Browsing by Author "Sivakumar, V."

Now showing 1 - 5 of 5

Antibacterial fabrics: ZnO nanoparticles infused polymer nanofiber membrane
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Yapa, Y. M. C. P. C. B.; Sivakumar, V.; Liyanage, J. P.
Bacterial infections are a leading global health crisis, ranking as the second largest cause of death worldwide. This study explores the innovative potential of using polyvinyl alcohol (PVA) nanofiber membranes infused with ZnO nanoparticles to create antibacterial clothing. ZnO, is a n-type semiconductor with a band gap of approximately 3.37 eV, is renowned for its biosafety and biocompatibility. It exists in various forms such as nanowires, nanorings, nanospheres, and nanohelices, showcasing its versatility. Additionally, ZnO nanoparticles exhibit significant antibacterial properties against a wide range of bacterial species due to their photocatalytic activity, making them a promising solution in the fight against transmission of bacterial infections. Electrospinning has been employed to fabricate PVA nanofiber membranes, with PVA emerging as the predominant polymer of choice due to its non-toxicity, biocompatibility, and superior electrospinning-ability compared to other polymers. The agar disc diffusion method was carried out to observe antibacterial activity of ZnO nanoparticles and PVA-ZnO nanofiber membranes against Escherichia coli DH-5α (E-coli) strain. A distinct inhibition, zone with an average width of approximately 0.5 cm, was clearly observable using commercially available ZnO nanoparticles. PVA-ZnO nanofiber membranes with different ZnO concentrations were fabricated starting from 0.5 wt% to 6.0 wt%, in steps of 0.5 wt%, on a gauze as a substrate, by electrospinning PVA-ZnO polymer solutions. The antibacterial activity of the PVA-ZnO nanofiber membranes started to appear when the ZnO concentration was 5.0 wt%. These membranes exhibited an average inhibition zone width of approximately 0.1 cm. Also, PVA nanofiber membrane alone did not show an inhibition zone. Surface morphology of each nanofiber was analyzed using scanning electron microscope (SEM). X-ray Fluorescence (XRF) analysis for the commercially available ZnO nanoparticles was performed to determine the chemical purity of the ZnO. Fourier Transform Infrared spectroscopy (FTIR) analysis was performed to determine the structural change due to the interaction between PVA and ZnO nanoparticles. Based on the findings, a minimum ZnO concentration of 5.0 wt% is necessary to achieve antibacterial activity against E-coli using PVA-ZnO nanofiber membranes. This concentration threshold underscores the critical role of ZnO in enhancing the membranes' effectiveness in fighting against bacterial pathogens.
Binder effects on CO2 gas sensitivity of Mn-doped copper oxide films: A comparative study using PEG, CMC, MEG
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Weerasooriya, R. M. A. U.; Dasanayake, N. L.; Sivakumar, V.
In today's world, with rising air pollution levels, it is essential to detect air quality, ensuring both environmental safety and public health. Gas sensors detect air quality, with sensor material as the main component. A binder is used to hold the sensor material together and ensure it sticks to the conductive glass plate, creating a uniform and stable sensing layer. However, the addition of binders can affect gas sensitivity because they modify the microstructure of the sensing layer. Therefore, it is important to identify which binder is the most suitable for sensor material for gas sensing purposes. The aim of this work was to examine the effects of three distinct binders; polyethylene glycol (PEG), carboxymethyl cellulose (CMC), and monoethylene glycol (MEG), on the surface morphological changes and carbon dioxide (CO2) gas sensitivity of Mn-doped (4%) copper oxide as a gas sensing material. Some previous studies had investigated binders for various sensor materials to detect different gases, but the novelty of this research lies in specifically comparing the CO2 gas sensitivity of Mn-doped (4%) copper oxide with the above mentioned binders separately. The film was prepared using the doctor blade method and coated samples were heated at 120 °C for 30 minutes. UV-visible absorption spectroscopy, XRD and SEM analysis were conducted to determine the optical and structural properties of the sample. The XRD analysis confirms the presence of both cuprous oxide (Cu₂O) and cupric oxide (CuO) in the sample, with CuO being the most dominant phase. The sample with the MEG binder had the lowest optical band gap of 2.93 eV, while the other two samples had the same optical band gap of 2.95 eV, demonstrating that there is no significant impact of the chosen binders on the optical band gap of Mn-doped (4%) copper oxide. The arithmetic average roughness (Ra) increases when CMC and MEG binders are added to the sample but decreases when PEG is added. Furthermore, the gas sensitivity, response time, and recovery time of Mn-doped copper oxide were measured for CO2 detection at room temperature. The flow rate of CO2 gas was varied from 10 SCCM to 20 SCCM for three different samples. Additionally, it shows less than 6% variation in results across multiple measurements. The sample with PEG quickly responded to CO2 gas in 90 s with a recovery time of 300 s and a CO2 gas sensitivity of 57.35%. The sample with CMC had the lowest gas sensitivity of 48% and also showed the best recovery time for CO2 gas in 280 s. High gas sensitivity is particularly important for breath analysis used in medical diagnostic procedures. For this purpose, the MEG added sample can be chosen because it has a comparatively high CO2 gas sensitivity of 62.23%. In conclusion, choosing the right binder with a copper oxide sample is essential for creating the optimal sensing layer to fulfill CO2 gas sensing purposes.
