Research on inherently nanolaminated transition metal carbides is inspired by their unique properties combining metals and ceramics, such as higher damage tolerance, better machinability and lower brittleness compared to the binary counterparts, yet retaining the metallic conductivity. The interesting properties are related to their laminated structure, composed of transition-metalcarbide layers interleaved by non-transition-metal (carbide) layers. These materials in thin-film form are particularly interesting for potential applications such as protective coatings and electrical contacts. The goal of this work is to explore nanolaminated transition metal carbides from the aspects of phase formation and crystal growth during thin-film synthesis. This was realized by studying phases in select material systems synthesized from two major approaches, namely, fromdirect-deposition and post-deposition treatment. The first approach was used in studies on the Mo-Ga-C and Zr-Al-C systems. In the former system, intriguing properties have been predicted for the 3D phases and their 2D derivatives (socalled MXenes), while in the latter system, the phases are interesting for nuclear applications. In this work, the discovery of a new Mo-based nanolaminated ternary carbide, Mo2Ga2C, is evidenced from thin-film and bulk processes. Its structure was determined using theoretical and experimental techniques, showing that Mo2Ga2C has Ga double-layers in simple hexagonal stacking between adjacent Mo2C layers, and therefore is structurally very similar to Mo2GaC, except for the additional Ga layers. For the Zr-Al-C system, the optimization of phase composition and structure of Zr2Al3C4 in a thin-film deposition process was studied by evaluating the effect of deposition parameters. I concluded that the formation of Zr2Al3C4 is favored with a plasma flux overstoichiometric in Al, and with a minimum lattice-mismatch to the substrates. Consequently, epitaxial Zr2Al3C4 thin film of high quality were deposited on 4H-SiC(001) substrates at 800 °C. With the approach of post-deposition treatment, the studies were focused on a new method of thermally-induced selective substitution reaction of Au for the non-transition-metal layers in nanolaminated carbides. Here, the reaction mechanism has been explored in Al-containing (Ti2AlC and Ti3AlC2) and Ga-containing (Mo2GaC and Mo2Ga2C) phases. The Al and Ga in these phases were selectively replaced by Au while the carbide layers remained intact, resulting in the formation of new layered phases, Ti2Au2C, Ti3Au2C2, Mo2AuC, and Mo2(Au1-xGax)2C, respectively. The substitution reaction was explained by fast outward diffusion of the Al or Ga being attracted to the surface Au, in combination with back-filling of Au, which is chemically inert to the carbide layers,to the vacancies. The substitution reaction was further applied to Ga-containing nanolaminated carbides, (Cr0.5Mn0.5)2GaC and Mo2GaC, motivated by development of novel magnetic nanolaminates. The former experiment resulted in the formation of (Cr0.5Mn0.5)2AuC, where the retained (Cr0.5Mn0.5)2C layers allowed a comparative study on the magnetic properties under the exchange of Ga for Au. After Au substitution, reduction in the Curie temperature and the saturation magnetization were observed, showing a weakened magnetic exchange interaction of the magnetic (Cr0.5Mn0.5)2 Clayers across the Au. In the Mo2GaC case, an Fe-containing MAX phase, Mo2AC with 50 at.% of Fe on the A site, was synthesized through selective substitution of Au-Fe alloy for the Ga layers, showing the first direct evidence for Fe in the MAX-phase structure. The substitution of Fe did not take place on another Mo2GaC sample tested for Fe exchange only, indicating the essential role of Au in catalyzing the Fe-substitution reaction. The knowledge gained from this thesis work contributes to improved approaches for attaining thin films of nanolaminated transition metal carbides with desired phase composition and crystal quality. The reports on the new nanolaminated phases through exchange interactions are likely to expand the family of nanolaminated carbides and advance their properties, and trigger more studies on related (quasi-) 2D materials.

