Showing papers on "Acetone published in 2020"

W18O49/Ti3C2Tx Mxene nanocomposites for highly sensitive acetone gas sensor with low detection limit

Abstract: The development of gas sensor that is capable of detecting ppb-level detection of acetone and possesses high response toward low-concentration acetone remains a great challenge. Herein, we present the construction of the W18O49/Ti3C2Tx composites based on the in situ grown of the 1D W18O49 nanorods (NRs) on the surfaces of the 2D Ti3C2Tx Mxene sheets via a facile solvothermal process. The W18O49/Ti3C2Tx composites exhibit high response to low concentration acetone (11.6 to 20 ppm acetone), ideal selectivity, long-term stability, very low limit of detection of 170 ppb acetone, and fast response and recover rates (5.6/6 s to 170 ppb acetone). Compared to the W18O49 NRs and Ti3C2Tx sheets, the W18O49/Ti3C2Tx composites show significant improvement on the acetone-sensing performance, which can be ascribed to the homogeneous distribution of the W18O49 NRs on the Ti3C2Tx surface, the removal of the fluorine-containing groups from the Ti3C2Tx after the solvothermal process, and the synergistic interfacial interactions between the W18O49 NRs and the Ti3C2Tx sheets. The synthesis of the 1D/2D W18O49/Ti3C2Tx Mxene composites provides a new avenue to develop other promising hybrids for acetone sensing.

Size effect, mutual inhibition and oxidation mechanism of the catalytic removal of a toluene and acetone mixture over TiO2 nanosheet-supported Pt nanocatalysts

Abstract: We prepare TiO2 nanosheet-supported Pt nanocatalysts with an average size of 1.3, 1.9, and 3.0 nm. Due to the great decrease in the adsorption ability for toluene and acetone, mutual inhibition is first observed over Pt1.9 nm/TiO2 for the catalytic removal of a toluene and acetone mixture. At 140 °C, the toluene and acetone reaction rate is 0.033 and 0.045 μmol/(gcat s), respectively, for the oxidation of 500 ppm toluene or acetone, which is much higher than the corresponding reaction rate (0.020 and 0.007 μmol/(gcat s)) for the oxidation of the mixture. Pt1.9 nm/TiO2 exhibits a good catalytic stability and H2O and CO2 tolerance. With strong evidence, we find that the co-presence of toluene and acetone does not change the catalytic mechanism, and the reaction pathway for the oxidative removal of toluene and acetone in the mixture may follow the pathway for the oxidation of single toluene or acetone.

Atomic Force Microscopy and Molecular Dynamics Simulations for Study of Lignin Solution Self‐Assembly Mechanisms in Organic–Aqueous Solvent Mixtures

Abstract: Lignin-based nanomaterials fabricated by solution self-assembly in organic-aqueous solvent mixtures are among the most attractive biomass-derived products. To accurately control the structure, size, and properties of lignin-based nanomaterials, it is important to achieve fundamental understanding of its dissolution and aggregation mechanisms. In this work, atomic force microscopy (AFM) and molecular dynamics (MD) simulations are employed to explore the dissolution and aggregation behavior of enzymatic hydrolysis lignin (EHL) in different organic-aqueous solvent mixtures at molecular scale. EHL was found to dissolve well in appropriate organic-aqueous solvent mixtures, such as acetone-water mixture with a volume ratio of 7:3, whereas it aggregated in pure water, ethanol, acetone, and tetrahydrofuran. The interactions between the EHL-coated AFM probe and the substrate were 1.21±0.18 and 0.75±0.35 mN m-1 in water and acetone, respectively. In comparison, the interaction decreased to 0.15±0.08 mN m-1 in acetone-water mixture (7:3 v/v). MD simulations further indicate that the hydrophobic skeleton and hydrophilic groups of lignin could be solvated by acetone and water molecules, respectively, which significantly promoted its dissolution. Conversely, only the hydrophobic skeleton or the hydrophilic groups were solvated in organic solvent or water, respectively, inducing serious aggregation of lignin.

