Teflon Reaction Research Articles

Crystal structure of poly[μ3-acetato-diaqua-μ3-sulfato-cerium(III)]: serendipitous synthesis of a layered coordination polymer exhibiting interlayer O—H...O hydrogen bonding

Single crystals of the title compound, [Ce(CH3COO)(SO4)(H2O)2] n , were obtained serendipitously by the reaction of Ce(NO3)3·6H2O with 2,5-thiophenedicarboxylic acid (H2TDC) and acetic acid in a mixture of ethanol and water, where it is assumed that the sulfate ions leached from the Teflon reactor, which was treated with peroxymonosulfuric acid prior to its use. Its asymmetric unit consists of one CeIII cation, one sulfate dianion, one acetate anion and two crystallographically independent water molecules, all of them located in general positions. The cerium cations are coordinated by three acetate anions (one O,O-chelating) and three sulfate dianions that are related by symmetry as well as two independent water molecules within an irregular CeO9 coordination geometry. The CeIII cations are linked by the acetate ions into [010] chains, which are further connected into (001) layers by the sulfate dianions. Intralayer and interlayer O—H...O hydrogen bonds are observed. Powder X-ray diffraction shows that only traces of the title compound have formed together with a large amount of an unknown crystalline phase. Attempts to prepare the title compound in larger amounts and as a pure phase were unsuccessful.

Characterizing Wall Loss Effects of Intermediate-Volatility Hydrocarbons in a Smog Chamber with a Teflon Reactor

Intermediate-volatility organic compounds (IVOCs) serve as pivotal precursors to secondary organic aerosol (SOA). They are highly susceptible to substantial wall losses both in indoor environments and within smog chambers even with Teflon walls. Accurately characterizing the wall loss effects of IVOCs is thus essential for simulation studies aiming to replicate their atmospheric behaviors in smog chambers to ensure precise modeling of their physical and chemical processes, including SOA formation, yet a comprehensive understanding of the wall loss behavior of IVOCs remains elusive. In this study, we conducted a thorough characterization of wall losses for typical intermediate-volatility hydrocarbon compounds, including eight normal alkanes (n-alkanes) and eight polycyclic aromatic hydrocarbons (PAHs), using the smog chamber with a 30 m3 Teflon reactor. Changes in the concentrations of gaseous IVOCs with the chamber were observed under dark conditions, and the experimental data were fitted to the reversible gas–wall mass transfer theory to determine the key parameters such as the wall accommodation coefficient (αw) and the equivalent organic aerosol concentration (Cw) for different species. Our results reveal that Cw values for these hydrocarbon IVOCs range from 0.02 to 5.41 mg/m3, which increase with volatility for the PAHs but are relative stable for alkanes with an average of 3.82 ± 0.92 mg/m3. αw span from 1.24 × 10−7 to 1.01 × 10−6, with the values for n-alkanes initially showing an increase followed by a decrease as carbon numbers rise and volatility decreases. The average αw for n-alkanes and PAHs are 3.34 × 10−7 and 6.53 × 10−7, respectively. Our study shows that IVOCs exhibit different loss rates onto clean chamber walls under dry and dark conditions, with increasing rate as the volatility decreases. This study demonstrates how parameters can be acquired to address wall losses when conducting smog chamber simulation on atmospheric processes of IVOCs.

Understanding the active role of water in laboratory chamber studies of reactions of the OH radical with alcohols of atmospheric relevance.

In this work, we studied the reactions of three cyclic aliphatic alcohols with OH at room temperature, atmospheric pressure and different humidities in a Teflon reaction chamber. It was determined that the lower the solubility of the alcohol in water, the larger the effect of the humidity on the acceleration of the reaction. This experimental evidence allows suggesting that the acceleration is due to the reaction of the co-adsorbed reactants at the air-water interface of a thin water film deposited on the Teflon walls of the reaction chamber, instead of between co-reactants dissolved in the water film or due to gas phase catalysis as previously suggested. Therefore, formation of thin water films on different surfaces could have some implications on the tropospheric chemistry of these alcohols in the tropical regions of the planet with high humidity.

