Dissertations / Theses on the topic 'Nanoparticles decoration'

In this communication, we present solution-based coating procedure of MoSI nanowires (NW) with platinum nanoparticles. The average particle diameter was found to be around 2.82 nm, showing a narrow size distribution. This single-step in situ reduction method at room temperature in water solution can easily be applied for large-scale applications. We also prepared two-dimensional networks of MoSI NW bundles by deposition via spraying from a purified stable dispersion in acetonitrile onto NaCl crystals and nonconductive silicon wafer with pre-assembled molybdenum electrodes. The formation of a conductive molybdenum network was achieved by annealing in hydrogen due to coalescence of the templates MoSI bundles during transformation. Stable water dispersion of molybdenum NW network was prepared by simply dissolving the NaCl substrate with molybdenum network on the surface. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35168

Nanotechnology has reached the status of the 21st century's leading science and technology based on fundamental and applied research during the last two decades. An important feature of nanotechnology is to bridge the crucial dimensional gap between the atomic and molecular fundamental sciences and microstructural scale of engineering. Accordingly, it is very important to have an in-depth understanding of the synthesis of nanomaterials for the use of state-of-the-art high technological devices with enhanced properties. Recently, the 'bottom-up' approach for the fabrication of nanomaterials has received a great deal of attention for its simplicity and cost effectiveness. Tailoring the various parameters during synthesis of selected nanoparticles can be used to fabricate technologically important components. During the last decade, carbon nanotubes (CNTs) have been envisioned for a host of different new applications. Although carbon nanotubes can be synthesized using a variety of techniques, large-scale synthesis is still a great challenge to the researchers. Three methods are commonly used for commercial and bulk productions of carbon nanotubes: arc-discharge, chemical vapor deposition and laser ablation. However, low-cost, large-scale production of high-quality carbon nanotubes is yet to be reported. One of the objectives of the present research is to develop a simplified synthesis method for the production of large-scale, low-cost carbon nanotubes with functionality. Herein, a unique, simple, inexpensive and one-step synthesis route of CNTs and CNTs decorated with nanoparticles is reported. The method is simple arc-discharge in solution (ADS). For this new method, a full-fledged optoelectronically controlled instrumen is reported here to achieve high efficiency and continuous bulk production of CNTs. In this system, a constant gap between the two electrodes is maintained using a photosensor which allows a continuous synthesis of the carbon nanostructures. The system operates in a feedback loop consisting of an electrode-gap detector and an analogue electronic unit, as controller. This computerized feed system was also used in single process step to produce in situ-decorated CNTs with a variety of industrially important nanoparticles. To name a few, we have successfully synthesized CNTs decorated with 3-4 nm ceria, silica and palladium nanoparticles for many industrially relevant applications. This process can be extended to synthesize decorated CNTs with other oxide and metallic nanoparticles. Sixty experimental runs were carried out for parametric analysis varying process parameters including voltage, current and precursors. The amount of yield with time, rate of erosion of the anode, and rate of deposition of carbonaceous materials on the cathode electrode were investigated. Normalized kinetic parameters were evaluated for different amperes from the sets of runs. The production rate of pristine CNT at 75 A is as high as 5.89 ± 0.28 g.min-1. In this study, major emphasis was given on the characterizations of CNTs with and without nanoparticles using various techniques for surface and bulk analysis of the nanostructures. The nanostructures were characterized using transmission electron microscopy, high resolution transmission electron microscopy, scanning transmission electron microscopy, energy dispersive spectroscopy and scanning electron microscopy, x-ray photo electron spectroscopy, x-ray diffraction studies, and surface area analysis. Electron microscopy investigations show that the CNTs, collected from the water and solutions, are highly pure except the presence of some amorphous carbon. Thermogravimetric analysis and chemical oxidation data of CNTs show the good agreement with electron microscopy analysis. The surface area analysis depicts very high surface area. For pristine multi-walled carbon nanotubes, the BET surface area is approximately 80 m2.g-1. X-ray diffraction studies on carbon nanotubes shows that the products are clean. Nano-sized palladium decorated carbon nanotubes are supposed to be very efficient for hydrogen storage. The synthesis for in-situ decoration of palladium nanoparticles on carbon nanotubes using the arc discharge in solution process has been extensively carried out for possible hydrogen storage applications and electronic device fabrication. Palladium nanoparticles were found to form during the reduction of palladium tetra-chloro-square planar complex. The formation of such a complex was investigated using ultraviolet-visible spectroscopic method. Pd-nanoparticles were simultaneously decorated on carbon nanotubes during the rolling of graphene sheets in the arc-discharge process. Zero-loss energy filtered transmission electron microscopy and scanning transmission electron microscopy confirm the presence of 3 nm palladium nanoparticles. The deconvoluted X-ray photoelectron spectroscopy envelope shows the presence of palladium. Surface area measurements using BET method show a surface area of 28 m2.g-1. The discrepancy with pristine CNTs can be explained considering the density of palladium (12023 kg.m-3). Energy dispersive spectroscopy suggests no functionalization of chlorine to the sidewall of carbon nanotubes. The presence of dislodged graphene sheets with wavy morphology as observed with high-resolution transmission electron microscopy supports the formation of CNTs through the 'scroll mechanism'.
Ph.D.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science and Engineering

