Hydrogen Chloride Vapor Research Articles

Relationships Between HCl, H2O, Aerosols, and Temperature in the Martian Atmosphere: 2. Quantitative Correlations

AbstractThe detection of hydrogen chloride (HCl) in the atmosphere of Mars was among the primary objectives of the ExoMars Trace Gas Orbiter (TGO) mission. Its discovery using the Atmospheric Chemistry Suite mid‐infrared channel (ACS MIR) showed a distinct seasonality and possible link to dust activity. This paper is part 2 of a study investigating the link between HCl and aerosols by comparing gas measurements made with TGO to dust and water ice opacities measured with the Mars Climate Sounder (MCS). In part 1, we showed, and compared, the seasonal evolution of vertical profiles of HCl, water vapor, temperature, dust opacity, and water ice opacity over the dusty periods around perihelion (solar longitudes 180°–360°) across Mars years 34–36. In part 2, we investigated the quantitative correlations in the vertical distribution between each quantity, as well as ozone. We show that there is a strong positive correlation between HCl and water vapor, which is expected due to fast photochemical production rates for HCl when reacting with water vapor photolysis products. We also show a strong positive correlation between water vapor and temperature, but are unable to show any correlation between temperature and HCl. There are weak correlations between the opacities of dust and water ice, and dust and water vapor, but only very low correlations between dust and HCl. We close with a discussion of possible sources and sinks and that interactions between HCl and water ice are the most likely for both, given the inter‐comparison.

Reversible Sensing Technologies Using Upcycled TPEE: Crafting pH and Light Responsive Materials towards Sustainable Monitoring.

Multiresponsive materials with reversible and durable characteristics are indispensable because of their promising applications in environmental change detections. To fabricate multiresponsive materials in mass production, however, complex reactions and impractical situations are often involved. Herein, a dual responsive (light and pH) spiropyran-based smart sensor fabricated by a simple layer-by-layer (LbL) assembly process from upcycled thermoplastic polyester elastomer (TPEE) materials derived from recycled polyethylene terephthalate (r-PET) is proposed. Positively charged chitosan solutions and negatively charged merocyanine-COOH (MC-COOH) solutions are employed in the LbL assembly technique, forming the chitosan-spiropyran deposited TPEE (TPEE-CH-SP) film. Upon UV irradiation, the spiropyran-COOH (SP-COOH)molecules on the TPEE-CH-SP film undergo the ring-opening isomerization, along with an apparent color change from colorless to purple, to transform into the MC-COOH molecules. By further exposing the TPEE-CH-MC film to hydrogen chloride (HCl) and nitric acid (HNO3) vapors, the MC-COOH molecules can be transformed into protonated merocyanine-COOH (MCH-COOH) with the simultaneous color change from purple to yellow.

LiCl in situ decorated metal-organic framework (MOF)-derived porous carbon for efficient solar-driven atmospheric water harvesting.

Solar-powered sorption-based atmospheric water harvesting (AWH) technology is a promising solution to the freshwater scarcity in arid regions. Existing adsorbent materials still face challenges in aspects such as cycling stability and adsorption kinetics and require further development. Herein, we presented a strategy for the in situ fabrication of high-performance adsorbents, lithium chloride (LiCl)-decorated metal-organic framework (MOF)-derived porous carbon sorbents (PCl), via high-temperature pyrolysis and hydrogen chloride (HCl) vapor treatment. The sorbents display high adsorption capacity across a wide range of humidity water adsorption capacities in a wide humidity range with the maximum adsorption capacity of 7.87 g g-1, and rapid response to the solar-driven process and excellent cyclic stability. The LiCl nanocrystals in PCl can be utilized efficiently and decorated within the porous framework stably, and demonstrate water adsorption at 20%, 40%, 60% and 80% RH, of 1.34, 1.69, 2.56 and 4.23 gH2O·gLiCl-1, respectively, and significantly higher water uptake and release rates than bulk LiCl. This may provide new guides for designing efficient solar-driven AWH.

