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1
Kandas, Ishac Lamei Nagiub. "Silica Microspheres Functionalized with Self-assembled Nanomaterials." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/19232.
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A major limitation of silica-based high-Q microcavities is the lack of functionalities such as gain, plasmonic resonance, and second-order nonlinearity. Silica possesses third order nonlinearity but cannot produce second order nonlinearity, plasmonic resonances, or fluorescence emission. The key to overcome this deficiency is to develop versatile methods that can functionalize the surface of a silica microsphere with appropriate nanomaterials. The goal of this thesis is to present and characterize an electrostatic self-assembly based approach that can incorporate a large number of functional materials onto the surface of a silica resonator with nanoscale control. We consider several types of functional materials: polar ionic self-assembled multilayer (ISAM) films that possess second order nonlinearities, Au nanoparticles (NPs) that support plasmonic resonances, and fluorescent materials such as CdSe/ZnS core/shell QDs. A major part of this thesis is to investigate the relationship between cavity Q factors and the amount of nanomaterials deposited onto the silica microspheres. In particular, we fabricate multiple functional microspheres with different ISAM film thickness and Au NPs density. We find that the Q factors of these microspheres are mainly limited by optical absorption in the case of the ISAM film, and a combination of optical absorption and scattering in the case of the Au NPs. By controlling the number of polymer layers or the NPs density, we can adjust the Q factors of these functional microspheres in the range of 106 to 107. An agreement between theoretical prediction and experimental data was obtained. The results may also be generalized to other functional materials including macromolecules, dyes, and non-spherical plasmonic NPs.
We also study the adsorption of Au NPs onto spherical silica surface from quiescent particle suspensions. The surfaces consist of microspheres fabricated from optical fibers and were coated with a polycation, enabling irreversible nanosphere adsorption. Our results fit well with theory, which predicts that particle adsorption rates depend strongly on surface geometry. This is particularly important for plasmonic sensors and other devices fabricated by depositing NPs from suspensions onto surfaces with non-trivial geometries.
We use two additional examples to illustrate the potential applications of this approach. First, we explored the possibility of achieving quasi-phase-matching (QPM) in a silica fiber taper coated with nonlinear polymers. Next, we carry out a preliminary investigation of lasing in a silica fiber coated with CdSe/ZnS core/shell quantum dots (QDs).
Ph. D.
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Hofmann, Matthias Colin. "Second Order Nonlinear Silica-Based Fibers and Microspheres." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/76786.
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After decades of development, optical fiber technology has reached a high degree of sophistication and maturity, and currently serves as the backbone of today''s internet. Despite its technical versatility and capability, current silica fiber technology still has a significant flaw: since silica fibers only possess very weak second order nonlinearity, it has been impossible to develop a large number of important nonlinear optical devices and instruments, such as optical parametric amplifiers (OPA) and optical parametric oscillators (OPO). In this thesis,we show how to overcome this intrinsic limitation, and introduce second order nonlinearity into silica fiber devices.Master of Science
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Ahmed, Adham Saleh. "Morphology control on porous monoliths and silica microspheres and applications in chromatography." Thesis, University of Liverpool, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.569199.
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Silica-based stationary phases have been under investigation since they were first produced, and studies still continue to try to improve their morphology and porosity. A handful of reliable and straightforward synthetic procedures are used routinely for their manufacture. The most widely applied procedures are variations of the modified Stober synthesis route that allow the manufacture of relatively monodisperse particles in the nanometer range, or the sol-gel route that produces larger porous microstructures. However, the controlled manufacture of silica stationary phase with the desired physical properties is still a challenge, and most of their preparation involves multi-step preparation, adding cost and time. This dissertation outlines work that introduces a set of new protocols that were developed for the preparation of silica with controlled morphology and porosity. Herein, silica microspheres with tuneable pore size and particle size distribution were synthesised using a modified Stober method. Hydrophilic polymers were introduced into the reaction system, which acted as stabilising agent. Further altering the reaction parameters resulted in the formation of silica microspheres with controlled surface morphology, beads-on-bead silica particles. The preparation conditions were extensively studied in order to understand the reason for such phenomena. The beads-on-beads particles exhibit chromatographic potential, especially for proteins separation. Moreover, porous silica microspheres were further used for the preparation of hierarchically porous silica monoliths by a controlled freezing approach. The macropore morphologies could be tuned with the addition of surfactants in the silica colloidal suspensions during the freezing process. The engineering of porosity and improvement on mechanical stability of the silica materials were achieved through a further soaking and sol-gel process. It was also possible to enhance the mechanical stability through thermal treatment of the materials. Directional freezing approach was also evaluated to direct the assembly of silica nanoparticles. The presence of water-soluble polymers resulted in better aligned features and acted as a gelling agent in the case of charged polymer. The monolith was successfully prepared inside a fused-silica capillary column and was investigated for chromatographic applications. Preformed emulsion-templated porous polyacrylamide beads and monolith were used as a scaffold for controlled growth of silica spheres on macroporous surface. A hierarchical hybrid structure was formed. The polymer scaffold could be removed to form porous silica spheres and macroporous structures. Further investigation was considered to control the porosity and the size of the forming microspheres. This study was further extended into the preparation of fluorescent silica spheres and composite materials. Furthermore, a simple and generic method was also developed for the preparation of gradient emulsion-templated structures. The gradient could be achieved with the aid of centrifugation mechanism. This method enabled the formation of dual gradient mesoporous and macroporous composites.
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Kong, Yupeng. "Modulation of like-charge attraction by lipid and protein functionalized silica microparticles." Thesis, University of Oregon, 2010. http://hdl.handle.net/1794/11436.
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xii, 138 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.Controlling colloidal interactions continues to receive a great deal of attention due both to basic scientific interests as well as industrial applications. However, many aspects of interactions between microparticles remain poorly understood, including the attraction observed between particles with the same kind of charge (like-charge attraction). This situation hinders progress in the generation of colloidal self-assembled structures. This thesis focuses on measurements of pair interactions of functionalized silica microspheres and the resulting insights into colloidal interactions. Silica microparticles were functionalized in two ways. For one method, each particle was coated with a lipid inlayer membrane. The charge density of the particle surface can thereby be easily tuned by controlling the type or amount of charged lipids. For the other method, the cholera toxin subunit B protein (CTB) was bound to lipid-functionalized microparticles. To measure pair interactions, we invented a line optical trap that enables nearly free one-dimensional Brownian motion of particles. Pair interaction energies of functionalized particles above the bottom of the experimental chamber can be extracted via a Boltzmann relationship. Both lipid-only and lipid-plus-protein functionalized microparticles show tunable, attractive pair interactions. For lipid-only coatings, the attraction becomes stronger by increasing the fraction of positively charged lipids. There is a linear relationship between pair potential and molar percentage of positively charged lipids. For lipid-plus-protein coatings, attractive potentials were weakened monotonically by binding more CTB. Decompositions of potential curves allow identification of directly charge-dependent and charge-independent contributions to colloidal like-charge attraction. Analysis shows that the correlations between attraction strength and range are opposite in these two sets of particles. Moreover, the correlations between particle-wall separation and attraction strength in lipid-only and lipid-plus-protein functionalized particles are also opposite. These comparisons show that like-charge attraction may result from more than one mechanism. Finally, we measured pair potential energies of lipid functionalized silica particles above a lipid functionalized glass chamber bottom, which exhibit a quadratic relationship between the attraction strength and the fraction of positively charged lipids. Compared with the situation of particle functionalization only, this relation indicates that confinement-induced like-charge attraction can be modulated by altering electrostatic properties of the confining wall.
Committee in charge: Dr. Stephen D. Kevan, Chair; Dr. Raghuveer Parthasarathy, Advisor; Dr. Hailin Wang; Dr. Miriam Deutsch; Dr. Marina G. Guenza
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Park, Young-Shin 1972. "Radiation pressure cooling of a silica optomechanical resonator." Thesis, University of Oregon, 2009. http://hdl.handle.net/1794/10559.
