Suspensions Of TiO2 Nanoparticles Research Articles

From nuclear waste to hydrogen production: From past consequences to future prospect

Nuclear wastes may not be considered as unusable materials in the sense that they deliver a free source of energy under the form of ionizing radiations that can be used to produce hydrogen (H2) through water radiolysis. The current paradigm that define these nuclear wastes as troublesome by-products which no one uses nowadays must be shifted into a new opportunity for pure H2 production with no CO2 emission. Here, we propose a low-tech method to boost H2 production by water radiolysis thanks to the catalytic effect of a suspension of TiO2 nano-particles. We also demonstrate the relevance of this concept by scaling up our laboratory results. From our calculations, this radiocatalytic process can supply until 60% of the actual global demand in hydrogen (42.9 MtH2.y-1) and open the door, together with the green and white hydrogen productions, to the “Hydrogen century”.

Study of the photocatalytic activity of clay supported TiO2 nanoparticles for methylene blue degradation.

The photocatalytic degradation of a methylene blue (MB) solution was studied using a formulation of TiO2 nanoparticles (NPs) suspended in a commercial antibacterial paint, and supported on clay strips. All experiments were carried out in a batch reactor containing a UV-C light source and the MB solution under stirring. Parameters such as catalyst mass loading, MB concentration, as well as catalyst properties were considered for the experimental procedure. The effect of the mass loading on the photocatalytic activity of the TiO2 formulations immobilized on the clay supports was evaluated using 100, 200, and 500 mg of TiO2 on 40 mL of paint, sampling the MB solution under degradation at 0, 2, 5, 10, 20, 50, 100 and 200 min. The aliquots were analyzed by optical spectroscopy in the 400-1000 range to determine the absorbance, calculate the concentration with the Beer-Lambert equation, and obtain the amount of MB degradation. The maximum photocatalytic degradation of MB for the supported photocatalyst was 52%, 55%, and 60%, respectively. For comparison, suspended TiO2 nanoparticles lead to ca. 95% of MB photodegradation in ca. 60 min. The supported photocatalysts were tested in three consecutive cycles of 200 min to study the mechanical and photocatalytic stability. The activity of the photocatalysts with mass loading of 100 and 200 mg TiO2 decreased to ca. 35% after the three cycles, while the formulation with 500 mg TiO2 remained stable for three cycles. The final samples of each cycle were characterized by XRF, discarding erosion of the material from the support.

Experimental investigation on parameter optimization of liquid spectral beam splitter for continuous photocatalytic hydrogen production accompanied with photovoltaic power generation under solar full spectrum

Effective utilization of solar energy is of great significance for a sustainable future. Herein, we report a cascade system for hydrogen-electricity co-production (PH-PV) utilizing solar full spectrum. The output performance of the system can be precisely adjusted by controlling certain parameters of liquid spectral beam splitter (LSBS) which contains TiO2 nanoparticle suspension simultaneously generating hydrogen via a photocatalytic reaction process. Typically, the thickness of LSBS, the loading amount of TiO2, the flowrate of suspension and the light intensity have been investigated in detail. It is found that LSBS is necessary in our system as it could ensure the safe operation of PV while the light intensities larger than 8 suns. With the decrease of the thickness or loading amount of photocatalyst, more electricity could be produced by PV module but less hydrogen from PH module. Further increase of above two parameters simultaneously could lead to aggregation and settlement of particle suspension in LSBS, which is detrimental to the optical absorbance of the system. Besides, changing the flowrate will diversify the surface features of particles by shear-induced effect. At optimal flowrate, the particles in LSBS could exhibit oscillation characteristics under synergistic effect of shear force and gravity, which would lead to excellent light absorption and transmittance. Furthermore, an obvious gain for both hydrogen and electricity output and system efficiency could be obtained through increasing light intensity appropriately. Finally, the improved merit function (MF) was employed to evaluate the performance of hybrid system and more obvious effect of flowrate on MF value than other parameters was found. The optimal MF value of 3.07 was reached when flowrate was 60 mL/min. Our work is expected to provide important guidance for the optimization of PH-PV cascade system driven by outdoor direct solar energy.

