Yi-Feng Lin

Piezoelectric nanogenerator using CdS nanowires

Vertically grown cadmium sulfide (CdS) nanowire (NW) arrays were prepared using two different processes: hydrothermal and physical vapor deposition (PVD). The NWs obtained from the hydrothermal process were composed of alternating hexagonal wurtzite (WZ) and cubic zinc blende (ZB) phases with growth direction along WZ ⟨0001⟩ and ZB [111]. The NWs produced by PVD process are single crystalline WZ phase with growth direction along ⟨0001⟩. These vertically grown CdS NW arrays have been used to converting mechanical energy into electricity following a developed procedure [Z. L. Wang and J. Song Science 312, 242 (2006)]. The basic principle of the CdS NW nanogenerator relies on the coupled piezoelectric and semiconducting properties of CdS, and the data fully support the mechanism previously proposed for ZnO NW nanogenerators and nanopiezotronics.

Large enhancement in photon detection sensitivity via Schottky-gated CdS nanowire nanosensors

The Schottky contact based photon detection was demonstrated using CdS (visible light responsive), silicon (indirect n-type oxygen-non-adsorbing), and CuO (indirect p-type oxygen-adsorbing) nanowire nanosensors. With changing one of the two nanowire-electrode contacts from ohmic to Schottky, detection sensitivities as high as 105% were achieved by the CdS nanowire nanosensor operated at the reverse bias mode of −8 V, which was 58 times higher than that of the corresponding ohmic contact device. The reset time was also significantly reduced. In addition, originally light nonresponsive silicon and CuO nanowires became light responsive when fabricated as a Schottky contact device. These improvements in photon detection can be attributed to the Schottky gating effect realized in the present nanosensor system by introducing a Schottky contact.

Mesoporous Fluorocarbon-Modified Silica Aerogel Membranes Enabling Long-Term Continuous CO2 Capture with Large Absorption Flux Enhancements

The use of a membrane contactor combined with a hydrophobic porous membrane and an amine absorbent has attracted considerable attention for the capture of CO2 because of its extensive use, low operational costs, and low energy consumption. The hydrophobic porous membrane interface prevents the passage of the amine absorbent but allows the penetration of CO2 molecules that are captured by the amine absorbent. Herein, highly porous SiO2 aerogels modified with hydrophobic fluorocarbon functional groups (CF3 ) were successfully coated onto a macroporous Al2 O3 membrane; their performance in a membrane contactor for CO2 absorption is discussed. The SiO2 aerogel membrane modified with CF3 functional groups exhibits the highest CO2 absorption flux and can be continuously operated for CO2 absorption for extended periods of time. This study suggests that a SiO2 aerogel membrane modified with CF3 functional groups could potentially be used in a membrane contactor for CO2 absorption. Also, the resulting hydrophobic SiO2 aerogel membrane contactor is a promising technology for large-scale CO2 absorption during the post-combustion process in power plants.

Reusable methyltrimethoxysilane-based mesoporous water-repellent silica aerogel membranes for CO2 capture

For the first time, highly mesoporous and water-repellent SiO2 aerogels were successfully coated onto a macroporous Al2O3 membrane using methyltrimethoxysilane (MTMS) precursors. The MTMS-derived hydrophobic SiO2 aerogel membranes exhibited at least 500% higher CO2 absorption flux than the uncoated MTMS-based aerogel membranes and could be reused and continuously operated for CO2 absorption for extended periods of time. As a result, MTMS-derived water-repellent silica aerogel membrane contactors are a potential candidate for large-scale CO2 absorption in industrial power plants.

Magnetic mesoporous iron oxide/carbon aerogel photocatalysts with adsorption ability for organic dye removal

Magnetic photocatalysts with strong Rhodamine B (RhB) dye adsorption ability, i.e., tri-functional mesoporous composite γ-Fe2O3/α-Fe2O3/carbon aerogel (CA) structures, are successfully developed in this study. The removal capacity of RhB dyes of the as-prepared mesoporous structures is increased from 83.5% to 91% under visible light irradiation. The mesoporous structures can also be separated by an external magnetic field to avoid further separation steps, such as centrifugation. This work demonstrates that the as-prepared tri-functional mesoporous composite γ-Fe2O3/α-Fe2O3/CA structures have great potential in wastewater treatments.