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xi, 125 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.This dissertation presents experimental and theoretical studies of radiation pressure cooling in silica optomechanical microresonators where whispering gallery modes (WGMs) are coupled to thermal mechanical vibrations. In an optomechanical system, circulating optical fields couple to mechanical vibrations via radiation pressure, inducing Stokes and anti-Stokes scattering of photons. In analogy to laser cooling of trapped ions, the mechanical motion can in principle be cooled to its ground state via the anti-Stokes process in the resolved-sideband limit, in which the cavity photon lifetime far exceeds the mechanical oscillation period. Our optomechanical system is a slightly deformed silica microsphere (with a diameter 25-30 μm ), featuring extremely high Q -factors for both optical ( Q o ∼ 10 8 ) and mechanical ( Q m ∼ 10 4 ) systems. Exploiting the unique property of directional evanescent escape in the deformed resonator, we have developed a free-space configuration for the excitation of WGMs and for the interferometric detection of mechanical displacement, for which the part of input laser that is not coupled into the microsphere serves as a local oscillator. Measurement sensitivity better than 5 × 10 -18 m /[Special characters omitted.] has been achieved. The three optically active mechanical modes observed in the displacement power spectrum are well described by finite element analysis. Both radiation pressure cooling and parametric instabilities have been observed in our experiments. The dependence of the mechanical resonator frequency and linewidth on the detuning as well as the intensity of the input laser show excellent agreement with theoretical calculations with no adjustable parameters. The free-space excitation technique has enabled us to combine resolved sideband cooling with cryogenic cooling. At a cryogenic temperature of 1.4 K, the sideband cooling leads to an effective temperature as low as 210 m K for a 110 MHz mechanical oscillator, corresponding to an average phonon occupation of 37, which is one of the three lowest phonon occupations achieved thus far for optomechanical systems. The cooling process is limited by ultrasonic attenuation in fused silica, which should diminish when bath temperature is further lowered, with a 3 He cryostat, to a few hundred millikelvin. Our experimental studies thus indicate that we are tantalizingly close to realizing the ground-state cooling for the exploration of quantum effects in an otherwise macroscopic mechanical system.
Committee in charge: Michael Raymer, Chairperson, Physics; Jens Noeckel, Member, Physics; Hailin Wang, Member, Physics; Paul Csonka, Member, Physics; Jeffrey Cina, Outside Member, Chemistry
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Knappett, Peter. "Evaluating the Effects of Grain Size and Divalent Cation Concentration on the Attenuation of Viruses and Microspheres through Crushed Silica Sand." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/906.
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Over the last decade in North America, an increasing number of microbiological drinking water regulations have been used to manage groundwater resources that are potentially influenced by surface water. Regulations such as the Ontario Ministry of Environment Regulation 505, which requires at least a 60 day groundwater travel time between surface waters and drinking water wells, have been created with limited understanding of subsurface pathogen transport processes. Groundwater Under Direct Influence studies (GUDI or GWUDI in USA) are conducted to assess the need to treat well water at an extraction point. Currently, there is a lack of knowledge regarding factors that affect the transport of pathogens through porous media at the surface water-groundwater interface. Such information is required to supply sufficient quantities of drinking water in a cost effective and safe manner. Factors that affect pathogen transport through porous media include: properties of the pathogen (i. e. surface charge, size, and morphology), properties of the granular media (i. e. mineralogy, size, texture, angularity) and properties of the water (i. e. pH, ionic strength and content, and natural organic matter). This study examines the effects of ionic strength, grain size and influent virus concentrations on pathogen transport in porous media. Fourteen column tests were conducted using the bacteriophage MS2 and 1. 5 µm microspheres; two commonly used non-pathogenic surrogates representative of human viruses and bacteria, respectively. Two size distributions of crushed silica sand, with median grain diameters of 0. 7 and 0. 34 mm, and two ionic strengths of 8 and 95 mmol/L were used. A 22 partial factorial design was used with a minimum of two replicates of each combination of the parameters.
The results show that complete breakthrough of both viruses and microspheres occurred in medium sand at low ionic strength. It was found that increasing ionic strength by Ca2+ addition precluded breakthrough of MS2 in both the medium and fine sands. This represents a greater than 8 log reduction in peak effluent concentration and essentially complete attenuation.
In fine sand, with low ionic strength water, a 5 log reduction in peak MS2 concentrations was observed. In the same sand at high ionic strength, no MS2 broke through the column, corresponding to a greater than 8 log removal. Since complete attenuation occurred in both grain sizes at high ionic strength, the effect of higher ionic strength in the fine sand was indistinguishable from the effect observed from raising the ionic strength in the medium sand.
In contrast to the viruses, microsphere transport was essentially unaffected by increasing ionic strength under the conditions investigated. A 1 log reduction in peak concentration was observed in the high ionic strength water in the medium sand. In spite of this, grain size had a profound effect on the attenuation of microspheres. There was no evidence of microsphere breakthrough in any of the fine sand columns at the low or high ionic strengths, yielding a greater than 5 log reduction in microsphere concentration associated with grain size alone. The effect of varying virus concentration was also investigated. It was found that varying the concentration of viruses between 105 and 107 pfu/ml had no discernable effect on their observed transport characteristics; normalised peak breakthrough concentration, percent attenuation and retardation relative to a bromide tracer.
Based on the results from this Thesis, in a riverbank filtration environment, there is reason to expect that, at comparable water qualities and in similar porous media, multiple logarithmic reductions of viruses and bacteria would occur over the much longer (than column length) flowpaths associated with RBF. There is also reason to expect this attenuation capability to vary based on riverbank grain size and water chemistry.
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Arraud, Nicolas. "Etude cinétique de la liaison élémentaire entre Annexine-A5 et membranes et mise au point d’un test de quantification des microparticules plasmatiques pro-coagulantes, par cytométrie en flux." Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14459/document.
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L’Annexine A5 (AnxA5) est une protéine soluble se liant aux membranes contenant de la phosphatidylsérine (PS) en présence de calcium (Ca2+). Le rôle central joué par l’AnxA5 dans les processus de réparation membranaire a été récemment mis en évidence. L’AnxA5 possède une très forte affinité pour les membranes biologiques contenant de la PS, cependant son mode de liaison aux membranes n’est pas encore élucidé.La première partie de mon travail de thèse a concerné le développement d’une approche originale d’étude de la liaison de l’AnxA5 à des microsphères de silice fonctionnalisées par une bicouche lipidique (µPSiO2@SLB pour supported lipid bilayer), par cytométrie en flux (FCM). Cette approche m’a permis d’étudier la liaison à l’équilibre et en cinétique à très faible concentration en AnxA5, de l’ordre du picomolaire. Cette approche représente une des méthodes les plus sensibles d’étude de liaison à l’équilibre et la première permettant d’accéder aux constantes cinétiques d’interaction pour l’AnxA5. Cette étude m’a également permis de mettre au point une stratégie de dosage indirect de liposomes contenant de la PS avec une sensibilité de l’ordre du nanogramme de lipides par millilitre.La seconde partie de ma thèse a concerné l’étude de microparticules (MP), fragments de membranes cellulaires présents dans les fluides biologiques. Dans le plasma sanguin la majorité des MP sont d’origine plaquettaire et exposent de la PS. Il existe une corrélation entre la concentration en MP plasmatiques exposant de la PS et le développement de pathologies thrombotiques. La FCM est la méthode de référence dans l’étude des MP cependant leur détection est rendue difficile par leur petite taille. J’ai appliqué aux MP plasmatiques le test de dosage développé pour les liposomes. Les résultats obtenus sont prometteurs et permettent d’envisager le développement d’un test de dosage de l’ensemble des MP exposant de la PSAnnexin-A5 (AnxA5) is a soluble membrane binding protein that binds to phosphatidylserine (PS) containing membranes in a calcium dependent manner and plays a central role in cell membrane repair processes. AnxA5 has a remarkably high affinity for PS containing membranes, but its binding mechanism remains unclear.The first part of my PhD work was to develop a new method for studying AnxA5 binding using supported lipid bilayer functionalized silica microspheres (µPSiO2@SLB) and Flow Cytometry (FCM). This approach allowed me to describe in details both equilibrium and kinetics of AnxA5 binding at picomolar concentrations in AnxA5. This study is one of the most sensitive for equilibrium binding studies and the first allowing to measure binding kinetics constants for AnxA5. This study also led to the development of a new strategy for determination of liposome concentration with sensitivity in the range of one nanogram of lipid per milliliter. The second part of my work focused on microparticles (MP) that are cell membrane fragments found in biological fluids. In plasma, the vast majority of MP originates from platelets and expresses PS at their surface. There is a correlation between MP concentration in plasma and thrombotic risk. FCM is the “golden standard” of hæmatologic analysis but the majority of MPs are too small to be detected. I have applied the test developed with liposomes for the quantification of MP. The results are promising and allow foreseeing the development of a test able to give the absolute quantity of PS exposing MPs in plasma samples
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Pazos, Cecilia. "Préparation et propriétés de microsphères de silice monodispersées /." [S.l.] : [s.n.], 1991. http://library.epfl.ch/theses/?nr=961.