Biogas production from food waste hydrolysate using a subcritical water pretreated process and pulp wastewater seed sludge

This study was investigated the biogas production performance from subcritical water hydrolysate (SCWH) using a pretreated food waste (FW) process, and pulp wastewater (PW) as seed sludge according to different volatile solid (VS) ratio of PW to SCWH, and different substrate concentration. The subcritical water hydrolysis was acted for 30 mins in a 70 ml Teflon reactor under different temperatures varied from 119, 129, 139, 159, and 195 ℃, respectively. A batch system for optimal biogas and methane production yields examination were fermented in a 60 ml flask under 37 °C and 120 rpm. A maximum biogas yield of 807.0 ml/g VSre and methane yield of 329.5 ml/g VSre were achieved at a VS ratio of PW to SCWH 1:3 and substrate concentration of 25 g/L with a hydrolysate under 159 ℃ and the volatile solids (VS) removal efficiency of 80%. These results indicated that the food waste pretreated by subcritical water hydrolysis can efficiently increase the biogas production under optimal conditions.

Analysis of Small-Mass Biological Samples by ICP MS Using Microwave Acid Digestion of Several Samples in the Common Atmosphere of a Standard Autoclave

To expand the available tools for the analysis of samples of biological and plant origin of small mass (10–20 mg) using ICP MS, we developed a construction made of three compact teflon reaction minivessels (inserts) of an internal volume of 3 mL, placed in a standard autoclave (EasyPrep) of a volume of 100 cm3 of a MARS-5 microwave system (CEM). The acid digestion of samples in reaction minivessels requires no more than 1.5 mL of highly pure acids. The digestion of samples proceeds in the common gas atmosphere of a standard autoclave filled with a needed volume of acids of pure for analysis grade. The method was tested on reference materials of plants and biological sample. The results obtained are in agreement with the certified values. The developed method ensures the decrease of the detection limits and obtaining new data on the concentrations of B, Ga, Y, Nb, Tl, Bi, and a number of rare-earth elements in the reference materials.

Characterization of a smog chamber for studying formation of gas-phase products and secondary organic aerosol

Smog chambers provide a potent approach to explore the secondary organic aerosol formation under varied conditions. This study describes the construction and characterization of a new smog chamber facility for studying the formation mechanisms of gas-phase products and secondary organic aerosol from the photooxidation of volatile organic compounds. The chamber is a 5.4 m3 Fluorinated Ethylene Propylene (FEP) Teflon reactor with the potential to perform photooxidation experiments at controlled temperature and relative humidity. Detailed characterizations were conducted for evaluation of stability of environmental parameters, mixing time, background contamination, light intensity, and wall losses of gases and particles. The photolysis rate of NO2 (JNO2) ranged from (1.02−3.32) ×10−3 sec−1, comparable to the average JNO2 in ambient environment. The wall loss rates for NO, NO2, and O3 were 0.47 × 10−4, 0.37 × 10−4, and 1.17 × 10−4 min−1, while wall loss of toluene was obsoletely found in a 6 hr test. The particle number wall loss rates are (0.01−2.46) ×10−3 min−1 for 40−350 nm with an average lifetime of more than one day. A series of toluene photooxidation experiments were carried out in absence of NOx under dry conditions. The results of the simulation experiments demonstrated that the chamber is well designed to simulate photolysis progress in the atmosphere.

