Characteristics of silica-coated TiO2 and its UV absorption for sunscreen cosmetic applications

Mechanochemical Solid-State Immobilization of Photofunctional Dyes on Amorphous Silica Particles and Investigation of Their Interactive Mechanisms

Amorphous silica particles (ASPs) have been reported to exhibit bioactive properties and are becoming the focus of attention as bioceramics. However, their interactions with proteins in living organisms remain to be understood and need to be investigated in order to achieve wider applications. Our research group found that chlorine (Cl)-containing ASPs are useful for protein immobilization. Photofunctional dyes (fluorescein (FS-), methylene blue (MB+)) that have the carboxy and amino groups as the main functional groups were immobilized on the Cl-containing ASPs via the mechanochemical method as the model molecule and their spectral properties were used to investigate and discuss the organic/inorganic interfacial bonding states. In FS-, the oxygen atoms of the carboxy groups in the molecule were immobilized by the hydrogen bonds with the silanol groups on the ASPs surfaces, indicating that there is an optimum Cl content for the immobilization as the monomer state. In the case of MB+, as the Cl concentration in the ASPs increases, the immobilization via the electrostatic interactions between the Cl in the ASPs and the terminal dimethylamino group, and the hydrogen bonding between the N atoms of the MB+ hetero ring and the particle silanol group were enhanced. These results mainly suggest that the protein adsorption system occurs through the hydrogen bonding between the carboxy groups of the protein and the silanol groups on the particles and via electrostatic interactions between the amino groups of the protein and the dissociated silanol groups and the contained Cl at the particles. Thus, the spectral characterization using dyes as probes is expected to predict the protein interactions with the amorphous silica particles.

The Solvent Role for the Decomposition of Paracetamol in Distilled and Drinking Water by Pure and Ag-Modified TiO2 Sol-Gel Powders

In this study, pure TiO2 gels were synthesized by applying the sol-gel method, using Ti(IV) butoxide with the addition of two different solvents, namely ethylene glycol (EG) and isopropanol (isop), with only air moisture present. It was established using XRD that the gel prepared with the addition of EG was amorphous even at 400 °C, while the other gel was amorphous up to 300 °C. It was found that TiO2 (anatase) had a dominant crystalline phase during heating to 600 °C, while at 700 °C, TiO2 (rutile) appeared. The as-obtained powdered materials were annealed at 500 °C and subsequently underwent photocatalytic tests with paracetamol. Additionally, the TiO2 samples were modified with Ag+ co-catalysts (10-2 M), using photofixation by UV illumination. The photocatalytic activity of the Ag-modified powders was also tested in the photodegradation of a commonly used paracetamol in aqueous solution under UV light illumination. The obtained data exhibited that the annealed samples had better photocatalytic efficiency and decomposed paracetamol faster in comparison to the non-annealed sol-gel powders. The highest degradation efficiency was observed for the TBT/isop/Ag material, with degradation efficiencies average values of 65.59% and 75.61% paracetamol achieved after the third cycle of photocatalytic treatment. The co-catalytically modified powders had higher photocatalytic efficiency in comparison to the pure nanosized powders. Moreover, the sol-gel powders of TBT/EG, TBT/EG/Ag (10-2 M), TBT/isop, and TBT/isop/Ag (10-2 M) demonstrated the ability to retain their photocatalytic activity even after three cycles of use, suggesting that they could find practical use in the treatment of pharmaceutical wastewater. The observed photocatalytic efficiency and positive impact of silver make the prepared powders a desirable choice for pharmaceutical drug degradation, helping to promote environmentally friendly and effective wastewater treatment technology.

Asphaltenes from Heavy Crude Oil as Ultraviolet Stabilizers against Polypropylene Aging

The destruction of polymers under the influence of ultraviolet (UV) radiation is the cause of their aging and deterioration of strength properties. Asphaltenes are low-value waste products after the refining and deasphalting of heavy crude oil, which absorb UV radiation well. Asphaltenes require rational utilization, which suggests their use as UV stabilizing agents for polymers. In this work, asphaltenes were used to prevent UV aging of polypropylene (PP) by adding them in a mass fraction from 5% to 30% within an asphaltene/PP composite material. Rheometry, calorimetry, X-ray diffraction analysis, and tensile strength of PP films containing asphaltenes were performed before and after their intense UV irradiation for accelerated aging. Asphaltenes slightly reduce the viscosity, crystallinity, and mechanical strength of the initial PP due to their plasticizing effect. However, this deterioration in properties is more than compensated when studying UV-aged samples. Intense UV aging causes multiple catastrophic drops in the viscosity and strength of pure PP with the preservation of crystallinity due to the break of polymer chains and a decrease in molecular weight by approximately eight times. Asphaltenes suppress the destruction of PP, which is expressed in a significantly smaller decline in its viscosity and strength due to UV aging. The most optimal content of asphaltenes is 20%, which suppresses UV destruction by six times and best preserves the strength properties of PP.

Efficient Removal of Tetracycline and Bisphenol A from Water with a New Hybrid Clay/TiO2 Composite

New TiO₂ hybrid composites were prepared from kaolin clay, predried and carbonized biomass, and titanium tetraisopropoxide and explored for tetracycline (TET) and bisphenol A (BPA) removal from water. Overall, the removal rate is 84% for TET and 51% for BPA. The maximum adsorption capacities (q_m) are 30 and 23 mg/g for TET and BPA, respectively. These capacities are far greater than those obtained for unmodified TiO₂. Increasing the ionic strength of the solution does not change the adsorption capacity of the adsorbent. pH changes only slightly change BPA adsorption, while a pH > 7 significantly reduces the adsorption of TET on the material. The Brouers-Sotolongo fractal model best describes the kinetic data for both TET and BPA adsorption, predicting that the adsorption process occurs via a complex mechanism involving various forces of attraction. Temkin and Freundlich isotherms, which best fit the equilibrium adsorption data for TET and BPA, respectively, suggest that adsorption sites are heterogeneous in nature. Overall, the composite materials are much more effective for TET removal from aqueous solution than for BPA. This phenomenon is assigned to a difference in the TET/adsorbent interactions vs the BPA/adsorbent interactions: the decisive factor appears to be favorable electrostatic interactions for TET yielding a more effective TET removal.

