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  • 1.
    Agrios, Alexander George
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Fysikalisk kemi (stängd 20110630). KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Cesar, I.
    Comte, P.
    Nazeeruddin, M. K.
    Grätzel, M.
    Nanostructured composite films for dye-sensitized solar cells by electrostatic layer-by-layer deposition2006Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 18, nr 23, s. 5395-5397Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The possibilities for making nanocomposite semiconductor films for DSC using the ELBL method was investigated. Coated slides were cut in half vertically giving two strips that can be subjected to different treatments for comparison. The electrode was heated to 450 °C for 30 min and then Cooled to 80 °C. Scanning electron microscopy of a sintered film with 5 cycles of TiO2 nanoparticles shows that the particles are well distributed and completely cover the transparent conducting oxide substrate. Spectroscopic measurements of a dye-coated film in acetonitrile found a dye concentration within the film of 0.15 mM based on an extinction coefficient. The solar cell including a scattering layer had more than double the current of the transparent layer-only cell. It was observed that ELBL method can produce TiO2 films for DSC with high efficiencies at low thickness.

  • 2.
    Andrén, Oliver C. J.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Zhang, Yuning
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Lundberg, Pontus
    Hawker, Craig J.
    Nyström, Andreas M.
    Malkoch, Michael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Therapeutic Nanocarriers via Cholesterol Directed Self-Assembly of Well-Defined Linear-Dendritic Polymeric Amphiphiles2017Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 29, nr 9, s. 3891-3898Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel platform of fluorescently labeled nanocarriers (NCs) is herein proposed based on amphiphilic linear-dendritic polymeric hybrids. These sophisticated polymers were synthesized with a high degree of structural control at a macro-molecular level, displayed hydrophobic cholesterol compartments as chain-terminus groups of the dendritic block and hydrophilic bifunctional linear poly(ethylene glycol) (PEG) block. Spherical supramolecular assemblies with therapeutically relevant properties were successfully achieved including (i) sizes in the region of 100 to 200 nm; (ii) narrow dispersity profile with values close to 0.12; and (iii) self-assembly down to nanomolar concentrations. The modular nature of the NCs permitted the encapsulation of single or dual anticancer drugs and in parallel provide intracellular fluorescent traceability. As polymer therapeutics, the NCs were proven to penetrate the cancerous cell membranes and deliver the cargo of drugs into the nuclei as well as the cytoplasm and mitochondria. The dual drug delivery of both doxorubicin (DOX) and triptolide substantially enhanced the therapeutic efficacy with a 63% significant increase against resistant breast cancer cells when compared to free DOX.

  • 3. Buscaglia, M. T.
    et al.
    Viviani, M.
    Zhao, Zhe
    Department of Physical Inorganic and Structural Chemistry, Stockholm University.
    Buscaglia, V.
    Nanni, P.
    Synthesis of BaTiO3 core-shell particles and fabrication of dielectric ceramics with local graded structure2006Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 18, nr 17, s. 4002-4010Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The coating of BaTiO3 particles with a different perovskite and the subsequent consolidation to dense ceramics retaining a radial composition gradient within the single grains are presented and discussed. A shell of SrTiO3 or BaZrO3 was directly grown on the surface of BaTiO3 spherical templates suspended in aqueous solution by means of a precipitation process making use of inorganic precursors. The overall composition and the particle size can be tailored over a wide range. Densification of the resulting core-shell particles was realized using spark plasma sintering or conventional sintering. Dense ceramics with locally graded structure can be only obtained by a careful choice of the sintering conditions, that is, controlling the interdiffusion between core and shell. The final materials show strongly modified dielectric properties in comparison to both the parent compounds and the homogeneous solid solutions. The proposed approach is generic and suggests a new avenue to create functional and structural polycrystalline materials with locally graded structure by the controlled sintering of core-shell particles.

  • 4.
    Buscaglia, Maria Teresa
    et al.
    IENI-CNR.
    Buscaglia, Vincenzo
    IENI-CNR.
    Curecheriu, Lavinia
    Alexandru Ioan Cuza University.
    Postolache, Petronel
    Polytechnic University of Bucharest.
    Mitoseriu, Liliana
    Polytechnic University of Bucharest.
    Ianculeschu, A.C
    Vasile, B.S
    Zhao, Zhe
    Department of Materials and Environmental Chemistry, Stockholm University.
    Nanni, Paolo
    University of Genoa.
    Fe2O3@BaTiO3 Core−Shell Particles as Reactive Precursors for the Preparation of Multifunctional Composites Containing Different Magnetic Phases2010Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 22, nr 16, s. 4740-4748Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Well-designed reactive precursors and templates allow for careful control of solid-state reactions at the nanoscale level, thus enabling the fabrication of materials with specific microstructures and properties. In this study, Fe2O3@BaTiO3 core−shell particles have been used as precursors for the in situ fabrication of multifunctional composites containing a dielectric/ferroelectric phase and two magnetic phases with contrasting coercivities (Fe2O3/Fe3O4, BaFe12O19/Ba12Fe28Ti15O84). The formation of new magnetic phases occurs during sintering or post-annealing via reaction between BaTiO3 and Fe2O3. The starting powders have been prepared using a multistep process that combines colloidal chemistry methods and a solid-state reaction. The nature and the amount of the magnetic phases and, consequently, the final magnetic properties of the composite can be controlled by varying the relative amount of Fe2O3 (30 or 50 vol %), the densification method (conventional or spark plasma sintering), and the processing temperature. The composites show constricted magnetic hysteresis loops with a coercivity of 0.1−2.5 kOe and a saturation magnetization of 5−16 emu/g. Composites obtained from powders containing 30 vol % Fe2O3 show, at temperatures of 20−80 °C and frequencies between 10 kHz and 1 MHz, a relative dielectric constant of 50 and dielectric losses of <10%.

  • 5. Chen, Ruikui
    et al.
    Yang, Xichuan
    Tian, Haining
    Wang, Xiuna
    Hagfeldt, Anders
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Effect of tetrahydroquinoline dyes structure on the performance of organic dye-sensitized solar cells2007Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 19, nr 16, s. 4007-4015Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Eleven novel donor acceptor pi-conjugated (D-pi-A) organic dyes have been engineered and synthesized as sensitizers for the application in dye-sensitized solar cells (DSSCs). The electron-donating moieties are substituted tetrahydroquinoline, and the electron-withdrawing parts are cyanoacrylic acid group or cyanovinylphosphonic acid group. Different lengths of thiophene-containing conjugation moieties (thienyl, thienylvinyl, and dithieno[3,2-b;2',3'-d]thienyl) are introduced to the molecules and serve as electron spacers. Detailed investigation on the relationship between the dye structure, photophysical and photoelectrochemical properties, and performance of DSSCs is described here. The bathochromic shift and increase of the molar extinction coefficient of the absorption spectrum are achieved by introduction of larger conjugation moiety. Even small structural changes of dyes result in significant changes in redox energies and adsorption manner of the dyes on TiO2 surface, affecting dramatically the performance of DSSCs based on these dyes. The higher performances are obtained by DSSCs based on the rigid dye molecules, C2 series dyes (Figure 1), although these dyes have lower light absorption abilities relative to other dyes. A maximum solar-to-electrical energy conversion efficiency (eta) of 4.53% is achieved under simulated AM 1.5 irradiation (100 mW/cm(2)) with a DSSC based on C2-2 dye (V-oc = 597 mV, J(sc) = 12.00 mA/cm(2), ff = 0.63). Density functional theory (DFT) calculations have been performed on the dyes, and the results show that electron distribution from the whole molecules to the anchoring moieties occurred during the HOMO-LUMO excitation. The cyanoacrylic acid groups or cyanovinylphosphonic acid group are essentially coplanar with respect to the thiophene units, reflecting the strong conjugation across the thiophene-anchoring groups.

