Acid Vapor Research Articles

Carbon-doped porous hollow alpha-Fe2O3 microtubules controlled by absorbent cotton bio-template to detect acetic acid vapor

To overcome the scarcity and costliness of noble metal dopants, carbon (C) doping, as a low-cost alternative, was achieved by absorbent cotton when the alpha (α)-Fe2O3 microtubules were synthesized with a facile hydrothermal method and necessary calcination. The absorbent cotton not only provided carbon source but controlled the microtubular morphology of α-Fe2O3. Meanwhile, for comparison, a pure α-Fe2O3 nanoparticles sample was also prepared without using absorbent cotton. Numerous techniques were employed to characterize the element composition and microstructures. The consequences demonstrated that carbon had been successfully incorporated into the porous hollow α-Fe2O3 microtubules composed of many nanoparticles. Compared with the α-Fe2O3 nanoparticles, the carbon-doped α-Fe2O3 microtubules possessed the unique morphology, large specific surface area and pore size, and abundant oxygen vacancies (OV). To reveal the function of the carbon-doped α-Fe2O3 microtubules and α-Fe2O3 nanoparticles, two chemical gas sensors were manufactured and researched systematically. Forasmuch as those advantages mentioned above, the sensor based on the carbon-doped α-Fe2O3 microtubules exhibited better gas sensing properties to acetic acid vapor at a lower optimal operating temperature of 260 °C, such as higher response value, shorter response and recovery time, good repeatability, and stability. And thence the carbon-doped α-Fe2O3 microtubules product could be considered as an excellent acetic acid vapor sensor in the future. In addition, the possible grown mechanism and gas sensing mechanism of the carbon-doped α-Fe2O3 microtubules were discussed in detail. The work provides a new strategy to improve the gas sensing performance of α-Fe2O3 material.

Self-Assembled Corn-Husk-Shaped Fullerene Crystals as Excellent Acid Vapor Sensors

Low-molecular-weight acid vapors cause aging and destruction in material processing. In this paper, facile fabrication of novel corn-husk-shaped fullerene C60 crystals (CHFCs) through the dynamic liquid–liquid interfacial precipitation method is reported. The CHFCs were grown at the liquid–liquid interface between isopropyl alcohol (IPA) and a saturated solution of C60 in mesitylene under ambient temperature and pressure conditions. The average length, outer diameter, and inner diameter of CHFCs were ca. 2.88 μm, 672 nm, and 473 nm, respectively. X-ray diffraction (XRD) analysis showed the CHFCs exhibit a mixed face-centered cubic (fcc) and hexagonal-close pack (hcp) crystal phases with lattice parameters a = 1.425 nm, V = 2.899 nm3 for fcc phase and a = 2.182 nm, c = 0.936 nm, a/c ratio = 2.33, and V = 3.859 nm3 for hcp phase. The CHFCs possess mesoporous structure as confirmed by transmission electron microscopy (TEM) and nitrogen sorption analysis. The specific surface area and the pore volume were ca. 57.3 m2 g−1 and 0.149 cm3 g−1, respectively, are higher than the nonporous pristine fullerene C60. Quartz crystal microbalance (QCM) sensing results show the excellent sensing performance CHFCs sensitive to acetic acid vapors due to the enhanced diffusion via mesoporous architecture and hollow structure of the CHFCs, demonstrating the potential of the material for the development of a new sensor system for aliphatic acid vapors sensing.

Reversible on/off conformational switching of pentafluorobenzoyl amide triggered by acid vapor and sublimation

Molecular switches composed of pentafluorobenzoyl amide can be controlled with an acid and sublimation in an on/off manner in the solid state.

