Acid Vapor Research Articles

Applications of Raman spectroscopy in art and archaeology

Applications of Raman spectroscopy in art and archaeology

Low temperature chemical treatment of graphene films made by double self-assembly process to improve sheet resistance

In this study, a low temperature hydro iodic acid (HI) vapor treatment of the self-assembled graphene films has been developed, and the electrical, optical, structural and morphological properties were investigated by four-point probe, UV–Visible spectroscopy, Raman spectroscopy and scanning electron microscopy (SEM). Mono-, double- and triple-layer of graphene flakes were deposited on glass substrates by using the Double Self-Assembly (DSA) process. The self-assembled graphene films were treated with HI vapors at 40 °C for different time intervals between 1 and 24 h. In addition, graphene deposition and HI-vapor treatment (at 40 °C for 1 h) was enforced three times to the same substrate. The optical transparency values of the self-assembled mono- (MGFs), double- (DGFs) and triple-layer graphene flakes (TGFs) were measured as 91, 85 and 80%, respectively (values at 550 nm). Due to the HI-vapor treatment, the sheet resistance of MGFs significantly reduced from 1.1 × 107 Ω □−1 to 2.9 × 104 Ω □−1, the transparency of the graphene films slightly reduced by 2–5%, the ID/IG ratio of the DGFs decreased from 1.01 to 0.81, while the I2D/IG ratio increased from 0.43 to 0.48 in the Raman spectrum. Thanks to its impressive reducing effect on sheet resistance, HI-vapor treatment can be a suitable method to improve the conductivity of low-cost large area graphene films.

Environmentally friendly biological nanofibers based on waste feather keratin by electrospinning with citric acid vapor modification

AbstractWaste feather keratin (FK)‐based nanofibers by electrospinning and citric acid (CA) vapor modification has been successfully prepared and investigated. FK, poly(vinyl alcohol), and poly(ethylene oxide) have been used as raw materials and CA vapor as cross‐linker. The structural, thermal, hydrophobicity, and mechanical properties of FK‐based nanofibers by CA vapor modification with various cross‐linking time have been completely explored. In order to investigate the effect of H2O vapor on CA vapor modification, H2O vapor modification was performed on the FK‐based nanofibers at the same conditions. The results show that the average diameter of nanofibers increased from 250.83 ± 29.65 nm to 338.79 ± 31.43 nm by CA vapor modification with 15 h. Similarly, the thermal stability and water resistance of FK‐based nanofibers by CA vapor modification have been significantly improved. The tensile strength (σb) and elongation at breakage point (εb) of FK‐based nanofibers after CA vapor modified for 15 h were about 1.5 and 2 times higher than that of nonmodified nanofibers, respectively. By comparison, scanning electron microscopy results suggest that the FK‐based nanofibers modified by H2O vapor cannot maintain the morphology of the nanofibers, resulting in large‐scale adhesion. The thermal properties of FK‐based nanofibers with H2O vapor modification have no obvious change. The hydrophobicity and mechanical properties of FK‐based nanofibers by H2O vapor modification are not as good as that of CA vapor modification. In summary, these results exhibit that nontoxic and natural CA can be used as cross‐linking agent to enhance the comprehensive performance of FK‐based nanofibers. This study provides a new method to modify FK‐based nanofibers and refined the waste feathers, which not only protected the environment, but also gained benefits, which has a broad application prospect.

Nghiên cứu chế tạo ống hấp thụ hơi axit dùng cho ống trinh độc OTĐ-36 để trinh sát chất độc quân sự HD công nghiệp

Sulfur mustard, also known as Mustard gas, Yperite or HD agent is strong cytotoxic and vesicant chemical warfare agent, causing chemical burns on the skin, eyes and lungs. Common method to detect presence of this substance to use OTĐ-36 (IT-36) chemical indicator tubes. However, when acid vapor presents in impure HD agent, OTĐ-36 can’t detect HD agent. In this paper, we present the results of research on manufacturing acid absorption tube to connect with OTĐ-36 test strip using in detection of industrial HD toxic.