Enhanced Acetone Oxidation over the CeO2/Co3O4 Catalyst Derived from Metal-Organic Frameworks.

Abstract: A novel CeO2/Co3O4 catalyst with a high catalytic activity has been designed and prepared by pyrolysis of metal-organic frameworks, and its catalytic performance was evaluated by the acetone catalytic oxidation reaction. The Co3O4-M catalyst with T90 at 194 °C was prepared by pyrolysis of the MOF-71 precursor, which was 56 °C lower than that of commercial Co3O4 (250 °C). By the addition of cerium to the MOF-71 precursor, an enhanced CeO2/Co3O4 catalyst with T90 at 180 °C was prepared. Importantly, the CeO2/Co3O4 catalyst exhibited superior stability for acetone oxidation. After 10 cycle tests, the conversion could also be maintained at 97% for at least 100 h with slight activity loss. Characterization studies were used to investigate the influence of cerium doping on the property of the catalyst. The results showed that addition of cerium could facilitate the expansion of the surface area and enhance the porous structure and reducibility at low temperature. Furthermore, the surface ratio of Co3+/Co2+ and mobile oxygen obviously improved with the addition of cerium. Therefore, the metal oxides prepared by this method have potential for the elimination of acetone.

UV assisted ppb-level acetone detection based on hollow ZnO/MoS2 nanosheets core/shell heterostructures at low temperature

Abstract: It is challenging for current metal oxides based acetone sensors to realize excellent ppb-level acetone sensing properties at low working temperature. Herein, the hollow ZnO/MoS2 nanosheets (HZnO/MoS2) core/shell heterogeneous structures are originally produced. Fast gas transport channels and n–p heterojunctions are produced by the decoration of MoS2 nanosheets on HZnO surface, resulting in high acetone response and fast response/recovery speed. Ultraviolet (UV) light is introduced to further improve acetone response and drastically reduce working temperature. The light diffraction and reflection caused by the decoration of hierarchical MoS2 nanosheets could significantly enhance light harvesting. Hence, the excellent acetone sensing properties are obtained by the synergistic effect of UV light and HZnO/MoS2 core/shell heterogeneous structures. Exactly, at 100 °C, the HZnO/MoS2 possesses a stable response (1.52) to 100 ppb acetone with UV irradiation while it exhibits no response to 100 ppb acetone without UV. Even at room temperature (30 ℃), UV activated HZnO/MoS2 still exhibits a stable response (∼1.33) and fast recovery/recovery time (19 s/97 s) to 50 ppm acetone. Furthermore, the DFT calculations are performed to demonstrate the underlying acetone sensing mechanism. The results demonstrate that UV activated HZnO/MoS2 heterostructure could achieve trace-acetone detection at low temperature.

Catalyst-free Highly Sensitive SnO2 Nanosheet Gas Sensors for Parts per Billion-Level Detection of Acetone.

Abstract: The development of a facile gas sensor for the ppb-level detection of acetone is required for realizing health diagnosis systems that utilize human breath. Controlling the crystal facet of a nanomaterial is an effective strategy to fabricate a high-response gas sensor without a novel metal catalyst. Herein, we successfully synthesized a SnO2 nanosheet structure, with mainly exposed (101) crystal facets, using a SnF2 aqueous solution at 90 °C. The SnO2 nanosheets obtained after various synthesis durations (2, 6, and 24 h) were investigated. The sample synthesized for 6 h (NS-6) exhibited a 10-fold higher response (Ra/Rg = 10.4) for 1 ppm of acetone compared to the other samples, where Ra and Rg are the electrical resistances under air and the target gas. Furthermore, NS-6 detected up to 200 ppb of acetone (response = 3). In this study, we attributed the high response (of low concentrations of acetone) to the (101) crystal facet, which is the main reaction surface. The (101) crystal facet allows the facile formation of a depletion layer due to the highly reactive Sn2+. Additionally, the acetone adsorption energy of the (101) crystal facet is relatively lower than that of other crystal facets. Owing to these factors, our pristine SnO2 nanosheet gas sensor exhibited significantly high sensitivity to ppb levels of acetone.

