Gaseous Acetic Acid Research Articles

Removal of gaseous acetic acid using ionic liquid [EMIM][BF4

This work proposed to use the ionic liquid [EMIM][BF4] as absorbent for the absorption of gaseous acetic acid. The feasibility of this technology was investigated from molecular level to industrial scale. The acetic acid absorption experiment was carried out using [EMIM][BF4], and the removal ratio of acetic acid in the gas product can achieve 88.6% at 20 °C under atmospheric pressure at the laboratory scale. Based on the experimental results, a reliable strict equilibrium phase model embedding the parameters of the UNIFAC model was established. On this basis, the conceptual process design and optimization of acetic acid removal by [EMIM][BF4] at an industrial scale was done, and the most suitable design and operation parameters were obtained. For a further step, the binding energy between [EMIM][BF4] and acetic acid was calculated to give some insights into the separation mechanism, and the results indicate that the interaction between acetic acid and IL is much stronger than that between nitrogen and IL. Moreover, hydrogen bond can be formed between the cation-acetic acid as well as the anion-acetic acid.

Photocatalytic Selectivities of Ethane, Methane and Dimethylether Controlled by Reaction Conditions and TiO2 Structure in the Degradation of Acetic Acid

AbstractThe impact of photon flux, humidity and residence time using TiO2 P25 and of the surface area of a series of CristalActiv PC TiO2 anatase, on the selectivities of products formed in the continuous photocatalytic degradation of gaseous acetic acid (AA) on the scale of a few hundred ppm, in the presence or absence of O2, was investigated. Under a continuous flow of air HCHO and C2H6 were the most important products detected. CH3OH was also formed but to a lesser extent. Under a continuous flow of N2, the formation of these three products decreases whereas CH3OCH3, an interesting product which can be used as alternative fuel and CH4, is yielded. The impact of the experimental conditions on product formation, taking into account the intermediate formation of H2O2 and the favorable impact of the surface area on the formation of CH4 in the absence of oxygen and its opposite effect on the formation of C2H6 in the presence of air, was discussed.The presence of rutile phase in TiO2 P25 was also highlighted.

Effects of a matrix-coated organic acids and medium-chain fatty acids blend on performance, and in vitro fecal noxious gas emissions in growing pigs fed in-feed antibiotic-free diets

This study evaluated the efficacy of a matrix-coated organic acids and medium-chain fatty acids blend (MCOFA) in growing pigs. Ninety six pigs [(Yorkshire × Landrace) × Duroc] with an average body weight (BW) of 47.71 ± 3.73 kg were used in a 6 wk experiment. Pigs were allotted to diets containing 0 or 2 g kg−1 of MCOFA, and 0 or 2.5 g kg−1 of antibiotic growth promoters (AGP) according to a 2 × 2 factorial arrangement of treatments. Pigs fed diets supplemented with MCOFA had improved growth efficiency compared with those fed a diet without MCOFA (P < 0.05). Pigs receiving the diets supplemented with both AGP and MCOFA had higher apparent total tract digestibility of crude protein, dry matter, fat, and gross energy (P < 0.05). Pigs fed AGP × MCOFA diet had increased serum urea nitrogen (P < 0.05). Pigs fed diets supplemented with AGP had reduced fecal ammonia (NH3) gas emissions compared with those fed without AGP (P < 0.05). Moreover, pigs fed diets supplemented with MCOFA had reduced fecal NH3 and acetic acid gas emissions compared with those fed without MCOFA (P < 0.05). In conclusion, dietary supplementation with MCOFA improved performance in growing pigs.

Size-tunable Ag nanoparticles sensitized porous ZnO nanobelts: controllably partial cation-exchange synthesis and selective sensing toward acetic acid

Porous ZnO nanobelts sensitized with Ag nanoparticles have been prepared via a partial cation-exchange reaction assisted by a thermal oxidation treatment, employing ZnSe·0.5N2H4 nanobelts as precursors. After partially exchanged with Ag+ cations, the belt-like morphology of the precursors is still preserved. Continuously calcined in air, they are in situ transformed into Ag nanoparticles sensitized porous ZnO nanobelts. The size of the Ag nanoparticles can be tuned through manipulating the amount of exchanging Ag+ cations. Considering the porous and belt-like nanostructure, sensing characteristics of ZnO and the catalytic activity of Ag nanoparticles, the gas sensing performances of the as-prepared Ag nanoparticles sensitized porous ZnO nanobelts have been carefully investigated. The results indicate that Ag nanoparticles significantly enhance the sensing performances of porous ZnO nanobelts toward typical volatile organic compounds. Especially, a good selectivity has been demonstrated toward acetic acid gas with a low detection limit less than 1 ppm. Furthermore, they also display a good reproducibility with a short response/recovery time due to the thin, uniform and porous sensing film, which is fabricated with the assembled technique and in situ calcined approach. Finally, their sensing mechanism has been further discussed.

