Nanocomposites of multilayer structures of zirconia/polymer thin-film coatings have been fabricated on quartz and single-crystal silicon substrates by the Ionically Self-Assembled Monolayer (ISAM) technique. Particle size distribution was measured to calculate the grain diameter of the zirconia particles. UV/Vis spectroscopy and ellipsometry were used to characterize the ISAM technique. SEM and AFM were used to observe the microscopic structure of the multilayer structures. Some mechanical properties were characterized by adhesion, abrasion, and nano-hardness tests. It was shown that an important distinction of this novel technique over conventional coating processes is the fabrication of excellent molecular-level uniform films with precise control of film thickness at the à ngström-level at ambient temperature and pressure conditions. It was also shown the maximum Vickers microhardness of ZrO2/polymer nanocomposite thin-film coatings prepared by this method was greater than 25 GPa. / Master of Science

Computational methodologies were employed to study a supramolecular micellar structure and its application, nanoreactor. This task was done through rigorous scale-up procedure using both atomistic and mesoscopic simulations. Primarily, density functional theory (DFT) calculation was used to characterize the smallest unit of complex molecules in the multicomponent mixture system. The following step involved transferring the information achieved by DFT calculation to larger scale simulation, such as molecular dynamics (MD) simulation. Lastly, based on the atomistic simulation results, we performed a series of dissipative particle dynamics (DPD) simulations to study a full body of polymeric multicompartment micelle. In the course of research, we built a systematic procedure to minimize the complexity of computation and efficiently characterize macromolecular structures and its application.

