HCl Vapor Research Articles

Development of white antibacterial pigment based on silver chloride nanoparticles and mesoporous silica and its polymer composite

We report the synthesis of silver chloride nanoparticles inside the pores of a mesoporous silica, SBA-15. The nanoparticles were formed by an ion exchange reaction of AgNO3 incorporated inside the pores with a HCl vapor. The incorporation of AgNO3 into the SBA-15 pores and its conversion into silver nanoparticles were proven by low angle X-ray diffraction, infrared spectroscopy, nitrogen adsorption–desorption experiments, and transmission electron microscopy. The resultant nanocomposite material between AgCl and SBA-15 (AgCl@SBA-15) was processed with polypropylene to form a polymer composite. The silver chloride nanoparticles inside the SBA-15 pores are found to be stable against reduction by photons and/or heat. Therefore, both AgCl@SBA-15 and its polymer composite have high antibacterial activity and maintain white color, enabling a variety of antibacterial consumer goods in various colors.

Polystyrene Microspheres Coated with Smooth Polyaniline Shells: Preparation and Characterization

Polystyrene/polyaniline core-shell structure microspheres were synthesized in the presence of poly(sodium 4-styrenesulfonate) as stabilizer and hydrochloric acid as dopant to improve the processibility of conducting polyaniline. After the one-pot reacting process, the product was easily purified by washing with water. The polyaniline shell covering the polystyrene sphere surface was confirmed with FT-IR and X-ray photoelectron spectroscopy. The conductivity of the polyaniline-coated polystyrene particles was 0.0017 S/cm and increased to 0.1 S/cm after being doped in the HCl vapor. The morphology of the microspheres was characterized by TEM and SEM. The particles show a more uniform and smooth surface than previous particles.

On-site monitoring of fish spoilage using vanadium pentoxide xerogel modified interdigitated gold electrodes

The development of a vanadium pentoxide xerogel (VXG)-based sensor for the detection of volatile inorganic (ammonia) and organic (dimethylamine, etc.) amines is described. The xerogel film was deposited on interdigitated gold electrodes by dip-coating using an aqueous solution of VXG. The morphology of the sensing layer, its interaction with ammonia, which was used as a model analyte throughout this work, as well as the regeneration of the surface of the sensor electrodes with vapors of HCl were examined with scanning electron microscopy and FTIR spectroscopy. Signal changes, due to changes of the RC-product of the electrochemical cell (Au-VXG-Au), as a result of its interactions with ammonia vapors, were probed with a portable, homemade charge meter, the Multipulser. Exposing the sensor electrodes to various concentrations of ammonia vapors resulted in proportional changes in the signal output. Finally, the proposed sensors were successfully used for on-site, real-time monitoring of fish spoilage in ambient conditions.

Material Properties, Thermal Stabilities and Electrical Characteristics of Ge MOS Devices, Depending on Oxidation States of Ge Oxide: Monoxide [GeO(II)] and Dioxide [GeO2(IV)

AbstractGe monoxide [GeO(II)] and dioxide [GeO2(IV)], which are selectively formed on Ge substrate by controlling pH and redox potential in pretreatment solution, are confirmed by XPS. ΔEC in GeO(II)/Ge and GeO2(IV)/Ge are almost the same, whereas ΔEV in GeO(II)/Ge is smaller than that in GeO2(IV)/Ge, resulting in smaller Eg of GeO(II). GeO(g) desorption is suppressed in LaAlO3/Ge gate stack, whereas GeO(g) desorbs through LaAlO3 layer when there is an intentional interfacial GeO(II) layer, leading to a large increase in Jg. GeO(g) desorption temperature in Ge oxide/Ge gate stacks decreases with the increase in the ratio of GeO(II) in Ge oxide and is independent of the oxidation techniques. Since GeO(g) desorption is accompanied by H2O(g) desorption, a new model to explain the GeO(g) desorption phenomena is proposed, in which Ge(OH)2 decomposes into GeO(g) and H2O(g). Highly effective etching methods of Ge oxide, using HCl solution and HCl vapor at higher temperature than boiling point of Ge (hydro-)chloride are demonstrated.

