<p> The use of spectrofluorometers to examine nanomaterials is quite popular using either fluorescence or synchronous measurements. However, understanding how a material&rsquo;s optical properties can influence spectral acquisition are of great importance to accurately characterize nanomaterials. This dissertation presents a series of computational and experimental studies aimed at enhancing the quantitative understanding of nanoparticle interactions with matter and photons. This allows for more reliable spectrofluorometer based acquisition of nanoparticle containing solutions. </p><p> Chapter I presents a background overview of the works described in this dissertation. Correction of the gold nanoparticle (AuNP) inner filter effect (IFE) on fluorophore fluorescence using PEGylated AuNPs as an external reference method is demonstrated in Chapter II. The AuNP IFE is corrected to quantify tryptophan fluorescence for surface adsorbed proteins. We demonstrate that protein adsorption onto AuNPs will only induce ~ 20% tryptophan fluorescence reduction instead of the commonly assumed 100% reduction. </p><p> Using water Raman intensities to determine the effective path lengths of a spectrofluorometer for correction of fluorophore fluorescence is discussed in Chapter III. Using Ni(NO3)2 and K2Cr2O7 as Raman IFE references, the excitation and emission path lengths are found to exhibit chromophore and fluorophore independence, however path lengths are spectrofluorometer dependent. </p><p> Finally, ratiometric resonance synchronous spectroscopy (R2S2) is discussed in Chapter IV. Using a combination of UV-vis and R2S2 spectroscopy, the optical cross sections of a wide range of nanomaterials were determined. Also on-resonance fluorescence in solution is demonstrated for the first time. The nanoparticles discussed range from photon absorbers, scatterers, simultaneous photon absorbers and scatterers, all the way to simultaneous photon absorbers, scatterers, and emitters.</p>

Polymeric materials are attractive candidates for the fabrication of low cost, large area photovoltaic devices. Controlling the band gap of the electroactive polymer is an essential factor in optimizing the resulting devices. In this dissertation, a methodology for the synthesis of well-defined semiconducting materials with tunable band gaps is described. First, the synthesis, characterization, and computational analysis of a variety of trimers consisting of two 3-hexylthiophene units flanking a central moiety consisting of thiophene, or one of the electron donating monomers isothianaphthene or thieno[3,4,b]thiophene will be described. From this analysis the influences of the electronic and steric structure of the materials will be investigated. Several of these trimers will then be used in the synthesis of well-defined, higher order, oligomers of thiophene and isothianaphthene in varying compositions. Polymerization of these oligomers yields polymers of known sequence allowing the band gap of the polymers to be systematically varied. Finally, preliminary investigations into the development of alternate oligomer core units will be described. The control over the band gap that this method affords will be useful in the optimization of polymeric semiconductor devices.

All organic photovoltaics (OPVs) undergo four major processes to convert sunlight in electrical energy. The first process is the absorbance of sunlight. Due to the limit of available acceptor molecules, the burden of light absorbance weighs heavily on the donor material. This thesis focuses heavily on the development of dyes consisting of donor-acceptor dyads and triads for improved light harvesting in OPVs. Squaraine dyes show impressive light harvesting properties with absorbances in the UV to near IR region with extinction coefficients on the order of 105 M-1 cm-1. Unfortunately, improved light harvesting is not enough to insure optimized OPVs. Energy level tuning to increase VOC and insure efficient exciton dissociation is also required. Functionalizing squaraine dyes with electron donating or electron withdrawing groups allow for the systematic tuning of the HOMO energy levels. This tunability allows for the concurrent optimization of bandgap and VOC. Cyanine dyes have been explored for small molecule OPVs due to their impressive absorbance properties. The absorbance of ketocyanine dyes can be tuned by manipulating the strength of the acceptor moiety. Stronger acceptors are better able to stabilize the negative charge in the charge separated state of the dye. This stabilization allows for a greater contribution from the cyanine structure of the dye, thus red shifting the absorbance. Stronger acceptors also increase the communication between the two amine functionalities as demonstrated by cyclic voltammetry. Block copolymers show impressive morphological control through the tuning of the molecular weight of the blocks as well as the compatibility of the functional groups. This allows for the access of morphologies with small, well ordered, and continuous domains thought to be beneficial in the active layer of OPVs. Unfortunately, block copolymers often show inferior light harvesting compared to their conjugated polymer counterparts. Donor-acceptor systems are explored as sensitizers for block copolymer OPVs. Small molecules without twists or bends or acetylene linkers were found to be most effective for lowering the bandgap and aligning the energy levels.

