Herstellung, Struktur und Polymerisation neuer Cyclodextrin-komplexierter (Meth)acrylate und radikalische Polymerisation neuer Monomere zur Steuerung rheologischer Eigenschaften

Zusammenfassung In der vorliegenden Arbeit wurden Polymerisationseigenschaften hydrophober Monomere untersucht, die mittels methyliertem b-Cyclodextrin (me-b-CD) als Wirt/Gast-Komplexe homogen in die wäßrige Phase überführt wurden. Mit diesem Verfahren steht eine neue Variante der Polymerisation hydrophober Monomere in Wasser zur Verfügung.Die Charakterisierung der Monomer/CD-Komplexe erfolgte mittels Röntgenstrukturanalyse und 1H-NMR-Spektroskopie: steigende Größe der Gast-Komponente erhöht die Wechselwirkungen zum CD. Zur Untersuchung der Polymerisationsreaktion wurden Copolymerisationsparameter von Komplexen und Übertragungskonstanten von Mercaptoverbindungen bei Polymerisationen von Komplexen ermittelt. In Abhängigkeit der Größe der Gastkomponente und ihrer Wasserlöslichkeit resultieren unterschiedliche Reaktivitäten relativ zu Polymerisationen unkomplexierter Reaktanden in organisch-wäßriger Lösung. Außerdem wurden Copolymerisationen zwischen hydrophoben, me-b-CD-komplexierten Monomeren und wasserlöslichen Monomeren untersucht wie z.B. N-Isopropylacrylamid oder Natrium-4-(acrylamido)phenyldiazosulfonat, dessen Copolymerisation mit Styrol bislang nicht möglich war. Eine weitere Aufgabe war die Herstellung wasserstoffbrückenbindender Polymere. Hierzu wurden assoziationsfähige Monomere hergestellt und mit Methylmethacrylat copolymerisiert. Lösungen der Copolymere wurden rheologisch untersucht. Die Lösungen besitzen hohe Nullscherviskositäten bei 20°C und sind strukturviskos. Die Untersuchung der Temperaturabhängigkeit der Nullscherviskositäten ergab insbesondere bei der Lösung von Poly(N-(methacryl-2-ethyl)-N'-(3-amino-(1,2,4-triazol-2-yl))harnstoff-co-methylmethacrylat) bei niedrigen Temperaturen eine hohe Fließaktivierungsenergie, die zu höheren Temperaturen sank. Die komplexe Viskosität dieser Lösung fiel mit zunehmender Temperatur zunächst ab, stieg dann wieder an und sank erneut. Mittels DSC-Messungen konnten Phasenübergänge für dieses Fließverhalten verantwortlich gemacht werden. Außerdem kann Poly(N-(methacryl-2-ethyl)-N'-(3-amino-(1,2,4-triazol-2-yl))harnstoff-co-methylmethacrylat) thermisch vernetzen.

