Editorial

3 pages, 171 KiB

Open AccessEditorial

Special Issue “Synthesis of TiO₂ Nanoparticles and Their Catalytic Activity”

by Wei Zhou

Nanomaterials 2023, 13(18), 2544; https://doi.org/10.3390/nano13182544 - 12 Sep 2023

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The current advances in the development of technologies for solar light utilization are largely due to the environmental and energy crisis caused by the rapid consumption of fossil fuels, and consequently, various applications have been implemented in domestic heating devices, the field of [...] Read more.

The current advances in the development of technologies for solar light utilization are largely due to the environmental and energy crisis caused by the rapid consumption of fossil fuels, and consequently, various applications have been implemented in domestic heating devices, the field of spaceflight, vehicles with clean energy, self-cleaning devices, the bio-pharmaceutical field, etc [...] Full article

(This article belongs to the Special Issue Synthesis of TiO₂ Nanoparticles and Their Catalytic Activity)

Research

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16 pages, 21739 KiB

Open AccessArticle

Construction of Built-In Electric Field in TiO₂@Ti₂O₃ Core-Shell Heterojunctions toward Optimized Photocatalytic Performance

by Tingting Hu, Panpan Feng, Liping Guo, Hongqi Chu and Fusheng Liu

Nanomaterials 2023, 13(14), 2125; https://doi.org/10.3390/nano13142125 - 21 Jul 2023

Cited by 1 | Viewed by 1116

Abstract

A series of Ti₂O₃@TiO₂ core-shell heterojunction composite photocatalysts with different internal electric fields were synthesized using simple heat treatment methods. The synthesized Ti₂O₃@TiO₂ core-shell heterojunction composites were characterized by means of SEM, XRD, [...] Read more.

A series of Ti₂O₃@TiO₂ core-shell heterojunction composite photocatalysts with different internal electric fields were synthesized using simple heat treatment methods. The synthesized Ti₂O₃@TiO₂ core-shell heterojunction composites were characterized by means of SEM, XRD, PL, UV–Vis, BET, SPV, TEM and other related analytical techniques. Tetracycline (TC) was used as the degradation target to evaluate the photocatalytic performance of the synthesized Ti₂O₃@TiO₂ core-shell heterojunction composites. The relevant test results show that the photocatalytic performance of the optimized materials has been significantly enhanced compared to Ti₂O₃, while the photocatalytic degradation rate has increased from 28% to 70.1%. After verification via several different testing and characterization techniques, the excellent catalytic performance is attributed to the efficient separation efficiency of the photogenerated charge carriers derived from the built-in electric field formed between Ti₂O₃ and TiO₂. When the recombination of electrons and holes is occupied, more charges are generated to reach the surface of the photocatalyst, thereby improving the photocatalytic degradation efficiency. Thus, this work provides a universal strategy to enhance the photocatalytic performance of Ti₂O₃ by coupling it with TiO₂ to build an internal electric field. Full article

(This article belongs to the Special Issue Synthesis of TiO₂ Nanoparticles and Their Catalytic Activity)

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16 pages, 6412 KiB

Open AccessArticle

Fabrication of Z-Type TiN@(A,R)TiO₂ Plasmonic Photocatalyst with Enhanced Photocatalytic Activity

by Wanting Wang, Yuanting Wu, Long Chen, Chenggang Xu, Changqing Liu and Chengxin Li

Nanomaterials 2023, 13(13), 1984; https://doi.org/10.3390/nano13131984 - 30 Jun 2023

Cited by 2 | Viewed by 937

Abstract

Plasmonic effect-enhanced Z-type heterojunction photocatalysts comprise a promising solution to the two fundamental problems of current TiO₂-based photocatalysis concerning low-charge carrier separation efficiency and low utilization of solar illumination. A plasmonic effect-enhanced TiN@anatase-TiO₂/rutile-TiO₂ Z-type heterojunction photocatalyst with the [...] Read more.