Co-conversion of wood and polyvinyl chloride to valuable chemicals and high-quality solid fuel

Polyvinyl chloride (PVC)-containing waste streams are difficult to recycle due to high chlorine content in PVC. Toxic dioxins or corrosive hydrogen chloride (HCl) vapor released from improper management of PVC-containing wastes can cause severe environmental pollution and human health problems. While PVC is usually treated as contamination and burden in waste recycling, a novel recycling approach was developed in this study to leverage PVC as an asset. Specifically, red oak and PVC were co-converted in γ-Valerolactone, a green biomass-derivable solvent. During the co-conversion, PVC-derived HCl in the solvent acted as an acid catalyst to produce up to 14.4% levoglucosenone and 14.3% furfural from red oak. On the other hand, dechlorinated PVC hydrocarbons and lignin fraction of red oak reacted each other to form chlorine-free solid fuels with high thermal stability. The higher heating value of the solids was up to 36.2 MJ/kg, which is even higher than the heating value of anthracite coal. After the co-conversion, more than 80% of PVC-contained chlorine turned into chloride ion and the rest formed 5-chlorovaleric acid. 5-chlorovaleric acid crystals were further recovered from the post-reaction liquid with a purity of 91.2%.

Functional Polyaniline/MXene/Cotton Fabrics with Acid/Alkali-Responsive and Tunable Electromagnetic Interference Shielding Performances.

Although two-dimensional transition-metal carbides (MXenes) and intrinsic conductive polymers have been combined to produce functional electromagnetic interference (EMI) shielding composites, acid/alkali-responsive EMI shielding textiles have not been reported. Herein, electrically conductive polyaniline (PANI)/MXene/cotton fabrics (PMCFs) are fabricated by an efficient vacuum filtration-assisted spray-coating method for acid/alkali-responsive and tunable EMI shielding applications on the basis of the high electrical conductivity of MXene sheets and the acid/alkali doping/de-doping feature of PANI nanowires. The as-prepared PMCF exhibits a sensitive ammonia response of 19.6% at an ammonia concentration of 200 ppm. The high EMI shielding efficiency of ∼54 dB is achieved by optimizing the decorated structure of the PANI/MXene coating on the cotton fabrics. More importantly, the PMCF can act adaptively as a "switch" for EMI shielding between the efficient strong shielding of 24 dB and the inefficient weak shielding of 15 dB driven by the stimulation of hydrogen chloride and ammonia vapors. This multifunctional fabric would possess promising applications for intelligent garments, flexible electronic sensors, and smart electromagnetic wave response in special environments.

Development of Continuous Gas Generation Method for Hydrogen Chloride Using Azeotropic Hydrochloric Acid System

Standard gases are often prepared using high-pressure gas cylinders. However, it is difficult to accurately prepare a known concentration of hydrogen chloride (HCl) gas using this method because HCl is highly corrosive and adsorptive. In this study, a simple method for the continuous generation of HCl gas was developed using a diffusion tube containing hydrochloric acid and a nitrogen carrier gas. The concentration of HCl produced from this system was almost unstable, but constant gas generation was realized for several hours when azeotropic hydrochloric acid (20.6% HCl in water) and a temperature near the azeotropic point (108.5 °C) were used, resulting in the generation of 103.6 ppm (mean, n = 5) of HCl gas with a relative standard deviation (RSD) of 2.34%. In this case, the percentage of HCl present in the entire gas mixture of HCl and water vapor was 22.5%, which is almost equivalent to the HCl content in the azeotropic hydrochloric acid (20.6%). The HCl concentration could also be controlled by changing the flow rate of the carrier gas. This work demonstrates a simple technique based on the diffusion theory that allows for the constant, controllable generation of a known concentration of HCl gas using an azeotropic hydrochloric acid system.

