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ABSTRACT: Three types of macromolecular organic matters (MOMs), i.e. humic acid (HA), kerogen+black carbon (KB), and black carbon (BC) were extracted from marine sediments of Xiamen Gulf, southeast of China. The chemical composition, morphological property and source of the three extractions were characterized by elemental analyzer/isotope ratio mass spectrometry (EA/IRMS) and scanning electron microscope (SEM). The results showed that KB was the predominant fraction in MOMs, which accounted for 61.79%-89.15% of the total organic content (TOC), while HA consisted less than 5%. The relative high contents of kerogen and BC, and low contents of HA in the samples indicated that anthropogenic input might be the major source of organic matter in marine sediments near the industrial regions. The characterization of SEM, not only revealed morphological properties of the three fractions, but also allowed a better understanding of the source of MOMs. The delta13C values of the three fractions suggested that materials from terrestrial C3 plants were predominant. Furthermore, the anthropogenic activities, such as the discharge of sewage, coal and biomass combustion from industry nearby and agricultural practices within drainage basin of the Jiulong River, were remarkably contributed to the variations in delta13C values of MOMs in the offshore marine sediments.
Journal of Environmental Sciences 02/2013; 25(2):287-94. · 1.66 Impact Factor
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ABSTRACT: We report a facile approach to synthesize narrow and long graphene nanoribbons (GNRs) by sonochemically cutting chemically
derived graphene sheets (GSs). The yield of GNRs can reach ∼5 wt% of the starting GSs. The resulting GNRs are several micrometers
in length, with ∼75% being single-layer, and ∼40% being narrower than 20 nm in width. A chemical tailoring mechanism involving
oxygen-unzipping of GSs under sonochemical conditions is proposed on the basis of experimental observations and previously
reported theoretical calculations; it is suggested that the formation and distribution of line faults on graphite oxide and
GSs play crucial roles in the formation of GNRs. These results open up the possibilities of the large-scale synthesis and
various technological applications of GNRs.
KeywordsGraphene nanoribbon-graphene oxide-synthesis-sonochemical cutting
Nano Research 04/2012; 3(1):16-22. · 6.97 Impact Factor
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ABSTRACT: Elemental and organic carbon (EC and OC), the principal short-lived climate forcers, were measured in fine particulate matter (PM 2.5) collected at urban and rural sites in continental edge in Southern China. The carbonaceous matter (CM) contributed an average of 28.5 ± 7.2% (1 SD) of the mass of PM 2.5 in urban areas and 30.3 ± 8.2% in rural areas. The annual average OC concentrations in PM 2.5 in urban and rural areas were 7.6 ± 4.3 and 5.7 ± 3.1 μg/m 3 , respectively; and the annual average EC concentrations were 2.4 ± 0.8 and 1.3 ± 0.7 μg/m 3 , respectively. The higher EC concentration in urban area than in rural area showed significant anthropogenic emissions to the urban atmosphere. EC and OC concentrations displayed good correlation in samples collected in urban area during winter monsoon season, suggesting a dominant emission source (mostly traffic-related) in urban area. The carbonaceous aerosol pollution in the rural coastal receptor area can be attributed to the local emission and transport of air pollutants from urbanized areas in the eastern part of China. The surface observation together with backward trajectory analysis, satellite imaging, and meteorological simulation indicate that air pollutants transported from emission hotspots in the urbanized Eastern China area had caused an increase in the concentration of carbonaceous aerosols in the rural continental edge by a factor of 2–3. This significant aerosol forcing of the Chinese outflow plume should be paid attention in the study of air quality and climate changes in Eastern/Southern Asia.
