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Photocatalytic Thin Films
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Photocatalytic Thin Films

A special issue of Coatings (ISSN 2079-6412). This special issue belongs to the section "Thin Films".

Deadline for manuscript submissions: closed (30 September 2020) | Viewed by 53476

Special Issue Editor

Prof. Dr. Carlos Jose Macedo Tavares

E-Mail Website
Guest Editor
Physics Centre of the Minho and Porto Universities (CF-UM-PT), University of Minho, Campus Azurem, 4804-533 Guimaraes, Portugal
Interests: photocatalysis; metal-oxide thin films; PVD deposition techniques
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

We would like to invite you to submit your work to this Special Issue on “Photocatalytic Thin Films”. Photocatalytic and superhydrophilic materials for applications in self-cleaning windows, anti-fogging lenses, antimicrobial surfaces, water-splitting, and air purification have gained considerable interest throughout the last two decades, with industrial and academic R&D being undertaken. Despite more than 100,000 publications on the foremost photocatalyst, TiO2, there are a multitude of production and testing techniques employed, often resulting in conflicting results and claims. Despite the fact that photocatalytic thin films have a lower specific surface area when compared to photocatalysts synthesized by a chemical route (e.g., nanoparticles and nanotubes), thin films have other properties that compensate this shortcoming, such as large-surface homogeneity, optical transmittance for self-cleaning window aplications, better control of film stoichiometry and impurities (which impacts favorably on hindering electron–hole recombination), and reprodicibility. Conventional powder photocatalysts normally require post-treatment separation in a slurry system. This can be overcome by immobilizing photocatalytic particles as thin films on a solid substrate. Moreover, thin film deposition by physical methods are more environmentally friendly due to the uncessecity of hazardous chemicals.

In particular, the topic of interest regarding photocatalytic thin films includes, but is not limited to:

  • Biomedical applications including antimicrobial;
  • Self-cleaning surfaces;
  • Environmental applications including water and air purification;
  • Assessement of photocatalytic activity;
  • Thin film bulk and surface characterisation;
  • Approaches towards standardisation;
  • Thin film chemical and physical deposition techniques;
  • Industrial applications and scale-up;
  • Alternative materials and emerging technologies.

Prof. Dr. Carlos Jose Macedo Tavares
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Coatings is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (12 papers)

