Surface Of nano-TiO2 Research Articles

Thermodynamic prediction of filler surface modification by APTES on corrosion resistance of nano-TiO2/waterborne epoxy coatings

Common techniques for creating novel coatings include chemically modifying inorganic fillers and exploring how modifications affect coating service performance. However, it frequently takes a lot of time and tedious attempts to get the ideal alteration degree for fillers. Although the surface energy of the fillers is thought to be a significant thermodynamic parameter, it is still unknown how chemical modification affects surface energy and how the properties of fillers in a coating relate to the quantization difference of thermodynamic parameters. In this study, the impact of chemical modification on the quantization difference of nano-TiO2 surface energy has been uncovered. Creating a “wetting-reagglomeration-adsorption” isogram by utilizing three surface interfacial parameters has also been achieved: the contact angle between the liquid resin and the filler, the driving energy of the filler reagglomeration, and the polymer molecules' diffusion energy at the filler/coating interface. The relationship between the quantitative difference of thermodynamic parameters and the dispersion, compatibility and interfacial strength of the fillers in the waterborne epoxy was predicted by the isocontour map. From the isocontour map, the modified nano-TiO2 fillers with 4.04 APTES molecules/nm2 shows the minimum ∆Wa of 16.17 mJ/m2 and the maximum Ws of 23.15 mJ/m2 in the composite coating, which is predicted to exhibit the best dispersibility and the strongest interfacial strength. The prediction results were successfully verified by the techniques of microscopic morphology observation (TEM and SEM), mechanical properties tests (DMA and tensile tests), and corrosion resistance tests (EIS and salt spray tests). This work has a significant guiding role in the development of the filler modifications for the creation of novel coatings.

Designing Co-coordinated phytic acid 3D network structure for superhydrophilic property of TiO2 nanoparticles

Traditionally, nano-TiO2 as one of the hydrophilic materials has garnered significant attention due to its inherent stability, non-toxicity, and abundance. However, its limited number of hydroxyl groups fails to meet the actual needs for superhydrophilic applications. Therefore, it is crucial to explore a simple and efficient method to introduce more hydroxyl groups to enhance the hydrophilicity of nano-TiO2. In this work, hydroxyl‑rich phytic acid (Pa) was introduced into the surface of nano-TiO2 and a 3D network structure of Co-coordinated phytic acid was further constructed to extremely enhance the hydrophilicity and stability of nano-TiO2. The TiO2@Pa-Co suspension was prepared by adsorbing hydroxyl‑rich Pa molecules on the surface of nano-TiO2 and assembling Co-coordinated Pa and then modified onto a glass slide by a conventional spin-coating method to obtain TiO2@Pa-Co thin film. The hydrophilic performance tests demonstrated that the TiO2@Pa-Co thin film presented innate superhydrophilic properties, as evidenced by a water contact angle of 2.0°, significantly smaller than that of the blank TiO2 (65.0°) and TiO2@Pa (29.1°) thin films. Notably, it also displays good durability, corrosion resistance, and anti-fogging properties. The superhydrophilic performances can be attributed to the ability of phytic acid to offer a large number of hydroxyl groups for improving the hydrophilicity of TiO2, while the Co ions act as a bridge, connecting with Pa and further construct a 3D network structure for the enhanced hydrophilic stability of TiO2. This study presents an inventive design concept to prepare superhydrophilic and stable TiO2 thin film by developing an organo-metallic coordination layer.

Oropharyngeal aspirated Ag/TiO2 nanohybrids: Transformation, distribution and toxicity

The wide application of Ag-loaded TiO2 nanohybrids photocatalysts on environment and energy increases the lung exposure risk to humans. Ag/TiO2 nanohybrids inhalation can cause pulmonary toxicity, and there are concerns about whether the loaded silver can be released and cause toxic effects on extrapulmonary organs. Therefore, in this study, the possible biotransformation, biodistribution, and toxicity of oropharyngeal aspirated Ag/TiO2 nanohybrids were investigated first time in vitro and in vivo to answer this question. Firstly, the results of biotransformation showed that the ultrafine silver nanoparticles (~3.5 nm, 2 w/w%) loaded on the surface of nano-TiO2 (~25 nm) could agglomerate and release in Gamble's solution, and the hydrodynamic diameter of the nanohybrids agglomerates increased from about 200 nm to 1 μm. Furthermore, after exposure 10 mg/kg Ag/TiO2 nanohybrids to C57BL/6 J male mice by oropharyngeal aspiration weekly, the biodistribution results showed that the released silver could result in blood, liver, and brain distribution within 28 d. Finally, body weight, organ coefficient, blood biochemical indicators of liver and kidney function, and pathological images demonstrated that although silver could release and lead to extrapulmonary organ distribution, it did not cause obvious extrapulmonary organ damage. The original lung was still the main toxicity and accumulation target organ of Ag/TiO2 nanohybrids, which mainly manifested as the pro-inflammatory and pro-fibrotic effects that should be focused on in the future. Therefore, this study is of great significance in evaluating the safety of Ag-loaded TiO2 nanoparticles and predicting their toxic mechanisms.