Aerosol and Air Quality Research 01/2012; · 2.83 Impact Factor
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ABSTRACT: In China, the areas that are undergoing rapid urban growth are faced with increasingly more complicated air pollution problems. Sources of air pollution need to be identified and their contributions quantified. In this study, PM2.5 (particulate matter with aerodynamic diameters < or =2.5 microm), PM2.5-10 (particulate matter with aerodynamic diameters 2.5-10 microm), organic carbon (OC), and elemental carbon (EC) concentrations were measured from April to July 2009 at four selected areas in Xiamen (the downtown area, an industrial park, a suburb, and one remote site). The contributions of carbonaceous aerosols to PM2.5 and PM2.5-10 were 20-30% and 10-20%, respectively, indicating that finer particles contained more carbonaceous aerosols. The EC concentrations in PM2.5 at the downtown, industrial, suburb, and remote sites were 2.16 +/- 0.61, 2.05 +/- 0.45, 1.69 +/- 0.54, and 0.65 +/- 0.43 microg m-3, respectively, showing a decrease from the urban and industrial hotspots to the surrounding areas. These data show that carbonaceous aerosols emitted from the combustion of fossil fuels in urban and industrial hotspots influence air quality at the regional scale. Higher levels of PM2.5 and PM2.5-10 were observed at the suburb site compared to the urban and industrial sites. Peak EC concentrations in PM2.5 were observed during the morning and evening rush hours. However, peak PM2.5 levels at the suburb site were observed around noon, which coincides with construction work hours, instead of the morning and evening rush hours when emissions from combustion dominated. These findings indicate that both fuel combustion and construction have exacerbated air pollution in coastal and urban areas in China.
Journal of the Air & Waste Management Association (1995) 11/2011; 61(11):1160-5. · 1.52 Impact Factor
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ABSTRACT: An intensive sampling program was conducted from October 2008 to September 2009 at the five different environmental sites in Xiamen, Fujian Province, to study the spatial and temporal characteristics of Polycyclic Aromatic Hydrocarbons (PAHs) in the gaseous and particulate phase, respectively. The PAHs concentrations at different sites were quite distinct during four seasons. The average concentrations of PAHs in winter were about 8.4 times higher than those in spring, and the concentrations of background were 0.56 times lower than those of industrial area. In addition, the higher temperature in summer affected the particle/gas partitioning of PAHs and led to the higher concentrations of gaseous PAHs. Diagnostic ratios of PAHs, which were employed to indicate the primary sources of PAHs in Xiamen, showed that the traffic vehicle exhaust was the largest contributor and the primary source for PAHs in Xiamen, especially in urban area; while the stationary combustion processes, such as petrochemical factories and power plants, were mainly responsible for PAHs sources in the industrial areas. The health risk of PAHs in the particulate phase was higher than those of the gaseous phase at the five sampling sites. The average toxic equivalent (BaPeq) of the benzo[a]pyrene values for PAHs were 0.14, 0.32, 1.38 and 3.59 ng m(-3) in spring, summer, autumn and winter, respectively. Furthermore, the results of average BaPeq in all four seasons indicated that the health risks of particulate PAHs were higher than those of the gaseous PAHs at different sampling sites.
Science of The Total Environment 09/2011; 409(24):5318-27. · 3.29 Impact Factor
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ABSTRACT: Xiamen, located on the southeastern coastal line of China, is undergoing rapid urbanization and industrialization, so its air quality has a trend of degradation. However, studies on level, temporal and spatial changes of fine particles (PM2.5) and their carbonaceous fractions are scarce. In this article, abundance, sources, seasonal and spatial variations, distribution of organic carbon (OC) and elemental carbon (EC) in PM2.5, were studied at suburban, urban and industrial sites in Xiamen during four season-representative months in 2009-2010. PM2.5 samples were collected with middle volume sampler and were analyzed for OC and EC with thermal optical transmittance (TOT) method. Results showed that the annual average PM2.5 concentrations were 63.88-74.80 microg/m3 at three sites. While OC and EC concentrations were in the range of 15.81-19.73 microg/m3 and 2.74-3.49 microg/m3, respectively, and clearly presented the summer minima and winter maxima in this study. The carbonaceous aerosol accounted for 42.8%-47.3% of the mass of PM2.5. The annual average of secondary organic carbon (SOC) concentrations in Xiamen were 9.23-11.36 micro/m3, accounting for approximately 56% of OC. Strong correlations between OC and EC was found in spring (R2 = 0.50) and autumn (R2 = 0.73), suggesting that there were similar emission and transport processes for carbonaceous aerosols in these two seasons, while weak correlations were found in summer (R2 = 0.33) and winter (R2 = 0.41). The OC/EC ratios in PM2.5 varied from 2.1 to 8.7 with an annual average of 5.7, indicating that vehicle exhaust, coal smoke and biomass burning were main source apportionments of carbonaceous fractions in Xiamen.