Chemically Functionalised Suspended-Core Fibre for Ammonia Gas Detection

An optical fibre ammonia gas sensor utilising a functionalised four-leaf-clover-shaped suspended-core fibre (SCF) is demonstrated. The fibre is functionalised by depositing a thin layer of an ammonia sensitive dye (tetraphenylporphyrin tetrasulfonic acid hydrate) (TPPS) on the wall of the inner cavities of the SCF through capillary action. An in-line fibre sensing structure is designed for light transmission through the SCF and also allows gas exchange with the atmosphere through two porous polyethylene housings. The sensing structure exhibits a temperature-dependent transmission due to the thermal expansion of the housings. A ratiometric method is applied for signal processing which is demonstrated to reduce significantly the effect of temperature change in the tested range (20-30 °C). The sensor is tested in ammonia concentration ranges from 0-10 ppm and demonstrates capability of detecting ammonia at ppb levels. The minimum tested concentration is 150 ppb in the experiment with a calculated limit of detection of 20 ppb. The sensor response time (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10-90%</sub> ) is 160 s and it is demonstrated to be reusable after treatment with hydrogen chloride vapour. Numerical simulation of evanescent absorption features of such an SCF indicates that approximately 0.02% of the optical power exists in the air holes for the fundamental propagation mode. Distinctive absorption bands observed in the transmission spectrum of the fabricated sensor can also be observed in the simulated model after adding the TPPS absorption layer in the holes.

Colorimetric sensing of acidic vapour through protonation of a Meisenheimer complex

AbstractIn the current work, we investigate the mechanism of protonation of a Meisenheimer complex derived from picric acid and N,N′‐dicyclohexylcarbodiimide to provide the correct structure of the protonated Meisenheimer complex with the proper mechanism. A substituted picramide derivative has also been synthesised and characterised using various spectroscopic techniques to rule out the previously suggested protonated Meisenheimer complexes and support our proposed protonated structure. Various other investigations, including the interactions of the Meisenheimer complex with bulky electrophile Lawesson's reagent and bulky Lewis acid Eu(fod)3, were also carried out to support the mechanism of protonation. Various bulky bases as well as bases of different strengths were treated with the protonated Meisenheimer complex to support our proposed structure. Based on the protonation of the Meisenheimer complex, a general colorimetric volatile acid sensor has been designed, where a distinct colour change from orange to colourless was found to take place after protonation. The sensor can detect volatile acids both in the solid and in the solution state. The sensor was also applied to detect hydrogen chloride vapour in an automated manner using a smartphone, where information regarding the leakage position can be obtained through wireless communication. The detection limit of hydrogen chloride vapour was found to be 43.5 ppm.

Aggregation State of Tetraphenylporphyrin Derivatives in Polymer Films Based on Poly-N-Vinylpyrrolidone

The spectral luminescent and electrophysical properties of polymer films based on poly-N-vinylpyrrolidone with the stabilized derivatives of tetraphenylporphyrin in various aggregation states (monomers, J- and H-aggregates) were investigated. Films containing a monomolecular form of porphyrins are characterized by intensive fluorescence. For films with J-aggregates an electric response that was not practically observed in the case of H-aggregates was detected. The films obtained are also characterized by optical and electric response to pH change, particularly in the presence of ammonia and hydrogen chloride vapors. The obtained data allow polymeric films with immobilized porphyrins to be considered as potential material for the creation of film systems for sensor applications, photovoltaics, molecular electronics, and photocatalysis. The variability of the film synthesis methodology allows the aggregation state of the immobilized porphyrins to be changed directionally, which provides the possibility of obtaining films of hybrid organic materials with the desired photophysical properties.

Shape change of submicron nickel particles under hydrogen and nickel chloride vapor

The shape of Ni particles is important. A spherical shape is favored for an electrode material in multilayer ceramic capacitor (MLCC) due to high packing density. A cubic shape is better for applications in catalysts and bioseparation due to its higher magnetic property than a spherical shape. It was found that cubic Ni particles which has a face-centered cubic (fcc) crystal structure, can be synthesized by chemical vapor synthesis (CVS). In this study, to examine whether the cubic shape of Ni particles synthesized by CVS is the growth or the equilibrium shape, the shape change of Ni particles by annealing under H2 and NiCl2 atmospheres was observed. It was confirmed by a density function theory (DFT) method that H2 and NiCl2 vapor favor respectively spherical and cubic shapes, which indicates that NiCl2 stabilizes the {1 0 0} faces of Ni. In this computational work, we provide gas adsorption energies and relaxed atomic structures of Ni(1 0 0) and Ni(1 1 1) surface models. Using this fact, suitable synthetic conditions for cubic and spherical Ni particles could be derived. It was confirmed that the high and low reduction rate favor respectively spherical and cubic shapes during CVS.

