Dissertations / Theses on the topic 'Silica Tubes'

Carbon nanotubes have been envisioned to become a very important material in various applications. This is due to the unique properties of carbon nanotubes which can be exploited in applications on length scales spanning from the nano world to our macroscopic world. For example, the electronic properties of carbon nanotubes makes them utterly suitable for nano electronics while the strength of them makes them suitable for reinforcements in plastics. Both of these applications do however require... mer the ability for systematic production of carbon nanotubes with certain properties. This is called selective carbon nanotube growth and today this has not been achieved with total success. In the work presented in the thesis several different computational methods have been applied in our contribution to the systematic search for selective carbon nanotube growth. Put in a context of previous knowledge about carbon nanotube growth our results provide valuable clues to which parameters that control the carbon nanotube growth. In association with the latest results we even dare to, with all modesty, speculate about a plausible control mechanism. The studies presented in the thesis addressed different stages of carbon nanotube growth, spanning from the properties affecting the initiation of the growth to the parameters affecting the termination of the growth. In some more detail this included studies of the melting temperatures of nanoscaled metal clusters. The expected size dependence of the melting temperatures was confirmed and the melting temperatures of clusters on substrates were seen to depend both on the material and shape of the surface. As this constitute the premises prior to the carbon nanotube growth it was followed by studies of the interaction between carbon nanotubes and metal clusters of different size and constitution. This was done using different computational methods and at different temperatures. It soon became apparent that the clusters adapted to the carbon nanotube and not vice versa. This held true irrespectively of the constitution of the cluster, that is for both pure metal and metal carbide. It was also seen that there exist a minimum cluster size that prevent the carbon nanotube end from closing. Closure of the carbon nanotube end is likely to lead to the termination of the growth which lead to studies of other reasons for growth termination, e.g., Ostwald ripening of the catalyst particles. This was investigated with the result that the rate of the Ostwald ripening may depend on both the chirality and diameter of the carbon nanotubes. It is suggested that this may provide some answers to the controlled growth of carbon nanotubes.

Disputationen sker fredagen den 3 december 2010, kl. 10:15, Kollektorn, Kemivägen 9

The purpose of this work is to determine the optimal parameters of synthesis of nano-tubular crystals Co-chrysotile. The optimal temperature ranges and pressure for the synthesis of nano-tubular crystals Co-chrysotile 573 – 673 K, 19.6 – 98.1 MPa at the time of isothermal exposure from 15 to 24 h. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35256

Zeolites are highly porous materials that are most commonly used in granular or beaded forms. In general, zeolite granules, beads or monoliths are manufactured by using an inorganic binder which helps to cement zeolite crystals together. However, this inorganic binder decreases the purity of the zeolite structures and accessibility to the zeolite pores. A new and relatively easy method was offered for the production of binderless zeolite A tubes and bars from amorphous alumina silicate extrudates in this study. Amorphous alumina silicate powder, which is obtained by filtering the homogenous hydrogel with a composition of 2.5Na2O:1Al2O3:1.7SiO2:150H2O, is mixed with an organic binder (HEC-Hydroxyethyl Cellulose) to obtain the paste. The paste is then extruded through a die of a home-made extruder into bars and tubes. These extrudates were dried at room temperature for 24 hours, then calcined at 600oC for 2 hours and finally synthesized at 80oC for 72 hours in hydrothermal conditions to convert amorphous alumina silicate to zeolite. The most appropriate amorphous alumina silicate powder (A) / 4wt% HEC solution (H) ratio to prepare paste, hence to prepare bars and tubes was found as 0.82. The crystallinity of bars and tubes was 91% and 97%, respectively, and zeolite A was the only crystalline material. The bars and tubes were composed of highly intergrown zeolite A crystals with high porosity. Porosity of the bars is approximately 39% and porosity of the tubes is 29%, with a narrow pore size distribution. Bars have macropores of 2 &
#956
m, while the macropores of the tubes are 3-4 &
#956
m. The BET surface area of the bars was 411 m2/g and of tubes was 439 m2/g, which are comparable with the commercial zeolite A beads. Bars had a crushing strength of 0.42 MPa, which is sufficiently high to handle. In conclusion, zeolite A bars and tubes, with their high purity, macroporous structure and high mechanical strength, can be used in adsorption and ion exchange processes. The developed synthesis method can be scaled up to prepare honeycomb monoliths that provide higher surface are per unit volume with an appropriate extruder die.

