Displaying publications 21 - 34 of 34 in total

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  1. Fulltext Facile Preparation of Carbon Nanotubes/Cellulose Nanofibrils/Manganese Dioxide Nanowires Electrode for Improved Solid-Sate Supercapacitor Performances
    Chin SX, Lau KS, Ginting RT, Tan ST, Khiew PS, Chia CH, et al.
    Polymers (Basel), 2023 Sep 14;15(18).
    PMID: 37765612 DOI: 10.3390/polym15183758
    Wearable energy storage devices require high mechanical stability and high-capacitance flexible electrodes. In this study, we design a flexible supercapacitor electrode consisting of 1-dimensional carbon nanotubes (CNT), cellulose nanofibrils (CNF), and manganese dioxide nanowires (MnO2 NWs). The flexible and conductive CNT/CNF-MnO2 NWs suspension was first prepared via ultrasonic dispersion approach, followed by vacuum filtration and hot press to form the composite paper electrode. The morphological studies show entanglement between CNT and CNF, which supports the mechanical properties of the composite. The CNT/CNF-MnO2 NWs electrode exhibits lower resistance when subjected to various bending angles (-120-+120°) compared to the CNT/CNF electrode. In addition, the solid-state supercapacitor also shows a high energy density of 38 μWh cm-2 and capacitance retention of 83.2% after 5000 cycles.
  2. Fulltext Toward a Circular Bioeconomy: Exploring Pineapple Stem Starch Film as a Plastic Substitute in Single Use Applications
    Namphonsane A, Suwannachat P, Chia CH, Wongsagonsup R, Smith SM, Amornsakchai T
    Membranes (Basel), 2023 Apr 24;13(5).
    PMID: 37233519 DOI: 10.3390/membranes13050458
    In this study, biodegradable starch film was developed from pineapple stem waste as a substitute for non-biodegradable petroleum-based films for single-use applications where strength is not too demanding. High amylose starch from a pineapple stem was used as the matrix. Glycerol and citric acid were used as additives to adjust the ductility of the material. Glycerol content was fixed at 25% while that of citric acid varied from 0 to 15% by weight of starch. Films with a wide range of mechanical properties can be prepared. As more citric acid is added, the film becomes softer and weaker, and has greater elongation at the break. Properties range from a strength of about 21.5 MPa and 2.9% elongation to a strength of about 6.8 MPa and 35.7% elongation. An X-ray diffraction study showed that the films were semi-crystalline. The films were also found to be water-resistant and can be heat-sealed. An example of a single-use package was demonstrated. A soil burial test confirmed that the material was biodegradable and completely disintegrated into sizes smaller than 1 mm within one month.
  3. Fulltext Toward a Circular Bioeconomy: Development of Pineapple Stem Starch Composite as a Plastic-Sheet Substitute for Single-Use Applications
    Thongphang C, Namphonsane A, Thanawan S, Chia CH, Wongsagonsup R, Smith SM, et al.
    Polymers (Basel), 2023 May 19;15(10).
    PMID: 37242963 DOI: 10.3390/polym15102388
    Plastic waste poses a significant challenge for the environment, particularly smaller plastic products that are often difficult to recycle or collect. In this study, we developed a fully biodegradable composite material from pineapple field waste that is suitable for small-sized plastic products that are difficult to recycle, such as bread clips. We utilized starch from waste pineapple stems, which is high in amylose content, as the matrix, and added glycerol and calcium carbonate as the plasticizer and filler, respectively, to improve the material's moldability and hardness. We varied the amounts of glycerol (20-50% by weight) and calcium carbonate (0-30 wt.%) to produce composite samples with a wide range of mechanical properties. The tensile moduli were in the range of 45-1100 MPa, with tensile strengths of 2-17 MPa and an elongation at break of 10-50%. The resulting materials exhibited good water resistance and had lower water absorption (~30-60%) than other types of starch-based materials. Soil burial tests showed that the material completely disintegrated into particles smaller than 1 mm within 14 days. We also created a bread clip prototype to test the material's ability to hold a filled bag tightly. The obtained results demonstrate the potential of using pineapple stem starch as a sustainable alternative to petroleum-based and biobased synthetic materials in small-sized plastic products while promoting a circular bioeconomy.
