Applications of photocatalytic titanium dioxide-based nanomaterials in sustainable agriculture

Impact of titanium dioxide (TiO2) nanoparticle and liquid leachate of mushroom compost on agronomic and biochemical response of marigold (Tagetes erecta L.) under saline stress

The cultivation of ornamental horticultural crops under salinity stress has been a challenge for growers all over the world. In this study, an attempt was made for pot cultivation of Marigold (Tagetes erecta L. var. Pusa Basanti Gainda) in salt-stressed (SS) soil (150 mM) with the combined use of mushroom compost leachate (CL) and foliar application of titanium dioxide nanoparticles (TiO2-NPs). For this purpose, a total of six pot treatments, i.e., borewell water (BW; control), T1 (BW with SS), T2 (BW with SS and TiO2-NPs), T3 (CL supplemented), T4 (CL with SS), and T5 (CL with SS and TiO2-NPs) were conducted in triplicate. The results of this study showed that CL supplementation significantly (p < 0.05) improved the physicochemical i.e., pH (14.5%), electrical conductivity (32.9%), total nitrogen (27.4%), total phosphorus (247.6%)), and nutrient (organic matter: 119.6%) profiles of soil which later helped in higher growth (30-35%) and yield (5.4-40.7%) of T. erecta. In CL-based treatments, the biochemical constituents were significantly (p < 0.05) higher than those in BW-irrigated ones. Also, the levels of selected stress defense enzymes were significantly increased under SS treatment but reduced under TiO2-NP application. Overall, it was observed that the combined application of CL and TiO2-NPs (T5 treatment) was the most helpful treatment for enhanced germination, growth, yield, biochemical parameters, and better plant enzymatic activities to cope with saline stress. This study provides a mechanistic understanding of T. erecta plants under saline stress which is crucial for the development of targeted interventions aimed at improving plant tolerance to saline conditions.

Unravelling the effects of nano SiO2, nano TiO2 and their nanocomposites on Zea mays L. growth and soil health

Amidst the challenges posed by climate change, exploring advanced technologies like nanotechnology is crucial for enhancing agricultural productivity and food security. Consequently, this study investigated the impact of nano SiO2 (nSiO2), nano TiO2 (nTiO2) and SiO2/TiO2 nanocomposites (NCs) on 30-day-old Zea mays L. plants and soil health at concentrations of 100 and 200 ppm. Results showed that nSiO2 and nTiO2 at 100 ppm and SiO2/TiO2 NCs at both concentrations, positively influenced plant growth, with the best stimulation observed at 200 ppm of SiO2/TiO2 NCs. Improved plant growth was associated with higher chlorophyll content, photosynthetic rate, transpiration rate, stomatal conductance, rhizospheric N-fixing and phosphate solubilizing bacterial population and plant nutrient uptake. Additionally, treated plants exhibited increased cellulose and starch levels. Malondialdehyde (MDA) content was lower or similar to that of the control, except at 200 ppm of nTiO2-treated shoots. Antioxidant enzyme activities fluctuated, indicating physiological adjustments. Overall, 100 ppm of nTiO2 as well as nSiO2 and 100 and 200 ppm of SiO2/TiO2 NCs improved soil fertility and Z. mays growth, suggesting potential benefits for sustainable agriculture. The findings lay the foundation for more comprehensive investigations into the long-term fate of nanomaterials in soil and their intricate molecular-level interactions with Z. mays.

A review on transition metal oxides based photocatalysts for degradation of synthetic organic pollutants

This review provides insight into the current research trend in transition metal oxides (TMOs)-based photocatalysis in removing the organic colouring matters from water. For easy understanding, the research progress has been presented in four generations according to the catalyst composition and mode of application, viz: single component TMOs (the first-generation), doped TMOs/binary TMOs/doped binary TMOs (the second-generation), inactive/active support-immobilized TMOs (the third-generation), and ternary/quaternary compositions (the fourth-generation). The first two generations represent suspended catalysts, the third generation is supported catalysts, and the fourth generation can be suspended or supported. The review provides an elaborated comparison between suspended and supported catalysts, their general/specific requirements, key factors controlling degradation, and the methodologies for performance evaluation. All the plausible fundamental and advanced dye degradation mechanisms involved in each generation of catalysts were demonstrated. The existing challenges in TMOs-based photocatalysis and how the researchers approach the hitch to resolve it effectively are discussed. Future research trends are also presented.

Nano protective membrane coated wheat to resist powdery mildew

The plant pathogenic fungus Blumeria graminis f. sp. tritici infects wheat and reduces its yield. The policy of reducing fertilizer and biocide use in sustainable agriculture has prompted researchers to develop more green and efficient management strategies. In this study, a novel nanoprotective membrane (kaolin-nano titanium dioxide-liquid paraffin, referred to as KTP) that could effectively prevent powdery mildew of wheat was prepared by using 1 g/L kaolin, 2 g/L nanotitanium dioxide and 8% (v/v) liquid paraffin. The prevention and control effects of KTP spraying in advance in the pot and field experiments were 98.45% and 83.04%, respectively. More importantly, the weight of 1000 grains of wheat pretreated with KTP was 2.56 g higher than that of wheat infected with powdery mildew, significantly improving wheat yield. KTP delayed the germination of powdery mildew spores on the leaf surface, and inhibited the formation of mycelia. In addition, KTP did not affect the growth of wheat or the survival of earthworms. KTP nanoprotective membrane are a green and safe prevention and control materials that are which is expected to be widely used in agriculture to control wheat powdery mildew.

Research progress, trends, and updates on pollutants removal by Bi2WO6-based photocatalysts under visible light irradiation

In recent years, extensive research has been conducted on bismuth tungstate (Bi2WO6) in the field of photocatalysis owing to its unique crystal structure and favorable bandgap. This study offers a comprehensive review of the research on Bi2WO6-based photocatalysts from 2007 to 2022 using bibliometric analysis. The analysis utilized the Web of Science Core Collection Database and encompassed a dataset of 2064 publications. The bibliometric analysis and science mapping were carried out using the bibliometix R-package and CiteSpace software. This analysis examined and discussed the network of relationships among countries, journals, organizations, authors, and keywords pertaining to the topic and subtopics under investigation. The findings demonstrate that China has played a significant role in this research area and has formed close collaborations with other countries. The identification of highly-cited emerging terms suggests that enhancing the photocatalytic performance of Bi2WO6-based nanomaterials is a primary research focus. Moreover, there has been increasing interest in exploring the synergistic effects of photocatalysis and adsorption as a means to improve catalytic efficiency. This study provides valuable insights for researchers seeking a deeper understanding of Bi2WO6-based photocatalysts.

Trichoderma cf. asperellum and plant-based titanium dioxide nanoparticles initiate morphological and biochemical modifications in Hordeum vulgare L. against Bipolaris sorokiniana

BACKGROUND

Spot blotch is a serious foliar disease of barley (Hordeum vulgare L.) plants caused by Bipolaris sorokiniana, which is a hemibiotrophic ascomycete that has a global impact on productivity. Some Trichoderma spp. is a promising candidate as a biocontrol agent as well as a plant growth stimulant. Also, the application of nanomaterials in agriculture limits the use of harmful agrochemicals and helps improve the yield of different crops. The current study was carried out to evaluate the effectiveness of Trichoderma. cf. asperellum and the biosynthesized titanium dioxide nanoparticles (TiO2 NPs) to manage the spot blotch disease of barley caused by B. sorokiniana and to assess the plant's innate defense response.

