Acetone Molecules Research Articles

Velocity measurements in a hypersonic flow using acetone molecular tagging velocimetry.

In the present work, a non-intrusive diagnostic technique known as molecular tagging velocimetry was used to collect quantitative freestream velocity measurements in the Mach 7 Ludwieg Tube Wind Tunnel located at The University of Texas at San Antonio. This laser-based diagnostic technique used a single Nd:YAG 4th harmonic laserline to excite acetone molecules seeded in the flow field. From the resulting emitted light, mean and instantaneous velocity profiles in the hypersonic freestream flow and facility boundary layer were measured. Uncertainty in the velocity measurements for individual test runs is estimated at ≤ 8% while overall 1D freestream mean velocity measurements were recorded with ±2.4% (± 21 m/s) accuracy. The effect of acetone seeding on the speed of sound was also quantified.

Design of Mn-SnO2 double-shell nanostructures for high-performance acetone gas sensor

• High-performance acetone sensor of double-shelled Mn-SnO 2 was prepared. • The response of Mn-SnO 2 towards acetone was as high as 75. • Mn-SnO 2 sensing mechanism was also discussed. In this study, a simple method to fabricate Mn-doped SnO 2 double-shell nanofibers by electrospinning was presented. The results demonstrated that Mn-SnO 2 nanofibers were unique tube-in-tube structures and possessed a high response of 75 towards 100 ppm acetone, which was higher three times than that of pure SnO 2 . It was believed that the excellent gas sensing properties of the sensor were that Mn-dopant dramatically enhanced the percentage of the defect-related oxygen species. The promising hollow double-shell structure was beneficial to gas absorption and penetration of oxygen and acetone molecules by offering more active sites. Hence, the Mn-doped double-shell nanofibers exhibited a promising application prospect in efficient sensing material in the future.

Cactus-inspired GO/ZnO sensors for fast and robust acetone sensing properties

Fabrication of fast, high-selectivity and reliable gas sensors for real-time monitoring of acetone in exhaled gases remains a key challenge for the development of accurate diabetes diagnosis systems. Inspired by the cactus, in this paper, acetone gas sensor using graphene oxide (GO) with porous zinc oxide (ZnO) nanotube clusters was introduced by room temperature liquid phase method. Porous ZnO nanotubes with lengths of 1∼2 μm formed nanoclusters and were uniformly dispersed on the GO sheets, presenting a specific “cactus-like” three-dimensional structure, which supplied more channels and active sites for the diffuse and adsorption of acetone molecules. The cactus-like GO/ZnO sensor exhibits a high response value of 54.3 (5.9-fold improvement compared to ZnO), fast response/recovery time of 3.8/2.9 s (15.7/19.8 s for ZnO), and robust stability to 50 ppm acetone at 180 °C. Special, the sensor can detect even acetone down to 0.1 ppm with a remarkable response (2.1). Moreover, the adsorption energies of different gases were calculated by density functional theory, which further confirmed the good acetone selectivity of the cactus-like GO/ZnO sensor. The appreciable gas sensing performances are mainly attributed to the unique cactus-like nanostructure with abundant holes and high specific surface area, as well as the heterojunctions between GO and ZnO. This unique biomimetic structure provides a promising strategy for designing acetone gas sensors with high practicality.

Construction of mesoporous WO3 nanofibers functionalized with nanoscale PtO catalysts for enhanced acetone sensing properties

In this study, we demonstrated a facile one-step electrospinning technique to construct mesoporous PtO−WO3 nanofibers (NFs) for highly sensitive and selective acetone sensing. The well-dispersed PtO nanocatalysts (∼6 nm) were evenly immobilized within the mesoporous WO3 NFs. These features provided efficacious catalysis, gas diffusion, and numerous active sites to maximize the interaction between active O2− and acetone molecules. Sensing results revealed that the PtO−WO3 NFs showed much enhanced acetone sensing properties in comparison with pure WO3 NFs. The response of the 0.5 % PtO−WO3 NFs to 100 ppm acetone at 260 °C was about 6.5-fold higher than that of the pure WO3 NFs at 375 °C. The optimum operating temperature shifted significantly from 375 °C of pure WO3 NFs to 260 °C of PtO−WO3 NFs. Moreover, good selectivity and stability to acetone were also observed for the 0.5 % PtO−WO3 NFs. The large improvement of acetone sensing characteristics can be ascribed to the mesopore fiber topography and heterogeneous sensitization and catalytic effects of PtO nanocatalysts. Our work revealed that mesoporous WO3 NFs with uniformly distributed PtO nanocatalysts have great potential in detecting acetone.