L'objectif de la thèse était de synthétiser des tubes de SiC monolithiques pour améliorer l'étanchéité de la structure composite SiC/SiC d'une gaine de combustible nucléaire. Des revêtements tubulaires de 8 mm de diamètre et quelques centaines de micromètres d'épaisseur ont été produits par dépôt chimique en phase vapeur à pression atmosphérique à partir d'un mélange CH3SiHCl2/H2. Le procédé a été développé de manière à réaliser en continu des tubes de SiC de plusieurs dizaines de centimètres de long. La composition chimique et la microstructure des tubes ont été déterminées par microsonde de Castaing, spectroscopie Raman, DRX et microscopie électronique (MEB, MET). Les propriétés mécaniques des tubes ont été caractérisées par nanoindentation et à travers des essais de compression C-ring. Le comportement thermomécanique a également été étudié. L'étude du procédé comprend une étude thermocinétique, un suivi de la phase gazeuse par IRTF et la modélisation 2D du réacteur.

Since the invention of Laser (in 1960) and low loss optical fiber (in 1966) [1], extensive research in fiber-optic sensing technology has made it a well-defined and matured field [1]. The measurement of physical parameters (such as temperature and pressure) in extremely harsh environment is one of the most intriguing challenges of this field, and is highly valued in the automobile industry, aerospace research, industrial process monitoring, etc. [2]. Although the semiconductor based sensors can operate at around 500oC, sapphire fiber sensors were demonstrated at even higher temperatures [3]. In this research, a novel sensor structure is proposed that can measure both pressure and temperature simultaneously. This work effort consists of design, fabrication, calibration, and laboratory testing of a novel structured temperature compensated pressure sensor. The aim of this research is to demonstrate an accurate temperature measurement, and pressure measurement using a composite Fabry-Perot interferometer. One interferometer measures the temperature and the other accurately measures pressure after temperature compensation using the temperature data from the first sensor.
Master of Science

In a worldwide pursuit for more Accident Tolerant nuclear Fuel (ATF), the quest to obtain and certify alternative nuclear fuel cladding tubes for light-water nuclear power reactors is still a key challenge. One of the facets in this program to develop more ATF is the heat transfer evaluation between the various proposed clad tubes manufactured from suitable replacement materials and the current problematic zirconium-alloy based clad tubes used in nuclear power reactors. For the heat transfer analysis, the accurate measurement of the temperature on the heat transfer surface of heated tubes to be tested was one of the important objectives for the effective analysis of the heat transfer characteristics to the water coolant. After extensive investigations, a suitable technique was developed and validated against recognised forced-convection heat transfer correlations. The results showed that this technique was well suited for external forced convection heat transfer studies from heated surfaces exposed to forced convection water coolants.
Dissertation (MSc)--University of Pretoria, 2019.
Mechanical and Aeronautical Engineering
MSc (Applied Science - Mechanics)
Unrestricted

High-performance liquid chromatography (HPLC) is the most widely used analysis technique. However, its sensitivity is limited. Sample preconcentration methods, such as fiber-based solid-phase microextraction (SPME) and in-tube SPME (capillary microextraction) offer improved detection limits. It is, however, difficult to couple fiber SPME on-line with HPLC due to the need for complicated desorption devices. Such coupling is further complicated due to the limited solvent stability of the extracting phase both in the fiber and in-tube formats of SPME. In this research, surface-bonded sol-gel sorbents were developed to provide the solvent stability required for effective on-line hyphenation of capillary microextraction (CME) with HPLC. These sol-gel sorbents were prepared using (1) silica-based, (2) titania-based, and (3) germania-based sol-gel precursors. Sol-gel reactions were performed within fused silica capillaries to create a number of organic-inorganic hybrid sorbents in the form of surface-bonded coatings: (1) alkyl (methyl, octyl, octadecyl), (2) polydimethyldiphenylsiloxane, (3) titania poly(tetrahydrofuran), and (4) germania tri-block polymer. The sol-gel coated microextraction capillaries were capable of efficiently extracting a wide variety of analytes, including polycyclic aromatic hydrocarbons, ketones, aldehydes, aromatic compounds, amines, alcohols, and phenols with ng/L to pg/L detection limits. The sol-gel methyl coating demonstrated a counterintuitive ability to extract polar analytes. Sol-gel polydimethyldiphenylsiloxane coatings were found to be resistant to high temperature solvent exposure (150°C and 200°C), making them suitable for use in high-temperature liquid phase separations. To better understand how extraction takes place, effects of alkyl chain length and sol-gel precursor concentration were evaluated in the study on sol-gel alkyl coatings. The sol-gel titania poly(tetrahydrofuran) coating was also capable of extracting underivatized aromatic acids and polypeptides at pHs near their respective isolectric points. The sol-gel titania poly(tetrahydrofuran) coatings and the sol-gel germania tri-block polymer coatings demonstrated impressive resistance to extreme pH conditions, surviving prolonged exposure to 1.0 M HCl (pH approx. 0.0) and 1.0 M NaOH (pH approx. 14.0) with virtually no change in extraction behavior. Sol-gel germania tri-block polymer coatings were also stable under high temperature solvent conditions (200°C). In addition, for the first time, the analyte distribution constants between a sol-gel germania coating and the aqueous samples (Kcs) were determined.

