Browsing by Author "Wong, Danny"

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    Facile and rapid synthesis of functionalized Zr-BTC for the optical detection of the blistering agent simulant 2-chloroethyl ethyl sulfide (CEES)
    (Royal Society of Chemistry, 2021-02) Abuzalat, Osama; Homayoonnia, Setareh; Wong, Danny; Tantawy, Hesham R.; Kim, Seonghwan
    2-chloroethyl ethyl sulfide (CEES) is a simulant for the chemical warfare agent, bis(2-chloroethyl) sulfide, also known as mustard gas. Here, we demonstrate a facile and rapid method to synthesize a functionalized metal-organic framework (MOF) material for the detection of CEES in trace level. While Zr-BTC is synthesized, in-situ encapsulation of fluorescent material (Fluorescein) into Zr-BTC voids is performed with a simple solvothermal reaction. The produced F@Zr-BTC is used as a fluorescent probe for CEES detections. The synthesized material shows fluorescence quenching under illumination at excitation wavelength of 470 nm when the F@Zr-BTC is exposed to CEES. This sensing material shows the highest fluorescence quenching at an emission wavelength of 534 nm with CEES concentration as low as 50 ppb. Therefore, the demonstrated sensing method with F@Zr-BTC offers a fast and convenient protocol for selective and sensitive detection of CEES in practical applications.
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    ItemOpen Access
    Facile and rapid synthesis of functionalized Zr-BTC for the optical detection of the blistering agent simulant 2-chloroethyl ethyl sulfide (CEES)
    (Royal Society of Chemistry, 2021-02) Kim, Seonghwan; Abuzalat, Osama; Homayoonnia, Setareh; Wong, Danny; Tantawy, Hesham R
    2-chloroethyl ethyl sulfide (CEES) is a simulant for the chemical warfare agent, bis(2-chloroethyl) sulfide, also known as mustard gas. Here, we demonstrate a facile and rapid method to synthesize a functionalized metal-organic framework (MOF) material for the detection of CEES in trace level. While Zr-BTC is synthesized, in-situ encapsulation of fluorescent material (Fluorescein) into Zr-BTC voids is performed with a simple solvothermal reaction. The produced F@Zr-BTC is used as a fluorescent probe for CEES detections. The synthesized material shows fluorescence quenching under illumination at excitation wavelength of 470 nm when the F@Zr-BTC is exposed to CEES. This sensing material shows the highest fluorescence quenching at an emission wavelength of 534 nm with CEES concentration as low as 50 ppb. Therefore, the demonstrated sensing method with F@Zr-BTC offers a fast and convenient protocol for selective and sensitive detection of CEES in practical applications.
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    High-Performance, Room Temperature Hydrogen Sensing With a Cu-BTC/Polyaniline Nanocomposite Film on a Quartz Crystal Microbalance
    (2019-01) Abuzalat, Osama; Wong, Danny; Park, Simon S.; Kim, Seonghwan
    In this paper, we demonstrate a high-performance hydrogen sensor under ambient conditions by growing a Cu-BTC/polyaniline (PANI) nanocomposite film on a quartz crystal microbalance (QCM) using intense pulsed light. The QCM was first sputter coated with a 200-nm-thin layer of copper. The copper layer was then oxidized by sodium hydroxide and ammonium persulfate. A solution containing the organic ligand (BTC) and PANI was then dropped and dried on the copper hydroxide surface of a QCM with intense pulsed light which resulted in Cu-BTC/PANI nanocomposite film on a QCM. The gas sensing performance of the Cu-BTC film and Cu-BTC/PANI composite film was compared under ambient conditions. It was found selectivity and sensitivity of the Cu-BTC/PANI nanocomposite film to hydrogen were significantly improved. In addition, a fast response time (from 2 to 5 s), operation at room temperature even in the presence of high relative humidity (up to 60%), good repeatability were achieved with the Cu-BTC/PANI nanocomposite film-grown QCM sensor.
