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1.
Langmuir ; 36(33): 9709-9718, 2020 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-32787058

RESUMO

A single semiconductor employed into photo(electro)catalysis is not sufficient for charge carrier separation. Designing a multiple heterojunction system is a practical method for photo(electro)catalysis. Herein, novel two-dimensional AgInS2/SnS2/RGO (AISR) photocatalysts with multiple junctions were prepared by a simple hydrothermal method. The synthesized AISR heterojunctions showed superior photoelectrochemical performance and photocatalytic degradation of norfloxacin, with a high degradation rate reaching 95%. More importantly, the toxicity of photocatalytic products decreased within the reaction process. High spatial separation efficiency of photogenerated electron-hole pairs was evidenced by optical and photoelectrochemical characterizations. Furthermore, a laser flash photolysis technique was carried on investigating the lifetime of the charge carrier of the fabricated dual heterostructures. In addition, sulfur and oxygen vacancies existed in AISR heterojunctions could largely constrain the recombination of electron-hole pairs. Density functional theory calculations were carried out to analyze the mechanism of photoinduced interfacial redox reactions, showing that reduced graphene oxide and AgInS2 act as electron and hole trappers in the photocatalytic reaction, respectively. Due to the interfacial electric field formed from AISR dual heterojunctions, the effective spatial charge separation and transfer contributed to the boosting photo(electro)catalytic performance.

2.
Water Res ; 185: 116244, 2020 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-32750570

RESUMO

A rational design of structure-tailored and functionalized nanocarbons for peroxymonosulfate (PMS) activation is important in metal-free catalysis for degradation of water contaminants. In this work, we employed ionic liquids (ILs) for synthesis of porous carbon materials (PCMs) as a PMS activator for oxidative removal of naproxen and systematically investigated the functions of structure defects, oxygen functional groups and heteroatom doping toward the catalytic oxidation. A positive linear correlation between reaction rate constants and carbon defect ratios of PCMs revealed that the structural defects played an important role in PMS activation. Electron paramagnetic resonance (EPR) spectra, radical quenching experiments and electrochemical analysis tests verified nonradical-dominated oxidations via electron transfer and 1O2. Structural vacancies, ketonic C=O groups and graphitic-N atoms on carbons have been revealed to be the active sites for the nonradical pathways via direct electron transfer or generation of O2•-/1O2. This work provides new insight into the reaction mechanism and structure-performance relationships of the catalytic centers in nonradical oxidation.

3.
Bioorg Chem ; 100: 103915, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32450383

RESUMO

In the present study, the effects of dihydroartemisinin (DHA) on inflammatory bowel diseases (IBD) mice model induced by dextran sulfate sodium (DSS) were determined. Hematoxylin and eosin staining was used to assess the intestines of mice treated with DSS and DHA. The expression of inflammatory factors and cell junction-associated genes was measured using reverse transcription-quantitative PCR (RT-qPCR) and Western blot. The effects of DSS and DHA on the gut microbiome were measured using 16S recombinant (r) DNA gene analysis. DHA could improve the diarrhea and bloody stool induced by DSS, and decrease the serum levels of TNF-α, IL-1ß and IL-23 of the DSS group. DHA could notably reduce the infiltration of the inflammatory cells and significantly decrease the expression of TNF-α and IL-1ß in the intestines of the DSS treated mice. The expression of cell junction-associated genes such as EpCAM and Claudins, were down-regulated in the DSS group, and DHA could recover the expression of these cell junction-associated genes. The 16S rDNA gene analysis demonstrated that Bacteroidetes and Verrucomicrobia decreased, while Firmicutes and Proteobacteria increased in the DSS group, and DHA could recover the abundance of these gut bacteria altered by DSS. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that DHA could partly recover the pathways altered by DSS. DHA could obviously ameliorate the symptoms of IBD induced by DSS by regulation of the expression of inflammation and cell junction-associated genes and gut microbiota, suggesting its potential for the treatment of IBD.