Known methods for production of phenoxyl radicals involve either bimolecular oxidations or photolysis of parent phenols. We have described the synthesis and characterization of three photochemical and thermal unimolecular leaving groups. These leaving groups are: aryloxy oxalyl tert-butylperoxides (AOB's), aryloxy oxalyl chlorides (AOC's), and diaryl oxalates (DAO's), of which the AOB and DAO are the most efficient and stable. The quantum efficiency of a typical AOB system is 0.42, while that of an analogous DAO system is 0.10. A photolysis time of $\sim$3.5 h yields $\sim$35% of radicals using the AOB method. Using these leaving groups, phenoxyl radicals can be obtained in good yield in solution and in the solid state. We have attempted to apply these leaving groups toward production of conjugated, non-Kekule phenoxy-based biradicals. Our results indicate production of a large amount of monoradical, which probably obscures any biradicals produced. In addition to producing radicals, photolysis of diaryl oxalates in the solid state yields up to three types of triplet phenoxy-phenoxy radical pairs, which we have termed the initial, wide, and narrow radical pairs. The initial radical pair has been observed only from photolysis of di(2,6-di-tert-butyl-4-methoxyphenyl) oxalate, and has $\vert$D/hc$\vert$ = 0.0108 cm$\sp{-1}$, with a corresponding interelectronic separation of 6.2A. We have observed the formation of the wide radical pair primarily through the use of short photolysis times; thermal annealing of the initial radical pair also leads to its observation in the case described above. Wide radical pairs are observed from photolysis of di(2,6-di-tert-butyl-4-methoxyphenyl) oxalate, 2,6-di-tert-butylphenyl phenyl oxalate, and di(2,4,6-tri-tert-butylphenyl) oxalate. These radical pairs have $\vert$D/hc$\vert$ = 0.0099 to 0.0124 cm$\sp{-1}$, corresponding to interelectronic separations of 6.0-6.4A. In the absence of oxygen, the wide radical pairs are stable at room temperature for from 2 h to $>$1 week. Narrow radical pairs are formed upon extended photolysis of all DAO's, and exhibit $\vert$D/hc$\vert$ = 0.0034 to 0.0070 cm$\sp{-1}$, corresponding to interelectronic distances of 7.2-9.2A.

An improved synthetic route to pentabenzylcyclopentadiene, $\rm C\sb5Bz\sb5H$, has been developed. Both pentabenzylcyclopentadiene and an isomer were obtained depending on the reaction conditions. Structural assignments of both compounds have been investigated based on $\sp1$H NMR, $\sp{13}$C NMR, $\sp1$N 2D COSY NMR spectral and X-ray crystallographic studies. Pentabenzylcyclopentadienyl-lithium, $\rm C\sb5Bz\sb5Li$, was readily prepared from pentabenzylcyclopentadiene and n-butyl-lithium. Both $\rm C\sb5Bz\sb5H$ and $\rm C\sb5Bz\sb5Li$ have been used in the syntheses of the "sandwich" compounds: decabenzyl-, pentabenzyl-, and pentamethylpenta-benzyl-ferrocene, as well as the preparation of the "half-sandwich" compound: $(h\sp5$-$\rm C\sb5Bz\sb5)Mn(CO)\sb3$, $(h\sp5$-$\rm C\sb5Bz\sb5)Re(CO)\sb3$, $\lbrack (h\sp5$-$\rm C\sb5Bz\sb5)Fe(CO)\sb2\rbrack \sb2$, $(h\sp5$-$\rm C\sb5Bz\sb5)Fe(CO)\sb2R$ (where R = H, Me, SiMe$\sb3$, SnMe$\sb3$, Cl, I), and $(h\sp5$-$\rm C\sb5Bz\sb5)TiCl\sb3$. The reaction of pentabenzylcyclopentadiene and Fe(CO)$\sb5$ produced a mixture of $(h\sp4$-$\rm C\sb5Bz\sb5H)Fe(CO)\sb3$ and $\lbrack (h\sp5$-$\rm C\sb5Bz\sb5)Fe(CO)\sb2\rbrack \sb2$. Treatment of $\lbrack (h\sp5$-$\rm C\sb5Bz\sb5)Fe(CO)\sb2\rbrack \sb2$ with Na/Hg generated $(h\sp5$-$\rm C\sb5Bz\sb5)Fe(CO)\sb2\sp-Na\sp+$. Subsequent reactions of this anion with CH$\sb3$COOH, MeI, SiMe$\sb3$Cl, or SnMe$\sb3$Cl, produced $(h\sp5$-$\rm C\sb5Bz\sb5)Fe(CO)\sb2$-R (where R = H, Me, SiMe$\sb3$, SnMe$\sb3$, respectively) in good yield. A reaction of $(h\sp4$-$\rm C\sb5Bz\sb5H)Fe(CO)\sb3$ with trityl cation led to the formation of $\lbrack (h\sp5$-$\rm C\sb5Bz\sb5)Fe(CO)\sb3\rbrack \sp+$; following by the addition of LiCl, $(h\sp5$-$\rm C\sb5Bz\sb5)Fe(CO)\sb2$Cl was obtained. $(h\sp5$-$\rm C\sb5Bz\sb5)Fe(CO)\sb2$I can also be prepared from the reaction of $(h\sp4$-$\rm C\sb5Bz\sb5H)Fe(CO)\sb3$ with n-BuLi, followed by the addition of MeI in THF. A reaction between trimethylsilylindene and TiCl$\sb4$ in hexane formed (indenyl)titanium trichloride in 52% yield. All the above compounds have been well-characterized by $\sp1$H NMR, $\sp{13}$C NMR, IR, and mass spectrometry, as well as by elemental analyses. Many of the new compounds were obtained as single crystals, and X-ray crystallographic studies of several of them are described. Some of the compounds, such as the isomer of pentabenzylcyclopentadiene and $\lbrack (h\sp5$-$\rm C\sb5Bz\sb5)Fe(CO)\sb2\rbrack \sb2$, cannot be completely elucidated in terms of their structures at the present time, however.

