Low Concentrations Of NO Research Articles

A visible-light activated gas sensor based on perylenediimide-sensitized SnO2 for NO2 detection at room temperature

A visible-light activated gas sensor has been successfully fabricated by impregnating perylenediimide into a SnO2 nanofilm. The perylenediimide/SnO2 heterojunction sensor exhibits a higher sensing performance in comparison to the SnO2-based sensor. Moreover, under the assistance of visible-light illumination, the hybrid sensor can work efficiently at room temperature for low concentration NO2 detection through increased sensitivity and reduction of the response and recovery times. These desirable sensing features can be attributed to the advanced heterostructure, since it not only enables the sensor to be activated by the visible-light but also has advantages for electron separation. Finally, the excellent selectivity and reproducibility of the hybrid sensor were also demonstrated. Our experimental results suggest that this hybrid sensor could be a promising candidate for room-temperature gas sensing applications.

Ambient Temperature NO Adsorber Derived from Pyrolysis of Co-MOF(ZIF-67).

Co-, Ni-, and Zn-containing MOFs are prepared and then pyrolyzed to generate materials for ambient temperature NO adsorption. Materials containing Co are much more efficient for NO adsorption than those containing Ni and Zn; therefore, Co is identified as the active phase. The best performing material studied here achieves 100% low concentration (10 ppm) NO adsorption for more than 15 h under a weight hourly space velocity of 120 000 mL g–1 h–1. Powder X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared, and Raman spectroscopies, along with scanning electron microscopy and TEM, are used to probe the physicochemical properties of the materials, particularly the Co active phase, and chemistries involved in NO adsorption–desorption. NO adsorbs on oxygen-covered Co nanoparticle surfaces in the form of nitrates and desorbs as NO at higher temperatures as a result of surface nitrate decomposition. NO storage capacity decreases gradually upon repeated NO adsorption–desorption cycles, likely because of Co3O4 formation during these processes.

AlGaN/GaN HEMT-based high-sensitive NO2 gas sensors

We report on a Pt/AlGaN/GaN HEMT-based gas sensor with interdigitated electrodes for NO2 sensing over the temperature range of 30 °C–300 °C. The sensors show a change in current (ΔI) of 0.5 mA with sensitivity of 1.2% for 10 ppm NO2 at 30 °C and recovers at elevated temperature. The sensitivity increases with the increase in relative humidity (0 to 90%) at 30 °C. High sensitivity of 5.5% with a corresponding ΔI of 1.8 mA is achieved for 10 ppm NO2 concentration at 300 °C, which is higher than the reported value under similar measurement conditions. The large surface area of the interdigitated electrodes and the catalytic property of the platinum functionalization layer enables high sensitivity for low NO2 concentrations of <10 ppm.

Nanoclustered Pd decorated nanocrystalline Zn doped SnO2 for ppb NO2 detection at low temperature

Nanoclustered Pd (2 mol%) was used to decorate Zn doped SnO2 (10 mol% Zn) in order to increase its sensing performances. Zn doped SnO2 built from nanoparticles was prepared by a hydrothermal method using a non-ionic surfactant - Brij52 and Tripropylamine (TPA) as co-templates. The presence of well-dispersed Zn2+ ions in the SnO2 matrix leads to a nonstoichiometric surface. Pd was deposited by subsequent wet impregnation using hydrazine as reducing agent. The as obtained powders were deposited as thick layers onto commercial substrates, in order to obtain the sensitive structures. The coexistence of a mixture of valence states (Pd0, Pd2+ and Pd4+) was highlighted on the surface of the as prepared layers. Several aspects have been followed regarding the Zn and Pd dispersion into the SnO2 matrix: the large scale and low scale morphology (SEM and TEM/HRTEM) in relation with the synthesis route, the obtained crystallographic phases (XRD, SAED) and the way in which the Zn2+ ions are inserted into the SnO2 structure (XRD, XPS, EPR), the spatial distribution of the added chemical elements, Zn and Pd (SEM, STEM, EDS). All these morphological and structural aspects, as well as the Pd surface chemistry, have been correlated with the sensing properties of the nanostructured materials under controlled gas atmosphere. Through this study, we could harvest the specific role of the aforementioned loadings towards selective detection of low NO2 concentrations, between 350 ppb to 5 ppm, at low operating temperature of 100 °C, for infield conditions.