Plasmonic effect-enhanced Z-type heterojunction photocatalysts comprise a promising solution to the two fundamental problems of current TiO₂-based photocatalysis concerning low-charge carrier separation efficiency and low utilization of solar illumination. A plasmonic effect-enhanced TiN@anatase-TiO₂/rutile-TiO₂ Z-type heterojunction photocatalyst with the strong interface of the N–O chemical bond was synthesized by hydrothermal oxidation of TiN. The prepared photocatalyst shows desirable visible light absorption and good visible-light-photocatalytic activity. The enhancement in photocatalytic activities contribute to the plasma resonance effect of TiN, the N–O bond-connected charge transfer channel at the TiO₂/TiN heterointerface, and the synergistically Z-type charge transfer pathway between the anatase TiO₂ (A-TiO₂) and rutile TiO₂ (R-TiO₂). The optimization study shows that the catalyst with a weight ratio of A-TiO₂/R-TiO₂/TiN of approximately 15:1:1 achieved the best visible light photodegradation activity. This work demonstrates the effectiveness of fabricating plasmonic effect-enhanced Z-type heterostructure semiconductor photocatalysts with enhanced visible-light-photocatalytic activities. Full article

(This article belongs to the Special Issue Synthesis of TiO₂ Nanoparticles and Their Catalytic Activity)

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13 pages, 2828 KiB

Open AccessArticle

Surface Modification of Hollow Structure TiO₂ Nanospheres for Enhanced Photocatalytic Hydrogen Evolution

by Gaomin Ning, Yan Zhang, Chunjing Shi, Chen Zhao, Mengmeng Liu, Fangfang Chang, Wenlong Gao, Sheng Ye, Jian Liu and Jing Zhang

Nanomaterials 2023, 13(5), 926; https://doi.org/10.3390/nano13050926 - 03 Mar 2023

Cited by 2 | Viewed by 1493

Abstract

Engineering the surface structure of semiconductor is one of the most promising strategies for improving the separation and transfer efficiency of charge, which is a key issue in photocatalysis. Here, we designed and fabricated the C decorated hollow TiO₂ photocatalysts (C–TiO₂ [...] Read more.

Engineering the surface structure of semiconductor is one of the most promising strategies for improving the separation and transfer efficiency of charge, which is a key issue in photocatalysis. Here, we designed and fabricated the C decorated hollow TiO₂ photocatalysts (C–TiO₂), in which 3-aminophenol-formaldehyde resin (APF) spheres were used as template and carbon precursor. It was determined that the C content can be easily controlled by calcinating the APF spheres with different time. Moreover, the synergetic effort between the optimal C content and the formed Ti–O–C bonds in C–TiO₂ were determined to increase the light absorption and greatly promote the separation and transfer of charge in the photocatalytic reaction, which is verified from UV–vis, PL, photocurrent, and EIS characterizations. Remarkably, the activity of the C–TiO₂ is 5.5-fold higher than that of TiO₂ in H₂ evolution. A feasible strategy for rational design and construction of surface-engineered hollow photocatalysts to improve the photocatalytic performance was provided in this study. Full article

(This article belongs to the Special Issue Synthesis of TiO₂ Nanoparticles and Their Catalytic Activity)

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10 pages, 2671 KiB

Open AccessArticle

Ultra-Violet-Assisted Scalable Method to Fabricate Oxygen-Vacancy-Rich Titanium-Dioxide Semiconductor Film for Water Decontamination under Natural Sunlight Irradiation

by Mohammed Alyami

Nanomaterials 2023, 13(4), 703; https://doi.org/10.3390/nano13040703 - 12 Feb 2023

Cited by 2 | Viewed by 1370

Abstract

This work reports the fabrication of titanium dioxide (TiO₂) nanoparticle (NPs) films using a scalable drop-casting method followed by ultra-violet (UV) irradiation for creating defective oxygen vacancies on the surface of a fabricated TiO₂ semiconductor film using an UV lamp [...] Read more.