Le but de la thèse est d'étudier l'influence de la microstructure des composites ZnO/TiO2 sur leurs propriétés dans la dégradation photocatalytique des polluants organiques et dans l'oxydation de l'eau photoassistée. Pour réaliser cette étude, nous avons choisi la conception basée sur des nano bâtonnets ZnO supportés sur une électrode de verre recouverte d'ITO (Indium Tin Oxide). Les nano bâtonnets de ZnO ont ensuite été recouverts d'une couche de TiO2 dans différentes conditions. La composition et la microstructure des composites ZnO(cœur)/TiO2(coquille) ont été modifiées dans le but d'élucider comment ces paramètres influencent leur activité photocatalytique. La couche TiO2 de morphologie différente (discontinue ou compacte) a été élaborée. Nous avons montré que le composite contenant la couche de TiO2 discontinue possède une activité plus élevée dans la dégradation de MB et dans l'oxydation de H2O sous 400 nm. Cette photoactivité améliorée a été attribuée à une meilleure accessibilité pour les réactifs de l'interface ZnO/TiO2 à travers la couche de TiO2. Aussi nous avons pu améliorer l'activité des composites sous la lumière visible. Dans ce but, les composites constitués de nano bâtonnets de ZnO supportés sur ITO ont été recouverts de TiO2 dopé à l'azote et décorés de nanoparticules d'or. Il a été trouvé que même une faible charge d'or (0,37% at.) permet une augmentation de 60% de la vitesse de décoloration photocatalytique du MB sous la lumière visible par rapport à l'échantillon sans or en raison de l'effet plasmonique. Un dopage simultané à l'azote et à l'or a permis également de multiplier par trois le photocourant dans l'oxydation photoassistée de l'eau
The aim of the thesis is to study the influence of microstructure of ZnO/TiO2 composites on their properties in photocatalytic degradation of organic pollutants, and in photoassisted water oxidation. To realize such study we chose the design based on ZnO nanorods supported on ITO (Indium Tin Oxide)-coated glass electrode. The ZnO nanorods were then covered with a layer of TiO2 under different conditions. The composition and microstructure of the obtained ZnO(core)/TiO2(shell) composites were modified in the aim to elucidate how these parameters influence their photocatalytic activity. The results of studies lead to elaboration of two most distinctive variants of sol-gel procedure that allow to deposit TiO2 layers of controlled thicknesses and different morphology (rugged or compact). The composite containing the rugged TiO2 layer was shown to possess significantly higher activity in MB degradation and in photoassisted H2O oxidation under 400 nm. This improved photoactivity was attributed to a higher porosity and better accessibility of ZnO/TiO2 interface region through the rugged TiO2 layer by the reagents. The effort was also made to enhance the visible light activity of the composites. To this aim the composites consisting of ITO-supported ZnO nanorods covered with nitrogen-doped titanium dioxide and decorated with Au nanoparticles. It was found that even a low Au loading (0.37% at.) resulted in 60% enhancement of photocatalytic decolorization of MB under visible light with respect to the Au-free sample owing to plasmonic effects. A simultaneous N-doping and Au decoration allowed also to multiply by three the photocurrent in photoassited water oxidation

