Browsing by Author "Liu, Tsung-Han"

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Femtosecond-Laser-Enhanced Amyloid Fibril Formation of Insulin
(2017-08-22)
Liu, Tsung-Han
;
Yuyama, Ken-ichi
;
Hiramatsu, Takato
;
Yamamoto, Naoki
;
Chatani, Eri
Femtosecond (fs)-laser-induced crystallization as a novel crystallization technique was proposed for the first time by our group, where the crystallization time can be significantly shortened under fs laser irradiation. Similarly, we have further extended our investigation to amyloid fibril formation, also known as a nucleation-dependence process. Here we demonstrate that the necessary time for amyloid fibril formation can be signifiCantly shortened by fs laser irradiation, leading to favorable enhancement. The enhancement was confirmed by both spectral measurements and direct observations of amyloid fibrils. The thioflavin T fluorescence intensity of laser-irradiated solution increased earlier than that of the control solution, and such a difference was simultaneously revealed by ellipticity changes. At the same time before intensity Saturation in fluorescence, the number of amykid fibrils obtained under laser irradiation was generally mote than that in the control. Solution. Besides, such an enhancement is correlated to the laser power threshold of cavitation bubbling. Possible mechanisms are proposed by referring to fs-laser-induced crystallization and ultrasonication-induced amyloid fibril formation.
Optical Trapping Dynamics of a Single Polystyrene Sphere: Continuous Wave versus Femtosecond Lasers
(2016-02)
Liu, Tsung-Han
;
Chiang, Wei-Yi
;
Usman, Anwar
;
Masuhara, Hiroshi
;
應用化學系
Understanding of optical trapping dynamics of a single particle in the trapping site is important to develop its optical manipulation for molecular assembly and chemical application. For micrometer-sized Mie particles, similar trapping efficiency of the conventional continuous wave (cw) laser or high-repetition-rate femtosecond (fs) laser pulse train has been established [Dholakia et al., Opt. Express 2010, 18, 7554-7568], in contrast to higher efficiency of the laser pulses to trap dielectric Rayleigh particles. To further explore and clarify the switching phenomena of optical trapping efficiency with cw laser and fs laser pulse and to elucidate its nature, we study the immobilization dynamics of a single polystyrene sphere with 500 nm in diameter (which is comparable to focal beam size) in shallow potential well. By observing trapping events and immobilization time of the particle with a size in Lorenz-Mie regime, distinct from well-known Rayleigh particle and ray optics approximations, we found that immobilization time is only linearly related to the incident laser power <= 40 mW, and at higher laser powers cw laser is more efficient than fs laser pulses to immobilize the particle. This finding means that the dynamics of the particle in this size region is still affected by the strong transient force fields induced by high-repetition-rate ultrashort pulse train as usually observed for Rayleigh particles. This may provide an understanding that the dynamics of the target particle in the trapping site is size- and laser mode-dependent.
Preparation and micropatterning of gold nanoparticles by femtosecond laser-induced optical breakdown
(2017-09-01)
Uwada, Takayuki
;
Wang, Shun-Fa
;
Liu, Tsung-Han
;
Masuhara, Hiroshi
;
應用化學系
We fabricated gold nanoparticles (NPs) via a femtosecond (fs) laser-induced cavitation bubbling. By introducing intense fs laser pulses into HAuCI4 aqueous solution containing 1-propanol, optical breakdown and the following cavitation bubble generation occurred at the focus through multiphoton absorption of water, resulting in the formation of gold nanoparticles (Au NPs). Intermediate species such as radicals and solvated electrons produced upon the bubbling contribute to gold ion reduction, while direct ionization of Au-chloride complex, photothermal decomposition and direct optical decomposition are excluded as possible mechanisms. Utilizing the fs laser-induced bubbling we demonstrate in-situ micropatterning of Au NPs on a substrate from the same HAuCI4 aqueous solution containing 1-propanol. (C) 2017 Elsevier B.V. All rights reserved.
Single femtosecond laser pulse-single crystal formation of glycine at the solution surface
(2013-03-01)
Liu, Tsung-Han
;
Uwada, Takayuki
;
Sugiyama, Teruki
;
Usman, Anwar
;
Hosokawa, Yoichiroh
We demonstrate femtosecond laser-induced crystallization of glycine from its supersaturated solution depending on laser tunable parameters (pulse energy and repetition rate) and focal position, and examine the crystallization probability, crystal morphology, and crystal polymorph. The generation of cavitation bubble through multiphoton absorption of water depends on input laser pulse energy and repetition rate, which strongly determine morphology and number of the obtained crystals. Significant increase in the crystallization probability is observed by irradiating the femtosecond laser pulses to the air/solution interface, and single pulse-induced single crystal formation is successfully achieved. The crystallization mechanism is discussed in view of inhomogeneous mechanical stress induced by cavitation bubble generation and molecular assembly characteristics of the surface. (C) 2012 Elsevier B.V. All rights reserved.