  • 6.
    Cheng, Ming
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Chen, Cheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Aitola, Kerttu
    Zhang, Fuguo
    Hua, Yong
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Boschloo, Gerrit
    Kloo, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. Dalian University of Technology (DUT), China.
    Highly Efficient Integrated Perovskite Solar Cells Containing a Small Molecule-PC70BM Bulk Heterojunction Layer with an Extended Photovoltaic Response Up to 900 nm2016Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 28, nr 23, s. 8631-8639Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We demonstrate a high efficiency perovskite solar cell (PSC) integrated with a bulk heterojunction layer, based on acceptor-donor-acceptor (A-D-A) type hole transport material (HTM) and PC70BM composite, yielding improved photoresponse. Two A-D-A-structured hole transporting materials termed M3 and M4 were designed and synthesized. Applied as HTMs in PSCs, power conversion efficiencies (PCEs) of 14.8% and 12.3% were obtained with M3 and M4, respectively. The HTMs M3 and M4 show competitive absorption, but do not contribute to photocurrent, resulting in low current density. This issue was solved by mixing the HTMs with PC70BM to form a bulk heterojunction (BHJ) layer and integrating this layer into the PSC as hole transport layer (HTL). Through careful interface optimization, the (FAPbI(3))(0.85)(MAPbBr(3))(0.15)/HTM:PC70BM integrated devices showed improved efficiencies of 16.2% and 15.0%, respectively. More importantly, the incident-photon-to-current conversion efficiency (IPCE) spectrum shows that the photoresponse is extended to 900 nm by integrating the M4:PC70BM based BHJ and (FAPbI(3))(0.85)(MAPbBr(3))(0.15) layers.

  • 7.
    Cheng, Ming
    et al.
    Dalian Univ Technol, Inst Artificial Photosynth, State Key Lab Fine Chem, DUT KTH Joint Educ & Res Ctr Mol Devices, China.
    Chen, Cheng
    Yang, Xichuan
    Huang, Jing
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Zhang, Fuguo
    Xu, Bo
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Novel Small Molecular Materials Based on Phenoxazine Core Unit for Efficient Bulk Heterojunction Organic Solar Cells and Perovskite Solar Cells2015Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 27, nr 5, s. 1808-1814Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two novel Acceptor-Donor-Acceptor (A-D-A) structured small molecular (SM-) materials POZ2 and POZ3 using an electron-rich phenoxazine (POZ) unit as a core building block were designed and synthesized. Their unique characteristics, such as suitable energy levels, strong optical absorption in the visible region, high hole mobility, and high conductivity, prompted us to use them both as p-type donor materials (DMs) in SM-bulk heterojunction organic solar cells (BHJ OSCs) and as hole transport materials (HTMs) in CH3NH3PbI3-based perovskite solar cells (PSCs). The POZ(2)-based devices yielded promising power conversion efficiencies (PCEs) of 7.44% and 12.8% in BHJ OSCs and PSCs, respectively, which were higher than the PCEs of 6.73% (BHJ-OSCs) and 11.5% (PSCs) obtained with the POZ3-based devices. Moreover, our results demonstrated that the POZ2 employing the electron-deficient benzothiazole (BTZ) as linker exhibited higher hole mobility and conductivity than that of the POZ3 using thiophene as linker, leading to better device performance both in BHJ-OSCs and PSCs. These results also provide guidance for the molecular design of high charge carrier mobility SM-materials for highly efficient BHJ OSCs and PSCs in the future.

  • 8.
    Guo, Baolin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Finne-Wistrand, Anna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Degradable and Electroactive Hydrogels with Tunable Electrical Conductivity and Swelling Behavior2011Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 23, nr 5, s. 1254-1262Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Degradable electrically conducting hydrogels (DECHs), which combine the unique properties of degradable polymers and electrically conducting hydrogels, were synthesized by introducing biodegradable segments into conductive hydrogels. These DECHs were obtained by joining together the photopolymerized macromer acrylated poly(D,L-lactide)-poly(ethylene glycol)-poly(D,L-lactide) (AC-PLA-PEG-PLA-AC), glycidyl methacrylate (GMA), ethylene glycol dimethacrylate (EGDMA) network and aniline tetramer (AT) by the coupling reaction between AT and the GMA The electrical conductivity and swelling behavior of these DECHs were tuned by changing the AT content in the hydrogels, the cross-linking degree, and the environmental pH value. The good electroactivity and thermal stability of these hydrogels were demonstrated by UV-vis spectroscopy, cyclic voltammetry, and TGA tests. The chemical structure and morphology of these polymers were characterized by NMR, FT-IR, SEC, and SEM. These hydrogels possessing both degradability and electrical conductivity represent a new class of biomaterial and will lead to various new possibilities in biomedical applications.

  • 9.
    Guo, Baolin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Finne-Wistrand, Anna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Simple Route to Size-Tunable Degradable and Electroactive Nanoparticles from the Self-Assembly of Conducting Coil-Rod-Coil Triblock Copolymers2011Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 23, nr 17, s. 4045-4055Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A simple route to size-tunable nanoparticles from the self-assembly of degradable and electrically conductive coil rod coil triblock copolymers based on an aliphatic polyester and conducting species is presented. A series of coil rod coil triblock copolymers consisting of a middle aniline pentamer (AP) segment and two polycaprolactone (PCL) segments were easily synthesized by a combination of a ring-opening polymerization of CL initiated by an aniline dimer (AD) giving AD-PCL and an oxidative coupling reaction between the AD-PCL and p-phenylenediamine. This strategy avoids the multistep reaction used in previous work. The electroactivity of these copolymers was investigated by UV and cyclic voltammetry. The conductivity of the copolymers was dependent on the AP content and the conductivity mechanism of the triblock copolymers is discussed. Interestingly, these triblock copolymers can undergo self-assembly in selective solvent such as CHCl(3) as indicated by NMR and transmission electron microscope (TEM) observations. Dynamic light scattering (DLS) showed that the size of the nanoparticles was dependent on the molecular weight of the copolymers and on the oxidation state of the AP, The morphology of the nanoparticles was studied by TEM and SEM. These triblock copolymers and their size-tunable nanopartides with degradability and electroactivity offer new possibilities in biomedical applications, such as controlled drug delivery, biosensors, and cardiovascular and neural tissue engineering.

  • 10. Harnish, B.
    et al.
    Robinson, J. T.
    Pei, Zhichao
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Ramström, Olof
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Yan, Mingdi
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    UV-cross-linked poly(vinylpyridine) thin films as reversibly responsive surfaces2005Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 17, nr 16, s. 4092-4096Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report that UV-cross-linked poly(4-vinylpyridine) (P4VP) films acted as reversibly responsive coatings that controlled surface wettability and swelling toward external stimuli: solvent and pH. The polymer films were prepared simply by spin-coating a solution of P4VP followed by UV irradiation. These cross-linked films, when treated with chloroform, showed similar to 31% increase in film thickness whereas films extracted with methylene chloride or n-butanol exhibited a slight decrease. The increase in film thickness was due to the protonation of pyridyl groups by hydrogen chloride resulting from the photodegeneration of chloroform. The film expanded to minimize repulsion around the charged centers. This hypothesis was further confirmed by exposing the cross-linked film to hydrogen chloride vapor. The film expanded similar to 37% whereas no thickness increase was observed for films exposed to ammonia or methanol vapors. The extent of swelling was monitored in situ using a quartz crystal microbalance sensor. Large oscillation frequency shifts were detected when the UV-cross-linked P4VP film was exposed to acidic buffer solutions. The changes were rapid, and the effect was reversible.