Efficient use of renewable energies is one of the most difficult technological challenges facing humanity. Among all renewable energy sources, the sunlight is considered as the most abundant and accessible one. To convert it into usable and controllable form, the modern technology relies on generation of electron-hole pairs in semiconductors upon light absorption. The obtained separated charge carriers possess extra energy brought by the converted sunlight which can be further utilized in various ways. Currently, the most common approach consists in its direct transformation into electricity in p-n junctions. Alternatively, the electrons and holes can be used to perform chemical reactions. The electrons can be transferred to reduce various organic compounds or inorganic species, while simultaneously the holes can play the role of oxidizer by subtracting the electrons from the other substances. Through these reactions it would be possible to accumulate the solar energy in chemical species allowing thus to alleviate the intermittence of the sunlight. Unfortunately, the existing materials do not easily cross the laboratory level to realize this approach on industrial scale. That is why the development of new semiconductor photocatalysts, which harvest and convert efficiently the visible part of solar spectrum, is of paramount importance. For many years the most often studied photocatalytic materials have been ZnO and TiO2. However, it has been recently shown that composites based on ZnO and TiO2 possess even more promising properties than many other semiconductors in various photocatalytic applications. Despite many works reporting high photoactivity of these composites in different applications, the detailed information about the structure–properties correlation is lacking. In order to fill this gap we decided to focus our attention to study the influence of microstructure of ZnO/TiO2 composites on their properties in photocatalytic degradation of organic pollutants, and in application in half-reaction of ‘solar fuel’ generation, namely photoassisted water electro-oxidation. To realize such study the composites should satisfy the requirements of a high surface area and good electric conductivity. We chose therefore the design based on ZnO nanorods supported on ITO (Indium Tin Oxide)-coated glass electrode. The ZnO nanorods (NRs) were then covered with a layer of TiO2 under different deposition conditions. The composition and microstructure of the obtained ZnO(core)/TiO2(shell) composites were modified in the aim to elucidate how these parameters influence their photocatalytic activity. Consequently, the efforts were made to impart visible light activity to the elaborated ZnO/TiO2 composites by modifying titanium dioxide layers with nitrogen and decoration with Au nanoparticles. The thesis consists of three parts: Bibliography, Experimental and Results and Discussion. First part of the present PhD thesis, Bibliography, is dedicated to the analysis of literature concerning fundamental properties of semiconductor materials, solid/electrolyte interface as well as principles of photocatalysis and photoelectrochemical water oxidation. Also, the photocatalytic properties of ZnO and TiO2, and those of their composites are reviewed in this section. Furthermore, methods for improvement visible-light absorption are also described, i.e. N-doping and surface plasmonic effects due to the noble metal nanoparticles (Au NPs) deposited on semiconductors. The second part, Experimental, covers the preparation procedures and characterization techniques used in the work. First, the details are given for electrochemical seeding of ITO support, hydrothermal growth of ZnO nanorods, sol-gel deposition of TiO2 (and N-doped TiO2), and photodeposition of Au NPs. Second, the characterization techniques used in realization of this project are described: SEM (Scanning Electron Microscopy), HAADF-STEM and HR-TEM (High Angle Annular Dark Field Scanning Electron Transmission Microscopy and High Resolution Transmission Electron Microscopy), XRD (X-ray Diffraction Analysis), XPS (X-ray Photoelectron Spectroscopy), EDS ‘or EDX’ (Energy Dispersive Spectroscopy) analyses connected with electron microscopy techniques, UV-vis Spectroscopy and DRS (Diffuse Reflectance UV-vis Spectroscopy, TGA-DSC (Thermogravimetry Differential Scanning Calorimetry Analysis), TOC (Total Organic Carbon) analysis, RT-PL (Room Temperature Photoluminescence Spectroscopy), electrochemical techniques including: LSV (Linear Sweep Voltammetry), CV (Cyclic Voltammetry), chronoamperometry, chronopotentiometry, as well as the set-ups elaborated by the author for the purpose of photocatalytic and photoelectrochemical measurements. The main results of the PhD thesis are presented in the third part, Results and Discussion, consisting of four chapters. In the first chapter (Chapter 4.1), the results of the studies on electrochemical seeding of ITO-electrode in Zn(CH3COO)2 solution are presented. The length and width of ZnO nanorods grown by hydrothermal method from Zn(NO3)2 aqueous solution on Zn/ZnO-seeded ITO substrate were shown to depend strongly on initial Zn2+ concentration and the synthesis duration. The arrays of well-separated ZnO ‘obelisk-like’ nanorods of width varied from 100 nm at tips to ~ 300 nm at bottom and average length of 1.9 µm were prepared under optimized conditions, and used as starting point for further fabrication of (core)ZnO/TiO2(shell) composites. In the second chapter (Chapter 4.2), a simple and low-cost sol-gel method was developed in order to form TiO2 thin layers on ZnO nanorods by hydrolysis of titanium(IV) butoxide. The results of studies lead to elaboration of two most distinctive variants of sol-gel procedure that allow to deposit TiO2 layers of controlled thicknesses and different morphology (rugged or compact). The rugged TiO2 layers were obtained after 6 hours of one step sol-gel synthesis followed by calcination of the sample at 450 oC, ensuring formation of anatase-TiO2, whereas the uniform coating of 25 nm – 40 nm thickness was obtained via three successive 30 min-synthesis with the intermediate calcination of the sample after each deposition cycle. The composite containing the rugged TiO2 layer was shown to possess significantly higher activity in model pollutant (methylene blue, MB) degradation and in photoassisted H2O electro-oxidation under 400 nm monochromatic light irradiation. This improved photoactivity was correlated with the composite microstructure and attributed to a higher porosity and better accessibility of ZnO/TiO2 interface region through the rugged TiO2 layer by the reagents. The TiO2 (shell) layers of similar morphology were also prepared by atomic layer (ALD) and chemical vapor deposition (CVD) techniques and it was shown that the composites fabricated by us with the use of simple sol-gel procedure yield comparable (or even higher) photoactivity. Finally, it was confirmed by total organic carbon (TOC) analysis that the ZnO/TiO2 composites elaborated in this work are also active in decomposition of the pollutants in a dumb hill leachate solution (waste water) under 400 nm monochromatic irradiation. In Chapter 4.3 it is shown that the ZnO/TiO2 interface plays a key role in enhancement of photodecomposition of MB under 400 nm illumination. The increase of photocatalytic activity was attributed to the shift of absorption edge of ZnO/TiO2 towards visible light in comparison to that of the ZnO(core)-etched TiO2. Further enhancement of photocatalytic activity of ZnO/TiO2 was achieved through its additional calcination at 450 °C for 3 h. This simple treatment brings 40% increase in the rate of MB decomposition and a two-fold rise of the photocurrent in H2O oxidation. Measurements of open circuit potential (VOC) showed that the improved properties of additionally calcined ZnO/TiO2 composites stem from the decrease of electron-hole recombination rate. STEM (Scanning Transmission Electron Microscopy) studies showed that the additional calcination resulted in formation of voids at the ZnO/TiO2 interface. EDX (Energy Dispersive X-ray) analysis and XPS (X-ray Photoelectron Spectroscopy) results proved that formation of voids is accompanied by the outward diffusion of Zn ions into TiO2 layer and allowed to conclude about the existence of the Kirkendall effect at ZnO/TiO2 interface. Occurrence of this effect observed for the first time at unusually moderate temperature (450 °C) was shown and attributed to a highly defective nature of the surface layer of the ZnO nanorods. In the last chapter (Chapter 4.4), the composites consisting of ITO-supported ZnO nanorods covered with nitrogen-doped titanium dioxide, TiO2(N), shell were decorated with gold nanoparticles (Au NPs) in order to improve their photocatalytic activity under visible light. The photocatalytic properties of ZnO/TiO2/Au and ZnO/TiO2(N)/Au ternary composites were studied under illumination with Xe lamp equipped with a 400 nm cut-off filter. It was found that low Au NPs loading (0.37% at.) resulted in 60% enhancement of photocatalytic decolorization of MB under visible light with respect to the Au-free sample owing to plasmonic effects. Also, a simultaneous N-doping and Au NPs-decoration allows to multiply by three the photocurrent in photoelectrochemical water oxidation at the potential of 0.8 V vs. Ag/AgCl. It was also demonstrated that the Au-decorated composites possess a strong electrocatalytic activity in reduction O2 to active oxygen species (via formation of O2⦁– radicals) under a small negative bias (–0.25 V vs. Ag/AgCl) in dark. Illumination of the polarized sample with visible light was shown to enhance this process resulting in rapid decomposition a model pollutant (MB) even in the presence of Na2SO4. This approach allows to completely overcome a problem of inhibition of the photocatalytic process by dissolved inorganic salts on non-polarized catalysts, thus meeting the aim of promising material for photoelectrocatalytic remediation of waste water, often containing a significant amount of inorganic ions.

