Presence Of Ammonia Vapor Research Articles

Ammonia vapor induced transformation of selected alkoxysilanes within artificial and natural polymer templates

The article demonstrates the series of silicas produced from various alkoxysilanes introduced into the Amberlite® XAD7HP and lyophilized agar, whose transformation took place in the presence of ammonia vapors as catalyst. The silicas have been investigated by the means of the up-to-date analytical methods for the full characterisation of produced solids including positronium annihilation lifetime spectroscopy. The morphology of the silica is the result of the specific conditions applied for precursors transformation. Usage of lyophilized agar as a template for the vapor-phase method does not lead to creation of highly porous silica. The same applies to SiO2 materials produced without any template, with one except for tetrapropoxysilane. On the contrary Amberlite® XAD7HP is a very effective template. This polymer used as a template allows to obtain porous silica (specific surface area > 300 m2 g−1) in a form of microspheres from each of the employed precursors.

A new inorganic-organic hybrid halide perovskite thin film based ammonia sensor

A new perovskite material based on ethylene-diamine-dichloride and lead iodide as organic and inorganic precursors respectively was synthesized. Thin films of perovskite material were characterized using SEM, UV-Visible spectroscopy, XRD, and FT-IR. Sensing properties of inorganic organic perovskite thin films were studied and it was found to be selective for ammonia detection. Ammonia being one of the most hazardous and volatile chemical becomes necessary to detect. Color change of perovskite film from yellow to orange was observed in the presence of ammonia vapors. Electrical measurements showed decrease in resistance in the presence of ammonia vapors. Low concentration upto 50 ppm can be easily detected in approximately 40 s. The present method for detecting ammonia is unique, simple, selective, low cost and can be easily implemented for the field studies.

Cost‐Effective Polymethacrylate‐Based Electrospun Fluorescent Fibers toward Ammonia Sensing

The fabrication of cost‐effective, polymer‐based electrospun fluorescent fibrous grids and their evaluation as candidates for sensing is reported, drawing useful results on their applicability and efficiency in gas sensing applications. A well‐defined, methacrylic homopolymer functionalized with anthracene moieties as fluorescent elements has been blended with a commercially available poly(methyl methacrylate) for the production of fluorescent electrospun polymer fibers. The formation of 3D grids can provide large interaction area with gas analytes and thus overcome quenching limitations induced by polymeric films, for more efficient sensing. These materials have been evaluated for ammonia sensing based on the fluorescence quenching of the anthracene fluorophores in the presence of ammonia vapors, exhibiting fast response at concentration up to 10 000 ppm. The covalent bonding of the anthracene fluorophore onto a hydrophobic polymethacrylate‐based backbone enables the future exploitation of the presented materials in sensing applications involving metal ions and biomolecules in aqueous media. image

Ammonia detection of one-dimensional nano-structured polypyrrole/metal oxide nanocomposites sensors

The nanocomposites based on polypyrrole (PPy) nanostructures containing tin dioxide (SnO2) or zinc oxide (ZnO) nanoparticles were prepared and studied via different methods such as Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), ultraviolet-visible (UV–vis) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The ammonia sensing performances of one-dimensional (1-D) nano-structured polypyrrole and its nanocomposites with metal oxides were investigated and the effect of nanofiller type on the sensors behaviour was studied. The PPy and its nanocomposites with metal oxides exhibited high selectivity for ammonia with respect to methanol and ethanol vapors. The response of the sensor based on PPy/ZnO nanocomposite was found to be much pronounced and more retainable than that of PPy and PPy/SnO2 when exposed to ammonia. The cyclability and linearity of the response for this sensor in presence of ammonia vapor has been investigated as well, suggesting a great potential in detection of ammonia for the prepared sensor.

Photoinduced electrical response in quantum dots/graphene hybrid structure

We report on the enhancement of the electrical photoresponse in a hybrid structure composed of multi-layer graphene flakes covered by a layer of CdSe/ZnS quantum dots (QDs) and placed between metal electrodes. The rate of the photoexcitation energy transfer from QDs to graphene, (0.5–2)×109 s−1 which controls the photoelectrical response of the structure, was found from the analysis of photoluminescence intensities and decay times for QDs in solution, on a bare glass substrate and on the surface of multilayer graphene, and in the presence of ammonia vapors.

A Novel Gas Sensor Transducer Based on Phthalocyanine Heterojunction Devices.

Experimental data concerning the changes in the current-voltage (I-V) perfor-mances of a molecular material-based heterojunction consisting of hexadecafluorinatednickel phthalocyanine (Ni(F16Pc)) and nickel phthalocyanine (NiPc),(Au|Ni(F16Pc)|NiPc|Al) are introduced as an unprecedented principle of transduction for gassensing performances. The respective n- and p-type doped-insulator behaviors of therespective materials are supported, owing to the observed changes in surface potential(using the Kelvin probe method) after submission to electron donor (ammonia) and electronacceptor gases (ozone). On the other hand, the bilayer device exhibits strong variations inthe built-in potential of the junction and in its rectification ratio. Moreover, large increasesoccur in forward and reverse currents in presence of ammonia vapors. These make possiblea multimodal principle of detection controlled by a combined effect between theheterojunction and the NiPc|Al contact. Indeed, this metal/organic junction plays a criticalrole regarding the steady asymmetry of the I-V profiles during the device's doping evenusing high ammonia concentrations. This approach offers a more sophisticated alternative tothe classically studied, but at times rather operation-limited, resistive gas sensors.

