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  • 1.
    Agthe, Michael
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Høydalsvik, Kristin
    Mayence, Arnaud
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Karvinen, Petri
    Liebi, Marianne
    Bergström, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Nygård, Kim
    Controlling Orientational and Translational Order of Iron Oxide Nanocubes by Assembly in Nanofluidic Containers2015Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, nr 45, s. 12537-12543Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We demonstrate that spatial confinement can be used to control the orientational and translational order of cubic nanoparticles. For this purpose we have combined X-ray scattering and scanning electron microscopy to study the ordering of iron oxide nanocubes that have self-assembled from toluene-based dispersions in nanofluidic channels. An analysis of scattering vector components with directions parallel and perpendicular to the slit walls shows that the confining walls induce a preferential parallel alignment of the nanocube (100) faces. Moreover, slit wall separations that are commensurate with an integer multiple of the edge length of the oleic acid-capped nanocubes result in a more pronounced translational order of the self-assembled arrays compared to incommensurate confinement. These results show that the confined assembly of anisotropic nanocrystals is a promising route to nanoscale devices with tunable anisotropic properties.

  • 2.
    Agthe, Michael
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Wetterskog, Erik
    Bergström, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Following the Assembly of Iron Oxide Nanocubes by Video Microscopy and Quartz Crystal Microbalance with Dissipation Monitoring2017Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 33, nr 1, s. 303-310Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have studied the growth of ordered arrays by evaporation-induced self-assembly of iron oxide nanocubes with edge lengths of 6.8 and 10.1 nm using video microscopy (VM) and quartz crystal microbalance with dissipation monitoring (QCM-D). Ex situ electron diffraction of the ordered arrays demonstrates that the crystal axes of the nanocubes are coaligned and confirms that the ordered arrays are mesocrystals. Time-resolved video microscopy shows that growth of the highly ordered arrays at slow solvent evaporation is controlled by particle diffusion and can be described by a simple growth model. The growth of each mesocrystal depends only on the number of nanoparticles within the accessible region irrespective of the relative time of formation. The mass of the dried mesocrystals estimated from the analysis of the bandwidth-shift-to-frequency-shift ratio correlates well with the total mass of the oleate-coated nanoparticles in the deposited dispersion drop.

  • 3. Atluri, Rambabu
    et al.
    Iqbal, Muhammad Naeem
    Bacsik, Zoltan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Hedin, Niklas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Villaescusa, Luis Angel
    Garcia-Bennett, Alfonso E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi. alfonso@mmk.su.se.
    Self-Assembly Mechanism of Folate-Templated Mesoporous Silica2013Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, nr 38, s. 12003-12012Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 4. Atluri, Rambabu
    et al.
    Sakamoto, Yasuhiro
    Stockholms universitet.
    Garcia-Bennettt, Alfonso E.
    Co-Structure Directing Agent Induced Phase Transformation of Mesoporous Materials2009Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, nr 5, s. 3189-3195Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The synthesis of cubic Pm (3) over barn mesocaged solid templated by cetyltrimethyl ammonium bromide (C(16)TMABr) surfactant by direct cocondensation of (3-aminopropyl)triethoxysilanes (APES) under strong alkaline conditions is reported. The novel route gives direct incorporation of amino functional groups on the porous silica wall, and the structural formation has been followed by means of in situ SAXS studies performed at a synchrotron beam line. Data shows that a molar ratio of C(16)TMABr/APES = 0.6 favors the formation of 3D cubic mesocaged solid with Pm3n symmetry which transforms to a cylindrical mesoporous phase with p6mm symmetry at higher molar ratios. Further structural evaluation has been performed by means electron crystallography (EC). Reconstructed 3D models based on EC show the presence of spherical cages (A-cages, 45 angstrom) and ellipsoidal cages (B-cages, 48 x 43 angstrom) whereby every cage in the unit cell is connected to 14 nearest cages with a window size of 18 angstrom. Finally, a mechanism is proposed, denoted S+similar to N degrees I-, in which penetration of the neutral aminopropyl moiety within the micellar corona is responsible for the formation of the Pm (3) over barn phase, accounting for the formation of the hexagonal phase at higher molar ratios and higher temperatures. In comparison to other mesocaged materials with the same symmetry this structure possesses a more open porous network which will help assess its potential in a variety of applications discussed herein.

  • 5.
    Aziz, Baroz
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Zhao, Guoying
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Hedin, Niklas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Carbon Dioxide Sorbents with Propylamine Groups-Silica Functionalized with a Fractional Factorial Design Approach2011Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, nr 7, s. 3822-3834Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mesoporous silica particles (Davisil) were functionalized with aminopropyltriethoxysilane (APTES) in a fractional factorial design with 19 different synthesis and uptake experiments. The number of amino groups and the uptake of CO(2) were optimized in a 2(V)(5-1) design. Most important to functionalizationwas the amount of water present during synthesis, the reaction time, and pretreating the silica with a mineral acid; certain two-way interactions were shown to be statistically significant as well. Modifications performed at 110 or 80 degrees C showed no significant differences concerning amine content or uptake of CO(2). Properly choosing center points for the discrete variables is problematic and is somewhat related to the lack of fit with respect to CO(2) uptake; the regression was good. Solid-state (29)Si NMR showed that the APTES was mainly fully condensed. Specific surface areas did not correlate with the number of n-propylamine groups on the silica, which is indicative of differential levels of heterogeneity in the coverage of propylamines. The uptake of CO(2) and N(2) was measured from -20 to 70 degrees C and from 0 to 1 bar and parametrized by the Freundlich isotherm. Amine-modified silica adsorbed significant amounts of CO(2), especially at the low partial pressure, which is important for CO(2) capture from flue gas. At such pressures, samples with a high density of amine (4 amines/nm(2)) showed a much higher uptake of CO(2) than did those with densities of similar to 2-3 amines/nm(2), reflecting differential tendencies to form propylammonium-propylcarbamate ion pairs; these require close proximity among amine groups to form. Water affected the uptake of carbon dioxide in different ways. Certain samples took up more moist CO(2) gas than dry CO(2), and others took up less moist CO(2) than dry CO(2), which is indicative of differential tendencies toward water adsorption. We conclude that experimental design is a time-efficient approach to the functionalization of silica with propylamine groups.

