Black hollow TiO2 nanocubes: Advanced nanoarchitectures for efficient visible light photocatalytic applications

Nano-sized heterogeneous photocatalyst Fe3O4@V/TiO2-catalyzed synthesis and antimycobacterial evaluation of 2-substituted benzimidazoles

The 2-substituted benzimidazole has emerged as a promising heterocyclic compound in the field of drug design. In pursuit of more sustainable photocatalysts for 2-substituted benzimidazole synthesis, the method for coating Fe3O4 with V-doped TiO2 was presented. On the base of characterizing composition, morphology, and properties, the prepared nano-sized Fe3O4@V/TiO2 composites were used as a heterogeneous photocatalyst to catalyze the synthesis of 2-substituted benzimidazoles under light. The photocatalyst Fe3O4@V/TiO2 composites showed the enhanced photocatalytic activity compared to no V-doped Fe3O4@TiO2, being able to yield various 2-substituted benzimidazoles in moderate to good yield with recyclability and stability. A possible photocatalysis mechanism was investigated. It was evident that holes, singlet oxygen, and ·O2̄ radical played important roles in the synthesis of 2-substituted benzimidazole. Moreover, some of the obtained products were demonstrated excellent antibacterial activity.

Black titanium oxide: synthesis, modification, characterization, physiochemical properties, and emerging applications for energy conversion and storage, and environmental sustainability

Since its advent in 2011, black titanium oxide (B-TiOx) has garnered significant attention due to its exceptional optical characteristics, notably its enhanced absorption spectrum ranging from 200 to 2000 nm, in stark contrast to its unmodified counterpart. The escalating urgency to address global climate change has spurred intensified research into this material for sustainable hydrogen production through thermal, photocatalytic, electrocatalytic, or hybrid water-splitting techniques. The rapid advancements in this dynamic field necessitate a comprehensive update. In this review, we endeavor to provide a detailed examination and forward-looking insights into the captivating attributes, synthesis methods, modifications, and characterizations of B-TiOx, as well as a nuanced understanding of its physicochemical properties. We place particular emphasis on the potential integration of B-TiOx into solar and electrochemical energy systems, highlighting its applications in green hydrogen generation, CO2 reduction, and supercapacitor technology, among others. Recent breakthroughs in the structure-property relationship of B-TiOx and its applications, grounded in both theoretical and empirical studies, are underscored. Additionally, we will address the challenges of scaling up B-TiOx production, its long-term stability, and economic viability to align with ambitious future objectives.

Ultra-fast green synthesis of a defective TiO2 photocatalyst towards hydrogen production

An ultra-fast green synthesis of defective titanium dioxide (TiO2) photocatalysts was conducted by the microwave-assisted method using l-ascorbic acid (l-As) as a reducing agent. Effect of l-As concentrations on the chemical-, optical- and photoelectrochemical properties as well as the photocatalytic performance towards the hydrogen (H2) production was explored. The obtained TiO2 nanoparticles (NPs) illustrated the brown fine powders with different brownness levels depending on the concentrations of l-As. A high l-As concentration provided a high brownness of TiO2 NPs with a high generation of Ti3+ defects and oxygen vacancies (Ov), which can extend the light absorption towards the visible and near-infrared regions, suppress the recombination rate of electron-hole pairs, promote the photocurrent response and minimize the interface charge transfer resistance. An appropriate quantity of generated defects and good porous properties played a crucial role in photocatalytic H2 production. Under fluorescence illumination, the sample synthesized with a TiO2 and l-As weight ratio of 1 : 0.25 (PAs0.25) exhibited the highest H2 production rate (∼162 μmol g-1 h-1 in the presence of 1 wt% Au co-catalyst) with a slight drop (∼8.2%) after the 5th use (15 h). The synthesis method proposed in this work provides a new insight to an ultra-fast synthesis of defective TiO2 NPs using an eco-friendly chemical precursor under non-severe conditions.