Pb(II) Uptake from Polluted Irrigation Water Using Anatase TiO2 Nanoadsorbent.

The adsorption characteristics of titanium dioxide nanoparticles (nano-TiO2) for the removal of Pb(II) from irrigation water were investigated in this work. To accomplish this, several adsorption factors, such as contact time and pH, were tested to assess adsorption efficiencies and mechanisms. Before and after the adsorption experiments, commercial nano-TiO2 was studied using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The outcomes showed that anatase nano-TiO2 was remarkably efficient in cleaning Pb(II) from water, with a removal efficiency of more than 99% after only one hour of contact time at a pH of 6.5. Adsorption isotherms and kinetic adsorption data matched the Langmuir and Sips models quite well, showing that the adsorption process occurred at homogenous sites on the surface of nano-TiO2 by forming a Pb(II) adsorbate monolayer. The XRD and TEM analysis of nano-TiO2 following the adsorption procedure revealed a non-affected single phase (anatase) with crystallite sizes of 9.9 nm and particle sizes of 22.46 nm, respectively. According to the XPS data and analyzed adsorption data, Pb ions accumulated on the surface of nano-TiO2 through a three-step mechanism involving ion exchange and hydrogen bonding mechanisms. Overall, the findings indicate that nano-TiO2 has the potential to be used as an effective and long-lasting mesoporous adsorbent in the treatment and cleaning of Pb(II) from water bodies.

In situ graphitization of small organic molecules on the surface of nano titanium dioxide to construct highly efficient photosynthetic hydrogen peroxide composite catalyst

Hydrogen peroxide (H2O2) is a good strategic choice for developing sustainable energy. In recent years, although many researchers have focused on photocatalytic preparation of H2O2, the progress is still limited for the problems of low efficiency of H2O2 production, complex catalyst preparation, and high cost of catalyst. Here, a novel method to construct a hybrid photocatalyst was developed with one-step graphitization of specific organic small molecules, in which C, N, and O could be introduced simultaneously along with the formation of graphite-like structures within the inner pores of the nano-TiO2 surface. It not only changed the surface defects of TiO2 to successfully reduce its promotion on the photodecomposition of H2O2 but also adjusted the band gap of the catalyst and broadened its visible light absorption range. Besides, it also provided another two-electron oxygen reduction reaction pathway to enhance the catalytic activity of the photosynthesis of H2O2; thus, 11.78 mM/h H2O2, which exceeds all previously reported productivities, was produced under simulated sunlight. The modified catalyst not only has excellent ultraviolet light activity with an apparent quantum efficiency of 34.9% at 365 ± 5 nm but also has very good visible light activity with apparent quantum efficiency of 17.8% at 420 ± 5 nm and more than 1.66% solar-to-chemical conversion (>420 nm), which is very rare for nano-TiO2 and much promising for application. Our present research has proved that the organic molecule tetraethyl 4,4'-(1,4-phenylene)bis(2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate) successfully changed the surface defect modes of TiO2, making the oxygen defect that promotes the decomposition of H2O2 change to the C defect that is conducive to the photocatalytic generation of H2O2, and thus, the photocatalytic performance has been greatly improved. Thus, it is an important instruction for developing highly efficient and low-cost photocatalysts for synthesizing H2O2.

Nano-TiO2 aggravates immunotoxic effects of chronic ammonia stress in zebrafish (Danio rerio) intestine

Ammonia and nano-TiO2 are commonly found pollutants in aquatic environments around the world. NH3 has been proved to be absorbed on nano-TiO2 surface, therefore, the biosafety and environmental effects of ammonia and co-occurring nano-TiO2 in aquatic environments has increased considerably in recent years. To explore the potential interactive effects and mechanisms of ammonia and nano-TiO2 on the intestinal immune system, three-month-old female zebrafish were exposed to total ammonia nitrogen (TAN; 0, 3, 30 mg/L) with or without nano-TiO2 (1 mg/L) for 60 d. The results showed that intestinal ammonia levels increased with the increase of TAN exposure concentration in the presence of nano-TiO2. Histopathological analysis demonstrated that both TAN and nano-TiO2 caused cell vacuolation, lymphocyte infiltration and goblet cells hyperplasia in the intestine mucosa. Our study also found that the contents and gene expression levels of lysozyme (lys) and β-defensin (def-β) in the intestine of zebrafish exposed to TAN alone or combined with nano-TiO2 were significantly reduced, suggesting a decline in the intestinal innate immunity of fish. A broad upregulation of TLRs-related genes indicated that TAN and nano-TiO2 could activate TLR4/5-mediated MyD88-dependent pathway, and eventually induce intestinal inflammation. It should be noted that TAN combined with nano-TiO2 had more significant inhibitory effects on the intestinal structure and innate immune responses than TAN alone. Current data suggested that ammonia and nano-TiO2 had a synergistic inhibitory effect on intestinal mucosal immunity, and their associated health risk to aquatic animals and the water ecosystem should not be underestimated.