Polycyclic aromatic hydrocarbons composed of benzenoid rings fused in a linear fashion comprise the class of compounds known as acenes. The structures containing three to six ring fusions are brightly colored and possess band gaps and charge transport efficiencies sufficient for semiconductor applications. These molecules have been investigated throughout the past several decades to assess their optoelectronic properties. The absorption, emission and charge transport properties of this series of molecules has been studied extensively to elucidate structure-property relationships. A wide variety of analogous molecules, incorporating heterocycles in place of benzenoid rings, demonstrate similar properties to the parent compounds and have likewise been investigated. Functionalization of acene compounds by placement of groups around the molecule affects the way in which molecules interact in the solid state, in addition to the energetics of the molecule. The use of electron donating or electron withdrawing groups affects the frontier molecular orbitals and thus affects the optical and electronic gaps of the molecules. The use of bulky side groups such as alkylsilylethynyl groups allows for crystal engineering of molecular aggregates, and changing the volume and dimensions of the alkylsilyl groups affects the intermolecular interactions and thus changes the packing motif. In chapter 2, a series of tetracene and pentacene molecules with strongly electron withdrawing groups is described. The investigation focuses on the change in energetics of the frontier molecular orbitals between the base acene and the nitrile and dicyanovinyl derivatives as well as the differences between the pentacene and tetracene molecules. The differences in close packing motifs through use of bulky alkylsilylethynyl groups is also discussed in relation to electron acceptor material design and bulk heterojunction organic photovoltaic characteristics. Chapter 3 focuses on molecular acceptor and donor molecules for bulk heterojunction organic photovoltaics based on anthrathiophene and benzo[1,2-b:4,5-b’]dithiophene central units like literature molecules containing fluorene and dithieno[2,3-b:2’,3’-d]silole cores. The synthetic strategies of developing reduced symmetry benzo[1,2-b:4,5-b’]dithiophene to study the effect of substitution around the central unit is also described. The optical and electronic properties of the donors and acceptors are described along with the performance and characteristics of devices employing these molecules. The final two data chapters focus on new nitrogen containing polycyclic hydrocarbons containing indolizine and (2.2.2) cyclazine units. The optical, electronic and other physical properties of these molecules are explored, in addition to the synthetic strategies for incorporating the indolizine and cyclazine units. By use of alkylsilylethynyl groups, crystal engineering was investigated for the benzo[2,3-b:5,6-b’]diindolizine chromophore described in chapter 4 to target the 2-D “brick-work” packing motif for application in field effect transistor devices. Optical and electronic properties of the cyclazine end-capped acene molecules described in chapter 5 were investigated and described in relation to the base acene molecules. In both cases, density functional theory calculations were conducted to better understand unexpected optical properties of these molecules, which are like the linear acene series despite the non-linear attachment.

RNA nanotechnology is an emerging field that holds great promise for advancing drug delivery and materials science. Recently, RNA nanoparticles have seen increased use as an in vivo delivery system. RNA was once thought to have little potential for in vivo use due to biological and thermodynamic stability issues. However, these issues have been solved by: (1) Finding of a thermodynamically stable three-way junction (3WJ) motif; (2) Chemical modifications to RNA confer enzymatic stability in vivo; and (3) the finding that RNA nanoparticles exhibit low immunogenicity in vivo. In vivo biodistribution and pharmacokinetics are affected by the physicochemical properties, such as size, shape, stability, and surface chemistry/properties, of the nanoparticles being delivered. RNA has an inherent advantage for nanoparticle construction as each of these properties can be finely tuned. The focus of this study is as follows: (1) Construction of diverse size and shape RNA nanoparticles with tunable physicochemical properties; (2) Investigation of the effect that size, shape, and nanoparticle properties have on in vivo biodistribution; (3) Development of drug encapsulation and release mechanism utilizing RNA nanotechnology; and (4) Establishment of large-scale synthesis and purification methods of RNA nanoparticles. In (1), RNA triangle, square, and pentagon shaped nanoparticles were constructed using the phi29 pRNA-3WJ as a core motif. Square nanoparticles were constructed with sizes of 5, 10, and 20 nanometers. The RNA polygons were characterized by AFM to demonstrate formation of their predicted geometry per molecular models. Furthermore, the properties of RNA polygons were tuned both thermodynamically and chemically by substitution of nucleic