  • 6.
    Bacsik, Zoltan
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Ahlsten, Nanna
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Ziadi, Asraa
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Zhao, Guoying
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Garcia-Bennett, Alfonso E.
    Uppsala universitet.
    Martin-Matute, Belen
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Hedin, Niklas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Mechanisms and Kinetics for Sorption of CO(2) on Bicontinuous Mesoporous Silica Modified with n-Propylamine2011Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, nr 17, s. 11118-11128Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We studied equilibrium adsorption and uptake kinetics and identified molecular species that formed during sorption of carbon dioxide on amine-modified silica. Bicontinuous silicas (AMS-6 and MCM-48) were postsynthetically modified with (3-aminopropyl)triethoxysilane or (3-aminopropyl)methyldiethoxysilane, and amine-modified AMS-6 adsorbed more CO(2) than did amine-modified MCM-48. By in situ FTIR spectroscopy, we showed that the amine groups reacted with CO(2) and formed ammonium carbamate ion pairs as well as carbamic acids under both dry and moist conditions. The carbamic acid was stabilized by hydrogen bonds, and ammonium carbamate ion pairs formed preferably on sorbents with high densities of amine groups. Under dry conditions, silylpropylcarbamate formed, slowly, by condensing carbamic acid and silanol groups. The ratio of ammonium carbamate ion pairs to silylpropylcarbamate was higher for samples with high amine contents than samples with low amine contents. Bicarbonates or carbonates did not form under dry or moist conditions. The uptake of CO(2) was enhanced in the presence of water, which was rationalized by the observed release of additional amine groups under these conditions and related formation of ammonium carbamate ion pairs. Distinct evidence for a fourth and irreversibly formed moiety was observed under sorption of CO(2) under dry conditions. Significant amounts of physisorbed, linear CO(2) were detected at relatively high partial pressures of CO(2), such that they could adsorb only after the reactive amine groups were consumed.

  • 7.
    Bacsik, Zoltan
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Atluri, Rambabu
    Uppsala universitet.
    Garcia-Bennett, Alfonso E.
    Uppsala universitet.
    Hedin, Niklas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Temperature-Induced Uptake of CO2 and Formation of Carbamates in Mesocaged Silica Modified with n-Propylamines2010Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, nr 12, s. 10013-10024Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Adsorption-mediated CO2 separation can reduce the cost of carbon capture and storage. The reduction in cost requires adsorbents with high capacities for CO2 sorption and high CO2-over-N2 selectivity. Amine-modified sorbents are promising candidates for carbon capture. To investigate the details of CO2 adsorption in such materials, we studied mesocaged (cubic, Pmn symmetry) silica adsorbents with tethered propylamines using Fourier transform infrared (FTIR) spectroscopy and volumetric uptake experiments. The degree of heterogeneity in these coatings was varied by either cosynthesizing or postsynthetically introducing the propylamine modification. In situ FTIR spectroscopy revealed the presence of both physisorbed and chemisorbed CO2 in the materials. We present direct molecular evidence for physisorption using FTIR spectroscopy in mesoporous silica sorbents modified with propylamines. Physisorption reduced the CO2-over-N2 selectivity in amine-rich sorbents. Samples with homogeneous coatings showed typical CO2 adsorption trends and large quantities of IR-observable physisorbed CO2. The uptake of CO2 in mesocaged materials with heterogeneous propylamine coatings was higher at high temperatures than at low temperatures. At higher temperatures and low pressures, the postsynthetically modified materials adsorbed more CO2 than did the extracted ones, even though the surface area after modification was clearly reduced and the coverage of primary amine groups was lower. The principal mode of CO2 uptake in postsynthetically modified mesoporous silica was chemisorption. The chemisorbed moieties were present mainly as carbamate−ammonium ion pairs, resulting from the quantitative transformation of primary amine groups during CO2 adsorption as established by NIR spectroscopy. The heterogeneity in the coatings promoted the formation of these ion pairs. The average propylamine−propylamine distance must be small to allow the formation of carbamate−propylammonium ion pairs.

  • 8.
    Bacsik, Zoltán
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Hedin, Niklas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Adsorption of Carbonyl Sulfide on Propylamine Tethered to Porous Silica2018Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, nr 26, s. 7708-7713Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Carbonyl sulfide (COS) reacts slowly with amines in the aqueous solutions used to absorb CO2 from natural gas and flue gas and can also deactivate certain aqueous amines. The effects of COS on amines tethered to porous silica, however, have not been investigated before. Hence, the adsorption of COS on aminopropyl groups tethered to porous silica was studied using in situ IR spectroscopy. COS chemisorbed mainly and reversibly as propylammonium propylthiocarbamate ion pairs [R-NH(C= O)S- +H3N-R] under dry conditions. In addition, a small amount of another chemisorbed species formed slowly and irreversibly. Nevertheless, the CO2 capacities of the adsorbents were fully retained after COS was desorbed.

  • 9. Bejhed, Rebecca S.
    et al.
    Tian, Bo
    Eriksson, Kristofer
    Brucas, Rimantas
    Oscarsson, Sven
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Strömberg, Mattias
    Svedlindh, Peter
    Gunnarsson, Klas
    Magnetophoretic Transport Line System for Rapid On-Chip Attomole Protein Detection2015Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, nr 37, s. 10296-10302Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A lab-on-a-chip traveling wave magnetophoresis approach for sensitive and rapid protein detection is reported. In this method, a chip-based magnetic microarray comprising lines of micrometer-sized thin film magnetic elements was used to control the movement of magnetic beads (MBs). The MBs and the chip were functionalized, forming a sandwich-type assay. The MBs were transported across a detection area, and the presence of target molecules resulted in the immobilization of MBs within this area. Target quantification was accomplished by MB counting in the detection area using an optical microscope. In order to demonstrate the versatility of the microarray, biotinylated antiavidin was selected as the target protein. In this case, avidin-functionalized MBs and an avidin-functionalized detection area were used. With a total assay time of 1 to 1.5 h (depending on the labeling approach used), a limit of detection in the attomole range was achieved. Compared to on-chip surface plasmon resonance biodetection systems, our method has a larger dynamic range and is about a factor of 500 times more sensitive. Furthermore, our MB transportation system can operate in any chip-based biosensor platform, thereby significantly improving traditional biosensors.