Determination of HCl and VOC Emission from Thermal Degradation of PVC in the Absence and Presence of Copper, Copper(II) Oxide and Copper(II) Chloride

Polyvinyl chloride (PVC) has played a key role in the development of the plastic industry over the past 40 years. Thermal degradation of PVC leads to formation of many toxic pollutants such as HCl, aromatic and volatile organic carbon vapors. Thermal degradation of PVC and PVC in the present of copper, cupric oxide and copper(II) chloride were investigated in this study using a laboratory scale electrical furnace. HCl and Cl- ion were analyzed by a Dionex ion chromatograph and VOCs compounds were analyzed using GC or GC‐MS. The results showed that HCl plus Cl- ion and benzene formed about 99% and 80% respectively in the first step of thermal degradation under air atmosphere. The presence of cupric oxide increases the percentage of short chain hydrocarbons more than 184% and decreases the amount of the major aromatic hydrocarbon and HCl plus Cl- ion to 90% and 65% respectively. The total aromatic hydrocarbon emitted less than when atmosphere was air and difference was statistically significant (Pvalue<0.000)

Effect of pH on Characteristics of Low‐Moisture Mozzarella Cheese during Refrigerated Storage

This study evaluated the effect of cheese pH on proteolysis, calcium distribution, and functional characteristics of Mozzarella cheese. On 4 occasions, cultured low-moisture part-skim Mozzarella cheeses were obtained from a commercial producer on the day after manufacture. Cheese blocks were randomly assigned to 2 groups. One group was shredded, subdivided, and exposed to either ammonia vapor to increase the pH or HCl vapor to decrease the pH. Samples were vacuum packaged, stored at 4 degrees C, and analyzed for pH 4.6 and 12% TCA soluble nitrogen, apparent viscosity, free oil, and water-soluble calcium on days 5, 12, 22, and 40. The 2nd group was sectioned into 23-mm thick slabs and similarly exposed to either ammonia vapor to increase the pH or HCl vapor to decrease the pH. The slabs were vacuum packaged, stored at 4 degrees C, and analyzed for pH 4.6 and 12% TCA soluble nitrogen, TPA hardness, springiness and cohesiveness, and meltability on days 17, 29, and 41. Data were analyzed by ANOVA according to a spilt-plot design. Experimentally induced pH differences persisted and significantly affected TPA hardness, apparent viscosity, meltability, and water-soluble calcium throughout 40 d of storage, but did not affect soluble nitrogen changes. Thus, cheese pH affected functional characteristics and calcium distribution but did not affect proteolysis rates. Higher cheese pH resulted in a harder cheese that required longer aging to develop desirable melting characteristics, whereas cheese with lower pH developed desirable melting characteristics more quickly but had a shorter functional shelf life.

Electrochemical Pinning of the Fermi Level: Mediation of Photoluminescence from Gallium Nitride and Zinc Oxide

Charge transfer between diamond and an electrochemical redox couple in an adsorbed water film has recently been shown to pin the Fermi level in hydrogen-terminated diamond. Here we show that this effect is a more general phenomenon and influences the properties of other semiconductors when the band lineup between the ambient and electronic states in the semiconductor is appropriate. We find that the luminescent intensities from GaN and ZnO change in different, but predictable, ways when exposed to HCl and NH3 vapors in humid air. The effect is reversible and has been observed on single crystals, nanowires, flakes, and powders. These observations are explained by electron exchange between the oxygen electrochemical redox couple in an adsorbed water film and electronic states in the semiconductor. This effect can take place in parallel with other processes such as defect formation, chemisorption, and surface reconstruction and may play an important, but previously unrecognized, role when electronic and optical measurements are made in air.

Construction and Evaluation of the Fiber-Optic Sensor System for Chemical Vapor Detection

The fiber optic sensor system for chemical vapor detection was desiged and constructed. The system consisted of three parts; the optic unit, the fiber-optic sensing head and the flow controlling unit. The optic unit included a He-Ne laser source which lazes a red laser into an aligned optical fiber, a photo detector, and a signal processing with computer interface controlled by the Labview® program version 7.1. The sensing head was made of a polyaniline thin film coated onto the de-cladded section of an optical fiber covered by a gas mixing cell. The concentration of measured gas was controlled by varying nitrogen gas flow rate. The nitrogen flow controller was set-up to obtain vapor concentration in the range of 0.04 to 0.40 % v/v. Vapors of hydrochloric acid (HCl) and n-butyl amine (a weak base) were used to test the performance of the sensor system. It was found that output intensity increases with an increasing HCl concentration and decreases with increasing n-butyl amine concentration. The response toward the amine vapor was faster than that of the HCl vapor (23 seconds for n-butyl amine and 72 seconds for HCl). Experiments performed at various concentrations of amine vapor (between 0.04 to 0.21 %v/v) found that a higher concentration yields faster response time.

