Gu Yuandong
Email Address
eleguyd@nus.edu.sg
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Publication Hybrid Photonic Cavity with Metal-Organic Framework Coatings for the Ultra-Sensitive Detection of Volatile Organic Compounds with High Immunity to Humidity(NATURE PUBLISHING GROUP, 2017-01-31) Tao, Jifang; Wang, Xuerui; Sun, Tao; Cai, Hong; Wang, Yuxiang; Lin, Tong; Fu, Dongliang; Ting, Lennon Lee Yao; Gu, Yuandong; Zhao, Dan; Assoc Prof Zhao Dan; ELECTRICAL AND COMPUTER ENGINEERING; CHEMICAL & BIOMOLECULAR ENGINEERING© The Author(s) 2017. Detection of volatile organic compounds (VOCs) at parts-per-billion (ppb) level is one of the most challenging tasks for miniature gas sensors because of the high requirement on sensitivity and the possible interference from moisture. Herein, for the first time, we present a novel platform based on a hybrid photonic cavity with metal-organic framework (MOF) coatings for VOCs detection. We have fabricated a compact gas sensor with detection limitation ranging from 29 to 99 ppb for various VOCs including styrene, toluene, benzene, propylene and methanol. Compared to the photonic cavity without coating, the MOF-coated solution exhibits a sensitivity enhancement factor up to 1000. The present results have demonstrated great potential of MOF-coated photonic resonators in miniaturized gas sensing applications.Publication An ultrahigh-accuracy Miniature Dew Point Sensor based on an Integrated Photonics Platform(2016) Tao, J; Luo, Y; Wang, L; Cai, H; Sun, T; Song, J; Liu, H; Gu, Y; ELECTRICAL AND COMPUTER ENGINEERINGThe dew point is the temperature at which vapour begins to condense out of the gaseous phase. The deterministic relationship between the dew point and humidity is the basis for the industry-standard "chilled-mirror" dew point hygrometers used for highly accurate humidity measurements, which are essential for a broad range of industrial and metrological applications. However, these instruments have several limitations, such as high cost, large size and slow response. In this report, we demonstrate a compact, integrated photonic dew point sensor (DPS) that features high accuracy, a small footprint, and fast response. The fundamental component of this DPS is a partially exposed photonic microring resonator, which serves two functions simultaneously: 1) sensing the condensed water droplets via evanescent fields and 2) functioning as a highly accurate, in situ temperature sensor based on the thermo-optic effect (TOE). This device virtually eliminates most of the temperature-related errors that affect conventional "chilled-mirror" hygrometers. Moreover, this DPS outperforms conventional "chilled-mirror" hygrometers with respect to size, cost and response time, paving the way for on-chip dew point detection and extension to applications for which the conventional technology is unsuitable because of size, cost, and other constraints.Publication Covalent organic nanosheets with large lateral size and high aspect ratio synthesized by Langmuir-Blodgett method(ELSEVIER SCIENCE INC, 2018-06-01) Cheng, Youdong; Ravi, Sai Kishore; Wang, Yuxiang; Tao, Jifang; Gu, Yuandong; Tan, Swee Ching; Zhao, Dan; Assoc Prof Zhao Dan; MATERIALS SCIENCE AND ENGINEERING; CHEMICAL & BIOMOLECULAR ENGINEERING© 2018 The Author Two-dimensional (2D) materials have attracted increasing attentions recently due to their unique physical and chemical properties. We herein report the synthesis of four chemically stable 2D covalent organic nanosheets (CONs) with large lateral sizes (up to 200 μm) and high aspect ratios (>20 000) at the air-water interface through the Langmuir-Blodgett method. These CONs exhibit good crystallinity proved by high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). In addition, the hydrophobicity of these CONs can be systematically adjusted by the introduction of various functional groups, making them suitable as functional coating and membrane materials.Publication ZnO Nanosheets Abundant in Oxygen Vacancies Derived from Metal-Organic Frameworks for ppb-Level Gas Sensing(WILEY-VCH VERLAG, 2019-03-15) Yuan, Hongye; Aljneibi, Saif Abdulla Ali Alateeqi; Yuan, Jiaren; Wang, Yuxiang; Liu, Hui; Fang, Jie; Tang, Chunhua; Yan, Xiaohong; Cai, Hong; Gu, Yuandong; Pennycook, Stephen John; Tao, Jifang; Zhao, Dan; Assoc Prof Zhao Dan; BIOMEDICAL ENGINEERING; ELECTRICAL AND COMPUTER ENGINEERING; MATERIALS SCIENCE AND ENGINEERING; CHEMICAL & BIOMOLECULAR ENGINEERING© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Surmounting the inhomogeniety issue of gas sensors and realizing their reproducible ppb-level gas sensing are highly desirable for widespread deployments of sensors to build networks in applications of industrial safety and indoor/outdoor air quality monitoring. Herein, a strategy is proposed to substantially improve the surface homogeneity of sensing materials and gas sensing performance via chip-level pyrolysis of as-grown ZIF-L (ZIF stands for zeolitic imidazolate framework) films to porous and hierarchical zinc oxide (ZnO) nanosheets. A novel approach to generate adjustable oxygen vacancies is demonstrated, through which the electronic structure of sensing materials can be fine-tuned. Their presence is thoroughly verified by various techniques. The sensing results demonstrate that the resultant oxygen vacancy-abundant ZnO nanosheets exhibit significantly enhanced sensitivity and shortened response time toward ppb-level carbon monoxide (CO) and volatile organic compounds encompassing 1,3-butadiene, toluene, and tetrachloroethylene, which can be ascribed to several reasons including unpaired electrons, consequent bandgap narrowing, increased specific surface area, and hierarchical micro–mesoporous structures. This facile approach sheds light on the rational design of sensing materials via defect engineering, and can facilitate the mass production, commercialization, and large-scale deployments of sensors with controllable morphology and superior sensing performance targeted for ultratrace gas detection.