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>

Comparison of pharmacokinetics and biodistribution of laser-synthesized plasmonic Au and TiN nanoparticles

Plasmonic nanostructures offer wide range of diagnostic and therapeutic functionalities for biomedical applications. Gold nanoparticles (Au NPs) present one of the most explored nanomaterial in this field, while titanium nitride nanoparticles (TiN NPs) is a new promising nanomaterial with superior plasmonic properties for biomedicine. However conventional chemical techniques for the synthesis of these nanomaterials cannot always match stringent requirements for toxicity levels and surface conditioning. Laser-synthesized Au and TiN NPs offer exceptional purity (no contamination by by-products or ligands) and unusual surface chemistry. Therefore, these NPs present a viable alternative to chemically synthesized counterparts. This work presents comparative analysis of pharmacokinetics and biodistribution of laser-synthesized 20 nm Au and TiN NPs under intravenous administration in mice model. Our data show that Au NPs and bare TiN NPs are rapidly eliminated from the blood circulation and accumulate preferentially in liver and spleen, while coating of TiN NPs by hydrophilic polymer polyethylene glycol (PEG) significantly prolongates blood circulation time and improves delivery of the NPs to tumor. We finally discuss potential applications of laser synthesized Au NPs in SERS, SEIRA and electrocatalysis, while TiN nanoparticles are considered as promising agents for photothermal therapy and photoacoustic imaging.

Bare laser-synthesized plasmonic Au and TiN nanoparticles as functional additives to polymer nanofiber platforms for tissue engineering applications

Exhibiting strong optical absorption in the visible – near-infrared, plasmonic nanomaterials can be used as transducers in optical biosensing, contrast agents in bioimaging and synthesizers of photothermal therapy. Such functionalities promise their employment as functional elements in tissue engineering platforms, but such applications typically require ultraclean nanomaterials to minimize toxicity problems, which is not easy using conventional chemical synthesis routes. We recently demonstrated the possibility of fabricating ultraclean bare (ligand-free) plasmonic Au and TiN nanoparticles by ultrashort laser ablation in liquid ambient. Exempt of any toxic contaminants and exhibiting a series of imaging and therapeutic functionalities, these nanomaterials present promising objects for various biomedical applications. Here, we review our recent progress in the co-electrospinning of laser-synthesized Au and TiN nanoparticles with polymers to form functionalized matrices for tissue engineering.

Influence of Duty Cycle and Pulse Frequency on Structures and Performances of Electrodeposited Ni-W/TiN Nanocomposites on Oil-Gas X52 Steels

This paper describes the pulse current electrodeposition (PCE) mediated preparation of Ni-W/TiN nanocomposites. Pulse current electrodeposition (PCE) was used to make Ni-W/TiN nanocomposites. The nanoindentation, wear, and corrosion of deposited Ni-W/TiN nanocomposites were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The influence of pulse frequency (PF) and duty ratio on the shape, structure, phase structure, wear, and corrosion resistance of Ni-W/TiN nanocomposites was studied. When the duty cycle (DC) was 10%, the results demonstrated that a considerable number of fine grains were present on the deposited Ni-W/TiN nanocomposites, forming smooth, uniform, and fine organization. Increasing DC decreased the content of TiN nanoparticles in Ni-W/TiN nanocomposites. The content of TiN nanoparticles reduced from 11.3 wt % to 7.3 wt % by increasing the DC from 10% to 50%. In contrast, as the PF was increased, the TiN content in Ni-W/TiN nanocomposites increased. When the PF was increased from 50 Hz to 150 Hz, the TiN content increased from 6.4 wt % to 9.6 wt %, respectively. Furthermore, with a PF of 150 Hz and a DC of 10%, the produced Ni-W/TiN nanocomposites had an average hardness of 934.3 HV with ~39.8 µm of an average thickness. The weight loss of the Ni-W/TiN nanocomposites was just 17.2 mg at a PF of 150 Hz, demonstrating the excellent wear resistance potential. Meanwhile, the greatest impedance was found in Ni-W/TiN nanocomposites made with a DC of 10% and a PF of 150 Hz, indicating the best corrosion resistance.