Browsing by Author "Ekanayake, G"

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Open Access
Fabrication of Naturally Derived Chitosan and Ilmenite Sand-Based TiO2/Fe2O3/Fe-N-Doped Graphitic Carbon Composite for Photocatalytic Degradation of Methylene Blue under Sunlight
(MDPI, 2023-04-01) Mendis, A; Thambiliyagodage, C; Ekanayake, G; Liyanaarachchi, H; Jayanetti, M; Vigneswaran, S
first_pagesettingsOrder Article Reprints Open AccessArticle Fabrication of Naturally Derived Chitosan and Ilmenite Sand-Based TiO2/Fe2O3/Fe-N-Doped Graphitic Carbon Composite for Photocatalytic Degradation of Methylene Blue under Sunlight by Amavin Mendis 1,Charitha Thambiliyagodage 1,*ORCID,Geethma Ekanayake 1,Heshan Liyanaarachchi 1ORCID,Madara Jayanetti 1 andSaravanamuthu Vigneswaran 2,3,* 1 Faculty of Humanities and Sciences, Sri Lanka Institute of Information Technology, Malabe 10115, Sri Lanka 2 Faculty of Engineering and Information Technology, University of Technology Sydney, P.O. Box 123, Sydney, NSW 2007, Australia 3 Faculty of Sciences & Technology (RealTek), Norwegian University of Life Sciences, P.O. Box N-1432 Ås, Norway * Authors to whom correspondence should be addressed. Molecules 2023, 28(7), 3154; https://doi.org/10.3390/molecules28073154 Received: 15 March 2023 / Revised: 29 March 2023 / Accepted: 30 March 2023 / Published: 1 April 2023 (This article belongs to the Section Materials Chemistry) Download Browse Figures Versions Notes Abstract Fabrication of chitosan and ilmenite sand-based novel photocatalysts through the catalytic graphitization of chitosan is reported. Nanocomposites consisted of TiO2, Fe2O3 and Fe nanoparticles dispersed on a nitrogen-doped graphitic carbon framework. The surface area, pore volume and macropore structure of the carbon matrix is disturbed by the heterogeneously distributed nanoparticles. The extent of graphitization expanded with increasing metal loading as indicated by variation in the ID/IG ratio. The nanomaterial’s surface consists of Fe3+ and Ti4+, and graphitic, pyridinic and pyrrolic nitrogen were found in the carbon matrix. The band gap values of the composites varied in the 2.06–2.26 eV range. The photocatalytic activity of the synthesized nanomaterials was determined, and the highest rate constant for the photodegradation of methylene blue under sunlight was 4.4 × 10−3 min−1, which resulted with 10 mg/L MB and 25 mg of the best-performing catalyst. The rate constant rose with increasing concentrations of persulfate added to the medium. The rate constant greatly diminished with the addition of isopropyl alcohol as it scavenged hydroxyl radicals. The presence of co-pollutants including Pb2+, rhodamine B, PO43− and Cl− curtailed the rate of reaction. The activity reduced with an increasing number of uses of the catalyst.
Open Access
In vitro influence of PEG functionalized ZnO–CuO nanocomposites on bacterial growth
(PubMed ID, 2024-01-14) Thambiliyagodage, C; Jayanetti, M; Liyanaarachchi, H; Ekanayake, G; Mendis, M; Usgodaarachchi, L
Polyethyleneglycol-coated biocompatible CuO–ZnO nanocomposites were fabricated hydrothermally varying Zn:Cu ratios as 1:1, 2:1, and 1:2, and their antibacterial activity was determined through the well diffusion method against the Gram-negative Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and the Gram-positive Staphylococcus aureus. The minimum inhibitory concentration and the minimum bactericidal concentration values of the synthesized samples were determined. Subsequently, the time synergy kill assay was performed to elucidate the nature of the overall inhibitory effect against the aforementioned bacterial species. The mean zone of inhibition values for all four samples are presented. The inhibitory effect increased with increasing concentration of the nanocomposite (20, 40 and 60 mg/ml) on all the bacterial species except for S. aureus. According to the MBC/MIC ratio, ZnO was found to be bacteriostatic for E. coli and P. aeruginosa, and bactericidal for S. aureus and K. pneumoniae. Zn:Cu 2:1 was bactericidal on all bacterial species. A bacteriostatic effect was observed on E. coli and P. aeruginosa in the presence of Zn:Cu 1:1 whereas, it showed a bactericidal effect on S. aureus and K. pneumoniae. Zn:Cu 1:2 exhibited a bacteriostatic effect on E. coli while a bactericidal effect was observed for E. coli, P. aeruginosa, and K. pneumoniae. The metal oxide nanocomposites were found to be more sensitive towards the Gram-positive strain than the Gram-negative strains. Further, all the nanocomposites possess anti-oxidant activity as shown by the DPPH assay.
