Nanoscale Titanium Dioxide Research Articles

Prenatal exposure to paraquat and nanoscaled TiO2 aerosols alters the gene expression of the developing brain

Nanopesticides are innovative pesticides involving engineered nanomaterials in their formulation to increase the efficiency of plant protection products, while mitigating their environmental impact. Despite the predicted growth of the nanopesticide use, no data is available on their inhalation toxicity and the potential cocktail effects between their components. In particular, the neurodevelopmental toxicity caused by prenatal exposures might have long lasting consequences. In the present study, we repeatedly exposed gestating mice in a whole-body exposure chamber to three aerosols, involving the paraquat herbicide, nanoscaled titanium dioxide particles (nTiO2), or a mixture of both. Particle number concentrations and total mass concentrations were followed to enable a metrological follow-up of the exposure sessions. Based on the aerosols characteristics, the alveolar deposited dose in mice was then estimated. RNA-seq was used to highlight dysregulations in the striatum of pups in response to the in utero exposure. Modifications in gene expression were identified at post-natal day 14, which might reflect neurodevelopmental alterations in this key brain area. The data suggest an alteration in the mitochondrial function following paraquat exposure, which is reminiscent of the pathological process leading to Parkinson disease. Markers of different cell lineages were dysregulated, showing effects, which were not limited to dopaminergic neurons. Exposure to the nTiO2 aerosol modulated the regulation of cytokines and neurotransmitters pathways, perhaps reflecting a minor neuroinflammation. No synergy was found between paraquat and nTiO2. Instead, the neurodevelopmental effects were surprisingly lower than the one measured for each substance separately.

Evaluation of enhanced darkfield microscopy and hyperspectral imaging for rapid screening of TiO2 and SiO2 nanoscale particles captured on filter media.

Here we report on initial efforts to evaluate enhanced darkfield microscopy (EDFM) and light scattering Vis-NIR hyperspectral imaging (HSI) as a rapid screening tool for the offline analysis of mixed cellulose ester (MCE) filter media used to collect airborne nanoparticulate from work environments. For this study, the materials of interest were nanoscale titanium dioxide (TiO2 ) and silicon dioxide (SiO2 ; silica), chosen for their frequent use in consumer products. TiO2 and SiO2 nanoscale particles (NPs) were collected on MCE filter media and were imaged and analyzed via EDFM-HSI. When visualized by EDFM, TiO2 and SiO2 NPs were readily apparent as bright spherical structures against a dark background. Moreover, TiO2 and SiO2 NPs were identified in hyperspectral images. EDFM-HSI images and data were compared to scanning transmission electron microscopy (STEM), a NIST-traceable technique for particle size analysis, and the current gold standard for offline analysis of filter media. As expected, STEM provided more accurate sizing and morphology data when compared to EDFM-HSI, but is not ideal for rapid screening of the presence of NPs of interest since it is a costly, low-throughput technique. In this study, we demonstrate the utility of EDFM-HSI in rapidly visualizing and identifying TiO2 and SiO2 NPs on MCE filters. This screening method may prove useful in expediting time-to-knowledge compared to electron microscopy. Future work will expand this evaluation to other industrially relevant NPs, other filter media types, and real-world filter samples from occupational exposure assessments.

Experimental Study of the Strength Characteristics of a Modified Polymer Base Material for Use in Orthopedic Dentistry

Acquired defects of the maxillofacial region require orthopedic treatment. When choosing a structural material for the manufacture of a jaw prosthesis, it is necessary to provide for functional loads on the prosthesis during operation. Defects in the jaw bones require a structural material with high strength characteristics. The article deals with the method of increasing the strength of polyamide dental material with nanoscale titanium dioxide. Objective: to improve the strength characteristics of orthopedic structures made of polyamide. The study of the polyamide material was carried out on control and experimental samples, in which a modifying component was introduced by the method of dispersion reinforcement-nanoscale titanium dioxide in an amount of up to 1 wt.%. The three-point bending strength (σmax, MPa) and Young’s modulus (E, MPa) were experimentally studied. These criteria are indicative when assessing the strength of the basic structural materials from which removable dentures are made. These parameters take into account both vertical and horizontal functional loads, similar to the forces that arise when using removable dentures. The results of the study showed an increase in the maximum voltage by 8.4%, and the Jung module by 7.2% in samples with nanoscale titanium dioxide introduced into their composition to 1 wt. %. This study is of practical importance for orthopedic dentistry in cases where it is necessary to strengthen the structural base material in the manufacture of jaw prostheses for patients with acquired defects of the jaw bones, which reduces the risk of fracture of the base structures under the influence of functional loads.

