Faculty of Humanities and Sciences-Q1
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Publication 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, UCoOx 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.Publication Open Access Fe3O4 Chitosan Nanocomposite as a pH-Responsive Delivery System for Enhanced Delivery of Punica Granatum L. Polyphenols(American Chemical Society, 2025-10-17) Rukshan, R; Rajapaksha, N; Wijayawardana, S; Thambiliyagodage, C; Senevirathne, U; Jayanetti, M; Samarakoon, UPunica granatum extract (PG), consisting of punicalagin, ellagic acid, and gallic acid, was loaded onto an Fe3O4/Chitosan (Fe3O4@Chi) nanocomposite (Fe3O4@Chi-PG) to enhance pharmacokinetic properties. Fe3O4was synthesized via the coprecipitation method and coupled with chitosan in 2% acetic acid solution via glutaraldehyde cross-linking. The presence of interested polyphenols in the pomegranate extract was confirmed by HPLC analysis, and the extract was post-loaded to the nanocarrier. XRD confirmed the crystallographic orientation of the nanocarrier, and SEM analysis confirmed the successful coupling of Fe3O4onto the chitosan surface during the fabrication of Fe3O4@Chi. BET surface area analysis revealed the presence of micro- and mesopores in the synthesized materials. Significant reduction of the BET surface area and the pore volume of Fe3O4@Chi-PG compared to Fe3O4@Chi suggested the loading of the porous network and surface by PG. The presence of vibrational bands corresponding to the functional groups of the relevant bioactive compounds was confirmed via FT-IR analysis. The IC50values of the nanocomposite for DPPH and egg albumin denaturation assays were 18.69 and 257.69 μg/mL, respectively. The PG encapsulation efficiency of Fe3O4@Chi-PG was reported to be 86.44%. The pH-responsive release of the polyphenols was studied by fitting the release data into five kinetic models, including Korsemeyer–Peppas (KP) and Peppas–Sahlin (PS). The KP and PS models were selected to interpret the release mechanism based on the R2≥ 0.95 value. A combination of Fickian diffusion, relaxation, and swelling dominates the polyphenol release. Quasi-Fickian diffusion is responsible for the release in media with pH 1–6.7, whereas anomalous transport occurs at pH 7.4 (n = 0.46) according to the KP model. Polymer relaxation is the dominant mechanism for the release of bioactive compounds at pH 7.4, as exhibited by R/F > 1. However, the contribution of relaxation to the release of polyphenols at pH 2.5, 4, and 5.5 was negligible according to the parameters (kR= 0). Characteristics of chitosan, including protonation and deprotonation of NH2groups, surface charge of Fe3O4, ionization of COOH and OH groups of the polyphenols, and molecular weight of the active compounds, contributed to the differences in the release behavior.Publication 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, SPhotocatalysts 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).