Vapor-liquid-solid (VLS) synthesis of alpha-monoclinic selenium and antimony selenide nanowires and sonication synthesis of blue photoluminescent zero-dimensional nanoparticles

Semiconducting nanostructures such as nanowires and 0-D nanoparticles have received great interest due to their improved properties in comparison with macroscopic materials. Therefore, these nanostructures have attracted considerable attention for optoelectronics and biological applications, among others. In this way, this thesis reports the synthesis of alpha-monoclinic selenium and antimony selenide (Sb2Se3) semiconducting nanowires using a physical vapor-liquid-solid (VLS) process for the first time. In addition, synthesis of naturally dispersed Sb2Se 3 0-D nanoparticles using a sonication process is also reported here for the first time.;Crystalline alpha-monoclinic selenium nanowires with diameters in the range between 20 nm and 1im and lengths up to 30 mum were synthesized. The majority of these VLS synthesized nanowires have a diameter of ~50 nm. As-obtained nanowires grew perpendicular to the (053) plane and exhibit an energy band-gap of 2.20 +/- 0.05 eV, showing a blue shift of 0.18 eV relative to the bulk than is attributed to quantum confinement from the most abundant produced nanowires (~50 nm).;Crystalline Sb2Se3 nanowires with diameters in the range between 20 nm and 2mum and lengths up to 30 mum were synthesized. The diameter of the most abundant produced nanowires is ~800 nm. Our nanowires are oriented along the [010] crystallographic direction. Growth along this orientation is being reported for the first time. Due to the anisotropy of the lattice, [010] oriented nanowires have properties different to the ones produced by the other methods that are [001] oriented.;This thesis also analyses the controversial band gap energy results reported in the literature and conclude that is due to incorrect interpretation of experimental measurements. Photoluminescence (PL) measurements of powdered crystalline bulk Sb2Se3 at room temperature and under UV excitation are reported here for the first time. The PL spectra show that Sb2Se3 crystalline exhibits high photoluminescence in the range between 1.79 and 4.35 eV. This photoluminescence seems to be the source of some erroneous energy band gaps that have been reported.;Synthesized Sb2Se3 0-D crystalline nanoparticles have diameters in the range between 2.0 +/- 0.1 nm and 6.0 +/- 0.1 nm, being ~ 3.8 +/- 0.1 nm the most produced size. Sb2Se 3 0-D nanoparticles in suspension exhibited blue luminescence detectable by the eye under UV excitation at room temperature, with a wide PL emission peak at 422 nm (2.94 eV). These Sb2Se3 nanoparticles have on the order of hundred times larger emission than the bulk material with the same molar concentration. Therefore, this effect is the result of the increase in the emission surface due to higher surface to volume ratio.