Irish Phthalocyanine Theses

2 entries; January 25, 2004

2003

CODE: 2003IE002
PY: 2003
AU-EN: NITSCHKE, Christian
TY: PhD
TI-EN: Fabrication, Microscopic and Spectroscopic Study of Phthalocyanine Nanoparticles
TUT-EN: Prof. BLAU, W.
UNI: Trinity College, Dublin, Ireland
ABST: A method for the fabrication of phthalocyanine (Pc) particles, with dimensions in the nanoscale regime, has been developed in this present study. Pcs are generally known to exhibit very interesting optical limiting properties. By fabricating Pc particles of nanometer sizes, intermolecular and spatial confinement effects were found to strongly influence the linear and nonlinear optical properties. Linear optical studies were used to investigate the interactions between the monomer molecules inside the particles. The UV/Vis spectra showed a quenched peak which was broadened, exhibiting red and blue shifted elements. Furthermore, a complete loss of fluoresce was observed for Pc in the nanoparticles. Surface enhanced Raman spectroscopy was performed showing a red shifted spectrum for the particles. All these results indicate an ordered system of monomers inside the particles. The Z-Scan technique was employed to examine the optical limiting effects in Pc nanoparticles compared to the corresponding monomers. The nanoparticles were found to have an increased ratio of the excited state absorption to the ground state absorption. This ratio has been utilised as an indicator of optical limiting performance. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) studies were performed to further investigate the particle structure. The observed images point towards an ellipsometric shape for all particles. Furthermore, x-ray diffraction measurements were made to monitor the monomer alignment in the particle. The appearance of distinct diffraction patterns proves a highly ordered or even semi crystalline monomer alignment in the nanoparticle state.
KW: phthalocyanines, nanoparticle, preparation, Optical Limiting

CODE: 2003IE001
PY: 2003
AU-EN: O'FLAHERTY, Sean
TY: PhD
TI-EN: Nonlinear Optical Extinction in Polymer-Carbon Nanotube and Phthalocyanine Systems
TUT-EN: Prof. BLAU, W.
UNI: Trinity College, Dublin, Ireland
ABST: The work presented in this thesis is based on experimental measurements of nonlinear optical extinction or optical limiting of nanosecond laser pulses by phthalocyanine and polymer-carbon nanotube systems. The nonlinear optical experiments were performed using an open aperture z-scan apparatus with 6 ns Gaussian pulses at 532 nm from a frequency doubled Q-switched Nd:Yag laser. Optical limiting resulting from reverse saturable absorption in forty one structurally different modified metallo-phthalocyanine and metallo-naphthalocyanine compounds are investigated where the response exhibited by the materials are theoretically fitted using electronic rate equations applied in a static state approximation. The compounds are modified with the addition of various groups to the peripheral of the macrocyclic systems and with the incorporation of various metals such as Zn, Pb, Co, Cu, Ni, In and Ga into the central cavity of the compounds. The effects on the nonlinear optical response of the basic phthalocyanine compound as a result of varying the central metal and the peripheral functional groups are investigated. The existence of molecular design rules linking the nonlinear optical properties with the molecular structure is also investigated. Two distinctly different polymer and carbon nanostructure composite materials dispersed in solution are investigated. The polymer poly(para-phenylenevinylene-co-2,5-dioctyloxy-meta-phenylenevinylene) was used to form exclusive multi-walled carbon nanotube and polymer composites. The polymer poly(9,9-di-n-octylfluorenyl-2,7’-diyl) was used to form composites consisting of multi-walled carbon nanotubes, other clearly defined carbon nanoparticles and polymer. The fabrication technique and material characterisation steps are described, where it was found that the carbon nanostructures were stably dispersed in the polymer matrix in both cases. A range of each of these composites was prepared and varied according to carbon nanostructure mass content. Furthermore, the scattering of high intensity light from the materials was qualitatively probed and its angular dependence investigated. The nature of the carbon nanostructure inclusions in each material was found to significantly influence the scattering response of the composites. Further investigations of composite dispersions composed of polymer and single-walled carbon nanotubes are conducted using concentration dependent optical extinction. The breaking up of single-walled carbon nanotube bundles through thermal dissociation is detected using nonlinear optical extinction as the probe. Novel scaling laws linking the nonlinear response to the geometrical structure of the nanotube bundles are revealed.
KW: nonlinear optics, optical limiting, nanosecond laser pulses, phthalocyanine, polymer, carbon nanotube, z-scan, Nd:Yag laser

Please also check the theses where the university and/or the year is unknown. If you have additional data about these, please tell me. Only with your help, this project will advance.

Dr. Michael Klaus Engel

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