Random lasing and amplified spontaneous emission from silk inverse opals: Optical gain enhancement via protein scatterers

Gain amplification and coherent lasing lines through random lasing (RL) can be produced by a random distribution of scatterers in a gain medium. If these amplified light sources can be seamlessly integrated into biological systems, they can have useful bio-optical applications, such as highly accurate sensing and high-resolution imaging. In this paper, a fully biocompatible light source showing RL and amplified spontaneous emission (ASE) with a reduced threshold is reported. Random cavities were induced in a biocompatible silk protein film by incorporating an inverse opal with an inherent disorder and a biocompatible dye for optical gain into the film. By choosing the appropriate air-sphere diameters, clear RL spikes in the emission spectra that were clearly distinguished from those of the ASE were observed in the silk inverse opal (SIO) with optical gain. Additionally, the RL output exhibited spatial coherence; however, the ASE did not. The high surface-to-volume ratio and amplification of the SIO led to highly efficient chemosensing in the detection of hydrogen chloride vapor. Moreover, SIO could be miniaturized to be made suitable for injection into biological tissues and obtain RL signals. Our results, which open the way for the development of a new generation of miniaturized bio-lasers, may be considered as the first example of engineered RL with biocompatible materials.

Effect of the modified silica on the conductivity and sensory properties of polyaniline nanocomposites

The introduction of nanosized fillers into composites with conductive polymers allows them to control physical and chemical characteristics of these polymers. Silica nanoparticles due to its remarkable properties, which include large ratio of surface area to volume, excellent chemical stability, low cost of synthesis, and low toxicity, especially convenient surface modification, have attracted much attention of researchers. Such materials may be as excellent platforms for development of smart sensing systems for numerous applications in analytical chemistry and bioanalysis, in medical diagnostics and therapy, environmental and food analysis, security. It is known that the presence of nanosized silica in the structure of hybrid polymeric composites can not only radically change the structure, but also lead to improved mechanical characteristics, sorption capacity, increase or decrease in specific conductivity. In this work the method of polymerization filling “in situ” was used for preparation of the hybrid composites of polyaniline with nanoparticles of silica modified by titanium (TAC-7) and phosphorus (F-2.1) compounds, studied their morphology, electrical and moisture absorption properties. Influence of the content of inorganic component in composites on their specific conductivity, activation parameters of conductivity and their changes under the action of moisture were studied. It is shown that the filler content of 1–4% increases the electrical conductivity of composites and the incorporation of modified nanoparticles F-2.1 helps stabilize the resistivity of nanocomposites at high humidity. The resistivity change less than 2% was observed throughout the whole range of possible moisture, therefore the obtained modified material can be recommended for using in the resistive sensors operating in the condition of high humidity. Moreover, F-2.1 enhances sensitivity of polymer matrix to hydrogen chloride vapors. So, the possibility of using chemically deposited thin films of polyaniline/modified silica nanocomposite for the optical gas sensors production for various purposes, including monitoring the state of environments in real conditions of atmosphere, is shown.

The Effect of Polymorphism on the Kinetics of Adsorption and Degradation: A Case of Hydrogen Chloride Vapor on Cellulose

AbstractControl of the reactivity of natural polymers – such as semicrystalline cellulose – through polymorphic transitions is a potent, yet underexplored tool in modern polymer science. Here, the degradation behavior of three artificial cellulose polymorphs (cellulose II, IIII, and IIIII) in the presence of hydrogen chloride vapor is explored. While the ultimate results of hydrolyses correspond to those found for aqueous HCl, the kinetic scission models exhibit a unique trend for each polymorph, unlike those reported for aqueous acid or enzymatic hydrolyses. In addition to the polymorphic distinctions, these atypical trends are attributed to the nonequilibrium in the hydrolysis set up and the irregular adsorption of HCl molecules to the substrate surfaces. The results point to a new way of approaching the reactivity of natural polymers where polymorphism is regarded as one of the parameters for the kinetics and outcome of chemical reactions.

