Research Papers - School of Natural Sciences
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Publication Open Access Ligand exchange reactions and PEG stabilization of gold nanoparticles(Elsevier, 2021-12-21) Thambiliyagodage, C. JGold nanoparticles (Au NPs) were synthesized by the citrate reduction method. Au NPs were aggregated when mixed with mercaptoethanol (ME), dopamine (DAH) and adenine (AD) as the surface passivating citrate molecules were incompletely but heavily replaced by them as supported by the occurrence of a new peak at a longer wavelength and eventual disappearance of the peak/s in the UV–Visible spectra due to the settlement of the aggregated NPs. Transmission electronic microscopic (TEM) images showed aggregated NPs. AD was increasingly replaced by an increasing concentration of dithiothreitol (DTT) in the range of 20 μM–10 mM, but an incomplete replacement was resulted even after using highly concentrated DTT (10 mM). mPEGSH passivates the gold surface where they bind to the gold surface via a mushroom-like configuration. mPEGSH stabilizes the Au NPs preventing aggregation upon mixing with ME, DAH and AD, as revealed by no change in the position and the absorbance of the localized resonance surface plasmon peak in the UV–Visible spectra and well-dispersed Au NPs in the TEM images. Mushroom-like arrangement of mPEGSH on the Au NPs allow adsorption of ME, DAH and AD as revealed by the surface enhanced Raman spectroscopic data.Publication Embargo One pot synthesis of α-Fe2O3/turbostratic carbon composites and their photocatalytic activity under sunlight(Elsevier, 2021-10-01) Thambiliyagodage, C. J; Nakandala, S; Siriwardana, B; Lansakara, BSucrose naturally obtained from sugar cane was catalytically graphitized by incorporation of varying amounts of iron (1, 5, 7.5 and 10%) as a one-pot synthesis. The weight of iron was varied relative to the weight of sucrose. Synthesized sucrose-Fe2O3 nanocomposites (FeGC) were characterized by X-ray diffractometry (XRD), Raman spectroscopy, and UV-Visible spectroscopy. It is observed that turbostratic carbon is produced upon the incorporation of iron and the percentage of graphitization increase with increasing loading of iron as revealed by XRD analysis. Quantitative analysis of Raman spectra confirm that the ordering of carbon increase with increasing loading of iron. The equilibrium adsorption capacity of carbon with the highest iron loading (10FeGC), 0.50 mg/g is higher than that with carbon without any metal, AC (0.2 mg/g), and the highest adsorption capacity (0.58 mg/g) resulted in carbon with 5% iron (5FeGC). Methylene blue adsorption to AC and carbon with 1% iron (1FeGC) followed pseudo-first-order kinetics and carbon materials with 5, 7.5 and 10% iron followed pseudo-second-order kinetics. The initial rate constant for the photodegradation of methylene blue in the presence of AC was 0.001 min−1 and that of 1FeGC (0.005 min−1) increased with increasing loading of iron where the highest initial rate constant (0.158 min−1) was obtained with 10FeGC. Ordered carbon enhances photocatalytic activity by being photoactive and increasing the separation of charges generated at α-Fe2O3.Publication Open Access Photocatalytic activity of Go/Fe3O4 fabricated by Sri Lankan graphite under visible light irradiation(Faculty of Science, University of Kelaniya, Sri Lanka, 2021-10) Usgodaarachchi, L; Thambiliyagodage, C. JGraphene oxide (GO) was synthesized using Sri Lankan naturally available graphite by modified Hummer’s method. Fe3O4 nanoparticles were synthesized successfully by co-precipitation of Fe3+ and Fe2+ in a 2:1 molar ratio via the addition of NH4OH. Magnetically separable GO/Fe3O4 nanocomposite was fabricated by synthesizing Fe3O4 nanoparticles in the presence of GO. The synthesized nanocomposites were characterized by X-ray diffractometry (XRD), Scanning electron microscopy (SEM), and FT-IR spectroscopy. The formation of GO was confirmed by the C(002) peak at 9.39° in the XRD pattern. XRD pattern of the nanoparticles confirms the formation of crystalline Fe3O4 nanoparticles, and the diffraction peak corresponds to graphene oxide disappear in the GO/ Fe3O4 due to the absence of the folded structure of graphene oxide. SEM image of GO shows the crumpled and wrinkled lamellae structure of graphene oxide, and the images of GO/ Fe3O4 show the distribution of Fe3O4 nanoparticles with an average size of 107 nm on GO where the folded structure of GO was not present while restacking of the nanosheets, was observed. FT-IR spectrum of GO shows the presence of polar oxygenated functional groups such as carboxylic acid (-COOH), hydroxyl (-OH), and epoxy (-COC-). The photocatalytic performance of the photocatalysts was evaluated on photodegradation of methylene blue under visible light irradiation. The GO/ Fe3O4 shows better adsorption behaviour and excellent photocatalytic activity where it could be successfully used for three cycles without significant activity loss. The rate constant for the degradation of MB (0.0187 min-1 ) at the first cycle decreased to 