Titanium biogenic nanoparticles to help the growth of Trichoderma harzianum to be used in biological control

BACKGROUND

The biogenic synthesis of metallic nanoparticles is a green alternative that reduces the toxicity of this nanomaterials and may enable a synergy between the metallic core and the biomolecules employed in the process enhancing biological activity. The aim of this study was to synthesize biogenic titanium nanoparticles using the filtrate of the fungus Trichoderma harzianum as a stabilizing agent, to obtain a potential biological activity against phytopathogens and mainly stimulate the growth of T. harzianum, enhancing its efficacy for biological control.

RESULTS

The synthesis was successful and reproductive structures remained in the suspension, showing faster and larger mycelial growth compared to commercial T. harzianum and filtrate. The nanoparticles with residual T. harzianum growth showed inhibitory potential against Sclerotinia sclerotiorum mycelial growth and the formation of new resistant structures. A great chitinolytic activity of the nanoparticles was observed in comparison with T. harzianum. In regard to toxicity evaluation, an absence of cytotoxicity and a protective effect of the nanoparticles was observed through MTT and Trypan blue assay. No genotoxicity was observed on V79-4 and 3T3 cell lines while HaCat showed higher sensitivity. Microorganisms of agricultural importance were not affected by the exposure to the nanoparticles, however a decrease in the number of nitrogen cycling bacteria was observed. In regard to phytotoxicity, the nanoparticles did not cause morphological and biochemical changes on soybean plants.

CONCLUSION

The production of biogenic nanoparticles was an essential factor in stimulating or maintaining structures that are important for biological control, showing that this may be an essential strategy to stimulate the growth of biocontrol organisms to promote more sustainable agriculture.

Controlling Superhydrophobicity and Oleophobicity of Polydimethylsiloxane-Coated Silica Hybrid Particles

Hierarchical functional organic-inorganic hybrid particles for versatile control of surface wettability have attracted much attention in a wide range of applications from makeup cosmetics to anti-smudging optoelectronic devices. In this study, superhydrophobic and oleophobic organic-inorganic hybrid particles were prepared by a simple and systematic fabrication strategy using the synergistic combination of commonly available silica particles and polydimethylsiloxanes (PDMSs) with hydrophobic chain ends. Various types of PDMSs with different chain lengths and chemical structures were surface-grafted to silica microparticles through facile physical dispersion and subsequent thermal treatment to form hydrogen bonds or covalent bonds between the inorganic silica and organic PDMS polymers and thus induce a core-shell structure for the hybrid particles, which imparts superhydrophobicity and oleophobicity to the surface of silica particles. The prepared PDMS-coated silica hybrid particles with long PDMS chains exhibited a water contact angle of 151.2° and an oil contact angle of 15.2° due to the rough surface morphology and hydrophobic long-chain effects. Furthermore, the resulting organic-inorganic hybrid particles were thermally stable up to 420 °C. This controlled approach endowed the organic-inorganic hybrid particles with both superhydrophobic and oleophobic surfaces and, therefore, these particles were proven to be suitable for waterproof applications.

Stabilizing both oil droplets and titanium dioxide nanoparticles in aqueous dispersion with nanofibrillated cellulose

Nanocellulose is a well-known stabilizer for several colloidal dispersions, including emulsions and solid nanoparticles, replacing surfactants, polymers, and other additives, and therefore providing more minimalistic and eco-friendly formulations. However, could this ability be extended to stabilize oil droplets and inorganic nanoparticles simultaneously in the same colloidal system? This work aimed to answer this question. We evaluated both cationic and anionic nanofibrillated celluloses to stabilize both titanium dioxide nanoparticles and oil droplets. The resulting suspensions held their macroscopic stability for up to 2 months, regardless of pH or surface charge. Cryo-TEM images revealed a complex network formation involving nanofibers and TiO₂ nanoparticles, which agrees with the high viscosity values and gel-like behavior found in rheology measurements. We propose that the formation of this network is responsible for the simultaneous stabilization of oil droplets and TiO₂ nanoparticles, and that this may be used as a formulation tool for other complex systems.

Asphaltene-Stabilized Polyisobutylene Pressure-Sensitive Adhesives for Ultraviolet Protection and Surface Bonding

The usual way to protect indoor areas from solar UV radiation is to use UV-absorbing materials, which are applied as a thin film on the surface of the windowpane. Asphaltenes are useless wastes from crude oil refining that absorb UV radiation well, which gave the idea of their use in protective coatings. Pressure-sensitive adhesives based on polyisobutylene containing from 5 to 30 wt% of asphaltenes were obtained. Deterioration of the adhesive properties with the introduction of 5-20 wt% of asphaltenes was shown by adhesion tests, which can be associated with the plasticization of the polymer matrix. At the same time, the use of 30 wt% of asphaltenes leads to the polymer matrix reinforcement with the restoration of adhesive properties to the original level or even slightly higher. The rheological study of adhesives at 25 °C and 120 °C showed the structural network formation by asphaltenes at a content of 30 wt%, explaining the increase in adhesion performance. According to microscopy, asphaltenes are flat brown glass shards in a polymer matrix. They absorb electromagnetic radiation, predominantly in the UV range, while maintaining relative translucency in the visible range. This makes it possible to obtain thin films from the asphaltene-filled adhesive for bonding glass sheets to produce UV-blocked and tinted windowpanes.