Thanks to European environmental rules and regulations establishment, waste recycling has become a more and more relevant problematic. For manufacturing plants, especially those producing hazardous wastes, expenses linked to waste production have drastically increased over the last decades. In the proposed work, various hazardous and non-hazardous wastes, among: soda-lime and borosilicate glass cullet, cathode ray tubes glass, exhausted lime from fume abatement systems residues, sludge and slags from ferrous and non-ferrous metallurgy, and pre-stabilized municipal solid waste incinerators ashes are used to elaborate several compositions of glass-ceramics. High-temperature treatment (minimum 800 °C) associated to a Direct Sintering process (30 min) was an efficient way to stabilize chemically the final products. The impact of each waste on the final product’s mechanical properties was studied, but also their synergies between each other, when mixed together. Statistic mixture designs enabled to develop interesting products for modern building applications, such as porous tiles and lightweight panels destined to insulation, with a purpose of fulfilling multifunctional properties.
Grazie alle regole e normative ambientali europee istituite, il riciclaggio dei rifiuti è diventato una problematica sempre più rilevante. Per gli impianti di produzione, in particolare quelli che producono rifiuti pericolosi, le spese connesse allo smaltimento sono drasticamente aumentate negli ultimi decenni. Nel lavoro proposto, vari rifiuti, pericolosi o no, vengono utilizzati per elaborare diverse composizioni di vetroceramiche. Si distinguono rottami di vetro della produzione di finestre, di contenitori farmaceutici e di tubi catodici. I rifiuti non vetrosi invece sono calce esausta da residui di sistemi di filtrazione di fumi, scorie metallurgiche da leghe ferrose e non e ceneri da inceneritori. E' presentata nel presente lavoro la ricerca di un metodo di trattamento ad alta temperatura (minima 800 ° C) efficace per stabilizzare chimicamente il prodotto finale, tramite i diversi processi di sinterizzazione diretta, sinter-cristallizzazione e vetrificazione. Sono stati studiati gli effetti di ogni rifiuto sulle proprietà meccaniche del prodotto finale, ma anche le nuove funzionalità ottenute attraverso le sinergie risultanti dalla loro miscela. Miscele calibrate hanno permesso di sviluppare prodotti interessanti per applicazioni edilizie moderne, come le piastrelle porose e pannelli leggeri destinati all’isolamento.

碩士
國立臺灣大學
職業醫學與工業衛生研究所
89
Silica gel is commonly used by industrial hygienists to collect gases and vapors in the workplace, in particular air contaminants with high polarity. The collected air pollutants are then treated and analyzed to identify their type and to determine the concentration using various methods and instrumentations. In addition to collection of gaseous pollutants, the silica gel tubes are also used for acid mist collection according to the listed official analytical methods (e.g., NIOSH method 7903 and OSHA method ID-165SG). However, the filtration characteristics of silica gel tubes have not been thoroughly investigated. A constant output aerosol generator and an ultrasonic atomizing nozzle were used to generate submicrometer-sized and micrometer-sized aerosol particles, respectively. A scanning mobility particle sizer and an aerodynamic particle sizer were used to measure particles smaller and larger than 0.6 μm, respectively. Potassium sodium tartrate and dioctylphthalate were used as the solid and liquid test agents, respectively. Two types of SKC silica gel tubes (Cat No. 226-10 and 226-10-03) were examined for aerosol penetration, air resistance and loading characteristics. The results show that the aerosol penetration through the silica gel tubes could be as high as 80% at the penetration maximum (or collection minimum) under the normal sampling flow of 0.5 L/min, well within the inertial impaction dominated region. Two glass wool plugs and one urethane plug between sorbent sections and at the back end of the SKC 226-10 contributed about 22% of the total air resistance, and the remaining 78% of the air resistance was caused by the silica gel. When the filtration efficiency by these separators was deduced, the aerosol penetration at the most penetrating size was as high as 90%. The aerosol penetration increased and the penetration curve shifted to smaller particle size as the sampling flow increased. However, this increase in aerosol penetration of particles smaller than the penetration maximum reached a maximum and thereafter decreased as the sampling flow was increased beyond 1.5 L/min (equivalent filtration velocity of 93 cm/sec), a clear evidence of inertial impaction surpassing the diffusion deposition. As a result, the use of silica gel tubes for acid mist collection may not be appropriate if the behavior of the complete aerosol size distribution is not considered as part of the assessment of these devices.