  4. Fulltext Toward a Circular Bioeconomy: Exploring Pineapple Stem Starch Film as Protective Coating for Fruits and Vegetables
    Bumrungnok K, Threepopnatkul P, Amornsakchai T, Chia CH, Wongsagonsup R, Smith SM
    Polymers (Basel), 2023 May 29;15(11).
    PMID: 37299292 DOI: 10.3390/polym15112493
    In order to reduce our dependence on nonrenewable plastics and solve the problem of non-biodegradable plastic waste, there has been much attention paid to the development of biodegradable plastics from natural resources. Starch-based materials have been widely studied and developed for commercial production, primarily from corn and tapioca. However, the use of these starches could generate food security problems. Therefore, the use of alternative starch sources, such as agricultural waste, would be of great interest. In this work, we investigated the properties of films prepared from pineapple stem starch, which has a high amylose content. Pineapple stem starch (PSS) films and glycerol-plasticized PSS films were prepared and characterized using X-ray diffraction and water contact angle measurements. All films exhibited some degree of crystallinity, making them water-resistant. The effect of glycerol content on mechanical properties and gas (oxygen, carbon dioxide and water vapor) transmission rates was also studied. The tensile modulus and tensile strength of the films decreased with increasing glycerol content, while gas transmission rates increased. Preliminary studies showed that coatings made from PSS films could slow down the ripening process of bananas and extend their shelf life.
  5. Fulltext Rapid Catalytic Reduction of 4-Nitrophenol and Clock Reaction of Methylene Blue using Copper Nanowires
    Hashimi AS, Nohan MANM, Chin SX, Zakaria S, Chia CH
    Nanomaterials (Basel), 2019 Jun 28;9(7).
    PMID: 31261696 DOI: 10.3390/nano9070936
    Copper nanowires (CuNWs) with a high aspect ratio of ~2600 have been successfully synthesized by using a facile hydrothermal method. The reductions of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) and methylene blue (MB) to leucomethylene blue (LMB) by using sodium borohydride (NaBH4) were used as models to test the catalytic activity of CuNWs. We showed that by increasing the CuNWs content, the rate of reduction increased as well. The CuNWs showed an excellent catalytic performance where 99% reduction of 4-NP to 4-AP occurred in just 60 s by using only 0.1 pg of CuNWs after treatment with glacial acetic acid (GAA). The rate constant (kapp) and activity factor (K) of this study is 18 and ~1010 fold in comparison to previous study done with no GAA treatment applied, respectively. The CuNWs showed an outstanding catalytic activity for at least ten consecutive reusability tests with a consistent result in 4-NP reduction. In clock reaction of MB, approximately 99% of reduction of MB into LMB was achieved in ~5 s by using 2 μg CuNWs. Moreover, the addition of NaOH can improve the rate and degree of recolorization of LMB to MB.
  6. Fulltext Seventeen-Armed Star Polystyrenes in Various Molecular Weights: Structural Details and Chain Characteristics
    Wong JC, Xiang L, Ngoi KH, Chia CH, Jin KS, Hirao A, et al.
    Polymers (Basel), 2020 Aug 23;12(9).