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TREUSSART, FRANCOIS-MICHEL. "Etude experimentale de l'effet laser dans des microspheres de silice dopees avec des ions neodyme." Paris 6, 1997. http://www.theses.fr/1997PA066733.
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Ce travail de these porte sur la mise en evidence de l'effet laser dans des microresonateurs optiques de tres haute surtension, bases sur les modes de galerie de microspheres de silice d'un diametre de 50 a 100 m. Ces modes resonnants correspondent a une propagation guidee par reflexion totale interne. La lumiere est ainsi confinee dans un anneau equatorial dont les dimensions transversales sont de l'ordre de la longueur d'onde, ce qui donne lieu a une forte exaltation du champ lumineux. Les pertes de ces modes guides sont extremement faibles. Ils offrent donc la combinaison remarquable d'une tres forte localisation du champ dans un tout petit volume et de tres longs temps de vie pour les photons. Ces proprietes en font des resonateurs de choix tant pour obtenir des effets d'optique non-lineaire a tres bas seuil que pour des experiences d'electrodynamique quantique en cavite. Ce memoire presente d'abord les proprietes de ces resonances et leur observation experimentale par spectroscopie laser. Le dedoublement de ces resonances par retrodiffusion interne est ensuite decrit et interprete par un modele d'oscillateurs couples, en bon accord avec les experiences. La realisation d'un microlaser avec des microbilles dopees au neodyme est ensuite presentee. Les tres bas seuils observes (200 nw) correspondent bien aux predictions theoriques obtenues par un modele semi-classique approprie. Pour renforcer les effets de cavite, ces experiences ont ete poursuivies en immergeant les microspheres dans l'helium superfluide. Le montage cryogenique mis au point nous permet de conserver des surtensions a 2 k de 10#9 et l'emission laser a pu etre observee, ouvrant la voie a la recherche d'un fonctionnement laser avec seulement quelques ions couples a quelques photons.
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COLLOT, LAURENT. "Etude theorique et experimentale des resonances de galerie de microspheres de silice : pieges a photons pour des experiences d'electrodynamique en cavite." Paris 6, 1994. http://www.theses.fr/1994PA066532.
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Ce travail de these porte sur l'etude des resonances de galerie de tres haute surtension observees sur des microspheres de silice d'un diametre voisin de 100m. Ces resonances correspondent a des modes de propagation du champ le long d'un anneau equatorial dont les dimensions transversales sont de l'ordre de la longueur d'onde. Les pertes de ces modes guides sont extremement faibles. Ils offrent donc une combinaison remarquable d'une tres forte localisation du champ dans un tout petit volume et de tres longs temps de vie pour les photons. Ces proprietes en font des resonateurs de choix tant pour de nombreuses applications pratiques que pour des experiences d'electrodynamiques quantique en cavite. Le memoire de these presente les proprietes de ces resonances, decrit leur observation experimentale par spectroscopie laser et analyse quelques perspectives ouvertes par ces etudes en physique appliquee et fondamentale. Les possibilites d'utiliser ces modes de galerie pour asservir en phase un laser a diode ou pour fabriquer des lasers microscopiques sont envisagees. Une experience de deflexion d'atomes froids dans l'onde evanescente associee a un mode de galerie est egalement etudiee. Une telle experience devrait permettre de mettre en evidence la nature discrete de l'intensite d'un champ lumineux constitue de quelques photons et realiser une mesure dispersive extremement sensible de tous petits champs optiques
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LIN, YI-JYUN, and 林毅峻. "Preparation and Physical Properties of the Hollow Silica Microspheres." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/w2c54b.
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碩士國立高雄應用科技大學
化學工程與材料工程系博碩士班
104
Hollow silica microspheres (HSMS) with different particle sizes were successfully prepared using reverse emulsion polymerization. Effects of different concentrations of alkyl-siloxane with varying polarity and different HLB values (hydrophilic lipophilic balance) of surfactant on the physical properties were also investigated. Tetraethyl orthosilicate (TEOS) was used as a silicate source, and an alkyl-siloxane with polar functional group was used as internal surfactant to prepare the HSMS. A simple way of solvent-etching method was used to form an internal hollow of the microsphere, instead of using the calcination method to remove template. Solvent-etching method can retain the hydroxyl group on the outer surface of the microsphere, which can be further modified to the other functional group or any hydrophilic or lipophilic moiety. Different concentrations of alkyl-siloxane with varying polarity were used to investigate the effect on the shell thickness of HSMS. Varied HLB values of 6, 7, 8, 10.4, 12 and 13.5 were used to explore the effect on the particle size of HSMS. TEM images show the formation of the internal hollow and the shell thickness. Particle size analyser (PSA) was used to demonstrate the particle size distribution. The results show that the type of polarized alkyl-siloxane significantly affect the formation and internal hollow size of microspheres. Meanwhile, the ratio of (polarized alkyl-siloxane/TEOS) bring about different shell thickness. Small R values produced thinner shell thickness and small values of HLB create a larger particle size. FTIR (Fourier transform infrared), FE-SEM (field emission scanning electron microscopy), SEM (scanning electron microscopy), EDS (energy dispersive spectrum), Zeta-potential and BET (surface area analyser/porosity analyser) were used as well to investigate the other properties of HSMS.
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Huang, Eric, and 黃苡叡. "Electrophoretic Self Assembly of Silica Microspheres for 3D Photonic Crystals." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/38893685902362815327.
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碩士逢甲大學
材料科學所
92
The aims of this study are consisted of the following aspects: (a) fabrication of monodispersed monosized silica microspheres (100~500 nm ±10%) is under sol-gel process, (b) preparation of high colloidal stability electrophoretic deposition (EPD) suspension is obtained by carefully adjusting the zeta potential of silica microspheres and pH value of suspension in terms of adding nitric acid or hydrogen ammonium, (c) a silica photonic crystal with face closely packed (FCC) structure can be made with respect to the electrophoretic self-assembly (EPSA) behavior of silica microspheres under the influence of exerting electrical forces in EPD tank, and (d) a three-dimensional (3-D) self-assembled pattern/structure of silica microspheres is produced with the aid of different specific arrangements of counter-electrode design and of establishing a non-uniform electrical field in the EPD environment. Monosized silica microspheres were prepared by a sol-gel process by using tetraethylorthosilicate (TEOS) as precursor. Silica microspheres of 3 g added in 150 ml ethanol solvent was formed as EPD suspension, of which pH value was modified by adding suitable amount of HNO3 or NH4OH to gain a reasonably good colloidal stability and a fair dispersion quality. The result of zeta potential measurement showed that the isoelectric point (IEP) of silica EPD suspension was located in the acidic condition (pH~3.0), where a poor SiO2 microsphere dispersion would appear due to the pronounced agglomeration of fine particles. A well-dispersed EPD suspension was obtained by adjusting suspension to be weakly basic (pH > 8). Also the EPD yield was relatively higher with EPD suspension in the basic condition. To evaluate the effect of various design of EPD setups on the self-assembly behaviors of silica microspheres, we particularly tested a number of counter-electrodes in different geometries. For the vertical counter-electrode and working electrode setup, the random packing of silica microspheres on the surface of the working electrode became more and more obvious along with using increased applied electrical field (>200 V/cm). A horizontal EPD setup of counter-electrode and working electrode with a very narrow spacing resulted in an excessively high exerting electrical field (>10 kV/cm) in the EPD environment, in which the necking phenomena between silica microspheres might occur occasionally. Finally a perfect electrophoretic self-assembly (EPSA) behavior of silica microspheres into the layered pattern with the FCC structure was observed due to the influence of vectored electrical forces from an electrical field gradient by using surrounding counter-electrode arrangement. Furthermore, a 3-D self-assembled pattern/structure of silica microspheres was prepared by means of specially etched gold conductor pattern on silicon substrate as well as different arrangements of counter-electrode setups to form a non-uniform electrical field in the EPD setting. Various self-assembled 3-D structures of silica microspheres in either symmetrical curvilinear profile or triangular ridges can be produced through the proposed EPSA route in this study, which renders us an exciting technical potential by using such 3-D FCC or BCC structures as the unique templates to develop a number of novel photonic crystals for the future work.