Metal-organic frameworks derived ZnO@MoS2nanosheets core/shell heterojunctions for ppb-level acetone detection: Ultra-fast response and recovery

Abstract: It is imperative to explore an accurate ppb-level acetone sensor for noninvasive detection of diabetes. In this work, two dimensional p-type MoS2 nanosheets are introduced on the surface of p-type ZnO derived from metal-organic frameworks (MOFs) to produce ZnO@MoS2 core/shell heterojunctions as a novel acetone sensor, showing a great enhancement of acetone response, about two orders of magnitude than that of pure ZnO derived from MOFs. For example, the ZnO@MoS2 exhibits about 80 times enhancement in response to 100 ppb acetone than that of pure ZnO. More importantly, this ZnO@MoS2 heterojunctions sensor exhibits an ultra-fast response/recovery to ultra-low concentration acetone (60 s/40 s @ 5 ppb), which is the best acetone sensing performance for the metal oxide-based materials reported to date. Moreover, the acetone sensing performances are negligibly affected by humidity and other gas, which is suitable for exhaled acetone detection. Finally, it is elucidated that the sharp increase of negative heterojunction interface resistance, ultra-fast gas diffusion rates in MoS2 nanosheets and strong interaction energy are key factors for the excellent acetone sensing properties of ZnO@MoS2. This work opens up a novel and efficient way for ultra-low concentration gas detection.

Superior Acetone Selectivity in Gas Mixtures by Catalyst-Filtered Chemoresistive Sensors.

Abstract: Acetone is a toxic air pollutant and a key breath marker for non-invasively monitoring fat metabolism. Its routine detection in realistic gas mixtures (i.e., human breath and indoor air), however, is challenging, as low-cost acetone sensors suffer from insufficient selectivity. Here, a compact detector for acetone sensing is introduced, having unprecedented selectivity (>250) over the most challenging interferants (e.g., alcohols, aldehydes, aromatics, isoprene, ammonia, H2, and CO). That way, acetone is quantified with fast response (<1 min) down to, at least, 50 parts per billion (ppb) in gas mixtures with such interferants having up to two orders of magnitude higher concentration than acetone at realistic relative humidities (RH = 30-90%). The detector consists of a catalytic packed bed (30 mg) of flame-made Al2O3 nanoparticles (120 m2 g-1) decorated with Pt nanoclusters (average size 9 nm) and a highly sensitive chemo-resistive sensor made by flame aerosol deposition and in situ annealing of nanostructured Si-doped e-WO3 (Si/WO3). Most importantly, the catalytic packed bed converts interferants continuously enabling highly selective acetone sensing even in the exhaled breath of a volunteer. The detector exhibits stable performance over, at least, 145 days at 90% RH, as validated by mass spectrometry.

Metal-organic frameworks derived hierarchical flower-like ZnO/ Co3O4 heterojunctions for ppb-level acetone detection

Abstract: The demand of acetone gas sensors with great response value and fast response/recovery time to low concentration acetone is increasing in practical diagnosis for diabetes. In this work, metal-organic frameworks (MOFs) derived flower-like ZnO/Co3O4 heterojunctions based sensor is prepared by a simple solution mixing method at room temperature. The sensor shows high acetone response value, short response/recovery time, excellent selectivity and good stability. For example, the response value of ZnO/Co3O4 heterojunctions based sensor is up to 120 % towards 500 ppb acetone at 300 ℃, which is about 30-fold enhancement than these of intrinsic ZnO and Co3O4. Moreover, its minimal detection limitation is 100 ppb acetone and it shows ultra-fast response/recovery time for ppb-level acetone (22 s/27 s@500 ppb). The excellent acetone sensing properties of flower-like ZnO/Co3O4 heterojunctions based sensor is attributed to the sharp resistance variation of heterojunction interface between ZnO and Co3O4 and the ultra-fast gas transport channel provided by ZnO nanosheets. This finding provides important insights and useful guidance for the detection of ppb-level acetone.