    PMID: 32842480 DOI: 10.3390/polym12091894
    Star-shaped polymers are very attractive because of their potential application ability in various technological areas due to their unique molecular topology. Thus, information on the molecular structure and chain characteristics of star polymers is essential for gaining insights into their properties and finding better applications. In this study, we report molecular structure details and chain characteristics of 17-armed polystyrenes in various molecular weights: 17-Arm(2k)-PS, 17-Arm(6k)-PS, 17-Arm(10k)-PS, and 17-Arm(20k)-PS. Quantitative X-ray scattering analysis using synchrotron radiation sources was conducted for this series of star polymers in two different solvents (cyclohexane and tetrahydrofuran), providing a comprehensive set of three-dimensional structure parameters, including radial density profiles and chain characteristics. Some of the structural parameters were crosschecked by qualitative scattering analysis and dynamic light scattering. They all were found to have ellipsoidal shapes consisting of a core and a fuzzy shell; such ellipse nature is originated from the dendritic core. In particular, the fraction of the fuzzy shell part enabling to store desired chemicals or agents was confirmed to be exceptionally high in cyclohexane, ranging from 74 to 81%; higher-molecular-weight star polymer gives a larger fraction of the fuzzy shell. The largest fraction (81%) of the fuzzy shell was significantly reduced to 52% in tetrahydrofuran; in contrast, the lowest fraction (19%) of core was increased to 48%. These selective shell contraction and core expansion can be useful as a key mechanism in various applications. Overall, the 17-armed polystyrenes of this study are suitable for applications in various technological fields including smart deliveries of drugs, genes, biomedical imaging agents, and other desired chemicals.
  7. Fulltext Enhanced biocatalytic esterification with lipase-immobilized chitosan/graphene oxide beads
    Lau SC, Lim HN, Basri M, Fard Masoumi HR, Ahmad Tajudin A, Huang NM, et al.
    PLoS One, 2014;9(8):e104695.
    PMID: 25127038 DOI: 10.1371/journal.pone.0104695
    In this work, lipase from Candida rugosa was immobilized onto chitosan/graphene oxide beads. This was to provide an enzyme-immobilizing carrier with excellent enzyme immobilization activity for an enzyme group requiring hydrophilicity on the immobilizing carrier. In addition, this work involved a process for the preparation of an enzymatically active product insoluble in a reaction medium consisting of lauric acid and oleyl alcohol as reactants and hexane as a solvent. This product enabled the stability of the enzyme under the working conditions and allowed the enzyme to be readily isolated from the support. In particular, this meant that an enzymatic reaction could be stopped by the simple mechanical separation of the "insoluble" enzyme from the reaction medium. Chitosan was incorporated with graphene oxide because the latter was able to enhance the physical strength of the chitosan beads by its superior mechanical integrity and low thermal conductivity. The X-ray diffraction pattern showed that the graphene oxide was successfully embedded within the structure of the chitosan. Further, the lipase incorporation on the beads was confirmed by a thermo-gravimetric analysis. The lipase immobilization on the beads involved the functionalization with coupling agents, N-hydroxysulfosuccinimide sodium (NHS) and 1-ethyl-(3-dimethylaminopropyl) carbodiimide (EDC), and it possessed a high enzyme activity of 64 U. The overall esterification conversion of the prepared product was 78% at 60 °C, and it attained conversions of 98% and 88% with commercially available lipozyme and novozyme, respectively, under similar experimental conditions.
  8. Fulltext Facile hydrothermal preparation of titanium dioxide decorated reduced graphene oxide nanocomposite
    Chang BY, Huang NM, An'amt MN, Marlinda AR, Norazriena Y, Muhamad MR, et al.
    Int J Nanomedicine, 2012;7:3379-87.
    PMID: 22848166 DOI: 10.2147/IJN.S28189
    A simple single-stage approach, based on the hydrothermal technique, has been introduced to synthesize reduced graphene oxide/titanium dioxide nanocomposites. The titanium dioxide nanoparticles are formed at the same time as the graphene oxide is reduced to graphene. The triethanolamine used in the process has two roles. It acts as a reducing agent for the graphene oxide as well as a capping agent, allowing the formation of titanium dioxide nanoparticles with a narrow size distribution (~20 nm). Transmission electron micrographs show that the nanoparticles are uniformly distributed on the reduced graphene oxide nanosheet. Thermogravimetric analysis shows the nanocomposites have an enhanced thermal stability over the original components. The potential applications for this technology were demonstrated by the use of a reduced graphene oxide/titanium dioxide nanocomposite-modified glassy carbon electrode, which enhanced the electrochemical performance compared to a conventional glassy carbon electrode when interacting with mercury(II) ions in potassium chloride electrolyte.
  9. Fulltext Antibacterial performance of Ag nanoparticles and AgGO nanocomposites prepared via rapid microwave-assisted synthesis method
    Chook SW, Chia CH, Zakaria S, Ayob MK, Chee KL, Huang NM, et al.