Synthesis and application of Ag-doped TiO2 nanoparticles with antifungal activity and ethylene inhibition in postharvest of avocado cv. Hass

Avocado is highly susceptible to postharvest diseases and rapid ripening, making it challenging to maintain its quality and shelf life. One potential solution is the use of nanoparticles that can act as both antimicrobial agents and ethylene inhibitors. In this study, we synthesized Ag-doped TiO2 nanoparticles through a solution combustion method and subjected them to various characterization techniques, including X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. These nanoparticles were then tested for their effectiveness in combating common avocado pathogens and their ability to inhibit ethylene production. To apply our findings practically, we treated Hass avocado fruits in the postharvest stage with a suspension of Ag-doped TiO2 nanoparticles and stored them under controlled conditions to simulate the ripening process. The Ag-doped TiO2 nanoparticles formed agglomerates within the nanometric range and exhibited oxidation-reduction characteristics, effectively inhibiting ethylene production and degrading Rhodamine-B dye. Moreover, these nanoparticles displayed robust antimicrobial activity, significantly suppressing the growth of Colletotrichum gloeosporioides sensu lato pathogens. Treated fruits in the postharvest phase showed reduced microbial growth, decreased incidence of anthracnose, stem and root diseases, and an extended shelf life compared to the control group, due to ethylene inhibition. Ag-doped TiO2 nanoparticles, with their dual capabilities of antimicrobial activity and ethylene inhibition, show promise in improving postharvest management of Hass avocados. They have the potential to enhance fruit quality, reduce postharvest losses, and improve marketability. Further research and field trials are essential to fully explore the practical applications of these nanoparticles in commercial avocado production and distribution.

Titanium dioxide nanoparticles embedded in assembled dipeptide hydrogels for microfluidic photodegradation

Dipeptides can be self-assembled via non-covalent bonds towards functional nanostructures for diverse applications in nanotechnology. Here, we introduce a convenient microfluidics-guided dipeptide design as a platform for photodegradation of contaminants in water. Titanium dioxide (TiO2) nanoparticles (NPs) are chosen as photocatalysts due to their vastly studied properties. By using a well-defined microchannel architecture, the dipeptide N-fluorenylmethoxycarbonyl diphenylalanine (Fmoc-FF) and TiO2 NPs are efficiently mixed leading to a self-assembled Fmoc-FF hydrogel with embedded TiO2. Owing to shear-thinning and rapid self-healing of Fmoc-FF hydrogels, we can transfer and inject Fmoc-FF/TiO2 hydrogels into any other microdevice for specific applications, where these low-molecular-weight-gelator- (LMWG-)based Fmoc-FF hydrogels fill out the microchannel volume. Different morphologies of Fmoc-FF/TiO2 hydrogels are obtained by simple concentration screening of TiO2 NPs and Fmoc-FF. Owing to the density of the three-dimensionally twined Fmoc-FF nanofibers, solutions swelling the dipeptide hydrogel can be exchanged without leaching out TiO2 NPs. By further analysis, our hydrogel-filled flow cell can be employed for continuous-flow photodegradation in water under light irradiation. Especially, compared to the TiO2 NPs suspension, Fmoc-FF/TiO2 hydrogels with relatively low concentrations of TiO2 exhibit enhanced photodegradation capabilities due to better dispersion of nanoparticles. Such strategy provides a versatile platform for embedment of small inorganic catalysts or enzymes for (bio-)chemical conversion of solutes passing through the hydrogel network.

EVALUATION OF OCCUPATIONAL EXPOSURE TO TIO2 NANOPARTICLES: MICROWAVE-ASSISTED ACID DIGESTION METHOD ON AIR MEMBRANE FILTERS

Titanium dioxide (TiO2) nanoparticles have been extensively used in various industrial sectors and applications, including cosmetics, catalysts, food additives, inks, paints, and coatings. However, the International Agency for Research on Cancer (IARC) has classified TiO2 nanoparticles as a potential carcinogen for humans, meaning they may cause cancer and pose serious health complications, particularly for manufacturing workers. This highlights the need for better evaluation to determine worker exposure. In this study, suspended TiO2 nanoparticles were sampled using a nanoparticle respiratory deposition (NRD) sampler fitted with specially designed membrane filters and analyzed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The digestion method used for titanium element recovery after nanoparticle sampling is crucial for optimal ICP-MS analysis. Therefore, this study aimed to investigate the most suitable digestion method. A microwave-acid digestion method using concentrated nitric acid and concentrated hydrochloric acid at a 7:4 ratio, with a run time of 30 minutes and the temperature set to 200°C showed remarkable titanium recovery compared to other methods. These findings may pave the way for optimal analysis of suspended TiO2 nanoparticles in assessing occupational exposure while promoting sustainability and eco-friendliness in resource utilization.

