Structure of polyaniline formed in different inorganic porous materials: A spectroscopic study

In this work, the electronic and structural characterization of polyaniline (PANI) formed in cavities of zeolites Y (ZY) and Mordenite (MOR) and montmorillonite (MMT) clay having Cu(II) as oxidant agent are presented. The formation of PANI and its structure is analyzed by Resonance Raman, UV-Vis-NIR, FT-IR and N K XANES techniques. In all cases the structure of PANT formed is different from the ""free"" polymer. The presence of azo bonds linked to phenazine-like rings are observed only for PANI-MMT composites, independent of the kind of oxidant agent employed in the synthesis. The presence of Cu(II) ions leads to the formation of Phenosafranine-like rings. The presence of these phenazine-like rings in the structure of confined PANT chains can also contribute to the enhancement of the thermal stability observed for all composites. (C) 2008 Elsevier Ltd. All rights reserved.

Structural and vibrational characterization of polyaniline nanofibers prepared from interfacial polymerization

This work deals with the structural and vibrational characterization of PANI nanofibers prepared through interfacial polymerization using different concentrations of HCl aqueous solution. The results were compared to those obtained by PANI prepared through the conventional route. X-ray diffraction and small-angle X-ray scattering techniques showed that high concentrations of HCl solutions used in the preparation of the PANI nanofibers reduce their crystallinity. The increase of regions with granular morphology was also observed in the scanning electron microscopy images. The changes in the resonance Raman spectra from 200 to 500 cm(-1), FTIR spectra, and the EPR data of the PANI nanofibers reveal an increase in the torsion angles of C-ring-N-C-ring segments owing the formation of bipolarons in the PANI backbone higher than the PANI samples prepared by conventional route.

Studies on the resonance Raman spectra of polyaniline obtained with near-IR excitation

The effects of near-IR (NIR) laser power over the Raman spectra of poly(aniline) emeraldine salt (PANIES) and base (PANI-EB) were investigated. The reasons for the existence of several bands from 1324 to 1500 cm-1 in the Raman spectra of poly(aniline) obtained at NIR region were also studied. The bands from 1324 to 1375 cm-` were associated to vC-N of polarons with different conjugation lengths and the bands from 1450 to 1500 cm-1 in Raman spectra of PANI emeraldine and pernigraniline base forms were correlated to vC=N modes associated with quinoid units having different conjugation lengths. The increase of laser power at 1064.0 run causes the deprotonation of PANI-ES and the formation of cross-linking segments having phenazine and/or oxazine rings. For PANI-EB only a small spectral change is observed when the laser power is increased, owing to the low absorption of this form in the NIR region. Copyright (c) 2007 John Wiley & Sons, Ltd.

Spectroscopic characterization of the structural changes of polyaniline nanofibers after heating

The thermal behavior of PANI nanofibers doped with beta-naphthalenesulfonic acid (beta-NSA) was investigated and their morphological and structural changes after heating were monitored by SEM, XRD and Raman techniques, respectively. By using electron-scanning microscopy it is possible to verify that the nanofiber morphology is stable and no polymer degradation is observed in thermogravimetric (TG) data up to 200 degrees C. Nevertheless, the heating promotes the formation of cross-linking structures (phenazine and/or oxazine-like rings), that is clearly demonstrated by the presence of bands at ca. 578, 1398, and 1644 cm(-1) in resonance Raman spectra of heated PANI-NSA samples. The most important consequence of the formation of cross-linking structures in PANI-NSA samples is that these samples retain their nanofiber morphology upon HCl doping in contrast to PANI-NSA nanofibers without heating. (c) 2007 Elsevier Ltd. All rights reserved.

