Rutile Titanium Dioxide Nanoparticles Research Articles

Fungal Colonization of Weathered Radiata Pine Surfaces Protected with Inorganic Nanoparticles and Coatings

Photoactive nanoparticles are used to reduce microbial colonization and self-clean surfaces of materials such as glass and ceramics. To test whether such an approach is feasible for wood surfaces, we treated radiata pine samples with TiO2 (rutile and anatase) or ZnO nanoparticles and then coated the samples with different finishes. Coated samples and uncoated controls were exposed outdoors for six months. After exposure, fungi colonizing wood surfaces were identified using molecular techniques and microscopy, and colour changes in the wood samples were also measured. Treatment of uncoated surfaces with nanoparticles reduced the discolouration of wood during weathering but had little effect on colonization of wood by black mould fungi. In contrast, pretreatment of samples with titanium dioxide nanoparticles increased the number and diversity of fungi including basidiomycetes colonizing coated samples, whereas zinc oxide nanoparticles had the opposite effect. Zinc oxide nanoparticles, however, were less effective than rutile titanium dioxide nanoparticles at reducing the discolouration of coated samples exposed to natural weathering. We conclude that none of the photoactive nanoparticles on their own are able to reduce microbial colonization and discoloration of samples. This suggests that it may be difficult to create self-cleaning wood surfaces using photoactive nanoparticles.

Production of rutile titanium dioxide nanoparticles by trans-ferulic acid and their biomedical applications

Titanium dioxide nanoparticles (TiO2NPs) are popular materials with high annual production and increasing applications in different fields. In the current research, we synthesized TiO2NPs with the help of the reducing potential of trans-ferulic acid (FA). FA-TiO2NPs are principally characterized by X-Ray Diffraction (XRD), Fourier Transform-Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM), Field-Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive X-Ray Analysis (EDX), and Thermogravimetric (TGA) techniques. Then, their biomedical properties were investigated by in vitro hemolysis, anti-inflammatory, and cytotoxicity tests. According to physiochemical analysis, FA-TiO2NPs had mostly rod-shaped morphology with a rutile crystallographic phase. These NPs were non-hemolytic with high anti-denaturation and membrane stabilization activity and thus excellent in vitro anti-inflammatory effects. FA-TiO2NPs decreased the cell viability of A375 (melanoma cell line), MCF-7 (breast cancer cell line), and human skin fibroblast (normal cell line) in a dose-dependent manner. The IC50 values of FA-TiO2NPs were above 12.5, 25, and 50 µg/mL against A375, MCF-7, and skin fibroblast cell lines, respectively. In this study, we demonstrated the biocompatibility and valuable potential of FA-TiO2NPs in biomedical applications.

Transport of anatase and rutile titanium dioxide nanoparticles in soils in the presence of phosphate: mechanisms and numerical modeling

Transport of anatase and rutile titanium dioxide nanoparticles in soils in the presence of phosphate: mechanisms and numerical modeling

Luteolin mediated synthesis of rod-shaped rutile titanium dioxide nanoparticles: Assay of their biocompatibility

Titanium dioxide nanoparticles (TiO2NPs) were produced using a crud flavonoid luteolin (LT) by the green process. Physicochemical characterizations of LT mediated synthesis of TiO2NPs (LT-TiO2NPs) were analyzed by different techniques. The biocompatibility of LT-TiO2NPs was evaluated by assessing their cytotoxicity, inhibition of protein denaturation, hemolysis effects, and membrane stabilization activity. The synthesized LT-TiO2NPs exhibited mostly rod-shaped morphology, rutile crystalline structure with length about 33.3–135 nm and width in 16.6–58 nm. Under LT-TiO2NPs treatments, the cell viability of cancer cells was decreased in a dose-dependent manner. According to the results, the IC50 values of LT-TiO2NPs were between 12.5–25 μg/mL for A375 and MCF-7 cancer cells, and its value was below 50 μg/mL for skin fibroblast. These NPs also induced intracellular reactive oxygen species (ROS) generation and caused mitochondrial disruption in cancer cells, leading to the induction of intrinsic apoptosis. These biosynthesized NPs did not show denaturation of bovine serum albumin (BSA) protein and hemolytic or heat-induced hemolytic effects, which confirmed their membrane stabilization activity without damaging red blood cells (RBCs) membrane integrity. Therefore, this research provides valuable results in the case of green synthesis of LT-TiO2NPs and their specific properties, biocompatibility, and their potential to be used in biomedical fields.

