Teses / dissertações sobre o tema "Wet chemical syntheses"

The ever-growing demand for high performance energy storage systems has become a driving force for seeking the ideal materials to deliver superior efficacy, and graphene oxide (GO) and vanadium oxide are such two promising nanostructured materials. However, neither of them has been widely adopted in the marketplace at the current stage, mainly limited by their costeffectiveness. While GO and vanadium oxide have been proved to outperform existing materials in the lab-scale studies, the more expensive and less scalable synthesis methods discourage industrial manufacturers from adopting the two materials. The research herein focuses on the novel low cost and scalable wet chemical synthesis methods, which may lead GO and vanadium oxide to greater commercial success. The PhD thesis generally is unfolded into two parts. In the first part, a simple hydrothermal method to synthesize tungsten-doped V6O13 is reported. The introduction of tungsten dopant can have a significant impact on the nanostructure evolution of vanadium oxide during hydrothermal reaction, which results in the formation of nanocrystalline structure. A realtime characterization of the hydrothermal reaction process was employed to reveal the complex phase changes of vanadium oxide in the course, which can be important guidance for controlling the product quality in larger-scale production. Moreover, when applied to lithium ion batteries (LIBs), the doped nanocrystalline V6O13-based electrode can provide better battery performance than the undoped V6O13. In the second part, graphite oxide route to synthesize graphene oxide is investigated in terms of the choices of graphite sources (expanded graphite, graphite intercalation compound and natural graphite), pre-treatment of expanded graphite (microwave-induced expansion of graphite in different atmospheres), reaction temperature, and post-processing of GO. It was found that the expanded graphite prepared in ambient air had higher dispersibility in organic solvent and finally led to higher GO yield, through the modified Hummers oxidation, than those prepared in pure carbon dioxide or argon. This is possibly due to the introduction of extra oxygen-containing functionalities accompanied by the rapid heating of graphite. We also found that graphite intercalation compound was a more suitable starting material for making large-sized GO at room temperature. One distinguishing feature of the GO produced at room temperature is that it has more thermal labile oxygen functional groups which allows the facile restoration of electrical conductivity via a mild thermal annealing. This characteristic will be very helpful to better combine GO with the electroactive particles in LIBs and thus benefit the overall battery performance. Finally, we further compared the cost-effectiveness between the room temperature synthesis method and the lower temperature method, using commercial expanded graphite powder as the graphite source. It revealed that the GO synthesized at room temperature could regain more conductive sp2 carbon and reached the same level of electrical conductivity through thermal or chemical reduction. Therefore, the room temperature method can produce conductive graphene for energy storage applications in a more cost-effective manner. On balance, this PhD thesis further develops the scalable wet chemical production of GO and vanadium oxide for energy storage by systematically investigating the key synthesis parameters and establishing the improved protocols. Ultimately, this work is anticipated to push forward the commercialization of GO and vanadium oxide in the field of energy storage in the near future.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment and Sc
Science, Environment, Engineering and Technology
Full Text

Les électrolytes solides sont aujourd’hui considérés comme la clé pour le développement des nouvelles générations de batteries. Deux types d’électrolytes solides ont majoritairement été étudiés, les polymères et les inorganiques, mais leurs performances restent limitées. Une piste prometteuse pour obtenir des électrolytes performants est d’utiliser des particules inorganiques incorporées dans une matrice polymère afin de former un électrolyte hybride. Parmi les matériaux inorganiques possibles, la famille des sulfures (Li3PS4, Li6PS5X avec X= Cl,Br, I) présente des conductivités ioniques très élevées. Cependant, ces matériaux sont généralement obtenus par voie solide menant à des particules micrométriques agrégées. De plus, bien que des synthèses en solution aient été récemment mises en évidence, le potentiel de contrôle de la taille, de la morphologie et de la prévention de leur agrégation n’est pas exploité. L’objectif de cette thèse est de mettre au point une méthodologie de synthèse de sulfures permettant de contrôler la taille, la morphologie et l’agrégation des particules afin de permettre leur incorporation dans une phase polymère. Plusieurs voies de synthèse en solution ont été développées afin de s’affranchir des limitations cinétiques de la synthèse conventionnelle. Ces différentes méthodes de synthèse ont permis d’obtenir un large panel de particules avec des morphologies et des taux d’agrégation différents. L’impact de la taille et de la morphologie des particules sur les performances électrochimiques des électrolytes a été étudié. Les électrolytes les plus performants ont été testés dans des formulations hybrides ainsi que dans des cellules électrochimiques tout solide complètes avec une anode Li/In
Solid electrolytes are now considered to be the key to the development of new generations of batteries. Two types of solid electrolyte have mainly been studied, polymers and inorganics, but their performance remains limited. One promising way of obtaining high-performance electrolytes is to use inorganic particles incorporated into a polymer matrix to form a hybrid electrolyte. Among the possible inorganic materials, the sulfide family (Li3PS4, Li6PS5X with X= Cl, Br, I) has very high ionic conductivities. However, these materials are generally obtained by the solid route, leading to aggregated micrometric particles. Furthermore, although solution syntheses have recently been demonstrated, the potential to control their size, morphology and prevent aggregation has not been exploited. The aim of this thesis is to develop a methodology for the synthesis of sulfides that enables the size, morphology and aggregation of particles to be controlled so that they can be incorporated into a polymer phase. Several solution synthesis routes were developed in order to overcome the kinetic limitations of conventional synthesis. These different synthesis methods have produced a wide range of particles with different morphologies and aggregation rates. The impact of particle size and morphology on the electrochemical performance of the electrolytes was studied. The best performing electrolytes were tested in hybrid formulations as well as in complete all-solid state electrochemical cells with a Li/In anode