Effects of KBr and KI on Photocatalytic Degradation of Dye W-7G with Nano-TiO2 as Catalyst

To investigate the influence of inorganic salt on the photocatalytic degradation, the effects of KBr and KI at various concentrations and pH values on the photocatalytic degradation of dye W-7G using nanoscaled titanium dioxide as photocatalyst in a bubbling fluidized bed photocatalytic reactor (BFBPR) were studied. The results indicated that the degradation apparent rate constant ( K app ) of the system with KI was clearly higher than that with KBr under acidic or alkaline conditions. And the maximum value of K app (0.01127) appeared at the KI concentration of 0.075 g L-1 with a pH value of 9.37, meaning the highest degradation efficiency. Furthermore, the possible mechanism of photocatalytic degradation of W-7G in the presence of KBr and KI was proposed, which could provide a theoretical support for the further study of inorganic salt effects on the photocatalytic degradation of dyes.

Nano White Food and the Reproduction of Whiteness

Abstract Since colonisation began in Australia, it has transformed the ecological, social, cultural, and economic bases of the biggest estate on earth, with outcomes driving the disruption of Indigenous food sovereignty, foodways and food knowledges alongside the reproduction of Whiteness. This article critically examines the place of White food, including the case of nanotechnologies, in the expansion of the settler colonial frontier, and its impacts for Indigenous health and relationships with food. To do this, we consider a widely commercialised nano-food application: the addition of nano-scale titanium dioxide to make foods White. Nano White food provides a unique lens to examine White authority and control across settler colonial food systems. We consider some of the impacts arising from this global colonial power matrix—to which Whiteness is organising principle for domination—for Aboriginal and Torres Strait Islander health, justice, and rights. We argue that unsettling Whiteness is vital to redressing the violence wrought by settler colonial agri-food systems, and for re-centring living ecologies and interconnected systems across foodways.

Carbon-based nanomaterials suppress tobacco mosaic virus (TMV) infection and induce resistance in Nicotiana benthamiana

Although nanomaterials (NMs) may inhibit viral pathogens, the mechanisms governing plant–virus–nanomaterial interactions remain unknown. Nicotiana benthamiana plants were treated with nanoscale titanium dioxide (TiO2) and silver (Ag), C60 fullerenes, and carbon nanotubes (CNTs) at 100, 200 and 500 mg L−1 for a 21-day foliar exposure before inoculation with GFP-tagged tobacco mosaic virus (TMV). Plants treated with CNTs and C60 (200 mg L−1) exhibited normal phenotype and viral symptomology was not evident at 5 days post-infection. TiO2 and Ag failed to suppress viral infection. RT-qPCR analysis revealed that viral coat protein transcript abundance and GFP mRNA expression were reduced 74–81% upon CNTs and C60 treatment. TEM revealed that the chloroplast ultrastructure in carbon NM-treated plants was unaffected by TMV infection. Fluorescence measurement of CNTs and C60 (200 mg L−1) treated plants indicated photosynthesis equivalent to healthy controls. CNTs and C60 induced upregulation of the defense-related phytohormones abscisic acid and salicylic acid by 33–52%; the transcription of genes responsible for phytohormone biosynthesis was elevated by 94–104% in treated plants. Our findings demonstrate the protective role of carbon-based NMs, with suppression of TMV symptoms via hindered physical movement and viral replication. Given the lack of viral phytopathogen treatment options, this work represents a novel area of nano-enabled agriculture.