Photo-oxidation of nitrite anions in aqueous solution for the benchmarking of nano-TiO2 photocatalytic coatings

Photocatalytic coatings have potential as an air purifying technology for removal of pollutants such as NOx gases, which are converted into and immobilized as nitrate via photo-oxidation. This work is an investigation of the photocatalytic conversion of nitrite into nitrate in the aqueous phase. The study of this reaction is important to understand the mechanism through which the immobilization of the NOx species as nitrates takes place during NOx conversion, especially in humid environments. We investigate the photocatalytic performance of TiO2 nanoparticles (Aeroxide® P25) and the corresponding photocatalytic coatings prepared using acrylic binder (TiO2 NP-acrylic) towards the photo-conversion of nitrite. The combination of a simple colorimetric method (Griess test) for nitrite quantification and UV–vis spectroscopy for nitrite and nitrate analysis is shown to be a useful method for monitoring the nitrite conversion. Photocatalytic tests with suspended TiO2 nanoparticles show that the nitrite conversion benefits from lower pH, higher temperature and higher concentration of the photocatalyst. The advantage of lower pH is attributed to electrostatic attraction between TiO2 with adsorbed H3O+ and NO2−, which facilitates transport of nitrite to the active surface. When the photocatalyst is immobilized in a coating the factor of primary significance is the pigment volume concentration relative to critical pigment volume concentration (λ), as the nitrite conversion increases linearly with λ in the range 0.6–1.2. This is attributed to the creation of a more porous structure that facilitates the access of nitrite and light to the active TiO2 surface sites.

Separation of TiO2 particles from suspension using indigenous low-cost ceramic microfiltration membrane

The increased use of TiO2 nanoparticles in manufacturing and commercial products has led to environmental contamination and health issues. This study aimed to apply tubular ceramic membrane fabricated using low-cost clays (kaolin, quartz) along with hydroxypropyl methylcellulose binder for the separation of TiO2 nanoparticles from water. The prepared tubular ceramic membrane exhibited excellent water permeability (1.4945 × 10−7 m3/m2s kPa) with an average pore size of 0.178 μm and porosity of 40 %. Cross flow microfiltration experiments using TiO2 nanoparticles suspension were performed by varying the applied pressure (138–414 kPa), cross flow velocity (2.41 × 10−3 - 5.63 × 10−3 m/s), pH (4–11) and feed concentration (0.05–1 wt%). The permeate flux increased linearly with an increase in the pressure as well as cross flow velocity with a maximum permeate flux of 4.24 × 10−5 m3/m2s at 414 kPa, whereas a reduction in permeate flux was observed with increasing feed concentration of TiO2. The membrane displayed 100 % separation efficiency at all the investigated pressures. Furthermore, the membrane fouling mechanism during the microfiltration process was analyzed using resistance-in-series model. Results demonstrated that filtration resistance (Rf) and total resistance (Rt) decreased with increasing cross flow velocity from 2.41 × 10−3 m/s to 5.63 × 10−3 m/s, whereas filtration resistance remained constant at high pressures. The estimated membrane cost is 253 USD/m2 based on raw materials, energy consumption, manpower and equipment cost. These promising results elucidated the suitability of tubular ceramic membrane towards the removal of TiO2 from wastewater.

A new Concentrated Photovoltaic Thermal-Hydrogen system with photocatalyst suspension as optical liquid filter

Although typical Concentrated Photovoltaic-Thermal systems can overcome high cell temperatures, the low-level heat generated not only increases the irreversible energy loss but also narrows the application scope of the system. Here, we established a new Concentrated Photovoltaic Thermal-Hydrogen system coupling the Pt loaded TiO2 nanoparticle suspension, serving as both a photothermal hydrogen catalyst and an optical liquid filter for spectrum beam splitting, with a GaInP/GaAs/Ge triple-junction photovoltaic cell connected to an electrolytic cell to achieve full-spectrum solar energy to hydrogen storage conversion. Besides the additional hydrogen production, the Concentrated Photovoltaic Thermal-Hydrogen system with spectral beam splitting of TiO2 suspension can reduce the cell temperature by 32.8%, increase the electrical power by 65.7%, and save 49% of the cell area at most, compared to the case without spectral beam splitting. Thermalization loss was also reduced, which, in turn, increased the photovoltaic electrical performance. The proposed system can produce hydrogen at a maximum solar-to-hydrogen efficiency of 14% when the TiO2 loading amount is 150 ppm. It is expected to provide a guiding reference for achieving full-spectrum and high-efficiency solar energy conversion.