This work reports the fabrication of titanium dioxide (TiO₂) nanoparticle (NPs) films using a scalable drop-casting method followed by ultra-violet (UV) irradiation for creating defective oxygen vacancies on the surface of a fabricated TiO₂ semiconductor film using an UV lamp with a wavelength oof 255 nm for 3 h. The success of the use of the proposed scalable strategy to fabricate oxygen-vacancy-rich TiO₂ films was assessed through UV–Vis spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The Ti 2p XPS spectra acquired from the UV-treated sample showed the presence of additional Ti³⁺ ions compared with the untreated sample, which contained only Ti⁴⁺ ions. The band gap of the untreated TiO₂ film was reduced from 3.2 to 2.95 eV after UV exposure due to the created oxygen vacancies, as evident from the presence of Ti³⁺ ions. Radiation exposure has no significant influence on sample morphology and peak pattern, as revealed by the SEM and XRD analyses, respectively. Furthermore, the photocatalytic activity of the fabricated TiO₂ films for methylene-blue-dye removal was found to be 99% for the UV-treated TiO₂ films and compared with untreated TiO₂ film, which demonstrated only 77% at the same operating conditions under natural-sunlight irradiation. The proposed UV-radiation method of oxygen vacancy has the potential to promote the wider application of photo-catalytic TiO₂ semiconductor films under visible-light irradiation for solving many environmental and energy-crisis challenges for many industrial and technological applications. Full article

(This article belongs to the Special Issue Synthesis of TiO₂ Nanoparticles and Their Catalytic Activity)

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11 pages, 3321 KiB

Open AccessCommunication

B-Doped g-C₃N₄/Black TiO₂ Z-Scheme Nanocomposites for Enhanced Visible-Light-Driven Photocatalytic Performance

by Yuwei Wang, Kelin Xu, Liquan Fan, Yongwang Jiang, Ying Yue and Hongge Jia

Nanomaterials 2023, 13(3), 518; https://doi.org/10.3390/nano13030518 - 28 Jan 2023

Cited by 2 | Viewed by 1572

Abstract

Black TiO₂ with abundant oxygen vacancies (OVs)/B-doped graphitic carbon nitride (g-C₃N₄) Z-scheme heterojunction nanocomposites are successfully prepared by the one-pot strategy. The OVs can improve not only photogenerated carrier separation, but also the sorption and activation of antibiotic [...] Read more.

Black TiO₂ with abundant oxygen vacancies (OVs)/B-doped graphitic carbon nitride (g-C₃N₄) Z-scheme heterojunction nanocomposites are successfully prepared by the one-pot strategy. The OVs can improve not only photogenerated carrier separation, but also the sorption and activation of antibiotic compounds (tetracycline hydrochloride, TC). The prepared heterojunction photocatalysts with a narrow bandgap of ∼2.13 eV exhibit excellent photocatalytic activity for the degradation of tetracycline hydrochloride (65%) under visible light irradiation within 30 min, which is several times higher than that of the pristine one. The outstanding photocatalytic property can be ascribed to abundant OVs and B element-dope reducing the bandgap and extending the photo-response to the visible light region, the Z-scheme formation of heterojunctions preventing the recombination of photogenerated electrons and holes, and promoting their effective separation. Full article

(This article belongs to the Special Issue Synthesis of TiO₂ Nanoparticles and Their Catalytic Activity)

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17 pages, 6226 KiB

Open AccessArticle

Bioactive Coatings Based on Nanostructured TiO₂ Modified with Noble Metal Nanoparticles and Lysozyme for Ti Dental Implants

by Emilian Chifor, Ion Bordeianu, Crina Anastasescu, Jose Maria Calderon-Moreno, Veronica Bratan, Diana-Ioana Eftemie, Mihai Anastasescu, Silviu Preda, Gabriel Plavan, Diana Pelinescu, Robertina Ionescu, Ileana Stoica, Maria Zaharescu and Ioan Balint

Nanomaterials 2022, 12(18), 3186; https://doi.org/10.3390/nano12183186 - 14 Sep 2022

Cited by 3 | Viewed by 1857

Abstract

This work presents the synthesis of nanostructured TiO₂ modified with noble metal nanoparticles (Au, Ag) and lysozyme and coated on titanium foil. Moreover, the specific structural and functional properties of the resulting inorganic and hybrid materials were explored. The purpose of this [...] Read more.