4.
Sensors (Basel) ; 20(10)2020 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-32429110

RESUMO

Reliable estimates of terrestrial latent heat flux (LE) at high spatial and temporal resolutions are of vital importance for energy balance and water resource management. However, currently available LE products derived from satellite data generally have high revisit frequency or fine spatial resolution. In this study, we explored the feasibility of the high spatiotemporal resolution LE fusion framework to take advantage of the Moderate Resolution Imaging Spectroradiometer (MODIS) and Chinese GaoFen-1 Wide Field View (GF-1 WFV) data. In particular, three-fold fusion schemes based on Enhanced Spatial and Temporal Adaptive Reflectance Fusion Model (ESTARFM) were employed, including fusion of surface reflectance (Scheme 1), vegetation indices (Scheme 2) and high order LE products (Scheme 3). Our results showed that the fusion of vegetation indices and further computing LE (Scheme 2) achieved better accuracy and captured more detailed information of terrestrial LE, where the determination coefficient (R2) varies from 0.86 to 0.98, the root-mean-square error (RMSE) ranges from 1.25 to 9.77 W/m2 and the relative RSME (rRMSE) varies from 2% to 23%. The time series of merged LE in 2017 using the optimal Scheme 2 also showed a relatively good agreement with eddy covariance (EC) measurements and MODIS LE products. The fusion approach provides spatiotemporal continuous LE estimates and also reduces the uncertainties in LE estimation, with an increment in R2 by 0.06 and a decrease in RMSE by 23.4% on average. The proposed high spatiotemporal resolution LE estimation framework using multi-source data showed great promise in monitoring LE variation at field scale, and may have value in planning irrigation schemes and providing water management decisions over agroecosystems.

5.
J Hazard Mater ; 395: 122695, 2020 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-32330786

RESUMO

In this study, carbon quantum dots (CQDs) were synthesized by a low-cost and scalable approach and the oxygen functional groups were fine-tuned by chemical post-treatment. It was found that the CQDs could be applied as visible-light-responsive photocatalysts for activation of peroxymonosulfate (PMS) and remediation of aqueous organic dyes. Phenylhydrazine modified CQDs (CQDs-PH) presented high efficiency for degradation of methylene blue due to selective removal of carboxylic groups and inhibited recombination of photogenerated electron-hole pairs. The effects of catalyst dosage, species and concentrations of dyes, and initial pH values on the photodegradation efficiency were systematically investigated and the alkaline condition facilitates the separation of photoinduced charge carriers and promotes the dye decoloration. The reactive oxygen species produced in the photocatalysis were identified by radical quenching tests and the mechanism was elucidated. Superoxide radicals were generated from PMS activation via electron transfer from CQDs and played the primary role in organic oxidation. In addition, photogenerated holes on the valence band of CQDs also participated in the dye decomposition.

6.
Small ; : e1906276, 2020 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-32130789

RESUMO

Direct conversion of syngas to dimethyl ether (DME) through the intermediate of methanol allows more efficient DME production in a simpler reactor design relative to the conventional indirect route. Although Cu/ZnO-based multicomponent catalysts are highly active for methanol synthesis in this process, the sintering issue of Cu during the prolonged reaction generally deteriorates their performance. In this work, Cu/ZnO catalysts in a novel octahedron structure are prepared by a two-step pyrolysis of Zn-doped Cu-BTC metal-organic framework (MOF) in N2 and air. The catalyst CZ-350/A, hybrid of MOF-derived Cu/ZnO sample CZ-350 and γ-Al2 O3 for methanol dehydration, displays the best activity for DME formation (7.74% CO conversion and 70.05% DME selectivity) with the lowest deterioration rate over 40 h continuous reaction. Such performance is superior to its counterpart CZ-CP/A made via the conventional coprecipitation method. This is mainly due to the confinement of Cu nanoparticles within the octahedron matrix hindering their migration and aggregation. Besides, partial reduction of ZnO in the activated CZ-350 prompts the formation of Cu+ -O-Zn, further facilitating the DME production with the highest selectivity compared to literature results. The results clearly indicate that Cu and ZnO distribution in the catalyst architecture plays an important role in DME formation.