The Pliocene Ixtacamaxtitlán low sulfidation epithermal deposit (Puebla, Mexico): A case of fossil fungi consortia in a steam-heated environment

The Ixtacamaxtitlán area in northern Puebla (central Mexico) contains middle Miocene Cu-Mo-Au porphyry/skarn and Pliocene low-sulfidation Au-Ag epithermal deposits that are geologically associated with the evolution of the Trans-Mexican Volcanic Belt (TMVB). In this paper, a new 40Ar/39Ar age (2.87 ± 0.41 Ma) is provided for rhombohedral alunite from a kaolinite + alunite ± opal ± cristobalite ± smectite advanced argillic alteration assemblage. This age contributes to the definition of a metallogenic province that is confined to the TMVB, a relevant feature for regional exploration. A ~12 My gap is established between the formation of the Cu-Mo-Au porphyry/skarn and low-sulfidation Au-Ag epithermal deposits, which rules out the possibility that their overlapping was the result of telescoping. Advanced argillic alteration is conspicuous throughout the mineralized area. This alteration assemblage consists of a widespread kaolinite-rich blanket that underlies silica sinters, polymictic hydrothermal breccias, and an alunite-rich spongy layer that consists of vertical tubular structures that are interpreted as the result of gas venting in a subaerial environment. The above indicate a shallow hypogene origin for the advanced argillic alteration assemblage—that is, formation by the partial condensation within a phreatic paleoaquifer of acidic vapors that were boiled-off along fractures that host epithermal veins at depth. The formation of the spongy alunite layer and silica sinters is interpreted to have been synchronous. Within the alunite-rich spongy layer, tubular structures hosted microbial consortia dominated by fungi and possible prokaryote (Bacteria or Archaea) biofilms. Such consortia were developed on previously formed alunite and kaolinite and were preserved due to their replacement by opal, kaolinite, or alunite. This means that the proliferation of fungi and prokaryotes occurred during a lull in acidic gas venting during which other organisms (i.e., algae) might have also prospered. Periodic acidic gas venting is compatible with a multi-stage hydrothermal system with several boiling episodes, a feature typical of active geothermal systems and of low-sulfidation epithermal deposits. The microstructures, typical for fungi, are mycelia, hyphae with septa, anastomoses between branches, and cord-like groupings of hyphae. Possible evidence for skeletal remains of prokaryote biofilms is constituted by cobweb-like microstructures composed of <1 µm thick interwoven filaments in close association with hyphae (about 2.5 µm thick). Bioweathering of previously precipitated minerals is shown by penetrative biobrecciation due to extensive dissolution of kaolinite by mycelia and by dissolution grooves from hyphae on alunite surfaces. Such bioweathering was possibly predated by inorganically driven partial dissolution of alunite, which suggests a lull in acidic gas venting that allowed living organisms to thrive. This interpretation is sustained by the occurrence of geometrical dissolution pits in alunite covered by hyphae. Fungal bioweathering is particularly aggressive on kaolinite due to its relatively poor nutrient potential. Such delicate microstructures are not commonly preserved in the geological record. In addition, numerous chalcopyrite microcrystals or microaggregates are found within the alunite layer, which could be related to sulfate reduction due to bacterial activity from the sulfate previously released by fungal bioweathering of alunite. Hydrogeochemical modeling constrains pH to between ~3.2 and ~3.6 and temperature to between 53 and 75 °C during the stage in which fungi and other organisms thrived. These waters were cooler and more alkaline than in earlier and later stages, which were characterized dominantly by steam-heated waters. The most likely process to account for this interlude would be mixing with meteoric water or with upwelling mature water that did not undergo boiling.

Doping-Induced Stacking Transition in Trilayer Graphene: Implications for Layer Stacking Manipulation

We demonstrate a crystallographic configurational transformation from rhombohedral (ABC) to Bernal (ABA) stacking by exposing large area exfoliated trilayer graphene (3LG) to nitric acid vapors and...