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Ye, Siou-hong, and 葉修宏. "Synthesis of Silica Oxide-Gold Core-Shell Microspheres and Assembly." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/k647y6.
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碩士國立雲林科技大學
材料科技研究所
105
This study would hope to achieve two goals. First, the preparation of SiO2/Au core-shell structure, the second is the silica spheres self-assembly. In the first part of the first stage using the sol gel method to prepare the same size, about 400nm size of silica spheres. In the second stage, making the surface of the silica spheres to have -NH2 with molecular weight of (10000, 60000, 70000) polyethyleneimine, and then the control solution became an isoelectric point environment with a pH of about 8 to optimize the silica spheres bound to gold nanoparticles. And then the use of formaldehyde to reduce gold ions to gold atoms to coated on the silica spheres. The morphology and composition of the core-shell sphere is analyized by SEM and EDS, and the crossection of the sphere made by FIB is observed by TEM. The gold on the surface of the silica spheres do not form the dense shell, and only the gold nanoparticles are scattered on the surface. The silica spheres treated with 10000, 60000, 70000 molecular weight polyethyleneimine were analyized by EDS, the results showed that were 0.45%, 0.73%, 1.40% gold on the surfaces, respectively. Then, it is showed that the spheres treated with 70,000 molecular weight polyethyleneimine adsorbed more gold nanoparticles on the surfaces. In the second part, the self-assembly of silica spheres prepared by natural sedimentation method, vertical deposition, and with different properties of the substrate were discussed. The results were observed by SEM. It is showed that the natural settlement with the ethanol as solvent, in the vacuum environment, and at room temperature are the best, and using methanol, water as solvent are poor. While the self-assembly of the vertical sedimentation method with ethanol, 40°, and in vacuum is the best condition. And the hydrophilic substrate is better than the hydrophobic substrate. Based on the above results, aluminum foil of rolling direction coated with titanium oxide film was used, and then, UV light to make it hydrophilic. It is found that the orientations are both increased by natural evaporation and vertical settlement methods. By the order of the self-assembly silica spheres, vertical deposition method is better than the natural evaporation method.
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Chen, Ya-Lang, and 陳雅璉. "Sol-Gel Preparation of Silica Hallow Microspheres via Colloidal Templating." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/07950039651658304750.
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碩士國立中興大學
材料工程學系所
94
Abstract This research synthesized hollow silica microspheres by using a sol-gel technique together with using organic particles to act as a sacrificial template. Precursor materials were first adsorbed on the template surface to form a core-shell composite structure before being subjected to thermal pyrolysis to remove the organic core. Both the surface morphology and the hollow structure of the synthesized silica microspheres were examined by electron microscopy under various sol-gel process parameters. The experimental preparation involved addition of hydrochloric acid (HCl) in de-ionized water to form pH=2 solution, the acidic solution was then mixed with ethanol and tetraethyl orthosilicate (TEOS) in proportions. The organic spacer microspheres were added into the hydrolyzed solution. The mixtures were stirred fully for dispersion, and were then heated to 40 - 70oC with 2 h duration in a water bath to allow the reaction product to adsorb preferentially on the organic template surface. Finally, the organic microspheres were removed by calcination in air and hollow silica spheres were formed. Both the precursor formulation (including the relative concentration of TEOS, water and ethanol) and process parameter were varied, and their effects to the morphology and structural configuration of the hollow spheres were examined by FTIR, BET, FE-SEM, TEM, XRD, TG/DTA and dynamic light-scattering particle size analyser. The synthesized hollow spheres are amorphous in structure. The hydrolyzed silica colloids bear surface charge of different sign when compare to the organic template, facilitating the preferential adsorption of the silica colloids onto the template surface. Particle size of the synthesized hollow spheres is about 1 µm from SEM observations. As the reaction temperature is reduced, hollow spheres appear less likely to form. Hollow silica spheres tend to form when the synthesized reaction temperature are at 50 - 60 oC and the water concentration less than 4 mole. From thermal analysis, weight loss occurs pronouncedly at temperatures above 300 oC in air and the residual weight increases with the reaction temperature. The particle size decreases with the increasing ethanol concentration., while the BET surface area decreases when the concentration of water is increased. Pore size measured from the as-synthesized particles is about 2.7 - 4 nm and this becomes slightly smaller after calcination which is about 3 - 5 nm. Key word：sol-gel、hollow sphere
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Lo, Ying-chih, and 羅英志. "Mg-Ni Hydrogen Storage Alloys and Release and Silica Hollow Microspheres." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/39730231658279723372.
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碩士逢甲大學
化學工程學所
95
In this study, hydrogen storage alloys of magnesium and nickel were synthesized by polyol process with ethylene glycol as reducing agent and polyvinylpyrrolidone （PVP）as dispersing agent. Finally added palladium chloride at 180 K to obtain alloys. Under high temperature and pressure, hydrogen will diffuse into the alloys. Hydrogen within the alloys will be trapped after the temperature and pressure go back to normal. On reheating the system, hydrogen will be released from within the alloys. We can approval when the proportion of magnesium and nickel was 4：1 the hydrogen stored quantity can achieve to 3.63%, it was higher than the hollow silica microsphere. The Mg2Ni alloys due to its high hydrogen absorption capacity, safety and low cost is considered as a promising candidate for hydrogen storage applications.
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Tseng, Guo-Huan, and 曾國桓. "Protoporphyrin IX Loaded Silica Microspheres for Photodynamic Therapy and Ultrasound Imaging." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/52700973159379886107.
Full textAbstract:
碩士國立陽明大學
醫學工程研究所
101
Silica demonstrated several characteristics which are advantageous to be a carrier material for PSs. First, it is relative transparent, thus light can penetrate and activate the PSs loaded in the shell or inside the carrier. Second, it’s rid and non-degradable, so the PpIX loaded in silica would not be released into the surrounding environment and cause dark cytotoxicity. Third, the biocompatibility of silica was good, and it would not have harmful effects to normal tissues. In this study, Protoporphyrin IX (PpIX, a photosensitizer) was loaded in the shell of silica hollow spheres with the expectation that PpIX-loaded silica hollow spheres (PpIX-SHS) might be employed as a PDT agent with ultrasound image contrast. The PpIX-loaded silica hollow spheres were fabricated using DMDES (dimethyldiethoxysilane) which could be transformed into PDMS (polydimethylsiloxane) templates. The PDMS templates were crosslinked via TEOS (tetraethoxysilane), followed by the addition of PpIX and APTES (3-aminopropyl triethoxysilane) to obtain biocompatible silica hollow spheres with the PpIX-containing shell.
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"Plasmon-modulated light scattering from gold nanocrystal-decorated hollow mesoporous silica microspheres." 2010. http://library.cuhk.edu.hk/record=b5894421.
Full textAbstract:
Xiao, Manda = 金納米晶修飾的空心介孔二氧化矽微球在表面等離子體激元調製下的光散射行為 / 肖蔓達.Thesis (M.Phil.)--Chinese University of Hong Kong, 2010.
Includes bibliographical references.
Abstracts in English and Chinese.
