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1.
Huan Jing Ke Xue ; 42(4): 1939-1945, 2021 Apr 08.
Artículo en Chino | MEDLINE | ID: mdl-33742829

RESUMEN

In order to study the effects of chlorine dioxide (ClO2) disinfection on the super antibiotic resistance genes (SARGs), the final effluents before and after chlorine dioxide were sampled throughout one year in a wastewater treatment plant (WWTP). The bacteria and extracellular nucleic acid were collected using microporous membrane filtration and nucleic acid adsorption particles, respectively. A total of 9 SARGs was detected through a quantitative real-time polymerase chain reaction (qPCR). The results revealed that both intracellular and extracellular NDM-1, MCR-1, and MEC-A could be positively detected in the samples. Overall, ClO2 disinfection enhanced the relative abundance of the iSARGs (P<0.05), exhibiting a seasonal pattern, and increasing in the spring, summer, and autumn. In spring, it improved the most, up to twice the abundance. No SARGs were detected positive in the winter, either intracellularly or extracellularly. There was no significant variation in the concentrations of eSARGs before and after ClO2 disinfection. Therefore, ClO2 disinfection cannot effectively remove iSARGs and eSARGs in the final effluent from the WWTP.


Asunto(s)
Compuestos de Cloro , Desinfectantes , Purificación del Agua , Antibacterianos/farmacología , Cloro , Compuestos de Cloro/farmacología , Desinfectantes/farmacología , Desinfección , Farmacorresistencia Microbiana/genética , Óxidos/farmacología
2.
Phys Chem Chem Phys ; 23(1): 388-398, 2021 Jan 06.
Artículo en Inglés | MEDLINE | ID: mdl-33315040

RESUMEN

Fluorophores and hydrogen bonding interactions play key roles in the fluorescence properties of bottom-up carbon dots. In this work, an excited-state intramolecular proton-transfer (ESIPT) active fluorophore, 5-chloro-6-ethoxy-4,7-dihydroxyisoindoline-1,3-dione (CEDD) and a non-ESIPT 7-cyano-5,8-dihydroxyquinoxaline-6-carboxamide (CDQC) are extracted from 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) based carbon dots. The enol form of CEDD shows a weak blue, small Stokes shift and short lifetime emission under the aprotic or alkali conditions, but the keto form exhibits a strong green, large Stokes shift and long lifetime emission in a protic or an acidic environment. Due to the lack of the ESIPT process, CDQC has no dual emission characteristics, but shows efficient solid-state emission. By virtue of the ESIPT ability of CEDD, multiple anti-counterfeiting methods are achieved by using hydrogen chloride, ammonia, and fluorescence lifetime imaging, as well as dimethyl sulfoxide as the encryption/decryption tools.

3.
ACS Appl Mater Interfaces ; 12(41): 46220-46230, 2020 Oct 14.
Artículo en Inglés | MEDLINE | ID: mdl-32938186

RESUMEN

Four noncovalently fused-ring electron acceptors p-DOC6-2F, o-DOC6-2F, o-DOC8-2F, and o-DOC2C6-2F have been designed and synthesized. p-DOC6-2F and o-DOC6-2F have the same molecular backbone but different molecular shapes and symmetries. p-DOC6-2F has an S-shaped molecular backbone and C2h symmetry, whereas o-DOC6-2F possesses a U-shaped molecular backbone and C2v symmetry. The molecular shape and symmetry can influence the dipole moment, solubility, optical absorption, energy level, molecular packing, and film morphology. Compared with the corresponding p-DOC6-2F, o-DOC6-2F exhibits better solubility, a wider band gap, and a larger dipole moment. When blended with the donor polymer PBDB-T, the C2v symmetric o-DOC6-2F can form an appropriate active layer morphology, whereas the C2h symmetric p-DOC6-2F forms oversized domains. Organic solar cells (OSCs) based on p-DOC6-2F, o-DOC6-2F, o-DOC8-2F, and o-DOC2C6-2F obtained power conversion efficiencies of 9.23, 11.87, 11.23, and 10.80%, respectively. The result reveals that the molecular symmetry can facilely regulate the performance of OSCs.

