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Water-soluble Phosphors for Hypoxia Detection in Chemical and Biological Media

Description: Water-soluble Pt(II) phosphors exist predominantly for photophysical studies. However, fewer are known to be candidates for cisplatin derivatives. If such a molecule could exist, it would be efficient at not only destroying the cancerous cells which harm the body, but the destruction would also be traceable within the human body as it occurred. Herein, research accomplished in chemistry describes the photophysical properties of a water-soluble phosphor. Spectroscopically, this phosphor is unique in that it possesses a strong green emission at room temperature in aqueous media. Its emission is also sensitive to the gaseous environment. These properties have been expanded to both analytical and biological applications. Studies showing the potential use of the phosphor as a heavy metal remover from aqueous solutions have been accomplished. The removal of toxic heavy metals was indicated by the loss of emission as well as the appearance of a precipitate. The gaseous sensitivity was elicited to be used as a potential cancerous cell biomarker. In vivo studies were accomplished in a wide variety of species, including bacteria (E. coli), worms (C. elegans), small crustaceans (Artemia), and fish (D. rerio and S. ocellatus). The phosphor in question is detectable in all of the above. This fundamental research lays the foundation for further expansion into bioinorganic chemistry, and many other possible applications.
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Date: December 2012
Creator: Satumtira, Nisa Tara
Partner: UNT Libraries

Biocompatible Hybrid Nanomaterials Involving Polymers and Hydrogels Interfaced with Phosphorescent Complexes and Toxin-Free Metallic Nanoparticles for Biomedical Applications

Description: The major topics discussed are all relevant to interfacing brightly phosphorescent and non-luminescent coinage metal complexes of [Ag(I) and Au(I)] with biopolymers and thermoresponsive gels for making hybrid nanomaterials with an explanation on syntheses, characterization and their significance in biomedical fields. Experimental results and ongoing work on determining outreaching consequences of these hybrid nanomaterials for various biomedical applications like cancer therapy, bio-imaging and antibacterial abilities are described. In vitro and in vivo studies have been performed on majority of the discussed hybrid nanomaterials and determined that the cytotoxicity or antibacterial activity are comparatively superior when compared to analogues in literature. Consequential differences are noticed in photoluminescence enhancement from hybrid phosphorescent hydrogels, phosphorescent complex ability to physically crosslink, Au(I) sulfides tendency to form NIR (near-infrared) absorbing AuNPs compared to any similar work in literature. Syntheses of these hybrid nanomaterials has been thoroughly investigated and it is determined that either metallic nanoparticles syntheses or syntheses of phosphorescent hydrogels can be carried in single step without involving any hazardous reducing agents or crosslinkers or stabilizers that are commonly employed during multiple step syntheses protocols for syntheses of similar materials in literature. These astounding results that have been discovered within studies of hybrid nanomaterials are an asset to applications ranging from materials development to health science and will have striking effect on environmental and green chemistry approaches.
Date: August 2011
Creator: Marpu, Sreekar B.
Partner: UNT Libraries

Microwave-Assisted Synthesis, Characterization, and Photophysical Properties of New Rhenium(I) Pyrazolyl-Triazine Complexes

Description: The reaction of the chelating ligand 4-[4,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)-1,3,5-triazin-2-yl]-N,N-diethyl-benzenamine, L, with pentacarbonylchlororhenium by conventional heating method produces the complexes fac-[ReL(CO)3Cl2] and fac-[Re2L(CO)6Cl2] in a period of 48 hours. The use of microwaves as the source of heat and the increase in the equivalents of one of the reactants leads to a more selective reaction and also decreases the reaction time to 1 hour. After proper purification, the photophysical properties of fac-[ReL(CO)3Cl] were analyzed. The solid-state photoluminescence analysis showed an emission band at 628 nm independent of temperature. However, in the solution studies, the emission band shifted from 550 nm in frozen media to 610 nm when the matrix became fluid. These results confirm that this complex possess a phenomenon known as rigidochromism.
Date: May 2010
Creator: Salazar Garza, Gustavo Adolfo
Partner: UNT Libraries