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Research

Jump to: Review

20 pages, 5888 KiB  
Article
On the Role of γ-Fe2O3 Nanoparticles and Reduced Graphene Oxide Nanosheets in Enhancing Self-Cleaning Properties of Composite TiO2 for Cultural Heritage Protection
by Maryam Mokhtarifar, Reyhaneh Kaveh, Marco Ormellese, Mojtaba Bagherzadeh, Maria Vittoria Diamanti and MariaPia Pedeferri
Coatings 2020, 10(10), 933; https://doi.org/10.3390/coatings10100933 - 29 Sep 2020
Cited by 5 | Viewed by 2889
Abstract
The durability of novel metallic artifacts and buildings is an open issue, and the role of smart protecting coatings in extending these artifacts’ lifetimes is crucial. In this paper, the role of γ-Fe2O3 nanoparticles and reduced graphene oxide (rGO) nanosheets [...] Read more.
The durability of novel metallic artifacts and buildings is an open issue, and the role of smart protecting coatings in extending these artifacts’ lifetimes is crucial. In this paper, the role of γ-Fe2O3 nanoparticles and reduced graphene oxide (rGO) nanosheets on enhancing the self-cleaning properties of composite TiO2 films and reducing metal alterations due to contact with acid rain and pollutants is investigated. The photocatalytic assessment of the TiO2 based films indicates that there are optimum contents for γ-Fe2O3 and rGO, which confer the film lower bandgap and tune the TiO2 anatase/rutile ratio. By adding a proper content of γ-Fe2O3, wettability is reduced both in dark and under illumination, which could be related to higher roughness. γ-Fe2O3 overloading causes increasing crack density and eventually a fully cracked structure. Adding an appropriate amount of rGO causes a sharp increase in roughness, due to the stacking of rGO nanosheets, while simultaneously avoiding cracking. At higher contents of rGO, wettability further decreases due to higher amounts of hydroxyl groups bound onto rGO; also in this case, overloading causes film cracking. Evaluation of self-cleaning performance and discoloration resistance under soiling and acid rain simulated tests demonstrates that proper loadings of γ-Fe2O3 and rGO present higher efficiency thanks to higher superhydrophilic tendency and higher photocatalytic activities, as well as an efficient barrier effect. Full article
(This article belongs to the Special Issue Photocatalytic Thin Films)
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17 pages, 4501 KiB  
Article
Photocatalytic Properties of g-C3N4–Supported on the SrAl2O4:Eu,Dy/SiO2
by Shielah Mavengere and Jung-Sik Kim
Coatings 2020, 10(10), 917; https://doi.org/10.3390/coatings10100917 - 24 Sep 2020
Cited by 10 | Viewed by 3043
Abstract
Graphitic carbon nitride (g-C3N4) was supported on SrAl2O4:Eu,Dy-SiO2 by a colloidal-sol coating method to improve its light absorption property. Transmission electron microscopy (TEM) revealed that the nanoparticles of g-C3N4 were coated [...] Read more.
Graphitic carbon nitride (g-C3N4) was supported on SrAl2O4:Eu,Dy-SiO2 by a colloidal-sol coating method to improve its light absorption property. Transmission electron microscopy (TEM) revealed that the nanoparticles of g-C3N4 were coated on sub-micron phosphor particles and nanoscale surface roughness was imparted by the SiO2-binder. Photoluminescence (PL) spectrum of the g-C3N4 supported on SrAl2O4:Eu,Dy exhibited a broadband emission from 400 to 650 nm. Increasing silica-binder in the g-C3N4/SrAl2O4:Eu,Dy composites suppressed the PL emission peak at 525 nm for SrAl2O4:Eu,Dy. Photocatalytic degradation activity was evaluated with 5 ppm methylene blue (MB) solutions under germicidal ultraviolet (UV) and visible (Vis) solar light illuminations. The UV/Vis photocatalytic efficiency was improved by supporting g-C3N4 on the SrAl2O4:Eu,Dy phosphor and with the addition of SiO2 as a binder. In addition, low silica addition effectively improved the adhesiveness of the g-C3N4 coating on the SrAl2O4:Eu,Dy surface. Recyclability tests of photocatalysis for the SrAl2O4:Eu,Dy-0.01M SiO2/50wt% g-C3N4 composites exhibited a remarkable stability by maintaining the degradation efficiencies above 90% in four cycles. Therefore, the composite of g-C3N4-supported SrAl2O4:Eu,Dy-SiO2 is a prospective photocatalyst activating under UV/Vis light irradiation for the elimination of environmental pollutants. Full article
(This article belongs to the Special Issue Photocatalytic Thin Films)
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11 pages, 5112 KiB  
Article
Photocatalytic Bi2O3/TiO2:N Thin Films with Enhanced Surface Area and Visible Light Activity
