Displaying publications 21 - 40 of 142 in total

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  1. Ozone-climate interactions and effects on solar ultraviolet radiation
    Bais AF, Bernhard G, McKenzie RL, Aucamp PJ, Young PJ, Ilyas M, et al.
    Photochem Photobiol Sci, 2019 Mar 01;18(3):602-640.
    PMID: 30810565 DOI: 10.1039/c8pp90059k
    This report assesses the effects of stratospheric ozone depletion and anticipated ozone recovery on the intensity of ultraviolet (UV) radiation at the Earth's surface. Interactions between changes in ozone and changes in climate, as well as their effects on UV radiation, are also considered. These evaluations focus mainly on new knowledge gained from research conducted during the last four years. Furthermore, drivers of changes in UV radiation other than ozone are discussed and their relative importance is assessed. The most important of these factors, namely clouds, aerosols and surface reflectivity, are related to changes in climate, and some of their effects on short- and long-term variations of UV radiation have already been identified from measurements. Finally, projected future developments in stratospheric ozone, climate, and other factors affecting UV radiation have been used to estimate changes in solar UV radiation from the present to the end of the 21st century. New instruments and methods have been assessed with respect to their ability to provide useful and accurate information for monitoring solar UV radiation at the Earth's surface and for determining relevant exposures of humans. Evidence since the last assessment reconfirms that systematic and accurate long-term measurements of UV radiation and stratospheric ozone are essential for assessing the effectiveness of the Montreal Protocol and its Amendments and adjustments. Finally, we have assessed aspects of UV radiation related to biological effects and human health, as well as implications for UV radiation from possible solar radiation management (geoengineering) methods to mitigate climate change.
    Matched MeSH terms: Ultraviolet Rays*
  2. Impact of UV radiation on Mxene-mediated tubulin dissociation and mitochondrial apoptosis in breast cancer cells
    Tan EW, Simon SE, Numan A, Khalid M, Tan KO
    Colloids Surf B Biointerfaces, 2024 Mar;235:113793.
    PMID: 38364521 DOI: 10.1016/j.colsurfb.2024.113793
    Breast cancer is a global health concern that requires personalized therapies to prevent relapses, as conventional treatments may develop resistance over time. Photothermal therapy using spectral radiation or intense light emission is a broad-spectrum treatment that induces hyperthermia-mediated cancer cell death. MXene, a two-dimensional material, has been reported to have potential biological applications in photothermal therapy for cancer treatment. In this study, we investigated the apoptotic activity of MXene and UV-irradiated MXene in MCF-7 breast cancer cells by treating them with varying concentrations of MXene. The cytotoxicity of MXene and UV was evaluated by analyzing cellular morphology, nuclei condensation, caspase activation, and apoptotic cell death. We also assessed the effect of the combined treatment on the expression and cellular distribution of Tubulin, a key component of microtubules required for cell division. At low concentrations of MXene (up to 100 µg/ml), the level of cytotoxicity in MCF-7 cells was low. However, the combined treatment of MXene and UV resulted in a synergistic increase in cytotoxicity, causing rounded cellular morphology, condensed nuclei, caspase activation, and apoptotic cell death. Furthermore, the treatment reduced Tubulin protein expression and cellular distribution, indicating a potent inducer of cell death with potential application for cancer treatment. The study demonstrates that the combined treatment of MXene and UVB irradiation is a promising strategy for inducing apoptotic cell death in breast cancer cells, suggesting its potential as a therapeutic intervention for breast cancer.
    Matched MeSH terms: Ultraviolet Rays*
  3. Comparison of UVA vs UVB Photoaging Rat Models in Short-term Exposure
    Mayangsari E, Mustika A, Nurdiana N, Samad NA
    Med Arch, 2024;78(2):88-91.
    PMID: 38566862 DOI: 10.5455/medarh.2024.78.88-91
    BACKGROUND: Prolonged exposure to sunlight is known to induce photoaging of the skin, leading to various skin changes and disorders, such as dryness, wrinkles, irregular pigmentation, and even cancer. Ultraviolet A (UVA) and ultraviolet B (UVB) radiation are particularly responsible for causing photoaging.