Open Access
In vitro release kinetics of bioactive compounds (gallic acid, ellagic acid, and eugenol) from chitosan polymer and the bioactivity of herb-loaded chitosan–CuO nanocomposites
(Nature Research, 2025-10-13) Ekanayake, G; Wijayawardana, S; Jayanetti, M; Thambiliyagodage, C; Liyanaarachchi, H; Mendis, A
The biological efficacy of nanocomposites comprised of chitosan, CuO nanoparticles, and extracts of Phyllanthus emblica, and Syzygium aromaticum was studied. The study assessed the pH– and ionic strength-responsive controlled release of the bioactive compounds, gallic acid, ellagic acid and eugenol, from the chitosan biopolymer. Release data were fitted into zero-order, first-order, Korsmeyer–Peppas (KP), Peppas–Sahlin (PS), Higuchi, and Hixson–Crowell kinetic models to evaluate the release mechanism. According to KP and PS models (R2 ≥ 0.96), release was governed by quasi-Fickian diffusion (n < 0.43), where the diffusion occurs along with the polymer relaxation and swelling. P.emblica-coated chitosan (PeC) composite exhibited a burst release at acidic media conditions, and a quasi-Fickian diffusion at pH 5.5–7.4. Higher ionic strength caused salting-in effects for PeC in 0.4 M media, resulting in a transiently increased release. In acidic conditions, diffusion-controlled release was observed for S.aromaticum-coated chitosan (SaC) composite, with the optimal release at pH 4 media. Release was facilitated by hydrophobic nanochannels at elevated pH (8.5–10) and ionic strength of 0.5 M NaCl. The PS model’s relaxation contributions were significant at 0.4 M NaCl and 5 mg drug loading. Both composites demonstrated enhanced release at physiological conditions (0.1–0.2 M NaCl, pH 7.4). Sustained release of SaC was achieved in near-neutral/moderate ionic strength media, whereas PeC exhibited sustained release in acid/low ionic strength media. The PeC and SaC composites showed IC50 values of 10.78 µg/mL and 19.27 µg/mL for the DPPH radical scavenging ability, respectively. Recorded IC50 values for the egg albumin denaturation assay were 467 µg/mL and 390.44 µg/mL, respectively. The antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Staphylococcus aureus showed maximum inhibition zones of 11.83 ± 0.06 mm (Chitosan: CuO 1:2), 12.67 ± 0.20 mm (1:4), 16.50 ± 0.09 mm (1:4), and 11.83 ± 0.08 mm (4:1), respectively. Among the herbal-coated samples, SaC exhibited the highest activity of 23.67 ± 2.84 mm against E. coli
Open Access
Persulfate assisted photocatalytic and antibacterial activity of TiO2–CuO coupled with graphene oxide and reduced graphene oxide
(https://www.nature.com, 2024-05-31) Thambiliyagodage, C; Liyanaarachchi, H; Jayanetti, M; Ekanayake, G; Mendis, A; Samarakoon, U; Vigneswaran, S
Photocatalysts of TiO2–CuO coupled with 30% graphene oxide (GO) were hydrothermally fabricated, which varied the TiO2 to CuO weight ratios to 1:4, 1:2, 1:1, 2:1 and 4:1 and reduced to form TiO2–CuO/reduced graphene oxide (rGO) photocatalysts. They were characterized using XRD, TEM, SEM, XPS, Raman, and DRS technologies. TiO2–CuO composites and TiO2–CuO/GO degrade methylene blue when persulfate ions are present. Persulfate concentration ranged from 1, 2, 4 to 8 mmol/dm−3 in which the highest activity of 4.4 × 10–2 and 7.35 × 10–2 min−1 was obtained with 4 mmol/dm−3 for TiO2–CuO (1:4) and TiO2–CuO/GO (1:1), respectively. The presence of EDTA and isopropyl alcohol reduced the photodegradation. TiO2–CuO coupled with rGO coagulates methylene blue in the presence of persulfate ions and such coagulation is independent of light. The catalyst dosage and the concentration of the dye were varied for the best-performing samples. The antibacterial activity of the synthesized samples was evaluated against the growth of Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Klebsiella pneumonia. Ti:Cu (1:2)-GO and Ti:Cu (1:4)-GO had the highest antibacterial activity against K. pneumoniae (16.08 ± 0.14 mm), P. aeruginosa (22.33 ± 0.58 mm), E. coli (16.17 ± 0.29 mm) and S. aureus (16.08 ± 0.88).