  • 10. Boily, Jean-Francois
    et al.
    Yesilbas, Merve
    Uddin, Munshi Md. Musleh
    Lu, Baiqing
    Trushkina, Yulia
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Salazar-Alvarez, German
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Thin Water Films at Multifaceted Hematite Particle Surfaces2015Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, nr 48, s. 13127-13137Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mineral surfaces exposed to moist air stabilize nanometer- to micrometer-thick water films. This study resolves the nature of thin water film formation at multifaceted hematite (alpha-Fe2O3) nanoparticle surfaces with crystallographic faces resolved by selected area electron diffraction. Dynamic vapor adsorption (DVA) in the 0-19 Torr range at 298 K showed that these particles stabilize water films consisting of up to 4-5 monolayers. Modeling of these data predicts water loadings in terms of an adsorption regime (up to 16 H2O/nm(2)) involving direct water binding to hematite surface sites, and of a condensation regime (up to 34 H2O/nm(2)) involving water binding to hematite-bound water nanodusters. Vibration spectroscopy identified the predominant hematite surface hydroxo groups (-OH, mu-OH, mu(3)-OH) through which first layer water molecules formed hydrogen bonds, as well as surface iron sites directly coordinating water molecules (i.e., as geminal eta-(OH2)(2) sites). Chemometric analyses of the vibration spectra also revealed a strong correspondence in the response of hematite surface hydroxo groups to DVA-derived water loadings. These findings point to a near-saturation of the hydrogen-bonding environment of surface hydroxo groups at a partial water vapor pressure of similar to 8 Torr (similar to 40% relative humidity). Classical molecular dynamics (MD) resolved the interfacial water structures and hydrogen bonding populations at five representative crystallographic faces expressed in these nanoparticles. Simulations of single oriented slabs underscored the individual roles of all (hydro)oxo groups in donating and accepting hydrogen bonds with first layer water in the adsorption regime. These analyses pointed to the preponderance of hydrogen bond-donating -OH groups in the stabilization of thin water films. Contributions of mu-OH and mu(3)-OH groups are secondary, yet remain essential in the stabilization of thin water films. MD simulations also helped resolve crystallographic controls on water water interactions occurring in the condensation regime. Water water hydrogen bond populations are greatest on the (001) face, and decrease in importance in the order (001) > (012) approximate to (110) > (014) >> (100). Simulations of a single (similar to 5 nm x similar to 6 nm x similar to 6 nm) nanometric hematite particle terminated by the (001), (110), (012), and (100) faces also highlighted the key roles that sites at particle edges play in interconnecting thin water films grown along contiguous crystallographic faces. Hydroxo water hydrogen bond populations showed that edges were the preferential loci of binding. These simulations also suggested that equilibration times for water binding at edges were slower than on crystallographic faces. In this regard, edges, and by extension roughened surfaces, are expected to play commanding roles in the stabilization of thin water films. Thus, in focusing on the properties of nanometric-thick water layers at hematite surfaces, this study revealed the nature of interactions between water and multifaced particle surfaces. Our results pave the way for furthering our understanding of mineral-thin water film interfacial structure and reactivity on a broader range of materials.

  • 11.
    Cheung, Ocean
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Bacsik, Zoltán
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Krokidas, Panagiotis
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Mace, Amber
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för fysikalisk kemi.
    Laaksonen, Aatto
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för fysikalisk kemi.
    Hedin, Niklas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    K+ Exchanged Zeolite ZK-4 as a Highly Selective Sorbent for CO22014Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, nr 32, s. 9682-9690Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 12.
    Church, Tamara L.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Bernin, Diana
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). University of Gothenburg, Sweden.
    Garcia-Bennett, Alfonso E.
    Hedin, Niklas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Dispersed Uniform Nanoparticles from a Macroscopic Organosilica Powder2018Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, nr 6, s. 2274-2281Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A colloidal dispersion of uniform organosilica nanoparticles could be produced via the disassembly of the non-surfactant-templated organosilica powder nanostructured folate material (NFM-1). This unusual reaction pathway was available because the folate and silica-containing moieties in NFM-1 are held together by noncovalent interactions. No precipitation was observed from the colloidal dispersion after a week, though particle growth occurred at a solvent-dependent rate that could be described by the Lifshitz-Slyozov-Wagner equation. An organosilica film that was prepared from the colloidal dispersion adsorbed folate-binding protein from solution but adsorbed ions from a phosphate -buffered saline solution to a larger degree. To our knowledge, this is the first instance of a colloidal dispersion of organosilica nanoparticles being derived from a macroscopic material rather than from molecular precursors.

  • 13. Eriksson, Kristofer L. E.
    et al.
    Chow, Winnie W. Y.
    Puglia, Carla
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Göthelid, Emmanuelle
    Oscarsson, Sven
    Performance of a biomimetic oxidation catalyst immobilized on silicon wafers: comparison with its gold congener2010Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, nr 21, s. 16349-16354Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    With the aim of extending the usefulness of an existing biomimetic catalytic system, cobalt porphyrin catalytic units with thiol linkers were heterogenized via chemical grafting to silicon wafers and utilized for the catalytic oxidation of hydroquinone to p-benzoquinone. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to analyze the morphology and composition of the heterogeneous catalyst. The results of the catalytic oxidation of hydroquinone obtained with porphyrins grafted on silicon were compared with those obtained earlier with the same catalyst in homogeneous phase and immobilized on gold. It was found that the catalysis could run over 400 h, without showing any sign of deactivation. The measured catalytic activity is at least 10 times higher than that measured under homogeneous conditions, but also 10 times lower than that observed with the catalytic unit immobilized on gold. The reasons of this discrepancy are discussed in term of substrate influence and overlayer organization. The silicon-immobilized catalyst has potential as an advanced functional material with applications in oxidative heterogeneous catalysis of organic reactions, as it combines long-term relatively high activity with low cost.