Inhibition of Pantoea agglomerans contamination of fresh-cut jackfruit by exposure to weak organic acid vapors

Fresh-cut jackfruit, purchased from markets in urban areas of Bangkok, were examined for bacterial contamination. Pantoea agglomerans was the predominant contaminant bacterium occurring in 90% of the 30 samples tested; many with high loads. Inhibition of surface contamination of P. agglomerans by vinegar, lactic acid or citric acid, either as liquid or vapor, were tested in vitro. For liquid-phase exposure, vinegar had a higher inhibitory effect than the other two, both of which that gave only slight inhibition. Exposure to vinegar vapor containing 3.36 mmol L−1 acetic acid for 90 min gave complete inhibition of P. agglomerans. In order to test this vaporized vinegar treatment on the quality of jackfruit, non-inoculated samples, with or without vinegar treatment, were stored for 7 d at 5 ± 2 °C and then tested by a sensory evaluation panel. Results showed that in all the attributes tested, color, texture and overall acceptability, vaporized vinegar treated sample were preferred to non-treated samples. It was concluded that exposure of fresh-cut jackfruit to vaporized vinegar is a simple method of controlling surface bacterial contamination without detrimentally affecting their acceptability.

Self-Healing Material with Reversible Luminescence Switch Behavior.

Luminescent materials with dynamic responsiveness to external stimuli have attracted extensive attention for the development of advanced sensors and smart materials; however, self-healing capability is also of great importance for functional soft materials. An acid/base vapor reversibly triggered luminescence switch with self-healing ability is achieved by incorporating dynamic lanthanide metal-ligand (Ln-L) coordination into the soft polydimethylsiloxane polymer network. The emission color of the resultant luminescent material could be modulated by altering either the Eu3+/Tb3+ molar ratio or the excitation wavelength. The luminescence "On-Off" reversible switch is realized via direct alternating exposure to acid and base vapor, realizing reversible information encryption and decryption. The dynamic Ln-L cross-link as well as the hydrogen bond in the luminescent material endow it with excellent self-healing capability, high toughness, and stretchability. We believe this acid/base vapor-triggered self-healing switching strategy provides new insights for expanding the application range of luminescent materials.

Strong Coupling of Organic Dyes Located at the Surface of a Dielectric Slab Microcavity.

Strong coupling to the electronic or vibronic transitions of an organic semiconductor has been extensively studied in microcavity structures in which a molecular film is placed between two closely spaced mirrors. Recent experiments suggest that such strong coupling can be used to modify chemical reactions; however, the geometry of conventional microcavity structures makes such studies difficult as they limit the ability of molecules to interact with their local environment. Here, we show that optical strong coupling to a molecular film can be achieved even when such molecules are located on the surface of a dielectric slab. We then show that such molecules on the surface of the slab can undergo facile interactions with molecules in their surrounding environment, and evidence a reversible protonation/deprotonation reaction by exposing a surface-bound porphyrin to an acidic or basic vapor. Although our proof-of-principle measurements do not evidence any change in reaction rates, we believe our structures represent a promising system in which to explore polariton-driven chemical phenomena.

SERS procedure using photoreduced substrates and reflection FTIR spectroscopy for the study of natural organic colourants

AbstractIn this work, we showed the potential of photoreduced surface‐enhanced Raman spectroscopy or surface‐enhanced Raman scattering (SERS) substrate for the detection of organic colourants (in mixtures) in lipid and proteinaceous paint layers. Different organic colourants such as madder lake pigment, cochineal lake pigment and lac dye were included in the study. SERS procedure with different approaches was tested, namely, direct application, soaking (incubation) of the sample in the substrate and hydrolysis with the hydrofluoric (HF) acid vapours. For the analysis of colourants bound in linseed oil, a pretreatment step was required (soaking/incubating or hydrolysing with HF). Moreover, exposing a cross‐section of a sample taken from a polychrome work of art to the vapours of HF enabled SERS detection of the cochineal lake pigment in the paint layer of this cross‐section. Therefore, the SERS substrate could be used also for the study of stratigraphy of real cultural heritage samples. As the analyses by means of SERS are (minimally) invasive, the potential of noninvasive reflection FTIR‐spectroscopy analyses for the identification of organic colourants was tested as well. Reflection infrared spectra of organic colourants are presented and discussed. Furthermore, within this study, it was shown that madder lake pigment could be identified in paint layers based on the characteristic bands of the hydrated alumina.