Luminescent materials can be found in a broad range of everyday applications. While in the seventies and eighties, the field of luminescent materials seemed to be fairly well covered, research in nineties has been revitalized both in industry and academia. Improvements over the last three decades have led to phosphor materials that operate close to their physical limits. It cannot be expected that properties such as quantum yield and spectral energy distribution will be significantly improved or that distinctly better materials will be found in the near future. Recently, there is a considerable research activity in the field of luminescent materials for lighting and displays to improve the chemical stability and to adopt the materials to the production technology. Ongoing miniaturization, lifetime improvement and spectral stability of fluorescent lamps on the one hand and brightness and contrast improvement in imaging systems on the other hand demand luminescent materials with very high stability that is invariable to operating conditions. All of the today's efficient lighting sources are based on either direct or indirect light emission from plasma discharges. During the pioneering stage, fluorescent lamp industries predominantly used mixtures of two photo luminescent materials: (Zn,Be)2SiO4.'Mn2+ having two emission maxima at 520 and 600 nm and MgW04 with 480 nm emission. The emission from these two phosphors covers the major portion of the visible spectrum. However, the compound (Zn,Be)2Si04 is hazardous to health because of its beryllium content. In 1942, Jenkins showed that Ca5(PO4)3(F,Cl):Sb,Mn was a very efficient emitter. The halophosphates emit both in the blue (Sb3+) as well as in the orange (Mn2+) spectral region, thus in addition yield white light. By carefully adjusting the ratio of Sb3+ and Mn2+ ion concentrations, a white light emitting phosphor was obtained with color temperatures ranging between 6500 and 2700K. However, the drawback of the halophosphate lamps is that it is impossible to have simultaneously high brightness and high color rendering; if the brightness is high (efficacy -80 lm W"1), the color rendering index (CRI) is of the order of 60, the CRI value can be improved up to 90, but then brightness decreases (-50 lm W"1). In 1974, another important breakthrough came in the form of compact fluorescent lamp, based on the trichromatic phosphor blend which resulted color rending values of 80-85 (color 80 lamps) at high efficiencies of 100 lm W"1. The fluorescent lamps with very high color rendering and efficiency can be obtained if three narrow band emitters with emission maxima at 450, 540 and 610 nm are employed. A typical trichromatic lamp phosphor blend comprises of (i) Sr5(PO4)3Cl:Eu2\ BaMgAl1()O,7:Eu2' as blue component, (ii) Ce0.67Tbo.33MgAl,,0,9, LaPO4,Le3\Tb3+ as green component and (iii)Y2C>3:Eiru as the red component. The color 80 lamps employ line emitters that generated light in discrete wavelength intervals. Colored objects that absorb outside these spectral regions appear with a slightly different body color when illuminated with these lamps rather than with a black body radiator such as the light bulb. For these purposes, color 90 or Deluxe lamps have been developed. The emission maximum of the blue phosphor can be shifted towards longer Wavelength by substituting BaMgAli0Oi7:Eu2+ with Sr4Ali4025:Eu2+. The red and green line emitters can be substituted by broad band emitters covering the whole spectral range. For this concept, (Ce,Gd,Tb)MgB5Oi0:Mn has been developed as a red emitter in which energy transfer from Ce3+ via Gd3+ to Mn2+ gives rise to an additional broad band at 630 nm. On the other hand, (Ba,Sr,Ca)2Si04:Eu has been developed as an alternative green-band emitter in which depending on the exact composition, the phosphor emits between 550 and 580 nm with a high quantum yield. Unfortunately, the host lattice is not stable in water, which prevents its deposition on the lamp bulb from aqueous suspensions and for environmental reasons more and more lamps producers use water as the suspending solvent in production instead of butyl acetate. Therefore, it is necessary to develop a new full color emitting phosphors, which has both thermal and chemical stability for application in luminescent lighting. The classical cathode ray tube (CRT) invented as the brown tube more than 100 years ago has developed into a remarkably mature product considering the complexity of its manufacturing process. Cathode rays are a beam of fast electrons, the accelerating voltage in a television picture tube is high (>10 kV). Basic requirements of display phosphors are stability (2000 hr operation) and emission color purity according to the standards set by the European Broadcasting Union (EBU). The blue and green phosphors are still the very cheep ZnS based materials, essentially the same ever since color-TV was introduced in fifties. On the other hand, (Zn,Cd)S, Ag+,C1" was originally used as the red phosphor however, the broad emission centered at 650 nm due to intrinsic donor-acceptor transition leads to rather low lumen equivalent as large fraction of the emission integral lies outside the eye sensitivity curve. For this and the environmental reasons, it has been replaced by the much more expensive Y2O2S:Eu with main emission lines at 612 and 628 nm. Recently, the big electronic companies are trying to enforce flat panel displays e.g. PDPs (plasma display panels) and FEDs (field emission displays). This is because of the fact that when compared to the CRT screen pigments, FED phosphors are required to operate at lower voltages and higher current densities. Although the voltages used in FEDs are only 0.1 to < 2 kV, the high-energy surface excitation on the phosphor particles causes degradation of sulfides, leaving the oxide hosts as the only favorable choice. The phosphor blends used are mixtures of SrTiO3:Pr3+ (red), Y2Si05:Tb (green) and Y2Si05:Ce (blue). However, the white light generation efficiency is very low (-5 lm W"1) and required improvement of phosphor efficacy because of its distinct advantages such as a very wide range of operational temperatures, stability under rugged conditions and wide viewing angle of emission. Similarly, in PDPs blue emitting BaMgAlioOniEu, green emitting Z^SiO^Mn and red emitting (Y,Gd)BO3:Eu are mostly used which shows a screen efficiency of about 1.5 lm W"1, just only half that of a CRT used in today's TV sets. However, the advantages of PDPs over CRTs are that it is not sensitive towards the display manufacturing process, which includes high temperature annealing up to about 600°C and it is stable under the harsh conditions of a Ne/Xe plasma used in PDPs (ion bombardment, VUV radiation). This puts pressure on the development of phosphor for maximum brightness and high stability to replace completely the classical CRTs. On the other hand, the invention of the blue-light emitting diode (LED) based on GaN can be regarded as a triumph of materials chemistry. In principle, it is possible to vary the emission wavelength of blue GaN-based LEDs between 370 nm (band-gap of pure GaN) and 470 nm by increasing the indium (In) content in InGaN devices. Assuming a conversion from the incident light by a phosphor material emitting at 555 nm, InGaN is coated with (Yi.xGdx)3(Ali-yGay)5Oi2:Ce (YAG:Ce) which has broad yellow band varying between 510 and 580 nm. This allows the adjustment of white color temperature from 8000 down to 3000 K. Recently, S^SiCU and S^SiOs have attracted current interest due to their potential applications in developing white light-emitting-diodes (LEDs) because GaN (400 nm chip)-coated with Sr2Si04:Eu2+ or Sr3SiC>5;Eu2+ exhibits better luminous efficiency than that of the industrially available product such as InGaN (460 nm chip)-coated with YAG:Ce. However, the major drawback of this combination is the strongly decreasing overall efficiency upon lowering the color temperature. This can be solved by using a phosphor material that has sufficient absorption at the emission wavelength of the blue diode, the quantum yield should be high under UV/Vis excitation and the FWHM of the emission band should be as small as possible in order to achieve high luminous output. The search for stable inorganic rare-earths phosphors with high absoiption in the near UV/blue spectral region is therefore an attractive research work. Since luminescence materials are a key component for lighting and display concept, research in the field of rare-earths doped oxide phosphors is carried out. Although state-of-the-art materials fulfill most requirements, improvements are still necessary to further boost the efficiency of the phosphor materials. Since it is not expected that materials will be found that perform better than the already established phosphor, the present work concentrates on the improvements of the phosphor by modifying the chemical and niicrostructurai features as well as the crystal structure. Chapter I gives a brief introduction to luminescence in solids, physical aspects and applications. Chapter II describes the synthesis and various experimental techniques employed in the investigation. Chapter III deals with photoluminescence and energy transfer involving charge transfer states in Sr2-xLnxCe04+x/2 (Ln = Eu and Sm) leading to an efficient full color emitting phosphor for luminescent lighting. Chapter IV and V describe charge transfer transition involving interface states associated with transitional nanophaseprecipitates leading to photoluminescence enhancement of SrTiO3:Pr3+,Al3+ and SrAli2Oi9:Pr3+,Ti4\ The light induced charge transfer leading to changing oxidation state of Eu in Sr2Si04 involving transient crystal structure results an efficient material for optical storage is presented in Chapter VI.Photoluminescence due to efficient energy transfer from Ce3+ to Tb3+ and Mn2t in SnAlioSi02o leading to an efficient phosphor for FEDs is presented in Chapter VII. Chapter VIII describes charge transfer transition involving trap states leading to long phosphorescence in SrAl2-xBxO4 (0<x<0.2) and Sr4Al14.xBxO25 (0.1<x<0.4) co-doped with Eu2+ and Dy3+. Chapter IX presents the role of particle size on the charge transfer associated luminescence of GdVO4:Ln3+ (Ln = Eu and Sm). A summary of the important findings and the conclusions arrived on the basis of results from these investigations are presented at the end of the thesis.