    OBJECTIVE: This study aims to identify and compare photoaging rat models exposed to UVA and UVB.

    METHODS: This research method compared macroscopic (scoring degree of wrinkling) and microscopic (histology) signs and symptoms on skin samples of rat exposed to UVA and UVB for 4 weeks at a radiation dose of 840mJ/cm2.

    RESULTS: The results of this study indicated that the degree of wrinkling was highest in rat skin exposed to UVB rays by 51% (p<0.05). UVB histological results showed that the epidermis layer (40 µm, p<0.05) was thickened and the dermis layer (283 µm, p<0.05) was thinned in the skin of mice exposed to UVB light. The UVB group, showed the density of collagen in the dermis with a mean value of 55% (p<0.05).

    CONCLUSION: Our results suggest that short-term exposure to UVB radiation (in the acute, subacute or subchronic phase) induces more rapid and pronounced damage to rat skin when compared to UVA radiation exposure.

    Matched MeSH terms: Ultraviolet Rays/adverse effects
  4. A Novel Optical Complex between an Organic Substrate and a Polyoxometalate. Crystal and Molecular Structure of alpha-H(4)SiW(12)O(40).4HMPA.2H(2)O (HMPA = Hexamethylphosphoramide)
    Niu Jy Jy, You Xz Xz, Duan Cy Cy, Fun Hk Hk, Zhou Zy Zy
    Inorg Chem, 1996 Jul 03;35(14):4211-4217.
    PMID: 11666630
    A solvated complex of alpha-H(4)SiW(12)O(40).4HMPA.2H(2)O composed the heteropolytungstate alpha-H(4)SiW(12)O(40) and the organic substrate hexamethylphosphoramide (HMPA) has been synthesised, purified, and characterized. The electronic spectra (lambda = 220-500 nm) as well as the (1)H NMR spectra for the title compound dissolved in CD(3)CN establish that this complex dissociates into free SiW(12)O(40)(4)(-) and HMPA moieties in solution unless the organic substrate HMPA is present in very high concentrations. The solid reflectance electronic spectra and IR spectra indicate that there is interaction between the alpha-H(4)SiW(12)O(40) and the organic substrate. The complex has no photosensitivity under irradiation of sunlight, but under the near-UV light result in a charge transfer by oxidation of the HMPA and the reduction of the polyoxometalate. Light yellow polyhedrons of the title compound crystallize from the aqueous solvent of acetonitrile and aqueous solution as the formula of alpha-H(4)SiW(12)O(40).4HMPA.2H(2)O in the monoclinic, space group P2(1). The unit cell has a = 12.791(3) Å, b = 22.103(6) Å, c = 15.532(4) Å, beta = 102.860(10) degrees, and Z = 2. From the bond-valence parameters, it was found that the four hydrogen atoms of the polyoxometalate were combined with the N atoms of the four HMPA respectively. The title compound shows a certain second-order and third-order nonlinear optical response of I(2)(omega) = 0.7I(2)(omega)(KDP) and chi((3)) = 2.63 x 10(-)(11) esu, respectively.
    Matched MeSH terms: Ultraviolet Rays
  5. Luminescent polymorphic aggregates of trinuclear Cu(I)-pyrazolate tuned by intertrimeric CuNPy weak coordination bonds
    Zhan SZ, Chen W, Zheng J, Ng SW, Li D
    Dalton Trans, 2021 Jan 18.
