This review summarizes the recent research efforts and developments in nanomaterials for sensing volatile organic compounds (VOCs). The discussion focuses on key materials such as metal oxides (e.g., ...ZnO, SnO
, TiO
WO
), conductive polymers (e.g., polypyrrole, polythiophene, poly(3,4-ethylenedioxythiophene)), and carbon-based materials (e.g., graphene, graphene oxide, carbon nanotubes), and their mutual combination due to their representativeness in VOCs sensing. Moreover, it delves into the main characteristics and tuning of these materials to achieve enhanced functionality (sensitivity, selectivity, speed of response, and stability). The usual synthesis methods and their advantages towards their integration with microsystems for practical applications are also remarked on. The literature survey shows the most successful systems include structured morphologies, particularly hierarchical structures at the nanometric scale, with intentionally introduced tunable "decorative impurities" or well-defined interfaces forming bilayer structures. These groups of modified or functionalized structures, in which metal oxides are still the main protagonists either as host or guest elements, have proved improvements in VOCs sensing. The work also identifies the need to explore new hybrid material combinations, as well as the convenience of incorporating other transducing principles further than resistive that allow the exploitation of mixed output concepts (e.g., electric, optic, mechanic).
Zinc oxide rod structures are synthetized and subsequently modified with Au, Fe2O3, or Cu2O to form nanoscale interfaces at the rod surface. X-ray photoelectron spectroscopy corroborates the presence ...of Fe in the form of oxide—Fe2O3; Cu in the form of two oxides—CuO and Cu2O, with the major presence of Cu2O; and Au in three oxidation states—Au3+, Au+, and Au0, with the content of metallic Au being the highest among the other states. These structures are tested towards nitrogen dioxide, ethanol, acetone, carbon monoxide, and toluene, finding a remarkable increase in the response and sensitivity of the Au-modified ZnO films, especially towards nitrogen dioxide and ethanol. The results for the Au-modified ZnO films report about 47 times higher response to 10 ppm of nitrogen dioxide as compared to the non-modified structures with a sensitivity of 39.96% ppm−1 and a limit of detection of 26 ppb to this gas. These results are attributed to the cumulative effects of several factors, such as the presence of oxygen vacancies, the gas-sensing mechanism influenced by the nano-interfaces formed between ZnO and Au, and the catalytic nature of the Au nanoparticles.
Synthesis of micro- and nano-sized crystalline BaFeO
4
particles by precipitation from the electrochemically synthesized potassium ferrate(VI) solution by means of barium hydroxide and its ...encapsulation in paraffin wax were explored using scanning electron microscopy, X-ray diffraction spectroscopy and FTIR spectroscopy. Experimental results showed effective synthesis of the micro-sized and nano-sized BaFeO
4
particles and their coating by the paraffin wax layer. The encapsulated micro- and nano-sized particles of BaFeO
4
were applied in investigating the possibility of degradation of pesticide clomazone in water. The removal of clomazone from water by oxidation using encapsulated BaFeO
4
could be almost 95%.
This work presents the effect of magnesium (Mg) doping on the sensing properties of tin dioxide (SnO2) thin films. Mg-doped SnO2 films were prepared via a spray pyrolysis method using three doping ...concentrations (0.8 at.%, 1.2 at.%, and 1.6 at.%) and the sensing responses were obtained at a comparatively low operating temperature (160 °C) compared to other gas sensitive materials in the literature. The morphological, structural and chemical composition analysis of the doped films show local lattice disorders and a proportional decrease in the average crystallite size as the Mg-doping level increases. These results also indicate an excess of Mg (in the samples prepared with 1.6 at.% of magnesium) which causes the formation of a secondary magnesium oxide phase. The films are tested towards three volatile organic compounds (VOCs), including ethanol, acetone, and toluene. The gas sensing tests show an enhancement of the sensing properties to these vapors as the Mg-doping level rises. This improvement is particularly observed for ethanol and, thus, the gas sensing analysis is focused on this analyte. Results to 80 ppm of ethanol, for instance, show that the response of the 1.6 at.% Mg-doped SnO2 film is four times higher and 90 s faster than that of the 0.8 at.% Mg-doped SnO2 film. This enhancement is attributed to the Mg-incorporation into the SnO2 cell and to the formation of MgO within the film. These two factors maximize the electrical resistance change in the gas adsorption stage, and thus, raise ethanol sensitivity.
Allan Kaprow conceived of his score-based "un-art" as unrepeatable yet open to reinvention: his Happenings, Environments, and Activities had to be radically reimagined, not reenacted on a stage set ...or reconstructed from photographs. Shortly before his death in 2006, Kaprow assembled visual and verbal information connected to his key works, but provided artists, curators, and scholars with few rules about how to approach them. Generally speaking, the reinventor's task is to produce difference through fidelity to whatever is so essential in the work that it can survive its dramatic transformation. While some understood this as careful attention to a work's central metaphor, others took a more literalist approach, reenacting the largely verbal scores to the letter; still others combined the two approaches, exploiting the productive tension-or parallax shift-between a work's literal and figurative elements. Through this notion of a parallax shift that brackets out certain elements to produce various meanings, this article explores different iterations of 18 Happenings in 6 Parts (1959), Yard (1961), Baggage (1972), and Easy (1972). Filled with the same productive contradictions as his writing, Kaprow's un-art here emerges through the interventions of André Lepecki, Otobong Nkanga, William Pope.L, Sharon Hayes, and Florian Dombois as central to the ongoing historicizing of live art.
