Nanocomposite thin films can find application in photovoltaics, optics, fabrication of sensors, or in biomedicine. This work investigates fabrication and characterization of thin metal-plasma polymer nanocomposite films which have direct application because of their unique optical properties (e.g. SERS - Surface-Enhanced Raman Spectroscopy) or antibacterial effects (biomedicine). We fabricated metal nanoparticles either by magnetron sputtering (island growth) or by means of gas aggregation source of nanoparticles, thereby we got nanoparticles with very different morphologies. We used silver as a material for nanoparticles because of its antibacterial effects. We incorporated these nanoparticles into sputtered Nylon and sputtered PTFE (polytetrafluoroethylene) plasma polymer matrix. These two polymers have very different chemical structure and related different surface energy. First, we compared growth of nanoparticles on substrates of sputtered Nylon and PTFE. Then we compared properties of sandwich nanocomposites polymer-Ag-polymer for both types of nanoparticles and for both matrix materials. We characterized produced thin films especially with respect to their stability in water (antibacterial films), thermal stability (sterilization by heating) and stability on the open air (storage). Finally, the tests...

Kyoto University (京都大学) / 0048 / 新制・論文博士 / 博士(工学) / 乙第12680号 / 論工博第4082号 / 新制||工||1548(附属図書館) / 29813 / (主査)教授 田中 庸裕, 教授 江口 浩一, 教授 安部 武志 / 学位規則第4条第2項該当

In this PhD thesis, seawater desalination by Membrane Distillation (MD) has been explored from the perspective of process and membrane. Regarding the process, an innovative, energy efficient, and environmentally friendly Zero Thermal Input Membrane Distillation (ZTIMD) process was proposed. ZTIMD uses thermal energy stored in seawater, which makes the process sustainable by being independent of the external sources of thermal energy, which is one of the major contributors to the cost and energy consumption of conventional MD desalination processes. Economic feasibility study was carried out for the ZTIMD process, and it was demonstrated that drinking water could be produced with a cost of $0.28/m3, which is approximately half of the cost of conventional desalination processes. Regarding the membrane, novel MD membranes were developed through incorporation of nanomaterials in polyvinylidene fluoride (PVDF). Different nanomaterials including superhydrophobic SiO2, amine modified hydrophilic SiO2, CuO, and CaCO3 were used for this purpose. It was shown that membrane structure and consequently its performance could be affected by the nanoparticle properties, concentration, presence of backing material, PVDF blend ratio, and penetration time. In a best membrane developed in this work, almost 2500% increase was observed in the Vacuum Membrane Distillation (VMD) flux over that of the neat PVDF membrane at a feed temperature of 27.5 °C and vacuum pressure of 1.2 kPa, when 7.0 wt.% hydrophilic SiO2 nanoparticles were added into a PVDF membrane supported with Non-Woven Fabric (NWF) polyester. The membrane possessed near perfect selectivity.

A kaolinite-nylon 6 composite was prepared by a polycondensation reaction from 6-aminohexanoic acid (AHA) intercalated in the kaolinite interlayer space. The basal spacing of kaolinite-AHA was 1.47 nm and the basal spacing of the heated products decreased to 1.16 nm. The signals attributed to nylon 6 were detected in the 13C CP/MAS NMR spectra of the heated products. Formation of nylon 6 in kaolinite was confirmed by appearance of IR band due to amide I and amide II. Sarcosine was intercalated in kaolinite for the first time by guest displacement with methanol from the kaolinite-methanol precursor. The basal spacing of kaolinite-sarcosine was 1.27 nm. This intercalation compound was characterized by NMR, TGA, XRD, and IR. The physical and chemical properties of natural clay sample from Mirandela formation (Portugal) were determined in terms of external skin treatment. The low CEC 4,45meq/100g is consistent with high content of kaolinite in the sample