Polyaniline-Functionalized Nanofibers for Colorimetric Detection of HCl Vapor.

Hydrogen chloride (HCl) gas is a hazardous byproduct of industrial processes. Colorimetric approaches to facilitate portable and remote detection are especially desirable. We graft polyaniline to the surface of electrospun nylon nanofibers to minimize mass transfer. Using the resulting nanofibers, we demonstrate colorimetric detection of HCl at sub-ppm levels. We investigated the reusability of the fibers and observed a twofold increase in the limit of detection with multiple uses because of dedoping of the PANi indicated by elemental analysis. The limit of detection using visual detection was compared to spectrophotometric analysis. The ΔE from CIE LAB color space analysis via diffuse reflectance spectroscopy enhances the limit of detection by ∼fivefold when compared to visual detection. This analysis is a promising approach for remote detection using simple commercial digital cameras to achieve low limits of detection.

Facile fabrication of CNT-based chemical sensor operating at room temperature

This paper describes a simple, low cost and effective route to fabricate CNT-based chemical sensors, which operate at room temperature. Firstly, the incorporation of silk fibroin in vertically aligned CNT arrays (CNTA) obtained through a thermal chemical vapor deposition (CVD) method makes the direct removal of CNT arrays from substrates without any rigorous acid or sonication treatment feasible. Through a simple one-step in situ polymerization of anilines, the functionalization of CNT arrays with polyaniline (PANI) significantly improves the sensing performance of CNT-based chemical sensors in detecting ammonia (NH3) and hydrogen chloride (HCl) vapors. Chemically modified CNT arrays also show responses to organic vapors like menthol, ethyl acetate and acetone. Although the detection limits of chemically modified CNT-based chemical sensors are of the same orders of magnitudes reported in previous studies, these CNT-based chemical sensors show advantages of simplicity, low cost and energy efficiency in preparation and fabrication of devices. Additionally, a linear relationship between the relative sensitivity and concentration of analyte makes precise estimations on the concentrations of trace chemical vapors possible.

Room-Temperature Nanowelding of a Silver Nanowire Network Triggered by Hydrogen Chloride Vapor for Flexible Transparent Conductive Films.

High contact resistance between silver nanowires (AgNWs) is a key issue in widespread application of AgNW flexible transparent conductive films as a promising candidate to replace the brittle and expensive indium tin oxide. A facile, room-temperature nanowelding method of an AgNW network triggered by hydrogen chloride (HCl) vapor is demonstrated to reduce the sheet resistance of the AgNW network. Under the visible light, O2 and HCl vapor serving as an etching couple induced silver atoms to be transferred from the bottom AgNW at the junction to the top one, and then, these silver atoms epitaxially recrystallized at the contact position with the lattice of the top AgNW as the template, ultimately resulting in the coalescence of the junction between AgNWs. Polydimethylsiloxane (PDMS) was spin-coated onto the HCl-vapor-treated (HVT) AgNW network on the polyethylene terephthalate substrate to fabricate PDMS/HVT AgNW films. The fabricated film with low sheet resistance and high transmittance retained its conductivity after 4000 bending cycles. Furthermore, excellent heating performance, electromagnetic interference shielding effectiveness, and foldability were obtained in the PDMS/HVT AgNW film. Thus, the role of the simple nanowelding process is evident in enhancing the performance of AgNW transparent conductive films for emerging soft optoelectronic applications.

Degradation and Crystallization of Cellulose in Hydrogen Chloride Vapor for High-Yield Isolation of Cellulose Nanocrystals.

Despite the structural, load-bearing role of cellulose in the plant kingdom, countless efforts have been devoted to degrading this recalcitrant polysaccharide, particularly in the context of biofuels and renewable nanomaterials. Herein, we show how the exposure of plant-based fibers to HCl vapor results in rapid degradation with simultaneous crystallization. Because of the unchanged sample texture and the lack of mass transfer out of the substrate in the gas/solid system, the changes in the crystallinity could be reliably monitored. Furthermore, we describe the preparation of cellulose nanocrystals in high yields and with minimal water consumption. The study serves as a starting point for the solid-state tuning of the supramolecular properties of morphologically heterogeneous biological materials.

