Optical Property And High Pressure Effects Of PPV And Nano Oxide

Pressure, temperature and composition play as three dominate parameters to determine the state of substance. The change of temperature and composition is the usual method for studying the property of matter and for the improvement. While with high pressure technique we can also obtain new materials which cannot be prepared at atmospheric pressure. The essential effect of pressure is to reduce interatomic distance, which leads to modification in lattice constants of crystalline material as well as to change in atomic positions within crystal-lographic cells, resulting in phase transition. Reductions of lattice spacing and force constants between atoms induce modifications in the band structures of solids and thus in electronic properties and optical properties. Thus the physical and chemical properties of substances at high pressure are quite abundant. In this thesis, the high pressure effects for the three kinds of substance, i.e. conjugated polymer, rare earth chelates, and nanocrystal/nanotube doped with rare earth ions, are investigated in order to give a more comprehensive understanding of new phenomena at high pressure. The thesis is made of following six chapters.In Chapter One, we present a brief introduction to historic development and research methods in high pressure study as well as a review on the recent progress in the study of high pressure effects.In Chapter Two, we synthesized two poly (p-phenyleneviny-lene)(PPV) samples, one is without filtering the low molecular weight molecules and another is that with the low molecular weight (up to 2000) molecules filtered. The FT-IR and Raman spectra indicate that there is no obvious difference for the PPV structures between two samples. However, it is found in the photoluminescence (PL) spectrum for the sample with low molecular weight molecules filtered, the peak at 510 nm disappears while the intensity for another peak at 550 nm increases. This is because, for the PPV with the low molecular weight molecules filtered, the enhanced PPV chain distortion results in the change of aggregation structure of molecular chain.The pressure effect on the PL and Raman spectra of the PPV with the low molecular weight molecules filtered has been investigated with a diamond anvil cell (DAC) under the hydrostatic pressure condition. It is found that the intensity ratios for Raman bands, I₁₁₆₇/I₁₆₂₂ and I₁₅₄₃/I₁₆₂₂ increase with pressure. This indicates that the conjugated length of PPV is enhanced at high pressure. In addition, appearing of a new Raman band at 1190 cm(-1) cor-...