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Environmental effect on the fluorescence lifetime and quantum yield of single extended luminescent conjugated polymers

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Journal of Physical Chemistry C 2009年第43期113卷 18681-18688页

作者： Rassamesard, Areefen Huang, Yi-Fang Lee, Hsu-Yang Lim, Tsong-Shin Li, Ming Chung White, Jonathon David Hodak, Jose Hector Osotchan, Tanakorn Peng, K.Y. Chen, S.A. Hsu, Jui-Hung Hayashi, Michitoshi Fann, Wunshain Institute of Atomic and Molecular Sciences Academia Sinica P.O. Box 23-166 Taipei 106 Taiwan Department of Physics Faculty of Science Mahidol University Rama 6 Rd. Bangkok 10400 Thailand Department of Physics Tunghai University Taichung 407 Taiwan Department of Chemistry National Tsing Hua University Hsinchu 30013 Taiwan Molecular Science and Technology Program Taiwan International Graduate Program Academia Sinica Taipei 115 Taiwan Center for Condensed Matter Sciences National Taiwan University Taipei 106 Taiwan Department of Photonics Engineering Yuan Ze University Taoyuan Taiwan ThEP Center Commission of Higher Education 328 Si Ayuthaya Rd Bangkok 10400 Thailand Department of Chemical Engineering National Tsing Hua University Hsinchu 300 Taiwan Department of Materials and Optoelectronic Science National Sun Yat-sen University Kaohsiung Taiwan Institute of Polymer Science and Engineering National Taiwan University Taipei 106 Taiwan Department of Physics National Taiwan University Taipei 106 Taiwan

To investigate the local environment's effect on the lifetime and quantum yield of extended polymer chains in the absence of intra-and interchain aggregation, short, rodlike polymers of poly(2,5-di-n-octyloxy-1,4- phenylenevinylene) (DO-PPV) were dissolved in chloroform and then embedded in a polystyrene matrix. The fluorescence lifetime was found to increase by 45% in moving from the solution to the matrix form. By using the absorption and emission spectra of the chloroform solution to estimate the radiative and nonradiative rate constants for the polymer in solution, along with calculations based on an exciton model, the corresponding decay rate constants for the polymer embedded in the matrix were obtained. The close agreement between the calculated and experimental values of fluorescent lifetime in the matrix proved the applicability of the exciton model used. On the basis of the model, the average quantum yield of isolated polymers in the matrix was calculated to be a factor of 2 higher than in solutionsan effect arising from a 59% decrease in the nonradiative rate constant and, to a smaller extent, from a 20% increase in the radiative decay rate due to the different dielectric constants of the environments. These results suggest that by extending and isolating single luminescent polymers, high quantum yield devices are possible. © 2009 American Chemical Society.

关键词： Rate constants

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Gratings on porous silicon structures for sensing applications

Gratings on porous silicon structures for sensing applicatio...

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Conference on Lasers and Electro-Optics, CLEO 2009

作者： Liscidini, M. Wei, X. Kang, C. Rong, G. Retterer, S.T. Patrini, M. Sipe, J.E. Weiss, S.M. Department of Physics University of Toronto 60 St. George St Toronto M5S 1A7 ON Canada Department of Electrical Engineering and Computer Science Vanderbilt University Nashville TN 37235 United States Interdisciplinary Graduate Program in Materials Science Vanderbilt University Nashville TN 37235 United States Center for Nanophase Materials Sciences Oak Ridge National Laboratory Oak Ridge TN 37831 United States CNISM and Dipartimento di Fisica 'A. Volta' Università degli Studi di Pavia via Bassi 6 27100 Pavia Italy

We investigate the use of gratings on porous silicon structures for sensing applications. Examples of two classes of systems are studied: grating-coupled waveguide biosensors, and diffraction-based biosensors. © ... 详细信息

ISBN: (纸本)9781557528698

关键词： Biosensors

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Tandem multimer expression of angiotensin I-converting enzyme inhibitory peptide in Escherichia coli

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Biotechnology Journal 2009年第9期4卷 1345-1356页

