The light-absorbing organic aerosol referred to as brown carbon (BrC) affects the global radiative balance. The linkages between its molecular composition and light absorption properties and how ...environmental factors influence BrC composition are not well understood. In this study, atmospheric dissolved organic matter (ADOM) in 55 aerosol samples from Guangzhou was characterized using Fourier transform ion cyclotron resonance mass spectrometry and light absorption measurements. The abundant components in ADOM were aliphatics and peptide-likes (in structure), or nitrogen- and sulfur-containing compounds (in elemental composition). The light absorption properties of ADOM were positively correlated with the levels of unsaturated and aromatic structures. Particularly, 17 nitrogen-containing species, which are identified by a random forest, characterized the variation of BrC absorption well. Aggregated boosted tree model and nonmetric multidimensional scaling analysis show that the BrC composition was largely driven by meteorological conditions and anthropogenic activities, among which biomass burning (BB) and OH radical were the two important factors. BrC compounds often accumulate with elevated BB emissions and related secondary processes, whereas the photolysis/photooxidation of BrC usually occurs under high solar radiance/•OH concentration. This study first illuminated how environmental factors influence BrC at the molecular level and provided clues for the molecular-level research of BrC in the future.
Microplastics (MPs) are one of the most prevalent and diverse contaminants, and wastewater treatment plants are significant MP aggregators. Controlling the pollution caused by microplastics requires ...an understanding of how they age. The properties of the MPs photoaging process under the influence of salt ions typical of biological nitrogen elimination processes were disclosed in this work. The aging process of polyvinyl chloride microplastics (PVC-MPs) was greatly slowed down by greater HCO3− and NO2− concentrations, according to a comparison of the carbonyl index changes that occurred during photoaging. The carbonyl index had a negative correlation with the thermal stability of the photo-aged PVC-MPs, and aging accelerated the elimination of chlorine from the water. The samples were aged by UV radiation after 36 h at 40 °C, and the amount of chlorine eliminated was 10.13 times greater than that of the original MPs samples. It was discovered that the leachate concentration of aged MPs dramatically increased with decreasing particle size and was positively connected with the level of aging by comparing the concentration of leachate for two particle sizes (1 mm and 100 m). Photoaging caused MPs to become rougher, which in turn improved the NO3−-N, NH4+-N, and NO2−-N adsorption by PVC-MPs.
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•NO2− and HCO3− retard the photoaging process of PVC-MPs.•MPs with the same mass and smaller particles release more pollutants during the aging process.•Aging promotes the surface chlorine of PVC-MPs to become unstable and thus more susceptible to release.•Aging promotes the adsorption of NO3−, NO2− and NH4+ by PVC-MPs.
This study demonstrates the synthesis of an efficient photocatalyst, CuO/TiO
2
heterojunction, for selective aerobic photo-oxidation of methanol to methyl formate. The CuO nanoparticles (size: 3.5 ± ...1.0 nm) are particularly deposited at the {101} facet of anatase TiO
2
nanosheets to minimize recombination of photo-generated electrons/holes. The photocatalysts are characterized by different methods, including powder X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis spectroscopy, X-ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy, and hydrogen temperature-programmed reduction (H
2
-TPR). The heterojunction catalysts exhibit an excellent photocatalytic performance under mild conditions (
i.e.
, 25-45 °C and gas reactions under UV irradiation with a wavelength of 365 nm) for the selective photo-oxidation of methanol using 0.5 vol% oxygen (O
2
) as an oxidizing agent. The 5 wt% CuO/TiO
2
photocatalyst exhibits a decent 95% methanol conversion with over 85% selectivity towards the formation of methyl formate. The by-product of the reaction is found to be merely CO
2
, which can be readily eliminated from the product. The formation rate for the methyl formate is 10.8 mmol g
−1
h
−1
at 25 °C, which is considerably higher than that for the corresponding CuO and TiO
2
nanosheets as well as for conventional catalysts. The superior catalytic activity of the CuO/TiO
2
is associated with its unique electronic structure and the synergistic effects at the interface of the photocatalysts' components. The results of this study offer guidelines for design of a new synthetic strategy for preparation of efficient photocatalysts for selective oxidation of methanol to methyl formate and related reactions.
This study demonstrates the synthesis of an efficient photocatalyst, CuO/TiO
2
heterojunction, for selective aerobic photo-oxidation of methanol to methyl formate.
