Sintering-driven effects on the band gap of (Pb,La)(Ti,Ni)O3 photovoltaic ceramics

In this work, the influence of the sintering temperature on the physical properties of (Pb_0.8La_0.2)(Ti_0.9Ni_0.1)O₃ (PLT-Ni) ceramics is reported. The experimental data revealed that the energy band gap of PLT-Ni ceramics could be tailored from approximately 2.7 to 2.0 eV by changing the sintering temperature from 1100°C to 1250°C. It is demonstrated that the simple substitution of Ti⁴⁺ by Ni²⁺ cations is effective to decrease the intrinsic band gap while increasing the tetragonality factor and the spontaneous polarization. However, the additional red-shift observed in the absorption edge of the PLT-Ni with increasing the sintering temperature was associated with a continuous increase in the oxygen vacancies () amount. It is believed that the impact of the creation of these thermally induced is manifold. The presence of and Ni²⁺ ions generate the Ni²⁺- defect-pairs that promoted both a decrease in the intrinsic band gap and an additional increase of the tetragonality factor, consequently, increasing the spontaneous polarization. The creation of Ni²⁺- defects also changed the local symmetry of Ni²⁺ ions from octahedral to a square pyramid, thus lifting the degeneracy of the Ni²⁺ 3d orbitals. With the increase in the sintering temperature, lower-energy absorbing intraband states were also formed due to an excess of , being responsible for an add-on shoulder in the absorption edge, extending the light absorption curve to longer wavelengths and leading to an additional absorption in “all investigated” spectrum as well.     

Sex pheromone of tomato fruit borer, Neoleucinodes elegantalis

Five candidate pheromone components were identified by analyzing pheromone gland extracts by gas chromatography (GC), coupled GC-electroantennographic detection (EAD), and coupled GC-mass spectrometry (MS): (E)-11-hexadecenol(E11–16 : OH), (Z)-11-hexadecenol (Z11–16 : OH),(E)-11-hexadecenal, (E)-11-hexadecenyl acetate, and (Z)-3,(Z)-6,(Z)-9-tricosatriene (Z3,Z6,Z9–23 : Hy). In electroantennogram (EAG) recordings, synthetic E11–16 : OH elicited stronger antennal responses at low doses than other candidate pheromone components. Field tests demonstrated that synthetic E11–16 : OH as a trap bait was effective in attracting males, whereas addition of Z11–16 : OH inhibited the males' response. Z3,Z6,Z9–23 : Hy strongly enhanced attractiveness of E11–16 : OH, but was not attractive by itself. A pheromone blend with synergistic behavioral activity of an alcohol (E11–16 : OH) and hydrocarbon (Z3,Z6,Z9–23 : Hy) component is most unusual in the Lepidoptera. The synthetic two-component pheromone is approximately 60 times more attractive than the female-produced blend and might facilitate the control of this pest.     

pH sensitive phosphate crosslinked films of starch-carboxymethyl cellulose

This work aims to develop hydrogel films of starch and carboxymethyl cellulose (CMC) crosslinked with sodium trimetaphosphate (STMP) and to characterize some of their properties. Starch and STMP (S/T), starch and CMC (S/C), and mixed (S/T/C) films were prepared by casting. The degree of substitution, morphology, swelling degree, FTIR, mechanical properties, and sorption isotherms were studied. Reticulated samples (S/T and S/T/C) showed the same degree of substitution (0.050 ± 0.001). All films presented homogeneous morphology, but the mixed film showed greater roughness. Crosslinking increased the swelling capacity of the mixed hydrogel at pH 7, although it remained decreased concerning the S/T hydrogel. However, this property was sensitive to pH variations. The mixed film (S/T/C) showed greater mechanical resistance. The casting process was efficient to produce hydrogel films of starch/CMC crosslinked with STMP and the general results demonstrated the advantages of the mixed hydrogel.     

Mixture design applied for the development of films based on starch,polyvinyl alcohol,and glycerol

Starch and polyvinyl alcohol (PVA) are biodegradable materials with potentiality to replace the conventional polymers in some applications. The aim of this work was to produce biodegradable films of PVA, cassava starch, and glycerol by thermoplastic extrusion using a mixture design to evaluate the effects of each component in the blend properties. Six formulations were prepared using a twin‐screw extruder coupled with a calender. All the materials were visually homogeneous and presented good processability. Mechanical properties were dependent on both the relative humidity conditioning and the formulation; higher relative humidities detracted the mechanical properties, which was associated to plasticizer effect of the water. Furthermore, the mechanical properties were better when higher concentrations of PVA were used, resulting in films with lower opacity, lower water vapor permeability, and higher thermal stability, according to TGA. Biodegradable materials based on starch, PVA, and glycerol have adequate mechanical and processing properties for commercial production. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42697.     