作者： Fida, Hasan M. Kumada, Yoichi Terashima, Masaaki Katsuda, Tomohisa Katoh, Shigeo Department of Molecular Science and Material Engineering Graduate School of Science and Technology Faculty of Engineering Kobe Japan Department of Chemistry and Materials Technology Kyoto Institute of Technology Kyoto Japan Department of Biosphere Sciences School of Human Science Kobe College Nishinomiya Japan Department of Chemical Engineering Hanyang University 1271 Sa-3-dong Sangrok-gu Ansan 426-791 Korea Republic of Department of Process Engineering and Applied Science Food Science and Technology Program Dalhousie University 1360 Barrington Street Halifax NS B3J 2X4 Canada

It is common for small tandem peptide multimer genes to be indirectly inserted into expression vectors and fused with a protein tag. In this study, a multimer of the tandem angiotensin I-converting enzyme inhibitory peptide (ACE-IP) gene was directly transferred to a commercially available vector and the designed gene was expressed as a repeated peptide in Escherichia coli BL21(DE3)pLysS. The process further developed in our study was the construction of six-repeated ACE-IP synthetic genes and their direct insertion. Protein expression in inclusion bodies was confirmed by SDS-PAGE and Western blot. Acid hydrolysis of inclusion bodies produced single-unit peptides through cleavage of the aspartyl-prolyl bonds. This cleaved recombinant peptide (rACE-IP) was purified using immuno-affinity chromatography followed by reversed phase-HPLC. 105-115 mg of the lyophilized recombinant peptide was obtained from 1 L E. coli culture. In vitro biological activity of rACE-IP was indistinguishable from that of the natural peptide produced by hydrolysis in artificial gastric juice or by acidic hydrolysis. The rACE-IP prepared by recombinant DNA technology and solid-phase synthesis methods showed a similar IC50. This strategy could be used for the expression of important peptides, which have N-terminal proline (P) and C-terminal aspartic acid residues (D) for commercial applications, e.g. functional foods and drinks. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

关键词： Peptides

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Probing surface plasmons in individual Ag nanoparticles in the ultra-violet spectral regime

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Nanotechnology 2009年第23期20卷 235705页

作者： Chu, Ming-Wen Sharma, Pradeep Chang, Ching-Pin Liou, Sz Chian Tsai, Kun-Tong Wang, Juen-Kai Wang, Yuh-Lin Chen, Cheng Hsuan Center for Condensed Matter Sciences National Taiwan University Taipei 106 Taiwan Institute of Atomic and Molecular Sciences Academia Sinica Taipei 106 Taiwan Taiwan International Graduate Program Academia Sinica Taipei 106 Taiwan Department of Physics National Taiwan University Taipei 106 Taiwan Department of Materials Science and Engineering National Taiwan University Taipei 106 Taiwan

Previous investigations of surface plasmons in Ag largely focused on their excitations in the visible spectral regime. Using scanning transmission electron microscopy with an electron beam of 0.2nm in conjunction with electron energy-loss spectroscopy, we spectrally and spatially probe the surface plasmons in individual Ag nanoparticles (∼30nm), grown on Si, in the ultra-violet spectral regime. The nanomaterials show respective sharp and broad surface-plasmon resonances at ∼3.5eV (∼355nm) and ∼7.0eV (∼177nm), and the correlated spectral calculations established their multipolar characteristics. The near-field distributions of the surface plasmons on the nanoparticles were also mapped out, revealing the predominant dipolar nature of the 3.5eV excitation with obvious near-field enhancements at one end of the nano-object. The unveiled near-field enhancements have potential applications in plasmonics and molecular sensing. © 2009 IOP Publishing Ltd.

关键词： Silver nanoparticles

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Microcellular Al2O3 ceramics from wood for filter applications

Microcellular Al2O3 ceramics from wood for filter applicatio...

