Wen-Yin Ko

Hydrothermally processed TiO2 nanowire electrodes with antireflective and electrochromic properties.

Dual functionalities of antireflective and electrochromic properties-based anatase TiO(2) nanowire devices with a high-porosity cross-linked geometry directly grown onto transparent conductive glass was achieved for the first time through a simple one-step hydrothermal process under mild alkali conditions. Devices fashioned from these TiO(2) nanowires were found to display enhanced optical transparency in the visible range, better color contrast, and faster color-switching time in comparison to devices made from nanoparticles. These improvements can be attributed to the low refractive index and high porosity of the TiO(2) nanowires and their larger accessible surface area for Li(+) intercalation and deintercalation, leading to enhanced capabilities for transparent electrochromic smart windows.

Porous honeycomb structures formed from interconnected MnO2 sheets on CNT-coated substrates for flexible all-solid-state supercapacitors

The use of lightweight and easily-fabricated MnO2/carbon nanotube (CNT)-based flexible networks as binder-free electrodes and a polyvinyl alcohol/H2SO4 electrolyte for the formation of stretchable solid-state supercapacitors was examined. The active electrodes were fabricated from 3D honeycomb porous MnO2 assembled from cross-walled and interconnected sheet-architectural MnO2 on CNT-based plastic substrates (denoted as honeycomb MnO2/CNT textiles).These substrates were fabricated through a simple two-step procedure involving the coating of multi-walled carbon nanotubes (MWCNTs) onto commercial textiles by a dipping-drying process and subsequent electrodeposition of the interconnected MnO2 sheets onto the MWCNT-coated textile. With such unique MnO2 architectures integrated onto CNT flexible films, good performance was achieved with a specific capacitance of 324 F/g at 0.5 A/g. A maximum energy density of 7.2 Wh/kg and a power density as high as 3.3 kW/kg were exhibited by the honeycomb MnO2/CNT network device, which is comparable to the performance of other carbon-based and metal oxide/carbon-based solid-state supercapacitor devices. Specifically, the long-term cycling stability of this material is excellent, with almost no loss of its initial capacitance and good Coulombic efficiency of 82% after 5000 cycles. These impressive results identify these materials as a promising candidate for use in environmentally friendly, low-cost, and high-performance flexible energy-storage devices.

The role of the fabrication of anatase-TiO2 chain-networked photoanodes.

Since Grätzel’s pioneering work on dye-sensitized solar cells (DSSCs), [ 1 ] much effort has been devoted to the fabrication of TiO 2 -based photoanode nanostructures. The most-promising nanoarchitecture is an array of 1D TiO 2 nanostructures, such as nanotubes, nanobelts, and nanowires; these nanostructures have been shown to enhance the effi ciencies of both charge collection and light-harvesting, in comparison to a random network of TiO 2 nanoparticles. [ 2 ] Recently, a variety of TiO 2 -based nanoarrays anchored on Ti foil have been reported, fabricated using electrochemical anodic oxidation and hydrothermal methods. [ 3 ]

Growth of Copper Phthalocyanine Rods on Au Plasmon Electrodes through Micelle Disruption Methods

To improve the efficiency of the photocurrent conversion process, we have utilized copper phthalocyanine (CuPc) rods, which are capable of enhancing the interfacial area of electron transport and plasmonic gold nanoparticles (Au NPs), which can increase the separation and photogeneration of excitons, to produce a more effective system. In-plane horizontal CuPc rods, with diameters ranging from 0.2 to 1.5 microm, were electrodeposited onto the surface of plasmonic (Au NP) monolayers predeposited onto ITO substrates through electrolytic micelle disruption (EMD) methods.

