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276 results on '"Wilson, James N."'

8. Excitation induced emission color change in conjugated polymers

Author

Schoeder, Raoul, Wilson, James N., Bunz, Uwe H.F., and Ullrich, Bruno

Subjects
Molecules -- Research, Molecules -- Chemical properties, Polymers -- Research, Polymers -- Chemical properties, Chemicals, plastics and rubber industries
Abstract

Luminescence color change of poly-(2,5-dioctyl para-phenyleneethynylene) through variations of excitation intensity was reported. The two ways of changing the emission color are possible and para-pheyleneethynylene is expected to be useful in color tuning applications.

Published
2003

14. Polyfluorophores on a DNA backbone: a multicolor set of labels excited at one wavelength

Author

Yin Nah Teo, Wilson, James N., and Kool, Eric T.

Subjects
DNA -- Structure, DNA -- Chemical properties, DNA -- Optical properties, Polystyrene -- Structure, Polystyrene -- Chemical properties, Polystyrene -- Optical properties, Solvation -- Analysis, Ultraviolet radiation -- Usage, Chemistry
Abstract

The identification of a multicolor set of water-soluble oligodeoxyfluoroside (ODF) dyes that exhibit emission colors across the visible spectrum and all of which can be simultaneously excited by long-wavelength ultraviolet (UV) light is described. The results have shown that ODF dyes are useful as labels in biological systems, which has allowed the simultaneous tracking of multiple species by color and the visualization in moving systems where classical fluorophores have failed.

Published
2009

15. Efficient quenching of oligomeric fluorophores on a DNA backbone

Author

Wilson, James N., Yin Nah Teo, and Kool, Eric T.

Subjects
Oligomers -- Research, Oligomers -- Chemical properties, Fluorides -- Chemical properties, Fluorides -- Research, Chemistry
Abstract

Oligomeric DNA-scaffolded fluorophores are efficiently quenched by methyl viologen and other known quenchers. The quenching efficiency has increased with increasing oligomer length and the efficient quenching can occur with oligomers of varied hydrocarbon fluorophores that exhibit excimer/exciplex excited-state emissions.

Published
2007

16. Switching of intramolecular charge transfer in cruciforms: Metal ion sensing

Author

Wilson, James N. and Bunz, Uwe H.F.

Subjects
Intermolecular forces -- Research, Cations -- Chemical properties, Charge transfer -- Observations, Chemistry
Abstract

The dramatic blue and/or red shifts of emission and adsorption upon coordination of metal cations to cruciforms are demonstrated. The optical properties of the cruciforms change via switching of the intramolecular charge-transfer band depending upon the binding preference of the metal.

Published
2005

20. Permanent bubble: arrays from a cross-linked poly(para-phenyleneethynylene): picoliter holes without microfabrication

Author

Erdogan, Belma, Song, Lulu, Wilson, James N., Park, Jung O., and Srinivasarao, Mohan; Bunz, Uwe H. F.

Subjects
Electrophoresis -- Analysis, Laboratory equipment -- Analysis, Organic semiconductors -- Analysis, Chemistry
Abstract

The arrays of self-assembled picoliter holes1-7 fabricated from poly (para-henyleneethynylene) (PPE, 4) are described. The thermal cross-linking of these arrays, leads to their collapse under formation of self-assembled picoliter hole array with a density of approximately 40000 holes per mm2.

Published
2004

24. Preferential end-to-end assembly of gold nanorods by biotin-streptavidin connectors

Author

Caswell, K.K., Wilson, James N., Bunz, Uwe H.F., and Murphy, Catherine J.

Subjects
Biotin -- Research, Nanotechnology -- Research, Gold compounds -- Research, Chemistry
Abstract

The gold nanorods, surface-functionalized with biotin, can be assembled prefentially in an end-to-end fashion upon the addition of a streptavidin linker is reported. These results provide evidence that the chemical reactivity of nanomaterials is shape-dependent and may be useful in construction of future nanoscale assemblies.

Published
2003

25. Chiroptical properties of poly(p-phenyleneethynylene) copolymers in thin films: Large g-values

Author

Wilson, James N., Steffen, Winfried, McKenzie, Trent G., Lieser, Gunter, and Oda, Masao

Subjects
Photoluminescence -- Spectra, Chemistry
Abstract

The amorphous poly[p-bis-(3,7-dimethyloctyl)phenyleneethynylene] is investigated in which all of the PE units are chirally substituted. It is concluded that the prominent peaks in the circular dichroism (CD) and circularly polarized photoluminescence (CPPL) spectra have the same physical origin, which most likely is not an interchain exicton coupling.

Published
2002

34. Reduced fluorescence quenching of cyclodextrin-acetylene dye rotaxanes

Author

Park, Jong S., Wilson, James N., Hardcastle, Kenneth I., Bunz, Uwe H.F., and Srinivasarao, Mohan

Subjects
Chemistry
Abstract

An acetylene dye rotaxane with alpha-cyclodextrin and its free dye (FD) analogue is synthesized using a Heck-Cassar-Sonogasgira-Hagihara-type reaction. The FD with four carboxylic acids is highly sensitive to various metal ions, showing high Stern-Volmer constants, [K.sub.SV] and there is no significant difference in the electronic absorption and emission spectra of free and rotaxanated dyes.

Published
2006

39. Design, testing, and utilization of a spherical shock-recovery system to investigate material response to ultrahigh pressure

Author

Wilson, James N

Subjects
Shock (Mechanics), Materials at high pressures
Abstract

The existing shock recovery systems can be classified as planar or convergent. Both systems are used extensively in the study of materials under high pressure. However, a three-dimensional system capable of substantially higher pressure with the capability of full sample recovery would add a new dimension to the analysis of materials exposed to ultra-high shock pressure. In this thesis, an explosive-based spherical shock-recovery system was designed, tested, and used to perform a series of three-dimensional shock-recovery experiments. A system was desired that would generate extremely high pressure in the sample while maintaining its structural integrity for post-shock analysis. The system consisted of a spherical metallic shell containing a sample of precursor materials at its center. The metallic shell was surrounded by a spherical layer of high explosive. Several detonators were placed at regular intervals around the outside of the explosive layer. To hold the detonators in place during assembly and transport, a spherical brass shell was placed around the explosive. The detonators were placed in holes drilled in the brass shell at the proper locations. To provide confinement for the explosive, this assembly was placed inside a short section of naval gun barrel. The remaining volume of the barrel was filled with sand to aid confinement. Several shock-recovery experiments were performed with the spherical system. Five experiments were performed with samples containing mixtures of nanograde nickel powder and buckeyballs. Two experiments were performed on solid spheres of steel with pearlitic (one inch diameter) and martensitic (1.5 inch diameter) microstructures. The post-shock analysis of the samples consisting of a metallic shell surrounding precursor materials revealed that it is possible to use this system to synthesize materials that under normal conditions are difficult to make. The analysis of the solid spheres revealed that, due to shock loading, a hole was formed at the center of each sphere. In the pearlitic steel sphere numerous changes were made to the microstructure, some of which have not been previously observed. The martensitic sample did not undergo as drastic a change as the pearlitic sample, which by itself is an interesting observation that deserves more study. According to two-dimensional computer simulations performed with the CTH hydocode, this shock-recovery system is capable of producing ultrahigh pressure levels in both solid and powder materials. The simulations indicate that the pressure in the one inch diameter sphere increases from 50 GPa at the surface of the sphere to about 1 TPa at its center, 0.5 inches away.

Published
2001

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