by Luís P. Dias, Filipe C. Correia, Joana M. Ribeiro and Carlos J. Tavares
Coatings 2020, 10(5), 445; https://doi.org/10.3390/coatings10050445 - 01 May 2020
Cited by 9 | Viewed by 3114
Abstract
Bi2O3 nanocone films functionalized with an overlayer of TiO2 were deposited by d.c. reactive magnetron sputtering. The aforementioned nanocone structures were formed via a vapour-liquid-solid (VLS) growth, starting from a catalytic bismuth seed layer. The resultant nanocones exhibit an [...] Read more.
Bi2O3 nanocone films functionalized with an overlayer of TiO2 were deposited by d.c. reactive magnetron sputtering. The aforementioned nanocone structures were formed via a vapour-liquid-solid (VLS) growth, starting from a catalytic bismuth seed layer. The resultant nanocones exhibit an improved surface area, measured by atomic force microscopy, when compared to non-VLS deposition of the same metal oxide. X-ray diffraction texture analysis enabled the determination of the crystallographic β-phase of Bi2O3. A very thin TiO2 overlayer (6 nm thick), undoped and doped with nitrogen, was deposited onto the nanocones template, in order to functionalize these structures with a photocatalytic, self-cleaning, cap material. N-doped TiO2 overlayers increased the selective absorption of visible light due to nitrogen doping in the anatase cell, thus, resulting in a concomitant increase in the overall photocatalytic efficiency. Full article
(This article belongs to the Special Issue Photocatalytic Thin Films)
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14 pages, 3510 KiB  
Article
Semiconducting p-Type Copper Iron Oxide Thin Films Deposited by Hybrid Reactive-HiPIMS + ECWR and Reactive-HiPIMS Magnetron Plasma System
by Zdenek Hubička, Martin Zlámal, Jiri Olejníček, Drahoslav Tvarog, Martin Čada and Josef Krýsa
Coatings 2020, 10(3), 232; https://doi.org/10.3390/coatings10030232 - 03 Mar 2020
Cited by 6 | Viewed by 6942
Abstract
A reactive high-power impulse magnetron sputtering (r-HiPIMS) and a reactive high-power impulse magnetron sputtering combined with electron cyclotron wave resonance plasma source (r-HiPIMS + ECWR) were used for the deposition of p-type CuFexOy thin films on glass with SnO2 [...] Read more.
A reactive high-power impulse magnetron sputtering (r-HiPIMS) and a reactive high-power impulse magnetron sputtering combined with electron cyclotron wave resonance plasma source (r-HiPIMS + ECWR) were used for the deposition of p-type CuFexOy thin films on glass with SnO2F conductive layer (FTO). The aim of this work was to deposit CuFexOy films with different atomic ratio of Cu and Fe atoms contained in the films by these two reactive sputtering methods and find deposition conditions that lead to growth of films with maximum amount of delafossite phase CuFeO2. Deposited copper iron oxide films were subjected to photoelectrochemical measurement in cathodic region in order to test the possibility of application of these films as photocathodes in solar hydrogen production. The time stability of the deposited films during photoelectrochemical measurement was evaluated. In the system r-HiPIMS + ECWR, an additional plasma source based on special modification of inductively coupled plasma, which works with an electron cyclotron wave resonance ECWR, was used for further enhancement of plasma density ne and electron temperature Te at the substrate during the reactive sputtering deposition process. A radio frequency (RF) planar probe was used for the determination of time evolution of ion flux density iionflux at the position of the substrate during the discharge pulses. Special modification of this probe to fast sweep the probe system made it possible to determine the time evolution of the tail electron temperature Te at energies around floating potential Vfl and the time evolution of ion concentration ni. This plasma diagnostics was done at particular deposition conditions in pure r-HiPIMS plasma and in r-HiPIMS with additional ECWR plasma. Generally, it was found that the obtained ion flux density iionflux and the tail electron temperature Te were systematically higher in case of r-HiPIMS + ECWR plasma than in pure r-HiPIMS during the active part of discharge pulses. Furthermore, in case of hybrid discharge plasma excitation, r-HiPIMS + ECWR plasma has also constant plasma density all the time between active discharge pulses ni ≈ 7 × 1016 m−3 and electron temperature Te ≈ 4 eV, on the contrary in pure r-HiPIMS ni and Te were negligible during the “OFF” time between active discharge pulses. CuFexOy thin films with different atomic ration of Cu/Fe were deposited at different conditions and various crystal structures were achieved after annealing in air, in argon and in vacuum. Photocurrents in cathodic region for different achieved crystal structures were observed by chopped light linear voltammetry and material stability by chronoamperometry under simulated solar light and X-ray diffraction (XRD). Optimization of depositions conditions results in the desired Cu/Fe ratio in deposited films. Optimized r-HiPIMS and r-HiPIMS + ECWR plasma deposition at 500 °C together with post deposition heat treatment at 650 °C in vacuum is essential for the formation of stable and photoactive CuFeO2 phase. Full article