Non-catalytic and template-free growth of aligned CdS nanowires exhibiting high field emission current densities

Various CdS nanostructures, including nanoparticle film, bundles of quasi-aligned and well-aligned nanowires, were fabricated with a non-catalytic and template-free MOCVD process. The well-aligned CdS nanowires exhibit unusually high field emission current densities of 225 mA cm(-2) at the applied electric field of 20 V microm(-1).

Magnetic mesoporous Fe/carbon aerogel structures with enhanced arsenic removal efficiency

Wastewater treatment has drawn significant research attention due to its associated environmental issues. Adsorption is a promising method for treating wastewater. The development of an adsorbent with a high surface area is important. Therefore, we successfully developed mesoporous Fe/carbon aerogel (CA) structures with high specific surface areas of 48 7m(2)/g via the carbonization of composite Fe3O4/phenol-formaldehyde resin structures, which were prepared using a hydrothermal process with the addition of phenol. The mesoporous Fe/CA structures were further used for the adsorption of arsenic ions with a maximum arsenic-ion uptake of calculated 216.9 mg/g, which is higher than that observed for other arsenic adsorbents. Ferromagnetic behavior was observed for the as-prepared mesoporous Fe/CA structures with an excellent response to applied external magnetic fields. As a result, the adsorbent Fe/CA structures can be easily separated from the solution using an external magnetic field. This study develops the mesoporous Fe/CA structures with high specific surface areas and an excellent response to an applied external magnetic field to provide a feasible approach for wastewater treatment including the removal of arsenic ions.

Synthesis of mesoporous maghemite (γ-Fe2O3) nanostructures with enhanced arsenic removal efficiency

We successfully developed mesoporous γ-Fe2O3 structures with a specific surface area of 35.7 m2 g−1 through atmospheric calcination of composite Fe3O4/phenol-formaldehyde resin structures, which were prepared by the addition of phenol during a hydrothermal process. For comparison, aggregated γ-Fe2O3 nanoparticles with a specific surface area of 29.6 m2 g−1 were also prepared. The mesoporous γ-Fe2O3 structures were used to adsorb arsenic ions, and the maximum uptake of arsenic ions was calculated to be 73.2 mg g−1, which is higher than that of the aggregated γ-Fe2O3 nanoparticles (32.3 mg g−1) because of the larger specific surface area, pore volume and pore sizes of the mesoporous γ-Fe2O3 structures. In this study, we developed a feasible approach to wastewater treatment, including the removal of arsenic ions.

The synthesis of Lewis acid ZrO2 nanoparticles and their applications in phospholipid adsorption from Jatropha oil used for biofuel.

ZrO(2) nanoparticles were successfully fabricated via a facile hydrothermal process. The diameter and surface area of the as-prepared ZrO(2) nanoparticles were approximately 5-10 nm and 102 m(2)/g, respectively. For the first time, Zr atoms with partial positive charges in a Lewis acid ZrO(2) nanoparticle adsorbent were used for the adsorption of negatively charged phospholipids from Jatropha oil. The capacity for phospholipid adsorption using the ZrO(2) nanoparticles was better than that of commercial ZrO(2) powder due to the larger surface area of the ZrO(2) nanoparticles. Phospholipid removal makes Jatropha oil a potential oil for biofuel applications.

Growth of zirconia and yttria-stabilized zirconia nanorod arrays assisted by phase transition

Well-aligned, densely distributed ZrO2 nanorod arrays were fabricated using a non-catalytic, template-free metal–organic chemical vapour deposition process at a reaction temperature of 1000 °C. The reaction temperature was found to play a key role in product morphology, with particle thin films obtained at 550 °C and nanorod arrays produced at 1000 °C. Increasing the reaction temperature led to the emergence of the medium-temperature tetragonal phase from the dominant low-temperature monoclinic phase, which is advantageous for anisotropic growth necessary for the nanorod formation. With the same deposition process, yttria-stabilized zirconia nanorod arrays of polycrystalline cubic phase were fabricated by co-feeding the dopant precursor, YCl3, with the zirconia precursor, Zr(C5H7O2)4. The present work demonstrated the first example of monoclinic to tetragonal phase-transition assisted one-dimensional (1D) growth, and the concept can be extended to the formation of 1D nanostructures of materials possessing the monoclinic-tetragonal polymorphism.