Coordination Structure Conversion of Hydrazone–Palladium(II) Complexes in the Solid State and in Solution

We prepared hydrazone-palladium(II) complexes of [PdCl2(HL(n))] and [PdCl(L(n))] (n = 1-3) by the reaction of [PdCl2(cod)] or [PdCl2(PhCN)2] and the hydrazone ligands of HL(n) {N'-(pyridin-2-ylmethylene)picolinohydrazide (HL(1)), N'-[1-(pyridin-2-yl)ethylidene]picolinohydrazide (HL(2)), and N'-[(6-methylpyridin-2-yl)methylene]picolinohydrazide (HL(3))}. The structures of the complexes were determined by X-ray analysis. The hydrazone ligands had κN(py1),κN(imine) and κN(amidate),κN(py2) bidentate coordination modes in [PdCl2(HL(n))] (1, n = 1; 2, n = 2) and in [PdCl2(HL(3))] (3), respectively. In contrast, tridentate coordination modes of κN(py1),κN(imine),κN(py2) and κN(py1),κN(amidate),κN(py2) were observed in [PdCl(L(n))] (4, n = 1; 5, n = 2) and in [PdCl(L(n))] (6, n = 1; 7, n = 2; 8, n = 3). Thermal conversion of complexes 1-3 to complexes 6-8 proceeded in acetonitrile. Complexes 4 and 5 were obtained from complexes 1 and 2, respectively, in a basic acetonitrile solution under dark conditions. Complex 4 reverted immediately to complex 1 in an acidic acetonitrile solution that included hydrochloric acid. However, under room light, in the basic acetonitrile solution that included trimethylamine, complex 4 converted photochemically to complex 6. The thermochromic or vapochromic structure conversion of these complexes also occurred in the solid state. On heating at 180 °C, the color of the crystals of complexes 1, 2, and 3 changed from yellow to orange in the solid state. (1)H NMR and/or UV-vis absorption spectroscopy confirmed that the orange complexes 6-8 were produced. The reddish-orange crystals of complexes 4 and 5 were exposed to hydrogen chloride vapor to yield the yellow products of complexes 1 and 2, respectively.

Creating internal conductivity in dry biological SEM samples by a simple vapour treatment.

Internal sample conductivity in scanning electron microscopy can be a valuable alternative to metal coating. Proton conductivity may be used for this purpose. Many solid materials with active hydrogen atoms, such as hydrogen- and ammonium-salts, organic acids, and even ice, are protonic conductors or semiconductors. Here we present a method to generate proton conductivity in dry biological materials. A simple treatment with hydrogen chloride gas or hydrochloric acid vapour for a few minutes provides sufficient conductivity for many samples. After a removal of excess hydrogen chloride vapour with a vacuum desiccator, the objects may be examined in the SEM without metal coating. The use of internally conductive samples extends the range of easy-to-perform SEM preparation techniques. It is advantageous for material contrast imaging of uncoated samples, and it can be used in combination with metal coating to enhance conductivity on difficult samples with complex overlapping surfaces, where simple metal coating does not reliably eliminate charging problems.

Kinetics of selective chlorination of pre-reduced limonitic nickel laterite using hydrogen chloride

The selective chlorination process of pre-reduced limonitic nickel laterite using hydrogen chloride was investigated in this work. In HCl–O 2–H 2O–N 2 atmosphere, the effects of variations in temperature, the partial pressures of hydrogen chloride, oxygen and water vapor, and total gas flow rate were all studied. It was found that the chlorination of nickel and cobalt could be described by two stages; and it was controlled by gas diffusion through product layer. Four apparent activation energies, including 20.43 kJ/mol and 12.89 kJ/mol for the first and second stage of nickel chlorination, 14.95 kJ/mol and 13.02 kJ/mol for the first and second stage of cobalt chlorination respectively, were obtained in the temperature range of 420–460 °C. And the apparent reaction order of hydrogen chloride was also obtained. During the selective chlorination, the oxidation of pre-reduced ore could take place with the selected conditions; chlorinated iron was mostly rejected as hematite and thus nickel and cobalt were selectively chlorinated by hydrogen chloride.