Photocatalytic selective oxidation represents an eco-friendly strategy for chemical transformation. Herein, a lead-free halide perovskite Cs3Bi2Br9 combined with TiO2 was facilely synthesized and ...applied for efficient photocatalytic selective oxidation of sulfides to sulfoxides with high yields and good compatibility under mild conditions. The Cs3Bi2Br9/TiO2 composite exhibited enhanced photocatalytic activity compared to bare Cs3Bi2Br9 particles, which could be ascribed to the strong interaction between Cs3Bi2Br9 NCs and TiO2 markedly accelerating the separation and transfer efficiency of photogenerated electron–hole pairs and simultaneously suppressing their recombination.
Glyoxal is an important precursor of aqueous secondary organic aerosol (aqSOA). Its photooxidation to form organic acids and oligomers and reactions with reduced nitrogen compounds to form brown ...carbon (BrC) have been extensively investigated separately, although these two types of reactions can occur simultaneously during the daytime. Here, we examine the reactions of glyoxal during photooxidation and BrC formation in premixed NH
NO
+ Glyoxal droplets. We find that nitrate photolysis and photosensitization can enhance the decay rates of glyoxal by a factor of ∼5 and ∼6 compared to those under dark, respectively. A significantly enhanced glyoxal decay rate by a factor of ∼12 was observed in the presence of both nitrate photolysis and photosensitization. Furthermore, a new organic phase was formed in irradiated NH
NO
+ Glyoxal droplets, which had no noticeable degradation under prolonged photooxidation. It was attributed to the imidazole oxidation mediated by nitrate photolysis and/or photosensitization. The persistent organic phase suggests the potential to contribute to SOA formation in ambient fine particles. This study highlights that glyoxal photooxidation mediated by nitrate photolysis and photosensitization can significantly enhance the atmospheric sink of glyoxal, which may partially narrow the gap between model predictions and field measurements of ambient glyoxal concentrations.
The formation and evolution of secondary organic aerosol
(SOA) were investigated at Yorkville, GA, in late summer (mid-August to mid-October 2016). The organic aerosol (OA) composition was
measured ...using two online mass spectrometry instruments, the
high-resolution time-of-flight aerosol mass spectrometer (AMS) and the
Filter Inlet for Gases and AEROsols coupled to a high-resolution
time-of-flight iodide-adduct chemical ionization mass spectrometer
(FIGAERO-CIMS). Through analysis of speciated organics data from
FIGAERO-CIMS and factorization analysis of data obtained from both
instruments, we observed notable SOA formation from isoprene and
monoterpenes during both day and night. Specifically, in addition to
isoprene epoxydiol (IEPOX) uptake, we identified isoprene SOA formation from non-IEPOX pathways
and isoprene organic nitrate formation via photooxidation in the presence of
NOx and nitrate radical oxidation. Monoterpenes were found to be the
most important SOA precursors at night. We observed significant
contributions from highly oxidized acid-like compounds to the aged OA factor
from FIGAERO-CIMS. Taken together, our results showed that FIGAERO-CIMS
measurements are highly complementary to the extensively used AMS
factorization analysis, and together they provide more comprehensive
insights into OA sources and composition.
Fast α‐oxyamination of stable enolates, silyl enol ethers, and in situ deprotonated dialkyl 2‐oxoalkane phosphonates and diphenyl‐2‐oxoalkyl phosphine oxides was performed in the presence of ...Ru(bpy)32+ (bpy = 2,2′‐bipyridyl) as a photocatalyst, 2,2,6,6‐tetramethylpiperidine nitroxide (TEMPO), and visible light. The key step was the light‐induced one‐electron oxidation of TEMPO into the 2,2,6,6‐tetramethylpiperidine‐1‐oxoammonium ion, which was nucleophilically attacked to yield α‐functionalized carbonyl compounds. The reaction time was significantly reduced by the use of the microreactor flow technique.
Fast and efficient visible‐light‐mediated α‐oxyamination of β‐keto enolates, silyl enol ethers, and deprotonated dialkyl 2‐oxoalkanephosphonates occurs in a microreactor in the presence of Ru(bpy)32+ (bpy = 2,2′‐bipyridyl) as a photocatalyst, 2,2,6,6‐tetramethylpiperidine nitroxide (TEMPO), and blue light. The key step is the light‐induced one‐electron oxidation of TEMPO.
