Lawrence L. Brott

Comparative reactivity of thiophene and 3,4‐(ethylenedioxy)thiophene as terminal electropolymerizable units in bis‐heterocycle arylenes

The monomers bis(2-thienyl)-9,9-didecylfluorene, BTDF, and bis(3,4-(ethylenedioxy)thien-2-yl)-9,9-didecylfluorene, BEDOT-DF, have been synthesized and electropolymerized to the corresponding conducting polymers. The potential for the electropolymerization of BTDF was found to be dependent on the solvent composition. In CH 2 Cl 2 , polymer film deposition is achieved only at potentials higher than 1.3 V vs. Ag/Ag + , while in a 30/70 mixture of CH 2 Cl 2 /CH 3 CN the polymerization is efficient at 0.9 V. BEDOT-DF polymerizes at significantly lower potentials and more rapidly than BTDF. The electron-donating alkoxy substituents of the EDOT units lead to stabilization of the cation radical intermediates allowing the electropolymerization to proceed at 0.55 V. The neutral polymers are insoluble in common organic solvents and are stable to 300°C under nitrogen. Upon oxidation, both polymers show two intragap transitions at intermediate doping levels due to the formation of bipolaronic states and the oxidized polymers exhibit conductivities up to 10 -4 S/cm. The redox-stimulated ion transport characteristics, studied by the electrochemical quartz crystal microbalance (EQCM) indicates that the electrolyte anions are the dominant mobile species.

Controlled formation of biosilica structures in vitro

Herein we describe the controlled formation of biosilica structures by manipulation of the physical reaction environment; we were able to synthesize arched and elongated silica structures using a synthetic peptide; the results presented here are evidence that in vitro biocatalysis may be controlled in order to form desired silica structures.

Bio-inspired approaches and biologically derived materials for coatings

The synthesis of composite materials that exhibit inhomogeneities on the sub-micron or nanometer scale using chemical and physical deposition processes is a challenge. The use of a biomimetic approach may compliment existing methods in creating materials that exhibit properties that would not be otherwise achieved. We describe herein our efforts to fabricate functional optical devices that incorporate biomolecules. By incorporating biomolecules into monomer systems that can be cured using a two-photon polymerization mechanism, greater spatial resolution and increased biological viability can be achieved. In addition, the polymer can be patterned using ultrafast nonlinear holography to create a functional optical device. By exploiting the use of biomolecules to control the deposition of inorganics, functional coatings can be fabricated for a variety of optical and electronic applications.

Optical power limiting in solution via two-photon absorption: new aromatic heterocyclic dyes with greatly improved performance

Organic compounds which exhibit optical power limiting exclusively via a two-photon absorption (TPA) mechanism have shown only little promise for providing the limiting activity necessary for the practical protection of eyes and sensors. Unfortunately, there have been few systematic studies of the molecular structure I two-photon absorption property relationships for organics documented in the literature. In order to enable the design and synthesis of new molecules with much larger two-photon absorption cross-sections and improved limiting properties, the synthetic chemist must have access to well defined structure Iproperty data. In an attempt to fill this void, work in our laboratory has centered on the design and synthesis of several new families of aromatic heterocyclic chromophores with systematic variations in their molecular structures. Careful characterization of these new materials in solution at the Photonics Research Laboratory, SUNY Buffalo has produced some well-defined structure Itwo-photon property relationships at 800 nm. In this presentation we will discuss the design and synthesis of these materials with special emphasis of how the flexibility of the synthetic scheme employed enables the incorporation of these chromophores into a wide variety of materials forms. The characterization of the twophoton properties of these materials and the relationship of these results to their optical limiting behavior in solution will also be reviewed.

EFFECT OF EXTERNAL ELECTRICAL STIMULI ON DNA-BASED BIOPOLYMERS

Biopolymers, such as deoxyribonucleic acid-hexadecyltrimethyl ammonium chloride (DNA-CTMA) and bovine serum albumin-polyvinyl alcohol (BSA-PVA), were studied using a novel capacitive test structure. A variety of external electrical stimuli were applied, including a low frequency alternating current signal and a rf/microwave frequency signal combined with a DC bias. The dynamic responses of the DNA-based biopolymer to the external stimuli are presented in this paper. The electrical transport measurements support the space-charge-limited conduction and the low frequency capacitance–voltage (CV) measurements showed large depletion layer capacitance at the Au–biopolymer interface, at 20 Hz, and the capacitance approaching bulk values at 1 MHz. Electric force microscopy (EFM) was utilized for visualization of charge dynamics and to examine the effect of DC bias combined with an AC signal. Ionic charges in the DNA-CTMA system seem to be responsible for the dynamic response to the various external electrical stimuli.