A facile method for the preparation of bifunctional Mn:ZnS/ZnS/Fe3O4 magnetic and fluorescent nanocrystals

Bifunctional magnetic and fluorescent core/shell/shell Mn:ZnS/ZnS/Fe3O4 nanocrystals were synthesized in a basic aqueous solution using 3-mercaptopropionic acid (MPA) as a capping ligand. The structural and optical properties of the heterostructures were characterized by X-ray diffraction (XRD), dynamic light scattering (DLS), transmission electron microscopy (TEM), UV–vis spectroscopy and photoluminescence (PL) spectroscopy. The PL spectra of Mn:ZnS/ZnS/Fe3O4 quantum dots (QDs) showed marked visible emission around 584 nm related to the 4T1 → 6A1 Mn2+ transition. The PL quantum yield (QY) and the remnant magnetization can be regulated by varying the thickness of the magnetic shell. The results showed that an increase in the thickness of the Fe3O4 magnetite layer around the Mn:ZnS/ZnS core reduced the PL QY but improved the magnetic properties of the composites. Nevertheless, a good compromise was achieved in order to maintain the dual modality of the nanocrystals, which may be promising candidates for various biological applications

ZnS quantum dots and their derivatives: Overview on identity, synthesis and challenge into surface modifications for restricted applications

Among different inert materials, quantum dots have been qualified by their fashion proprieties especially those related to structure and sizes. This review talks about the structural identity and some relevant methods to synthesize quantum dots, there is a challenge in the adaptation of nanoparticles to fulfill the biological, chemical and physical applications which demonstrate the crucial role of the surface. Modifications of the surface, cross stepwise the electronic transition layers of the particles, contribute to the functionalization in order to incorporate atoms in the main structure or immobilize small molecules onto the surface which lead to a restricted application. Finally, quantum dots are revealed to be an attractive material that can be a support for large potential applications in the future

Vers une quantification de l'érosion éolienne des sols labourés dans le sud tunisien

International audienceLa Tunisie, par sa situation géographique, possède un climat diversifié dominé par l'aridité. Globalement, les trois quarts du pays sont menacés par la désertification, les milieux arides de la Tunisie méridionale et centrale et les milieux semi-arides de la Dorsale et d'une partie du Tell septentrional étant plus particulièrement concernés. Ces terres du sud tunisien, au-dessous de l'isohyète 200 mm an-1 , connaissent de sérieux problèmes d'ensablement qui résultent de la sévérité des conditions climatiques et d'un mode d'exploitation inapproprié des ressources naturelles qui est à l'origine de la vulnérabilité du couvert végétal naturel et des sols. Par ailleurs, le labour des sols sensibles à l'érosion éolienne pour des pratiques de céréaliculture et de culture des oliviers est à l'origine de l'amplification de ce phénomène au cours des dernières décennies. Le but de cette étude est d'utiliser les résultats de trois expériences menées à l'échelle de la parcelle dans le sud tunisien, pour quantifier l'érosion éolienne sur des surfaces agricoles, pour tester la capacité d'un outil de modélisation numérique à reproduire les flux en masse mesurés. L'approche adoptée repose sur des paramétrisations reliant le flux horizontal de particules aux dimensions géométriques des sillons. La validation expérimentale de cette approche est basée sur différentes expériences de terrain menées sur des parcelles travaillées avec différents outils de labour. Les résultats montrent un bon accord entre simulations et observations. Mots-clefs : érosion éolienne, processus physique, pertes en sol brutes, sud tunisie

Quantification de l'érosion éolienne dans le sud tunisien

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What is the impact of mineral dust on air quality in southern Tunisia? Analysis of 2 years of PM10 concentration, and meteorology monitoring

International audienceSouthern Tunisia is a region very prone to wind erosion because of its features, and the development of mechanized agriculture. Moreover, this region is located downwind the Sahara, which is the main source of mineral dust in the world. For these reasons, dust haze is frequently observed in this region. If some authors have already documented air quality in the northern part of Tunisia, no equivalent studies have ever been conducted for southern regions even though Dahech and Beltrando (2012) highlighted the potential negative impact of mineral dust on air quality in Sfax. This is why a ground-based station dedicated to the monitoring of mineral dust was installed at the Institut des Régions Arides (IRA) of Médenine to document the temporal variability of mineral dust concentrations in southern Tunisia. We present here the results from the two first years of measurements of meteorology, PM10 concentration, and direct solar radiation

Sub-chapter 3.5.2. Soils and desertification in the Mediterranean region

Introduction The Mediterranean region – and more specifically North Africa – have been subject to climate change throughout the period 1860-2005 (Mariotti et al. 2015). Simulations predict an average rise in annual temperatures of more than 2 °C with more intense heat waves. Precipitation is projected to decrease compared to 1980–2005 especially in Spain, Morocco, Tunisia and parts of the Middle East region. This is expected to modify soil temperature and soil water content, and consequently ..

Soils and desertification in the Mediterranean region

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