RESULTS

Aloe vera L. aqueous leaf extract was used to biosynthesize TiO2 NPs by reducing TiCl4 salt into TiO2 NPs and the biosynthesized NPs were detected using SEM and TEM. It was confirmed that the NPs are anatase-crystalline phases and exist in sizes ranging from 10 to 25 nm. The T. cf. asperellum fungus was detected using morphological traits and rDNA ITS analysis. This fungus showed strong antagonistic activity against B. sorokiniana (57.07%). Additionally, T. cf. asperellum cultures that were 5 days old demonstrated the best antagonistic activity against the pathogen in cell-free culture filtrate. Also, B. sorokiniana was unable to grow on PDA supplemented with 25 and 50 mg/L of TiO2 NPs, and the diameter of the inhibitory zone increased with increasing TiO2 NPs concentration. In an in vivo assay, barley plants treated with T. cf. asperellum or TiO2 NPs were used to evaluate their biocontrol efficiency against B. sorokiniana, in which T. cf. asperellum and TiO2 NPs enhanced the growth of the plant without displaying disease symptoms. Furthermore, the physiological and biochemical parameters of barley plants treated with T. cf. asperellum or TiO2 NPs in response to B. sorokiniana treatment were quantitively estimated. Hence, T. cf. asperellum and TiO2 NPs improve the plant's tolerance and reduce the growth inhibitory effect of B. sorokiniana.

CONCLUSION

Subsequently, T. cf. asperellum and TiO2 NPs were able to protect barley plants against B. sorokiniana via enhancement of chlorophyll content, improvement of plant health, and induction of the barley innate defense system. The present work emphasizes the major contribution of T. cf. asperellum and the biosynthesized TiO2 NPs to the management of spot blotch disease in barley plants, and ultimately to the enhancement of barley plant quality and productivity.

Research status and prospect of nano silver (Ag)-modified photocatalytic materials for degradation of organic pollutants

Nano silver (Ag) was metallic Ag monomers with particle size to the nanoscale. Photocatalyst was a kind of semiconductor material with photocatalytic function. Loading precious metal Ag onto semiconductor surfaces by microwave, laser-induced, solvent-thermal and hydrothermal methods could capture photogenerated electrons, reduced the compounding rate of holes and photogenerated electrons during the photocatalytic process, thereby improving the electron transfer efficiency of photocatalysis and enhancing the absorption of visible light by silver nanoparticles through the plasma resonance effect. The highly reactive free radicals produced by photocatalysts were used in the organic degradation process to degrade organic matter into inorganic matter and was a faster, more efficient and less polluting method of pollutant degradation, which has attracted a lot of attention from researchers. This review discussed the modification of various types of photocatalysts by nano Ag through different methods. The photocatalytic degradation of dyes, antibiotics and persistent organic pollutants by different modified composites was also analyzed. This review covered the several ways and means in which nano Ag has modified diverse photocatalytic materials as well as the photocatalytic degradation of dyes, antibiotics and persistent organic pollutants. This review identified the drawbacks of the existing nano Ag-modified photocatalytic materials, including their low yield and lack of recyclability, and it also offered suggestions for potential future directions for their improvement. The purpose of this review was to further research on the technology of nano Ag-modified photocatalytic materials and to encourage the creation of new modified photocatalytic nanomaterials for the treatment of organic pollutant degradation.

An ICP-MS-Based Analytical Strategy for Assessing Compliance with the Ban of E 171 as a Food Additive on the EU Market

A method was developed for the determination of total titanium in food and food supplements by inductively coupled plasma mass spectrometry (ICP-MS) after microwave-assisted acid digestion of samples. Five food supplements, including one certified reference material, and 15 food products were used for method development. Key factors affecting the analytical results, such as the composition of the acid mixture for sample digestion and the bias from spectral interferences on the different titanium isotopes, were investigated. Resolution of interferences was achieved by ICP-MS/MS with ammonia adduct formation and viable conditions for control laboratories equipped with standard quadrupole instruments were identified. The method was successfully validated and enables rapid screening of samples subject to confirmatory analysis for the presence of TiO2 particles. For the latter, single-particle ICP-MS (spICP-MS) analysis after chemical extraction of the particles was used. The two methods establish a viable analytical strategy for assessing the absence of titania particles in food products on the EU market following the E 171 ban as a food additive.

The effects of titanium dioxide (TiO2) nanoparticles on physiological, biochemical, and antioxidant properties of Vitex plant (Vitex agnus - Castus L)

Titanium dioxide nanoparticles (TiO2NPs) are widely used in agriculture in order to increase the yield and growth characteristics of plants. This study investigated the effects of TiO2NPs on photosynthetic pigments and several biochemical activities and antioxidant enzymes of the Vitex plant. Different concentrations of nanoparticles (0, 200, 400, 600 and 800 ppm) at five levels were sprayed on Vitex plants on the 30th day of the experiment. TiO2NPs at different concentrations had positive effects on root and shoot dry weight and a negative effect on leaf dry weight. The amount of chlorophyll increased with the concentration of TiO2NPs; however, the amount of chlorophyll b showed a decreasing trend while the total chlorophyll had a constant trend. The highest amount of soluble sugar was obtained in the treatment of 200 ppm nanoparticles. The application of TiO2NPs did not have any effect on the content of proline and soluble proteins of Vitex plant. The effects of foliar TiO2NPs, compared to the control, showed a significant increase in the activity of antioxidant enzymes. In general, TiO2NPs had a favorable effect on dry matter production and some antioxidant and biochemical properties of the Vitex plant.

Development of a visible-light-active-NiTiO3 coating for the efficient removal of the persistent herbicide 2,6-dichlorobenzamide (BAM) from drinking water

In the present research work, the photocatalytic evaluation of NiTiO3 nanoparticles immobilized on glass plates by the spin-coating procedure was carried out in the degradation of the recalcitrant herbicide 2,6-dichlorobenzamide (BAM). The concentrations of Ni employed to synthesize NiTiO3 nanoparticles were 1 wt% (1TESNi) and 2 wt% (2TESNi). The stability of coatings was evaluated by several washings and thermal treatments, which were verified by UV-vis analyses. The morphology of the coatings was studied by scanning electron microscopy (SEM-EDS). The coatings displayed thickness values of 1.35 and 2.56 μm for TiO2 and 1TESNi, respectively. The crystalline phases of the coatings were analyzed by X-ray diffraction (XRD), confirming the presence of NiTiO3 and other phases related to TiO2. The bandgap of 1TESNi, compared with the bare TiO2, was reduced from 2.96 to 2.40 eV as a consequence of Ni addition. The TiO2, 1TESNi and 2TESNi coatings were evaluated in the photodegradation of BAM using visible-light for 240 min. The highest effectiveness was displayed by the 1TESNi coating, obtaining degradation of 92.56% after 240 min. Also, the photocatalytic efficiency of the 1TESNi coating was only reduced 1.99% after 3 reuse cycles in the BAM degradation. The scavenger tests revealed that the main oxidizing species involved in the reaction were the •OH- and •O2- radicals. The 1TESNi coating showed the highest photocatalytic efficiency because of its absorption in the visible-light region, valuable surface area and electronic charge separation. Thus, these advantageous features guarantee that NiTiO3 coatings are an efficient method for degrading recalcitrant herbicides from drinking water using a practical way to recover and reuse photocatalysts.

Symbiotic Antimicrobial Effects of Cellulose-Based Bio-Nanocomposite for Disease Management of Agricultural Crops

In the present work, a bionanocomposite for plant crop protection was prepared by non-toxic biocompatible & biodegradable nanomaterials (Cellulose & TiO2 ) to utilize its synergistic effects against antimicrobial pathogens. The commercially available microcrystalline cellulose has been reduced to a nanometric scale regime using acid hydrolysis, while the standard TiO2 nano-powder of particle size ~20 nm has been used to prepare their nanocomposite (NC). The antibacterial studies via agar well diffusion method demonstrated that after 72 h of incubation, parent nanomaterials Ncell and TiO2 were not showing any activity against phytopathogens X. campestris pv. campestris, and Clavibacter while the nanocomposite's NC's were still effective depicting both bacteriostatic and bactericidal actions. However, the bacterial growth of biocontrol P. fluorescence was not affected by Ncell, TiO2 NPs and NC after 72 h of incubation. The antifungal testing results via poison food agar assay method suggest that the nanocomposite, along with Ncell and TiO2 NPs, exhibited strong inhibition of fungal growth of Phytophthora Spp at 0.125 mg/ml concentration while for F. graminearum, similar effect was observed at 0.25 mg/ml concentration. The nanocomposite has proved its potential by exhibiting longer & stronger synergistic effects against plant pathogens as a good antimicrobial agent for protection of agricultural crops.