The economical feasibility of commercial, single-junction solar cells is limited by high costs and limited efficiencies. New solar cell concepts and materials are sought to decrease the production costs and increase the efficiency. Intermediate band solar cells (IBSCs) show a promising concept for increased efficiency up to 46.77% as they employ three band gaps that can be matched to the solar spectrum to minimize fundamental losses. Doping of copper gallium disulphide (CuGaS2) with transition metals like Fe and Ni to high concentrations can theoretically form an intermediate band (IB), which for Fe doping gives nearly optimal band gaps for IBSC applications. Copper gallium disulphide is synthesized in an environmentally friendly, inexpensive and simple hydrothermal synthesis which may contribute to decreased costs of solar cell production.The hydrothermal synthesis is developed to produce copper gallium disulphide from copper(I) chloride (CuCl), gallium(III) chloride (GaCl3) and excess thiourea (Tu) (SC(NH2)2) in deionized water. The influence of varying synthesis parameters on product purity, yield and morphology has been investigated through X-ray diffraction (XRD) and scanning electron microscopy (SEM). Energy dispersive X-ray spectroscopy (EDS) is used to investigate doping of copper gallium disulphide and identify particle morphologies formed by different phases. Formation of copper gallium disulphide proceeds through slow decomposition of Tu, driven by an equilibrium shift due to hydrogen disulphide (H2S) evolution and precipitation of sulphides like the intermediate phase digenite (Cu2-δS) into which Ga3+ ions are incorporated. An additional impurity of copper(II) sulphide (CuS) is commonly formed, and gallium(III) hydroxyoxide (GaO(OH)) forms at pH > 0.5. Products of high purity and yield are obtained at 250 °C with concentrations above 0.060 M copper(I) chloride and gallium(III) chloride with the complexing agent 1-pentanethiol, and 0.319 M without 1-pentanethiol. Introducing nickel(II) chloride (NiCl2) or iron(III) chloride (FeCl3) in the hydrothermal synthesis forms vaesite (NiS2) or iron pyrite (FeS2) impurities, respectively, and copper gallium disulphide is not doped to a desirable concentration for IB formation.Color variations in the products reveal off-stoichiometries which contribute to a wide range of particle and crystallite morphologies within each product. Yellow, stoichiometric copper gallium disulphide particles have been deposited on a Si(100) substrate and growth of a red, Ga-rich film was achieved with 1-pentanethiol. These products were subject to photoluminescence spectroscopy (PL) along with off-stoichiometric powders of doped and undoped products, but no luminescence was obtained, possibly due to high defect densities and non-radiative recombination. Dispersions of powders were also subject to absorption spectroscopy which indicate extensive scattering due to wide ranges of particle sizes. The morphology of powder products shows particularly large variations within and between the products. Nanoplate and pyramidal crystallites are produced through nucleation and growth to form network structures and polycrystalline spheres, rods and rose-like particles, which along with the crystallites have varying irregularities and sizes.

In this work a new wet-chemical method of preparing tungsten oxide thin films is described. This involves the dissolution of tungsten metal in aqueous hydrogen peroxide and reaction with acetic acid to form an alcohol-soluble precursor. All synthesis stages of this new precursor, termed peroxotungstic ethoxide, are characterized to determine possible reactions. The chemical and microstructural evolution of films is described as a function of firing temperature, utilizing infrared spectroscopy, diffraction and other optical data. A novel method of increasing the crack-free thickness of the films is given: a combination of oxalic acid dihydrate as a solution additive and film firing under controlled humidity. With this combination, fired crack-free films up to one micron in thickness were prepared. Oxalic acid dihydrate roughened and also caused crystallization of these films at lower temperatures (250°C) than expected. These rougher films exhibited an improved electrochromic response, as measured by optical and electrochemical characterizations.

Doped ZnO nanoparticles were synthesized by three different methods – electrochemical deposition under oxidizing conditions (EDOC) , combustion method and wet chemical synthesis – for investigating the oxygen gas sensing response. Ga-doped ZnO was mostly synthesized but also In-doped ZnO was made. The samples were analyzed by XRD, SEM, EDX and TEM. Gas response curves are given alongside with Langmuir fitted curves and data for pure ZnO and Ga-doped ZnO. DFT quantum chemical investigation of cluster models ZnO nanoparticles were performed to evaluate defect effects and oxygen and nitrogen dioxide reactions with the ZnO surface. Defects were investigated by DOS and HOMO-LUMO plots , and are oxygen vacancy, zinc vacancy, zinc interstitial and gallium doping by replacing zinc with gallium. Oxygen and nitrogen dioxide reactions were investigated by computing Mulliken charges, bond lengths, DOS spectra and HOMO-LUMO plots.

