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Nam-Hyoung Lim
Department of Civil and Environmental Engineering, Korea University

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Review
Published: 29 June 2021 in Trends in Environmental Analytical Chemistry
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Nanomaterial-enabled electrochemical sensors are designed as an economical, efficient, and user-friendly analytical tool for on-site and routine nitrate analysis over a wide range of environmental samples. The remarkable advances and tunable attributes of nanomaterials have greatly improved the analytical performance of electrochemical nitrate sensors. In this review, a comprehensive elucidation of the recent advances in nanomaterial-based electrochemical nitrate sensors is presented. The review firstly provides a general introduction, followed by typical electrochemical sensing methods. The next two sections detail various nanomaterials, including graphene derivatives, carbon nanotubes/fibers, metal/bimetal/metal oxide nanoparticles, and conducting polymers for modifying electrodes in enzymatic and non-enzymatic electrochemical nitrate sensors. Finally, the perspectives and current challenges in achieving real-world applications of nanomaterial-based electrochemical nitrate sensors are outlined.

ACS Style

R.K.A. Amali; H.N. Lim; I. Ibrahim; N.M. Huang; Z. Zainal; S.A.A. Ahmad. Significance of nanomaterials in electrochemical sensors for nitrate detection: A review. Trends in Environmental Analytical Chemistry 2021, e00135 .

AMA Style

R.K.A. Amali, H.N. Lim, I. Ibrahim, N.M. Huang, Z. Zainal, S.A.A. Ahmad. Significance of nanomaterials in electrochemical sensors for nitrate detection: A review. Trends in Environmental Analytical Chemistry. 2021; ():e00135.

Chicago/Turabian Style

R.K.A. Amali; H.N. Lim; I. Ibrahim; N.M. Huang; Z. Zainal; S.A.A. Ahmad. 2021. "Significance of nanomaterials in electrochemical sensors for nitrate detection: A review." Trends in Environmental Analytical Chemistry , no. : e00135.

Review
Published: 18 June 2021 in Polymers
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Polyaniline (PANI) is a famous conductive polymer, and it has received tremendous consideration from researchers in the field of nanotechnology for the improvement of sensors, optoelectronic devices, and photonic devices. PANI is doped easily by different acids and dopants because of its easy synthesis and remarkable environmental stability. This review focuses on different preparation processes of PANI thin film by chemical and physical methods. Several features of PANI thin films, such as their magnetic, redox, and antioxidant, anti-corrosion, and electrical and sensing properties, are discussed in this review. PANI is a highly conductive polymer. Given its unique properties, easy synthesis, low cost, and high environmental stability in various applications such as electronics, drugs, and anti-corrosion materials, it has attracted extensive attention. The most important PANI applications are briefly reviewed at the end of this review.

ACS Style

Mahnoush Beygisangchin; Suraya Abdul Rashid; Suhaidi Shafie; Amir Sadrolhosseini; Hong Lim. Preparations, Properties, and Applications of Polyaniline and Polyaniline Thin Films—A Review. Polymers 2021, 13, 2003 .

AMA Style

Mahnoush Beygisangchin, Suraya Abdul Rashid, Suhaidi Shafie, Amir Sadrolhosseini, Hong Lim. Preparations, Properties, and Applications of Polyaniline and Polyaniline Thin Films—A Review. Polymers. 2021; 13 (12):2003.

Chicago/Turabian Style

Mahnoush Beygisangchin; Suraya Abdul Rashid; Suhaidi Shafie; Amir Sadrolhosseini; Hong Lim. 2021. "Preparations, Properties, and Applications of Polyaniline and Polyaniline Thin Films—A Review." Polymers 13, no. 12: 2003.

Journal article
Published: 27 May 2021 in Polymers
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In the present study, we explored the effectiveness of PES-Ag3PO4/g-C3N4 film photocatalyst in degrading methyl orange dye under visible light irradiation. The PES-Ag3PO4/g-C3N4 film photocatalyst was prepared via a non-solvent-induced phase inversion process and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), laser scanning microscopy (LSM), X-ray photoelectron spectra (XPS), UV-diffuse reflectance (DRS), and water contact angle. The incorporation of the Ag3PO4/g-C3N4 composite into the PES matrix improved the pristine PES film’s hydrophilicity, as evidenced by the reduction of water contact angle from 79.03° to 54.33° for a film containing 15 wt % of Ag3PO4/g-C3N4 composite. The film’s photoactivity showed that 13 wt % was the best loading of Ag3PO4/g-C3N4 composite, and the degradation performance was maintained up to three cycles. The •O2 and h+ were the predominant species responsible for the methyl orange degradation.

ACS Style

Hayati Mukhair; Abdul Abdullah; Zulkarnain Zainal; Hong Lim. PES-Ag3PO4/g-C3N4 Mixed Matrix Film Photocatalyst for Degradation of Methyl Orange Dye. Polymers 2021, 13, 1746 .

AMA Style

Hayati Mukhair, Abdul Abdullah, Zulkarnain Zainal, Hong Lim. PES-Ag3PO4/g-C3N4 Mixed Matrix Film Photocatalyst for Degradation of Methyl Orange Dye. Polymers. 2021; 13 (11):1746.

Chicago/Turabian Style

Hayati Mukhair; Abdul Abdullah; Zulkarnain Zainal; Hong Lim. 2021. "PES-Ag3PO4/g-C3N4 Mixed Matrix Film Photocatalyst for Degradation of Methyl Orange Dye." Polymers 13, no. 11: 1746.