Ab-Initio Investigation of Finite Size Effects in Rutile Titania Nanoparticles with Semilocal and Nonlocal Density Functionals

In this work, we employ hybrid and generalized gradient approximation (GGA) level density functional theory (DFT) calculations to investigate the convergence of surface properties and the electronic gap of rutile titania (TiO2) nanoparticles with particle size. The surface energies and electronic gaps are calculated for cuboidal particles with minimum dimension ranging from 3.7 Å (24 atoms) to 10.3 Å (384 atoms) using a highly parallel real-space DFT code to enable hybrid-level DFT calculations of larger nanoparticles than are typically practical. We deconvolute the geometric and electronic finite size effects in surface energy and evaluate the influence of defects on the electronic gap and density of states (DOS). The electronic finite size effects in surface energy vanish when the minimum length scale of the nanoparticles becomes greater than 10 Å. We show that this length scale is consistent with a computationally efficient numerical analysis of the characteristic length scale of electronic interactions. The surface energy of nanoparticles having a minimum dimension beyond this characteristic length can be approximated using slab calculations that account for the geometric defects. In contrast, the finite size effects on the electronic gap and DOS are highly dependent on the shape and size of these particles. The DOS for cuboidal particles and more realistic particles constructed using the Wulff algorithm reveal that defect states within the electronic gap play a key role in determining the eigenvalue distribution of nanoparticles and the electronic gap does not converge to the bulk limit for the particle sizes investigated.

Soil-aged nano titanium dioxide effects on full-grown carrot: Dose and surface-coating dependent improvements on growth and nutrient quality

Rutile titanium dioxide nanoparticles (nTiO2) were weathered in field soil at 0, 100, 200, and 400 mg Ti/kg soil for four months. Two types of nTiO2 with different surface coatings (hydrophilic and hydrophobic), uncoated nTiO2 (pristine), and the untreated control were included. Thereafter, carrot seeds (Daucus carota L.) were sown in those soils and grown in a growth chamber for 115 days until full maturity. A comparison was made between this and our previous unaged study, where carrots were treated in the same way in soil with freshly amended nTiO2. The responses of plants depended on the nTiO2 surface coating and concentration. The aged hydrophobic and hydrophilic-coated nTiO2 induced more positive effects on plant development at 400 and 100 mg Ti/kg soil, respectively, compared with control and pristine treatments. Taproot and leaf fresh biomass and plant height were improved by up to 64%, 40%, and 40% compared with control, respectively. Meanwhile, nutrient elements such as Fe in leaves, Mg in taproots, and Ca, Zn, and K in roots were enhanced by up to 66%, 64%, 41, 143% and 46%, respectively. However, the contents of sugar, starch, and some other metal elements in taproots were negatively affected, which may compromise their nutritional quality. Taken together, the overall growth of carrots was benefited by the aged nTiO2 depending on coating and concentration. The aging process served as a potential sustainable strategy to alleviate the phytotoxicity of unweathered nanoparticles.

Toxicity evaluation of TiO2 nanoparticles embedded in toothpaste products

The present study evaluates the toxicity of titanium dioxide nanoparticles (TiO2 NPs) that were extracted from toothpaste products by solid-liquid extraction method. The NPs structures were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). Ultraviolet spectrophotometer (UV) was also used to determine the band gab energy of these NPs. The XRD results indicated that the mixture of TiO2 NPs was formed (anatase and rutile titanium dioxide nanoparticles). XRD results also indicated the crystalline size of NPs, which were small and ranging from 2.5 to 53.2 nm. The toxicity effect of TiO2 NPs was evaluated on Chlorella vulgaris micro marine algae over 3 days. The results indicate a negative effect on the growth algae and concentration of chlorophyll a during the early growth stages. In contrast, at the late growth stages these NPs had a positive effect. Also, the toxicity effect of TiO2 NPs was evaluated on Jurkat, HepG2, T-47D and S180 cancer cell lines. Cells were cultured with various concentrations of TiO2 NPs (10, 20, 50, 100 and 200 µg/mL) for 48 hours using the Water-Soluble Tetrazolium (WST) method. The results showed that the TiO2 NPs had a negative effect on the growth of the Jurkat, T-47D and S180 cancer cell lines. In contrary, a positive effect was seen on the HepG2 cell line.