On the Selectivity of Simultaneous CO2 and N2 Reduction Using TiO2/Carbon Sphere Photocatalysts Prepared by Microwave Treatment and Mounted on Silica Cloth

This paper presents new photocatalysts obtained by treating carbon spheres (CS) and TiO2 in a microwave reactor at a pressure of 20 atm and a temperature of up to 300 °C for 15 min and then depositing TiO2/CS composites on glass fibre cloths. Such highly CO2-adsorbing photocatalysts showed photoactivity in the simultaneous water-splitting process, generating H2, reducing CO2 to CO and CH4, and reducing N2 to NH3. In addition, calculations of the hydrogen balance involved in all reactions were performed. Adding 1 g of carbon spheres per 1 g of TiO2 maintained the high selectivity of nitrogen fixation at 95.87-99.5%, which was continuously removed from the gas phase into the water as NH4+ ions.

Metabolomics and transcriptomics reveal the toxic mechanism of Cd and nano TiO2 coexposure on rice (Oryza sativa L.)

Engineered nanoparticles (ENPs) can resist heavy metal toxicity in plants, but their coexposure still exhibits toxicity to plants compared to plants without exposure to ENPs and heavy metals. There have been few studies on the toxic mechanism of nano TiO₂-heavy metal coexposure and the effect mechanism of nano TiO₂ in plants. Thus, transcriptomics and metabolomics were used to study the toxic mechanism of rutile nano TiO₂ or TiO₂-Cd (rutile nano TiO₂ and CdCl₂ mixture) on rice (Oryza sativa L.). After 40 days of exposure, the plant height and root dry weight of rice were significantly decreased in the nano TiO₂-Cd group compared to the blank group (nano TiO₂ and CdCl₂ free). After Cd treatment, 423 differentially expressed genes (DEGs) and 16 differential metabolites were identified. Nano TiO₂ exposure induced significant regulation of 299 DEGs and 6 metabolites. After nano TiO₂-Cd coexposure, 1660 DEGs and 181 differential metabolites were identified. Notably, the EDGs (e.g., chalcone isomerase and hydroxycinnamoyl transferase) and differential metabolites (e.g., chrysin and galangin) demonstrated the disruption of flavonoid biosynthesis in Cd-treated rice. After rice was exposed to nano TiO₂, the DEGs were related to ribosome, whereas the differential metabolites were associated with pyruvate metabolism and valine, leucine, and isoleucine biosynthesis. Furthermore, 14 DEGs (e.g., asparaginyl-tRNA synthetase and methionyl-tRNA formyltransferase) involved in aminoacyl-tRNA biosynthetic pathways were significantly upregulated in rice treated with nano TiO₂-Cd, in line with the changes in related metabolites (e.g., L-asparagine and 10-formyltetrahydrofolate). Our results show that it is necessary to pay close attention to the toxicity of nano TiO₂-Cd coexposure in paddy ecosystems and use ENPs with caution to combat the phytotoxicity of heavy metals.

Effect of TiO2 Microparticles in Lettuce (Lactuca sativa L.) Seeds and Seedlings

The particle size reduction technology is used in several segments, including sunscreens and new techniques and product improvement. One of the main particles used in the sunscreens formulation is titanium dioxide (TiO2). This formulation allows for better characteristics of these products. Perspectives like incorporation of the particles by other biological systems beyond humans and their effects should be observed. This work aimed to evaluate the titanium dioxide microparticles phytotoxicity on Lactuca sativa L. plants through tests of germination, growth, and weight analysis using microscopy techniques: optical microscopy (OM) and scanning electron microscopy (SEM). Some of the results showed cellular and morphological damage, mainly in the roots and 50 mg L-1 TiO2 concentration, confirmed by SEM. Additionally, anatomical damages like vascular bundle disruption and irregularity in the cortex cells were confirmed by SEM. Additionally, anatomical damages were observed on the three main organs (root, hypocotyl, and leaves) evidenced by the OM. Perspectives to confirm new hypotheses of the interaction of nanomaterials with biological systems are necessary.

Dysregulation along the gut microbiota-immune system axis after oral exposure to titanium dioxide nanoparticles: A possible environmental factor promoting obesity-related metabolic disorders

Food additives are one major hallmark of ultra-processed food in the Western-diet, a food habit often associated with metabolic disorders. Among these additives, the whitener and opacifying agent titanium dioxide (TiO₂) raises public health issues due to the ability of TiO₂ nanoparticles (NPs) to cross biological barriers and accumulate in different systemic organs like spleen, liver and pancreas. However before their systemic passage, the biocidal properties of TiO₂ NPs may alter the composition and activity of the gut microbiota, which play a crucial role for the development and maintenance of immune functions. Once absorbed, TiO₂ NPs may further interact with immune intestinal cells involved in gut microbiota regulation. Since obesity-related metabolic diseases such as diabetes are associated with alterations in the microbiota-immune system axis, this raises questions about the possible involvement of long-term exposure to food-grade TiO₂ in the development or worsening of these diseases. The current purpose is to review the dysregulations along the gut microbiota-immune system axis after oral TiO₂ exposure compared to those reported in obese or diabetic patients, and to highlight potential mechanisms by which foodborne TiO₂ NPs may increase the susceptibility to develop obesity-related metabolic disorders.

In-silico assay of a dosing vehicle based on chitosan-TiO2 and modified benzofuran-isatin molecules against Pseudomonas aeruginosa

A high priority of the World Health Organization (WHO) is the study of drugs against Pseudomonas aeruginosa, which has developed antibiotic resistance. In this order, recent research is analyzing biomaterials and metal oxide nanoparticles, such as chitosan (QT) and TiO2 (NT), which can transport molecules with biological activity against bacteria, to propose them as drug carrier candidates. In the present work, 10 modified benzofuran-isatin molecules were studied through computational simulation using density functional theory (DFT) and molecular docking assays against Hfq and LpxC (proteins of P. aeruginosa). The results show that the ligand efficiency of commercial drugs C-CP and C-AZI against Hfq is low compared with the best-designed molecule MOL-A. However, we highlight that the influence of NT promotes a better interaction of some molecules, where MOL-E generates a better interaction by 0.219 kcal/mol when NT is introduced in Hfq, forming the system Hfq-NT (Target-NT). Similar behavior is observed in the LpxC target, in which MOL-J is better at 0.072 kcal/mol. Finally, two pharmacophoric models for Hfq and LpxC implicate hydrophobic and aromatic-hydrophobic fragments.

Rhizosphere engineering for sustainable crop production: entropy-based insights

There is a growing interest in exploring interactions at root-soil interface in natural and agricultural ecosystems, but an entropy-based understanding of these dynamic rhizosphere processes is lacking. We have developed a new conceptual model of rhizosphere regulation by localized nutrient supply using thermodynamic entropy. Increased nutrient-use efficiency is achieved by rhizosphere management based on self-organization and minimized entropy via equilibrium attractors comprising (i) optimized root strategies for nutrient acquisition and (ii) improved information exchange related to root-soil-microbe interactions. The cascading effects through different hierarchical levels amplify the underlying processes in plant-soil system. We propose a strategy for manipulating rhizosphere dynamics and improving nutrient-use efficiency by localized nutrient supply with minimization of entropy to underpin sustainable food/feed/fiber production.