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    In situ encapsulation of ZrQ in UiO-66 (Zr-BDC) for pore size control to enhance detection of a nerve agent simulant dimethyl methyl phosphonate (DMMP)
    (Wiley, 2022-06-08) Wong, Danny; Kim, Seonghwan; Abuzalat, Osama
    Chemical warfare agents are toxic chemicals that require rapid, easy-to-use, sensitive, and selective sensors to countermeasure. Simulants, such as dimethyl methyl phosphonate (DMMP), are used to test the effectiveness of sensors toward nerve agents. Metal organic frameworks (MOFs) offer large surface area and selective accessibility to active sites making them appealing for chemical sensing applications. In this work, we propose a fast, facile, direct synthesis method for manufacturing fluorescent MOFs with high sensitivity and selectivity. Zr-BDC is synthesized with 1, 4-benzenedicarboxylic acid (BDC) as an organic ligand and zirconium (Zr) metal. Fluorescent materials are then encapsulated in a novel and rapid in situ approach with strong solvents. X-ray diffraction, UV–visible spectroscopy, Fourier-transform infrared spectroscopy, and Raman spectroscopy are used to verify the successful formation of fluorescent MOFs. Compared to other methods, the gel synthesis method helps to control crystal growth leading to higher BET surface areas of ~1150 m2 g−1 for Zr-BDC and 850 m2 g−1 for ZrQ@Zr-BDC. Titration experiments show the sensitivity of the material to DMMP down to 8.3 nM with a highly linear response. Enhanced fluorescence and occupation of mesopores by ZrQ enable lower limit of detection than those of comparable works in literature. The encapsulation mechanism also prevents substantial defects that would otherwise lead to water adsorption.
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    Near Field Electrospinning of Nanofibers for Multi-Modal Hydrogen Sensing
    (2018-09-06) Wong, Danny; Park, Simon S.; Lu, Qingye; Ghasemloonia, Ahmad; Enns, Silvanus T.
    Hydrogen gas is a common byproduct in industrial processes. It is also frequently used in practical applications such as fuel cell vehicles. It has no smell and no taste, but it may pose immediate safety risks because it is combustible in air. It is also un wanted in manufacturing processes as it causes hydrogen-assisted cracking. Sensitive and selective gas sensors are critical to rapidly detect and minimize potential hazards. In this study, we propose a multi-modal hydrogen sensor that combines electrochemical and resonance-based sensing approaches using both quartz tuning forks (QTF) and quartz crystal microbalances (QCM). Near-field electrospinning is used to deposit uniform, semi-conductive nanofibers connecting the two prongs of a QTF. Electrospinning parameters are also optimized on QCM to maximize sensing performance. The most important parameters include polymer concentration, additive concentration and tip-to-collector distance. Treated multi-walled carbon nanotubes (MWCNT), platinum nanoparticles and polyaniline (PANI) are used as the sensing materials with polyethylene oxide (PEO) being used as an electrospinning guide. The effects of intensive pulsed light (IPL) for welding the nanofibers to the platinum coated surfaces are also investigated. The attached sensing materials caused the resonance frequency to shift due to increased stiffness but provided increased surface area for selective adsorption and allowed for electrical impedance changes to be measured. The resonance frequency and electrical impedance both decrease when exposed to hydrogen gas. The sensing methods are combined to develop sensitive gas sensors that are selective to hydrogen compared to a multitude of other gases. Models are developed to back calculate the hydrogen concentration based on the sensor response. The development of these sensors lead to new methods for compact multi-modal sensing.
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    Sonochemical fabrication of Cu(II) and Zn(II) metal-organic framework films on metal substrates
    (2018-07) Abuzalat, Osama; Wong, Danny; Elsayed, Mohamed; Park, Simon; Kim, Seonghwan
    In this article, we demonstrate a rapid and facile method for in-situ growth of metal-organic framework (MOF) films on Cu or Zn metal substrates by sonochemical techniques. The substrates were first treated with a strong oxidizing agent to convert the metal to the corresponding metal hydroxide. Ultrasonic irradiation provided the energy to drive the reaction between the metal ion sources and organic ligands. Four MOF films (Cu-BTC, Cu-BDC, ZIF-8 and MOF-5) were successfully fabricated by this approach. The produced films were characterized by scanning electron microscopy and X-ray diffraction analysis. The effects of organic ligand concentration and ultrasonic irradiation time on MOF film synthesis were also systematically investigated. The rapid and facile fabrication method presented in this article could serve a new route to grow MOF films on various gas sensor surfaces. Of the MOF films, ZIF-8 film was tested as a potential methane sensor.