Hollow Nanoreactors for Controlled Photocatalytic Behaviors: Fundamental Theory, Structure-Performance Relationship, and Catalytic Advantages

Hollow nanoreactors (HoNRs) have regarded as an attractive catalytic material for photocatalysis due to their exceptional capabilities in enhancing light harvesting, facilitating charge separation and transfer, and optimizing surface reactions. Developing novel HoNRs offers new options to realize controllable catalytic behavior. However, the catalytic mechanism of photocatalysis occurring in HoNRs has not yet been fully revealed. Against this backdrop, this review elaborates on three aspects: 1) the fundamental theoretical insights of HoNRs-driven photocatalytic kinetics; 2) structure-performance relationship of HoNRs to photocatalysis; 3) catalytic advantages of HoNRs in photocatalytic applications. Specifically, the review focuses on the fundamental theories of HoNRs for photocatalysis and their structural advantages for strengthening light scattering, promoting charge separation and transfer, and facilitating surface reaction kinetics, and the relationship between key structural parameters of HoNRs and their photocatalytic performance is in-depth discussed. Also, future prospects and challenges are proposed. It is anticipated that this review paper will pave the way for forthcoming investigations in the realm of HoNRs for photocatalysis.

A membrane/mediator-free high-power density dual-photoelectrode PFC aptasensor for lincomycin detection in milk and chicken

Over use of lincomycin (LIN) as antibiotic in animals can lead to multiple harmful impacts to public health, thus detection of LIN at trace level in milk and chicken sample matrixes is vital. In this work, Zinc phthalocyanine nanoparticles sensitized MoS₂ (ZnPc/MoS₂) was firstly developed as a novel photocathode material combined with nitrogen-doped graphene-loaded TiO₂ nanoparticles (TiO₂/NG) as photoanode material to construct a dual-photoelectrode photofuel cell (PFC). The as-prepared membrane/mediator-free PFC achieved excellent output performance that the maximum power density (P_max) reached 11.83 μW cm^-2. Specific aptamers are adopted as LIN recognition elements, the as-proposed self-powered aptasensor for LIN exhibited a linear scope in 10^-11 -10^-5 mol L^-1 along with a low detection limit (3S/N) of 3.33 pmol L^-1. Consequently, such high-power density dual-photoelectrode PFC aptasensor may be a reassuring candidate electrochemical sensor for the detection of trace contamination in food samples.

Nano-architectural design of TiO2 for high performance photocatalytic degradation of organic pollutant: A review

In the past several decades, significant efforts have been paid toward photocatalytic degradation of organic pollutants in environmental research. During the past years, titanium dioxide nano-architectures (TiO2 NAs) have been widely used in water purification applications with photocatalytic degradation processes under Uv/Vis light illumination. Photocatalysis process with nano-architectural design of TiO2 is viewed as an efficient procedure for directly channeling solar energy into water treatment reactions. The considerable band-gap values and the subsequent short life time of photo-generated charge carriers are showed among the limitations of this approach. One of these effective efforts is the using of oxidation processes with advance semiconductor photocatalyst NAs for degradation the organic pollutants under UV/Vis irradiation. Among them, nano-architectural design of TiO2 photocatalyst (such as Janus, yolk-shell (Y@S), hollow microspheres (HMSs) and nano-belt) is an effective way to improve oxidation processes for increasing photocatalytic activity in water treatment applications. In the light of the above issues, this study tends to provide a critical overview of the used strategies for preparing TiO2 photocatalysts with desirable physicochemical properties like enhanced absorption of light, low density, high surface area, photo-stability, and charge-carrier behavior. Among the various nanoarchitectural design of TiO2, the Y@S and HMSs have created a great appeal given their considerable large surface area, low density, homogeneous catalytic environment, favorable light harvesting properties, and enhanced molecular diffusion kinetics of the particles. In this review was summarized the developments that have been made for nano-architectural design of TiO2 photocatalyst. Additional focus is placed on the realization of interfacial charge and the possibility of achieving charge carriers separation for these NAs as electron migration is the extremely important factor for increasing the photocatalytic activity.