Charge-switchable magnetic separation and characterization of food additive titanium dioxide nanoparticles from commercial food

Growing concerns about the potential health effects of nanoscale titanium dioxide (TiO2) have necessitated the need for monitoring the size distribution and physicochemical properties of food additive TiO2 that are present in commercial food. Acid digestion is by far the most widely used method to remove interfering food matrices, but the highly corrosive nature of the reaction could alter the physicochemical properties of the TiO2, which may give a skewed information about the materials. Here, we report an effective approach to extract intact form of food additive TiO2 nanoparticles from processed food through charge-charge interaction between TiO2 particles and charge-switchable starch magnetic beads (PL@SMBs), of which the captured TiO2 is readily harvested by switching the surface charge of PL@SMBs to neutral. The size and surface property of extracted TiO2 were shown to be well maintained due to the mild nature of the reaction. The extracted TiO2 particles from 10 commercial processed food showed a size distribution from 40 to 250 nm with a mean diameter of 115 nm, of which 22 % of them were less than 100 nm. The extracted TiO2 did not exhibit short-term cytotoxicity, but induced cellular oxidative stress at high concentration.

Effect of titanium dioxide nanoparticles on DNA methylation in multiple human cell lines

Nanoscale titanium dioxide (TiO2) is manufactured in wide scale, with a range of applications in consumer products. Significant toxicity of TiO2 nanoparticles has, however, been recognized, suggesting considerable risk to human health. To evaluate fully their toxicity, assessment of the epigenetic action of these nanoparticles is critical. However, only few studies are available examining capability of nanoparticles to alter epigenetic integrity. In the present study, the effect of TiO2 nanoparticles exposure on DNA methylation, a major epigenetic mechanism, was investigated in in vitro cellular model systems. A panel of cells relevant to portals of human exposure (Caco-2 (colorectal), HepG2 (liver), NL20 (lung), and A-431 (skin)) was exposed to TiO2 nanoparticles to assess effects on global methylation, gene-specific methylation, and expression levels of DNA methyltransferases, MBD2, and UHRF1. Global methylation was determined by enzyme-linked immunosorbent assay-based immunochemical analysis. Degree of promoter methylation across a defined panel of genes was evaluated using EpiTect Methyl II Signature PCR System Array technology. Expression of DNMT1, DNMT3a, DNMT3b, MBD2, and URHF1 was quantified by qRT-PCR. Decrease in global DNA methylation in cell lines Caco-2, HepG2, and A-431 exposed to TiO2 nanoparticles was shown. Across four cell lines, eight genes (CDKN1A, DNAJC15, GADD45A, GDF15, INSIG1, SCARA3, TP53, and BNIP3) were identified in which promotors were methylated after exposure. Altered expression of these genes is associated with disease etiology. The results also revealed aberrant expression of epigenetic regulatory genes involved in DNA methylation (DNMT1, DNMT3a, DNMT3b, MBD2, and UHRF1) in TiO2 exposed cells, which was cell type dependent. Findings from this study clearly demonstrate the impact of TiO2 nanoparticles exposure on DNA methylation in multiple cell types, supporting potential involvement of this epigenetic mechanism in the toxicity of TiO2 nanoparticles. Hence for complete assessment of potential risk from nanoparticle exposure, epigenetic studies are critical.

The role of Fe oxyhydroxide coating, illite clay, and peat moss in nanoscale titanium dioxide (nTiO2) retention and transport in geochemically heterogeneous media