4.
Sci Total Environ ; 743: 140641, 2020 Nov 15.
Artículo en Inglés | MEDLINE | ID: mdl-32653709

RESUMEN

Human enteric virus occurrence in bathing beaches poses a potential health risk to swimmers. They may come from several sources, but the understanding of the seasonal contribution of contamination sources to virus occurrence is still lacking. Here, the surveillance of human enteric viruses at the First Bathing Beach in Qingdao was performed January-December 2018. The occurrence of Enteric viruses, assayed with quantitative polymerase chain reaction (qPCR), was analyzed at temporal and spatial levels to determine the viral contamination sources. The results showed that only Astroviruses (AstVs) and Adenoviruses (HAdVs) were found in the swimming area. Their occurrence correlated significantly with the sewage-polluted area, but HAdVs were only found in autumn and AstVs in spring. Meanwhile, enteric viruses in the swimming area showed significantly higher levels than the surrounding area, particularly AstVs in summer with the swimmer crowd. All these data imply that sewage discharge and swimmers co-contribute to the viral occurrence in a seasonal pattern, with the former being more focused in warm seasons (spring and autumn) and the latter in hot seasons (summer). These results indicate that sewage discharge and crowd swimmers, as unsafe swimming conditions, should be avoided to improve public health at the bathing beaches.


Asunto(s)
Microbiología del Agua , Agua , Playas , Monitoreo del Ambiente , Heces , Humanos , Estaciones del Año
5.
ISME J ; 14(7): 1847-1856, 2020 07.
Artículo en Inglés | MEDLINE | ID: mdl-32327733

RESUMEN

Chlorine disinfection to drinking water plays an important role in preventing and controlling waterborne disease outbreaks globally. Nevertheless, little is known about why it enriches the antibiotic resistance genes (ARGs) in bacteria after chlorination. Here, ARGs released from killed antibiotic-resistant bacteria (ARB), and culturable chlorine-injured bacteria produced in the chlorination process as the recipient, were investigated to determine their contribution to the horizontal transfer of ARGs during disinfection treatment. We discovered Escherichia coli, Salmonella aberdeen, Pseudomonas aeruginosa and Enterococcus faecalis showed diverse resistance to sodium hypochlorite, and transferable RP4 could be released from killed sensitive donor consistently. Meanwhile, the survival of chlorine-tolerant injured bacteria with enhanced cell membrane permeabilisation and a strong oxidative stress-response demonstrated that a physiologically competent cell could be transferred by RP4 with an improved transformation frequency of up to 550 times compared with the corresponding untreated bacteria. Furthermore, the water quality factors involving chemical oxygen demand (CODMn), ammonium nitrogen and metal ions (Ca2+ and K+) could significantly promote above transformation frequency of released RP4 into injured E. faecalis. Our findings demonstrated that the chlorination process promoted the horizontal transfer of plasmids by natural transformation, which resulted in the exchange of ARGs across bacterial genera and the emergence of new ARB, as well as the transfer of chlorine-injured opportunistic pathogen from non-ARB to ARB. Considering that the transfer elements were quite resistant to degradation through disinfection, this situation poses a potential risk to public health.

6.
ACS Appl Mater Interfaces ; 12(1): 807-817, 2020 Jan 08.
Artículo en Inglés | MEDLINE | ID: mdl-31820911

RESUMEN

Multicarbonyl polyimide derivatives were synthesized by a facial condensation polymerization of dianhydrides with a new diamine monomer containing a benzoquinone unit that was prepared according to the Michael addition reaction. The ingenious combination of dedicated carbonyl groups from the benzoquinone and dianhydride with an aniline structure linkage not only provided stable polymeric chains with a high number of carbonyl groups per unit but also guaranteed their large π-conjugated main chains, which is favorable to their long cycle life and fast kinetics. When explored as cathode materials for lithium-ion batteries, the polyimide derivatives based on naphthalic dianhydride delivered a reversible specific capacity of 145 mAh/g at 0.1 C, a high rate performance with a capacity of 108 mAh/g at 1 C, and an ultralong stable cyclic performance with a capacity retention of 80.3% after 1000 cycles at 0.5 C. Based on the theoretical calculations and the exploration of the electrochemical behaviors, sensible predictions for the reversible ion-insertion reaction of the as-prepared sample were proposed to deeply understand the charge storage mechanisms. Moreover, a stable solid electrolyte interphase film formed in the ether-based electrolyte was confirmed to improve the electrochemical properties.

7.
Nat Prod Res ; 34(16): 2323-2327, 2020 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-30526052

RESUMEN

Phytochemical investigation of the roots of Leontopodium longifolium, led to the isolation of a novel norsesquiterpene, named as longifolactone (1), along with three known diterpenes. The structures of these compounds were elucidated by analysis of HR-ESI-MS, UV, IR and 1D and 2D NMR spectroscopic data. The absolute configuration of the new compound was determined by electronic circular dichroism (ECD) using both experimental and calculated ECD spectra. Furthermore, their anti-inflammatory effects were evaluated in LPS-activated RAW264.7 cells to determine their effects on the release of NO. Longifolactone (1) showed weak cytotoxicity towards two human cancer cell lines.