Adsorption behavior of molecules on Zn2SnO4(1 1 1) crystal plane and its effect on electrical conductivity

• O 2 molecules bond with Sn atoms on the crystal plane and H 2 O molecules bond with Zn atoms to form characteristic adsorbed species. • As the characteristic adsorbed species, H 2 O molecules further promoted the natural adsorption of O 2 molecules in the form of hydrogen bond. • The crystal conductivity changes with the adsorption and desorption. • High temperature facilitates the adsorption of O 2 molecules. The molecular adsorption behavior of Zn 2 SnO 4 (1 1 1) crystal plane was studied. DFT theoretical simulation result shows that O 2 and H 2 O molecules are adsorbed on the crystal plane by bonding with Zn atom and Sn atom respectively and forming characteristic adsorption species. H 2 O molecules as characteristic adsorbed species promote the natural adsorption of O 2 molecules in the form of hydrogen bonds, N 2 molecules adsorb naturally in the form of physical adsorption. Meanwhile, the crystal surface conductivity varies with the adsorption and desorption of different gases. When the adsorbent is only O 2 molecule, the crystal surface conductivity decreases, the DOS of Fermi is from 8.00 to 4.01 electrons/eV. The conductivity of crystal surface increases when H 2 O molecule acts as a characteristic adsorbent and further adsorbs O 2 molecule, the DOS of Fermi is from 5.74 to 8.51 electrons/eV. When oxygen molecules are directly adsorbed on Zn 2 SnO 4 (1 1 1) crystal plane, the adsorption energy is +0.79 eV, while when oxygen molecules are further adsorbed on Zn 2 SnO 4 (1 1 1) crystal plane through water molecule, the adsorption energy is +2.71 eV. This conclusion was confirmed by EIS. In situ Raman spectroscopy detection of acetone molecule gas sensitive experiment showed that the adsorption of O 2 molecules is slow at room temperature and fast at high temperature, which is consistent with the calculation result that O 2 molecule belongs to endothermic adsorption. The results show that, through the method of combining experiment and theory, the influencing mechanism is analyzed, which effects of different gases on adsorption properties of crystal surfaces. This work provides guidance for optimizing catalytic and gas sensitive properties of materials and realizing controllable optimization of surface properties of materials.

ADSORPTION STUDY OF ACETONE ON THE SORBENTS BASED ON MONTMORILLONITE

Corresponding cation forms of the montmorillonite samples taken from the Ag-Dere bentonite deposit were obtained by processing them with Co2+ and Ni2+ salts. The nature and amount of acid sites formed on the surfaces of the obtained samples were studied by adsorption of acetone using the derivatographic method. The critical diameter of the acetone molecule is d = 5.6A0 and pkα = -7.2. Analysis of derivatograms shows that the mass loss changes depending on the ionic radius, nature and temperature of the cation exchanges as follows: Co2+ mont> Ni2+ mont> natural mont. Based on the conducted study it was estableshed that there are weak, medium and strong electron-acceptor centers on the surface of the sorbent which differ energetically. The endothermic effect observed on the DTA curve at a temperature range of 219.3–566.30C characterizes the physical adsorption of an acetone molecule on the surface of a montmorillonite sample. The effects observed at 706.9 and 775.70C characterize the strong acid sites. The amount of electron-acceptor centers formed on the surface of monmorillonite changes depending on the charge of cation exchangers. The number of electron-acceptor centers formed on the surface of Co2+ bentonite is higher than in other samples. The amount (a.mmol.g) and desorption energy (E, kDc, mol-1) of acetone molecule desorbed from the active sites in different temperature ranges were calculated. It was determined that the most capable of adsorbing acetone molecules is Co2+-montimorillonite, which can be used as a sorbent to prevent envoiremental pollution with acetone. Corresponding cation forms of the montmorillonite samples taken from the Ag-Dere bentonite deposit were prepared by processing with Co2+ and Ni2+ salts. The nature and amount of acid sites formed on the surfaces of the obtained samples were studied by adsorption of acetone using the derivatographic method. Based on the conducted study it was estableshed that there are weak, medium, strong electron-acceptor centers on the surface of the sorbent which differ energetically. The amount (a.mmol.\g) and desorption energy (E, kDc, mol-1) of acetone molecule desorbed from the active sites in different temperature ranges were calculated. As a result of the research, it was found that the most capable of adsorbing acetone molecules is Co2+-form of montimorillonite, which can be used as a sorbent to prevent envoiremental pollution with acetone