Investigation of P3HT PCBM particle-based solar cells

Die Herstellung von Polymer-Solarzellen aus wässriger Phase stellt eine attraktive Alternative zu der konventionellen lösemittelbasierten Formulierung dar. Die Vorteile der aus wässriger Lösung hergestellten Solarzellen liegen besonders in dem umweltschonenden Herstellungsprozess und in der Möglichkeit, druckbare optoelektronische Bauteile zu generieren. Die Prozessierbarkeit von hydrophoben Halbleitern im wässrigen Milieu wird durch die Dispergierung der Materialien, in Form von Nanopartikeln, erreicht. Der Transfer der Halbleiter in eine Dispersion erfolgt über die Lösemittelverdampfungsmethode. Die Idee der Verwendung von partikelbasierte Solarzellen wurde bereits umgesetzt, allerdings blieben eine genaue Charakterisierung der Partikel sowie ein umfassendes Verständnis des gesamten Fabrikationsvorgangs aus. Deshalb besteht das Ziel dieser Arbeit darin, einen detaillierten Einblick in den Herstellungsprozess von partikelbasierten Solarzellen zu erlangen, mögliche Schwächen aufzudecken, diese zu beseitigen, um so zukünftige Anwendungen zu verbessern. Zur Herstellung von Solarzellen aus wässrigen Dispersionen wurde Poly(3-hexylthiophen-2,5-diyl)/[6,6]-Phenyl-C61-Buttersäure-Methylester (P3HT/PCBM) als Donor/Akzeptor-System verwendet. Die Kernpunkte der Untersuchungen richteten sich zum einen die auf Partikelmorphologie und zum anderen auf die Generierung einer geeigneten Partikelschicht. Beide Parameter haben Auswirkungen auf die Solarzelleneffizienz. Die Morphologie wurde sowohl spektroskopisch über Photolumineszenz-Messungen, als auch visuell mittels Elektronenmikroskopie ermittelt. Auf diese Weise konnte die Partikelmorphologie vollständig aufgeklärt werden, wobei Parallelen zu der Struktur von lösemittelbasierten Solarzellen gefunden wurden. Zudem wurde eine Abhängigkeit der Morphologie von der Präparationstemperatur beobachtet, was eine einfache Steuerung der Partikelstruktur ermöglicht. Im Zuge der Partikelschichtausbildung wurden direkte sowie grenzflächenvermittelnde Beschichtungsmethoden herangezogen. Von diesen Techniken hatte sich aber nur die Rotationsbeschichtung als brauchbare Methode erwiesen, Partikel aus der Dispersion in einen homogenen Film zu überführen. Des Weiteren stand die Aufarbeitung der Partikelschicht durch Ethanol-Waschung und thermische Behandlung im Fokus dieser Arbeit. Beide Maßnahmen wirkten sich positiv auf die Effizienz der Solarzellen aus und trugen entscheidend zu einer Verbesserung der Zellen bei. Insgesamt liefern die gewonnen Erkenntnisse einen detaillierten Überblick über die Herausforderungen, welche bei dem Einsatz von wasserbasierten Dispersionen auftreten. Die Anforderungen partikelbasierter Solarzellen konnten offengelegt werden, dadurch gelang die Herstellung einer Solarzelle mit einer Effizienz von 0.53%. Dieses Ergebnis stellt jedoch noch nicht das Optimum dar und lässt noch Möglichkeiten für Verbesserungen offen.

In-situ detection of defect formation in organic flexible electronics by Kelvin Probe Force Microscopy

Organic semiconductor technology has attracted considerable research interest in view of its great promise for large area, lightweight, and flexible electronics applications. Owing to their advantages in processing and unique physical properties, organic semiconductors can bring exciting new opportunities for broad-impact applications requiring large area coverage, mechanical flexibility, low-temperature processing, and low cost. In order to achieve highly flexible device architecture it is crucial to understand on a microscopic scale how mechanical deformation affects the electrical performance of organic thin film devices. Towards this aim, I established in this thesis the experimental technique of Kelvin Probe Force Microscopy (KPFM) as a tool to investigate the morphology and the surface potential of organic semiconducting thin films under mechanical strain. KPFM has been employed to investigate the strain response of two different Organic Thin Film Transistor with active layer made by 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-Pentacene), and Poly(3-hexylthiophene-2,5-diyl) (P3HT). The results show that this technique allows to investigate on a microscopic scale failure of flexible TFT with this kind of materials during bending. I find that the abrupt reduction of TIPS-pentacene device performance at critical bending radii is related to the formation of nano-cracks in the microcrystal morphology, easily identified due to the abrupt variation in surface potential caused by local increase in resistance. Numerical simulation of the bending mechanics of the transistor structure further identifies the mechanical strain exerted on the TIPS-pentacene micro-crystals as the fundamental origin of fracture. Instead for P3HT based transistors no significant reduction in electrical performance is observed during bending. This finding is attributed to the amorphous nature of the polymer giving rise to an elastic response without the occurrence of crack formation.

Designing surfaces that kill bacteria on contact

Poly(4-vinyl-N-alkylpyridinium bromide) was covalently attached to glass slides to create a surface that kills airborne bacteria on contact. The antibacterial properties were assessed by spraying aqueous suspensions of bacterial cells on the surface, followed by air drying and counting the number of cells remaining viable (i.e., capable of growing colonies). Amino glass slides were acylated with acryloyl chloride, copolymerized with 4-vinylpyridine, and N-alkylated with different alkyl bromides (from propyl to hexadecyl). The resultant surfaces, depending on the alkyl group, were able to kill up to 94 ± 4% of Staphylococcus aureus cells sprayed on them. A surface alternatively created by attaching poly(4-vinylpyridine) to a glass slide and alkylating it with hexyl bromide killed 94 ± 3% of the deposited S. aureus cells. On surfaces modified with N-hexylated poly(4-vinylpyridine), the numbers of viable cells of another Gram-positive bacterium, Staphylococcus epidermidis, as well as of the Gram-negative bacteria Pseudomonas aeruginosa and Escherichia coli, dropped more than 100-fold compared with the original amino glass. In contrast, the number of viable bacterial cells did not decline significantly after spraying on such common materials as ceramics, plastics, metals, and wood.