  • 14.
    Eriksson, Kristofer
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Palmgren, Pal
    Nyholm, Leif
    Oscarsson, Sven
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Electrochemical Synthesis of Gold and Protein Gradients on Particle Surfaces2012Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, nr 28, s. 10318-10323Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A straightforward, versatile approach to the production of protein gradients on planar and spherical particle surfaces is described. The method is based on the spatially controlled oxidation of thiolated surfaces by Au(III) ions generated via the electrochemical oxidation of a gold electrode in a phosphate-buffered saline solution (10 mM PBS, pH 7.2, 150 mM NaCl). Because the gold electrode is in direct contact with the thiolated surfaces, the released Au(III) ions, which are present as Au(III) chloride complexes, give rise to the formation of a surface gradient of Au(I)-thiolate complexes depending on the local redox potential given by the local Au(III) concentration. As is shown on the basis of the use of X-ray photoelectron spectroscopy and fluorescently labeled proteins, the Au(I)-thiolate complexes can subsequently be functionalized with thiolated proteins, yielding surface density protein gradients on micrometer-sized nonconducting polymer beads as well as linear Au(I)-thiolate gradients on planar silicon surfaces.

  • 15. Farzaneh, Amirfarrokh
    et al.
    Zhou, Ming
    Antzutkin, Oleg N.
    Bacsik, Zoltan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Hedlund, Jonas
    Holmgren, Allan
    Grahn, Mattias
    Adsorption of Butanol and Water Vapors in Silicalite-1 Films with a Low Defect Density2016Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 32, nr 45, s. 11789-11798Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Pure silica zeolites are potentially hydrophobic and have therefore been considered to be interesting candidates for separating alcohols, e.g., 1-butanol, from water. Zeolites are traditionally synthesized at high pH, leading to the formation of intracrystalline defects in the form of silanol defects in the framework. These silanol groups introduce polar adsorption sites into the framework, potentially reducing the adsorption selectivity toward alcohols in alcohol/water mixtures. In contrast, zeolites prepared at neutral pH using the fluoride route contain significantly fewer defects. Such crystals should show a much higher butanol/water selectivity than crystals prepared in traditional hydroxide (OH-) media. Moreover, silanol groups ate present at the external surface of the zeolite crystals; therefore, minimizing the external surface of the studied adsorbent is important. In this work, we determine adsorption isotherms of 1-butanol and water in silicalite-1 films prepared in a fluoride (F-) medium using in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. This film was composed of well intergrown, plate-shaped b-oriented crystals, resulting in a low external area. Single-component adsorption isotherms of 1-butanol and water were determined in the temperature range of 35-80 degrees C. The 1-butanol isotherms were typical for an adsorbate showing a high affinity for a microporous material and a large increase in the amount adsorbed at low partial pressures of 1-butanol. The Langmuir-Freundlich model was successfully fitted to the 1-butanol isotherms, and the heat of adsorption was determined. Water showed a very low affinity for the adsorbent, and the amounts adsorbed were very similar to previous reports for large silicalite-1 crystals prepared in a fluoride medium. The sample also adsorbed much less water than did a reference silicalite-1(OH-) film containing a high density of internal defects. The results show that silicalite-1 films prepared in a F- medium with a low density of defects and external area are very promising for the selective recovery of 1-butanol from aqueous solutions.

  • 16. Farzaneh, Amirfarrokh
    et al.
    Zhou, Ming
    Potapova, Elisaveta
    Bacsik, Zoltan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Ohlin, Lindsay
    Holmgren, Allan
    Hedlund, Jonas
    Grahn, Mattias
    Adsorption of Water and Butanol in Silicalite-1 Film Studied with in Situ Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy2015Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, nr 17, s. 4887-4894Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Biobutanol produced by, e.g., acetone-butanol-ethanol (ABE) fermentation is a promising alternative to petroleum-based chemicals as, e.g., solvent and fuel. Recovery of butanol from dilute fermentation broths by hydrophobic membranes and adsorbents has been identified as a promising route. In this work, the adsorption of water and butanol vapor in a silicalite-1 film was studied using in situ attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy to better understand the adsorption properties of silicalite-1 membranes and adsorbents. Single-component adsorption isotherms were determined in the temperature range of 35-120 degrees C, and the Langmuir model was successfully fitted to the experimental data. The adsorption of butanol is very favorable compared to that of water. When the silicalite-1 film was exposed to a butanol/water vapor mixture with 15 mol % butanol (which is the vapor composition of an aqueous solution containing 2 wt % butanol, a typical concentration in an ABE fermentation broth, i.e., the composition of the gas obtained from gas stripping of an ABE broth) at 35 degrees C, the adsorption selectivity toward butanol was as high as 107. These results confirm that silicalite-1 quite selectively adsorbs hydrocarbons from vapor mixtures. To the best of our knowledge, this is the first comprehensive study on the adsorption of water and butanol in silicalite-1 from vapor phase.

  • 17.
    Faure, Bertrand
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Salazar-Alvarez, German
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Bergström, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Hamaker Constants of Iron Oxide Nanoparticles2011Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, nr 14, s. 8659-8664Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Hamaker constants for iron oxide nanoparticles in various media have been calculated using Lifshitz theory. Expressions for the dielectric responses of three iron oxide phases (magnetite, maghemite, and hematite) were derived from recently published optical data. The nonretarded Hamaker constants for the iron oxide nanopartides interacting across water, A(1w1) = 33 - 39 zJ, correlate relatively well with previous reports, whereas the calculated values in nonpolar solvents (hexane and toluene), A(131) = 9 29 zJ, are much lower than the previous estimates, particularly for magnetite. The magnitude of van der Waals interactions varies significantly between the studied phases (magnetite < maghemite < hematite), which highlights the importance of a thorough characterization of the particles. The contribution of magnetic dispersion interactions for particle sizes in the superparamagnetic regime was found to be negligible. Previous conjectures related to colloidal stability and self-assembly have been revisited on the basis of the new Lifshitz values of the Hamaker constants.