(This article belongs to the Special Issue Photocatalytic Thin Films)
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11 pages, 3765 KiB  
Article
Enhanced Photoelectrochemical Properties from Mo-Doped TiO2 Nanotube Arrays Film
by Danni Xue, Jie Luo, Zhong Li, Yanlin Yin and Jie Shen
Coatings 2020, 10(1), 75; https://doi.org/10.3390/coatings10010075 - 15 Jan 2020
Cited by 29 | Viewed by 3398
Abstract
Mo-doped TiO2 nanotube arrays are prepared successfully by a combined method of direct current (DC) magnetron sputtering and anodic oxidation. The doping amount of Mo can be modified by changing the number of molybdenum blocks on the Ti target while a Ti–Mo [...] Read more.
Mo-doped TiO2 nanotube arrays are prepared successfully by a combined method of direct current (DC) magnetron sputtering and anodic oxidation. The doping amount of Mo can be modified by changing the number of molybdenum blocks on the Ti target while a Ti–Mo alloy film is prepared by magnetron sputtering on a metal Ti substrate, following a Mo-doped TiO2 nanotube array grown by anodization. Morphology test shows that the doping of Mo could inhibit the phase transition and growth of crystal of TiO2. X-ray photoelectron spectroscopy (XPS) results show that Mo has successfully been embedded in the TiO2 crystal lattice and mainly exists in the valence states of Mo6+. Mo-doping samples show slightly increased visible light absorption as the red shift of TiO2 absorption edge with the band gap dropping from 3.24 to 3.16 eV with 0.5 at.% Mo doping. The enhanced photocurrent is demonstrated for a 0.5 at.% Mo-doped TiO2 electrode. Through photoelectric performance testing under UV-visible light irradiation, the nanotube array film with a Mo-doped content of 0.5% produced the maximum photocurrent density, which is about four times the undoped TiO2 nanotube array film, exhibiting a considerable photoelectric effect gain. The controllable Mo doping TiO2 nanotube array film prepared by this combining technique is expected as a promising material for efficient applications in photoelectric conversion. Full article
(This article belongs to the Special Issue Photocatalytic Thin Films)
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15 pages, 4011 KiB  
Article
Micro-Patterning of Magnetron Sputtered Titanium Dioxide Coatings and Their Efficiency for Photocatalytic Applications
by Marina Ratova, David Sawtell and Peter J. Kelly
Coatings 2020, 10(1), 68; https://doi.org/10.3390/coatings10010068 - 12 Jan 2020
Cited by 6 | Viewed by 3023
Abstract
Titanium dioxide thin films were deposited onto sola-lime glass substrates by reactive magnetron sputtering. Fine stainless steel mesh sheets with different aperture sizes were applied as masks over glass substrates to allow the deposition of the coatings with micro-patterned structures and, therefore, enhanced [...] Read more.
Titanium dioxide thin films were deposited onto sola-lime glass substrates by reactive magnetron sputtering. Fine stainless steel mesh sheets with different aperture sizes were applied as masks over glass substrates to allow the deposition of the coatings with micro-patterned structures and, therefore, enhanced surface area. Non-patterned titania films were deposited for comparison purposes. The titanium dioxide films were post-deposition annealed at 873 K for crystallinity development and then extensively analysed by a number of analytical techniques, including scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDX), optical and stylus profilometry, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-Vis spectroscopy. The photocatalytic activity of non-patterned and micro-patterned titania films was assessed under UV light irradiation by three different methods; namely methylene blue, stearic acid, and oleic acid degradation. The results revealed that the micro-patterned coatings significantly outperformed non-patterned titania in all types of photocatalytic tests, due to their higher values of surface area. Increasing the aperture of the stainless steel mesh resulted in lower photocatalytic activity and lower surface area values, compared to the coatings deposited through a smaller aperture mesh. Full article