acid type used during nanoparticle assembly. In (2), the biodistribution of RNA nanosquares of diverse sizes and RNA polygons of diverse shapes were investigated using tumor models in nude mice. It was found that increasing the size of the nanosquares led to prolonged circulation time in vivo and higher apparent accumulation in the tumor. However, it was observed that changing of shape had little effect on biodistribution. Furthermore, the effect of the hydrophobicity on RNA nanoparticles biodistribution was examined in mouse models. It was found that incorporation of hydrophobic ligands into RNA nanoparticles causes non-specific accumulation in healthy organs, while incorporation of hydrophilic ligands does not. Lower accumulation in vital organs of hydrophobic chemicals was observed after conjugation to RNA nanoparticles, suggesting RNA has the property to solubilize hydrophobic chemicals and reduce accumulation and toxicity in vital organs. In (3), a 3D RNA nanoprism was constructed to encapsulate a small molecule fluorophore acting as a model drug. The fluorophore was held inside the nanoprism by binding to an RNA aptamer. The ability of the stable frame of the nanoprism to protect the fragile aptamer inside was evidenced by a doubling of the fluorescent half-life in a degrading environment. In (4), a method for large-scale in vitro synthesis and purification of RNA nanoparticles was devised using rolling circle transcription (RCT). A novel method for preparing circular double stranded DNA was developed, overcoming current challenges in the RCT procedure. RCT produced more than 5 times more RNA nanoparticles than traditional run-off transcription, as monitored by gel electrophoresis and fluorescence monitoring. Finally, large-scale purification methods using rate-zonal and equilibrium density gradient ultracentrifugation, as well as gel electrophoresis column, were developed.

The use of graphene and conductive polyaniline nanomaterials in the field of electrochemistry is increasing due to their excellent conductivity, rapid electron transfer and high specific surface area. However, these properties are strongly dependent on the preparation processes. To accelerate the development of advanced electrochemical sensors for the simultaneous detection of trace amounts of heavy metal ions, two facile and green methods are proposed to improve their performance in this thesis. The first one was dedicated to make graphene-carbon nanotube hybrid nanocomposites. The introduction of carbon nanotubes not only greatly enhances the conductivity of graphene but also suppresses, to some degree, the aggregation between graphene nanosheets. Another method proposed in this thesis work was to synthesize a phytic acid doped polyaniline nanofiber based nanocomposite. The synergistic contribution from polyaniline nanofibers and phytic acid enhances the accumulation efficiency and the charge transfer rate of metal ions during the differential pulse anodic stripping voltammetry analysis. The above-mentioned nanocomposite modified electrodes were all successfully applied to real samples for the simultaneous detection of Cd2+ and Pb2+ with good recovery rates. Meanwhile, corrosion protection is another important branch in the field of electrochemistry. In this direction, an active alkyd-polyaniline composite coating with self-healing functionality was prepared. The polyaniline used in this thesis was doped with p-toluene sulfonic acid, which was employed to increase the conductivity of polyaniline, and 1 wt.% of as-prepared polyaniline nanoparticles were found to offer an effective conductive network for anticorrosion. Finally, the reasons that such low loading levels of nanomaterials can result in significantly reinforced properties in nanocomposites were studied with combined atomic force microscopy (AFM) techniques. The results demonstrated that the interphase for a 40-nm-sized silica particle could extend to 55–70 nm in poly(ethyl methacrylate) (PEMA) and poly(isobutyl methacrylate) (PiBMA) polymer matrix, and the interphase exhibited a gradient distribution in surface nanomechanical properties. / <p>QC 20170315</p>

To date, the search efforts have shifted from the toxic II-VI, III-V and IV-VI semiconductors to more environmentally friendly materials. Among Group II-V semiconductors, Zn3P2 has shown to be a more benign option, similar to Group IV (Ge, Si) materials, for future applications in photovoltaics and optoelectronics. This work is dedicated to the development of wet-chemical synthetic routes of (1) Zn3P2 and (2) Group IV (Ge, Si, Si1-xGex) nanocrystals with precise control over composition, crystal structure, size and dispersity by adjusting different reaction parameters such as temperature, time and solvent composition. Different characterizations will also be employed to probe the size- and composition-dependent physical and optical properties of resulting products. The first part of this work illustrates the synthesis of luminescent Zn3P2 nanocrystals, an earth-abundant and a direct-gap semiconductor possessing high absorption coefficient and long carrier diffusion length, which uphold promising potential in many optoelectronic applications. A hot injection method by