Xiao, Manda = Jin na mi jing xiu shi de kong xin jie kong er yang hua xi wei qiu zai biao mian deng li zi ti ji yuan diao zhi xia de guang san she xing wei / Xiao Manda.
Abstract --- p.i
摘要 --- p.iii
Acknowledgement --- p.iv
Table of Contents --- p.vi
List of Figures --- p.viii
List of Tables --- p.x
Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Plasmonic Properties of Noble Metal Nanocrystals --- p.1
Chapter 1.2 --- Light Scattering from Dielectric Spheres --- p.6
Chapter 1.3 --- Motivations and Outline of the Thesis --- p.9
Chapter 2 --- Characterization Techniques --- p.17
Chapter 2.1 --- Instrumentation --- p.17
Chapter 2.2 --- Extinction Measurement of Au Nanocrystals and the HMSMSs Decorated with the Au Nanocrystals --- p.17
Chapter 2.3 --- Sample Preparation for the TEM and SEM Characterization --- p.18
Chapter 2.4 --- Dark-Field Imaging and Spectroscopy of the Individual Microspheres --- p.19
Chapter 3 --- Fabrication of Hollow Mesoporous Silica Microspheres Decorated with the Au Nanocrystals --- p.25
Chapter 3.1 --- Preparation of the Hollow Mesoporous Silica Microspheres --- p.25
Chapter 3.2 --- Growth of the Au Nanocrystals --- p.29
Chapter 3.3 --- Assembly of the Au Nanocrystals onto the Hollow Mesoporous Silica Microspheres --- p.32
Chapter 4 --- Resonant Scattering Properties of the Hollow Mesoporous Silica Microspheres --- p.38
Chapter 4.1 --- Experimental Results --- p.38
Chapter 4.2 --- Calculation of the Scattering Spectra by Mie Theory --- p.42
Chapter 4.3 --- Summary --- p.46
Chapter 5 --- Resonant Scattering Properties of the Au Nanocrystal-Decorated Hollow Mesoporous Silica Microspheres --- p.49
Chapter 5.1 --- Effect of the Plasmon Resonances of the Au Nanocrystals on the Resonant Scattering Behaviors of the HMSMSs --- p.49
Chapter 5.2 --- Estimation of the Scattering Enhancement Factors --- p.54
Chapter 5.3 --- Summary --- p.59
Chapter 6 --- Summary --- p.61
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Lin, Ting-En, and 林廷恩. "Effect of surfactants on synthesis of silica hollow microspheres via colloidal templating." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/48539108548476535616.
Full textAbstract:
碩士國立中興大學
材料工程學系所
95
When sol-gel method was used to prepare silica hollow microspheres via colloidal templating, well-dispersed hollow spheres were difficult to attain due mainly to the agglomeration of colloidal templates before coating of the silica precursors. This research aims to modify the template surface by preferential adsorption of polyelectrolyte surfactants for facilitating the dispersion of template particles in sol solvents. The precursor molecules then coat on the templates surface so that the population of inter-connecting hollow spheres can be reduced after calcinations for removal of the polymeric template cores. In this regard, three different polyelectrolyte surfactants, i.e., PSS, PDADMAC and TX-100, were used. TEM, FE-SEM, FT-IR, Particle Size and Zeta Potential Analyzer, Surface Area and Porosity Analyzer were used for characterization of the synthesized hollow microspheres. The Particle Size and Zeta Potential Analyzer showed that the addition of PSS surfactant (concentration was held at 0.75wt%) improved dispersion of colloidal templates in solvent mixtures. This finding was also confirmed by SEM and TEM observations. When reaction temperature (20oC-80oC) was changed in the fabrication process, the outer diameter of hollow spheres appeared to increase with the reaction temperature. From Surface Area and Porosity Analyzer, the synthesized hollow silica spheres have a high BET surface area due to the presence of porous shell structure. The pore size distribution of the shell was estimated 1-1.5nm. The shell structure seemed to become denser when the organic PSS surfactant was used
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Torano, Aniela Zarzar. "Chemical Modifications of Hollow Silica Microspheres for the Removal of Organic Pollutants in Simulated Wastewater." Thesis, 2017. http://hdl.handle.net/10754/623473.
Full textAbstract:
Aqueous industrial effluents containing organic pollutants, such as textile dyes and crude oil, represent environmental and human health concerns due to their toxicity and possible carcinogenic effects. Adsorption is the most promising wastewater treatment method due to its efficiency, ease of operation, and low cost. However, currently used adsorbents have either high regeneration costs or low adsorption capacities. In this work, new organic/inorganic hybrids based on hollow silica microspheres were successfully synthesized, and their ability to remove Methylene Blue from wastewater and crude oil from simulated produced water was evaluated.
By employing four different silanes, namely triethoxy (octyl) silane, triethoxy (dodecyl) silane, trichloro (octadecyl) silane, and triethoxy (pentafluorophenyl) silane, hydro and fluorocarbons were grafted onto the surface of commercially available silica microspheres. These silica derivatives were tested as adsorbents by exposing them to Methylene Blue aqueous solutions and synthetic produced water. Absorbance and oil concentration were measured via a UV/Vis Spectrophotometer and an HD-1000 Oil-in-Water Analyzer respectively. Methylene Blue uptake experiments showed that increasing the adsorbent dosage and decreasing initial dye concentration might increase adsorption percentage. On the other hand, adsorption capacities were improved with lower adsorbent dosages and higher initial dye concentrations. Varying the initial solution pH, from pH 5 to pH 9, and increasing ionic strength did not seem to have a significant impact on the extent of adsorption of Methylene Blue. Overall, the silica derivative containing aromatic functional groups, Caro, was proven to be the most effective adsorbent due to the presence of π-π and cation-π interactions in addition to the van der Waals and hydrophobic interactions occurring with all four adsorbents. Although the Langmuir Model did not accurately represent the equilibrium data, it produced consistent maximum adsorption values and adsorption equilibrium constants. Preliminary experiments demonstrated the potential to recover and reuse the silica microspheres by washing with NaOH and organic solvents.
The preferential adsorption of oil micro-droplets onto the surface of functionalized hollow silica microspheres was evidenced. However, preparing synthetic produced water that was stable enough to carry out kinetics experiments remained a challenge.
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蔡宗哲. "Electrophoretic Self-Assembly of 3-D Photonic Crystal Templates of Polystyrene Microspheres and Hydrophobic Thin Slabs of Silica Microspheres via Various Counter-electrode Geometries." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/47998902399061840106.
Full textAbstract:
碩士逢甲大學
材料科學與工程學系
104
This work is nvolved in the following major aspects, including (a) production of 3D photonic crystal templates with polystyrene (PS) microspheres on ITO glass substrates via electrophoretic self-aseembly (EPSA) techqiue, (b) synthesis of monodispsered silica microsphere by sol-gel process, (c) formation of ordered photonic crystal templaes of SiO2 microspheres on ITO glass substrates by EPSA roite, and (d) surface modification of photonic crystal temaplates of silica microspheres becoming hydrophobic by dip-coating method. The average size of SiO2 microspheres via sol-gel route was in a range of 200~300 nm. The wettability of templates of SiO2 microspheres on ITO glass substrates was achieved by dip-coating process, making the specimens being from hydrophilic into hydrophobic. Both photonic crystal templates of PS and SiO2 microspheres have tested to exhibit the photonic bandgap phenomena by UV-Vis spectroscopy. It is believed that the results obtained from this work will make some substantial contributions on developing the novel photonic devices involved in enhanced photonic bandgap properties.
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Chen, Yung-Hsing, and 陳永星. "Electrophoretic Self-Assembly Behavior of Polystyrene and Silica Microspheres for 3-D Photonic Crystal Templates." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/99949218938132859952.