Open Access
Recent Advances in Chitosan-Based Applications—A Review
(MDPI, 2023-03-03) Thambiliyagodage, C; Jayanetti, M; Mendis, A; Ekanayake, G; Liyanaarachchi, H; Liyanaarachchi, S
Chitosan derived from chitin has gathered much interest as a biopolymer due to its known and possible broad applications. Chitin is a nitrogen-enriched polymer abundantly present in the exoskeletons of arthropods, cell walls of fungi, green algae, and microorganisms, radulae and beaks of molluscs and cephalopods, etc. Chitosan is a promising candidate for a wide variety of applications due to its macromolecular structure and its unique biological and physiological properties, including solubility, biocompatibility, biodegradability, and reactivity. Chitosan and its derivatives have been known to be applicable in medicine, pharmaceuticals, food, cosmetics, agriculture, the textile and paper industries, the energy industry, and industrial sustainability. More specifically, their use in drug delivery, dentistry, ophthalmology, wound dressing, cell encapsulation, bioimaging, tissue engineering, food packaging, gelling and coating, food additives and preservatives, active biopolymeric nanofilms, nutraceuticals, skin and hair care, preventing abiotic stress in flora, increasing water availability in plants, controlled release fertilizers, dye-sensitised solar cells, wastewater and sludge treatment, and metal extraction. The merits and demerits associated with the use of chitosan derivatives in the above applications are elucidated, and finally, the key challenges and future perspectives are discussed in detail.
Open Access
The photocatalytic and antibacterial activity of graphene oxide coupled CoOx /MnOx nanocomposites
(Elsevier B.V., 2025-02) Liyanaarachchi, H; Thambiliyagodage, C; Jayanetti, M; Ekanayake, G; Wijayawardana, S; Samarakoon, U
CoOx and MnOx metal oxide composites were fabricated via co-precipitation varying the Co:Mn (CM) weight ratio as 4:1, 2:1, 1:1, 1:2 and 1:4, and they hydrothermally coupled with 30 wt% of graphene oxide (GO). XRD analysis revealed the presence of Co3O4 and CoO, and Mn2O3 and Mn3O4 phases in pure CoOx and MnOx metal oxides, respectively. The irregularly shaped metal oxide nanocomposites comprised Co3O4, Mn2O3 and Mn3O4 phases and were immobilized on GO. The band gap values of the composites varied in the range of 1.86 – 2.22 eV. The highest photocatalytic activity with a rate constant of 3.5 × 10−3 min−1 was obtained with CMG (1:4). The total removal of MB increased by 55.8 % when CM (1:4) were coupled with GO. The rate of photocatalysis was dramatically increased in the presence of S2O82- and was decreased in the presence of EDTA and isopropyl alcohol. The effect of catalyst dosage was determined by varying the weight to 25, 50, 75, and 100 mg, and the dye concentration was varied in the range of 25, 50, 75 and 100 mg/L. The presence of Pb2+ and Rhodamine B decreased the photocatalytic activity, while it remained the same in the presence of Cl- and PO43- as co-pollutants. The photocatalytic activity of CMG (1:4) was reduced to 72 % upon using the catalyst for five cycles. All the synthesized nanocomposites exhibited greater sensitivity to the Gram-positive strain than the Gram-negative strains.