Estimation and comparison of patient doses in lumbar spine X-ray examination: A case study at a government hospital in Sri Lanka
(Faculty of Science, University of Kelaniya Sri Lanka, 2022) Welarathna, W. D. S. D.; Sivakumar, V.; Wanninayake, W. M. N. M. B.; Sarasanandarajah, S.
The number of projection X-ray examinations is rising rapidly worldwide due to its extensive usage in accurately diagnosing diseases and injuries in patients. Apart from the enormous benefits of X-ray examinations, the patients are exposed to substantial radiation doses, which may cause stochastic and deterministic effects that could be harmful to the patients. The lumbar spine X-ray test is considered the most routinely performed projection X-ray examination for the proper diagnosis of various clinical indications, including low back pain, fractures, arthritis, spondylolisthesis, tumours, and degenerative pathologies. Diagnostic Reference Levels (DRLs), the concept introduced by the International Commission on Radiological Protection (ICRP), can be used to assist in optimising radiation doses during radiographic procedures. Accordingly, radiation doses associated with lumbar spine X-ray examinations need to be assessed, justified, and optimised in terms of benefits and risks to improve patient protection. The objective of this study was two-fold: first, assess the kerma-area product (KAP) of adult patients undergoing lumbar spine X-ray examinations (anteroposterior (AP) and lateral (LAT)), and then compare the obtained patient doses with the DRLs reported in some other countries: United Kingdom (UK), Ireland, Austria, Germany, France, Greece, India, Iran, and Australia. This study was conducted in a government hospital in Sri Lanka with 80 adult patients. The ages of the patients involved were from 18 years to 84 years, while their weights ranged from 38 kg to 78 kg. The AP and LAT projections of the lumbar spine examination were acquired on a digital radiography system with flat-panel detectors in the supine position. Patient characteristics (age, sex, weight, height, and body mass index) and corresponding exposure parameters (tube voltage [kV] and the product of tube current and exposure time [mAs]) were obtained. The KAP values were measured by a direct method, and descriptive statistics were utilised for the data analysis. The results showed wide variations in the KAP values for both AP and LAT of the lumbar spine examination. The mean value (1.91 Gy.cm2) of the KAP of LAT projection of the lumbar spine X-ray examination was higher than 200% of the value of AP projection (0.86 Gy.cm2). The KAP ranges for lumbar spine AP and LAT projections were 0.29-1.55 and 0.73-3.55 Gy.cm2, respectively. The mean KAP values for the AP and LAT projections of the lumbar spine examination were lower than the reported values (AP%, LAT%), respectively in the following countries: UK (43%, 24%), Ireland (46%, 15%), Austria (57%, 40%), Germany (57%, 45%), France (68%, 51%), Greece (43%, 15%), India (8%, 39%), Iran (16%, 3%), Australia (46%, 11%). The overall findings of this preliminary study ensure the commitment of the radiographers in following the ALARA (as low as reasonably achievable) principle in this hospital and make further optimisation unessential.
Incorporation of Sri Lanka’s natural minerals, zircon and apatite, in radiation shielding
(Faculty of Science, University of Kelaniya Sri Lanka, 2022) Ranasinghe, M. U.; Hathnagoda, E. M. D. K. B.; Nanayakkara, D. K. K.; Wijayaratne, K.; Bandara, T. M. W. J.; Jayasinghe, U. J. M. A. L.; Jayalath, C. P.; Sivakumar, V.