7.
J Colloid Interface Sci ; 569: 12-21, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32097798

RESUMO

Organic contaminants, dyes and antibiotics, discharged in wastewater systems, have posed great threats to the sustainability of the ecosystem. This study was performed to prepare graphitic carbon nitride (GCN) nanocomposites modified by nanocarbons, including carbon quantum dots (CQD), carbon nanotube (CNT), reduced graphene oxide (rGO), and carbon nanospheres (CNS), by a straightforward one-pot method. The characterization results suggest that after the modification with nanocarbons, GCN demonstrated slight red shift and stronger light absorption. The resultant photocatalysts revealed prominent performances for total photodegradation of organic contaminants. The degradation processes were investigated by in situ electron paramagnetic resonance (EPR). The mechanistic studies on the enhanced photoelectrochemical and photocatalytic performances were also conducted. Results indicate that GCN modified by the nanocarbon spheres displayed a substantial improvement in the degradation of sulfachloropyridazine (SCP) and dyes, compared favourably with other GCN samples modified by carbon nanotubes, quantum dots and layered graphene oxide. The photocatalytic degradation difference is mainly stemmed from the higher contents of COOH and CO functional groups. The intimate contact or interaction between the two phases of GCN and nanocarbon in the nanocomposites may further improve the activity. This work provides insight in the design of highly efficient metal-free photocatalysts to better utilise the clean and free solar energy for environmental remediation.

8.
J Colloid Interface Sci ; 564: 418-427, 2020 Mar 22.
Artigo em Inglês | MEDLINE | ID: mdl-31923829

RESUMO

Spinel-type structured materials have attracted considerable attention and been regarded as promising alternative catalysts for oxygen evolution reaction (OER). However, the regulation of catalytically active octahedral sites in spinel structure to realize high activity and good stability for OER electrocatalysis is still a great challenge. Herein, we propose a self-doping strategy to boost OER performance of spinel-type Ni3S4 enriched high valence Ni3+ as active sites. By sacrificing Ni-based metal-organic framework, the ultrathin Ni3S4 manosheets are topologically grown on conductive Ni foam substrate and realize the simultaneous Ni3+ self-doping and surface oxygen incorporation during in situ sulfidation conversion process. These compositional and structural characteristics endow it with enhanced adsorption binding strength, enabling the highly efficient OER. As a result, the Ni3S4/NF exhibits excellent activity and outstanding stability toward OER electrocatalysis in alkaline medium, which only demands an ultralow overpotential of 266 mV to deliver a current density of 10 mA cm-2 and manifests the stable OER process for at least 75 h. Moreover, when used as an effective overall water splitting electrolyzer, the Ni3S4/NF achieves a current density of 10 mA cm-2 at only 1.638 V with good long-term stability.

9.
Adv Mater ; 32(18): e1904037, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31793723

RESUMO

Low-cost, nonprecious transition metal (TM) catalysts toward efficient water oxidation are of critical importance to future sustainable energy technologies. The advances in structure engineering of water oxidation catalysts (WOCs) with single TM centers as active sites, for example, single metallic molecular complexes (SMMCs), supported SMMCs, and single-atom catalysts (SACs) in recent reports are examined. The efforts made on these configurations in terms of design principle, advanced characterization, performances and theoretical studies, are critically reviewed. A clear roadmap with the correlations between the single-TM-site-based structures (coordination and geometric structure, TM species, support), and the catalytic performances in water oxidation is provided. The insights bridging SMMCs with SACs are also given. Finally, the challenges and opportunities in the single-TM-site catalysis are proposed.