碩士
國立交通大學
應用化學系
91
Si/SiO2 tubes were successfully synthesized by using SiCl4 as a precursor to react with Na tubes which decomposed from NaH and flowed into AAO channel. The diameter of the synthesized Si/SiO2 tubes consist with that of AAO channels. The samples were characterized by SEM, TEM, EDS, ED, IR, XRD and XPS to examine the morphology and composition. SEM studies indicated that the tubes with porous walls were found at the reaction temperature of 623 K and annealing temperature of 873 K. From EDS analysis, those tubes consisted of Si and O elements. ED and XRD studies showed that the tubes were amorphous, and Si-O-Si absorption was observed by IR. According to the XPS data, there were two types of chemical environment for Si in this sample — Si and SiO2. The Si/SiO2 tubes were oxidized futher by O2 stream to form pure SiO2 tubes. The reason of forming the pores on the wall was detemined by EDS and XRD, it is speculated that NaCl was formed during the reaction to insert on the wall, and dissolved with HCl solution for removing AAO membranes.

碩士
國立清華大學
化學系
89
By utilizing a new approach to fabricate carbon tubes, conducting polymer(PAni), sol-gel reaction and following thermal treatments, the well-organized silica tubes were successfully synthesized. Electrochemical and chemical appraoches were used in the period of developing silica tubes. SEM, TEM, EDS, ESCA, ATRIR, PXRD, TGA and other instruments were utilized to investigate chemical and structural properties. The products are amorphous, tubular, porous silica.

