Synthesis of Carbon Nanotube-Nanotubular Titania Composites by Catalyst-Free CVD Process: Insights into the Formation Mechanism and Photocatalytic Properties

Understanding the influence of electrolyte aging in electrochemical anodization of titanium

Titania nanotubes or nanopores self-ordered on electrochemically anodized (EA) titanium have been widely applied towards photocatalysis, solar cells, purification and biomedical implants. As a result, significant research has been focused towards optimizing anodization to fabricate controlled, stable and reproducible nanostructures. Among these, the use of organic-based electrolyte, like ethylene glycol (with NH₄F and water), to anodize Ti has been widely applied and researched. Interestingly, among the various influencing EA factors, electrolyte aging (repeated EA using non-target Ti, prior to EA of target Ti substrate) has been underexplored, with only few studies aiming to optimize electrolyte aging and its influence on the nanostructures fabricated. Moreover, many research laboratories utilize electrolyte aging in Ti anodization, but this practice is seldom reported. In this extensive and pioneering review, we discuss and detail electrolyte aging in Ti anodization to fabricate controlled nanostructures, and its influence on nanostructure characteristics including morphology, chemistry, stability and application-specific performance. This review will inform future research aimed at optimizing electrolyte aging and Ti anodization to fabricate controlled nanostructures catering to specific application needs.

Recent Progress in the Synthesis and Applications of Composite Photocatalysts: A Critical Review

Photocatalysis is an advanced technique that transforms solar energy into sustainable fuels and oxidizes pollutants via the aid of semiconductor photocatalysts. The main scientific and technological challenges for effective photocatalysis are the stability, robustness, and efficiency of semiconductor photocatalysts. For practical applications, researchers are trying to develop highly efficient and stable photocatalysts. Since the literature is highly scattered, it is urgent to write a critical review that summarizes the state-of-the-art progress in the design of a variety of semiconductor composite photocatalysts for energy and environmental applications. Herein, a comprehensive review is presented that summarizes an overview, history, mechanism, advantages, and challenges of semiconductor photocatalysis. Further, the recent advancements in the design of heterostructure photocatalysts including alloy quantum dots based composites, carbon based composites including carbon nanotubes, carbon quantum dots, graphitic carbon nitride, and graphene, covalent-organic frameworks based composites, metal based composites including metal carbides, metal halide perovskites, metal nitrides, metal oxides, metal phosphides, and metal sulfides, metal-organic frameworks based composites, plasmonic materials based composites and single atom based composites for CO₂ conversion, H₂ evolution, and pollutants oxidation are discussed elaborately. Finally, perspectives for further improvement in the design of composite materials for efficient photocatalysis are provided.

Influence of sterilization on the performance of anodized nanoporous titanium implants

Towards clinical translation of bioactive nano-engineered titanium implants, achieving appropriate sterilization and understanding its influence on the modified implant characteristics is essential. With limited studies exploring the influence of sterilization techniques on electrochemically anodized titanium with TiO₂ nanostructures, we aimed to advance this domain by performing an in-depth evaluation of the influence of common sterilization techniques (ethanol immersion, various UV irradiation times, gamma irradiation, and dry/wet autoclaving) on TiO₂ nanopores fabricated on micro-rough Ti surfaces (dual micro-nano) via single step anodization. Various sterilized surfaces were systematically compared in terms of topographical, chemical, crystalline, wettability and mechanical characteristics. Next, we investigated the protein adhesion capacity and functions of primary gingival fibroblasts (proliferation, adhesion/alignment and spreading morphology) to compare the bioactivity of the sterilized nanopores. Ethanol immersion, gamma irradiation and UV irradiation conserved the topography of the fabricated nanopores, while autoclave sterilization (both dry and wet) compromised the nanoporous structures. Various duration of UV-sterilization resulted in no significant changes in the surface topography and chemistry of the fabricated TNPs. Our findings revealed that UV irradiation is the most appropriate technique to sterilize nano-engineered titanium implants for appropriate wettability, protein adhesion capacity and enhanced metabolism and proliferation of human gingival fibroblasts (hGFs). This study systematically investigated the influence of sterilization on anodized nano-engineered titanium implants towards achieving reproducible outcomes (in terms of topography, chemistry and bioactivity), and found that UV irradiation holds great promise for application across different nano-engineered metal surfaces.

Fabrication of TiO2 Nanosheet Aarrays/Graphene/Cu2O Composite Structure for Enhanced Photocatalytic Activities

TiO₂ NSAs/graphene/Cu₂O was fabricated on the carbon fiber to use as photocastalysts by coating Cu₂O on the graphene (G) decorated TiO₂ nanosheet arrays (NSAs). The research focus on constructing the composite structure and investigating the reason to enhance the photocatalytic ability. The morphological, structural, and photocatalytic properties of the as-synthesized products were characterized. The experimental results indicate that the better photocatalytic performance is ascribed to the following reasons. First, the TiO₂ NSAs/graphene/Cu₂O composite structure fabricated on the carbon cloth can form a 3D structure which can provide a higher specific surface area and enhance the light absorption. Second, the graphene as an electron sink can accept the photoelectrons from the photoexcited Cu₂O which will reduce the recombination. Third, the TiO₂ nanosheet can provide more favorable carrier transportation channel which can reduce the recombination of carriers. Finally, the Cu₂O can extend the light absorption range.