    PMID: 33459321 DOI: 10.1039/d0dt03661g
    Five luminescent polymorphic aggregates of trinuclear Cu(i)-pyrazolate, namely [anti-Cu3L3]2 (1), [syn-Cu3L3·C2H5OH]2 (2), [anti-Cu3L3·C2H5OH]n (3), [anti-Cu3L3·0.5C7H8]n (4) and [syn-Cu3L3·C8H10]n (5) (HL = 4-(pyridin-4-ylthio)-3,5-dimethyl-1H-pyrazole), were reported. The trimeric Cu3L3 fragments present syn- and anti-conformations dependent on the dangled direction of 4-pyridyl groups on the two sides of the Cu3Pz3 plane (Pz = pyrazolate). Intertrimeric NPyCu weak coordination bonds associate these Cu3L3 fragments together to form dimeric or polymeric structures, which are further stabilized by crystallized solvent molecules or intertrimeric CuCu interactions. The solvated complexes (3-5) may be transformed into the unsolvated complex 1 by evacuation of the crystallized solvents upon heating. All these complexes emit from green to yellow under UV irradiation, which originated from the triplet excited states of metal to ligand charge transfer (3MLCT) mixed with intertrimeric CuCu interactions. This work provides a novel kind of supramolecular aggregate based on Cu3Pz3 beyond the classical π-acidbase adducts and metallophilicity-dependent dimers/oligomers.
    Matched MeSH terms: Ultraviolet Rays
  6. Bacterial disinfection and cell assessment post ultraviolet-C LED exposure for wound treatment
    Sheikh J, Swee TT, Saidin S, Yahya AB, Malik SA, Yin JSS, et al.
    Med Biol Eng Comput, 2021 May;59(5):1055-1063.
    PMID: 33866479 DOI: 10.1007/s11517-021-02360-8
    Ultraviolet-C sourced LED (UVC-LED) has been widely used for disinfection purposes due to its germicidal spectrum. In this study, the efficiencies of UVC-LED for Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus) disinfections were investigated at three exposure distances (1, 1.5, and 2 cm) and two exposure times (30 and 60 s). The respective bacterial inhibition zones were measured, followed by a morphological analysis under SEM. The viabilities of human skin fibroblast cells were further evaluated under the treatment of UVC-LED with the adoption of aforesaid exposure parameters. The inhibition zones were increased with the increment of exposure distances and times. The highest records of 5.40 ± 0.10 cm P. aeruginosa inhibition and 5.43 ± 0.11 cm S. aureus inhibition were observed at the UVC-LED distance of 2 cm and 60-s exposure. Bacterial physical damage with debris formation and reduction in size were visualized following the UVC-LED exposures. The cell viability percentages were in a range of 75.20-99.00% and 82-100.00% for the 30- and 60-s exposures, respectively. Thus, UVC-LED with 275-nm wavelength is capable in providing bacterial disinfection while maintaining accountable cell viability which is suitable to be adopted in wound treatment. Bacterial disinfection and human skin fibroblast cell assessment using UVC-LED.
    Matched MeSH terms: Ultraviolet Rays
  7. Fulltext Browning assessment methods and polyphenol oxidase in UV-C irradiated Berangan banana fruit
    Phebe, Ding, Yap, Shi Ling
    International Food Research Journal, 2014;21(4):1667-1674.
    MyJurnal
    Ultraviolet (UV) light especially UV-C has been used to sterilize fruits and vegetables. However, overdose of UV-C irradiation could cause brownish-red colouration to products such as banana fruit. Therefore, the objectives of this study were to: (1) examine the effect of UV-C irradiation at different doses on the surface colour of Berangan banana fruit during ripening; (2) determine polyphenol oxidase (PPO) activity after irradiated with different doses of UV-C, and (3) examine the effectiveness of three browning assessment methods (subjective score, browning index derived from Lab colour space and optical density of 420 nm) in response to PPO activity of UV-C irradiated Berangan banana fruit. Mature green Berangan banana fruit were irradiated with 0, 0.01, 0.02, 0.03 and 0.04 kJ/m2 UV-C. After irradiation, the fruit were initiated to ripening using 1 mL/L ethylene for 24 h. Then, the fruit were allowed to ripen in 27oC and fruit of day 0, 1, 3 and 5 were sampled for peel colour (L*, a*, b*, C* and ho), browning assessment (three methods) and PPO assay. The peel colour, browning assessment using subjective score and optical density, and PPO activity of Berangan banana fruit were affected significantly (P ≤ 0.05) by interaction of radiation dose x ripening day. The values of L*, b*, C* and ho decrease while a* values increase as fruit irradiated with 0.03 and 0.04 kJ/m2 UV-C indicating brownish-red has occurred. Fruit irradiated with 0.04 kJ/m2 UV-C discoloured by ripening day 3 while those irradiated with 0.03 kJ/m2 discolored by day 5. Similar result was obtained when fruit assessed for its browning using subjective score and optical density. A contrary result was obtained in PPO activity where UV-C irradiation has inhibited Berangan banana fruit PPO activity by ripening day 5. Correlation analysis showed that browning index that derived from colour space is highly related to PPO activity with coefficients of 0.93. As conclusion, the lethal dose causing browning for Berangan banana fruit is 0.03 kJ/m2 and browning index that derived from colour space is most effective to correlate browning with PPO activity.