Preparation of chitosan membranes for filtration and concentration of compounds under high pressure process

Chitosan membranes of three types: i) dried in ammonia atmosphere (CSA); ii) double layer crosslinked with glutaraldehyde (CSG); and iii) prepared from aqueous-ethanolic solution and dried in the presence of ammonia vapor (CSE) were developed by casting chitosan solutions onto a glossy paper used as a support in the process of filtration under high pressures. All the membranes were characterized by infrared spectroscopy, scanning electron microscopy and by permeation experiments. Addition of ethanol to the chitosan solution decreased the time of membrane preparation and of the filtration process. The performance (solute rejection) of these membranes was found to be efficient with organic compounds such as methylene blue, truncated hemoglobin and bovine serum albumin (BSA) with molecular weights of 319.8 Da 17.7 kDa and 66.4 kDa respectively, since it retained practically 100% of the sample.

Effect of Gas Adsorption on the Photoconductivity of CdSe∕Dielectric Thin Film Structures

The sensitivity of CdSe/PETP thin-film structures with respect to the adsorption of ammonia, aqueous ammonia, and water vapor from the gas phase at room temperature has been studied. The photoconductivity of the best samples exhibited reversible variations within two orders of magnitude in response to the presence of ammonia vapor. The concentration of ammonia in the gas phase can be measured in the interval from 0.25 to 25 vol %.

Effect of Gas Addition on Ozone Ashing

The effect of gas addition on ozone ashing was investigated for the purpose of increasing the ashing rate and decreasing the ashing temperature. Ashing rate increased with the addition of alcohol gas or ammonia vapor to ozone gas. The higher the flow rate and ozone concentration, the greater was the effect of increasing the ashing rate, however, no effect was observed when the ashing rate was low due to the insufficient ozone concentration. Infrared spectra indicated that C‒D bonds exist in the ashing‐treated resist, when deuterated methanol is used as an additive. In the case of alcohol gas addition, hydrogen atoms of alcohol reacted with the double bonds of the resist to generate radicals in the resist, leading to an increase in the rate of oxidative decomposition of the resist. On the other hand, in the case of ozone ashing in the presence of ammonia vapor, the results of X‐ray photoelectron spectroscopy and Fourier transform infrared spectroscopy showed that N‒H bonds were formed on the resist surface by the ashing. It is considered that species containing the N‒H of ammonia were added to the resist structure to accelerate the oxidative decomposition of resist, leading to an increase in the ashing rate.

Energy of adhesion of polydimethylsiloxane networks / glass and polycarbonate assemblies

The reversible energy of adhesion of polydimethylsiloxane (PDMS) networks/substrate assemblies evaluated from surface energy values obtained by wettability measurements is compared with that determined by Johnson, Kendall and Roberts' (JKR) approach. The role of the hydroxyl groups of the PDMS chains in the establishment of the interactions with the glass substrate is confirmed. Indeed, by using the hydrosilylation reaction between vinyl functional groups on PDMS chains on the one hand and silyl hydride functional groups carried by other PDMS chains on the other, polymer networks are obtained without any by-products. Moreover, no hydroxyl groups are present in the polymer network and only interactions of the van der Waals type should occur between the polymer and the glass substrate, even in the presence of ammonia vapor, which has a catalytic effect on the formation of the polymer-substrate interactions involving the hydroxyl groups, as already shown. The JKR approach indicates that the interactions are stronger with the glass substrate than with the polycarbonate substrate, although the calculated reversible energy of adhesion is of the same order of magnitude. This result is expected, considering the characteristics of the glass surface, especially its acid-base character compared with that of the polycarbonate.

Flavonoids of Alzateaceae (Myrtales)

Flavonoids of Alzateaceae (Myrtales)

A CHROMATOGRAPHIC STUDY OF RETICULATE EVOLUTION IN THE APPALACHIAN ASPLENIUM COMPLEX

Smith, Dale M. and Donald A. Levin. (U. Illinois, Urbana.) A chromatographic study of reticulate evolution in the Appalachian Asplenium complex. Amer. Jour. Bot. 50(9): 952–958. Ilus. 1963.—The reticulate relationships of the members of the Appalachian Asplenium complex were studied by means of paper chromatography. Substances could be observed with ultraviolet light in the presence of ammonia vapor in all the taxa of the complex. The diploid species (A. montanum, A. platyneuron and A. rhizophyllum) had characteristic biochemical substances. Interspecific hybrids and/or their allotetraploid derivatives showed a complete complementation of all the substances of their known or presumed diploid ancestors. A combination of all the substances of the 3 diploids was found in the hybrids A. X kentuckiense and A. X gravesii. The results agree in all respects with the concept of reticulate evolution in the group which was advanced by Wagner on the basis of comparative morphology, hybridization and karyology.

A Chromatographic Study of Reticulate Evolution in the Appalachian Asplenium Complex

Smith, Dale M. and Donald A. Levin. (U. Illinois, Urbana.) A chromatographic study of reticulate evolution in the Appalachian Asplenium complex. Amer. Jour. Bot. 50(9): 952–958. Ilus. 1963.—The reticulate relationships of the members of the Appalachian Asplenium complex were studied by means of paper chromatography. Substances could be observed with ultraviolet light in the presence of ammonia vapor in all the taxa of the complex. The diploid species (A. montanum, A. platyneuron and A. rhizophyllum) had characteristic biochemical substances. Interspecific hybrids and/or their allotetraploid derivatives showed a complete complementation of all the substances of their known or presumed diploid ancestors. A combination of all the substances of the 3 diploids was found in the hybrids A. X kentuckiense and A. X gravesii. The results agree in all respects with the concept of reticulate evolution in the group which was advanced by Wagner on the basis of comparative morphology, hybridization and karyology.