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Aujourd’hui, seulement 20 à 50% des composés organiques réfractaires (COR), menaçant les sources d’eau et la santé publique, sont éliminés par les stations d’épuration traditionnelles. Pour relever ce défi, des technologies innovantes comme la photocatalyse avec des photocatalyseurs à base de TiO2 sont développées. 

L’objectif de ce travail est l’étude de l’amélioration de l’activité photocatalytique du TiO2 sous lumière UV-visible et visible par dopage avec du tantale (Ta) ou du vanadium (V). Des photocatalyseurs à base de TiO2 ont ainsi été préparés à température ambiante via une synthèse sol-gel aqueuse, selon une méthode adaptée de Mahy et al. (2016). Les rapports molaires de dopants testés variaient de 0,1% à 5% pour le Ta et de 0,1% à 16% pour le V. Les propriétés physico-chimiques des photocatalyseurs ont aussi été caractérisées par diverses techniques complémentaires. 
La diffraction des rayons X (DRX) a permis de déterminer la distribution des phases cristallines et la proportion de TiO2 amorphe. Les photocatalyseurs obtenus, composés de nanoparticules de TiO2 anatase-brookite de 5 à 6 nm, présentent une surface spécifique élevée (182 à 292 m²/g) déterminée par mesure d’adsorption-désorption d’azote par la méthode de Brunauer-Emmett-Teller (BET). L’augmentation de la surface spécifique, de la microporosité et de la mésoporosité a été majoritairement observée pour les échantillons dopés comparés au TiO2 pur. 

Les micrographies de microscopie électronique à balayage (MEB) et en transmission (MET) révèlent une morphologie similaire entre les échantillons dopés et non dopé, constitués d’agrégats de nanoparticules sphériques de TiO2. Les analyses de spectroscopies d’émission atomique par plasma couplé par induction (ICP-AES), par dispersion d’énergie des rayons X (EDX) et photoélectronique à rayons X (XPS) confirment la présence des éléments Ti, O, Ta ou V. Les spectres XPS montrent l’incorporation d’azote et la formation d’espèces comme V2O5 et Ta2O5. Par ailleurs, les largeurs de bande interdite mesurées par spectroscopie UV-visible en réflectance diffuse (DRS) sont plus faibles pour les échantillons dopés au V par rapport au TiO2 pur mais augmentent pour ceux dopés au Ta.

Le criblage de l’activité photocatalytique a été réalisé en évaluant la dégradation du p-nitrophénol (PNP) sous lumière UV-visible et visible. L’activité photocatalytique est influencée par la nature et la teneur en dopant. Les tests montrent une amélioration de l’activité avec le dopage au Ta, tandis qu’une diminution notable est observée avec le dopage au V. Le dopage au Ta améliore la séparation des porteurs de charge photogénérés, tandis que le dopage au V entraîne une recombinaison plus rapide des paires e⁻/h⁺, réduisant l’activité photocatalytique.
À côté de ça, la calcination de l’échantillon le plus faiblement dopé au vanadium entraîne une nette amélioration de son activité photocatalytique, mais celle-ci reste largement inférieure à celle associée au TiO2 pur. Aussi, il a été remarqué, par spectrophotométrie, que mis à part le pic du PNP centré sur λ ∼ 318 nm, aucun autre pic n’est observé dans les spectres UV-vis des échantillons entre 260 et 500 nm, ce qui indique une minéralisation complète du polluant par les photocatalyseurs synthétisés.

Pour finir, un premier montage expérimental d’électrophotocatalyse, sous des conditions de fonctionnement non optimales, a été mis en place et paraît montrer une amélioration de la minéralisation de la solution de PNP lorsque l’anode est revêtue de TiO2 par rapport à une anode non revêtue. Ce test constitue une base prometteuse pour des améliorations et des recherches futures qui s’inscrivent dans le cadre d’un projet plus général mené par Julien Mahy, chercheur postdoctoral au FNRS. Today, only 20 to 50% of refractory organic compounds (ROCs), which threaten water sources and public health, are removed by traditional wastewater treatment plants. To address this challenge, innovative technologies such as photocatalysis with TiO2-based photocatalysts are being developed.

The objective of this work is to study the improvement of the photocatalytic activity of TiO2 under UV-visible and visible light by doping with tantalum (Ta) or vanadium (V). TiO2-based photocatalysts were prepared at room temperature via an aqueous sol-gel synthesis, according to a method adapted from Mahy et al. (2016). The tested molar ratios of dopants varied from 0.1% to 5% for Ta and from 0.1% to 16% for V. The physicochemical properties of the photocatalysts were also characterised by various complementary techniques.