Photoelectrocatalytic degradation of diclofenac with a boron-doped diamond electrode modified with titanium dioxide as a photoanode

The electrophoretic deposition of titanium dioxide (TiO2) nanoparticles (Degussa P25) onto a boron-doped diamond (BDD) substrate was carried out to produce a photoanode (TiO2/BDD) to apply in the degradation and mineralization of sodium diclofenac (DCF-Na) in an aqueous medium using photoelectrocatalysis (PEC). This study was divided into three stages: i) photoanode production through electrophoretic deposition using three suspensions (1.25%, 2.5%, 5.0% w/v) of TiO2 nanoparticles, applying 4.8 V for 15 and 20 s; ii) characterization of the TiO2/BDD photoanode using scanning electron microscopy and cyclic voltammetry response with the [Fe(CN)6]3-/4- redox system; iii) degradation of DCF-Na (25 mg L−1) through electrochemical oxidation (EO) on BDD and PEC on TiO2/BDD under dark and UVC-light conditions. The degradation of DCF-Na was evaluated using high-performance liquid chromatography and UV–Vis spectroscopy, and its mineralization measured using total organic carbon and chemical oxygen demand. The results showed that after 2 h, DCF-Na degradation and mineralization reached 98.5% and 80.1%, respectively, through PEC on the TiO2/BDD photoanode at 2.2 mA cm−2 under UVC illumination, while through EO on BDD applying 4.4 mA cm−2, degradation and mineralization reached 85.6% and 76.1%, respectively. This difference occurred because of the optimal electrophoretic formation of a TiO2 film with a 9.17 μm thickness on the BDD (2.5% w/v TiO2, time 15 s, 4.8 V), which improved the electrocatalysis and oxidative capacity of the TiO2/BDD photoanode. Additionally, PEC showed a lower specific energy consumption (1.55 kWh m−3). Thus, the use of nanostructured TiO2 films deposited on BDD is an innovative photoanode alternative for the photoelectrocatalytic degradation of DCF-Na, which substantially improves the degradation capacity of bare BDD.

Effect of TiO2 nanoparticles on the tribological properties of lubricating oil: an experimental investigation

Nano-lubricants offer improved tribological properties in many applications, such as machines and engines. The presence of nanoparticles in the lubricating oil affects its wear, friction, thermal, chemical and physical properties in many ways. Titanium dioxide (TiO2) is a promising lubricant additive for enhanced engine efficiency. This article reports the effect of 10 W-30 pure base engine oil suspended TiO2 nanoparticles. Four different volume concentrations (0.01%, 0.025%, 0.050% and 0.075%) of TiO2 nanoparticles in the base lubricating oil are used for the analysis. The tribological tests were performed at ambient temperature as well as at 75 °C using a four ball tribometer. Scanning electron microscope (SEM) and Alicona Inginite Focus G5 microscope were used to analyze the worn surface. The results show that the surface-modified TiO2 nanoparticles can remarkably improve the load-carrying capacity, the friction reducing, and anti-wear abilities of the additive oil. The diameter of the wear trace and the coefficient of friction are the tribological properties analyzed for the nano-lubricant prepared at different volume concentration (VC). It was found that the diameter of the wear scar and the coefficient of friction increase with increasing VC of TiO2 nanoparticles in the lubricating oil. The main objective of the paper is to present the recent progress and, consequently, to develop a comprehensive understanding of the tribological behavior of engine oil mixed with TiO2 nanoparticles.

Multi-Scale Modelling of Aggregation of TiO2 Nanoparticle Suspensions in Water.