Journal article
Published: 09 February 2021 in Journal of Electroanalytical Chemistry
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An electrochemical sensor based on Al-MOF (CAU-1-MOF) fabricated glassy carbon electrode (GCE) was utilized for hydroquinone (HQ) detection, an environmental pollutant. The CAU-1 MOF was synthesized by simple heating approach and characterized by FT-IR spectroscopy, XRD, SEM and B.E.T. techniques. The FT-IR results revealed the presence of CO vibration for CAU-1, which proved the incorporation of the amino-terephthalic acid into CAU-1. The XRD of the synthesized CAU-1-MOF was in good agreement with the existing CAU-1 (CCDC: 723320). Further, CAU-1 showed rod-shaped morphology with 280 nm size in average. Besides, CAU-1 had a huge surface area, 1349 m2 g−1 and a micropore volume, 0.41 cm3 g−1. The CAU-1 MOF was successfully fabricated on GCE using nafion as a binder and its electrochemical behaviour was investigated. The electrochemical behaviour of HQ was investigated at GCE/CAU-1 and studied its oxidation kinetics. The GCE/CAU-1 showed higher oxidation current for HQ than the bare GCE. Besides, this sensor shows good selectivity and anti-interference activities in HQ detection with the lowest detection limit, 0.067 µM and excellent sensitivity, 1471.4 µA/mM cm2. Furthermore, the proposed sensor was utilized in the determination of HQ in water samples and exhibited good recovery of 99.34%–103.93%, which suggested the practicability and reliability of the sensor, GCE/CAU-1 in the real-life application.

ACS Style

Sim Siew Ming; N.S.K. Gowthaman; H.N. Lim; P. Arul; E. Narayanamoorthi; I. Ibrahim; H. Jaafar; S. Abraham John. Aluminium MOF fabricated electrochemical sensor for the ultra-sensitive detection of hydroquinone in water samples. Journal of Electroanalytical Chemistry 2021, 883, 115067 .

AMA Style

Sim Siew Ming, N.S.K. Gowthaman, H.N. Lim, P. Arul, E. Narayanamoorthi, I. Ibrahim, H. Jaafar, S. Abraham John. Aluminium MOF fabricated electrochemical sensor for the ultra-sensitive detection of hydroquinone in water samples. Journal of Electroanalytical Chemistry. 2021; 883 ():115067.

Chicago/Turabian Style

Sim Siew Ming; N.S.K. Gowthaman; H.N. Lim; P. Arul; E. Narayanamoorthi; I. Ibrahim; H. Jaafar; S. Abraham John. 2021. "Aluminium MOF fabricated electrochemical sensor for the ultra-sensitive detection of hydroquinone in water samples." Journal of Electroanalytical Chemistry 883, no. : 115067.

Journal article
Published: 21 January 2021 in Solar Energy
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This work describes the efficient improvement of dye-sensitized solar cells (DSSC) utilizing a photoanode with a plasmonic sandwiched silicon dioxide/silver/titanium dioxide (SiO2/Ag/TiO2) structure and a counter electrode (CE) of polypyrrole/reduced graphene oxide/indium tin oxide (Ppy/rGO/ITO) assembled with an aluminium (Al) foil as a reflective layer. The localized surface plasmonic resonance induced from Ag increases the absorption of the dye molecules, and hence significantly improves the electron collection and light-harvesting efficiencies. Compared with conventional photoanode of DCCSs composed of TiO2 paste, the photovoltaic cells containing the plasmonic sandwiched structure exhibits a remarkable improvement in the power conversion efficiency (ƞ), with up to a 2-fold enhancement (from 0.6% to 1.2%), along with a 68.37% increment in the short-circuit current density (Jsc), from 2.15 to 3.62 mA cm−2. The reflective layer of Al foil contributes to a significant enhancement of ƞ of 1.7-fold for the DSSC.

ACS Style

I. Ibrahim; H.N. Lim; N.W.K. Wan; N.M. Huang; S.P. Lim; W. Busayaporn; H. Nakajima. Plasmonic silver sandwich structured photoanode and reflective counter electrode enhancing power conversion efficiency of dye-sensitized solar cell. Solar Energy 2021, 215, 403 -409.

AMA Style

I. Ibrahim, H.N. Lim, N.W.K. Wan, N.M. Huang, S.P. Lim, W. Busayaporn, H. Nakajima. Plasmonic silver sandwich structured photoanode and reflective counter electrode enhancing power conversion efficiency of dye-sensitized solar cell. Solar Energy. 2021; 215 ():403-409.

Chicago/Turabian Style

I. Ibrahim; H.N. Lim; N.W.K. Wan; N.M. Huang; S.P. Lim; W. Busayaporn; H. Nakajima. 2021. "Plasmonic silver sandwich structured photoanode and reflective counter electrode enhancing power conversion efficiency of dye-sensitized solar cell." Solar Energy 215, no. : 403-409.

Journal article
Published: 26 August 2020 in Electrochimica Acta
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A versatile photo-electrochemical (PEC) sensor protocol was established to quantitatively monitor dopamine (DA) levels by utilizing a triple interconnected structure of cadmium sulfide (CdS) modified with gold and graphene quantum dots (Au/GQDs). The introduction of Au and GQDs on the photocatalytic active center of CdS act as a charge separation mediator and photosensitizer, respectively, which are favorable for charge separation and transportation and PEC conversion. When the CdS/Au/GQDs photoelectrode was utilized for DA sensing in a weak alkaline solution, DA was oxidized and converted to poly(dopamine) (PDA), which possesses abundant benzoquinone (BQ) groups that act as electron acceptors. Consequently, the electron acceptors formed in-situ on the surface of the photoelectrode, reducing the anodic photocurrent signal. Under the optimal conditions, the photocurrent decreased when the DA concentration increased in a dynamic working range from 0.1 to 350 µM and with a limit of detection (LoD) of 0.0078 μM. Herein, the proposed strategy involving photoelectron transfer between the electron acceptor and semiconductor provides a new and versatile protocol for PEC sensor development.

ACS Style

Izwaharyanie Ibrahim; Hong Ngee Lim; Nay Ming Huang. In-situ formation of electron acceptor to inhibit charge separation of photo-electrochemical sensor of dopamine-based CdS/Au/GQDs. Electrochimica Acta 2020, 360, 137013 .

