Chun-Hua Chen

Great enhancements in the thermoelectric power factor of BiSbTe nanostructured films with well-ordered interfaces

An innovative concept of twin-enhanced thermoelectricity was proposed to fundamentally resolve the high electrical resistance while not degrading the phonon scattering of the thermoelectric nanoassemblies. Under this frame, a variety of highly oriented and twinned bismuth antimony telluride (BixSb2-xTe3) nanocrystals were successfully fabricated by a large-area pulsed-laser deposition (PLD) technique on insulated silicon substrates at various deposition temperatures. The significant presence of the nonbasal- and basal-plane twins across the hexagonal BiSbTe nanocrystals, which were experimentally and systematically observed for the first time, evidently contributes to the unusually high electrical conductivity of ~2700 S cm(-1) and the power factor of ~25 μW cm(-1) K(-2) as well as the relatively low thermal conductivity of ~1.1 W m(-1) K(-1) found in these nanostructured films.

Hollow V2O5 Nanoassemblies for High-Performance Room-Temperature Hydrogen Sensors

Nanostructured oxides with characteristic morphologies are essential building blocks for high-performance gas-sensing devices. We describe the high-yield fabrication of a series of functionalized V2O5 nanoassemblies through a facile polyol approach with specific varieties of polyvinylpyrrolidone. The synthesized V2O5 nanoassemblies consisting of tiny one-dimensional nanoblocks with the absence of any extrinsic catalysts exhibit distinct hemispherical or spherical hollow morphologies and operate as room-temperature hydrogen sensors with remarkable sensitivities and responses.

Superassembling of Bi2Te3 hierarchical nanostructures for enhanced thermoelectric performance

We describe a facile and one-step pulsed laser deposition (PLD) technique that was utilized for the first time to systematically fabricate a series of innovative Bi2Te3 superassembly-on-epitaxy bi-layer nanostructures, by uniquely coupling the upper self-assembled well-ordered Bi2Te3 hierarchical nanostructures with unusually high surface- and interface-to-volume ratios and a highly electrical conductive epitaxial bottom thin layer on insulated SiO2/Si substrates, as an emerging new class of the most advanced thermoelectric nanomaterials. The optimized power factor of the present superassembly-on-epitaxy films is one to three orders of magnitude higher than that of most Bi2Te3 nanoassemblies defined as the assemblies of nanocrystals, evidently proving the significance and potential of the present new concept and the resulting thermoelectric nanomaterials.

Controlled synthesis of Pt and Co3O4 dual-functionalized In2O3 nanoassemblies for room temperature detection of carbon monoxide

We have designed and successfully synthesized innovative Pt and Co3O4 nanostructure co-decorated In2O3 nano-branches via stepwise facile chemical approaches for room-temperature CO gas sensing. The present results indicate that the combination of well-dispersed tiny Pt nanoparticles and the secondary oxide, p-type Co3O4, nanostructures with optimized fractions onto the n-type In2O3 nano-branches is an effective strategy which could lead to lowering the operating temperature to room temperature and significantly improving the sensitivity as well as the detection limit to a sub-ppm level, for meeting the requirement of advanced gas sensors for the next generation.

Laser co-ablation of bismuth antimony telluride and diamond-like carbon nanocomposites for enhanced thermoelectric performance

A novel design of thermoelectric hetero-nanocomposite films comprising well-aligned oriented (Bi,Sb)2Te3 (BST) nanocrystals and randomly dispersed diamond-like carbon (DLC) clusters has been realized for the first time using dual-beam pulsed laser co-deposition on SiO2 insulated Si substrates. The simultaneously deposited DLC additives were found not only to successfully prevent the thermally induced rapid growth of BST for having consistent nanostructures across the whole BST:DLC film, but also to effectively reduce the thermal transport as qualitatively evidenced by micro-Raman characterizations. The significantly enhanced Seebeck coefficients up to 550 μV K−1 and the corresponding power factor of ∼46 μW cm−1 K−2 revealed comparable to or higher than previously reported values for BST or BST-based nanocomposites, which evidently originated from the presence of multiple BST:DLC hetero-interfaces as clarified in the Pisarenko plot.

Facile Synthesis of Diamino-Modified Graphene/Polyaniline Semi-Interpenetrating Networks with Practical High Thermoelectric Performance

p-Phenediamino-modified graphene (PDG) has been newly synthesized via a facile green one-step chemical route as a functionalized graphene-based additive to copolymerize with aniline for fabricating innovative PDG/polyaniline conducting polymer composites containing very special semi-interpenetrating networks (S-IPNs). The S-IPNs not only provide additional pathways by creating chemically bonded PDG and PANI for smoothly transporting carriers but greatly reduce the amount of graphene required to less than a few percent could effectively improve the overall electrical conductivity, Seebeck coefficient, and thus the thermoelectric (TE) performance. The found optimized TE figure of merit (ZT) of 0.74 approaches a practical high level which is comparable or much higher than previously reported ones for TE polymers.

Copolymer and platinum ion assisted growth of functionalized gold nanonests

This paper describes a facile low-toxicity synthesis of two different types of Au nanonests and one binary Au–Pt core–shell nanonest with high yield and excellent uniformity in size and morphology using block copolymer P123 (EO20PO70EO20) as a soft template and the main reductant in an ice water bath. The introduction of a suitable second metallic source, i.e. Pt ions in the present case, was proven to be a unique strategy for effectively governing the reduction sites of P123 for Au nucleation, which leads to significant changes especially in the crystallite size of the grown Au nanonests. The Au nanonests exhibited a distinct morphology-dependent surface plasmon resonance (SPR) that is red-shifted by ∼140 nm from the spherical particles wavelength, and significant surface-enhanced Raman scattering (SERS), allowing the rapid determination of rare malachite green oxalate (MGO).