Nitrogen and Fluorine Codoped, Colloidal TiO2 Nanoparticle: Tunable Doping, Large Red-Shifted Band Edge, Visible Light Induced Photocatalysis, and Cell Death

Dye decomposition and air de-pollution performance of TiO2/SiO2 and N-TiO2/SiO2 photocatalysts coated on Portland cement mortar substates

In this study, the newly synthesized TiO₂ and N doped TiO₂ clusters were added to silica sol to synthesize N-TiO₂/SiO₂ composites via the sol-gel method. Afterwards, the prepared sols were applied by brushing on portland cement. Doping with nitrogen significantly increased the absorption of TiO₂ towards the visible region, thus, increasing the photocatalytic activity. SEM characterization of the treated samples showed that the clusters were distributed in form of aggregates on the samples' surface. The self-cleaning and air de-polluting performances were assessed through methylene blue degradation and the oxidation of nitrogen oxide, resulting in methylene blue (MB) removal of 85% and 78% after 60 min of irradiation for SN10TiO₂ and STiO₂, respectively. Regarding air de-pollution performance, the newly synthesized photocatalysts showed the ability of NOx reduction. However, their efficiency was somewhat lower, in which 23.81% of NO has been oxidized by the sample SN10TiO₂, while SP25 showed a total NO conversion of 38.98%. The powdered xerogels of the newly synthesized nanoparticles revealed high photocatalytic efficiency concerning NO oxidation, resulting in a higher performance compared to those obtained by the xerogel containing P25.

Cytotoxicity of ZnO Nanoparticle Under Dark via Oxygen Vacancy Dependent Reactive Oxygen Species Generation

Antimicrobial and cytotoxic effect of zinc oxide nanomaterials are popularly thought due to zinc ion leaching, but the exact mechanism of cytotoxicity is controversial and not fully understood. Recent works...

Subtle structure matters: boosting surface-directed photoelectron transfer via the introduction of specific monovalent oxygen vacancies in TiO2

Oxygen vacancies (O_v) are widely considered to play crucial roles in photocatalysis, but how and why they contribute to improved performances remains controversial. In this work, we studied the promotional effect of O_v on photoelectron transfer in TiO₂, using first-principles density functional theory calculations with correction for on-site Coulomb interactions. We explicitly identified three types of O_v with different charge states (i.e., charge-neutral , monovalent , divalent O_v²⁺) via electronic structure analysis. Electron transfer energy calculations revealed that the ionized O_v in anatase TiO₂ are able to collect excess electrons whereas those in the rutile phase are not. The presence of ionized O_v further endows anatase TiO₂ with directional electron transfer along the [100] orientation, in favor of anatase TiO₂(101) for photocatalytic reduction surpassing the (001) termination. After examining various combination modes of ionized O_v involving different charge states and spatial distributions, we demonstrated that the vertical chain in anatase TiO₂(101) is the most catalytically effective O_v pattern in TiO₂. These results signify the importance of subtle defects in photocatalysis and may assist future photocatalyst design toward higher photocatalytic efficiency.

Enhancement of Interfacial Charge Transfer of TiO2/Graphene with Doped Ca2+ for Improving Electrical Conductivity

Imparting surface coatings with conductivity is an effective way to prevent fire and explosion caused by electrostatic discharge. TiO₂ is a commonly used paint; however, intrinsic TiO₂ has poor electrical conductivity. Herein, we develop a method to make TiO₂ coating highly conductive by doping Ca²⁺ into the TiO₂ lattice based on the introduction of graphene. It is demonstrated that doping Ca²⁺ increases the carrier density of TiO₂ and its morphology changes from a sphere to a spindle shape, which increases the interfacial contact area between TiO₂ and graphene. Therefore, resistivity can be greatly decreased due to the construction of fast charge transport pathways from TiO₂ to graphene, resulting from an increase in the speed of interfacial charge transfer. In addition, the electronic properties of the samples are also studied through first-principles calculations before and after Ca²⁺ doping. The result of the theoretical analysis is in agreement with that of experiments. Thus, the lowest resistivity of Ca²⁺-TiO₂/graphene can reach 0.004 Ω cm. Consequently, the feature of superior conductivity of the Ca²⁺-TiO₂/graphene composite endows it with practical application potential in the field of antistatic coating.

A review on TiO2-based photocatalytic systems applied in fruit postharvest: Set-ups and perspectives

Titanium dioxide (TiO₂) is a photocatalytic material used to degrade ethylene, and it has been studied as an alternative postharvest technology. Although several studies have indicated the effective action of TiO₂ photocatalysis for delaying the fruit ripening, photocatalytic systems need to be well-designed for this application. Fruit is susceptible to environmental conditions like temperature, relative humidity, atmosphere composition and exposure to UV-light. This fragility associated with its variable ethylene production rate over its maturation stage limits the photocatalysis parameters optimization. Thus, this review aims to detail the reaction mechanisms, set-up, advantages, and limitations of TiO₂ photocatalytic systems based on polymers-TiO₂ nanocomposites and reactors containing TiO₂ immobilized into inorganic supports designed for fruit applications. It is expected that this review can elucidate the fundamental aspects that should be considered for the use of these systems.