Titanium dioxide nanoparticles have risen concerns about their possible toxicity and the European Food Safety Authority recently banned the use of TiO2 nano-additive in food products. Following the intent of relating nanomaterials atomic structure with their toxicity without having to conduct large-scale experiments on living organisms, we investigate the aggregation of titanium dioxide nanoparticles using a multi-scale technique: starting from ab initio Density Functional Theory to get an accurate determination of the energetics and electronic structure, we switch to classical Molecular Dynamics simulations to calculate the Potential of Mean Force for the connection of two identical nanoparticles in water; the fitting of the latter by a set of mathematical equations is the key for the upscale. Lastly, we perform Brownian Dynamics simulations where each nanoparticle is a spherical bead. This coarsening strategy allows studying the aggregation of a few thousand nanoparticles. Applying this novel procedure, we find three new molecular descriptors, namely, the aggregation free energy and two numerical parameters used to correct the observed deviation from the aggregation kinetics described by the Smoluchowski theory. Ultimately, molecular descriptors can be fed into QSAR models to predict the toxicity of a material knowing its physicochemical properties, enabling safe design strategies.

Effect of TiO2 Nanoparticles on the Yield and Photophysiological Responses of Cherry Tomatoes during the Rainy Season

The rainy season occurs mainly from June to July in Korea, and this season causes insufficient ambient light intensity for the growth of cherry tomato in a greenhouse. Titanium dioxide (TiO2), as a photocatalyst, is known to affect photosynthesis in plants. This study was carried out to investigate the influence of TiO2 foliar spray application on the yield and photophysiological responses of cherry tomato under low ambient light intensity during the rainy season in a greenhouse. Cherry tomato plants were treated with 100 mg·L−1 TiO2 (T1) or 200 mg·L−1 TiO2 (T2) nanoparticle suspension on 26 June. The control group was not treated with TiO2. In the O–J phase of the OJIP transient under a cloudy day (2 July), the slope in the control and T1 groups rose more sharply than that in the T2 group. Conversely, on a clear day (10 July), the J–I phase of the T2 group sharply increased compared to that of the control and T1 groups. On a cloudy day with low ambient light intensity, the rate of electron transport flux from QA to QB per photosystem II reaction center (ET0/RC) and carbon dioxide (CO2) fixation of TiO2-treated plants were increased compared to those of the control. However, on a clear day of high light intensity, the ET0/RC and CO2 fixation of the T2 group were lower than those of the control and Tl groups. The yield of fruit was increased in the T1 group over that in other treatments. TiO2 treatment reduced the size of the fruit and delayed the ripening time, but greatly increased the fruit hardness. These results suggest that setting the concentration and supply amount of TiO2 nanoparticles suitable for various environmental conditions should be prioritized in order to improve the effect of TiO2 nanoparticles in tomato cultivation.

Photocatalytic exoskeleton: Chitin nanofiber for retrievable and sustainable TiO2 carriers for the decomposition of various pollutants

Loading a photocatalytic TiO2 to organic carriers has been desired for volumetric TiO2 incorporation, facile retrieval, and sustainable utilization. Traditionally, suspended TiO2 nanoparticles or its thin film on two-dimensional substrate are popularly fabricated for pollutants decomposition without carriers; due to poor thermomechanical properties of the organic carriers. Herein, a combination of the chitin nanofiber carrier and atomic layer deposition proves relevance for formation of anatase TiO2 thin layer so that photocatalytic decomposition in three-dimensional surface. Moreover, chitin nanofiber is capable of holding the TiO2 nanoparticles for multiple cycles of photocatalysis. Those types of TiO2 show characteristic degradation performance for gaseous (acetaldehyde) and aqueous pollutants (4-chlorophenol and rhodamine B). After catalytic reaction, chitin/TiO2 is retrievable owing to carrier's robustness even in water without TiO2 aggregation and loss. This work suggests that chitin-based photocatalyst is applicable to numerous pollutants through chitin's relatively high chemical resistance and stably wedged TiO2 during photocatalytic reaction.

Synergistic Engineering of Conduction Band, Conductivity, and Interface of Bilayered Electron Transport Layers with Scalable TiO2 and SnO2 Nanoparticles for High-Efficiency Stable Perovskite Solar Cells

