Electropolymerizable 2,2'-Carboranyldithiophenes. Structure-Property Investigations of the Corresponding Conducting Polymer Films by Electrochemistry, UV-Visible Spectroscopy and Conducting Probe Atomic Force Microscopy

Carborane-functionalized conducting polymer films have been electrogenerated in dichloromethane from the anodic oxidation of ortho- (1), meta- (3) and para-carborane (4) isomers linked to two 2-thienyl units. The corresponding electrochemical response was characterized by a broad reversible redox system corresponding to the p-doping/undoping of the polythiophene backbone, the formal potential of which increased in the order poly(1) < poly(3) < poly(4), from ca. 0.50 to 1.15 V vs Ag/Ag(+) 10(-2) M. From further UV-visible spectroscopy analysis, the optical band gap was estimated at 1.8, 2.0 and 2.2 eV for poly(1), poly(3) and poly(4), respectively. The more conjugated and electroconductive character of poly(1) is ascribed to a more planar conformation of the conjugated backbone resulting from an intramolecular β-β' cyclization reaction in the monomer, consequently yielding a fused conjugated polymer. Molecular modeling calculations using the DFT method support this hypothesis. The surface topography and maps of the conductive domains of the electropolymerized films were evaluated by conducting probe AFM. The three polymers exhibit fairly similar morphological characteristics and a surface roughness of ~2 nm. Current-voltage (I-V) characteristics of conducting AFM tip-carborane polymer-ITO junctions showed that poly(1) had the highest conductivity.     

Improved analysis of ladderane lipids in biomass and sediments using high-performance liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometry

Ladderane lipids, containing three or five linearly concatenated cyclobutane moieties, are considered to be unique biomarkers for the process of anaerobic ammonium oxidation, an important link in the oceanic nitrogen cycle. Due to the thermal lability of the strained cyclobutane moieties, the ladderane lipids are difficult to analyze by gas chromatography. A method combining high-performance liquid chromatography coupled to positive ion atmospheric pressure chemical ionization tandem mass spectrometry (HPLC/APCI-MS/MS) was developed for the analysis of the most abundant ladderane lipids, occurring as fatty acids and ether-bound to glycerol. Detection was achieved by selective reaction monitoring of four specific fragmentations per ladderane lipid. Detection limits of 30-35 pg injected on-column and a linear response (r(2) > 0.99) over nearly 3 orders of magnitude were achieved for all compounds. Using this method, these unique ladderane lipids were for the first time identified in a surface sediment from the Gullmarsfjorden, in concentrations ranging from 1.1-5.5 ng/g for the ladderane fatty acids and of 0.7 ng/g for the monoether. It is foreseen that this method will allow the investigation of the occurrence of anaerobic ammonium oxidation in natural settings in much greater detail than before.     

Fabrication of nanopatterned films of bovine serum albumin and staphylococcal protein A using latex particle lithography

Arrays of protein nanostructures can be formed on surfaces such as mica(0001) and Au(111) using lithography with polystyrene latex particles. To create arrays of protein nanostructures, monodisperse latex spheres are mixed with the desired protein (e.g. BSA, protein A or IgG) and deposited onto substrates. Protein-coated nanospheres self-assemble into organized crystalline layers when dried on flat surfaces. After rinsing with water, dried latex spheres are displaced to expose periodic arrays of uncovered circular cavities. The immobilized proteins remain attached to the surface and form nanopatterns over broad areas (microns) corresponding to the thickness of a single layer of proteins. The nanostructures of immobilized proteins maintain the order and periodicity of the latex scaffold. The morphology and diameter of the protein nanostructures are tuneable by selecting the ratios of protein-to-latex and the diameters of latex spheres. Well-defined nanostructured surfaces of proteins supply a tool for fundamental investigations of protein binding interactions in biological systems at the nanoscale and have potential applications in biochip and biosensing systems.     

