentially useful in packaging and insulation and other applications due to their light weight and/or intrinsically low thermal conductivity and associated mechanical and transport properties.

  • 43.
    Mille, Christian
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Tyrode, Eric C.
    Corkery, Robert W.
    3d titania photonic crystals replicated from gyroid structures in butterfly wing scales: approaching full band gaps at visible wavelengths2013In: RSC Advances, E-ISSN 2046-2069, Vol. 3, no 9, p. 3109-3117Article in journal (Refereed)
    Abstract [en]

    3D titania photonic crystals are replicated from single gyroid structures found in the butterfly Callophrys rubi. Photonic crystals were characterised using SEM imaging, X-ray and Raman scattering and reflection spectroscopy. The overall symmetry and topology of the original single gyroid structures is replicated with high fidelity. Titania replicas display photonic responses that are thermal history dependent. Replicas treated at 700 degrees C, show up to 96% reflectivity at similar to 505 nm, while at lower and higher treatment temperatures the photonic response was not as pronounced. Simulated band structures fitted to the observed spectral reflectivity data constrain the solid volume fractions and dielectric constants of the replicas. The titania photonic crystals were also found to be optically active, with both left- and right-handed single gyroids contributing to the chiral response. The 3D titania photonic crystals replicated here have nearly complete overlapping of partial band gaps, strongly suggesting that materials with full photonic band gaps are experimentally within reach using the general replication approach reported here.

  • 44.
    Mille, Christian
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Tyrode, Eric C.
    Corkery, Robert W.
    Stockholm University.
    Inorganic chiral 3-D photonic crystals with bicontinuous gyroid structure replicated from butterfly wing scales2011In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 47, no 35, p. 9873-9875Article in journal (Refereed)
    Abstract [en]

    Three dimensional silica photonic crystals with the gyroid minimal surface structure have been synthesized. The butterfly Callophrys rubi was used as a biotemplate. This material represents a significant addition to the small family of synthetic bicontinuous photonic crystals.

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  • 45.
    Moreno, Adrian
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Sipponen, Mika H.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Lignin-based smart materials: a roadmap to processing and synthesis for current and future applications2020In: Materials Horizons, ISSN 2051-6347, E-ISSN 2051-6355, Vol. 7, no 9, p. 2237-2257Article, review/survey (Refereed)
    Abstract [en]

    Biomass-derived materials are green alternatives to synthetic plastics and other fossil-based materials. Lignin, an aromatic plant polymer, is one of the most appealing renewable material precursors for smart materials capable of responding to different stimuli. Here we review lignin-based smart materials, a research field that has seen a rapid growth during the last five years. We describe the main processing and chemical synthesis routes available for the fabrication of lignin-based smart materials, and focus on their use as sensors, biomedical systems, and shape-programmable materials. In addition to benchmarking their performance to the state of the art fossil counterparts, we identify challenges and future opportunities for the development of lignin-based smart materials towards new high-performance applications.

  • 46.
    Munier, Pierre
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Apostolopoulou-Kalkavoura, Varvara
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Persson, Michael
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Strong silica-nanocellulose anisotropic composite foams combine low thermal conductivity and low moisture uptake2020In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 27, no 18, p. 10825-10836Article in journal (Refereed)
    Abstract [en]

    We report the fabrication of anisotropic lightweight composite foams based on commercial colloidal silica particles and TEMPO-oxidized cellulose nanofibrils (TOCNF). The unidirectional ice-templating of silica-TOCNF dispersions resulted in anisotropic foams with columnar porous structures in which the inorganic and organic components were homogeneously distributed. The facile addition of silica particles yielded a significant enhancement in mechanical strength, compared to TOCNF-only foams, and a 3.5-fold increase in toughness at a density of 20 kg m−3. The shape of the silica particles had a large effect on the mechanical properties; anisotropic silica particles were found to strengthen the foams more efficiently than spherical particles. The water uptake of the foams and the axial thermal conductivity in humid air were reduced by the addition of silica. The composite foams were super-insulating at dry conditions at room temperature, with a radial thermal conductivity value as low as 24 mW m−1 K−1, and remained lower than 35 mW m−1 K−1 up to 80% relative humidity. The combination of high strength, low thermal conductivity and manageable moisture sensitivity suggests that silica-TOCNF composite foams could be an attractive alternative to the oil-based thermal insulating materials.

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  • 47.
    Ménard, Delphine
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Blaschek, Leonard
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Kriechbaum, Konstantin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lee, Cheng Choo
    Serk, Henrik
    Zhu, Chuantao
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lyubartsev, Alexander P.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry. Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Science for Life Laboratory (SciLifeLab).
    Nuoendagula, Nuoendagula
    Bacsik, Zoltán
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Mathew, Aji
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kajita, Shinya
    Pesquet, Edouard
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Dynamic incorporation of specific lignin residues controls the biomechanics of the plant vasculature and its resilience to environmental changesManuscript (preprint) (Other academic)
    Abstract [en]