With the rapid increase in the application of ionizing radiation, radiation protection has become a predominant factor in ensuring the safety of humans and the environment. Blocking high-energy photon radiation has proven to be much more challenging due to its excessive penetrating power. Lead-based materials are commonly used for shielding due to their high efficiency in attenuating gamma rays and X-rays. However, the cumulative toxicity of lead to the ecosystem, the weight and the stiffness have made it unpopular when portable shielding application is considered. This study aims to investigate the possibilities of using naturally available minerals in Sri Lanka to develop multifunctional shielding devices for various radiation protection applications. In this preliminary work, zircon and appetite were utilized as the primary attenuating materials due to their elemental compositions. Using silicone rubber and epoxy as binding materials 0.5 cm thick composite layers of zircon and apatite were prepared separately. The selection of binders and the weight ratio of the filler to the binder were chosen to fulfil the requirement of flexibility, low-weight and processability. The capability of radiation shielding of each sample was tested for 662 keV gamma radiation emitted from Cs-137 isotope. Radiation was detected by a NaI (Tl) scintillation detector and analysed by a multi-channel analyser. The linear attenuation coefficient of the binders, single layers of zircon and apatite, and the effective linear attenuation coefficient of two-layer systems with possible orders of layer-arrangement were calculated. The linear attenuation coefficient of epoxy was considerably higher than that of silicone rubber. Among the fillers used, zircon showed more attenuation than apatite due to the higher effective atomic number. In addition, the higher electron density of zircon leads to a higher Compton scattering rate compared to apatite. The linear attenuation coefficients of pure zircon and apatite are calculated to be 0.092 and 0.059 cm-1, respectively, for 662 keV photons. It was observed that in the two-layer composite system effective attenuation coefficient depends on the order of the material layer. Out of the two-layer structures studied, apatite-zircon combination with epoxy as the binding material showed better shielding with 18.1% blocking rate where the apatite layer was placed towards the source. The effective linear attenuation coefficient of this composite system is calculated to be 0.087 cm-1 with an effective half-value layer thickness of 7.9 cm.
UV light absorption of reduced graphene oxide - titanium dioxide composite coating for sustainable UV protection
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Karunachandra, R. T. D. K. B.; Sivakumar, V.; Mendis, R. A.
The depletion of the ozone layer causes irreversible medical issues related to the increased fractions of Ultraviolet A (UV-A) and Ultraviolet B (UV-B) radiation reaching the Earth’s surface. Therefore, introducing a material with a wide range of UV absorption capabilities is crucial. Recent studies show that both UV-A and UV-B can cause cancer in deep layer epidermis of keratinocyte cells. It is reported that titanium dioxide (TiO2) nanoparticles (anatase phase, spherical shape) absorb UV-B light. Once doped with reduced graphene oxide (RGO), the composite material is observed to absorb both UV-A and UV-B radiation. The aim of this study was to utilize the shift from UV-B to UV-A to enhance the UV absorption of RGO - TiO2 composite material for UV protection applications. The sun protecting factor (SPF) describes the ability of a material to absorb UV-B region. The UV-A protection factor (UVAPF) indicates the level of protection a material provides against UV-A radiation. In this study, indirect band gap, SPF and UVAPF values were studied for undoped, 1%, 2%, 3%, 4%, 5%, and 6% RGO doped TiO2 composite coatings. According to the results, the indirect band gap value of the nanocomposite material decreases from 3.38 eV to 2.98 eV, and the critical wavelength of the absorption spectrum shifts from 314 nm to 331 nm at room temperature when increasing the mass percentage of RGO in the composite material. From the Scanning Electron Microscope (SEM) measurements, the diameter of TiO2 varies from 18.2 nm to 44.3 nm with an average diameter of TiO2 is determined to be 71.3 nm. Undoped TiO2 nanoparticles showed SPF and UVAPF values of 12.5±1.0 and 10.3±1.4, respectively. The UVAPF values for 1%, 2%, 3%, 4%, 5%, and 6% RGO doped TiO2 composite coatings were determined, and the best UVAPF value of 18.3±1.4 was obtained for the 1% RGO doped TiO2 composite coating. The UVAPF value decreases when increasing the mass percentage of RGO in the composite material. To develop a sun protection material, the RGO doped TiO2 composite material was mixed with glycerin solution. The SPF values were evaluated for glycerin solution, TiO2 mixed glycerin solution, and 1% RGO doped TiO2 nano-composite mixed glycerin solution were determined to be 0.970±0.004, 4.01±0.08, and 10.5±1.3, respectively, at 25 °C. The UVAPF values were determined to be 1.13±0.09, 5.97±0.76, and 10.8±0.6, respectively, at 25 °C. This study demonstrated that 1% RGO doped TiO2 composite showed higher UV light protection ability rather than using TiO2 alone.