Nickel and sulfur codoped TiO2 nanoparticles for efficient visible light photocatalytic activity

In this work, Nickel (Ni) and sulfur (S) codoped TiO2 nanoparticles were prepared by a sol-gel technique. The as-prepared catalyst was characterized using X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), FT-Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectra (DRS) for investigating crystal structure, crystal phase, particle size and bandgap energy of these samples. The photocatalytic performances of all the prepared catalysts have been investigated for the degradation of methylene blue (MB) under visible light irradiation. It was noticed that Ni-S codoped TiO2(Ni-S/TiO2) nanoparticles exhibited much higher photocatalytic activity compared with pure, Ni and S doped TiO2 due to higher visible light absorption and probable decrease in the recombination of photo-generated charges. It was decided that the great visible light absorption was created for codoped TiO2 by the formation of impurity energy states near both the edges of the collection, which works as trapping sites for both the photogenerated charges to decrease the recombination process.

Hydroxyl-enriched highly crystalline TiO2 suspensible photocatalyst: facile synthesis and superior H2-generation activity

A facile ethanol-controlled strategy was reported to simultaneously realize the excellent suspendability and high-crystallinity of a hydroxyl-enriched TiO₂ nanocrystal for efficient photocatalytic H₂ generation.

Enhancing the photocatalytic efficiency of the BiOCl/Bi3O4Cl composite modified with WO3 for environmental purification under visible light

The role of WO3 in enhancing the photocatalytic behavior of the composite photocatalyst towards the decomposition of organic pollutants in the environment under visible light has been demonstrated.

TiO2-Templated BaTiO3 Nanorod as a Piezocatalyst for Generating Wireless Cellular Stress

Although the piezoelectric property of a BaTiO₃ nanoparticle is routinely used in energy harvesting application, it can also be exploited for wireless cell stimulation and cell therapy. However, such biomedical application is rare due to limited availability of colloidal BaTiO₃ nanoparticles of <100 nm hydrodynamic size with good piezocatalytic property and efficient biolabeling performance. Here, we report a colloidal form of a piezocatalytic BaTiO₃-based nanorod of <100 nm hydrodynamic size that can offer wireless cell stimulation. The nanorod is prepared using a TiO₂ nanorod as the template, and the resultant TiO₂-BaTiO₃-based composite nanorod is coated with a hydrophilic polymer shell. These nanorods can label cells and, under the ultrasound exposure, produce reactive oxygen species inside cells via piezocatalysis, leading to cell death. These nanorods can be used for wireless modulation of intracellular processes.

Regulation of Cell Uptake and Cytotoxicity by Nanoparticle Core under the Controlled Shape, Size, and Surface Chemistries

Nanoparticle structural parameters, such as size, surface chemistry, and shape, are well-recognized parameters that affect biological activities of nanoparticles. However, whether the core material of a nanoparticle also plays a role remains unknown. To answer this long-standing question, we synthesized and investigated a comprehensive library of 36 nanoparticles with all combinations of three types of core materials (Au, Pt, and Pd), two sizes (6 and 26 nm), and each conjugated with one of six surface ligands of different hydrophobicity. Using this systematic approach, we were able to identify cellular perturbation specifically attributed to core, size, or surface ligand. We discovered that core materials exhibited a comparable regulatory ability as surface ligand on cellular ROS generation and cytotoxicity. Pt nanoparticles were much more hydrophilic and showed much less cell uptake compared to Au and Pd nanoparticles with identical size, shape, and surface ligands. Furthermore, diverse core materials also regulated levels of cellular redox activities, resulting in different cytotoxicity. Specifically, Pd nanoparticles significantly reduced cellular H₂O₂ and promoted cell survival, while Au nanoparticles with identical size, shape, and surface ligand induced higher cellular oxidative stress and cytotoxicity. Our results demonstrate that nanoparticle core material is as important as other structural parameters in nanoparticle-cell interactions, making it also a necessary consideration when designing nanomedicines.

pH-Controllable regeneration and visible-light photocatalytic redox of carbon and nitrogen co-doped Zn3Nb2O8 towards degradation of multiple contaminants

N/C–Zn₃Nb₂O₈ with a compatible band structure and negative surface demonstrates enhanced visible light photocatalytic activity and stability in degradation of multiple pH-sensitive contaminants.