10.
J Hazard Mater ; 384: 121471, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-31677914

RESUMO

In this work, porous SiO2 coated AlxFeyZr1-x-yO2 solid superacid nanoparticles with negative charge (CS-SAFZr) were synthesized via hydrolysis, sulfation and sulfonation, and characterized by SEM, TEM, XRD, BET and so on. The results show that the size of CS-SAFZr nanoparticles prepared under the optimum preparation conditions is around 80 nm, thickness of the porous SiO2 shell is about 20 nm, Hammett acidity is -16.197 and ion exchange capacity (IEC) is 0.98 mmol·g-1. Correspondingly, ferrum (Fe) and aluminum (Al) elements are successfully doped into the ZrO2 lattice and the doped nanoparticles present a specific surface area of 396.2 m2 g-1 with abundant hydroxyl and sulfonic acid groups on the surface. To investigate the properties of the nanoparticles as the filler, polyvinylidene fluoride (PVDF) was used as a candidate to prepare CS-SAFZr/PVDF ultrafiltration (UF) composite membranes and the performance were characterized via cleaning and desalinating seawater. Results indicate that the CS-SAFZr nanoparticles strengthen their compatibility with the membrane via hydrogen bonds and improve performances of PVDF membrane. The suspended solid and conductivity decline ratio of permeate seawater was 1.8 mg L-1 and 13.20% respectively, indicating that CS-SAFZr/PVDF membrane performs seawater cleaning and partial desalination. Therefore, CS-SAFZr nanoparticles can be a promising candidate to modify PVDF membrane for cleaning and desalinating seawater.

11.
Sci Total Environ ; 695: 133787, 2019 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-31756871

RESUMO

Satellite-derived terrestrial latent heat flux (LE) models are useful tools to understand regional surface energy and water cycle processes for terrestrial ecosystems in the Heihe River basin (HRB) of Northwest China. This study developed a satellite-derived hybrid LE model parameterized by three soil moisture (SM) constraints: SM, relative humidity (RH), and diurnal air temperature range (DT); and assessed model performance and sensitivity. We used MODerate Resolution Imaging Spectroradiometer (MODIS) and eddy covariance (EC) data from 12 EC flux tower sites across the HRB. The hybrid model was trained using observed LE over 2012/2013-2014, and validated using observed LE for 2015 and leave-one-out cross-validation. The results show that the three SM constraints schemes exhibited some modeling differences at the flux tower site scale. LE estimation using SM achieved the highest correlation (R2 = 0.87, p < 0.01) and lowest root mean square error (RMSE = 20.1 W/m2) compared to schemes using RH or DT schemes. We then produced regional daily LE maps at 1 km × 1 km across the HRB for 2013-2015. Regional analysis shows that our LE estimates from all three constraint models exhibited large spatial variability and strong seasonal and annual variations, attributed to differences in parameterizing the model water constraints. This study provides data and model based evidence to improve satellite-derived hybrid LE models with regard to water constraints.

12.
ACS Appl Mater Interfaces ; 11(51): 47894-47903, 2019 Dec 26.
Artigo em Inglês | MEDLINE | ID: mdl-31738508

RESUMO

The great promise of hydrogen energy and hydrogen production from water through proton exchange membrane (PEM) or membrane-free electrolysis drives the pursuit of highly active and acid-stable electrocatalysts with dual functionality and reduced cost for overall water splitting in acidic media. Here, we report a new Ru-modified cobalt-based electrocatalyst embedded in a nitrogen-doped carbon (NC) matrix with rationally designed Mott-Schottky heterostructure to realize high activity and stability toward overall water splitting in a strongly acidic environment. Such a composite was facilely prepared by carbonization of cobalt-based MOF, followed by galvanic exchange between cobalt and Ru, and then controlled partial oxidation. The partial oxidation of RuCo implanted inside the NC matrix led to the formation of a class of RuO2/Co3O4-RuCo@NC composites with rich metal-semiconductor interfaces to facilitate the charge-transfer process. As a result, the composite displayed remarkable electrocatalytic activity toward both oxygen/hydrogen evolutions in acidic media. Significantly, they also afforded low overpotentials of 247 and 141 mV for OER and HER, respectively, and a cell voltage of 1.66 V for overall water splitting at 10 mA cm-2. In addition, excellent operation stability in 0.5 M H2SO4 solutions, comparable to those of them working in alkaline conditions, is demonstrated due to the protection of a coated carbon thin film. The presented work opens a new opportunity toward designing bifunctional electrocatalysts for acidic water electrolysis.