Mechanistic role of protonated polar additives in ethanol for selective transformation of biomass-related compounds

Abstract: We report on a combined experimental, spectroscopic and theoretical study of acid catalysed dehydration-etherification of fructose in ethanol for understanding the mechanistic role of polar solvent additives and product selectivity. Herein, we show that polar solvent additives (e.g. tetrahydrofuran, acetone, acetonitrile, gamma-valerolactone, dimethyl sulfoxide) protonated with a common solid acid catalyst in ethanol allow transformation of biomass-related compounds into desired dehydration or etherification products. Fructose in ethanol with DMSO additive is selectively transformed into 5-hydroxymethylfurfural with negligible formation of 5-ethoxymethylfurfural due to preferential DMSO protonation according to its polarity. Spectroscopic methods and density functional theory show that additives having higher polarity than ethanol are readily protonated and act as the key catalytic protonation species and as the key stabilization species for reaction intermediates. Understanding the mechanism of protonated polar additives in reaction systems allows one to tailor selectivity in acid-catalyzed dehydration-etherification schemes and to develop sustainable chemistry for biomass resources.

Labile oxygen promotion of the catalytic oxidation of acetone over a robust ternary Mn-based mullite GdMn2O5

Abstract: Mn-based mullite catalyst GdMn2O5 is developed via the hydrothermal method to efficiently remove volatile organic compound acetone with a high efficiency and stability in total oxidation. The T90 over GdMn2O5 approaches to 160 s°C in contrast to 191 °C over 1 wt % Pt/Al2O3. The catalytic performance maintains after reaction at 200 °C for 260 h with 5.0 % H2O. The surface labile oxygen is the key to superior catalytic performance. According to the in situ DRIFTS and the oxidation pathway proposed by DFT calculations, the acetate species decomposition is assigned as the rate-limiting step. And the calculated kinetic barrier for the rate-limiting step, 151.7 kJ/mol (1.58 eV), is in line with the apparent activation energy from acetone oxidation over GdMn2O5 of 150.0 kJ/mol (1.56 eV). This work provides insights into developing highly efficient and hydrothermally stable volatile organic compounds removal catalysts via surface oxygen activation.

Production of Jet Fuel Intermediates from Biomass Platform Compounds via Aldol Condensation Reaction Over Iron-Modified MCM-41 Lewis Acid Zeolite

Abstract: Liquid fuel intermediates could be produced via aldol condensation reaction between furfural or 5-hydroxymethylfurfural (HMF) and acetone. It was found that iron-modified MCM-41 zeolite can be an effective Lewis acid catalyst for C-C bond formation via aldol condensation of furfural or HMF with acetone. The 4-(2-furyl)-3-buten-2-one and 1, 5-di-2-furanyl-1, 4-pentadien-3-one (FAc and F2Ac), or 1, 5-di-2-furanyl-1, 4-pentadien-3-one and 1, 5-bis[(5-hydroxlmethyl)-2-furanyl]-1, 4-pentadien-3-one (HAc and H2Ac), as two main condensation products of furfural with acetone or HMF with acetone, were observed. After 24 h at 160℃, 86.9% conversion of furfural with 60.0% yield of the FAc as well as 7.5% yield of the F2Ac and 88.9% conversion of the HMF with 41.1% yield of the HAc as well as 3.5% yield of the H2Ac were achieved. Although furfural or HMF conversion was almost same after 24 h at 160℃, iron-modified MCM-41 zeolite catalyst displayed an enhanced selectivity to condensation products of furfural with acetone. In addition, catalysts showed an improved selectivity to the F2Ac and H2Ac at higher reaction temperature. The reusability and regeneration studies showed that iron-modified MCM-41 zeolite catalyst could not be reused directly, but could be regenerated by calcination in air, and the catalytic performance of regenerated catalyst was acceptable.