Asunto(s)
Antiinflamatorios/aislamiento & purificación , Asteraceae/química , Óxido Nítrico/antagonistas & inhibidores , Raíces de Plantas/química , Terpenos/farmacología , Animales , Antiinflamatorios/química , Antiinflamatorios/farmacología , Línea Celular Tumoral , Diterpenos/química , Diterpenos/aislamiento & purificación , Humanos , Ratones , Conformación Molecular , Estructura Molecular , Óxido Nítrico/biosíntesis , Células RAW 264.7 , Sesquiterpenos/aislamiento & purificación , Terpenos/aislamiento & purificación
8.
Zhongguo Ying Yong Sheng Li Xue Za Zhi ; 36(6): 668-672, 2020 Nov.
Artículo en Chino | MEDLINE | ID: mdl-33719279

RESUMEN

Objective: To establish a high performance liquid chromatography tandem mass spectrometry (HPLC / MS) method for the simultaneous determination of three antidepressant drugs in feces. Methods: Samples were pretreated with n-hexane isopropanol (95:5, v/v). Gradient elution was carried out with mixed liquid of ultrapure water and acetonitrile as mobile phase and separated by Agilent ZORBAX SB-C18 liquid chromatography column (2.1 mm×100 mm, 3.5 m). The samples were detected by electrospray ionization tandem mass spectrometry and quantified by internal standard method. Results: The recoveries of duloxetine, fluoxetine and escitalopram in fecal samples were 61.6% - 116.5%, with precision of 2.80% - 12.9% (n=5). The correlation coefficients (r) of linear equations were all greater than 0.995. The detection limits were 0.1, 1, and 0.001 µg/g, and the limits of quantification were 0.5, 2 and 0.005 µg/g, respectively. Conclusion: The method is simple and accurate to detect the contents of three antidepressants in feces, such as duloxetine, fluoxetine and escitalopram.


Asunto(s)
Citalopram , Espectrometría de Masas en Tándem , Antidepresivos , Cromatografía Líquida de Alta Presión , Heces
9.
J Comput Chem ; 40(28): 2473-2481, 2019 Oct 30.
Artículo en Inglés | MEDLINE | ID: mdl-31281983

RESUMEN

We investigate the effects of the electronic structure of carbon atom on the organofluorine hydrogen bonds, C─F⋯H─F. Our results show that we can modulate the strength of organofluorine hydrogen bonds by adjusting the volume of fluorine atom in C─F via changing the electronic structure of adjacent carbon atoms. Different with the conventional hydrogen bonds, we found that instead of carbon rehybridization and hyperconjugative effects, the magnitude of fluorine atomic volume plays important roles in determining the strength of the C─F⋯H─F organofluorine hydrogen bonds. The lone pair electrons at both the proximal and the vicinal carbon dramatically reinforce the strength of C─F⋯H─F organofluorine hydrogen bond with its interaction energy in the range of about 15-25 kcal/mol, that is, the carbanion-mediated organofluorine hydrogen bond could be very strong. Due to the high electronegativity of fluorine atom, it easily attracts the excess electron from the proximal and vicinal carbon, which results in the increase of its volume and negative charge. The enhanced volume of fluorine atom gives rise to the large polarization energy, and its enhanced negative charge favors the large electrostatic interaction, both of which substantially contribute to making the organofluorine hydrogen bonds strong. © 2019 Wiley Periodicals, Inc.

10.
Molecules ; 24(1)2018 Dec 20.
Artículo en Inglés | MEDLINE | ID: mdl-30577501

RESUMEN

Carbon bonding is a weak interaction, particularly when a neutral molecule acts as an electron donor. Thus, there is an interesting question of how to enhance carbon bonding. In this paper, we found that the ⁻OCH3 group at the exocyclic carbon of fulvene can form a moderate carbon bond with NH3 with an interaction energy of about -10 kJ/mol. The ⁻OSiH3 group engages in a stronger tetrel bond than does the ⁻OGeH3 group, while a reverse result is found for both ⁻OSiF3 and ⁻OGeF3 groups. The abnormal order in the former is mainly due to the stronger orbital interaction in the ⁻OSiH3 complex, which has a larger deformation energy. The cyano groups adjoined to the fulvene ring not only cause a change in the interaction type, from vdW interactions in the unsubstituted system of ⁻OCF3 to carbon bonding, but also greatly strengthen tetrel bonding. The formation of tetrel bonding has an enhancing effect on the aromaticity of the fulvene ring.


