A study of thin solid organic films by Fourier transform surface-enhanced Raman scattering and atomic force microscopy.

摘要

Fourier transform surface-enhanced Raman scattering (FT-SERS) in the near-infrared and atomic force microscopy (AFM) have been used to characterize thin solid organic films. The pigments studied were phthalocyanines and perylenes which have applications as charge generation materials in organic photoreceptors. Techniques for film preparation such as Langmuir-Blodgett (LB) deposition and vacuum evaporation are discussed. The literature was reviewed for FT-Raman spectroscopy, surface-enhanced Raman spectroscopy and atomic force microscopy. A model according to Gersten and Nitzan was applied and SERS enhancement factors in the near-IR were calculated for various metal hemi-spheroids. FT-Raman spectra were presented for thin vacuum evaporated films of titanyl phthalocyanine (TiOPc) and vanadyl phthalocyanine (VOPc) prepared on glass substrates held at a range of temperatures during deposition. The frequencies were assigned and different polymorphic forms were apparent. In order to improve the signal intensity, thin films were deposited on metal substrates which produced SERS in the near-IR. The substrates selected for FT-SERS were vacuum evaporated metal island films of copper and gold of 20 nm mass thickness prepared with the glass substrate held at 200$spcirc$C. Thin films of 3 nm mass thickness of VOPc and 3,4:9,10-perylenetetracarboxylic dianhydride (PTCDA) were vacuum evaporated onto the metal island substrates and produced FT-SERS with an enhancement factor of approximately 100. Single Langmuir-Blodgett monolayers of phthalocyanines and perylenes on the metal island substrates gave FT-SERS. The FT-SERS spectra of vacuum evaporated films and LB monolayers were compared with visible laser excitation. Phthalocyanines and perylenes absorb in the visible region and produced surface-enhanced resonance Raman scattering (SERRS). The morphology and structure of single LB monolayers on mica and Si(111) wafers have been determined using atomic force microscopy. AFM results for a perylene on Si(111) showed good agreement with the orientation inferred from reflection-absorption infrared spectroscopy and transmission IR measurements.Dept. of Chemistry and Biochemistry. Paper copy at Leddy Library: Theses u26 Major Papers - Basement, West Bldg. / Call Number: Thesis1994 .J475. Source: Dissertation Abstracts International, Volume: 56-11, Section: B, page: 6134. Co-Advisers: Ricardo Aroca; Gregory Kovacs. Thesis (Ph.D.)--University of Windsor (Canada), 1995.