  • 18.
    Hedin, Niklas
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Rzepka, Przemyslaw
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Jasso-Salcedo, Alma Berenice
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Church, Tamara L.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Bernin, Diana
    Intracrystalline Transport Barriers Affecting the Self-Diffusion of CH4 in Zeolites vertical bar Na-12 vertical bar-A and vertical bar Na12-xKx vertical bar-A2019Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 35, nr 40, s. 12971-12978Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Carbon dioxide must be removed from biogas or natural gas to obtain compressed or liquefied methane, and adsorption-driven isolation of CO2 could be improved by developing new adsorbents. Zeolite adsorbents can select CO2 over CH4, and the adsorption of CH4 on zeolite vertical bar Na12-xKx vertical bar-A is significantly lower for samples with a high K+ content, i.e., x > 2. Nevertheless, we show, using H-1 NMR experiments, that these zeolites adsorb CH4 after long equilibration times. Pulsed-field gradient NMR experiments indicated that in large crystals of zeolites vertical bar Na12-xKx vertical bar-A, the long-time diffusion coefficients of CH4 did not vary with x, and the upper limit of the mean-square displacement was about 1.5 mu m, irrespective of the diffusion time. Also for zeolite vertical bar Na-12 vertical bar-A samples of three different particle sizes (similar to 0.44, similar to 2.9, and similar to 10.6 mu m), the upper limit of the mean-square displacement of CH4 was 1.5 mu m and largely independent of the diffusion time. This similarity provided further evidence for an intracrystalline diffusion restriction for CH4 within the medium- and large-sized zeolite A crystals and possibly of clustering and close contact among the small zeolite A crystals. The upper limit of the long-time diffusion coefficient of adsorbed CH4 was (at 1 atm and 298 K) about 10(-10) m(2)/s irrespective of the size of the zeolite particle or the studied content of K+ in zeolites and vertical bar Na-12 vertical bar-A. The T-1 relaxation time for adsorbed CH4 on zeolites vertical bar Na12-xKx vertical bar-A with x > 2 was smaller than for those with x < 2, indicating that the short-time diffusion of CH4 was hindered.

  • 19. Hodgkins, Robert P.
    et al.
    Ahniyaz, Anwar
    Parekh, Kinnari
    Belova, Lyubov M.
    Bergström, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Maghemite nanocrystal impregnation by hydrophobic surface modification of mesoporous silica2007Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, nr 17, s. 8838-8844Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 20. Kozin, Philipp A.
    et al.
    Salazar-Alvarez, German
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Boily, Jean-Francois
    Oriented Aggregation of Lepidocrocite and Impact on Surface Charge Development2014Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, nr 30, s. 9017-9021Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The impact of lepidocrocite (gamma-FeOOH) nanoparticle aggregation on mineral surface charge development was resolved in aqueous solutions of NaCl and NaClO4. Synthetic rod-like particles exhibiting charged edge (100) and neutrally/low-charged (010) faces self-aggregated in salt-free solutions. Aggregation was notably imaged by high-resolution transmission electron microscopy, and inferred by decreases in N-2(g)-B.E.T. specific surface area from 94 m(2)/g to 77 m(2)/g after 12 months, and to 66 m(2)/g after 33 months storage. Potential determining (H+, OH-) ions loadings in the 4-11 pH range were unchanged only if the particles remained aggregated in NaCI but only if they were disaggregated in NaClO4. These differences, alongside molecular simulations and experimental ion loadings resolved in other studies from our group, point to important controls on background electrolyte ion identity on the aggregation and charge development in lepidocrocite. These results may apply further to other mineral surfaces of comparable surface (hydr)oxo populations.

  • 21.
    Liu, Yingxin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Wallenberg Wood Science Center, KTH, Sweden.
    Schütz, Christina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Wallenberg Wood Science Center, KTH, Sweden.
    Salazar-Alvarez, German
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Wallenberg Wood Science Center, KTH, Sweden.
    Bergström, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Assembly, Gelation, and Helicoidal Consolidation of Nanocellulose Dispersions2019Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 35, nr 10, s. 3600-3606Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The ability to probe the assembly, gelation, and helicoidal consolidation of cellulose nanocrystal (CNC) dispersions at high concentrations can provide unique insight into the assembly and can assist optimized manufacturing of CNC-based photonic and structural materials. In this Feature Article, we review and discuss the concentration dependence of the structural features, characterized by the particle separation distance and the helical pitch, at CNC concentrations (c) that range from the isotropic state, over the biphasic range, to the fully liquid crystalline state. The structure evolution of CNC dispersions probed by time resolved small-angle X-ray scattering during evaporation-induced assembly highlighted the importance of gelation and consolidation at high concentrations. We briefly discuss how the homogeneity of helicoidal nanostructures in dry CNC films can be improved and present an outlook for future work.

  • 22.
    Navarro, Julien R. G.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). University of Claude Bernard, France; Universidade de Sao Paulo, Brazil.
    Mayence, Arnaud
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Andrade, Juliana
    Lerouge, Frederic
    Chaput, Frederic
    Oleynikov, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Bergström, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Parola, Stephane
    Pawlicka, Agnieszka
    WO3 Nanorods Created by Self-Assembly of Highly Crystalline Nanowires under Hydrothermal Conditions2014Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, nr 34, s. 10487-10492Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    WO3 nanorods and wires were obtained via hydrothermal synthesis using sodium tungstate as a precursor and either oxalic acid, citric acid, or poly(methacrylic add) as a stabilizing agent. Transmission electron microscopy images showed that the organic acids with different numbers of carboxylic groups per molecule influence the final sizes and stacking nanostructures of WO3 wires. Three-dimensional electron diffraction tomography of a single nanocrystal revealed a hexagonal WO3 structure with preferential growth along the c-axis, which was confirmed by high-resolution transmission electron microscopy. WO3 nanowires were also spin-coated onto an indium tin oxide/glass conducting substrate, resulting in the formation of a film that was characterized by scanning electron microscopy. Finally, cyclic voltammetry measurements performed on the WO3 thin film showed voltammograms typical for the WO3 redox process.