  • 11. Högberg, D.
    et al.
    Soberats, B.
    Yatagai, R.
    Uchida, S.
    Yoshio, M.
    Kloo, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Segawa, H.
    Kato, T.
    Liquid-crystalline dye-sensitized solar cells: Design of two-dimensional molecular assemblies for efficient ion transport and thermal stability2016Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 28, nr 18, s. 6493-6500Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nanostructured liquid-crystalline (LC) electrolytes have been developed for efficient and stable quasi-solid-state dye-sensitized solar cells (DSSCs). Two types of ionic LC assemblies for electrolytes have been designed: (i) noncovalent assemblies of two-component mixtures consisting of I2-doped imidazolium ionic liquids and carbonate-terminated mesogenic compounds (noncovalent type) and (ii) single-component mesogenic compounds covalently bonding an imidazolium moiety doped with I2 (covalent type). These mesogenic compounds are designed with flexible oligooxyethylene spacers connecting the mesogenic and the polar moieties. The oligooxyethylene-based material design inhibits crystallization and leads to enhanced ion transport as compared to alkyl-linked analogues due to the higher flexibility of the oligooxyethylene spacer. The noncovalent type mixtures exhibit a more than 10 times higher I3- diffusion coefficient compared to the covalent type assemblies. DSSCs containing the noncovalent type liquid crystals show power conversion efficiencies (PCEs) of up to 5.8 ± 0.2% at 30 °C and 0.9 ± 0.1% at 120 °C. In contrast, solar cells containing the covalent type electrolytes show significant increase in PCE up to 2.4 ± 0.1% at 120 °C and show superior performance to the noncovalent type-based devices at temperature above 90 °C. Furthermore, the LC-DSSCs exhibit excellent long-term stability over 1000 h. These novel electrolyte designs open unexplored paths for the development of DSSCs capable of efficient conversion of light to electricity in a wide range of temperatures.

  • 12.
    Högberg, Daniel
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Soberats, Bartolome
    Uchida, Satoshi
    Yoshio, Masafumi
    Kloo, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Segawa, Hiroshi
    Kato, Takashi
    Nanostructured Two-Component Liquid-Crystalline Electrolytes for High-Temperature Dye-Sensitized Solar Cells2014Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 26, nr 22, s. 6496-6502Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nanostructured liquid-crystalline (LC) ion transporters have been developed and applied as new electrolytes for dye-sensitized solar cells (DSSCs). The new electrolytes are two-component liquid crystals consisting of a carbonate-based mesogen and an ionic liquid that self-assemble into two-dimensional (2D) nanosegregated structures forming well-defined ionic pathways suitable for the I-/I-3(-) redox couple transportation. These electrolytes are nonvolatile and they show LC phases over wide temperature ranges. The DSSCs containing these electrolytes exhibit exceptional open-circuit voltages (V-oc) and improved power conversion efficiencies with increasing temperature. Remarkably, these solar cells operate at temperatures up to 120 degrees C, which is, to the best of our knowledge, the highest working temperature reported for a DSSC. The nature of the LC electrolyte and the interactions at the TiO2 electrode/electrolyte interface lead to a partial suppression of electron recombination reactions, which is key in the exceptional features of these LC-DSSCs. Thus, this type of solar cells are of interest, because they can produce electricity efficiently from light at elevated temperatures.

  • 13. Karlsson, Roger H
    et al.
    Herland, Anna
    Hamedi, Mahiar
    Wigenius, Jens A
    Åslund, Andreas
    Liu, Xianjie
    Fahlman, Mats
    Inganäs, Olle
    Konradsson, Peter
    Iron-Catalyzed Polymerization of Alkoxysulfonate-Functionalized 3,4-Ethylenedioxythiophene Gives Water-Soluble Poly(3,4-ethylenedioxythiophene) of High Conductivity2009Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 21, nr 9, s. 1815-1821Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Chemical polymerization of a 3,4-ethylenedioxythiophene derivative bearing a sulfonate group (EDOTS) is reported. The polymer, PEDOT-S, is fully water-soluble and has been produced by polymerizing EDOT-S in water, using Na2S2O8 and a catalytic amount of FeCl 3. Elemental analysis and XPS measurements indicate that PEDOT-S is a material with a substantial degree of self-doping, but also contains free sulfate ions as charge-balancing counterions of the oxidized polymer. Apart from selfdoping PEDOT-S, the side chains enable full water solubility of the material; DLS studies show an average cluster size of only 2 nm. Importantly, the solvation properties of the PEDOT-S are reflected in spin-coated films, which show a surface roughness of 1.2 nm and good conductivity (12 S/cm) in ambient conditions. The electro-optical properties of this material are shown with cyclic voltammetry and spectroelectrochemical experiment reveals an electrochromic contrast (̃48% at λmax ) 606 nm).

  • 14. Khan, A.
    et al.
    Toprak, Muhammet
    University of California at Santa Barbara, Chemistry Department.
    et al.,
    Holographic recording in cross-linked polymeric matrices through photoacid generation2008Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 20, nr 11, s. 3669-3674Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report a novel strategy for writing volume holograms by photoacid generation and subsequent acid-catalyzed degradation leading to increased free volume/refractive index modulation in the exposed regions of a cross-linked rigid polymeric matrix. This strategy offers nondestructive read out and high diffraction efficiency and allows optical-quality, millimeter thick films to be fabricated that possess excellent thermal and dimensional stability. A key feature of this approach is the efficient acid-catalyzed degradation of functional groups in the cross-linked matrix leading to release of volatile products which diffuse readily out of the thick films. Furthermore, the reported data storage material is lightweight and inexpensive and can be easily processed into different shapes, making it an attractive candidate for data storage applications.

  • 15. Kim, D. K.
    et al.
    Mikhaylova, M.
    Wang, F. H.
    Kehr, J.
    Bjelke, B.
    Zhang, Y.
    Tsakalakos, T.
    Muhammed, Mamoun
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Starch-coated superparamagnetic nanoparticles as MR contrast agents2003Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 15, nr 23, s. 4343-4351Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Superparamagnetic iron oxide nanoparticles (SPION) with suitable bio-compatible coatings have been used in biomedicine, particularly in magnetic resonance imaging (MRI), tissue engineering, and drug delivery applications. In this study, we describe the synthesis of SPION and its use for experimental in-vivo applications in MRI. SPION with a mean size of 6 nm have been prepared under inert atmosphere, in a polymeric starch matrix, by controlled chemical coprecipitation of magnetite phase from aqueous solutions containing suitable salts of Fe2+ and Fe3+. X-ray powder diffraction was used to confirm a pure magnetite phase for the SPION. The influence of oxidizing agents on the cleavage of the starch chains was investigated by changing the concentration of H2O2. An aqueous solution of H2O2/NaOH cleaves the glycosidic bonds and reduces the polymer chains to a critical average molecular weight. From the dynamic light scattering (DLS) size distribution, the bulk agglomeration size was decreased by approximately 50% of the bulk size when treated by H2O2. Freshly synthesized starch-coated SPION in buffered artificial cerebro-spinal fluid were injected into the brain parenchyma of anaesthetized rats for in-vivo monitoring. Analysis of T-2*-weighted images and T-2*-maps revealed formation of a. concentration gradient for the SPION at the injection site, indicating SPION dispersion in the living brain parenchyma from the center of the injection site toward the periphery. The starch-coated SPION show a biocompatibility and possibility of being transported in the extracellular space as well as being internalized in nerve cells.

  • 16. Kim, D. K.
    et al.
    Mikhaylova, M.
    Zhang, Y.
    Muhammed, Mamoun
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Protective coating of superparamagnetic iron oxide nanoparticles2003Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 15, nr 8, s. 1617-1627Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Magnetic nanoparticles are becoming increasingly important for several biomedical applications. For example, superparamagnetic magnetite nanoparticles with suitable biocompatible coatings are useful in magnetic resonance imaging, tissue engineering, and drug delivery, etc. In this study we report the synthesis of magnetite nanoparticles and the further coating of these particles by several types of protective layers. Thermodynamic modeling of the chemical system has been adopted as a rational approach to establish routes to better synthesis conditions for pure phase magnetite. Quantitative analysis of different reaction equilibria involved in the precipitation of magnetite from aqueous solutions has been used to determine optimum synthesis conditions. Superparamagnetic magnetite nanoparticles (SPION) with diameters of 6 and 12 nm have been prepared by controlled chemical coprecipitation of magnetite phase from aqueous solutions containing suitable salts of Fe2+ and Fe3+ under inert atmosphere. Pure magnetite phase SPION could be observed from X-ray diffraction. Magnetic colloid suspensions containing particles with three different types of coatings (sodium oleate (NaOl), starch, and methoxypoly(ethylene glycol) (MPEG)) have been prepared by using different stabilization methods. SPION coatings were studied by determining the change of the surface charge by electrokinetic sonic amplitude (ESA) measurements, as a function of varying NaOl in the solution, where the amount of NaOl needed to form a stable suspension was determined. For stable suspension, the optimum concentration of sodium oleate (NaOl) chemisorbed at 2.5 g of SPION surface is 5.2 x 10(-7) M NaOl which shows maximum ESA value of 0.034 mPa(.)M/V. SPION coating by starch results in the formation of agglomerate. The agglomeration size of starch-coated SPION can be decreased by introducing H2O2 as an oxidizing agent; the resulting particle size is 42 nm as determined by dynamic light scattering (DLS). For the modification of SPION surfaces with MPEG, the surface was first silanized by 3-aminopropyltrimethoxy silane (APTMS) as a coupling agent with a thickness of two or three molecular layers. AFM image shows that each cluster includes several magnetite single particles with the cluster size around 120 nm. SPION, both coated and uncoated, have been characterized by several techniques. AFM was used to image the MPEG-coated SPION. FTIR study indicated that the different coating agents cover the SPION surface. Magnetic characterization was carried out using SQUID and Mossbauer spectroscopy.