Highly sensitive photoelectrochemical immunosensor based on anatase/rutile TiO2 and Bi2S3 for the zero-biased detection of PSA

A novel label-free photoelectrochemical immunosensor was developed for the determination of prostate-specific antigen (PSA) based on fluorine-doped tin oxide (FTO) electrode modified with anatase and rutile titanium dioxide nanoparticles (TiO2(a-r)) as a platform for the electrodeposition of bismuth sulfide (Bi2S3). The photoelectrochemical response of the TiO2(a-r) platform sensitized with Bi2S3 for the ascorbic acid donor molecule (AA) was about 34-fold higher than that observed in the absence of Bi2S3. The Bi2S3/TiO2(a-r)/FTO platform was modified with PSA antibodies to produce the anti-PSA/Bi2S3/TiO2(a-r)/FTO immunosensor, which was incubated in solutions of PSA antigen to inhibit the photocurrent of the immunosensor for AA. The photocurrent of the anti-PSA/Bi2S3/TiO2(a-r)/FTO immunosensor presented a linear relationship with the logarithm of the PSA concentration ranging from 1 pg mL−1 to 100 ng mL−1 with good sensitivity and a limit of detection of 0.870 pg mL−1. The sensor was successfully employed for the determination of PSA in artificial blood plasma samples, with recoveries between 94.6 and 98.6%.

Genotoxicity analysis of rutile titanium dioxide nanoparticles in mice after 28 days of repeated oral administration

Titanium dioxide (TiO2) or titania has demonstrated excellent potential for commercial use in various arenas, such as in the paint, in pharmaceuticals and food industry. However information on the genotoxic potential of rutile form of TiO2-NP after repeated (28 days) low dose oral exposure in major organs of the reticuloendothelial system (liver, spleen, bone marrow, lymph nodes) is not known. In this study Swiss albino male mice were gavaged TiO2-NP at sub-acute concentration (0.2, 0.4 and 0.8 mg/kg body weight) over a period of 28 days. Results revealed that TiO2-NP administered was of rutile form with mean average size of 25 nm by transmission electron microscopy. The values of PDI and Zeta potential from DLS of TiO2-NP in suspension specified that the nanomaterial was stable without much agglomeration. Chromosomal aberration assay showed that TiO2-NP was genotoxic and cytotoxic. DNA damage evaluation by comet assay confirmed that long term exposure to TiO2-NP at low concentrations can induce genotoxicity systemically in organs, such as liver, spleen, and thymus cells. Structural chromosomal aberration test from bone marrow cells revealed the clastogenicity of TiO2-NP at sub chronic low concentrations. Further in vivo studies are needed to elucidate the underlying mechanisms at the molecular level.

Evaluation of zeta potential of nanomaterials by electrophoretic light scattering: Fast field reversal versus Slow field reversal modes

Zeta potential of nanomaterials designed to be used in nanomedicine is an important parameter to evaluate as it influences in vivo behaviour hence biological activity, efficacy and safety. As mentioned by the International Organization for Standardization (ISO), electrophoretic light scattering is a relevant method for evaluating zeta potential. The present work aimed to validate a new protocol based on the application of Fast Field Reversal mode and to explore its scope with nanomaterials investigated as nanomedicines. Its scope was then compared with that of an already validated protocol which uses both Fast Field Reversal and Slow Field Reversal modes. The new protocol was validated within the framework of the application of the Smoluchowski approximation. Its performances complied with the ISO standard. The protocol could be applied to evaluate mean zeta potential of soft nanomaterials including polymer-based nanoparticles and liposomes. However, it appeared unsuitable to evaluate zeta potential of dense nanomaterials including rutile titanium dioxide nanoparticles. Compared with the previously validated protocol which only applied to the determination of zeta potential of polymer nanoparticles, this new validated protocol gives access to the determination of zeta potential to a wider range of nanomedicines under conditions complying with quality control assessments.