Lignin-derived red-emitting carbon dots for colorimetric and sensitive fluorometric detection of water in organic solvents.

Abstract: Water contained in organic solvents or products in chemical industries, as contaminants, poses an adverse risk in chemical reaction, life or environmental safety. However, conventional fluorescent water sensing suffers from drawbacks, including limited organic solvents, narrow linear range, lack of visual detection, single detection strategy, and others. Herein, a novel type of red-emitting carbon dots (RCDs) has been created via one-step solvothermal synthesis based on biomass (e.g., lignin) as the carbon source and p-phenylenediamine (PPD) as the nitrogen source. Colorimetric and fluorometric detection of water in organic solvents has been demonstrated. The RCDs showed excitation-independent photoluminescence (PL) in different solvents and solvatochromic behavior, red in water, orange in ethanol, yellow in N,N-dimethyl formamide (DMF), and green in acetone. Remarkably, detection of water content in six organic solvents, including polar solvents (ethanol, acetone, dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), and DMF) and apolar solvent (ether), was performed. With increasing water content in solvents, emission colors changed from green to red, or yellow to red, offering qualitative sensing of water. Furthermore, a broad linear detection range (10–90%), low limits of detection (LOD) (e.g., 0.36% for ethanol and 0.082% for acetone), and good generality for various organic solvent systems were realized. Particularly, dual sensing strategies, including PL quenching and shift with water in various solvents, were achieved simultaneously, showing great potential for the development of advanced optical sensors with high performance.

Catalytic Filter for Continuous and Selective Ethanol Removal Prior to Gas Sensing.

Abstract: Ethanol is a major confounder in gas sensing because of its omnipresence in indoor air and breath from disinfectants or alcoholic beverages. In fact, most modern gas sensors (e.g., graphene, carbon nanotubes, or metal oxides) are sensitive to ethanol. This is challenging because ethanol is often present at higher concentrations than target analytes. Here, a simple and modular packed bed filter is presented that selectively and continuously removes ethanol (and other alcohols like 1-butanol, isopropanol, and methanol) over critical acetone, CH4, H2, toluene, and benzene at 30-90% relative humidity. This filter consists of catalytically active ZnO nanoparticles (dBET = 55 nm) made by flame aerosol technology and annealing. Continuous oxidation of ethanol to CO2 and H2 was observed at filter temperatures above 260 °C while below that, unwanted acetaldehyde was formed. Most remarkably, ethanol concentrations up to 185 ppm were removed from exhaled breath in preliminary tests with an alcohol intoxicated volunteer, as confirmed by mass spectrometry. At the same time, almost 4 orders of magnitude lower (e.g., 0.025 ppm) acetone concentrations were preserved. This was superior to previous catalyst filters (e.g., CuO, SnO2, and Fe2O3) with overlapping ethanol and acetone conversions and related to ZnO's surface basicity. The ZnO filter performance was stable (±2.5% conversion variability) for, at least, 21 days. Finally, when combined with a Si-doped WO3 sensor, the filter effectively mitigated ethanol interference when sensing acetone without compromising the sensor's fast response and recovery times. Such catalytic filters can be combined readily with all gas sensors.

A Resource utilization method for volatile organic compounds emission from the semiconductor industry: Selective catalytic oxidation of isopropanol to acetone Over Au/α-Fe2O3 nanosheets

Abstract: We prepare α-Fe2O3 nanosheet supported 0.38, 0.81, and 1.36 wt% Au (average particle size = 4.0 nm) nanocatalysts, and investigate their performance and mechanism for the selective catalytic oxidation of isopropanol to acetone. In the presence of 1.2 vol% isopropanol and 40 vol% O2, 1.36 wt% Au/α-Fe2O3 exhibits excellent catalytic performance, due to its moderate acidic sites and better redox properties, with acetone selectivity and yield being as high as 99% and 95% at 220 oC, respectively. In addition to acetone, little propylene, acetic acid, acetaldehyde, methyl vinyl ketone, 2-butanone, isopropyl ether, isopropyl acetate, 3-penten-2-one, isopropyl acrylate, isopropyl propionate, and 2, 4-dimethylfuran are detected. The possible reaction mechanism is proposed for the selective catalytic oxidation of isopropanol to acetone over the present catalysts. We believe the present selective catalytic oxidation method, rather than the traditional complete catalytic oxidation method, provides an alternative and economic method for VOCs emissions control.