Interfacial Assemblies of Cyanine Dyes and Gemini Amphiphiles with Rigid Spacers: Regulation and Interconversion of the Aggregates

A series of gemini amphiphiles with a pyridinium headgroup and rigid spacers were designed, and their interfacial assemblies with cyanine dyes, 3,3-disulfopropyl-9-methyl-selenacarbocyanine (SeCy) and 3,3-disulfopropyl-4,5,4',5'-dibenzo-9-methyl-thiocarbocyanine (MTC), through the air/water interface were investigated. Although the dyes have intrinsic tendencies to form J- or H-aggregates in aqueous solutions, their aggregation could be regulated in the complex films. Depending on the spacer, both J- and H-aggregates were formed for SeCy, whereas an H-aggregate with different absorption bands was obtained for MTC. Furthermore, the formed aggregates in the films could be reversibly switched by treating the complex films with HCl, NH3 gas, or water vapor. The J-aggregates of SeCy could be changed into H-aggregates and recovered through an alternative HCl/NH3 exposure in the films. The H-aggregate of the MTC film could be changed into J-aggregate upon exposure to HCl gas and subsequently put into air or NH 3 gas, and the thus-formed J-aggregate could be changed into H-aggregate under hot water vapor. In addition, such a reversible switch between different aggregates of MTC was only observed when the gemini amphiphiles with rigid spacers were applied. A possible explanation related to the protonation of the dye and the reorganizations in the film during the interconversion between different aggregates was proposed.

Chemical and Morphological Consequences of Acidification of Pure, Phosphated, and Phosphonated CaO: Influence of CO2 Adsorption

In situ Fourier transform infrared (FTIR) spectroscopy was employed to characterize the adsorption behavior (as a function of pressure or time) and surface species of CO2 molecules on pure, phosphated, and phosphonated CaO. Carbonate and bicarbonate species were found to form on the pure oxide, whereas on the phosphated and phosphonated oxide samples the carbonate species were found to substitute favorably some of the OH(-) and PO4(3-) groups thereon exposed, respectively. Before and after carbonation, the test samples were further examined by in situ FTIR spectroscopy of adsorbed pyridine species, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Then they were in situ acidified by exposure to a wet atmosphere of HCl vapor at 673 K for 10 min and re-examined similarly to reveal the influence of CO2 adsorption on the chemical and morphological consequences of acidification. The results obtained show the carbonate substitution of PO4(3-) groups to enhance agglomeration of the otherwise fine, longitudinal material particles into much bulkier ones and to render the otherwise more stable phosphonate groups less stable to acid treatment than the phosphate groups. Moreover, the bulky particle agglomerates of the carbonated test samples were detectably eroded following the acid treatment.

Generation of Local Concentration Gradients by Gas−Liquid Contacting

We present a generic concept to create local concentration gradients, based on the absorption of gases or vapors in a liquid. A multilayer microfluidic device with crossing gas and liquid channels is fabricated by micromilling and used to generate multiple gas-liquid contacting regions, separated by a hydrophobic membrane. Each crossing can acts as both a microdosing and microstripping region. Furthermore, the liquid and gas flow rate can be controlled independently of each other. The focus of this conceptual article is on the generation of pH gradients, by locally supplying acidic or basic gases/vapors, such as carbon dioxide, hydrochloric acid, and ammonia, visualized by pH-sensitive dyes. Stationary and moving gradients are presented in devices with 500-microm channel width, depths of 200-400 microm, and lengths of multiple centimeters. It is shown that the method allows for multiple consecutive switching gradients in a single microchannel. Absorption measurements in a microcontactor with the model system CO2/water are presented to indicate the dependence of gas absorption rate on channel depth and residence time. Achievable concentration ranges are ultimately limited by the solubility of used components. The reported devices are easy to fabricate, and their application is not limited to pH gradients. Two proof of principles are demonstrated to indicate new opportunities: (i) local crystallization of NaCl using HCl vapor and (ii) consecutive reactions of ammonia with copper(II) ions in solution.