13.
ACS Appl Mater Interfaces ; 11(45): 41988-41999, 2019 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-31622550

RESUMO

Oxygen vacancy-rich porous Co3O4 nanosheets (OV-Co3O4) with diverse surface oxygen vacancy contents were synthesized via facile surface reduction and applied to NO reduction by CO and CO oxidation. The structure-activity relationship between surface oxygen vacancies and catalytic performance was systematically investigated. By combining Raman, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and O2-temperature programmed desorption, it was found that the efficient surface reduction leads to the presence of more surface oxygen vacancies and thus distinctly enhance the surface oxygen amount and mobility of OV-Co3O4. The electron transfer towards Co sites was promoted by surface oxygen vacancies with higher content. Compared with the pristine porous Co3O4 nanosheets, the presence of more surface oxygen vacancies is beneficial for the catalytic performance enhancement for NO reduction by CO and CO oxidation. The OV-Co3O4 obtained in 0.05 mol L-1 NaBH4 solution (Co3O4-0.05) exhibited the best catalytic activity, achieving 100% NO conversion at 175 °C in NO reduction by CO and 100% CO conversion at 100 °C in CO oxidation, respectively. Co3O4-0.05 exhibited outstanding catalytic stability and resistance to high gas hour space velocity in both reactions. Combining in situ DRIFTS results, the enhanced performance of OV-Co3O4 for NO reduction by CO should be attributed to the promoted formation and transformation of dinitrosyl species and -NCO species at lower and higher temperatures. The enhanced performance of OV-Co3O4 for CO oxidation is due to the promotion of oxygen activation ability, surface oxygen mobility, as well as the enhanced CO2 desorption ability. The results indicate that the direct regulation of surface oxygen vacancies could be an efficient way to evidently enhance the catalytic performance for NO reduction by CO and CO oxidation.

14.
Int J Mol Med ; 44(5): 1908-1920, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31573042

RESUMO

Diallyl disulfide (DADS) is one of the primary components of garlic and it exhibits a broad range of biological activities. In the present study, the effects of DADS on lipid metabolism and its potential role in the modulation of the gut microbiome were determined. Hematoxylin and eosin and oil­red O staining were used to assess the liver and intestinal tissues of mice treated with DADS. The expression of lipid metabolism­associated genes was measured using reverse transcription­quantitative PCR (RT­qPCR). The effects of DADS on the gut microbiome were measured using 16S recombinant (r)DNA gene analysis. The results revealed that the serum non­esterified free fatty acids, high density lipoprotein­cholesterol, low density lipoprotein­cholesterol, serum total cholesterol, liver triglyceride and total cholesterol levels of the mice fed with a low­dose of DADS was significantly higher when compared with the control. Hematoxylin and eosin and oil­red O staining demonstrated that DADS induced fatty liver in mice. The results of the RT­qPCR revealed that the expression levels of a number of lipid metabolism­associated genes were altered in the livers of mice treated with DADS. The 16S rDNA gene analysis demonstrated that the mice fed on a normal diet treated with a low­dose of DADS had decreased levels of bacteria from the Bacteroidetes phyla and increased levels of bacteria from the Firmicutes phyla. The Kyoto Encyclopedia of Genes and Genomes pathway analysis revealed the top 20 pathways enriched in the low­dose DADS group of mice fed with a normal diet. In the present study, low­dose DADS induced fatty liver and altered the gut microbiota, similar to the phenotype induced by a high fat diet, by regulating the expression of lipid metabolism associated genes.

