Carbon quantum dots（CQDs） have emerged as a new generation of photoluminescent nanomaterials with wide applications.Among the various synthetic routes for CQDs,the acid-refluxing method,which belongs to the group of...Carbon quantum dots（CQDs） have emerged as a new generation of photoluminescent nanomaterials with wide applications.Among the various synthetic routes for CQDs,the acid-refluxing method,which belongs to the group of ＂top-down＂ methods,offers the advantage of large-scale production of CQDs and uses cheap and abundantly available starting materials.In this study,we evaluated the potential of fullerene carbon soot（FCS）,a by-product obtained during the synthesis of fullerene,as the starting material for CQD production.It was found that FCS can be successfully converted to CQDs in high production yield in mixed acids,i.e.,concentrated HNO_3 and H_2SO_4,under mild conditions.The fluorescence quantum yield（0） of the as-produced CQDs is in the range of 3%-5%,which is the highest value for CQDs obtained from ＂top-down＂ methods.Importantly,the CQDs prepared by this method show emission in the yellow range of the visible light,which is advantageous for their various potential applications.Further investigations reveal that the CQDs are highly photostable over a wide pH range and show good resistance against ionic strength and long-term UV irradiation.This further expands their potential use under harsh conditions.展开更多
Diesel soot aggregates emitted from a model dynamometer and 11 on-road vehicles were segregated by a micro-orifice uniform deposit impactor （MOUDI）. The elemental contents and morphological parameters of the aggrega...Diesel soot aggregates emitted from a model dynamometer and 11 on-road vehicles were segregated by a micro-orifice uniform deposit impactor （MOUDI）. The elemental contents and morphological parameters of the aggregates were then examined by scanning electron microscopy coupled with an energy dispersive spectrometer （SEM-EDS）, and combined with a fractional Brownian motion （fBm） processor. Two mode-size distributions of aggregates collected from diesel vehicles were confirmed. Mean mass concentration of 339 mg/m3 （dC/dlogdp） existed in the dominant mode （180-320 nm）. A relatively high proportion of these aggregates appeared in PM 1, accentuating the relevance regarding adverse health effects. Furthermore, the fBm processor directly parameterized the SEM images of fractal like aggregates and successfully quantified surface texture to extract Hurst coefficients （H） of the aggregates. For aggregates from vehicles equipped with a universal cylinder number, the H value was independent of engine operational conditions. A small H value existed in emitted aggregates from vehicles with a large number of cylinders. This study found that aggregate fractal dimension related to H was in the range of 1.641-1.775, which is in agreement with values reported by previous TEM-based experiments. According to EDS analysis, carbon content ranged in a high level of 30%-50% by weight for diesel soot aggregates. The presence of Na and Mg elements in these sampled aggregates indicated the likelihood that some engine enhancers composed of biofuel or surfactants were commonly used in on-road vehicles in Taiwan. In particular, the morphological H combined with carbon content detection can be useful for characterizing chain-like or cluster diesel soot aggregates in the atmosphere.展开更多
To improve the tribological behavior of biodiesel soot(BDS) in liquid paraffin(LP), the order of biodiesel soot was increased through thermally oxidized treatment at 500 ℃, and the oil solubility was then improved th...To improve the tribological behavior of biodiesel soot(BDS) in liquid paraffin(LP), the order of biodiesel soot was increased through thermally oxidized treatment at 500 ℃, and the oil solubility was then improved through a modification using oleylamine(OLA). The BDS and thermally oxidized oleylamine-modified BDS(T-BDS-OLA)were characterized through various methods including the use of