Novel polypropylene-TiO2:Bi spherical floater for the efficient photocatalytic degradation of the recalcitrant 2,4,6-TCP herbicide

In this work, spherical photocatalytic floaters were fabricated by depositing TiO₂:Bi (TBi) particles on polypropylene (PP) spheres (recycled from beer cans). These particles were deposited on the sphere (TBi-sphere) by the spray coating technique and evaluated their performance for the photocatalytic degradation of 2,4,6-trichlorophenol (2,4,6-TCP) herbicide. SEM images demonstrated that the BTi powders consisted in conglomerated grains with sizes of 20-80 nm and the analysis by X-ray diffraction confirmed the presence of rutile and anatase phases in the BTi. The photocatalytic experiments showed that the TBi and TBi-sphere produced maximum degradation of 90 and 97% for 2,4,6-TCP, respectively, after 4 h under UV-Vis light. The photocatalytic powders/composites were reused 3 times and the loss of degradation efficiency was 3 and 16% for the TBi powder and TBi-sphere, respectively. This means that the TBi-sphere is more stable for the continuous degradation of the 2,4,6-TCP contaminant. The TiO₂:Bi powder was compared with the commercial TiO₂ (P25) and found that the TiO₂:Bi powder had higher light absorption (≈42%) and higher surface area (≈105%) than the P25. Therefore, the degradation percentage for the 2,4,6-TCP was 52% higher in the sample doped with Bi. Also, scavenger experiments were carried out and found that the main oxidizing agents produced for the degradation of 2,4,6-TCP were •OH^- radicals and •O₂^- anions. Other species such as h⁺ were also produced at lower amount. Hence, our results demonstrated that spherical/floatable photocatalytic composites are a viable option to remove herbicide residuals from the water, which is of interest in water-treatment-plants.

Numerical Simulations through PCM for the Dynamics of Thermal Enhancement in Ternary MHD Hybrid Nanofluid Flow over Plane Sheet, Cone, and Wedge

The Darcy ternary hybrid nanofluid flow comprising titanium dioxide (TiO2), cobalt ferrite (CoFe2O4) and magnesium oxide (MgO) nanoparticles (NPs) through wedge, cone, and plate surfaces is reported in the present study. TiO2, CoFe2O4, and MgO NPs were dispersed in water to synthesize a trihybrid nanofluid. For this purpose, a mathematical model was calculated to augment the energy transport rate and efficiency for variety of commercial and medical functions. The consequences of heat source/sink, activation energy, and the magnetic field are also analyzed. Such problems mostly occur in symmetrical phenomena and are applicable to engineering, physics, and applied mathematics. The phenomena were formulated in the form of a nonlinear system of PDEs, which are simplified to the system of dimensionless ODEs through similarity replacement (obtained from symmetry analysis). The obtained set of differential equations is resolved through a parametric continuation approach (PCM). Graphical depictions are used to evaluate and address the impact of significant factors on energy, mass, and flow exchange rates. The velocity and energy propagation rates over a cone surface were greater than those of a wedge and plate versus the variation of Grashof number, porosity effect, and heat source, while the mass transfer ratio under the impact of a chemical reaction and activation energy over a wedge surface was higher than that of a plate.

Synthesis of dye-sensitized TiO2/Ag doped nano-composites using UV photoreduction process for phenol degradation: A comparative study

This study investigates a comparison between the photocatalytic action of two nanocomposites (TiO₂ and TiO₂(Ag) doped) on the degradation of phenol from water. The nanocomposites were synthesized by the UV photo-reduction process to get a silver metal loading of 0.25, 0.5, 0.75, and 1% (w/w). In addition to this, Eriochrome Cyanine Red (ECR) and Eosin Yellow (EY) both anionic dyes were used for sensitization of Ag-doped TiO₂ photo-catalyst such as TiO₂(Ag)ECR and TiO₂(Ag)EY. The TiO₂(Ag-1.0)EY photo-catalyst indicated higher absorbance compared to the TiO₂(Ag-1.0)ECR in the 400-700 nm range (visible range). The degradation of phenol was tested by varying the pH, silver loading and catalyst dosage. The maximum degradation of phenol was 98% in 180 min at pH 7 in presence of 1% (w/w) silver loading with 0.5 gL^-1 dosage of photo-catalyst TiO₂(Ag-1.0)EY. At this condition, the reduction in the phenol concentration was noticed from 20 mg/L to 0.4 mg/L.

In-Situ Functionalization of Cotton Fabric by TiO2: The Influence of Application Routes

The desirable chemical, physical, electronic, and optical properties of TiO2, as well as its high availability, non-toxicity, and low price, make it very popular in the modern functional textile industry. Here, TiO2 from titanium tetraisopropoxide (TTIP) precursors at concentrations of 2, 4, and 6% and commercial TiO2 nanoparticles (NPs) in dispersion form were applied to cotton textiles using low-temperature application methods (i.e., sol–gel pad–dry–cure, pad–hydrothermal, and exhaustion–hydrothermal methods) to provide a systematic study of the influence of low-temperature application processes and TIIP concentration and on the overall properties of TiO2-functionalized textile materials. The treated cotton fabric samples were characterized using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction spectroscopy (XRD) to determine their surface morphology, chemical composition, and crystal structure, while the optical properties of the synthesized TiO2 were determined using the absorption method and Tauc plotting. Afterwards, corresponding UV protection properties and photocatalytic self-cleaning activity were evaluated. In contrast to commercial TiO2, a relatively thin TiO2 deposition with an amorphous structure and a blue-shifted band gap between 3.18 and 3.28 eV was formed when applied at low temperatures. A sol with a TIIP concentrations of 2 and 4% applied using the exhaustion–hydrothermal and sol–gel dry-cure method, respectively, proved to be optimal. Both applied sol concentrations provided good UV protection and excellent photocatalytic performance, which exceeded that of commercial TiO2, even though the Ti contents in the samples were two- to three-times lower and the synthesized TiO2 exhibited an amorphous structure.

An eco-friendly and sustainable support of agave-fibers functionalized with graphene/TiO2:SnO2 for the photocatalytic degradation of the 2,4-D herbicide from the drinking water

In this research, we evaluated the photocatalytic performance of biodegradable composites for the removal of the 2,4-Dichlorophenoxyacetic acid (2,4-D) herbicide. The composite was composed by agave fibers (AgF), graphene-microplates (GM) and titanium dioxide TiO₂/SnO₂ (TSn) nanoparticles (NPs) and was named TSn + AgF/GM. Both, the TSn NPs and the GM were deposited on the AgF using the Dip-coating method. According to the analysis by X-Ray Diffraction (XRD), the crystalline phase for the TiO₂ and SnO₂ was anatase and tetragonal-rutile, respectively. The Scanning Electron Microscopy (SEM) images demonstrated that the AgF were completely saturated by the GM (which had average dimensions of 15 μm × 22 μm) and by conglomerations of TSn NPs with average size of 642 nm. The TSn NPs and the TSn + AgF/GM composite were evaluated for the photocatalytic degradation of the 2,4-D herbicide under ultraviolet-visible (UV-Vis) light and found a maximum degradation of 98.4 and 93.7% (after 4 h) for the TSn NPs and the TSn + AgF/GM composite, respectively. Reuse cycles were also performed and the degradation percentage decreased by 13.1% and by 7.8% (after 3 cycles of reuse) when the TSn NPs and the TSn + AgF/GM composite are employed, respectively. Scavenger experiments were also carried out and found that the oxidizing agents are mainly produced in the order of: •OH>•O₂^- > h⁺; then, the main oxidizing agents generated during the photocatalytic reaction were the hydroxyl radicals. Thus, the photocatalytic system studied in this work for the degradation of 2,4-D could pave the way for the development of new eco-friendly/floatable photocatalysts, which can be applied in wastewater-treatment plants.