Co3O4/TiO2 catalysts studied in situ during the preferential oxidation of carbon monoxide: the effect of different TiO2 polymorphs

This study reveals the influence of different TiO2 supports on the catalytic performance and phase transformations of Co3O4 during CO-PrOx.

Hollow Silica Nano and Micro Spheres with Polystyrene Templating: A Mini-Review

Synthesis of monodisperse hollow silica nanospheres, especially using a hard template route, has been shown to be successful, but a high yield is needed for this strategy to be used on an industrial scale. On the other hand, there is a research gap in the synthesis of hollow silica microspheres due to the popularity and easiness of the synthesis of silica nanospheres despite the larger spheres being beneficial in some fields. In this review, current trends in producing hollow silica nanospheres using hard templates, especially polystyrene, are briefly presented. Soft templates have also been used to make highly polydisperse hollow silica spheres, and complex designs have improved polydispersity. The effect of the main parameters on the coating is presented here to provide a basic understanding of the interactions between the silica and template surface in the absence or presence of surfactants. Surface charge, surface modification, parameters in the sol-gel method and interaction between the silica and templates need to be further improved to have a uniform coating and better control over the size, dispersity, wall thickness and porosity. As larger organic templates will have lower surface energy, the efficiency of the micro sphere synthesis needs to be improved. Control over the physical structure of hollow silica spheres will open up many opportunities for them to be extensively used in fields ranging from waste removal to energy storage.

Water structure, dynamics and reactivity on a TiO2-nanoparticle surface: new insights from ab initio molecular dynamics

Water structure, dynamics and reactivity at the surface of a small TiO₂-nanoparticle fully immersed in water was investigated by an ab initio molecular dynamics simulation. Several modes of water binding were identified by assigning each atom to an atom type, representing a distinct chemical environment in the ab initio ensemble, and then computing radial distribution functions between the atom types. Surface reactivity was investigated by monitoring how populations of atom types change during the simulation. In order to acquire further insight, electron densities for a set of representative system snapshots were analyzed using an atoms-in-molecules approach. Our results reveal that water dissociation, where a water molecule splits at a bridging oxygen site to form a hydroxyl group and a protonated oxygen bridge, can occur by a mechanism involving transfer of a proton over several water molecules. The hydroxyl group and protonated oxygen bridge formed in the process persist (on a 10 ps time scale) and the hydroxyl group undergoes exchange using a mechanism similar to the one responsible for water dissociation. Rotational and translational dynamics of water molecules around the nanoparticle were analyzed in terms of reorientational time correlation functions and mean square displacement. While reorientation of water O-H vectors decreases quickly in the proximity of the nanoparticle surface, translational diffusion slows down more gradually. Our results give new insight into water structure, dynamics and reactivity on TiO₂-nanoparticle surfaces and suggest that water dissociation on curved TiO₂-nanoparticle surfaces can occur via more complex mechanisms than those previously identified for flat defect-free surfaces.

Classification, Synthetic, and Characterization Approaches to Nanoparticles, and Their Applications in Various Fields of Nanotechnology: A Review

Nanoparticles typically have dimensions of less than 100 nm. Scientists around the world have recently become interested in nanotechnology because of its potential applications in a wide range of fields, including catalysis, gas sensing, renewable energy, electronics, medicine, diagnostics, medication delivery, cosmetics, the construction industry, and the food industry. The sizes and forms of nanoparticles (NPs) are the primary determinants of their properties. Nanoparticles’ unique characteristics may be explored for use in electronics (transistors, LEDs, reusable catalysts), energy (oil recovery), medicine (imaging, tumor detection, drug administration), and more. For the aforementioned applications, the synthesis of nanoparticles with an appropriate size, structure, monodispersity, and morphology is essential. New procedures have been developed in nanotechnology that are safe for the environment and can be used to reliably create nanoparticles and nanomaterials. This research aims to illustrate top-down and bottom-up strategies for nanomaterial production, and numerous characterization methodologies, nanoparticle features, and sector-specific applications of nanotechnology.

A Review on Gallium Oxide Materials from Solution Processes

Gallium oxide (Ga₂O₃) materials can be fabricated via various methods or processes. It is often mentioned that it possesses different polymorphs (α-, β-, γ-, δ- and ε-Ga₂O₃) and excellent physical and chemical properties. The basic properties, crystalline structure, band gap, density of states, and other properties of Ga₂O₃ will be discussed in this article. This article extensively discusses synthesis of pure Ga₂O₃, co-doped Ga₂O₃ and Ga₂O₃-metal oxide composite and Ga₂O₃/metal oxide heterostructure nanomaterials via solution-based methods mainly sol-gel, hydrothermal, chemical bath methods, solvothermal, forced hydrolysis, reflux condensation, and electrochemical deposition methods. The influence of the type of precursor solution and the synthesis conditions on the morphology, size, and properties of final products is thoroughly described. Furthermore, the applications of Ga₂O₃ will be introduced and discussed from these solution processes, such as deep ultraviolet photodetector, gas sensors, pH sensors, photocatalytic and photodegradation, and other applications. In addition, research progress and future outlook are identified.

Preparation and modification methods of defective titanium dioxide-based nanoparticles for photocatalytic wastewater treatment-a comprehensive review

The rapid population growth and industrial expansion worldwide have created serious water contamination concerns. To curb the pollution issue, it has become imperative to use a versatile material for the treatment. Titanium dioxide (TiO₂) has been recognized as the most-studied nanoparticle in various fields of science and engineering due to its availability, low cost, efficiency, and other fascinating properties with a wide range of applications in modern technology. Recent studies revealed the photocatalytic activity of the material for the treatment of industrial effluents to promote environmental sustainability. With the wide band gap energy of 3.2 eV, TiO₂ can be activated under UV light; thus, many strategies have been proposed to extend its photoabsorption to the visible light region. In what follows, this has generated increasing attention to study its characteristics and structural modifications in different forms for photocatalytic applications. The present review provides an insight into the understanding of the synthesis methods of TiO₂, the current progress in the treatment techniques for the degradation of wide environmental pollutants employing modified TiO₂ nanoparticles, and the factors affecting its photocatalytic activities. Further, recent developments in using titania for practical applications, the approach for designing novel nanomaterials, and the prospects and opportunities in this exciting area have been discussed.

