James M. Duff

Vibrational spectra of lutetium and ytterbium bis-phthalocyanine in thin solid films and SER(R)S on silver island films

Abstract Thin solid films of lutetium and ytterbium diphthalocyanine (Pc 2 ) complexes have been studied using vibrational and electronic absorptions, spontaneous and resonant Raman (RR) and surface enhanced Raman scattering (SERS) on silver island films. Surface enhanced resonance Raman spectra (SERRS) are identical to the RRS spectra with an enhancement factor of about 500. Vibrational data were consistent with a C 4 v molecular symmetry.

Reflection Absorption Infrared Spectra of Thin Solid Films. Molecular Orientation and Film Structure

The calculated and observed vibrational spectra of a new series of perylene tetracarboxylic derivatives (PTCDs) with different alkyl lateral chain lengths (5, 10, 15, and 20 C) are reported. With the use of characteristic vibrational modes, the question about the degree of molecular organization and packing in these PTCD evaporated films has been resolved by using transmission and reflection-absorption infrared spectroscopy (RAIRS) techniques. From vibrational analysis, it was extracted that the molecules are preferentially oriented with the PTCD moiety head on the surface substrate. The molecular organization detected (by using RAIRS) in the evaporated films is not changed when the films are exposed to different solvents, such as water, methanol, and propanol, or when they are annealed up to 155 °C under normal atmospheric conditions or in vacuum. Evidence of molecular packing in the evaporated films is also provided by the observation of strong excimer emission.

INFRARED AND RAMAN SPECTRA OF THIN SOLID FILMS OF 1,2-BIS(PROPYLIMIDO PERYLENE) ETHANE

Abstract The synthesis, the fabrication of thin solid films, the vibrational spectra and the surface-enhanced resonance Raman scattering (SERRS) of a member of a new series of bisperylene materials: 1,2-bis(propylimido perylene) ethane (Pr 2 et) are reported. The objective of the present work was to study the fabrication of submicron evaporated thin solid films of this high molecular weight perylene dye. Transmission and reflection–absorption infrared spectroscopy were used to determine the molecular organisation of the vacuum evaporated nanometric films formed on dielectric and metallic substrates. The electronic absorption and emission spectra are discussed. The vibrational assignment of characteristic wavenumbers is proposed based on experimental data and aided with semi-empirical quantum chemical calculations. The SERRS allows the observation of vibrational fundamentals as well as combinations and overtones.

Surface enhanced resonance Raman scattering imaging of Langmuir–Blodgett monolayers of bis (benzimidazo) thioperylene

The synthesis, spectroscopic characterization and surface-enhanced spectroscopy of a new electro active organic material bis (benzimidazo) thioperylene (Monothio BZP) are reported. Langmuir monolayers of Monothio BZP were successfully formed on water subphase and characterized by the pi-A surface-pressure area isotherm. Langmuir-Blodgett (LB) monomolecular layers of Monothio BZP were fabricated onto glass substrates and onto silver island films for surface-enhanced spectroscopic studies. The results of surface-enhanced resonance Raman scattering (SERRS), SERRS imaging and surface-enhanced fluorescence (SEF) studies for Monothio BZP LB monolayers are reported. Raman imaging (global imaging and point-by-point mapping) of the SERRS signal for a single monomolecular layer on silver islands were obtained using the 514.5 nm laser line. The SERRS imaging permits a visualization of the variation of the SERRS intensity across of the rough metal surface. The SEF was recorded for the excimer emission of aggregates in the LB film. The distance dependence and the enhancement factor of SEF were determined using fatty acid spacing layers. A temperature dependence study of the LB monolayer SERRS and SEF spectra was carried out between -190 degrees and + 200 degrees C confirming the thermal stability of the LB monolayer on silver. The specificity and the sensitivity of SERRS signal on metal island films was probed using mixed LB films with 0.01% molecular ratio of Monothio BZP in Arachidic Acid (AA). The micro-Raman SERRS spectra from ca. 10(-3) attomole of the dye were recorded.

Spectroscopic characterization of thin solid films of a bis(chlorobenzylimidoperyleneimido)octane derivative

The synthesis, the fabrication of thin solid films and the spectroscopic characterization of a member of a new series of bis(perylene) materials, bis(chlorobenzylimidoperyleneimido)octane (BPTCDOc), are reported. The objective of the present work was to study the fabrication of submicron evaporated thin solid films of this high molecular mass perylene dye. The molecular organization of the vacuum evaporated nanometric films formed on dielectric substrates was probed using transmission infrared spectroscopy. Films fabricated on metallic surfaces were studied by reflection-absorption infrared spectroscopy (RAIRS). The fundamental vibrational modes were obtained from the FT-IR, FT-Raman and resonance Raman scattering (RRS) of isotropic solid samples. The vibrational assignment of characteristic wavenumbers is proposed. Surface-enhanced resonance Raman scattering (SERRS) allows the observation of vibrational fundamentals as well as combinations and overtones. The report includes the electronic absorption and emission spectra, extinction coefficients, monomer and excimer fluorescence.