  • 17. Kordas, K.
    et al.
    Mustonen, T.
    Toth, G.
    Vahakangas, J.
    Uusimaki, A.
    Jantunen, H.
    Gupta, A.
    Rao, K. V.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Vajtai, R.
    Ajayan, P. M.
    Magnetic-field induced efficient alignment of carbon nanotubes in aqueous solutions2007Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 19, nr 4, s. 787-791Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Efficient alignment of aqueous carboxyl-functionalized multiwalled carbon nanotubes having remanent iron catalyst particles are carried out in relatively low external magnetic fields (B <= 1017 mT). The nanotubes were grown by catalytic chemical vapor deposition and then functionalized in a multistep oxidation process using nitric acid and potassium permanganate. In the field-induced ordering, the ferromagnetic property of iron nanoparticles entrapped in the inner-tubular cavity of nanotubes is exploited. Considerable dichroism of nanotube solutions (up to 3.02) is measured and deposition of aligned CNT networks from the solutions on silicon substrates is demonstrated.

  • 18.
    Li, Shanghua
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Soliman, Hesham M. A.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Zhou, Jian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Toprak, Muhammet
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Platzek, Dieter
    Ziolkowski, Pawel
    Müller, Eckhard
    Effects of annealing and doping on nanostructured bismuth telluride thick films2008Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 20, nr 13, s. 4403-4410Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Bismuth telluride is the state-of-the-art thermoelectric (TE) material for cooling applications with a figure of merit of ∼1 at 300 K. There is a need for the development of TE materials based on the concept of thick films for miniaturized devices due to mechanical and manufacturing constraints for the thermoelement dimensions. We reported earlier a method for the fabrication of high-quality nanostructured bismuth telluride thick films with thickness from 100 to 350 μm based on electrochemical deposition techniques. In this paper, annealing is performed to further improve the TE performance of the nanostructured bismuth telluride thick films and n/p-type solid solutions are successfully fabricated by doping Se and Sb, respectively. The conditions for both annealing and doping for the thick films are investigated, and the effects of annealing and doping on morphology, crystalline phase, grain size, Seebeck coefficient, homogeneity, electrical conductivity, and power factor of the bismuth telluride thick films have been studied.

  • 19.
    Li, Shanghua
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Toprak, Muhammet S.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Soliman, Hesham M. A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Zhou, Jian
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Muhammed, Mamoun
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Platzek, Dieter
    Institute of Materials Research, German Aerospace Center (DLR).
    Müller, Eckhard
    Institute of Materials Research, German Aerospace Center (DLR).
    Fabrication of nanostructured thermoelectric bismuth telluride thick films by electrochemical deposition2006Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 18, nr 16, s. 3627-3633Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Bismuth telluride ( Bi2Te3)-based solid solutions are state-of-the-art thermoelectric (TE) materials for cooling applications at room temperature with a high figure of merit ZT. Nanostructured TE bismuth telluride thick films have been fabricated by electrodeposition from a solution containing bismuth nitrate and tellurium dioxide in 1 M nitric acid onto gold-sputtered aluminum substrates. A conventional three-electrode cell was used with a platinum sheet as the counter electrode and a saturated calomel electrode (SCE) as the reference electrode. Ethylene glycol (EG) was added to the electrolyte in order to increase the thickness of the deposited films, and its effect on the structure, morphology, and compositional stoichiometry of the deposited film was investigated. SEM and XRD were used for structural and compositional characterization. Bismuth telluride films with thicknesses of ca. 350 mu m, a stoichiometric composition of Bi2Te3, and a hexagonal crystal structure were obtained. A microprobe technique was used to measure the lateral Seebeck coefficient in several samples. The free-standing films were shown to be of high homogeneity, where the abundance distribution of the Seebeck coefficient showed a half width of less than 1 mu V K-1 and a high electrical conductivity of around 450 S cm(-1) at room temperature.

  • 20.
    Mikhaylova, Maria
    et al.
    KTH, Tidigare Institutioner, Materialvetenskap.
    Kim, Do-Kyung
    KTH, Tidigare Institutioner, Materialvetenskap.
    Berry, CC
    Zagorodni, Andrei
    KTH, Tidigare Institutioner, Materialvetenskap.
    Toprak, Muhammet S.
    KTH, Tidigare Institutioner, Materialvetenskap.
    Curtis, ASG
    Muhammed, Mamoun
    KTH, Tidigare Institutioner, Materialvetenskap.
    BSA immobilization on amine-functionalized superparamagnetic iron oxide nanoparticles2004Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 16, nr 12, s. 2344-2354Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Immobilization of bovine serum albumin (BSA) on surface-modified superparamagnetic iron oxide nanoparticles (SPION) has been performed by two different double-step immobilization approaches. The first approach consists of preparation of SPION by controlled chemical coprecipitation in the presence of BSA solution, whereas the second approach includes preliminary surface modification of SPION with an amine group using a coupling agent of 3-aminepropyltrimethoxysilane (APTMS). Both procedures are followed by 1-ethyl-3-(3-dimethylaminepropyl) carbodiimide hydrochloride (EDC) activation with sequential immobilization of the layer of BSA. Additionally, an attempt to modify the surface of SPION with amine and carboxylic groups is undertaken by using L-aspartic acid (LAA). TEM shows that the particle size varies in the range 10-15 nm and does not change significantly after the coating process. The presence of BSA and amine groups on the surface of SPION is confirmed by FT-IR. Magnetic properties are investigated by VSM and results indicate that the superparamagnetic properties are retained for BSA-coated SPION while reducing the value of saturation magnetization (M-s). The binding capacity is estimated from thermo-gravimetric and chemical analyse;. APTMS-coated SPION show higher BSA binding capacity compared to that of coprecipitated SPION in the presence of BSA. In vitro tests have been performed after the functionalization of SPION with LAA and BSA. Human dermal fibroblasts are incubated with the surface-modified SPION for 6 and 24 h to observe cell behavior, morphology, cytoskeletal organization, and interactions between cell and SPION. BSA-coated SPION incubated with cells demonstrated a cell response similar to that of control cells, with no adverse cell damage and no endocytosis, whereas LAA-coated SPION show partial endocytosis without cytoskeletal disorganization.

  • 21.
    Målberg, Sofia
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Plikk, Peter
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Finne Wistrand, Anna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Design of Elastomeric Homo- and Copolymer Networks of Functional Aliphatic Polyester for Use in Biomedical Applications2010Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 22, nr 9, s. 3009-3014Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An unsaturated aliphatic polyester was synthesized by condensation polymerization to yield the pre-polymer, poly(but-2-ene-1,4-diyl malonate) (PBM), which is applicable as an elastomeric network and as a macroinitiator for the polymerization of cyclic ester monomers. The method of preparation was simple and straightforward with no need to purify the monomers or add a potentially harmful catalyst. The number average molecular weight of the pre-polymer could easily be increased from 5000 to 12000 by extending the reaction time. The pre-polymer PBM was successfully cross-linked with UV-radiation to form a clear, transparent, colorless, flexible, and strong film. PBM as a macroinitiator for L-lactide (LLA) and epsilon-caprolactone (CL) polymerizations highly increased the ductility of the LLA-polymer, while maintaining the strength, compared to PLLA polymerized with common initiators. The tensile properties of PCL were also improved. The linear PCL-PBM and PLLA-PBM polymers were easily cross-linked to give polymers with greater strength and higher modulus as the result.