Controllable Microemulsion Synthesis of Hybrid TiO2-SiO2 Hollow Spheres and Au-Doped Hollow Spheres with Enhanced Photocatalytic Activity

Hollow structures in TiO₂ materials can enhance the photocatalytic properties by reducing the diffusion length and improving the accessibility of active sites for the reactants. However, existing approaches for preparing hollow TiO₂ materials have two drawbacks that restrict their engineering applicability: first, a heavy reliance on templates to form a hollow structure, which makes the preparation laborious, complicated, and costly; second, difficult-to-achieve high crystallization while maintaining the small grain size in calcinated TiO₂, which is crucial for enhancing photocatalytic activity. Herein, a simple, effective method is proposed that not only enables the preparation of hybrid TiO₂-SiO₂ hollow spheres without the template fabrication and removal process via microemulsion technology but also achieves both high crystallization and a small grain size in calcinated TiO₂ at once through the calcination of amorphous TiO₂ with organosilane at a high temperature of 850 °C. The prepared TiO₂-SiO₂ hollow spheres with tunable sizes demonstrate high photocatalytic activity with a maximum k value of 133.74 × 10^-3 min^-1, which is superior to commercial photocatalyst P25 (k = 114.97 × 10^-3 min^-1). In addition, Au can be doped in the hybrid TiO₂-SiO₂ shell to gain Au-doped hollow spheres that show a high k value of up to 694.14 × 10^-3 min^-1, which is 6 times larger than that of P25 and much better than that reported in the literature. This study not only provides an effective approach to stabilize and tune the grain growth of the TiO₂ photocatalyst during calcination but also enables the simple preparation of hollow TiO₂-based materials with controllable hollow nanostructures.

Strategies for preparing TiO2/CuS nanocomposites with cauliflower-like protrusions for photocatalytic water purification

A simple and controllable method was developed to prepare TiO2/CuS nanocomposites with high photocatalytic efficiency.

Advances in Nanomaterials-Based Electrochemical Biosensors for Foodborne Pathogen Detection

Electrochemical biosensors utilizing nanomaterials have received widespread attention in pathogen detection and monitoring. Here, the potential of different nanomaterials and electrochemical technologies is reviewed for the development of novel diagnostic devices for the detection of foodborne pathogens and their biomarkers. The overview covers basic electrochemical methods and means for electrode functionalization, utilization of nanomaterials that include quantum dots, gold, silver and magnetic nanoparticles, carbon nanomaterials (carbon and graphene quantum dots, carbon nanotubes, graphene and reduced graphene oxide, graphene nanoplatelets, laser-induced graphene), metal oxides (nanoparticles, 2D and 3D nanostructures) and other 2D nanomaterials. Moreover, the current and future landscape of synergic effects of nanocomposites combining different nanomaterials is provided to illustrate how the limitations of traditional technologies can be overcome to design rapid, ultrasensitive, specific and affordable biosensors.

Anisotropic morphology, formation mechanisms, and fluorescence properties of zirconia nanocrystals

ZrO₂ nanocrystals with spheres and elongated platelets were systemically prepared through a simple hydrothermal method by the use of ZrOCl₂·8H₂O and CH₃COOK as raw materials. The anisotropic morphology and formation mechanism of the monoclinic and/or tetragonal ZrO₂ were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscope, and high-resolution transmission electron microscope techniques. The uniform elongated platelets and star-like structures were composed of short nanorods with a diameter of approximately 5 nm and a length of approximately 10 nm. The different morphologies were formed due to the different contents of CH₃COO^- and Cl^- and their synergy. The fluorescence band position and the band shape remained about the same for excitation wavelengths below 290 nm and the different morphologies of the nanocrystals.