Organic thin-film transistors (OTFTs) have been widely studied because of their promising potential for application in low-cost, large-area and flexible electronics. However, several challenges remain on the way towards practical OTFT devices, such as a high operating voltage (> 20 V) induced by the low charge carrier mobility of organic semiconductors and low capacitance of organic gate dielectrics. A low operating voltage is essential for various OTFTs applications, such as portable displays, radio frequency identification tags (RFIDs), smart textiles and sensors. The key to low voltage operation of OTFTs is reduction of the threshold voltage, inverse subthreshold slope which can be fulfilled by using a high-capacitance gate dielectric with superior interface properties. Since field-effect current is proportional to field-induced charge density, using a gate dielectric layer with high dielectric constant (high-k) enhances output current densities at much lower applied voltages. Very thin dielectric layers have reportedly suffered from poor dielectric properties, while very high-k gate dielectrics have led to inferior dielectric-semiconductor interface. As a result, unsatisfactory device performance, such as low charge carrier mobility and high gate leakage current, has been obtained. In addition, solution-processability on a variety of substrates and compatibility with most common semiconducting materials make high-k dielectric materials an unrivalled candidate for low-voltage, low-cost applications. Consequently, the aim of this project was to produce a high-quality, high-capacitance gate dielectric with excellent properties which is consistent with cheap, basic solution-processing manufacturing techniques. With great promise in hybrid materials, a novel, high-k dielectric material based on alternative organic-inorganic nanocomposites that combine very high dielectric constant values intrinsic to ferroelectric ceramic materials (nanoparticles) with mechanical flexibility, low-cost and easy processing of polymers was developed. Both low- and high-k polymer matrices have been used in formulating high-k nanocomposite dielectric suspensions. The uniformity of suspensions has been improved by surface modification of nanoparticles in the case of low-k polymers, while a combination of polymer choice, solvents and nanoparticle-to-polymer ratio led to homogenous suspensions based on high-k polymers. The nanocomposite preparation technique was also unique to this work and gave reproducibly stable nanocomposite suspensions. Finally, ultralow-voltage (~ 1) OTFTs have been successfully demonstrated by integrating nanocomposite bilayer dielectrics using a high-k fluorinated polymer. Bilayer dielectrics were formed by (partially) capping the surface of the nanocomposite films with an ultrathin capping layer. The capping layer was the key to the operation of low-voltage OTFTs as it allowed remarkable and advantageous use of the nanocomposite surface roughness while improving the dielectric-semiconductor surface roughness. Ultimately, such nanocomposite bilayers have a potential to pave the way towards low-cost fabrication and integration of low-voltage components and circuits on flexible substrates.

Graphene nanocomposites have been successfully prepared in this study in the form of a sandwich structure of PMMA/graphene/SU-8. It has been proved that Raman spectroscopy is a powerful technique in the characterisation of the structure and deformation of graphene. The 2D band of the monolayer graphene has been used in the investigation of stress transfer in the graphene reinforced nanocomposites. It has been demonstrated that the 2D band moves towards low frequency linearly under tensile stress, which is shown to be significant method of monitoring the strain in graphene in a deformed specimen. The Raman spectroscopy behaviour under deformation validates that the monolayer graphene acts as a reinforcing role in nanocomposites although it is only one atom thick.A systematic investigation of the deformation of bilayer, trilayer and few-layer graphene has been undertaken with a view to determine the optimum number of layers for the reinforcement of nanocomposites. It has been demonstrated that monolayer graphene is not necessarily the optimum material to use for reinforcement in graphene-based polymer nanocomposites and bilayer graphene will be equally as good as monolayer graphene. There is therefore a balance to be struck in the design of graphene-based nanocomposites between the ability to achieve higher loadings of reinforcement and the reduction in effective Young’s modulus of the reinforcement, as the number of layers in the graphene is increased.Both the G and 2D bands have been found to undergo splitting under high strain levels or asymmetric band broadening in lower strain deformation. The G band polarisation property has been utilized to determine the crystallographic orientation of monolayer graphene by measuring the intensity ratio of G-/G+ bands. Analogously, the 2D band also undergoes strain-induced splitting where the 2D- band has higher Raman shift rate than that of the 2D+ band.

>Magister Scientiae - MSc / Magnetic luminescent nanoparticles of an iron oxide (Fe₃O₄) superparamagnetic core and an indium phosphide/zinc selenide (InP/ZnSe) quantum dot shell are reported. The magnetic nanoparticles (MNP’s) and quantum dots (QD’s) were each synthesized separately before conjugation. The MNP’s were functionalized with a thiol-group allowing the QD shell to bind to the surface of the MNP by the formation of a thiol-metal bond. The nanocomposite was capped with 3-mercaptopropionic acid, 1-propanethiol, 2-methyl-1-propanethiol and their properties investigated using the characterization techniques: high- resolution transmission electron microscopy (HR-TEM), energy-dispersive spectroscopy (EDS), UV-vis, scanning electron microscopy (SEM), superconducting quantum interference device (SQUID), and photoluminescence. These techniques yielded significant information on particle size, morphology, dispersion, and chemical composition including luminescence and florescence.

