Wei-Cheng Tsai

A high performance dye-sensitized solar cell with a novel nanocomposite film of PtNP/MWCNT on the counter electrode

An imide-functionalized material, poly(oxyethylene)-segmented polymer, was synthesized from the reaction of poly(oxyethylene)diamine of 2000 g mol−1Mw and 4,4′-oxydiphthalic anhydride and used to disperse hybrid nanomaterials of platinum nanoparticles and multi-wall carbon nanotubes (PtNP/MWCNT). The composite material was spin-coated into film and further prepared as the counter electrode (PtNP/MWCNT-CE) for a dye-sensitized solar cell (DSSC). The short-circuit current density (JSC) and power-conversion efficiency (η) of the DSSC with PtNP/MWCNT-CE were found to be 18.01 ± 0.91 mA cm−2 and 8.00 ± 0.23%, respectively, while the corresponding values were 14.62 ± 0.19 mA cm−2 and 6.92 ± 0.07% for a DSSC with a bare platinum counter electrode (Pt-CE). The presence and distribution of PtNP/MWCNT on the CE were characterized by using scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The attachment of PtNPs on MWCNTs was observed by transmission electron microscopy (TEM). Cyclic voltammetry (CV), incident-photo-to-current efficiency (IPCE) and electrochemical impedance spectra (EIS) were correlated to explain the efficacy of this nanocomposite system.

Copper-ion-assisted self-assembly of silicate clays in rod- and disklike morphologies.

Self-assembled rodlike (0.3-2.5 microm in diameter and 5.3-31 microm in length) and disklike microstructures (1.8-10.6 microm in width and 0.1-1.0 microm in thickness) are uniquely present in amorphous clay aggregates. Clay units were prepared by intercalation of Na(+)-montmorillonite (Na(+)-MMT) with copper ions (Cu(2+)) and poly(oxypropylene)-amine salt (POP) in simultaneous or stepwise ionic exchange reactions. Differences in process control during incorporation of Cu(2+) and hydrophobic POP greatly affected the layer structure of the clay units (d spacing of 12-53 A) and consequently their amphiphilic dispersion properties. By controlling the dispersion in water and drying at 80 degrees C, highly ordered self-assembly structures were obtained, presumably as a result of self-piling of clay units in competing vertical and horizontal directions. In general, association with Cu(2+) yielded units with a disklike microstructure, in contrast to the rod-like structure obtained for POP-intercalated clay. The self-assembled structures were characterized using X-ray diffraction, UV adsorption, thermal gravimetric analysis, zeta potential, scanning electron microscopy, and energy-dispersive X-ray spectroscopy techniques. Control of the clay self-piling process provides a new synthetic route for the fabrication of bottom-up microstructures that are potentially useful for templates, sensors, and electronic devices.

High Surface Clay-Supported Silver Nanohybrids

Conventionally, silver nanoparticles (AgNPs) have been prepared by using either physical methods such as electron beamand photo-reductions or chemical methods with various reducing agents and organic stabilizers. Many researches have been conducted previously in the following areas: tailoring of particle size, polydispersity, geometric shape, and nucleation. Low-molecular-weight surfactants or functional polymers such as poly(vinylpyrrolidone) have also been commonly employed for stabilizing the generated AgNPs. The presence of organic stabilizers may provide soft templates for controlling the growth of the AgNPs with different shapes such as spherical, triangular, and fibrous. In this review, various syntheses involving the applications of inorganic supports such as alumina and aluminosilicate clays in place of organic stabilizers are discussed; in this manner, the synthesis of AgNPs supported on inorganic substrates is reviewed. The function of inorganic supports is primarily to stabilize the homogeneity of colloidal Ag0. In the absence of contamination by organic components during the synthesis, the prepared AgNPs were found to exhibit unique properties such as catalytic performance, high stability for longterm storage, low-temperature Ag melting, and high efficacy for antimicrobial properties. This new class of AgNP nanohybrids on inorganic supports is expected to have considerable impact on biomedical fields and on several applications such as optoelectronic devices.