Prediction of Liquid Molar Volume and Heat of Vaporization of Fatty Acids Using an Equation of State

Background:: The liquid molar volume (V) and the heat of vaporization (ΔHVAP) of four fatty acids (n-Heptanoic acid, Hexadecanoic acid, n-Hexanoic acid and n- Dodecanoic acid) have been estimated. Objective:: This paper aims to calculate the liquid molar volume and the heat of vaporization of four fatty acids under the critical point using two traditional equations of state: Peng-Robinson (PR) [21] and Soave-Redlich-Kwong. Methods: The area rules method applicable to obtaining the saturation pressure of the compounds has been used. The properties of the acids investigated in this work have been compared with those provided by literature. For molar volumes, the equations of state have given improved predictions when compared to traditional equations such as Rackett equation and so on. According to the vapor enthalpy calculations, no reference value was required. Results: In general, the Clausius-Clapeyron equation provides a better estimation of the vaporization enthalpy of fatty acids when Soave-Redlich-Kwong (SRK) equation was used. The heat of vaporization for fatty acids can be calculated with good reliability in comparison with the Watson equation if suitable equation of state is used. Conclusion: Accurate results for heat of vaporization can be reached in comparison with the Watson equation if the reliable equation of state is used.

Enhancement of Spontaneous Polarization and Acid Vapor-Induced Polymerization in the Thin-Film States of Phenylterthiophene Derivative Bearing a Cyclotetrasiloxane Ring

We have achieved the measurement of spontaneous polarization of spin-coated thin films of a ferroelectric liquid crystal based on a phenylterthiophene skeleton. Uniaxially aligned spin-coated films with a thickness of 100 nm were prepared by the friction transfer method. The spontaneous polarization of the spin-coated films was measured by the Sawyer–Tower method and polarization inversion current technique under the application of triangular-wave bias. These measurements revealed the spontaneous polarization of 50 nC cm−2 in the thin-film state which is 1.5 times larger than the value of 35 nC cm−2 in the bulk state. This result should be attributed to the strong anchoring of the liquid-crystalline molecules on the substrate surface and the inhibition of polarization relaxation caused by the formation of the helical structure. Moreover, insolubilization of the thin films was carried out by an in situ ring-opening polymerization induced by acid vapors. The molecular alignment in the thin films of the ferroelectric liquid crystal was retained during the polymerization process.

Second-Generation Phosgene and Diphosgene Detection Tube

We have developed a second-generation detection tube for colorimetric and fluorescence detection of phosgene and diphosgene in air. The tube is packed with pellets made of a mixture of microcrystalline cellulose and magnesium aluminum metasilicate treated with a suitable monoterpene (camphor, menthol) to increase porosity and specific surface area. We impregnated the pellets with a specific o-phenylenediamine-pyronin (PY-OPD) based reagent. The detector with this novel indication charge enables phosgene or diphosgene to be selectively and sensitively detected at concentrations lower than as would those posing acute health risk. Owing to the analytical colorimetric and, at the same time, fluorescence signal, the detector is very robust while featuring good sensitivity and variability. The colorimetric limits of detection were 0.3 mg/m3 (tristimulus colorimeter), resp. 5 mg/m3 (with the naked eye), fluorescence detection limits of 0.3 mg/m3 (with the naked eye), all at an air sample volume of 1 dm3. The response was practically immediate, acid vapors and gases, or diethyl chlorophosphate as a simulant of nerve warfare chemical agents, were disruptive.

