| 1. |
- Chen, Zhuoying, et al.
(författare)
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Enhanced charge transport by incorporating additional thiophene units in the poly(fluorene-thienyl-benzothiadiazole) polymer
- 2011
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Ingår i: Organic electronics. - : Elsevier. - 1566-1199 .- 1878-5530. ; 12:3, s. 461-471
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Tidskriftsartikel (refereegranskat)abstract
- We report a comparative study of optical properties, structure and morphology, field-effect transistor (FET) and solar cell performance between poly(4-(3,4-dihexyl-2,2-bithiophen-5-yl)-7-(5-(9,9-dioctyl-9H-fluoren-2-yl)-3,4-dihexyl-2,2-bithiophen-5-yl)benzo[c][1,2,5]-thiadiazole) (F8TTBTT), and its predecessor poly((9,9-dioctylfluorene)-2,7-diyl-alt[4,7-bis(3-hexylthien-5-yl)-2,1,3-benzothiadiazole]-2,2 -diyl) (F8TBT). Compared to F8TBT, F8TTBTT has two more thiophene units incorporated in its monomer structure. Such a modification leads to a reduced optical band gap, improved charge injection and significantly enhanced ambipolar field-effect mobilities reaching 5 x 10 (2) cm(2) V (1) s (1) for holes and 4 x 10 (3) cm(2) V (1) s (1) for electrons. The enhanced carrier mobilities are most likely a result of an increased backbone planarization and interchain interaction. As a consequence of ambipolar transport, light-emission was observed from the transistor channel during operation. The reduced band gap and improved charge transport make F8TTBTT an interesting candidate also for solar cell applications. Unoptimized solar cells based on F8TTBTT: PCBM blends were found to exhibit power conversion efficiency under AM 1.5 illumination of similar to 1.54%. (C) 2011 Published by Elsevier B.V.
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| 2. |
- Fang, Junfeng, et al.
(författare)
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Conjugated Zwitterionic Polyelectrolyte as the Charge Injection Layer for High-Performance Polymer Light-Emitting Diodes
- 2011
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society. - 0002-7863 .- 1520-5126. ; 133:4, s. 683-685
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Tidskriftsartikel (refereegranskat)abstract
- A new zwitterionic conjugated polyelectrolyte without free counterions has been used as an electron injection material in polymer light-emitting diodes. Both the efficiency and maximum brightness were considerably improved in comparison with standard Ca cathode devices. The devices showed very fast response times, indicating that the improved performance is, in addition to hole blocking, due to dipoles at the cathode interface, which facilitate electron injection.
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| 3. |
- Gautrot, Julien E, et al.
(författare)
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Protein-Resistant NTA-Functionalized Polymer Brushes for Selective and Stable Immobilization of Histidine-Tagged Proteins
- 2010
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Ingår i: Applied Materials & Interfaces. - : ACS. - 1944-8244 .- 1944-8252. ; 2:1, s. 193-202
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Tidskriftsartikel (refereegranskat)abstract
- Protein-resistant polymeric coatings that allow highly selective immobilization of specific biomolecules are essential for biomedical applications such as microarrays, biosensing, heterogeneous catalysis, and bioengineering. Polymer brushes are particularly interesting for this purpose because their chemical structure and physical properties can easily be tailored to meet specific needs. This article explores the functionalization of two protein-resistant polymer brushes, poly(oligoethylene glycol methacrylate) (POEGMA) and poly(hydroxyethyl methacrylate) (PHEMA), with nitrilotriacetic acid (NTA) moieties that can complex histidine-tagged (His-tagged) proteins selectively and reversibly. Using fluorescence microscopy, IR spectroscopy, X-ray photoelectron spectroscopy, surface plasmon resonanace, and ellipsometry, we demonstrate that His-tagged green fluorescent protein can be immobilized on NTA brushes with high stability and loading. The loading saturation reached for NTA-POEGMA is higher than that for NTA-PHEMA because of increased swelling of the former brush. Despite this higher loading capacity, NTA-POEGMA remained highly protein-resistant, which shows its potential for “clean” and specific protein immobilization. Finally, we showed that the preserved protein resistance of NTA-POEGMA brushes can be used to generate well-defined binary biofunctional patterns via a simple protocol of incubations and washes. These patterns may find applications in cell arraying and screening.
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| 4. |
- He, Ximin, et al.
