Organic–inorganic hybrids featuring tunable material
properties can be readily generated by applying vapor- or liquid-phase
infiltration (VPI or LPI) of inorganic materials into organic templates,
with resulting properties controlled by type and quantity of infiltrated
inorganics. While LPI offers more diverse choices of infiltratable
elements, it tends to yield smaller infiltration amount than VPI,
but the attempt to address the issue has been rarely reported. Here,
we demonstrate a facile temperature-enhanced LPI method to control
and drastically increase the quantity and kinetics of Pt infiltration
into self-assembled polystyrene-block-poly(2-vinylpyridine)
block copolymer (BCP) thin films. By applying LPI at mildly elevated
temperatures (40–80 °C), we showcase controllable optical
functionality of hybrid BCP films along with conductive three-dimensional
(3D) inorganic nanostructures. Structural analysis reveals enhanced
metal loading into the BCP matrix at higher LPI temperatures, suggesting
multiple metal ion infiltration per monomer of P2VP. Combining temperature-enhanced
LPI with hierarchical multilayer BCP self-assembly, we generate BCP-metal
hybrid optical coatings featuring tunable antireflective properties
as well as scalable conductive 3D Pt nanomesh structures. Enhanced
material infiltration and control by temperature-enhanced LPI not
only enables tunability of organic–inorganic hybrid nanostructures
and properties but also expands the application of BCPs for generating
uniquely functional inorganic nanostructures.
Novel positive-tone hybrid resists developed by vapor-phase inorganic infiltration feature fully tunable resist performance parameters and high-aspect-ratio pattern transfer capability.
With the progress in the synthesis of high quality ZnO nanowires, their implementation as gas sensors has gained popularity. Relying on the surface ionosorption, these devices have demonstrated exquisite sensitivity with further improvement achieved through various functionalisation methods. Both resistive and transistor based methodologies are employed for gas sensing while integration of micro-heaters has also been attempted for portability of the devices. In order to achieve successful inclusion amongst semiconductor fabrication processes, top-down approaches are being explored along with conventional bottom-up synthesis routes. Major challenge of low selectivity can be overcome by Electronic Nose systems. This article reviews the progress in synthesis, functionalisation, and device implementation of ZnO nanowire gas sensors, concluding with remarks on associated challenges and future prospects.
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