Journal of Environmental Sciences 01/2011; 23(8):1342-9. · 1.66 Impact Factor
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ABSTRACT: Xiamen, as a southeastern coastal city, is hardly affected by dust storms (DSs) sourced from the arid and semiarid areas in North or Northwestern China in spring. Unfortunately, during 21–23 March, 2010, the heaviest DS that had been recorded in past 50 years affected air quality seriously. Continuous particulate matter monitor was employed for the observation of PM 2.5 (aerodynamic diameter less than 2.5 μm) and PM 10 (aerodynamic diameter less than 10 μm) during 20–24 March 2010. Total suspended particulate (TSP) samples during this episode were also collected and their characteristics of element species and water-soluble ions were illustrated to characterize the heavy pollution in Xiamen. The DS peaked on 21 March, with the highest concentrations of 454.51 μg/m 3 and 990.24 μg/m 3 for PM 2.5 and PM 10 , respectively. The variations of ratio for PM 2.5 /PM 10 indicated that PM 10 was the main particles that were influenced by DS. The higher ratios (DS/Non dust days) of Al, Fe, Mg, Mn, and Ba were over 5.0, which are primarily from a soil. However, the ratios of Zn, V, As, Ti, and Cr, mainly from anthropogenic sources, had a range of 1.3 to 3.4. These results suggested that the soil-sourced species made more contribution to DS particles compared to the anthropogenic species. The mass fractions of water-soluble ions in TSP indicated that the concentrations of K + , Ca 2+ , Mg 2+ , F -, NO 2 -, and NO 3 -were evidently higher in DS samples than those of non-DS samples. The compositions of ions in dust aerosols showed that the multi-sources of aerosol were ubiquitous during the dust episode. The highest concentrations of sulfate and nitrate occurred in the day when dust ended in Xiamen, which demonstrated the formation of secondary pollutants from dust during the long-range transport, as well as from local environmental pollution.
01/2011; 11:299-308.
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ABSTRACT: We developed an ambient pressure chemical vapor deposition (CVD) for rapid growth of high-quality graphene films on Cu foils. The quality and growth rate of graphene films are dramatically increased with decreasing H <sub>2</sub> concentration. Without the presence of H <sub>2</sub> , continuous graphene films are obtained with a mean sheet resistance of <350 Ω/ sq and light transmittance of 96.3% at 550 nm. Because of the ambient pressure, rapid growth rate, absence of H <sub>2</sub> and readily available Cu foils, this CVD process enables inexpensive and high-throughput growth of high-quality graphene films.
Applied Physics Letters 12/2010; · 3.84 Impact Factor
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ABSTRACT: Large-area sheets are highly desirable for fundamental research and technological applications of graphene. Here we introduce a modified chemical exfoliation technique to prepare large-area graphene oxide (GO) sheets. The maximum area of the GO sheets obtained can reach ∼40000 μm(2). We found that the GO area is strongly correlated with the C-O content of the graphite oxide, which enables the area of the synthesized GO sheets to be controlled. By simply changing oxidation conditions, GO sheets with an average area of ca. 100-300, ca. 1000-3000, and ∼7000 μm(2) were selectively synthesized. For transparent conductive film applications, thin GO films were fabricated by self-assembly on a liquid/air interface and reduced by HI acid. We found that the sheet resistance of the reduced GO (rGO) films decreases with increasing sheet area at the same transmittance because of the decrease in the number of intersheet tunneling barriers. The rGO film made from GO sheets with an average area of ∼7000 μm(2) shows a sheet resistance of 840 Ω/sq at 78% transmittance, which is much lower than that (19.1 kΩ/sq at 79% transmittance) of a rGO film made from small-area GO sheets of ca. 100-300 μm(2), and comparable to that of graphene films grown on Ni by chemical vapor deposition.