Fluorinated Titania Nanoparticle-Induced Piezoelectric Phase Transition of Poly(vinylidene fluoride)

We prepared F-coated rutile titanium dioxide nanoparticles (r-TiO2 NPs) via simple thermal annealing of titania NPs in poly(vinylidene fluoride) (PVDF) and demonstrated that the F-coated r-TiO2 NP-doped composite film could efficiently induce piezoelectric phase transition of non-electroactive PVDF due to highly electronegative F bonds on the surface of these NPs. In the case of a 2.0 wt % composite film, 99.20% of the non-electroactive PVDF was transformed into the electroactive phase. Additionally, utilizing the F-coated r-TiO2 NPs for a piezoelectric device led to an enhancement of the piezoelectric performance. With the 5.0 wt % composite film, the resulting piezoelectric device exhibited voltage generation of 355 mV, whereas a device with the innate r-TiO2 NPs exhibited voltage generation of only 137 mV. Furthermore, because of optical inactivity of F-coated r-TiO2 NPs, the piezoelectric films exhibited high stability under 64 h of photoirradiation at an intensity of 0.1 W/cm2. These results indicate that the F-coated r-TiO2 NP-doped composite films could be useful for various applications, including outdoor energy-harvesting, self-powered wearable devices, and portable sensors.

Separation of water–oil mixture on poly methyl methacrylate surface using TiO2 nanoparticles via molecular dynamics simulation

The current work investigates the separation of water–oil mixture on amorphous poly methyl methacrylate (PMMA) surface in the absence and presence of Anatase and Rutile titanium dioxide nanoparticles using molecular dynamics simulation. The presence of nano domains with positive and negative charges on PMMA surface causes the water molecules to form water clusters of various sizes. Water clusters can slide on the PMMA surface which leads to the formation of larger clusters and in continues formation of large clusters was the reason of separation water–oil mixture. In the presence of Anatase and Rutile nanoparticles, accumulation of water molecules around the particles leads to formation of larger water clusters and improves the separation of water–oil mixture. Anatase nanoparticle acts faster than Rutile nanoparticle in the adsorption of water molecules, while Rutile nanoparticle forms larger clusters and is more successful in adsorbing water molecules from the water–oil mixture. The orientation and the order parameter of water molecules in different layers from PMMA surface and around the Anatase and Rutile nanoparticles are investigated as well.

Pulmonary and pleural toxicity of potassium octatitanate fibers, rutile titanium dioxide nanoparticles, and MWCNT-7 in male Fischer 344 rats

Potassium octatitanate (K2O·8TiO2, POT) fibers are used as an alternative to asbestos. Their shape and biopersistence suggest that they are possibly carcinogenic. However, inhalation studies have shown that respired POT fibers have little carcinogenic potential. We conducted a short-term study in which we administered POT fibers, and anatase and rutile titanium dioxide nanoparticles (a-nTiO2, r-nTiO2) to rats using intra-tracheal intra-pulmonary spraying (TIPS). We found that similarly to other materials, POT fibers were more toxic than non-fibrous nanoparticles of the same chemical composition, indicating that the titanium dioxide composition of POT fibers does not appear to account for their lack of carcinogenicity. The present report describes the results of the 3-week and 52-week interim killing of our current 2-year study of POT fibers, with MWCNT-7 as a positive control and r-nTiO2 as a non-fibrous titanium dioxide control. Male F344 rats were administered 0.5 ml vehicle, 62.5 µg/ml and 125 µg/ml r-nTiO2 and POT fibers, and 125 µg/ml MWCNT-7 by TIPS every other day for 2 weeks (eight doses: total doses of 0.25 and 0.50 mg/rat). At 1 year, POT and MWCNT-7 fibers induced significant increases in alveolar macrophage number, granulation tissue in the lung, bronchiolo-alveolar cell hyperplasia and thickening of the alveolar wall, and pulmonary 8-OHdG levels. The 0.5 mg POT- and the MWCNT-7-treated groups also had increased visceral and parietal pleura thickness, increased mesothelial cell PCNA labeling indices, and a few areas of visceral mesothelial cell hyperplasia. In contrast, in the r-nTiO2-treated groups, none of the measured parameters were different from the controls.