    Nanoscale Res Lett, 2012;7(1):541.
    PMID: 23020815 DOI: 10.1186/1556-276X-7-541
    Silver nanoparticles and silver-graphene oxide nanocomposites were fabricated using a rapid and green microwave irradiation synthesis method. Silver nanoparticles with narrow size distribution were formed under microwave irradiation for both samples. The silver nanoparticles were distributed randomly on the surface of graphene oxide. The Fourier transform infrared and thermogravimetry analysis results showed that the graphene oxide for the AgNP-graphene oxide (AgGO) sample was partially reduced during the in situ synthesis of silver nanoparticles. Both silver nanoparticles and AgGO nanocomposites exhibited stronger antibacterial properties against Gram-negative bacteria (Salmonella typhi and Escherichia coli) than against Gram-positive bacteria (Staphyloccocus aureus and Staphyloccocus epidermidis). The AgGO nanocomposites consisting of approximately 40 wt.% silver can achieve antibacterial performance comparable to that of neat silver nanoparticles.
  10. Citric acid modified kenaf core fibres for removal of methylene blue from aqueous solution
    Sajab MS, Chia CH, Zakaria S, Jani SM, Ayob MK, Chee KL, et al.
    Bioresour Technol, 2011 Aug;102(15):7237-43.
    PMID: 21620692 DOI: 10.1016/j.biortech.2011.05.011
    Chemically modified kenaf core fibres were prepared via esterification in the presence of citric acid (CA). The adsorption kinetics and isotherm studies were carried out under different conditions to examine the adsorption efficiency of CA-treated kenaf core fibres towards methylene blue (MB). The adsorption capacity of the kenaf core fibres increased significantly after the citric acid treatment. The values of the correlation coefficients indicated that the Langmuir isotherm fitted the experimental data better than the Freundlich isotherm. The maximum adsorption capacity of the CA-treated kenaf core fibres was found to be 131.6mg/g at 60°C. Kinetic models, pseudo-first-order, pseudo-second-order and intraparticle diffusion, were employed to describe the adsorption mechanism. The kinetic data were found to fit pseudo-second-order model equation as compared to pseudo-first-order model. The adsorption of MB onto the CA-treated kenaf core fibres was spontaneous and endothermic.
  11. Fulltext Production of Rigid Polyurethane Foams Using Polyol from Liquefied Oil Palm Biomass: Variation of Isocyanate Indexes
    Amran UA, Salleh KM, Zakaria S, Roslan R, Chia CH, Jaafar SNS, et al.
    Polymers (Basel), 2021 Sep 11;13(18).
    PMID: 34577973 DOI: 10.3390/polym13183072
    Development of polyurethane foam (PUF) containing bio-based components is a complex process that requires extensive studies. This work reports on the production of rigid PUFs from polyol obtained via liquefaction of oil palm empty fruit bunch (EFB) biomass with different isocyanate (NCO) indexes. The effect of the NCO index on the physical, chemical and compressive properties of the liquefied EFB-based PUF (EFBPUF) was evaluated. The EFBPUFs showed a unique set of properties at each NCO index. Foaming properties had affected the apparent density and cellular morphology of the EFBPUFs. Increasing NCO index had increased the crosslink density and dimensional stability of the EFBPUFs via formation of isocyanurates, which had also increased their thermal stability. Combination of both foaming properties and crosslink density of the EFBPUFs had influenced their respective compressive properties. The EFBPUF produced at the NCO index of 120 showed the optimum compressive strength and released the least toxic hydrogen cyanide (HCN) gas under thermal degradation. The normalized compressive strength of the EFBPUF at the NCO index of 120 is also comparable with the strength of the PUF produced using petrochemical polyol.
  12. Fulltext Exceedingly biocompatible and thin-layered reduced graphene oxide nanosheets using an eco-friendly mushroom extract strategy
    Muthoosamy K, Bai RG, Abubakar IB, Sudheer SM, Lim HN, Loh HS, et al.