Quantification of regional contributions to fine particles at downwind areas under Asian continental outflows during winter 2014

Effective reduction strategies for fine particles (PM2.5) in areas downwind of Asian continental outflows require quantification of regional and local contributions to PM2.5. To quantify the chemical compositions of long-range transported and locally produced aerosol particles during a severe haze episode, aerosol particles were collected at a remote background site in Baengnyeong Island (BN) and an inland urban site in Daejeon (DJ) in the Republic of Korea from 7 February to 6 March 2014. Aerosol samples were analyzed for PM2.5, inorganic ions, carbonaceous species, and heavy metals. During a severe haze episode (EP) from 22 February to 1 March 2014, elevated PM2.5 concentrations of 73.3 ± 18.3 μg m−3 and 74.9 ± 14.3 μg m−3 were measured at the BN and DJ sites, respectively. Although both sites were influenced by long-range transported haze from China, SO42− was determined to be the most abundant species at the BN site during the EP period with an average of 29.9 ± 11.5 μg m−3, whereas NO3− was the most abundant species at the DJ site with an average of 20.9 ± 5.4 μg m−3. Low NO2 concentrations (2.6 ± 1.9 ppb) and a northwesterly air-mass trajectory suggest that most air pollutants at the BN site underwent long-range transport from China during the EP period and were minimally affected by local emissions from the Korean Peninsula. The chemical components of long-range transported and locally produced PM2.5 were quantified using arsenic (As) as a tracer for long-range transported haze from China. It was found that large fractions of SO42− (87% ± 31%), OC (70% ± 16%), and NH4+ (65% ± 10%) at the DJ site underwent long-range transport from China during the EP period. However, a significant fraction (67% ± 15%) of NO3− was determined to be secondarily produced from NO2 emitted from local sources during the EP period. On average, 34% of PM2.5 was locally produced at the DJ site during the EP period. Local production of PM2.5 is attributed mainly to NO3− (57%), followed by NH4+ (18%), SO42− (11%), and OC (9%). Results from this work suggest that when severe haze undergoes long-range transport from China to the Korean Peninsula during winter, a reduction of local NO2 emissions is the most effective strategy to reduce PM2.5 levels in inland of the Korean Peninsula.

Improvement in NO2 Sensing Properties of Semiconductor-Type Gas Sensors by Loading of Au Into Porous In2O3 Powders

Porous (pr-) In2O3 powders loaded with and without noble metals (Au, Pd, or Pt) were prepared by ultrasonic spray pyrolysis employing the PMMA microspheres as a template (typical particle size (ps): 28 or 70 nm with a diameter), and their NO2 sensing properties were examined. The Au loading on the pr-In2O3 was effective to increase the NO2 response at lower operating temperature (≤200°C), while the metal loading of Pd or Pt were hardly effective. In addition, a decrease in the PMMA microspheres (from 70 to 28 nm in ps) largely increased the NO2 response, and an optimized amount of Au loaded on the pr-In2O3 sensor was 1.0 wt%. The decrease in the thickness of the sensing layer improved the NO2 response and response speed. It was suggested that the Au loading enhanced the amount of the negatively adsorbed NO2 on the bottom part of the sensing layer, leading to the increase in the NO2 response. Furthermore, the introduction of additional macropores (ps: 150 nm) to the 1.0 wt% Au loaded pr-In2O3 sensor increased the response to a low concentration of NO2 (0.025 ppm) at 30°C. Therefore, it was found that easy gas diffusion from the surface to the bottom part of the sensing layer increased the effective concentration of NO2, and thus the NO2 response was increased.

The reaction of peroxy radicals with OH radicals

Abstract The reaction of peroxy radicals, RO2, with OH radicals has long been ignored to play any role in atmospheric chemistry. Recent experimental and modeling studies show however that these reactions are fast and can play a role in remote atmospheres with low NO concentrations when the major fate of peroxy radicals, its reaction with NO, slows down. The present article summarizes recent work on this class of reactions and its implications in different environments.

