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Anatase Chemistry, Nanostructures and Functionalities‎

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A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Materials Science and Engineering".

Deadline for manuscript submissions: closed (20 August 2022) | Viewed by 19328

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Special Issue Editor

Dr. Regina Ciancio

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Guest Editor

CNR-IOM, 34149 Trieste, Italy
Interests: complex oxides; transmission electron microscopy; nanostructural and electronic characterization

Special Issue Information

Dear Colleagues,

The last few years have witnessed a great rate of technological advancement in the synthesis of anatase. Regardless of the specific fabrication technique, all anatase samples—for example, thin films, crystals, and powders—have in common that their functional properties strongly depend on chemical and phase composition, crystalline structure, presence of defects, interface properties, and surface-related properties.

The capability to control and tune the structural properties of anatase has given an enormous boost toward the understanding on fundamental properties of anatase but also to engineer heterostructures with desired properties.

This Special Issue aims to collect original research articles as well as review articles featuring the latest achievements and developments in fabrication and processing of anatase as well as in the characterization of their structural, electronic and functional properties. Subject areas include (but are not limited to) anatase thin films fabrication and processing, theory and simulation, anatase nanostructure and properties, device applications.

Dr. Regina Ciancio
Guest Editor

Manuscript Submission Information

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Keywords

metal oxides
anatase
thin films
defects
oxygen vacancies
anatase devices
interdiffusion
nanostructure
heterogeneous catalysis

Published Papers (6 papers)

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Research

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16 pages, 4725 KiB

Open AccessArticle

Study of Oxygen Vacancies in TiO₂ Nanostructures and Their Relationship with Photocatalytic Activity

by Alba Arenas-Hernandez, Carlos Zuñiga Islas, Mario Moreno, Wilfrido Calleja Arriaga, Julio César Mendoza-Cervantes, Netzahualcoyotl Carlos, Carlos Roberto Ascencio-Hurtado and Aurelio Heredia Jiménez

Appl. Sci. 2022, 12(7), 3690; https://0-doi-org.brum.beds.ac.uk/10.3390/app12073690 - 06 Apr 2022

Cited by 7 | Viewed by 2442

Abstract

In this research work, we present the synthesis and characterization of four different TiO₂ structures, such as nanotubes, nanocavities, nanosheets assembled on nanocavities and nanobowls assembled on nanocavities, prepared by electrochemical anodization using organic electrolytes. After synthesis, the structures were thermally annealed to pass from the amorphous phase to the anatase phase, which is one of the most important crystalline structures of TiO₂ due to its high photocatalytic activity and stability. The unique morphology and topography were studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The elemental composition was determined by energy-dispersive X-ray spectroscopy (EDS). The anatase phase was verified by Raman microscopy and X-ray diffraction (XRD), the band gap energy was calculated by the Kubelka–Munk function, and the main defect states that generate the emission, as well as their lifetime, were determined by photoluminescence spectroscopy and time response photoluminescence (TRPL), respectively. The TiO₂ nanomaterials were tested as catalysts in the photodegradation of a solution of methylene blue using a UV lamp at room temperature. The results showed complex morphologies and different surface roughness areas of these nanomaterials. Furthermore, a relationship between defect states, band gap energy, and photocatalytic activity was established. We found that the catalytic activity was improved as an effect of geometric parameters and oxygen vacancies. Full article

(This article belongs to the Special Issue Anatase Chemistry, Nanostructures and Functionalities‎)

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18 pages, 9430 KiB

Open AccessArticle

Synthesis and Characterization of Anatase TiO₂ Nanorods: Insights from Nanorods’ Formation and Self-Assembly

by Seyed Naveed Hosseini, Xiaodan Chen, Patrick J. Baesjou, Arnout Imhof and Alfons van Blaaderen

Appl. Sci. 2022, 12(3), 1614; https://0-doi-org.brum.beds.ac.uk/10.3390/app12031614 - 03 Feb 2022