Reduction of histamine and heavy metals in mackerel hydrolyzates produced by catalysts associated-subcritical water hydrolysis

Various catalysts such as formic acid, acetic acid, sodium hydroxide, sodium bicarbonate, carbon dioxide and nitrogen gas were used for hydrolyzates production from deoiled mackerel muscle by subcritical water hydrolysis. Above 99% hydrolysis yield was obtained using sodium bicarbonate catalyst at 260°C/70bar. Histamine and heavy metals concentration were reduced in hydrolyzates. Highest amount of amino acid (400.36mg/g) and reducing sugar (24.75mg/g) were found in hydrolyzate obtained at 260°C/70bar and 220°C/30bar, respectively with sodium bicarbonate catalyst. Antioxidant and ACE-inhibitory activities were significantly higher in hydrolyzates obtained using sodium bicarbonate than that of others.

Enhanced Acidity of Acetic and Pyruvic Acids on the Surface of Water.

Understanding the acid-base behavior of carboxylic acids on aqueous interfaces is a fundamental issue in nature. Surface processes involving carboxylic acids such as acetic and pyruvic acids play roles in (1) the transport of nutrients through cell membranes, (2) the cycling of metabolites relevant to the origin of life, and (3) the photooxidative processing of biogenic and anthropogenic emissions in aerosols and atmospheric waters. Here, we report that 50% of gaseous acetic acid and pyruvic acid molecules transfer a proton to the surface of water at pH 2.8 and 1.8 units lower than their respective acidity constants p Ka = 4.6 and 2.4 in bulk water. These findings provide key insights into the relative Bronsted acidities of common carboxylic acids versus interfacial water. In addition, the work estimates the reactive uptake coefficient of gaseous pyruvic acid by water to be γPA = 0.06. This work is useful to interpret the interfacial behavior of pyruvic acid under low water activity conditions, typically found in haze aerosols, clouds, and fog waters.

Analysis of acetic acid gas phase reactivity: Rate constant estimation and kinetic simulations

The gas phase reactivity of acetic acid was investigated combining first principle calculations with kinetic simulations. Rate constants for the unimolecular decomposition of acetic acid were determined integrating the 1D master equation over a Potential Energy Surface (PES) investigated at the M06-2X/aug-cc-pVTZ level. Energies were computed at the CCSD(T)/aug-cc-pVTZ level using a basis set size correction factor determined at the DF-MP2/aug-cc-pVQZ level. Three decomposition channels were considered: CO2 + CH4, CH2CO + H2O, and CH3 + COOH. Rate constants were computed in the 700–2100 K and 0.1–100 atm temperature and pressure ranges. The simulations show that the reaction is in fall off above 1200 K at pressures smaller than 10 atm. Successively, the PESs for acetic acid H-abstraction by H, OH, OOH, O2, and CH3 were investigated at the same level of theory. Rate constants were computed accounting explicitly for the formation of entrance and exit van der Waals wells and their collisional stabilization. Energy barriers were determined at the CASPT2 level for H-abstraction by OH of the acidic H, since it has a strong multireference character. The calculated rate constant is in good agreement with experiments and supports the experimental finding that at low temperatures it is pressure dependent. The calculated rate constants were used to update the POLIMI kinetic model and to simulate the pyrolysis and combustion of acetic acid. It was found that acetic acid decomposition and the formation of its direct decomposition products can be reasonably predicted. The formation of secondary products, such as H2 and C2 hydrocarbons, is underpredicted. This suggests that reaction routes not incorporated in the model may be active. Some hypotheses are formulated on which these may be.