ACS Nano 09/2010; 4(9):5245-52. · 10.77 Impact Factor
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ABSTRACT: Guangzhou is the central city in the Pearl River Delta (PRD), China, and is one of the most polluted cities in the world. To characterize the ambient falling dust pollution, two typical sampling sites: urban (Wushan) and suburban (University Town) areas in Guangzhou city were chosen for falling dust collection over 1 year at time intervals of 1 or 2 months. The flux of dry deposition was calculated. In addition, mineral composition and morphology of atmospheric falling dust were studied by X-ray diffraction, scanning electron microscopy, and microscopic observation. The results revealed that the dust flux in Guangzhou city was 3.34-3.78 g/(m(2) month) during the study period. The main minerals in the dust were quartz, illite, calcite, kaolinite, gypsum, plagioclase, dolomite, and amorphous matter. The morphological types included grained and flaky individual minerals, chain-like aggregates, spherical flying beads, and irregular aggregates, with the chain-like and spherical aggregates indicators of industrial ash. The major dusts were derived from industrial and construction activities. The gypsum present in the dust collected in winter season was not only derived from cement dust but may also have originated from the reaction of calcic material with sulfuric acids resulting from photooxidation of SO(x) and NO(x), which confirmed serious air pollution due to SO(x) and NO(x) in Guangzhou. The abatement of fossil fuel combustion emissions and construction dust will have a significant beneficial effect on dust reduction.
Air Quality Atmosphere & Health 09/2010; 3(3):139-147.
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ABSTRACT: Hydrous ruthenium oxide (RuO2)/graphene sheet composites (ROGSCs) with different loadings of Ru are prepared by combining sol-gel and low-temperature annealing processes. The graphene sheets (GSs) are well-separated by fine RuO2 particles (5-20 nm) and, simultaneously, the RuO2 particles are anchored by the richly oxygen-containing functional groups of reduced, chemically exfoliated GSs onto their surface. Benefits from the combined advantages of GSs and RuO2 in such a unique structure are that the ROGSC-based supercapacitors exhibit high specific capacitance (similar to 570 F g(-1) for 38.3 wt% Ru loading), enhanced rate capability, excellent electrochemical stability (similar to 97.9% retention after 1000 cycles), and high energy density (20.1 Wh kg(-1)) at low operation rate (100 mA g(-1)) or high power density (10000 W kg(-1)) at a reasonable energy density (4.3 Wh kg(-1)). Interestingly, the total specific capacitance of ROGSCs is higher than the sum of specific capacitances of pure GSs and pure RuO2 in their relative ratios, which is indicative of a positive synergistic effect of GSs and RuO2 on the improvement of electrochemical performance. These findings demonstrate the importance and great potential of graphene-based composites in the development of high-performance energy-storage systems.
Advanced Functional Materials 08/2010; 20(20):3595 - 3602. · 10.18 Impact Factor
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ABSTRACT: We report a facile strategy to synthesize the nanocomposite of Co(3)O(4) nanoparticles anchored on conducting graphene as an advanced anode material for high-performance lithium-ion batteries. The Co(3)O(4) nanoparticles obtained are 10-30 nm in size and homogeneously anchor on graphene sheets as spacers to keep the neighboring sheets separated. This Co(3)O(4)/graphene nanocomposite displays superior Li-battery performance with large reversible capacity, excellent cyclic performance, and good rate capability, highlighting the importance of the anchoring of nanoparticles on graphene sheets for maximum utilization of electrochemically active Co(3)O(4) nanoparticles and graphene for energy storage applications in high-performance lithium-ion batteries.
ACS Nano 06/2010; 4(6):3187-94. · 10.77 Impact Factor
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ABSTRACT: An intensive sampling program had been undertaken in autumn (October, 2008) and winter (December, 2008 and January, 2009) at urban (Xiamen University and Xianyue residential area), suburban (Institute of Urban Environment), industrial area (Lulian Hotel) and background (Tingxi Reservoir) in Xiamen, Fujian Province, to characterize the atmospheric concentration and gas-particle phase partitioning of PAHs. The average concentration of total PAHs in winter was almost 1.7 times higher than those in autumn. The log scale plot of Kp versus sub-cooled liquid vapor pressure (P(L)0 for all the data of autumn and winter season samples gave significantly different slopes. The slope for the winter samples (-0.72) was steeper than that for the autumn samples (-0.58). The partitioning results indicated that slope values varied depending on characteristics of specific site, source region and meteorological conditions which play important roles in the partitioning of PAHs. In addition, local emission sources had a stronger effect on partitioning results than long-transported polluted plume. The sources of PAHs in five sampling sites in Xiamen also have been discussed initially. Diagnostic ratios showed that the primary source of PAHs in urban, suburban and industrial area was from vehicle exhausts. While emission from petrochemical factory and power plant was another main contributor to industrial area.
