A comparative study of the gas sensing properties of hierarchical ZnO nanostructures

International audienc

Growth mechanism studies of ZnO nanowire arrays via hydrothermal method

International audienc

Enhanced Photocatalytic Activity of Iron-Doped ZnO Nanowires for Water Purification

International audienc

Direct growth of ZnO nanowires on civil engineering materials: smart materials for supported photodegradation

International audiencePhotocatalysis is one of the most promising processes for treating air and water pollution. Innovative civil engineering materials for environmental depollution by photocatalysis have already been synthesized by incorporating TiO 2 or ZnO nanoparticles in cement. This method suffers from two flaws: first, most of the NPs are incorporated into the cement and useless for photocatalysis; second, rain and wind could spread the potentially carcinogenic nanoparticles from the cement surface into nature. Thus, we propose the efficient synthesis of nontoxic and biocompatible ZnO nanostructures solely onto the surface of commercially available concrete and tiling pavements by a low-cost and low-temperature hydrothermal method. Our samples exhibited enhanced photocatalytic activity for degrading organic dyes in aqueous media, and dye molecules are commonly used in the pharmaceutical, food, and textile industries. Durability studies showed no loss of efficiency after four photocatalysis experiments. Such supported structures, which are easy to implement onto the varying surfaces of commercially available materials, are promising for integration into civil engineering surfaces for environmental depollution in our daily life

Enhanced photocatalytic activity of ZnO nanostructure for water purification

International audienc

Enhanced steam generation based on a bilayer water and light absorber: Modelling and optimization of capillary imbibition and water evaporation

International audienceEnhanced steam generation is a robust and promising process for water purification. This is a method of increasing the evaporation efficiency by localizing the heat at the water-air interface using a black absorber. It is worth mentioning at this stage that the two functions of localized heating and water imbibition are different functions that can be separated in their implementation. However, one can note that a vast majority of state-of-the-art implementations show that both functions are integrated together, which is typically a black and porous medium, hence providing simultaneous light absorption and water absorption capabilities. In addition, there is a concern about thermal conductivity so as to minimize loss of the surface-localized generated heat into the surrounding water bulk. As of late, bilayer structure black absorbers (Fig.1) have been developed in different combinations of photothermal materials and porous media aiming to achieve efficient steam generation.Here we report the modelling of a bilayer structure and obtain the structural optimization design of black absorber through theoretical analysis. Simultaneously, we launch the simulation model in COMSOL and our simulation results are in good agreement with the water imbibition rate in the literature. The results show several key parameter trends for determining the geometry of bilayer structure, especially the water imbibition rate caused by capillary fluid flow. According to the establishment of this theoretical and numerical model, the optimization geometry structure can be designed for enhanced steam generation

Effect of growth time and annealing on the structural defect concentration of hydrothermally grown ZnO nanowires

International audienc

ZnO nanowires-on-quartz for efficient water purification: The issue of Volatile organic compounds (VOCs) degradation using solar energy

International audiencePhotocatalysis is proved to be the most efficient way for the degradation process of organic pollutants. ZnO and TiO2 are supposed to be the most common photocatalysts due to their high performance in degradation by producing the oxidative free radical after being illuminated by UV light. Taking the advantages of these chemical properties, the environmental applications were developed by many research groups using micro-nano technologies. Furthermore, ZnO has biocompatibility advantage, and easy to obtain the high aspect ratio nanowires (NWs) via low-cost synthesis method with the further advantage of being firmly anchored to the substrate, leading to more sustainable applications. Here we report on ZnO NWs-on-quartz based photocatalysis for water purification, more specifically, the VOCs contaminants, which have been chosen because these pollutants cannot be removed by conventional purification such as steam generation, as shown in Figure 1 (a). SEM observation (Figure 1(b)) showed homogeneous ZnO NW array successfully grown using hydrothermal synthesis method on a quartz substrate (transparent to solar radiation including UV spectrum). Thus, our demonstration combines both steam generation and photocatalytic degradation to obtain purified water. UV-Visible spectrometry revealed a gap value of 3.23eV, while the theoretical value is 3.30 eV. Simultaneously, targeting the degradation of VOCs in the water, a series of validation experiments showed that our ZnO NWs have a good photocatalytic efficiency as shown in our previous work in the case of the microfluid chamber, confirmed both by UV-Vis spectrometry and gas chromatography

Nanowire Length, Density, and Crystalline Quality Retrieved from a Single Optical Spectrum

International audienc

Rapid assessment of nanomaterial homogeneity reveals crosswise structural gradients in zinc-oxide nanowire arrays

International audienc