using highly reactive P and Zn precursors (P[Si(CH3)3]3 and diethyl zinc) in hexadecylamine and octadecene was developed to prepare a series of alkyl-amine-passivated tetragonal Zn3P2 crystallites with varying size sizes. Substantial blue shifts in the absorption onsets (2.11−2.73 eV) in comparison to the bulk counterpart (1.4−1.5 eV) and a clear red shift with increasing particle size indicates the quantum confinement effects. This is also consistent with the photoluminescent studies with the size-tunable maxima in the visible region (469−545 nm) as a function of growth temperature and time. The phase purity and alkyl-amine passivation of the nanocrystals were determined by structural and surface analysis, confirming the presence of N–Zn and N–P bonds on the tetragonal Zn3P2 crystallites. The second part of this works focuses on the development of a colloidal synthetic strategy of alkyl-amine capped Si1-xGex nanocrystals with control over size- and composition-dependent optical properties. Despite their high miscibility at all compositions, developing a wet-chemical synthesis of Si1-xGex alloys in the nanoscale remains a challenging task, owing to the difference of their crystallization temperatures and the high surface oxidation of Si. Thus an adapted colloidal method is utilized to fabricate single-element Ge and Si nanocrystals. Powder X-ray diffraction indicates successful production of cubic crystalline Ge and amorphous Si nanoparticles individually in oleylamine/octadecene (surfactant/solvent) mixture at 300°C. Absorption onset values of 1.28 eV and 3.11 eV are obtained for resulting Ge and Si colloids, respectively. By alloying these two materials in their nano-regime, tunable optical properties can be achieved throughout the visible to the near IR region by simply varying their elemental compositions. The success of this bandgap engineering process offers more options for new material design by taking advantage of unique properties from each component material.

This diploma thesis is focused on development and production of functional parts and new materials for the purpose of supporting educational website www.studiumchemie.cz on evaluation of its operation. The changes were made in graphical, structural and functional parts of website, which were designed based on the analysis of behavior of visitors to the website and by direct reaction of visitors. Changes were related to structure of database of chemical experiments or creating new features for registered users, such as evaluation of materials or personification of user profile. In cooperation with specialists have been incorporated several new materials, focusing on the issues of nuclear magnetic resonance (NMR). In addition to that, two new games have been prepared - Chemical pentathlon and Identify molecules. New materials should be used to expand the portfolio of educational materials on the website. Furthermore, the administration interface has been created and designed to meet the needs of editorial contributors site without prior programming experience. Evaluation of the statistics associated with the operation of the site showed that web traffic continues to grow. The most visited parts of the site are database of educational materials and videos of chemical experiments. The current site traffic is...

The active response of a series of polymeric materials was investigated. Both solvent activated and light activated thin films and wire systems show dynamic behaviors when exposed to different stimuli. Solvent mediated fluxional behavior of polymer thin films involved extensive, rapid curling both on infusion and evaporation of good solvents. These films can be either lab-fabricated ones or commercial ones, and the curling behavior can be as fast as seconds. Conditions including polymer materials, chosen solvents, and film geometry can affect the behavior. Methods that allowed for the creation and retention of distorted wire structures were also developed; the asymmetric sputtering of metal components on micron-sized wires permitted for the capture of curled wire components on solvent exposure. The asymmetric metal coated wires which were fabricated within a template of glass capillary arrays (GCA) membrane have shown instant (< 1 s) deformation when exposed to the proper solvents. Deformed shapes can be retained or the original linear shape recovered, depending on the metal film thicknesses. Photostimulation of wires was also investigated and showed a notable dynamic response but not as extensive as with the solvent induced behavior. Micron sized wires made with azobenzene-polyacrylate, exhibited a bending behavior when irradiated with 365 nm UV light and recovered under visible light. The bending behavior can be as slow as several minutes per degree while recovery was relatively faster. Additional efforts with polymers involved the formation of polymeric organic-inorganic hybrids where organic monomers, grafted to perovskite layers, were polymerized within the oxide’s interlayers. Reactions were carried out on protonated perovskite, hydrogen lanthanum niobate (HLaNb2O7). Alcoxyl groups were first grafted to the oxide and the monomer was substituted by exchange reaction with the alcoxyl groups.