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作者： Rambo, Carlos Renato Andrade, Tarcisio Fey, Tobias Sieber, Heino Martinelli, Antônio Eduardo Greil, Peter Materials Science and Engineering Graduate Program-PGMAT Chemical Engineering Department-EQA Federal University of Santa Catarina 88040-900 Florianópolis SC Brazil Materials Science and Engineering Graduate Program-PPGCEM UFRN-Federal University of Rio Grande Do Norte 59072-970 Natal RN Brazil Department of Materials Science Glass and Ceramics University of Erlangen-Nuremberg D-91058 Erlangen Germany American Ceramic Society

Microcellular biomorphous Al2O3 was produced by Al-vapor infiltration in pyrolyzed rattan and pine wood-derived biocarbon preforms. At 1600°C the biocarbon preforms reacted with gaseous aluminum to form Al4C3. After oxidation in air at temperatures between 1550° and 1650°C, for 3 h, the biocarbon preforms were fully converted into α-Al2O3. Owing to the high anisotropy of biomorphous Al2O3, the compressive strength behavior was strongly dependent on the loading direction. The compressive strength of the specimens (0.1-11 MPa) is strongly dependent on their overall porosity and their behavior could be explained using the Gibson-Ashby model. The Darcian permeability (k1), as well as the non-Darcian permeability (k 2), increased with an increase of the total porosity. The Darcian permeability of biomorphous Al2O3 was found to be in the range of 1-8 × 10-9 m2, which is in the order of magnitude of gas filters, and, therefore, suitable for several technological applications. © 2008 The American Ceramic Society.

关键词： Wood products

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Light scattering by white-emitting CdSe nanocrystals and traditional YAG:Ce3+ phosphor particles

Light scattering by white-emitting CdSe nanocrystals and tra...

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2008 MRS Fall Meeting

作者： Gosnell, Jonathan D. Weiss, Sharon M. Interdisciplinary Graduate Program in Materials Science Vanderbilt University Station B 350106 Nashville TN 37235 United States Department of Electrical Engineering and Computer Science Vanderbilt University Station B 351824 Nashville TN 37235 United States

ISBN: (纸本)9781615677740

In order for solid state lighting technology to become a mainstream technology, one of the major challenges to overcome is increasing the efficiency of these devices while maintaining a proper color balance. A significant source of efficiency loss in commercial phosphor-based white light-emitting diodes (LEDs) is light scattering off large, micron-sized phosphor particles. The use of recently reported single-size CdSe white-light nanocrystals in place of traditional phosphors, such as YAG:Ce3+, could lead to lower scattering losses and higher device efficiencies as a result of the extremely small CdSe core diameter of approximately 1.5 nm. This work theoretically and experimentally investigates the absorption, scattering, and extinction coefficients and cross sections of CdSe white-light nanocrystals in comparison to YAG:Ce3+ phosphor particles. Calculations were performed based on the Rayleigh approximation and Mie theory of scattering. Experiments were carried out using thin films of encapsulated nanocrystals. By measuring the absorbance and thickness of the films, in addition to the concentration of the nanocrystals, extinction coefficients and cross sections were determined using the Beer-Lambert law. A reasonable agreement was obtained between theoretical and experimental data showing that the size of the particle has a significant impact on the extinction, absorption, and scattering properties of thin films. The considerably reduced scattering from the nanocrystals compared to traditional phosphors, along with their inherent high quality white light emission, makes them a promising candidate for future solid state lighting applications. © 2009 materials Research Society.

关键词： Cadmium compounds

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Temperature Dependent Fluorescence of Nanocrystalline Ce-doped Garnets For Use as Thermographic Phosphors

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MRS Online Proceedings Library 2008年第1期1076卷 1-6页

作者： Hansel, Rachael Allison, Steve Walker, Greg Interdisciplinary Graduate Program in Materials Science Vanderbilt University Nashville USA Oak Ridge National Laboratory Oak Ridge USA Department of Mechanical Engineering Vanderbilt University Nashville USA