Titanium Dioxide: Structure, Impact, and Toxicity

Titanium dioxide, first manufactured a century ago, is significant in industry due to its chemical inertness, low cost, and availability. The white mineral has a wide range of applications in photocatalysis, in the pharmaceutical industry, and in food processing sectors. Its practical uses stem from its dual feature to act as both a semiconductor and light scatterer. Optical performance is therefore of relevance in understanding how titanium dioxide impacts these industries. Recent breakthroughs are summarised herein, focusing on whether restructuring the surface properties of titanium dioxide either enhances or inhibits its reactivity, depending on the required application. Its recent exposure as a potential carcinogen to humans has been linked to controversies around titanium dioxide's toxicity; this is discussed by illustrating discrepancies between experimental protocols of toxicity assays and their results. In all, it is important to review the latest achievements in fast-growing industries where titanium dioxide prevails, while keeping in mind insights into its disputed toxicity.

Damaging effects of TiO2 nanoparticles on the ovarian cells of Bombyx mori

As a new type of biologically compatible material, TiO₂ NPs are widely used in the industry as additives, drug carriers, and components of skin care products. Due to their wide use, residual TiO₂ NPs in the environment are a safety concern that has attracted extensive attention. In this study, the ovarian cell line BmN of the model organism Bombyx mori was used to reveal the damaging effects of TiO₂ NPs exposure. The results demonstrated that TiO₂ NPs exhibited a dose-dependent effect on the relative cell viability, with significant toxic effects being observed above 20 mg/L. Oxidative damage analysis showed that ROS accumulated significantly in BmN cells after exposure to TiO₂ NPs (P ≤ 0.05) and induced DNA damage. Further analysis revealed that the transcriptional levels of key superoxide dismutase genes (SOD) decreased significantly, while the transcriptions of key genes of the MAPK/NF-κB signaling pathway (P38, MEK, ERK and REL) and the downstream inflammatory factor genes (IL6 and TNFSF5) were all significantly up-regulated (P ≤ 0.05). Overall, our results indicate that exposure to TiO₂ NPs leads to reduced transcription of antioxidant genes, accumulation of peroxides, and inflammation. These findings provide valuable data for the safety evaluation of environmental residues of TiO₂ NPs.

Photocatalytic CO2 Reduction Using TiO2-Based Photocatalysts and TiO2 Z-Scheme Heterojunction Composites: A Review

Photocatalytic CO₂ reduction is a most promising technique to capture CO₂ and reduce it to non-fossil fuel and other valuable compounds. Today, we are facing serious environmental issues due to the usage of excessive amounts of non-renewable energy resources. In this aspect, photocatalytic CO₂ reduction will provide us with energy-enriched compounds and help to keep our environment clean and healthy. For this purpose, various photocatalysts have been designed to obtain selective products and improve efficiency of the system. Semiconductor materials have received great attention and have showed good performances for CO₂ reduction. Titanium dioxide has been widely explored as a photocatalyst for CO₂ reduction among the semiconductors due to its suitable electronic/optical properties, availability at low cost, thermal stability, low toxicity, and high photoactivity. Inspired by natural photosynthesis, the artificial Z-scheme of photocatalyst is constructed to provide an easy method to enhance efficiency of CO₂ reduction. This review covers literature in this field, particularly the studies about the photocatalytic system, TiO₂ Z-scheme heterojunction composites, and use of transition metals for CO₂ photoreduction. Lastly, challenges and opportunities are described to open a new era in engineering and attain good performances with semiconductor materials for photocatalytic CO₂ reduction.

Evaluation of Reducing NO and SO2 Concentration in Nano SiO2-TiO2 Photocatalytic Concrete Blocks

The use of titanium dioxide in concrete block pavements is a promising approach to reduce air pollution in the roadside. When TiO₂ is used as an additive of cement concrete or mortar, it is not dispersed uniformly due to agglomeration between particles causing the degradation of photocatalytic reaction. To improve the photocatalytic performance of TiO₂, the Nano SiO₂-TiO₂ (NST) has been developed by coating TiO₂ with SiO₂ as a support using the sol-gel method. The environmental performance of concrete blocks incorporating NST as an additive was evaluated using both laboratory and full-scale chamber experiments. It was observed from laboratory environment chamber testing that the NO reduction efficiency of concrete blocks with 4% NST ranged from 16.5 to 59.1%, depending on the UV intensity. Results of the full-scale chamber test on NST concrete blocks indicated that the NO and SO₂ reduction efficiencies were 22.3% and 14.4% at a 564 W/m² of solar radiation, respectively. It was found that the increase in UV intensity and solar radiation had a positive effect on decreasing NO and SO₂ concentration. In the future, the NST will be applied at in-service photocatalytic block pavements to validate the environmental performance in field conditions.

Potential consumer exposure to respirable particles and TiO2 due to the use of eyebrow powders

BACKGROUND

Cosmetic powders contain numerous components, including titanium dioxide (TiO₂), which is classified as possibly carcinogenic to humans (Group 2B). However, little is known about potential inhalation exposures to particles that are released during cosmetic powder applications.

METHODS

We realistically simulated the application of five different eyebrow powders using a mannequin and then determined concentrations of total suspended particles (TSP), PM₁₀, and PM₄ fractions of particles that would be inhaled during powder application. We determined the size and shape of particles in the original powders and released particles, as well as their TiO₂ concentrations and Ti content of individual particles.