Estudo de sistema de absorção de 1,3-butadieno em NMP.

O propósito deste trabalho foi o desenvolvimento de um procedimento simulador de processo reproduzindo a etapa de destilação extrativa de uma unidade de extração de butadieno a partir de uma corrente de hidrocarbonetos na faixa de quatro átomos de carbono, através da adição do solvente n-metil-2- pirrolidona (NMP). Os resultados obtidos foram comparados e validados com dados de processo obtidos por uma unidade industrial de extração de butadieno. O aprofundamento nos conceitos do processo de separação através de uma ferramenta em simulador de processo capaz de predizer condições de operação permitiu avaliações de aumento de capacidade. A capacidade dos elementos internos dos equipamentos envolvidos na separação pode ser avaliada e a identificação do ponto inicial de engargalamento da unidade foi possível. O procedimento proposto também permite reduzir incertezas para identificação de novos pontos de engargalamento a partir de uma nova configuração dos elementos internos identificados como ineficientes com a elevação de carga processada.

Controlling PbS nanocrystal aggregation in conducting polymers

PbS nanocrystals were synthesized directly in the conducting polymer, poly (3 -hexylthiophene-2,5-diyl). Transmission electron microscopy shows that the PbS nanocrystals are faceted and relatively uniform in size with a mean size of 10 nm. FFT analysis of the atomic lattice planes observed in TEM and selected area electron diffraction confirm that the nanocrystals have the PbS rock salt structure. The synthesis conditions are explored to show control over the aggregation of PbS nanocrystals in the thiophene conducting polymer.

Growing semiconductor nanocrystals directly in a conducting polymer

We describe a single step method to synthesise lead sulphide (PbS) nanocrystals directly in the conjugated polymer poly (2-methoxy-5-(2'-ethyl-hexyloxy)-p-phenylene vinylene) (MEH-PPV). This method allows size control of the nanocrystal via co-solvent ratios. We find good agreement between nanocrystal sizes determined by transmission electron microscopy and sizes theoretically determined from the absorption edge of the nanocrystals. Finally we show that this synthesis technique is not restricted to MEH-PPV and demonstrate that nanocrystals can be grown in Poly(3-hexylthiophene-2,5-diyl) (P3HT). (C) 2005 Elsevier B.V. All rights reserved.

Anaerobic metabolism of propionate by polyphosphate-accumulating organisms in enhanced biological phosphorus removal systems

Propionate, a carbon substrate abundant in many prefermenters, has been shown in several previous studies to be a more favorable substrate than acetate for enhanced biological phosphorus removal (EBPR). The anaerobic metabolism of propionate by polyphosphate accumulating organisms (PAOs) is studied in this paper. A metabolic model is proposed to characterize the anaerobic biochemical transformations of propionate uptake by PAOs. The model is demonstrated to predict very well the experimental data from a PAO culture enriched in a laboratory-scale reactor with propionate as the sole carbon source. Quantitative fluorescence in-situ hybridization (FISH) analysis shows that Candidatus Accumulibacter phosphatis, the only identified PAO to date, constitute 63% of the bacterial population in this culture. Unlike the anaerobic metabolism of acetate by PAOs, which induces mainly poly-beta-hydroxybutyrate (PHB) production, the major fractions of poly-beta-hydroxyalkanoate (PHA) produced with propionate as the carbon source are poly-beta-hydroxyvalerate (PHV) and poly-beta-hydroxy-2-methylvalerate (PH2MV). PHA formation correlates very well with a selective (or nonrandom) condensation of acetyl-CoA and propionyl-CoA molecules. The maximum specific propionate uptake rate by PAOs found in this study is 0.18 C-mol/C-mol-biomass h, which is very similar to the maximum specific acetate uptake rate reported in literature. The energy required for transporting 1 carbon-mole of propionate across the PAO cell membrane is also determined to be similar to the transportation of 1 carbon-mole of acetate. Furthermore, the experimental results suggest that PAOs possess a similar preference toward acetate and propionate uptake on a carbon-mole basis. (c) 2005 Wiley Periodicals, Inc.

