Journal article 619 views
Heterogeneous nucleation for synthesis of sub-20nm ZnO nanopods and their application to optical humidity sensing
Analytica Chimica Acta, Volume: 812, Pages: 206 - 214
Swansea University Author: Kenith Meissner
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DOI (Published version): 10.1016/j.aca.2014.01.012
We present a novel method for colloidal synthesis of one-dimensional ZnO nanopods by heterogeneous nucleation on zero-dimensional ZnO nanoparticle ‘seeds’. Ultra-small ZnO nanopods, multi-legged structures with sub-20 nm individual leg diameters, can be synthesized by hydrolysis of a Zn2+ precursor...
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We present a novel method for colloidal synthesis of one-dimensional ZnO nanopods by heterogeneous nucleation on zero-dimensional ZnO nanoparticle ‘seeds’. Ultra-small ZnO nanopods, multi-legged structures with sub-20 nm individual leg diameters, can be synthesized by hydrolysis of a Zn2+ precursor growth solution in presence of ∼4 nm ZnO seeds under hydrothermal conditions via microwave-assisted heating in as little as 20 min of reaction time. One-dimensional ZnO nanorods are initially generated in the reaction mixture by heterogeneous nucleation and growth along the  direction of the ZnO crystal. Growth of one-dimensional nanorods subsequently yields to an ‘attachment’ and size-focusing phase where individual nanorods fuse together to form multi-legged nanopods having diameters ∼15 nm. ZnO nanopods exhibit broad orange-red defect-related photoluminescence in addition to a near-band edge emission at 373 nm when excited above the band-gap at 350 nm. The defect-related photoluminescence of the ZnO nanopods has been applied towards reversible optical humidity sensing at room temperature. The sensors demonstrated a linear response between 22% and 70% relative humidity with a 0.4% increase in optical intensity per % change in relative humidity. Due to their ultra-small dimensions, ZnO nanopods exhibit a large dynamic range and enhanced sensitivity to changes in ambient humidity, thus showcasing their ability as a platform for optical environmental sensing.
Published in a leading analytical science journal (Impact factor: 4.712), this work elucidates the dynamics and mechanisms of ZnO nanopods and applies the resulting structures to humidity sensing. Through understanding of this mechanism, the work enables rational design of nanostructures to optimise their sensing capabilities. The work follows from the Meissner group’s extensive expertise in the microwave production of nanostructures from ZnO (5 journal publications) and CdSe (5 journal publications) since 2010. Preliminary data from this work formed the core of an invited talk at an international conference (SPIE, Photonics West, 2011).
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