  • 23.
    Ng, Jovice Boon Sing
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Bergström, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Brismar, Hjalmar
    Kamali-Zare, Padideh
    Release and molecular transport of cationic and anionic fluorescent molecules in mesoporous silica spheres2008Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, nr 19, s. 11096-11102Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We describe here a method for study of bulk release and local molecular transport within mesoporous silica spheres. We have analyzed the loading and release of charged fluorescent dyes from monodisperse mesoporous silica (MMS) spheres with an average pore size of 2.7 nm. Two different fluorescent dyes, one cationic and one anionic, have been loaded into the negatively charged porous material and both the bulk release and the local molecular transport within the MMS spheres have been quantified by confocal laser scanning microscopy. Analysis of the time-dependent release and the concentration profiles of the anionic dye within the spheres show that the spheres are homogeneous and that the release of this nonadsorbing dye follows a simple diffusion-driven process. The concentration of the cationic dye varies radially within the MMS spheres after loading; there is a significantly higher concentration of the dye close to the surface of the spheres (forming a “skin”) compared to that at the core. The release of the cationic dye is controlled by diffusion after an initial period of rapid release. The transport of the cationic dye within the MMS spheres of the dye from the core to near the surface is significantly faster compared to the transport within the surface “skin”. A significant fraction of the cationic dye remains permanently attached to the negatively charged walls of the MMS spheres, preferentially near the surface of the spheres. Relating bulk release to the local molecular transport within the porous materials provides an important step toward the design of new concepts in controlled drug delivery and chromatography.

  • 24.
    Ng, Jovice Boon Sing
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi, Avdelningen för oorganisk kemi.
    Kamali-Zare, Padideh
    Division of Cell Physics, Department of Applied Physics, AlbaNova, KTH.
    Sörensen, Malin
    YKI, Institute of Surface Chemistry.
    Alberius, Peter
    YKI, Institute of Surface Chemistry.
    Brismar, Hjalmar
    Division of Cell Physics, Department of Applied Physics, AlbaNova, KTH.
    Hedin, Niklas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi, Avdelningen för oorganisk kemi.
    Bergström, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi, Avdelningen för oorganisk kemi.
    Intraparticle Transport and Release of Dextran in Silica Spheres with Cylindrical Mesopores2010Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 6, nr 1, s. 466-470Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The transport of oligomeric molecules in silica spheres with cylindrical mesopores has been quantified and related to the features of the internal structures in the spherical particles and the interactions at the polymer-pore interface. An emulsion-solvent-evaporation method was used to produce silica spheres having cylindrical mesopores with an average pore diameter of 6.5 nm. The transport of dextran molecules (fluorescently tagged) with molecular weights of 3000 and 10000 g/mol were quantified using confocal laser scanning microscopy (CLSM). The intraparticle concentrations profiles in the dextran-containing spheres were flat at all times, suggesting that the underpinning diffusion is not fully isotropic and the release is controlled by the pores close to the external surface of the spheres. The release of dextran into the solution is characterized by an initial burst, followed by a long-term sustained release. This behaviour cannot be described by a spherical model with a single diffusion constant (or a surface-induced mass transfer resistance). The release follows a logarithmic time-dependency that can be described by a Temkin model.

  • 25.
    Nordlund, Gustav
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    Lönneborg, Rosa
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    Brzezinski, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    Formation of supported lipid bilayers on silica particles studied using flow cytometry2009Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, nr 8, s. 4601-4606Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Silica colloidal particles with functionalized surfaces are used, for example, in studies of membrane proteins or for drug delivery, where novel applications are based on the use of particles covered by lipid membrane bilayers. The mechanism by which such supported lipid bilayers are formed on spherical support is not fully understood. Here, we present results from studies of this process using a new method based on flow cytometry. The approach enabled us to detect particle populations coated and uncoated with lipids in the same sample according to the vesicle:particle surface area ratio. The data suggest that DOPC lipid vesicles efficiently break upon interaction with the silica colloidal particle surface; only a small fraction of the adsorbed vesicles remain unbroken. Furthermore, the data support earlier observations showing that formation of the lipid bilayer at the surface is a cooperative process, where bilayer formation is catalyzed by previously bound membrane fragments.

  • 26. Rengaraj, Selvaraj
    et al.
    Venkataraj, Selvaraj
    Jee, Sun Hee
    Kim, Younghun
    Tai, Cheuk-wai
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Repo, Eveliina
    Koistinen, Arto
    Ferancova, Adriana
    Sillanpaa, Mika
    Cauliflower-like CdS Microspheres Composed of Nanocrystals and Their Physicochemical Properties2011Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, nr 1, s. 352-358Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cauliflower-like cadmium sulfide (CdS) microspheres composed of nanocrystals have been successfully synthesized by a hydrothermal method using poly(ethylene glycol) (PEG) as the template coordination agent and characterized by a variety of methods. Our experiments confirmed that the size of the CdS microspheres could be easily modified by controlling the chain length of PEG. Powder X-ray diffraction and Raman spectroscopy measurements revealed the cubic structure of the CdS microspheres; morphological studies performed by HR-SEM and HR-TEM methods showed the cauliflower-like structure of the synthesized CdS microspheres. Each microsphere was identified to be created by the self-assembly of CdS nanocrystals and is attributed to the oriented aggregation of the CdS nanocrystals around a polymer-Cd(2+) complex spherical framework structure. X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray (EDX) analysis confirmed the stoichiometries of the CdS microspheres. Diffuse reflectance spectrum (DRS) measurements showed that increasing the PEG chain length increased the band gap value of the CdS microspheres slightly, from 1.99 to 2.06 eV. The cauliflower-like CdS microspheres could be applied to photocatalytic degradation studies.