The present Ph.D. thesis provides some examples of innovative 2nd generation catalytic processes for the conversion of renewable raw materials into green value-added chemicals. In particular, D-glucose and some its derivatives, all ideally representing waste materials of dedicated biomasses, agricultural residues, or solid organic urban waste exploitation in the biorefinery plant, were converted into useful chemical building-blocks. After a brief introduction to the topic and the description of the experimental method, each chapter of the work is based on one or more scientific articles either published or submitted. Among the possible catalytic reactions, the hydrogenation, oxidation and hydrodeoxygenation were investigated: for this purpose, several novel catalysts were synthetized, tested and characterized. The catalysts were made from precursor solutions with the incipient wet impregnation method or with the solution combustion synthesis, depending by the catalyst type. The conversion of glucose and some glucose-derivatives was typically performed under gentle operative conditions and in aqueous mean. Pt-based catalysts were tested for glucose conversion to adipic acid in a two-step process carried out in water solution without any pH control by investigating the effect of a series of supporting materials (active carbon, alumina, silica and ceria). The process consisted in the D-saccharic acid (SacA) production by D-glucose catalytic wet air oxidation followed by a hydrodeoxygenation treatment of SacA to adipic acid (AA) with the same catalyst. The main limit of using Pt for D-glucose oxidation is represented by the catalyst inhibition operated by the first product of the reaction, the gluconic acid (GluA), which prevents the consecutive reaction of SacA formation, but a deeper investigation of the reaction scheme allowed us to assess that over Pt/alumina the consecutive oxidation of gluconic acid to SacA is slightly favored under uncontrolled pH too.We have demonstrated that a 5.2 wt.% Pt on γ-alumina sample, the catalysts presenting the larger amount of strong Brønsted acid sites, was the best material for obtaining SacA (with a molar yield of about 13.5%); afterward, by performing the halogen-promoted hydrodeoxygenation of the resulting solution, the SacA was quantitatively converted into AA (and thus the overall adipic acid molar yield from glucose was about 13.0%). Effectively, The efficient conversion of common biomass derivatives, as D-glucose, into value-added chemicals has received a great deal of attention in the last few years. Several heterogeneous catalytic systems, characterized by noble metals, have already been investigated for the Catalytic Wet Air Oxidation (CWAO) of derived biomass. Nevertheless, the redox effect of such catalysts on biobased compounds has not been described in detail. In the present thesis, some perovskite type oxides (Fe, Co, Mn) that present high redox properties and stability under hydrothermal conditions have been tested to establish their ability to convert D-glucose into C6 aldaric acid, lactic acid (LacA) and levulinic acid (LevA). The influence of the reaction temperature, and the affinity of the catalysts to hydrogen and oxygen on the distribution of the liquid products have been investigated. In the best conditions, 50.3 mol.% and 69.5 mol.% of lactic and levulinic acid have been obtained by employing LaCoO3 and LaMnO3, respectively. Apart from the oxidative effect, which has led to several oxidation products, a high reductive effect of the catalysts has enabled the conversion of some key intermediates, such as pyruvic acid (PyrA) and hydroxymethylfurfural (HMF), into the desired products. LaMnO3, which has resulted to be the most oxidizable/reducible catalyst over a low temperature range, has shown the best performance of the studied perovskite type oxides; it has been found to promote the conversion of hydroxymethylfurfural to levulinic acid and to give the highest overall molar yield. Moreover, performing catalysts have been synthetized through incipient wet impregnation and tested for cis,cis-muconic acid (ccMA) hydrogenation to adipic acid. Before the hydrogenation, the investigation on the solubility of ccMA dissolution in different polar solvents has been carried out by characterizing and modelling the dissolution as a function of temperature. Water, ethanol, 2-propanol and acetic acid have been investigated as solvents in the range temperatures from a 298.15 to 348.15 K. Owing to the absence of ccMA solubility data, the reliability of the adopted experimental set-up was validated comparing published and experimental solubility data of a similar compound, that is, AA. From the results, it has emerged that the employed system is appropriate for the determination of molar fractions of an organic compound dissolved in polar solvents. The molar fraction and temperature were correlated using the Apelblat equation model, which is applied for the mathematic fitting of experimental data. A total relative average deviation of 3.54% was obtained for the experimental results and the solubility data obtained with the model, thus attesting the adequacy for this study. The use of Apelblat equation also allowed to determine the apparent molar enthalpy and molar entropy of dissolution. The dissolution of ccMA in water, ethanol, 2-propanol and acetic acid, over temperatures ranging from 298.15 to 348.15 K, has been shown to be endothermic. The activity of Pt-based catalysts has been compared with a Ni-based catalyst at a gentle condition. A supported 14.2 wt.% Ni on γ-alumina converted 100% of muconic acid, yielding 99.4 mol.% of AA. Finally, the oxidative cracking of 5-keto-L-aldonic acids to tartaric acid (TarA) was successfully performed at room temperature and atmospheric pressure in a carbonate buffer (pH = 10.34), by employing various V-based catalysts. The performance of the novel heterogeneous V-based catalysts was compared with the one of a conventional homogeneous system. The effect of the catalysts was obvious and 2%VOx/ZrO2 was found to be the best catalyst for the 5-keto-aldonic acids conversion to tartaric acid. The tartaric acid selectivity was equal to 74.5% and 44.3% starting from the 5-keto-D-gluconic acid (5kGl) and 5-keto-L-galactonic acid (5kGa), respectively. The best performances in terms of tartaric acid selectivity were obtained at the beginning of reaction, and about one fourth of the carbon moles were converted into tartaric acid after 24 h of reaction. The substrate was entirely converted after 24 h indicating that several by-products were also produced during the reaction. So, an overall reaction pathway was supposed and the effect of the vanadium structure to the catalytic activity was hypothesized. Moreover, the reaction mechanism of the 5-keto-aldonic acids conversion to tartaric acid promoted by the anchoring VOx-support bond was described.