(författare)
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Formation of Nanopatterned Polymer Blends in Photovoltaic Devices
- 2010
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Ingår i: Nano letters (Print). - : American Chemical Society. - 1530-6984 .- 1530-6992. ; 10:4, s. 1302-1307
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we demonstrate a double nanoimprinting process that allows the formation of nanostructured polymer heterojunctions of composition and morphology that can be selected independently. We fabricated photovoltaic (PV) devices with extremely high densities (10(14)/mm(2)) of interpenetrating nanoscale columnar features in the active polymer blend layer. The smallest feature sizes are as small as 25 nm on a 50 nm pitch, which results in a spacing of hererojunctions at or below the exciton diffusion length. Photovoltaic devices based on double-imprinted poly((9,9-dioctylfluorene)-2,7-diyl-alt-[4,7-bis(3-hexylthien-5-yl)-2,1,3-benzothiadiazole]-2,2 diyl) (F8TBT)/poly(3-hexylthiophene) (P3HT) films are among the best polymer polymer blend devices reported to date with a power conversion efficiency (PCE, eta(e)) of 1.9%.
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| 5. |
- He, Ximin, et al.
(författare)
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Formation of Well-Ordered Heterojunctions in Polymer: PCBM Photovoltaic Devices
- 2011
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Ingår i: Advanced Functional Materials. - : Wiley-VCH Verlag. - 1616-301X .- 1616-3028. ; 21:1, s. 139-146
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Tidskriftsartikel (refereegranskat)abstract
- The nanoscale morphology in polymer:PCBM based photovoltaic devices is a major contributor to overall device performance. The disordered nature of the phase-separated structure, in combination with the small length scales involved and the inherent difficulty of reproducing the exact morphologies when spin-coating and annealing thin blend films, have greatly hampered the development of a detailed understanding of how morphology impacts photo voltaic device functioning. In this paper we demonstrate a double nanoimprinting process that allows the formation of nanostructured polymer: PCBM heterojunctions of composition and morphology that can be selected independently. We fabricated photovoltaic (PV) devices with extremely high densities (10(14) mm(-2)) of interpenetrating nanoscale columnar features (as small as 25 nm; at or below the exciton diffusion length) in the active layer. By comparing device results of different feature sizes and two different polymer: PCBM combinations, we demonstrate how double imprinting can be a powerful tool to systematically study different parameters in polymer photovoltaic devices.
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| 6. |
- Ramstedt, Madeleine, et al.
(författare)
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Bacterial and mammalian cell response to poly(3-sulfopropyl methacrylate) brushes loaded with silver halide salts
- 2009
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612 .- 1878-5905. ; 30:8, s. 1524-31
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the antibacterial and cytotoxic effect of surfaces with sulphonate brushes containing silver salts. By using the same type of samples for both cytotoxicity and antibacterial studies, these two parameters could be compared in a controlled way. The silver was incorporated into the brush in four different forms to enable release of silver ions at different concentrations and different rates. It was found that although the surfaces displayed very good antibacterial properties in buffer solutions, this effect disappeared in systems with high protein content. Similarly, the silver-containing surfaces displayed cytotoxic effects in the absence of serum proteins but this effect was reduced in the presence of serum. The speciation of silver in the different solutions is discussed. Cytotoxic and antibacterial effects are compared at the different silver concentrations released. The implications of a concentration range where silver could be used to kill bacterial without harmful effects on mammalian cells are also discussed and questioned.
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| 7. |
- Ramstedt, Madeleine, et al.
(författare)
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Synthesis and characterization of poly(3-sulfopropylmethacrylate) brushes for potential antibacterial applications
- 2007
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 23:6, s. 3314-21
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Tidskriftsartikel (refereegranskat)abstract
- This article describes the aqueous atom transfer radical polymerization synthesis of poly(3-sulfopropylmethacrylate) brushes onto gold and Si/SiO2 surfaces in a controlled manner. The effect of Cu(I)/Cu(II) ratio was examined, and a quartz crystal microbalance was used to study the kinetics of the brush synthesis. The synthesized brushes displayed a thickness from a few nanometers to several hundred nanometers and were characterized using atomic force microscopy, ellipsometry, Fourier transform infrared spectroscopy (FTIR), contact angle measurements, and X-ray photoelectron spectroscopy (XPS). The as-synthesized sulfonate brushes had very good ion-exchange properties for the ions tested in this study, i.e., Na+, K+, Cu2+, and Ag+. FTIR and XPS show that the metal ions are coordinating to sulfonate moieties inside the brushes. The brushes were easily loaded with silver ions, and the effect of silver ion concentration on silver loading of the brush was examined. The silver-loaded brushes were shown to be antibacterial toward both gram negative and gram positive bacteria. The silver leaching was studied through leaching experiments into water, NaNO3, and NaCl (physiological medium). The results from these leaching experiments are compared and discussed in the article.