  • 27. Rengaraj, Selvaraj
    et al.
    Venkataraj, Selvaraj
    Tai, Cheuk-wai
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Kim, Younghun
    Repo, Eveliina
    Sillanpaa, Mika
    Self-Assembled Mesoporous Hierarchical-like In(2)S(3) Hollow Microspheres Composed of Nanofibers and Nanosheets and Their Photocatalytic Activity2011Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, nr 9, s. 5534-5541Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Novel template-free hierarchical-like In(2)S(3) hollow microspheres were synthesized using thiosemicarbazide (NH(2)NHCSNH(2)) as both a sulfur source and a capping ligand in a ethanol/water system. In this study, we demonstrate that several process parameters, such as the reaction time and precursor ratio, strongly influence the morphology of the final product. The In(NO(3))(3)/thiosemicarbazide ratios were found to effectively play crucial roles in the morphologies of the hierarchical-like In(2)S(3) hollow microsphere nanostructure. With the ratios increasing from two to four, the In(2)S(3) crystals exhibited almost spherical morphologies. The synthesized products have been characterized by a variety of methods, including X-ray powder diffraction (XRD), Raman spectroscopy, field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray (EDX) analysis, X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible diffused reflectance spectroscopy (UV-vis DRS). XRD analysis confirmed the tetragonal structure of the In(2)S(3) hollow microspheres. The products show complex hierarchical structures assembled from nanoscale building blocks. The morphology evolution can be realized on both outside (surface) and inside (hollow cavity) the microsphere. The surface area analysis showed that the porous In(2)S(3) possesses a specific surface area of 108 m(2)/g and uniform distribution of pore sizes corresponding to the size of pores resulting from the self-assembled structures with flakes. The optical properties of In(2)S(3) were also investigated by UV-vis DRS, which indicated that our In(2)S(3) microsphere samples possess a band gap of similar to 1.96 eV. Furthermore, the photocatalytic activity studies revealed that the synthesized In(2)S(3) hollow microspheres exhibit an excellent photocatalytic performance in rapidly degrading aqueous methylene blue dye solution under visible light irradiation. These results suggest that In(2)S(3) hollow microspheres will be an interesting candidate for photocatalytic detoxification studies under visible light radiation.

  • 28. Ruan, Juanfang
    et al.
    Kjellman, Tomas
    Sakamoto, Yasuhiro
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Alfredsson, Viveka
    Transient Colloidal Stability Controls the Particle Formation of SBA-152012Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, nr 31, s. 11567-11574Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A hypothesis about (transient) colloidal stability as a controlling mechanism for particle formation in SBA-15 is presented. The hypothesis is based on results from both in situ and ex situ investigations, including cryogenic transmission electron microscopy (cryo-TEM), UV-vis spectroscopy, and dynamic light scattering (DLS). Cryo-TEM images show that particles grow via the formation of silica-Pluronic-water flocs, which coalesce in a seemingly arbitrary manner. Despite this, the final material consists of well-defined particles with a small size distribution. We argue that the interface between the flocs and surrounding media is covered by Pluronic molecules, which provide steric stabilization. As the flocs grow, the coverage of polymers at the interface is increased until a stable size is reached, and that regulates the particle size. By targeting the characteristics of the Pluronic molecules, during the on-going synthesis, the hypothesis is tested. The results are consistent with the concept of (transient) colloidal stability.

  • 29.
    Schütz, Christina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Royal Institute of Technology, Sweden.
    Agthe, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Fall, Andreas B.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Gordeyeva, Korneliya
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Guccini, Valentina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Royal Institute of Technology, Sweden.
    Salajkova, Michaela
    Plivelic, Tomas S.
    Lagerwall, Jan P. F.
    Salazar-Alvarez, German
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Royal Institute of Technology, Sweden.
    Bergström, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Rod Packing in Chiral Nematic Cellulose Nanocrystal Dispersions Studied by Small-Angle X-ray Scattering and Laser Diffraction2015Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, nr 23, s. 6507-6513Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The packing of cellulose nanocrystals (CNC) in the anisotropic chiral nematic phase has been investigated over a wide concentration range by small-angle X-ray scattering (SAXS) and laser diffraction. The average separation distance between the CNCs and the average pitch of the chiral nematic phase have been determined over the entire isotropic-anisotropic biphasic region. The average separation distances range from 51 nm, at the onset of the anisotropic phase formation, to 25 nm above 6 vol % (fully liquid crystalline phase) whereas the average pitch varies from approximate to 15 mu m down to approximate to 2 mu m as phi increases from 2.5 up to 6.5 vol %. Using the cholesteric order, we determine that the twist angle between neighboring CNCs increases from about 1 degrees up to 4 degrees as phi increases from 2.5 up to 6.5 vol %. The dependence of the twisting on the volume fraction was related to the increase in the magnitude of the repulsive interactions between the charged rods as the average separation distance decreases.

  • 30. Van Rie, Jonas
    et al.
    Schütz, Christina
    Gencer, Alican
    Lombardo, Salvatore
    Gasser, Urs
    Kumar, Sugam
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Salazar-Alvarez, Germán
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Kang, Kyongok
    Thielemans, Wim
    Anisotropic Diffusion and Phase Behavior of Cellulose Nanocrystal Suspensions Jonas2019Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 35, nr 6, s. 2289-2302Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we use dynamic light scattering in polarized and depolarized modes to determine the translational and rotational diffusion coefficients of concentrated rodlike cellulose nanocrystals in aqueous suspension. Within the range of studied concentrations (1-5 wt %), the suspension starts a phase transition from an isotropic to an anisotropic state as shown by polarized light microscopy and viscosity measurements. Small-angle neutron scattering measurements also confirmed the start of cellulose nanocrystal alignment and a decreasing distance between the cellulose nanocrystals with increasing concentration. As expected, rotational and translational diffusion coefficients generally decreased with increasing concentration. However, the translational parallel diffusion coefficient was found to show a local maximum at the onset of the isotropic-to-nematic phase transition. This is attributed to the increased available space for rods to move along their longitudinal axis upon alignment. This increased parallel diffusion coefficient thus confirms the general idea that rodlike particles gain translational entropy upon alignment while paying the price for losing rotational degrees of freedom. Once the concentration increases further, diffusion becomes more hindered even in the aligned regions due to a reduction in the rod separation distance. This leads once again to a decrease in translational diffusion coefficients. Furthermore, the relaxation rate for fast mode translational diffusion (parallel to the long particle axis) exhibited two regimes of relaxation behavior at concentrations where significant alignment of the rods is measured. We attribute this unusual dispersive behavior to two length scales: one linked to the particle length (at large wavevector q) and the other to a twist fluctuation correlation length (at low wavevector q) along the cellulose nanocrystal rods that is of a larger length when compared to the actual length of rods and could be linked to the size of aligned domains.