In-situ electrosynthesis of hydrogen peroxide and wastewater treatment application: A novel strategy for graphite felt activation

Electrochemical synthesis of hydrogen peroxide (H2O2) through O2 electroreduction is an attractive alternative to the currently used anthraquinone process, and highly desirable for green chemical industries and environmental remediation. However, it remains a great challenge to develop cost-effective and durable electrocatalysts. Hence, rational strategy for developing electrocatalyst materials to achieve highly efficient 2e− pathway oxygen reduction reaction (ORR) electrocatalysis is extremely important for in situ electrochemical synthesis of H2O2.In the present work, an economical activated graphite felt (AGF) material, following a simple and low-cost gaseous acetic acid activation method, is developed. With this activation process, the electrochemical performance of the AGF shows a great promotion for H2O2 production rate. Compared with raw graphite felt (RGF) material, the yield of H2O2 achieved on AGF is enhanced by several folds. The enhanced performance might be attributed to its specific pore structure, high content of defects and transformation of surface chemical bonds, which derives from the activation with gaseous acetic acid at high temperature.It is found that the factors responsible for the remarkable electrocatalytic performance of AGF1100 are: 1) the special pore structure, which offers large area for reaction, obtained through gaseous acetic acid activation process at high temperature; 2) high content of sp3C bonds, defects, and oxygen-containing functional groups, which can act as active sites for oxygen adsorption or reduction during the electrocatalytic process.

Facile and fast electrospinning of crystalline ZnO 3D interconnected nanoporous nanofibers for ammonia sensing application

One-dimensional nanoporous metal oxide nanostructures have attracted great interest for their noticeable properties in gas sensor applications. In this paper, we report fabrication of crystalline sub 100 nm 3D interconnected nanoporous nanofibers with about 250 nm diameter. Theses nanostructures have high surface to volume ratio. Glycerol monostearate is used in precursor solution using electrospinning technique and then a subsequent heat treatment is performed on it by calcination process at high temperature. We achieve high crystalline structure of ZnO wurtzite phase. The fabricated crystalline ZnO interconnected nanoporous nanofiber (C–ZnO–INN) is characterized by scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, energy dispersive spectroscopy, and X-ray diffraction. In addition, gas sensitivity of C–ZnO–INN is studied at room temperature. Cobalt is doped in C–ZnO–INN as a gas catalyst to increase sensitivity of the sensor. The results of the tests indicate that the sensor sensitivity is high for ammonia in the range of 1–800 ppm at room temperature. Moreover, the results show that the gas responsivity is linear to methanol, 2-propanol, acetone, acetic acid, and ammonia gases for Co doped C–ZnO–INN comparing with bare ZnO nanofibers. The C–ZnO–INN can be a best candidate for applications in diverse fields including sensor sensing or catalytic fields due to high surface to volume ratio of fabricated nanoporous nanofibers. Furthermore, it has the potential to be used in various semiconductor nanosensor applications (biosensors, high performance chemoresistive gas sensors, and etc.) because of using the facile and fast electrospinning nanoporous nanofibers fabrication method.

Aerosol optical properties and trace gas emissions by PAX and OP-FTIR for laboratory-simulated western US wildfires during FIREX

Abstract. Western wildfires have a major impact on air quality in the US. In the fall of 2016, 107 test fires were burned in the large-scale combustion facility at the US Forest Service Missoula Fire Sciences Laboratory as part of the Fire Influence on Regional and Global Environments Experiment (FIREX). Canopy, litter, duff, dead wood, and other fuel components were burned in combinations that represented realistic fuel complexes for several important western US coniferous and chaparral ecosystems including ponderosa pine, Douglas fir, Engelmann spruce, lodgepole pine, subalpine fir, chamise, and manzanita. In addition, dung, Indonesian peat, and individual coniferous ecosystem fuel components were burned alone to investigate the effects of individual components (e.g., “duff”) and fuel chemistry on emissions. The smoke emissions were characterized by a large suite of state-of-the-art instruments. In this study we report emission factor (EF, grams of compound emitted per kilogram of fuel burned) measurements in fresh smoke of a diverse suite of critically important trace gases measured using open-path Fourier transform infrared spectroscopy (OP-FTIR). We also report aerosol optical properties (absorption EF; single-scattering albedo, SSA; and Ångström absorption exponent, AAE) as well as black carbon (BC) EF measured by photoacoustic extinctiometers (PAXs) at 870 and 401 nm. The average trace gas emissions were similar across the coniferous ecosystems tested and most of the variability observed in emissions could be attributed to differences in the consumption of components such as duff and litter, rather than the dominant tree species. Chaparral fuels produced lower EFs than mixed coniferous fuels for most trace gases except for NOx and acetylene. A careful comparison with available field measurements of wildfires confirms that several methods can be used to extract data representative of real wildfires from the FIREX laboratory fire data. This is especially valuable for species rarely or not yet measured in the field. For instance, the OP-FTIR data alone show that ammonia (1.62 g kg−1), acetic acid (2.41 g kg−1), nitrous acid (HONO, 0.61 g kg−1), and other trace gases such as glycolaldehyde (0.90 g kg−1) and formic acid (0.36 g kg−1) are significant emissions that were poorly characterized or not characterized for US wildfires in previous work. The PAX measurements show that the ratio of brown carbon (BrC) absorption to BC absorption is strongly dependent on modified combustion efficiency (MCE) and that BrC absorption is most dominant for combustion of duff (AAE 7.13) and rotten wood (AAE 4.60): fuels that are consumed in greater amounts during wildfires than prescribed fires. Coupling our laboratory data with field data suggests that fresh wildfire smoke typically has an EF for BC near 0.2 g kg−1, an SSA of ∼ 0.91, and an AAE of ∼ 3.50, with the latter implying that about 86 % of the aerosol absorption at 401 nm is due to BrC.