(This article belongs to the Special Issue Photocatalytic Thin Films)
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15 pages, 2577 KiB  
Article
ZnO (Ag-N) Nanorods Films Optimized for Photocatalytic Water Purification
by Luis Sanchez, Carlos Castillo, Willy Cruz, Bryan Yauri, Miguel Sosa, Clemente Luyo, Roberto Candal, Silvia Ponce and Juan M. Rodriguez
Coatings 2019, 9(11), 767; https://doi.org/10.3390/coatings9110767 - 19 Nov 2019
Cited by 8 | Viewed by 2863
Abstract
ZnO nanorods (NRs) films, nitrogen-doped (ZnO:N), and ZnO doped with nitrogen and decorated with silver nanostructures (ZnO:N-Ag) NRs films were vertically supported on undoped and N doped ZnO seed layers by a wet chemical method. The obtained films were characterized structurally by X-ray [...] Read more.
ZnO nanorods (NRs) films, nitrogen-doped (ZnO:N), and ZnO doped with nitrogen and decorated with silver nanostructures (ZnO:N-Ag) NRs films were vertically supported on undoped and N doped ZnO seed layers by a wet chemical method. The obtained films were characterized structurally by X-ray diffraction. Morphological and elemental analysis was performed by scanning electron microscopy, including an energy dispersive X-ray spectroscopy facility and their optical properties by Ultraviolet-Visible Spectroscopy. Analysis performed in the NRs films showed that the nitrogen content in the seed layer strongly affected their structure and morphology. The mean diameter of ZnO NRs ranged from 70 to 190 nm. As the nitrogen content in the seed layer increased, the mean diameter of ZnO:N NRs increased from 132 to 250 nm and the diameter dispersion decreased. This diameter increase occurs simultaneously with the incorporation of nitrogen into the ZnO crystal lattice and the increase in the volume of the unit cell, calculated using the X-ray diffraction patterns and confirmed by a slight shift in the XRD angle. The diffractograms indicated that the NRs have a hexagonal wurtzite structure, with preferential growth direction along the c axis. The SEM images confirmed the presence of metallic silver in the form of nanoparticles dispersed on the NRs films. Finally, the degradation of methyl orange (MO) in an aqueous solution was studied by UV-vis irradiation of NRs films contained in the bulk of aqueous MO solutions. We found a significant enhancement of the photocatalytic degradation efficiency, with ZnO:N-Ag NRs film being more efficient than ZnO:N NRs film, and the latter better than the ZnO NRs film. Full article
(This article belongs to the Special Issue Photocatalytic Thin Films)
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9 pages, 3092 KiB  
Article
Optical and Superhydrophilic Characteristics of TiO2 Coating with Subwavelength Surface Structure Consisting of Spherical Nanoparticle Aggregates
by Yuki Kameya and Hiroki Yabe
Coatings 2019, 9(9), 547; https://doi.org/10.3390/coatings9090547 - 26 Aug 2019
Cited by 38 | Viewed by 4636
Abstract
It is expected that the applications of photocatalytic coatings will continue to extend into many areas, so it is important to explore their potential for enhanced functionality and design flexibility. In this study, we investigated the effect of a subwavelength surface structure in [...] Read more.
It is expected that the applications of photocatalytic coatings will continue to extend into many areas, so it is important to explore their potential for enhanced functionality and design flexibility. In this study, we investigated the effect of a subwavelength surface structure in a TiO2 coating on its optical and superhydrophilic characteristics. Using submicron-scale spherical aggregates of TiO2 nanoparticles, we fabricated a TiO2 film with a subwavelength surface structure. Optical examination showed the enhanced transmittance of visible light compared to that of a plain surface. This was considered to be a result of a graded refractive index at the air–TiO2 interface. The effect of the subwavelength surface structure on optical transmittance was also demonstrated by the numerical simulation of visible light propagation in which Maxwell’s equations were solved using the finite-difference time-domain method. In addition, superhydrophilic behavior without ultraviolet light illumination was observed for the subwavelength-structure film via the measurement of the contact angle of a water drop. Furthermore, it was confirmed that the photocatalytic activity of the proposed film was comparable with that of a standard TiO2 film. It was suggested that the control of the subwavelength surface structure of a TiO2 film could be utilized to achieve novel properties of photocatalytic coatings. Full article