The physicochemical properties and contact angle of sodium dodecyl sulfate in water–acetone with and without sodium nitrate (NaNO3)

Conductivity measurements at room temperature were performed to study the physicochemical behavior of anionic surfactant SDS in water and acetone–water mixture in the presence and absence of NaNO3.The concentration of SDS was 0.05 M and the concentration of NaNO3 was 0.01 M and 0.05 M. We calculated the degree of dissociation (α) and critical micelle concentration (CMC) from the pre-micellar (S1) and post-micellar slopes (S2). When acetone is added to SDS, CMC and α increase, but decreased with an increase in NaNO3.The standard free energy of micellization (ΔGm°) was evaluated using CMC and α. Micellization becomes less likely when the acetone content is higher as the negative values of ΔGm° decrease, indicating less spontaneous micellization. Due to the electrostatic repulsion of the head groups, adding salt NaNO3 decreases the CMC of SDS. A drop shape analyzer (DSA-25E) was used to measure the contact angles (CAs). For SDS, acetone and NaNO3 molecules mixed at varying concentrations, simulations were conducted.

Structural and spectroscopic studies of Na+ – Quercetin-5′-sulfonic acid polymeric complexes obtained via solvothermal synthesis

New sodium complexes of quercetin-5′-sulfonic acid (HQSA) have been obtained. The aqua complex of the general formula [NaQSA∙(H2O)2]·2H2O (1) was a starting compound for solvothermal syntheses of acetone and dimethylsulfoxide (S) complexes: [NaQSA(S)](S) (2 – acetone) and [NaQSA(S)]∙2(S) (3a and 3b – DMSO). The fourth complex obtained from the reaction of HQSA excess used in the reaction with NaOH is [Na(QSA)2·2H2O][(EtOH)2H] (4). The molecular and crystal structures of 1 – 4 were determined by X-ray crystallography. The sodium cations are coordinated by six or seven oxygen atoms; Na+ coordinating groups are sulfonic, hydroxyl, and carbonyl of the QSA− anion. The bridging role of some functional groups causes the formation of polymeric complexes. The coordination spheres are completed by oxygen atoms from the coordinating water (in 1 and 4), acetone (2) or DMSO molecule (3a and 3b). In each structure non-coordinating interstitial solvate molecules are also present; they are two H2O (1), acetone (2), two DMSO (3a and 3b), and the hydrogen bisethanol cation [EtOH…H+…EtOH] (4). The last of these is a rare type of Zundel type cation. Unstable complexes (2 and 3), that decompose under normal conditions, are formed and they have a structure of intercalation clathrates. The solvating molecules, located between 1D or 2D polymeric complexes, play a unique role as a network bonding agent. Theoretical calculations showed charge separation between Na+ and SO3−. The FTIR and Raman spectra are consistent with the solved crystal structures and, importantly, enable the identification of acetone and DMSO molecules in the powder samples.

Acetone and Toluene Gas Sensing by WO3: Focusing on the Selectivity from First Principle Calculations.