This paper shows the effects of ferrate(VI) application in the treatment of
industrial wastewater effluent in laboratory conditions. Samples used are a
mixture of wastewater effluent from various ...industrial plants whose
composition was determined by analyzing samples before the ferrate(VI)
treatment. Determining physical-chemical characteristics of the samples
showed very high chemical oxygen demand (COD) and the concentrations of
individual pollutants are higher than the maximum allowed. In the tested
samples, the COD was from 18 (sample 1) to 580 times (sample 2) greater than
allowed (allowed 45 - 150 mg/l), while the concentrations of certain metals
were several times higher than allowed (Cu allowed 0,1 mg/l, Zn allowed 0,2
mg/l). Also, a high concentration of total phosphorus content (allowed 2
mg/l) and fluoride was found (allowed 20 mg/l), 2-3 times higher than
permissible. The applied Na2FeO4 was synthesized by electrochemical method
and applied in situ. Physical-chemical testing of samples, after treatment
with different amounts (2, 5, 8, and 10 ml) of Na2FeO4, concentration of 8
g/l showed that ferrate(VI) can be used as a multifunctional agent in the
purification of industrial wastewater, where in the amount of contaminating
matter is reduced below the maximum permitted level. It was demonstrated the
high efficiency of ferrate(VI) as a strong oxidant in the removal of total P
and suspended materials. Also pointed out was the high sorption power of the
generated ferric(III)hydroxide, which with its developed surface absorbs
95,5% of the F- and removes it from the solution in the form of sludge.
Showed a high efficiency of ferrate(VI) in the total removal of P (70 to
99,5%), and F- (89 to 95,5%), but depending on the presence of the total COD
value or the presence of the total organic substances. At high values of the
COD major part of ferrate(VI) is consumed in the oxidation of organic
material and the formation of Fe(OH)3, which accelerate the process of
decomposition of ferrate(VI), which contributes to lower the efficiency of
the removal of P and F-.
Allan Kaprow conceived of his score-based "un-art" as unrepeatable yet open to reinvention: his Happenings, Environments, and Activities had to be radically reimagined, not reenacted on a stage set ...or reconstructed from photographs. Shortly before his death in 2006, Kaprow assembled visual and verbal information connected to his key works, but provided artists, curators, and scholars with few rules about how to approach them. Generally speaking, the reinventor"s task is to produce difference through fidelity to whatever is so essential in the work that it can survive its dramatic transformation. While some understood this as careful attention to a work"s central metaphor, others took a more literalist approach, reenacting the largely verbal scores to the letter; still others combined the two approaches, exploiting the productive tension - or parallax shift - between a work"s literal and figurative elements. Through this notion of a parallax shift that brackets out certain elements to produce various meanings, this article explores different iterations of 18 Happenings in 6 Parts (1959), Yard (1961), Baggage (1972), and Easy (1972). Filled with the same productive contradictions as his writing, Kaprow"s un-art here emerges through the interventions of André Lepecki, Otobong Nkanga, William Pope.L, Sharon Hayes, and Florian Dombois as central to the ongoing historicizing of live art. (Author abstract)
Gas sensitive cerium oxide-tungsten oxide core-shell nanowires are synthesized and integrated directly into micromachined platforms via aerosol assisted chemical vapor deposition. Tests to various ...volatile organic compounds (acetone, ethanol, and toluene) involved in early disease diagnosis demonstrate enhanced sensitivity to acetone for the core-shell structures in contrast to the non-modified materials (i.e., only tungsten oxide or cerium oxide). This is attributed to the high density of oxygen vacancy defects at the shell, as well as the formation of heterojunctions at the core-shell interface, which provide the modified nanowires with 'extra' chemical and electronic sensitization as compared to the non-modified materials.
The solid salts of the ferrate anion might offer significant advantages over conventional materials used as cathodes because of the three electron transfer associated with the reduction of Fe(VI) to ...Fe(III). In the present study, we try to improve the performance of the electrochemically synthesized barium ferrate cathode using non-stoichiometric binary titanium oxides: titanium monoxide (TiOx) and Magnѐli phases (TinO2n-1) addition performed throughout fabrication of plastic bonded cathode. It is shown that the addition of conductive Magnѐli phase materials into active material improves the performance of a cathode in terms of specific capacity, reversibility, and more positive equilibrium potential compared to BaFeO4 − based cathodes. It is believed that Magnѐli phase material enhances connectivity of the active BaFeO4 material and acts as reinforcement to the active mass thereby aiding retention of feature and porosity during cycling improving the reaction kinetics of the electrode. Also, our preliminary results demonstrate that the porous plastic bonded thin foil electrodes based on electrochemically synthesized barium ferrate can be considered in spiral wound battery geometry for higher rate capability.
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