Browsing by Author "Teng, Hsisheng"

Now showing 1 - 5 of 5

Graphene oxide dot-based microstructures via dispersion and support of bovine serum albumin
(2016-10-01)
Chang, Hsin-Yu
;
Lin, Chun-Yu
;
Chang, Chia-Yuan
;
Teng, Hsisheng
;
Campagnola, Paul J.
Three-dimensional graphene oxide-based microstructures have great potential for use in microelectronic and biomedical applications and can be fabricated by using two-photon excitation photochemical processes. In such excitation processes, rose Bengal is the preferred candidate as the photoactivator in two-photon crosslinking; nevertheless, it induces graphene oxide self-aggregation. Herein, bovine serum albumin (BSA) is adopted to prevent graphene oxide dot (GOD) aggregation even at very high GOD fabrication-solution concentrations, yet still supports GOD microstructures. In this manner, three-dimensional freeform GOD microstructures with different GOD concentrations were developed. Furthermore, the biocomparability of the GOD microstructure with the help of added biomaterials such as BSA was verified under living cell incubation. (C) 2016 Optical Society of America
Microstructure and Composition of TiO(2) Nanotube Arrays Fabricated with HF and NH(4)F Electrolytes and Their Evolution during Annealing
(2011-01-01)
Hsu, Ming-Yi
;
Yang, Wei-Chun
;
Teng, Hsisheng
;
Leu, Jihperng
;
材料科學與工程學系
The evolution of microstructure and composition of titanium dioxide (TiO(2)) nanotube arrays fabricated with hydrofluoric acid (HF) and NH(4)F electrolytes as a function of annealing temperature up to 400 degrees C was investigated and compared using X-ray diffraction, scanning electron microscopy, and X-ray absorption near-edge structure spectroscopy. Results showed that TiO(2) nanotube arrays grown in HF electrolyte contained 90% amorphous TiO(2) and 10% lower oxidation states of titanium from Ti(2+) (TiO) and Ti(3+) (Ti(2)O(3)) cations. After annealing at 400 degrees C, TiO(2) nanotube arrays underwent charge transfer and phase transformation to 93% anatase phase, 6% amorphous TiO(2), and 1% suboxides. In contrast, as-grown TiO(2) nanotube arrays using NH(4)F electrolyte possessed less amorphous TiO(2) (82%) but more suboxides (18%) due to lower oxygen ion formation from scanty 3 wt % of H(2)O addition. Its onset temperature of phase transformation was found to be higher than TiO(2) nanotube arrays prepared by HF solution. Moreover, when annealed to 400 degrees C, the crystallinity of TiO(2) nanotube arrays increased only by 86% for the anatase phase. The lower anatase phase could be attributed to the formation of (NH(4))(2)TiF(6) type compounds presumably formed by the reaction of TiF(6)(2-) and NH(4)(+) ions dissociated from NH(4)F. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3533388] All rights reserved.
Microstructure and Composition of TiO2 Nanotube Arrays Fabricated with HF and NH4F Electrolytes and Their Evolution during Annealing
(2011-01-01)
Hsu, Ming-Yi
;
Yang, Wei-Chun
;
Teng, Hsisheng
;
Leu, Jihperng
;
材料科學與工程學系
The evolution of microstructure and composition of titanium dioxide (TiO2) nanotube arrays fabricated with hydrofluoric acid (HF) and NH4F electrolytes as a function of annealing temperature up to 400 degrees C was investigated and compared using X-ray diffraction, scanning electron microscopy, and X-ray absorption near-edge structure spectroscopy. Results showed that TiO2 nanotube arrays grown in HF electrolyte contained 90% amorphous TiO2 and 10% lower oxidation states of titanium from Ti2+ (TiO) and Ti3+ (Ti2O3) cations. After annealing at 400 degrees C, TiO2 nanotube arrays underwent charge transfer and phase transformation to 93% anatase phase, 6% amorphous TiO2, and 1% suboxides. In contrast, as-grown TiO2 nanotube arrays using NH4F electrolyte possessed less amorphous TiO2 (82%) but more suboxides (18%) due to lower oxygen ion formation from scanty 3 wt % of H2O addition. Its onset temperature of phase transformation was found to be higher than TiO2 nanotube arrays prepared by HF solution. Moreover, when annealed to 400 degrees C, the crystallinity of TiO2 nanotube arrays increased only by 86% for the anatase phase. The lower anatase phase could be attributed to the formation of (NH4)(2)TiF6 type compounds presumably formed by the reaction of TiF62- and NH4+ ions dissociated from NH4F. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3533388] All rights reserved.
Roles of nitrogen functionalities in enhancing the excitation-independent green-color photoluminescence of graphene oxide dots
(2017-06-28)
Teng, Chiao-Yi
;
Ba-Son Nguyen
;
Yeh, Te-Fu
;
Lee, Yuh-Lang
;
Chen, Shean-Jen
Fluorescent graphene oxide dots (GODs) are environmentally friendly and biocompatible materials for photoluminescence (PL) applications. In this study, we employed annealing and hydrothermal ammonia treatments at 500 and 140 degrees C, respectively, to introduce nitrogen functionalities into GODs for enhancing their green-color PL emissions. The hydrothermal treatment preferentially produces pyridinic and amino groups, whereas the annealing treatment produces pyrrolic and amide groups. The hydrothermally treated GODs (A-GODs) present a high conjugation of the nonbonding electrons of nitrogen in pyridinic and amino groups with the aromatic pi orbital. This conjugation introduces a nitrogen nonbonding (n(N 2p)) state 0.3 eV above the oxygen nonbonding state (n(O 2p) state; the valence band maximum of the GODs). The GODs exhibit excitation-independent green-PL emissions at 530 nm with a maximum quantum yield (QY) of 12% at 470 nm excitation, whereas the A-GODs exhibit a maximum QY of 63%. The transformation of the solvent relaxation-governed pi* -> n(O 2p) transition in the GODs to the direct pi* -> n(N 2p) transition in the A-GODs possibly accounts for the substantial QY enhancement in the PL emissions. This study elucidates the role of nitrogen functionalities in the PL emissions of graphitic materials and proposes a strategy for designing the electronic structure to promote the PL performance.
Three-dimensional patterned graphene oxide-quantum dot microstructures via two-photon crosslinking
(2017-12-01)
Lin, Chun-Yu
;
Chang, Hsin-Yu
;
Yeh, Te-Fu
;
Teng, Hsisheng
;
Chen, Shean-Jen
The two-photon crosslinking of graphene oxide-quantum dots (GOQDs) adopts rose Bengal as the photoactivator to induce the GOQD assembly process. Based on the Forster resonance energy transfer mechanism with oxygen as the crosslinking medium, three-dimensional patterned GOQD microstructures with near diffraction-limit spatial resolution have been fabricated and analyzed by a multiphoton excited fabrication instrument/microscope. (C) 2017 Optical Society of America