Four samples of (Y1−xCex)3(Al1−y Gay)5O12 (where x=0.01, 0.02 and y=0, 0.5) were synthesized via the simple, efficient combustion synthesis method in order to determine the effect of substituting Ga3+ for Al3+ on the temperature-dependent fluorescent lifetime. X-ray diffraction shows that the Ga-doped samples have longer lattice constants and transmission electron microscopy data show that each sample consists of nanocrystallites which have agglomerated in micron-sized particles. Photoluminescence data reveal that the addition of gallium into the YAG:Ce matrix induces a red shift in the absorption spectra and a blue-shift in the emission spectra. The laser-induced fluorescent lifetime was determined as a function of temperature over the range of 0-125°C using two different emission filters. Increasing the amount of dopant ultimately results in a decrease of the fluorescent lifetime. The quenching temperatures for the Ga-doped samples were lower than the samples without gallium. The results of this work show that combustion synthesis is viable method for making highly luminescent, nanocrystalline TGPs. In addition, these results show that the quenching temperature of YAG:Ce can be altered by substituting ions which alter the location of the charge transfer state and by changing the morphology of the sample.

关键词： crystalline sensor dopant

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Nanoscale porous silicon waveguides for biosensing applications

Nanoscale porous silicon waveguides for biosensing applicati...

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21st Annual Meeting of the IEEE Lasers and Electro-Optics Society, LEOS 2008

作者： Rong, G. Wei, X. Kang, C. Liscidini, M. Sipe, J.E. Mernaugh, R.L. Weiss, S.M. Department of Electrical Engineering and Computer Science Vanderbilt University Nashville TN 37235 United States Interdisciplinary Graduate Program in Materials Science Vanderbilt University Nashville TN 37235 United States Department of Physics Institute for Optical Sciences University of Toronto Toronto ON M5S 1A7 Canada Department of Biochemistry Vanderbilt University Nashville TN 37235 United States

Nanoscale porous silicon waveguides, both on silicon substrates and free-standing membranes, are explored for biosensing applications. Measured detection limits in the nanomolar range are reported for DNA sensing. ... 详细信息

ISBN: (纸本)9781424419326

关键词： Porous silicon

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Linear and nonlinear plasmonic effects modulated by a metalinsulator transition

Linear and nonlinear plasmonic effects modulated by a metali...

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IEEE/LEOS Winter Topical Meeting Series

作者： R. F. Haglund E. U. Donev L. C. Feldman D. W. Ferrara R. Lopez J. Y. Suh K.A. Tetz Department of Physics and Astronomy Interdisciplinary Graduate Program in Materials Science and Vanderbilt Institute for Nanoscale Science and Engineering Vanderbilt University Nashville TN USA Department of Physics and Astronomy and Department of Materials Science and Engineering Rutgers University Piscataway NJ USA Department of Physics and Astronomy and Institute for Advanced Materials Nanoscience and Technology North Carolina State University Chapel Hill NC USA

Localized and propagating plasmonic effects in noble-metal nanostructures are receiving worldwide attention as potential enabling principles for optical and electro-optic devices. A critical need in plasmonic device design is a general technique for active modulation of the plasmon response. In this paper, we describe the use of a reversible, solid-solid phase transition in VO 2 to modulate plasmonic response. Case studies are drawn from experiments on nano structured hole and particle arrays in which VO 2 acts as a modulator by altering the local dielectric constant.

关键词： Plasmons Optical devices Optical propagation Nanostructures Nonlinear optical devices Nonlinear optics Optical modulation Electrooptic devices Phase modulation Dielectric constant

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Nanoscale porous silicon waveguides for biosensing applications

Nanoscale porous silicon waveguides for biosensing applicati...

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IEEE Photonics Conference (IPC)

作者： G. Rong X. Wei C. Kang M. Liscidini J. E. Sipe R. L. Mernaugh S. M. Weiss Department of Electrical Engineering and Computer Science Vanderbilt University Nashville TN USA Interdisciplinary Graduate Program in Materials Science Vanderbilt University Nashville TN USA Department of Physics and Institute for Optical Sciences University of Toronto Toronto ONT Canada Department of Biochemistry Vanderbilt University Nashville TN USA

关键词： Silicon Biosensors Optical waveguides Gratings Biomembranes Resonance DNA Biological materials Optical materials Optical surface waves

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