No description available.

No description available.

No description available.

Luminescent metal organic frameworks (MOFs) are promising new materials with applications as sensors, photocatalysts, and other luminescent devices. Although MOFs retain the chemical and physical properties of their constituents, the properties of the MOF are often altered from those of its building blocks, making rational design and synthesis difficult. Anthracene is a polyaromatic hydrocarbon whose photophysical properties have been found to be easily tuned through structural modifications. The tunability of anthracene makes it an ideal candidate for use in luminescent devices, such as photoprobes and organic light emitting diodes. MOFs designed with π conjugated molecules like anthracene ligands possess similar photophysical properties such as absorption and fluorescence in the UV and visible spectrum. In hopes of better understanding how the photophysical properties of the organic ligand is altered upon incorporation into a MOF, the spectroscopic properties of anthracenedicarboxylic acids were studied before and after integration into zinc based MOFs. Steady state and time resolved measurements were performed on three anthracenedicarboxylic acids: 9,10-anthracenedicarboxylic acid, 2,6-anthracendicarboxylic acid, and 1,4-anthracenedicarboxylic acid. The position of the carboxylic acid groups on anthracene was found to effect the position and structure of the absorption and emission spectra. The difference in the spectra is attributed to the perturbation by the acid groups on certain electronic transitions with dipole moments across two of the three axes of anthracene. The position of the acid groups had different effects on the fluorescence quantum yields and lifetimes of the three anthracenic acids studied. Two of the linkers were synthesized into MOFs through a solvothermal reaction with zinc nitrate, to form PCN-13, from 9,10-anthracenedicarboxylic acid, and [Zn(C₁₆H₈O₄)(H₂O)]_n, from 2,6-anthracenedicarboxylic acid. The luminescent properties of the two MOFs were studied and compared to those of the free based linker. Incorporation of the luminescent anthracenedicarboxylic acids into Zn based MOFs were found to either increase or decrease the luminescent properties of the ligands. / Master of Science

Typescript (photocopy). / Digitized by Kansas Correctional Industries

published_or_final_version / Physics / Master / Master of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

The research described in this dissertation is the first evaluation and application of a new class of optical detectors, two-dimensional charge-coupled device (CCD), for low-light level chemiluminescence and other luminescence spectroscopies. This research conclusively demonstrates the superior qualitative and quantitative performance of spectrometric systems which employ these detectors. It is experimentally shown that a single detector element of a CCD has comparable or superior sensitivity to the most sensitive single channel detectors; photomultiplier tubes (PMT). The results from the application of the CCD detector system to molecular spectroscopies (fluorescence, chemiluminescence, fluorescence detection of high performance liquid chromatography (HPLC) effluents, and chemiluminescence detection of HPLC effluents) and atomic spectroscopies (spatially and spectrally resolved spark and direct current plasma are presented). The results of operating the CCD in specialized readout modes developed in this research termed charge dependent variable binning (CDVB), simultaneous variable binning (SVB), and continuous high speed spectral framing (CHSF) are described and applied. The CDVB and SVB techniques allow very sensitive quantitation of spectrally resolved and unresolved signals with very wide dynamic ranges without prior knowledge of the signal intensity. Finally, CHSF technique provides spectrally resolved temporal study of extended period luminescence emission with millisecond time resolution. The results of unique algorithms to restore the integrity of the image obtained with a two-dimensional CCD detector are described and applied. The algorithms implemented are for removing variations in detector sensitivity and responsivity and spectrometer efficiency, as well as providing digital image filtering.

The research summarized in this dissertation is aimed at the design and exploratory synthesis, characterization, and property investigation of lanthanide-based functional materials. The substances prepared in this work, including small molecular complexes and nanostructured particles, are of fundamental scientific interest as well as practical significance due to the unique chemical and physical properties of the lanthanide elements. Envisioned applications include their uses as light-emitting materials in modern display technology, optical amplifiers, and high-density magnetic recording media. This research seeks to develop general methods for directing the formation of lanthanide materials, particularly as a means of influencing the physical properties of such materials. These efforts are elaborated in distinct yet related projects.In Chapter 2, exploratory synthesis, structural characterization, and photo-physical investigation of adducts of lanthanide β-diketonates with a tridentate neutral ligand, TPTZ are described.In Chapter 3, analogous studies utilizing p,p'-disubstituted bipyridine and phenathroline type bidentate neutral ligands are detailed. The structures of the complexes have been established by single crystal X-ray diffraction. Compositional and structural differences among the various complexes are caused by different structural and electronic properties of the ligands and overall steric compactness of the coordination sphere. Red and green luminescence characteristics of Eu(III) and Tb(III) ions are observed for the corresponding complexes, upon UV excitation, consistent with the well-established ligand-mediated energy transfer and light emission mechanism.In Chapter 4, the electroluminescence properties of various europium complexes are evaluated for their potential as emissive materials in organic light-emitting diodes.The synthesis and characterization of Er-doped LaPO4 nanoparticles are described in Chapter 5 together with the preparation and studies of hybrid nanocomposites composed of nanoparticle-doped sol-gels. A single-mode waveguide system was fabricated, wherein Er-doped nanoparticles solubilized in a sol-gel matrix has shown promising performance in propagating light signals (1.54 µm) without significant optical losses.In Chapter 6, synthesis, electron microscopic characterization and magnetic studies of crystalline Sm(III)- and Eu(III)-doped Fe3O4 nanoparticles are detailed. Magnetic studies suggest the ferromagnetic behavior of the lanthanide-doped Fe3O4 nanoparticles at room temperature and therefore, the significant effects of lanthanide doping.

As a wide band semiconductor with a large binding energy (about 60meV), ZnO is a promising candidate semiconductor material for the next generation of optoelectronic , light emission or high power and high frequency devices. In order to make electrical device from ZnO, it is necessary to investigate optical properties of ZnO.In this thesis, PL setup and the properties of ZnO are introduced briefly and the optical properties of ZnO are investigated in detail. Temperature dependence of PL spectra of ZnO are measured and analyzed. Sharp emission line of PL spectra of rare earth (RE) doped ZnO are also investigated.