Sensing Parts per Million Level Ammonia and Parts per Billion Level Acetic Acid in the Gas Phase by Common Black Film with a Fluorescent pH Probe.

Relying on the nanometer-thick water core and large surface area-to-volume ratio (∼2 × 108 m-1) of common black film (CBF), we are able to use a pH-sensitive dye (carboxy-seminaphthorhodafluor-1, SNARF-1) to detect ammonia and acetic acid gas adsorption into the CBF, with the limit of detection reaching 0.8 ppm for NH3 gas and 3 ppb for CH3COOH gas in the air. Data analysis reveals that fluorescence signal change is linearly proportional to the gas concentration up to 15 ppm and 65 ppb for NH3 and CH3COOH, respectively.

The acetic acid gas sensing properties of graphene quantum dots (GQDs)–ZnO nanocomposites prepared by hydrothermal method

Graphene quantum dots (GQDs) and GQDs–ZnO composites with different amounts of GQDs have been synthesized via a hydrothermal method. The GQDs were characterized HRTEM and size distribution analyzer. The GQDs–ZnO composites were studied by XRD, SEM, TG, FTIR, Raman and XPS, respectively. The gas sensing properties of GQDs–ZnO composites were investigated. It was found that the amount of GQDs in the composite has great influence on the gas response and gas sensing selectivity of the composite; the sensors based on GQDs–ZnO composites could be operated at room temperature and showed higher response to acetic acid gas than pure ZnO sensor; the sensor based on GQDs–ZnO (S-10) composite could detect 1 ppm acetic acid vapor at room temperature.

Fabrication of biomass-derived C-doped Bi2WO6 templated from wood fibers and its excellent sensing of the gases containing carbonyl groups

In this work, wood fibers (Populus ussuriensis Kom) were used as biotemplate to synthesize Bi2WO6. In corporation of biomass-derived C, the sensitivity to the gases containing carbonyl groups of gas sensors is improved. The experimental results showed that the C-doped Bi2WO6 sensors presented high sensitivities to acetone, acetic acid and ethyl acetate molecules at low temperature (370°C). The gas sensitivities of C-doped Bi2WO6 sensors on exposure to 1000ppm of acetone, acetic acid and ethyl acetate gas are 4.4, 3.0 and 2.4 times higher than that exposure to 1000ppm of ethanol, respectively. That is because the biomass-derived C can adsorb more oxygen molecules and the carbonyl groups in the gases can react with more oxygen molecules and release more electrons leading a resistance decrease of the sensors due to the electronic structure of carbonyl groups. The reported strategy opened up a new way for the development of gas sensors.

Excitonic, vibrational, and van der Waals interactions in electron energy loss spectroscopy

The pioneer, Ondrej L. Krivanek, and his collaborators have opened up many frontiers for the electron energy loss spectroscopy (EELS), and they have demonstrated new potentials of the EELS method for investigating materials. Here, inspired by those achievements, we show further potentials of EELS based on the results of theoretical calculations, that is excitonic and van der Waals (vdW) interactions, as well as vibrational information of materials. Concerning the excitonic interactions, we highlight the importance of the two-particle calculation to reproduce the low energy-loss near-edge structure (ELNES), the Na-L2,3 edge of NaI and the Li-K edge of LiCl and LiFePO4. Furthermore, an unusually strong excitonic interaction at the O-K edge of perovskite oxides, SrTiO3 and LaAlO3, is shown. The effect of the vdW interaction in the ELNES is also investigated, and we observe that the magnitude of the vdW effect is approximately 0.1eV in the case of the ELNES from a solid and liquid, whereas its effect is almost negligible in the case of the ELNES from the gaseous phase owing to the long inter-molecular distance. In addition to the “static” information, the influence of the “dynamic” behavior of atoms in materials to EELS is also investigated. We show that measurements of the infrared spectrum are possible by using a modern monochromator system. Furthermore, an estimation of the atomic vibration in core-loss ELNES is also presented. We show the acquisition of vibrational information using the ELNES of liquid methanol and acetic acid, solid Al2O3, and oxygen gas.