Asunto(s)
Ciclopentanos/química , Carbono/química , Enlace de Hidrógeno , Modelos Moleculares , Electricidad Estática
11.
Phys Chem Chem Phys ; 19(42): 28653-28665, 2017 Nov 01.
Artículo en Inglés | MEDLINE | ID: mdl-29043307

RESUMEN

Recently, graphene nanodots (GNDs) have been frequently considered as inherently heterogeneous systems, leading to multicolor emission under a changeable excitation wavelength. However, an accurate picture of the GNDs and an exhaustive structure-property correlation are still lacking. Using a two dimensional photoluminescence excitation (2D-PLE) map, molecular orbital calculation, reduction level dependent PL analysis, absorption spectroscopy and time-resolved PL spectroscopy, three cases of quasi-molecular PL are determined in ethylenediamine (EDA) reduced GNDs, including the C[double bond, length as m-dash]O related electronic state, graphenol related electronic state and large π-conjugated domains. The graphenol structure is expected to be created via nucleophilic addition-elimination reactions between epoxide groups and EDA, contributing most to the blue-shifted and enhanced PL of GNDs. The multiple quasi-molecular PL provides deeper insights into the commonly called "excitation wavelength dependent PL". An effort is made to utilize the heterogeneous photoluminescence through phosphor-based light-emitting diodes employing reduced GNDs as a phosphor, which are capable of converting blue light into white light.

12.
J Chem Phys ; 145(22): 224310, 2016 Dec 14.
Artículo en Inglés | MEDLINE | ID: mdl-27984914

RESUMEN

The complexes of XH3F⋯N3-/OCN-/SCN- (X = C, Si, Ge, and Sn) have been investigated at the MP2/aug-cc-pVTZ(PP) level. The σ-hole of X atom in XH3F acts as a Lewis acid forming a tetrel bond with pseudohalide anions. Interaction energies of these complexes vary from -8 to -50 kcal/mol, mainly depending on the nature of X and pseudohalide anions. Charge transfer from N/O/S lone pair to X-F and X-H σ* orbitals results in the stabilization of these complexes, and the former orbital interaction is responsible for the large elongation of X-F bond length and the remarkable red shift of its stretch vibration. The tetrel bond in the complexes of XH3F (X = Si, Ge, and Sn) exhibits a significant degree of covalency with XH3F distorted significantly in these complexes. A breakdown of the individual forces involved attributes the stability of the interaction to mainly electrostatic energy, with a relatively large contribution from polarization. The transition state structures that connect the two minima for CH3Br⋯N3- complex have been localized and characterized. The energetic, geometrical, and topological parameters of the complexes were analyzed in the different stages of the SN2 reaction N3- + CH3Br → Br- + CH3N3.

13.
Anal Bioanal Chem ; 408(20): 5527-35, 2016 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-27251197

RESUMEN

An innovative and effective extraction procedure based on molecularly imprinted solid-phase extraction (MISPE) was developed for the isolation of gonyautoxins 2,3 (GTX2,3) from Alexandrium minutum sample. Molecularly imprinted polymer microspheres were prepared by suspension polymerization and and were employed as sorbents for the solid-phase extraction of GTX2,3. An off-line MISPE protocol was optimized. Subsequently, the extract samples from A. minutum were analyzed. The results showed that the interference matrices in the extract were obviously cleaned up by MISPE procedures. This outcome enabled the direct extraction of GTX2,3 in A. minutum samples with extraction efficiency as high as 83 %, rather significantly, without any need for a cleanup step prior to the extraction. Furthermore, computational approach also provided direct evidences of the high selective isolation of GTX2,3 from the microalgal extracts.