Journal of Environmental Sciences 01/2010; 22(7):1014-22. · 1.66 Impact Factor
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ABSTRACT: Freestanding and flexible graphene/polyaniline composite paper was prepared by an in situ anodic electropolymerization of polyaniline film on graphene paper. This graphene-based composite paper electrode, consisting of graphene/polyaniline composite sheets as building blocks, shows a favorable tensile strength of 12.6 MPa and a stable large electrochemical capacitance (233 F g(-1) and 135 F cm(-3) for gravimetric and volumetric capacitances), which outperforms many other currently available carbon-based flexible electrodes and is hence particularly promising for flexible supercapacitors.
ACS Nano 07/2009; 3(7):1745-52. · 10.77 Impact Factor
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ABSTRACT: We developed a hydrogen arc discharge exfoliation method for the synthesis of graphene sheets (GSs) with excellent electrical conductivity and good thermal stability from graphite oxide (GO), in combination with solution-phase dispersion and centrifugation techniques. It was found that efficient exfoliation and considerable deoxygenation of GO, and defect elimination and healing of exfoliated graphite can be simultaneously achieved during the hydrogen arc discharge exfoliation process. The GSs obtained by hydrogen arc discharge exfoliation exhibit a high electrical conductivity of approximately 2 x 10(3) S/cm and high thermal stability with oxidization resistance temperature of 601 degrees C, which are much better than those prepared by argon arc discharge exfoliation (approximately 2 x 10(2) S/cm, 525 degrees C) and by conventional thermal exfoliation (approximately 80 S/cm, 507 degrees C) with the same starting GO. These results demonstrate that this hydrogen arc discharge exfoliation method is a good approach for the preparation of GSs with a good quality.
ACS Nano 03/2009; 3(2):411-7. · 10.77 Impact Factor
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ABSTRACT: Diurnal air samples were collected from the E-waste dismantling region Guiyu and the underwear industry region Chendian. This was the first report to present the diurnal variation of PBDEs in the atmosphere. The average concentrations of 11 PBDE congeners were 11,742 pgm(-3) in the daytime, and 4830 pgm(-3) at night in Guiyu, while the concentrations were lower in Chendian with 376 pgm(-3) in the daytime, and 237 pgm(-3) at night. BDE-209 accounted for 22% and 31.3% of the total PBDEs in Guiyu and Chendian, respectively. The diurnal variation trends of BDE-47, -99, -153, -183, and -209 were also analyzed in detail in the two regions.
Environmental pollution (Barking, Essex: 1987) 01/2009; 157(3):1051-7. · 3.43 Impact Factor
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ABSTRACT: The organic matter in tropospheric aerosol plays an important role in atmospheric physical and chemical processes. The bulk of organic matter, representing a significant proportion of the total suspended particulate (TSP) mass, is bound to polymeric material whose structure and properties are largely unknown. Here we used thermodesorption gas chromatography/mass spectrometry (Td-GC/MS) to study organic compounds of low molecular mass and pyrolysis gas chromatography/mass spectrometry (Py-GC/MS) to characterize the chemical structure of macromolecules in TSP samples collected in different seasons from different sites in Guangzhou. n-Alkanes, fatty acids and nitriles were the predominant compounds in the thermodesorption products, whereas aromatics, fatty acids, nitriles and n-alkanes/alkenes were the major compounds in the pyrolysates. The results indicated that aromatics were main units in macromolecules. The fatty acids and nitriles formed from carboxylic ammonium salts were detected in both thermodesorption products and pyrolysates at a certain concentration, indicating the importance of these compounds in TSP formation. The TSP source mainly determined the occurrence of compounds in samples from urban, suburban and forest sites, whereas the TSP source and formation process maybe controlled the seasonal variation in compounds detected. High levels of nitriles in summer samples from suburban and forest sites coincide with the release of ammonium from the land and of fatty acids from vegetation at these sites.