This work presents the synthesis of nanostructured TiO₂ modified with noble metal nanoparticles (Au, Ag) and lysozyme and coated on titanium foil. Moreover, the specific structural and functional properties of the resulting inorganic and hybrid materials were explored. The purpose of this study was to identify the key parameters for developing engineered coatings on titanium foil appropriate for efficient dental implants with intrinsic antibacterial activity. TiO₂ nanoparticles obtained using the sol–gel method were deposited on Ti foil and modified with Au/Ag nanoparticles. Morphological and structural investigations (scanning electron and atomic force microscopies, X-ray diffraction, photoluminescence, and UV–Vis spectroscopies) were carried out for the characterization of the resulting inorganic coatings. In order to modify their antibacterial activity, which is essential for safe dental implants, the following aspects were investigated: (a) singlet oxygen (¹O₂) generation by inorganic coatings exposed to visible light irradiation; (b) the antibacterial behavior emphasized by titania-based coatings deposited on titanium foil (TiO₂/Ti foil; Au–TiO₂/Ti foil, Ag–TiO₂/Ti foil); (c) the lysozyme bioactivity on the microbial substrate (Micrococcus lysodeicticus) after its adsorption on inorganic surfaces (Lys/TiO₂/Ti foil; Lys/Au–TiO₂/Ti foil, Lys/Ag–TiO₂/Ti foil); (d) the enzymatic activity of the above-mentioned hybrids materials for the hydrolysis reaction of a synthetic organic substrate usually used for monitoring the lysozyme biocatalytic activity, namely, 4-Methylumbelliferyl β-D-N,N′,N″-triacetylchitotrioside [4-MU-β- (GlcNAc)₃]. This was evaluated by identifying the presence of a fluorescent reaction product, 7-hydroxy-4-metyl coumarin (4-methylumbelliferone). Full article

(This article belongs to the Special Issue Synthesis of TiO₂ Nanoparticles and Their Catalytic Activity)

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12 pages, 2306 KiB

Open AccessArticle

Synthesis of Uniform Size Rutile TiO₂ Microrods by Simple Molten-Salt Method and Its Photoluminescence Activity

by Hieu Minh Ngo, Amol Uttam Pawar, Jun Tang, Zhongbiao Zhuo, Don Keun Lee, Kang Min Ok and Young Soo Kang

Nanomaterials 2022, 12(15), 2626; https://doi.org/10.3390/nano12152626 - 29 Jul 2022

Cited by 4 | Viewed by 2262

Abstract

Uniform-size rutile TiO₂ microrods were synthesized by simple molten-salt method with sodium chloride as reacting medium and different kinds of sodium phosphate salts as growth control additives to control the one-dimensional (1-D) crystal growth of particles. The effect of rutile and anatase [...] Read more.

Uniform-size rutile TiO₂ microrods were synthesized by simple molten-salt method with sodium chloride as reacting medium and different kinds of sodium phosphate salts as growth control additives to control the one-dimensional (1-D) crystal growth of particles. The effect of rutile and anatase ratios as a precursor was monitored for rod growth formation. Apart from uniform rod growth study, optical properties of rutile microrods were observed by UV−visible and photoluminescence (PL) spectroscopy. TiO₂ materials with anatase and rutile phase show PL emission due to self-trapped exciton. It has been observed that synthesized rutile TiO₂ rods show various PL emission peaks in the range of 400 to 900 nm for 355 nm excitation wavelengths. All PL emission appeared due to the oxygen vacancy present inside rutile TiO₂ rods. The observed PL near the IR range (785 and 825 nm) was due to the formation of a self-trapped hole near to the surface of (110) which is the preferred orientation plane of synthesized rutile TiO₂ microrods. Full article