Determination and Correlation of the Solubility of l-Cysteine in Several Pure and Binary Solvent Systems

Abstract: l-Cysteine solubility in 12 monosolvents (water, methanol, ethanol, n-propanol, n-butanol, sec-butanol, isopropanol, isobutanol, ethyl acetate, 1,4-dioxane, acetonitrile, and acetone) and three binary solvents (water + methanol, water + ethanol, and water + isopropanol) was determined by the gravimetric method from 283.15 to 323.15 K under the atmospheric pressure. The solubility order in pure solvents was acetonitrile < isobutanol < ethyl acetate ≈ sec-butanol < n-butanol < 1,4-dioxane < isopropanol < n-propanol < ethanol < methanol < acetone < water, and it was positively related to the experimental temperature and solvent composition for all solvent systems. For polar protic solvents, the key factors influencing the solubility were the length of the carbon chain and the solvent properties. The effect of solvent–solvent and solvent–solute intermolecular interactions on the solubility behavior was analyzed by the KAT-LSER model. The modified Apelblat, Jouyban–Acree, and Apelblat–Jouyban–Acree models were used to correlate the solubility data, and the values calculated by the three thermodynamic models were found to agree well with the experimental data.

Measurement and Correlation of Solubility and Thermodynamic Properties of Fluoxetine Hydrochloride in 15 Pure Solvents and a Methanol + Water Binary Solvent System

Abstract: The solubilities of fluoxetine hydrochloride (FH) in pure solvents including methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, s-butanol, n-pentanol, i-pentanol, acetone, 2-butanone,...

A Highly Sensitive and Selective ppb-Level Acetone Sensor Based on a Pt-Doped 3D Porous SnO2 Hierarchical Structure.

Abstract: In view of the low sensitivity, high operating temperature and poor selectivity of acetone measurements, in this paper much effort has been paid to improve the performance of acetone sensors from three aspects: increasing the surface area of the material, improving the surface activity and enhancing gas diffusion. A hierarchical flower-like Pt-doped (1 wt %) 3D porous SnO2 (3DPS) material was synthesized by a one-step hydrothermal method. The micropores of the material were constructed by subsequent annealing. The results of the experiments show that the 3DPS-based sensor's response is strongly dependent on temperature, exhibiting a mountain-like response curve. The maximum sensor sensitivity (Ra/Rg) was found to be as high as 505.7 at a heating temperature of 153 °C and with an exposure to 100 ppm acetone. Additionally, at 153 °C, the sensor still had a response of 2.1 when exposed to 50 ppb acetone gas. The 3DPS-based sensor also has an excellent selectivity for acetone detection. The high sensitivity can be explained by the increase in the specific surface area brought about by the hierarchical flower-like structure, the enhanced surface activity of the noble metal nanoparticles, and the rapid diffusion of free-gas and adsorbed gas molecules caused by the multiple channels of the microporous structure.

Determination and Correlation of the Solubility of Sodium Naphthalene-1,5-disulfonate in Five Pure Solvents and Three Binary Solvent Systems at the Temperature Range from 283.15 to 323.15 K

Abstract: Experimental solubility data of sodium naphthalene-1,5-disulfonate in five neat solvents (water, methanol, ethanol, 2-propanol, acetone) and three binary solvent systems (water + ethanol, water + 2...

Determination and Correlation of the Solubility of Monosodium Fumarate in Different Neat and Binary Solvent Systems

Abstract: Monosodium fumarate solubility in 12 monosolvents (water, methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 2-propanol, 2-methyl-1-propanol, ethyl acetate, 1,4-dioxane, acetonitrile, and aceton...