AMA Style

Izwaharyanie Ibrahim, Hong Ngee Lim, Nay Ming Huang. In-situ formation of electron acceptor to inhibit charge separation of photo-electrochemical sensor of dopamine-based CdS/Au/GQDs. Electrochimica Acta. 2020; 360 ():137013.

Chicago/Turabian Style

Izwaharyanie Ibrahim; Hong Ngee Lim; Nay Ming Huang. 2020. "In-situ formation of electron acceptor to inhibit charge separation of photo-electrochemical sensor of dopamine-based CdS/Au/GQDs." Electrochimica Acta 360, no. : 137013.

Letter
Published: 21 August 2020 in Sensors
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The need for environmental protection and water pollution control has led to the development of different sensors for determining many kinds of pollutants in water. Ammonia nitrogen presence is an important indicator of water quality in environmental monitoring applications. In this paper, a high sensitivity sensor for monitoring ammonia nitrogen concentration in water using a tapered microfiber interferometer (MFI) as a sensor platform and a broad supercontinuum laser as the light source is realized. The MFI is fabricated to the waist diameter of 8 µm producing a strong interference pattern due to the coupling of the fundamental mode with the cladding mode. The MFI sensor is investigated for a low concentration of ammonia nitrogen in water in the wide wavelength range from 1500–1800 nm with a high-power signal provided by the supercontinuum source. The broad source allows optical sensing characteristics of the MFI to be evaluated at four different wavelengths (1505, 1605, 1705, and 1785 nm) upon exposure towards various ammonia nitrogen concentrations. The highest sensitivity of 0.099 nm/ppm that indicates the wavelength shift is observed at 1785 nm operating wavelength. The response is linear in the ammonia nitrogen range of 5–30 ppm with the best measurement resolution calculated to be 0.5 ppm. The low concentration ammonia nitrogen detected by the MFI in the unique infrared region reveals the potential application of this optical fiber-based sensor for rivers and drinking water monitoring.

ACS Style

Saad Hayatu Girei; Hong Ngee Lim; Muhammad Zamharir Ahmad; Mohd Adzir Mahdi; Ahmad Rifqi Md Zain; Mohd Hanif Yaacob. High Sensitivity Microfiber Interferometer Sensor in Aqueous Solution. Sensors 2020, 20, 4713 .

AMA Style

Saad Hayatu Girei, Hong Ngee Lim, Muhammad Zamharir Ahmad, Mohd Adzir Mahdi, Ahmad Rifqi Md Zain, Mohd Hanif Yaacob. High Sensitivity Microfiber Interferometer Sensor in Aqueous Solution. Sensors. 2020; 20 (17):4713.

Chicago/Turabian Style

Saad Hayatu Girei; Hong Ngee Lim; Muhammad Zamharir Ahmad; Mohd Adzir Mahdi; Ahmad Rifqi Md Zain; Mohd Hanif Yaacob. 2020. "High Sensitivity Microfiber Interferometer Sensor in Aqueous Solution." Sensors 20, no. 17: 4713.

Journal article
Published: 18 August 2020 in Journal of Geophysical Research: Atmospheres
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In recent years, significant progress has been made in fast radiative transfer model (RTM) simulation of daytime Non‐Local Thermal Equilibrium (NLTE) emission. However, NLTE remains as one important reason that prevents the hyperspectral shortwave infrared (SWIR) radiance observations from being assimilated into Numerical Weather Prediction (NWP) models. To better understand the limitations of existing RTM based NLTE simulation, this study introduces a new statistical method, called Spectral Correlations to Estimate Non‐local Thermal Equilibrium (SCENTE), to estimate the NLTE radiances in the Cross‐track Infrared Sounder (CrIS) SWIR radiance observations. SCENTE is applied to four typical season days, including spring equinox, summer solstice, fall equinox, and winter solstice. By analyzing calculation/background minus observation (BMO) of CrIS SWIR brightness temperature (BT), results show that SCENTE characterizes the NLTE well with standard deviations (STD) comparable to observation noise for both daytime and nighttime, while the community radiative transfer model (CRTM) has substantially larger STD at night, mainly due to the lack of daytime NLTE just beyond the day/night terminator and the lack of aurora related NLTE. Detailed investigation of the biases of BMO shows that CRTM underestimates daytime SWIR NLTE effects by 0.76 K, while SCENTE overestimates SWIR NLTE effects by 0.70 K. The overestimation is because SCENTE uses CRTM simulated SWIR local thermal equilibrium (LTE) radiances in the training, which is underestimated by 0.70 K in BT. SCENTE, complementary to RTM based simulations, can be used for quality control of SWIR radiances for assimilation and retrieval of atmospheric soundings.

ACS Style

Zhenglong Li; W. Paul Menzel; James Jung; Agnes Lim; Jun Li; Marco Matricardi; Manuel López‐Puertas; Sergio DeSouza‐Machado; L. Larrabee Strow. Improving the Understanding of CrIS Full Spectral Resolution Nonlocal Thermodynamic Equilibrium Radiances Using Spectral Correlation. Journal of Geophysical Research: Atmospheres 2020, 125, 1 .

AMA Style

Zhenglong Li, W. Paul Menzel, James Jung, Agnes Lim, Jun Li, Marco Matricardi, Manuel López‐Puertas, Sergio DeSouza‐Machado, L. Larrabee Strow. Improving the Understanding of CrIS Full Spectral Resolution Nonlocal Thermodynamic Equilibrium Radiances Using Spectral Correlation. Journal of Geophysical Research: Atmospheres. 2020; 125 (16):1.