Vibrational spectra and thin solid films of a bi(propylperylenediimide)

The synthesis, the fabrication of thin solid films and the optical spectra of a member of a new series of bis-perylene materials—the bi(propylperylenediimide),N′,N′″-dipropyl-N,N″-bi[perylene-3,4:9,10-bis(dicarboximide)] (Pr2)—are reported. The objective of the present research effort is to provide the fundamental spectroscopic characterization of the ground electronic state and the methods for the fabrication of submicron thin solid films of these new materials which are being tested for performing elementary electrical functions of electronic devices. Pr2 is a high molecular weight perylene dye and the molecular organization formed in vacuum evaporated nanometric films is one of the key elements determining the electrical and optical properties of thin solid films. The spectroscopic techniques used in the study of fundamental vibrational modes were transmission and reflection–absorption infrared spectroscopy (RAIRS). The inelastic scattering was investigated using out-of-resonance excitation (FT-Raman), resonance Raman scattering (RRS) and surface-enhanced resonance Raman scattering (SERRS) on silver island films. The vibrational assignment of characteristic wavenumbers was assisted with semi-empirical quantum mechanical calculations.

Surface-Enhanced Raman Scattering and Imaging of Langmuir—Blodgett Monolayers of Bis(Phenethylimido)perylene on Silver Island Films

The optical spectra of bis(phenethylimido)perylene (PhPTCD) are discussed. Surface-pressure area isotherms of floating Langmuir monomolecular layers have been obtained, and Langmuir-Blodgett (LB) molecular monolayers of the material have been fabricated on silver island substrates for surface-enhanced vibrational studies. The electronic absorption and emission spectra of solutions and thin solid films are described. The vibrational spectra, infrared and Raman for the bulk, and the surface-enhanced Raman (SERS) and resonance Raman scattering (SERRS) spectra of LB monolayers have been obtained. Surface-enhanced fluorescence (SEF) for LB films is also demonstrated. Given the unique properties of the LB coated silver surfaces, the mapping of the SERS/SERRS signal and global Raman images, at a particular vibrational wavenumber, were obtained by using the 780 and 514.5 nm laser lines. The images give a visual picture of the variation of the SERRS and SERS signal intensity on the rough metal surface.

Spectroscopic characterization of thin solid films of 1,3 bis(3- chlorobenzylimido perylene) propane

Abstract This is the first report on the electronic and vibrational spectra of thin solid films of a representative member of new class of materials: 1,3 bis(3-chlorobenzylimido perylene) propane (BPTDPr). The objective of the study is the fabrication of thin solid films and their spectroscopic characterization. It is shown that evaporated films can be prepared for this high molecular weight perylene dye. The molecular organization in the film was probed using transmission and reflection absorption infrared (RAIRS) spectroscopy. The spectroscopic study of the neat materials and the solid films also includes UV–Visible absorption, steady state fluorescence, and FT-Raman scattering. Surface-enhanced resonant Raman spectra of the material adsorbed onto silver island films are also reported.

Material and physicochemical properties of electrostatically-based liquid developers

Abstract During the last decade, liquid immersion development (LID) of a latent electrostatic image has become established as an important alternative to dry toning. In this development method, charged, colloidally stable pigment particles dispersed in a dielectric liquid undergo electrophoresis under the influence of an applied field. These particles thus neutralize a latent electrostatic image of opposite sign, which resides on either a photoreceptor drum or on dielectric paper and results in a hard copy of the latent image being obtained. This paper is concerned with the materials and physicochemical properties of LID developers and has been organized into three parts. In Part 1, the criteria pertaining to selection of the materials for such developers is reviewed. In Part 2, a discussion of the physicochemical properties of the materials is given, while in Part 3 we report some of the results of a systematic study that has been undertaken in order to understand the behavior and limitations of LID toners. The materials package considered in detail in this paper consisted of a dispersion of a laked carbon black in Isopar G that was colloidally stabilized by a soluble alkyl methacrylate based copolymer, Goodyear Pliolite OMS. The developer was electrostatically charged using a variety of heavy metal soaps. Experimental results concerning the colloidal stability, charge-to-mass ratio and evaluation of the final image properties of this developer are discussed. It is concluded that only by making a systematic investigation of the complex interactions that occur in such LID inks will a materials package with optimal shelf life and imaging properties be obtained.

Hydrocarbon Based Inks for Electronic Printing

Electrostatically assisted liquid inks have firmly established themselves as a viable developer option for certain printer applications. In this process a particle, either a pigment or a latex particle, is dispersed and electrostatically charged in a dielectric fluid. Under the influence of an electrostatic field within a development housing the particles undergo electrophoresis to neutralise a latent image that resides on the surface of a dielectric substrate. This results in a hard copy of the latent image being obtained. In this paper we review the properties demanded of a liquid toner, methods of preparing such inks, their colloidal behaviour and their electrical and imaging characteristics. The trade-offs that need to be made when optimising such developers is also discussed. Some conclusions are drawn regarding future materials directions for this toning technology.