Heat-Induced Polycondensation Reaction with Self-Generated Blowing Agent Forming Aromatic Thermosetting Copolyester Foams

This work presents a unique chemical strategy and a facile fabrication scheme toward development of novel aromatic thermosetting copolyester foams. Designed aromatic-based acetoxy and carboxylic acid end-group oligomers carry out an endothermic condensation polymerization reaction, which self-generates acetic acid blowing agent forming macrocellular porous morphology within cross-linked ester backbone polymer matrix. Herein, we provide a visual insight into the foaming reaction between the constituent oligomer groups via optical micrographs captured at polymerization phase transformation stages; oligomer melt-compounding, bubble nucleation via release of gaseous acetic acid, and subsequently bubble growth at elevated temperatures. Furthermore, we show cure and postcure characteristics of the constituent oligomers in the course of the foaming reaction that the most favorable pair of cure temperature and cure time is determined. Then, combining these outcomes, we design an optimum cure cycle and fabrication...

Heterogeneous Reactions of Acetic Acid with Oxide Surfaces: Effects of Mineralogy and Relative Humidity.

We have investigated the heterogeneous uptake of gaseous acetic acid on different oxides including γ-Al2O3, SiO2, and CaO under a range of relative humidity conditions. Under dry conditions, the uptake of acetic acid leads to the formation of both acetate and molecularly adsorbed acetic acid on γ-Al2O3 and CaO and only molecularly adsorbed acetic acid on SiO2. More importantly, under the conditions of this study, dimers are the major form for molecularly adsorbed acetic acid on all three particle surfaces investigated, even at low acetic acid pressures under which monomers are the dominant species in the gas phase. We have also determined saturation surface coverages for acetic acid adsorption on these three oxides under dry conditions as well as Langmuir adsorption constants in some cases. Kinetic analysis shows that the reaction rate of acetic acid increases by a factor of 3-5 for γ-Al2O3 when relative humidity increases from 0% to 15%, whereas for SiO2 particles, acetic acid and water are found to compete for surface adsorption sites.

Effects of Lactobacillus acidophilus supplementation in different energy and nutrient density diets on growth performance, nutrient digestibility, blood characteristics, fecal microbiota shedding, and fecal noxious gas emission in weaning pigs

This study was conducted to evaluate the effects of Lactobacillus acidophilus supplementation in different energy and nutrient density diets on growth performance, nutrient digestibility, blood characteristics (blood urea nitrogen and creatinine), fecal microbiota shedding, and fecal noxious gas emission in weaning pigs. A total of 140 crossed [(Landrace×Yorkshire)×Duroc] weaning pigs with an initial body weight (BW) of 7.51±0.79kg were used in a 42-day trial. Pigs were randomly allocated into one of four treatment groups in a 2×2 factorial arrangement with two levels of energy and nutrient density (Phase1: 3750 and 3900kcal/kg; Phase2: 3550 and 3700kcal/kg) and L. acidophilus (0 and 0.1%) according to sex and BW (7 replicates each with 2 gilts and 3 barrows). Pigs fed high energy and nutrient density diets increased (P<0.05) average daily gain (ADG), gain:feed (G:F) ratio, as well as H2S and acetic acid emission than those fed low energy and nutrient density diets. Pigs fed L. acidophilus supplementation diets increased ADG and G:F (P<0.05) compared with pigs fed diets without L. acidophilus supplementation. Moreover, L. acidophilus supplementation led to a significant (P<0.05) increase in DM digestibility on day 14 and shift microbiota by increasing fecal Lactobacillus, while decreasing E.coli counts, as well as a significant (P<0.05) decrease in serum BUN concentration and fecal noxious gas emission. The interactive effects (P<0.05) of dietary energy and nutrient density and L. acidophilus supplementation were observed on the fecal H2S and acetic acid gases emission. In conclusion, dietary supplementation of L. acidophilus improved growth performance, ATTD of DM, shifted microbiota by increasing fecal Lactobacillus and decreased E. coli counts, decreased BUN concentration and fecal noxious gas emission in weaning pigs. No interactive effects of L. acidophilus supplementation and dietary energy and nutrient density on growth performance, nutrient digestibility (DM, N, and GE), blood characteristics (BUN and creatinine) and microbiota (Lactobacillus and E. coli). While the beneficial effects of L. acidophilus supplementation on H2S and acetic acid gases emission are more dramatic with high energy and nutrient density diets.