Chicago/Turabian Style

Zhenglong Li; W. Paul Menzel; James Jung; Agnes Lim; Jun Li; Marco Matricardi; Manuel López‐Puertas; Sergio DeSouza‐Machado; L. Larrabee Strow. 2020. "Improving the Understanding of CrIS Full Spectral Resolution Nonlocal Thermodynamic Equilibrium Radiances Using Spectral Correlation." Journal of Geophysical Research: Atmospheres 125, no. 16: 1.

Journal article
Published: 22 July 2020 in Solid State Sciences
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The performance of dye-sensitized solar cells (DSSCs) can be influenced by the sensitizer. Therefore, three heteroleptic ruthenium complexes, cis-[Ru(dcbpy)(bpy)(NCS)2] (Ru-bpy), cis-[Ru(dcbpy)(dppz)(NCS)2] (Ru-dppz) and cis-[Ru(dcbpy)(dppx)(NCS)2] (Ru-dppx) (dcbpy = 4,4′-dicarboxylic-2,2′-bipyridine, NCS = isothiocyanate) sensitizers, were synthesized using one pot synthesis. The structures and functionalization of the ligands in each complex sensitizer were confirmed using FT-IR and NMR analyses. They were then systematically studied to determine their light absorption spectrum, the metal-centered oxidation peak, and electron recombination properties using a UV–vis spectrophotometer and electroanalytical techniques (i.e., CV, EIS, and LSV). The criteria for an efficient DSSC ruthenium sensitizer were drawn based on the structure-property relationship. It was found that the power conversion efficiency (ɳ) of the sensitizers were in the sequence of Ru-dppz (ɳ = 0.40%) < Ru-bpy (ɳ = 0.58%) < Ru-dppx (ɳ = 0.61%) in comparison to a commercialized sensitizer N719 (ɳ = 0.93%), The introduction of the dimethyl group altered the LUMO to enhance the electron injection to the TiO2 conduction band and thus increased the power conversion efficiency of the DSSC.

ACS Style

Keng Fuong Chan; Hong Ngee Lim; Haslina Binti Ahmad; N.S.K. Gowthaman. Photovoltaic performance of bipyridine and dipyridophenazine ligands anchored ruthenium complex sensitizers for efficient dye-sensitized solar cells. Solid State Sciences 2020, 107, 106368 .

AMA Style

Keng Fuong Chan, Hong Ngee Lim, Haslina Binti Ahmad, N.S.K. Gowthaman. Photovoltaic performance of bipyridine and dipyridophenazine ligands anchored ruthenium complex sensitizers for efficient dye-sensitized solar cells. Solid State Sciences. 2020; 107 ():106368.

Chicago/Turabian Style

Keng Fuong Chan; Hong Ngee Lim; Haslina Binti Ahmad; N.S.K. Gowthaman. 2020. "Photovoltaic performance of bipyridine and dipyridophenazine ligands anchored ruthenium complex sensitizers for efficient dye-sensitized solar cells." Solid State Sciences 107, no. : 106368.

Journal article
Published: 09 July 2020 in Remote Sensing
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The Direct Broadcast Network (DBNet) provides near-real-time delivery of low-earth-orbiting (LEO) meteorological satellites to operational numerical weather prediction (NWP) systems that need short data cut-off times to allow for the assimilation of the most recent satellite measurements. The NWP model requires timely delivery of observations including atmospheric temperature, humidity, and surface wind vectors. The World Meteorological Organization (WMO) Space Program (WSP) recommends the data latency of no more than 20 min for the satellite measurements. Currently, not all DBNet stations are delivering satellite data within the 20-min time frame. In this study, the forecast impact of the observations of LEO satellite sounders with data latency of 20 min or less was evaluated using the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS). Reducing the data latency up to 5 min increases the number of LEO infrared (IR) and microwave (MW) sounder observations delivered to the NCEP GFS data assimilation system by more than 20%. Overall, this study demonstrates a positive impact on the global weather forecasts when the IR and MW sounder data are delivered by 20 min anywhere in the world. Additional forecast benefits are not obvious for shorter data latency. Results from this study support the WSP recommendation of 20–minute data latency.

ACS Style

Young-Chan Noh; Agnes Lim; Hung-Lung Huang; Mitchell Goldberg. Global Forecast Impact of Low Data Latency Infrared and Microwave Sounders Observations from Polar Orbiting Satellites. Remote Sensing 2020, 12, 2193 .

AMA Style

Young-Chan Noh, Agnes Lim, Hung-Lung Huang, Mitchell Goldberg. Global Forecast Impact of Low Data Latency Infrared and Microwave Sounders Observations from Polar Orbiting Satellites. Remote Sensing. 2020; 12 (14):2193.

Chicago/Turabian Style

Young-Chan Noh; Agnes Lim; Hung-Lung Huang; Mitchell Goldberg. 2020. "Global Forecast Impact of Low Data Latency Infrared and Microwave Sounders Observations from Polar Orbiting Satellites." Remote Sensing 12, no. 14: 2193.

Research article
Published: 10 June 2020 in ACS Omega
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Excess levels of nitrite ion in drinking water interact with amine functionalized compounds to form carcinogenic nitrosamines, which cause stomach cancer. Thus, it is indispensable to develop a simple protocol to detect nitrite. In this paper, a Cu-metal–organic framework (Cu-MOF) with graphene oxide (GO) composite was synthesized by ultrasonication followed by solvothermal method and then fabricated on a glassy carbon (GC) electrode for the sensitive and selective determination of nitrite contamination. The SEM image of the synthesized Cu-MOF showed colloidosome-like structure with an average size of 8 μm. Interestingly, the Cu-MOF–GO composite synthesized by ultrasonic irradiation followed by solvothermal process produce controlled size of 3 μm colloidosome-like structure. This was attributed to the formation of an exfoliated sheet-like structure of GO by ultrasonication in addition to the obvious influence of GO providing the oxygen functional groups as a nucleation node for size-controlled growth. On the other hand, the composite prepared without ultrasonication exhibited 6.6 μm size agglomerated colloidosome-like structures, indicating the crucial role of ultrasonication for the formation of size-controlled composites. XPS results confirmed the presence of Cu(II) in the as-synthesized Cu-MOF–GO based on the binding energies at 935.5 eV for Cu 2p3/2 and 955.4 eV for Cu 2p1/2. The electrochemical impedance studies in [Fe(CN)6]3–/4– redox couple at the composite fabricated electrode exhibited more facile electron transfer than that with Cu-MOF and GO modified electrodes, which helped to utilize Cu-MOF–GO for trace level determination of nitrite in environmental effluent samples. The Cu-MOF–GO fabricated electrode offered a superior sensitive platform for nitrite determination than the Cu-MOF and GO modified electrodes demonstrating oxidation at less positive potential with enhanced oxidation current. The present sensor detects nitrite in the concentration range of 1 × 10–8 to 1 × 10–4 M with the lowest limit of detection (LOD) of 1.47 nM (S/N = 3). Finally, the present Cu-MOF–GO electrode was successfully exploited for nitrite ion determination in lake and dye contaminated water samples.