Sensitivity and selectivity are the two major parameters that should be optimized in chemiresistive devices with boosted performances towards Volatile Organic Compounds (VOCs). Notwithstanding a plethora of metal oxides/VOCs combinations that have been investigated so far, a close inspection based on theoretical models to provide guidelines to enhance sensors features has been scarcely explored. In this work, we measured experimentally the sensor response of a WO3 chemiresistor towards gaseous acetone and toluene, observing a two orders of magnitude higher signal for the former. In order to gain insight on the observed selectivity, Density Functional Theory was then adopted to elucidate how acetone and toluene molecules adsorption may perturb the electronic structure of WO3 due to electrostatic interactions with the surface and hybridization with its electronic structure. The results of acetone adsorption suggest the activation of the carbonyl group for reactions, while an overall lower charge redistribution on the surface and the molecule was observed for toluene. This, combined with acetone’s higher binding energy, justifies the difference in the final responses. Notably, the presence of surface oxygen vacancies, characterizing the nanostructure of the oxide, influences the sensing performances.

Hierarchical Nitrogen‐Enriched Carbon from Rationally Designed Polyimide Precursor for Exceptional Acetone Adsorption

AbstractThe adsorption capacity of porous adsorbent to volatile organic compounds (VOCs) is restricted by pore size distribution and surface functionalities. In this study, we report an effective N‐doped porous carbon synthesis strategy using rationally designed polyimide as precursor and subsequently copper chloride (CuCl2) mild activation. Specifically, by carefully changing the thiourea/urea ratio, polyimide precursors of different configurations can be designed and synthesized, which not only facilitates the transformation to a mesoporous structure, but also slightly enriches the surface heteroatoms. These unique properties result in a series of hierarchical porous carbon with high surface area (2045 m2/g), large mesopore volume (1.32 cm3/g) and rich nitrogen content (8.95 at %). Such carbon consequently shows exceptional static acetone adsorption performance of 768 mg/g (25 °C) and 799 mg/g (15 °C) and fast dynamic transfer rate. The abundant mesoporous structure provides the necessary diffusion channels to shorten the transmission distance and transmission resistance of acetone molecules, thereby contributing to this high acetone adsorption performance. Moreover, electrostatic potential (ESP) charge analysis shows that the doping of nitrogen atoms can significantly change the charge distribution on the sample surface, and enhance the affinity with acetone molecules through electrostatic interaction and Lewis acid‐base interaction

Semiconductor Metal Oxides Doped with Gold Nanoparticles for Use in Acetone Gas Sensors

The effect of nanosized gold particles on the adsorption-sensitive properties of SnO2–Au sensors under the detection of acetone vapors has been studied. Different techniques for the preparation of SnO2–Au nanocomposites with an average Au particle size of 2 nm were applied. It has been found that a fivefold increase in the sensor response to acetone vapors and threshold sensitivity (C lim) of 0.1 ppm are achieved by adding gold to tin dioxide in the colloidal form during synthesis. While adding gold in ion form (Au (III)) leads to a growth of the sensor response to acetone vapors by 2.7 times and defines C lim of 0.2 ppm. The slope of the calibration curves of the SnO2–Au sensors allows registering acetone vapors at concentrations ranging from C lim to 5 ppm. This concentration range can be used for express diagnostics in diabetes. The enhanced sensitivity of SnO2–Au sensors to acetone vapors can be explained by an increase in the adsorption-catalytic activity of tin ions as a result of the modifying effect of sulfate groups and the envolving of highly dispersed gold in the adsorption – catalytic process of oxidation of acetone molecules.

Kinetics of reactions of NH4 + with some biogenic organic molecules and monoterpenes in helium and nitrogen carrier gases: A potential reagent ion for selected ion flow tube mass spectrometry.