碩士
國立成功大學
化學工程學系碩博士班
100
This study concerns the synthesis and catalytic properties of graphene oxide/platinum and graphene/gold nanocomposites. For the synthesis of composites, graphene oxide was prepared by Hummer’s method at first and then platinum or gold nanoparticles were decorated onto its surface via the microwave-assisted synthesis method. For the hydrogen generation from the hydrolysis of sodium borohydride catalyzed by graphene oxide/platinum nanocomposite, it was found that the hydrogen generation rate increased with increasing the temperature. As the catalyst amount increased, the amount of hydrogen generated increased but the specific activity decreased. In addition, with increasing the concentration of sodium borohydride, the hydrogen generation rate increased at first and then decreased. The optimal sodium borohydride concentration was 1 wt%. For the catalytic reduction of 4-nitrophenol by graphene/gold nanocomposite, it was found that the reaction obeyed the pseudo-first-order kinetic model. The reaction rate increased with increasing the temperature and the initial concentration of 4-nitrophenol. However, with increasing the initial concentration of 4-nitrophenol, the rate constant decreased. It was suggested that the reaction was diffusion controlled.

碩士
國立成功大學
化學工程學系
103
As a non-toxic material and abundant resource in the face of the earth, bismuth sulfide was studied extensively in many fields. In this study, rGO/Bi2S3 was synthesized using various methods to observe its morphology and properties. The methods used to synthesized Bi2S3 are hydrothermal and solvothermal methods. Both of them led to nanorod structured Bi2S3 with a very large size and heavy agglomeration. In the presence of graphene oxide, there are some changes in the morphology of Bi2S3, which have shorter rod size and lower agglomeration degree. Parameter changes was done to see its effect on Bi2S3 and rGO/Bi2S3 morphology, these parameters are, precursor concentration, synthesis time, GO content, solvents, the presence of capping agent, and the presence of other metal sulfide. The other metal sulfide used for this experiment is silver sulfide (Ag2S), which also synthesized using hydrothermal method. The combination of two metal sulfides with rGO, which is rGO/Bi2S3-Ag2S, was synthesized using 1-step hydrothermal and 2-step hydrothermal method. From these two methods the morphology of product produced was different and has different crystal structure. The photocatalytic properties of synthesized nanocomposites was observed by photodegradation of methylene blue dye under the irradiation of light from 300 W xenon lamp and also using various photocatalytic parameters. From the test results, the photocatalytic performance of product synthesized was not good for practical use, thus this material is not suitable for photocatalyst but for other applications such as supercapacitor and electrochemical sensor.

