Facile synthesis of ZnO/GO nanoflowers over Si substrate for improved photocatalytic decolorization of MB dye and industrial wastewater under solar irradiation

Hydrogen gas sensing methods, materials, and approach to achieve parts per billion level detection: A review

α-Fe2O3 loaded rGO nanosheets based fast response/recovery CO gas sensor at room temperature

We report here excellent H 2 gas response property of Co-doped ZnO nanorods (Co:ZnO NRs). Co:ZnO NRs have been synthesized by hydrothermal method by varying the Co content from 0 to 10 mol%. It is found that Co:ZnO NRs with 8 mol% of Co exhibits the highest and faster H 2 gas response ability compared to the undoped ZnO resulting in a ∼5 fold enhancement in the gas response in the presence of air at 150 °C. While the gas response value (S (%) = [(I g -I a )/I a ] × 100, where I a is the current of the sensors in the presence of air only and I g is the current in the presence of certain H 2 concentration) to 3000 ppm H 2 for undoped ZnO NRs’sensor is 11%, an unprecedented high value of 53.7% is obtained for the Co:ZnO with 8 mol% of Co. Based on the electrical current and photoluminescence results, a mechanism for the enhanced H 2 response of Co:ZnO is proposed that involves donor-related oxygen vacancies (V O ) introduced by the Co dopants in the ZnO lattice.

Highly enhanced H2 gas sensing characteristics of Co:ZnO nanorods and its mechanism

In this work, we report an effective water filtration system based on the photocatalytic performance of semiconducting dense nano-brushes under natural sunlight. During thin-film photocatalysis, which is usually performed by a deposited layer of photocatalyst, a stagnant boundary layer is created near the catalyst which adversely affects the rate of adsorption because of diffusional restrictions. One strategy that may be used is to disrupt this laminar boundary layer by creating a super-dense nanostructure near the surface of the catalyst. Furthermore, it is useful to fabricate a structured filter element for the passage of water with the use of nanostructures protruding out of the surface. Herein, dye remediation is performed by solar means. This remediation was initially limited to a lower efficiency because of diffusional restrictions but has now become a fast process due to microhole incorporation in the filter materials with protruding dense nanostructures. Theoretical analysis predicts that there is an optimal film thickness that yields the maximum adsorption and also a highly nonlinear behaviour of diffusivity with respect to the fraction adsorbed. The effect of increased surface area due to microholes on the fraction adsorbed is also investigated and it is found that there is an optimum value of hole diameter for maximum adsorption.

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Solar light based degradation of organic pollutants using ZnO nanobrushes for water filtration

ZnO nanobundles were grown via a nano-templating technique over a porous silica bed using an aqueous chemical route. The growth of nanobundles initiated from ZnO nano-seeds positioned at various levels over a nanoporous matrix of self-assembled polymethylsilsesquioxane nanoparticles. Bundles of different features like nanowires, nanorods and nanotubes with a high surface roughness were grown over these templates by a day-long incubation in an aqueous solution of hexamethylene tetra-amine and zinc nitrate. We envisage these ZnO nanostructures for sensitive hydrogen detection. Photoluminescence spectra indicate the nanotubes to be most sensitive towards H2. We observe high reconditionability, moderate sensitivity and a temperature dependent charge carrier reversal phenomenon.

Subhashish Basu Majumder

Papers

Hydrogen sensing based on nanoporous silica-embedded ultra dense ZnO nanobundles