A Fast-Response Acidic and Basic Vapor Visual Indicator Film Based on Black Wolfberry Anthocyanin for Monitoring Chicken and Shrimp Freshness

A Fast-Response Acidic and Basic Vapor Visual Indicator Film Based on Black Wolfberry Anthocyanin for Monitoring Chicken and Shrimp Freshness

Multi-stimuli distinct responsive D–A based fluorogen oligomeric tool and efficient detection of TNT vapor

P1 shows distinct emission responses with multi-stimuli, i.e., quenching for TNT sensing, red shifting for acid and base vapors, blue shifting against MFC behavior, and solvent polarity-dependent emission.

Vacuum ultraviolet photochemistry of sulfuric acid vapor: a combined experimental and theoretical study.

We present a vacuum ultraviolet (VUV) photoionization study of the gas-phase sulfuric acid (H2SO4) molecule in the 11-14 eV energy range by using the method of synchrotron radiation-based double imaging photoelectron photoion coincidence (i2PEPICO) spectroscopy complemented with accurate theoretical calculations. The slow photoelectron spectrum (SPES) of H2SO4 has been acquired and the three electronic states of H2SO4+, X2A, A2A and B2A have been populated and assigned. The adiabatic ionization energy of the H2SO4 molecule towards the X2A cationic ground state is measured at 11.684 ± 0.006 eV, in accordance with high-level calculated findings. With increasing photon energies, the H2SO4+ cation dissociates into HSO3+ and OH fragments and their adiabatic appearance energy is measured at 13.498 ± 0.007 eV. Then, the enthalpies of formation for the species involved in the photoionization and dissociative photoionization have been determined through a thermochemical cycle.

Fluorescent litmus film for detecting acid vapors: free-standing and robust AIE sensing film fabricated by photopolymerization of self-assembled hierarchical triphenylamine-based gelators

Free-standing fluorescent litmus film fabricated by polymerization of aggressive induced emission (AIE) organogel for detecting acid vapors provides the sensing properties for industrial safety.

Assessing Repeated Oxalic Acid Vaporization in Honey Bee (Hymenoptera: Apidae) Colonies for Control of the Ectoparasitic Mite Varroa destructor.

The American beekeeping industry continually experiences colony mortality with annual losses as high as 43%. A leading cause of this is the exotic, ectoparasitic mite, Varroa destructor Anderson & Trueman (Mesostigmata: Varroidae). Integrated Pest Management (IPM) options are used to keep mite populations from reaching lethal levels, however, due to resistance and/or the lack of suitable treatment options, novel controls for reducing mites are warranted. Oxalic acid for controlling V. destructor has become a popular treatment regimen among commercial and backyard beekeepers. Applying vaporized oxalic acid inside a honey bee hive is a legal application method in the U.S., and results in the death of exposed mites. However, if mites are in the reproductive stage and therefore under the protective wax capping, oxalic acid is ineffective. One popular method of applying oxalic is vaporizing multiple times over several weeks to try and circumvent the problem of mites hiding in brood cells. By comparing against control colonies, we tested oxalic acid vaporization in colonies treated with seven applications separated by 5 d (35 d total). We tested in apiaries in Georgia and Alabama during 2019 and 2020, totaling 99 colonies. We found that adult honey bees Linnaeus (Hymenoptera: Apidae), and developing brood experienced no adverse impacts from the oxalic vaporization regime. However, we did not find evidence that frequent periodic application of oxalic during brood-rearing periods is capable of bringing V. destructor populations below treatment thresholds.

A general acetic acid vapour etching strategy to synthesize layered carbon nitride with carbon vacancies for efficient photoredox catalysis

A chemical etching strategy has been developed to prepare polymeric carbon nitride (PCN) nanosheets with carbon vacancies (CVs). The CVs can regulate the electronic properties of the Pt cocatalyst, thereby achieving superior hydrogen production.

Real-time monitoring of aerosol particle formation from sulfuric acid vapor at elevated concentrations and temperatures.