    Matched MeSH terms: Ultraviolet Rays
  8. Fulltext Light transmission through UV coated contact lenses
    Bariah Mohd Ali, Goh, E.H.
    Jurnal Sains Kesihatan Malaysia, 2005;3(2):1-8.
    MyJurnal
    The objective of this study was to determine the efficiency of UV blocking monomers in contact lenses in providing eye protection from UV radiation. The spectral transmission of 8 contact lenses (7 soft contact lenses: Precision UV, Acuvue 2, Surevue, Omega, Encore UV, Durasoft 3 and Lunelle UV and 1 rigid gas permeable contact lens: Boston 7) was evaluated by using a dual beam spectrophotometer. Durasoft 3, a non UV absorbent contact lens was used as the control. The results showed that Precision UV contact lens absorbed UV light up to wavelength of 380 nm, whereas Acuvue 2 and Surevue absorbed up to 360 nm only. Omega, Encore UV and Lunelle UV lenses absorbed UV light up to 335 nm with spectral transmission of Lunelle UV being the highest among all soft contact lenses tested, which was 17%. Boston 7 could absorb UV light up to 385 nm, but the amount of UV light transmitted was higher than soft lenses, which was 30%. Durasoft 3 only blocked UV light at 200-245 nm. Precision UV lens had better UV blocker characteristics than the other contact lenses tested. UV blocking soft contact lenses could be an alternative for spectacles in protecting internal ocular structures from UV radiation.
    Matched MeSH terms: Ultraviolet Rays
  9. Fulltext The effect of storage on the quality attributes of ultraviolet-irradiated and thermally pasteurised pineapple juices
    Chia, S. L., Rosnah, S., Noranizan, M. A., Wan Ramli, W. D.
    International Food Research Journal, 2012;19(3):1001-1010.
    MyJurnal
    The effect of storage time on the quality of ultraviolet-irradiated and thermally pasteurised pineapple juice was evaluated. The juices were irradiated with ultraviolet light (UV-C) at wavelength 254 nm (53.42 mJ/cm2, 4.918 s), thermally pasteurised at 800C for 10 minutes and stored at 40C for 13 weeks. There were significant changes in the total soluble solids, pH, titratable acidity and turbidity of UV-irradiated juice during storage, whereas for the same quality attributes of thermally pasteurised juice remained stable throughout the storage time. There were no significant changes in total phenolics for both treatments throughout the storage period. Other quality parameters (ascorbic acid, colour L, hue angle and chroma) were significantly affected by the storage time. Regarding the microbiological analysis, the total plate counts and yeast and mould counts of the UV-irradiated juice increased gradually throughout the 13 weeks of storage while these parameters remained unchanged in the thermally pasteurised juice with almost no microorganism growth. UV-irradiated pineapple juice preserved better quality attributes (TSS, pH, titratable acidity, ascorbic acid, turbidity, total phenolic, L (lightness), hue angle and chroma) than the thermal pasteurised juice during the storage time. Hence, UV irradiation has great potential as an alternative technology to thermal pasteurisation in producing products of high nutritive values.
    Matched MeSH terms: Ultraviolet Rays
  10. Exploring the relationship between molecular structure of dyes and light sources for photodegradation and electricity generation in photocatalytic fuel cell
    Lee SL, Ho LN, Ong SA, Wong YS, Voon CH, Khalik WF, et al.