X-ray diffraction (XRD) was used to determine the distribution of crystalline phases and the proportion of amorphous TiO2. The obtained photocatalysts, composed of TiO2 anatase-brookite nanoparticles of 5 to 6 nm, exhibit a high specific surface area (182 to 292 m²/g) determined by nitrogen adsorption-desorption measurement using the Brunauer-Emmett-Teller (BET) method. An increase in specific surface area, microporosity, and mesoporosity was mostly observed for the doped samples compared to pure TiO2.

Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) micrographs reveal a similar morphology between doped and undoped samples, consisting of aggregates of spherical TiO2 nanoparticles. Inductively coupled plasma atomic emission spectroscopy (ICP-AES), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) analyses confirm the presence of Ti, O, Ta, or V elements. XPS spectra show the incorporation of nitrogen and the formation of species such as V2O5 and Ta2O5. Furthermore, the band gap widths measured by UV-visible diffuse reflectance spectroscopy (DRS) are lower for V-doped samples compared to pure TiO2 but increase for Ta-doped ones.

Photocatalytic activity screening was carried out by evaluating the degradation of p-nitrophenol (PNP) under UV-visible and visible light. Photocatalytic activity is influenced by the nature and content of the dopant. Tests show an improvement in activity with Ta doping, whereas a notable decrease is observed with V doping. Ta doping improves the separation of photogenerated charge carriers, whereas V doping leads to faster recombination of e⁻/h⁺ pairs, reducing photocatalytic activity.

Additionally, calcination of the V-doped sample with the lowest dopant content leads to a significant improvement in its photocatalytic activity, though it remains significantly lower than that associated with pure TiO2. Moreover, spectrophotometry revealed that, apart from the PNP peak centred at λ ∼ 318 nm, no other peaks were observed in the UV-vis spectra of the samples between 260 and 500 nm, indicating complete mineralisation of the pollutant by the synthesised photocatalysts.

Finally, an initial electrophotocatalysis experimental setup, under non-optimal operating conditions, was established and appears to show an improvement in the mineralisation of the PNP solution when the anode is coated with TiO2 compared to an uncoated anode. This test constitutes a promising basis for improvements and future research, which are part of a more general project led by Julien Mahy, a postdoctoral researcher at FNRS.

Électrophotocatalyse --- Traitement de l'eau --- TiO2 --- Synthèse sol-gel aqueuse --- Précipitation-peptisation --- Dopage au tantale --- Dopage au vanadium --- Photocatalyse --- Photocatalyseurs --- Dégradation du p-nitrophénol --- Ingénierie, informatique & technologie > Science des matériaux & ingénierie

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The book "Green Synthesis of Nanomaterials and Their Biological Applications" present novel advances about the green synthesis of nanomaterials, as well as on the possible biological applications, including studies dealing with entomology, parasitology, biomedicine, and environmental research.

Medicine --- metamaterial --- multiple resonances --- biochemical sensing --- environment sensor --- net formulations --- stored product insects --- knockdown --- mortality --- long-term effect --- European grapevine moth --- green pesticide --- insect pest --- Integrated Pest Management --- Larvicide --- nano-insecticide --- Tortricidae --- hydatid cyst --- protoscoleces --- nanomedicine --- in vitro --- in vivo --- ex vivo --- zinc oxide --- nanoparticles --- black tea extract --- gallic acid --- green synthesis --- antioxidants --- antimicrobial activity --- silver nanoparticles --- Diospyros malabarica --- antibacterial --- anticancer --- catalyst --- 4-nitrophenol --- electromechanically --- tunability --- metamaterials --- multi-functionalities --- terahertz --- refraction index sensor --- n/a

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This book, entitled “Mesoporous Metal Oxide Films”, contains an editorial and a collection of ten research articles covering fundamental studies and applications of different metal oxide films. Mesoporous materials have been widely investigated and applied in many technological applications owing to their outstanding structural and physical properties. In this book, important developments in this fast-moving field are presented from various research groups around the world. Different preparation methods and applications of these novel and interesting materials have been reported, and it was demonstrated that mesoporosity has a direct impact on the properties and potential applications of such materials. The potential use of mesoporous metal oxide films and coatings with different morphology and structures is demonstrated in many technological applications, particularly chemical and electrochemical sensors, supercapacitors, solar cells, photoelectrodes, bioceramics, photonic switches, and anticorrosion agents.