Protein encapsulation in mesoporous silica: Influence of the mesostructured and pore wall properties

The goal of this work is to study the influence of the structured mesoporous silica (SMS), used as scaffolds for tissue engineering, on the encapsulation and on the release of a model bone morphogenetic proteins (BMP), i.e. Soybean Trypsin Inhibitor (STI). First, SBA-15 silica samples were synthesized using tetraethyl orthosilicate (TEOS) as silica precursor in the presence of P123 as the surfactant in an acidic medium. Three homemade high-pressure stainless steel reactors (with smaller Teflon reactors inside), each equipped with a temperature probe, were used for the syntheses. In addition, a swelling agent was added to increase the pore size. Indeed, the common pore size for those mesostructured materials lies between 6 nm and 8 nm, while the STI has an average radius of 4 nm. The reagent addition sequence was also investigated, by playing on the time of addition of the swelling agent. It was observed that when the swelling agent was added with TEOS, an ordered mesoporous silica was produced. On the contrary, if the swelling agent was added during the surfactant dissolution step, it resulted in an unstructured yet still mesoporous silica. Because of the high affinity of STI for hydrophobic surfaces, SMS were also produced using silica precursors containing phenylene bridging groups (1,4-bis(triethoxysilyl)benzene, BTEB). The BTEB samples exhibited two 2D-hexagonal structures with different wall thicknesses. Synthesized materials were further characterized by infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), nitrogen sorption at 77 K, transmission electron microscopy (TEM), and small-angle X-ray scattering (SAXS). The influence of both the silica composition and structure on STI encapsulation/release was studied. For samples synthesized with TEOS, the unstructured sample showed a higher protein loading and a higher protein release, which could be explained by a difference in the pore interconnectivity within the sample. In fact, a fast release of STI was observed during the first 24 h. Afterwards, the STI release slowed down and seemed to reach a plateau. On the opposite, the structured sample showed a steady release over time. Finally, the sample synthesized with BTEB did not show a significant release over the same period of time. This led us to the conclusion that the hydrophobicity of the silica surface plays a major role on the protein encapsulation and its release rate.

Novel synthesis and characterization of crystalline fluorapatite from Moroccan phosphogypsum waste

In the present study, phosphogypsum waste (PG) was utilized to synthesize fluorapatite (FAP) via a simple precipitation method. The FAP was prepared using a novel mixing technique with anhydrite obtained from PG and phosphoric acid solution in the presence of pure fluoride ammonium in a Teflon reactor. The characteristics of the prepared FAP were investigated with various methods including Scanning Electron Microscopy (SEM) coupled with Energy-Dispersive Spectroscopy (EDS), X-Ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). The FAP derived from PG exhibited a hexagonal structure with a particle size ranging from 1.5 to 9 μm along with a high purity. FAP also showed an excellent Ca/P ratio equals to 1.67. These results proved that the FAP was successfully synthesized from phosphogypsum waste.

Alteration conditions on the CM and CV parent bodies – Insights from hydrothermal experiments with the CO chondrite Kainsaz