Crown-ether-substituted asymmetric phthalocyanine derivatives/CdS self-assembled hybrid films with an unprecedented high response toward NO2

Two asymmetrical amphiphilic phthalocyanines simultaneously containing hydrophobic alkoxy and hydrophilic 15-crown-5-ether substituents at the phthalocyanine periphery H2{Pc(15C5)3[(OC8H[Formula: see text]]}(Pc-1) and H2{Pc(15C5)[(OC8H[Formula: see text]]}(Pc-2) and their symmetrical analogue H2[Pc(OC8H[Formula: see text]] (Pc-3) have been synthesized and characterized. The Pc-n/CdS ([Formula: see text] 1, 2 and 3, respectively) hybrid films are obtained successfully via a simple quasi-Langmuir–Shäfer (QLS) method using H2S-vapor annealing over the Pc-n/Cd[Formula: see text] self-assembled film formed at the interface of the air/CdCl2 aqueous solution. The film-structure and properties of both the hybrid Pc-n/CdS and pure Pc-n films are comparatively studied by a wide range of methods including UV-vis, polarized UV-vis, XRD, SEM and I–V measurements. Experimental results exhibit a slipped co-facial stacking mode in an “edge-on” conformation ([Formula: see text]-type aggregate) formed for the phthalocyanine molecules in both pure Pc-n films and the corresponding Pc-n/CdS hybrid films, with increasing intermolecular [Formula: see text]–[Formula: see text] interactions in the order of Pc-n &lt;Pc-n/CdS and Pc-3/CdS &lt;Pc-2/CdS &lt;Pc-1/CdS, respectively. Accordingly, film-microstructures, crystallinity and conductivity are effectively improved by introducing CdS nanoparticles into the 15-crown-5-substituented phthalocyanines forming Pc-1/CdS and Pc-2/CdS hybrid films. These render excellent sensing performance towards NO2 in the 0.05–2.5 ppm range within a fast dynamic exposure period of 30 s. Strikingly, Pc-1/CdS hybrid film presents an unprecedented high sensitivity of 157.3%.ppm[Formula: see text] vs. very low NO2 concentration range of 0.05˜0.25 ppm, achieving one of the best room temperature sensing performances in terms of high sensitivity, rapid responsibility and low detection limit among self-assembled film-based NO2 sensors.

Effect of trans(NO, OH)-[RuFT(Cl)(OH)NO](PF6) ruthenium nitrosyl complex on methicillin-resistant Staphylococcus epidermidis

Antibiotic resistance is becoming a global scourge with 700,000 deaths each year and could cause up to 10 million deaths by 2050. As an example, Staphylococcus epidermidis has emerged as a causative agent of infections often associated with implanted medical devices. S. epidermidis can form biofilms, which contribute to its pathogenicity when present in intravascular devices. These staphylococci, embedded in the biofilm matrix, are resistant to methicillin, which had long been the recommended therapy and which has nowadays been replaced by less toxic and more stable therapeutic agents. Moreover, current reports indicate that 75 to 90% of Staphylococcus epidermidis isolates from nosocomial infections are methicillin-resistant strains. The challenge of successfully combating antibiotics resistance in biofilms requires the use of compounds with a controlled mode of action that can act in combination with antibiotics. Ruthenium nitrosyl complexes are potential systems for NO release triggered by light. The influence of trans(NO, OH)-[RuFT(Cl)(OH)NO](PF6) on Staphylococcus epidermidis resistant to methicillin is described. The results show a 50% decrease in cell viability in bacteria treated with low concentrations of NO. When combined with methicillin, this low dose of NO dramatically decreases bacterial resistance and makes bacteria 100-fold more sensitive to methicillin.

Hydrophobic Tungsten-Containing MFI-Type Zeolite Films for Exhaust Gas Detection.

The assembly of highly hydrophobic nanosized tungsten-containing MFI-type zeolite nanocrystals (W-MFI) in films and further use of the films for selective exhaust gas (CO, CO2, NO, and NO2) detection were investigated by operando IR spectroscopy. Because of the hydrophobic nature and presence of tungsten in the framework, the W-MFI films showed excellent sorption capacity toward all analytes, in comparison to the pure silica (Si-MFI) film. The high sensitivity of the W-MFI film toward low concentration of CO2 and NO2 (1-3 ppm) was demonstrated. In addition, the interactions between the analytes and zeolite films have been studied by quantum chemical calculation modeling of the W centers based on the density functional theory method.