Jinlong Gong

Angewandte Chemie International EditionVolume 57, Issue 36 p. 11504-11504 Author ProfileFree Access Jinlong Gong First published: 07 August 2018 https://doi.org/10.1002/anie.201807832AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Graphical Abstract “My favorite place on earth is my hometown—Lanzhou, Gansu Province. I chose chemistry as a career because chemistry changes the world and chemistry creates the world …” Find out more about Jinlong Gong in his Author Profile. Jinlong Gong The author presented on this page has published more than 10 articles in Angewandte Chemie in the last 10 years. His most recent contribution is featured on the inside back cover of this issue: “Low-Coordinated Edge Sites on Ultrathin Palladium Nanosheets Boost Carbon Dioxide Electroreduction Performance”: W. Zhu, L. Zhang, P. Yang, C. Hu, Z. Luo, X. Chang, Z.-J. Zhao, J. Gong, Angew. Chem. Int. Ed. 2018, https://doi.org/10.1002/anie.201806432; Angew. Chem. 2018, https://doi.org/10.1002/ange.201806432. The work of J. Gong has been featured on the cover of Angewandte Chemie: “Dendritic Hematite Nanoarray Photoanode Modified with a Conformal Titanium Dioxide Interlayer for Effective Charge Collection”: Z. Luo, T. Wang, J. Zhang, C. Li, H. Li, J. Gong, Angew. Chem. Int. Ed. 2017, 56, 12878; Angew. Chem. 2017, 129, 13058. Date of birth: June 24, 1979 Position: Cheung Kong Chair Professor, School of Chemical Engineering and Technology, Tianjin University E-mail: jlgong@tju.edu.cn Homepage: www.gonglab.org ORCID: 0000-0001-7263-318X Education: 2001 BS, Tianjin University 2004 MS, Tianjin University 2008 PhD supervised by C. Buddie Mullins, University of Texas at Austin 2009–2010 Postdoc with Prof. George M. Whitesides, Harvard University Awards: 2014 Te-Pan Hou Chemical Engineering Innovation Award; 2015 NSFC Outstanding Young Investigator Award; 2016 Cheung Kong Chair Professor (Ministry of Education); 2017 The SCEJ (Society of Chemical Engineers, Japan) Award for Outstanding Asian Researcher and Engineer; 2017 ACS Sustainable Chemistry & Engineering Lectureship Award Current research interests: Heterogeneous catalysis; surface science; green energy conversion; CO2 utilization; synthesis and applications of nanostructured material Hobbies: Hiking, reading, soccer, table tennis, billiards My favorite place on earth is my hometown—Lanzhou, Gansu Province. I chose chemistry as a career because chemistry changes the world and chemistry creates the world. If I won the lottery, I would donate the money to support education in underdeveloped areas of northwest China. If I were not a scientist, I would probably be a military surgeon or a professional cat/dog breeder. Guaranteed to make me smile is when I see my daughter after I get home from work or traveling. My favorite author (fiction) is The Count of Monte Cristo (Alexandre Dumas). My favorite food is Lanzhou beef noodles. My favorite music is albums by Wei Dou (a Chinese rock singer). My favorite motto is “Seek the truth from facts”. I like refereeing because it makes me more critical and thoughtful. My 5 top papers: 1“Enhanced Surface Reaction Kinetics and Charge Separation of p–n Heterojunction Co3O4/BiVO4 Photoanodes”: X. Chang, T. Wang, P. Zhang, J. Zhang, A. Li, J. Gong, J. Am. Chem. Soc. 2015, 137, 8356. (Properly designed cocatalysts can achieve higher charge-separation efficiency in the bulk as well as faster surface reaction kinetics.) 2“Sub-10 nm rutile titanium dioxide nanoparticles for efficient visible-light-driven photocatalytic hydrogen production”: L. Li, J. Yan, T. Wang, Z.-J. Zhao, J. Zhang, J. Gong, N. Guan, Nat. Commun. 2015, 6, 5881. (New insights into the functionalities of defects in visible-light photocatalytic activity.) 3“Synergistic Cocatalytic Effect of Carbon Nanodots and Co3O4 Nanoclusters for the Photoelectrochemical Water Oxidation on Hematite”: P. Zhang, T. Wang, X. Chang, L. Zhang, J. Gong, Angew. Chem. Int. Ed. 2016, 55, 5851; Angew. Chem. 2016, 128, 5945. (Can help design effective cocatalytic systems with multiple functional components.) 4“Hydroxyl-Mediated Non-oxidative Propane Dehydrogenation over VOX/γ-Al2O3 Catalysts with Improved Stability”: Z.-J. Zhao, T. Wu, C. Xiong, G. Sun, R. Mu, L. Zeng, J. Gong, Angew. Chem. Int. Ed. 2018, 57, 6791; Angew. Chem. 2018, 130, 6907. (Catalytic performance is closely connected to the concentration of superficial V−OH species on the catalyst.) 5“On the role of Ce in CO2 adsorption and activation over lanthanum species”: X. Li, Z.-J. Zhao, L. Zeng, J. Zhao, H. Tian, S. Chen, K. Li, S. Sang, J. Gong, Chem. Sci. 2018, 9, 3426. (Ce addition can promote the formation of bidentate carbonate, and results in the best coke elimination performance.) Volume57, Issue36September 3, 2018Pages 11504-11504 ReferencesRelatedInformation