碩士
國立交通大學
工學院半導體材料與製程設備學程
104
Tin oxide is an n-type metal oxide semiconductor (MOS), and widely used as the sensing material of MOS gas sensors. To improve the sensing performance of SnO2 sensors, noble metals are usually used as a sensitizer. Pd is one of the mostly used sensitizer. Metal Pd can be oxidized under a high temperature sensing condition, while PdO can be reduced by reducing target gases in the similar temperature regime. The simultaneous occurrence of Pd oxidation and PdO reduction on the SnO2 sensor surface can significantly affect the gas sensing behavior of SnO2. In this study, we deposited PdO nanoparticles on the SnO2 thin film by sputter deposition followed by high temperature annealing, and study the CO sensing behavior of the Pd-decorated SnO2 sensor. X-ray diffraction spectroscopy (XRD), x-ray photoelectron spectroscopy (XPS), secondary electron microscopy (SEM) an transmission electron microscopy (TEM) were used to study the material properties, including chemical composition, morphology and crystallinity. When the SnO2 thin film is exposed to the gas mixture of CO and dry air, superoxide ion(O2-) and peroxide ion (O22-) adspecies on the SnO2 sensor can be reduced by CO, and the lattice oxygen can also be reduced at high temperatures forming oxygen vacancies in the SnO2 lattice. These surface reactions increase the electron concentration of the SnO2 thin film exposed to toward carbon the CO gas mixture. A thinner SnO2 thin film has a higher sensing response because of a larger volume ratio of the depletion zone to the thin film. PdO decoration greatly increases the sensing response of the SnO2 thin film toward CO. The PN junction formed between SnO2 and PdO modifies the electrical properties of the SnO2 thin film both before and after the CO gas sensing, resulting in an improved sensing performance. According to XPS analyses, the chemical state of the SnO2 thin film varies trivially after the CO sensing. Upon the CO exposure at 150℃and above, oxygen vacancies are formed in SnO2, leading to the increase in the conductivity of the SnO2 sensor. PdO is reduced by CO producing Pd nanoislands, and the conductivity of the SnO2 sensor significantly drops because oxygen can be dissociatively adsorbed on Pd nanoislands. Pd nanoislands can be reoxidized at 150℃as they are grown to a critical size, thereby alleviating the reduction in the sensing current. At temperatures above 150℃, the conductivity reduction as a result of the Pd nanoisland formation becomes insignificant because the higher temperature result in a faster reoxidation rate for Pd nanoislands.

碩士
臺灣大學
物理研究所
98
We have demonstrated that the field emission performance of ZnO nanorods can be greatly enhanced by the decoration of ZnO nanoparticles. It was found that the turn-on electric field (the electric field at which the current density reaches 10 μA/cm^2) can be reduced by about three times, and the field enhancement factor can be enlarged by about 2.5 times. The underlying mechanisms can be attributed to both effects of surface passivation as well as the enhanced electric potential gradient generated by nanoparticle geometry, with the latter one as the dominant factor. Our finding shown here may pave an excellent route for the improvement of field emission properties in many materials.

碩士
國立成功大學
材料科學及工程學系碩博士班
101
N-methly-2-pyrrolidone (NMP) has been used for efficient extraction of coals due to its high-boiling point and oxygen-scavenging properties. In this study, we performed reduction of graphene oxide (GO) with NMP/H2O open-air system and demonstrated fast and efficient reduction within two hours. In the first part of this work, we synthesized graphene oxide with modified Hummer’s method as starting material, and characterized its structure and chemical properties. In the second part, we provided a hydrothermal-solvothermal transition at about 60-80 minutes of reduction that causes efficient removal of oxygen-containing functional groups, and rapid decrease of band gap from about 3 eV to 1 eV during the reduction process. Moreover, a 30-40 eV blue shift in the green emission region was shown in photoluminescence (PL) characterization, which correlates to the structural restoration of sp2 carbon rings. In the last part of work, NMP was used in developing silver nanoparticles-decorated (reduced) GO sheets, which exhibited enhancement in the PL intensity by surface plasmon resonance and size adjustable properties of silver nanoparticles. In summary, tunable optical properties by reducing GO with a fast and efficient solvothermal method is provided in this work. In addition, the use of NMP as chemical reagent improves stabilization of silver nanoparticles on reduced GO with adjustable size, and enhancement of the emission intensity. We expect this work to attribute in the development in optoelectronics, energy, and biomedical techniques.

碩士
國立中山大學
電機工程學系研究所
106
In this thesis, we investigated zinc oxide (ZnO) nanotubes/ITO glass substrate decorated with two different metal oxides’ nanoparticles (TiO2 and MnO2) for non-enzymatic glucose sensors. Firstly, a ZnO seed layer was deposited on ITO glass substrate by RF sputtering system. ZnO nanorods were then grown by hydrothermal synthesis. Alkaline etching solution was prepared to etch ZnO nanorods into nanotubes (ZnO NTs/ITO). In addition, TiO2 nanoparticles and MnO2 nanoparticles were also grown in this study. TiO2 and MnO2 nanoparticles were decorated on ZnO NTs by dip coating and drop coating respectively to complete the dip-coated TiO2/ ZnO/ ITO, the drop-coated TiO2/ ZnO/ ITO and the drop-coated MnO2/ ZnO/ ITO sensing elements. The ZnO NTs structure is used because it has a stable and excellent nano-scale morphology, which can effectively increase the contact area between the analyte and the electrode. With decoration of two different metal oxides, the sensing ability to glucose is effectively improved. The experimental results show that the 17.5mg drop-coated MnO2/ ZnO/ ITO sensing element has the best sensing performance to glucose. The sensitivity is 109.612μAmM-1cm-2, the value of R2 is 0.9959, and the linear sensing range is 0.1mM~7.0mM. The addition of interferents has an effect on the current of less than 10% and the response time is less than 3 seconds. Excellent glucose sensors for detecting diabetes is more accurately and quickly. It is also important to the development of food industry.