碩士
國立臺南大學
材料科學系碩士班
96
We investigated "Producing cadmium telluride alloy material by wet chemical synthesis process" in this paper. In the concept of molecular self-assembly, we synthesized the powders of cadmium telluride with forceps by using hydrothermal method in the condition of low-temperature and high pressure. First we add sodium hydroxide and gradually eliminate organic solvents which need the effect of chelation. In this step we can know the importance of sodium hydroxide to the reaction. Then we investigated the effect of reaction temperature to reaction, the effect of timeto the reaction and PH by changing reaction with fixed time, changing reaction time with fixed temperature and changing amount of sodium hydroxide particularly. We analyzing the producty by XRD, SEM and EDX showed that the cadmium telluride prepared ingredients, cadmium telluride and the elements ratio has near 1, it also proves that the duration of response, the reaction temperature, PH value of the . The best results is getting by the use of 10M sodium hydroxide solution in the 180℃, reaction time is 72 hours. The results show that comparing to other chemical synthesis methods which need expensive equipment, complex conditions and even expensive drugs, using hydrothermal method to prepared cadmium telluride powder is relatively simple and cheap to produce cadmium telluride alloy material.

碩士
逢甲大學
材料科學所
96
Liquid Organic Law for the Preparation of a group II-IV semiconductor cadmium selenide (CdSe) nanometer particles of simple wet chemical synthesis methods, this is the use of organic solvents and Cd ion source configured to respond precursor solution, and the proportion of different solvents Synthesis of the environment. This experiment to study law at different organic liquid preparation derived from experimental parameters of the Characteristic CdSe nanoparticles growth and optical properties of the study. For the reaction time, temperature, TBP dosage, HDA / TOPO and Se / CdO chemical dosage than the organic liquid, and other relevant parameters of the legal system-a series of analysis. Formation of core-shell structure of the optical properties of the impact from the excited photoelectron spectrum of ultraviolet light - absorption spectrum of visible light, X-ray diffraction patterns, transmission electron microscope photos to understand Ⅱ - Ⅵ family nanometer grains The optical properties and structure. In the optical properties, CdSe quantum dots show quantum confinement effect, it means that as the particle size of the increase in energy gap become smaller, in light absorption and excited map of displacement in the red shift phenomenon, in the structure Nature, from the graphics of the XRD, CdSe quantum dots for the wurtzite structure, belonging to the six-party most of the accumulation, is in line with the theoretical value.

碩士
國立臺北科技大學
資源工程研究所
101
In the first part, Cu nanostructures deposited on the top of self-assembled molecular patterns generated by Dip-pen Nanolithography (DPN), and the Ni was selectively reduced by electroless deposition of Ni on Cu nanostructures. The magnetic property of Ni/Cu nanoarrays was measured by magnetic force microscopy via the tip-sample magnetic interactions. On the other hand, the substrate with Cu nanostructures also was reacted with HAuCl4 aqueous by Galvanic replacement reaction since the reduction potential of AuCl4－ is higher than Cu. If the pH value is well controlled in this system, Au/Cu composite structure will be obtained. In the second part, the needle-like nanostructures and nanobundles of Cu compounds were grown by the redox reaction of Cu in HAuCl4 aqueous at pH 12 and 12.5. Their morphology and atomic composition were investigated by using SEM, TEM and EDS. On the other hand, the effects of cetyltrimethylammonium bromide (CTAB) and pH value on the crystal morphologies of Cu compounds were studied. It was found that the formation of nanoplates of Cu compounds dependent on the presence of surfactant CTAB. Finally, SERS properties of the Cu compounds prepared in the system were also studied.

碩士
逢甲大學
材料科學與工程學系
102
The aim of this study is to employ a low-temperature wet chemical synthesis method, namely chemical bath deposition (CBD), to effectively fabricate indium tin oxide (In2O3:Sn; ITO) thin films as transparent conductive oxide (TCO) films. We have achieved ITO films with very good materials properties through CBD process at 80oC for deposition duration of 2~8 hrs and the post-heat treatment. The essential processing parameters regarding such fabrication of ITO films by CBD route consist of deposition temperature, deposition time, types and concentrations of chemical precursors and complexing agents, amount of tin dopants, annealing temperature (100~500oC) and atmosphere. The obtained ITO films by CBD technique turned out to be very smooth, dense and uniform in thickness with average thickness of 70 nm on various substrates such as glasses and PET polymer sheets. The deposited ITO films were analyzed by FE-SEM, AFM, EDS, UV-Vis spectrometer, XPS, four-point probe electrical resistance measurement, and electrostatic discharge (ESD) testing. In addition, the simulation and calculation of energy gap for these In2O3:Sn semiconductive materials were performed. The ITO films produced with the optimized processing parameters and heat treated at 500oC could reach reasonably good properties with electrical resistivity of 3.29×10-3 Ω-cm and optical transmittance of 90% and above, which meet the specification requirements for most of industrial applications. We have successfully demonstrated this pioneering study that ITO thin film can be fabricated with CBD process and this would provide a feasible technical solution for the development of next generation flexible electronics. Keywords: chemical bath deposition (CBD), indium tin oxide (In2O3:Sn; ITO), tin dopant, transparent conductive oxide (TCO), low-temperature wet chemical synthesis.