RESULTS

The application of eyebrow powders resulted in the release and inhalation of airborne particles at concentrations ranging from 21.2 to 277.3 µg/m³, depending on the particle fraction and the powder. The concentrations of TiO₂ in PM₄ and PM₁₀ samples reached 2.7 µg/m³ and 9.3 µg/m³, respectively. The concentration of TiO₂ in airborne particle fractions was proportional to the presence of TiO₂ in the bulk powder.

CONCLUSION

The application of eyebrow powders results in user exposures to respirable PM₄ and PM₁₀ particles, including those containing TiO₂. This information should be of interest to stakeholders concerned about inhalation exposure to TiO₂.

Single cell encapsulation in a Pickering emulsion stabilized by TiO2 nanoparticles provides protection against UV radiation for a biopesticide

A new formulation for biological pest control with significant UV protection capability has been developed in this research. The formulation is based on individual encapsulation of fungal conidia in an oil/water Pickering emulsion. The droplets size of the emulsions was tuned to meet the demands of single conidia encapsulation in the oil droplets. The emulsions are stabilized by amine-functionalized TiO₂ (titania) nanoparticles (NPs). The droplet size, stability, and structure of the emulsions were investigated at different TiO₂ contents and oil/water phase ratios. Most of the emulsions remained stable for 6 months. The structural properties of the Pickering emulsions were characterized by confocal microscopy and high-resolution cryogenic scanning electron microscopy (cryo-HRSEM). The presence of the TiO₂ particles at the interface was confirmed by both confocal microscopy and cryo-HRSEM. Metarhizium brunneum-7 (Mb7) conidia were added to the emulsions. The successful encapsulation of individual conidia in the oil droplets was confirmed by confocal microscopy. The individual encapsulation of the conidia in the emulsions was significantly improved by dispersing the conidia in a 0.02 % Triton X-100 solution prior to emulsification. In addition, the bioassay results have shown, that exposure of the encapsulated conidia to natural UV light did not change their germination rates, however, the unprotected conidia demonstrated a dramatic decrease in their germination rates. These results confirm the UV protection capability of the studied emulsions.

Highlights Regarding the Use of Metallic Nanoparticles against Pathogens Considered a Priority by the World Health Organization

The indiscriminate use of antibiotics has facilitated the growing resistance of bacteria, and this has become a serious public health problem worldwide. Several microorganisms are still resistant to multiple antibiotics and are particularly dangerous in the hospital and nursing home environment, and to patients whose care requires devices, such as ventilators and intravenous catheters. A list of twelve pathogenic genera, which especially included bacteria that were not affected by different antibiotics, was released by the World Health Organization (WHO) in 2017, and the research and development of new antibiotics against these genera has been considered a priority. The nanotechnology is a tool that offers an effective platform for altering the physicalchemical properties of different materials, thereby enabling the development of several biomedical applications. Owing to their large surface area and high reactivity, metallic particles on the nanometric scale have remarkable physical, chemical, and biological properties. Nanoparticles with sizes between 1 and 100 nm have several applications, mainly as new antimicrobial agents for the control of microorganisms. In the present review, more than 200 reports of various metallic nanoparticles, especially those containing copper, gold, platinum, silver, titanium, and zinc were analyzed with regard to their anti-bacterial activity. However, of these 200 studies, only 42 reported about trials conducted against the resistant bacteria considered a priority by the WHO. All studies are in the initial stage, and none are in the clinical phase of research.

Charge Carrier Processes and Optical Properties in TiO2 and TiO2-Based Heterojunction Photocatalysts: A Review

Photocatalysis based technologies have a key role in addressing important challenges of the ecological transition, such as environment remediation and conversion of renewable energies. Photocatalysts can in fact be used in hydrogen (H₂) production (e.g., via water splitting or photo-reforming of organic substrates), CO₂ reduction, pollution mitigation and water or air remediation via oxidation (photodegradation) of pollutants. Titanium dioxide (TiO₂) is a “benchmark” photocatalyst, thanks to many favorable characteristics. We here review the basic knowledge on the charge carrier processes that define the optical and photophysical properties of intrinsic TiO₂. We describe the main characteristics and advantages of TiO₂ as photocatalyst, followed by a summary of historical facts about its application. Next, the dynamics of photogenerated electrons and holes is reviewed, including energy levels and trapping states, charge separation and charge recombination. A section on optical absorption and optical properties follows, including a discussion on TiO₂ photoluminescence and on the effect of molecular oxygen (O₂) on radiative recombination. We next summarize the elementary photocatalytic processes in aqueous solution, including the photogeneration of reactive oxygen species (ROS) and the hydrogen evolution reaction. We pinpoint the TiO₂ limitations and possible ways to overcome them by discussing some of the “hottest” research trends toward solar hydrogen production, which are classified in two categories: (1) approaches based on the use of engineered TiO₂ without any cocatalysts. Discussed topics are highly-reduced “black TiO₂”, grey and colored TiO₂, surface-engineered anatase nanocrystals; (2) strategies based on heterojunction photocatalysts, where TiO₂ is electronically coupled with a different material acting as cocatalyst or as sensitizer. Examples discussed include TiO₂ composites or heterostructures with metals (e.g., Pt-TiO₂, Au-TiO₂), with other metal oxides (e.g., Cu₂O, NiO, etc.), direct Z-scheme heterojunctions with g-C₃N₄ (graphitic carbon nitride) and dye-sensitized TiO₂.

Sponges as bioindicators for microparticulate pollutants?