碩士
國立中興大學
電機工程學系所
104
This study aims to form a metal-semiconductor-metal gas sensor on three substrates, that is, glass, convex and concave sapphire, with different surface morphologies to prepare zinc oxide nanorod arrays, which are decorated with aluminum and copper nanoparticles and finally are coated with 350 nm-thick interdigital aluminum electrode. The ZnO nanorod arrays are prepared with the concentration 0.03 M zinc acetate hydrothermal method and different growth time (30, 45, 60 min). It is found that the maximal surface area and volume appear on the zinc oxide nanorod with the growth time 60 min on convex sapphire substrate, while the nanorods prepared on the concave sapphire substrate have the minimal surface area and volume. Photoluminescence (PL) analysis reveals that the strongest UV intensity appears on the growth time 60 min of zinc oxide nanorod, for decorating Cu nanoparticles. The zinc oxide nanorod array with the growth time 60 min on convex sapphire substrates show better H2 & CO responses. After decorating copper nanoparticles, the responses increase for H2 & CO gases. With H2 and CO from 100 to 2000 ppm, the optimal operating temperature and optimal gas concentration are 300 °C and 2000 ppm, respectively. The response values (Rair/Rgas) measured in H2 and CO environments with 2000 ppm are 2.89 and 2.91, respectively; the response times for H2 and CO appears 90 s and 115 s, and the recovery times are 75 s and 85 s. The response values of H2 and CO increase by 26% and 30% for aluminum nanoparticles decorated devices and 54% and 57% for copper nanoparticles decorated devices as compared with those without metal nanoparticles. For copper nanoparticles decorated devices, the responses of H2 and CO for the convex substrate are 6% and 10% higher than those on the glass substrates and 11% and 15% higher than those on the concave substrates.

碩士
國立虎尾科技大學
電子工程系碩士班
105
Zinc oxide is low-cost and practical Ⅱ-Ⅵ chemical materials, which utilized to absorb Platinum nanoparticle on zinc oxide nanorods (Pt/ZnO NRs). It can improve the electrical characteristics of the zinc oxide. Prior to NRs growth, a 100 nm-thick ZnO seed layer was deposited by RF magnetron sputtering on a glass substrate. Subsequently, the ZnO NRs were grown on these seed layers by the hydrothermal method at 90 °C for 6 hours and deposited Platinum nanoparticle on ZnO NRs by RF magnetron Sputter system. A set of samples have been prepared for different concentration of Pt precursors and named as ZnO, and Pt/ZnO NRs with 0s, and 30s sputter deposited times, respectively. The results indicate that ZnO NRs which have an average diameter and maximum length of around ~50nm and ~1.9 um, respectively. The structural characteristics of the ZnO NRs and Pt/ZnO NRs were measured by X-ray diffraction (XRD).Using the Joint Committee on Powder Diffraction Standards (JCPDS), it was found that the peaks observed were related to the wurtzite structured ZnO (002), (102), (103), and (112) diffractions. The ZnO NRs grown at 90 °C were structurally uniform and well oriented with pure wurtzite structure. It was also found that turn-on fields were 2.85 and 2.52 V/μm while field-enhancement factors β were 702.19 and 1924.98 for the ZnO NRs and Pt/ZnO NRs in the dark, respectively. In the results with an operating temperature, the sensitivities of the ZnO NRs and Pt/ZnO NRs gas sensors were about 1.34, and 121.03, respectively. Hence, the sensitivity and response presented good performance at increasing operating temperatures 270°C and Methanol concentrations of 1000ppm. The hydrothermal method was successfully applied for making ZnO gas sensors with large-scale production and low cost.

碩士
國立交通大學
生醫工程研究所
107
This study employed localized Joule heating and Plasma-Enhanced Atomic Layer Deposition (PEALD) to deposit palladium nanoparticles selectively on the n- region of a double-junction (n+/n-/n+) polysilicon nanobelt (PNB) device. The selective Pd-decorated nanodevices were then characterized as hydrogen sensors. To control the device surface temperature within Pd depositon window during PEALD process, a constant power technique was introduced. The particle size of Pd nanoparticle was control by adjusting the deposition cycle number of the plasma-assisted atomic layer deposition. It is found that the surface roughness of the 300-cycle deposited Pd was around 1.77 nm and exhibited a sensitivity of 1.2% at room temperature. We suspected that the 300-cycle deposited Pd possess an adequate particle size and a largest surface coverage on n- region. In addition, device was functioned under self-heating during H2 sensing by applying a voltage 10 V (358 K) on the nanobelt device. Device with 300-cycle deposited Pd presented a maximum sensitivity (2.5%), and this device can detect 100 ppm of H2.Finally,carbonaceous device via environmental contamination was cleaned by a combination of oxygen plasma and hydrogen plasma treatment. A return of sensitivity from 1.9% to 2.3% was observed after the plasma treatments.