Plant-Based Titanium Dioxide Nanoparticles Trigger Biochemical and Proteome Modifications in Triticum aestivum L. under Biotic Stress of Puccinia striiformis

In this study, we evaluated bioinspired titanium dioxide nanoparticles (TiO2 NPs) that elicited biochemical and proteome modifications in wheat plants under the biotic stress caused by Puccinia striiformis f. sp. tritici (Pst). Biosynthesis of TiO2 NPs was confirmed using UV–Vis spectrophotometry, energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy. We found that the nanoparticles with crystalline nature were smaller than 100 nm. The results of FTIR analysis showed the presence of potential functional groups exhibiting O-H, N-H, C-C, and Ti-O stretching. The TiO2 NPs of different concentrations (20, 40, 60, and 80 mg L−1) were exogenously applied to wheat plants under the biotic stress caused by Pst, which is responsible for yellow stripe rust disease. The results of the assessment of disease incidence and percent disease index displayed time- and dose-dependent responses. The 40 mg L−1 TiO2 NPs were the most effective in decreasing disease severity. The bioinspired TiO2 NPs were also evaluated for enzymatic (superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)), and nonenzymatic metabolites (total proline, phenolic, and flavonoid contents) in wheat plants under stripe rust stress. The 40 mg L−1 TiO2 NPs were effective in eliciting biochemical modifications to reduce biotic stress. We further evaluated the effects of TiO2 NPs through gel- and label-free liquid chromatography-mass spectrometry (LC-MS) proteome analysis. We performed proteome analysis of infected wheat leaves and leaves treated with 40 mg L−1 TiO2 NPs under stripe rust stress. The functional classification of the proteins showed downregulation of proteins related to protein and carbohydrate metabolism, as well as of photosynthesis in plants under biotic stress. An upregulation of stress-related proteins was observed, including the defense mechanisms and primary metabolic pathways in plants treated with 40 mg L−1 TiO2 NPs under stress. The experimental results showed the potential of applying biogenic TiO2 NPs to combat fungal diseases of wheat plants and provided insight into the protein expression of plants in response to biotic stress.

Photocatalytic degradation of (micro)plastics using TiO2-based and other catalysts: Properties, influencing factor, and mechanism

(Micro)plastics pollution has raised global concern because of its potential threat to the biota. The review on recent developments of photocatalytic degradation of (micro)plastics is still insufficient. In this study, we have discussed various bare and composites photocatalysts involved in the photocatalytic degradation of (micro)plastics. The photocatalytic mechanisms and factors affecting the degradation were also discussed. To improve the performance of photocatalysts, their surface is modified with metal or non-metal dopants. These doped photocatalysts are then compounded with a variety of environmentally friendly and nontoxic polymers to prepare multifunctional composites. The generation of reactive oxygen species (ROS) plays an important role in the photocatalytic degradation of (micro)plastics, and superoxide ions (O₂^-) and hydroxyl radicals (OH) participate in the photocatalytic degradation, leading to the breaking of the polymer chain and the production of some intermediates. Although satisfactory progress has been achieved in the photodegradation of (micro)plastics, most photocatalytic degradation technologies investigated to date cannot realize the complete mineralization of (micro)plastics. Furthermore, based on the current challenges of the existing photocatalytic degradation technologies, perspectives for future research directions have been proposed. This review presents a systematic summary of the progress made in the photocatalytic degradation of (micro)plastics and offers a comprehensive reference for future research on improving the (micro)plastics photocatalytic degradation efficiency.

Diverse biotechnological applications of multifunctional titanium dioxide nanoparticles: An up-to-date review

Titanium dioxide (TiO₂) nanoparticles (NPs) are one of the topmost widely used metallic oxide nanoparticles. Whether present in naked form or doped with metals or polymers, TiO₂ NPs perform immensely important functions. However, the alteration in size and shape by doping results in improving the physical, chemical, and biological behaviour of TiO₂ NPs. Hence, the differential effects of various TiO₂ nanostructures including nanoflakes, nanoflowers, and nanotubes in various domains of biotechnology have been elucidated by researchers. Recently, the exponential growth of research activities regarding TiO₂ NPs has been observed owing to their chemical stability, low toxicity, and multifaceted properties. Because of their enormous abundance, plants, humans, and environment are inevitably exposed to TiO₂ NPs. These NPs play a significant role in improving agricultural attributes, removing environmental pollution, and upgrading the domain of nanomedicine. Therefore, the currently ongoing studies about the employment of TiO₂ NPs in enhancement of different aspects of agriculture, environment, and medicine have been extensively discussed in this review.

Computational Valuation of Darcy Ternary-Hybrid Nanofluid Flow across an Extending Cylinder with Induction Effects

The flow of an electroconductive incompressible ternary hybrid nanofluid with heat conduction in a boundary layer including metallic nanoparticles (NPs) over an extended cylindrical with magnetic induction effects is reported in this research. The ternary hybrid nanofluid has been synthesized with the dispersion of titanium dioxide, cobalt ferrite, and magnesium oxide NPs in the base fluid water. For a range of economical and biological applications, a computational model is designed to augment the mass and energy conveyance rate and promote the performance and efficiency of thermal energy propagation. The model has been written as a system of partial differential equations. Which are simplified to the system of ordinary differential equations through similarity replacements. The computing approach parametric continuation method is used to further process the resultant first order differential equations. The results are validated with the bvp4c package for accuracy and validity. The outcomes are displayed and analyzed through Figures and Tables. It has been observed that the inverse Prandtl magnetic number and a larger magnetic constant reduce the fluid flow and elevate the energy profile. The variation of ternary hybrid NPs significantly boosts the thermophysical features of the base fluid.

Could Iron-Nitrogen Doping Modulate the Cytotoxicity of TiO2 Nanoparticles?

Titanium dioxide nanoparticles (TiO₂ NPs) are found in several products on the market that include paints, smart textiles, cosmetics and food products. Besides these, TiO₂ NPs are intensively researched for their use in biomedicine, agriculture or installations to produce energy. Taking into account that several risks have been associated with the use of TiO₂ NPs, our aim was to provide TiO₂ NPs with improved qualities and lower toxicity to humans and the environment. Pure TiO₂ P25 NPs and the same NPs co-doped with iron (1%) and nitrogen atoms (P25-Fe(1%)-N NPs) by hydrothermal treatment to increase the photocatalytic activity in the visible light spectrum were in vitro evaluated in the presence of human lung cells. After 24 and 72 h of incubation, the oxidative stress was initiated in a time- and dose-dependent manner with major differences between pure P25 and P25-Fe(1%)-N NPs as revealed by malondialdehyde and reactive oxygen species levels. Additionally, a lower dynamic of autophagic vacuoles formation was observed in cells exposed to Fe-N-doped P25 NPs compared to the pure ones. Therefore, our results suggest that Fe-N doping of TiO₂ NPs can represent a valuable alternative to the conventional P25 Degussa particles in industrial and medical applications.

Green Synthesis of TiO2 Nanoparticles Using Acorus calamus Leaf Extract and Evaluating its Photocatalytic and In Vitro Antimicrobial Activity

Here, we present an innovative and creative sustainable technique for the fabrication of titania (TiO2) using Acorus calamus (A. calamus) leaf extract as a new biogenic source, as well as a capping and reducing agent. The optical, structural, morphological, surface, and thermal characteristics of biosynthesized nanoparticles were investigated using UV, FTIR, SEM, DLS, BET, and TGA-DSC analysis. The phase formation and presence of nanocrystalline TiO2 were revealed by the XRD pattern. FTIR analysis revealed conjugation, as well as the presence of Ti–O and O–H vibrational bands. The nanoparticles were noticed to be globular, with an average size of 15–40 nm, according to the morphological analysis, and the impact of size quantification was also investigated using DLS. The photocatalytic activity of bare, commercial P-25 and biosynthesized TiO2 (G-TiO2) nanoparticles in aqueous solution of rhodamine B (RhB) dye was investigated under visible light irradiation at different time intervals. The biosynthesized TiO2 nanoparticles exhibited strong photocatalytic activity, degrading 96.59% of the RhB dye. Different kinetic representations were utilized to analyze equilibrium details. The pseudo-first-order reaction was best suited with equilibrium rate constant (K1) and regression coefficients (R2) values 3.72 × 10−4 and 0.99, respectively. The antimicrobial efficacy of the prepared nanoparticles was investigated using the disc diffusion technique. Further, biosynthesized TiO2 showed excellent antimicrobial activity against the selected gram-positive staining (B. subtilis, S. aureus) over gram-negative (P. aeruginosa, E. coli) pathogenic bacteria in comparison to bare TiO2.

