Browsing by Author "De Silva, C. R."

Now showing 1 - 2 of 2

Comparative Effect of Nanoparticles of Sliver, Europium Doped ZnO and CaF2 on Aedes aegypti and Daphnia magna
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Kumarasinghe, G. D. S. S.; Amarasinghe, L. D.; De Silva, C. R.
Aedes aegypti mosquitoes are responsible for transmitting dengue fever. Using nanoparticles is a better suggestion to combat vector mosquito spread. Daphnia magna is the keystone species in freshwater food webs. The sensitivity of Daphnia magna to low metal concentrations underscores its importance in evaluating the impact of nanoparticles on the ecosystem. This study examined the impact of Silver, ZnO, CaF2, Europium-doped ZnO, and CaF2 nanoparticles on Aedes aegypti larvae and adult Daphnia magna. The batch of 25 third instar larvae of Aedes aegypti and the batch of 25 adult Daphnia magna were exposed to each nanoparticle in a concentration series for 24 and 48 hours. For Aedes aegypti, nanoparticles of ZnO and CaF2 at 20 mg/L, 40 mg/L, 60 mg/L, 80 mg/L, and 100 mg/L; nanoparticles of Europium-doped ZnO and CaF2 at 50 mg/L; and Silver nanoparticles at 1 mg/L, 2 mg/L, 3 mg/L, 4 mg/L, and 5 mg/L. For the Daphnia magna, ZnO nanoparticles at 0.2 mg/L, 0.4 mg/L, 0.6 mg/L, 0.8 mg/L, and 1 mg/L; Europium-doped ZnO nanoparticles at 0.5 mg/L; CaF2 nanoparticles at 1 mg/L, 2 mg/L, 3 mg/L, 4 mg/L, and 5 mg/L; Europium-doped CaF2 nanoparticles at 4 mg/L; and Silver nanoparticles at 2.36 mg/L. The percentage mortality of Aedes aegypti larvae and Daphnia magna was calculated for each nanoparticle. The study revealed that nanoparticles of ZnO and CaF2 did not affect Aedes aegypti larvae but caused significant mortality in Daphnia magna. LC50 value at 24 hours for ZnO nanoparticles was 0.51 mg/L, while for CaF2 nanoparticles, it was 4.44 mg/L. The study also revealed that increasing europium doping in ZnO and CaF2 nanoparticles led to higher Daphnia magna mortality. The study revealed that exposure to silver nanoparticles for 24 hours significantly increased Aedes aegypti larvae mortality rates. LC50 value was 2.36 mg/L. All Daphnia magna were dead within 24 hours of exposure to silver nanoparticles. The study concludes that ZnO and CaF2 nanoparticles did not affect Aedes aegypti larvae. Silver nanoparticles showed lethal effects but cannot be recommended for Aedes aegypti control due to being toxic to Daphnia magna, a keystone species in aquatic ecosystems.
Synthesis and characterization of lanthanide-based nanoparticles for potential biomedical applications
(Faculty of Science, University of Kelaniya, Sri Lanka, 2021) De Silva, C. R.
Lanthanide-based nanoparticles show unique luminescent properties including monochromatic light emission, longer luminescent lifetimes, stable and well-defined emission bands, large Stokes shifts, and limited photo-bleaching. Our current research efforts are focused on developing lanthanide-based nanomaterials for biomedical applications including high throughput drug screening and cellular imaging. We have developed organic solvent-based high temperature decomposition methods and aqueous-based microwave-assisted synthetic methods to make nanoparticles with high colloidal stability and monodispersity. Europium metal ion doping was successfully achieved using sodium yttrium fluoride, lanthanum fluoride, calcium fluoride, and zinc oxide crystal matrices. The nanoparticles were characterized using transmission electron microscopy, powder X-ray diffraction, Energy dispersive X-ray, absorption spectroscopy, and luminescent methods. Sodium yttrium fluoride and calcium fluoride matrices produced nanoparticles with a diameter of 20 nm and 40 nm, respectively. The zinc oxide matrix resulted nanoparticles with a diameter of 30 nm. Powder X-ray diffraction studies confirmed that yttrium fluoride, calcium fluoride, and zinc oxide matrices produced nanoparticles with cubic closed packed, cubic, and hexagonal wurtzite crystal packing, respectively. Lanthanide metal ion doping did not significantly alter the basic crystal structure of the nanoparticles. Increasing reactant metal concentrations from 0.02 to 0.065 M decreased the calcium fluoride nanoparticle size from 1000 nm to 66 nm. Luminescent quantum yield was sensitive to the crystal matrix and the europium metal doping levels. The highest luminescent quantum yield of 17 % was observed for 10 % europium-doped sodium yttrium fluoride nanoparticles. All nanoparticle systems exhibited narrow emission bands at 615 nm with a full-width at half maximum around 15 nm upon 340 nm lamp excitation. Preliminary in vitro epifluorescence imaging studies confirmed the uptake of europium-doped zinc oxide nanoparticles by human embryonic kidney (HEK) 293 cells