Min-Chiao Tsai

Large-scale synthesis of uniform Cu2O nanocubes with tunable sizes by in-situ nucleation

Uniform Cu2O nanocubes with various sizes were synthesized by reducing Cu(OH)2 using ascorbic acid in the presence of various amounts of sodium citrate. The monodispersed nanocubes with an edge length of approximately 80 nm used as an anode exhibit excellent lithium storage behavior.

Self-carbonized lamellar nano/micro hierarchical structure C/TiO2 and its Li-ion intercalation performance

In this study, two new layered titanates, fibrillar TiO2·(CH3COOH)1.4 and chrysanthemum-like TiO2·(CH3COOH)0.9 (named as FT and CT) with acetic acid and acetate intercalation have been synthesized by reacting titanium isopropoxide (TTIP) with acetic acid at different temperatures. Furthermore, nano/micro hierarchical structure TiO2 with high TiO2-B/anatse ratio was obtained by annealing the titanate (CT). For use as an anode for lithium ion batteries, uniform carbon coated titanium dioxide with high TiO2-B content was obtained by “self-carbonizing” CT under argon atmosphere at 350 °C, and the compound was named SC-CT350. The capacity of the anode made from SC-CT350 can reach 144 mA h g−1 under a high charging/discharging rate (10 C) and showed excellent retention ability.

Detecting HER2 on Cancer Cells by TiO2 Spheres Mie Scattering

This work is the first to describe a bioimaging method that uses highly uniformly sized TiO(2) submicrometer and micrometer spheres based on Mie scattering. Transmembrane proteins (HER2) located on the surface of cancer cells were detected by bonded antibody-linked TiO(2) spheres using optic microscopy and UV-vis spectroscopy. A particular HER2 bond on cancer cells, which has a weaker binding affinity than the biotin/avidin interaction, can be identified between TiO(2) spheres that are linked to anti-HER2 antibodies and those that are linked to nonspecific mouse IgG antibodies by observing the cells under an optical microscope or by measuring absorbance from a UV-vis spectrum. The TiO(2) spheres used in this work was prepared by reacting TTIP with carboxylic acid, as described elsewhere and the uniformity of the TiO(2) sphere was further improved by adjusting the amount of water used. The water content was inversely related to particle size and the size distribution: as more water was used, smaller spheres with a narrower size distribution were obtained. The most uniform sphere obtained had a diameter of about 1 microm with a size variation of 3%.

Anatase and brookite TiO2 with various morphologies and their proposed building block

In this work, brookite TiO2 has been synthesized by a simple hydrothermal approach using sodium titanate as a precursor in the presence of a sodium fluoride aqueous solution. The ratio of brookite and anatase TiO2 can be tailored by the NaF concentration. In a concentrated NaF solution, high quality brookite TiO2 was acquired. Pure anatase nanoparticles were obtained in only deionized water. Moreover, the morphology and size of brookite TiO2 can be tailored by using various acid treated titanates which influence the stability of the building blocks and nucleation points of TiO2. Micro-sized flower-like brookite, submicro-sized urchin-like brookite and brookite nanorods with anatase nanoparticles were obtained. The micro-sized flower-like brookite remains the same shape and phase even at 800 °C, whereas obvious grains were formed on the matrix with brookite, rutile and anatase mixture phases at 900 °C. On the other hand, as the submicro-sized urchin-like brookite was heated, a rutile phase appeared at 750 °C and 100% grain-like rutile was obtained at 900 °C.

Alkali metal ion assisted synthesis of faceted anatase TiO2

This work reports on a simple hydrothermal method for tuning the shape and exposed face of TiO2 nanocrystal by using sodium titanate as a precursor in the presence of different alkali metal ion salts. The {101}-exposed anatase TiO2 was synthesized in lithium salt solution. The formation of anatase TiO2 with exposed high-index {301} facet, obtained in the presence of sodium ions, has never before been reported upon. When the reaction proceeded in potassium salt solution, the obtained anatase TiO2 with a high aspect ratio was elongated in the direction. Anatase TiO2 with a high aspect ratio was obtained in hydrothermal process in the presence of low charge density high atomic number alkali metal ions, which were not easily absorbed by the {001} planes of anatase, so the growth along this direction was not restrained. The photodegradation of methylene blue, assisted by anatase TiO2 with various exposed faces reveals that the photoactivity of anatase {101} planes is larger than that of {301} planes.

Size-controlled wurtzite zinc oxide spheres with the characteristics of visible absorption and Mie scattering

The enhancement of the light harvesting efficiency over a metal oxide is crucial to optic-related applications which can convert solar energy into chemical energy. Here, we demonstrated a method to develop the characteristics of visible light absorption and visible Mie scattering over wurtzite ZnO microspheres. Size-controlled ZnO microspheres were successfully prepared in the thermal decomposition of amorphous/layered basic zinc salt (LBZ) spheres. Firstly, trisodium citrate was employed as the chelating agent to synthesize amorphous/LBZ microspheres in a nucleation-controlled method. The sphere size was controlled by the nuclei number, which depends on the competition between hydroxyl ions and citrate to the ligand with Zn2+. Secondly, visible-active wurtzite ZnO spheres were obtained by thermal decomposition. The uniform sized microspheres exhibited Mie scattering in the visible range due to the interaction with specific incident electromagnetic radiation, and the full absorption spectrum was easily obtained by tuning the size of the spheres. Such uniform spheres exhibited superior visible absorption and scattering effects and thus are expected to be good candidates for the optic-related applications.

Photodegradation by a Heterogeneous Mixture of Micro-Sized Anatase and Truncated Rhomboid Anatase Hollow Spheres

Highly uniform hollow spheres were assembled from truncated rhomboid anatase TiO2 nanoparticles (HS), which were synthesized from the hydrothermal treatment of a NaF solution by using amorphous TiO2 spheres as a precursor and template. The submicron hollow spheres with highly photocatalytic active surfaces exhibited excellent photocatalytic behavior. In this investigation, the factors that enhanced the photocatalytic performance were examined in terms of light harvesting, photoefficiency, and reaction activity. The photocatalytic performance was increased by a factor of approximately 1.5 for the scattering structure of submicron hollow spheres than that of nanofragments of submicron hollow sphere powder. The rate constant of anatase TiO2 with specific photoactive surfaces at {0 0 1} and {1 0 1} was approximately six times higher than that of randomly exposed TiO2 particles. Furthermore, a heterogeneous mixture of the submicron hollow spheres and micro‐sized anatase TiO2 (HS@micro‐sized TiO2) prohibited electron–hole recombination in the catalyst during the degradation reaction. The rate constant for the heterojunction system was 3.4 times greater than that of the individual constituents. The rate constant for HS@micro‐sized TiO2 (k=0.175 min−1) was 1.8 times larger than that of commercial P25 (k=0.099 min−1). HS@micro‐sized TiO2 is a promising photocatalytic material.