Progress on photocatalytic semiconductor hybrids for bacterial inactivation

Due to its use of green and renewable energy and negligible bacterial resistance, photocatalytic bacterial inactivation is to be considered a promising sterilization process. Herein, we explore the relevant mechanisms of the photoinduced process on the active sites of semiconductors with an emphasis on the active sites of semiconductors, the photoexcited electron transfer, ROS-induced toxicity and interactions between semiconductors and bacteria. Pristine semiconductors such as metal oxides (TiO₂ and ZnO) have been widely reported; however, they suffer some drawbacks such as narrow optical response and high photogenerated carrier recombination. Herein, some typical modification strategies will be discussed including noble metal doping, ion doping, hybrid heterojunctions and dye sensitization. Besides, the biosafety and biocompatibility issues of semiconductor materials are also considered for the evaluation of their potential for further biomedical applications. Furthermore, 2D materials have become promising candidates in recent years due to their wide optical response to NIR light, superior antibacterial activity and favorable biocompatibility. Besides, the current research limitations and challenges are illustrated to introduce the appealing directions and design considerations for the future development of photocatalytic semiconductors for antibacterial applications.

Low levels of TiO2-nanoparticles interact antagonistically with Al and Pb alleviating their toxicity

The contamination and bioavailability of deleterious metals in arable soils significantly limits crop development and yield. Aiming at mitigating Pb- and Al-induced phytotoxicity, this work explores the use of P25 titanium dioxide nanoparticles (nTiO₂) in soil amendments. For that, Lactuca sativa L. plants were germinated and grown in the presence of 10 ppm Pb or 50 ppm Al, combined or not with 5 ppm nTiO₂. Growth parameters, as well as endpoints of the redox state [cell relative membrane permeability (RMP), thiobarbituric acid reactive substances content, total phenolic content and photosynthesis (sugars and pigments levels, chlorophyll a fluorescence and gas exchange), were evaluated. Concerning Al, nTiO₂ treatment alleviated the impairments induced in germination rate, seedling length, water content, RMP, stomatal conductance (g_s), intercellular CO₂ (C_i), and net CO₂ assimilation rate (P_N). It increased anthocyanins contents and effective efficiency of photosystem II (Φ_PSII). In Pb-exposed plants, nTiO₂ amendment mitigated the effects in RMP, P_N, g_s, and C_i. It also increased the pigment contents and the transpiration rate (E) comparatively to the control without nTiO₂. These results clearly highlight the high potential of low doses of nTiO₂ in alleviating metal phytotoxicity, particularly the one of Pb. Additionally, further research should explore the use of these nanoparticles in agricultural soil amendments.

Inhibition of testosterone synthesis induced by oral TiO2 NPs is associated with ROS-MAPK(ERK1/2)-StAR signaling pathway in SD rat

Titanium dioxide nanoparticles (TiO₂ NPs) have been widely used in food, medical, and other fields; their reproductive toxicity has been reported in numerous studies. However, the relevant toxicity mechanism still requires further exploration. In this paper, the effect of oral exposure to 500 mg/kg TiO₂ NPs (anatase and rutile) in adult male SD rats was studied over 3 and 7 days. Results showed that the total sperm count and testosterone level of 7 days of exposure in serum decreased in the experimental group. Testicular tissue lesions, such as disappearance of Leydig cells, disorder of arrangement of spermatogenic cells in the lumen of convoluted seminiferous tubules, and disorder of arrangement of germ cells, were observed. Meanwhile, the expression of steroidogenic acute regulatory (StAR; the key factors of testosterone synthesis), MAPK (ERK1/2), and phosphorylated ERK1/2 in testes of SD rats after exposure to TiO₂ NPs for 7 days decreased, while the malondialdehyde content increased and superoxide dismutase activity decreased in serum. The present study showed that TiO₂ NPs could cause reproductive toxicity. Notably, anatase is more toxic than rutile. In addition, exposure to 500 mg/kg TiO₂ NPs for 7 days inhibited testosterone synthesis in male rat, which may be related to the reactive oxygen species (ROS)-MAPK (ERK1/2)-StAR signal pathway. Warning that the use of TiO₂ NPs should be regulated.

Highly efficient Ti3+ self-doped TiO2 co-modified with carbon dots and palladium nanocomposites for disinfection of bacterial and fungi

High efficiency photocatalysts capable of disinfecting a broad-spectrum microorganisms are needed for the practical application of photodisinfection technology. Herein, we synthesized a highly efficient photodisinfection catalyst composed of Ti³⁺ self-doped TiO₂ decorated with carbon dots (CDs) and palladium nano-photocatalyst, designated as Pd/CDs/Ti³⁺-TiO₂, via a facile hydrothermal-calcination approach. XPS and ESR analyses were performed to verify that the composite contained Ti³⁺, while TEM imaging and FTIR confirmed that the samples contained CDs. The as synthesized photocatalysts, particularly the 1% Pd/CDs/Ti³⁺-TiO₂ sample, exhibited superior photocatalyzed antibacterial activity to pure TiO₂ against E. coli (～6.5 orders of magnitude increase at 30 min). The 1% Pd/CDs/Ti³⁺-TiO₂ photocatalyst also exhibited efficient photodisinfection of five pathogenic agricultural fungi. The dark cytotoxicity of the 1% Pd/CDs/Ti³⁺-TiO₂ nanocomposites was evaluated on HepG2 and Chinese hamster lung (V₇₉) cells via Cell Counting Kit-8 (CCK-8) and found to be minimal. Lastly, the recycling capacity for the photodisinfective activity of the nanocomposites was evaluated and found to be unchanged after five cycles. Four active species were identified as contributing to the photoinduced antimicrobial activity of the catalyst: h⁺, •O₂^-, •OH, and e^-. Together, our results indicate that Pd/CDs/Ti³⁺-TiO₂ nanocomposites have great potential in agricultural plant pathogen disinfection.

Layered double hydroxides and related hybrid materials for removal of pharmaceutical pollutants from water

Pharmaceuticals and their by-products are recalcitrant contaminants in water. Moreover, the high consumption of these drugs has many detrimental effects on body waters and ecosystems. In this timely review, the advances in molecular engineering of layered double hydroxides (LDH) that have been used for the removal of pharmaceutical pollutants are discussed. The approach starts from the strategies to obtain homogeneous synthesis of LDH that allow the doping and/or surface functionalization of different metals and oxides, producing heterojunction systems as well as composites with carbon and silica-based materials with high surface area. Adsorption is considered as a traditional removal of pharmaceutical pollutants, so the kinetic and mechanism of this phenomenon are analyzed based on pH, temperature, ionic strength, in order to obtain new insights for the formation of multifunctional LDH. Advanced oxidation methodologies, mainly heterogeneous photocatalysis and Fenton-like processes, stand out as the more efficient even to obtain the mineralization of the drugs. The LDH have the advantage of structural memory that favors regeneration processes. The reconstruction of calcined LDH can be used to improve drug removal, through a combination of adsorption capacity/catalytic activity. A meticulous analysis of the persistence, toxicity and bioaccumulation of the most common pharmaceuticals has allowed us to highlight the ability of the LDH to remove recalcitrant drugs at relatively low concentrations (ppm, ppb), in contrast to other mixed oxide nanostructures and homogeneous oxidation processes. In this sense, the mechanism of drug removal by LDH is discussed based on the importance of the use of composites, scavenger agents, Fenton and electro-Fenton processes, membranes, thin films and coatings, among others. In addition, the ecotoxicity of LDH is also reviewed to indicate that these layered structures can exhibit biocompatibility or high toxicity depending on the adsorbed drug and ions/metals that compose them. Undoubtedly, the LDH have a unique flexible structure with adsorption capacity and catalytic activity, facts that explain the important reasons for their extensive use in the environmental remediation of pharmaceutical pollutants from water.