碩士
朝陽科技大學
環境工程與管理系碩士班
101
Sodium pentachlorophenol is an organic compound that is difficult to break down in the environment. Once it contaminates soil and groundwater, it can enter the human body through bioaccumulation and lead to severe human diseases such as deformation or cancer. Because of the strong reductive capability of zero-valent metal in general, zero-valent iron is most widely used in the treatment of groundwater contamination. This study used a wet chemical synthesis method to mix sodium carboxymethyl cellulose (CMC) and citric acid (CA) together into a single and a composite zero-valent metal for dispersant preparation. The degradation rate of sodium pentachlorophenol (PCP-Na) in water was used as a test to analyze and explore the effect of various parameters such as metal dosage, reaction time, and different dispersants on the degradation efficiency of PCP-Na, and to measure the pH of water samples and oxidation-reduction potential (ORP) in order to facilitate comparison of these parameters for their impact. Zero-valent iron-nickel bimetallic obtained in the 24-hour degradation test yielded the best result, with a 98.6% degradation rate. Brunauer-Emmett-Teller (BET) analysis showed that the addition of CMC before the wet chemical is synthesized can effectively raise the zero-valent metal surface area from 39.9 m2 / g to 197.2 m2 / g. Under the conditions of temperature at 25℃, water sample volume at 20 mL, water concentration at 300 mg / L, and weight of metal at 1 g, the 24-hour degradation test results showed that zero-valent iron-nickel bimetallic within the wet chemical synthesized CMC increased the rate from 15.8% to 98.6%. Kinetic study demonstrated that zero-valent metal degradation of the PCP-Na test was in line with first-order kinetics, with a reaction rate constant at 2.53 × 10-3 min-1.

博士
國立中山大學
材料與光電科學學系研究所
107
This dissertation describes the synthesis of low-dimensional nanostructures via a series of facile aqueous solution methods at low temperature (<2000C). We started with the fabrication of vertically aligned ZnO nanorods (NRs) on aluminum-doped zinc oxide (AZO) substrates by a single-step aqueous solution method. In order to strengthen photoluminescence (PL) property, ZnO nanorod arrays were annealed at various temperature. We found that the annealing temperature strongly affects both the near-band-edge (NBE) and visible (defect-related) emissions, this eventually leads to the understanding of the optimum annealing condition to achieve enhanced optical properties. Some important findings were found from the PL study, for example, the enhancement of NBE is due to the activation of radiative recombinations associated to hydrogen donors (Ho), and the reduction of visible emission is mainly because of the annihilation of OH groups from the ZnO surface. This interesting finding motivated us to synthesis ZnO hybrids so that we can exploit its promising optical properties in the photocatalysis application under UV or visible light illumination. Next, the plasmonic Au nanoparticles were deposited on the ZnO nanorod arrays to fabricate a noble metal/semiconductor hybrid structures. Interestingly, this Au/ZnO platform exhibits amazing UV-Vis photocatalytic activity alongside the strong luminescent properties. The visible-light active photocatalysis is assisted by localized surface plasmon resonance (LSPR) excitations while the strong absorption and charge separation under UV irradiation is responsible for enhanced catalytic performance. Besides, the enhancement in optical properties is mainly due to local field enhancement effect and the coupling between exciton and LSPR. For the first time, we showed that the plasmonic enhancement of photocatalytic performance is not necessarily a trade-off for enhanced near-band-edge emission in Au/ZnO. The excellent emission property and photocatalytic activity results motivated us to combine low-dimensional ZnO nanostructures with some earth-abundant two-dimensional (2D) materials as a replacement of expensive noble metals. Thus, we prepared heterodimensional nanostructures of 2D ultrathin MoS2 nanosheets interspersed with ZnO nanoparticles by using a facile two-step method. Foremost sonication-aided liquid phase exfoliation technique (LPE) was used to exfoliate ultrathin MoS2 nanosheets in ethanol/water solvent, subsequently a wet chemical process was employed to realize interspersion of ZnO nanoparticles onto the MoS2 surface. In this case, ultra-thin MoS2 nanosheets acted as the support for the nucleation of various concentrated small ZnO dots. The photocatalytic activity of the ZnO/MoS2 nanocomposites was performed with organic dye pollutants and tetracycline, a common antibiotic, as a model compound under visible-light irradiation. We found extremely high catalytic efficiency with these composites under visible light, where the reaction rate of pollutant degradation is about eight times higher than those of commercial P25-TiO2 photocatalysts. This outstanding photocatalytic activity of the heterodimensional hybrids results from the synergetic effects of ZnO and MoS2. Most importantly, the heterojunction formation between ZnO and MoS2 facilitates the separation of photogenerated active charge carriers, leading to the enhancement of photocatalytic performance. Moreover, a tentative mechanism for photocatalytic degradation was proposed in this report, which can provide valuable insights for the exploration of cost-effective nanoscale hybrids constructed from atomically thin layered materials. Finally, we have synthesized mesoporous C-ZnO nanostructured via a facile one-step hydrothermal process, and then liquid-exfoliated 2D MoS2 nanosheets were integrated with the C-ZnO through simple thermal treatment to obtain C-ZnO@MoS2 composites. The photocatalytic activity was evaluated under visible light irradiation and we found the significant enhancement in photodegradation of organic dye molecules by the introduction of MoS2 nanosheet on C-ZnO. Such a significant photoactivity could be attributed to the MoS2 nanosheets that strengthen the visible-light absorption to create the electrons and holes in the system and their favourable separation occur by the electron transaction between ZnO, and MoS2. The synergistic effect between carbon, MoS2 and ZnO makes C-ZnO@MoS2 composites a suitable visible-light driven photocatalyst.

