Effect of the Surface Morphology of TiO<sub>2</sub> Nanotubes on Photocatalytic Efficacy Using Electron-Transfer-Based Assays and Antimicrobial Tests
The application of titanium oxide nanotubes for the removal of contaminants from freshwater is a rapidly growing scientific interest, especially when it comes to water conservation strategies. In this study we employed four different titanium oxide nanotube surfaces, prepared by a two-electrode anod...
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MDPI AG
2020-07-01
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| Online Access: | https://www.mdpi.com/2076-3417/10/15/5243 |
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| author | Frederick Lia Clayton Farrugia Maria Antonietta Buccheri Giancarlo Rappazzo Edwin Zammit Alex Rizzo Maurice Grech Paul Refalo Stephen Abela |
| author_facet | Frederick Lia Clayton Farrugia Maria Antonietta Buccheri Giancarlo Rappazzo Edwin Zammit Alex Rizzo Maurice Grech Paul Refalo Stephen Abela |
| author_sort | Frederick Lia |
| collection | DOAJ |
| description | The application of titanium oxide nanotubes for the removal of contaminants from freshwater is a rapidly growing scientific interest, especially when it comes to water conservation strategies. In this study we employed four different titanium oxide nanotube surfaces, prepared by a two-electrode anodic oxidation. Two of the surfaces were synthesised in aqueous media, while the other two surfaces were synthesised in ethylene glycol. One of the arrays synthesised in the organic medium was impregnated with silver nanoparticles, while the remaining surfaces were not. The chemical reactivity of the various surfaces was assessed using 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) as free electron sensitive probe molecules, in parallel with tannic acid degradation and copper ion reducing capacity. The potential antimicrobial activity of the surfaces was assessed against a panel of microorganisms composed of yeast, fungi, Gram-positive and Gram-negative bacteria. Field emission scanning electron microscopy revealed that surfaces produced in the aqueous medium had a smaller tube length and a smaller tube diameter. It was noted that one of the materials using sodium sulfate as the supporting electrolyte had the most irregular nanostructure morphology with tubes growing to the side rather than vertically. The structural variation of the surfaces directly reflected both the chemical and biological activity, with the nanotubes formed in ethylene glycol showing the fastest rates in the stabilization of DPPH and ABTS radicals, the fastest tannic acid decomposition under various pH conditions and the fastest metal reducing activity. Furthermore, the surface containing silver and its bare counterpart showed the most effective antimicrobial activity, removing approximately 82% of Gram-negative bacteria, 50% of Gram-positive bacteria, 70% of yeast and 40% of fungi, with Gram-negative bacteria being the most susceptible to these surfaces. |
| first_indexed | 2024-03-10T18:07:03Z |
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| language | English |
| last_indexed | 2024-03-10T18:07:03Z |
| publishDate | 2020-07-01 |
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| series | Applied Sciences |
| spelling | doaj.art-a65c0a4dd2984035bc466bf8979be4812023-11-20T08:25:46ZengMDPI AGApplied Sciences2076-34172020-07-011015524310.3390/app10155243Effect of the Surface Morphology of TiO<sub>2</sub> Nanotubes on Photocatalytic Efficacy Using Electron-Transfer-Based Assays and Antimicrobial TestsFrederick Lia0Clayton Farrugia1Maria Antonietta Buccheri2Giancarlo Rappazzo3Edwin Zammit4Alex Rizzo5Maurice Grech6Paul Refalo7Stephen Abela8Applied Research & Innovation Centre, Malta College of Arts, Science & Technology MCAST, 9032 Paola, MaltaFaculty of Engineering, University of Malta, 2080 Msida, MaltaDepartment of Biological, Geological and Environmental Sciences, University of Catania, 95124 Catania, ItalyDepartment of Biological, Geological and Environmental Sciences, University