The barrier properties of polymers are a significant factor in determining the shelf or device lifetime in polymer packaging. Nanocomposites developed from the dispersion of nanometer thick platelets into a host polymer matrix have shown much promise. The magnitude of the benefit on permeability has been different depending on the polymer investigated or the degree of dispersion of the platelet in the polymer. In this dissertation, the effect of density changes in the bulk and at the polymer-platelet interface on permeability of polymer nanocomposites is investigated. Nanocomposites of nylon, PET, and PEN were processed by extrusion. Montmorillonite layered silicate (MLS) in a range of concentrations from 1 to 5% was blended with all three resins. Dispersion of the MLS in the matrix was investigated by using one or a combination of X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Variation in bulk density via crystallization was analyzed using differential scanning calorimetry (DSC) and polarized optical microscopy. Interfacial densification was investigated using force modulation atomic force microscopy (AFM) and ellipsometry. Mechanical properties are reported. Permeability of all films was measured in an in-house built permeability measurement system. The effect of polymer orientation and induced defects on permeability was investigated using biaxially stretched, small and large cycle fatigue samples of PET and nylon nanocomposites. The effect of annealing in nylon and nanocomposites was also investigated. The measured permeability was compared to predicted permeability by considering the MLS as an ideal dispersion and the matrix as a system with concentration dependent crystallinity.

Recent progress in the development of artificial skin concepts is a result of the increased demand for providing environment perception such as touch and flow sensing to robots, prosthetics and surgical tools. Tactile sensors are the essential components of artificial skins and attracted considerable attention that led to the development of different technologies for mimicking the complex sense of touch in humans. This dissertation work is devoted to the development of a bioinspired tactile sensing technology that imitates the extremely sensitive hair-like cilia receptors found in nature. The artificial cilia are fabricated from permanent magnetic, biocompatible and highly elastic nanocomposite material, and integrated on a giant magneto-impedance magnetic sensor to measure the stray field. A force that bends the cilia changes the stray field and is therefore detected with the magnetic sensor, providing high performance in terms of sensitivity, power consumption and versatility. The nanocomposite is made of Fe nanowires (NWs) incorporated into polydimethylsiloxane (PDMS). Fe NWs have a high remanent magnetization, due the shape anisotropy; thus, they are acting as permanent nano-magnets. This allows remote device operation and avoids the need for a magnetic field to magnetize the NWs, benefiting miniaturization and the possible range of applications. The magnetic properties of the nanocomposite can be easily tuned by modifying the NWs concentration or by aligning the NWs to define a magnetic anisotropy. Tactile sensors are realized on flexible and rigid substrates that can detect flow, vertical and shear forces statically and dynamically, with a high resolution and wide operating range. The advantage to operate the sensors in liquids and air has been utilized to measure flows in different fluids in a microfluidic channel. Various dynamic studies were conducted with the tactile sensor demonstrating the detection of moving objects or the texture of objects. Overall, the results confirm the possibility to easily control the sensors’ performance with the cilia arrangement and dimensions. The cost effective mold-based microfabrication process and magnetic operation enable a high degree of integration, which together with the extremely low power consumption make the artificial cilia sensor reported in this dissertation an attractive solution for many applications.

This Thesis is devoted to synthesis and characterization of conjugated polymers of three types: (i) copolymers of fluorene-based units with comonomers derived from benzene, anthracene and diphenyloxadiazole; (ii) copolymers combining new thiophene monomers carrying oxadiazole and triazole moieties with various comonomers. Copolymers are designed with the respect to the tuning the optical properties and an improvement in charge transport properties; (iii) polythiophene based polyelectrolytes of two types and the basic characterization of selected physical and optical properties is reported as well as a study of interactions with noble metal nanoparticles. An incorporation of oxadiazole side groups into the fluorene copolymers was followed by the substantial increase in the stability of emission (photoluminescence). Another increase in the emission stability was achieved by the substitution of alkyl side groups on fluorene for the aryl counterparts. Such a change resulted in almost complete suppression of the undesired green emission. Further method was the incorporation of anthracene monomeric units into the main chains which resulted in the best stabilization of emission. An experiment was also made in order to shed some light on the explanation of the mechanism of emission stabilization caused by...