    Int J Nanomedicine, 2015;10:1505-19.
    PMID: 25759577 DOI: 10.2147/IJN.S75213
    PURPOSE: A simple, one-pot strategy was used to synthesize reduced graphene oxide (RGO) nanosheets by utilizing an easily available over-the-counter medicinal and edible mushroom, Ganoderma lucidum.

    METHODS: The mushroom was boiled in hot water to liberate the polysaccharides, the extract of which was then used directly for the reduction of graphene oxide. The abundance of polysaccharides present in the mushroom serves as a good reducing agent. The proposed strategy evades the use of harmful and expensive chemicals and avoids the typical tedious reaction methods.

    RESULTS: More importantly, the mushroom extract can be easily separated from the product without generating any residual byproducts and can be reused at least three times with good conversion efficiency (75%). It was readily dispersible in water without the need of ultrasonication or any surfactants; whereas 5 minutes of ultrasonication with various solvents produced RGO which was stable for the tested period of 1 year. Based on electrochemical measurements, the followed method did not jeopardize RGO's electrical conductivity. Moreover, the obtained RGO was highly biocompatible to not only colon (HT-29) and brain (U87MG) cancer cells, but was also viable towards normal cells (MRC-5).

    CONCLUSION: Besides being eco-friendly, this mushroom based approach is easily scalable and demonstrates remarkable RGO stability and biocompatibility, even without any form of functionalization.

  13. Current attempts to implement microRNA-based diagnostics and therapy in cardiovascular and metabolic disease: a promising future
    Thanikachalam PV, Ramamurthy S, Wong ZW, Koo BJ, Wong JY, Abdullah MF, et al.
    Drug Discov Today, 2018 Mar;23(3):460-480.
    PMID: 29107764 DOI: 10.1016/j.drudis.2017.10.020
    MicroRNAs (miRNAs) are small, noncoding RNAs regulating gene expression at the post-translational level. miRNA-based therapeutic agents are important because of the functionality of miRNAs in regulating lipid and glucose metabolism and their role in the pathogenesis of metabolic disorders such as diabetes and obesity, where dysregulation leads to disease; they are also important in angiogenesis. miRNAs additionally serve as biomarkers in the diagnosis, prognosis and risk assessment of disease and in monitoring the response to treatment. Here, we provide a brief overview of progress in miRNA-based therapeutics in the preclinical and clinical setting and highlight the novel outcomes and opportunities in the diagnosis and treatment of metabolic conditions. In addition, we present the role of miRNAs in stem cell therapy which could have great potential in regenerative medicine.
  14. An overview on the key advantages and limitations of batch and dynamic modes of biosorption of metal ions
    Malbenia John M, Benettayeb A, Belkacem M, Ruvimbo Mitchel C, Hadj Brahim M, Benettayeb I, et al.
    Chemosphere, 2024 Apr 20.
    PMID: 38648988 DOI: 10.1016/j.chemosphere.2024.142051
    Water purification using adsorption is a crucial process for maintaining human life and preserving the environment. Batch and dynamic adsorption modes are two types of water purification processes that are commonly used in various countries due to their simplicity and feasibility on an industrial scale. However, it is important to understand the advantages and limitations of these two adsorption modes in industrial applications. Also, the possibility of using batch mode in industrial scale was scrutinized, along with the necessity of using dynamic mode in such applications. In addition, the reasons for the necessity of performing batch adsorption studies before starting the treatment on an industrial scale were mentioned and discussed. In fact, this review article attempts to throw light on these subjects by comparing the biosorption efficiency of some metals on utilized biosorbents, using both batch and fixed-bed (column) adsorption modes. The comparison is based on the effectiveness of the two processes and the mechanisms involved in the treatment. Parameters such as biosorption capacity, percentage removal, and isotherm models for both batch and column (fixed bed) studies are compared. The article also explains thermodynamic and kinetic models for batch adsorption and discusses breakthrough evaluations in adsorptive column systems. The review highlights the benefits of using convenient batch-wise biosorption in lab-scale studies and the key advantages of column biosorption in industrial applications.
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