Effects of Particle Size on the Structure and Photocatalytic Performance by Alkali-Treated TiO2

Particle size of nanomaterials has significant impact on their photocatalyst properties. In this paper, TiO₂ nanoparticles with different crystalline sizes were prepared by adjusting the alkali-hydrothermal time (0–48 h). An annealing in N₂ atmosphere after hydrothermal treatment caused TiO₂ reduction and created defects, resulting in the visible light photocatalytic activity. The evolution of physicochemical properties along with the increase of hydrothermal time at a low alkali concentration has been revealed. Compared with other TiO₂ samples, TiO₂-24 showed higher photocatalytic activity toward degrading Rhodamine B and Sulfadiazine under visible light. The radical trapping and ESR experiments revealed that O₂^•- is the main reactive specie in TiO₂-24. Large specific surface areas and rapid transfer of photogenerated electrons are responsible for enhancing photocatalytic activity. The above findings clearly demonstrate that particle size and surface oxygen defects can be regulated by alkali-hydrothermal method. This research will deepen the understanding of particle size on the nanomaterials performance and provide new ideas for designing efficient photocatalysts.

A novel self-powered aptasensor for digoxin monitoring based on the dual-photoelectrode membrane/mediator-free photofuel cell

Self-powered sensor is considered as a promising, rapid, portable and miniaturized detection device that can work without external power input. In this work, a novel dual-photoelectrode self-powered aptasensor for digoxin detection was designed on the basis of a photofuel cell (PFC) composed of a black TiO₂ (B-TiO₂) photoanode and a CuBr photocathode in a single-chamber cell. The sensing platform avoided the use of membrane, free mediator, bioactive components and costly metal Pt electrodes. The large inherent bias between the Fermi energy level of B-TiO₂ and that of CuBr improved the electricity output of PFC that the open circuit potential (OCP) and the maximum power density (P_max) reached 0.58 V and 6.78 μW cm^-2 respectively. Based on the excellent output of PFC, digoxin aptamer was immobilized on photoanode as the recognition element to capture digoxin molecules, which realized the high sensitive and selective detection of digoxin. The self-powered aptasensor displayed a broad linear in the range from 10^-12 M to 10^-5 M with a detection limit (3 S/N) of 0.33 pM. This work paved a luciferous way for further rapid, portable, miniaturized and on-site self-powered sensors.

Formation mechanism of porous rose-like WO3 and its photoresponse and stability study

Fabrication of rose-like WO₃ by chemical bath method.

Insights into the TiO2-Based Photocatalytic Systems and Their Mechanisms

Photocatalysis is a multifunctional phenomenon that can be employed for energy applications such as H2 production, CO2 reduction into fuels, and environmental applications such as pollutant degradations, antibacterial disinfection, etc. In this direction, it is not an exaggerated fact that TiO2 is blooming in the field of photocatalysis, which is largely explored for various photocatalytic applications. The deeper understanding of TiO2 photocatalysis has led to the design of new photocatalytic materials with multiple functionalities. Accordingly, this paper exclusively reviews the recent developments in the modification of TiO2 photocatalyst towards the understanding of its photocatalytic mechanisms. These modifications generally involve the physical and chemical changes in TiO2 such as anisotropic structuring and integration with other metal oxides, plasmonic materials, carbon-based materials, etc. Such modifications essentially lead to the changes in the energy structure of TiO2 that largely boosts up the photocatalytic process via enhancing the band structure alignments, visible light absorption, carrier separation, and transportation in the system. For instance, the ability to align the band structure in TiO2 makes it suitable for multiple photocatalytic processes such as degradation of various pollutants, H2 production, CO2 conversion, etc. For these reasons, TiO2 can be realized as a prototypical photocatalyst, which paves ways to develop new photocatalytic materials in the field. In this context, this review paper sheds light into the emerging trends in TiO2 in terms of its modifications towards multifunctional photocatalytic applications.