ACS Style

P. Arul; N. S. K. Gowthaman; S. Abraham John; Hong Ngee Lim. Ultrasonic Assisted Synthesis of Size-Controlled Cu-Metal–Organic Framework Decorated Graphene Oxide Composite: Sustainable Electrocatalyst for the Trace-Level Determination of Nitrite in Environmental Water Samples. ACS Omega 2020, 5, 14242 -14253.

AMA Style

P. Arul, N. S. K. Gowthaman, S. Abraham John, Hong Ngee Lim. Ultrasonic Assisted Synthesis of Size-Controlled Cu-Metal–Organic Framework Decorated Graphene Oxide Composite: Sustainable Electrocatalyst for the Trace-Level Determination of Nitrite in Environmental Water Samples. ACS Omega. 2020; 5 (24):14242-14253.

Chicago/Turabian Style

P. Arul; N. S. K. Gowthaman; S. Abraham John; Hong Ngee Lim. 2020. "Ultrasonic Assisted Synthesis of Size-Controlled Cu-Metal–Organic Framework Decorated Graphene Oxide Composite: Sustainable Electrocatalyst for the Trace-Level Determination of Nitrite in Environmental Water Samples." ACS Omega 5, no. 24: 14242-14253.

Journal article
Published: 01 June 2020 in Energies
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In this paper the synthesis of self-organized Titania nanotubes (TNTs) by a facile potentiostatic anodization in a glycerol-based electrolyte is reported. The optimized TNTs were subsequently reduced through a cathodic reduction process to enhance its capacitive performance. FESEM and XRD were used to characterize the morphology and crystal structure of the synthesized samples. XPS analysis confirmed the reduction of Ti4+ to Ti3+ ions in the reduced Titania nanotubes (R-TNTs). The tube diameter and separation between the tubes were greatly influenced by the applied voltage. TNTs synthesized at voltage of 30 V for 60 min exhibited 86 nm and 1.1 µm of tube diameter and length, respectively and showed high specific capacitance of 0.33 mF cm−2 at current density of 0.02 mA cm−2. After reduction at 5 V for 30 s, the specific capacitance increased by about seven times (2.28 mF cm−2) at 0.5 mA cm−2 and recorded about 86% capacitance retention after 1000 continuous cycling at 0.2 mA cm−2, as compared to TNTs, retained about 61% at 0.01 mA cm−2. The charge transfer resistance drastically reduced from 6.2 Ω for TNTs to 0.55 Ω for R-TNTs, indicating an improvement in the transfer of electrons and ions across the electrode–electrolyte interface.

ACS Style

Muhammad Muhammad Muzakir; Zulkarnain Zainal; Hong Ngee Lim; Abdul Halim Abdullah; Noor Nazihah Bahrudin; Mahanim [email protected] Ali. Electrochemically Reduced Titania Nanotube Synthesized from Glycerol-Based Electrolyte as Supercapacitor Electrode. Energies 2020, 13, 2767 .

AMA Style

Muhammad Muhammad Muzakir, Zulkarnain Zainal, Hong Ngee Lim, Abdul Halim Abdullah, Noor Nazihah Bahrudin, Mahanim [email protected] Ali. Electrochemically Reduced Titania Nanotube Synthesized from Glycerol-Based Electrolyte as Supercapacitor Electrode. Energies. 2020; 13 (11):2767.

Chicago/Turabian Style

Muhammad Muhammad Muzakir; Zulkarnain Zainal; Hong Ngee Lim; Abdul Halim Abdullah; Noor Nazihah Bahrudin; Mahanim [email protected] Ali. 2020. "Electrochemically Reduced Titania Nanotube Synthesized from Glycerol-Based Electrolyte as Supercapacitor Electrode." Energies 13, no. 11: 2767.

Journal article
Published: 23 April 2020 in Molecules
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Melanoma is the most serious type of skin cancer and remains highly drug-resistant. Therefore, the discovery of novel effective agents against melanoma is in high demand. Herein, we investigated the cytotoxic activities in melanoma cells and underlying molecular mechanisms of beauvericin (BEA) and its analogue beauvericin G1 (BEA G1), which are cyclohexadepsipeptides isolated from fungi. BEA and BEA G1 significantly suppressed the growth, clonogenicity, migration, and invasion of A375SM human melanoma cells and promoted caspase-dependent apoptosis through upregulation of death receptors, as well as modulation of pro- and anti-apoptotic Bcl-2 family members. Furthermore, the effects of BEA and BEA G1 were associated with the suppression of multiple molecular targets that play crucial roles in melanoma oncogenesis, including ERK, JNK, p38, NF-κB, STAT3, and MITF. Notably, the cytotoxic efficacy of BEA G1 against A375SM cells was stronger than that of BEA. These findings suggest that BEA and BEA G1 can be further investigated as potent cytotoxic natural compounds for the suppression of melanoma progression.

