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10. Motor-like microlasers functioning in biological fluids

Author

Wang, Ziyihui, primary, Shang, Linwei, additional, Gao, Zehang, additional, Chan, Kok Ken, additional, Gong, Chaoyang, additional, Wang, Chenlu, additional, Xu, Tianhua, additional, Liu, Tiegen, additional, Feng, Shilun, additional, and Chen, Yu-Cheng, additional

Published
2022
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16. Two-Dimensional MoS2 Nanosheet-Functionalized Optical Microfiber for Room-Temperature Volatile Organic Compound Detection.

Author

Yap, Stephanie Hui Kit, Chan, Kok Ken, Yeh, Chen-Hao, Chien, Yi-Hsin, and Yong, Ken-Tye

Abstract

Two-dimensional (2D) transition-metal dichalcogenides such as molybdenum disulfide (MoS2) have received a great deal of attention for high-performance gas sensing applications. Unfortunately, before their translation to commercial use, several scientific problems remain to be solved. The challenges include poor stability in a humid environment, random deposition manner of MoS2 flakes that makes the process unscalable, and incomplete recovery at room temperature. Herein, we report a strategy for the room-temperature volatile organic compound (VOC) sensor using the optical microfiber sensing technology. We demonstrated well-controlled immobilization of MoS2 nanosheets onto the optical sensing region using the optical deposition technique. The experimental results show that the MoS2-functionalized optical microfiber sensor achieves high selectivity to polar aprotic and nonpolar VOCs. The sensor demonstrated high sensitivity of 0.0195, 0.0143, 0.0072, and 0.0058 nm/ppm to acetone, ethyl acetate, cyclohexane, and IPA, respectively. Finally, the repeatability and complete recovery capabilities of the sensor have also been validated in this work. [ABSTRACT FROM AUTHOR]

Published
2021
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17. NIR-responsive nanomaterials and their applications; upconversion nanoparticles and carbon dots: a perspective

Author

Chien, Yi-Hsin, Chan, Kok Ken, Yap, Stephanie Hui Kit, Yong, Ken-Tye, and School of Electrical and Electronic Engineering

Subjects
Engineering::Electrical and electronic engineering::Electric apparatus and materials [DRNTU], Carbon Dots, NIR-Nanoparticles
Abstract

Near‐infrared (NIR) light responsive materials have received much attention for diverse applications due to their excellent optical properties. This type of material exhibits upconverted luminescence, a non‐linear optical process in which two or more low energy photons, usually from NIR light irradiation are transformed to high energy photons emission through energy transfer upconversion, excited state absorption, photon avalanche or multiphoton absorption. The NIR range of excitation source is favorable for biological imaging and cancer theranostic applications due to their high penetration depth, low autofluorescence, minimal light scattering, reduced photodamage, and negligible phototoxicity. Having these properties, NIR responsive materials such as upconversion nanoparticles (UCNPs) and carbon dots (CDs) which perform upconversion luminescence are actively exploited in a wide variety of applications such as display and sensory technology. While CDs are well known for their versatility in using different chemicals and green precursors to achieve tunable optical properties, UCNPs also have the advantage that a continuous‐wave NIR laser can be used as the excitation source. This article reviews the properties of these two materials in the aspects of luminescence mechanisms and their recent developments in cancer theranostics, display technology, biosensing and metal ions sensing applications. © 2018 Society of Chemical Industry

Published
2018

23. Biodegradable Polymer-Coated Multifunctional Graphene Quantum Dots for Light-Triggered Synergetic Therapy of Pancreatic Cancer

Author

Yang, Chengbin, primary, Chan, Kok Ken, additional, Xu, Gaixia, additional, Yin, Mingjie, additional, Lin, Guimiao, additional, Wang, Xiaomei, additional, Lin, Wei-Jen, additional, Birowosuto, Muhammad Danang, additional, Zeng, Shuwen, additional, Ogi, Takashi, additional, Okuyama, Kikuo, additional, Permatasari, Fitri Aulia, additional, Iskandar, Ferry, additional, Chen, Chih-Kuang, additional, and Yong, Ken-Tye, additional

Published
2018
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28. Four-quadrant operation ZVS DC/DC LUO converters

Author

Chan, Kok Ken., Luo Fang Lin, and School of Electrical and Electronic Engineering

Subjects
Engineering::Electrical and electronic engineering [DRNTU]
Abstract

DC-DC converters are an important aspect in portable electronic devices such as cell phones, laptop computers and electric cars which power are supplied primarily from batteries. These electronic devices may require several voltage level requirements for different parts of the device. DC-DC converter is a method to convert a voltage level to another voltage level to suit the application needs rather than having multiple batteries to suit each and every part of a particular application. Generally, there are two different methods used to convert DC voltages, namely switched-mode fixed frequency pulse width modulation (PWM) DC-DC converter and the variable frequency quasi-resonant converters. Switched-mode fixed frequency pulse width modulation (PWM) DC-DC converter usually has high electronic noise and is usually complex. Master of Science (Power Engineering)

Published
2012

30. Tunable Optical Vortex from a Nanogroove-Structured Optofluidic Microlaser.

Author

Qiao Z, Gong C, Liao Y, Wang C, Chan KK, Zhu S, Kim M, and Chen YC

Abstract

Optical vortices with tunable properties in multiple dimensions are highly desirable in modern photonics, particularly for broadly tunable wavelengths and topological charges at the micrometer scale. Compared to solid-state approaches, here we demonstrate tunable optical vortices through the fusion of optofluidics and vortex beams in which the handedness, topological charges, and lasing wavelengths could be fully adjusted and dynamically controlled. Nanogroove structures inscribed in Fabry-Pérot optofluidic microcavities were proposed to generate optical vortices by converting Hermite-Gaussian laser modes. Topological charges could be controlled by tuning the lengths of the nanogroove structures. Vortex laser beams spanning a wide spectral band (430-630 nm) were achieved by alternating different liquid gain materials. Finally, dynamic switching of vortex laser wavelengths in real-time was realized through an optofluidic vortex microlaser device. The findings provide a robust yet flexible approach for generating on-chip vortex sources with multiple dimensions, high tunability, and reconfigurability.

Published
2022
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