Synthesis of N-doped graphene quantum dots from bulk N-doped carbon nanofiber film for fluorescence detection of Fe3+ and ascorbic acid

Nitrogen doped graphene quantum dots (N-GQDs) have attracted much attention because of their superior electronic and optical properties. The preparation of N-GQDs can be usually performed via a top-down method using vairous nanocarbon as raw materials. However, most carbon materials are powder, which increases the difficulty of separating quantum dots from the reaction solution. Herein, we verified a feasibility of N-GQDs preparation with a bulk carbon film composed of N-doped carbon nanofibers as raw mateial via an acid vapor cutting approach (only 1 ml nitric acid was used in the method). The synthesis method effectively voids a tedious separation process. And the as-prepared N-GQDs exhibit good dispersion, high photostability and blue-green fluorescence. Subsequently, fluorescence experiments confirmed the fluorescence of N-GQDs was quenched selectively by Fe3+ via the unique coordination interaction between them and recovered with the addition of AA. Based on the quenching (off) and recovering (on) processes, fluorescent sensor for Fe3+ and OFF-ON fluorescent sensor for AA were fabricated, showing good selectivity and wide linear range. Finally, the constructed sensors were successfully applied for Fe3+ and AA detection in real samples such as tap water and human urine.

Venus night-side photometry with “cleaned” Akatsuki/IR2 data: Aerosol properties and variations of carbon monoxide

We have developed a novel method called Restoration by Simple Subtraction (RSS) to clean and restore the Venus night-side disk in “contaminated” Akatsuki/IR2 images at 2.26 and 1.735 μm. Light spread from the intense day crescent is cancelled by subtracting a near-simultaneous 2.32-μm image (scaled) from a 2.26-μm image. Net-contamination over the night-side disk is effectively separated and subsequently used to clean a 1.735-μm image. For the first time ever, the IR2 night-side data have become of photometric quality. Ten data sets from Orbits 24 (August 16–20, 2016) and 25 (August 26–30, 2016) were processed by the RSS method and analyzed to study the aerosol properties and variations of low-altitude carbon monoxide (CO). A new coordinate system called “M3L” is introduced to interpret the data in terms of mixtures of different mode aerosols. No simultaneous increases/decreases in mode 3 and other modes were found, but they are rather anti-correlated, indicating interchanges between them in the Venus atmosphere. A prominent feature called clouds aligned linearly in M3L coordinates (CALM) is interpreted as an indicator of the most quiescent regions with gentle convection, which maintains the cloud microphysics (interchange between mode 3 and other modes plus sulfuric acid vapor) in an organized manner. The mid-latitude bright streaks are found to deviate from CALM, suggesting the existence of forced downwelling which was previously reported based on high-resolution numerical simulations. Latitudinal variations of mode mixtures as interpreted by the M3L coordinates were compared with those in the Venus Express observation-based studies. A common trend, more mode 3 particles near the equator, which decreases toward the middle latitudes, is observed despite a decade of difference in the observation periods. CO abundance in low latitude regions was found to be characterized either by a constant or with a possible local-time variation. Although statistically favored, controversial local-time variations of CO require further investigation.

Optical Vapor Sensors Based on Periodic Resonant Nanopillar Structures.

In this work, it is reported for the first time the use of a network of periodic optical resonant nanopillars for sensing vapors of volatile organic components. In particular, this work evaluates the presence of methanol, ethanol, isopropanol, acetic acid, propionic acid, and toluene vapors at different working distances between the transducer and the surface of the sample in the liquid state, obtaining the sensing curve response of each one of them. In addition, it studies the thin film of liquid condensed onto the nanopillar surface, estimating their corresponding thickness value by means of numerical photonic simulations and their correlation with the corresponding vapor pressure of different specimens.

Mineralogy, Fluid Inclusion and H‐O‐C‐S Stable Isotopes of Mengqiguer Uranium Deposit in the Southern Yili Basin, Xinjiang: Implication for Ore Formation