15.
Int J Mol Med ; 44(3): 1063-1077, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31524221

RESUMO

Epithelial cell adhesion molecule (EpCAM) is highly expressed during liver development and carcinogenesis, However, its functions and underlying mechanisms remain unclear. Clustered regularly interspaced short palindromic repeats (CRISPRs)/CRISPR­associated protein 9 (Cas9) technology was used in the current study to establish EpCAM­/­ mice. The expression of EpCAM in the livers of the mice at embryonic day (E)18.5 and post­natal day (P)0 was detected by immunofluorescence staining. The expression of genes associated with the development and glycogen metabolism was also assessed by reverse transcription­quantitative PCR. Additionally, the liver tissue of the EpCAM­/­ and wild­type mice was used for non­coding RNA sequencing. The results of RNA sequencing revealed 11 up­regulated and 12 downregulated circular RNAs (circRNAs). Kyoto Encyclopedia of Genes and Genomes analysis for resource genes determined that the top altered pathways included cell junctions, cell cycle, immune signaling and metabolism. This analysis was also utilized to predict the target association of the circRNA­microRNA­mRNA network. The comprehensive liver tissue circRNA expression profiles produced in the present study may help to elucidate the functions and mechanisms of EpCAM during liver development.


Assuntos
Biomarcadores , Molécula de Adesão da Célula Epitelial/deficiência , Fígado/metabolismo , RNA Circular , Animais , Sequência de Bases , Biologia Computacional/métodos , Molécula de Adesão da Célula Epitelial/química , Molécula de Adesão da Célula Epitelial/genética , Perfilação da Expressão Gênica , Ontologia Genética , Redes Reguladoras de Genes , Genótipo , Camundongos , Camundongos Knockout , MicroRNAs/genética , Fenótipo , RNA Mensageiro/genética , Reprodutibilidade dos Testes
16.
Environ Sci Technol ; 53(19): 11391-11400, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31436973

RESUMO

The maximization of the numbers of exposed active sites in supported metal catalysts is important to achieve high reaction activity. In this work, a simple strategy for anchoring single atom Fe on SBA-15 to expose utmost Fe active sites was proposed. Iron salts were introduced into the as-made SBA-15 containing the template and calcined for simultaneous decomposition of the iron precursor and the template, resulting in single atom Fe sites in the nanopores of SBA-15 catalysts (SAFe-SBA). X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and extended X-ray absorption fine structure (EXAFS) imply the presence of single atom Fe sites. Furthermore, EXAFS analysis suggests the structure of one Fe center with four O atoms, and density functional theory calculations (DFT) simulate this structure. The catalytic performances of SAFe-SBA were evaluated in Fenton-like catalytic oxidation of p-hydroxybenzoic acid (HBA) and phenol. It was found that the single atom SAFe-SBA catalysts displayed superior catalytic activity to aggregated iron sites (AGFe-SBA) in both HBA and phenol degradation, demonstrating the advantage of SAFe-SBA in catalysis.


Assuntos
Ferro , Fenol , Catálise , Oxirredução , Difração de Raios X
17.
J Phys Chem Lett ; 10(12): 3465-3471, 2019 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-31184156

RESUMO

Herein we employed a first-principles method based on density functional theory to investigate the surface energy and growth kinetics of wurtzite nanoplatelets to elucidate why nanoplatelets exhibit a uniform thickness of eight monolayers. We synthesized a series of wurtzite nanoplatelets (ZnSe, ZnS, ZnTe, and CdSe) with an atomically uniform thickness of eight monolayers. As a representative example, the growth mechanism of 1.39 nm thick (eight monolayers) wurtzite ZnSe nanoplatelets was studied to substantiate the proposed growth kinetics. The results show that the growth of the seventh and eighth layers along the [112̅0] direction of 0.99 nm (six monolayers) ZnSe magic-size nanoclusters is accessible, whereas the growth of the ninth layer is unlikely to occur because the formation energy is large. This work not only gives insights into the synthesis of atomically uniform thick wurtzite semiconductor nanoplatelets but also opens up new avenues to their applications in light-emitting diodes, catalysis, detectors, and lasers.