Hydrophilic/hydrophobic block copolymers as proton exchange membranes (PEMs) has become an emerging area of research in recent years. Three series of hydrophilic/hydrophobic, fluorinated/sulfonated multiblock copolymers were synthesized and characterized in this thesis. These copolymers were obtained through moderate temperature (~100°C) coupling reactions, which minimize the ether-ether interchanges between hydrophobic and hydrophilic telechelic oligomers via a nucleophilic aromatic substitution mechanism. The hydrophilic blocks were based on the nucleophilic step polymerization of 3,3′-disulfonated, 4,4′-dichlorodiphenyl sulfone with an excess 4,4′-biphenol to afford phenoxide endgroups. The hydrophobic (fluorinated) blocks were largely based on decafluoro biphenyl (excess) and various bisphenols. The copolymers were obtained in high molecular weights and were solvent cast into tough membranes, which had nanophase separated hydrophilic and hydrophobic regions. The performance and structure-property relationships of these materials were studied and compared to random copolymer systems. NMR results supported that the multiblock sequence had been achieved. They displayed superior proton conductivity, due to the ionic proton conducting channels formed through the self-assembly of the sulfonated blocks. The nano-phase separated morphologies of the copolymer membranes were studied and confirmed by atomic force microscopy. Through control of a variety of parameters, including ion exchange capacity and sequence lengths, performances as high, or even higher than those of the state-of-the-art PEM, Nafion, were achieved. / Ph. D.