To assess the suitability of NH4 + as a reagent ion for trace gas analysis by selected ion flow tube mass spectrometry, SIFT-MS, its ion chemistry must be understood. Thus, rate coefficients and product ions for its reactions with typical biogenic molecules and monoterpenes need to be experimentally determined in both helium, He, and nitrogen, N2 , carrier gases. NH4 + and H3 O+ were generated in a microwave gas discharge through an NH3 and H2 O vapour mixture and, after m/z selection, injected into He and N2 carrier gas. Using the conventional SIFT method, NH4 + reactions were then studied with M, the biogenic molecules acetone, 1-propanol, 2-butenal, trans-2-heptenal, heptanal, 2-heptanone, 2,3-heptanedione and 15 monoterpene isomers to obtain rate coefficients, k, and product ion branching ratios. Polarisabilities and dipole moments of the reactant molecules and the enthalpy changes in proton transfer reactions were calculated using density functional theory. The k values for the reactions of the biogenic molecules were invariably faster in N2 than in He but similar in both bath gases for the monoterpenes. Adducts NH4 + M were the dominant product ions in He and N2 for the biogenic molecules, whereas both MH+ and NH4 + M product ions were observed in the monoterpene reactions; the monoterpene ratio correlating (R2 =0.7) with the proton affinity, PA, of the monoterpene molecule as calculated. The data indicate that this adduct ion formation is the result of bimolecular rather than termolecular association. NH4 + can be a useful reagent ion for SIFT-MS analyses of molecules with PA(M) < PA(NH3 ) when the dominant single product ion is the adduct NH4 + M. For molecules with PA(M) > PA(NH3 ), such as monoterpenes, both MH+ and NH4 + M ions are likely products, which must be determined along with k by experiment.

Poly(sulfobetaine)-Based Diblock Copolymer Thin Films in Water/Acetone Atmosphere: Modulation of Water Hydration and Co-nonsolvency-Triggered Film Contraction.

The water swelling and subsequent solvent exchange including co-nonsolvency behavior of thin films of a doubly thermo-responsive diblock copolymer (DBC) are studied via spectral reflectance, time-of-flight neutron reflectometry, and Fourier transform infrared spectroscopy. The DBC consists of a thermo-responsive zwitterionic (poly(4-((3-methacrylamidopropyl) dimethylammonio) butane-1-sulfonate)) (PSBP) block, featuring an upper critical solution temperature transition in aqueous media but being insoluble in acetone, and a nonionic poly(N-isopropylmethacrylamide) (PNIPMAM) block, featuring a lower critical solution temperature transition in water, while being soluble in acetone. Homogeneous DBC films of 50-100 nm thickness are first swollen in saturated water vapor (H2O or D2O), before they are subjected to a contraction process by exposure to mixed saturated water/acetone vapor (H2O or D2O/acetone-d6 = 9:1 v/v). The affinity of the DBC film toward H2O is stronger than for D2O, as inferred from the higher film thickness in the swollen state and the higher absorbed water content, thus revealing a pronounced isotope sensitivity. During the co-solvent-induced switching by mixed water/acetone vapor, a two-step film contraction is observed, which is attributed to the delayed expulsion of water molecules and uptake of acetone molecules. The swelling kinetics are compared for both mixed vapors (H2O/acetone-d6 and D2O/acetone-d6) and with those of the related homopolymer films. Moreover, the concomitant variations of the local environment around the hydrophilic groups located in the PSBP and PNIPMAM blocks are followed. The first contraction step turns out to be dominated by the behavior of the PSBP block, whereas the second one is dominated by the PNIPMAM block. The unusual swelling and contraction behavior of the latter block is attributed to its co-nonsolvency behavior. Furthermore, we observe cooperative hydration effects in the DBC films, that is, both polymer blocks influence each other's solvation behavior.