Aggregation and transport of rutile titanium dioxide nanoparticles with montmorillonite and diatomite in the presence of phosphate in porous sand

Crop soil is inevitably contaminated by the excess of phosphate (P) fertilizers. A large amount of nanoparticle titanium dioxide (nTiO2) entered soils as well due to the wide use of engineered nanomaterials. It is of great urgency and a high priority to investigate the mechanisms of nTiO2 deposition with the presence of P in crop soils. This study investigated the transport behavior of (1.0 g L−1) rutile nTiO2 with two representative clay particles (montmorillonite or diatomite) in the presence of P through the saturated quartz sand. In 10 mM NaCl electrolyte solution at pH 6.0, the recovery percentage of nTiO2 was 36.3% from sand column. Nevertheless, it was reduced to 18.6% and 11.1% while montmorillonite and diatomite present in suspensions, respectively. Obviously, the improvement of nTiO2 retention in sand was more pronounced by diatomite than montmorillonite. The likely mechanism for this result was that large aggregates were formed due to the attachment of nTiO2 to montmorillonite and diatomite. Moreover, the surface of diatomite with the larger hydrodynamic radius was less negatively charged by comparison with montmorillonite. However, this phenomenon disappeared with the addition of P. P adsorption increases the repulsive force between particles and sand and the fast release of attached nTiO2-montmorillonite and diatomite from sand. The two-site kinetic retention model and the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory suggested that the combination of k1/k1d, k2 and secondary minimum energy can be used to accurately describe the attachment of nTiO2-montmorillonite and diatomite to sand in the presence of P.

Chemi-resistive response of rutile titania nano-particles towards isopropanol and formaldehyde: a correlation with the volatility and chemical reactivity of vapors

The performance of phase pure rutile titania nano-particles for gas/vapor sensing is not well explored in open literature, mostly because of their moderate chemical activity. However, the high thermal stability of rutile titania could be beneficial towards making a stable chemi-resistive sensor, operable generally at higher temperature. Herein, we have investigated the chemi-resistive response characteristics of rutile phase titania nano-particles for the detection of isopropanol and formaldehyde vapors. Titania nano-particles are synthesized through a hydrothermal route and characterized in terms of their phase formation behavior and micro-structural features. The sensing characteristics of the particles are measured by varying the operating temperature (275 °C–350 °C) of the sensor and concentrations (20–200 ppm) of the vapors, using a static flow gas sensing measurement set-up. The rutile titania particles are found more responsive towards isopropanol than formaldehyde. An attempt is made here to correlate the sensing performance of titania sensors with the volatility and chemical reactivity of studied vapors. The higher response of the sensor towards isopropanol is predicted, due to its comparatively lower volatility and more suitable chemical structure for oxidation on the sensor surface.

Transport and aggregation of rutile titanium dioxide nanoparticles in saturated porous media in the presence of ammonium

The widely used artificial nanoparticles (NPs) and the excess of ammonium (NH4+) fertilizers are easily released into the natural environment. So, clarifying the mobility of NPs in the presence of NH4+ is therefore of great urgency and high priority. Currently, few studies focus on the transport and deposition of nanoparticle titanium dioxide (nTiO2) in single and binary systems containing NH4+, especially describing this process by a mathematical model. In this work, the comparison between the transport and retention of rutile nTiO2 in single and binary electrolyte solutions of NH4Cl and/or NaCl (0.5–50 mM) were conducted at pH 6.0 and 8.0 through running the column experiments. Experimental results show that the aggregation and retention of nTiO2 in solution containing mono-valence cations obeys the order as follows: NH4+ > Na+ > Na+ + NH4+ at the same ion strength (IS). It is attributed to the lower critical coagulation concentration (CCC) of rutile nTiO2 in NH4+ than that in Na+ solution. In particular, the simultaneous presence of NH4+ and Na+ favors the transportability of nTiO2 due to the strong competitive adsorption on the surface of NPs. The two-site kinetic retention model provides the good simulation for their transport behavior. The likely mechanism is that the secondary energy minimum of nTiO2 in NH4+ system associated with the greater K2 at surface Site 2 (from model) on sand can be explained for the more reversible deposition. Ammonium leachate associated with NPs can thus be considered a serious concern.