of Catania, 95124 Catania, ItalyApplied Research & Innovation Centre, Malta College of Arts, Science & Technology MCAST, 9032 Paola, MaltaApplied Research & Innovation Centre, Malta College of Arts, Science & Technology MCAST, 9032 Paola, MaltaFaculty of Engineering, University of Malta, 2080 Msida, MaltaFaculty of Engineering, University of Malta, 2080 Msida, MaltaFaculty of Engineering, University of Malta, 2080 Msida, MaltaThe application of titanium oxide nanotubes for the removal of contaminants from freshwater is a rapidly growing scientific interest, especially when it comes to water conservation strategies. In this study we employed four different titanium oxide nanotube surfaces, prepared by a two-electrode anodic oxidation. Two of the surfaces were synthesised in aqueous media, while the other two surfaces were synthesised in ethylene glycol. One of the arrays synthesised in the organic medium was impregnated with silver nanoparticles, while the remaining surfaces were not. The chemical reactivity of the various surfaces was assessed using 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) as free electron sensitive probe molecules, in parallel with tannic acid degradation and copper ion reducing capacity. The potential antimicrobial activity of the surfaces was assessed against a panel of microorganisms composed of yeast, fungi, Gram-positive and Gram-negative bacteria. Field emission scanning electron microscopy revealed that surfaces produced in the aqueous medium had a smaller tube length and a smaller tube diameter. It was noted that one of the materials using sodium sulfate as the supporting electrolyte had the most irregular nanostructure morphology with tubes growing to the side rather than vertically. The structural variation of the surfaces directly reflected both the chemical and biological activity, with the nanotubes formed in ethylene glycol showing the fastest rates in the stabilization of DPPH and ABTS radicals, the fastest tannic acid decomposition under various pH conditions and the fastest metal reducing activity. Furthermore, the surface containing silver and its bare counterpart showed the most effective antimicrobial activity, removing approximately 82% of Gram-negative bacteria, 50% of Gram-positive bacteria, 70% of yeast and 40% of fungi, with Gram-negative bacteria being the most susceptible to these surfaces.https://www.mdpi.com/2076-3417/10/15/5243titanium oxidenanotubesDPPHABTSCUPRACantimicrobial activity |
| spellingShingle | Frederick Lia Clayton Farrugia Maria Antonietta Buccheri Giancarlo Rappazzo Edwin Zammit Alex Rizzo Maurice Grech Paul Refalo Stephen Abela Effect of the Surface Morphology of TiO<sub>2</sub> Nanotubes on Photocatalytic Efficacy Using Electron-Transfer-Based Assays and Antimicrobial Tests Applied Sciences titanium oxide nanotubes DPPH ABTS CUPRAC antimicrobial activity |
| title | Effect of the Surface Morphology of TiO<sub>2</sub> Nanotubes on Photocatalytic Efficacy Using Electron-Transfer-Based Assays and Antimicrobial Tests |
| title_full | Effect of the Surface Morphology of TiO<sub>2</sub> Nanotubes on Photocatalytic Efficacy Using Electron-Transfer-Based Assays and Antimicrobial Tests |
| title_fullStr | Effect of the Surface Morphology of TiO<sub>2</sub> Nanotubes on Photocatalytic Efficacy Using Electron-Transfer-Based Assays and Antimicrobial Tests |
| title_full_unstemmed | Effect of the Surface Morphology of TiO<sub>2</sub> Nanotubes on Photocatalytic Efficacy Using Electron-Transfer-Based Assays and Antimicrobial Tests |
| title_short | Effect of the Surface Morphology of TiO<sub>2</sub> Nanotubes on Photocatalytic Efficacy Using Electron-Transfer-Based Assays and Antimicrobial Tests |
| title_sort | effect of the surface morphology of tio sub 2 sub nanotubes on photocatalytic efficacy using electron transfer based assays and antimicrobial tests |
| topic | titanium oxide nanotubes DPPH ABTS CUPRAC antimicrobial activity |
| url | https://www.mdpi.com/2076-3417/10/15/5243 |
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