18.
Phys Chem Chem Phys ; 21(21): 10947-10954, 2019 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-31099364

RESUMO

Graphene is widely used in numerous scientific fields including physics, chemistry and materials science due to its exceptional electrical, thermal, optical and mechanical properties. However, the poor solubility/dispersibility strongly limits the practical applications of graphene. In this work, hydroxypropyl hydrazine (HPH) was synthesized to reduce graphene oxide (GO) under mild conditions. The as-produced graphene sheets with a 3D-porous structure show admirable dispersion stability in N,N-dimethylacetamide (DMAc) and the graphene sheets are more effective absorbents for Cu2+ removal than those reduced by hydrazine hydrate. A mechanism for removal of epoxides and carboxides from GO by HPH has been proposed. This one-step reducing and dispersing process of GO is more efficient, environmentally benign and safer for the bulk-scale production of 3D porous graphene.

19.
R Soc Open Sci ; 6(3): 190002, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31032057

RESUMO

Flavour is a special way to discriminate extra virgin olive oils (EVOOs) from other aroma plant oils. In this study, different ratios (5, 10, 15, 20, 30, 50, 70 and 100%) of peanut oil (PO), corn oil (CO) and sunflower seed oil (SO) were discriminated from raw EVOO using flavour fingerprint, electronic nose and multivariate analysis. Fifteen different samples of EVOO were selected to establish the flavour fingerprint based on eight common peaks in solid-phase microextraction-gas chromatography-mass spectrometry corresponding to 4-methyl-2-pentanol, (E)-2-hexenal, 1-tridecene, hexyl acetate, (Z)-3-hexenyl acetate, (E)-2-heptenal, nonanal and α-farnesene. Partial least square discrimination analysis (PLS-DA) was used to differentiate EVOOs and mixed oils containing more than 20% of PO, CO and SO. Furthermore, better discrimination efficiency was observed in PLS-DA than PCA (70% of CO and SO), which was equivalent to the correlation coefficient method of the fingerprint (20% of PO, CO and SO). The electronic nose was able to differentiate oil samples from samples containing 5% mixture. The discrimination method was selected based on the actual requirements of quality control.

20.
Molecules ; 24(8)2019 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-30999650

RESUMO

Aroma profiles, key aroma compound quantification, and cluster analysis of 15 brands of extra-virgin olive oils (EVOOs) from three countries (Spain, Italy, and Greece) were investigated in the current study. Aroma compounds were isolated from the oil by using solvent-assisted flavor evaporation (SAFE) and solid-phase micro-extraction (SPME) and analyzed by gas chromatography-olfactometry mass spectrometry (GC-MS/O). A total of 89 compounds were screened by SPME/SAFE-GC-MS/O with chromatographic columns in 15 brands of samples. Eighty and 54 compounds were respectively identified by SPME- and SAFE-GC-MS/O. Of those, 44 compounds were detected by both methods. Undecanol, (Z)-4-decenal, (E)-2-dodecenal, and 2-nonanone extracted by SAFE were not found in EVOOs before. Eight classes of aroma compounds were identified, including 17 alcohols, 22 aldehydes, 9 ketones, 4 acids, 14 esters, 5 aromatics, 12 alkene, and 6 others. Eleven compounds were identified as the key aroma compounds in alternative brands of EVOOs by SAFE-aroma extract dilution analysis (AEDA). Hexanal, (E)-2-hexenal, (E)-3-hexenol, acetic acid, and (E)-2-heptenal were the common key aroma compounds by AEDA and odor activity values (OAVs). From the cluster analysis of the heatmap, the aroma compounds of all the Spain EVOOs were similar, and there were some differences from the samples of Italy and Greece. It suggested that both the amount and concentration of aroma compounds determine the similarity of aroma in EVOOs.


Assuntos
Azeite de Oliva/análise , Compostos Orgânicos Voláteis/análise , Cromatografia Gasosa-Espectrometria de Massas/métodos , Olfatometria/métodos , Microextração em Fase Sólida/métodos , Compostos Orgânicos Voláteis/química
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