(This article belongs to the Special Issue Photocatalytic Thin Films)
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11 pages, 1516 KiB  
Article
Application of Photocatalytic Falling Film Reactor to Elucidate the Degradation Pathways of Pharmaceutical Diclofenac and Ibuprofen in Aqueous Solutions
by Kosar Hikmat Hama Aziz, Khalid M. Omer, Ali Mahyar, Hans Miessner, Siegfried Mueller and Detlev Moeller
Coatings 2019, 9(8), 465; https://doi.org/10.3390/coatings9080465 - 25 Jul 2019
Cited by 41 | Viewed by 4286
Abstract
Diclofenac (DCF) and ibuprofen (IBP) are common pharmaceutical residues that have been detected in the aquatic system. Their presence in the aquatic environment has become an emerging contaminant problem, which has implications for public health. The degradation pathway and identification of transformation products [...] Read more.
Diclofenac (DCF) and ibuprofen (IBP) are common pharmaceutical residues that have been detected in the aquatic system. Their presence in the aquatic environment has become an emerging contaminant problem, which has implications for public health. The degradation pathway and identification of transformation products of pharmaceutical residues are crucial to elucidate the environmental fate of photocatalytic decomposition of these pollutants in aqueous media. The degradation process might lead to creation of other possible emerging contaminates. In this study, the degradation of DCF and IBP in aqueous solutions was investigated. To this end, coated TiO2 on a Pilkington Active glass was used as a photocatalyst under UVA illumination, in a planar falling film reactor. Pilkington ActivTM glass was used as a photocatalyst and a falling liquid film generator. Degradation kinetics of both pharmaceuticals followed a pseudo-first-order model. The transformation products of both diclofenac and ibuprofen during the degradation process were detected and identified with gas chromatography–mass spectrometry (GC–MS) and ion chromatography. The results showed that the mineralization rate of both pharmaceuticals through photocatalysis was very low. Low chain carboxylic acids, such as formic, acetic, oxalic, malonic, and succinic acids were the main by-products. A pathway of DCF and IBP degradation was proposed. Full article
(This article belongs to the Special Issue Photocatalytic Thin Films)
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10 pages, 3252 KiB  
Article
Tridoped TiO2 Composite Films for Improved Photocatalytic Activities
by Li-Zhu Zhao, Ke Han, Fang Li and Ming-Ming Yao
Coatings 2019, 9(2), 127; https://doi.org/10.3390/coatings9020127 - 19 Feb 2019
Cited by 5 | Viewed by 3020
Abstract
The Fe/B/F tridoped TiO2-ZnO composite films attached to glass substrates were prepared via a simple sol–gel method. We appraised all samples’ photocatalytic activities by the degradation of methyl green and formaldehyde solutions. The samples were characterized by photoluminescence (PL) spectra, UV-Vis [...] Read more.
The Fe/B/F tridoped TiO2-ZnO composite films attached to glass substrates were prepared via a simple sol–gel method. We appraised all samples’ photocatalytic activities by the degradation of methyl green and formaldehyde solutions. The samples were characterized by photoluminescence (PL) spectra, UV-Vis diffraction reflectance absorption spectra (DRS), X-ray diffraction (XRD), differential thermal analysis-thermogravimetry (DTA-TG), field emission scanning electron microscopy (FE-SEM) equipped with energy-dispersive spectroscopy (EDS), and Brunner–Emmet–Teller (BET) measurements. According to the results of DRS and PL spectroscopy, the multi-modification could not only enhance visible light absorption intensity, but also decrease the recombination rate of photo-generated electron-hole pairs. XRD results revealed that the sample was mainly in anatase crystal type. FE-SEM results shown that the sample had fewer particle aggregates and almost no cracks. The specific surface area of the Fe/B/F tridoped TiO2-ZnO was 104.9 m2·g−1, while that of the pure TiO2 was 84.0 m2·g−1. Compared to pure TiO2 and TiO2-ZnO, the Fe/B/F tridoped TiO2-ZnO composite film had the highest photocatalytic activity due to their synergies. Full article
(This article belongs to the Special Issue Photocatalytic Thin Films)
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Review