Transition metal ion coordination in hydrophilic polymer membranes

The research described within this thesis is concerned with the investigation of transition metal ion complexation within hydrophilic copolymer membranes. The membranes are copolymers of 4-methyl-4'-vinyl-2,2'-bipyridine, the 2-hydroxyethyl ester of 4,4'- dicarboxy-2,2'-bipyridine & bis-(5-vinylsalicylidene)ethylenediamine with 2-hydroxyethyl methacrylate. The effect of the polymer matrix on the formation and properties of transition metal iron complexes has been studied, specifically Cr(III) & Fe(II) salts for the bipyridyl- based copolymer membranes and Co(II), Ni(II) & Cu(II) salts for the salenH2- based copolymer membranes. The concomitant effect of complex formation on the properties of the polymer matrix have also been studied, e.g. on mechanical strength. A detailed body of work into the kinetics and thermodynamics for the formation of Cu(II) complexes in the salenH2- based copolymer membranes has been performed. The rate of complex formation is found to be very slow while the value of K for the equilibrium of complex formation is found to be unexpectedly small and shows a slight anion dependence. These phenomena are explained in terms of the effects of the heterogeneous phase provided by the polymer matrix. The transport of Cr(III) ions across uncomplexed and Cr(III)-pre-complexed bipyridyl-based membranes has been studied. In both cases, no Cr(III) coordination occurs within the time-scale of an experiment. Pre-complexation of the membrane does not lead to a change in the rate of permeation of Cr(III) ions. The transport of Co(II), Ni(II) & Cu(II) ions across salenH2- based membranes shows that there is no detectable lag-time in transport of the ions, despite independent evidence that complex formation within the membranes does occur. Finally, the synthesis of a number of functionalised ligands is described. Although they were found to be non-polymerisable by the methods employed in this research, they remain interesting ligands which provide a startmg pomt for further functionalisation.

Formulation and characterisation of cationic microparticles for the delivery of DNA vaccines

The aim of this research was to formulate a novel biodegradable, biocompatible cationic microparticle vector for the delivery of DNA vaccines. The work builds upon previous research by Singh et al which described the adsorption of DNA to the surface of poly (D,L-lactide-co-glycolide) (PLG) microparticles stabilised with the surfactant cetyltrimethyl ammonium bromide (CT AB). This work demonstrated the induction of antibody and cellular immune responses to HIV proteins encoded on plasmid DNA adsorbed to the particle surface in mice, guinea pigs and non-human primates (Singh et aI, 2000; O'Hagan et aI, 2001). However, the use of surfactants in microparticle formulations for human vaccination is undesirable due to long term safety issues. Therefore, the present research aim was to develop an adsorbed DNA vaccine with enhanced potency and increased safety compared to CTAB stabilised PLG microparticles (PLG/CTAB) by replacement of the surfactant CTAB with an alternative cationic agent. The cationic polymers chitosan and poly (N- vinylpyrrolidone/2-dimethylaminoethyl methacrylate), dimethyl sulfate quaternary (PVP-PDAEMA) were investigated as alternative stabilisers to CTAB. From a variety of initial formulations, the most promising vector(s) for DNA vaccination were selected based on physicochemical data (chapter 3) and in vitro DNA loading and release characteristics (chapter 4). The chosen formulation(s) were analysed in greater depth (chapters 3 and 4), and gene expression was assessed by in vitro cell transfection studies using 293T kidney epithelial and C2C12 myoblast non-phagocytic cell lines (chapter 5). The cytotoxicity of the microparticles and their constituents were also evaluated in vitro (chapter 5). Stability and suitability of the formulation(s) for commercial production were assessed by cryopreparation and lyophilisation studies (chapters 3 and 4). Gene expression levels in cells of the immune response were evaluated by microparticle transfection of the dendritic cell (DC) line 2.4 and primary bone marrow derived DCs (chapter 6). In vivo, mice were injected i.m. with the formulations deemed most promising on the basis of in vitro studies and humoral and cellular immune responses were evaluated (chapter 6).