Natural media such as soil and sediment contain mineralogical and organic components with distinct chemical, surface, and electrostatic properties. To better understand the role of various soil and sediment components on particle transport, columns were packed with quartz sand and natural sediment with added Fe oxyhydroxide coating, illite clay, and peat moss to investigate how these added components influence nTiO2 retention and transport in geochemically heterogeneous medium. Results showed that nTiO2 transport was low at pH 5, attributable to the electrostatic attraction between positively-charged nTiO2 and negatively-charged medium. While illite did not notably affect nTiO2 transport at pH 5, Fe oxyhydroxide coating increased nTiO2 transport due to electrostatic repulsion between Fe oxyhydroxide and nTiO2. Peat moss also increased nTiO2 transport at pH 5, attributable to the increased DOC concentration, which resulted in higher DOC adsorption to nTiO2 and intensified electrostatic repulsion between nTiO2 and the medium. At pH 9, nTiO2 transport was high due to the electrostatic repulsion between negatively-charged nTiO2 and medium surfaces. Fe oxyhydroxide coating at pH 9 slightly delayed nTiO2 transport due to electrostatic attraction, while illite clay and peat moss substantially inhibited nTiO2 transport via straining/entrapment or electrostatic attraction. Overall, this study demonstrated that pH has a considerable effect on how minerals and organic components of a medium influence nTiO2 transport. At low pH, electrostatic attraction was the dominant mechanism, therefore, nTiO2 mobility was low regardless of the differences in mineralogical and organic components. Conversely, nTiO2 mobility was high at high pH and nTiO2 retention was dominated by straining/entrapment and sensitive to the mineralogical and organic composition of the medium.

Sulfur Dioxide Degradation by Composite Photocatalysts Prepared by Recycled Fine Aggregates and Nanoscale Titanium Dioxide.

To alleviate the heavy burden on landfilling, construction and demolition wastes (C&DWs) are recycled and reused as aggregates in cementitious materials. However, the inherent characteristics of recycled fine aggregates (RFA), such as the high crushing index and high-water absorption, magnify the reusing difficulty. Nevertheless, attributing to the high porosity and high level of calcium hydroxides existing in the old mortar, RFA is featured with a high specific surface area and a high alkalinity. These features are useful to augment the total photo-degradation of SO2 by nano-TiO2 (NT) intermixed mortar, leading RFA to be an excellent potential carrier to load nano-TiO2 and prepare the composite photocatalyst. Hence, this study proposed to load NT onto the surface of RFAs and river sands (RSs) (the control) by the soaking method, preparing composite photocatalysts denoted as NT@RFA and NT@RS, respectively. The prepared composite photocatalysts were then utilized as sands in photocatalytic mortar to evaluate for SO2 degradation. Experiments identified a 50% higher amount of NT was loaded onto the surface of FRA relative to the control. This higher loading amount plus higher alkalinity ultimately translated into a higher photocatalytic activity. In addition, the mortar containing NT@RFA exhibited 46.3% higher physiochemical absorption and 23.9% higher photocatalytic activity than that containing NT@RS. In addition, the durability, embodied by the reuse and anti-abrasive properties, of NT@RFA exceeded that of NT@RS. The overall findings reveal that the NT@RFA not only garners beneficial effect from the high porosity but also generates positive effect from the high alkalinity. Though a number of studies deal with building materials with NT, this study is the first to load NT onto RFA and prepare composite photocatalysts which were then used as fine aggregates in building materials. Consequently, this study proves the potential high-added-value reusability of RFA in green construction materials and provides a low-cost, high-efficiency approach to degrade atmospheric SO2.

Cellulose nanofibrils and nano-scaled titanium dioxide-reinforced biopolymer nanocomposites: Selecting the best nanocomposites with multicriteria decision-making methods

The aim of the paper is to determine the effects of nano fillers such as cellulose nanofibrils and nano-scaled titanium dioxide on some properties of polyhydroxybutyrate and polylactic acid biopolymers; it also determined the selection of biopolymer nanocomposites with the optimum properties by using multicriteria decision-making methods such as multi-attribute utility theory, simple additive weighting, and weighted aggregated sum product assessment. Test results showed that the mechanical properties of the biopolymer nanocomposites generally increased with the addition of the cellulose nanofibrils and nano-scaled titanium dioxide. However, the addition of nano-scaled titanium dioxide decreased the tensile modulus. The addition of the cellulose nanofibrils had a higher effect on the tensile and flexure modulus of elasticity than the addition of the nano-scaled titanium dioxide. Thermal properties were generally found to improve with the addition of the cellulose nanofibrils and nano-scaled titanium dioxide. Melting temperature (Tm) generally decreased with the addition of the nano fillers. The scanning electron microscopic images showed that the nano fillers were dispersed as white dots in the biopolymer matrix. After accelerated weathering and decay test, outdoor performance of the biopolymer nanocomposites was found to be improved with the addition of the nano fillers. Multicriteria decision-making methods were conducted to determine the biopolymer nanocomposites having the optimum properties, and all the methods showed that the best biopolymer nanocomposites was polylactic acid with 1% cellulose nanofibrils.