Journal of Environmental Sciences 01/2009; 21(12):1658-66. · 1.66 Impact Factor
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ABSTRACT: We report a simple but highly-effective hydrohalic acid reducing method to reduce graphene oxide (GO) films into highly conductive graphene films without destroying their integrity and flexibility at low temperature based on the nucleophilic substitution reaction. GO films reduced for 1 h at 100 °C in 55% hydroiodic (HI) acid have an electrical conductivity as high as 298 S/cm and a C/O ratio above 12, both of which are much higher than films reduced by other chemical methods. The reduction maintains good integrity and flexibility, and even improves the strength and ductility, of the original GO films. Based on this reducing method, a flexible graphene-based transparent conductive film with a sheet resistance of 1.6 kΩ/sq and 85% transparency was obtained, further verifying the advantage of HI acid reduction.
Carbon.
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ABSTRACT: The chemical compositions of organic macromolecules in dust are very complex and have not yet been investigated in detail. In this paper, we study the organic macromolecules in 12 dust samples collected from an urban and suburban area of Guangzhou, China. Organic macromolecules in the dust were firstly separated into humic acids (HA), kerogen and black carbon (KB) and black carbon (BC) fractions by chemical treatment with NaOH, HCl/HF and K2Cr2O7/H2SO4, respectively. The isolated fractions were subsequently characterized using elementary analysis (EA), organic petrographic examination (OPE), scanning electron microscopy (SEM), and solid state 13C cross-polarization and magic angle spinning nuclear magnetic resonance spectroscopy (13C-CP/MAS NMR) etc. The results showed that the major organic macromolecules were KB, which accounted for 64.8%–95.8% of total organic carbon (TOC) in the dusts. Isolated HAs were characterized by high H/C, N/C and O/C atomic ratios, and high carboxyl, methoxyl and aliphatic carbon contents in the overall carbon structure; meanwhile, kerogens (K) showed lower H/C, N/C and O/C atomic ratios than those of HAs and had chemical compositions enriched in hydroxyl carbon; further, the optical features of K were similar to those of “vitrinite”. BC is formed from the combustion of biomass and fossil fuels, so that aromatic and aliphatic carbons are the most important components in its carbon skeleton. Under the microscope, BC appeared to belong to the petrographic groups, such as “semifusinte” and “fusinite”, and showed a distinct texture when observed by SEM. Compared with the HAs and K isolated from soils and sediments, HAs in dust were relatively lower in aromatic carbon and K in dust was always “type III”. These results are strongly consistent with the dust samples originating from the photochemical degradation of volatile organic compounds, in contrast to the geological HAs and K which are sourced from the biodegradation of lignin and algae or from bacterial activities in water and sediment.Highlights► It is the first time using the isolation and characterization approaches applied to dust, and get HA, KB and BC. ► The main source of HA and K in dust is derived from photochemical reactions of VOCs. ► The main source of BC in dust is formed from the combustion of biomass and fossil fuels. ► The results we obtained strongly suggest HA and K in the dust originating from the photochemical degradation of VOCs. ► HA in dust has a relatively lower aromatic ratio in its structure, and K in dust is always type III.
Atmospheric Environment. 45(31):5612-5620.
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ABSTRACT: Using surface and interference co-enhanced Raman scattering measurements, we detected two well-distinguished Raman bands at 1450 and 1530 cm−1 from individual mono- and few-layer graphene nanoribbons (GNRs) prepared by chemical exfoliation and mechanical cleavage of graphite. The intensities of these two peaks strongly depend on the width and edge structure of the GNRs. Combining with first-principles calculations, the 1450 and 1530 cm−1 Raman bands are assigned to the localized vibration of the edge atoms of zigzag and armchair GNRs terminated with H atoms, respectively. In addition, two weak peaks at ∼1140 and 1210 cm−1 are also observed, which are coupled with 1450 and 1530 cm−1, respectively. These findings enrich the understanding on the fine structure of mono- and few-layer GNRs by Raman spectroscopy.
Phys. Rev. B. 81(3).