This study simulates the hydrothermal conditions that existed on carbonaceous chondrite planetesimals in the early solar system. Our experiments are relevant to alteration conditions that existed on the CV parent body and the late stage oxidizing alteration of the CM chondrites. We conducted 11 alteration experiments using chips of the CO3 chondrite Kainsaz. Water was added to each chip and sealed in separate Teflon reaction vessels for 175 days. Samples were altered at different initial water-to-rock ratios (W/R: 0.2–0.8) and temperatures (50 °C and 150 °C). Isotopically doped 17O-rich heavy water (δ17O: +64.5‰) was used in five runs. All samples experienced pronounced alteration under a partially open system environment where gases were able to escape the reaction vessels.The style of alteration (Fe-alkali metasomatism) is similar in all cases. The principal alteration minerals formed are Fe-oxyhydroxides (goethite) and Fe-oxides (magnetite), with smaller quantities of Fe-sulphides. Minor phases formed include fayalite, sulphates (gypsum and Fe-sulphate) and calcite. Nanophase, poorly crystalline phyllosilicates formed in the high-temperature samples but are absent from the low-temperature experiments. In all instances, Mg-rich chondrule silicates remained chemically unaltered although some grains suffered hydrothermal fracture. Chondrule mesostases remained largely unaffected. By contrast, kamacite readily dissolved, acting as a source of Fe and Ni for the fluid phase. A new generation of nanophase Fe-sulphides formed within the matrix, while pre-existing pyrrhotite group sulphides experienced Ni enrichment (<3 at%). In the high temperature samples these sulphides were also partially oxidized, lowering their (Fe + Ni)/S ratio. High-Ni sulphides (pyrrhotite with Ni > 10 at%) were formed in the 150 °C samples, most likely by sulphidation of taenite.Matrix alteration cemented grains together, reducing porosity. The fine-grained matrix shows highly variable degrees of alteration, with minimally altered matrix in direct contact with regions of heavily altered matrix. Chondrule fine-grained rims (FGRs) were preferentially altered. These textures imply that the unaltered matrix readily reacted with the fluid phase, resulting in an efficient depletion of dissolved ions (Fe2+ and S2-), limiting reactivity until further primary phases were dissolved. At larger length-scales the distribution of heavily altered matrix reveals the presence of large ∼100 µm wide channels that meander through the specimens. Their textures resemble features seen in some CM chondrites and the ungrouped CO-like chondrite MIL 07687. We suggest that alteration fronts developed by sustained rapid reaction of matrix with dissolved cations in solution. Our observations provide a mechanism for the establishment and maintenance of geochemical microenvironments on chondritic asteroids. The effects of open system loss notwithstanding, our experiments demonstrate that more advanced alteration is correlated with higher initial W/R ratios.The use of 17O-rich doped water allowed the isotopic effects of aqueous alteration to be observed. Bulk rock compositions evolved towards the initial water composition, reflecting the incorporation of heavy O into hydrated minerals. Additionally, altered samples shifted in δ18O space, reflecting the competing effects of water–mineral fractionation and mass fractionation due to the preferential escape of isotopically light water.

Miniaturized and improved method for Apparent Total N-Nitroso Compounds determination in beer

A miniaturized and improved method for Apparent Total Nitroso Compounds determination in liquid matrices was developed. The main improvement is based on a miniaturized and modified apparatus for chemical denitrosation of nitroso compounds by hydrogen bromide in a glacial acetic acid mixture. The reaction is carried out in a teflon reaction coil while the reaction product, gaseous nitric oxide, is drifted to a chemiluminescence detector by the flow of argon together with a vacuum obtained by the detector's oil pump. The apparatus significantly increased the efficiency of the Apparent Total N-Nitroso Compounds determination (compared to the previous method), specifically, the dead volume of the apparatus was significantly decreased, and the effect of the reverse reaction was eliminated as well. The apparatus shortens the analysis time (1.4 min/injection), further it provides a lower detection limit (3 μg(N-NO)/l), quantification limit (10 μg(N-NO)/l), and method uncertainty (15%), and is simpler for the operation.

Impact of ozone and inlet design on the quantification of isoprene-derived organic nitrates by thermal dissociation cavity ring-down spectroscopy (TD-CRDS)

Abstract. We present measurements of isoprene-derived organic nitrates (ISOP-NITs) generated in the reaction of isoprene with the nitrate radical (NO3) in a 1 m3 Teflon reaction chamber. Detection of ISOP-NITs is achieved via their thermal dissociation to nitrogen dioxide (NO2), which is monitored by cavity ring-down spectroscopy (TD-CRDS). Using thermal dissociation inlets (TDIs) made of quartz, the temperature-dependent dissociation profiles (thermograms) of ISOP-NITs measured in the presence of ozone (O3) are broad (350 to 700 K), which contrasts the narrower profiles previously observed for, for example, isopropyl nitrate (iPN) or peroxy acetyl nitrate (PAN) under the same conditions. The shape of the thermograms varied with the TDI's surface-to-volume ratio and with material of the inlet walls, providing clear evidence that ozone and quartz surfaces catalyse the dissociation of unsaturated organic nitrates leading to formation of NO2 at temperatures well below 475 K, impeding the separate detection of alkyl nitrates (ANs) and peroxy nitrates (PNs). The use of a TDI consisting of a non-reactive material suppresses the conversion of isoprene-derived ANs at 473 K, thus allowing selective detection of PNs. The potential for interference by the thermolysis of nitric acid (HNO3), nitrous acid (HONO) and O3 is assessed.