Quercetin Effects on Hepatotoxicity Induced by Titanium Dioxide Nanoparticles in Rats

Background: Most nanoparticles have adverse impacts on the liver, which is a vital body organ, by the induction of oxidative stress. Objectives: This study was designed to evaluate the hepatoprotective effects of quercetin (QCT) against the toxicity of nanoscale titanium dioxide (NTiO2) in Wistar rats. Methods: The present study was conducted on 32 adult female Wistar rats assigned into 4 groups of control, NTiO2 (50 mg/kg), NTiO2 + Quercetin (50 + 75 mg/kg), and Quercetin (75 mg/kg). The animals exposed to NTiO2 were administered by 50 mg/kg of NTiO2 for 21 days. The Quercetin + NTiO2 rats received Quercetin before exposing to NTiO2 for 7 days. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) of serum were considered indicators of the hepatotoxicity. The oxidative stress was assessed by measuring the activity of catalase (CAT) and superoxide dismutase (SOD) as well as the level of malondialdehyde (MDA) in the liver. TUNEL assay and histological changes were also assessed. Results: The NTiO2 significantly elevated the MDA level (P < 0.01), enhanced the serum biomarker levels, reduced the CAT (P < 0.01) and SOD (P < 0.01) activities. The NTiO2 also aggregated the red blood cells, and caused inflammatory cell infiltration, nuclear pyknosis and fat deposit in hepatocytes, as well as induced apoptosis in the liver tissue. Pretreatment with QCT quenched oxidative stress, attenuated the histological changes, elevated the CAT (P < 0.01) and SOD (P < 0.01) activities, normalized the serum biomarker levels and decreased apoptosis (P < 0.001). Conclusions: The QCT has an inhibitory impact on hepatotoxicity induced by nanoparticles in rats.

Facile preparation and electrochemistry performance of quasi solid-state polymer lithium–sulfur battery with high-safety and weak shuttle effect

With a higher theoretical energy density relative to Li ion batteries (LIBs) and abundance of elemental sulfur, the lithium sulfur (L-S) batteries were regarded as the promising next-generation high energy density storage devices for the protable electronics and electric vehicles. However, there were some main challenges stemming from the polysulphide dissolution and the high flammability of the sulfur which limited the further application of the lithium sulfur Li–S batteries. Here, we reported a facile method to prepare the quasi solid-state Li–S batteries (LSBs) with sulfur nanoparticles electrode and PVDF-based solid polymer electrolyte (SPE), which had less flammability, electrochemical stability and ionic conductivity. The prepared PVDF-based solid polymer electrolyte possessed the conductivity ∼10−4 S cm−1 at 25 °C and the lithium ions transference number of 0.49. GITT demonstrated the Li+ transport diffusion mechanism in the active S@nano-TiO2 cathode of the quasi solid-state lithium–sulfur battery. It was important to get the smooth diffusion path for the lower resistance in the charging process. Because of the high content and the sulfur uniform distribution on the nanoscale titanium dioxide (TiO2), the S@nano-TiO2 cathode exhibited its performance. The first cycle discahrge specific capacity was 1160 mAh g−1 at 0.15C at room temperature.