The role of solvent on the doping of polyaniline with Fe(III) ions

The products formed from the reaction of emeraldine base polyaniline (EB-PANI) with Fe(III) ions in N-methyl-pyrrolidone (NMP), dimethylacetamide (DMA), dimethylformamide (DMF) and m-cresol media have been investigated using UV-VIS-NIR and resonance Raman (lambda(0) = 632.8 and 1064 nm) spectroscopies. Through these results it was verified that the different PANI forms in solution can be formed by the suitable choice of the solvent. The behavior of Fe(III)/EB-PANI in different solvents was rationalized in terms of the interactions among Fe(III) ions, EB-PANI and solvent. In basic NMP, DMA and DMF media, the reaction of Fe(III) with EB-PANI yields EB-PANI doping giving ES-PANI and/or the EB-PANI oxidation to PB-PANI. The formation of ES-PANI is favored in DMF while PB-PANI is formed in a greater extension in NMP and DMA. In acidic m-cresol, only ES-PANI is produced in Fe(III)/EB-PANI solutions indicating the important role played by the solvent in the nature of the product. (C) 2010 Elsevier B.V. All rights reserved.

Charge-transfer behavior of polyaniline single wall carbon nanotubes nanocomposites monitored by resonance Raman spectroscopy

Highly dispersed nanocomposites of polyaniline(PANI) and oxidized single wall carbon nanotubes(SWNTs) have been prepared using dodecylbenzenesulfonic acid as dispersant. The materials were characterized via resonance Raman and electronic absorption spectroscopies. The behavior of the composites as a function of the applied potential was also investigated using in situ Raman electrochemical measurements. The results obtained at E(laser) = 1.17 eV suggest that a charge-transfer process occur between PANI and semiconducting nanotubes for samples where the metallic tubes are previously oxidized. The spectroelectrochemical data show that the presence of SWNTs prevents the oxidation of PANI rings. Copyright (C) 2010 John Wiley & Sons, Ltd.

Surface-Enhanced Resonance Raman Scattering of Polyaniline on Silver and Gold Colloids

The interaction of emeraldine base (PANI-EB) with silver and gold colloids was probed by using Surface-Enhanced Resonance Raman Scattering (SERRS) at 3 different exciting radiations. Due to the great sensitivity of SERRS technique the detection limit of PANI-EB concentration was ca. 2 x 10(-7) mol L(-1) in Ag and Au colloidal suspensions. The UV-vis-NIR spectra of metal colloids in function of PANI-EB concentrations showed that gold colloids present a higher degree of aggregation than silver colloids. SERRS of PANI-EB on metal colloids allowed the study of the polymeric species formed primarily on the metallic surface. The polymer formed after the adsorption of PANI-EB on metallic nanoparticles is strongly dependent on the nature of the metal colloids. The oxidation of PANI-EB to pernigraniline occurred for silver colloids, while a doping process of PANI-EB on Au nanoparticles was evidenced through the observation of the characteristic SERRS spectrum of emeraldine salt at 1064nm.

Thioxanthone Sensitized Photodegradation of Poly(alkyl methacrylate) Films

The thioxanthone-sensitized photodegradation of poly(alkyl methacrylate) films [alkyl = methyl, ethyl, butyl, and hexyl] was studied using near UV-vis light. The photooxidation process continued even after the total consumption of the sensitizer, possibly due to the excitation of the ketyl groups formed during the first stages of the process. The rate of oxidation, as well as the formation of hydroxy, peroxy, and ketyl groups was faster for polymers with larger ester groups. The decrease of the molecular weight of the degradated polymers was also larger for the hexyl substituted polymer. The side-chain size effect was attributed to the larger amount of secondary hydrogens available for abstraction by the triplet state of thioxanthone, present in the larger ester groups. The lower glass transition temperature of the hexyl substituted polymer allows a better diffusion of oxygen to the deeper layers of the films that also contributes to the faster photodegradation rate. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 1283-1288, 2010

Cytotoxicity of Diepoxybutane and Epichlorohydrin in Relation to Stages of the Cell Cycle