Iron oxide magnetic nanoparticle synthesis and their surface functionalization hold a crucial position in the design and fabrication of functional materials for a variety of biomedical applications. Non-uniform nanoparticles with poor crystallinity, prepared by conventional methods, have only limited value in biological areas. Large scale synthesis methods that are able to produce high quality, mono-dispersed iron oxide nanoparticles using low cost and environment friendly chemicals are highly desirable. Following synthesis, appropriate surface functionalization is necessary to direct the dispersibility of nanoparticles in aqueous solution in order to provide them with acceptable colloidal stability against the ion strength and many biomolecules that nanoparticles may encounter under physiological conditions. Poorly stabilized nanoparticles that easily aggregate and form large size agglomerates would be quickly cleared by the liver and other organs and are not suitable for clinical purposes. Additionally, many interesting functionalities such as fluorescence, targeting and anti-cancer properties can be immobilized onto the surface of iron oxide magnetic nanoparticles during the surface functionalization process so as to build multifunctional platforms for disease diagnosis and treatment. Polyol method can be an effective way to prepare magnetite nanoparticles that are suitable for biological applications. In a polyol system, selected surface functionalities were introduced to the nanoparticle surface via a hot injection technique. The morphology, uniformity, crystallinity and magnetic properties were examined to understand the effect of different ligand molecules on the final product. Their surface chemistry, colloidal properties and surface reactivity were also studied to evaluate their practicability in different applications. A high efficiency in-situ method for the preparation of magnetite nanoparticles attached to silica nanospheres was also developed in a polyol system. This approach eliminates several time-consuming processing steps that are in the conventional fabrication route and directly produces water-stable magnetite-silica hybrid materials with surface availability for subsequent modifications. In addition to polyalcohol, the potential of polyamine in the preparation of water-soluble magnetite nanoparticles with amine surface functionalities was also evaluated. And it is suggested that polyamine acts as solvent, stabilizing agent and reducing agent simultaneously during the synthesis. The characterization of polyamine coated nanoparticles, their surface functionalization, and subsequent application for bioseparation and drug delivery were reported.

The ability to encapsulate linear nanoparticle (NP) chains in scrolled nanosheets is an important advance in the formation of nanocomposites.These nanopeapods (NPPs) exhibit interesting properties that may not be achieved by individual entities. Consequently, to fully exploit the potential of NPPs, the fabrication of NPPs must focus on producing composites with unique combinations of morphologically uniform nanomaterials. Various methods can produce NPPs, but expanding these methods to a wide variety of material combinations can be difficult. Recent work in our group has resulted in the in situ formation of peapod-like structures based on chains of cobalt NPs. Building on this initial success, a more versatile approach has been developed that allows for the capture of a series of preformed NPs in NPP composites. In the following chapters, various synthetic approaches for NPPs of various material combinations will be presented and the key roles of various reaction parameters will be discussed. Also, uniform hexaniobate nanoscrolls were fabricated via a solvothermal method induced by heating up a mixture of TBAOH, hexaniobate crystallites, and oleylamine in toluene. The interlayer spacing of the nanoscrolls was easily tuned by varying the relative amount and chain lengths of the primary alkylamines. To fabricate NPPs, as-synthesized NPs were treated with hexaniobate crystallite in organic mixtures via solvothermal method. During solvothermal treatment, exfoliated hexaniobate nanosheets scroll around highly ordered chains of NPs to produce the target NPP structures in high yield. Reaction mixtures were held at an aging temperature for a few hours to fabricate various new NPPs (Fe3O4@hexaniobate, Ag@hexaniobate, Au@hexaniobate, Au-Fe3O4@hexaniobate, TiO2@hexaniobate, CdS@hexaniobate, CdSe@hexaniobate, and ZnS@hexaniobate). This versatile method was first developed for the fabrication of