Browsing by Author "Tsai, Min-Chiao"

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Alkali metal ion assisted synthesis of faceted anatase TiO2
(2013)
Yang, Min-Han
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Chen, Po-Chin
;
Tsai, Min-Chiao
;
Chen, Ting-Ting
;
Chang, I-Chun
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 < 001 > 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.
Anatase and brookite TiO2 with various morphologies and their proposed building block
(2014)
Yang, Min-Han
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Chen, Po-Chin
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Tsai, Min-Chiao
;
Chen, Ting-Ting
;
Chang, I-Chun
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 degrees C, whereas obvious grains were formed on the matrix with brookite, rutile and anatase mixture phases at 900 degrees C. On the other hand, as the submicro-sized urchin-like brookite was heated, a rutile phase appeared at 750 degrees C and 100% grain-like rutile was obtained at 900 degrees C.
Artificial Synthesis of Platelet-Like Kassite and Its Transformation to CaTiO(3)
(2010-03-01)
Huang, Yi-Jen
;
Tsai, Min-Chiao
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Chiu, Hsin-Tien
;
Sheu, Hwo-Shuenn
;
Lee, Chi-Young
Platelet-like kassite, a rare mineral CaTi(2)O(4)(OH)(2), wits synthesized by a wet chemical route using Ca(OH)(2) and TiO(2) as reagents in base Solution. The microstructure of the obtained kassite examined by synchrotron radiation and Rietveld refinement are hexagonal (P312) with a = b = 0.52451(2) and c = 0.47844(3) nm. This cell is slightly different from JCPDS No. 88-1722. At heating above 500 degrees C, the layered crystalline kassite rearranges to form disk-like CaTiO(3) and amorphous TiO(2) by removing H(2)O completely. Furthermore, transmission electron microscopy analysis reveals that the vertical axis of disk-like CaTiO(3) along the [0 (2) over bar1] direction converts from that of [001] orkassite.
Artificial Synthesis of Platelet-Like Kassite and Its Transformation to CaTiO3
(2010-03-01)
Huang, Yi-Jen
;
Tsai, Min-Chiao
;
Chiu, Hsin-Tien
;
Sheu, Hwo-Shuenn
;
Lee, Chi-Young
Platelet-like kassite, a rare mineral CaTi2O4(OH)(2), wits synthesized by a wet chemical route using Ca(OH)(2) and TiO2 as reagents in base Solution. The microstructure of the obtained kassite examined by synchrotron radiation and Rietveld refinement are hexagonal (P312) with a = b = 0.52451(2) and c = 0.47844(3) nm. This cell is slightly different from JCPDS No. 88-1722. At heating above 500 degrees C, the layered crystalline kassite rearranges to form disk-like CaTiO3 and amorphous TiO2 by removing H2O completely. Furthermore, transmission electron microscopy analysis reveals that the vertical axis of disk-like CaTiO3 along the [0 (2) over bar1] direction converts from that of [001] orkassite.
Detecting HER2 on Cancer Cells by TiO(2) Spheres Mile Scattering
(2009-09-15)
Tsai, Min-Chiao
;
Tsai, Tsung-Lin
;
Shieh, Dar-Bin
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Chiu, Hsin-Tien
;
Lee, Chi-Young
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 mu m with a size variation of 3%.
Detecting HER2 on Cancer Cells by TiO2 Spheres Mile Scattering
(2009-09-15)
Tsai, Min-Chiao
;
Tsai, Tsung-Lin
;
Shieh, Dar-Bin
;
Chiu, Hsin-Tien
;
Lee, Chi-Young
This work is the first to describe a bioimaging method that uses highly uniformly sized TiO2 submicrometer and micrometer spheres based on Mie scattering. Transmembrane proteins (HER2) located on the surface of cancer cells were detected by bonded antibody-linked TiO2 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 TiO2 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 TiO2 spheres used in this work was prepared by reacting TTIP with carboxylic acid, as described elsewhere and the uniformity of the TiO2 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 mu m with a size variation of 3%.
Effects of size and shell thickness of TiO2 hierarchical hollow spheres on photocatalytic behavior: An experimental and theoretical study
(2014-04-05)
Tsai, Min-Chiao
;
Lee, Jeng-Yi
;
Chen, Po-Chin
;
Chang, Yuan-Wei
;
Chang, Ya-Chen
Through a self-sacrificing template method, highly uniform hollow-spheres of TiO2 anatase are synthesized with controllable diameter from 365 nm to 930 nm. Compared to large hollow spheres, a large enhancement in the photocatalytic activity is reported for the small hollow spheres (with a thickness of 50 nm). By extending Mie\'s scattering theory from solid- to hollow-spheres, for a spherical scatter with a diameter of 300-900 nm, theoretical calculation reveal that each singular hollow sphere has absorption power equivalent to a solid sphere as the shell thickness parameter reaches a critical value of 0.3-0.6. This critical thickness parameter is independent to the size of a single hollow sphere, demonstrating that hollow spheres have quantitative advantages over solid spheres of the same weight. Moreover, calculation supported that small hollow spheres have stronger absorption power than large hollow spheres due to higher thickness. This greatly enhance the performance of small hollow spheres under a photocatalytic test. Our theoretical results showed good agreement to the experimental measurements, and provided a framework for the design of hollow-sphere nano-particles for optimized absorption power. (C) 2013 Elsevier B.V. All rights reserved.