ACS Style

Haet Nim Lim; Jun-Pil Jang; Hee Jeong Shin; Jae-Hyuk Jang; Jong Seog Ahn; Hye Jin Jung. Cytotoxic Activities and Molecular Mechanisms of the Beauvericin and Beauvericin G1 Microbial Products against Melanoma Cells. Molecules 2020, 25, 1974 .

AMA Style

Haet Nim Lim, Jun-Pil Jang, Hee Jeong Shin, Jae-Hyuk Jang, Jong Seog Ahn, Hye Jin Jung. Cytotoxic Activities and Molecular Mechanisms of the Beauvericin and Beauvericin G1 Microbial Products against Melanoma Cells. Molecules. 2020; 25 (8):1974.

Chicago/Turabian Style

Haet Nim Lim; Jun-Pil Jang; Hee Jeong Shin; Jae-Hyuk Jang; Jong Seog Ahn; Hye Jin Jung. 2020. "Cytotoxic Activities and Molecular Mechanisms of the Beauvericin and Beauvericin G1 Microbial Products against Melanoma Cells." Molecules 25, no. 8: 1974.

Journal article
Published: 15 April 2020 in Applied Sciences
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This study aims to suggest a rational analysis method for a track ballast–wheel interaction that could be further developed to model the interaction in a train-derailment event, based on the discrete-element method (DEM). Track ballast is filled with gravel to form the trackbed. Although finite-element analysis (FEA) is widely applied in structural analysis, track ballast cannot be analyzed using conventional FEA because this approach does not allow separation of elements that share nodes. The DEM has been developed to analyze the dynamic behavior of separable objects, assuming that the objects are rigid. Therefore, track ballast can be modeled as separable rigid pieces of gravel, and its dynamic behavior can be analyzed using a rational contact model. In this study, a rational numerical strategy for track ballast–wheel interaction was investigated using the DEM approach. The suggested analysis method was validated through comparison with the experimental results of a drop test. In addition, case studies were conducted to investigate the effects of the contact-model parameters on the simulation result.

ACS Style

Nam-Hyoung Lim; Kyoung-Ju Kim; Hyun-Ung Bae; Seungjun Kim. DEM Analysis of Track Ballast for Track Ballast–Wheel Interaction Simulation. Applied Sciences 2020, 10, 2717 .

AMA Style

Nam-Hyoung Lim, Kyoung-Ju Kim, Hyun-Ung Bae, Seungjun Kim. DEM Analysis of Track Ballast for Track Ballast–Wheel Interaction Simulation. Applied Sciences. 2020; 10 (8):2717.

Chicago/Turabian Style

Nam-Hyoung Lim; Kyoung-Ju Kim; Hyun-Ung Bae; Seungjun Kim. 2020. "DEM Analysis of Track Ballast for Track Ballast–Wheel Interaction Simulation." Applied Sciences 10, no. 8: 2717.

Journal article
Published: 11 February 2020 in Applied Surface Science
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A superparamagnetic graphene-based magnetite nanocomposite (rGO-Fe3O4) was synthesized via a simple in-situ chemical approach. This rGO-Fe3O4 nanocomposite can be used as a drug carrier that is able to be guided by external magnetic fields to the specific site of interest for targeted drug delivery application to treat cancer. Ganoderma lucidum extract (GL) was employed, which successfully stabilized the rGO-Fe3O4 via hydrogen bonding and resulted in enhancement of water dispersibility and stability of the prepared nanocomposite, while Pluronic F-127 (PF) was introduced to reduce the overall cytotoxicity. The presence of both GL and PF on the surface of nanocomposite was successfully validated by cyclic voltammetry (CV). Quercetin (Que), a naturally-available polyphenolic flavonoid with anti-cancer properties was utilized to study the potential of rGO-Fe3O4-GL-PF for controlled drug delivery application. The loading capacity of Que on rGO-Fe3O4-GL-PF was determined to be 11 wt% through UV–visible spectroscopy. The Que was loaded on rGO plane via π-π stacking and hydrophobic interaction, which was validated through CV. Furthermore, the in-vitro cytotoxicity of the synthesized nanocomposite showed obvious cytotoxicity toward A549 cells due to the anti-cancer properties of GL which has high potential to be developed into a targeted drug delivery carrier for cancer therapeutics.

ACS Style

Xin Jie Lee; Hong Ngee Lim; N.S.K. Gowthaman; Mohd Basyaruddin Abdul Rahman; Che Azurahanim Che Abdullah; Kasturi Muthoosamy. In-situ surface functionalization of superparamagnetic reduced graphene oxide – Fe3O4 nanocomposite via Ganoderma lucidum extract for targeted cancer therapy application. Applied Surface Science 2020, 512, 145738 .

AMA Style

Xin Jie Lee, Hong Ngee Lim, N.S.K. Gowthaman, Mohd Basyaruddin Abdul Rahman, Che Azurahanim Che Abdullah, Kasturi Muthoosamy. In-situ surface functionalization of superparamagnetic reduced graphene oxide – Fe3O4 nanocomposite via Ganoderma lucidum extract for targeted cancer therapy application. Applied Surface Science. 2020; 512 ():145738.

Chicago/Turabian Style

Xin Jie Lee; Hong Ngee Lim; N.S.K. Gowthaman; Mohd Basyaruddin Abdul Rahman; Che Azurahanim Che Abdullah; Kasturi Muthoosamy. 2020. "In-situ surface functionalization of superparamagnetic reduced graphene oxide – Fe3O4 nanocomposite via Ganoderma lucidum extract for targeted cancer therapy application." Applied Surface Science 512, no. : 145738.