Partial Order–Disorder Transformation of Interpenetrated Porous Coordination Polymers

Controlling interpenetration and flexibility behaviors is intriguing and fundamental for porous coordination polymers. We report exceptional interpenetration behaviors involving controllable partia...

Preparation of zeolite coatings by induction heating of the substrate

Induction heating was used as a tool to prepare zeolite coatings on stainless steel substrates. The substrates were double-layer wire meshes which were placed in a Teflon reactor and were heated from a distance by the alternating magnetic field produced by a generator. The reaction mixture, also heated to some extent in the reactor, was circulated in the system to be cooled in a water bath to a temperature lower than that of the mixture at the exit of the reactor. Different synthesis conditions were investigated and the coatings obtained initially using two previously published synthesis compositions were characterized by X-ray diffraction (XRD) and thermogravimetry (TG). Induction heating was shown to allow the formation of crystalline zeolite A and X coatings. Relatively thick coatings of these zeolites could be prepared in much shorter times than by conventional synthesis, and even the substrate heating method using conduction. The cylindrical geometries of the induction coil and the substrate allowed the uniform heating of the substrate, leading to the formation of uniformly thick coatings. Utilizing substrates consisting of two layers of wire meshes, also played significant role in obtaining thick and highly stable coatings by the induction heating synthesis method.

Efficient photochemical vapor generation of bismuth using a coiled Teflon reactor: Effect of metal sensitizers and analytical performance with flame-in-gas-shield atomizer and atomic fluorescence spectrometry

Photochemical vapor generation (PVG) of bismuth was accomplished in a simple flow–injection system with a standard Hg low-pressure tube lamp and a coiled Teflon reactor. The influence of a reaction medium flow rate (irradiation time) and composition was investigated using a miniature diffusion flame atomizer and high-resolution continuum source atomic absorption spectrometry. Combination of 40% (v/v) acetic acid, 1.25% (v/v) formic acid and a metal sensitizer at a flow rate of 3 mL min−1 (irradiation time of 90 s) was found optimal. The use of various metals as sensitizers was studied to initiate and enhance PVG substantially. The evident positive effect was found for four metal cations and the enhancement effect was in the following order: Cu2+<Cd2+<Fe2+ ≪ Co2+. At 50 mg L−1 Co2+ as the sensitizer, the overall PVG efficiency of 54 ± 2% was determined from relative comparison of sensitivities obtained with PVG and liquid nebulization coupled simultaneously to inductively coupled plasma mass spectrometry. In order to reach low limits of detection (LOD) at low operation cost, a coupling of PVG to atomic fluorescence spectrometry was tested and conditions of atomization in two flame atomizers were optimized. A blank-limited LOD of 12 ng L−1 was obtained with an advanced flame-in-gas-shield atomizer, which competes with PVG coupled to inductively coupled plasma mass spectrometry (5 ng L−1). Interferences from commonly used inorganic acids (HNO3, HCl and H2SO4) and other elements (As3+, Pb2+, Sb3+, Se4+ and Te4+) were also investigated and the accuracy was verified by analysis of water Standard Reference Material NIST 1643f.

Mathematical Models to Determine the Conductivity of a Cztis Photovoltaic Material as a Function of the Synthesis Temperature

Study on the conductivity of the material Cu2ZnTiS4 (CZTiS), obtained under a hydrothermal route from precursor nitrates treated in a teflon reactor under constant pressure with a stainless steel jacket, involving different heat treatments (200, 225, 250, 275 and 300°C) for reaction times of 48 hours in all cases and subsequent calcination at 550°C in a tube oven, under nitrogen flow (50 mL min-1). The materials were characterized by X-ray Diffraction (XRD), Raman spectroscopy, Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM). The results showed materials with structural and crystalline properties concordant with a kesterite type phase, evidencing homogeneous surfaces, unique morphological properties derived from the process with regular distribution of particles and size of the nanometric order (5-6 nm) as well as the characteristics of the roughness of the material. Solid state impedance spectroscopy (IS) evidenced its electrical behavior and validated the proposed mathematical models.