Geographic Variation in Attraction to Human Odor Compounds by Aedes aegypti Mosquitoes (Diptera: Culicidae): A Laboratory Study

Previous investigations of Aedes aegypti response to human odor components have revealed a number of compounds that attract host-seeking females. However, such studies have utilized only a small number of long-term laboratory Ae. aegypti colonies. Using laboratory y-olfactometers, we studied the attraction of four different Ae. aegypti populations (North Queensland, Australia; Florida, USA; Singapore; and Minas Gerais, Brazil) to a key attractant compound from human skin, lactic acid. Combinations of lactic acid with ammonia and a fatty acid (caproic acid) were also investigated. The aims were to determine the extent of variation in lactic acid dose response among populations and to see whether all four populations responded equally to combinations of human odor components. Although all Ae. aegypti populations were attracted to lactic acid, there were differences in the threshold dose: Florida 0.03 μg/min, Singapore 0.17 μg/min, North Queensland 1.92 μg/min, and Brazil 10.27 μg/min. Attraction to lactic acid alone (maximum <40%) was significantly lower than for human odor (>87% for all populations). Significant increases in attraction were observed when lactic acid was combined with ammonia or caproic acid, although not for all populations. In addition, the highest doses of caproic acid tested decreased attraction when combined with lactic acid. The divergent responses to host kairomones seen here may be evidence of adaptation to locally available hosts in different parts of the geographic range of Ae. aegypti.     

A thin PANI and carrageenan–gold nanoparticle film on a flexible gold electrode as a conductive and low-cost platform for sensing in a physiological environment

In this work, we report the production of a layer-by-layer (LbL) film of gold nanoparticles stabilized with carrageenan (carr-AuNPs) interspersed with a conductive polyaniline (PANI) layer. Conventionally, PANI has poor electroactivity in physiological buffers, limiting its using in electrochemical biosensors. The films were prepared on low cost and easy to manufacture flexible gold electrodes (FEAu). Two adsorption sequences were tested for production of the films—PANI/carr-AuNP and carr-AuNP/PANI. The gold nanoparticle size and colloidal stability were characterized. The films were characterized by cyclic voltammetry, UV–visible spectroscopy and atomic force microscopy. The results showed the synergistic effects of the carr-AuNPs (120 nm) and PANI, which improved both the electrochemical response and the stability of the conductive polymer in physiological medium by three times. The presence of the carr-AuNPs in the film caused a significant increase in roughness of the FEAu-modified electrode compared to that of an unmodified electrode, resulting in an increased active electrode area. Studies of film growth by UV–Vis spectroscopy indicated that the deposition mechanisms of both films involved an auto-regulating adsorption process, with the same amount of material adsorbed in each coating step. The PANI/carr-AUNP film showed considerable improvement in stability and conductivity compared to PANI-only films in the physiological environment, which confers advantages for use as a biosensor.     

Chemically modified babassu coconut (<Emphasis Type="Italic">Orbignya sp.)</Emphasis> biopolymer: characterization and development of a thin film for its application in electrochemical sensors

The babassu coconut is a plant very abundant in northeast of Brazil and other countries, and any part of plant and fruit becomes residue. In this study, babassu mesocarp (Orbignya sp) (BM) was chemically modified with phthalic anhydride (BMPA) to increase its solubility in an aqueous medium, and thus facilitate its processing in the form of thin films. The reaction of modification of the babassu mesocarp with phthalic anhydride (PA), obtaining BMPA, was confirmed by FTIR, XRD, TG/DTG, Zeta Potential and SEM analysis, from the differences in the bands of the FTIR spectra, increase in crystallinity, new thermal profile, changes in zeta potential value and morphology, respectively. The thin monolayer films of BM and BMPA were produced by the self-assembly monolayer (SAM) technique, and adsorbed onto conductive glass substrates (tin-doped indium oxide, ITO). The electroactive properties of these thin films were evaluated by cyclic voltammetry (CV). BM exhibited a pair redox pair process of +0.57 V(oxidation) and?+?0.19 V (reduction) for BM. In BMPA these redox processes were observed at +0.37 V (oxidation) and 0.24 V vs. ECS (reduction), verifying that both BM and BMPA are electroactive materials that can be used in the construction of sensor platforms, without the necessity of being conjugated with other electroactive materials, such as conductive polymers, metal phthalocyanines, or dyes. Furthermore, under the experimental conditions used, the BMPA presented a more reversible redox process and higher electrochemical stability in comparison to BM. This effect occurs because BMPA has higher solubility in aqueous media, which favors the preparation of films with smaller grain sizes compared to BM films, as observed by Atomic Force Microscopy (AFM). This study showed that BMPA is a new material with potential for applications in electrochemical sensors.

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Graphical abstract Obtaining and modifying babassu mesocarp for the electrochemical studies