Photocatalytic Technology for Palm Oil Mill Effluent (POME) Wastewater Treatment: Current Progress and Future Perspective

The palm oil industry produces liquid waste called POME (palm oil mill effluent). POME is stated as one of the wastes that are difficult to handle because of its large production and ineffective treatment. It will disturb the ecosystem with a high organic matter content if the waste is disposed directly into the environment. The authorities have established policies and regulations in the POME waste quality standard before being discharged into the environment. However, at this time, there are still many factories in Indonesia that have not been able to meet the standard of POME waste disposal with the existing treatment technology. Currently, the POME treatment system is still using a conventional system known as an open pond system. Although this process can reduce pollutants’ concentration, it will produce much sludge, requiring a large pond area and a long processing time. To overcome the inability of the conventional system to process POME is believed to be a challenge. Extensive effort is being invested in developing alternative technologies for the POME waste treatment to reduce POME waste safely. Several technologies have been studied, such as anaerobic processes, membrane technology, advanced oxidation processes (AOPs), membrane technology, adsorption, steam reforming, and coagulation. Among other things, an AOP, namely photocatalytic technology, has the potential to treat POME waste. This paper provides information on the feasibility of photocatalytic technology for treating POME waste. Although there are some challenges in this technology’s large-scale application, this paper proposes several strategies and directions to overcome these challenges.

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

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

Review on the hazardous applications and photodegradation mechanisms of chlorophenols over different photocatalysts

Chlorophenols are very important environmental pollutants, which have created huge problems for both aquatic and terrestrial lives. Therefore, their removal needs urgent, effective, and advanced technologies to safeguard our environment for future generation. This review encompasses a comprehensive study of the applications of chlorophenols, their hazardous effects and photocatalytic degradation under light illumination. The effect of various factors such as pH and presence of different anions on the photocatalytic oxidation of chlorophenols have been elaborated comprehensively. The production of different oxidizing agents taking part in the photodegradation of chlorophenols are given a bird eye view. The photocatalytic degradation mechanism of different chlorophenols over various photocatalyts has been discussed in more detail and elaborated that how different photocatalysts degrade the same chlorophenols with the aid of different oxidizing agents produced during photocatalysis. Finally, a future perspective has been given to deal with the effective removal of these hazardous pollutants from the environment.

Recent advances in the applications of nano-agrochemicals for sustainable agricultural development

Modern agricultural practices have triggered the process of agricultural pollution. This process can cause the degradation of eco-systems, land, and environment owing to the modern-day by-products of agriculture. The substantial use of chemical fertilizers, pesticides, and, contaminated water for irrigation cause further damage to agriculture. The current scenario of the agriculture and food sector has therefore become unsustainable. Nanotechnology has provided innovative and resourceful frontiers to the agriculture sector by contributing practical applications in conventional agricultural ways and practices. There is a large possibility that agri-nanotechnology can have a significant impact on the sustainable agriculture and crop growth. Recent research has shown the potential of nanotechnology in improving the agriculture sector by enhancing the efficiency of agricultural inputs and providing solutions to agricultural problems for improving food productivity and security. The prospective use of nanoscale agrochemicals such as nanofertilizers, nanopesticides, nanosensors, and nanoformulations in agriculture has transformed traditional agro-practices, making them more sustainable and efficient. However, the application of these nano-products in real field situations raises concern about nanomaterial safety, exposure levels, and toxicological repercussions to the environment and human health. The present review gives an insight into recent advancements in nanotechnology-based agrochemicals that have revolutionized the agriculture sector. Further, the implementation barriers related to the nanomaterial use in agriculture, their commercialization potential, and the need for policy regulations to assess possible nano-agricultural risks are also discussed.

Titanium dioxide nanoparticles elicited agro-morphological and physicochemical modifications in wheat plants to control Bipolaris sorokiniana

The current study involves the biogenesis of titanium dioxide nanoparticles (TiO2 NPs) by using Moringa oleifera Lam. aqueous leaf extract for the reduction of titanium dioxide salt into TiO2 nanoparticles. The biosynthesized TiO2 nanoparticles were observed by using the UV-visible spectrophotometry, SEM, EDX and XRD analytical methods. It was confirmed that the nanoparticles are crystalline and exist in the size range of 10-100 nm. The FTIR analysis confirmed the presence of O-H (hydrogen bonding), N-H (amide), C-C (alkanes) and C-I (Iodo-stretch) functional groups responsible for the stabilization of nanoparticles. Various concentrations (20, 40, 60 and 80 mg/L) of TiO2 NPs were applied exogenously on wheat plants infected with a fungus Bipolaris sorokiniana responsible to cause spot blotch disease at different time intervals. The measurement of disease incidence and percent disease index showed the time-dependent response and 40 mg/L was reported a stable concentration of TiO2 NPs to reduce the disease severity. The effects of biosynthesized TiO2 NPs were also evaluated for agro-morphological (leaf and root surface area, plant fresh and dry weight and yield parameters), physiological (relative water content, membrane stability index and chlorophyll content) and non-enzymatic metabolites (soluble sugar, protein, soluble phenol and flavonoid content) in wheat plants under biotic stress and 40 mg/L concentration of TiO2 NPs was found to be effective to elicit modifications to reduce biotic stress. The current study highlights the significant role of biosynthesized TiO2 NPs in controlling fungal diseases of wheat plants and thus ultimately improving the quality and yield of wheat plants.

Photocatalytic study of nanocomposite membrane modified by CeF3 catalyst for pharmaceutical wastewater treatment

Cerium fluoride (CeF₃) nanoparticles (NPs) were synthesized and applied in polysulfone (PS) membrane fabricated by phase inversion method. The produced nanocomposite membranes (PS/CeF₃) with different contents of CeF3 NPS (0.25%, 0.5%, 0.75% and 1% w/w) were used to treat pharmaceutical wastewaters. The membranes were characterized by FESEM, EDX, XRD, FTIR, porosity, and water contact angle analyses. Evaluation of the characteristics and performance of the nanocomposite membranes confirmed that utilizing photocatalytic CeF₃ NPs in membrane structure could effectively decompose organic contaminants in pharmaceutical wastewaters. It also improves the hydrophilicity and antifouling ability of membrane during filtration especially, in the presence of UV irradiation. The permeate flux of the PS membrane increased from 35.1 to 63.77 l/m²h by embedding 0.75% of CeF₃ NPs in membrane structure due to the porosity enhancement from 71.36-78.42% and the decrease in contact angle from 62.9º to 53.73º. Moreover, the flux decline of PS/CeF₃-0.75% membrane under UV irradiation was from 63.6 to 46.1 l/m²h that considerably lower than that of the neat PS membrane (from 34.7 to 4.9). On the other hand, the degradation efficiency of PS/CeF₃-0.75% membrane was more than 97%, and COD removed was more than 65% while they were 75% and 31%, respectively for the nascent PS membrane. Therefore, applying the appropriate amount of CeF₃ NPs in PS membranes not only greatly increased the permeate flux but also significantly enhanced the degradation efficiency and COD removal. This indicates that nanocomposite membranes can be confidently applied for pharmaceutical wastewater treatment UV irradiation.

