High aspect ZnO nanostructures based hydrogen sensing

Self-Assembled Hierarchical Interfaces of ZnO Nanotubes/Graphene Heterostructures for Efficient Room Temperature Hydrogen Sensors.

Abstract: Herein, we report the novel nanostructural interfaces of self-assembled hierarchical ZnO nanotubes/graphene (ZNT/G) with three different growing times of ZNTs on graphene substrates (namely, SH1, SH2, and SH3). Each sample was fabricated with interdigitated electrodes to form hydrogen sensors, and their hydrogen sensing properties were comprehensively studied. The systematic investigation revealed that SH1 sensor exhibits an ultrahigh sensor response even at a low detection level of 10 ppm (14.3%) to 100 ppm (28.1%) compared to those of the SH2 and SH3 sensors. The SH1 sensor was also found to be well-retained with repeatability, reliability, and long-term stability of 90 days under hydrogenation/dehydrogenation processes. This outstanding enhancement in sensing properties of SH1 is attributed to the formation of a strong metalized region in the ZNT/G interface due to the inner/outer surfaces of ZNTs, establishing a multiple depletion layer. Furthermore, the respective band models of each nanostructure we...

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

Abstract: 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.

Superhydrophobic polymethylsilsesquioxane pinned one dimensional ZnO nanostructures for water remediation through photo-catalysis

Abstract: ZnO nanostructures have been heavily explored for a variety of sensing properties and of late a major emphasis by researchers has been to find applications for ZnO materials in the domain of photo-catalysis. ZnO nanoparticles have been found as a better alternative to other materials for removing organic dyes from polluted water and the abolition of several hazardous materials etc. In this work we have developed ultra-dense high aspect ratio ZnO nano-forest like structures and explored their potential as photo-catalysts. The films formulated are superhydrophobic (contact angle ∼ 154°) in nature and have been evaluated as containing a high density of oxygen defects in the crystalline state of the ZnO (as validated through photoluminescence measurements). The samples were found to possess enhanced photo-catalytic properties, as measured through a dye degradation process using an UV-Vis spectrophotometer. These photo-catalytic properties may be due to the high defect density and also the enhanced area of the interactive surface as one goes from nano-particles to nano-rod like structures. The paper gives an insight into highly unique carpeted nano-wire bundles of ZnO and offers immense utility to the realization of high efficiency remediation filters.

Fabrication of Nanostructures with Bottom-up Approach and Their Utility in Diagnostics, Therapeutics, and Others

Abstract: Nanofabrication has been a critical area of research in the last two decades and has found wide-ranging application in improvising material properties, sensitive clinical diagnostics, and detection, improving the efficiency of electron transport processes within materials, generating high energy densities leading to pulse power, novel therapeutic mechanisms, environmental remediation and control. The continued improvements in the various fabrication technologies have led to realization of highly sensitive nanostructure-based devices. The fabrication of nanostructures is in principle carried out primarily using top-down or bottom-up approaches. This chapter summarizes the important bottom-up nanofabrication processes for realizing nanostructures and also highlights the recent research conducted in the domain of therapeutics and diagnostics.

Reduced graphene oxide based hybrid functionalized films for hydrogen detection: Theoretical and experimental studies

Abstract: In this work, hydrogen sensing characteristics of reduced graphene oxide (rGO) based functional nanomaterials are investigated with first principle calculations and experimental analysis. rGO doped with zinc oxide nanomaterial (i.e. rGO-ZnO), rGO-ZnO with silver nanoparticles (rGO-ZnO-Ag), rGO-ZnO with zirconium oxide (rGO-ZnO-ZrO2), rGO-ZnO doped with silver and palladium (rGO-ZnO-Ag-Pd) are investigated for their sensing capabilities. The influence of gas adsorption on the electronic features of the functional nanostructures are analyzed using the first principles density functional theory. The results of the computation reveal a considerable improvement of graphene oxide sensitivity in the hydrogen gas molecules following hybridization by ZnO, ZnO–Ag, ZnO–Ag–Pd and ZrO2. Fabrication and characterization of aforementioned functional materials and their hydrogen sensing performances are performed and essential sensing characteristics viz., sensitivity, response time, recovery time, reproducibility are also investigated. Out of the fabricated films, rGO-ZnO-Ag-Pd film is found to have the highest sensitivity towards hydrogen. It showed the sensitivity of ∼60% and highest performance factor (evaluated as the ratio of sensitivity to cycle time) among all films, including response time as 10 s and recovery time as 14 s. While performing sensing investigation, the distinct p-type behavior was observed for all the fabricated film. Obtained outcomes relate the promising future of rGO doped ZnO–Ag, ZnO–Ag–Pd and ZrO2 hybrid nano sensor in the advancement of sensitive gas sensors.