碩士
中原大學
機械工程研究所
102
In this study, using different boron weight percentages on mixed-phase (anatase and rutile) TiO2 nanoparticles were prepared to investigate structure morphology, defect states, luminescence properties and energy conversion. The result shows boron doping crystallite size and increases the rutile-phase percentage in an anatase matrix. Decreasing the band gap by boron doping can expand the absorption to the visible region, when undoped TiO2 exhibits high UV absorption. Oxygen vacancy defects are generated by boron ions reducing Ti+4 and influence electron transport on dye-sensitized solar cells. Excess electrons originating from the oxygen vacancies of doped TiO2 affect a downward shift in the conduction band edge and prompt the transfer of photoelectrons from the conduction band of the rutile phase to the lower energy anatase trapping sites; they separate charges to enhance the photocurrent and Jsc. Even though the resistance of the electron recombination (Rk) between doped TiO2 photoanode and the electrolyte for the doped TiO2 sample is lower, but a longer electron lifetime (τ) of 19.7 ms with a higher electron density (ns) of 2.1´1018 cm-3 contributes to high solar conversion efficiency.

碩士
國立中興大學
化學系所
106
Surface-enhanced Raman scattering (SERS) is a powerful means for chemical analysis. This SERS effect can be observed when target molecules adsorbed or nearby metal nanoparitcles with a proper size and shape. To prepare active substrates for SERS measurements, ZnS and ZnSe crystals were selected as solid support in this work as they are commonly used optical windows, which exhibit photocatalytic ability with unique chemical properties. Methods based on electroless displacement and the assistance of photoreduction were developed to decorate SERS active gold nanoparticles (AuNPs) on the selected ZnS and ZnSe crystals. Several parameters, such as the concentration of reaction solution, the temperature of reaction, photo irradiation time, and the additive, were examined their contributions to the production of suitable AuNPs for SERS measurements. pHydroxythiophenol (pHTP) was used to probe the SERS performances for the prepared SERS substrates. After correlation of the observed Raman signals, the morphology of produced AuNPs by SEM with reaction parameters, mechanisms in production of AuNPs on ZnS and ZnSe were found significantly different. For produced AuNPs on ZnS crystal, AuxSy particles were formed rather than AuNPs, which degraded their SERS performances. On the other hand, when ZnSe crystals were used, Se atoms in the ZnSe crystals are capable to reduce the gold ions through formation of higher oxidation state of Se and hence, AuxSe particles formed on the surface of ZnSe is limited. On the other hand, SERS substrates based on ZnSe showed much better performances than that of ZnS. By tuning the reaction conditions, SERS substrates based on ZnS and ZnSe could be successfully prepared. Based on the optimized condition in preparation of SERS substrates, SERS intensity of pHTP on ZnS substrate was found an order weaker than that of ZnSe. In conclusion, a new method to prepare AuNPs on ZnS and ZnSe was successfully developed in this work and both the mechanism in formation and the impact of each parameter to the formation of AuNPs were well explored.

碩士
國立中正大學
物理系研究所
105
In this work, tubular graphene architectures as supporting materials for the decoration of Au-Pt nanoparticles (NPs) can enhance the electrocatalytic activity in direct methanol fuel cells. Au-Pt heterostructures were successfully decorated on tubular graphene surface with different concentrations and used as electrocatalysts for methanol oxidation. The activities of electrocatalysts were strongly improved in the presence of Au-Pt NPs, which were evidenced by the increase of the forward peak current densities in the cyclic voltammetry (CV) curves. Furthermore, the enhancement of the ratios between the forward and backward peak current densities of the CV curves shows the good tolerant ability towards the poisoning effect of intermediate carbonaceous species. The morphology and properties of Au-Pt decorated tubular graphene structures were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, electrochemical measurements and Raman spectroscopy techniques. The goal of the research is using tubular graphene meshes as supporting materials for enhancing the electrocatalytic in direct methanol fuel cells. Keywords : Graphene tube, Au-Pt nanoparticles, methanol oxidation, direct methanol fuel cell, Electrocatalyst

