Physico-chemical processes and kinetics of sunlight-induced hydrophobic ↔ superhydrophilic switching of transparent N-doped TiO₂ thin films

Ti4+-dopamine/sodium alginate multicomponent complex derived N-doped TiO2@carbon nanocomposites for efficient removal of methylene blue

A one-pot route for the preparation of TiO₂@carbon nanocomposite from Ti⁴⁺/polysaccharide coordination complex has been developed and shown advantages in operation, cost, environment, etc. However, the photodegradation rate of methylene blue needs to be improved. N-doping has been proven as an efficient means to enhance photodegradation performance. Thus, the present study upgraded the TiO₂@carbon nanocomposite to N-doped TiO₂@carbon nanocomposite (N-TiO₂@C) from Ti⁴⁺-dopamine/sodium alginate multicomponent complex. The composites were characterized by FT-IR, XRD, XPS, UV-vis DRS, TG-DTA, and SEM-EDS. TiO₂ was a typical rutile phase, and the carboxyl groups existed on N-TiO₂@C. The photocatalyst consequently showed high removal efficiency of methylene blue (MB). The cycling experiment additionally indicated the high stability of N-TiO₂@C. The present work provided a novel route for preparing N-TiO₂@C. Moreover, it can be extended to prepare N-doped polyvalent metal oxides@carbon composites from all water-soluble polysaccharides such as cellulose derivatives, pectin, starch, and guar gum.

Dental Materials for Oral Microbiota Dysbiosis: An Update

The balance or dysbiosis of the microbial community is a major factor in maintaining human health or causing disease. The unique microenvironment of the oral cavity provides optimal conditions for colonization and proliferation of microbiota, regulated through complex biological signaling systems and interactions with the host. Once the oral microbiota is out of balance, microorganisms produce virulence factors and metabolites, which will cause dental caries, periodontal disease, etc. Microbial metabolism and host immune response change the local microenvironment in turn and further promote the excessive proliferation of dominant microbes in dysbiosis. As the product of interdisciplinary development of materials science, stomatology, and biomedical engineering, oral biomaterials are playing an increasingly important role in regulating the balance of the oral microbiome and treating oral diseases. In this perspective, we discuss the mechanisms underlying the pathogenesis of oral microbiota dysbiosis and introduce emerging materials focusing on oral microbiota dysbiosis in recent years, including inorganic materials, organic materials, and some biomolecules. In addition, the limitations of the current study and possible research trends are also summarized. It is hoped that this review can provide reference and enlightenment for subsequent research on effective treatment strategies for diseases related to oral microbiota dysbiosis.

N-Doped TiO2 Photocatalyst Coatings Synthesized by a Cold Atmospheric Plasma

This work presents a simple, fast (20 min treatment), inexpensive, and highly efficient method for synthesizing nitrogen-doped titanium dioxide (N-TiO₂) as an enhanced visible light photocatalyst. In this study, N-TiO₂ coatings were fabricated by atmospheric pressure dielectric barrier discharge (DBD) at room temperature. The composition and the chemical bonds of the TiO₂ and N-TiO₂ coatings were characterized by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectroscopy (ToF-SIMS). The results indicate that the nitrogen element has doped the TiO₂ lattice, which was further confirmed by Raman spectroscopy and grazing incidence X-ray diffraction (GIXRD). The doping mechanism was investigated using OES to study the plasma properties under different conditions. It suggests that the NH radicals play a key role in doping TiO₂. The concentration of nitrogen in the N-TiO₂ coatings can be controlled by changing the concentration of NH₃ in the plasma or the applied power to adjust the concentration of NH radicals in the plasma. The band gap of N-TiO₂ was reduced after NH₃/Ar plasma treatment from 3.25 to 3.18 eV. Consequently, the N-TiO₂ coating showed enhanced photocatalytic activity under white-light-emitting-diode (LED) irradiation. The photocatalytic degradation rate for the N-TiO₂ coating was about 1.4 times higher than that of the undoped TiO₂ coating.

Structural studies of spray pyrolysis synthesized oxygen deficient anatase TiO2 thin films by using X-ray absorption spectroscopy

The present work focuses on synthesis and X-ray absorption studies of single phase oxygen deficient anatase TiO₂ thin films.