Asunto(s)
Materiales Biocompatibles/síntesis química , Dinoflagelados/química , Modelos Químicos , Imagen Molecular/métodos , Saxitoxina/análogos & derivados , Extracción en Fase Sólida/métodos , Simulación por Computador , Ensayo de Materiales , Saxitoxina/química , Saxitoxina/aislamiento & purificación
14.
Yi Chuan ; 38(5): 363-90, 2016 05.
Artículo en Chino | MEDLINE | ID: mdl-27232486

RESUMEN

Steady progress has been achieved in the medical genetics in China in 2015, as numerous original researches were published in the world's leading journals. Chinese scientists have made significant contributions to various fields of medical genetics, such as pathogenicity of rare diseases, predisposition of common diseases, somatic mutations of cancer, new technologies and methods, disease-related microRNAs (miRNAs), disease-related long non-coding RNAs (lncRNAs), disease-related competing endogenous RNAs (ceRNAs), disease-related RNA splicing and molecular evolution. In these fields, Chinese scientists have gradually formed the tendency, from common variants to rare variants, from single omic analyses to multipleomics integration analyses, from genetic discovery to functional confirmation, from basic research to clinical application. Meanwhile, the findings of Chinese scientists have been drawn great attentions of international peers. This review aims to provide an overall picture of the front in Chinese medical genetics, and highlights the important findings and their research strategy.


Asunto(s)
Genética Médica , Metilación de ADN , Evolución Molecular , Predisposición Genética a la Enfermedad , Humanos , MicroARNs/fisiología , Mutación , Neoplasias/genética , Enfermedades Raras/genética
15.
Chem Commun (Camb) ; 52(49): 7683-6, 2016 Jun 08.
Artículo en Inglés | MEDLINE | ID: mdl-27230421

RESUMEN

Harvesting high-purity semiconducting single-walled carbon nanotubes (s-SWCNTs) with removable dispersants remains a challenge. In this work, we demonstrate that small heteroacene derivatives may serve as promising selective dispersants for sorting s-SWCNTs. A rich N "doped" and thiophene-substituted hexaazapentacene molecule, denoted as 4HP, was found to be more favorable for high-purity s-SWCNTs with large diameters. Importantly, 4HP is photodegradable under 365 nm or blue light, which enables a simple deposition approach for the formation of clean s-SWCNT networks. The as-fabricated thin film transistors show excellent performance with a charge-mobility of 30-80 cm(2) V(-1) s(-1) and an on-off ratio of 10(4)-10(6).

16.
J Chem Phys ; 144(11): 114306, 2016 Mar 21.
Artículo en Inglés | MEDLINE | ID: mdl-27004875

RESUMEN

Selenium-gold interaction plays an important role in crystal materials, molecular self-assembly, and pharmacochemistry involving gold. In this paper, we unveiled the mechanism and nature of selenium-gold interaction by studying complexes F2CSe⋯AuY (Y = CN, F, Cl, Br, OH, and CH3). The results showed that the formation of selenium-gold interaction is mainly attributed to the charge transfer from the lone pair of Se atom to the Au-Y anti-bonding orbital. Energy decomposition analysis indicated that the polarization energy is nearly equivalent to or exceeds the electrostatic term in the selenium-gold interaction. Interestingly, the chalcogen-gold interaction becomes stronger with the increase of chalcogen atomic mass in F2CX⋯AuCN (X = O, S, Se, and Te). The cyclic ternary complexes are formed with the introduction of NH3 into F2CSe⋯AuY, in which selenium-gold interaction is weakened and selenium-nitrogen interaction is strengthened due to the synergistic effects.

17.
Molecules ; 21(2)2016 Feb 06.
Artículo en Inglés | MEDLINE | ID: mdl-26861280

RESUMEN

A total of forty novel glycyrrhetinic acid (GA) derivatives were designed and synthesized. The cytotoxic activity of the novel compounds was tested against two human breast cancer cell lines (MCF-7, MDA-MB-231) in vitro by the MTT method. The evaluation results revealed that, in comparison with GA, compound 42 shows the most promising anticancer activity (IC50 1.88 ± 0.20 and 1.37 ± 0.18 µM for MCF-7 and MDA-MB-231, respectively) and merits further exploration as a new anticancer agent.


Asunto(s)
Antineoplásicos/síntesis química , Ácido Glicirretínico/análogos & derivados , Ácido Glicirretínico/síntesis química , Antineoplásicos/farmacología , Supervivencia Celular/efectos de los fármacos , Doxorrubicina/farmacología , Ensayos de Selección de Medicamentos Antitumorales , Ácido Glicirretínico/farmacología , Humanos , Concentración 50 Inhibidora , Células MCF-7
18.
Arch Environ Contam Toxicol ; 71(1): 133-45, 2016 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-26498763

