Synthesis and Characterization of Tin and Germanium Based Semiconductor Nanocrystals

<p>Inorganic nanomaterials are being actively researched due to their unique physical and chemical properties. These materials can be used for a wide variety of applications and technologies which have stimulated research into the discovery, understanding and control of the morphology of materials at the nanoscale. Biologists have recently integrated biomaterials with semiconductor nanoparticles to expand their applications to include biosensing, bioimaging and therapeutic strategies. Since the water solubility of semiconductor nanoparticles is crucial for bioapplications, the fabrication of water-soluble semiconductor nanocrystals with tailored properties has become more significant. This thesis is focused on the solution phase synthesis of nanoparticles and nanowires containing the element tin. This includes tin nanoparticles, tingermanium alloy nanowires, tin sulphide nanoparticles and tin telluride nanoparticles. The aim of this research was to synthesize nanocrystals with tightly controlled size and shape for various applications,in particular for bioapplications. The properties, potential applications and crystal structure of target materials have been discussed in Chapter 1. The target materials synthesized by using chemical reaction in the presence of surfactant were characterized primarily by Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Spectroscopy (EDX) and Selected Area Electron Diffraction (SAED). Powder X-ray Diffraction (XRD), Scanning Transmission Electron Microscopy (STEM), Scanning Electron Microscopy (SEM), Ultraviolet-Visible Microscopy Absorption (UV-VIS), Fourier Transform Infrared (FTIR), Photoluminescence (PL) and Diffuse Reflectance were also used extensively (Chapter 2). The third chapter of this thesis focuses on the the development of a facile and cheap route for the synthesis of tin nanoparticles by reducing a tin precursor in an organic solvent. The low-melting tin nanoparticles have been considered as a good catalyst for the growth of semiconductor nanowires. The fourth chapter in this thesis focuses on the development of a convenient synthesis of tin germanium alloy nanowires via solution-liquid-solid growth (SLS). Tin germanium alloy nanowires were synthesized through a self-catalyzed process in which the wires were grown from in situ made Sn droplets and Ge(Ph)₃Cl. The factors affecting morphology were ascertained and the growth direction, composition, local crystal structure and possible growth mechanism have been investigated. The fifth chapter in this thesis focuses on the development of a novel one-pot synthesis of water-soluble SnS nanoparticles. The synthesis of SnS nanoparticles involves the reaction of inorganic starting materials SnBr₂ and Na₂S in the presence of various ethanolamine derivatives in ethylene glycol. Optical studies of as synthesized SnS nanoparticle show size dependent effects in both absorbance and reflectivity. The sixth chapter in this thesis focuses on the development of a facile direct synthesis of water dispersible SnTe nanoparticles. The optical properties of prepared SnTe nanoparticles were determined. The final chapter in this thesis summarizes the main findings of this study and draws out recommendations for future work. In this study, some novel contributions have been made to produce facile one-pot synthesis of tin germanium nanowires and water soluble, size controlled tin chalcogenides nanoparticles. The main future work for tin germanium alloy naowires is to develop the method to produce nanowires without seed nanoparticles for optoelectronics applications. Further work is also needed to optimize the water synthesis of SnTe nanoparticles.</p>

Synthesis and Characterization of Tin and Germanium Based Semiconductor Nanocrystals

<p>Inorganic nanomaterials are being actively researched due to their unique physical and chemical properties. These materials can be used for a wide variety of applications and technologies which have stimulated research into the discovery, understanding and control of the morphology of materials at the nanoscale. Biologists have recently integrated biomaterials with semiconductor nanoparticles to expand their applications to include biosensing, bioimaging and therapeutic strategies. Since the water solubility of semiconductor nanoparticles is crucial for bioapplications, the fabrication of water-soluble semiconductor nanocrystals with tailored properties has become more significant. This thesis is focused on the solution phase synthesis of nanoparticles and nanowires containing the element tin. This includes tin nanoparticles, tingermanium alloy nanowires, tin sulphide nanoparticles and tin telluride nanoparticles. The aim of this research was to synthesize nanocrystals with tightly controlled size and shape for various applications,in particular for bioapplications. The properties, potential applications and crystal structure of target materials have been discussed in Chapter 1. The target materials synthesized by using chemical reaction in the presence of surfactant were characterized primarily by Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Spectroscopy (EDX) and Selected Area Electron Diffraction (SAED). Powder X-ray Diffraction (XRD), Scanning Transmission Electron Microscopy (STEM), Scanning Electron Microscopy (SEM), Ultraviolet-Visible Microscopy Absorption (UV-VIS), Fourier Transform Infrared (FTIR), Photoluminescence (PL) and Diffuse Reflectance were also used extensively (Chapter 2). The third chapter of this thesis focuses on the the development of a facile and cheap route for the synthesis of tin nanoparticles by reducing a tin precursor in an organic solvent. The low-melting tin nanoparticles have been considered as a good catalyst for the growth of semiconductor nanowires. The fourth chapter in this thesis focuses on the development of a convenient synthesis of tin germanium alloy nanowires via solution-liquid-solid growth (SLS). Tin germanium alloy nanowires were synthesized through a self-catalyzed process in which the wires were grown from in situ made Sn droplets and Ge(Ph)₃Cl. The factors affecting morphology were ascertained and the growth direction, composition, local crystal structure and possible growth mechanism have been investigated. The fifth chapter in this thesis focuses on the development of a novel one-pot synthesis of water-soluble SnS nanoparticles. The synthesis of SnS nanoparticles involves the reaction of inorganic starting materials SnBr₂ and Na₂S in the presence of various ethanolamine derivatives in ethylene glycol. Optical studies of as synthesized SnS nanoparticle show size dependent effects in both absorbance and reflectivity. The sixth chapter in this thesis focuses on the development of a facile direct synthesis of water dispersible SnTe nanoparticles. The optical properties of prepared SnTe nanoparticles were determined. The final chapter in this thesis summarizes the main findings of this study and draws out recommendations for future work. In this study, some novel contributions have been made to produce facile one-pot synthesis of tin germanium nanowires and water soluble, size controlled tin chalcogenides nanoparticles. The main future work for tin germanium alloy naowires is to develop the method to produce nanowires without seed nanoparticles for optoelectronics applications. Further work is also needed to optimize the water synthesis of SnTe nanoparticles.</p>