Cited by 7 | Viewed by 2663

Abstract

Highly crystalline, organic-solvent-dispersible titanium dioxide (TiO₂) nanorods (NRs) present promising chemicophysical properties in many diverse applications. In this paper, based on a modified procedure from literature, TiO₂ NRs were synthesized via a ligand-assisted nonhydrolytic sol-gel route using oleic acid as the solvent, reagent, and ligand and titanium (IV) isopropoxide as the titanium precursor. This procedure produced monodisperse TiO₂ NRs, as well as some semi-spherical titania nanocrystals (NCs) that could be removed by size-selective precipitation. X-ray diffraction and selected area electron diffraction results showed that the nanorods were anatase, while the semipheres also contained the TiO₂(B) phase. By taking samples during the particle growth, it was found that the average length of the initially grown NRs decreased during the synthesis. Possible reasons for this unusual growth path, partially based on high-resolution transmission electron microscopy (HRTEM) observations during the growth, were discussed. The dispersion of anatase TiO₂ nanorods was capable of spontaneous formation of lyotropic liquid crystals on the TEM grid and in bulk. Considering high colloidal stability together with the large optical birefringence displayed by these high refractive index liquid crystalline domains, we believe these TiO₂ NRs dispersions are promising candidates for application in transparent and switchable optics. Full article

(This article belongs to the Special Issue Anatase Chemistry, Nanostructures and Functionalities‎)

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9 pages, 2276 KiB

Open AccessFeature PaperArticle

HAADF STEM and Ab Initio Calculations Investigation of Anatase TiO₂/LaAlO₃ Heterointerface

by Mahabul Islam, Piu Rajak, Daniel Knez, Sandeep Kumar Chaluvadi, Pasquale Orgiani, Giorgio Rossi, Goran Dražić and Regina Ciancio

Appl. Sci. 2022, 12(3), 1489; https://0-doi-org.brum.beds.ac.uk/10.3390/app12031489 - 29 Jan 2022

Viewed by 3336

Abstract

The understanding of the origin of a two-dimensional electron gas (2DEG) at the surface of anatase TiO₂ remains a challenging issue. In particular, in TiO₂ ultra-thin films, it is extremely difficult to distinguish intrinsic effects, due to the physics of the TiO₂, from extrinsic effects, such as those arising from structural defects, dislocations, and the presence of competing phases at the film/substrate interface. It is, therefore, mandatory to unambiguously ascertain the structure of the TiO₂/substrate interface. In this work, by combining high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), density functional theory calculations, and multislice image simulations, we have investigated the nature of strainless anatase TiO₂ thin films grown on LaAlO₃ substrate. In particular, the presence of oxygen vacancies in anatase TiO₂ has been proved to stabilize the formation of an extra alloy layer, Ti₂AlO₄, by means of interface rearrangement. Our results, therefore, elucidate why the growth of anatase TiO₂ directly on LaAlO₃ substrate has required the deposition of a TiO_x extra-layer to have a 2DEG established, thus confirming the absence of a critical thickness for the TiO₂ to stabilize a 2DEG at its surface. These findings provide fundamental insights on the underlying formation mechanism of the 2DEG in TiO₂/LAO hetero-interfaces to engineer the 2DEG formation in anatase TiO₂ for tailored applications. Full article

(This article belongs to the Special Issue Anatase Chemistry, Nanostructures and Functionalities‎)

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16 pages, 2986 KiB

Open AccessArticle

Photocatalytic Phenol Degradation by Silica-Modified Titanium Dioxide

by Diana Rakhmawaty Eddy, Soraya Nur Ishmah, Muhamad Diki Permana, M. Lutfi Firdaus, Iman Rahayu, Yaser A. El-Badry, Enas E. Hussein and Zeinhom M. El-Bahy

Appl. Sci. 2021, 11(19), 9033; https://0-doi-org.brum.beds.ac.uk/10.3390/app11199033 - 28 Sep 2021

Cited by 15 | Viewed by 2652

Abstract

Titanium dioxide (TiO₂) has been widely applied as a photocatalyst for wastewater treatment due to its high photocatalytic activity and it can remove various harmful organic pollutants effectively. Under heated system, however, TiO₂ is prone to agglomeration that decrease its abilities as a photocatalyst. In order to overcome the agglomeration and increase its thermal resistance, addition of silica (SiO₂) as supporting material is proposed in this research. Silica or silicon dioxide can be extracted from natural resources such as beach sand. Here, we report the application of a composite photocatalyst of TiO₂/SiO₂ to remove phenolic compounds in wastewater. The photocatalyst was synthesized by adding SiO₂ from beach sand onto TiO₂ through impregnation methods. The results of the X-ray diffraction (XRD) showed that TiO₂ was present in the anatase phase. The highest crystallinity was obtained by TiO₂/SiO₂ ratios of 7:1. SEM results showed that the shape of the particles was spherical. Further characterizations were conducted using Fourier-transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) analysis, and a particle size analyzer (PSA). By using the optimized condition, 96.05% phenol was degraded by the synthesized photocatalyst of TiO₂/SiO₂, under UV irradiation for 120 min. The efficiency of the TiO₂/SiO₂ is 3.5 times better than commercial TiO₂ P25 for the Langmuir–Hinshelwood first-order kinetic model. Full article