Full textAbstract:
碩士逢甲大學
材料科學所
95
The aims of this study are consisted of the following aspects: (a) the sol-gel synthesis of monodispersed silica nanospheres and microspheres with the size range of 70�{700 nm by using tetraethylorthosilicate (TEOS), accompanying a proper ratio to other chemical reagent such as ammonium hydroxide, ethanol, and deionized water at different gelation temperatures, (b) the electrophoretic self-assembly (EPSA) behavior of silica and polystyrene microspheres under the direct influence of exerting electrical forces to build up the 3-D photonic crystal templates, and (c) the characterization of band gap and optical properties of 3-D ordered silica and polystyrene photonic crystal templates. The proposed EPSA process has been manifested as a very promising technique to assemble colloidal particles from the suspension or colloid onto the surface of various electrically conductive substrates. The EPSA process can easily produce a deposit of three-dimensionally ordered structure composed of microspheres on the surface of the electrode substrate for a relatively short period of time. In sum, the EPSA method demonstrates many merits including its process simplicity, low equipment cost and maintenance, high deposition yield, easiness of thickness control, and capability to obtain complex 3-D shapes and patterns. A high colloidal stability of EPSA suspension can be achieved by carefully adding suitable surfactants such as SDS and by adding suitable amount of HNO3 or NH4OH to adjust the desirable pH value (9.4~10) of colloid. In order to evaluate the effect of various design of EPSA setups on the self-assembly behaviors of microspheres, we particularly tested a number of counter-electrodes in different geometric designs. The result showed that a perfect electrophoretic self-assembly behavior of microspheres into the layered structure of the close-packed structure was successfully attained by means of the influence of vectored electrical forces derived from an electrical field gradient when the surrounding arrangement of counter-electrode was used.
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WEI, CHEN TECK, and 曾大瑋. "Preparation of Silica Microspheres by Sol-Gel Method and Fabrication of Regularly Arrayed, Colloidal Crystal Structure." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/22493125598161497506.
Full textAbstract:
碩士中國文化大學
材料科學與製造研究所
91
The objectives of this research were two: First, to explore and discuss the synthesized particle diameters by altering reaction temperature condition and reaction time in the preparation of silica microspheres by sol-gel method. Second, we used gravitational sedimentation method, i.e. a bottom-up self-assembly, to obtain regularly arrayed colloidal crystal structure using mono sized SiO2 spherical particles. 1. The preparation of submicron monodispersive silica microspheres by sol-gel method: The synthesis started from tetra-ethyl orthosilicate (TEOS) as precursor, ethanol as reaction solvent, and ammonia solution as catalyst, and processed in basic-catalyzed aqueous medium. After hydrolysis, condensation, cross-linking and gelation reactions, submicron silica microspheres were formed. The synthesis reaction temperature ranged from 0oC~75oC and the reaction time was 2 hours. The particle diameter of the synthesized spheres were analyzed by the particle-size analyser. Experimental results indicated that the size of the synthesized silica microspheres varied from 0.443 mm to 0.625 mm. As the reaction time was increased the diameter of silica microspheres increased (from 0.473 to 0.625mm). As the reaction temperature was increased the diameter of silica microspheres was fond to decrease accordingly (from 0.625 to 0.443mm). 2. Use of mono-sized SiO2 particles for self-assembly of regularly arrayed, colloidal crystal structure: In this work, we used gravitational sedimentation method to assemble SiO2 particles on Si wafer template epitaxially to grow regularly crystal-like structure, and to use the field emission scanning electron microscope (FE-SEM) to observe the packing structure. Experimental results indicated that in different volume fraction (0.5 vol.%~3 vol.%) and sedimentation temperature range (50oC and 100oC, respectively), as the solids fraction was held at 3 vol.% and the sedimentation temperature was 50oC, a larger area (about 250 ´ 250 mm2) of regularly arrayed, colloidal crystal structure was resulted.
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Yen-MingLiu and 劉硯鳴. "Synthesis and luminescent properties of (Eu, Tb, Al) co-doped silica microspheres by sol- gel microencapsulation." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/86354634397493038768.
Full text
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Pang, Chin-Poh, and 彭進寶. "Linear and Nonlinear Optical Properties of Soft Matters: Liquid Crystals, Ferrofluids and Liquids Suspended with Silica Microspheres." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/31575744926971333823.
Full textAbstract:
博士國立清華大學
物理學系
93
Assisted with Monte Carlo simulation, linear optical properties of soft matters such as liquid crystals, ferrofluids and liquids suspended with silica microspheres were investigated by transmittance, Faraday rotation and attenuated total reflection by exciting surface plasmons resonance. The microscopic structure of a thin liquid crystal film embedded between two glass plates when applying with electric fields was studied by the grand-canonical-ensemble Monte Carlo simulation. The time duration to reach the equilibrium state is successfully verified from the direct experimental measurement of light transmissions. The Kretschmann–Raether and the Otto configurations are implemented to generate surface plasmons and to examine the change of the refractive index of liquid crystals (LCs) by an applied field. The change of the minimum ATR angles does not agree with the calculation based on field-induced refractive-index change suggesting that the orientation of LC molecules adjacent to an electrode surface is unaffected by the external field because of the strong-anchoring effect. The aggregation and rearrangement of nanoparticles embedded in a thin cell of ferrofluid at various applied magnetic fields was studied by Monte Carlo simulation. Our model successfully simulate the reported experimental results by which the column size decreases as the ramp speed increases, implying that the time to arrive the final assembling state diminishes for a given final magnetic field. Physical parameters such as dielectric constant and susceptibility of dilute Fe3O4 ferrofluids derived directly from ATR and ferromagnetic resonance, respectively, were exploited to delineate the corresponding Faraday rotation angles with respect to the applied magnetic fields. Theoretical estimation was compared with experimental measurements ensuring that the effective medium theory is admittedly correct. Finally, the linear refractive indices of hydrated and dehydrated silica micro-spheres were studied under Kretschmann configuration to excite surface plasmons (SP), while the nonlinear second-order susceptibility was measured in direct transmission. An inconspicuous change for the case of dehydrated silica spheres is expected to be due to the small electro-optic (Pockels) effect, which is measured to have a linear electro-optic coefficients of . The SHG emission comes from the third-order susceptibility , which is a coupling of two photons and the electrostatic field induced by the surface –OH charges as characterized by the Gouy-Chapman model. The vanishing of SH signal from the dehydrated silica results from the loss of -OH group on the particle surfaces. Optical properties of dried silica spheres do not recover to its original hydrated state when pure water is refilled.
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Chen, Yanz-Hang, and 陳彥彰. "Functional Nano-silver particles decorated with silica hollow microspheres used in low thermal conductivity of antibacterial coatings." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/tchk4e.
Full textAbstract:
碩士國立勤益科技大學
化工與材料工程系
106
The outer layer of the hollow glass sphere is composed of an inert gas in-side the glass structure, so it has the characteristics of light weight and low heat conduction, so it can be effectively added to the resin coating to improve the thermal insulation properties of the coating, while the nano-silver is very good bactericidal function, this study uses hollow glass spheres as a carrier, the surface is modified by alkaline washing to have -OH functional groups, and then the hot reflux method is used to graft the silane coupling agent (APTES) to give the surface -NH2 group, The nano-silver particles are then adsorbed onto the hollow glass spheres using these amine functional groups. At the beginning of the study, different concentrations of sodium hydroxide and time change were used for modification. FTIR was used to observe the 3450 cm -1 hydroxyl absorption change and the SEM surface type identification and the residual amount after centrifugation recovery to find the most suitable parameters. The subsequent grafted silane coupling agent showed the characteristic peak of the silane at 2965 cm-1 and 1488 cm-1 by FTIR diagram, and confirmed that the hollow glass sphere was connected with the -NH2 group and allowed the silver nanoparticles to be coated. Adsorbed on the hollow glass sphere. The nano- silver synthesis was maintained at a nanometer size and good dispersibility after adding a protective agent, and the particle size was analyzed by TEM and particle size analyzer to fall between about 10-50 nm. It was found from the UV diagram that the nano-silver solution was absorbed at a wavelength of 410 nm. Finally, the identification of the nano-silver-adsorbed hollow glass spheres by XPS and elemental composition analysis confirmed that there was a silver signal on the hollow glass sphere. In the thermal conductivity test, different levels of hollow glass spheres and hollow glass spheres containing nano-silver were added to the coating and the thermal conductivity of different thicknesses was compared. When the hollow glass sphere content was added to 20 wt% at 0.3, 0.5 mm. In the case of a film, the thermal conductivity decreases from about 0.2 W/m･K to about 0.145 W/m･K, and the thermal conduc-tivity of the hollow microspheres containing nano silver is also reduced from the original 0.2 W/m·K to 0.135 W/m・K or so, it is suspected that the content of nano silver on the hollow glass sphere is small and the concentration is low, so the thermal conductivity of the film is not affected by the high thermal conductivity (428 W/m･K) after the addition of silver, and both are also in the film thickness. When it is 0.1 mm, it can be reduced from 0.2 W/m･K to 0.084 W/m･K and 0.087 W/m･K. The SEM cross-sectional view shows that the degree of floating of the microspheres on the surface and the remaining thickness of the film will affect the thermal conductivity. The surface temperature and time change of the coating show that the surface temperature of the pure coating coating continues to rise and the nano-silver is added. The ball is relatively stable in temperature, and it is concluded that the thermal conductivity of the coating and the change in surface temperature will affect the thermal in-sulation effect of the coating. The effect of initial inhibition of bacteria in the antibacterial test is affected by the solid content of the coating and the area of the contact with E. coli by the nano-silver microspheres, resulting in poor effect. In the later stage, the colony number test method is used to greatly increase the contact of the nano-silver microspheres with the large intestine. After the area of the bacillus, it was found that the amount of bacteria began to decrease over time until the disappearance of the completely after 12 hours, which proved that the nano-silver microspheres can effectively kill the bacteria, and the effect lasts for 24 hours without any bacteria growing again.