<p>In this study novel composite electrodes were developed, in which the catalytic components were deposited in nanoparticulate form. The efficiency of the nanophase catalysts and membrane electrodes were tested in an important electrocatalytic process, namely hydrogen production by water electrolysis, for renewable energy systems. The activity of electrocatalytic nanostructured electrodes for hydrogen production by water electrolysis were compared with that of more conventional electrodes. Development of the methodology of preparing nanophase materials in a rapid, efficient and simple manner was investigated for potential application at industrial scale. Comparisons with industry standards were performed and electrodes with incorporated nanophases were characterized and evaluated for activity and durability.</p>

<p>In this study novel composite electrodes were developed, in which the catalytic components were deposited in nanoparticulate form. The efficiency of the nanophase catalysts and membrane electrodes were tested in an important electrocatalytic process, namely hydrogen production by water electrolysis, for renewable energy systems. The activity of electrocatalytic nanostructured electrodes for hydrogen production by water electrolysis were compared with that of more conventional electrodes. Development of the methodology of preparing nanophase materials in a rapid, efficient and simple manner was investigated for potential application at industrial scale. Comparisons with industry standards were performed and electrodes with incorporated nanophases were characterized and evaluated for activity and durability.</p>

Doctor Scientiae - DSc / In this study novel composite electrodes were developed, in which the catalytic components were deposited in nanoparticulate form. The efficiency of the nanophase catalysts and membrane electrodes were tested in an important electrocatalytic process, namely hydrogen production by water electrolysis, for renewable energy systems. The activity of electrocatalytic nanostructured electrodes for hydrogen production by water electrolysis were compared with that of more conventional electrodes. Development of the methodology of preparing nanophase materials in a rapid, efficient and simple manner was investigated for potential application at industrial scale. Comparisons with industry standards were performed and electrodes with incorporated nanophases were characterized and evaluated for activity and durability. / South Africa

Title: Multicomponent plasma polymers with spatially controlled properties Author: MSc. Pavel Pleskunov Department / Institute: Department of Macromolecular Physics/Charles University Supervisor of the doctoral thesis: Prof. Ing. Andrey Shukurov, PhD, Department of Macromolecular Physics / Charles University Abstract: Mixing of two (or more) polymers often leads to phase separation and to the formation of nanoscale architecture, which can be highly attractive in various applications including controllable drug delivery, fabrication of separation and solid electrolyte membranes, gas storage, etc. Different wet-chemistry techniques already exist to produce nanophase-separated polymers; however, capturing the resultant polymeric structure in a predictable manner remains a challenging task. In this thesis, a low-temperature plasma-based strategy is investigated for the production of multicomponent thin films of plasma polymers with spatially discriminated nanoscale domains. Gas aggregation cluster source is used for the fabrication of nanoparticles of plasma polymerized acrylic acid, whereas Plasma-Assisted Vapor Phase Deposition is used for the deposition of thin films of poly(ethylene oxide) plasma polymer. Embedding of nanoparticles into matrices of thermodynamically incompatible plasma polymer as well as...

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One of the main challenges to transform highly useful Direct Methanol Fuel Cells (DMFC) into a commercially viable technology has been to develop a low cost polymer electrolyte membrane (PEM) with high proton conductivity, high stability and low methanol crossover under operating conditions desirably including high temperatures. Nafion, the widely used PEM, fails to meet all of these criteria simultaneously. Recently developed acid-base polymer blend membranes constitute a promising class of PEMs alternative to Nafion on above criteria. Even though some of these membranes produce better performance than Nafion, they still present numerous opportunities for maximizing high temperature proton conductivity and dimensional stability with concomitant minimization of methanol crossover. Our contribution embarks on the fundamental study of one such novel class of blend membranes viz., sulfonated poly (ether ether ketone) (SPEEK)(95 % by weight) blended with polysulfone tethered with base (5 % by weight) such as 2-aminobenzimidazole (ABIm), 5-amino-benzotriazole (BTraz) and 1H-perimidine (PImd), developed by Manthiram group at The University of Texas at Austin. In this work, we report extensive all-atom classical as well as ab-initio molecular dynamics (MD) simulations of such water-methanol solvated blend membranes (as well as pure SPEEK and Nafion) the first time. Our approach consists of three steps: (1) Predict dynamical properties such as diffusivities of water, methanol and proton in such membranes (2) Validate against experiments (3) Develop understanding on the interplay between basic chemistry, structure and properties, the knowledge that can potentially be used to develop better candidate membranes. In particular, we elucidate the impact of simple, fundamental physiochemical features of the polymeric membranes such as hydrophilicity, hydrophobicity, structure or the size of the base on the structural manifestations on the bigger scale such as nanophase segregation, hydrogen bonding or pore sizes, which ultimately affect the permeant transport through such systems. / text