  • 22. Nissinen, T. A.
    et al.
    Kiros, Yohannes
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Gasik, M.
    Leskela, M.
    MnCo2O4 preparation by microwave-assisted route synthesis (MARS) and the effect of carbon admixture2003Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 15, nr 26, s. 4974-4979Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Catalyst spinel MnCo2O4 with particle size <30 nm was prepared by a novel microwave-assisted route. To determine the optimal amount of carbon needed as a microwave susceptor, varying amounts of amorphous carbon powder (7-26 wt %) were mixed with the aqueous solutions of Mn- and Co-nitrates. After heat treatment at 200degreesC in a conventional oven, the mixtures were heat-treated in a microwave oven (2.45 GHz) at a power of 350 W. The effect of the carbon amount on the formation and properties of the catalysts was studied. In this production method, 13 wt % of carbon was found to be the minimum needed for spinel MnCo2O4 formation. Most of the carbon was oxidized during the microwave treatment. When the carbon content in the nitrate-carbon mixture was increased beyond 13 wt %, the carbon content and the specific surface area of the final catalyst started to decrease. However, the carbon amount of 18 wt % in the initial nitrate-carbon mixture was found to be the most preferable when considering the catalytic activity of the spinel toward oxygen reduction reaction in alkaline electrolyte.

  • 23. Nylen, Johanna
    et al.
    Lidin, Sven
    Andersson, Magnus
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Iversen, Bo Brummerstedt
    Liu, Hongxue
    Newman, Nate
    Haussermann, Ulrich
    Low-temperature structural transitions in the phonon-glass thermoelectric material beta-Zn4Sb3: Ordering of Zn interstitials and defects2007Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 19, nr 4, s. 834-838Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The low-temperature phase transitions of thermoelectric Zn4Sb3 have been characterized using single-crystal X-ray diffraction, electrical resistance, and thermal conductivity measurements. Room-temperature stable, disordered beta-Zn4Sb3 undergoes a phase transition at 254 K to ordered alpha-Zn4Sb3, which has an ideal composition Zn13Sb10. Below 235 K, a second low-temperature phase (alpha'-Zn4Sb3) can be detected. The sequence of phase transitions beta-alpha-alpha' is reversible. The alpha-alpha' transformation originates from a slight Zn deficiency with respect to Zn13Sb10. The actual composition of Zn4Sb3 is Zn13-delta Sb10.

  • 24.
    Nyström, Andreas
    et al.
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Vestberg, Robert
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Lindgren, Mikael
    Malmström, Eva
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Hult, Anders
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Porphyrin-Cored 2,2-Bis(methylol)propionic Acid Dendrimers2004Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Chemistry of materials, Vol. 16, nr 14, s. 2794-2804Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The synthesis and characterization of dendron-coated porphyrins up to the fifth generation are described. Both free base and zinc-cored tetraphenylporphyrin (TPPH2 and TPPZn) were used, from which the dendrons were divergently grown using the anhydride of acetonide-protected bis-MPA (acetonide-2,2-bis(methoxy)propanoic anhydride). It is shown that a spacer must be attached to the porphyrin to increase the hydrolytic stability and allow synthesis of higher generations. Direct coupling of dendrons to the porphyrins was also investigated but failed to give full substitution of the porphyrin core. The absorption and fluorescence emission data for the TPPZn dendrimers indicate that the porphyrin configuration may change at higher generations. The hydrodynamic volume of the dendrimers is calculated from the polarization anisotropy decay data. It is shown that these bis-MPA dendrimers are significantly smaller than the same generation Frechet-type benzyl ether TPP dendrimer.

  • 25.
    Olsson, Richard T.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Ström, Valter
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Deng, Jinglan
    School of Science, Wuhan University of Technology.
    Savage, Stephen J.
    Swedish Defence Research Agency (FOI), Linköping.
    Gedde, Ulf W.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Core-shell nanostructured cobalt ferrite-sisesquioxane-epoxy composites: nanofiller surface treatment, particle dispersion, mechanical and magnetic propertiesInngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, s. 1-44Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Magnetic core-shell cobalt ferrite-silsesquioxane-epoxy nanocomposites have been prepared with uniform nanoparticle distribution. The nanoparticles were surface-treated with methyl- (MTMS), aminopropyl- (APTMS), glycidoxypropyl- (GPTMS) trimethoxy-silane. The optimum coating process was performed in a water/merthanol solution on the particles directly after their synthesis without prior drying. The GPTMS-coatings were 30 nm thick and the nanoparticles dispersed well in epoxy without sedimentation. The MTMS-coated nanoparticles (3 nm coating) formed weak agglomerates in epoxy but showed no sedimentation. The APTMS-coated particles formed stronger agglomerates, which led to sedimentation of the aorticles during molding. The GPTMS-based composites showed higher fracture toughness than the MTMS-based composites. This was attributed to the presence of large agglomerates in the latter systems and to the stronger interface between coating and epoxy in the former systems. Ultrasonic alkaline etching allowed precis determination of the ferrite content of the core-shell nanoparticles. Magnetometry showe a markedly lower coercivity for nanoparticles with thin coatings (MTMS) than for the nanoparticles with thicker coatings (GPTMS) suggesting the occurrence of magnetic exchange interaction in the former systems. The nanocomposites showed no influence of surface coating on coercivity or saturation magnetization suggesting that the inter-particle distances were greater than 0.5 nm.

  • 26.
    Olsson, Richard T.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Salazar-Alvarez, German
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Gedde, Ulf W.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Lindberg, F.
    Structural Chemistry, Arrhenius Laboratory, Stockholm University.
    Savage, Steven J.
    Swedish Defense Research Agency (FOI), Linköping.
    Controlled synthesis of near-stoichiometric cobalt ferrite nanoparticles2005Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 17, nr 20, s. 5109-5118Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Large batches of more than 18 g of cobalt ferrite nanoparticles (CoxFe3-xO4, x being close to 1) have been prepared by the chemie douce approach using aqueous solutions of metal salts at 90 degrees C mixed with solutions of hydroxide ions under air atmosphere. By suitable choice of the metal ion to hydroxide ion ratio, it was possible to prepare nanoparticles with the stoichiometric composition (CoFe2O4). The composition and the density of the nanoparticles could be controlled by varying the metal ion to hydroxide ion molar ratio in the reactor. Adjusting the initial concentration ratios of the reactants prior to the mixing allowed the variation of the average size of the nanoparticles. The repeatability of the average particle diameter of the synthesis was typically 5 nm and average particle sizes could be controlled between 50 and 80 nm determined by nitrogen adsorption measurements (consistent with the number size average 35-60 mn obtained by transmission electron microscopy studies). Aging of the suspensions resulted in a narrowing of the initial broad unimodal distribution. The narrowing of the size distribution was associated with the phase transformation of delta-FeOOH platelets to spinel phase. The spinel nanoparticles had different morphologies: cubic, spherical, and occasionally irregular. Nanoparticles with the stoichiometric composition were a mixture of cubical and spherical shapes. Nanoparticles with less than the stoichiometric cobalt content had an irregular morphology, whereas nanoparticles with greater than the stoichiometric concentration of cobalt were predominantly spherical.

