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2008年07月28日

【期刊论文】Simultaneous measurement of electronic and vibrational dynamics to clarify a geometrical relaxation process in a conjugated polymer

封伟

,-0001,():

-1年11月30日

摘要

The real-time vibrational spectroscopy was utilized to obtain both electronic and vibrational dynamics in a conjugated polymer under the same excitation and probing condition by using the same sample and observing at the same time. Most of the conjugated polymers are in an amorphous phase, in which there is a relatively broad distribution of chain length, conjugation length, and degree of interaction strength between neighboring chains. Because of the varieties, a simultaneous measurement of electronic and vibrational dynamics in a broad spectral range is considered to be most powerful to study such systems as conjugated polymers. In the present paper, we performed this type of experiment of the simultaneous probing of electronic and vibrational relaxations at 128 wavelengths. The sample studied here is an amino-moiety-containing conjugated polymer, poly3-hexylthiophene-2,5-diyl-p-dimethylaminobenzylidenequinoidmethene PHTDMABQ, whose monomer is a derivative of a thiophene oligomer. The light source is a few-cycle pulse laser with an ultimate time resolution of 0.2 fs in the visible and near IR ranges. The data containing both electronic relaxation and vibrational dynamics were analyzed to obtain a more reliable relaxation mechanism of the excitations than a combination of individual studies of electronic and vibrational relaxations. By utilizing the ultrafast pumpprobe spectroscopic system, we could identify the exciton state with a -electron delocalized in benzilidene ring. In the polymer PHTDMABQ, the geometrical relaxation from the free exciton to the exciton polaron takes place in 60–100 fs. This time is close to that observed in several polydiacetylenes previously reported. The C-C single bond stretching frequencies of the free exciton and exciton polaron are about 1300 and 1350 cm−1. The coherent molecular vibration after the geometrical relaxation is considered to be a kind of reaction induced coherence. This coherent vibration decays with the time constant of about 450 fs.

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2007年12月28日

【期刊论文】Perylene

封伟, W.

Carbon 43 (2005) 2501-2507,-0001,():

-1年11月30日

摘要

Perylene-sensitized multi-walled carbon nanotubes (PV-MWNT) have been prepared by a π-stacking between nanotubes and perylene derivatives, N,N'-diphenyl glyoxaline-3,4,9,10-perylene tetracarboxylic acid diacidamide (PV). The resultant nanocomposites have been characterized by transmission electron microscope (TEM), UV–vis absorption, photoluminescence (PL) and photocurrent spectra. Long range ordering can be observed in the form of PV-MWNT via π-stacking by TEM. Red-shift in the optical spectra consisting of the UV–vis absorption and PL spectra with the attraction of PV on the surface of the MWNTs were observed. The evident quenching in PL spectra of PV-MWNT was ascribed to the absorption and transfer of recombination energy by MWNT. Photosensitivity spectra demonstrated an increasing photocurrent in the ultraviolet region and a broadening photosensitivity in the red spectral region for solar cells based on PV-MWNT.

Carbon

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    天津大学,天津

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