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12 pages, 4347 KiB

Open AccessArticle

Construction of Spindle-Shaped Ti³⁺ Self-Doped TiO₂ Photocatalysts Using Triethanolamine-Aqueous as the Medium and Its Photoelectrochemical Properties

by Zunfu Hu, Qi Gong, Jiajia Wang, Xiuwen Zheng, Aihua Wang and Shanmin Gao

Nanomaterials 2022, 12(13), 2298; https://doi.org/10.3390/nano12132298 - 04 Jul 2022

Cited by 1 | Viewed by 1675

Abstract

To enhance the utilization efficiency of visible light and reduce the recombination of photogenerated electrons and holes, spindle-shaped TiO₂ photocatalysts with different Ti³⁺ concentrations were fabricated by a simple solvothermal strategy using low-cost, environmentally friendly TiH₂ and H₂O [...] Read more.

To enhance the utilization efficiency of visible light and reduce the recombination of photogenerated electrons and holes, spindle-shaped TiO₂ photocatalysts with different Ti³⁺ concentrations were fabricated by a simple solvothermal strategy using low-cost, environmentally friendly TiH₂ and H₂O₂ as raw materials and triethanolamine-aqueous as the medium. The photocatalytic activities of the obtained photocatalysts were investigated in the presence of visible light. X-ray diffraction (XRD), Raman spectra, transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT-IR) spectra were applied to characterize the structure, morphologies, and chemical compositions of as-fabricated Ti³⁺ self-doped TiO₂. The concentration of triethanolamine in the mixed solvent plays a significant role on the crystallinity, morphologies, and photocatalytic activities. The electron–hole separation efficiency was found to increase with the increase in the aspect ratio of as-fabricated Ti³⁺ self-doped TiO₂, which was proved by transient photocurrent response and electrochemical impedance spectroscopy. Full article

(This article belongs to the Special Issue Synthesis of TiO₂ Nanoparticles and Their Catalytic Activity)

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12 pages, 24643 KiB

Open AccessArticle

Efficient Charge Transfer Channels in Reduced Graphene Oxide/Mesoporous TiO₂ Nanotube Heterojunction Assemblies toward Optimized Photocatalytic Hydrogen Evolution

by Zhenzi Li, Decai Yang, Hongqi Chu, Liping Guo, Tao Chen, Yifan Mu, Xiangyi He, Xueyan Zhong, Baoxia Huang, Shiyu Zhang, Yue Gao, Yuxiu Wei, Shijie Wang and Wei Zhou

Nanomaterials 2022, 12(9), 1474; https://doi.org/10.3390/nano12091474 - 26 Apr 2022

Cited by 4 | Viewed by 1739

Abstract

Interface engineering is usually considered to be an efficient strategy to promote the separation and migration of photoexcited electron-hole pairs and improve photocatalytic performance. Herein, reduced graphene oxide/mesoporous titanium dioxide nanotube heterojunction assemblies (rGO/TiO₂) are fabricated via a facile hydrothermal method. [...] Read more.

Interface engineering is usually considered to be an efficient strategy to promote the separation and migration of photoexcited electron-hole pairs and improve photocatalytic performance. Herein, reduced graphene oxide/mesoporous titanium dioxide nanotube heterojunction assemblies (rGO/TiO₂) are fabricated via a facile hydrothermal method. The rGO is anchored on the surface of TiO₂ nanosheet assembled nanotubes in a tightly manner due to the laminated effect, in which the formed heterojunction interface becomes efficient charge transfer channels to boost the photocatalytic performance. The resultant rGO/TiO₂ heterojunction assemblies extend the photoresponse to the visible light region and exhibit an excellent photocatalytic hydrogen production rate of 932.9 μmol h⁻¹ g⁻¹ under simulated sunlight (AM 1.5G), which is much higher than that of pristine TiO₂ nanotubes (768.4 μmol h⁻¹ g⁻¹). The enhancement can be ascribed to the formation of a heterojunction assembly, establishing effective charge transfer channels and favoring spatial charge separation, the introduced rGO acting as an electron acceptor and the two-dimensional mesoporous nanosheets structure supplying a large surface area and adequate surface active sites. This heterojunction assembly will have potential applications in energy fields. Full article