Polymorphic gabapentin: thermal behaviour, reactivity and interconversion of forms in solution and solid-state

The various crystal forms of the neuroleptic drug gabapentin have been investigated, and in some cases re-investigated, by a combination of differential scanning calorimetry, hot stage microscopy and variable temperature powder diffraction methods in order to establish the relative stability of both its anhydrous and hydrated forms. A series of steps involving slurrying, heating, de-hydration and reaction with vapours of HCl have been performed. In this latter case, it has been possible to show that the reaction with HCl vapour leads to the same product as that obtained in solution. In slurry experiments in the absence of water, the most stable form, Form II, is invariably obtained, whereas in water, the slurry leads to the conversion of all crystal forms to the hemihydrated Form I. The conditions for the solid-state formation of the gabapentin-lactam de-hydration product have been analysed. Co-crystal formation has also been attempted. In the course of one such experiment, 1 : 1 co-crystals of gabapentin-lactam and benzoic acid were obtained.

Practical Surface Treatments and Surface Chemistry of n-Type and p-Type GaN

X-ray and ultraviolet photoelectron spectroscopies (XPS and UPS) were used to study the electronic structure of n-GaN and p-GaN(0001) surfaces after three ex situ surface treatments: aq-HCl, annealing in NH3, and annealing in HCl vapor. The combination of in situ vacuum annealing and re-exposure of samples to air revealed that the adsorption of ambient contaminants can reduce the surface state density and subsequent band bending on both n-GaN and p-GaN surfaces. Insights derived from first-principles calculations of the adsorption of relevant species on the Ga-terminated GaN(0001) surface are used to explain these experimental observations qualitatively.

Surface charge driven size evolution during the formation of self-assembled nanostructuresfrom discrete hydrophilic silver nanoparticles

We investigate the spontaneous evolution of mercaptosuccinic acid-capped silver nanoparticles (MSA-Ag)of size 2.5 ± 1.0 nm during the formation of assembled nanostructures at the air/water interface. In thephase transfer approach induced by the cationic surfactant cetyltrimethylammoniumbromide (CTAB), the fusion among MSA-Ag nanoparticles is notably accelerated owing tothe formation of a CTA–MSA bilayer on the particle surface. Provided that thesize-selective separation is carried out in advance for these polydisperse MSA-Agnanoparticles, either a unitary or a binary orderly superlattice composed of evolvednanoparticles is obtained at the air/water interface. For self-corrective equilibrium growthby adjusting the pH value of the bulk solution through the diffusion of HCl vapor, acompetition is found between the superlattice formation and the size growth. The possiblesize evolution mechanism of each method is proposed. This work also shows thatcontrollable evolution is a useful approach to prepare nanostructures with structuraldiversity.

Nucleation of Bulk Phases in the HCl/H2O System

We report experimental results on the low-temperature uptake of HCl on H(2)O ice (ice). HCl was deposited on the surface at greater than monolayer amounts at 85 K, and the ice substrate was heated. The temperature dependence of the HCl vapor pressure from this phase was measured from 110 to 150 K, with the nucleation of a bulk hydrate phase observed at 150 K. Measurements were conducted in a closed system by simultaneous application of gas phase mass spectrometry and surface spectroscopy to characterize vapor/solid equilibrium and the nucleation of bulk hydrate phases. Combining the nucleation data reported here with data we reported previously (180 to 200 K) and data from two other laboratories (165 and 170 K), the thermodynamic boundaries for the nucleation of both the metastable bulk solution and bulk hydrate phases subsequent to monolayer adsorption of HCl have been determined. The nucleation of the metastable bulk solution phase occurs promptly at monolayer coverage at the ice/liquid coexistence boundary on the binary bulk phase diagram. The nucleation of the bulk hexahydrate occurs from this metastable solution along a locus of points defining a state of constant solution free energy. This measured free energy is -51.2 +/- 0.9 kJ/mol. Finally, the temperature dependence of the HCl vapor pressure from the low-temperature phase is reported here for the first time and is consistent with that of the metastable solution predicted by this thermodynamic model of uptake, extending the range of validity of this model of adsorption followed by bulk solution and hydrate nucleation to a lower bound in temperature of 110 K.

Development of a magnetic quartz crystal microbalance

A new technique for measurement of magnetic properties of materials is demonstrated. It can be used for the measurement of thin magnetic films during their chemical modification. The resonance frequency of a quartz crystal microbalance (QCM) with conducting polymer (polyaniline) suspension in poly(ethylene glycol) was observed to increase with increasing the externally applied uniform dc magnetic field. Slowly sweeping the magnetic field between 0 and 3.1 T results in a frequency-field response curve. Chemical doping was done by exposing the polyaniline-emeraldine base film to HCl vapor. The change in population of free spins is reflected in increased frequency-field curve magnitude after HCl doping. Two working hypotheses explaining this observation are offered to explain how frequency of QCM with deposited magnetic film shifts with increasing intensity of the magnetic field.