Es liegt in der menschlichen Natur, nach Attraktivität zu streben. Zeit und Geld werden darauf verwendet, einem bestimmten Schönheitsideal zu entsprechen. Unser Kauorgan betreffend, können Funktion und Ästhetik durch kieferorthopädische Therapie optimiert werden. Bei gegebener Indikation ist die Kieferorthopädie eine Therapieoption in jedem Lebensalter. Aufgrund der steigenden Anzahl erwachsener Patienten in der kieferorthopädischen Praxis ergibt sich, dass kieferorthopädische Hilfselemente immer häufiger auch auf keramischen Restaurationsflächen zuverlässig verankert werden müssen. Aus der Vielfalt der auf dem Markt verfügbaren Keramiken sind insbesondere Restaurationen aus Silikatkeramik sehr beliebt. Um Zähne im Rahmen einer kieferorthopädischen Behandlung kontrolliert bewegen zu können, ist die Befestigung von Hilfselementen wie Brackets, Tubes oder Attachments obligat. Die Anforderungen an den Haftverbund sind dabei komplex: Die Scherhaftfestigkeit (shear bond strength, SBS) muss ausreichen, um kieferorthopädischen Kräften standzuhalten und ein vorzeitiges Versagen des Haftverbundes zu verhindern. Nur so können kontinuierliche Zahnbewegungen zeitoptimiert ablaufen und ungewollte Bewegungen vermieden werden. Bei der Verankerung auf keramischen Oberflächen sollten weder durch den Konditionierungsvorgang, noch durch das Debonding nach abgeschlossener Behandlung irreversible Veränderungen auf der Restaurationsoberfläche resultieren. Je nach Ausmaß der Schädigung hat das nicht nur ästhetische Folgen: die erhöhte Rauigkeit begünstigt die bakterielle Besiedlung der Oberfläche und durch subkritisches Risswachstum (subcritical crack growth, SCG) ist die Beeinträchtigung der Langzeitstabilität der Restauration denkbar. Um kieferorthopädische Hilfselemente zuverlässig auf silikatkeramischen Oberflächen zu verankern, müssen diese Oberflächen konditioniert werden. In der kieferorthopädischen Praxis stehen dafür verschiedene Methoden mit individuellen Vor- und Nachteilen zu Verfügung. Wirkprinzip der Konditionierungsmaßnahmen ist zunächst das Etablieren einer mikroretentiven Oberfläche mittels Anrauen durch einen Präparierdiamant, Ätzen durch Flusssäure oder Sandstrahlen mit Aluminiumoxid und anschließend das Herstellen des Haftverbundes durch Auftragen eines Silans. Diese Maßnahmen führen zu irreversiblen Veränderungen der Keramikoberfläche, die bereits makroskopisch sichtbar sind. Ein alternatives Wirkprinzip versprechen neue Einkomponenten-Keramikprimer: Diese ätzen die Keramikoberfläche durch Ammoniumpolyfluorid und lassen dann den Haftverbund durch das ebenfalls enthaltene Trimethoxysilylpropyl-Methacrylat entstehen. Im Rahmen dieser Studie wurden Probekörper nach Vorlage einer Molarenkrone des Zahnes 36 durch ein computer-aided design/computer-aided manufacturing (CAD/CAM)-Verfahren hergestellt. Die Fläche zur Aufnahme des Bukkalröhrchens wurde entsprechend der Randomisierungsliste konditioniert: In Gruppe 1 bestand der Konditionierungsvorgang aus Anrauen und Ätzen mittels Flusssäure sowie Auftragen eines Silans, in Gruppe 2 aus Sandstrahlen mit Aluminiumoxid und Auftragen eines Silans, in Gruppe 3 aus Anrauen und Auftragen des Einkomponenten-Keramikprimers, in Gruppe 4 aus Auftragen des Einkomponenten-Keramikprimers, in Gruppe 5 lediglich aus Anrauen und in Gruppe 6 (Kontrollgruppe) erfolgte keine Konditionierung. Abschließend wurde das Tube mittels Befestigungskomposit verankert. Die SBS-Werte wurden bestimmt und die Integrität der Keramikoberfläche nach Debonding anhand des Adhesive-Remnant-Index (ARI) und des Crack-Tear-out-Index bewertet. Die Konditionierungsmaßnahmen der Gruppen I-IV konnten SBS-Werte generieren, die kieferorthopädischen Kräften standhalten. Deutliche Unterschiede zwischen den Gruppen konnten in Bezug auf Veränderungen an der Restaurationsoberfläche festgestellt werden. So kam es in den Gruppen I-III sowohl zu Rückständen von Befestigungskomposit auf der Oberfläche als auch zu Brüchen in/ Ausrissen aus der Keramik. Besonders geringe Veränderungen der Oberfläche bewirkte die Konditionierung mittels Einkomponenten-Keramikprimer. Um dem stetig steigenden Anspruch der Patienten an die kieferorthopädische Behandlung zu genügen, muss der Kieferorthopäde auf die Verlässlichkeit der verwendeten Materialien vertrauen können. Die in naher Zukunft neu auf dem Dentalmarkt verfügbaren Einkomponenten-Keramikprimer scheinen ein aussichtsreiches Hilfsmittel zur intraoralen Befestigung kieferorthopädischer Hilfselemente auf silikatkeramischen Oberflächen zu sein und konnten die an sie im Rahmen dieser in-vitro-Studie gestellten Anforderungen erfüllen.:1 Einführung 4 1.1 Zahnbewegung 4 1.2 Kräftesysteme 6 1.3 Kieferorthopädische Hilfselemente 7 1.4 Auswahl des Probekörpers 8 1.5 Dentale Keramiken 9 1.6 Verbund zwischen kieferorthopädischem Attachment und Restauration 11 2 Publikationsmanuskript 16 3 Zusammenfassung der Arbeit 24 4 Literaturverzeichnis 27 5 Anlagen 31 6 Darstellung des eigenen Beitrags 31 7 Erklärung über die eigenständige Abfassung der Arbeit 32 8 Lebenslauf 33 9 Publikationen 34 10 Danksagung 35