MULTI-MAGNON LUMINESCENCE SIDEBANDS IN ANTIFERROMAGNETS

Description: Using pulsed excitation and detection, the authors have observed multi-magnon ({le} 7) luminescence sidebands of the {sup 4}T{sub 1g} ({sup 4}G) {yields} {sup 6}A{sub 1g} ({sup 6}S) excitonic transition in MnF{sub 2}, KMnF{sub 3}, and RbMnF{sub 3}. A simple model is proposed to explain the results qualitatively.
Date: December 1, 1977
Creator: Chiang, T.C; Salvi, P.; Davies, J. & Shen, Y.R
Partner: UNT Libraries Government Documents Department

Microwave-Assisted Synthesis and Photophysical Properties of Poly-Imine Ambipolar Ligands and Their Rhenium(I) Carbonyl Complexes

Description: The phenomenon luminescence rigidochromism has been reported since the 1970s in tricarbonyldiimine complexes with a general formula [R(CO)3LX] using conventional unipolar diimine ligands such as 2,2;-bipyridine or 1,10-phenanthroline as L, and halogens or simple solvents as X. As a major part of this dissertation, microwave-assisted synthesis, purification, characterization and detailed photoluminescence studies of the complex fac-[ReCl(CO)3L], 1, where L = 4-[4,6-bis(3,5-dimethyl-1H-pyrazol-1-yl]-N,N-diethylbenzenamine are reported. The employment of microwaves in the preparation of 1 decreased the reaction time from 48 to 2 hours compared to the conventional reflux method. Stoichiometry variations allows for selective preparation of either a mononuclear, 1, or binuclear, fac-[Re2Cl2(CO)6], 2, complex. The photophysical properties of 1 were analyzed finding that it possesses significant luminescence rigidochromism. The steady state photoluminescence emission spectra of 1 in solution shift from 550 nm in frozen media to 610 nm when the matrix becomes fluid. Moreover, a very sensitive emission spectral analysis of 0.1 K temperatures steps shows a smooth transition through the glass transition temperature of the solvent host. Furthermore, synthetic modifications to L have attained a family of ambipolar compounds that have tunable photophysical, thermophysical and other material properties that render them promising candidates for potential applications in organic electronics and/or sensors - either as is or for their future complexes with various transition metals and lanthanides.
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Date: August 2017
Creator: Salazar Garza, Gustavo Adolfo
Partner: UNT Libraries

Photophysics and Photochemistry of Copper(I) Phosphine and Collidine Complexes: An Experimental/Theoretical Investigation

Description: Copper(I) complexes have been studied through both experimental and computational means in the presented work. Overall, the work focuses on photophysical and photochemical properties of copper(I) complexes. Photophysical and photochemical properties are found to be dependent on the geometries of the copper(I) complexes. One of the geometric properties that are important for both photochemical and photophysical properties is coordination number. Coordination numbers have been observed to be dependent on both ligand size and recrystallization conditions. The complexes geometric structure, as well as the electronic effects of the coordination ligands, is shown both computationally as well as experimentally to affect the emission energies. Two-coordinate complexes are seen to have only weak emission at liquid nitrogen temperature (77 K), while at room temperature (298 K) the two-coordinate complexes are not observed to be luminescent. Three-coordinate complexes are observed to be luminescent at liquid nitrogen temperature as well as at room temperature. The three-coordinate complexes have a Y-shaped ground (S0) state that distorts towards a T-shape upon photoexcitation to the lowest lying phosphorescent state (T1). The geometric distortion is tunable by size of the coordinating ligand. Luminescence is controllable by limiting the amount of non-radiative emission. One manner by which non-radiative emission is controlled is the amount of geometric distortion that occurs as the complex undergoes photoexcitation. Bulky ligands allow for less distortion than smaller ligands, leading to higher emission energies (blue shifted energies) with higher quantum efficiency. Tuning emission and increasing quantum efficiencies can be used to create highly efficient, white emitting materials for use in white OLEDS.
Date: August 2011
Creator: Determan, John J.
Partner: UNT Libraries

A Computational Investigation of the Photophysical, Electronic and Bonding Properties of Exciplex-Forming Van der Waals Systems

Description: Calculations were performed on transition-metal complexes to (1) extrapolate the structure and bonding of the ground and phosphorescent states (2) determine the luminescence energies and (3) assist in difficult assignment of luminescent transitions. In the [Pt(SCN)4]2- complex, calculations determined that the major excited-state distortion is derived from a b2g bending mode rather than from the a1g symmetric stretching mode previously reported in the literature. Tuning of excimer formation was explained in the [Au(SCN)2]22- by interactions with the counterion. Weak bonding interactions and luminescent transitions were explained by calculation of Hg dimers, excimers and exciplexes formed with noble gases.
Date: December 2007
Creator: Sinha, Pankaj
Partner: UNT Libraries