Interconversion of rutile TiO2 and layered ramsdellite-like titanates: New route to elongated mesoporous rutile nanoplates
(2008-10-01)
Peng, Chih-Wei
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Richard-Plouet, Mireille
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Tsai, Min-Chiao
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Lee, Chi-Young
;
Chiu, Hsin-Tien
We report the first soft chemistry synthesis of a new "layered ramsdellite-like" titanate structure, NaTi2O4(OH) (lattice parameters: primitive monoclinic system, a = 4.09 nm, b = 0.29 nm, c = 0.94 nm, and beta = 80 degrees), with high-aspect-ratio, platelike morphology (diameter. 20-200 nm; thickness. 10-40 nm; length. 0.05-5 mu m) from TiO2 rutile. The newly prepared titanate can be transformed back to TiO2 rutile with uniquely shaped mesoporous elongated nanoplate morphology. The reaction proceeds via the disintegration of rutile in NaOH(aq) into NaTi2O4(OH). Ion exchange of Na+ in NaTi2O4(OH) into H+ forms another new layered ramsdellite-like titanate, HTi2O4(OH). A final topotatic condensation of the titanate layers in HTi2O4(OH) by heat treatment at relatively low 673 K produces the mesoporous TiO2 rutile product with highly exposed (110) surfaces.
Large-scale synthesis of uniform Cu2O nanocubes with tunable sizes by in-situ nucleation
(2013)
Chang, I-Chun
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Chen, Po-Chin
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Tsai, Min-Chiao
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Chen, Ting-Ting
;
Yang, Min-Han
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.
Lithium Ion Intercalation Performance of Porous Laminal Titanium Dioxides Synthesized by Sol-Gel Process
(2009-02-10)
Tsai, Min-Chiao
;
Chang, Jian-Chia
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Sheu, Hwo-Shuenn
;
Chiu, Hsin-Tien
;
Lee, Chi-Young
We have synthesized novel mesoporous titanate nanosheets by reacting titanium isopropoxide (TTIP) with formic acid. The porous nanosheets were characterized as a new titanate structure with intercalation of formate groups and protons, in the form of HCOOH-intercalated titanate. Most interestingly, TiO(2)-B, a well-known but unusual titanium dioxide phase with great potential in applications in Li-ion batteries, was obtained after the nanosheets were heated above 250 degrees C. Mesoporous nanosheets of HCOOH-intercalated titanate, titanium dioxide with mostly TiO(2)-B and titanium dioxide with traces of TiO(2)-B were obtained by heating the as prepared mesoporous titanate nanosheets at 200, 300, and 550 degrees C, respectively. The method reported here is the first to utilize the sol-gel process to synthesize TiO(2)-B. In addition, different anodes were made from HCOOH-intercalated titanate and titanium dioxide with different ratios of TiO2-B to examine the performance of the charging/discharging capacity in Li ion intercalation. The discharging capacity of titanium dioxide with major TiO2-B can reach 357 mA h/g at the first charging cycle and is highest among TiO(2)-B reports so far.
Photodegradation by a Heterogeneous Mixture of Micro-Sized Anatase and Truncated Rhomboid Anatase Hollow Spheres
(2013-07-01)
Yang, Min-Han
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Tsai, Min-Chiao
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Chang, Yuan-Wei
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Chang, Ya-Chen
;
Chiu, Hsin-Tien
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 {001} and {101} 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 3.4times greater than that of the individual constituents. The rate constant for HS@micro-sized TiO2 (k=0.175min-1) was 1.8times larger than that of commercial P25 (k=0.099min-1). HS@micro-sized TiO2 is a promising photocatalytic material.
Quantitative appraisal of the interfacial anchoring state of polyaromatic hydrocarbons during the formation of C/C composites
(2010-04-01)
Lin, Cheng-Te
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Tsai, Min-Chiao
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Lee, Chi-Young
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Chiu, Hsin-Tien
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Chin, Tsung-Shune
The preferred anchoring state for polycyclic aromatic hydrocarbons (PAHs) pyrolyzed onto carbon substrates has been studied by semi-quantitative methods, examining their interfacial lattice arrangements. The samples were prepared by decomposing petroleum pitch inside carbon nanotubes resulting in a variety of crystallinities forming one-dimensional C/C composites. Studies indicate that the preferred anchoring state of PAH molecules depends on the nature of the substrate. Accordingly the PAHs in mesophase pitch should exhibit a face-on orientation on the carbonaceous substrates, including a graphite sheet, glassy carbon, and pyrolytic carbon. However, it showed that the anchoring state (face-on or edge-on) of PAH units can be altered even on carbonaceous substrates. The results demonstrated that in C/C composites the anchoring state is predominantly determined by the relative degree of crystallinity of the pitch/carbon substrate, and can be semi-quantitatively estimated using the I(D)/I(G) ratio from Raman spectra. Face-on anchoring is preferred when the I(D)/I(G); ratio of substrate is smaller (higher crystallinity) than that of the pyrolyzed precursor, whereas edge-on anchoring is favored when it is larger. Such an estimation method is useful in tailoring microstructures in the fabrication of C/C composites using PAH precursors. (C) 2009 Elsevier Ltd. All rights reserved.