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| 8. |
- Tan, Khooi Y., et al.
(författare)
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Study of thiol-ene chemistry on polymer brushes and application to surface patterning and protein adsorption
- 2016
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Ingår i: Polymer Chemistry. - 1759-9954 .- 1759-9962. ; 7:4, s. 979-990
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Tidskriftsartikel (refereegranskat)abstract
- Polymer brushes are attractive polymeric coatings for biomedical applications such as tissue engineering, biosensor design and the purification of biological samples. In order to confer bioactivity to these coatings, their functionalisation with biomolecules, proteins and peptides, is required. In this respect, thiol-ene coupling offers interesting features as it is regioselective, efficient and can be controlled by photo-irradiation to allow surface patterning. The efficiency of thiol-ene and the related thiol-yne couplings to poly(glycidyl methacrylate) brushes was quantified. The impact of the structure of thiols to be tethered and reaction conditions on the brush loading and the kinetics of reaction were investigated. Thiol-ene reactions were then used to pattern brushes via direct irradiation through a mask or via reactive micro-contact printing. The resulting patterns were used to control albumin adsorption and the formation of protein patterns.
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| 9. |
- Trmcic-Cvitas, Jelena, et al.
(författare)
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Biofunctionalized protein resistant oligo(ethylene glycol)-derived polymer brushes as selective immobilization and sensing platforms
- 2009
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Ingår i: Biomacromolecules. - : American Chemical Society. - 1526-4602 .- 1525-7797. ; 10:10, s. 2885-94
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Tidskriftsartikel (refereegranskat)abstract
- Poly(oligo(ethylene glycol) methacrylate) (POEGMA) brushes are extremely protein resistant polymer coatings that can reduce nonspecific adsorption of proteins from complex mixtures such as blood, sera and plasma. These coatings can be prepared via atom transfer radical polymerization with excellent control of their thickness and grafting density. We studied their direct functionalization with streptavidin and developed an assay for determining which coupling conditions afford the highest streptavidin loading efficiency. Disuccinimidyl carbonate was found to be the most efficient activating agent for covalent capture of the receptor. Using infrared and X-ray photoelectron spectroscopy, fluorescence microscopy, surface plasmon resonance, and ellipsometry, we examined how structural parameters such as the length of the oligo(ethylene glycol) side chain affect streptavidin functionalization, but also immobilization of biotinylated antibodies, subsequent selective secondary recognition and nonspecific binding of proteins. We found evidence that large macromolecules cannot infiltrate dense polymer brushes and that bulky antibody recognition occurs in the upper part of these coatings.
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| 10. |
- van Poll, Maaike L, et al.
(författare)
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A self-assembly approach to chemical micropatterning of poly(dimethylsiloxane)
- 2007
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 46:35, s. 6634-7
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Tidskriftsartikel (refereegranskat)abstract
- The surface of a silicone elastomer (poly(dimethylsiloxane); PDMS) can be selectively modified through minimization of interfacial free energy and self-assembly of functional molecules at the surface by mirroring the distribution of template surface energies (see scheme for formation of POEGMA brushes; SAM=self-assembled monolayer, bipy=2,2′-bipyridyl, POEGMA=poly[oligo(ethylene glycol) methacrylate]).
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| 11. |
- van Poll, Maaike L, et al.
(författare)
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Surface modification of PDMS via self-organization of vinyl-terminated small molecules
- 2009
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Ingår i: Soft Matter. - : RSC Publishing. - 1744-683X .- 1744-6848. ; 5:11, s. 2286-2293
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Tidskriftsartikel (refereegranskat)abstract
- Polydimethylsiloxane (PDMS) elastomers are widely used in soft lithography, microfluidics and biomedical applications as they combine a range of desirable chemical and physical properties. We studied the surface of PDMS modified using surface enrichment with long-chain alkenes. These alkenes were immobilized during crosslinking of the PDMS pre-polymer mixture cast against a template of matching surface energy. A range of different functional groups was introduced, including perfluorinated and oligoethylene glycol groups, alkyl chains and initiators for controlled radical polymerization. A detailed analysis of the composition of the modified PDMS surfaces was carried out using contact angle measurements, AFM, SIMS and XPS. The results demonstrate that the PDMS was enriched with small molecules near the surface and show that the functional molecules follow the template surface energy on patterned surfaces with edge resolutions equal to the template. By introducing hydrophilic alkenes receding contact angles on PDMS can be lowered below 5°, and we investigated how these surfaces rearrange in air due to the chain mobility of the PDMS backbone and PDMS short-chain fragments.
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