TG, FETEM, Raman spectroscopy, FTIR, and a zeta potentiometer. The tribological properties and mechanisms of the BDS before and after the thermally oxidized treatment modification were investigated using a ball-on-disc reciprocating tribometer, FESEM, 3 D laser-scanning microscopy, and Raman spectroscopy. The results showed that T-BDS-OLA has a higher degree of order than the BDS, with an onion-like microstructure. BDS and T-BDS-OLA can both improve the antifriction and antiwear properties of LP at a soot content of 0.1%-0.4%, while T-BDS-OLA in LP shows better antifriction and antiwear properties than BDS. The tribological mechanisms can be attributed to both types of soot acting as spacing and roll bearing between the friction surfaces. In addition, the exfoliated graphitic sheets from T-BDS-OLA can form a carbon lubrication layer providing easy sliding.展开更多
In this work, contact angle measurements for soot samples collected from a kerosene lantern, wood-burning fireplace, and municipal bus engine exhaust lines are reported. Contact angles for both freshly collected soot ...In this work, contact angle measurements for soot samples collected from a kerosene lantern, wood-burning fireplace, and municipal bus engine exhaust lines are reported. Contact angles for both freshly collected soot and samples treated with various doses of O3 (g), HNO3 (g), and H2SO4 (g) are considered. Use of a literature method has allowed estimation of the enthalpy of immersion (Himm) for the soot samples based on contact angle observed. Contact angles for freshly collected soot were 65 - 110 deg. indicating its hydrophobic nature. Chemical processing of soot usually resulted in smaller contact angles and large increases in immersion enthalpy. However, the dose of ozone, nitric or sulfuric acid vapor required to achieve alteration of the soot surface appeared to be considerably larger than that expected to be experienced by authentic atmospheric samples during the soot particles lifetime. The most significant variability of soot contact angle was observed for the municipal bus exhaust samples, suggesting that combustion chemistry may significantly affect wetting behavior.展开更多
本试验旨在测定植物炭黑(百草霜)的微晶结构及其对霉菌毒素的体外吸附效果。按文中试验方法,测定植物炭黑(百草霜)的微晶结构及其在p H 6.0磷酸盐缓冲液(PBS)下对呕吐毒素(DON)、黄曲霉毒素B1(AFB1)、玉米赤霉烯酮(ZEN)和赭曲霉毒素(OTA...本试验旨在测定植物炭黑(百草霜)的微晶结构及其对霉菌毒素的体外吸附效果。按文中试验方法,测定植物炭黑(百草霜)的微晶结构及其在p H 6.0磷酸盐缓冲液(PBS)下对呕吐毒素(DON)、黄曲霉毒素B1(AFB1)、玉米赤霉烯酮(ZEN)和赭曲霉毒素(OTA)的吸附率及吸附量。结果表明:(1)植物炭黑(百草霜)的比表面积为1440.09 m2/g、孔体积为1.28 cm^(3)/g、孔径为3.56 nm,其微晶结构(比表面)明显优于蒙脱石。(2)在pH 6.0磷酸盐缓冲液(PBS)中,对不同浓度霉菌毒素均具有较好的吸附效果。对呕吐毒素(DON)的吸附率在91%以上,对黄曲霉毒素B1(AFB1)、玉米赤霉烯酮(ZEN)及赭曲霉毒素(OTA)的吸附率均在99%以上,且不受以上3种霉菌毒素浓度的影响。展开更多
基金supported by the National Natural Science Foundation of China(21402215 and 61474124)the Hundred Talents Program of the Chinese Academy of Sciences(Y20245YBR1)
文摘Carbon quantum dots（CQDs） have emerged as a new generation of photoluminescent nanomaterials with wide applications.Among the various synthetic routes for CQDs,the acid-refluxing method,which belongs to the group of ＂top-down＂ methods,offers the advantage of large-scale production of CQDs and uses cheap and abundantly available starting materials.In this study,we evaluated the potential of fullerene carbon soot（FCS）,a by-product obtained during the synthesis of fullerene,as the starting material for CQD production.It was found that FCS can be successfully converted to CQDs in high production yield in mixed acids,i.e.,concentrated HNO_3 and H_2SO_4,under mild conditions.The fluorescence quantum yield（0） of the as-produced CQDs is in the range of 3%-5%,which is the highest value for CQDs obtained from ＂top-down＂ methods.Importantly,the CQDs prepared by this method show emission in the yellow range of the visible light,which is advantageous for their various potential applications.Further investigations reveal that the CQDs are highly photostable over a wide pH range and show good resistance against ionic strength and long-term UV irradiation.This further expands their potential use under harsh conditions.