Cytotoxicity, cellular uptake, and subcellular localization of a nitrogen oxide and aminopropyl-β-lactose derivative ruthenium complex used as nitric oxide delivery agent

This work investigates how the luminescent ruthenium-nitrite complexes cis-[Ru(py-bodipy)(dcbpy)2(NO2)](PF6) (I) and cis-[Ru(py-bodipy)(dcbpy-aminopropyl-β-lactose)2(NO2)](PF6) (II) behave toward the melanoma cancer cell line B16F10. The chemical structure and purity of the synthesized complexes were analyzed by UV-Visible and FTIR spectroscopy, MALDI, HPLC, and 1H NMR. Spectrofluorescence helped to determine the fluorescence quantum yields and lifetimes of each of these complexes. In vitro MTT cell viability assay on B16F10 cancer cells revealed that the complexes possibly have a tumoricidal role. The metal-nitrite complexes evidenced the dichotomous NO nature: at high concentration, NO exerted a tumoricidal effect, whereas cancer cells grew at low NO concentration. Flow cytometry or fluorescence microscopy aided cellular uptake calculation. Cell staining followed by fluorescence microscopy associated with organelle markers such as DAPI and Rhodamine 123 detected preferential intracellular localization of the ruthenium-nitrite py-bodipy and aminopropyl lactose derivative ruthenium complex in mitochondria. Thus, the cytotoxicity of compounds (I) and (II) against B16F10 cancer cell line show concentration-dependent results. The present studies suggest that nitric oxide ruthenium derivative compounds could be new potential chemotherapeutic agents against cytotoxic cells.

The effect of radiation parameters on the performance of photo-activated gas sensors

The gas sensing characteristics of several favorable metal oxide semiconductors, such as ZnO, In2O3, SnO2, and WO3, under various irradiation conditions, utilizing ultraviolet light emitting diodes (UV-LED), were investigated. The morphology and structure of sensing materials prepared by precipitation route were analyzed, and the sensors’ performances were evaluated against low concentrations of NO2. In particular, the effects of several UV source-related operating parameters, such as irradiation wavelength, irradiance, and irradiation pattern, were studied, and the underlying mechanism for the adsorption/desorption kinetics of gas molecules under different UV irradiation was demonstrated. The effect of radiation specifications was found to play an essential role in the response of the sensors. Thus, appropriate conditions must be applied to the design and operation of the UV-LED activated gas sensors for optimal performance.

NO₂ Selective Sensor Based on α-Fe₂O₃ Nanoparticles Synthesized via Hydrothermal Technique.

In the present work, hematite (α-Fe2O3) nanopowders were successfully prepared via a hydrothermal route. The morphology and microstructure of the synthesized nanopowders were analyzed by using scanning and transmission electron microscopy (SEM and TEM, respectively) analysis and X-ray diffraction. Gas sensing devices were fabricated by printing α-Fe2O3 nanopowders on alumina substrates provided with an interdigitated platinum electrode. To determine the sensor sensitivity toward NO2, one of the main environmental pollutants, tests with low concentrations of NO2 in air were carried out. The results of sensing tests performed at the operating temperature of 200 °C have shown that the α-Fe2O3 sensor exhibits p-type semiconductor behavior and high sensitivity. Further, the dynamics exhibited by the sensor are also very fast. Lastly, to determine the selectivity of the α-Fe2O3 sensor, it was tested toward different gases. The sensor displayed large selectivity to nitrogen dioxide, which can be attributed to larger affinity towards NO2 in comparison to other pollutant gases present in the environment, such as CO and CO2.