Macrophages and lymphocyte responiveness to mitogen

Purified B-cells fail to proliferate in response to the strong thymus-independent (TI) antigen Lipopolysaccharide (LPS) in the absence of macrophages (Corbel and Melchers, 1983). The fact that macrophages, or factors derived from them are required is supported by the inability of marginal zone B-cells in infants to respond to highly virulent strains of bacteria such as Neisseria meningitidis and Streptococcus pneumoniae (Timens, 1989). This may be due to the lack of CD21 expression on B-cells in infants which could associate with its co-receptor (C3d) on adjacent macrophages. It is not clear whether cell surface contacts and/or soluble products are involved in lymphocyte-macrophage interactions in response to certain antigens. This thesis describes the importance of the macrophage in lymphocyte responses to T-dependent (TD) and TI antigens. The major findings of this thesis were as follows: (1). Macrophages were essential for a full proliferative response to a range of T - and B-cell mitogens and TI-1 and TI-2 antigens, including Concanavalin A, LPS, Pokeweed mitogen (PWM), Dextran sulphate, Phytohaemagglutinin-P (PHA-P) and Poly[I][C]. (2). A ratio of 1 macrophage to 1000 lymphocytes was sufficient for the mitogens to exert their effects. (3). The optimal conditions were established for the activation of an oxidative burst in cells of the monocyte/macrophage lineage as measured by luminometry. The order of ability was OpZ >PMA/lonomycin >f-MLP >Con A >DS >PHA >Poly[I][C] >LPS >PWM. Responses were only substantial and protracted with OpZ and PMA. Peritoneal macrophages were the most responsive cells, whereas splenic and alveolar macrophages were significantly less active and no response could be elicited with Kupffer cells, thus demonstrating heterogeneity between macrophages. (4). Activated macrophages that were then fixed with paraformaldehyde were unable to restore mitogenic responsiveness, even with a ratio of 1 macrophage to 5 lymphocytes. (5). Although highly purified T- and B-cells could respond to mitogen provided live macrophages were present, maximum activation was only observed when all 3 cell types were present. (6). Supernatants from purified macrophage cultures treated with a range of activators were able to partially restore lymphocyte responses to mitogen in macrophage-depleted splenocyte cultures, and purified T - and B-cell cultures. In fact supernatants from macrophages treated with LPS for only 30 minutes could restore responsiveness. Supernatants from OpZ treated macrophages were without effect. (7). Macrophage supernatants could not induce proliferation in the absence of mitogen. They therefore provide a co-mitogenic signal required by lymphocytes in order to respond to mitogen. (8). Macrophage product profiles revealed that LPS and Con A-treated macrophage supernatants showed elevated levels of IL-1β, TNF -α L TB4 and TXB2. These products were therefore good candidates as the co-mitogenic factor. The possible inhibitory factors secreted by OpZ-treated macrophages were PGE2, IL-10 and NO. (9). The removal of cytokines, eicosanoids and TNF-α from LPS-treated macrophage supernatants using Cycloheximide, Dexamethasone and an MMPI respectively, resulted in the inability of these supernatants to restore macrophage-depleted lymphocyte responses to mitogen. (10). rIL-1β and rTNF-α are co-mitogenic factors, as macrophage-depleted lymphocytes incubated with rIL-1β and rTNF-α can respond to mitogen.

Skin adhesive hydrogels for the topical delivery of active agents

This thesis illustrates the development of tailor-made, partially hydrated skin adhesive hydrogels as a vehicle for the topical delivery of moisturising agents. Maintaining an optimum hydration level of the stratum corneum ensures that the barrier properties of the skin are preserved. An unsaturated ionic monomer 2-acrylamido-2-methylpropanesulfonic acid sodium salt, glycerol, water, a photoinitiator Irgacure 184 and crosslinker Ebacryl II facilitated the production of monophasic sheet skin adhesives using photopolymerisation. The exploration and modification of the hydrogel components coupled with their influence on the adhesive and dynamic mechanical behaviour led to the development of novel monophasic and biphasic hydrogels. Biphasic pregels comprising of a hydrophobic monomer (epoxidised soybean oil acrylate, lauryl acrylate or stearyl acrylate) micellised with a non ionic surfactant Tween 60 allowed a homogeneous distribution throughout a predominantly hydrophilic phase (2-acrylamido-2-methylpropanesulfonic acid sodium salt, 4-acryloylmorpholine, glycerol and water). Further development of biphasic hydrogel technology led to the incorporation of preformed commercial O/W emulsions (Acronal, Flexbond 150, DM137 or Texicryl 13056WB) allowing the hydrophobic component to be added without prior stabilisation. The topical release of moisturising agents 2-pyrrolidone-5-carboxylic acid, lactobionic acid and d-calcium pantothenate results in the deposition onto the skin by an initial burst mechanism. The hydration level of the stratum corneum was measured using a Comeometer CM 825, Skin Reader MY810 or FT-ATR. The use of hydrophilic actives in conjunction with lipophilic agents for example Vitamin E or Jojoba oil provided an occlusive barrier, which reduced the rate of transepidermal water loss. The partition coefficients of the release agents provided invaluable information which enabled the appropriate gel technology to be selected. In summary the synthetic studies led to the understanding and generation of transferable technology. This enabled the synthesis of novel vehicles allowing an array of actives with a range of solubilities to be incorporated.