(This article belongs to the Special Issue Anatase Chemistry, Nanostructures and Functionalities‎)

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15 pages, 4988 KiB

Open AccessArticle

Effect of Urea Addition on Anatase Phase Enrichment and Nitrogen Doping of TiO₂ for Photocatalytic Abatement of Methylene Blue

by Maira Asif, Muhammad Zafar, Parveen Akhter, Murid Hussain, Adeel Umer, Abdul Razzaq and Woo-Young Kim

Appl. Sci. 2021, 11(17), 8264; https://0-doi-org.brum.beds.ac.uk/10.3390/app11178264 - 06 Sep 2021

Cited by 9 | Viewed by 2990

Abstract

TiO₂-based materials are commonly employed as photocatalysts for industrial wastewater treatment. The primary reasons of employing TiO₂ include cost effectiveness, ready availability, eco-friendliness, non-toxic behavior, and exceptional resistance towards photo-corrosion. However, the wider band gap of pure TiO₂ restricts its performance because of its optical absorption of solar light to the ultraviolet (UV) region only, and to some extent of photo-excited charge recombination. In the present work an attempt is made to develop a facile synthesis approach by using urea, a cheap chemical precursor, to form nitrogen doped TiO₂ with the key objective of extended light absorption and thus enhanced photocatalytic performance. It was also observed that the urea-induced anatase phase enrichment of TiO₂ is another key factor in promoting the photocatalytic performance. The photocatalysts prepared by varying the amount of urea as a nitrogen dopant precursor, are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and photoluminescence (PL) to evaluate their crystallinity, morphology, functional groups, and charge separation properties, respectively. Moreover, the surface area was also estimated by physicochemical adsorption. The maximum nitrogen-doped sample yielded >99% photodegradation efficiency of methylene blue (MB) dye-simulated wastewater as compared to a pure TiO₂ sample which exhibited 6.46% efficiency. The results show that the simultaneous factors of nitrogen doping and anatase phase enhancement contributes significantly towards the improvement of photocatalytic performance. Full article

(This article belongs to the Special Issue Anatase Chemistry, Nanostructures and Functionalities‎)

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Review

Jump to: Research

32 pages, 3582 KiB

Open AccessFeature PaperReview

Titanium Dioxide-Based Photocatalysts for Degradation of Emerging Contaminants including Pharmaceutical Pollutants

by Rafal Krakowiak, Joanna Musial, Paweł Bakun, Marcin Spychała, Beata Czarczynska-Goslinska, Dariusz T. Mlynarczyk, Tomasz Koczorowski, Lukasz Sobotta, Beata Stanisz and Tomasz Goslinski

Appl. Sci. 2021, 11(18), 8674; https://0-doi-org.brum.beds.ac.uk/10.3390/app11188674 - 17 Sep 2021

Cited by 34 | Viewed by 4033

Abstract

Contamination of the environment has been a growing problem in recent years. Due to the rapid growth in human population, the expansion of cities, along with the development of industry, more and more dangerous chemicals end up in the environment, especially in soil and water. For the most part, it is not possible to effectively remove chemicals through traditional remediation techniques, because those used in treatment plants are not specifically designed for this purpose. Therefore, new approaches for water remediation are in great demand. Many efforts have been focused on applications of photocatalysis for the remediation of chemical pollutants including drugs. Titanium(IV) oxide nanoparticles have particularly been considered as potential photocatalysts due to their favorable properties. In this article, we present the problem of emerging contaminants including drugs and discuss the use of photocatalysts based on titanium(IV) oxide nanoparticles for their degradation. A wide selection of materials, starting from bare TiO₂, via its hybrid and composite materials, are discussed including those based on carbonaceous materials or connections with macrocyclic structures. Examples of photodegradation experiments on TiO₂-based materials including those performed with various active pharmaceutical ingredients are also included. Full article

(This article belongs to the Special Issue Anatase Chemistry, Nanostructures and Functionalities‎)

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