Au/TiO2 photocatalysts were studied, characterized, and compared for CO2 photocatalytic gas-phase reduction. The impact of the nature of the TiO2 support was studied. It was shown that the surface ...area/porosity/TiO2 crystal phase/density of specific exposed facets and oxygen vacancies were the key factors determining CH4 productivity under solar-light activation. A 0.84 wt.% Au/TiO2 SG (Sol Gel) calcined at 400 °C exhibited the best performance, leading to a continuous mean CH4 production rate of 50 μmol.h−1.g−1 over 5 h, associated with an electronic selectivity of 85%. This high activity was mainly attributed to the large surface area and accessible microporous volume, high density of exposed TiO2 (101) anatase facets, and oxygen vacancies acting as reactive defects sites for CO2 adsorption/activation/dissociation and charge carrier transport.
In this paper, a facile one step synthesis method for the preparation of C-, B-, P- and S-doped g-C3N4 by incorporation of small concentration of doping element precursor into urea during thermal ...polycondensation is reported leading to much lower doping levels than the ones usually reported. The as-obtained doped g-C3N4 photocatalytic materials are deeply characterized in terms of structural, morphological, surface and optical properties. Doping yields beneficial surface morphology modulation along with improved optical, electronic and photocatalytic properties. In particular, C-doped and S-doped g-C3N4 show, after deposition of gold nanoparticles (<1 wt%), enhanced photocatalytic performance (at least twice as high as the undoped photocatalyst, to achieve ca. 610 μmol/h/g) for the production of H2 by water splitting under solar light in the presence of low content (1 vol%) of triethanolamine (TEOA) as sacrificial agent. The most remarkable activity results from the incorporation of traces of S dopant, mainly inserted into interplanar hollow cavities. The enhanced activity is attributed to a combination of high surface area, location of the S dopant and small size of the co-catalyst NPs, which induces enhanced visible light harvesting, enhanced charge carrier separation and enhanced proton recombination. This work highlights the benefits of the optimized low-level doping strategy to overcome the main limitations of g–C3N4–based photocatalysts.
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•H2 production by water splitting on traces non-metal doped g-C3N4 with 1 vol% TEOA.•Enhanced H2 production rate induced by traces level (<0.1 wt%) of S-dopant.•Benefits of low-level doping strategy to overcome the main limitations of g-C3N4.•One-pot easy synthesis of non-metal doping of g-C3N4 thermal polycondensation.•Those photocatalyst exhibit enhanced visible light harvesting properties.
Asteriscus graveolens
(Asteraceae) is a medicinal herb, used in Algeria to treat diabetes, hypertension, pain, fever, inflammation and gastrointestinal diseases. Doxorubicin (DOX) is an antibiotic ...antineoplastic drug used to treat many types of cancers; unfortunately, its antitumor activity links toxic effects to several organs including the heart, liver and testis. The appropriate mechanism of its organotoxicity is linked to free reactive oxygen species (ROS) generation and oxidative stress induction. In this study, the antioxidant and protective role of
A. graveolens
and vitamin E (Vit E) against DOX-induced hepatic and testicular toxicity was assessed. Thirty-five rats were distributed equally into five groups and orally administered with
n
-butanol extract of
A. graveolens
(75 mg/kg bw) or Vit E (100 mg/kg bw) for 10 days in the absence or presence of a single intraperitoneal injection of DOX (15 mg/kg bw). The results revealed that DOX toxicity induced a significant elevation in the liver serum marker enzymes and lipid profile levels (cholesterol, triglycerides and LDL). In addition, DOX-induced hepatic and testicular oxidative injury was indicated due to a significant increase of malondialdehyde levels along with a noticeable reduction of the antioxidant system.
A. graveolens
and Vit E treatment might improve the biochemical and histopathological changes induced by DOX.
A. graveolens
has antioxidant and hypolipidemic properties and it can reduce DOX-induced oxidative damage in the liver and testis.
A. graveolens
showed a similar protective effect of Vit E against DOX damage due to the presence of an abundant amount of phenolics such as flavonoids. This protection is mediated by their direct free-radical scavenging activity and their ability to prevent DOX depletion of the hepato-testicular antioxidant defense systems.