Preparation and Properties of Conducting Polymeric Ultrathin Films

A multilayer ultrathin film of poly(3,4-ethylene dioxythiophene) (PEDOT) was first prepared by a modified Langmuir- Blodgett (LB) technique. The polymerization of PEDOT monomer occurred in a multilayer as-prepared LB film by exposing the film to EDOT vapor. The formation of PEDOT particles in the LB film was confirmed by UV-Vis-near IR (UV-Vis-NIR) absorption spectrum and X-ray photoelectron spectroscopy (XPS). By using scanning electron microscopy (SEM), investigation on the film surface exhibited small PEDOT particles distributed in stearic acid (SA) LB films. Secondary ion mass spectrometry (SIMS) was employed to analyze the location of PEDOT formed and the results showed that PEDOT was well confirmed in the multilayer structure. A 60-layer PEDOT LB film had higher conductivity (2.6 S·cm −1) than a conventional PEDOT film, and exhibited excellent doping/dedoping characteristics. An investigation on the relationship between film conductivity and exposure time on EDOT ambience revealed that the film obtained steady conductivity after 120 min and it was concluded that lower oxidizer density in LB film might slow the polymerization speed of EDOT. In a study of sensitive characteristics, the PEDOT film showed faster and nonlinear responses to analyte gas in a lower concentration (ϕ<30×10 −6), and exhibited a linear response to analyte in a higher concentration (ϕ=(30–120)×10 −6). The result of gas sensitivity also showed that the film had excellent reversible and reproducible response to HCl vapor. The mechanism of conductivity and gas sensitivity of composite LB films was also included.

Identification of berberine in ancient and historical textiles by surface‐enhanced Raman scattering

AbstractThe highly fluorescent natural dye berberine can be easily identified in microscopic textile samples by surface‐enhanced Raman spectroscopy employing citrate‐reduced Ag colloid. The ordinary Raman (OR) and SERS spectra of berberine are presented and discussed in the light of a DFT calculation. Using FT‐Raman and FT‐SERS we could reliably compare relative intensity shifts and investigate the adsorption geometry of berberine on Ag nanoparticles. The significant enhancement in the FT‐SERS spectrum of the out‐of‐plane ring system bending deformation mode at 729 cm−1 relative to a group of in‐plane vibrations at around 1500 cm−1 was interpreted as evidence of a ‘flat‐on’ adsorption geometry. SERS was successfully used to identify berberine in silk fiber samples coated with colloidal Ag following a pretreatment with HCl vapor. The SERS method allowed us to detect berberine in a microscopic sample of a single silk fiber from a severely degraded and soiled 17th Century Chinese textile fragment. Copyright © 2007 John Wiley &amp; Sons, Ltd.

Single and Combined Removal of HCl and Alkali Metal Vapor from High-temperature Gas by Solid Sorbents

The amounts of HCl and alkali metal vapor in hot gas are generally small, compared to those of sulfur compounds, nitrogen compounds, and particulates. Nevertheless, the removal of these contaminants is very beneficial in any power plant because of corrosion when they contact metal components. In this paper, the experiments by single and combined methods were carried out to remove HCl and alkali metal vapor in hot gas cleaning. The results indicated that all sorbents for the removal of HCl vapor can reduce HCl to less than 1 mg/m3 at 550 °C; sorbent E1 self-prepared by montmorillonite and Mg(OH)2 presents the highest chlorine content and the longest breakthrough time. It is found that the activated Al2O3 having a specific surface area of 258.3 m2/g displays the highest efficiency for the removal of alkali metal vapor at 840 °C. The tests indicate that the removal of alkali metal vapor with activated Al2O3 is not a physical adsorption process in the presence of moisture. A multifunctional four-zone reactor ...

Solid‐State Interconversions of Coordination Networks and Hydrogen‐Bonded Salts

Thermal or chemical treatment of crystalline 4,4-bipyridinium salts of [MCl4]2- (M=Co, Zn, Fe, or Pt) leads to HCl loss and formation of coordination network solids [{MCl2(4,4-bipy)}n]. For M=Co, Zn, and Fe, these solids can also be prepared by mechanochemical means. Their exposure to HCl vapor or the mechanochemical reaction of metal dichlorides with [4,4-H2bipy]Cl2 gives [4,4-H2bipy]2+ salts of [CoCl4]2-, [ZnCl4]2-, and, for the first time, [FeCl4]2-.