碩士
國立中興大學
化學系所
104
To increase the sensitivity in detection of analyte in aqueous solution, a new method was proposed to prepare multi-dimensional substrates for surface-enhanced Raman scattering (SERS) measurements. Multi-dimensional SERS substrates were fabricated by chemically decorating of silver nanoparticles (AgNPs) on porous polymelamine, which exhibits frame-like structure. To successfully decorate AgNPs, agarose was further employed to alter the surface property of the polymelamine. Meanwhile, a seed-mediated method was employed to improve the decoration of AgNPs on the surface of the frame structure of polymelamine. To successfully produce such SERS substrates, several parameters were studies, including concentration of agarose in surface treatment, the concentration of silver nitrate in the agarose solution for formation of Ag seeds, the concentration of silver nitrate in growth of AgNPs, and the reaction time. The SERS performances of the prepared substrates were examined by probing with para-hydroxylthiophenol (pHTP). Also, the morphologies of the formed SERS substrates were examined by scanning electron microscope (SEM). The results indicated that agarose layer and Ag seed play critical roles to grow proper AgNPs for SERS measurements. With the optimal preparation condition, an enhancement factor larger than 106 can be obtained easily. To combine the advantages of the simplify of fiber-optic. in chemical sensing and the ability of SERS in spectral analysis, a series of fiber-optic sensors with different sensing geometry was constructed and characterized their sensing abilities for SERS detection. AgNPs were chemically decorated on polymelamine to form SERS substrate. Also, quartz optical fiber with a diameter of 550 μm was shaped by HF to form different geometry. By inserting optical fiber into the prepared SERS substrate, a sensitive SERS probe could be constructed, which is at least 10 times more sensitive than reported SERS probe. Both influences of the condition in preparation of SERS substrate and the geometry of optical fibers were systematically examined and optimized condition, the detection of adenine in aqueous solution reached a detection limit of 5 μM. The linear range was up to 50 μM. Practical application of the prepare SERS probe showed that adenine could be detected accurately in urine samples with a recovery ranged between 93.9% and 110.0%.

碩士
國立中興大學
化學系所
103
To increase the sensitivity in Surface–enhanced Raman scattering (SERS) measurement with a minimal matrix effect for real–world sample analysis, a new method based on decoration of silver nanoparticles (AgNPs) on magnetic microspheres (MMs) was proposed. In the production of AgNPs decorated MMs (named Ag@MMs), iron oxide was first used to produce magnetic particles by co–precipitation method. These particles were further dispersed in water with a surfactant of oleic acid to form well separated micelles. These magnetic particles were further protected and stabilized by formation of cross–linked polymethylmethacrylate (PMMA) on the surface of the MMs. To increase the efficiency in adsorption of AgNPs and stability of AgNPs on MMs, the PMMA protected MMs were further functionalized with two classes of compounds; different chain length and different end functional group. These functionalized MMs (fMMs) were used to decorate AgNPs by photochemical reduction method. The fMMs offer much higher efficiency in decoration of AgNPs than that of none functionalized MMs. Also, amino compound gave the best SERS performance among the used compounds. Based on the scanning electron microscope (SEM) images, MMs produced in this work show a round shape with a size of 10 μm in diameter. Ag@fMMs prepared in this work were further applied to detect creatinine in urine sample. Highly sensitive and selective results were obtained.

Carbon nanotubes are made into films or bulks, their surface or junction morphology in the networks can be modified to obtain desired electrical transport properties by various surface modification methods. The methods include incorporation of organic molecules or inorganic nanoparticles, debundling of nanotubes by dispersing agents, and microwave irradiation. Because carbon nanotubes have unique carrier transport characteristics along a sheet of graphite in a cylindrical shape, the properties can be dramatically changed by the modification. This is ideal for developing high-performance materials for thermoelectric and photovoltaic energy conversion applications. In this research, decoration of various organic/inorganic nanomaterials on carbon nanotubes was employed to enhance their electrical conductivity, to improve thermoelectric power factor by modulating their electrical conductance and thermopower, or to obtain n-type converted carbon nanotube. The electrical conductivity of double-wall nanotubes (DWNTs) decorated with tetrafluoro-tetracyanoquinodimethane (F4TCNQ) was increased up to 5.9 × 10^5 S/m. The sheet resistances were measured to be 42 Ω/sq at 75% of transmittance for HNO3/SOCl2-treated DWNT films, making their electrical conductivities 200~300% better than those of the pristine DWNT films. A series of experiments at different ion concentrations and reaction time periods were systematically performed in order to find optimum nanomaterial formation conditions and corresponding electronic transport changes for better thermoelectric power factor. For example, the thermoelectric power factors were improved by ~180% with F4TCNQ on DWNTs, ~200% with Cu on SWNTs, and ~140% with Fe on single-walled nanotubes (SWNTs). Also SWNTs was converted from p-type to n-type with a large thermopower (58 μV/K) by using polyethyleneimine (PEI) without vacuum or controlled environment. This transport behavior is believed to be from charge interactions resulted from the difference between the work functions/reduction potentials of nanotubes and nanomaterials. In addition, different dispersing agents were utilized with DWNT and SWNTs to see a debundling effect in a film network. The highest electrical conductivity of ~1.72×10^6 S/m was obtained from DWNT film which was fabricated with a nanotube solution dispersed by chlorosulfonic acid. Debundling of nanotubes in the film network has been demonstrated to be a critical parameter in order to get such high electrical property. In the last experiment, Au nanoparticle decoration on carbon nanotube bundle was performed and a measurement of themophysical properties has done before and after modifying carbon nanotube surface. Carbon nanotube bundle, herein, was bridged on microdevice to enable the measurement work. This study demonstrates a first step toward a breakthrough in order to extract the potential of carbon nanotubes regarding electron transport properties.