博士
國立彰化師範大學
物理學系
102
This dissertation presents experimental practices conducted to study the effect of synthesis methods on the thermoelectric properties of n-type cobalt skutterudite. In this effort, wet chemical preparation procedures are adopted. The produced powders are characterized using x-ray diffraction pattern, scanning electron microscopy, Hall and density measurements. The Seebeck coefficient (thermopower), electrical and thermal conductivity measurements are performed for all the fabricated samples. Various reaction conditions have been carried out to stabilize the CoSb3 phase by modified polyol processes. The power factor of the parent CoSb3 is significantly enhanced via Ni substituting in Co site of Co4-xNixSb12 compounds (x= 0.0, 1.5ε, 2.5ε, 3.0ε, 4.0ε, and ε= 0.03125) synthesized by a rapid preparation procedure using modified polyol process. We have succeeded also in producing n-type CoSb3 using hydrothermal synthesis method. Different synthesis temperatures with reaction duration of time of 12 h are investigated to obtain the single phase of CoSb3. The remarkable low thermal conductivity of 1.33 - 1.46 Wm-1K-1 at room temperature is attained for the pristine CoSb3, which is comparable with or even lower than the filled CoSb3 obtained from solid state reaction. Enhancement of the power factor of CoSb3 samples synthesized using hydrothermal method is practiced via Ni-doping into the Co1-xNixSb3 structure with x=0.03215, 0.07 and 0.125. To study the effect of simultaneously electrons and holes doping on thermoelectric properties of CoSb3, we have succeeded in hydrothermally synthesizing co-doped Co1-x-yNixFeySb3 compounds with weighted compositions of {(x,y)}={(0.07,0.0), (0.07,0.03), (0.07,0.05), (0.14,0.10), (0.14,0.12), (0.14,0.14)}. The obtained results show thermal conductivity can be more reduced by co-doping of Ni and Fe, while the power factor is also enhanced. We have used solid state reaction to produce tungsten ditelluride. Based on the measured thermoelectric properties of produced WTe2 samples, we found it suitable candidate for investigating the thermoelectric properties of CoSb3 composite. As a result, the largest zT value of about 0.5 is achieved at 562 K for CoSb3 +yWTe2 composites for simultaneously y=3 and 12 wt. %. The In-filled InxCo4Sb12 compounds (x=0.25 and 0.50) are successfully produced using hydrothermal process combined with solid vapor reaction procedure. The largest room-temperature zT of 0.39 is attained for indium content, x=0.25. The thermal conductivity is reduced with increasing indium fillers. The density of InxCo4Sb12 bulks is increased markedly, which can confirm the insertion of In ions into the Sb-icosahedrons of Co4Sb12.

碩士
國立中央大學
化學工程與材料工程學系
105
A co-crystal is formed when the assembly of two or more distinct molecular species in a definite stoichiometric ratio occurred through the interactions of hydrogen bonds and non-covalent bonds in a long range order. Co-crystallization is a way to alter or enhance the solubility and mechanical properties of active pharmaceutical ingredient (API). In this research, acetaminophen and theophylline were chosen to generated the 1:1 co-crystal of acetaminophen-theophylline (1:1 Ace-Thy co-crystal) to enhance the solubility and mechanochemical properties of theophylline by co-crystallized with acetaminophen. The mechanism for mechanochemistry of 1:1 Ace-Thy co-crystal was also discussed. Three preparation methods for 1:1 Ace-Thy co-crystal were studied: (a) direct co-crystal assembly, (b) re-crystallization, and (c) solvent-less ball-milling. The dissolution rates of pure 1:1 Ace-Thy co-crystals prepared by different methods also be conducted and compared. To the best of our knowledge, a few studies had investigated the wet granulation and the dissolution of formulated co-crystals. In this research, USP Dissolution Apparatus – Paddle (37°C) was chosen to do the dissolution test for the formulated granules of 1:1 Ace-Thy co-crystals obtained from different preparation methods. Although co-crystallization had been integrated with high-shear and wet granulation by other research groups, co-crystallization in ball mill was completely a solvent-less step because it was separated from wet granulation. The chemical stability of 1:1 Ace-Thy co-crystals in the presence of excipients and binders was studied and verified in this research. Water could be the binder liquid, but not acetone, for wet granulation.　　Five advantages were offered: (1) co-crystal formation was clean and easy to be monitored by characterization tools, (2) no other impure phase was detected, (3) the theophylline drug release was increased (T50 = 3.6 min) by the co-crystal formation (T50 = 2.8 to 3.0 min), (4) in the presence of formulation and water, no influence of co-crystal formation (T50 = 3.5 to 3.9 min) on chemical stability or on theophylline drug release (T50 = 3.8 min), and (5) the environmentally benign solvent-less ball mill methods was as good as the other conventional solution crystallization methods in terms of the co-crystal quality and dissolution behavior of the same particle size.