    Chemosphere, 2018 Oct;209:935-943.
    PMID: 30114743 DOI: 10.1016/j.chemosphere.2018.06.157
    Reactive green 19, acid orange 7 and methylene blue are employed as the organic pollutants in this work. A photocatalytic fuel cell is constructed based on the idea of immobilizing zinc oxide onto zinc photoanode and platinum loaded carbon cathode, both evaluated under sunlight and ultraviolet irradiation, respectively. Influence of light and dye structures on the performance of photocatalytic fuel cell are examined. With reactive green 19, 93% and 86% of color removal are achieved after 8 h of photocatalytic fuel cell treatment under sunlight and ultraviolet irradiation, respectively. The decolorization rate of diazo reactive green 19 is higher than acid orange 7 (monoazo dye) when both dyes are treated by photocatalytic fuel cell under sunlight and ultraviolet irradiation, as the electron releasing groups (-NH-triazine) allow reactive green 19 easier to be oxidized. Comparatively, acid orange 7 is less favorable to be oxidized. The degradation of methylene blue is enhanced under sunlight irradiation due to the occurrence of self-sensitized photodegradation. When methylene blue is employed in the photocatalytic fuel cell under sunlight irradiation, the short circuit current (0.0129 mA cm-2) and maximum power density (0.0032 mW cm-2) of photocatalytic fuel cell greatly improved.
    Matched MeSH terms: Ultraviolet Rays
  11. Development of the compact UV illuminator with single UV lamp
    Lee DJ, Kim SY, Kim JD, Kim YS, Song HJ, Park CY
    Sains Malaysiana, 2015;44:1693-1699.
    This paper presents a low-cost method of constructing the compact UV illuminator, which is considered as an important
    component of a gel documentation system. The procedure involves using a smallest-possible UV lamp and a motor which
    moves the UV lamp in the UV illuminator instead of conventional 4 UV lamps. A comparative analysis of images produced
    by using the commercial gel documentation system and our prototype was carried out. These comparisons were done
    in real DNA gel as well as a reference plate made of quantum dot. The plate was composed of the chambers filled with
    various densities of the quantum dot instead of the Agarose gel containing the ETBR in order to increase the accuracy of
    comparison and the convenience of experiments. Despite the use of only 1 UV lamp, the proposed system demonstrated
    a similar imaging performance compared with the conventional gel documentation system equipped with 4 UV lamps,
    resulting in the great reduction of the system cost.
    Matched MeSH terms: Ultraviolet Rays
  12. Fulltext Experimental relationships between surface roughness, irradiation time and photodecomposition rate constant of pvc films doped by polyphosphates
    Yousif, Emad, Ahmed, Dina S., Ahmed, Ahmed A., Hameed, Ayad S., Yusop, Rahimi M., Redwan, Amamer, et al.
    Science Letters, 2018;12(2):19-27.
    MyJurnal
    The photodegradation rate constant and surface morphology of poly(vinyl chloride), upon irradiation with ultraviolet light was investigated in the presence of polyphosphates as photostabilizers. Poly(vinyl chloride) photodegradation rate constant was lower for the films containing polyphosphates compared to the blank film. In addition, the surface morphology of the irradiated poly(vinyl chloride) containing polyphosphates, examined by scanning electron microscopy, indicates that the surface was much smoother compared to the blank film.
    Matched MeSH terms: Ultraviolet Rays
  13. Fulltext Enhancement of astaxanthin accumulation using black light in Coelastrum and Monoraphidium isolated from Malaysia
    Kaha M, Iwamoto K, Yahya NA, Suhaimi N, Sugiura N, Hara H, et al.
    Sci Rep, 2021 06 03;11(1):11708.