In the present study, time-resolved aerosol particle formation from sulfuric acid vapor is examined with special attention to the stabilization of molecular clusters in the early phase of unary nucleation. An important factor governing this process is the amount of condensable acid vapor. Here it is produced from fast gas-phase reactions in a batch-type reaction cell for which we introduce modifications enabling real-time monitoring. The key component for size- and time-resolved detection of ultrafine particles is a new 1 nm-SMPS. With this new tool at hand, the effect of varying the precursor concentration over two orders of magnitude is investigated. We demonstrate the ability to tune between different growth scenarios as indicated by the size-resolved particle traces which exhibit a transition from sigmoidal over quasi-stationary to peak-like shape. The second key parameter relevant for nucleation studies is the temperature-dependent cluster evaporation. Due to a temperature rise during the mixing stage of the experiment, evaporation is strongly promoted in the early phase. Therefore, the present study extends the T-range used in, e.g., smog chambers. We investigate this temperature effect in a kinetic simulation and can successfully combine simulated and measured data for validating theoretical evaporation rates obtained from DLPNO-CCSD(T0)-calculations.

Dual-function fluorescent hydrazone-linked covalent organic frameworks for acid vapor sensing and iron(iii) ion sensing

Fluorescent hydrazone-linked COFs and their aerogel composites applied in acid vapor sensing and Fe3+sensing.

An amino-type halogen-bonded organic framework for the selective adsorption of aliphatic acid vapors: insight into the competitive interactions of halogen bonds and hydrogen bonds

A novel amino-type 2D halogen-bonded organic framework (XOF-TPPA) could serve as an efficient and recyclable adsorbent for MeCOOH/EtCOOH vapors.

Effects of Organic Acid Vapors on Inactivation of Salmonella Newport on Blueberries and Their Sensory Attributes

Effects of Organic Acid Vapors on Inactivation of Salmonella Newport on Blueberries and Their Sensory Attributes

Capture of Pollutants from Exhaust Gases by Low-Temperature Heating Surfaces

One of the most effective methods towards improving the environmental safety of combustion engines is the application of specially prepared water-fuel emulsions (WFE). The application of WFE makes it possible to reduce primary sulfur fuel consumption and reveals the possibility of capturing the pollutants from exhaust gases by applying condensing low-temperature heating surfaces (LTHS). In order to realize such a double effect, it is necessary to investigate the pollution processes on condensing LTHS of exhaust gas boilers (EGB), especially the process of low-temperature condensing a sulfuric acid vapor from exhaust gases to investigate the influence of condensing LTHS on the intensity of pollutants captured from the exhaust gases. The aim of this research is to assess the influence of the intensity of pollutants captured from exhaust gases by condensing LTHS in dependence of water content in WFE combustion. Investigations were carried out at a special experimental setup. The processing of the results of the experimental studies was carried out using the computer universal statistical graphic system Statgraphics. Results have shown that in the presence of a condensing heating surface, the degree of capture (purification) of pollutants from the exhaust gas flow is up to 0.5–0.6.

Highly Ordered Polymer Nanostructures via Solvent On-Film Annealing for Surface-Enhanced Raman Scattering.

Surface-enhanced Raman scattering (SERS) has been a useful sensing technique, in which inelastic light scattering can be significantly enhanced by absorbing molecules onto rough metal surfaces or nanoparticles. Although many methods have been developed to prepare SERS substrates, it is still highly desirable and challenging to design SERS substrates, especially with highly ordered and controlled three-dimensional (3D) structures. In this work, we develop novel SERS substrates with regular volcano-shaped polymer structures using the versatile solvent on-film annealing method. Polystyrene (PS) nanospheres are first synthesized by surfactant-free emulsion polymerization and assembled on poly(methyl methacrylate) (PMMA) films. After annealing in acetic acid vapors, PMMA chains are selectively swollen and wet the surfaces of the PS nanospheres. By selectively removing the PS nanospheres using cyclohexane, volcano-shaped PMMA films can be obtained. Compared with flat PMMA films with water contact angles of ∼74°, volcano-shaped PMMA films exhibit higher water contact angles of ∼110° due to the sharp features and rough surfaces. The volcano-shaped PMMA films are then coated with gold nanoparticles (AuNPs) as SERS substrates. Using rhodamine 6G as the probe molecules, the SERS results show that the Raman signals of the volcano-shaped PMMA/AuNP hybrid substrates are much higher than those of the pristine PMMA films and PMMA films with AuNPs. For the volcano-shaped PMMA/AuNP hybrid substrates using 400 nm PS nanospheres, a high enhancement factor (EF) value of ∼1.12 × 105 with a detection limit of 10-8 M is obtained in a short integration time of 1 s. A linear calibration line with an R2 value of 0.918 is also established, demonstrating the ability to determine the concentrations of the analytes. This work offers significant insight into developing novel SERS substrates, which is crucial for improving the detection limits of analytes.