The present thesis discusses the beneficial effects of confining biologically relevant molecules inside porous structures of varying morphology and dimensions. Confinement of a biomolecule such as protein, enzymes drugs leads alteration in structural features and to a significant improvement in its biophysical properties. These properties include electrochemical redox behavior (for electroactive biomolecules) and thermal stability (denaturation temperature) of the concerned biomolecule. Silica (SiO2) based materials were primarily used as substrates for confining proteins and drugs. The confinement effects were probed in depth using various electrochemical, spectroscopic, and scattering techniques. The outcomes of confinement were utilized for developing electrochemical biosensors for the protein detection. Confinement of drugs effects their structural properties which gets reflected in their release kinetics studies. Electrochemical sensing was carried out using porous structure modified electrodes. These were used not only for detection of biological analytes but also extended to environmental pollutants. In the thesis, Chapters 2-4 deal with discussions related to electrochemical, spectroscopic, and scattering studies of protein confined inside SiO2 as well as polymer capsules. In Chapter 5A and 5B, Titania (TiO2) based nanotubes were utilized for demonstration of realistic electrochemical biosensors for the detection of myoglobin and a penicillin binding protein. In Chapters 6 and 7, enzyme and inhibitors, drug release kinetics from mesoporous oxides and TiO2 tubes have been discussed. Using the same approach as in chapter 5, electrochemical sensing of model environmental pollutants using TiO2 microwires have been discussed in chapters 8A and B. The use of TiO2 microwires for photocatalytic applications have also been considered in detail. A brief discussion of the contents and highlights of the individual chapters are described below: Chapter 1 discusses in detail about the porous substrates extensively used for biomolecular (proteins and drugs) confinement and structural features of these substrates. These substrates include the mesoporous materials of varying pore dimensions and pore arrangement. The alteration in the biophysical properties of the molecules because of confinement within these mesoporous substrates and its effects on related applications such as bio catalysis, drug release rates, electrochemical biosensing have been considered. A brief discussion on the present state of art in the field of drug delivery, enzyme catalysis and electrochemical biosensing have been included. The principles related to electrochemical, spectroscopic and the scattering techniques used to characterize the properties have been discussed in detail in this chapter. Chapter 2 include discussions on the investigations on the structure and function of hemoglobin (Hb) confined inside sol-gel template synthesized silica tubes (SiO2-tubes) Immobilization of hemoglobin inside SiO2-tubes resulted in the facile electron transfer to electroactive heme center leading to an enhanced electrochemical response. The consequences of confinement on protein structures and activity were further probed via ligand binding and thermal stability studies. Reversible binding of n-donor liquid ligands such as pyridine and its derivatives and predictive variation in their redox potentials were obtained from detailed electrochemical investigations. The results suggested absence of adverse effect on structure and function of Hb confined inside the channels of SiO2-tubes. Additionally, the thermal stability of confined Hb was compared to that of free Hb in solution. The melting or denaturation temperature of Hb immobilized inside SiO2-tubes increased by approximately 4 oC compared to that of free Hb. In Chapter 3A, the configuration of hemoglobin (Hb) in solution and confined inside silica tubes (SiO2-tubes) have been studied using synchrotron small angle x-ray scattering (SAXS) and the consequences were correlated to its electrochemical activity. Confinement inside silica tubes aided in preventing protein aggregation compared to that observed for unconfined protein in solution. In case of confined Hb, the radius of gyration (Rg) and size polydispersity (p) was considerably lower than in solution. The difference in configuration between the confined and unconfined protein were reflected in their electrochemical response. Reversible electrochemical response (from cyclic voltammograms) were obtained in case of the confined hemoglobin in contrary to only cathodic response for the unconfined protein in solution. This led to the conclusion of difference in orientation of the electroactive heme center. The electron transfer coefficient () and electron transfer rate constant (ks) were also calculated to further support the structural differences between the unconfined and confined states of the hemoglobin. Thus, absence of any adverse effects on confinement of proteins inside the inorganic matrices such as silica nanotubes opens new prospects for utilizing inorganic matrices as protein “encapsulators” as well as sensors at varying temperatures. Chapter 3B discusses the implications of host dimensions on the protein structure. This is a very important parameter as it considerably influences the protein properties under confinement. This study probes the structure of same Hb molecules, confined inside silica tubes of pore diameters varying by one order in magnitude: ~ 20-200 nm. The confinement effect on structure was probed vis-à-vis the protein in solution. Small angle neutron scattering (SANS), which provides information on the protein tertiary and quaternary structures, was employed to study the influence of tube pore diameter on confined protein structure and configuration. Depending on the SiO2-tubes pore diameter, confinement significantly influenced the structural stability of Hb. High radius of gyration (Rg) and polydispersity (p) of Hb in case of the 20 nm diameter SiO2-tubes indicated that Hb undergoes significant amount of aggregation. However, for SiO2-tubes with pore diameters > 100 nm, Rg of Hb was found to be in very close proximity to that obtained from the protein data bank (PDB) reported structure. This strongly indicated that the protein has a preference for the more native like non-aggregated state when confined inside tubes of diameter ~ 100 nm. Further insight in to the Hb structure was obtained from distance distribution function, p(R) and ab-initio models calculated from the SANS patterns. These also suggest that the size of SiO2-tubes is a key parameter for the protein stability and structure. In Chapter 4 we have introduced an organic substrate to investigate the effect of confinement on structure of hemoglobin (Hb). Like as discussed in chapters 3(A and B), Hb transformed from an aggregated state in solution to non-aggregated state when confined inside the polymer capsules. Synchrotron small angle x-ray scattering (SAXS) studies directly confirmed this fact. The radius of gyration (Rg) and polydispersity (p) of the proteins in the confined state were smaller compared to that in solution. In fact, the Rg value was very similar to theoretical values obtained using protein structures generated from protein databank. The Rg value was almost constant in the temperature range (25-85 °C, Tm = 59 °C), for the confined Hb. This observation is in contrary to the increasing Rg values obtained for the free Hb in solution suggesting higher thermal stability of confined Hb inside the polymer capsule. Protein functions gets significantly altered as a result this. It resulted in an enhancement of the electroactivity of confined Hb. While Hb in solution showed dominance of the cathodic process (Fe3+→ Fe2+), efficient reversible Fe3+/Fe2+ redox response is observed in case of the confined Hb. This again gave an indication of the difference in orientation of electroactive heme group