Abstract
An important industrial process that often occurs on the surface of a heterogeneous catalyst using thermochemical or photochemical could help in the oxidation of methanol-based wastewater to ...formaldehyde. Titania-based photocatalysts have drawn a lot of interest from scientists because they are a reliable and affordable catalyst material for photocatalytic oxidation processes in the presence of light energy. In this study, a straight-forward hydrothermal method for producing n-TiO
2
@α-Fe
2
O
3
composite photocatalysts and hematite (α-Fe
2
O
3
) nanocubes has been done. By adjusting the ratio of n-TiO
2
in the prepared composite photocatalysts, the enhancing influence of the nitrogen-doped titania on the photocatalytic characteristics of the prepared materials was investigated. The prepared materials were thoroughly characterized using common physiochemical methods, such as transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX), X-ray photoelectrons spectroscopy (XPS), physisorption (BET), and others, in order to learn more about the structure The results obtained showed that nitrogen-doped titania outperforms non-doped titania for methanol photooxidation. The addition of nitrogen-doped titania to their surfaces resulted in an even greater improvement in the photooxidation rates of the methanol coupled with hematite. The photooxidation of methanol in the aqueous solution to simulate its concentration in the wastewater has been occurred. After 3 h, the four weight percent of n-TiO
2
@α-Fe
2
O
3
photocatalyst showed the highest rate of HCHO production.
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•Bi modified Bi2S3 pillared g-C3N4 photocatalyst (BBC) is successfully developed in a mixed solvothermal environment.•The possible reaction mechanisms for g-C3N4/Bi2S3 and the novel ...photocatalyst BBC are proposed.•BBC exhibits higher photocatalytic reduction and oxidation performance than g-C3N4/Bi2S3 and pure g-C3N4.•Improved charge separation is responsible for the enhanced photocatalytic performance.•. The photocatalytic mechanism of BBC is tentatively proposed.
A novel efficient Bi modified Bi2S3 pillared g-C3N4 (BBC) plasmonic semiconductor photocatalyst has been successfully developed in a mixed solvothermal environment. The photocatalytic abilities of the as-prepared samples are examined by the photocatalytic reduction of Cr(VI) and oxidation of tetracycline (TC). And the chemical composition, structure, morphology and photo-absorption properties of the photocatalysts have been investigated by XRD, FT-IR, XPS, TEM, HRTEM and DRS methods, respectively. It is found that the addition of triethanolamine (TEA) results in the formation of the pillared-g-C3N4 (PG) nanostructure. The agglomeration of g-C3N4 nanosheets moiety and Bi2S3 nanorods moiety can be both hindered effectively by the special PG structure. And the photocatalytic results indicate that BBC exhibits the best photoreduction and photooxidation performances among all the samples, and meanwhile possesses superior photo-stability during the recycling runs. The enhanced photocatalytic activity of BBC could be ascribed to the furtherance of charge separation, localized surface plasma resonance (SPR) effect of metallic Bi and the excellent reaction interface. Finally, a tentative mechanism of BBC for photocatalytic reduction of Cr(VI) and oxidation of TC is discussed in detail.
Photosensitizers have attracted considerable attention in various fields such as organic synthesis and medical care. For the development of high-performance photosensitizers, highly efficient and ...persistent singlet oxygen generators (1O2) having a high oxidation tolerance are strongly required. This study presents a detailed investigation of dithieno3,2-b:2′,3′-darsole-fluorene copolymer for its 1O2 generation ability and application as a photooxidation catalyst in vital organic reactions. Photoirradiation of an air-saturated solution of the polymer generates 1O2, which was detected by 1O2 scavengers such as dihydronaphthoquinone and diphenylisobenzofuran. The polymer photosensitizer was completely stable in the presence of the strong oxidant 1O2. The photosensitizer showed the highest quantum yield of 1O2 generation (Φ = 0.54) in single-component main-chain type π-conjugated polymers. The quantum yield of the arsenic-free analogue of the polymerbithiophene-fluorene copolymerwas significantly lower (Φ = 0.14), suggesting that the heavy-atom effect of arsenic can improve the efficiency of intersystem crossing (ISC) from the singlet excited state to the triplet excited state of the photosensitizer. In addition, when utilized as a recyclable photocatalyst for the oxidation reaction, the photosensitizer exhibited excellent oxidation resistance without losing its recognizable catalytic activity. Finally, we demonstrated the release of 1O2 into the air by a film of the present polymer. Persistent 1O2 generation was observed on film irradiation without polymer decomposition. These results suggested that the polymer exhibited excellent oxidation resistance in solution as well as in the solid state. The present molecular design concept of the photosensitizer using the main group element can facilitate the development of further functional optical materials.
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