Under-Oil Switchable Superhydrophobicity to Superhydrophilicity Transition on TiO2 Nanotube Arrays

Recently, smart interfacial materials that can reversibly transit between the superhydrophobicity and superhydrophilicity have aroused much attention. However, all present performances happen in air, and to realize such a smart transition in complex environments, such as oil, is still a challenge. Herein, TiO₂ nanotube arrays with switchable transition between the superhydrophobicity and superhydrophilicity in oil are reported. The switching can be observed by alternation of UV irradiation and heating process, and the smart controllability can be ascribed to the cooperative effect between the surface nanostructures and the chemical composition variation. By using the controllable wetting performances, some applications such as under-oil droplet-based microreaction and water-removal from oil were demonstrated on our surface. This paper reports a surface with smart water wettability in oil, which could start some fresh ideas for wetting control on interfacial materials.

Recent Advances in TiO2 -Based Nanostructured Surfaces with Controllable Wettability and Adhesion

Bioinspired surfaces with special wettability and adhesion have attracted great interest in both fundamental research and industry applications. Various kinds of special wetting surfaces have been constructed by adjusting the topographical structure and chemical composition. Here, recent progress of the artificial superhydrophobic surfaces with high contrast in solid/liquid adhesion has been reviewed, with a focus on the bioinspired construction and applications of one-dimensional (1D) TiO2-based surfaces. In addition, the significant applications related to artificial super-wetting/antiwetting TiO2-based structure surfaces with controllable adhesion are summarized, e.g., self-cleaning, friction reduction, anti-fogging/icing, microfluidic manipulation, fog/water collection, oil/water separation, anti-bioadhesion, and micro-templates for patterning. Finally, the current challenges and future prospects of this renascent and rapidly developing field, especially with regard to 1D TiO2-based surfaces with special wettability and adhesion, are proposed and discussed.

Preparation and Characterization of Polyhedral Oligomeric Silsesquioxane-Containing, Titania-Thiol-Ene Composite Photocatalytic Coatings, Emphasizing the Hydrophobic-Hydrophilic Transition

Coatings prepared from titania-thiol-ene compositions were found to be both self-cleaning, as measured by changes in water contact angle, and photocatalytic toward the degradation of an organic dye. Stable titania-thiol-ene dispersions at approximately 2 wt % solids were prepared using a combination of high-shear mixing and sonication in acetone solvent from photocatalytic titania, trisilanol isobutyl polyhedral oligomeric silsesquioxane (POSS) dispersant, and select thiol-ene monomers, i.e., trimethylolpropane tris(3-mercaptopropionate) (TMPMP), pentaerythritol allyl ether (APE), and 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TTT). The dispersed particle compositions were characterized by DLS and TEM. The synthetic methods employed yield a strongly bound particle/POSS complex, supported by IR, 29Si NMR, and TGA. The factors of spray techniques, carrier solvent volatility, and particle size and size distributions, in combination, likely all contribute to the highly textured but uniform surfaces observed via SEM and AFM. Polymer composites possessed thermal transitions (e.g., Tg) consistent with composition. In general, the presence of polymer matrix provided mechanical integrity, without significantly compromising or prohibiting other critical performance characteristics, such as film processing, photocatalytic degradation of adsorbed contaminants, and the hydrophobic-hydrophilic transition. In all cases, coatings containing photocatalytic titania were converted from superhydrophobic to superhydrophilic, as defined by changes in the water contact angle. The superhydrophilic state of samples was considered persistent, since long time durations in complete darkness were required to observe any significant hydrophobic return. In a preliminary demonstration, the photocatalytic activity of prepared coatings was confirmed through the degradation of crystal violet dye. This work demonstrates that a scalable process can be found to prepare titania-thiol-ene coatings having improved coating properties which also exhibit photocatalytic and self-cleaning attributes.

Nucleation dynamics of nanostructural TiO2 films with controllable phases on (001) LaAlO3

Microstructure evolution and nucleation dynamics of TiO2 nanostructural thin films on (001) LaAlO3 substrates grown by the polymer-assisted deposition technique have been systematically studied with the increase of annealing temperature. Epitaxial anatase TiO2 phase with nanometer-scaled periodic surface strip patterns can be achieved when the sample is annealed at 900 ° C. It is also found that the morphology of the surface pattern is related to the ramping rate of the temperature during annealing. The formation of the surface strip pattern can be considered to be associated with the diffusion limit growth dynamics. The surface pattern structure was found to strongly affect the hydrophilic properties of the thin films.