4 research outputs found
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Biological detection and tagging using tailorable, reactive, highly fluorescent chemosensors.
This program was focused on the development of a fluorogenic chemosensor family that could tuned for reaction with electrophilic (e.g. chemical species, toxins) and nucleophilic (e.g. proteins and other biological molecules) species. Our chemosensor approach utilized the fluorescent properties of well-known berberine-type alkaloids. In situ chemosensor reaction with a target species transformed two out-of-plane, weakly conjugated, short-wavelength chromophores into one rigid, planar, conjugated, chromophore with strong long wavelength fluorescence (530-560 nm,) and large Stokes shift (100-180 nm). The chemosensor was activated with an isourea group which allowed for reaction with carboxylic acid moieties found in amino acids
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Synthesis of a photoresponsive polymer and its incorporation into an organic superlattice.
The synthesis of a photoswitchable polymer by grafting an azobenzene dye to methacrylate followed by polymerization is presented. The azobenzene dye undergoes a trans-cis photoisomerization that causes a persistent change in the refractive index of cast polymer films. This novel polymer was incorporated into superlattices prepared by spin casting and the optical activity of the polymer was maintained. A modified coextruder that allows the rapid production of soft matter superlattices was designed and fabricated
Constitution, configuration, and the optical activity of chiral dendrimers
The efficient preparation of four chiral AB2 monomers suitable for the construction of dendrimers is presented. Chirality is introduced in the form of a 1,2-diol unit, protected as an acetonide derivative, using the osmium catalyzed asymmetric dihydroxylation. reaction (AD) (\u3e97% ee in all cases). Using these cinnamate and stilbene based monomer subunits, dendrons and dendrimers have been prepared up to the third generation using a convergent dendrimer synthesis. Investigation of the chiroptical properties of the dendrons and dendrimers prepared revealed a significant change in molar rotation per chiral subunit ([Φ]D/n) upon increasing generation for the cinnamate based series, a possible indication of chiral conformational order in this system. However, preparation and investigation of the chiroptical properties of low molecular weight model compounds, prepared to simulate different regions of the dendrimer structure, revealed that any observed chiroptical anomalies were a result of slight constitutional changes within the dendritic architecture and not chiral conformational order. ^ The deprotection of the chiral 1,2-diol units for dendrimers up to the first generation is presented. We found that the solubility of these more polar polyhydroxylated chiral dendrimers was low in non-polar organic solvents. Consequently, dendrimer peripheries were modified with long chained alkyl groups, resulting in dendrimers which were more compatible with non-polar media (e.g. n-hexane). Dendrimers; like these, containing chiral polar interiors (after deprotection) and non-polar peripheries, may potentially serve as chiral inverse unimolecular micelles. ^ The novel construction of photolabile dendrimers containing o-nitrobenzyl ether linkages is presented. A variety of dendrimers were prepared with photolabile linkers positioned at the core, interior, or periphery of the dendrimer. Irradiation with ca. 350 nm light effectively cleaves the o-nitrobenzyl groups, as evidenced by UV, 1H NMR, and chiroptical data. Photolabile dendrimers offer great potential as hosts for the selective encapsulation and release of guests through the implementation of light energy.
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Assuring ultra-clean environments in microsystem packages : irreversible and reversible getters.
A new generation of irreversible, chemically reacting getters specifically targeted toward assuring the integrity of the local environment within microsystem packages were developed and evaluated. These reactive getters incorporate volatile species into a polymer through covalent bonds, thus producing a non-volatile product. These reactive getters will be combined with getters that rely on absorption media (e.g. zeolites and high surface area carbon fibers) to scavenge non-reactive species, like solvents. Our getter systems will rely on device packaging to limit exchange between the microsystem and the global environment. Thus, the internal getters need only provide local environmental control within the microsystem package. A series of experiments were conducted to determine uptake rates and capacities absorption and reactive-based getters. Diffusion rates through the binder used to hold the getter particles together were also investigated. Getters were evaluated in environments with a saturated headspace and with a limited amount of the volatile species of interest. One- and two-dimensional numerical models and analysis techniques have been developed and used to predict the transport of contaminant species within a representative microsystem package consisting of an open gas-filled volume adjacent to a polymer layer containing embedded particles of getter. The two-dimensional model features explicit representation of the individual getter particles while the one-dimensional treatment assumes a homogeneous distribution of getter material within the getterlpolymer layer. Example calculations illustrate the dependence of getter performance on reaction rates, polymer diffusivity, and getter particle volume fraction. In addition, the model is used to deduce surface reaction rates, solid phase diffusivities, and maximum-loading densities by least-squares fitting of model predictions to measured histories of gas-phase contaminant concentration and getter weight gain