Rapid separation of beryllium and lanthanide derivatives by capillary gas chromatography

Previous studies describe derivatization of metal ions followed by analysis using gas chromatography, usually on packed columns. In many of these studies, stable and volatile derivatives were formed using fluorinated β‐diketonate reagents. This paper extends previous work by investigating separations of the derivatives on small‐diameter capillary gas chromatography columns and exploring on‐fiber, solid‐phase microextraction derivatization techniques for beryllium. The β‐diketonate used for these studies was 1,1,1,2,2,6,6,7,7,7‐decafluoro‐3,5‐heptanedione. Derivatization of lanthanides also required addition of a neutral donor, dibutyl sulfoxide, in addition to 1,1,1,2,2,6,6,7,7,7‐decafluoro‐3,5‐heptanedione. Unoptimized separations on a 100‐μm i.d. capillary column proved capable of rapid separations (within 15 min) of lanthanide derivatives that are adjacent to one another in the periodic table. Full‐scan mass spectra were obtained from derivatives containing 5 ng of each lanthanide. Studies also developed a simple on‐fiber solid‐phase microextraction derivatization of beryllium. Beryllium could be analyzed in the presence of other alkali earth elements (Ba(II) and Sr(II)) without interference. Extension of the general approach was demonstrated for several additional elements (i.e. Cu(II), Cr(III), and Ga(III)).     

Sonochemically prepared organozinc reagents1. conjugate additions to α-β unsaturated aldehydes

Organozinc reagents, prepared by sonication from organic halides, lithium and zinc bromide, add conjugatively to α-enals in the presence of nickel acetylacetonate. Satisfactory yields are obtained from arylbromides.     

Plasma and beam facility atomic oxygen erosion of a transition metal complex

Glassy residues of the complex bis(N,N-disalicylidene-1,2-phenylenediamino)zirconium(IV), Zr(dsp)₂, on glass slides were exposed to atomic oxygen in a plasma asher or an atomic beam facility for various amounts of lime in order to study the erosion process, determine the rate of erosion, and learn the chemical identity of the residue. The exposed films were characterized by weight loss, optical photography, profilometry, diffuse reflectance and total transmittance spectroscopy, scanning electron microscopy (SEM) with wavelength dispersive X-ray spectrometry (WDS), X-ray diffraction, and X-ray photoelectron spectroscopy (XPS). Results indicate that these films erode much more slowly polyimide (Kapton) film under identical conditions, that the erosion is very nonuniform, and that zirconium dioxide is the predominant product after extended exposure. This complex is currently being evaluated as a polymer additive.     

Synthesis and Characterization of Optically Active Surfactants Derived from Phenylalanine and Leucine

Two optically active cationic surfactants, (2S)-N-hexadecyl-N, N-dimethyl-(1-hydroxy-3-phenylpropyl)-2-ammonium chloride 1 and (2S)-N-hexadecyl-N,N-dimethyl-(1-hydroxy-4-methylpentyl)-2-ammonium chloride 2, have been selected and synthesized for use as enantioselective micellar catalysts in aqueous media. Their surface and aggregation behavior has been investigated at 298 K using surface tension and light scattering studies, which revealed that both molecules associate at low concentrations to produce micellar aggregates. Interestingly, although the area per molecule occupied by the surfactants at the air-water interface (43.6 ?(2) for 1 and 54.6 ?(2) for 2) is similar to that of related cationic surfactants, their aggregation number (23 for 1 and 19 for 2) is much smaller, perhaps reflecting the influence of the size or homochiral nature of the head group in the packing of the micelle. Copyright 2001 Academic Press.     

Qualitative determination of low-molecular-weight organic acids in mixed hazardous wastes using thermospray liquid chromatography/mass spectrometry

A technique has been developed for the qualitative determination of low-molecular-weight organic acids in radioactive, mixed hazardous wastes using thermospray liquid chromatography/mass spectrometry. A tank waste was analyzed, and the results indicated the presence of citric, glycolic, acetic, and nitrosoiminodiacetic acid (NIDA). Further investigation revealed NIDA was formed under acidic conditions with the reaction of iminodiacetic acid and the high nitrate/nitrite concentration present in the waste.     

“I Actually Learned A Lot from This”: A Field Assignment to Prepare Future Preservice Math Teachers for Culturally Diverse Classrooms

Teacher education programs are cognizant of the need to prepare preservice teachers (PTs) to work effectively with children from diverse cultural backgrounds. Well-constructedfield experiences can help PTs develop awareness and gain understanding of important cultural considerations related to effective teaching and learning ( Sleeter, 2001 ). This paper describes a unique field assignment created for an Elementary Math Methods course in which 61 PTs were trained to conduct a semi-structured interview with a student whose cultural background was different than their own. PTs transcribed their own interviews and completed a guided reflection on their experiences. Reflections were submitted and analyzed for emerging themes. Analyses suggest that the structured interview component of this field assignment provided PTs with increased insight into mathematics instruction and the learning needs of diverse students. We also discuss the value and limitations of this instructional innovation and propose avenues by which to continue to help PTs grow toward becoming culturally relevant pedagogists ( Irvine, 2003 ).