Original
Published: 06 February 2020 in Chromatographia
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A new automated flow-through adsorption/desorption procedure using a multiwalled carbon nanotube immobilised mixed matrix membrane is described. The membrane consisted of 25% (w/w) multiwall carbon nanotube loading in a cellulose triacetate polymer matrix as support and was cast and embedded in a flow-through cell with a channel of an approximate length of 20 mm, a width of 2 mm, and a depth of 1.5 mm. The membrane immobilised with nanoparticles was activated using 1-octanol as a conditioning solvent. For the analyte adsorption process, 6 mL of the sample was passed through the cell at a flow rate of 0.2 mL min−1. The entrapped target analytes were then desorbed dynamically with 60 µL of 2-propanal at a flow rate of 5 µL min−1 prior to HPLC/UV analysis. The performance of the system was demonstrated for the determination of chlorinated phenoxyacetic acid herbicides in sewage water samples. Under the optimum conditions, the linearity of this method ranged from 50 to 1000 ng mL−1, with a correlation coefficient (r) ≥ 0.993 and a detection limit varying from 15 to 20 ng mL−1. Enrichment factors of up to 55 were achieved with relative recoveries of 95–99% and precision values of 6.1–7.5%.

ACS Style

Thipashini Ganesan; Hong Ngee Lim; Hong Heng See. Automated Mixed Matrix Membrane Microextraction Prior to Liquid Chromatography for the Determination of Chlorophenoxy Acid Herbicides in Sewage Water Samples. Chromatographia 2020, 83, 497 -505.

AMA Style

Thipashini Ganesan, Hong Ngee Lim, Hong Heng See. Automated Mixed Matrix Membrane Microextraction Prior to Liquid Chromatography for the Determination of Chlorophenoxy Acid Herbicides in Sewage Water Samples. Chromatographia. 2020; 83 (4):497-505.

Chicago/Turabian Style

Thipashini Ganesan; Hong Ngee Lim; Hong Heng See. 2020. "Automated Mixed Matrix Membrane Microextraction Prior to Liquid Chromatography for the Determination of Chlorophenoxy Acid Herbicides in Sewage Water Samples." Chromatographia 83, no. 4: 497-505.

Journal article
Published: 05 February 2020 in Journal of Hazardous Materials
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Nowadays, increasing the risk for copper leaching into the drinking water in homes, hotels and schools has become unresolved issues all around the countries such as Canada, the United States, and Malaysia. The leaching of copper in tap water is due to a combination of acidic water, damaged pipes, and corroded plumbing fixtures. To remedy this global problem, a triple interconnected structure of CdS/Au/GQDs was designed as a photo-to-electron conversion medium for a real time and selective visible-light-prompt photoelectrochemical (PEC) sensor for Cu2+ ions in real water samples. The synergistic interaction of the CdS/Au/GQDs enabled the smooth transportation of charge carriers to the charge collector and provided a channel to inhibit the charge recombination reaction. Thus, a detection limit of 2.27 nM was obtained, which is 10,000 fold lower than that of WHO’s Guidelines for Drinking-water Quality (∼30 μM). The photocurrent reduction was negligible after 30 days of storage under ambient conditions, suggesting the high stability of photoelectrode. Moreover, the real-time monitoring of Cu2+ ions in real samples was performed with satisfactory results, confirming the capability of the investigated photoelectrode as the most practical detector for trace amounts of Cu2+ ions.

ACS Style

Izwaharyanie Ibrahim; Hong Ngee Lim; Nay Ming Huang; Zhong-Tao Jiang; Mohammednoor Altarawneh. Selective and sensitive visible-light-prompt photoelectrochemical sensor of Cu2+ based on CdS nanorods modified with Au and graphene quantum dots. Journal of Hazardous Materials 2020, 391, 122248 .

AMA Style

Izwaharyanie Ibrahim, Hong Ngee Lim, Nay Ming Huang, Zhong-Tao Jiang, Mohammednoor Altarawneh. Selective and sensitive visible-light-prompt photoelectrochemical sensor of Cu2+ based on CdS nanorods modified with Au and graphene quantum dots. Journal of Hazardous Materials. 2020; 391 ():122248.

Chicago/Turabian Style

Izwaharyanie Ibrahim; Hong Ngee Lim; Nay Ming Huang; Zhong-Tao Jiang; Mohammednoor Altarawneh. 2020. "Selective and sensitive visible-light-prompt photoelectrochemical sensor of Cu2+ based on CdS nanorods modified with Au and graphene quantum dots." Journal of Hazardous Materials 391, no. : 122248.

Research article
Published: 03 February 2020 in ACS Sustainable Chemistry & Engineering
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Exploring a non-enzymatic sensor electrocatalyst for the accurate determination of biomolecules is a paramount task. A weird morphology of the nanomaterial may influence remarkable activity to enhance the sensitivity of the electrode and hence, tuning the shape of the nanomaterials is one of the important criteria in electrochemical sensors. Thus, the present study missioned the fabrication of non-enzymatic sensor with different CuO morphologies by eco-friendly and facile approach. Surfactant-free different CuO nanostructures were fabricated on the highly conductive flexible aluminum-carbide substrate for the electrochemical determination of glucose and H2O2 in human fluids. The CuO nanostructures were initially electrodeposited at -0.1, -0.3, -0.5 and -0.7 V and then calcinated in air at 120 C for 2 h. Different CuO nanostructures with polygonal and cactus-like morphology were observed from scanning electron microscopic (SEM) images. The as-fabricated electrodes were also characterized by XRD, XPS and electrochemical impedance spectroscopy (EIS) analysis. Texture coefficient (TC) of different CuO nanostructures were calculated from XRD analysis and the CuO nanostructures grown at -0.5 V exhibited the highest TC with its texture along (022) plane. The different CuO nanostructures grown electrodes exhibited shape dependent electrocatalytic activity against glucose and H2O2 and the cactus-like CuO nanostructures grown at -0.5 V showed superior electrochemical behavior than the other nanostructures by showing superior sensitivity of 3892.6 and 2015.7 µA/mM.cm2 respectively against glucose and H2O2. Further, the cactus-like CuO nanostructures grown sensor exhibited high selectivity, storage capability and good practicability. The present sensor was proved practically by determining glucose and H2O2 levels in human fluids. It is believed that the proposed electrochemical sensor becomes highly impactable in the dual in-line sensing of biomarker both in biological and clinical field in the near future.