    PMID: 34083633 DOI: 10.1038/s41598-021-91128-z
    Microalgae are important microorganisms which produce potentially valuable compounds. Astaxanthin, a group of xanthophyll carotenoids, is one of the most powerful antioxidants mainly found in microalgae, yeasts, and crustaceans. Environmental stresses such as intense light, drought, high salinity, nutrient depletion, and high temperature can induce the accumulation of astaxanthin. Thus, this research aims to investigate the effect of black light, also known as long-wave ultraviolet radiation or UV-A, as a stressor on the accumulation of astaxanthin as well as to screen the antioxidant property in two tropical green algal strains isolated from Malaysia, Coelastrum sp. and Monoraphidium sp. SP03. Monoraphidium sp. SP03 showed a higher growth rate (0.66 day-1) compared to that of Coelastrum sp. (0.22 day-1). Coelastrum sp. showed significantly higher accumulation of astaxanthin in black light (0.999 g mL culture-1) compared to that in control condition (0.185 g mL-1). Similarly, Monoraphidium sp. SP03 showed higher astaxanthin content in black light (0.476 g mL culture-1) compared to that in control condition (0.363 g mL culture-1). Coelastrum sp. showed higher scavenging activity (30.19%) when cultured in black light condition, indicating a correlation between the antioxidant activity and accumulation of astaxanthin. In this study, black light was shown to possess great potential to enhance the production of astaxanthin in microalgae.
    Matched MeSH terms: Ultraviolet Rays
  14. Fabrication, characterization, and application of BiOI@ZIF-8 nanocomposite for enhanced photocatalytic degradation of acetaminophen from aqueous solutions under UV-vis irradiation
    Mengting Z, Duan L, Zhao Y, Song Y, Xia S, Gikas P, et al.
    J Environ Manage, 2023 Nov 01;345:118772.
    PMID: 37597373 DOI: 10.1016/j.jenvman.2023.118772
    This work investigates the use of novel BiOI@ZIF-8 nanocomposite for the removal of acetaminophen (Ace) from synthetic wastewater. The samples were analyzed using FTIR, XRD, XPS, DRS, PL, FESEM-EDS, and ESR techniques. The effects of the loading capacity of ZIF-8 on the photocatalytic oxidation performance of bismuth oxyiodide (BiOI) were studied. The photocatalytic degradation of Ace was maximized by optimizing pH, reaction time and the amount of photocatalyst. On this basis, the removal mechanisms of the target pollutant by the nanocomposite and its photodegradation pathways were elucidated. Under optimized conditions of 1 g/L of composite, pH 6.8, and 4 h of reaction time, it was found that the BiOI@ZIF-8 (w/w = 1:0.01) nanocomposite exhibited the highest Ace removal (94%), as compared to that of other loading ratios at the same Ace concentration of 25 mg/L. Although this result was encouraging, the treated wastewater still did not satisfy the required statutory of 0.2 mg/L. It is suggested that the further biological processes need to be adopted to complement Ace removal in the samples. To sustain its economic viability for wastewater treatment, the spent composite still could be reused for consecutive five cycles with 82% of regeneration efficiency. Overall, this series of work shows that the nanocomposite was a promising photocatalyst for Ace removal from wastewater samples.
    Matched MeSH terms: Ultraviolet Rays
  15. Fulltext N95 respirator hybrid decontamination method using Ultraviolet Germicidal Irradiation (UVGI) coupled with Microwave-Generated Steam (MGS)
    Gopalan T, Muhamad MR, Wai Hoe VC, Hassandarvish P
    PLoS One, 2024;19(2):e0296871.
    PMID: 38319932 DOI: 10.1371/journal.pone.0296871
    The Coronavirus Disease 2019 (COVID-19) pandemic has induced a critical supply of personal protective equipment (PPE) especially N95 respirators. Utilizing respirator decontamination procedures to reduce the pathogen load of a contaminated N95 respirator can be a viable solution for reuse purposes. In this study, the efficiency of a novel hybrid respirator decontamination method of ultraviolet germicidal irradiation (UVGI) which utilizes ultraviolet-C (UV-C) rays coupled with microwave-generated steam (MGS) against feline coronavirus (FCoV) was evaluated. The contaminated 3M 1860 respirator pieces were treated with three treatments (UVGI-only, MGS-only, and Hybrid-UVGI + MGS) with variable time. The virucidal activity was evaluated using the TCID50 method. The comparison of decontamination efficiency of the treatments indicated that the hybrid method achieved at least a pathogen log reduction of 4 logs, faster than MGS and UVGI. These data recommend that the proposed hybrid decontamination system is more effective comparatively in achieving pathogen log reduction of 4 logs.
