Maximum Absorption Wavelength (maximum + absorption_wavelength)

Distribution by Scientific Domains

Selected Abstracts

A New Sol,Gel Material Doped with an Erbium Complex and Its Potential Optical-Amplification Application,

L.-N. Sun
Abstract The crystal structure of a ternary Er(DBM)3phen complex (DBM,=,dibenzoylmethane; phen,=,1,10-phenanthroline) and its in-situ synthesis via a sol,gel process are reported. The infrared (IR), diffuse reflectance (DR), and fluorescence spectra of the pure complex and the Er3+/DBM/phen co-doped luminescent hybrid gel, formed via an in-situ method (ErDP gel), have been investigated. The results reveal that the erbium complex is successfully synthesized in situ in the ErDP gel. Excitation at the maximum absorption wavelength of the ligands resulted in the typical near-IR luminescence (centered at around 1.54,,m) resulting from the 4I13/2,,,4I15/2 transition of the Er3+ ion, which contributes to the efficient energy transfer from the ligands to the Er3+ ion in both the Er(DBM)3phen complex and the ErDP gel (an antenna effect). The full width at half maximum (FWHM) centered at 1541,nm in the emission spectrum of the ErDP gel is 72,nm, which has potential for optical-amplification applications. Further theoretical analysis on the Er3+ ion in the ErDP gel shows that it appears to be a promising candidate for tunable lasers and planar optical amplifiers. [source]

Effect of aniline formaldehyde resin on the conjugation length and structure of doped polyaniline: Spectral studies

Ko-Shan Ho
Abstract A DBSA (n -dodecylbenzene sulfate)-complexed aniline formaldehyde [AF(DBSA)1.0] was successfully synthesized with excess aniline (compared with formaldehyde) in the presence of n -dodecylbenzene sulfonic acid (HDBSA), which was complexed with aniline monomer before polymerization. The resin was carefully characterized with 1H and 13C NMR, electron spectroscopy for chemical analysis, and Fourier transform infrared and was demonstrated to be a polymer in which anilines were all complexed with HDBSA and became anilinium salts. A drastic decrease of the maximum absorption wavelength (ultraviolet,visible spectra) of DBSA-doped polyaniline [PANI(DBSA)0.5] was found when AF(DBSA)1.0 was mixed, and this resulted from the reduced conjugation length. A similar effect on PANI(DBSA)0.5 was found when free HDBSAs were mixed with PANI(DBSA)0.5. Visual inspection with an optical microscope revealed that PANI(DBSA)0.5/AF(DBSA)1.0 gave uniform morphologies in various compositions, showing possible miscibility for this system. X-ray diffraction patterns of PANI(DBSA)0.5/AF(DBSA)1.0 showed that the layered structure of PANI(DBSA)0.5 was still present but became shorter in the polyblend because of the presence of AF(DBSA)1.0. Solid-state 13C NMR spectra revealed that the reduced conjugation length was derived from the interaction of alkyl groups between HDBSA, complexed DBSA, and dopant DBSAs. 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3116,3125, 2005 [source]

UV Absorption and Photoisomerixation of p -Methoxycinnamate Grafted Silicone,

Supason Pattanaargson
ABSTRACT p -Methoxycinnamate moieties, UV-B-absorptive chromophores of the widely used UV-B filter, 2-ethylhexyl p -methoxycinnamate (OMC), were grafted onto the 7 mol% amino functionalized silicone polymer through amide linkages. Comparing with OMC, the resulting poly [3(p -methoxycinnamido)(propyl)(methyl)-dimethyl] siloxane copolymer (CAS) showed less E to Z isomerization when exposed to UV-B light. The absorption profiles of the product showed the maximum absorption wavelength to be similar to that of OMC but with less sensitivity to the type of solvent. Poly (methylhydrosiloxane) grafted with 10 mol%p -methoxycinnamoyl moieties was prepared through hydrosilylations of 2-propenyl- p -methoxycinnamate, in which the resulting copolymer showed similar results to those of CAS. [source]

Synthesis, Structure, and Nonlinear Optical Properties of Cross-Conjugated Perphenylated iso -Polydiacetylenes

Yuming Zhao Prof.
Abstract Monodisperse, cross-conjugated perphenylated iso- polydiacetylene (iso- PDA) oligomers, ranging from monomer 15 to pentadecamer 25, have been synthesized by using a palladium-catalyzed cross-coupling protocol. Structural characteristics elucidated by X-ray crystallographic analysis demonstrate a non-planar backbone conformation for the oligomers due to the steric interactions between alkylidene phenyl groups. The electronic absorption spectra of the oligomers show a slight red-shift of the maximum absorption wavelength as the chain length increases from dimer 17,b to pentadecamer 25, a trend that has saturated by the stage of nonamer 22. Fluorescence spectroscopy confirms that the pendent phenyl groups present on the oligomer framework enhance emission, and the relative emission intensity consistently increases as a function of chain length n. The molecular third-order nonlinearities, ,, for this oligomer series have been measured via differential optical Kerr effect (DOKE) detection and show a superlinear increase as a function of the oligomer chain length n. Molecular modeling and spectroscopic studies suggest that iso- PDA oligomers (n>7) adopt a coiled, helical conformation in solution. [source]