Photocatalytic Inactivation of Plant Pathogenic Bacteria Using TiO2 Nanoparticles Prepared Hydrothermally

Exploitation of engineered nanomaterials with unique properties has been dynamically growing in numerous fields, including the agricultural sector. Due to the increasing resistance of phytopathogenic microbes, human control over various plant pathogens in crop production is a big challenge and requires the development of novel antimicrobial materials. Photocatalytic active nanomaterials could offer an alternative solution to suppress the plant pathogens. In this work, titanium dioxide nanoparticles (TiO₂ NPs) with high photocatalytic activity were synthesized by hydrothermal post-treatment of amorphous titania at different temperatures (250 °C or 310 °C) without using any additives or doping agents. The obtained samples were investigated through X-ray diffraction, N₂-sorption measurements, diffuse reflectance UV-Vis spectroscopy, transmission electron microscopy, electron paramagnetic resonance spectroscopy, and X-ray photoelectron spectroscopy. The applied hydrothermal treatment led to the formation of TiO₂ nanocrystallites with a predominant anatase crystal phase, with increasing crystallinity and crystallite size by prolonging treatment time. The photocatalytic activity of the TiO₂ NPs was tested for the photo-degradation of phenol and applied for the inactivation of various plant pathogens such as Erwinia amylovora, Xanthomonas arboricola pv. juglandis, Pseudomonas syringae pv. tomato and Allorhizobium vitis. The studied bacteria showed different susceptibilities; their living cell numbers were quickly and remarkably reduced by UV-A-irradiated TiO₂ NPs. The effectiveness of the most active sample prepared at 310 °C was much higher than that of commercial P25 TiO₂. We found that fine-tuning of the structural properties by modulating the time and temperature of the hydrothermal treatment influenced the photocatalytic properties of the TiO₂ NPs considerably. This work provides valuable information to the development of TiO₂-based antimicrobial photocatalysts.

An approach to the photocatalytic mechanism in the TiO2-nanomaterials microorganism interface for the control of infectious processes

The approach of this timely review considers the current literature that is focused on the interface nanostructure/cell-wall microorganism to understand the annihilation mechanism. Morphological studies use optical and electronic microscopes to determine the physical damage on the cell-wall and the possible cell lysis that confirms the viability and microorganism death. The key parameters of the tailoring the surface of the photoactive nanostructures such as the metal functionalization with bacteriostatic properties, hydrophilicity, textural porosity, morphology and the formation of heterojunction systems, can achieve the effective eradication of the microorganisms under natural conditions, ranging from practical to applications in environment, agriculture, and so on. However, to our knowledge, a comprehensive review of the microorganism/nanomaterial interface approach has rarely been conducted. The final remarks point the ideal photocatalytic way for the effective prevention/eradication of microorganisms, considering the resistance that the microorganism could develop without the appropriate regulatory aspects for human and ecosystem safety.

Physiological and anti-oxidative response of biologically and chemically synthesized iron oxide: Zea mays a case study

The synthesis methodology, particle size and shape, dose optimization, and toxicity studies of nano-fertilizers are vital prior to their field application. This study investigates the comparative response of chemically synthesized and biologically synthesized iron oxide nanorods (NRs) using moringa olefera along with bulk FeCl3 on summer maize (Zea mays). It is found that FeCl3 salt and chemically synthesized iron oxides NRs caused growth retardation and impaired plant physiological and anti-oxidative activities at a concentration higher than 25 mg/L due to toxicity by over accumulation. While iron released form biologically synthesized NRs have shown significantly positive results even at 50 mg/L due to their low toxicity, an improved leaf area (13%), number of leaves per plant (26%), total chlorophyll content (80%) and nitrate content (6%) with biologically synthesized NRs are obtained. Moreover, the plant anti-oxidative activity also increased on treatment with biologically synthesized NRs because of their ability to form a complex with metal ions. These findings suggest that biologically synthesized iron oxides NRs are an efficient iron source and can last for a long time. Thus, proving that nanofertilizer are required to have specific surface chemistry to release the nutrient in an appropriate concentration for better plant growth.

Highly Active Rutile TiO2 Nanocrystalline Photocatalysts

The controllable synthesis of rutile TiO₂ single crystal particles with the preferential orientation of {111} facets still remains a scientific and technological challenge. Here, we developed a facile route for fabrication of rutile TiO₂ nanorod crystals (RTiO₂NRs) having high ratios of oxidative {111} to reductive {110} surfaces. RTiO₂NRs were synthesized using a peroxo-titanium complex (PTC) approach, which was controlled by changing the Ti/H₂O₂ ratio. The thus obtained RTiO₂NRs revealed a high tendency to agglomerate through orientation-dependent attachment along the {110} facets. This resulted in an increased {111}/{110} surface ratio and led to a markedly improved photocatalytic activity of RTiO₂NR aggregates. The reported findings illustrate the rich potential of the herein proposed facile and energy-efficient synthesis of nanostructured rutile TiO₂-based photocatalysts.

Visible light driven Ti3+ self-doped TiO2 for adsorption-photocatalysis of aqueous U(VI)

The photocatalytic reduction of U(VI) is recognized as an economical and effective way for U(VI) removal/recovery from solutions. To improve the photocatalytic activity of TiO₂ under visible light, TiO₂ was hydrogenated by NaBH₄ to generate Ti³⁺ self-doped black TiO₂ (BT_n). The self-doped Ti³⁺ alongside oxygen vacancies (Ov) could act as interband level to increase visible light capture and reduce the recombination of photogenerated carriers. The obtained BT_n samples showed high performance for U(VI) elimination under near neutral conditions, and held an outstanding anti-interference for U(VI) over competing metal cations and anions. Methanol and ethanol could act as sacrificial donors, being favorable for the photocatalytic reduction of U(VI), while the presence of EDTA inhibited the photoreduction of U(VI). The BT_n photocatalysts showed relatively high stability and reusability during the photocatalysis and elution processes. The XPS, TEM and XRD results revealed that U(VI) was photo-reduced to form UO₂ on the surface of BT_n. This work may serve as an important reference for improving the photocatalytic reactivity of TiO₂ as well as for the efficient removal/recovery of U(VI) from aqueous solutions.

Metabolomics reveals differential mechanisms of toxicity of hyperbranched poly(ethyleneimine)-derived nanoparticles to the soil-borne fungus Verticillium dahliae Kleb

There is a consensus on the urge for the discovery and assessment of alternative, improved sources of bioactivity that could be developed as plant protection products (PPPs), in order to combat issues that the agrochemical sector is facing. Based on the recent advances in nanotechnology, nanoparticles seem to have a great potential towards the development of the next generation nano-PPPs used as active ingredients (a.i.) per se or as nanocarriers in their formulation. Nonetheless, information on their mode(s)-of-action (MoA) and mechanisms of toxicity is yet largely unknown, representing a bottleneck in their further assessment and development. Therefore, we have undertaken the task to assess the fungitoxicity of hyperbranched poly(ethyleneimine) (HPEI), quaternized hyperbranched poly(ethyleneimine) (QPEI), and guanidinylated hyperbranched poly(ethyleneimine) (GPEI) nanoparticles to the soil-born plant pathogenic fungus Verticillium dahliae Kleb, and dissect their effects on its metabolism applying GC/EI/MS metabolomics. Results revealed that functionalization of HPEI nanoparticles with guanidinium end groups (GPEI) increases their toxicity to V. dahliae, while functionalization with quaternary ammonium end groups (QPEI) decreases it. The treatments with the nanoparticles affected the chemical homeostasis of the fungus, altering substantially its amino acid pool, energy production, and fatty acid content, causing additionally oxidative and osmotic stresses. To the best of our knowledge, this is the first report on the comparative toxicity of HPEI, QPEI, and GPEI to filamentous fungi applying metabolomics. The findings could be exploited in the study of the quantitative structure-activity relationship (QSAR) of HPEI-derived nanoparticles and their further development as nano-PPPs.