Scattering resonance enhanced dye absorption of dye sensitized solar cells at optimized hollow structure size
(2014-12-05)
Tsai, Min-Chiao
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Lee, Jeng-Yi
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Chang, Ya-Chen
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Yang, Min-Han
;
Chen, Tin-Tin
This study elucidates the size effect on dye-sensitized solar cells (DSSCs) by synthesizing highly uniform hierarchical hollow sphere TiO2 samples, with the diameters from 220 nm to 800 nm. Experimental results indicate that the optimum conversion efficiency using N719 dye can be achieved around 5.5%, as the diameter of hierarchical hollow spheres is 450-550 nm. According to the incident photon-to-current conversion efficiency (IPCE) spectra, large-sized hierarchical hollow spheres significantly enhance the light harvesting by scattering; whereas small-sized hallow spheres (<360 nm) improve negligibly. Additionally, mesoporous and solid spheres with an identical diameter, 440 nm in this study, are also studied as a comparison. Our results demonstrate that hollow spheres perform the same conversion efficiency as that of mesoporous spheres owing to the equivalent adsorption of dye molecules in both hierarchical structures - regardless of the surface area of the interior of mesoporous structure, which shows that hollow spheres have higher conversion efficiency per unit volume than that of mesoporous spheres. (C) 2014 Elsevier B.V. All rights reserved.
Self-carbonized lamellar nano/micro hierarchical structure C/TiO2 and its Li-ion intercalation performance
(2012)
Chen, Po-Chin
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Tsai, Min-Chiao
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Chen, Huang-Chin
;
Lin, I-Nan
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Sheu, Hwo-Shuenn
In this study, two new layered titanates, fibrillar TiO2 center dot(CH3COOH)(1.4) and chrysanthemum-like TiO2 center dot(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 degrees 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.
Simple chemical preparation of perovskite-based materials using alkali treatment
(2012)
Chen, Po-Chin
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Tsai, Min-Chiao
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Huang, Yi-Jen
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Chiu, Hsin-Tien
;
Lee, Chi-Young
In this work, a simple alkali treatment process was introduced to synthesize ABO(3) perovskite related materials: CaTiO3 (CTO), SrTiO3 (STO), BaTiO3 (BTO) and BaxSr1-xTiO3 (BST). The perovskite materials, synthesized by using stoichiometric amounts of corresponding alkaline solutions Ba(OH)(2), Sr(OH)(2), Ca(OH)(2) and powdered TiO2, are pure phase and well-crystallized. The obtained powders are round, round-edged cubes and cubes with sharp edges for BaTiO3, SrTiO3 and CaTiO3 respectively. What's more, the Ba content (x) in BST can be directly and precisely modified to be any value between one and zero. And, the morphology of SrTiO3 can be manipulated by altering the reaction time. As time is prolonged, the morphology of the product changes from round to round-edged cubes to sharp-edged cubes. In the future, materials with such specific microstructure and morphologies may be used in electro-optical and photocatalytic applications.
Size-controlled wurtzite zinc oxide spheres with the characteristics of visible absorption and Mie scattering
(2014)
Chen, Ting-Ting
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Chang, I-Chun
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Tsai, Min-Chiao
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Chang, Yi-Chun
;
Yang, Min-Han
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.
The "cascade effect" of nano/micro hierarchical structure: A new concept for designing the high photoactivity materials - An example for TiO2
(2013-10-01)
Chen, Po-Chin
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Tsai, Min-Chiao
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Yang, Min-Han
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Chen, Ting-Ting
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Chen, Huang-Chin
The chrysanthemum-like TiO2 (CT800) was synthesized. It exhibited excellent photoactivity, which greatly exceeded that of conventional P25. To discover the key factors that governed the photocatalytic properties, the specific reduction of Ag+ ions was carried out and EPR spectra of CT800 were obtained. Both an HADDF image and EDX mapping indicated that the Ag+ ions tended to be reduced close to the center of the micro matrix of CT800. Moreover, the EPR spectra strongly suggest that the excited electrons tended to migrate toward the center of the micro matrix, resulting from a multiple junction, cascade effect, which efficiently reduces the recombination of excited electrons and holes and greatly increases the photoactivity. Additionally, the special morphology of CT800 was responsible for the hot spots at the surface of nano sheets and then contributing to its outstanding photocatalytic activity. Furthermore, the unidirectional electron transfer, because of the cascade effect, by materials of different sizes provides a new avenue for the design of electronic and photoelectrochemical devices. (c) 2013 Elsevier B.V. All rights reserved.