resulting it to reside in a chemically different environment compared to when it is in solution. This has important implications on protein functional properties and related applications. Thus, in this chapter we get a detailed overview of how confinement orients different groups’ viz., electroactive heme center to take up positions that makes it favorable to participate in biochemical activities such as sensing of analytes from small to macromolecules and controlled delivery of drugs. The conclusions derived from the studies in previous chapters have been utilized in chapters 5A and 5B for developing a realistic electrochemical biosensor. Since the sensing based on electrochemical response largely depends on the location of heme group, the location of the heme center was altered in a controlled manner using chemical treatment. Chapter 5A deals with an alternate antibody-free strategy for the rapid electrochemical detection of cardiac myoglobin (having heme center) using hydrothermally synthesized TiO2 nanotubes (TiO2-NT). In this strategy, myoglobin was unfolded using denaturants to expose deeply buried electroactive heme center into the solution very close to the electrode. This leads to an efficient reversible electron transfer from protein to electrode surface. The sensing performance of the TiO2-NT modified electrodes were compared vis á vis commercially available titania and GCE electrodes. The tubular morphology of the TiO2-NT led to facile transfer of electrons to the electrode surface which eventually provided linear current response (obtained from cyclic voltammetry) over a wide range of Mb concentration. The sensitivity of the TiO2-NT based sensor was remarkable and was equal to 18 A/ mg ml-1 (detection limit= 50 nM). This coupled with the rapid analysis time of few tens of minutes (compared to few days for ELISA) demonstrates its potential usefulness for the early detection of the acute myocardial infarction (AMI). Chapter 5B comprises of a discussion of employing a rapid electrochemical detection method of proteins without any electroactive center. The protein was transformed to an electrochemically active protein via metal tagging (Fe3+ in this case). This biosensor was also based on titania (TiO2-NT) nanotubes which was used to modify the working electrode. To reduce the detection volumes drastically, screen printed carbon electrodes (SPCE) was introduced in this detection. It was possible to detect as low as 1 ng l-1 of protein in very small sample volumes (as low as 30 l). The feasibility of this method for the detection of PBP2a, a marker for methicillin resistant Staphylococcus aureus (MRSA) was demonstrated here. This biosensor could effectively detect PBP2a in whole cell lysate samples. To mimic the practical detection conditions, the selectivity and efficiency was also validated using other non-selective proteins such as PTP10D, a protein tyrosine phosphatase, and bovine serum albumin (BSA). As already mentioned, this electrochemical detection strategy could reproducibly detect protein samples within minutes compared to standard ELISA methods (3-4 h) or a modified ELISA protocols (FAST-ELISA; 30 mins) excluding the time taken for sample preparation. These observations suggest the potential of the titania nanotube based electrochemical biosensor in both clinical and community settings for the detection of infectious pathogen In Chapter 6, the feasibility of utilizing mesoporous matrices of alumina and silica for inhibition of enzymatic activity have been presented. These studies were performed on a protein tyrosine phosphatase by the name chick retinal tyrosine phosphotase-2 (CRYP- 2), a protein that is identical in sequence to the human glomerular epithelial protein-1 and involved in hepatic carcinoma. The inhibition of CRYP-2 is of tremendous therapeutic importance. Inhibition of catalytic activity was examined using the sustained delivery of para nitrocatechol sulfate (pNCS) from bare and amine functionalized mesoporous silica (MCM-48) and mesoporous alumina (Al2O3). Amine functionalized MCM-48 was found to exhibit the best release of pNCS among the various mesoporous matrices studied and hence inhibition of CRYP-2 was maximum in this case. The maximum speed of reaction, vmax (= 160 ± 10 μmols min-1mg-1) and inhibition constant, Ki (= 85.0 ± 5.0 μmols) estimated using a competitive inhibition model were found to be very similar to inhibition activities of protein tyrosine phosphatases using other methods. In Chapter 7, we have demonstrated another very attractive application of the TiO2-NT which have been already used for protein sensing application. Due to the porous nature of the surface and its other attractive features, TiO2-NT has a great potential in drug delivery applications. The TiO2-NT mimicked the pore channels of the mesoporous substrates that have been used in the previous chapter. The drug release from these TiO2- NT exhibited a completely different sigmoidal release profile compared to our previous reports from the group. Additionally, the effect of surface functionalization and solution pH on drug release profile have also been considered during our studies. The release profiles were modelled with theoretical Hill equation to extract several physical parameters to explain the extent of drug substrate interactions. These results further supplemented the unique nature of the release profile. In Chapter 8A we have again demonstrated an electrochemical detection strategy but this time for chemical pollutants. Commercial textile industry effluents such as dyes were chosen for the model studies. Mesoporous anatase titania microwires synthesized via an optimized polyol method were used for sensing and photocatalysis of these dyes. Using spectroscopic investigations, we have showed that these titania microwires preferentially sense cationic (e.g. methylene blue, Rhodamine B) over anionic (e.g. Orange G, Remazol Brilliant Blue R) dyes. It was observed that variation in microwire dimensions and pH of dye solution, led to an increase in the concentration of the adsorbed dye. These findings were later corroborated with much faster electrochemical sensing. The effect of microwire length on electrochemical detection sensitivity have also been accounted in these studies. The photochemical performance of these titania microwires have been compared with the commercial P25-TiO2 nano powders. The photochemical performance was also studied as a function of exposure times and pH of dye solution. Excellent sensing ability and photocatalytic activity of the titania microwires was attributed to increased effective reaction area of the controlled nanostructured morphology. This makes them an attractive substrate for commercial sensing applications In Chapter 8B, anatase TiO2 microwires used in previous chapter were chemically modified to silver (Ag) decorated TiO2 microwires (Ag-TiO2). This was done with an aim to improve the detection sensitivity and photodegradation performance. The Ag-TiO2 microwires were synthesized via polyol synthesis route followed by a simple surface modification and chemical reduction approach for attachment of silver. The electrochemical sensing performance of Ag-TiO2 microwires have been subsequently compared with the base TiO2 microwires in the detection of cationic dye such as methylene blue. The superior performance of the Ag-TiO2 composite microwires was attributed to improved surface reactivity, mass transport and catalytic property because of decorating the TiO2 surface with Ag nanoparticles. Further studies were also carried out to compare its photocatalytic activity with TiO2 microwires at constant illumination protocols and observation times. As demonstrated the improved photocatalytic performance of Ag-TiO2 composite microwires was attributed to the formation of a Schottky barrier between TiO2 and Ag nanoparticles leading to a fast transport of photogenerated electrons to the Ag nanoparticles.