Simulating the impact of gas-wall partitioning on SOA formation using the explicit gas mechanism integrated with aqueous reactions containing electrolytes

The impact of the Teflon reactor wall on secondary organic aerosol (SOA) formation was explicitly simulated by using the Unified Partitioning Aerosol Phase Reaction (UNIPAR) model integrated with gas-wall partitioning (GWP). The formation of oxygenated semivolatile organic compounds (SVOCs) from the photooxidation of hydrocarbons (HC) was simulated by using an explicit gas-kinetic mechanism (MCM V3.3.1). In the model, SVOC's GWP and gas-particle partitioning onto preexisting particulate matter were kinetically treated with the absorption and desorption processes. The UNIPAR model streamlined aerosol growth via the oligomerization of reactive SVOCs in the organic phase and aqueous reactions in the inorganic phase. Two important GWP parameters, GWP coefficient (Kw, i) and the deposition rate constant (k_onw, i) of SVOCs (i) to the wall were predicted by using a quantitative structure activity relationship (QSAR) employing SVOCs' physicochemical descriptors. This GWP model was then incorporated with the UNIPAR model in the DSMACC-KPP platform and simulated SOA chamber data. The three different HCs (toluene, 1,3,5-trimethylbenzene, and α-pinene) were photochemically oxidized in the presence of NOx and inorganic seed aerosols in an outdoor photochemical smog chamber (UF-APHOR). The impact of GWP on SOA mass varied ranging from 9% to 71% with HCs, seed conditions, NOx, and temperature. Toluene SOA in the absence of inorganic aerosol was the most sensitive to GWP. However, in the presence of wet-inorganic seed, the impact of GWP on SOA was smaller than that of non-seed SOA owing to rapid reactions of organic species in the aqueous phase. SOA mass can be significantly underestimated in the absence of wet-inorganic seed when the aerosol model employs parameters derived using SOA data with GWP artifacts.

Kinetic Measurements of Cl Atom Reactions with C5–C8 Unsaturated Alcohols

The reactions of five structurally similar unsaturated alcohols, i.e., (Z)-2-penten-1-ol, (E)-2-hexen-1-ol, (E)-3-hexen-1-ol, (Z)-3-hexen-1-ol, and 1-octen-3-ol, with Cl atoms in the gas phase, were investigated at 296 ± 2 K and 1 atm by the relative-rate kinetic technique using a 600-L Teflon reaction chamber. Selected ion flow tube mass spectrometry (SIFT-MS) was used simultaneously to monitor the decay of the alcohols of interest and selected reference compounds. Tetrahydrofuran (THF), propan-1-ol, and octane were used as reference compounds. Chlorine atoms were produced by the photolysis of molecular chlorine (Cl2) using broadband actinic lamps near 365 nm. The estimated rate constant values (in 10−10 cm3∙molecule−1∙s−1) followed the order 2.99 ± 0.53 ((Z)-2-penten-1-ol) &lt; 3.05 ± 0.59 ((E)-3-hexen-1-ol) &lt; 3.15 ± 0.58 ((Z)-3-hexen-1-ol) &lt; 3.41 ± 0.65 ((E)-2-hexen-1-ol) &lt; 4.03 ± 0.77 (1-octen-3-ol). The present work provides the first value of the rate constant for the reaction of 1-octen-3-ol with Cl atoms. The results are discussed and interpreted in relation to other studies where literature data are available. The structure–activity relationship and the atmospheric implications are discussed as well.

