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

Research Output
Now showing 1 - 5 of 5
  • 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
    Recent advancements in smart materials for the removal of organic, inorganic and microbial pollutants in water treatment: a review
    (Elsevier, 2025-02)
    Soon Wah Goh
    ;
    Ng Qi Hwa
    ;
    Siti Kartini Enche Ab Rahim
    ;
    Siew Chun Low
    ;
    Hoo Peng Yong
    ;
    Ryan Yow Zhong Yeo
    ;
    Thiam Leng Chew
    ;
    Zeinab Abbas Jawad
    As the expeditious urban and industrial expansion, a substantial portion of wastewater is produced annually, posing a significant threat to environmental contamination and dwindling the availability of clean water resources. Water contaminants are generally categorized into organic, inorganic, and microbial pollutants. This escalating water pollution crisis has initiated the research community to innovate novel, effective and economical cost methods for water treatment applications. Among the approaches, adsorption has been marked by its importance in water treatment. Recent advancements in the field have focused on developing smart adsorbent materials capable of modifying their physicochemical properties in response to various external stimuli (light and magnetic field) and internal stimuli (thermal and pH fluctuation). The exploration of smart materials has captivated the interest of researchers worldwide and opened up exciting avenue for more efficient water treatment outcomes towards removing different types of pollutants. Notably, these smart materials demonstrate high pollutant uptake and release efficacy when responding to specific stimuli changes, ensuring efficient removal of contaminants and exerting self-cleaning properties. Such materials offer an environmentally benign advantage by eliminating the need for toxic organic solvents during regeneration. The review compiles and highlights the characteristics and performance of several stimuli-responsive smart materials, including thermal, light, magnetic and pH regarding organic, inorganic and microbial pollutants removal efficiencies. A particular focus is given to multi-stimuli responsive materials in environmental applications that represent the modern era and transformation of water treatment methodologies, followed by a discussion on the challenges and prospects of this particular research area.
  • Publication
    Advanced dual-wetting membrane for enhanced CO₂ capture: asymmetric hydrophobic and CO₂-philic thin film in membrane gas absorption
    (Korean Society of Industrial Engineering Chemistry, 2025-09)
    Pei Thing Chang
    ;
    Ng Qi Hwa
    ;
    Pei Ching Oh
    ;
    Siew Chun Low
    CO₂ is a major contributor to climate change, making efficient carbon capture essential for emission reduction. Membrane gas absorption (MGA) offers a cost-effective solution, with research often focusing on enhancing membrane hydrophobicity to reduce wettability. However, the potential of CO₂-philic membranes for mixed gas separation remains underexplored. This study addresses the gap by developing asymmetric wetting membranes (PVDF/EDA/GO) with a superhydrophobic side to prevent wetting and a CO₂-philic side to enhance CO₂ capture. The CO₂-philic surface was created by coating PVDF with ethylenediamine (EDA) and graphene oxide (GO). Computational analysis confirmed strong binding energy (−21.07 kcal/mol) between EDA and GO, forming a stable amine complex. The membranes displayed asymmetric wetting, with the CO₂-philic side showing a water static angle (WSA) of 49.6 ± 2.6°, and the superhydrophobic side achieved a WSA of 149.7 ± 3.3° and a water gliding angle (WGA) of 9.8 ± 1.1°. In MGA, these membranes demonstrated improved performance, with a CO₂ absorption flux of 0.0040 mol/m2s and CO₂/N2 selectivity of 6. This work highlights the promise of dual-wetting membranes for enhancing CO₂ capture in MGA systems.
  • 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
      11  1
  • Publication
    Study on the enhancement of colloidal stable poly(sodium 4‐styrene sulfonate) coated magnetite nanoparticles and regeneration capability for rapid magnetophoretic removal of organic dye
    (Society of Chemical Industry (SCI), 2020)
    Wai Hong Chong
    ;
    Ng Qi Hwa
    ;
    Jit Kang Lim
    ;
    Swee Pin Yeap
    ;
    Siew Chun Low
    BACKGROUND: A good colloidal stability of magnetite nanoparticles (MNPs) dispersion is of utmost importance for its environmentally related applications. In the present work, a water-soluble anionic polyelectrolyte, poly(sodium 4-styrene sulfonate) (PSS), was used to stabilize dispersions of MNPs in a pH-dependent aqueous medium. RESULTS: An excellent methylene blue (MB) dye removal efficiency at equilibrium of up to 94% has been observed by the colloidally stabilized nano-magnetites. Dynamic light scattering and electrophoretic analysis showed that the PSS-coated MNPs exhibited better colloidal stability, with an almost constant hydrodynamic diameter of ~150 nm and insignificant clustering behavior throughout the measuring time scale of 5 h. Transmission electron microscopy evidenced the success coating of PSS onto MNPs. In terms of its chemical resistance, the PSS-coated MNPs were able to tolerate a wide pH range from 2 to 10. This work depicts a simple physiochemical coating method to stabilize dispersions of nano-magnetites, which promoted a better MB adsorption capacity of PSS-coated MNPs at 14.9 mg g–1 than the naked MNPs at 10.38 mg g–1. The adsorption process follows Langmuir isotherm and pseudo-second-order reaction kinetics with both correlations R2 > 0.99. PSS-coated MNPs demonstrated outstanding regeneration capacity for four batch adsorption cycles with an almost consistent MB removal efficiency higher than 85%. CONCLUSION: This in-house developed nano-sorbent has potential in economical applications with a less budgeted adsorbent replacement (at least 4 cycles of regeneration) for low-cost separation of pollutants, such as MB from polluted water.
      6  4