An enclosed inductively coupled plasma (ICP) was designed to overcome the limitations of the conventional ICP torch for the analysis of toxic and reactive gases. In particular, the extreme toxicity of arsine prevents the safe application of a standard ICP torch and gas exhaust for the direct determination of impurities in arsine. The enclosed ICP provides containment of toxic gases in a quartz discharge container. The total volume of toxic gas consumed is minimized as well. Parameter characterization of a sealed ICP system was investigated. The choice and role of the additive gas, effect of flow rate, discharge container size and geometry, rf power, signal reproducibility, operating parameters, and procedures were determined. Modifiers were investigated to prevent deposition of arsenic and metallic impurities to the cooler container walls. The first reported direct qualitative analysis of semiconductor-grade arsine is described. Chlorine was found to be the most effective additive gas for arsenic vaporization for both flowing and static ICP operation. Chlorine addition to the argon stream extended the arsine introduction to concentrations of up to 10% into the discharge. An rf generator (40.68 MHz) power of 1.0 kW and 30% chlorine content for 7.11% arsine in a 65-mm diameter spherical container were applied to identify eight impurities qualitatively: C, Fe, Ge, Mg, Mo, Ni, Sn, and V. A vapor phase introduction system was developed to calibrate the SICP. Theoretical detection limits for tin in arsine and chlorine were calculated as 2.00 and 0.218 ppb, respectively. A hypothesis was formulated to describe the stability of the chlorine-containing arsine plasma. Proof of this hypothesis will require techniques to probe the presence and distribution of ion and atom species within the sealed discharge. The absolute noise power spectra of atomic emission signals from the SICP for flowing and static operation demonstrated that noise below 5 Hz was lower than observed in conventional ICP discharges. White noise levels were lower for the SICP than a conventional ICP. The implications of this result is the improvement in signal-to-noise ratio signal averaging techniques. This can provide very low analyte detection limits measured in the sealed inductively coupled plasma.

2D solid-state exchange NMR has been used to investigate the motion of a cross-link unit in a model network. The $\sp{31}$P chemical shift anisotropy provides an orientational probe of the tris(4-isocyanatophenyl)thiophosphate (TIPTP) cross-link in the network interconnected with telechelic poly(propylene glycol). 2D spectra were taken at two temperatures near the glass transition and at a series of mix times. From the variation of the 2D NMR pattern with temperature and mix time, the motion of the cross-link is identified as Brownian reorientational diffusion. Good simulations of the spectra were obtained using a distribution of the Williams-Watts stretched exponential correlation times. The temperature dependence of the cross-link motion follows the WLF equation. The parameters derived from the NMR data are sufficient to describe the temperature dependence and breadth of both the dielectric and mechanical loss associated with the glass transition. Solid $\sp{31}$P spin-lattice relaxation times (T$\sb1\sp{\rm P})$ have been measured over a wide range of temperatures for a series of network polymers with molecular weights between cross-links (M$\sb{\rm c})$ ranging from 250 to 2900. The networks were formed from poly(tetrahydrofuran) and TIPTP. The chain length dependence of the T$\sb{\rm g}$ obeys the Fox-Loshaek relation. The dominant mechanism for T$\sb1\sp{\rm P}$ relaxation was found to be chemical shift anisotropy. The data fitted equally well to the Cole-Cole or the Williams-Watts relaxation functions. The motion of cross-links can be described quantitatively by the activation energies and the coupling parameters. The effect of increasing M$\sb{\rm c}$ is to reduce the width of the distributions and the co-operative motional mode in the cross-link point. $\sp{13}$C NMR spectra and relaxation times have been measured as a function of extension on a segmented polyester and polyether-polyurethane elastomer by both cross-polarization and Bloch decay techniques. A sample spooling technique was developed for magic angle spinning of elastomers under extension. Analysis of cross-polarization dynamics allows semiquantitative analysis of three soft segment motional regimes over the full extension range: bulk, strained, and crystalline. The characteristic times for dipolar dephasing (T$\sb2\sp*),$ spin-lattice relaxation (T$\sb1\sp{\rm C}$ and T$\sb1\sp{\rm H}),$ and rotating-frame relaxation (T$\sb{1\rho}\sp{\rm H}$) were sensitive to the extension on thermoplastic elastomers.