Emission characteristics of carboxylates in PM2.5 from incense burning with the effect of light on acetate

Incense burning produces potentially harmful particulate matter. In this study we investigated the emissions of PM2.5 and gaseous acetic acid from four brands of traditional incense; Liao and Shang Lao Shan (SLS), sold in Taiwan, and Thai Yellow (Thai Y) and Thai Black (Thai B), sold in Thailand. Additionally, photochemical reactions of PM2.5 carboxylates emitted from incense burning were studied via a simulated light experiment. The average PM2.5 mass emission factor of each incense type was inversely correlated with the ash production of that incense. The Thailand incense carboxylate emissions were markedly higher than the Taiwan incense. Acetate accounted for 87.46% of total carboxylate emissions, with acetate emitted from the Thailand incense 1.26 times higher than from the Taiwan incense. Phthalate was detected in the PM2.5, indicating the presence of plasticizer. Concentrations of PM2.5 acetate, formate, pyruvate, glutarate, succinate, fumarate and tartarate were reduced in simulated light (51.5%–97.1% of those under dark), indicating that these seven types of carboxylate are easily photodegradable. In contrast, malonate, maleate, oxalate and phthalate concentrations in light were 1.17–1.84 times higher than in darkness, indicating photochemical reactions contribute to the formation of these species. The formation of the low-molecular weight dicarboxylates oxalate and malonate was most noticeable. Acetic acid, highly irritating to the respiratory system and skin, was present at high levels for all four incense types, as shown by the gaseous acetic acid/PM2.5 acetate ratios of 1.03–3.61. Burning incense indoors can generate high concentrations of PM2.5 acetate that increases the risks of respiratory and contact irritation, particularly when burning the Thailand incense. Moreover, burning incense in poorly ventilated, dimly lit indoor areas (e.g., temples and homes) can markedly increase the risk of irritation because the gaseous acetic acid is not degraded as it would be in light.

Au-Polypyrrole Framework Nanostructures for Improved Localized Surface Plasmon Resonance Volatile Organic Compounds Gas Sensing.

In this paper, we propose an Au-polypyrrole (Ppy) nanorod gas sensor for the detection of volatile organic compound (VOC) gases. This gas sensor operates on the principle of localized surface plasmon resonance (LSPR). The Au-Ppy nanorods used in this experiment were synthesized using an anodic aluminum oxide template by the electrochemical deposition method. Using field emission scanning electron microscopy, we confirmed that the Au-Ppy nanorod arrays were successfully fabricated with a uniform size. By depositing gold, the Au-Ppy nanorods exhibited both optical and LSPR interference. The gas sensing properties of the fabricated nanorods were tested for VOCs such as acetic acid, benzene, and toluene with a short response time (~1 min). Moreover, the proposed VOC gas sensing system was tested with three types of VOC gases over a wide concentration range from 10 to 100 ppm. Highest sensitivity was observed for acetic acid gas, which had a linear relation with the gas concentration, indicating that the system can be used as a gas sensor.

Synthesis of hierarchical SnO2 nanoflowers with enhanced acetic acid gas sensing properties

Different morphologies hierarchical flower-like tin dioxide (SnO2) nanostructures were fabricated by changing the volume ratio of glycol and de-ionized water (Vg:Vw=0, 1:2, 1:1 and 2:1) under a template-free and low-cost hydrothermal method and subsequent calcinations. The architectures, morphologies and gas sensing performances of the products were characterized by X-ray diffraction patterns (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) and gas-sensing measurement device. It can be observed that all the nanoflowers were composed of two-dimensional (2D) nanosheets, and the thickness of nanosheets is only about 9nm when Vg:Vw=1:1. The sensor based on the product of Vg:Vw=1:1 exhibited excellent gas sensing performance toward 500ppm acetic acid at 260°C, and the response value of this sensor was about 153.6, which was above 7.5 times higher than that of ammonia (about 20.3). In addition, the 3D flower-like SnO2 nanostructures exhibited not only high response and selectivity to ppm level acetone, but also fast response and recovery time within 10s, demonstrating it can be used as a potential candidate for detecting acetic acid. Finally, the possible formation mechanism was proposed, too.