  • 27. Philippe, Bertrand
    et al.
    Saliba, Michael
    Correa-Baena, Juan-Pablo
    Cappel, Ute B.
    Uppsala University, Sweden.
    Turren-Cruz, Silver-Hamill
    Gratzel, Michael
    Hagfeldt, Anders
    Rensmo, Hakan
    Chemical Distribution of Multiple Cation (Rb+, Cs+, MA(+), and FA(+)) Perovskite Materials by Photoelectron Spectroscopy2017Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 29, nr 8, s. 3589-3596Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Lead-based mixed perovskite materials have emerged in the last couple of years as promising photovoltaic materials. Recently, it was shown that improved material stability can be achieved by incorporating small amounts of inorganic cations (Cs+ and Rb+), partially replacing the more common organic cations (e.g., methylammonium, MA, and formamidinium, FA). Especially, a mixed cation composition containing Rb+, Cs+, MA(+), and FA(+) was recently shown to have beneficial optoelectronic properties and was stable at elevated temperature. This work focuses on the composition of this material using synchrotron-based photoelectron spectroscopy. Different probing depths were considered by changing the photon energy of the X-ray source providing insights on the chemical composition and the chemical distribution near the surface of the samples. Perovskite materials containing two, three, or four monovalent cations were analyzed and compared. The presence of Cs and Rb was observed both at the sample surface and toward the bulk, and we found that in the presence of three or four cations, less unreacted PbI2 remains in the sample. Interestingly, Rb and Cs appear to act jointly resulting in a different cation depth profile compared to that of the triple counterparts. Our findings provide significant understanding of the intricate depth-dependent chemical composition in perovskite materials using the common practice of cation mixing.

  • 28.
    Phuyal, Dibya
    et al.
    Uppsala Univ, Dept Phys & Astron, Solid State Phys, Angstrom Lab, Box 516, SE-75121 Uppsala, Sweden..
    Safdari, Majid
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Pazoki, Meysam
    Uppsala Univ, Dept Engn Sci, Solid State Phys, Angstrom Lab, SE-75121 Uppsala, Sweden..
    Liu, Peng
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Philippe, Bertrand
    Uppsala Univ, Dept Phys & Astron, Solid State Phys, Angstrom Lab, Box 516, SE-75121 Uppsala, Sweden..
    Kyashnina, Kristina O.
    ESRF, Rossendorf Beamline, CS40220, F-38043 Grenoble 9, France.;HZDR, Inst Resource Ecol, POB 510119, D-01314 Dresden, Germany..
    Karis, Olof
    Uppsala Univ, Dept Phys & Astron, Solid State Phys, Angstrom Lab, Box 516, SE-75121 Uppsala, Sweden..
    Butorin, Sergei M.
    Uppsala Univ, Dept Phys & Astron, Solid State Phys, Angstrom Lab, Box 516, SE-75121 Uppsala, Sweden..
    Rensmo, Hakan
    Uppsala Univ, Dept Phys & Astron, Solid State Phys, Angstrom Lab, Box 516, SE-75121 Uppsala, Sweden..
    Edvinsson, Tomas
    Uppsala Univ, Dept Engn Sci, Solid State Phys, Angstrom Lab, SE-75121 Uppsala, Sweden..
    Kloo, Lars
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Gardner, James M.
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Electronic Structure of Two-Dimensional Lead(II) Iodide Perovskites: An Experimental and Theoretical Study2018Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 30, nr 15, s. 4959-4967Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Layered two-dimensional (2D) hybrid organic-inorganic perovskites (HOP) are promising materials for light-harvesting applications because of their chemical stability, wide flexibility in composition and dimensionality, and increases in photovoltaic power conversion efficiencies. Three 2D lead iodide perovskites were studied through various X-ray spectroscopic techniques to derive detailed electronic structures and band energetics profiles at a titania interface. Core-level and valence band photoelectron spectra of HOP were analyzed to resolve the electronic structure changes due to the reduced dimensionality of inorganic layers. The results show orbital narrowing when comparing the HOP, the layered precursor PbI2, and the conventional 3D (CH3NH3)PbI3 such that different localizations of band edge states and narrow band states are unambiguously due to the decrease in dimensionality of the layered HOPs. Support from density functional theory calculations provide further details on the interaction and band gap variations of the electronic structure. We observed an interlayer distance dependent dispersion in the near band edge electronic states. The results show how tuning the interlayer distance between the inorganic layers affects the electronic properties and provides important design principles for control of the interlayer charge transport properties, such as the change in effective charge masses as a function of the organic cation length. The results of these findings can be used to tune layered materials for optimal functionality and new applications.

  • 29.
    Qin, Jian
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Nogués, Josep
    Mikhaylova, Maria
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Roig, Anna
    Munõz, Juan S.
    Muhammed, Mamoun
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Differences in the Magnetic Properties of Co, Fe and Ni 250-300 nm Wide Nanowires Electrodeposited in Amorphous Anodized Alumina Templates2005Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 17, nr 7, s. 1829-1834Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Anodized alumina membranes (AAMs) were synthesized by a three-step electrochemical anodization of aluminum. The anodization results in a hexagonally pseudo-ordered 2D array of nanochannels. The AAMs were used as templates to grow Ni, Co, Fe nanowires, with diameters in the range of 250-300 nm, by electrodeposition. The AAM appears to be amorphous, while the metal nanowires are polycrystalline. The angular dependence of the coercivity, HC, of the Ni nanowires presents a smooth variation from a moHC = 5.5 mT when the field is applied perpendicular to the wires to moHC = 53 mT when the field is applied parallel to them. However, the Co and Fe nanowires exhibit a peak in the angular dependence of HC for fields applied close to the AAM plane (i.e. perpendicular to the wires). The competition between shape anisotropy and dipolar interaction between the nanowires seems to be responsible for the difference in magnetic behavior between the different metals.

  • 30. Rousset, Jean
    et al.
    Olsson, Pär
    Département de Matériaux et Mécanique des Composants, EDF-R and D, Les Renardières, France.
    McCandless, Brian
    Lincot, Daniel
    Structure and Optoelectronics of Electrodeposited Cadmium Ditelluride (CdTe(2))2008Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 20, nr 20, s. 6550-6555Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Electrodeposition is a powerful method to perform low cost, large area CdTe deposition. Good quality semiconductor materials for photovoltaic applications as well as high growth rates have been achieved using this technique. Electrodeposition in acidic solution is considered in this work. In these conditions, depending on the applied potential, a transition from the crystalline CdTe compound to a quasi-amorphous CdTe, compound has been shown. The present work explores the properties of this new compound and compares them to those of the classical electrodeposited CdTe. The experimental study (X-ray diffraction (XRD), optical transmission, and ellipsometry measurements) is complemented by theoretical results obtained by first principles modeling using density functional theory. The pyrite structure, with a lattice parameter a = 7.250 angstrom and an internal parameter u = 0.389, is found as the theoretically favored crystal structure. The corresponding calculated X-ray diffraction diagram is comparable to those experimentally obtained. Considering both experimental and modeling results the band-ap should be indirect with a value (1.08 eV) lower than that of electrodeposited CdTe. Moreover, this Te-rich compound is shown to be highly absorbent in the 1.5-4 eV energy range. This property can be partially explained by the flat band structure profile obtained by ab initio calculations. Finally, XRD under heating carried out on CdTe(2) shows that this compound is decomposed into CdTe + Te at relatively low temperature (> 150 degrees C).

  • 31.
    Salazar-Alvarez, German
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Sort, Jordi
    Institució Catalana de Recerca i Estudis Avançats (ICREA).
    Macedo, Waldemar A. A.
    Laboratório de Física Aplicada, Centro de Desenvolvimento da Tecnologia Nuclear, Minais Gerais.
    Ardisson, Jose D.
    Laboratório de Física Aplicada, Centro de Desenvolvimento da Tecnologia Nuclear, Minais Gerais.
    Baro, Maria Dolors
    Departament de Física, Universitat Autònoma de Barcelona, Bellaterra.
    Gedde, Ulf W.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Nogués, Josep
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Enhanced coercivity in Co-rich near-stoichiometric CoFe3-xO4+delta nanoparticles prepared in large batches2007Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 19, nr 20, s. 4957-4963Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The relationship between the structure and composition with the magnetic properties of near stoichiometric cobalt ferrite nanoparticles CoxFe3-xO4+delta (0.85 < x < 1.1) prepared in large batches with average sizes in the range 60-210 nm has been investigated. Chemical analysis and Rietveld refinement of the X-ray diffraction data in conjunction with Mossbauer spectroscopy allowed us to identify an interplay between particle size, microstructure (concentration of interstitial ions, microstrain, cation arrangement in octahedral and tetrahedral sites), and composition, which sensitively controls the magnetic properties such as coercivity and saturation magnetization. In all cases, cobalt-rich compositions resulted in a higher coercivity, whereas lower degrees of inversion and higher iron contents led to slightly higher saturation magnetization values.