In an attempt to ascertain the relationship between the structure and the electronic spin ground state of open-shell species, various model $\pi$-conjugated dinitrene systems of the general structure:N-Ph-X-Ph-N: were synthesized. Variable low temperature electron spin resonance (ESR) spectroscopy was used to determine the ground state multiplicity of the dinitrenes and to determine the degree of exchange coupling between the unpaired electrons on each nitrogen. The experimentally determined ground state spin multiplicity could be predicted using Borden and Davidson's disjointness criterion, even for heterocyclic non-alternant ring systems. Parity-based predictions did not provide such consistent agreement with the experimental results as the latter method. Many similarities between the ESR spectra of the quintet dinitrenes are proposed to arise from different conformers of the same quintet state. Analysis of two conformationally restrained dinitrenes tend to support this view, and imply that geometric considerations are of importance in the design of an organic ferromagnet.

A series of bis(arylnitrene) compounds was generated for studies by ESR spectroscopy at cryogenic temperature. Zfs $\vert$D/$h$c$\vert$ and $\vert$E/$h$c$\vert$ were determined and temperature dependent studies were done on some of the bis(arylnitrene)s. Bis(p-phenylnitrene) compounds were generated, and their ESR spectra showed mononitrene signals and triplet dinitrene signals including $\Delta$m$\sb{\rm s}$ = 2 transitions. Zfs $\vert$D/$hc\vert$ of mononitrenes and triplet dinitrenes decreased as conjugation between phenylnitrenes increased. Zfs $\vert$E/$h$c$\vert$ was estimated to be zero except for 1,4-phenyldinitrene. The temperature dependent studies concluded that all bis(p-phenylnitrene)s have ground state singlets. Triplet zero field splitting observed for bis(p-phenylnitrene)s are due mostly to one-center interaction of $\sigma$ and $\pi$-electrons of the nitrenes. Three biphenyldinitrenes were generated: the 4,4$\sp\prime$-isomer, 3,4$\sp\prime$-isomer, and 3,3$\sp\prime$-isomer. The 4,4$\sp\prime$-isomer showed an ESR spectrum typical of a triplet dinitrene, and a temperature study showed a singlet ground state. The 3,4$\sp\prime$-isomer showed a complex ESR spectrum typical of a quintet state, and a temperature study showed a ground state quintet. The 3,3$\sp\prime$-isomer showed only a mononitrene signal in the ESR spectrum, so it is presumed to be a disjoint compound with almost no interaction between nitrene sites. Three phenylether dinitrene compounds were generated for comparison with the biphenyl compounds. The 4,4$\sp\prime$-isomer had only a mononitrene ESR signal, so a ground state singlet is assumed due to a superexchange mechanism between the paired electrons of oxygen and the $\pi$-electrons of the nitrenes. The 3,4$\sp\prime$-isomer showed very weak quintet signals, so a ground state quintet was assumed. The 3,3$\sp\prime$-isomer showed a very weak quintet signal, and a temperature study showed this to be an excited quintet state. Bis(4$\sp\prime$-nitrenophenyl)-1,3-butadiyne was generated for a study of the effect of acetylene as a coupling spacer. Its ESR spectra showed a strong mononitrene signal only and very weak signals presumed to be a quintet state. The spectrum suggests that this acetylene is a twisted structure where any coupling between nitrenes was changed from linear behavior.

Thesis (Ph. D.)--Indiana University, Dept. of Chemistry, 2008. / Title from home page (viewed Oct 7, 2009). Source: Dissertation Abstracts International, Volume: 70-02, Section: B, page: 1017. Adviser: Dongwhan Lee. Includes supplementary digital materials.