A simple, synergistic engineering of the conduction band (CB), conductivity, and interface of TiO2-based bilayered electron transport layers (ETLs) via scalable TiO2 and SnO2 nanoparticles processed at low temperature (≤ 100 °C) for regular planar perovskite solar cells (PSCs) was developed. The bottom layer (Lt-TiO2:SnO2 nanocomposite film) was prepared by spin coating from the ethanol suspension of small ground TiO2 nanoparticles with big ground SnO2 nanoparticles as the additive. The top C-SnO2 layer (spin-coated from the concentrated commercial SnO2 nanoparticles (C-SnO2 NPs, 20 wt %, 7 nm in size suspended in H2O)) can be regarded as an interlayer between Lt-TiO2:SnO2 and perovskite (Psk) absorbers. Bilayered Lt-TiO2:SnO2/C-SnO2 ETLs are dense films with a cascade CB, good conductivity, facile electron extraction/transport ability, and a highly hydrophilic surface for depositing high-quality Psk films. Regular planar PSCs based on Lt-TiO2:SnO2/C-SnO2 ETLs combined with a (FAI)0.90(PbI2)0.94(MABr)0.10(PbBr2)0.10 absorber and a spiro-OMeTAD hole transporter achieved the highest power conversion efficiency of 22.04% with a negligible current hysteresis. The champion cell lost less than 3% of the initial efficiency under continuous room lighting (1000 lux) for 1000 h (lost 10% after 2184 h) without encapsulation under an inert atmosphere. Four related low-temperature-processed ETLs (Lt-TiO2/C-SnO2, Lt-C-SnO2, Lt-TiO2:SnO2, and Lt-TiO2) were fabricated using the same metal oxide nanoparticle suspensions and studied simultaneously to reveal the function of each metal oxide in the bilayered Lt-TiO2:SnO2/C-SnO2 ETLs. In the bottom Lt-TiO2:SnO2 layer, small TiO2 nanoparticles were needed for making a dense film, and highly conducting big SnO2 nanoparticles are used to increase the conductivity of ETLs and a handy electron transport path for reducing the charge accumulation and series resistance of the cell. A top C-SnO2 layer (regarded as an interlayer between Psk and Lt-TiO2:SnO2) was used to extract/transport electrons facilely, to form a bilayered ETL with a cascade CB, and to create a hydrophilic surface to deposit high-quality Psk films to enhance the photovoltaic performance of the PSCs. This study provides a blueprint for designing good-performance ETLs for high-efficiency, stable regular planar PSCs using various sized nanoparticles prepared in a very simple and low-cost way.

Sequential Changes in Antioxidant Potential of Oakleaf Lettuce Seedlings Caused by Nano-TiO2 Treatment.

Nowadays, there is an increasing interest in nanoparticle (NP) technology used in household and industrial products. It could cause an accumulation and dispersion of NPs in the environment, with possible harmful effects on living organisms. Nanoparticles significantly affect plants and alter their physiology and biochemical pathways, and nanotechnology can be used to improve plant characteristics that are desirable by humans. Therefore, more extensive studies of NP interactions with plants are still needed. The aim of this report is to investigate the effect of TiO2 nanoparticles (TiO2-NPs) on the enzymatic and non-enzymatic antioxidants, fresh and dry weights, and malondialdehyde contents in oakleaf lettuce seedlings. Plants were foliar treated with a 0.75% suspension of TiO2-NPs, while control plants were sprayed with deionized water. Leaves were sampled 4, 7, 9, 11, and 13 days after the treatment. The effects of TiO2-NPs were time-dependent, but the most spectacular changes were observed 4 days after the treatment. Exposure of the plants to TiO2-NPs significantly increased the contents of glutathione at all sampling points, total phenolics at days 4 and 13, and L-ascorbic acid at 4, 7, and 11 days after the treatment. Elevated levels of ascorbate peroxidase and guaiacol peroxidase activities were recorded at days 4 and 13, respectively. Total antioxidant capacity increased initially in treated seedlings, when compared with the control, and then decreased. On day 7, higher fresh and dry weights, as well as malondialdehyde contents in TiO2-NPs treated plants were observed, compared with the control. The study demonstrated that the activation of some antioxidant system components due to TiO2-NPs treatment was connected with the induction of mild oxidative stress, with no external symptoms of NP toxicity in oakleaf lettuce.

Titanium Dioxide Nanoparticles Induce Root Growth Inhibition in Soybean Due to Physical Damages