Nanoscale titanium dioxide (nTiO2) aggregation and transport in the co-presence of dissolved phosphate, illite colloid, and Fe oxyhydroxide coating

Many studies have been conducted to understand the fate and transport of nanoscale titanium dioxide (nTiO2) in subsurface environments. However, most of these studies are under simplified conditions which do not represent the complex physicochemical conditions in the natural environment, where nTiO2 simultaneously encounter various groundwater/aquifer components. To better understand the mechanisms that control the transport of this emerging contaminant in groundwater, column experiments were conducted under low ionic strength conditions at pH 5 and 9 to clarify the influence of co-present dissolved component, suspended natural particle, and medium geochemical heterogeneity on nTiO2 transport through water-saturated porous media. Results showed that when using nTiO2 as influent at pH 5, Fe oxyhydroxide coating increased the nTiO2 mobility owing to the repulsive forces between positively charged nTiO2 and the Fe oxyhydroxide coating. Conversely, illite inhibited nTiO2 transport due to illite straining and nTiO2 entrapment. Phosphate served as a bridge between nTiO2 particles at pH 5, resulting in large aggregates and consequent straining, and therefore inhibited transport. At pH 9, the mobility of nTiO2 was high in quartz sand columns, regardless of the presence of phosphate/illite colloids, due to the repulsive forces between negatively charged nTiO2, phosphate, illite colloids, and quartz surface. However, Fe oxyhydroxide coating reduced nTiO2 mobility, attributable to pH buffering, which resulted in attractive electrostatic forces between the Fe oxyhydroxide coating and the negatively charged nTiO2. Findings from this study showed that under complex physicochemical conditions nTiO2 transport is controlled by the interactions between nTiO2 and common groundwater/aquifer components, as well as the interactions between these components.

Titanium dioxide nanoparticles induce apoptosis by interfering with EGFR signaling in human breast cancer cells

Titanium dioxide nanoparticles, due to their smaller size and increased surface area comparted to the bulk form, are known to be bioreactive and have unexpected toxicological outcomes. Previous studies have shown that nanoscale titanium dioxide induces reactive oxygen species (ROS)-mediated cytotoxicity and genotoxicity. Although many reports have discussed the ROS-mediated cytotoxic effects of titanium dioxide nanoparticles (TiO2-NPs), their effects on the receptor–ligand association are unknown. In this study, the possibility that TiO2-NPs can interfere with the receptor–ligand binding was assessed by monitoring alterations in the phosphorylation status of proteins downstream of the epidermal growth factor receptor (EGFR) signaling cascade. TiO2-NPs blocked ligand-induced EGFR autophosphorylation, leading to the deactivation of EGFR downstream effectors such as Akt and extracellular signal-regulated kinase signaling, inducing cell death.

Surface modification of TiO2 for the preparation of full-dull polyamide-6 polymers

In this study, a novel surface modification approach for preparation of nanoscale titanium dioxide using aluminate coupling agent was developed. By optimizing the adding content of aluminate coupling agent and the reaction temperature, modified titanium dioxide (A-TiO2) particles with a minimum Z-average size of 32 nm and a narrow PDI of 0.214 were obtained. Further tests revealed that A-TiO2 was super-hydrophobic with water contact angle of 151.39°. Moreover, the dispersion behaviors and morphologies of TiO2 and A-TiO2 particles in different solvents were further investigated. The results indicated that A-TiO2 could be well dispersed in hot liquid caprolactam, making it suitable for preparing full-dull polyamide-6 polymers.

Combination of bioanalytical approaches and quantitative proteomics for the elucidation of the toxicity mechanisms associated to TiO2 nanoparticles exposure in human keratinocytes

Titanium dioxide nanoparticles (TiO2-NPs) are being used in several consumer products. The high refractive index of nano-scaled titanium dioxide particles allows them to protect from UV radiation, and so, they can be found as one of the main components of cosmetics and suncreens. Many studies have reported the potential toxicological effects associated to TiO2-NPs such as ROS generation, DNA damage, apoptosis and cell cycle arrest, among others. The continuous and systematic use of TiO2-NPs in cosmetic products requires a full comprehension of the risks involving their sustained contact with the human skin. Thus, it is important to evaluate not only the hazardous effects but to elucidate the biomolecular mechanisms involved in such effects. Based on this premises, we have evaluated the potential toxicity of TiO2-NPs using a human epithelial cell culture (HaCaT cells) as in-vitro model, together with different bioanalytical approaches and mass spectrometry-based quantitative proteomics, to gain a deeper insight into the molecular mechanisms of toxicity associated to TiO2-NPs exposure.