(This article belongs to the Special Issue Synthesis of TiO₂ Nanoparticles and Their Catalytic Activity)

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Review

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43 pages, 5005 KiB

Open AccessReview

A Review on Nano Ti-Based Oxides for Dark and Photocatalysis: From Photoinduced Processes to Bioimplant Applications

by Christine Joy Querebillo

Nanomaterials 2023, 13(6), 982; https://doi.org/10.3390/nano13060982 - 08 Mar 2023

Cited by 9 | Viewed by 1984

Abstract

Catalysis on TiO₂ nanomaterials in the presence of H₂O and oxygen plays a crucial role in the advancement of many different fields, such as clean energy technologies, catalysis, disinfection, and bioimplants. Photocatalysis on TiO₂ nanomaterials is well-established and has [...] Read more.

Catalysis on TiO₂ nanomaterials in the presence of H₂O and oxygen plays a crucial role in the advancement of many different fields, such as clean energy technologies, catalysis, disinfection, and bioimplants. Photocatalysis on TiO₂ nanomaterials is well-established and has advanced in the last decades in terms of the understanding of its underlying principles and improvement of its efficiency. Meanwhile, the increasing complexity of modern scientific challenges in disinfection and bioimplants requires a profound mechanistic understanding of both residual and dark catalysis. Here, an overview of the progress made in TiO₂ catalysis is given both in the presence and absence of light. It begins with the mechanisms involving reactive oxygen species (ROS) in TiO₂ photocatalysis. This is followed by improvements in their photocatalytic efficiency due to their nanomorphology and states by enhancing charge separation and increasing light harvesting. A subsection on black TiO₂ nanomaterials and their interesting properties and physics is also included. Progress in residual catalysis and dark catalysis on TiO₂ are then presented. Safety, microbicidal effect, and studies on Ti-oxides for bioimplants are also presented. Finally, conclusions and future perspectives in light of disinfection and bioimplant application are given. Full article

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27 pages, 11544 KiB

Open AccessReview

Recent Advances in Black TiO₂ Nanomaterials for Solar Energy Conversion

by Lijun Liao, Mingtao Wang, Zhenzi Li, Xuepeng Wang and Wei Zhou

Nanomaterials 2023, 13(3), 468; https://doi.org/10.3390/nano13030468 - 24 Jan 2023

Cited by 8 | Viewed by 2538

Abstract

Titanium dioxide (TiO₂) nanomaterials have been widely used in photocatalytic energy conversion and environmental remediation due to their advantages of low cost, chemical stability, and relatively high photo-activity. However, applications of TiO₂ have been restricted in the ultraviolet range because [...] Read more.

Titanium dioxide (TiO₂) nanomaterials have been widely used in photocatalytic energy conversion and environmental remediation due to their advantages of low cost, chemical stability, and relatively high photo-activity. However, applications of TiO₂ have been restricted in the ultraviolet range because of the wide band gap. Broadening the light absorption of TiO₂ nanomaterials is an efficient way to improve the photocatalytic activity. Thus, black TiO₂ with extended light response range in the visible light and even near infrared light has been extensively exploited as efficient photocatalysts in the last decade. This review represents an attempt to conclude the recent developments in black TiO₂ nanomaterials synthesized by modified treatment, which presented different structure, morphological features, reduced band gap, and enhanced solar energy harvesting efficiency. Special emphasis has been given to the newly developed synthetic methods, porous black TiO₂, and the approaches for further improving the photocatalytic activity of black TiO₂. Various black TiO₂, doped black TiO₂, metal-loaded black TiO₂ and black TiO₂ heterojunction photocatalysts, and their photocatalytic applications and mechanisms in the field of energy and environment are summarized in this review, to provide useful insights and new ideas in the related field. Full article

(This article belongs to the Special Issue Synthesis of TiO₂ Nanoparticles and Their Catalytic Activity)

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