Plasma-Introduced Oxygen Defects Confined in Li4Ti5O12 Nanosheets for Boosting Lithium-Ion Diffusion

Although Li₄Ti₅O₁₂ (LTO) is considered as a promising anode material for high-power Li-ion batteries with high safety, the sluggish Li-ion diffusion coefficient restricts its widespread application. In this work, oxygen vacancy was successfully incorporated into LTO by an eco-friendly and cost-effective plasma process. The deficient LTO delivers much higher capacities of 173.4 mAh g^-1 at 1C rate after 100 cycles and 140.5 mAh g^-1 at 5C after 1000 cycles than those of pristine LTO. Meanwhile, even at a high rate of 20C, it displays an ultrahigh capacity of 133.1 mAh g^-1 after 500 cycles with a Coulombic efficiency of 100%. Detailed analysis reveals that the lithium storage mechanisms in the oxygen-deficient LTO, especially at high rate, were dominated by the insertion behavior and dual-phase conversion due to the fast ion-diffusion ability, rather than the widely reported surface capacitance by other approaches. This work highlights that defect generation by plasma in nanomaterials is an effective way to promote ion mobility, especially at high rates, and thus can be extended to other electrode materials for advanced energy-storage applications.

3D Yolk@Shell TiO2- x/LDH Architecture: Tailored Structure for Visible Light CO2 Conversion

CO2 photoconversion into hydrocarbon solar fuels by engineered semiconductors is considered as a feasible plan to address global energy requirements in times of global warming. In this regard, three-dimensional yolk@shell hydrogenated TiO2/Co-Al layered double hydroxide (3D Y@S TiO2- x/LDH) architecture was successfully assembled by sequential solvothermal, hydrogen treatment, and hydrothermal preparation steps. This architecture revealed a high efficiency for the photoreduction of CO2 to solar fuels, without a noble metal cocatalyst. The time-dependent experiment indicated that the production of CH3OH was almost selective until 2 h (up to 251 μmol/gcat. h), whereas CH4 was produced gradually by increasing the time of reaction to 12 h (up to 63 μmol/gcat. h). This significant efficiency can be ascribed to the engineering of 3D Y@S TiO2- x/LDH architecture with considerable CO2 sorption ability in mesoporous yolk@shell structure and LDH interlayer spaces. Also, oxygen vacancies in TiO2- x could provide excess sites for sorption, activation, and conversion of CO2. Furthermore, the generated Ti3+ ions in the Y@S TiO2 structure as well as connecting of structure with LDH plates can facilitate the charge separation and decrease the band gap of nanoarchitecture to the visible region.

Rational design of yolk–shell nanostructures for photocatalysis

Yolk–shell structures provide an ideal platform for the rational regulation and effective utilization of charge carriers because of their void space and large surface areas. Furthermore, the efficiency of charge behavior in every step can be further improved by many strategies. This review describes the synthesis of yolk–shell structures and their effect for the enhancement of heterogeneous photocatalysis.

Role of the growth step on the structural, optical and surface features of TiO2/SnO2 composites

TiO2/SnO2 composites have attracted considerable attention for their application in photocatalysis, fuel cells and sensors. Structural, morphological, optical and surface features play a pivotal role in photoelectrochemical applications and are critically related to the synthetic route. Most of the reported synthetic procedures require high-temperature treatments in order to tailor the sample crystallinity, usually at the expense of surface hydroxylation and morphology. In this work, we investigate the role of a treatment in an autoclave at a low temperature (100°C) on the sample properties and photocatalytic performance. With respect to samples calcined at 400°C, the milder crystallization treatment promotes anatase phase, mesoporosity and water chemi/physisorption, while reducing the incorporation of heteroatoms within the TiO2 lattice. The role of Sn content was also investigated, showing a marked influence, especially on the structural properties. Notably, at a high content, Sn favours the formation of rutile TiO2 at very low reaction temperatures (100°C), thanks to the structural compatibility with cassiterite SnO2. Selected samples were tested towards the photocatalytic degradation of tetracycline in water under UV light. Overall, the low-temperature treatment enables to tune the TiO2 phase composition while maintaining its surface hydrophilicity and gives rise to well-dispersed SnO2 at the TiO2 surface.

Engineering of highly active Au/Pd supported on hydrogenated urchin-like yolk@shell TiO2 for visible light photocatalytic Suzuki coupling

An engineered hydrogenated urchin-like yolk@shell TiO₂ structure decorated with Au/Pd nanoparticles was designed via sequential steps and employed in visible light photocatalytic Suzuki coupling.