  • 32.
    Sang, Lingzi
    et al.
    Univ Illinois, Dept Chem, Urbana, IL 61801 USA..
    Bassett, Kimberly L.
    Univ Illinois, Dept Chem, Urbana, IL 61801 USA..
    Castro, Fernando C.
    Northwestern Univ, Dept Mat Sci & Engn, Evanston, IL 60208 USA..
    Young, Matthias J.
    Argonne Natl Lab, Appl Mat Div, Lemont, IL 60439 USA..
    Chen, Lin
    Argonne Natl Lab, Appl Mat Div, Lemont, IL 60439 USA..
    Haasch, Richard T.
    Univ Illinois, Frederick Seitz Mat Res Lab, Urbana, IL 61801 USA..
    Elam, Jeffrey W.
    Argonne Natl Lab, Appl Mat Div, Lemont, IL 60439 USA..
    Dravid, Vinayak P.
    Northwestern Univ, Dept Mat Sci & Engn, Evanston, IL 60208 USA..
    Nuzzo, Ralph G.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap.
    Gewirth, Andrew A.
    Univ Illinois, Dept Chem, Urbana, IL 61801 USA..
    Understanding the Effect of Interlayers at the Thiophosphate Solid Electrolyte/Lithium Interface for All-Solid-State Li Batteries2018Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 30, nr 24, s. 8747-8756Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    All-solid-state Li-ion batteries afford possibilities to enhance battery safety while improving their energy and power densities. Current challenges for achieving high-performance all-solid-state batteries with long cycle life include shorting resulting predominantly from Li dendrite formation and infiltration through the solid electrolyte (SE) and increases in cell impedance induced by SE decomposition at the SE/electrode interface. In this work, we evaluate the electrochemical properties of two interlayer materials, Si and LixAl(2-x/3)O3 (LiAlO), at the Li7P3S11 (LPS)/Li interface. Compared to the Li/LPS/Li symmetric cells in absence of interlayers, the presence of Si and LiAlO both significantly enhance the cycle number and total charge passing through the interface before failures resulting from cell shorting. In both cases, the noted improvements were accompanied by cell impedances that had increased substantially. The data reveal that both interlayers prevent the direct exposure of LPS to the metallic Li and therefore eliminate the intrinsic LPS decomposition that occurs at Li surfaces before electrochemical cycling. After cycling, a reduction of LPS to Li2S occurs at the interface when a Si interlayer is present; LiAlO, which functions to drop the potential between Li and LPS, suppresses LPS decomposition processes. The relative propensities toward SE decomposition follows from the electrochemical potentials at the interface, which are dictated by the identities of the interlayer materials. This work provides new insights into the phase dynamics associated with specific choices for SE/electrode interlayer materials and the requirements they impose for realizing high efficiency, long lasting all-solid-state batteries.

  • 33. Scragg, Jonathan J.
    et al.
    Kubart, Tomas
    Wätjen, J. Timo
    Ericson, Tove
    Linnarsson, Margareta K.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Platzer-Björkman, Charlotte
    Effects of Back Contact Instability on Cu2ZnSnS4 Devices and Processes2013Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 25, nr 15, s. 3162-3171Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cu2ZnSnS4 (CZTS) is a promising material for thin film solar cells based on sustainable resources. This paper explores some consequences of the chemical instability between CZTS and the standard Mo "back contact" layer used in the solar cell. Chemical passivation of the back contact interface using titanium nitride (TiN) diffusion barriers, combined with variations in the CZTS annealing process, enables us to isolate the effects of back contact chemistry on the electrical properties of the CZTS layer that result from the synthesis, as determined by measurements on completed solar cells. It is found that instability in the back contact is responsible for large current losses in the finished solar cell, which can be distinguished from other losses that arise from instabilities in the surface of the CZTS layer during annealing. The TiN-passivated back contact is an effective barrier to sulfur atoms and therefore prevents reactions between CZTS and Mo. However, it also results in a high series resistance and thus a reduced fill factor in the solar cell. The need for high chalcogen pressure during CZTS annealing can be linked to suppression of the back contact reactions and could potentially be avoided if better inert back contacts were to be developed.

  • 34. Sun, Xuan
    et al.
    Chen, Weiwei
    Liang, Lijun
    Hu, Wei
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Wang, Huanhuan
    Pang, Zhenfeng
    Ye, Yuxun
    Hu, Xiurong
    Wang, Qi
    Kong, Xueqian
    Jin, Yizheng
    Lei, Ming
    Construction of Electron Transfer Network by Self-Assembly of Self-n-Doped Fullerene Ammonium Iodide2016Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 28, nr 23, s. 8726-8731Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Construction of pi-conjugation network in ordered fullerenes by self-assembly remains challenging for improving their optoelectronic performance and developing advanced materials. Here, we present a layered stacking of self-n-doped fullerene ammonium iodide (PCBANI) through a delicate balance among iodide anion-C-60 pi, electrostatic, and C-60 pi-pi interactions to construct an unprecedented supra molecular system. X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and computational modeling are carried out to clarify the structure. Remarkably, the formation of intermolecular iodide anion pi interactions between iodide and the surrounded fullerene cores yields an iodide-linked C-60 pi-pi two-dimensional (2-D) network. Consequently, the ordered and tightly packed fullerenes sandwiching iodide could facilitate electron transfer along the network system. Comparative devices incorporating the disordered films show dramatically decreased current densities and manifest the importance of the pi-extended network for electron transfer. This work provides a key strategy to control the packing of ordered electron-transport materials to suppress defect formation. Moreover, engineering self-assembly of self-n-doped fullerenes with novel architectures, such as nanowire, nanotube, and nanoparticle would yield new functionalities that are suitable for photovoltaic devices, nanoelectronics, etc.

  • 35. Tenga, A.
    et al.
    Garcia-Garcia, F. J.
    Mikhaylushkin, A. S.
    Espinosa-Arronte, B.
    Andersson, Magnus
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Haussermann, U.
    Sphalerite-chalcopyrite polymorphism in semimetallic ZnSnSb22005Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 17, nr 24, s. 6080-6085Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have investigated the system ZnSnSb2 in the course of our attempts to modify thermoelectric Zn-Sb frameworks. ZnSnSb2 is only accessible when employing Sn as reactive flux in the synthesis. The material shows an order-disorder transition in the temperature interval between 225 and 240 degrees C and decomposes peritectically at about 360 degrees C. The high-temperature form of ZnSnSb2 adopts the Zn/Sn disordered cubic sphalerite-type structure. Electron microscopy investigations reveal that samples quenched from 350 degrees C already contain domains of the low-temperature form, which has the Zn/Sn ordered tetragonal chalcopyrite structure. The c/a ratio of the tetragonal structure is, within experimental errors, identical to the ideal value 2. This gives rise to intricate microtwinning in the low-temperature chalcopyrite form of ZnSnSb2 as obtained in samples quenched from 250 degrees C. First principles electronic structure calculations demonstrate that the tetragonal low-temperature form of ZnSnSb2 has a narrow band gap of about 0.2 eV. This is in agreement with the semimetallic behavior of the material found from resistivity measurement. The shape of the electronic density of states for ZnSnSb2 is similar to thermoelectric binary Zn-Sb frameworks. However, the thermopower of ZnSnSb2 is rather low with room-temperature values ranging from 10 to 30,mu V/K.