Transition metal ion co-ordination in hydrophilic polymer membrane

This thesis is concerned with the investigation of transition metal (TM) ion complexation with hydrophilic membranes composed of copolymers of 4-vinyl pyridine & 4-methyl-4'vinyl- 2,2'-bipyridine with 2-hydroxyethyl methacrylate. The Cu(II), CoCII) & Fe(II) complexes with these coordinating membranes were characterised by a variety of techniques, in order to assess the effect of the polymer on the properties of the complex, and vice versa. A detailed programme of work was instigated into the kinetics of formation for the polymer-bound tris(bipyridyl) iron(II) complex; the rate and extent of complex formation was found to be anion-dependent. This is explained in terms of the influence of the anion on the transport properties and water content of the membrane, the controlling factor in the development of the tris-complex being the equilibrium concentration of Fe(II) in the gel matrix. A series of transport studies were performed with a view to the potential application of complexing hydrogel membranes for aqueous TM ion separations. A number of salts were studied individually and shown to possess a range of permeabilities; the degree of interaction between particular metal-ion:ligand combinations is given by the lag-time observed before steady-state permeation is achieved. However, when two TM salts that individually display different transport properties were studied in combination, they showed similar lag-times & permeabilities, characteristic of the more strongly coordinating metal ion. This 'anti-selective' nature thus renders the membrane systems unsuitable for TM ion separations. Finally, attempts were made to synthesise and immobilise a series of N ,0-donor macrocyclic ligands into hydrogel membranes. Although the functionalisation reactions failed, limited transport data was obtained from membranes in which the ligands were physically entrapped within the polymer matrix.

Functional carbon nanotubes for photonic applications

Carbon nanomaterials are an active frontier of research in current nanotechnology. Single wall Carbon Nanotube (SWNT) is a unique material which has already found several applications in photonics, electronics, sensors and drug delivery. This thesis presents a summary of the author’s research on functionalisation of SWNTs, a study of their optical properties, and potential for an application in laser physics. The first significant result is a breakthrough in controlling the size of SWNT bundles by varying the salt concentrations in N-methyl 2-pyrrolidone (NMP) through a salting out effect. The addition of Sodium iodide leads to self-assembly of CNTs into recognizable bundles. Furthermore, a stable dispersion can be made via addition polyvinylpyrrolidone (PVP) polymer to SWNTs-NMP dispersion, which indicates a promising direction for SWNT bundle engineering in organic solvents. The second set of experiments are concerned with enhancement of photoluminescence (PL), through the formation of novel macromolecular complexes of SWNTs with polymethine dyes with emission from enhanced nanotubes in the range of dye excitation. The effect appears to originate from exciton energy transfer within the solution. Thirdly, SWNT base-saturable absorbers (SA) were developed and applied to mode locking of fibre lasers. SWNT-based SAs were applied in both composite and liquid dispersion forms and achieved stable ultrashort generation at 1000nm, 1550nm, and 1800 nm for Ytterbium, Erbium and Thulium-doped fibre laser respectively. The work presented here demonstrates several innovative approaches for development of rapid functionalised SWNT-based dispersions and composites with potential for application in various photonic devices at low cost.

Salting out in organic solvents:a new route to carbon nanotube bundle engineering

In this study we investigate salt effects on bundle formation of carbon nanotubes (CNTs) dispersed in an organic solvent, N-methyl-2-pyrrolidone (NMP). Addition of NaI salt leads to self-assembly of CNTs into well-recognizable bundles. It is possible to control the size of the CNT bundles by varying the salt concentration. © the Owner Societies 2011.