Photosensitizer Tailored Surface Functionalized Carbon Dots for Visible Light Induced Targeted Cancer Therapy

Herein, a photosensitizer (riboflavin) tailored surface functionalized carbon dot (RCD1s) was designed to utilize it in visible light induced targeted cancer therapy. At first, phenylboronic acid appended biotinylated blue emitting carbon dot (CD1s) was synthesized. Riboflavin having "diol" moiety was covalently linked with this CD1s to prepare RCD1s by using complementary boronate-diol linkage. Lewis acid-base interaction facilitated the covalent linkage formation between the surface functionalizing agent of CD1s and riboflavin to develop water-soluble, green emitting RCD1s. Interestingly, this newly synthesized RCD1s has the ability to produce reactive oxygen species (ROS) such as hydroxyl and superoxide radicals under exposure of visible light (wavelength: 460-490 nm). These ROS also can destroy the structure of DNA by oxidative pathway. Thus, under irradiation of visible light (wavelength: 460-490 nm), RCD1s was found to kill HeLa and B16F10 melanoma cells over noncancer cell NIH3T3 by ∼5-fold higher efficacy through ROS induced oxidative DNA damage. The presence of biotin on the surface of the riboflavin tethered carbon dot is essential for the selective killing of cancer cells over normal cells. In the presence of UV light (340-420 nm), RCD1s showed no notable killing of cancer cells as well as normal cells. Besides, RCD1s in the presence of visible light selectively stained HeLa and B16F10 cells over noncancerous cell NIH3T3 by exploiting its fluorescence and cancer cell targeting moiety, biotin. Hence, the newly developed RCD1s can be utilized in theranostic applications including bioimaging and selective killing of cancer cells in the presence of visible light (460-490 nm).

A Review of Recent Applications of Ion Beam Techniques on Nanomaterial Surface Modification: Design of Nanostructures and Energy Harvesting

Nanomaterials have gained plenty of research interest because of their excellent performance, which is derived from their small size and special structure. In practical applications, to acquire nanomaterials with high performance, many methods have been used to modulate the structure and components of materials. To date, ion beam techniques have extensively been applied for modulating the performance of various nanomaterials. Energetic ion beams can modulate the surface morphology and chemical components of nanomaterials. In addition, ion beam techniques have also been used to fabricate nanomaterials, including 2D materials, nanoparticles, and nanowires. Compared with conventional methods, ion beam techniques, including ion implantation, ion irradiation, and focused ion beam, are all pure physical processes; these processes do not introduce any impurities into the target materials. In addition, ion beam techniques exhibit high controllability and repeatability. Here, recent progress in ion beam techniques for nanomaterial surface modification is systematically summarized and existing challenges and potential solutions are presented.

Extraordinary catalysis induced by titanium foil cathode plasma for degradation of water pollutant

The present paper reports a rapid and cost-effective bifunctional approach to the degradation of organic pollutants in the aqueous solution. This in situ hybrid induced photocatalytic method involves the advanced oxidation process, and photocatalytic process induced by ultraviolet radiated from the plasma discharge to improve the degradation efficiency. This powerful plasma allows the organic molecules to be cleaved either in the plasma zone or on the plasma/solution interface through hydrogen abstraction and electron transfer. Four parallel metal foil electrodes (i.e. Ta, Cu, Ti and Au coated Ti), used as cathodes in the two-electrode system, were evaluated in terms of their degradable performance to organic pollutants. It was found that the degradation rates are dependent on the electrical conduction of metal cathodes. During the discharge process, the Ti-based foil produces TiO₂ particles, which then act as catalyst in the electrolyte and perform the photocatalytic process along with the plasma discharge process to degrade organic pollutants. It is of particular interest that gold nanoparticles, generated from Au coated Ti foil film during electrode discharging, are less than 5 nm in size and further enhance the TiO₂ photocatalytic activity. In fact, this bifunctional plasma discharge process to the degradation of water pollutant provides an insight into more applications such as chemical conversion, water purification and dust pollution.

Enhanced photocatalytic performance of WON@porous TiO2 nanofibers towards sunlight-assisted degradation of organic contaminants

In the last few decades, TiO₂ has been widely used in different types of photocatalytic applications. However, the relatively large optical band gap (∼3.2 eV), low charge carrier mobility and consequently its low quantum efficiency limit its photocatalytic activity. Herein, we construct a novel nanostructured heterojunction of WON/TiO₂ nanofibers (NFs) by integration of TiO₂ nanofibers synthesized by electrospinning of a polymer solution containing a titanium(iv) butoxide precursor with WON nanoparticles fabricated via annealing of a WO₃ precursor in dry ammonia at 700 °C. The synthesized photocatalysts were characterized using different spectroscopic techniques. Their photocatalytic performance towards the degradation of methyl orange, methylene blue, and phenol as model contaminants was investigated and the charge transfer process was elucidated and compared to that of a TiO₂/WO₃ heterojunction.

Coupling of WON with TiO₂ nanofibers creates a novel heterojunction with enhanced photocatalytic activity.