Amongst other threats, the world's oceans are faced with man-made pollution, including an increasing number of microparticulate pollutants. Sponges, aquatic filter-feeding animals, are able to incorporate fine foreign particles, and thus may be a potential bioindicator for microparticulate pollutants. To address this question, 15 coral reef demosponges sampled around Bangka Island (North Sulawesi, Indonesia) were analyzed for the nature of their foreign particle content using traditional histological methods, advanced light microscopy, and Raman spectroscopy. Sampled sponges accumulated and embedded the very fine sediment fraction (<200 μm), absent in the surrounding sand, in the ectosome (outer epithelia) and spongin fibers (skeletal elements), which was confirmed by two-photon microscopy. A total of 34 different particle types were identified, of which degraded man-made products, i.e., polystyrene, particulate cotton, titanium dioxide and blue-pigmented particles, were incorporated by eight specimens at concentrations between 91 and 612 particle/g dry sponge tissue. As sponges can weigh several hundreds of grams, we conservatively extrapolate that sponges can incorporate on average 10,000 microparticulate pollutants in their tissue. The uptake of particles, however, appears independent of the material, which suggests that the fluctuation in material ratios is due to the spatial variation of surrounding microparticles. Therefore, particle-bearing sponges have a strong potential to biomonitor microparticulate pollutants, such as microplastics and other degraded industrial products.

Antioxidant Activity in Supramolecular Carotenoid Complexes Favored by Nonpolar Environment and Disfavored by Hydrogen Bonding

Carotenoids are well-known antioxidants. They have the ability to quench singlet oxygen and scavenge toxic free radicals preventing or reducing damage to living cells. We have found that carotenoids exhibit scavenging ability towards free radicals that increases nearly exponentially with increasing the carotenoid oxidation potential. With the oxidation potential being an important parameter in predicting antioxidant activity, we focus here on the different factors affecting it. This paper examines how the chain length and donor/acceptor substituents of carotenoids affect their oxidation potentials but, most importantly, presents the recent progress on the effect of polarity of the environment and orientation of the carotenoids on the oxidation potential in supramolecular complexes. The oxidation potential of a carotenoid in a nonpolar environment was found to be higher than in a polar environment. Moreover, in order to increase the photostability of the carotenoids in supramolecular complexes, a nonpolar environment is desired and the formation of hydrogen bonds should be avoided.

Toxicity of TiO2 Nanoparticles: Validation of Alternative Models

There are many studies concerning titanium dioxide (TiO₂) nanoparticles (NP) toxicity. Nevertheless, there are few publications comparing in vitro and in vivo exposure, and even less comparing air–liquid interface exposure (ALI) with other in vitro and in vivo exposures. The identification and validation of common markers under different exposure conditions are relevant for the development of smart and quick nanotoxicity tests. In this work, cell viability was assessed in vitro by WST-1 and LDH assays after the exposure of NR8383 cells to TiO₂ NP sample. To evaluate in vitro gene expression profile, NR8383 cells were exposed to TiO₂ NP during 4 h at 3 cm² of TiO₂ NP/cm² of cells or 19 μg/mL, in two settings—submerged cultures and ALI. For the in vivo study, Fischer 344 rats were exposed by inhalation to a nanostructured aerosol at a concentration of 10 mg/m³, 6 h/day, 5 days/week for 4 weeks. This was followed immediately by gene expression analysis. The results showed a low cytotoxic potential of TiO₂ NP on NR8383 cells. Despite the absence of toxicity at the doses studied, the different exposures to TiO₂ NP induce 18 common differentially expressed genes (DEG) which are involved in mitosis regulation, cell proliferation and apoptosis and inflammation transport of membrane proteins. Among these genes, we noticed the upregulation of Ccl4, Osm, Ccl7 and Bcl3 genes which could be suggested as early response biomarkers after exposure to TiO₂ NP. On the other hand, the comparison of the three models helped us to validate the alternative ones, namely submerged and ALI approaches.

Nanostructured Materials for Artificial Tissue Replacements

This paper review current trends in applications of nanomaterials in tissue engineering. Nanomaterials applicable in this area can be divided into two groups: organic and inorganic. Organic nanomaterials are especially used for the preparation of highly porous scaffolds for cell cultivation and are represented by polymeric nanofibers. Inorganic nanomaterials are implemented as they stand or dispersed in matrices promoting their functional properties while preserving high level of biocompatibility. They are used in various forms (e.g., nano- particles, -tubes and -fibers)-and when forming the composites with organic matrices-are able to enhance many resulting properties (biologic, mechanical, electrical and/or antibacterial). For this reason, this contribution points especially to such type of composite nanomaterials. Basic information on classification, properties and application potential of single nanostructures, as well as complex scaffolds suitable for 3D tissues reconstruction is provided. Examples of practical usage of these structures are demonstrated on cartilage, bone, neural, cardiac and skin tissue regeneration and replacements. Nanomaterials open up new ways of treatments in almost all areas of current tissue regeneration, especially in tissue support or cell proliferation and growth. They significantly promote tissue rebuilding by direct replacement of damaged tissues.

Spherical Composite Powder by Coupling Polymethyl Methacrylate and Boron Nitride via Spray Drying for Cosmetic Application

In the present study, spherical composite powder was successfully prepared via spray drying process using polymethyl methacrylate (PMMA) and hexagonal boron nitride (h-BN) powders. The pristine and as-prepared composite powders were examined using scanning electron microscopy, a particle size analyzer, oil absorption, and specific surface area analyses. These powders were then mixed with linseed oil to prepare samples for UV-Visible-Near Infrared spectroscopy investigation to determine their light absorption ability. Blank and powder-added blemish balm creams were examined using a sun protection factor tester and a thermal conductivity tester. In addition, transmittances of these creams were also evaluated. The experimental results show that spray-dried spherical composite powder exhibited good oil absorption ability. The blemish balm cream with 10 wt.% spray-dried composite powder not only exhibited superior sunscreen protection ability, but also good thermal conductivity.