Titanium dioxide (TiO2) nanoparticles (NPs) are the most widely released nanomaterials in the environment and are considered an emerging contaminant. Although the phytotoxicity mechanism of TiO2 NPs on plants involves the elevated generation of reactive oxygen species (ROS), it is still not well established in soybean. Herein, we evaluated the effects of 250–1000 mg L−1 TiO2 NPs on seed germination, growth, content of ROS, lipid peroxidation, and activity of antioxidant enzymes in roots of soybean plants. Our data revealed that up to 1000 mg L−1 TiO2 NPs did not affect soybean seed germination. Transmission electron microscopy images and determinations of zeta potential and hydrodynamic diameter of a suspension of TiO2 NPs demonstrated that they form aggregates, favoring their adsorption to the root surface with consequent physical damage. The main deleterious effects noted on roots were reduced cell viability, reduced root hair number, striated aspect of root apexes, and reduced fresh and dry weights of roots. In disagreement with other studies, plant exposure to TiO2 NPs reduced the level of total ROS and lipid peroxidation, probably due to increased superoxide dismutase (SOD) activity. Altogether, our data suggest that the toxicity mechanism of TiO2 NPs on soybean roots involves physical damage resulting from their adsorption to the root surface, but not the generation of ROS.

Effect of the suspension of Ag-incorporated TiO2 nanoparticles (Ag-TiO2 NPs) on certain growth, physiology and phytotoxicity parameters in spinach seedlings.

In this work, the effect of the inoculation of silver-incorporated titanium dioxide nanoparticles (Ag-TiO2 NPs) in spinach seeds was evaluated on certain growth, physiology and phytotoxicity parameters of the plants. This is an important crop for human consumption with high nutritional value due to their low calorie and fat content, providing various vitamins and minerals, especially iron. These NPs were obtained by means of the sol-gel method and heat treatment; the resulting powder material was characterized using X-ray diffraction and scanning electron microscopy and the influence of these NPs on plants was measured by estimating the germination rate, monitoring morphological parameters and evaluating phytotoxicity. The photosynthetic activity of the spinach plants was estimated through the quantification of the Ratio of Oxygen Evolution (ROE) by the photoacoustic technique. Samples of TiO2 powder with particle size between 9 and 43 nm were used to quantify the germination rate, which served to determine a narrower size range between 7 and 26 nm in the experiments with Ag-TiO2 NPs; the presence of Ag in TiO2 powder samples was confirmed by energy-dispersive X-ray spectroscopy. The analysis of variance showed that the dependent variable (plant growth) could be affected by the evaluated factors (concentration and size) with significant differences. The statistical trend indicated that the application of the Ag-TiO2 NPs suspension of lowest concentration and smallest particle size could be a promoting agent of the growth and development of these plants. The inoculation with NPs of 8.3 nm size and lowest concentration was related to the highest average ROE value, 24.6 ± 0.2%, while the control group was 20.2 ± 0.2%. The positive effect of the Ag-TiO2 NPs treatment could be associated to the generation of reactive oxygen species, antimicrobial activity, increased biochemical attributes, enzymatic activity or improvements in water absorption.

Effect of isopropanol co-product on the long-term stability of TiO2 nanoparticle suspensions produced by microwave-assisted synthesis

In this paper we evaluate the effect of isopropanol arising from the reagent Ti(O-iPr)4 on the long-term stability of nanoparticle size of TiO2 produced during a microwave assisted sol-gel synthesis. Different configurations of microwave apparatus have been considered: the synthesis was carried out both in vessel or flask, and both performing or not isopropanol distillation through a modified microwave apparatus. Results revealed that isopropanol distillation after a short reaction time provided suspensions with slightly smaller particle size, that also show longer stability over time, especially for syntheses carried out at certain temperatures. Reactions performed distilling isopropanol from vessel and flasks showed comparable results, superior to the corresponding suspensions obtained without distilling isopropanol. This study is intended to provide a useful contribution to those applications where the need for stable TiO2 suspensions is critical.

Sustainable Bleaching Process of Raw Cotton by TiO2 Light-Activated Nanoparticles

Nanoparticles (NPs) of titanium dioxide (TiO2) are promising for the photocatalytic degradation of organic compounds, arising as an excellent alternative to conventional bleaching processes. Within this background, aqueous suspensions of TiO2 NPs were impregnated by the pad-dry method in raw cotton. The hydrophilic properties and whiteness index (WI) of Berger were the main parameters examined before and after the TiO2 treatment. In the absence of water, using a UV-Vis lamp, high hydrophilicity was found for raw cotton. Diversely, under UV-LED radiation, the presence of water molecules in the coated cotton was revealed to be a crucial parameter in enhancing its whiteness. A comparable WI of Berger with conventional bleaching methods was obtained using 0.5 g L-1 TiO2 suspension under UV-LED radiation, suggesting that the impregnation of TiO2 NPs can be a promising alternative for the industrial bleaching methods, as it proves to be more sustainable and with low operating costs.