Ng Qi Hwa
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Ng Qi Hwa
Official Name
Ng, Qi Hwa
Alternative Name
Ng, Q. H.
Qi, Hwa Ng
Ng, Qi H.
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Scopus Author ID
54413018300
Researcher ID
A-9192-2019

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  • Publication
    Enhancement of electrode surface hydrophilicity and selectivity with Nafion-PSS composite for trace heavy metal sensing in electrochemical sensors
    (Elsevier B.V., 2025-01)
    Chyh Shyang Ong
    ;
    Ng Qi Hwa
    ;
    Abdul Latif Ahmad
    ;
    Siew Chun Low
    Background: Effective electrochemical sensing requires optimal signal output value and sensitivity, which often pose a challenge due to their counter-intuitive relationship. In order to enhance both aspects, this study designs a modified screen-printed electrode (Nafion-PSS/SPE) comprising a composite formed by two sulfonate-rich polymers, namely Nafion and poly(sodium 4-styrenesulfonate) (PSS). The Nafion-PSS/SPE was utilized in the electrochemical determination of lead (Pb2+) and cadmium (Cd2+) via square wave anodic stripping voltammetry (SWASV). This innovative approach aims to improve detection limits and overall analytical performance in complex matrices. (84) Results: The addition of hydrophilic PSS positively improves surface wettability of Nafion-PSS/SPE, as confirmed by water contact angle analysis. Despite the improved wettability, the modified sensor maintains a high selectivity towards heavy metal ions. Cyclic voltammetry (CV) reveals a large electrochemically active surface area (ECSA) for cations (0.5646 cm2) and a relatively low ECSA for anions (0.3221 cm2). Under optimized conditions, the stripping responses for Pb2+ and Cd2+ exhibited linearity within the concentration ranges of 0.025–0.7 ppm and 0.0125–0.4 ppm, respectively. The detection limits achieved by the modified sensor are 6.478 ppb (Pb2+) and 5.277 ppb (Cd2+). The enhancement observed can be ascribed to the following factors, including presence of sulfonate ligands (Nafion and PSS), enhanced wettability (PSS), and surface selectivity (Nafion). Furthermore, even in the presence of interfering ions replicating the composition of effluent from the pesticide industry, the Nafion-PSS/SPE showcases remarkable selectivity for the target Pb2+ and Cd2+ ions. (148) Significance: This work presents a facile screen-printing technique that could be potentially adopted for batch production of heavy metal sensing devices. Besides, by scrutinizing the surface properties of the modified sensor, this work aims to provide insights on how the proposed modification approach can help to improve the sensor's detection performance.
  • Publication
    Morphology and atomic configuration control of heavy metal attraction modified layer on screen-printed electrode to enhance electrochemical sensing performance
    (Elsevier B.V., 2023)
    Chyh Shyang Ong
    ;
    Nurul Hanisarina binti Zaharum
    ;
    Noorhashimah Mohamad Nor
    ;
    Abdul Latif Ahmad
    ;
    Ng Qi Hwa
    ;
    Khairunisak Abdul Razak
    ;
    Siew Chun Low
    The sensitivity of screen-printed electrochemical (SPE) sensors is heavily dependent on the selection of appropriate modifiers that can optimize the chemical (functional ligands, surface charge, binding energy) and physical (morphological structure) properties of the sensor surface. This study aimed to investigate the impact of these chemical and physical factors on the sensitivity of modified SPEs for the detection of lead and cadmium. The study employed anodic stripping voltammetry to evaluate the sensing performance of SPEs modified with different modifiers, including cellulose acetate, chitosan, Nafion, nylon-6, and silver nanoparticles. Results showed that metal-attracting functional groups and surface charged electrode were the dominant factors affecting the sensitivity of SPEs in heavy metal sensing. Specifically, negatively charged electrode surfaces and metal-attracting -SO32- ligands, as found in Nafion-modified SPE, were identified as the key factors in improving sensor selectivity, rather than the rough physical morphology of the SPE, which was believed to provide more metal detection sites. This conclusion was supported by the combination analyses of electrochemical impedance spectroscopy, electrochemically active surface area and computational molecular binding energy of bare and modified SPEs. The findings of this study provide valuable insights for selecting appropriate SPE modifiers and designing sensor architectures for heavy metal detection
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