Herein, visible light‐driven gas‐phase photocatalytic CO
2
reduction into CH
4
is tuned by designing optimized three‐component Au/doped C
3
N
4
/TiO
2
composite photocatalysts. The key point strategy ...consists in the formation of high‐quality C
3
N
4
/TiO
2
heterojunction by associating low containing doped graphitic carbon nitride to commercially available TiO
2
UV‐100. Those heterojunctions result in both visible light sensitization and increased charge‐carrier separation. Further deposition of small Au nanoparticles (≈3 nm), quite exclusively onto TiO
2
surfaces, mainly acts as electron trapping/cocatalytic functions without excluding surface plasmonic effects. The resulting doped g‐C
3
N
4
material exhibits enhanced visible light harvesting properties, especially in the case of C‐doping. In addition, it is assumed that B– and C–C
3
N
4
doping, leading to a more or less lower conduction band position, is the impacting factor toward total CH
4
selectivity achievement. The (0.77 wt%)Au/(0.59 wt%)C–C
3
N
4
/TiO
2
composite photocatalyst, exhibiting the best compromise between the various impacting factors, leads to a continuous productivity rate of CH
4
of 8.5 μmol h
−1
g
−1
under visible light irradiation over at least 10 h. To the best of knowledge, this level of performance is unprecedented under continuous gas‐phase flowing CO
2
in the presence of water as reducing agent, without addition of any sacrificial agent.
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•Phytochemical study of Saharan medicinal plant.•Two new astericunolides and one humulene were isolated.•X-ray of astericunolide I.
Three new sesquiterpene-humulenes, (−)- ...asteriscunolides I (1), J (2) and (−)-(2Z,6E,9Z)-8-oxo-1α-acetoxy-2,6,9-humulatrien-12-oic acid (3) were isolated from the leaves-flowers of the Saharan medicinal plant Asteriscus graveolens along with six known compounds. The structures of the compounds were determined on the basis of spectroscopic mono and bidimensional NMR, mass spectrometry and by single-crystal X-ray diffraction. Compounds 1–3 were evaluated for cytotoxic assay, no significant activity was detected.
Herein, visible light‐driven gas‐phase photocatalytic CO2 reduction into CH4 is tuned by designing optimized three‐component Au/doped C3N4/TiO2 composite photocatalysts. The key point strategy ...consists in the formation of high‐quality C3N4/TiO2 heterojunction by associating low containing doped graphitic carbon nitride to commercially available TiO2 UV‐100. Those heterojunctions result in both visible light sensitization and increased charge‐carrier separation. Further deposition of small Au nanoparticles (≈3 nm), quite exclusively onto TiO2 surfaces, mainly acts as electron trapping/cocatalytic functions without excluding surface plasmonic effects. The resulting doped g‐C3N4 material exhibits enhanced visible light harvesting properties, especially in the case of C‐doping. In addition, it is assumed that B– and C–C3N4 doping, leading to a more or less lower conduction band position, is the impacting factor toward total CH4 selectivity achievement. The (0.77 wt%)Au/(0.59 wt%)C–C3N4/TiO2 composite photocatalyst, exhibiting the best compromise between the various impacting factors, leads to a continuous productivity rate of CH4 of 8.5 μmol h−1 g−1 under visible light irradiation over at least 10 h. To the best of knowledge, this level of performance is unprecedented under continuous gas‐phase flowing CO2 in the presence of water as reducing agent, without addition of any sacrificial agent.
Au/TiOsub.2 photocatalysts were studied, characterized, and compared for COsub.2 photocatalytic gas-phase reduction. The impact of the nature of the TiOsub.2 support was studied. It was shown that ...the surface area/porosity/TiOsub.2 crystal phase/density of specific exposed facets and oxygen vacancies were the key factors determining CHsub.4 productivity under solar-light activation. A 0.84 wt.% Au/TiOsub.2 SG (Sol Gel) calcined at 400 °C exhibited the best performance, leading to a continuous mean CHsub.4 production rate of 50 μmol.hsup.−1.gsup.−1 over 5 h, associated with an electronic selectivity of 85%. This high activity was mainly attributed to the large surface area and accessible microporous volume, high density of exposed TiOsub.2 (101) anatase facets, and oxygen vacancies acting as reactive defects sites for COsub.2 adsorption/activation/dissociation and charge carrier transport.
Cet article examine la question de la participation de la diaspora algérienne dans le mouvement du Hirak de février 2019. La méthodologie employée repose sur la théorie de la présence connectée et ...l'entretien. Les résultats obtenus mettent en évidence que, grâce aux réseaux sociaux numériques (RSN), la diaspora algérienne a réussi à prendre part au mouvement malgré la distance géographique, en occupant régulièrement l'espace public dans les sociétés d'accueil et en se mobilisant sur la toile. Cette étude a également mis en lumière d'autres dimensions de la diaspora algérienne établie en France, au Canada et aux États-Unis. Le Hirak a favorisé le retour aux racines, le renforcement des liens intra et intercommunautaires, et a révélé une étendue cosmopolite.
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