Luminescence Resonance Energy Transfer-Based Modeling of Troponin in the Presence of Myosin and Troponin/Tropomyosin Defining Myosin Binding Target Zones in the Reconstituted Thin Filament

Description: Mechanistic details on the regulation of striated muscle contraction still need to be determined, particularly the specific structural locations of the elements comprising the thick and thin filaments. Of special interest is the location of the regulatory component, troponin, on the actin filament and how its presence influences the behavior of myosin binding to the thin filament. In the present study: (1) Luminescence resonance energy transfer was used to monitor potential conformational changes in the reconstituted thin filament between the C-terminal region of troponin T and myosin subfragment 1; (2) Location of troponin in previously derived atomic models of the acto-myosin complex was mapped to visualize specific contacts; and (3) Shortened tropomyosin was engineered and protein binding and ATPase assays were performed to study the effect of myosin binding close to the troponin complex. Analysis of the results suggest the following: (1) Irrespective of calcium levels, the C-terminal region of troponin T is located close to myosin loop 3 and a few actin helices that may perturb strong acto-myosin interactions responsible for force production. (2) Atomic models indicate myosin subfragment 1 cannot attain the post- powerstroke state due to the full motion of the lever arm being sterically hindered by troponin. (3) A shortened tropomyosin with five actin binding modules (instead of the native seven in muscle cells) binds actin contiguously in a head-to-tail manner and serves to increase the periodicity of troponin complexes on the actin filament. Such behavior eliminates the structure of the actin filament being responsible for the binding location of tropomyosin. (4) Differential behavior of myosin subfragment 1 i.e. (a) binding adjacent to troponin and (b) binding further away from troponin, is apparent as tropomyosin and troponin appear to govern the regions or "target zones" where myosin can bind productively along the actin filament. Physiologically, myosins ...
Date: May 2009
Creator: Patel, Dipesh A.
Partner: UNT Libraries

BaBrI:Eu2 + , a new bright scintillator

Description: The scintillation properties of BaBrI:Eu2+ are reported. Crystals were produced by the vertical Bridgman technique in a sealed quartz ampoule. Excellent scintillation properties were measured. A light yield of 81,0007 +- 3000 photons per MeV (ph/MeV) of absorbed gamma-ray energy was measured. An energy resolution (FWHM over peak position) of 4.870.5percent was observed for the 662keV full absorption peak. Pulsed X-ray luminescence measurements show two exponential decay components of 297 and 482 ns with a contribution to the total light output of 23percent and 77percent, respectively. Under X-ray and UV excitation, the emission corresponds to a broadband center at 413 nm. These initial values make BaBrI:Eu2+ one of the brightest and the fastest known Eu2+ doped scintillators.
Date: November 7, 2009
Creator: Bourret-Courchesne, E.D.; Bizarri, G.; Hanrahan, S.M.; Gundiah, G.; Yan, Z. & Derenzo, S.E.
Partner: UNT Libraries Government Documents Department

Selective excitation of the yellow luminescence of GaN

Description: The yellow luminescence of n-type GaN has been studied with selective excitation using a combination of Ar ion and dye lasers. Narrower structures whose peak energies follow the excitation photon energy over the width of the yellow luminescence have been observed. Unlike the yellow luminescence excited by above band gap excitations, these fine structures exhibits thermal activated quenching behavior. We propose that these fine structures are due to emission occurring at complexes of shallow donors and deep acceptors which can be resonantly excited by photons with energies below the band gap. The activation energy deduced from their intensity is that for delocalization of electrons out of the complexes. Our results therefore suggest that there is more than one recombination channel (usually assumed to be due to distant donor-acceptor pairs) to the yellow luminescence in GaN.
Date: July 1, 1999
Creator: Colton, J. S.; Yu, P. Y.; Teo, K. L.; Weber, E. R.; Grzegory, I. & Uchida, K.
Partner: UNT Libraries Government Documents Department

Strong Circularly Polarized Luminescence from Highly Emissive Terbium Complexes in Aqueous Solution