A Facile Approach to Fabricate Dual Purpose Hybrid Materials for Tissue Engineering and Water Remediation

Creating hybrid materials with multifunctionality and robust mechanical stability from natural resources is a challenging proposition in materials science. Here, we report the scalable synthesis of hybrid collagen scaffolds using collagen extracted from leather industry wastes and sago starch derived from agro-industry. The hybrid scaffolds were incorporated with TiO2 nanoparticles and cross-linked with oxidized sago starch. The biocompatibility, thermal stability and antimicrobial property of hybrid scaffold enabled its application in burn wound healing demonstrated through albino rat models. The highly porous hybrid scaffolds are shown to be super-compressible, which is typically forbidden in materials of biological origin. We demonstrate that the hybrid scaffolds concurrently display both adsorption and absorption behavior in the removal of oil and dye molecules, respectively from contaminated water. This study paves the way for the development of novel multifunctional and shape recoverable hybrid materials specifically from renewable resources.

Study of the synergic effect between mica and biosurfactant to stabilize Pickering emulsions containing Vitamin E using a triangular design

HYPOTHESIS

Vitamin E has interesting biological functions for the cosmetic and pharmaceutical industry because it can act as a fat-soluble antioxidant, as well as peroxyl radical scavenger. However, this vitamin is formed by a group of compounds that include tocopherols (γ-tocopherols, α-tocopherol) characterized by their poor solubility in water, what implies the need of using stabilizing agents such as biosurfactants or minerals, in order to make them soluble or stable in formulations composed by water and oil.

EXPERIMENTS

In this work, it has been evaluated the synergic effect between a mining silicate mineral (mica) and a biosurfactant extract, obtained from corn steep liquor, to stabilize emulsions containing water and a non-aqueous soluble antioxidant consisting of Vitamin E, through the use of a triangular design.

FINDINGS

The results show that the presence of biosurfactant extract improves the emulsion volume up to 70% after 22 days, for an emulsion composed of Vitamin E and biosurfactant, whereas the mica component was able to increase the emulsion stability until values of 80% after 30 days of experiment, for those emulsions containing 10% of mica. Hence, both novel ingredients produce a synergistic effect on the Pickering emulsions carried out in the study.

Multifunctional Photostable Nanocomplex of ZnO Quantum Dots and Avobenzone via the Promotion of Enolate Tautomer

Ideal multifunctional ultraviolet radiation (UVR) absorbents with excellent photostability, high molar absorptivity, broadband UVR screening, and desired skin sensorial properties remain a significant challenge for the sunscreen industry. The potential of the nanocomplex (NCx) formed by microwave synthesis of ZnO quantum dots (QDs) in the presence of Avobenzone (Av) for achieving these goals is reported. The NCx exhibits unique synergy between ZnO QD and Av components, which enhances the photostability and molar absorptivity, extends UVA filtering range, and provides a visible emission that matches the typical human in vivo skin emission color. Density functional theory (DFT) and time-dependent DFT calculations of ZnO-Av hybrid structures and comparison of their spectroscopic features with experiments suggest that ZnO QDs catalyze the formation of highly photostable surface enolate species via aldol condensation reaction. The combination of experiments and computations used in this study can advance the science and technology of photoprotection.

Synthesis of cosmetic grade TiO2-SiO2 core-shell powder from mechanically milled TiO2 nanopowder for commercial mass production

TiO₂ nanoparticles as an active sunscreen ingredient generate reactive oxygen species (ROS) upon UVA irradiation which is cytotoxic, genotoxic and potential to damage the DNA. The health concern and potential risks from TiO₂ can be mitigated by shielding the particles through the suitable coating. Considering the advantages of SiO₂, SiO₂ coated TiO₂ nanoparticles can be a potential material which can replace TiO₂ for thickening, whitening, lubricating, and sunscreen ingredient in cosmetics. This article reports the synthesis of cosmetic grade TiO₂-SiO₂ core-shell nanopowder from mechanically milled TiO₂ nanopowder for commercial mass production. From commercial TiO₂ nanopowder was fabricated through size reduction by nanoset milling. Followed by the fabricated TiO₂ nanopowder coated with SiO₂ through sol-gel technique. A suitable optimum condition was explored for cosmetic grade TiO₂-SiO₂ core-shell nanopowder. Various physical properties and optical properties were analyzed. Synthesized of cosmetic grade TiO₂-SiO₂ core-shell nanopowder found to be at 100 nm size, with a homogeneous SiO₂ coating having UVA protection factor 39 and sun protection factor (SPF) is 42. From the size, safety, and SPF perspective it can be an excellent cosmetic grade powder and from process simplicity perspective it can be commercially viable.

Effects of coating materials on antibacterial properties of industrial and sunscreen-derived titanium-dioxide nanoparticles on Escherichia coli

Organic or inorganic stabilizers are often used for coating nanoparticles (NPs) in consumer products. However, upon release of stabilized NPs into the environment, uncertainty exists as to the antimicrobial properties of NPs due to stabilizers and the resultant bioaccumulation in organisms. This study investigates antibacterial effects and subsequent mechanisms of TiO₂ NPs on Escherichia coli (E. coli) in the presence and absence of stabilizers (CMC, PVP, and SiO₂) commonly used in consumer products. Compared with uncoated TiO₂ NPs, the presence of any stabilizers tested in this study increased toxicity of NPs and enhanced growth inhibition in E. coli. While the particle sizes of TiO₂ were smaller as the result of coating with PVP or CMC and appeared to contribute to E. coli cell damage, the generation of reactive oxygen species (ROS) was independent of stabilizer type. In fact, coating with PVP and CMC exerted ROS scavenging properties. In contrast, increased ROS production was observed at higher concentrations of TiO₂ and upon coating with SiO₂. This impact of SiO₂ can be related to the formation of a TiOSi chemical bond. The results of the present study emphasize the importance of nanoparticle coating to their anti-bacterial activity and toxicity.