Numerical investigation on NOx emission in co-firing with ammonia and pulverized coal in a large-scale boiler

Recently, the technology of co-firing ammonia (NH3) with coal in boiler has been paid more and more attention, because NH3 is a carbon-free carrier of hydrogen with lower cost in transportation and storage. In this study, the computational fluid dynamics simulation was performed to investigate the difference in NOx emission behavior between coal firing and NH3 co-firing, and the effects of NH3 injection positions on NOx emission in a large-scale pulverized coal boiler. In this boiler, three stages (lower, middle, and upper) of burners with different heights are installed on both the front and rear walls. According to the simulation results, the condition of NH3 co-firing, in which NH3 is injected into all burners with co-firing ratio (CR) of 20 cal.%, shows a lower NO concentration at outlet than coal firing, because of the DeNOx effect of unreacted NH3 and less char NOx. In addition, in order to investigate the effect of injection position of NH3, the results of three cases, which include NH3 co-firing in all burners, NH3 co-firing in middle burners (CR: single burner 20 cal.%, whole furnace 8 cal.%), and NH3 co-firing in upper burners (CR: single burner 20 cal.%, whole furnace 8 cal.%), were compared. It can be known that NH3 co-firing in upper burners shows a highest NO concentration at outlet, because of quick mixing between NH3 from upper burner and two-stage combustion air. Thus, in order to delay the mixing between NH3 and two-stage combustion air, and ensure enough time for DeNOx reaction of NH3, injecting NH3 into the upper burners should be avoided.

Synthesis of Nano Manganese Oxide with Assistance of Ultrasonic for Removal of Low Concentration NO

Synthesis of Nano Manganese Oxide with Assistance of Ultrasonic for Removal of Low Concentration NO

Interaction of Dissolved CO2, SOx and NOx with the Moolayember Formation Underlying the Precipice Sandstone

An injected CO2 or greenhouse gas (GHG) stream will dissolve into formation water forming carbonic acid, especially in the case of low salinity reservoir storage. Industrial GHG streams from coal combustion, cement or streel production may contain accessory gases including N2, Ar, SOx, NOx, or O2, several including SOx and NOx form stronger acids. The dissolved GHG stream will have reactivity to some rock forming minerals, potentially modifying porosity or water chemistry, or mineral trapping CO2. The Precipice Sandstone in the Surat Basin, Australia, is a low salinity target reservoir for CO2 storage. The Surat CCS project proposes to a demonstration-scale injection test of 60,000 t per year of a GHG stream captured from black coal PCC into the quartz rich Lower Precipice Sandstone. The dissolved GHG stream is expected to interact with the Lower and Upper Precipice Sandstone and sink to interact with the underlying Moolayember Formation of the Bowen Basin. However little was known about the lithologies of the Moolayember Formation which unconformably underlies the projects proposed injection site. Drill cores from the Moolayember Formation were sampled and characterized: indicating a high proportion of carbonate cements, potentially reactive clays, feldspars, and trace amounts of sulphides and coal. Complex carbonate assemblages and secondary textures indicate this may already be a valuable example of a natural analogue of CO2 alteration. Kinetic geochemical modelling was performed to predict the CO2 or CO2-SO2-NO reactivity of several lithologies. This indicted that after 30 years, low concentrations of SOx and NO (100 ppm) had minimal effect on the pH which was buffered to similar values relative to pure CO2 for these reactive mineralogies. The pH was instead controlled by the carbonate mineral content, which buffered acidity. Reaction of clay and feldspar rich lithologies resulted in dissolution of K-feldspar, chlorite, and plagioclase to form kaolinite, smectite, and additionally siderite mineral trapping CO2. SO2 was predicted to be mineral trapped as pyrite or alunite. The net predicted mineral volumes or porosities however did not change significantly. Experiments at reservoir conditions and further characterization are planned to validate and improve model predictions.

Chemical Adsorption of Nitrogen Dioxide with an Activated Carbon Adsorption System

ABSTRACT Nitrogen dioxide (NO2) is a pollutant that directly harm the human respiratory system, lead to inflammation, as well as to form the secondary aerosol pollutants. The main NO2 sources, combustion or thermal processes, were well controlled. However, the metal etching operation in semiconductor industry emits flue gases with reddish-brown NO2 fume that leads to visibility reduction, acidic odor, as well as negative effects on human health. In this study, a stream of flue gases with low NO2 (230 ± 10 ppm) and NO (50 ppm) concentrations were conducted to pass through an activated carbon-packed fixed bed for analyzing the adsorptive conversion behavior of NO2 by the activated carbon (AC) at room temperature. The repeated adsorption test was carried out by washing the regenerated waste carbon with a caustic solution and water and drying. Results propose that at the beginning of adsorption, nitrogen dioxide combined with carbon to form NO and desorbed from carbon surface. The net adsorptive conversion removal capacity of NO2 by the virgin AC and regenerated AC was 224 and 155 mg g–1 AC, respectively. Regeneration restored around 70–75% of effective surface area, pore volume, and adsorptive conversion capacity of the virgin AC. Leached caustic solution obtained from the carbon regeneration contained only nitrate and the phenomena indicates the adsorbed -C2(ONO2) hydrolyzed following the Eq. (2) -C2(ONO2) + H2O → 3 -C* + -C(O) + 2 HNO3, where -C* denotes active site on the carbon surface.

