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ABSTRACT Exposures of occupants in school buses to on-road vehicle emissions, including emissions from the bus itself, can be substantially greater than those in outdoor settings. A dual tracer method [...]

The production of a variety of ion-molecule complexes between metal cations and coronene or pyrene is described. The complexes were produced using laser vaporization of mixed powder samples containing the PAH with pure metal, metal halides, metal oxides, metal carbides, or organometallic complexes.

An examination is done on the optical absorption spectra, which were calculated in liquid solutions at ambient temperature for comparatively nonpolar chromophores -- polymethine dyes, polycyclic hydrocarbons and tetrapyrrolic compounds. In conclusion, the long-range electrostatic interactions must lead to the slope values less than Bt.

A novel series of thermally stable yellow light emitting fluoranthenes with an amine donor and a nitrile acceptor is prepared from a ketene-S,S-acetal under mild conditions without using an organometal catalyst. The organic light emitting device of yellow fluoranthene has displayed low turn-on voltage and maximum brightness with luminance efficiency of 2.0 Cd/A without using any dopant.

The fabrication of two distinct supramolecular species of perylene bisimide by mixing melamine-appended perylene bisimides (MPBIs) and cyanurates is described. Supramolecular architectures are determined by the number of carbon atoms at the linker moieties of MPBIs and can be applied to generate a variety of other functional [pi]-conjugated molecules.

Five core-cyanated perylene carboxylic diimides end-functionalized with fluorine-containing linear and cyclic substituents are prepared and used in the fabrication of air-stable n-channel organic thin-film field-effect transistors. The studies have shown that the role of the fluorine functionalization in the air-stable n-channel operation of the transistors is very different.

The isolation and X-ray crystallographic structural characterization of two conformers arising from rotation along a diacetylenic bond is reported. The results demonstrate the [pi]-stacking in novel pyrene derivatives in solution as well as in solid state.

The studies of the physicochemical properties of host-guest complexes with polycyclic aromatic hydrocarbon probes (guests) varying in size from four (pyrene) to five (benzo(e)pyrene) and seven aromatic rings (coronene) is reported. The results indicate that the hydrophobic guest probes prefer to locate in the hydrophobic cavities formed by the host molecules in an aqueous solution.

A study was conducted to understand the role of phenyl radical in the growth of PAHs (polycyclic aromatic hydrocarbons), pyrolysis of toluene with and without benzene. The results showed that the PAC (phenyl addition/cylization) mechanism is efficient for the growth of PAHs without the triple fusing site, for which the HACA (hydrogen abstraction/[C.sub.2][H.sub.2] addition) step is inefficient, and produces PAHs with five-membered rings.

The synthesis and photophysical properties of a series of covalently bound cofacial dimers and trimers of perylene-3,4:9,10-bis(dicarboximide) (PDI) and 1,7-bis(3',5'-di-t-butylphenoxy)perylene-3,4:9,10-bis(dicarboximide) (PPDI) is demonstrated. The dimer-like nature of lowest excited singlet states of PDI and PPDI trimers suggest that the structural distortions that accompany formation of the trimers are sufficient to confine the electronic interaction on two chromophore within the systems.

The steady state and time-resolved spectroscopies are used foe examining the photoinduced electron transfer (ET) from the singlet excited state of rubrene to p-benzoquinone derivatives in benzonitrile (PhCN). It is shown that the charge recombination (CR) in a highly exergonic ET has occurred at a longer distance with large solvent reorganization energy, thus resulting in faster ET to the ground state than to the triplet excited state that is lower in energy than the CS state.

The adsorption properties of self-assembly of rubrene molecules on the copper oxide nanotemplate formed by high-temperature exposure of Cu(110) to molecular oxygen are examined. The analysis has shown a complex variety of self-assembled motifs, driven by competing effects like the chemical affinity between the organic molecule and the surface, surface coverage and spatial confinement of the rubrene molecules within the rows of the template.

Numerous experiments are conducted to explain the symmetry of two-photon absorption tensor of fluorophores dissolved in liquid solutions. The first excited electronic state of the compound is found to be the dominating intermediate.

The structural, thermodynamic, and mid-infrared spectroscopic studies of neutral and cationic model iron-polycyclic aromatic hydrocarbon (PAH) complexes with increasing size, such as, naphthalene, ([C.sub.10][H.sub.8]), pyrene ([C.sub.16][H.sub.10]), and coronene ([C.sub.24][H.sub.12]) is reported. The result shed light onto the astrophysical implications of iron-PAH complexes in the conditions of the interstellar medium.

In situ x-ray absorption spectroscopy is used for investigating conformation and molecular orientation of rubrene films grown on Au(111) and Si(111). Ex situ atomic force microscopy measurements show that rubrene film grown on Au(111) is crystalline and the growth direction is along its crystallographic c axis.

The comparison results from the optical spectra of rubrene single crystals to those of the molecule in solution are presented. The results reveal that complex dielectric tensor is derived in the spectral region of the excitonic transitions of the crystal between 2.2 eV band 4.4 eV.

An asymmetric perylene tetracarboxylic diimide (PTCDI) molecule is employed for the preparation and fabrication of millimeter long nanobelts by a seeded one-dimensional (1-D) self-assembling method. The long length of the belts allows efficient conductivity modulation through surface doping, which in turn makes them extremely useful for various optoelectronic applications.

A novel design principle was adopted to incorporate two strongly demanding factors for molecular packing, a planar aromatic core and multiple hydrogen-bonding sites into a single molecule structure. The designed molecule, an amide-substituted tetraphenylpyrene derivative C6TPPy, successfully showed a piezochromic luminescence by pressure-induced alteration of the molecular packing and subsequent heating-induced restoration.

A regioselective oxidative cyclization reaction promoted by FeCl3 is developed for the construction of a series of polycyclic aromatic hydrocarbons containing a 10H-indeno[1,2-b]triphenylene skeleton. Their photophysical properties in dilute solution are studied for possible applications in optoelectronic devices.

The adsorption and photochemical reactivity of naphthalene, a typical polycyclic aromatic hydrocarbon (PAH), in thin films of water films formed on borosilicate glass surface in a horizontal flow-reactor, are investigated. The results reveal that the equilibrium partition constant between the water film and air decreases with increase in temperature.

A group of aggregating flat and rigid polycyclic aromatic hydrocarbons (PAHs) that form emissive aggregates and extend the device lifetime when used as light-emitting-layer (LEL) additives are described and the role of aggregation phenomenon in the lifetime increase are investigated. In spite of the similarity between the two additives with respect to their initial device performance, perylene's ability to aggregate has correlated with the eight times longer half-life versus that for 2,5,8,11-tetra-t-butylperylene (TBP).

A synthetic strategy promising the establishment of a new star-shaped and linear polycyclic aromatic hydrocarbons (PAHs) family with distinct molecular topologies is developed. The electronic and photophysical properties are studied by orthogonal comparisons of the absorption and fluorescence spectra in THF solutions, which give insight into the interactions among aromatic submoieties in each molecule.

Femtosecond and picosecond transient grating spectroscopy is used to study ultrafast relaxation dynamics for photoexcited PAH cations isolated in boric acid glass. No temperature dependence or isotope effect was observed for the fast component, whereas the slow component exhibits both the H/D isotope effect (1.1-1.3) and a strong temperature dependence (15 to 300 K).