Exposure to airborne nano-titanium dioxide during airless spray painting and sanding

The objectives of the study were to measure and characterize exposure to airborne nanoscale titanium dioxide during airless spraying and sanding of a nano-enabled paint, and to evaluate the effectiveness of dust capture methods in reducing airborne nanoparticle concentrations. A tradesperson performed the work activities in an environmentally controlled chamber. Samples were collected in the tradesperson's breathing zone and in surrounding areas to assess bystander exposure. Filter-based samples were analyzed using gravimetric methods, scanning electron microscopy, and energy dispersive spectroscopy. Differential particle count data were obtained by means of a scanning mobility particle sizer. Local exhaust ventilation provided statistically significant reductions of airborne nanoparticle concentrations during sanding. Sanding the paint after drying with a handheld power sander generated relatively low levels of airborne titanium dioxide. In contrast, task-based exposure measurements collected during the initial airless spray application of the nano-enabled paint suggested a potential for occupational exposures to exceed the time-weighted average exposure limit for ultrafine titanium dioxide recommended by the National Institute for Occupational Safety and Health. Painters applying nano-enabled coatings may have little recourse but to rely, in some instances, on lower tiers of the hierarchy of controls, such as personal protective equipment. In light of these findings, employers and industrial hygienists should characterize exposures and implement the hierarchy of controls to ensure painters are sufficiently protected.

Polarization and Trap Characteristics Modification of Oil-Impregnated Paper Insulation by TiO₂ Nanoparticles.

Polarization and traps determine the electrical property of oil-paper insulation, but most attention has been paid to the modification of insulating oil with nanoparticles, so there are is little research about oil-impregnated paper, and the origin for performance variation is not understood yet. In this paper, spherical nanoscale titanium dioxide was prepared by the hydrolysis method and nanofluid-impregnated paper (NP) was fabricated through oil-impregnation. The frequency domain spectrum was measured for polarization analysis, and both thermally stimulated depolarization current (TSDC) and isothermal surface potential decay (ISPD) methods were used to reveal trap parameters. Results show that NP’s low frequency permittivity is much larger, and another peak appears in the spectrum even though the content of nanoparticles is very low. With the addition of TiO2 nanoparticles, TSDC’s amplitude and peak temperature increase, and the trap energy becomes shallower. TiO2 nanoparticles’ strong polarization and high activation energy contribute to NP’s larger interface polarization intensity and activation energy. Furthermore, because of oxygen vacancies, TiO2 nanoparticles offer a transfer site for holes and electrons to escape from deep traps; thus, the trap energy is greatly reduced.

Different toxicities of nanoscale titanium dioxide particles in the roots and leaves of wheat seedlings.

Despite previous studies on exploring the environmental effects of titanium dioxide nanoparticles particle (nTiO2) on plants, the detailed impacts of nTiO2 on the antioxidant system and photosynthesis of plants is still not well understood. This study was aimed at investigating the physiological and biochemical responses to nTiO2 by oxidative damage, Ti bioaccumulation, cell death, and photosynthesis in wheat. The results showed that 5.0 g nTiO2 L−1 resulted in a significant decrease in plant growth, chlorophyll contents, and photosynthetic activity. However, the obvious accumulation of reactive oxygen species (ROS) and cell death were observed under nTiO2 treatments in wheat roots and leaves. In addition, the concentrations of Ti in the roots were significantly higher than that in leaves with increased nTiO2 concentrations. Significant increase in enzyme activities and the levels of ascorbate were found in leaves exposed to 1.0 and 5.0 g nTiO2 L−1. Furthermore, the level of D1 and PsbS remarkably decreased in wheat leaves at 5.0 g nTiO2 L−1. However, the strong phosphorylation of photosystem II (PSII) reaction center protein D1 and D2 was observed at 5.0 g nTiO2 L−1. Altogether, these findings demonstrated that the roots suffered from more severe toxic damage from nTiO2 than the leaves and wheat plants respond to nTiO2 through the different physiological and biochemical mechanisms in the roots and leaves.