A General and Programmable Synthesis of Graphene-Based Composite Aerogels by a Melamine-Sponge-Templated Hydrothermal Process

Three-dimensional (3D) graphene networks are performance boosters for functional nanostructures in energy-related fields. Although tremendous intriguing nanostructures-decorated 3D graphene network...

Secondary organic aerosol formation from OH-initiated oxidation of m-xylene: effects of relative humidity on yield and chemical composition

Abstract. The effect of relative humidity (RH) on secondary organic aerosol (SOA) formation from the photooxidation of m-xylene initiated by OH radicals in the absence of seed particles was investigated in a Teflon reactor. The SOA yields were determined based on the particle mass concentrations measured with a scanning mobility particle sizer (SMPS) and reacted m-xylene concentrations measured with a gas chromatograph–mass spectrometer (GC-MS). The SOA components were analyzed using a Fourier transform infrared (FTIR) spectrometer and an ultrahigh-performance liquid chromatograph–electrospray ionization–high-resolution mass spectrometer (UPLC-ESI-HRMS). A significant decrease was observed in SOA mass concentration and yield variation with the increasing RH conditions. The SOA yields are 14.0 %–16.5 % and 0.8 %–3.2 % at low RH (14 %) and high RH (74 %–79 %), respectively, with the difference being nearly 1 order of magnitude. Some of the reduction in the apparent yield may be due to the faster wall loss of semi-volatile products of oxidation at higher RH. The chemical mechanism for explaining the RH effects on SOA formation from m-xylene–OH system is proposed based on the analysis of both FTIR and HRMS measurements, and the Master Chemical Mechanism (MCM) prediction is used as the assistant. The FTIR analysis shows that the proportion of oligomers with C-O-C groups from carbonyl compounds in SOA at high RH is higher than that at low RH, but further information cannot be provided by the FTIR results to well explain the negative RH effect on SOA formation. In the HRMS spectra, it is found that C2H2O is one of the most frequent mass differences at low and high RHs, that the compounds with a lower carbon number in the formula at low RH account for a larger proportion than those at high RH and that the compounds at high RH have higher O : C ratios than those at low RH. The HRMS results suggest that the RH may suppress oligomerization where water is involved as a by-product and may influence the further particle-phase reaction of highly oxygenated organic molecules (HOMs) formed in the gas phase. In addition, the negative RH effect on SOA formation is enlarged based on the gas-to-particle partitioning rule.

Real-time analysis of the homogeneous and heterogeneous reactions of pyrene with ozone by SPAMS and CRD-EAS

Single particle aerosol mass spectrometry (SPAMS) and Cavity ring-down aerosol extinction albedo spectroscopy (CRD-EAS) were applied in this work to real-time investigate the chemical and physical characteristics of the homogeneous and heterogeneous reactions of O3 with pyrene in a Teflon reaction chamber. Suspended pyrene coated polystyrene latex spheres (PSLs) were generated by vaporization-condensation. Ozonation products and particle size distribution during the reactions were detected in real-time using a SPAMS instrument. Among these products, the peaks at m/z of 262 and 278, assigned to 4,5,9,10-dipyrenequinone and 1-hydroxy-4,5,9,10-dipyrenequinone, respectively, were first detected to our knowledge. The mechanism for the formation of reaction product was also proposed based on the real time monitoring. With increasing the ozone concentration, the size growth of the original pyrene-coated particles and the formation of new fine particles and size growth were observed continuously. The optical characteristics were also investigated using a laboratory-developed CRD-EAS instrument. The extinction and scattering coefficients were observed to increase approximately five and four times, respectively. The absorption coefficient also increased because more polar oxidation products coated on the particles exhibiting higher light absorption ability than pyrene, and meanwhile, the single scattering albedo reduced from 0.88 to 0.77 which indicated the reactions could cause positive climate forcing. Using the on-line mass spectrometry and optic spectroscopy instruments, a systematic analysis method was developed to characterize the chemical and physical properties of homogeneous and heterogeneous reactions in real-time, which will help to investigate and understand the formation of new particles and particle growth in the atmosphere.