magnetic peapod nanocomposites with preformed nanoparticles (NPs). This approach is effectively demonstrated on a series of ferrite NPs (≤ 14 nm) where Fe3O4@hexaniobate NPPs are rapidly (~ 6 h) generated in high yield. When NP samples with different sizes are reacted, clear evidence for size selectivity is seen. Magnetic dipolar interactions between ferrite NPs within the Fe3O4@hexaniobate samples leads to a significant rise in coercivity, increasing almost four-fold relative to free particles. Other magnetic ferrites NPPs, MFe2O4@hexaniobate (M = Mn, Co, Ni), can also be prepared. This synthetic approach to nanopeapods is quite versatile and should be readily extendable to other, non-ferrite NPs or NP combinations so that cooperative properties can be exploited while the integrity of the NP assemblies is maintained. Further, this approach demonstrated selectivity by encapsulating NPs according to their size. The use of polydispersed NP systems is also possible and in this case, evidence for size and shape selectivity was observed. This behavior is significant in that it could be exploited in the purification of inhomogeneous NP samples. Other composite materials containing silver and gold NPs are accessible. Partially filled Fe3O4@hexaniobate NPPs were used as templates for the in situ growth of gold to produce the bi-functional Au- Fe3O4@hexaniobate NPPs. Encapsulation of Ag and Au NP chains with a hexaniobate nanoscroll was shifted the surface plasmon resonance to higher wavelengths. In these composites NPs can be incorporated to form NPP structures, decorated on nanosheets before scrolling, or attached to the surfaces of the nanoscrolls. The importance of this advancement is the promise it holds for the design and assembly of active nanocomposites. One can create important combinations of nanomaterials for potential applications in a variety of areas including catalysis, solar conversion, thermoelectrics, and multiferroics.

Development of synthetic routes toward two general organometallic frameworks was undertaken. The first project involved synthetic attempts of substituted and unsubstituted ferroceno[c]thiophene while the second one was the synthesis of 1,2-dithienylmetallocenes. The long-term goal of this work is to lay the foundations for study of electronic, electrochromic, redox, and optical properties of thiophene-based materials integrated with organometallic systems such as ferrocene, ruthenocene and cymantrene. The synthetic pathway for the target molecule in the first project involved converting 1,2-bis(hydroxymethyl)ferrocene to 1,2-bis(thiouroniummethyl)ferrocene with thiourea under acidic conditions. Refluxing the salt in base followed by acidification resulted in 1,2-bis(mercaptomethyl)ferrocene, which is oxidized to the cyclic ferroceno[d]-1,2-dithiane. Ring contraction of cyclic dithiane gave the thioether, ferroceno[c]-2,5-dihydrothiophene. Periodate oxidation of the thioether gave ferroceno[c]-2,5-dihydrothiophene-S-oxide (1), a potential precursor for ferroceno[c]thiophene via Pummerer dehydration. Attempts to dehydrate 1 and to trap the resulting thiophene in situ indicated instability of the target compound. Synthesis of ferroceno[c]thiophene with electron-donating as well as electron-withdrawing substituents at the 2,5-positions of the thiophene ring was attempted. 1,2–Dithienylethenes and their derivatives have gained increased attention due to their exceptional photochromic property. They tend to be thermally irreversible but photochemically reversible, which is a vital for their potential use in optical memories, switches and other optoelectronic applications. Inspiration of the second project was that incorporation of 1,2-dithienyl systems into metallocenes would enhance the general properties of the molecule, including stability, fatigue resistance, solid-state reactivity and higher sensitivity. 1,2-Dithienylferrocene was successfully synthesized. The synthetic pathway for 1,2-dithienylferrocene involved the reaction of α-bromo-3-acetyl-2,5-dimethylthiophene (1) with ethyl 4-(2,5-dimethylthiophen-3-yl)-3-oxobutanoate (2) to give 2,3-diarylcyclopent-2-en-1-one (3). Compounds 1 and 2 were synthesized following literature methods. Compound 3 was then converted to its cyclopentadienide form by first reducing the ketone to alcohol using LAH, followed by dehydration and then deprotonation of the substituted cyclic diene using butyllithium to give 1,2-bis(2,5-dimethylthiophene)-2,4-cyclopentadien-1-yl)lithium (4). [Fe(fluorenyl)(Cp)] was then used as a transfer reagent and reacted with 4 to yield the target compound.