基金supported by the "National"Science Council of Taiwan, China (No. NSC 92-2211-E-241-008,96-2221-E-241-011-MY3)
文摘Diesel soot aggregates emitted from a model dynamometer and 11 on-road vehicles were segregated by a micro-orifice uniform deposit impactor （MOUDI）. The elemental contents and morphological parameters of the aggregates were then examined by scanning electron microscopy coupled with an energy dispersive spectrometer （SEM-EDS）, and combined with a fractional Brownian motion （fBm） processor. Two mode-size distributions of aggregates collected from diesel vehicles were confirmed. Mean mass concentration of 339 mg/m3 （dC/dlogdp） existed in the dominant mode （180-320 nm）. A relatively high proportion of these aggregates appeared in PM 1, accentuating the relevance regarding adverse health effects. Furthermore, the fBm processor directly parameterized the SEM images of fractal like aggregates and successfully quantified surface texture to extract Hurst coefficients （H） of the aggregates. For aggregates from vehicles equipped with a universal cylinder number, the H value was independent of engine operational conditions. A small H value existed in emitted aggregates from vehicles with a large number of cylinders. This study found that aggregate fractal dimension related to H was in the range of 1.641-1.775, which is in agreement with values reported by previous TEM-based experiments. According to EDS analysis, carbon content ranged in a high level of 30%-50% by weight for diesel soot aggregates. The presence of Na and Mg elements in these sampled aggregates indicated the likelihood that some engine enhancers composed of biofuel or surfactants were commonly used in on-road vehicles in Taiwan. In particular, the morphological H combined with carbon content detection can be useful for characterizing chain-like or cluster diesel soot aggregates in the atmosphere.
基金supported by the National Natural Science Foundation of China (Grant No. 51675153)the Major Science and Technology Special Project in Anhui (Grant No. 17030901084)
文摘To improve the tribological behavior of biodiesel soot(BDS) in liquid paraffin(LP), the order of biodiesel soot was increased through thermally oxidized treatment at 500 ℃, and the oil solubility was then improved through a modification using oleylamine(OLA). The BDS and thermally oxidized oleylamine-modified BDS(T-BDS-OLA)were characterized through various methods including the use of TG, FETEM, Raman spectroscopy, FTIR, and a zeta potentiometer. The tribological properties and mechanisms of the BDS before and after the thermally oxidized treatment modification were investigated using a ball-on-disc reciprocating tribometer, FESEM, 3 D laser-scanning microscopy, and Raman spectroscopy. The results showed that T-BDS-OLA has a higher degree of order than the BDS, with an onion-like microstructure. BDS and T-BDS-OLA can both improve the antifriction and antiwear properties of LP at a soot content of 0.1%-0.4%, while T-BDS-OLA in LP shows better antifriction and antiwear properties than BDS. The tribological mechanisms can be attributed to both types of soot acting as spacing and roll bearing between the friction surfaces. In addition, the exfoliated graphitic sheets from T-BDS-OLA can form a carbon lubrication layer providing easy sliding.
文摘In this work, contact angle measurements for soot samples collected from a kerosene lantern, wood-burning fireplace, and municipal bus engine exhaust lines are reported. Contact angles for both freshly collected soot and samples treated with various doses of O3 (g), HNO3 (g), and H2SO4 (g) are considered. Use of a literature method has allowed estimation of the enthalpy of immersion (Himm) for the soot samples based on contact angle observed. Contact angles for freshly collected soot were 65 - 110 deg. indicating its hydrophobic nature. Chemical processing of soot usually resulted in smaller contact angles and large increases in immersion enthalpy. However, the dose of ozone, nitric or sulfuric acid vapor required to achieve alteration of the soot surface appeared to be considerably larger than that expected to be experienced by authentic atmospheric samples during the soot particles lifetime. The most significant variability of soot contact angle was observed for the municipal bus exhaust samples, suggesting that combustion chemistry may significantly affect wetting behavior.