    Matched MeSH terms: Ultraviolet Rays
  16. Fulltext Vacuum ultraviolet field emission lamp consisting of neodymium ion doped lutetium fluoride thin film as phosphor
    Yanagihara M, Tsuji T, Yusop MZ, Tanemura M, Ono S, Nagami T, et al.
    ScientificWorldJournal, 2014;2014:309091.
    PMID: 25302320 DOI: 10.1155/2014/309091
    A vacuum ultraviolet (VUV) field emission lamp was developed by using a neodymium ion doped lutetium fluoride (Nd(3+) : LuF3) thin film as solid-state phosphor and carbon nanofiber field electron emitters. The thin film was synthesized by pulsed laser deposition and incorporated into the lamp. The cathodoluminescence spectra of the lamp showed multiple emission peaks at 180, 225, and 255 nm. These emission spectra were in good agreement with the spectra reported for the Nd(3+) : LuF3 crystal. Moreover, application of an acceleration voltage effectively increased the emission intensity. These results contribute to the performance enhancement of the lamp operating in the VUV region.
    Matched MeSH terms: Ultraviolet Rays
  17. Fulltext Influence of Solvents' Polarity on the Physicochemical Properties and Photocatalytic Activity of Titania Synthesized Using Deinbollia pinnata Leaves
    Rufai Y, Chandren S, Basar N
    Front Chem, 2020;8:597980.
    PMID: 33344417 DOI: 10.3389/fchem.2020.597980
    Nanotechnology is one of the most interesting areas of research due to its flexibility to improve or form new products from nanoparticles (NPs), and as a fast, greener, more eco-friendly and sustainable solution to technological and environmental challenges. Among metal oxides of photocatalytic performance, the use of titania (TiO2) as photocatalyst is most popular due to its unique optical and electronic properties. Despite the wide utilization, the synthesis of TiO2 NPs bears many disadvantages: it utilizes various less environmental-friendly chemicals, high cost, requires high pressure and energy, and potentially hazardous physical and chemical methods. Hence, the development of green synthesis approach with eco-friendly natural products can be used to overcome these adverse effects. In this work, TiO2 NPs have been prepared by using Deinbollia pinnata leaves extracts, obtained by different solvents (n-hexane, ethyl acetate, and ethanol) with different polarities. The extracts acted as the reducing agent, while titanium isopropoxide as the precursor and water as the solvent. X-ray diffraction (XRD) pattern confirmed the synthesized TiO2 consist of anatase phase in high purity, with average crystallite size in the range of 19-21 nm. Characterization by using field emission scanning electron microscopy (FESEM) showed the TiO2 NPs possess a uniform semi-spherical shape in the size range of 33-48 nm. The energy dispersive X-ray (EDX) spectra of green TiO2 NPs showed two peaks for the main elements of Ti (61 Wt.%) and O (35 Wt.%). The band-gap energy of 3.2 eV was determined using UV-Vis spectroscopy. From the nitrogen sorption analysis, type V isotherm of the material was obtained, with BET surface area of 31.77 m2/g. The photocatalytic activity of synthesized TiO2 was evaluated for photodegradation of methyl orange (MO) under UV light irradiation. Based on the results, it is shown that TiO2 NPs synthesized with D. pinnata leaves extracted using ethyl acetate showed the most effective photodegradation performance, achieving 98.7% of MO conversion within 150 min. It can be concluded that the use of plant extracts in synthesis with TiO2 managed to produce highly crystalline anatase TiO2 with superior photocatalytic activity in the photodegradation of organic dye.
    Matched MeSH terms: Ultraviolet Rays
  18. Fulltext Preparation and Characterization of Low-Molecular-Weight Natural Rubber Latex via Photodegradation Catalyzed by Nano TiO₂
    Ibrahim S, Othman N, Sreekantan S, Tan KS, Mohd Nor Z, Ismail H
    Polymers (Basel), 2018 Nov 01;10(11).