碩士
國立中央大學
機械工程研究所
99
An investigation of adsorption bed using flat-tube in a adsorption cooling system with siliga gel as adsorbent and water as refrigerant is described. The new type adsorption bed is in order to increase the amount of adsorbent and decease the thermal resistance. Otherwise, the performance of the adsorption bed with difference thickness of silica gel coated layer on the flat-tube is discussed. The results show that the performance of the flat-tube adsorption bed is better than the circular tube. The amount of water adsorbed of flat-tube adsorption is 2.2 times than the circular tube in 10 minutes at adsorption cycle. Otherwise, it is smaller thermal resistance and better performance of mass transfer by thin thickness of silica gel coated layer. It means that the 2.8 mm coated layer has better performance of adsorption and cooling power.

碩士
義守大學
機械與自動化工程學系碩士班
94
This study mainly focused on the characteristics of carbon nano tubes (CNTs) and CNTs embedded with silicon or copper nano particles formations by the microwave plasma enhanced chemical vapor deposition system. Initially, the silicon substrates were surface treated by Ar atmospheric plasma to achieve higher roughness, and investigated the influences on the adhesion between the silicon substrate and the nickel catalyst film. Subsequently, adopted three different deposition methods to deposit the nickel catalyst films, i.e., e-beam, sputter, electro-less plating, and compared the differences for growing CNTs. At the same time, we can obtain the optimum processes combinations to form the reasonable CNTs. Finally, we tried to fill the reasonable CNTs with silicon or copper nano particles by different manufacturing time, and investigate the differences of luminescence behaviors. The experimental results indicated the silicon wafer with argon atmospheric plasma treatment resulted in the larger size and density for the nickel catalyst particles of hydrogen etching, and revealed the higher adhesion phenomena. The grown CNTs examined by SEM, TEM, Raman analysis to calculate the length, the density, the diameter, and the ratio of amorphous carbon to graphite, and found CNTs formed on the nickel catalyst film deposited by sputter method seem to appear optimum selection for next filling processes. Oxygen gas plasma was used to open the closed CNTs, and electrical feed-through and evaporation systems were adopted to fill the silicon and copper nano particles, respectively, into the open-ended CNTs. HRTEM observations showed that the more nano particles existence as the increasing manufacturing process time, and will be studied the luminescence behavior difference by PL and EL analysis. Therefore, we had finished the relative manufacturing processes of CNTs and CNTs with silicon or copper nano particles, and build up the preliminary procedures of PL and EL luminescence measurement. These results maybe can be used as the database of relative research.