ACS Style

N. S. K. Gowthaman; P. Arul; Hong Ngee Lim; S. Abraham John. Negative Potential-Induced Growth of Surfactant-Free CuO Nanostructures on an Al–C Substrate: A Dual In-Line Sensor for Biomarkers of Diabetes and Oxidative Stress. ACS Sustainable Chemistry & Engineering 2020, 8, 2640 -2651.

AMA Style

N. S. K. Gowthaman, P. Arul, Hong Ngee Lim, S. Abraham John. Negative Potential-Induced Growth of Surfactant-Free CuO Nanostructures on an Al–C Substrate: A Dual In-Line Sensor for Biomarkers of Diabetes and Oxidative Stress. ACS Sustainable Chemistry & Engineering. 2020; 8 (7):2640-2651.

Chicago/Turabian Style

N. S. K. Gowthaman; P. Arul; Hong Ngee Lim; S. Abraham John. 2020. "Negative Potential-Induced Growth of Surfactant-Free CuO Nanostructures on an Al–C Substrate: A Dual In-Line Sensor for Biomarkers of Diabetes and Oxidative Stress." ACS Sustainable Chemistry & Engineering 8, no. 7: 2640-2651.

Journal article
Published: 03 February 2020 in Chemical Engineering and Processing: Process Intensification
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This work proposes the optimization of 2-ethylhexyl (2-EH) caprylate/caprate synthesis in a pulsed loop reactor, and the energy efficiency of the reactor was assessed. 2-EH caprylate/caprate can be used as a biodegradable base fluid. Only 0.4 wt% catalyst concentration was used in the reaction. The face-centred central composite design (FCCD) experiment coupled response surface methodology (RSM) has been implemented to screen independent parameters. The optimization process showed that vacuum pressure was the most influential factor followed by oscillation speed, temperature and time. The maximum conversion of 98 % and yield of 89 % were achieved under optimal conditions of 78 °C, 10 mbar, 20 min and 155 rpm. Meanwhile, energy balance calculation indicated that the usage of low vacuum pressure not only significantly reduced the total heat duty from 1381 kJ (1 atm) to 823 kJ (10 mbar) but also alleviated the reaction temperature from 172 °C (1 atm) to 78 °C (10 mbar). The calculation also demonstrated that the reflux-stirred tank reactor produced a lower conversion and yield of ester yet 6 kJ higher total heat duty compared to the pulsed loop reactor, indicating a cost-saving with the pulsed loop reactor.

ACS Style

Siti Zulaika Razali; R. Yunus; Suraya Abdul Rashid; Hong Ngee Lim; B. Mohamad Jan; Hamidah Abd Hamid; A.R. Suraya; Janet Lim Hong Ngee. Process intensification of 2-ethylhexyl caprylate/caprate synthesis via a pulsed loop reactor: Multi-objective optimization. Chemical Engineering and Processing: Process Intensification 2020, 149, 107837 .

AMA Style

Siti Zulaika Razali, R. Yunus, Suraya Abdul Rashid, Hong Ngee Lim, B. Mohamad Jan, Hamidah Abd Hamid, A.R. Suraya, Janet Lim Hong Ngee. Process intensification of 2-ethylhexyl caprylate/caprate synthesis via a pulsed loop reactor: Multi-objective optimization. Chemical Engineering and Processing: Process Intensification. 2020; 149 ():107837.

Chicago/Turabian Style

Siti Zulaika Razali; R. Yunus; Suraya Abdul Rashid; Hong Ngee Lim; B. Mohamad Jan; Hamidah Abd Hamid; A.R. Suraya; Janet Lim Hong Ngee. 2020. "Process intensification of 2-ethylhexyl caprylate/caprate synthesis via a pulsed loop reactor: Multi-objective optimization." Chemical Engineering and Processing: Process Intensification 149, no. : 107837.

Journal article
Published: 22 December 2019 in Applied Sciences
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As the operating speed of a train increases, there is a growing interest in reducing damage caused by derailment and collision accidents. Since a collision with the surrounding structure after a derailment accident causes a great damage, protective facilities like a barrier wall or derailment containment provision (DCP) are installed to reduce the damage due to the secondary collision accident. However, the criteria to design a protective facility such as locations and design loads are not clear because of difficulties in predicting post-derailment behaviors. In this paper, we derived a simplified frame model that can predict post derailment behaviors in the design phase of the protective facilities. The proposed vehicle model can simplify for various frames to reduce the computation time. Also, the actual derailment tests were conducted on a real test track to verify the reliability of the model. The simulation results of the proposed model showed reasonable agreement to the test results.

ACS Style

In-Ho Song; Jun-Woo Kim; Jeong-Seo Koo; Nam-Hyoung Lim. Modeling and Simulation of Collision-Causing Derailment to Design the Derailment Containment Provision Using a Simplified Vehicle Model. Applied Sciences 2019, 10, 118 .

AMA Style

In-Ho Song, Jun-Woo Kim, Jeong-Seo Koo, Nam-Hyoung Lim. Modeling and Simulation of Collision-Causing Derailment to Design the Derailment Containment Provision Using a Simplified Vehicle Model. Applied Sciences. 2019; 10 (1):118.

Chicago/Turabian Style

In-Ho Song; Jun-Woo Kim; Jeong-Seo Koo; Nam-Hyoung Lim. 2019. "Modeling and Simulation of Collision-Causing Derailment to Design the Derailment Containment Provision Using a Simplified Vehicle Model." Applied Sciences 10, no. 1: 118.