Controllable acid vapor oxidation growth of complex SnO2 nanostructures for ultrasensitive ethanol sensing

Controllable assembly from one-dimensional (1-D) and two-dimensional (2-D) nanoscale structures to three-dimensional (3-D) complex nanostructures has attracted great interest. For the first time, nanorods and nanosheets were controllably assembled into 3-D SnO2 nanoflower architectures based on a facile and shape-controlled acid vapor oxidation (AVO) method from the substrate in a simple reaction system. The as-prepared 3-D SnO2 nanoflowers have diameters ranging from 625 to 875 nm and are self-assembled by many nanorods and nanosheets with diameters and thicknesses of 33 nm. The growth of SnO2 with different morphologies was studied by controlling the reaction temperature and hydrochloric acid concentration. Their application in gas sensing was evaluated, indicating that the 3-D SnO2 nanoflower-based sensor is ultrasensitive to ethanol with a response of 2.54–50 ppb at the optimal working temperature of 230 °C. This work offers a facile, shape-controlled, and efficient route to synthesize complex SnO2 nanoflowers for gas detection with high performance, including ultrahigh sensitivity, good selectivity, and reversibility.

Distribution of hypogene alteration and fluid evolution in the Los Humeros Geothermal Field (Puebla, Mexico): Multiple sourced fluids, interrelations, and processes in a superhot system

The Los Humeros Geothermal Field (LHGF) is one of the highest producing geothermal areas in Mexico. This paper aims essentially to determine high-resolution patterns of distribution of hypogene alteration assemblages and the distribution of temperatures in space and time of geothermal fluids in the LHGF. The zoning of hypogene alteration assemblages in the LHGF consists of (1) shallow advanced argillic alteration assemblages that grade into (2) argillic and (3) zeolitic assemblages with depth, followed by (4) low-temperature and (5) high-temperature propylitic, and (6) deep high-temperature high-silica advanced argillic alteration assemblages. The distribution of deep advanced argillic alteration assemblages is associated with the occurrence of acidic supercritical fluids prior to their deep boiling. Capping these, high-temperature propylitic assemblages are associated with the occurrence of subcritic brines (barely exceeding 13 wt% NaCl equiv.) that stemmed from magmatic supercritic fluids (upon degassing and/or conductive cooling) and that were diluted by deeply circulated and thermally equilibrated meteoric water. Conductively cooled subcritic fluids, which eventually kept being diluted on their way to the surface, would be likely associated with the generation of shallow low-temperature propylitic assemblages. Relatively fresh meteoric water might have been increasingly relevant in such dilution as upwelling fluids neared the surface. Shallow boiling occurred mostly between high- and medium-temperature propylitic zones, and generated acidic vapors that eventually condensated in the phreatic water table and, in part, in the argillic alteration zone. Shallow hypogene advanced argillic (and argillic) alteration consisting of kaolinite, platy alunite, native sulfur and the newly found cuprocopiapite occurred in steam-heated grounds. Fluid inclusion and present-day geothermal fluid data allow to introduce relative time as a variable in the characterization of hydrothermal fluids in the LHGF. These sets of temperature data allow to independently determine patterns of temperature distribution as isotherms. Concave shapes in isotherms are interpreted to spearhead preferential passageways for hydrothermal fluids. Some areas (for instance, in the southern part of the LHGF) record relatively stable passageways through time, but these may significantly shift their positions in other areas. Stable passageways, apparently undisturbed by geothermal exploitation, may identify robust portions of the system that ensure a long-lasting exploitation. They also correspond to sound inputs of high-salinity and hot magmatic fluids, which may be sandwiched between cooler low-salinity fluids, dominantly meteoric in origin, and collectively make a case for convection (and partial mixing). Also, we determined that “older” inclusion fluids are ∼50 °C higher than “younger” fluids from geothermal wells, but such decrease can be compatible with the cooling down of the system due to geothermal exploitation. Therefore, such differences in temperature do not necessarily reflect an actual cooling in the system.