Description: Two luminescent terbium(III) complexes have been prepared from chiral ligands containing 2-hydroxyisophthalamide (IAM) antenna chromophores and their non-polarized and circularly-polarized luminescence properties have been studied. These tetradentate ligands, which form 2:1 ligand/Tb{sup III} complexes, utilize diaminocyclohexane (cyLI) and diphenylethylenediamine (dpenLI) backbones, which we reasoned would impart conformational rigidity and result in Tb{sup III} complexes that display both large luminescence quantum yield ({phi}) values and strong circularly polarized luminescence (CPL) activities. Both Tb{sup III} complexes are highly emissive, with {phi} values of 0.32 (dpenLI-Tb) and 0.60 (cyLI-Tb). Luminescence lifetime measurements in H{sub 2}O and D{sub 2}O indicate that while cyLI-Tb exists as a single species in solution, dpenLI-Tb exists as two species: a monohydrate complex with one H{sub 2}O molecule directly bound to the Tb{sup III} ion and a complex with no water molecules in the inner coordination sphere. Both cyLI-Tb and dpenLI-Tb display increased CPL activity compared to previously reported Tb{sup III} complexes made with chiral IAM ligands. The CPL measurements also provide additional confirmation of the presence of a single emissive species in solution in the case of cyLI-Tb, and multiple emissive species in the case of dpenLI-Tb.
Date: March 15, 2010
Creator: Samuel, Amanda; Lunkley, Jamie; Muller, Gilles & Raymond, Kenneth
Partner: UNT Libraries Government Documents Department

The Luminescence of Chlorophyll-Containing Plant Material

Description: The luminescence of various chlorophyll-containing plant materials has been investigated under a variety of conditions. The results have been shown to be consistent with a mechanism involving the recombination of electrons and holes trapped in a quasi-crystalline lattice. Some details of such a mechanism have been proposed which suggest the mode of entry of the light energy into the photosynthetic pathway.
Date: July 1, 1957
Creator: Tollin, Gordon & Calvin, Melvin
Partner: UNT Libraries Government Documents Department

Distinguishing Sedimentary Depositional Environments on Mars Using In-Situ Luminescence Measurements and Neural Network Analysis.

Description: Although not recognized as a true geologic period on Mars, the term 'Martian Quaternary' emerged at the 2001 LPSC. The phrase helps focus attention on the fact that Mars does indeed exhibit dynamic surface processes andd geomorphic features active on time scales less than 10{sup 6} years. As on earth evolving landscapes can serve as important storehouses for paltoclimatic and paIeoenvironmental records. However, deciphering the 'Quaternary' history of Mars will require the development of 4 new set of tools that are uniquely suited to examining youthful sediments and geomorphic features.
Date: January 1, 2001
Creator: Lepper, K. E. (Kenneth E.) & Whitley, V. H. (Von H.)
Partner: UNT Libraries Government Documents Department

Aqueous Ln(III) Luminescence Agents Derived from a Tasty Precursor

Description: The synthesis, aqueous stability and photophysical properties are reported for a novel tetradentate ligand derived from maltol, a commonly used flavor enhancer. In aqueous solution, this chelate forms stable complexes with Ln(III) cations, and sensitized emission was observed from Eu(III), Yb(III), and Nd(III). A comparison with recently reported and structurally analogous ligands reveals a slightly higher basicity but lower complex stability with Eu(III) [pEu = 14.7 (1)]. A very poor metal centered quantum yield with Eu(III) was observed ({Phi}{sub tot} = 0.04%), which can be rationalized by the similar energy of the ligand triplet state and the Eu(III) {sup 5}D{sub 0} emissive level. Instead, sensitized emission from the Yb(III) and Nd(III) cations was observed, which emit in the Near Infra-Red (NIR).
Date: June 2, 2008
Creator: Jocher, C.J.; Moore, E.G.; Pierce, J.D. & Raymond, K.N.
Partner: UNT Libraries Government Documents Department

Brilliant Sm, Eu, Tb and Dy chiral lanthanide complexes withstrong circularly polarized luminescence

Description: The synthesis, characterization and luminescent behavior of trivalent Sm, Eu, Dy and Tb complexes of two enantiomeric, octadentate, chiral, 2-hydroxyisophthalamide ligands are reported. These complexes are highly luminescent in solution. Functionalization of the achiral parent ligand with a chiral 1-phenylethylamine substituent on the open face of the complex in close proximity to the metal center yields complexes with strong circularly polarized luminescence (CPL) activity. This appears to be the first example of a system utilizing the same ligand architecture to sensitize four different lanthanide cations and display CPL activity. The luminescence dissymmetry factor, g{sub lum}, recorded for the Eu(III) complex is one of the highest values reported, and this is the first time the CPL effect has been demonstrated for a Sm(III) complex with a chiral ligand. The combination of high luminescence intensity with CPL activity should enable new bioanalytical applications of macromolecules in chiral environments.
Date: July 10, 2006
Creator: Petoud, Stephane; Muller, Gilles; Moore, Evan G.; Xu, Jide; Sokolnicki, Jurek; Riehl, James P. et al.
Partner: UNT Libraries Government Documents Department

