Narrow Results

In the present work, we determined the electrical properties of octachlorinated metallophthalocyanines with Co(II) and Cu(II) ions as metal centers. We engaged them in heterojunctions, with lutetium bisphthalocyanine as a partner. Surprisingly, cobalt and copper complexes show opposite behaviors, the first being an $n$-type material whereas the latter is a $p$-type material, as deduced from the response of the heterojunctions towards ammonia; showing the unusual key role played by the metal center. While the LuPc${}_{\mathrm{\text{2}}}$/Cu(Cl${}_{\mathrm{\text{8}}}$Pc) complex exhibits a negative response to ammonia, the LuPc${}_{\mathrm{\text{2}}}$/Co(Cl${}_{\mathrm{\text{8}}}$Pc) complex exhibits a positive response to ammonia, with a sensitivity of 1.47% ppm${}^{\mathrm{\text{-1}}}$ at concentrations lower than 10 ppm and a limit of detection of 250 ppb. All the devices operate at room temperature and in real atmosphere.

Cellulose nanocrystals were extracted from cellulose raw material through hydrothermal process, and then polyaniline layer was coated on the surface of cellulose nanocrystals via in-situ chemical oxidative polymerization of aniline monomers. The resulting nanocomposite was investigated by scanning electron microscopy, Fourier transform infrared spectrometry, thermal gravimetric analysis, and gas sensing measurement. The results show the nanocomposite with good core-shell structure exhibited high thermal stability. For ammonia gas detection, high sensitivity, relative fast response, short recovery time, and good reproducibility can be achieved for the nanocomposite.

Polypyrrole (PPy)–Zn₂SnO₄ nanocomposites with different weight percentages (0–20%) of Zn₂SnO₄ were successfully prepared by chemical oxidative polymerization. The prepared nanocomposites were deposited on epoxy glass substrate using a spin coating technique and have been characterized using various techniques such as X-ray diffractometer, field emission scanning electron microscopy (FESEM) and Fourier transform infrared (FTIR) spectrometer. The physicochemical characterization confirmed well-formed dodecylbenzene (DBSA)-doped PPy–Zn₂SnO₄ nanocomposites with granular morphology and high porosity. Among various nanocompositions, DBSA-doped PPy–Zn₂SnO₄ (10 wt.%) nanocomposite was found to be highly sensitive towards NH₃ vapor at room temperature i.e. with a chemiresistive response of 5.44% at 27 ppm with a reasonably fast recovery time of 76 s. Additionally, it shows a linear response and appropriate recovery time at all concentrations of NH₃ vapor. The DBSA-doped PPy–Zn₂SnO₄ nanocomposite response is four times better than pure PPy toward NH₃ vapor at room temperature. Therefore, it is expected that such material with excellent gas sensing properties at room temperature can be used for high-performance NH₃ sensors.

In the present work, the optical response of CoPcF₁₆ films upon exposure to ammonia vapor in the concentration range 50 to 1000 ppm was measured by total internal reflection ellipsometry. It was demonstrated that the sorption of NH₃ molecules causes substantial shift of the Δ(λ) spectrum which is determined by the increase in film thickness and change of its optical parameters. It was found that the CoPcF₁₆ films deposited at substrate temperature of 220 °C are characterized by larger grains and more developed surface demonstrating higher optical response than films deposited at substrate temperature of 60 °C. In order to gain an insight into the sorption mechanism at molecular level, we have studied the interaction of ammonia vapor with hexadecafluorinated cobalt phthalocyanine using infrared spectroscopy. It was shown that the detection of ammonia was found to be governed primarily by coordination to the metal center.

Isoindole-diimine, which can be obtained by bubbling ammonia gas into a solution of phthalonitrile derivatives in the presence of Na${}^{+}$ ion, is a final and best precursor for phthalocyanine synthesis. In this study, isoindole-diimine and various derivatives have been prepared without bubbling ammonia gas using in situ generated ammonia that was produced from formamide and a strong alkali such as NaOH and NaNH₂. A longer reaction time, higher temperature, and larger amount of formamide were required for phthalonitrile derivatives with electron-donating groups, but this method is recommendable in that an NH₃ gas cylinder and concomitant gas regulator, which are not inexpensive, are not required. Attempts were made to interpret the IR and absorption spectra of the resultant diimines. The signals due to imino proton or N-H of diimino compounds were experimentally found to appear at around 8.2$\sim$9.5 ppm in ¹H-NMR and ca. 3500–3000 cm${}^{-1}$ in IR spectra.

Resorption refrigeration system, a novel type of chemisorption technique, employs two or more inorganic salts as sorbent reactants, which co-operate as working pair. The working conditions and some evaluation indicators of the resorption system with different working pairs in previous studies are collected and summarized in this work. The performance of the reactant salts is compared, and further effort direction of the selection of working pairs is also analyzed.

We have previously hypothesized that density-dependent natural selection is responsible for a genetic polymorphism in crowded cultures of Drosophila. This genetic polymorphism entails two alternative phenotypes for dealing with crowded Drosophila larval cultures. The first phenotype is associated with rapid development, fast larval feeding rates but reduced absolute viability, especially in the presence of nitrogenous wastes like ammonia. The second phenotype has associated with it the opposite set of traits, slow development, slow feeding rates and higher viability. We suggested that these traits are associated due to genetic correlations and that an important selective agent in crowded larval cultures was high levels of ammonia. To test this hypothesis we have examined viability and larval feeding rates in populations kept at low larval densities but selected directly for (i) rapid egg-to-adult development, (ii) tolerance of ammonia in the larval environment and (iii) tolerance of urea in the larval environment. Consistent with our hypothesis we found that (i) larvae selected for rapid development exhibited increased feeding rates, and decreased viability in food laced with ammonia or urea relative to controls, and (ii) larvae selected to tolerate either ammonia or urea in their larval environment show reduced feeding rates but elevated survival in toxin-laced food relative to controls. It would appear that development time and larval feeding rate are important characters for larvae adapting to crowded cultures. The correlated fitness effects of these characters provide important insights into the nature of density-dependent natural selection.

Observing inversion lines of ammonia (NH3), complemented by rotational lines of NH3 and other molecular species, provides stringent constraints on potential variations of the proton-to-electron mass ratio, μ. While a limit of |Δμ|/μ ~ 10⁻⁶ is derived for a lookback time of 7 × 10⁹ yr, nearby dark clouds might show a significant variation of order (2 − 3) × 10⁻⁸, possibly being related to chameleon fields. The detection of radioloud quasars with strong molecular absorption lines at redshifts z > 1 as well as the identification of a larger sample of nearby molecular clouds with exceptionally narrow lines (ΔV < 0.2kms⁻¹) would be essential to improve present limits and to put the acquired results onto a firmer statistical basis.