Electrochemical Hydrogenation and Corrosion Behaviour of LaNi5-xGex (x = 0.3 and 0.6) Alloys

The capacitive and kinetic parameters of hydride electrodes obtained on the basis of single-phase LaNi5-xGex alloys (x = 0.3 and 0.6) were related to their corrosive properties. The content of the article is important from the point of view of the improvement of LaNi5 type materials for hydrogen energy storage used as anodes in NiMH batteries. The presence of large amounts of germanium (10% at.) in the alloy results in much less surface degradation compared to the low-germanium alloy (5% at.), which, on the one hand, leads to an improvement in the resistance of the high-germanium LaNi4.4Ge0.6 alloy to long-term cycling, but on the other hand, contributes to lower hydrogen absorption by this material. The maximum discharge capacity of 293 mAh g−1 was obtained for the low-germanium alloy using a charge/discharge current density of 185 mA g−1. The studied electrode also shows a lower tendency to self-discharge and a clearly higher exchange current density.

Phase Change Material of Copper–Germanium Alloy as Solar Latent Heat Storage at High Temperatures

A copper–germanium alloy (Cu–Ge alloy) was examined as a phase change material, at temperatures exceeding 600°C, for latent heat storage in solar thermal applications. First, the thermo-physical properties of the Cu–Ge alloy were examined using differential scanning calorimetry, thermomechanical analysis, and laser flash analysis. Second, to evaluate the thermal response and reliability of the Cu–Ge alloy, the cyclic properties of thermal charge/discharge were examined under various thermal conditions. The alloys obtained after the tests were examined for their chemical compatibility with the stainless steel container using an electron probe micro analyzer. The elemental distribution of each Cu–Ge alloy was evaluated using cyclic performance tests. Finally, the chemical compatibility of the Cu–Ge alloy was evaluated using a high-temperature test with candidate materials of a phase change material container vessel [stainless steel (SUS310S), Inconel625, silicon carbide (SiC), and alumina (Al2O3)]. The Cu–Ge alloy exhibited significant potential as a latent heat storage material in next-generation solar thermal power plants because it demonstrates various advantages, including a superior storage capacity at a temperature of 644°C, temperature coherence to the phase diagram, a quick thermal response, satisfactory cyclic behavior of charge/discharge modes, a thermodynamically stable metallographic structure, and non-reactivity with container ceramic materials (SiC and Al2O3).

Theoretical Study of Electronic, Structural, and Optical properties of Armchair, Zigzag and Chiral Silicon-Germanium Nanotubes

In this work we have studied infinite silicon-germanium alloy nanotubes of several types: armchair, zigzag and chiral, using a theoretical analysis based on the density functional theory as implemented in...

Fabrication of Microbolometer Arrays Based on Polymorphous Silicon–Germanium

This work reports the development of arrays of infrared sensors (microbolometers) using a hydrogenated polymorphous silicon–germanium alloy (pm-SixGe1-x:H). Basically, polymorphous semiconductors consist of an amorphous semiconductor matrix with embedded nanocrystals of about 2–3 nm. The pm-SixGe1-x:H alloy studied has a high temperature coefficient of resistance (TCR) of 4.08%/K and conductivity of 1.5 × 10−5 S∙cm−1. Deposition of thermosensing film was made by plasma-enhanced chemical vapor deposition (PECVD) at 200 °C, while the area of the devices is 50 × 50 μm2 with a fill factor of 81%. Finally, an array of 19 × 20 microbolometers was packaged for electrical characterization. Voltage responsivity values were obtained in the range of 4 × 104 V/W and detectivity around 2 × 107 cm∙Hz1/2/W with a polarization current of 70 μA at a chopper frequency of 30 Hz. A minimum value of 2 × 10−10 W/Hz1/2 noise equivalent power was obtained at room temperature. In addition, it was found that all the tested devices responded to incident infrared radiation, proving that the structure and mechanical stability are excellent.