AbstractThe Mengqiguer deposit in the southern Yili basin Ili Basin is a large interlayer‐oxidation‐zone type uranium deposit. In this paper, we applied multiple methods including microscopic observation, scanning electron microscope and electronic probe, to analyze the systematical alteration characteristics of the ore‐bearing sandstone layer. Fluid inclusion and stable isotope studies on the ore‐bearing sandstone have also been carried out to discuss the internal relations between fluid activities, epigenetic alteration and the uranium mineralization. Major epigenetic alteration include clay alteration, carbonatization and pyritization, of which biogenetic pyritization is most closely related to the uranium mineralization. This suggests the existence of microorganism during the uranium mineralization process. The mineralization fluids of low temperature, medium density but varied salinities are suggested to be derived from multi‐source, including the meteoric water and organic acidic vapor components from coal‐bearing strata. Uranium mineralization, grain‐dispersed kaolinite, limonite, colloidal pyrite, and the carbonate cements associated with sulfate‐reducing bacteria were formed by meteoric water and vermicular‐shaped kaolinite, autologous pyrite, and the carbonate cementation associated with the dehydroxylation of organic matter was formed by organic acidic. Based on these results, we consider that the uranium mineralization and epigenetic alteration both resulted from the reciprocity of organic–inorganic fluid and fluid–rock during the formation of the interlayer oxidation zone.

Molecularly imprinted sol-gel/Au@Ag core-shell nano-urchin localized surface plasmon resonance sensor designed in reflection mode for detection of organic acid vapors

A molecularly imprinted sol-gel (MISG)/Au@Ag core-shell NU sensor is proposed for organic vapor detection in an optical fiber-based reflection mode. The compact structure design of the system in the reflection model is promising for practical use as a portable and rapid responsivity sensing probe. Volatile organic acids (OAs) are analogs to biogenetic volatile organic vapors related to specific human diseases. Here, Au@Ag core-shell nano-urchins exhibiting branched tips were synthesized and deposited on indium tin oxide (ITO) glass in small dimer and trimmer clusters to generate an enhanced electric field. A MISG solution was then spin-coated on the substrate to fabricate MISG-LSPR sensors, and three types of MISGs were developed for the detection of hexanoic acid, heptanoic acid and octanoic acid. The normalized spectral response indicated selectivity of the MISG-LSPR sensors for the corresponding template OAs. With Native Bayes and linear discriminant analysis of the sensor responses, where the latter were detected by the proposed system, single- and mixed-OA vapors could be classified into separate clusters. This signified that the proposed MISG-LSPR sensor can be applied toward pattern recognition of single vapors or multiple vapor mixtures.

Facile synthesis of an indacenodithiophene-based conjugated polymer for acid vapor sensing

The use of organic conjugated polymers in sensors has attracted greater attention due to their application in materials technology. In the present communication, we utilized Schiff's condensation polymerization reaction for the synthesis of a novel conjugated polymer poly(tetrahexadecyl-dihydroindacenodithiophene)-alt-(p-phenylenediimine) (PIDTPD) consisting of indacenodithiophene (IDT) and p-phenylene diamine (PDA) units for use in acid vapor sensing. Conventionally, the characteristics and applications of conjugated polymers are affected by their constituents. The imine bond between the components of organic materials has received little attention compared to their active counterparts. In order to explore the practical application of conjugated polymers in sensors, we employed PIDTPD in a paper sensor and illustrated the impact of mono- and bis-protonation on the pristine material in driving a noteworthy protonation-induced color shift toward the longer wavelength region via acidochromism.

A MC-spiropyran for smartphone assisted reversible, selective and nanomolar level detection of formic acid in water and gas phase

ABSTRACT A p-toluenesulfonate salt of benzothiazonium (merocyanine) dye substituted with diethylamine was synthesized to act as an optical probe. The probe was characterized using FT-IR, NMR, HR-MS and examined for a response towards polar molecular and ionic species using UV-Visible, fluorescence spectroscopic techniques. The probe displayed remarkable formic acid-responsive optical and aggregation properties in distilled water and at pH 7.6 (1.0 mM HEPES). The change in color was also exploited for smartphone assisted digital colorimetric analysis of formic acid and formate ions. The formic acid response can be switched off thermally. The emission response of the probe appeared in the visible region. The receptor can also be used to detect the vapors of formic acid reversibly in air. The computational calculations based on M06-2X/6-31+G(d), M06-2X/6-31+G(d,p) and CAM-B3LYP/6-31+G(d,p) methods were performed to investigate the complex formation at a molecular level. The time-dependent CAM-B3LYP/6-31+G(d,p) method-based calculations were also implemented to study the observed absorption spectra of the complex.