  • 31.
    Weber, Jens
    et al.
    Max Planck Institute of Colloids and Interfaces, Department of Colloid Chemistry.
    Bergström, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Mesoporous Hydrogels: Revealing Reversible Porosity by Cryoporometry,X-ray Scattering, and Gas Adsorption2010Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, nr 12, s. 10158-10164Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mesoporous poly(2-hydroxyethyl methacrylate-co-ethylene glycol dimethacrylate) networks, with cross-linkercontents ranging from 100 to 5 mol %, were prepared using a hard-templating approach. The imbibition of the silicapellets with a monomer/cross-linker mixture resulted in mesoporous gels with a pore size of ~10 nm, which correspondswell with the average size of the fumed silica particles (10-11 nm). The highly cross-linked materials showed permanentsurface areas of up to 230m2 g-1 and porosities up to ~33 vol %. The porosity of the hydrogels was investigated in bothdry and water-saturated state by nitrogen sorption, cryoporometry, and small-angle X-ray scattering (SAXS). It is onlypolymeric materials that contain 50 mol % or more of the cross-linker that showed a significant porosity afterevaporative drying. Freeze-drying is able to preserve the porosity also for hydrogels of intermediate cross-linker content,but the pores of the materials of low cross-linker content collapses completely upon solvent removal. The observedcritical cross-linker ratio for pore stability compared favorably with a simple estimate of the critical cross-linker densityneeded to make the material sufficiently stiff to withstand the Laplace pressure during solvent removal. Analysis of thehydrogels in the water swollen state revealed that gels having cross-linker contents down to 5 mol % still possessedmesoporosity. The pores got less defined at very low cross-linker contents, while their size was rather constant atintermediate to high cross-linking densities. Closed pores could be reopened upon swelling, which suggests that theobserved pore collapse upon drying may be at least partly reversible.

  • 32.
    Ye, Weihua
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    Lind, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik. Karolinska Institutet, Sweden.
    Eriksson, Jonny
    Mäler, Lena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    Characterization of the Morphology of Fast-Tumbling Bicelles with Varying Composition2014Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, nr 19, s. 5488-5496Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Small, fast-tumbling bicelles are frequently used in solution NMR studies of protein lipid interactions. For this purpose it is critical to have information about the organization of the lipids within the bicelle structure. We have studied the morphology of small, fast-tumbling bicelles containing DMPC and DHPC as a function of temperature, lipid concentration, and the relative ratio (q value) of lipid (DMPC) to detergent (DHPC) amounts. Dynamic light scattering and cryo-transmission electron microscopy techniques were used to measure the size of the bicelles and to monitor the shape and dispersity of the particles in the samples. The stability and size of DMPC-containing bicelle mixtures were found to be highly dependent on temperature and the total lipid concentration for mixtures with q = 1 and q = 1.5. Stable DMPC/DHPC bicelles are only formed at low q values (0.5). Bicelle mixtures with q > 0.5 appear to be multidisperse containing more than one component, one with r(H) around 2.5 nm and one with r(H) of 6-8 nm. This is interpreted as a coexistence of small (possibly mixed micelles) bicelles and much larger bicelles. Incubating the sample at 37 degrees C increases the phase separation. Moreover, low total amphiphile concentrations and low q values lead to the formation of a temperature-independent morphology, interpreted as the formation of small particles in which the DHPC and DMPC are more mixed. On the basis of these results, we propose the existence of a critical bicelle concentration, a parameter that determines the existence of bilayered bicelles, which varies with q value. This polymorphism was not observed at any concentrations for q = 0.5 bicelles, for which a small but detectable temperature dependence was observed at high concentrations. The results demonstrate that q = 0.5 mixtures predominantly form classical bicelles, but that caution is needed when using fast-tumbling mixtures with q values higher than 0.5.

  • 33.
    Zhu, Chuantao
    et al.
    Luleå University of Technology, Sweden.
    Dobryden, Illia
    Rydén, Jens
    Öberg, Sven
    Holmgren, Allan
    Mathew, Aji P.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Luleå University of Technology, Sweden.
    Adsorption Behavior of Cellulose and Its Derivatives toward Ag(I) in Aqueous Medium: An AFM, Spectroscopic, and DFT Study2015Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, nr 45, s. 12390-12400Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this study was to develop a fundamental understanding of the adsorption behavior of metal ions on cellulose surfaces using experimental techniques supported by computational modeling, taking Ag(I) as an example. Force interactions among three types of cellulose microspheres (native cellulose and its derivatives with sulfate and phosphate groups) and the silica surface in AgNO3 solution were studied with atomic force microscopy (AFM) using the colloidal probe technique. The adhesion force between phosphate cellulose microspheres (PCM) and the silica surface in the aqueous AgNO3 medium increased significantly with increasing pH while the adhesion force slightly decreased for sulfate cellulose microspheres (SCM), and no clear adhesion force was observed for native cellulose microspheres (CM). The stronger adhesion enhancement for the PCM system is mainly attributed to the electrostatic attraction between Ag(I) and the negative silica surface. The observed force trends were in good agreement with the measured zeta potentials. The scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) analyses confirmed the presence of silver on the surface of cellulose microspheres after adsorption. This study showed that PCM with a high content of phosphate groups exhibited a larger amount of adsorbed A(I) than CM and SCM and possible clustering of Ag(I) to nanoparticles. The presence of the phosphate group and a wavenumber shift of the P-OH vibration caused by the adsorption of silver ions on the phosphate groups were further confirmed with computational studies using density functional theory (DFT), which gives support to the above findings regarding the adsorption and clustering of Ag(I) on the cellulose surface decorated with phosphate groups as well as IR spectra.

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