Work conducted in the Millard Biochemistry Research Laboratory examines the dual nature of molecules as carcinogens and anti-tumor agents through the molecular mechanisms of duplex DNA damage by bifunctional alkylating agents. Diepoxybutane (DEB) and epichlorohydrin (ECH) are polar molecules that form covalent DNA interstrand lesions by cross-linking the N7 position of deoxyguanosine residues. A recent experiment indicated that ECH preferentially targets nuclear DNA over mitochondrial DNA, whereas DEB shows similar rates of lesion formation for both loci. It was concluded that preferential targeting of nuclear DNA results from relatively poor uptake of ECH across the mitochondrial membrane. The objective of my honors research was to determine if the cytotoxicities of DEB and ECH vary according to the presence of the nuclear envelope in 6C2 chicken erythro-progenitor cells. The cytotoxicity of DEB and ECH was compared between cells randomly distributed throughout the cell cycle (Go/G, and S » G2/M) and cells enriched in G2/M stages. Results indicated that ECH is more cytotoxic than DEB in both unsynchronized control 6C2 cells and synchronized 6C2 cells enriched in G2/M stages of the cell cycle. Treatment with either bifunctional alkylating agent induced greater cytotoxicity in 6C2 cells enriched in G2/M stages than in unsynchronized control 6C2 cells, suggesting that the presence of the nuclear envelope-or any plasma membrane-may inhibit the reactivity of DEB and ECH.

Kinetic Analysis of Gill (Na+,K+)-ATPase Activity in Selected Ontogenetic Stages of the Amazon River Shrimp, (Decapoda, Palaemonidae): Interactions at ATP- and Cation-Binding Sites

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

First record of molluscs naturally infected with Angiostrongylus cantonensis (Chen, 1935) (Nematoda: Metastrongylidae) in Brazil

Seeking the identification of Angiostrongylus cantonensis as a potential etiological agent of three clinical cases of eosinophilic meningitis, mollusc specimens were collected in the state of Espírito Santo, Brazil. The snails were identified as Sarasinula marginata (45 specimens), Subulina octona (157), Achatina fulica (45) and Bradybaena similaris (23). Larvae obtained were submitted to polymerase chain reaction and restriction fragment length polymorphism diagnosis. Their genetic profile were corresponded to A. cantonensis. Rattus norvegicus experimentally infected with third-stage larvae, developed menigoencephalitis, and parasites became sexually mature in the lungs. Additionally, larvae obtained from A. fulica snails, from São Vicente, state of São Paulo, also showed genetic profiles of this nematode. This is the first record of Brazilian molluscs infected with this nematode species.

First record of Trypanosoma sp. (Protozoa: Kinetoplastida) in tuvira (Gymnotus aff. inaequilabiatus) in the Pantanal wetland, Mato Grosso do Sul State, Brazil

O objetivo do presente estudo foi reportar a infecção por Trypanosoma sp. em tuviras (Gymnotus aff. inaequilabiatus) oriundas do Pantanal Sul-mato-grossense, Brasil. Dez peixes provenientes do rio Paraguai, Pantanal Sul-mato-grossense, foram avaliados quanto à presença de hemoflagelados. Tripomastigotas de Trypanosoma sp. foram observados nas extensões sanguíneas de três peixes (30% de prevalência), e algumas formas encontravam-se em divisão. Por meio do exame a fresco e da centrifugação do sangue em capilar de hematócrito como métodos para diagnóstico, a taxa de prevalência foi de 80%. Esse é o primeiro relato de Trypanosoma sp. em tuviras no Brasil.

NOTES on THE BIOLOGY and BEHAVIOUR of THE JEWEL WASP, AMPULEX COMPRESSA (FABRICIUS, 1781) (HYMENOPTERA; AMPULICIDAE), IN THE LABORATORY, INCLUDING FIRST RECORD of GREGARIOUS REPRODUCTION

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

The preimaginal stages of the ensign wasp Evania appendigaster (Hymenoptera, Evaniidae), a cockroach egg predator

Evania appendigaster is a cosmopolitan wasp that deposits eggs in the oothecae of some species of cockroaches; its larvae then consume the cockroach eggs and embryos. It is a candidate for the biological control of cockroaches, but little is known about its basic biology. Here we describe the external morphology of all immature stages of E. appendigaster and compare them with the larvae of related species. The life cycle of E. appendigaster includes three larval instars, each with 13 body segments. Their mouthparts were generally reduced, except for the mandibles, which were always sclerotized and toothed, and were especially robust in second-instar larvae. Antennal and mouthpart sensilla were basiconic and difficult to observe. Larvae of E. appendigaster are similar in form to other described evaniid larvae, but quite different from the two available descriptions of larvae of gasteruptiid and aulacid wasps. Further descriptions of evaniid larvae will be useful in determining how widespread this morphology is within the family, and in understanding phylogenetic relationships within Hymenoptera.