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Ding, L. P., S. L. He, D. C. Chen, M. Huang, J. Z. Xu, Stephen G. Hickey, A. Eychmüller, S. H. Yu, and S. Miao. "Encapsulated Cd3P2 quantum dots emitting from the visible to the near infrared for bio-labelling applications." 2014. http://hdl.handle.net/10454/10441.
Full textAbstract:
NoCd3P2 quantum dots (QDs) have been synthesized in both aqueous and high boiling point surfactant solutions via a gas-bubbling method. The synthesized QDs exhibit photoluminescent wavelengths spanning across the visible red to the near-infrared (NIR) spectral region. Two types of shell materials, SiO2 nanobeads and PS micro-spheres, have been employed to encapsulate the Cd3P2 QDs which provide protecting layers against physiological solutions. The coating layers are proven to enhance the optical and chemical stability of Cd3P2 QDs, and make the fluorescent particles capable of sustaining long-term photo-oxidation. To demonstrate the applicability of the bio-labelling, the fluorescent composite particles (PS@QDs, SiO2@QDs) were injected into a culture medium of colorectal carcinoma (LoVo) cells. The results demonstrated that the PS@QDs exhibited a brighter fluorescence, but the SiO2@QDs provided a better photostability which consequently led to long-term cancer cell detection as well as a much lower release of toxic Cd2+ into the PBS solutions.
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Jen, Heng-Li, and 任恆立. "Hydrogen Storage Efficiency Analysis of Hollow Silica Microsphere." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/24292726292090696146.
Full textAbstract:
碩士逢甲大學
化學工程學所
94
Hydrogen is generally acknowledged the most abundant and inexhaustible energy on the earth. Besides, hydrogen is a kind of clean energy. It will not produce smoke, dust, and SOx to pollute environment while burning. Its combustion product is water which will not harm the ecology of the earth. However, its full commercialization as a fuel depends strongly on its purification, storage, and transport. The development of those technologies would affect the profit of hydrogen energy. Current storage systems are either of safety concerns, energy inefficient, or costly. Hence, storing hydrogen with absorbing materials has caught much attention in recent years. The thesis aims using silicate microspheres as a hydrogen-storing material to save the transport cost due to their safeness, light weight, and high volumetric storage density. They come from two sources: one is commercial and the other is home-made with hollow phenolic spheres as template to deposit silica shells over them. Under high temperature and pressure, hydrogen will diffuse into the hollow microspheres. Hydrogen within the microspheres will be trapped after the temperature and pressure go back to normal. On reheating the system, hydrogen will be released from within the microspheres. The experiments are to compares the weight percents of hydrogen storage between the nature and synthetic silicate hollow microspheres, expecting that the synthetic one could achieve the specified level by DOE, USA for commercial, material-based hydrogen storage.
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Chen-Show and 楊辰琇. "Preparation and Properties ofCalcium Carbonate/Calcium Silicate Composite Microspheres." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/85933778037427597198.
Full textAbstract:
碩士中山醫學大學
口腔科學研究所
100
Bioceramic microspheres for bone regeneration applications should have good properties of bioactivity, biodegradability, and controlled drug-release ability. Calcium carbonate has high degradable feature and calcium silicate exhibits good bioactivity and controlled drug-release ability. However calcium carbonate has not good drug loading capacity in incorporation method, and calcium silicate is difficult to prepares for sphere shape. Therefore, calcium carbonate/calcium silicate composite microspheres (Ca/Si sphere) with desirable properties were prepared using the chemical precipitation methods. The effect of silicate ions and carbon dioxide and two kinds of calcium ions on the properties of the composite microspheres was investigated with scanning electron microscopy (SEM), energy dispersive spectroscopic (EDS), X-ray diffraction (XRD), and fourier transform infrared spectroscopy (FTIR). The biodegradability and bioactivity were examined by immersing in simulated body fluid (SBF). The cell proliferation and differtiation assays were performed by extraction method with MG63 cell line. Additionally, gentamicine (Gen) and methylene blue (MB) were used as model for evaluating the feasibility of Ca/Si spheres as a drug-delivery system. The SEM images illustrated monodispersed microspheres with size of about 7–15 μm. XRD and FTIR demonstrated that the structure consisted of calcite and vaterite phases. After immersion in SBF, the Ca/Si spheres retained vaterite phase. While silicate ions were incorporated into microspheres, the loading capacity of Gen and MB were remarkably enhanced from original 2.19% 3.65 to 27.09% 2.78 and original 0.22% 0.01 to 7.22% 1.33, respectively. The viability of MG63 cells seeded with Ca/Si spheres revealed good cell proliferation. It is concluded that the developed Ca/Si microspheres might have potential to be used as the drug carriers and for bone repair applications.
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Chen, Jian-Hong, and 陳建宏. "Fabrication and analysis of silicon-cored fibers and applications of produced silicon microspheres." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/88v2q9.
Full textAbstract:
博士國立臺灣大學
光電工程學研究所
104
Single-crystal silicon-cored fibers were made by using a combined techniques of powder-in-tube and vertical-drawing. Much cheaper polycrystalline Si powders substituting expensive single-crystal Si powders or seed rods were packed into a fused silica tube. By optimizing the drawing parameters, meter-long silicon-cored fibers were obtained. The silicon-cored fibers were drawn with resultant silica cladding and Si core diameters being in the range of 100-300 um and 10-30 um, respectively. According to energy-dispersive x-ray spectroscopy, the fabricated Si core is in high purity. From Raman spectrum and X-Ray diffraction analysis, the silicon-cored fiber is high crystalline. The single crystalline property of silicon-cored fibers could last for more than 100 um according to electron backscatter diffraction analysis. We applied solution based metal-assisted chemical etching method with silver catalyst to create anti-reflection structures on the end surface of a silicon-cored fiber. The measured reflectance of the etched silicon area of a silicon-cored fiber could reach to 2.4 %, approaching the simulated low value. The laser splicing loss was reduced to 1 dB when spliced with a silica fiber for working in 1550nm wavelength. When mode propagating from a silicon-cored fiber to a single mode fiber (high NA to low NA) direction, the large modal mismatch which leads to high coupling loss. Here, we propose a design of fabricating a microlens on Si core with electric arc to increase the coupling efficiency. Silicon microsphere resonators which exhibited high quality factor (Q) whispering-gallery-modes (WGMs) could be rapidly fabricated from silicon-cored fibers using CO2 laser reformation. WGMs were excited by using the tapered silica fiber coupling technique, and a record resonant Q as high as 4 x 10^5 was obtained. The shift of resonant wavelength caused by thermo-optic effect of Si material was also observed. We heated a silicon-cored fiber to produce silicon microspheres sequentially by arc discharges, and a silicon microsphere thus obtained was put in a hollow core fiber spliced with a single mode fiber to form a temperature fiber sensor. The measured thermal sensitivity was ~80pm/℃ for temperature range up to 700℃. With its open cavity structure such an in-line optical fiber sensor may find other sensing applications because of its ability of direct interaction with external environments. In the field of microfiber, arrayed Poly(methyl methacrylate) (PMMA) microfibers were drawn from a polymer solution and packaged with polydimethylsiloxane (PDMS). The exposed end face of packaged microfiber was tuned to have a size corresponding to a single cell. To demonstrate its capability for single cell optogenetics, HEK293T cells expressing channelrhodopsin-2 (ChR2) were cultured on the platform and excited with UV laser.