    PMID: 30961141 DOI: 10.3390/polym10111216
    Natural rubber is one of the most important renewable biopolymers used in many applications due to its special properties that cannot be easily mimicked by synthetic polymers. To sustain the existence of natural rubber in industries, modifications have been made to its chemical structure from time to time in order to obtain new properties and to enable it to be employed in new applications. The chemical structure of natural rubber can be modified by exposure to ultraviolet light to reduce its molecular weight. Under controlled conditions, the natural rubber chains will be broken by photodegradation to yield low-molecular-weight natural rubber. The aim of this work was to obtain what is known as liquid natural rubber via photodegradation, with titanium dioxide nanocrystals as the catalyst. Titanium dioxide, which was firstly synthesized using the sol⁻gel method, was confirmed to be in the form of an anatase, with a size of about 10 nm. In this work, the photodegradation was carried out in latex state and yielded low-molecular-weight natural rubber latex of less than 10,000 g/mol. The presence of hydroxyl and carbonyl groups on the liquid natural rubber (LNR) chains was observed, resulting from the breaking of the chains. Scanning electron microscopy of the NR latex particles showed that titanium dioxide nanocrystals were embedded on the latex surface, but then detached during the degradation reaction.
    Matched MeSH terms: Ultraviolet Rays
  19. Fulltext Mechanisms of removal of heavy metal ions by ZnO particles
    Le AT, Pung SY, Sreekantan S, Matsuda A, Huynh DP
    Heliyon, 2019 Apr;5(4):e01440.
    PMID: 31008388 DOI: 10.1016/j.heliyon.2019.e01440
    Effluent discharges from industry and domestic waste containing unknown inorganic pollutants. In this work, different mechanisms of heavy metal ions removal using ZnO particles were studied. ZnO particles were synthesized using solid precipitation technique. The morphology of ZnO particles was rod-like shape. The average length and diameter of ZnO particle were 497.34 ± 15.55 and 75.78 ± 10.39nm, respectively. These particles removed effectively heavy metal ions such as Cu(II), Ag(I) and Pb(II) ions with efficiency >85% under exposure of 1 hour of UV light. However, poor removal efficiency, i.e. <15% was observed for Cr(VI), Mn(II), Cd(II) and Ni(II) ions. The removal of these heavy metal ions was in the forms of metals or metal oxide via reduction/oxidation or adsorption mechanism.
    Matched MeSH terms: Ultraviolet Rays
  20. Formation of grassy TiO2 nanotube thin film by anodisation in peroxide electrolyte for Cr(VI) removal under ultraviolet radiation
    Taib MAA, Alias N, Jaafar M, Razak KA, Tan WK, Shahbudin IP, et al.
    Nanotechnology, 2020 Oct 23;31(43):435605.
    PMID: 32640434 DOI: 10.1088/1361-6528/aba3d8
    Arrays of TiO2 nanotubes (TiO2 NTs) with grassy surfaces were observed on titanium foil anodised at 60 V in fluorinated ethylene glycol (EG) with added hydrogen peroxide (H2O2). The grassy surface was generated by the chemical etching and dissolution of the surface of the TiO2 NTs walls, which was accelerated by the temperature increase on the addition of H2O2 . Upon annealing at 600 °C, the grassy part of the TiO2 NTs was found to consist of mostly anatase TiO2 whereas the bottom part of the anodic oxide comprised a mixture of anatase and rutile TiO2. The TiO2 NTs were then used to reduce hexavalent chromium (Cr(VI)) under ultraviolet radiation. They exhibited a rather efficient photocatalytic effect, with 100% removal of Cr(VI) after 30 min of irradiation. The fast removal of Cr(VI) was due to the anatase dominance at the grassy part of the TiO2 NTs as well as the higher surface area the structure may have. This work provides a novel insight into the photocatalytic reduction of Cr(VI) on grassy anatase TiO2 NTs.
    Matched MeSH terms: Ultraviolet Rays
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