RESUMEN

Ready biodegradation is the primary biodegradability of a compound, which is used for discriminating whether a compound could be rapidly and readily biodegraded in the natural ecosystems in a short period and has been applied extensively in the environmental risk assessment of many chemicals. In this study, the effects of 24 molecular properties (including 2 physicochemical parameters, 10 geometrical parameters, 6 topological parameters, and 6 electronic parameters) on the ready biodegradation of 24 kinds of synthetic aromatic compounds were investigated using the OECD 301B CO2 Evolution test. The relationship between molecular properties and ready biodegradation of these aromatic compounds varied with molecular properties. A significant inverse correlation was found for the topological parameter TD, five geometrical parameters (Rad, CAA, CMA, CSEV, and N c), and the physicochemical parameter K ow, and a positive correlation for two topological parameters TC and TVC, whereas no significant correlation was observed for any of the electronic parameters. Based on the correlations between molecular properties and ready biodegradation of these aromatic compounds, the importance of molecular properties was demonstrated as follows: geometrical properties > topological properties > physicochemical properties > electronic properties. Our study first demonstrated the effects of molecular properties on ready biodegradation by a number of experiment data under the same experimental conditions, which should be taken into account to better guide the ready biodegradation tests and understand the mechanisms of the ready biodegradation of aromatic compounds.


Asunto(s)
Dióxido de Carbono/química , Hidrocarburos Aromáticos/química , Modelos Químicos , Biodegradación Ambiental , Ecosistema , Monitoreo del Ambiente , Organización para la Cooperación y el Desarrollo Económico , Medición de Riesgo
19.
Arch Environ Contam Toxicol ; 70(3): 595-606, 2016 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-26215542

RESUMEN

Bioaccessibility describes the fraction of contaminants released from the food matrix into the digestive tracts of humans, which is beneficial for improving the health risk assessment of contaminants. In this study, the bioaccessibilities of cadmium (Cd), copper (Cu), and zinc (Zn) in two severely contaminated green oyster (Crassostrea angulate) and blue oyster (Crassostrea hongkongensis) populations were investigated. A human health risk assessment of these metals was then performed based on bioaccessibility measurements. Among the three metals, the bioaccessibility was the highest for Cu (42-95%), and Cd and Zn had comparable bioaccessibility (13-58%). There was no major difference in the bioaccessibility between green and blue oysters. A significant correlation between the tissue Cu and Zn concentrations was found in these highly contaminated oysters. A health risk assessment showed that all three metals in both oyster species seriously exceeded the levels recommended by the United States Environmental Protection Agency. Thus, oysters from these locations, and the metals contained therein, presented quite high risks for human consumption, which should be a great cause of concern. A significant relationship was only found between metal bioaccessibility and its tissue concentration instead of between metal bioaccessibility and subcellular distribution. In addition, a significant relationship was only observed between metal health risks and its tissue concentration. The influence of metal bioaccessibilities on the health risks was limited. This may suggest that in the case of the colored oysters examined in this study, metal concentration instead of metal subcellular distribution could be the driving factor of the metal bioaccessibility, and metal concentration, instead of metal bioaccessibility, could be the driving factor of the metal health risks.


Asunto(s)
Cadmio/análisis , Cobre/análisis , Crassostrea/química , Monitoreo del Ambiente , Contaminantes Químicos del Agua/análisis , Zinc/análisis , Animales , Humanos , Mariscos
20.
J Am Chem Soc ; 137(29): 9281-8, 2015 Jul 29.
Artículo en Inglés | MEDLINE | ID: mdl-26148208

RESUMEN

We present quantum chemical simulations demonstrating how single-walled carbon nanotubes (SWCNTs) form, or "nucleate", on the surface of Al2O3 nanoparticles during chemical vapor deposition (CVD) using CH4. SWCNT nucleation proceeds via the formation of extended polyyne chains that only interact with the catalyst surface at one or both ends. Consequently, SWCNT nucleation is not a surface-mediated process. We demonstrate that this unusual nucleation sequence is due to two factors. First, the π interaction between graphitic carbon and Al2O3 is extremely weak, such that graphitic carbon is expected to desorb at typical CVD temperatures. Second, hydrogen present at the catalyst surface actively passivates dangling carbon bonds, preventing a surface-mediated nucleation mechanism. The simulations reveal hydrogen's reactive chemical pathways during SWCNT nucleation and that the manner in which SWCNTs form on Al2O3 is fundamentally different from that observed using "traditional" transition metal catalysts.


Asunto(s)
Óxido de Aluminio/química , Metano/química , Simulación de Dinámica Molecular , Nanotubos de Carbono/química , Catálisis , Hidrógeno/química , Conformación Molecular , Nanopartículas/química , Teoría Cuántica , Silicio/química , Volatilización
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