Enhanced Gas Sensing Performance of Photo-Activated, Pt-Decorated, Single-Crystal ZnO Nanowires

ZnO nanoparticles and nanowires decorated with platinum nanoparticles in different loading concentrations were prepared to detect low concentrations of NO2 under 365-nm ultraviolet-light emitting diode (UV-LED) irradiation at room temperature. Solution precipitation, self-assembly crystallization, and photo-deposition techniques were used to synthesize the sensing material. The synthesized sensors at different stages of development were characterized by XRD, HRTEM and FE-SEM analyses. Although the sensing response of the pristine ZnO nanoparticles was 0.41 for NO2 detection, the response improved significantly to 1.5 using ZnO nanowires in the identical photo-activation settings of 365 nm UV wavelength and 25 mW/cm2 irradiance. The decoration of the surface of the ZnO nanowires with Pt nanoparticles further enhanced the sensing performance, whereas the 0.1wt% Pt-decorated ZnO nanowire sensor exhibited a response of 4.33 with a 140-s response time, which is more than one order of magnitude higher and 50s faster than the response generated by the ZnO nanoparticles. This improved performance is attributed to the role of Pt active sites in promoting NO2 adsorption on the ZnO nanowires’ surface as well as enhancing the layer electron utilization.

On Low-Emission Annular Combustor Based on Designing of Liner Air Admission Holes

Numerical experiments was carried out to predict the total temperature characteristics and formation of nitrogen oxide emissions and pattern factor in an annular combustor liner based on geometrical parameters and location and rows of different air admission holes, for 6 various cases, using computational fluid dynamics (CFD) .The simulation has been performed using ANSYS CFX including finite rate chemistry and eddy dissipation model, for simulation of liquid kerosene (Jet A) – air combustion after fuel droplet evaporation. The spray modeling was performed, including Rosin-Rammler droplet distribution. Thermal and prompt nitrogen oxide (NO x ) formation was performed to predicting NO x emission characteristics with a k -e model of turbulent. In this investigation the 3D CAD model of the realistic annular combustion chamber is presented for the simulation with double radial air swirler for the better mixing fuel with air. Beside this the characteristic and the flame structure is presented including the contour plots of total temperature and NO concentration at the outlet of the combustor liner and in cross section plane along the X axis from the injector center of the combustor including the chart of the velocity and NO, CO, CO 2 , O 2 and the total temperature along the liner from the injector center. For the combustion of kerosene with air 2 step kinetic schemes are presented in this study. The results show that the best result with the low concentration of NO is the case 5 but with a high percentage of pressure drop and the case 3 have the maximum concentration of NO with the low percentage of pressure drop.

Sensing properties of amperometric ppb-level NO2 sensor based on sodium ion conductor with sensing electrodes comprising different WO3 nanostructures

In this study, amperometric NO2 sensors based on Na+ superionic conductor electrolyte and sensing electrodes with different WO3 nanostructures (WO3 nanoparticles, WO3 nanosheets, and mesoporous WO3) have been fabricated and compared. Sensing properties, such as optimum test temperature, sensitivity, repeatability, and selectivity have been determined and compared. Compared with the literatures, the sensors, prepared using three different WO3 nanostructures, all showed improved sensing properties to 100–1000 ppb NO2 at low work temperatures of 100–150 °C. Among above sensors, the sensor equipped with mesoporous WO3 sensing electrode exhibited the best amperometric sensitivity characteristics and the minimum test temperature. The relationship between the sensing properties and the mesoporous structure has also been discussed. What’s more, the sensor can test ppb-level NO2 in low temperature, which makes it possible to monitor low concentrations of NO2 in the air.