A [Cyclentetrakis(methylene)]tetrakis[2-hydroxybenzamide]Ligand That Complexes and Sensitizes Lanthanide(III) Ions

Description: The synthesis of a cyclen derivative containing four isophthalamide groups (L{sup 1}) is described. The spectroscopic properties of the Ln(III) complexes of L{sup 1} (Ln = Gd, Tb, Yb, Eu) reveal changes of the UV/visible absorption, circular dichroism absorption, luminescence and circularly polarized luminescence properties. It is shown that at least two metal complex species are present in solution, whose relative amounts are pH dependent. When at pH > 8.0, an intense long lived emission is observed (for [L{sup 1}Tb] and [L{sup 1}Yb]) while at pH < 8.0, a weaker, shorter-lived species predominates. Unconventional Ln(III) emitters (Pr, Nd, Sm, Dy and Tm) were sensitized in basic solution, both in the visible and in the near infra-red, to measure the emission of these ions.
Date: April 30, 2009
Creator: D'Aleo, Anthony; Xu, Jide; Do, King; Muller, Gilles & Raymond, Kenneth N.
Partner: UNT Libraries Government Documents Department

X-ray absorption spectroscopy from H-passivated porous Si and oxidized Si nanocrystals

Description: Quantum confinement in nanoscale Si structures is widely believed to be responsible for the visible luminescence observed from anodically etched porous silicon (por-Si), but little is known about the actual size or shape of these structures. Extended x-ray absorption fine structure data from a wide variety of por-Si samples show significantly reduced average Si coordination numbers due to the sizable contribution of surface-coordinated H. (The IUSI ratios, as large as 1.2, were independently confirmed by ir-absorption and {alpha}-recoil measurements.) The Si coordinations imply very large surface/volume ratios, enabling the average Si structures to be identified as crystalline particles (not wires) whose dimensions are typically <15 {Angstrom}. Comparison of the size-dependent peak luminescence energies with those of oxidized Si nanocrystals, whose shapes are known, shows remarkable agreement. Furthermore, near-edge x-ray absorption fine structure measurements of the nanocrystals shows the outer oxide and interfacial suboxide layers to be constant over a wide range of nanocrystal sizes. The combination of these results effectively rules out surface species as being responsible for the observed visible luminescence in por-Si, and strongly supports quantum confinement as the dominant mechanism occurring in Si particles which are substantially smaller than previously reported or proposed.
Date: November 1, 1994
Creator: Schuppler, S.; Marcus, M.A. & Friedman, S.L.
Partner: UNT Libraries Government Documents Department

Annealing studies of visible light emission from silicon nanocrystals produced by implantation

Description: The annealing behavior of silicon implanted SiO{sub 2} layers is studied using continuous and time-gated photoluminescence (PL). Two PL emission bands are observed. A band centered at 560 nm is present in as implanted samples and it is still observed after 1000 {degrees}C annealing. The emission time is fast (0.2 -2 ns). A second band centered at 780 nm further increases when hydrogen annealing was performed. The emission time is long (1 {mu}s - 0.3 ms).
Date: December 31, 1996
Creator: Ghislotti, G.; Nielsen, B. & Di Mauro, L.F.
Partner: UNT Libraries Government Documents Department

Star in a jar

Description: A sonoluminescing bubble has been modeled as a thermally conducting, partially ionized two-component plasma. The use of accurate equations-of-state, plasma physics, and radiation physics distinguishes our model from all previous models. The model provides an explanation of many features of single bubble sonoluminescence that have not been collectively accounted for in previous models, including the origin of the picosecond pulse widths and spectra. The calculated spectra for sonoluminescing nitrogen and argon bubbles suggest that a sonoluminescing air bubble probably contains only argon, in agreement with a recent theoretical analysis.
Date: August 11, 1997
Creator: Moss, W.C.; Clarke, D.B. & Young, D.A.
Partner: UNT Libraries Government Documents Department