Highly conductive, transparent flexible films based on metal nanoparticle-carbon nanotube composites

Metallic nanoparticles decorated on MWCNTs based transparent conducting thin films (TCFs) show a cheap and efficient option for the applications in touch screens and the replacement of the ITO film because of their interesting properties of electrical conductivity, mechanical property, chemical inertness, and other unique properties, whichmay not be accessible by their individual components. However, a great challenge that always remains is to develop effective ways to prepare junctions between metallic nanoparticles and MWCNTs for the improvement of high-energy barriers, high contact resistances, and weak interactions which could lead to the formation of poor conducting pathways and result in the CNT-based devices with low mechanical flexibility. Herein, we not only discuss recent progress in the preparation of MNP-CNT flexible TCFs but also describe our research studies in the relevant areas. Our result demonstrated that the MNP-CNT flexible TCFs we prepared could achieve a highly electrical conductivity with the sheet resistance of ∼100 ohm/sq with ∼80% transmittance at 550 nm even after being bent 500 times. This electrical conductivity is much superior to the performances of other MWCNT-based transparent flexible films, making it favorable for next-generation flexible touch screens and optoelectronic devices.

Green synthesis of carbon quantum dots embedded onto titanium dioxide nanowires for enhancing photocurrent

The green synthesis of nanowired photocatalyst composed of carbon quantum dots-titanium hybrid-semiconductors, CQDs/TiO2, are reported. Where graphite-based CQDs with a size less than 5 nm are directly synthesized in pure water electrolyte by a one-step electrochemistry approach and subsequently electrodeposited onto as-prepared TiO2 nanowires through a voltage-driven reduction process. Electron paramagnetic resonance studies show that the CQDs can generate singlet oxygen and/or oxygen radicals to decompose the kinetic H2O2 intermediate species upon UV light illumination. With the effect of peroxidase-like CQDs, photocurrent density of CQDs/TiO2 is remarkably enhanced by a 6.4 factor when compared with that of as-prepared TiO2.

Sonophysically Exfoliated Individual Multi-Walled Carbon Nanotubes in Water Solution and Their Straightforward Route to Flexible Transparent Conductive Films

Flexible transparent conducting films (TCFs) with low electric resistance and high optical transmittance have received considerable attention for niche applications such as flexible/foldable displays, touch screens, solar cells, transistors, and transparent electrodes for liquid crystal displays. (Calnan & Tiwari, 2010; Gruner, 2006; Heo et al., 2010; Jo et al., 2010; Takenobu et al., 2006) Deposition of indium tin oxide (ITO) onto plastic substrates to prepare the flexible TCFs has been an attractive strategy owing to its transparency, conductivity, and wide usability. (D. H. Kim et al., 2006; Lin et al., 2008; Na et al., 2008; Sierros et al., 2009; Wang et al., 2008) Nevertheless, the flexible ITO-based TCFs still suffer from several drawbacks. For example, the films are often prepared under vacuum and high temperature conditions, resulting in the limitation of their suitability for many polymer substrates such as polyethylene terephthalate (PET), which are often used in flexible devices and touch screen panels. Also, ITO is expensive owing to the limited supply of indium; it is brittle and will crack under a 2% strain, resulting in loss of conductivity. Furthermore, the film transparency is poor in the near-infrared range. (Feng et al., 2010; Manivannan et al., 2010; Park et al., 2010) Therefore, a substitute for ITO is necessary. To address this issue, carbon nanotubes (CNTs), because of their high flexibility, specific surface area, low density, and excellent electrical, optical, and mechanical properties, have been regarded as the most promising alternative. CNTs have a preeminent status in nanomaterials and have a huge range of potential applications. (Z. R. Li et al., 2007; Paul & Kim, 2009; Simien et al., 2008) Single-walled CNT (SWCNT)–based conductors and semiconductors were used as the active material in the fabrication of flexible CNT-TCFs. Recent efforts towards the fabrication of SWCNTs on several substrates of glass, UV-ozone (UV-O3) treated glass, poly(styrenesulfonate) (PEDOT:PSS) coated glass, flexible PET films, and other substrates to form transparent conducting SWCNT films with sheet resistance and transparency equivalent to ITO have been attempted. These attempts used various approaches such as spin coating, spray coating, solution dipping where the SWCNTs were pre-formulated in combination with surfactants and polymers. (Chen et al.; Dan et al., 2009; Manivannan et al., 2010; Paul & Kim, 2009; Saran et al., 2004; Xiao et al., 2010) However, the