     The accumulation of the cell wall polymer lignin in vascular cells enables long-distance water conduction and structural support in plants. Independently of the plant species, each different vascular cell type accumulates specific lignin amount and composition affecting both aromatic and aliphatic substitutions of its residues. However, the biological role of this conserved and specific lignin chemistry for each cell type remains unclear. Herein, we performed single cell analyses on plant vascular cell morphotypes to investigate the role of specific lignin composition for cellular function. We showed that distinct amounts and compositions of lignin accumulated in the different morphotypes of the sap conducting vascular cells. We discovered that lignin accumulates dynamically, increasing in quantity and changing composition, to fine-tune the cell wall mechanical properties of each conducting cell morphotype. Modification this lignin specificity impaired specifically the cell wall mechanical properties of each morphotype and consequently their capacity to optimally conduct water in normal but also to recover from drought conditions. Altogether, our findings provide the biological role of specific lignin chemistry in sap conducting cells, to dynamically adjust the hydraulic properties of each conducting cell during developmental and environmental constraints.

  • 48.
    Oliynyk, Vitaliy
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Mille, Christian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Ng, Jovice B. S.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    von Ballmoos, Christoph
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Corkery, Robert W.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Selective and atp driven transport of ions across supported membranes into nanoporous carriers using gramicidin a and atp synthase2013In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 15, no 8, p. 2733-2740Article in journal (Refereed)
    Abstract [en]

    We report a robust and versatile membrane protein based system for selective uptake and release of ions from nanoporous particles sealed with ion-tight lipid bilayers of various compositions that is driven by the addition of ATP or a chemical potential gradient. We have successfully incorporated both a passive ion channel-type peptide (gramicidin A) and a more complex primary sodium ion transporter (ATP synthase) into the supported lipid bilayers on solid nanoporous silica particles. Protein-mediated controlled release/uptake of sodium ions across the ion-tight lipid bilayer seal from or into the nanoporous silica carrier was imaged in real time using a confocal laser scanning microscope and the intensity changes were quantified. ATP-driven transport of sodium ions across the supported lipid bilayer against a chemical gradient was demonstrated. The possibility of designing durable carriers with tight lipid membranes, containing membrane proteins for selective ion uptake and release, offers new possibilities for functional studies of single or cascading membrane protein systems and could also be used as biomimetic microreactors for controlled synthesis of inorganic multicomponent materials.

  • 49. Petkov, V.
    et al.
    Buscaglia, V.
    Buscaglia, M. T.
    Zhao, Zhe
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Ren, Y.
    Structural coherence and ferroelectricity decay in submicron- and nano-sized perovskites2008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 78, no 5, p. 54107-Article in journal (Refereed)
    Abstract [en]

    Understanding the loss of ferroelectricity in submicron- and nano-sized perovskites is an issue that has been debated for decades. Here we report results from a high-energy x-ray diffraction (XRD) study on a prime example of the perovskite's family, BaTiO3 ceramics with a grain size ranging from 1200 to 5 nm. We find that the loss of ferroelectricity in submicron- and nano-sized BaTiO3 has an intrinsic origin related to the increased atomic positional disorder in spatially confined physical systems. Our results imply that no particular critical size at which ferroelectricity in BaTO3, in particular, and perovskites, in general, is completely lost exists. Rather it weakens exponentially with the decreasing of their physical size. Smart technological solutions are needed to bring it back.

  • 50. Petzelt, J.
    et al.
    Ostapchuk, T.
    Gregora, I.
    Nuzhnyy, D.
    Rychetsky, I.
    Maca, K.
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Grain boundary and size effect on the dielectric, infrared and Raman response of SrTiO3 nanograin ceramics2008In: Ferroelectrics (Print), ISSN 0015-0193, E-ISSN 1563-5112, Vol. 363, p. 227-244Article in journal (Refereed)
    Abstract [en]

    The recently revealed giant grain size effect on dielectric properties in undoped SrTiO3 ceramics (J. Petzelt et al., J. Phys.: Con dens. Matter 19, 196222 (2007) and references therein), was extended to smaller grains of 80 nm mean grain size. Like for previously studied ceramics with larger grain size, in addition to dielectric permittivity also the infrared and Raman responses were studied and discussed. It was shown that the reduced effective permittivity is fully accounted for by the infrared soft mode behaviour and, similar to single crystals and other ceramics studied, no dielectric dispersion appears below the THz frequency range. The rather universal (independent of the grain size and sintering process) double dead layer structure was proposed to be responsible for the observed changes in the infrared and Raman spectra, allowing the grain core to keep the single crystal dielectric function. The outer dead layer shell (obviously charged due to an oxygen deficit) is very thin (similar to 1 nm) having frequency and temperature independent low permittivity (similar to 10) and is responsible for the static permittivity suppression. The inner layer of only slightly distorted perovskite structure is polar with local polarization normal to grain boundaries gradually decreasing towards the grain centre. This polarization and/or the thickness of the polar layers, which compensate the charged grain boundaries, appear to increase on decreasing temperature, particularly below the structural phase transition. Its nature is still not fully understood. In agreement with our previous suggestions, from the Raman data it con be also concluded that in the low-temperature tetragonal phase of all SrTiO3 ceramics, the local tetragonal axes tend perpendicular to the grain boundaries and the tetragonality is strongly reduced compared to single crystals.

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