Acetone Vapor Sensors Based on Tin Dioxide Doped by Au Nanoparticles

The effect of nano-sized gold particles on the adsorption-sensitive properties of SnO2–Au sensors under the detection of acetone vapors has been studied. Different techniques for the preparation of SnO2–Au nanocomposites with an average Au particle size of 2 nm were applied. It has been found that a fivefold increase in the sensor response to acetone vapors and threshold sensitivity (Clim) of 0.1 ppm are achieved by adding gold to tin dioxide in the colloidal form during synthesis. While adding gold in ion form (Au (III)) leads to a growth of the sensor response to acetone vapors by 2.7 times and defines Clim of 0.2 ppm. The slope of the calibration curves of the SnO2–Au sensors allows registering acetone vapors at concentrations ranging from Clim to 5 ppm. This concentration range can be used for the express diagnostics in diabetes. The enhanced sensitivity of SnO2–Au sensors to acetone vapors can be explained by an increase in the adsorption-catalytic activity of tin ions as a result of the modifying effect of sulfate groups and the envolving of highly dispersed gold in the adsorption – catalytic process of oxidation of acetone molecules.

Porous carbon fibers from low-temperature sodium amide activation for acetone adsorption

The low energy consumption and facile activation methods are of great significance to synthesize porous carbon fibers. In this work, polyacrylonitrile-based porous carbon fiber (ACFN-X) was synthesized by sodium amide activation at the temperature ranges of 400–600 °C. The characterization of ACFN-X proves the formation of porous structure and N–O doped surface. Acetone was used as an adsorbate to explore the adsorption performance of the ACFN-X samples. The maximum acetone adsorption capacity is 4.80 mmol g−1 (at 25 °C, 18 kPa). The experimental results are well fitted by the Freundlich model, Sips model and Langmuir model to express the equilibrium adsorption, which indicates that the ACFN-X has a positive adsorption cooperativity on the acetone. Besides, the pseudo-first-order and pseudo-second-order kinetic model could well describe the kinetic processes. The rate constant k2 is mainly affected by the positive effect of the nitrogen functional groups. Moreover, the coupling roles of pore structure and functional groups on acetone adsorption performance were also explored. The results show that micropores play a crucial role in acetone adsorption. Nitrogen functional groups play a promoting role in micropores, and the addition of the pyrrolic exhibits the highest affinity with acetone molecules in the presence of oxygen functional groups. This study provides ideas an option for the preparation of porous carbon fibers as VOCs adsorption.

Precise control of surface oxygen vacancies in ZnO nanoparticles for extremely high acetone sensing response

ZnO has been studied intensely for chemical sensors due to its high sensitivity and fast response. Here, we present a simple approach to precisely control oxygen vacancy contents to provide significantly enhanced acetone sensing performance of commercial ZnO nanopowders. A combination of H2O2 treatment and thermal annealing produces optimal surface defects with oxygen vacancies on the ZnO nanoparticles (NPs). The highest response of ∼27,562 was achieved for 10 ppm acetone in 0.125 M H2O2 treated/annealed ZnO NPs at the optimal working temperature of 400 °C, which is significantly higher than that of reported so far in various acetone sensors based on metal oxide semiconductors (MOSs). Furthermore, first-principles calculations indicate that pre-adsorbed O formed on the surface of H2O2 treated ZnO NPs can provide favorable adsorption energy, especially for acetone detection, due to strong bidentate bonding between carbonyl C atom of acetone molecules and pre-adsorbed O on the ZnO surface. Our study demonstrates that controlling surface oxygen vacancies by H2O2 treatment and re-annealing at optimal temperature is an effective method to improve the sensing properties of commercial MOS materials.

Monitoring Catalytic 2-Propanol Oxidation over Co3O4 Nanowires via In Situ Photoluminescence Spectroscopy.

Spectroscopic methods enabling real-time monitoring of dynamic surface processes are a prerequisite for identifying how a catalyst triggers a chemical reaction. We present an in situ photoluminescence spectroscopy approach for probing the thermocatalytic 2-propanol oxidation over mesostructured Co3O4 nanowires. Under oxidative conditions, a distinct blue emission at ∼420 nm is detected that increases with temperature up to 280 °C, with an intermediate maximum at 150 °C. Catalytic data gained under comparable conditions show that this course of photoluminescence intensity precisely follows the conversion of 2-propanol and the production of acetone. The blue emission is assigned to the radiative recombination of unbound acetone molecules, the n ↔ π* transition of which is selectively excited by a wavelength of 270 nm. These findings open a pathway for studying thermocatalytic processes via in situ photoluminescence spectroscopy, thereby gaining information about the performance of the catalyst and the formation of intermediate products.