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19 pages, 2335 KiB  
Review
Recent Advances in TiO2 Films Prepared by Sol-Gel Methods for Photocatalytic Degradation of Organic Pollutants and Antibacterial Activities
by Bishweshwar Pant, Mira Park and Soo-Jin Park
Coatings 2019, 9(10), 613; https://doi.org/10.3390/coatings9100613 - 25 Sep 2019
Cited by 96 | Viewed by 10650
Abstract
Photocatalysis has recently emerged as an advanced, green, and eco-friendly process for the treatment of wastewater and air, and antimicrobial disinfection applications. In this context, TiO2 nanostructures have been shown to be the prominent photocatalyst candidates due to their low cost, non-toxicity, [...] Read more.
Photocatalysis has recently emerged as an advanced, green, and eco-friendly process for the treatment of wastewater and air, and antimicrobial disinfection applications. In this context, TiO2 nanostructures have been shown to be the prominent photocatalyst candidates due to their low cost, non-toxicity, and ease of fabrication. This review highlights the investigation and development of TiO2 photocatalyst film by sol-gel method with special emphasis on the photodecolorization of synthetic dyes and antibacterial activities. Furthermore, various synthesis methods for the preparation of TiO2 films and their advantages, as well as limitations, are summarized. Finally, recent advances in TiO2 films by sol-gel method for dye degradation and antibacterial activities, challenges, and future perspective are discussed. Full article
(This article belongs to the Special Issue Photocatalytic Thin Films)
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13 pages, 3846 KiB  
Review
Mechanisms of the Antibacterial Effects of TiO2–FeOx under Solar or Visible Light: Schottky Barriers versus Surface Plasmon Resonance
by John Kiwi and Sami Rtimi
Coatings 2018, 8(11), 391; https://doi.org/10.3390/coatings8110391 - 04 Nov 2018
Cited by 18 | Viewed by 4551
Abstract
This study reports the significant mechanistic difference between binary-oxide antibacterial films with the same composition but different microstructures. Binary TiO2-FeOx films were found to present a faster bacterial inactivation kinetics under visible light irradiation than each single oxide acting independently. [...] Read more.
This study reports the significant mechanistic difference between binary-oxide antibacterial films with the same composition but different microstructures. Binary TiO2-FeOx films were found to present a faster bacterial inactivation kinetics under visible light irradiation than each single oxide acting independently. The interaction between the film active surface species and the bacteria within the disinfection period was followed by X-ray photoelectron spectroscopy (XPS) and provided the evidence for a redox catalysis taking place during the bacterial inactivation time. The optical and surface properties of the films were evaluated by appropriate surface analytical methods. A differential mechanism is suggested for each specific microstructure inducing bacterial inactivation. The surface FeOx plasmon resonance transferred electrons into the conduction band of TiO2 because of the Schottky barrier after Fermi level equilibration of the two components. An electric field at the interface between TiO2 and FeOx, favors the separation of the photo-generated charges leading to a faster bacterial inactivation by TiO2–FeOx compared to the bacterial inactivation kinetics by each of the single oxides. Full article
(This article belongs to the Special Issue Photocatalytic Thin Films)
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