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Goodey, Adrian Paul. "The development of a polymer microsphere multi-analyte sensor array platform." Thesis, 2003. http://hdl.handle.net/2152/29819.
Full textAbstract:
The development of a chip-based sensor array composed of individually addressable polystyrene-polyethylene glycol and agarose microspheres has been demonstrated. The microspheres are selectively arranged in micromachined cavities localized on silicon wafers. These cavities are created with an anisotropic etch and serve as miniaturized reaction vessels and analysis chambers. The cavities possess pyramidal pit shapes with trans-wafer openings that allow for both fluid flow through the microreactors/analysis chambers as well optical access to the chemically sensitive microspheres. Identification and quantification of analytes occurs via colorimetric and fluorescence changes to receptor and indicator molecules that are covalently attached to termination sites on the polymeric microspheres. Spectral data is extracted from the array efficiently using a charge-coupled device (CCD) allowing for the near-real-time digital analysis of complex fluids. The power and utility of this new microbead array detection methodology is demonstrated here for the analysis of complex fluids containing a variety of important classes of analytes including acids, bases, metal cations, sugars and antibody reagents. The application of artificial neural network analyses to the microbead array is demonstrated in the context of pH measurements. To assess the utility of the analysis and gain an understanding of the molecular level design of the sensor, parameters such as the choice of the indicator dyes, array size, data pre-processing techniques, as well as different network types and architectures were evaluated. Additionally, the development of miniaturized chromatographic systems localized within individual polymer microspheres and their incorporation into an array is reported. The integrated chromatographic and detection concept is based on the creation of distinct functional layers within the microspheres. Such beads have been incorporated into the array platform and used for speciation and concentration determination of aqueous metal cation solutions.text
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Chang, Shih-Shin, and 張世昕. "Fabrication of Silicon Microspheres by Using Silicon-Cored Fibers and Their Applications in Temperature and Refractive Index Sensing." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/t34gx2.
Full textAbstract:
碩士國立臺灣大學
光電工程學研究所
105
Silicon-cored fibers were made by using a combined techniques of powder-in-tube and vertical-drawing. Much cheaper polycrystalline Si powders substituting expensive single-crystal Si powders or seed rods were packed into a fused silica tube. By optimizing the drawing parameters, several meters long silicon-cored fibers were obtained. The silicon-cored fibers were drawn with resultant silica cladding and Si core diameters being in the range of 100-300 m and 10-30 m, respectively. According to energy-dispersive x-ray spectroscopy, the fabricated Si core is in high purity. From Raman spectrum and X-Ray diffraction analysis, the silicon-cored fiber is high crystalline. The single crystalline property of silicon-cored fibers could continue for more than 100 m long according to electron backscatter diffraction analysis. We also demonstrated a fiber drawing system for fabricating tapered silicon-cored fiber. A fiber drawing system equipped with arc discharges and motorized translation stage was used. We successfully fabricated tapered silicon-cored fibers with diameter of 2.9 μm in the waist section from an original SCF with diameter of 20 μm. We heated a silicon-cored fiber to produce silicon microspheres sequentially by arc discharges. By tuning the splicing current parameter, SCF was slowly heated by arc discharging. And a silicon microsphere thus obtained was put in a hollow core fiber spliced with a single mode fiber to form a temperature fiber sensor. The measured thermal sensitivity was ~80pm/℃ for temperature range up to 700℃. The thermal sensitivity was about five times higher than those of silica fiber based. The structure could allow direct contact with an external environment, the fiber probe could also serve as a refractive index sensor with a sensitivity about -5.326±0.223/RIU.
32
CHOU, CHUN-MING, and 周俊銘. "The Influence of Mixed Vulcanization Systems on the Physical Properties of Lightweight Mixed Rubber/Silica/Hollow Glass Microsphere Composites." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/88mhp5.
Full textAbstract:
碩士國立雲林科技大學
化學工程與材料工程系
106
The mechanical properties of rubber materials can be improved by the addition of silica particles. However, they increase the weight of rubber materials. Since hollow glass microspheres are low-density fillers, they are used to reduce the weight of rubber and plastic products. However, they decrease the strength of materials. The mechanical properties of rubber materials are related to the cross-link density. Both sulfur and peroxide have been widely used as cross-linking agents for rubbers. Sulfur vulcanization of rubber exhibits an excellent mechanical strength, but poor ageing resistance. Peroxide vulcanization of rubber possess a good ageing stability, but poor mechanical strength. In this study, rubber was compounded with hollow glass microspheres to reduce the weight of rubber composites. The mechanical properties of rubber composites were improved by optimizing the ratio of sulfur to peroxide. Firstly, the rubber/silica/hollow glass microsphere-based composites were prepared by using an open mill. The vulcanization time was measured by the moving die rheometer. It demonstrated that the mixed vulcanization system required a longer vulcanization time than the sulfur vulcanization system. The torque difference and hardness of the rubber composites decreased initially and then increased with increasing weight ratio of dicumyl peroxide to sulfur. The density of the composites decreased from 1.21 g/cm3 to 0.99 g/cm3 when 25 wt% of silica was replaced by hollow glass microspheres. The weight ratio of dicumyl peroxide to sulfur had no significant effect on the density of the composites. The SEM images of the cross-sectional morphology of composites showed that the hollow glass microspheres were well dispersed without agglomeration. However, the addition of hollow glass microspheres reduced the hardness, tensile strength, elongation at break and tear strength of the composites. When the weight ratio of sulfur to dicumyl peroxide was 0.5 to 1.5, the composite had better mechanical properties, of which the tensile strength and tear strength could reached 10.21 MPa and 43.95 N/mm, respectively. Moreover, the tensile strength and elongation at break changed little after ageing. Therefore, the mixed vulcanization system could improve the mechanical properties of the rubber/silica/hollow glass microsphere-based lightweight composites.
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Ling, Liao-Man, and 廖曼伶. "Fabrication of the ordered silicon nanorod array through the microsphere lithography method and investigations on its photovoltaic properties." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/04403182196995810801.
Full textAbstract:
碩士國立清華大學
材料科學工程學系
100
To improve anti reflection and enhance the p-n junction of a Si-based solar cell, single-layer polystyrene spheres (PS) were self-assembled onto Si substrates by spin coating followed by plasma treatment for reducing the size of PS spheres. The reduced spheres were used as a template for synthesizing Si nanorods (SiNRs) through the metal-assisted chemical etching process. Using this method, diameter and height of the SiNRs can be accurately controlled. Reflectivity of the silicon nanorods was tested by the UV/vis spectrometer, it is found that longer nanorods are more effective for light trap and absorption, which is applicable as an anti-reflection layer in solar cells. However, the etching process for silicon nanorods will cause surface defects, which limits the carrier transfer. In order to study the effects of SiNR dimension on the performance of Si-based solar cell and measured the conversion efficiency of the solar cell using SiNR array as the antireflection layer, this work fabricated SiNR array with different length and diameter. Phosphorus doping was performed using the spin-on-doping (SOD) technique. According to the results, SiNR solar cell with 720 nm in diameter and 800 nm in length, subjected to phosphorus doping for two times reveals a high performance with an efficiency of 6.79%, which is 22% higher than that of planar one.