Steam pretreatment-mediated catalytic activity modulation for ammonia borane hydrolysis over ruthenium nanoclusters on nitrogen/oxygen-rich carbon nanotubes

Supported metal nanoclusters (NCs) have been demonstrated as essential kinds of catalytic materials for hydrolysis of ammonia borane (AB). The uniform anchoring of metal NCs on carbon matrix is challenging using traditional impregnation and immobilization routes without any stabilizing ligands. In this study, we report an economical, simple and efficient steam pretreatment-mediated strategy of using nitric acid vapor to adjust the surface chemistry and textural structure of carbon nanotubes (f-CNTs) and thereby achieving the uniform deposition of well-defined Ru NCs onto the f-CNTs toward hydrogen production from AB hydrolysis. Compared to its pristine carbon nanotube analogues, the rich N/O-functional groups, increased defects and specific surface area of f-CNTs enable the formation of Ru NCs (1.71 nm in diameter) with high dispersion, which considerably boost the catalytic hydrolysis of AB to produce hydrogen under mild conditions. Specifically, Ru@f-CNTs with an optimal metal loading of 2 wt% delivers a considerable activity in hydrogen generation from AB hydrolysis with turnover frequency of 764 min−1 at 298 K, superior to many reported Ru-based catalysts. The present strategy provides an efficient way to prepare various carbon supported metal catalysts that possess great promise in catalytic application.

Cocrystal engineering: Tuning the charge transfer excitons for highly sensitive luminescent switching materials under multiple stimuli

This paper presents a multi-stimuli responsive cocrystal system with luminescent properties that can be dynamically controlled and demonstrates the responsive mechanism of cocrystals under multiple stimuli (acid/alkali vapor, force, and heat). Detailed spectroscopic, computational, and structural studies exhibit that obvious charge transfer interactions occur in loosely mixed-stacking cocrystals. Such interactions can be weakened by acid vapor fuming due to the strong electron-withdrawing effect of acid cations and strengthened under mechanical grinding. Furthermore, the response time of the cocrystal is in the order of seconds, which is much superior to those of most previously reported stimuli-responsive cocrystals. Accordingly, a high-sensitive fluorescence switching is demonstrated under multiple stimuli, providing an effective strategy to develop smart materials.

Hydrophilic nanoporous copper surface prepared by modified formic acid vapor treatment

Hydrophilic copper surface with average water contact angle down to 18° can be developed through pre-oxidation and low-temperature reduction treatment using Pt-catalyzed formic acid vapor at 200 °C. The high aspect ratio capillary nanoporous structures of reduced pure copper effectively enhance the hydrophilicity, which is almost the same as hydrophilic oxidized surface with a mixture of CuO and Cu2O. Real-time Fourier transform infrared spectroscopy was employed to monitor the reduction kinetics of the oxidized copper surface. The effect of formic acid vapor concentration was studied and the comparison with N2-5%H2 gas was also done. The porosity of reduced copper can be ascribed to CO2 outgassing from formate dissociation. The great potential in industrial applications such as flat-plate heat pipes with narrow slots was also demonstrated.