Reactive magnetron sputtering deposition of bismuth tungstate onto titania nanoparticles for enhancing visible light photocatalytic activity

Titanium dioxide − bismuth tungstate composite materials were prepared by pulsed DC reactive magnetron sputtering of bismuth and tungsten metallic targets in argon/oxygen atmosphere onto anatase and rutile titania nanoparticles. The use of an oscillating bowl placed beneath the two magnetrons arranged in a co-planar closed field configuration enabled the deposition of bismuth tungstate onto loose powders, rather than a solid substrate. The atomic ratio of the bismuth/tungsten coatings was controlled by varying the power applied to each target. The effect of the bismuth tungstate coatings on the phase, optical and photocatalytic properties of titania was investigated by X-ray diffraction, energy-dispersive X-ray spectroscopy (EDX), Brunauer–Emmett–Teller (BET) surface area measurements, transmission electron microscopy (TEM), UV–vis diffuse reflectance spectroscopy and an acetone degradation test. The latter involved measurements of the rate of CO2 evolution under visible light irradiation of the photocatalysts, which indicated that the deposition of bismuth tungstate resulted in a significant enhancement of visible light activity, for both anatase and rutile titania particles. The best results were achieved for coatings with a bismuth to tungsten atomic ratio of 2:1. In addition, the mechanism by which the photocatalytic activity of the TiO2 nanoparticles was enhanced by compounding it with bismuth tungstate was studied by microwave cavity perturbation. The results of these tests confirmed that such enhancement of the photocatalytic properties is due to more efficient photogenerated charge carrier separation, as well as to the contribution of the intrinsic photocatalytic properties of Bi2WO6.

Toxicity assessment of anatase and rutile titanium dioxide nanoparticles: The role of degradation in different pH conditions and light exposure

Titanium dioxide nanoparticles (TiO2NPs), in the two crystalline forms, rutile and anatase, have been widely used in many industrial fields, especially in cosmetics. Therefore, a lot of details about their safety issues have been discussed by the scientific community. Many studies have led to a general agreement about TiO2NPs toxicity, in particular for anatase form, but no mechanism details have been proved yet. In this study, data confirm the different toxic potential of rutile and anatase TiO2NPs in two cell lines up to 5nM nanoparticles concentration. Moreover, we evaluated the role of titanium ions released by TiO2NPs in different conditions, at pH=4.5 (the typical lysosomal compartment pH) and at pH=5.5 (the skin physiological pH) in conditions of darkness and light, to mimic the dermal exposure of cosmetics. Anatase nanoparticles were proner to degradation both in the acidic conditions and at skin pH. Our study demonstrates that pH and sunlight are dominant factors to induce oxidative stress, TiO2NPs degradation and toxicity effects.

Comparative study of the effects of anatase and rutile titanium dioxide nanoparticles on the structure and properties of waterborne polyurethane

The anatase and rutile titanium dioxide (TiO2) were prepared and characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscope and UV–vis spectrophotometer. Then they were introduced into waterborne polyurethane (WPU) to prepare hybrid films. The effects of anatase and rutile TiO2 on the structure and properties of hybrid films were comparatively studied. The results showed that the incorporation of nano-TiO2 into WPU can highly improve the UV protection ability, mechanical property, photocatalytic ability and antifungal capacity of the hybrid films. Moreover, the anatase TiO2 incorporated WPU exhibited the best UV protection ability, photocatalytic ability and antifungal capacity. However, the rutile TiO2 incorporated WPU had higher tensile strength at appropriate nano-TiO2 content, which may be resulted from the special asymmetric acicular sharp of rutile TiO2. The results indicated that the cooperation of anatase and rutile TiO2 may give the best performances of polymer–TiO2 nanocomposites.