0.0101 min-1 at the third cycle. The conversion of MB decreased from 98.31% at the first cycle to 92.15% at the third cycle. The drop in the conversion is only 6.16% going from cycle 1 to 3, which could be due to the accumulation of the MB molecules at the pore structure. The obtained high photocatalytic activity could be due to the enhanced charge separation resulted due to the presence of GO sheets and better interactions between GO and Fe 3O4.Publication Open Access Leaching of ilmenite to produce titanium based materials: a review(Springer International Publishing, 2021-12) Thambiliyagodage, C. J; Wijesekera, R; Bakker, M. GNaturally available ilmenite mineral is being used as a starting material to produce titanium based products that have wide applications. Transformation of ilmenite to diferent titanium based materials by strong and weak acid, and base digestion, is discussed. Efects of temperature, concentration of acid/base, reaction time on dissolution of ilmenite are extensively reviewed. Characterization of the starting materials, intermediates and the products by x-ray difraction, thermogravimetry, brunauer–emmett–teller surface area analysis, and scanning electron microscopy are presented. Further, advantages and disadvantages associated with the digestion methods are discussed.Publication Embargo Efficient removal of methylene blue by turbostratic carbon/Fe3C/Fe composite synthesized by catalytic graphitization of sucrose(Elsevier, 2021-12-07) Thambiliyagodage, C. J; Usgodaarachchi, LTurbostratic carbon/Fe3C/Fe composite was prepared by catalytic graphitization of sucrose by α-Fe2O3. The synthesized composites were characterized by X-ray diffractometry (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). XRD patterns revealed the formation of turbostratic carbon with a d spacing of 0.3412 nm and the presence of Fe3C and Fe nanoparticles. Raman spectrum exhibited the D, G and G' peaks. XPS analysis shows the presence of graphitic carbon and +3 oxidation state of iron. Synthesized composite can remove methylene blue with an adsorption capacity of 17.8 mg/g at pH 7. Adsorption follows pseudo second order kinetics and the Langmuir isotherm model. As the synthesized composite is magnetic it could be easily separated from the mixture and could be reused effectively without significant activity loss for five cycles.Publication Open Access Ball milling–A green and sustainable technique for the preparation of titanium based materials from ilmenite(Elsevier, 2022-01-01) Thambiliyagodage, C. J; Wijesekera, RIlmenite is a naturally available mineral that is highly applicable in the synthesis of pure TiO2. Titania mainly presents in four polymorphs as rutile, anatase, brookite and TiO2–B. Titania could be mined from minerals such as ilmenite, leucoxene and rutile among which ilmenite is the main source. Ball milling is a mechanical activation method used before subjecting ilmenite to chemical treatment methods to produce titanium based materials. Effect of milling time, milling intensity, milling atmosphere, the introduction of reducing agents on the particle size, surface area, annealing temperature, and the crystal structure of the products are reviewed. The effect of ball milling on acid digestion of ilmenite in hydrochloric acid and sulfuric acid is discussed. Further, the effect of mechanical activation on hydrothermal treatment of ilmenite is explained in detail.Publication Open Access Ligand exchange reactions and PEG stabilization of gold nanoparticles(Elsevier, 2022-01-01) Thambiliyagodage, C. JGold nanoparticles (Au NPs) were synthesized by the citrate reduction method. Au NPs were aggregated when mixed with mercaptoethanol (ME), dopamine (DAH) and adenine (AD) as the surface passivating citrate molecules were incompletely but heavily replaced by them as supported by the occurrence of a new peak at a longer wavelength and eventual disappearance of the peak/s in the UV–Visible spectra due to the settlement of the aggregated NPs. Transmission electronic microscopic (TEM) images showed aggregated NPs. AD was increasingly replaced by an increasing concentration of dithiothreitol (DTT) in the range of 20 μM–10 mM, but an incomplete replacement was resulted even after using highly concentrated DTT (10 mM). mPEGSH passivates the gold surface where they bind to the gold surface via a mushroom-like configuration. mPEGSH stabilizes the Au NPs preventing aggregation upon mixing with ME, DAH and AD, as revealed by no change in the position and the absorbance of the localized resonance surface plasmon peak in the UV–Visible spectra and well-dispersed Au NPs in the TEM images. Mushroom-like arrangement of mPEGSH on the Au NPs allow adsorption of ME, DAH and AD as revealed by the surface enhanced Raman spectroscopic data.Publication Embargo Photocatalytic activity of N, Fe and Cu co-doped TiO2 nanoparticles under sunlight(Elsevier, 2021-01-01) Thambiliyagodage, C. J; Usgodaarachchi, LPhotocatalytic activity of N doped with one transition metal is well known. This article reports the synthesis of TiO2 