  • 36.
    Yan, Mingdi
    et al.
    Department of Chemistry, Portland State University.
    Ren, J.
    Covalent immobilization of ultrathin polymer films by thermal activation of perfluorophenyl azide2004Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 16, nr 9, s. 1627-1632Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The attachment of thin films on solid materials is an effective way to tailor the chemical and physical properties of the surface layer. In this article, we report an alternative approach to the covalent immobilization of ultrathin polymer films. The immobilization chemistry is based on the C-H/N-H insertion reaction of perfluorophenyl nitrenes that were generated by the thermal activation of perfluorophenyl azides (PFPAs). In the process, a silicon wafer was treated with PFPA-silane 1 to give a monolayer of azido groups on the surface. A polymer was then spin coated on the functionalized wafer and the sample was heated. Thermolysis produced perfluorophenyl nitrenes which underwent insertion reactions with the neighboring polymer chains. Removal of the excess polymer by solvent extraction resulted in nanometer-thick polymer thin films covalently attached to the wafer surface. Using polystyrene and poly(2-ethyl-2-oxazoline) as examples, covalently immobilized thin films with thicknesses ranging from a few to over a hundred A were obtained. The thickness of the film could be controlled by the type and the molecular weight of the polymer. Patterned polymer films were also fabricated using this method.

  • 37.
    Zhang, Xiaoliang
    et al.
    Beihang Univ, Sch Mat Sci & Engn, Beijing 100191, Peoples R China..
    Cappel, Ute B.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Jia, Donglin
    Beihang Univ, Sch Mat Sci & Engn, Beijing 100191, Peoples R China..
    Zhou, Qisen
    Beihang Univ, Sch Mat Sci & Engn, Beijing 100191, Peoples R China..
    Du, Juan
    Beihang Univ, Sch Mat Sci & Engn, Beijing 100191, Peoples R China..
    Sloboda, Tamara
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Svanström, Sebastian
    Uppsala Univ, Dept Phys & Astron, Div Mol & Condensed Matter Phys, Box 516, SE-75120 Uppsala, Sweden..
    Johansson, Fredrik O. L.
    Uppsala Univ, Dept Phys & Astron, Div Mol & Condensed Matter Phys, Box 516, SE-75120 Uppsala, Sweden..
    Lindblad, Andreas
    Uppsala Univ, Dept Phys & Astron, Div Mol & Condensed Matter Phys, Box 516, SE-75120 Uppsala, Sweden..
    Giangrisostomi, Erika
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Ovsyannikov, Ruslan
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Liu, Jianhua
    Beihang Univ, Sch Mat Sci & Engn, Beijing 100191, Peoples R China..
    Rensmo, Håkan
    Uppsala Univ, Dept Phys & Astron, Div Mol & Condensed Matter Phys, Box 516, SE-75120 Uppsala, Sweden..
    Gardner, James M.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Johansson, Erik M. J.
    Uppsala Univ, Phys Chem, Dept Chem Angstrom, S-75120 Uppsala, Sweden..
    Probing and Controlling Surface Passivation of PbS Quantum Dot Solid for Improved Performance of Infrared Absorbing Solar Cells2019Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 31, nr 11, s. 4081-4091Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Surface properties of colloidal quantum dots (CQDs) are critical for the transportation and recombination of the photoinduced charge carrier in CQD solar cells, therefore dominating the photovoltaic performance. Herein, PbS CQD passivated using liquid-state ligand exchange (LSLX) and solid-state ligand exchange (SSLX) strategies are in detail investigated using photoelectron spectroscopy (PES), and solar cell devices are prepared to understand the link between the CQD surface properties and the solar cell function. PES using different energies in the soft and hard Xray regime is applied to study the surface and bulk properties of the CQDs, and the results show more effective surface passivation of the CQDs prepared with the LSLX strategy and less formation of lead-oxide. The CQD solar cells prepared with LSLX strategy show higher performance, and the photoelectric measurements suggest that the recombination of photoinduced charges is reduced for the solar cell prepared with the LSLX approach. Meanwhile, the fabricated solar cells exhibit good stability. This work provides important insights into how to fine-tune the CQD surface properties by improving the CQD passivation, and how this is linked to further improvements of the device photovoltaic performance.

  • 38.
    Zhao, Weifeng
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi. Sichuan University, China .
    Glavas, Lidija
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Odelius, Karin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Edlund, Ulrica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Albertsson, Ann Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Facile and Green Approach towards Electrically Conductive Hemicellulose Hydrogels with Tunable Conductivity and Swelling Behavior2014Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 26, nr 14, s. 4265-4273Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A one-pot reaction to synthesize electrically conductive hemicellulose hydrogels (ECHHs) is developed via a facile and green approach in water and at ambient temperature. ECHHs were achieved by cross-linking O-acetyl-galactoglucomannan (AcGGM) with epichlorohydrin in the presence of conductive aniline pentamer (AP) and were confirmed by infrared spectroscopy (IR) and elemental analysis. All hydrogels had macro-porous structures, and the thermal stability of ECHHs was improved by the addition of AP. Hydrogel equilibrium swelling ratios (ESRs) varied from 13.7 to 11.4 and were regulated by cross-linker concentration. The ESRs can also be tuned from 9.6 to 6.0 by changing the AP content level from 10 to 40% (w/w) while simultaneously altering conductivity from 9.05 x 10(-9) to 1.58 X 10(-6) S/cm. ECHHs with controllable conductivity, tunable swelling behavior, and acceptable mechanical properties have great potential for biomedical applications, such as biosensors, electronic devices, and tissue engineering.

  • 39. Zhao, Y. S.
    et al.
    Yang, W. S.
    Xiao, D. B.
    Sheng, X. H.
    Yang, X.
    Shuai, Z. G.
    Luo, Yi
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Yao, J. N.
    Single crystalline submicrotubes from small organic molecules2005Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 17, nr 25, s. 6430-6435Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The single crystalline submicrotubes of a small organic functional molecule, 2,4,5-triphenylimidazole (TPI), were successfully prepared with a facile method. A series of characterizations indicated that the tubes were obtained from the rolling followed by seaming of a preorganized two-dimensional sheet-like structure, whose formation was due to the efficient cooperation of several molecular recognition elements. The length and diameter of the TPI tubes can be readily controlled by adjusting the experimental conditions. The as-prepared submicrotubes have intensive luminescence and size-dependent optical properties, which allows them to find potential applications in novel optical and optoelectronic devices together with their single crystalline structure and good stability. The strategy described here should give a useful enlightenment for the design and fabrication of tubular structures from small organic molecules.

  • 40.
    Zhou, Yunyun
    et al.
    Fudan Univ, Dept Macromol Sci, State Key Lab Mol Engn Polymers, Shanghai 200433, Peoples R China..
    Baryshnikov, Gleb V.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Bogdan Khmelnitsky Natl Univ, Dept Chem & Nanomat Sci, UA-18031 Cherkassy, Ukraine..
    Li, Xuping
    Fudan Univ, Dept Macromol Sci, State Key Lab Mol Engn Polymers, Shanghai 200433, Peoples R China..
    Zhu, Mingjie
    Fudan Univ, Dept Macromol Sci, State Key Lab Mol Engn Polymers, Shanghai 200433, Peoples R China..
    Ågren, Hans
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Zhu, Liangliang
    Fudan Univ, Dept Macromol Sci, State Key Lab Mol Engn Polymers, Shanghai 200433, Peoples R China..
    Anti-Kasha's Rule Emissive Switching Induced by Intermolecular H-Bonding2018Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 30, nr 21, s. 8008-8016Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The exploration of emission pathways from high-excited states in organic luminogens has recently become prosperous owing to improved possibilities to study so-called anti-Kasha's rule emission with the potential of improving the luminescent quantum efficiency. However, emission pathway switching among different high-excited states has rarely been addressed through external control. We here present a rational design and synthesis of a novel azulene-based emitter to achieve a responsive control of its anti-Kasha's rule emissive switching. The emitter initially gives rise to an S-3-to-S-0 dominant emission as indicated by our experimental and theoretical studies. On this basis, it can be toggled into an S-2-to-S-0 dominant emission upon the H-bond formation between the triformyl groups and water molecules. Such a process, which originates from the H-bonding regulated distribution of excited state energy, is accompanied by a remarkable fluorescent color conversion and a significant improvement of the fluorescent quantum yield in the azulene family. Moreover, a reversible emissive switching in doped films was observed to depend on a solid-state H-bond tuning process with moisture sensitivity. These results may provide new insight for building advanced chemical systems for visualized sensing with high distinguishability.

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