碩士
國立中興大學
材料科學與工程學系所
101
In this experiment, CuO-V2O5 heterogeneous nanostructures was synthesized by a two-stages chemical process where V2O5 nanowires were synthesized by using a hydrothermal method in the first stage, and then CuO nanoparticles were decorated on the surface of V2O5 nanowires through wet-chemical reaction in the second stage. The morphologies. compositions, and crystalline structures of the as-synthesized products were characterized by SEM, XRD, and TEM. To study the growth mechanism of V2O5 nanowires, the synthesis process was terminated at different growth times and the corresponding morphologies and structures were examined. Gas sensors based on V2O5 nanowires and CuO-V2O5 heterogeneous nanostructures were fabricated to investigate their gas sensing properties to CO and NO2 gases. The experimental results show that the growth mechanism of V2O5 nanowires is deduced to be the oriented attachment (OA) mechanism. The V2O5 nanoparticles will first nucleate in the precursor solution and then grow into nanorods. In the meantime, the growing nanorods will rotate each other to find the orientation with the lowest surface energy and attach together to from V2O5 nanowires oriented along the [110] direction. At the aspect of gas sensing properties, the gas sensitivities of the V2O5 nanowires can be enhanced as the operation temperature is increase due to the thermal activation effect. The CuO-V2O5 heterogeneous nanostructures have a better gas sensing performance than the bare V2O5 nanowires because of their larger surface-to-volume ratios and the existence of extra p-n junctions.

碩士
逢甲大學
材料科學所
97
We used two wet chemical synthesis methods, namely, to fabricate the zinc oxide (ZnO) thin film on the polyethylene terephthalate (PET) film as flexible polymer substrate. The relationship between microstructure and optical properties of ZnO films and process conditions of both CBD and SILAR were thoroughly explored. In CBD process, the type of precursors as zinc ion source, concentration of chemical bath, and the deposition temperature and time were investigated along with the use of different complexing agents such as ammonium nitrate and sodium citrate to effectively control growth mechanism of ZnO film. In SILAR process, the number of deposition cycles is a strong connection to the final thickness and microstructure pf ZnO films. The adhesion strength and film failure modes of deposited ZnO films were examined under a substrate bending tester with various bending angle and folding length. The optimized process parameters derived from CBD and SILAR techniques for PET substrates were also employed to other available substrates including stainless steel foil, glass, and silicon wafer to compare resultant performances of film deposition. Moreover, the post-deposition heat treatment was used to promote the densification of ZnO films and to enhance its optical and crystallnity for the applications as window layers of Cu(In,Ga)Se2 or CIGS thin film solar cells. The ZnO film through rapid microwave annealing had satisfactory optical property and crystallnity. The ZnO films on flexible PET substrates with thickness of 30~130 nm and transmittance over 90% can be achieved by CBD and SILAR.

We report the large scale synthesis of nanostructured copper oxide (CuO) synthesized by cost effective and simple wet chemical route. Nanorods and Nanoflowers and Nanowires have been uniformly grown on Cu foil by the oxidation of Copper. Their growth mechanism has been reported to understand the optimal parameters for controlled growth via a simple coordination self-assembly method on substrates. The composition, morphology and structural identity have been characterized by Scanning Electron Microscope (SEM), X-ray Diffraction (XRD), Energy-Dispersive X-ray spectroscopy (EDX), Fourier Transform Infrared Spectroscopy (FTIR) and Transmission Electron Microscope (TEM). These characterizations clearly show formation of CuO nanorods and nanoflowers having diameter in the range of 16-30 nm. The synthesized structures will have the potential applications as gas sensors, an active electrode material for Li-ion batteries, heterogeneous catalysts, field emission [FE] emitters and solar cells etc.

Post-discovery and advancement in graphene, the field of layered materials, have gained enormous research interest. These materials have unique and diverse range of properties. Layered materials further provide an opportunity to tune the properties through control over morphology and heterostructure/hybrid formation based on them - often exploitable for targeted applications in electronics, optoelectronics, electrocatalysis and sensing. In general, heterostructures exhibit properties superior to their individual counterparts. Thus, control over morphology and heterostructure formation is a major challenge owing to the necessity of controlled nucleation and growth of the material for targeted application. Although various physical and chemical vapor deposition methods are available to synthesize the pristine layered materials and their hybrids, solution methods are also promising route for synthesis owing to the simplicity and morphology control. In this work, we demonstrate simple wet-chemical methods to synthesize layered materials and hybrid/heterostructures based on them and further investigated them through different characterization techniques especially using (S)-TEM. A Solvothermal method has been designed to tune the morphology of SnSe2 (a member of layered materials) from 3D to 2D nanosheets. Density function theory has been performed to rationalize the observed morphology control. As-synthesized SnSe2-nanosheets have been integrated with graphene and investigated for photodetection. The graphene-SnSe2 hybrid device exhibits high photo-detectivity for near IR range photodetection. Followed by a simple wet-chemical method has been designed to synthesizeMoSe2 and WSe2. The reaction kinetics studies reveal feasible synthesis of MoSe2 in comparison to WSe2. The reaction kinetic difference in the synthesis of MoSe2 and WSe2 has been exploited to synthesize hierarchical MoSe2@WSe2 hybrid nanostructure. The nanostructure has been investigated as a robust bifunctional electrocatalyst for total water-splitting reactions involving hydrogen and oxygen evolution reactions. The hybrid nanostructure exhibits better electrochemical activity as compared to MoSe2 and WSe2. The hybrid nanostructure also shows better electrochemical stability as compared to commercial Pt/C and RuO2. Thirdly, electron microscopic investigation has been carried out to study the transformation that occurred during anion exchange in layered material considering SnS2 nanosheets as a template. The mechanistic study has shown that the exchange initiates from the side and moves inward. Using the channeled exchange reaction, lateral hybrid nanostructure SnSe2-SnS2 has been synthesized. Finally, phase transformation of layered metal oxide WO3 has been studied through aberration-corrected STEM. The phase transformation of the hydrated WO3 phase reveals that the transformation o-WO3.0.33H2O to monoclinic phase occurs gradually with the coexistence of 2 phases, namely monoclinic and hexagonal. Both phases exist in the same nanostructure with atomically smooth boundaries between them.