nanoparticles doped with only N, N co-doped with Fe, N co-doped with Cu and N co-doped with both Fe and Cu by sol-gel method. Their photocatalytic activity was evaluated for the degradation of methylene blue under sunlight. Nanoparticles were characterized by X-ray diffractometry (XRD), Raman spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and diffuse reflectance UV–visible spectroscopy (DRS). XRD analysis revealed the presence of anatase phase TiO2 nanoparticles which was confirmed by Raman spectroscopic and TEM analysis. The crystal structure has not been disturbed by doping with N, Fe and Cu as shown by both XRD and Raman analysis. TEM and SEM images exhibit the nanoparticles which are interconnected due to sintering. XPS analysis revealed the presence of the only Ti4+ in undoped TiO2 but both Ti4+ and Ti3+ are present in doped TiO2 nanoparticles. According to the DRS analysis, the band gap of all doped TiO2 is lower than that of the undoped TiO2, where N, Fe and Cu co-doped TiO2 showed the lowest band gap (2.51 eV) proving that the visible light sensitivity of TiO2 increase with metal and non-metal doping. The rate of photodegradation of methylene blue in the presence of undoped TiO2 (0.016 min−1) is higher than all the doped TiO2 nanoparticles. N doped TiO2 show the highest activity among the doped TiO2 nanoparticles (0.006 min−1). Doped TiO2 nanoparticles showed a lower photocatalytic activity due to the electron hole pair recombination and the shielding effect of the dopants.Publication Open Access Effect of surfactants on morphology and textural parameters of silica nanoparticles derived from paddy husk and their efficient removal of methylene blue(International Conference on Innovations in Energy Engineering & Cleaner Production (IEE CP’21), 2021) Gunathilaka, H; Thambiliyagodage, C. J; Usgodaarchchi, L; Angappan, SEffective removal of textile dyes is important in environmental remediation especially for decontamination of wastewater. Herein, we report the synthesis of mesoporous silica nanoparticles (MSNs) from paddy husk with varying concentrations of surfactants, Cetyltrimethylammonium bromide (CTAB), and Polyethyleneglycol (PEG) by sol-gel synthesis method. Ratios of the surfactants CTAB: PEG were varied as 2:0 (MSN1),1:1 (MSN2), 0:2 (MSN3). MSNs were characterized by scanning electron microscope (SEM), Brunauer-Emmett-Teller surface area analyzer (BET), Thermogravimetric analyzer (TGA), and X-ray diffractometer. According to the SEM images, MSNs of all the combinations were aggregated with spherical and irregular shaped nanoparticles. MSNs synthesized with a 1:1 surfactant ratio showed more spherical nanoparticles. BET surface areas of MSN1, MSN2, and MSN3 are 468.35, 95.94, 177.46 m2/g, respectively. TGA curve indicated that desorption of the physisorbed water was completed at 125 °C. The effect of dye removal by the MSNs was studied on the adsorption of methylene blue (MB). Effect of dye concentration (5-30 mg/l), adsorbent dosage (5-20 mg), pH of the medium (2-10), ionic strength of the medium (0-6g/l NaCl), presence of a heavy metal (Pb2+- 0-500 mg/l) and temperature (25-55 °C) on MB adsorption was studied. At all the varied parameters, the adsorption efficiency of MB varied as MSN1> MSN3> MSN2, being similar to the trend of the surface area. The percentage of MB adsorption decreased with increasing MB concentration while it increased with increasing adsorbent dosage. The highest efficiency of MB adsorption was obtained at pH 10 and it decreased with increasing ionic strength and increasing concentration of heavy metal ions. The maximum percentage of MB adsorption resulted at 55 °C. Therefore, it can be concluded that the MSNs synthesized using only CTAB as the surfactant is an effective adsorbent in removing textile dyes from wastewater.Publication Embargo Activity enhanced TiO2 nanomaterials for photodegradation of dyes-A review(Elsevier, 2021-12-01) Thambiliyagodage, C. JWastewater generation due to anthropogenic activities has become a tremendous problem that the world is struggling to solve. Dyes release to normal water reservoirs badly impacts the environment causing severe issues. Removal of dyes from wastewater streams is important. The advanced oxidation process is advantageous as the dye molecules are degraded into harmless species. TiO2 is the most promising semiconductor that has been researched. However, the use of it in the visible range is restricted due to its high band gap (3.0 eV). TiO2 has been modified in order to enhance visible light sensitivity. This review mainly focused on the effects of doping TiO2 with metals and non-metals and coupling with metal and non-metal oxides to improve its efficiency in photodegrading dyes. TiO2 doped with Fe, Cu and Ag as the main metal species, N, S, and C as the main non-metals are summarized. Further, the effect of doping with multi non-metals and co-doping of metals and non-metals are also discussed. Moreover, coupling TiO2 with metal oxides and graphene oxide for enhanced photocatalytic activity is also summarized in this review.