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Millbury, OH, United States

De P.K.,Bowling Green State University | De P.K.,Spectra Group Limited, Inc. | Neckers D.C.,Bowling Green State University
Journal of Photochemistry and Photobiology A: Chemistry | Year: 2013

A facile method for preparation of polymer-CdSe quantum dot (QD)-carbon nanotube (CNT) composite under visible light irradiation is described. This photochemical method for such composite formation is based on a photoinduced hole transfer from the CdSe core to the ligand resulting in the formation of polymeric quantum dots on the surface of the CNT. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) methods were used to confirm the formation of thiophene based polymer-QD-CNT composites. The composites maintain the quantum confinement characteristics of the CdSe nanoparticle, retaining its broad absorption in the spectrum of the sun. The composites thus produced can, therefore, be potentially used as the absorbing material in photovoltaic cells. © 2012 Elsevier B.V. Source

Houk A.L.,University of Kansas | Zheldakov I.L.,University of Kansas | Zheldakov I.L.,Spectra Group Limited, Inc. | Tommey T.A.,University of Kansas | And 2 more authors.
Journal of Physical Chemistry B | Year: 2015

The photoisomerization dynamics of trans-stilbene have been well studied in the lowest excited state, but much less is known about the behavior following excitation to higher-lying electronically excited states. This contribution reports a combined study of the spectroscopy and dynamics of two-photon accessible states above S1. Two-photon absorption (2PA) measurements using a broadband pump-probe technique reveal distinct bands near 5.1 and 6.4 eV. The 2PA bands have absolute cross sections of 40 ± 16 and 270 ± 110 GM, respectively, and a pump-probe polarization dependence that suggests both of the transitions access Ag-symmetry excited states. Separate transient absorption measurements probe the excited-state dynamics following two-photon excitation into each of the bands using intense pulses of 475 and 380 nm light, respectively. The initially excited states rapidly relax via internal conversion, leading to the formation of an S1 excited-state absorption band that is centered near 585 nm and evolves on a time scale of 1-2 ps due to intramolecular vibrational relaxation. The subsequent evolution of the S1 excited-state absorption is identical to the behavior following direct one-photon excitation of the lowest excited state at 4.0 eV. The complementary spectroscopy and dynamics measurements provide new benchmarks for computational studies of the electronic structure and dynamics of this model system on excited states above S1. Probing the dynamics of molecules in their higher-lying excited states is an important frontier in chemical reaction dynamics. (Graph Presented). © 2014 American Chemical Society. Source

Spectra Group Limited, Inc. | Date: 2014-11-18

A non-biological simulant liquid that includes about 30 to about 95 parts by weight of a polymer dispersion or a wax emulsion or dispersion, about 5 to about 70 parts by weight of a rheology modifying agent, and a pigment or a pigment combination. The non-biological simulant has a viscosity that is shear-dependent, such that the viscosity is from about 30 cP to about 300 cP at a shear rate from 0 s

Agency: Department of Defense | Branch: Defense Health Program | Program: SBIR | Phase: Phase I | Award Amount: 145.97K | Year: 2011

Several approaches to make a fully functional commercial blood simulant are proposed. The simulant will have similar flow characteristics, tactile properties, color, and coagulation capabilities to blood. In this effort, Spectra Group will formulate a p

Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase I | Award Amount: 100.00K | Year: 2007

Two approaches are proposed for formulating a bond primer that can be cured at ambient or mildly elevated temperatures in 24 (preferably 12) hours. Both approaches use a light source to accelerate cure but the cure acceleration results from different chemical processes. In the first approach, a two pack system will be activated with light to release a base from a photolatent base that will subsequently accelerate anionic cure. In the second, a dual cure system uses a light source to activate the hardening of a free radical curing component while anionic cure will continue at ambient or at the allowed temperatures until final cure is achieved. A combination of both approaches may be needed to achieve the overall goal.

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