博士
國立清華大學
化學工程學系
99
The main purpose of this study was to develop the techniques of the preparation of nanocrystals. In this dissertation, three techniques including (I) the deaggregation of silver powders assisted by supercritical CO2, (II) the synthesis of silver nanoparticles in CO2-expanded liquids, and (III) the synthesis of metal sulfide nanocrystals using wet-chemical method had been studied. System I. The deaggregation of silver powders assisted by supercritical CO2 The mixture of silver particles/organic solvent/dispersing agent in the reactor was pressurized with CO2 ranging from 800 to 2000 psi for a period of time, followed by the depressurization through a nozzle rapidly. The organic solvents of toluene, hexane and ethyl acetate and the dispersing agents of isostearic acid and dodecanethiol were used. The process temperature was ranged from 25 to 50°C. After the process of depressurization, the silver particles solution was investigated by dynamic laser scattering (DLS). It was found that the operation with the pressurized CO2, especially in the supercritical condition, could help the deaggregation of silver powders and the size of deaggregated silver particles was less than 1000 nm. However, part of the deaggregated silver particles tended to assemble into thin films on the surface of solution and the wall of receiver. The anti-solvent effect induced by adding CO2 or insufficient amount of dispersing agent to cap the surface of silver particles might be the reasons. In addition, during depressurization through nozzle, the volume of gas expanded greatly leading to the nebulization of organic solvent. Thus, the huge receiver to collect the nebulizing solvent droplets was required. System II. The synthesis of silver nanoparticles in CO2-expanded liquids A soluble form of silver carboxylate, silver isostearate (AgISt), was synthesized and characterized. The results of ATR-FTIR, 1H-NMR, XRD, DSC and TGA indicated that the methylated branched alky chains in AgISt exhibited a steric hindrance to impede the growth of layered structure of AgISt molecules, which led to the high solubility of AgISt in non-polar solvents. A novel technique to synthesize silver nanoparticles (AgNPs) using CO2-expanded liquids as the processing medium was proposed. AgISt and hydrogen (H2) were utilized as silver precursor and reducing agent, respectively. The operative pressure of H2 and CO2 were ranged from 14 to 800 psi and from 200 to 800 psi, respectively. At 40°C, the averaged size of synthesized AgNPs was ranged from 2 to 7 nm. While the applied pressures of H2 and CO2 were increased, the size distribution of AgNPs was narrower and the formation rate of AgNPs was increased. The investigations of HRTEM, SAED, ATR-FTIR showed that AgNPs were grown in face-centered cubic phase and capped with isostearic acid, which was derived from the reduction of AgISt with H2. Further increase the reaction temperature to 60 or 80°C, the formation rate of AgNPs was reduced and the size distribution of AgNPs became broader. The reason might be that the resistance of mass transfer of H2 in CO2-expanded liquids limited the reduction reaction of AgISt and H2 as temperature was increased. System III. The synthesis of metal sulfide nanocrystals using wet-chemical method Metal isostearates including zinc isostearate (ZnISt2), cadmium isostearate (CdISt2), and copper isostearate (CuISt2) were synthesized by the cation exchange reaction of sodium isostearate with the corresponding metal ions. The results of XRD and DSC indicated that no layered structure was form in metal isostearate, which led to their high solubility in non-polar solvents. Metal isostearates were employed as precursors to react with H2S to synthesis metal sulfide nanocrystals in wet-chemical method. By using ZnISt2 as precursor, ZnS nanowires were formed at 40~120°C, whereas nanorods were formed at 160°C. By using CdISt2 as precursor, rod, bipod, tripod, and tetrapod shapes of CdS nanocrystals were formed at 40~120°C. The investigation of HRTEM indicated that the arms and cores of multipod-shaped CdS were grown in wurtzite phase and zinc blende phase, respectively. Further increased the temperature to 160°C, spherical, rod-like and warm-like CdS nanocrystals were formed. By using CuISt2 as precursor, irregular aggregated CuS were form at 40°C, whereas circular, triangular, and hexagonal CuS nanocrystals were form at 80~160°C. The XRD pattern indicated that CuS nanocrystals were grown in covellite phase.