Synthesis of Porous Carbon for Acetone Adsorption: Specific Surface Area, Porous Structure and Oxygen Functional Groups

AbstractThe porous carbon material is widely used as acetone adsorbent. The low‐cost, facile and efficient synthesis method of porous carbon material is of great significance to the removal of acetone. Potassium citrate, a common organic salt, was self‐activated in the current study at the temperatures of 600–900 °C to form porous carbons (KAC−X) with rich microporous structures. The KAC−X showed excellent specific surface area (763–2100 m2 g−1) and oxygen content (5.95–16.29 wt%). The sample obtained at the temperature of 900 °C showed promising acetone adsorption capacities of 8.33 mmol g−1 (15 °C) and 7.27 mmol g−1 (25 °C), respectively. The acetone adsorption results were well fitted by the Langmuir‐Freundlich and Freundlich models. Moreover, the influence of physical structure and oxygen functional group on the acetone adsorption performance was explored. The results showed that: (1) one of the main methods for promoting the acetone adsorption capacity is to increase the specific surface area; (2) the other method is to increase the optimal pore volume, and the optimal pore size is 2–5 times of the acetone molecule diameter; (3) carboxyl and carbonyl groups can significantly increase the adsorption affinity between acetone molecule and KAC−X, and play an auxiliary role on the acetone adsorption. This study provides guidance for the facile synthesis of porous carbons from organic salt for the sake of acetone adsorption.

Fluoride-assisted highly-active tungsten oxide with modulating exposed facets and defect sites for efficient ppb-level acetone detection

Defect engineering is currently one of the most effective strategies to improve material sensing performance, which always need to be processed under harsh and complicated experimental conditions. Herein, a simple fluoride-assisted hydrothermal method is reported for preparing highly defective and active WO3. The obtained WO3 shows an urchin-like morphology and a mixed crystal structure. The optimized sensor based on the WO3 exhibits a high response, excellent selectivity, and good reproducibility to acetone at 200 °C. More precisely, the response to 0.5 ppm acetone attains 3.3 and the detection limit reaches the ppb-level, showing a potential application in noninvasive diagnosis of diabetes. The unique sensing performance can be attributed to the dominated h-WO3 with preferential exposed (002) facets and the increased structural defects in the synthesized WO3, resulting in an extent of local electric polarization on the surface and an easier and selective chemical adsorption to acetone molecules. The abundant oxygen vacancies act as preferential adsorption sites for absorbing oxygen species that can react with acetone molecules. The sensing mechanism for the unique sensing performance was further proved by a semi-in-situ controlled experiment. It is believed that the present work provides a simple and controllable approach to prepare highly active nanomaterials for application in various fields.

Water-Selective Nanostructured Dehumidifiers for Molecular Sensing Spaces.

Humidity and moisture effects, frequently called water poisoning, in surroundings are inevitable for various molecular sensing devices, strongly affecting their sensing characteristics. Here, we demonstrate a water-selective nanostructured dehumidifier composed of ZnO/TiO2/CaCl2 core-shell heterostructured nanowires for molecular sensing spaces. The fabricated nanostructured dehumidifier is highly water-selective without detrimental adsorptions of various volatile organic compound molecules and can be repeatedly operated. The thermally controllable and reversible dehydration process of CaCl2·nH2O thin nanolayers on hydrophilic ZnO/TiO2 nanowire surfaces plays a vital role in such water-selective and repeatable dehumidifying operations. Furthermore, the limitation of detection for sensing acetone and nonanal molecules in the presence of moisture (relative humidity ∼ 90%) was improved more than 20 times using nanocomposite sensors by operating the developed nanostructured dehumidifier. Thus, the proposed water-selective nanostructured dehumidifier offers a rational strategy and platform to overcome water poisoning issues for various molecular and gas sensors.