Effects of noble metal nanoparticles on the hydroxyl radical scavenging ability of dietary antioxidants

Noble metal nanoparticles (NPs) have been widely used in many consumer products. Their effects on the antioxidant activity of commercial dietary supplements have not been well evaluated. In this study, we examined the effects of gold (Au NPs), silver (Ag NPs), platinum (Pt NPs), and palladium (Pd NPs) on the hydroxyl radical (·OH) scavenging ability of three dietary supplements vitamin C (L-ascorbic acid, AA), (-)-epigallocatechin gallate (EGCG), and gallic acid (GA). By electron spin resonance (ESR) spin-trapping measurement, the results show that these noble metal NPs can inhibit the hydroxyl radical scavenging ability of these dietary supplements.

Acute exposure to TiO2 nanoparticles produces minimal apparent effects on oyster, Crassostrea virginica (Gmelin), hemocytes

The response of oyster (Crassostrea virginica) hemocytes was studied following exposure to anatase nanoparticles (ca. 7.4nm), surface-coated rutile nanocomposites (UV-Titan M212, ca. 86nm) and bulk titanium dioxide (TiO₂) particles (anatase and rutile crystalline forms; 0.4-0.5μm). Hemocytes were collected from oysters and exposed to one of the four particle types at concentrations of 0.1, 0.5, and 1.0mg/L under dark and environmentally-relevant light conditions for periods of two and four hours. Hemocyte mortality, phagocytosis, and reactive oxygen species (ROS) production were then evaluated using flow-cytometric assays. Bulk and nanoparticulate TiO₂ had little effect on viability of oyster hemocytes or on production of ROS. Significant changes in phagocytosis occurred after exposure to anatase nanoparticles for 4h under dark conditions, and UV-Titan for 2h under light conditions. Results demonstrate that TiO₂ particles (bulk or nanoscale) produce minimal effects on hemocyte biomarkers examined following acute, in vitro exposures.

Adverse effect of nano-TiO2 on the marine macroalgae Gracilaria lemaneiformis (Gracilariales, Rhodophyta): growth and antioxidant activity

Macroalgae, the major contributor of primary productivity in coastal seas, contribute to the material cycle and energy flow in marine ecosystems. The purpose of this work was to evaluate the toxic effect of nano-TiO₂ on the growth and antioxidant activity of Gracilaria lemaneiformis. An obvious inhibition of growth was observed in this study. The algae exposed to nano-TiO₂ showed a negative growth rate at 20 mg L⁻¹ and 40 mg L⁻¹ during the 15 days exposure. The concentration of soluble protein increased slightly during the first 3 days of exposure, but it gradually diminished thereafter due to the high concentrations of nano-TiO₂ and to prolonged exposure. Nano-TiO₂ caused oxidative damage in G. lemaneiformis; superoxide anions accumulated, and nitrate reductase activity decreased linearly with the increase in nano-TiO₂. Furthermore, extracts of G. lemaneiformis can scavenge DPPH· and hydroxyl radicals for their antioxidant capacity. However, the capacity to scavenge DPPH· and hydroxyl radicals in vitro decreased slightly with the increase in nano-TiO₂. The results from this work imply that macroalgae can be an effective biomarker of nano-TiO₂ contamination and can be useful indicators to evaluate the oxidative damage of increasing pollutants in marine ecosystems.

Macroalgae, the major contributor of primary productivity in coastal seas, contribute to the material cycle and energy flow in marine ecosystems.

Effects of TiO2 crystal structure on the luminescence quenching of [Ru(bpy)2(dppz)]2+-intercalated into DNA

The intercalation of [Ru(bpy)₂(dppz)]²⁺ labeled as Ru(II) (bpy=2,2'-bipyridine and dppz=dipyrido[3,2,-a:2',3'-c]phenazine) into herring sperm DNA leads to the formation of emissive Ru(II)-DNA dyads, which can be quenched by TiO₂ nanoparticles (NPs) and sol-gel silica matrices at heterogeneous interfaces. The calcinations temperature exhibits a remarkable influence on the luminescence quenching of the Ru(II)-DNA dyads by TiO₂ NPs. With increasing calcinations temperature in the range from 200 to 850°C, the anatase-to-rutile TiO₂ crystal structure transformation increases the average particle size and hydrodynamic diameter of TiO₂ and DNA@TiO₂. The anatase TiO₂ has the stronger ability to unbind the Ru(II)-DNA dyads than the rutile TiO₂ at room temperature. The TiO₂ NPs and sol-gel silica matrices can quench the luminescence of the Ru(II) complex intercalated into DNA by selectively capturing the negatively DNA and positively charged Ru(II) complex to unbind the dyads, respectively. This present results provide new insights into the luminescence quenching and competitive binding of dye-labeled DNA dyads by inorganic NPs.

Bacterial cellulose–TiO2 nanocomposites promote healing and tissue regeneration in burn mice model

The development of novel cutaneous wound treatments particularly for burns is of paramount importance due to complex pathophysiology, prevalent infection and clinical complexities associated with burn care.

Detection of SiO2 nanoparticles in lung tissue by ToF-SIMS imaging and fluorescence microscopy

We demonstrate the suitability of the ToF-SIMS technique for the detection of SiO₂ nanoparticles in lung tissue sections by a comparison to fluorescence microscopy.

Multiphase TiO2nanostructures: a review of efficient synthesis, growth mechanism, probing capabilities, and applications in bio-safety and health

This review article provides an exhaustive overview of efficient synthesis, growth mechanism and research activities of multiphase TiO₂nanostructures to provide their structural, morphological, optical and biological properties co-relations.