History of engineering & technology --- SnO2 --- Metglas --- hemin --- H2O2 --- cyclic voltammetry --- magnetoelastic resonance --- sensor --- titanium dioxide --- mesoporous --- thin film --- multi-layered --- photoanode --- semiconductor --- photoelectrochemical water oxidation --- Mn2O3 --- mesoporous materials --- electrochemical characterizations --- electrode --- supercapacitors --- gadolinium oxide --- hydrazine --- p-nitrophenol --- electrochemical sensing --- amperometric --- selective sensor --- nanocrystal --- ZnO --- density of states --- optical and electrical properties --- TiO2 films --- Ag nanoparticles --- optical properties --- spectroelectrochemistry --- surface plasmon --- Fe-doped TiO2 --- hydrothermal --- GCE --- chemical sensor --- amperometry --- dye-sensitized solar cells --- working electrode --- TiO2 --- NiO nanoparticles --- electron transport --- corrosion --- guar gum --- coatings --- electrochemical impedance spectroscopy (EIS) --- SECM --- AFM --- calcium phosphate silicate --- PEG --- bioceramics --- sol-gel preparation --- hard tissue engineering --- metal oxide --- sol-gel --- supercapacitor --- photoelectrode --- dye sensitized solar cell --- NiO

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Layered double hydroxides (LDHs), also known as two-dimensional anionic clays, as well as the derived materials, including hybrids, nanocomposites, mixed oxides, and supported metals, have been highlighted as outstanding heterogeneous catalysts with unlimited applications in various processes involving both acid–base (addition, alkylation, acylation, decarboxylation, etc.) and redox (oxidation, reduction, dehydrogenation, etc.) mechanisms. This is mainly due to their flexibility in chemical composition, allowing the fine tuning of the nature of the active sites and the control of the balance between them. Additionally, LDHs display a large anion exchange capacity and the possibility to modify their interlayer space, constraining the size and type of reactants entering in the interlamellar space. Furthermore, their easy and economic synthesis, with high levels of purity and efficiency, at both the laboratory and industrial scales, make LDHs and their derived materials excellent solid catalysts. This Special Issue collects original research papers, reviews, and commentaries focused on the catalytic applications of these remarkable materials.

Research & information: general --- Chemistry --- layered double hydroxides (LDH) --- polyoxometalates (POM) --- catalytic materials --- Michael addition --- cobalt-based LDHs --- ultrasonic irradiation --- synergistic effect --- photocatalysis --- nitrophenol degradation --- Zn,Al-hydrotalcite --- ZnO dispersed on alumina --- reusability --- layered double hydroxide --- LDH --- catalytic oxidation --- ethanol --- toluene --- VOC --- photocatalysts --- Cu electrodes --- diazo dyes --- electrocatalysts --- layer double hydroxides --- photoelectrochemical degradation --- hydrotalcites --- mixed oxides --- aldol condensation --- basic catalysts --- exfoliation --- nanosheets --- oxidation --- layered double hydroxides --- base catalysts --- epoxide --- formaldehyde --- oxidation removal --- BiOCl --- manganese --- biodiesel --- transesterification --- hydrothermal --- nickel --- aluminum --- solid base --- structured catalyst --- ethanol steam reforming --- aluminum lathe waste strips --- Ni nanoparticle --- mechano-chemical/co-precipitation synthesis --- organic alkalis (tetramethylammonium hydroxide) --- memory effect --- Claisen-Schmidt condensation --- self-cyclohexanone condensation --- n/a

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With the increasing global usage of water and the continuous addition of contaminants to water sources, new challenges have arisen that are associated with the abatement of organic pollutants, particularly those that are refractory to conventional water and wastewater treatment technologies. Advanced oxidation processes (AOPs) present a competitive alternative to promote the oxidation of organic contaminants by strong oxidative radicals generated from oxygen, ozone, wet peroxide, and UV radiation. The use of catalysts not only improves efficiency but may present remarkable cost advantages for practical applications of AOPs in the abatement of several pollutants. In this Special Issue of Catalysts, we invite authors to submit original research papers focused on the synthesis and characterization of novel heterogeneous catalysts and their uses in advanced oxidation processes for the removal of organic pollutants from aqueous solutions.

CdS --- Bi2MoO6 microspheres --- antibiotic removal --- charge separation --- visible-light-driven --- carbon xerogel --- carbon nanotubes --- activated carbon --- adsorption --- catalytic wet peroxidation --- heterogeneous Fenton’s oxidation --- p-nitrophenol --- magnetic materials --- chemical vapour deposition --- photocatalytic ozonation --- organic pollutants --- advanced oxidation process --- wastewater treatment --- contaminants of emerging concern --- pharmaceuticals --- environmental catalysis --- biochar --- iron mineral --- heterogeneous catalysts --- antibiotic --- advanced oxidation processes --- water treatment --- Fenton reactions --- LCA --- environmental impact --- Fenton --- photocatalysis --- visible light --- SBA15 --- magnetite --- graphene --- tin oxide --- antimony doped tin oxide --- electrochemical oxidation --- atomic layer deposition --- TiO2-SiO2 --- immobilized photocatalyst --- methylene blue adsorption --- metal-free carbon catalysts --- N, S-co-doping --- catalytic wet air oxidation --- n/a --- heterogeneous Fenton's oxidation