Preparation and properties of nano-TiO2-modified photosensitive materials for 3D printing

Abstract The surface of nano-TiO2 was modified by a silane coupling agent KH570, and the photosensitive resin was modified by blending the modified nano-TiO2 with three-dimensional (3D) printing light-curing resin. The modified nano-TiO2 powder was characterized by infrared spectrum, X-ray diffraction, contact angle test, and scanning electron microscope. The effects of different content of modified TiO2 on the viscosity, curing shrinkage, tensile strength, elongation at break, hardness, thermal stability, and cross-section morphology of 3D printing photosensitive resin were studied. The results showed that the mechanical properties of epoxy resin were improved obviously after surface modification with a silane coupling agent. When the mass fraction of TiO2 was 1.5%, the mechanical properties of the molded parts were the best. The tensile strength, impact strength, and elongation at break were increased by 51.1, 43.8, and 10.8%, respectively, and the hardness value was maintained at 81–83 HD. The addition of modified TiO2 can improve the heat resistance of the epoxy resin. When the amount of TiO2 is 1.5%, the T 50%, T max, and carbon residue rate of the epoxy resin are increased by 3.44°C, 6.34°C, and 25.3%, respectively.

Preparation of nano-TiO2 sensitized by new ruthenium complex for photocatalytic degradation of methylene blue under visible light irradiation

In this work we have synthesized cis/trans-[Cl(L)Ru(tppz)Ru(L)Cl](ClO4)2 (L = 2,2'-bipyridine-4,4′-dicarboxylic acid, tppz = tetra-2-pyridinylpyrazine) with the main objective to apply it in photocatalytic reactions. The TiO2 is sensitized with the complex to apply visible light more effectively in the photocatalytic reactions. The structure and optical properties of the photocatalyst were characterized by FT-IR, XRD, TEM, FE-SEM, EDX, DRS, BET and UV–vis spectroscopy. The FT-IR and EDX analysis confirmed the chemisorption of the ruthenium complex on the nano-TiO2 surface. According to the XRD, TEM and FE-SEM analysis it is concluded that the existence of ruthenium complex is not affected by the crystal structure and morphology of nano-TiO2. However, BET showed an increase in the surface area after dye-sensitization. The characterization results revealed that the dye-sensitized TiO2 has a wider absorption spectrum range than nano-TiO2. To evaluate the photocatalytic activity of the product, the photo degradation of the methylene blue was studied. The synthesized product could degrade 87% methylene blue in simulating waste water.

Molecular simulation of adsorption properties of thiol-functionalized titanium dioxide (TiO2) nanostructure for heavy metal ions removal from aqueous solution

We investigated the adsorption of Cd ion as a primary contaminant heavy metal in drinking water on titanium dioxide (TiO2) and thiol-functionalized TiO2 (thiol-TiO2). The dispersion corrected density functional theory (DFT-D2) calculation is used for structural relaxation and second-order MP2 (second-order Møller-Plesset) calculations for interaction energy (Eint) estimation. The results reveal that the Cd bound very strongly (Eint: −4.566 eV) to the TiO2 and strongly to the thiol-TiO2 (Eint: −1.882 eV). Our findings show that the H2O molecule is adsorbed very strongly on the TiO2 surface (Eint−4.535 eV) while it is attached weakly to the thiol-TiO2 (Eint−0.076 eV). The DFT-based molecular dynamic (MD) simulations at ambient conditions reveal that water molecules are first adsorbed on the nano-TiO2 surface, and then the Cd ion is co-adsorbed on the surface. Meanwhile, for thiol-nanoTiO2, a new chemical bond was formed between the Cd ion and S atom of the thiol group at 1 ps. The analysis of the AIM (Atom-In-Molecule) theory demonstrated that the types of interactions are typical for the electrostatics accompanied with partial covalent bonding between Cd ion and both O and S atoms. Our molecular simulations offer a well-founded understanding of the adsorption mechanisms of heavy metals on TiO2 and thiol-TiO2 at ambient conditions.

Preparation and Characterization of a Novel Sulfonated Titanium Oxide Incorporated Chitosan Nanocomposite Membranes for Fuel Cell Application.

In this study, nano-TiO2 sulfonated with 1,3-propane sultone (STiO2) was incorporated into the chitosan (CS) matrix for the preparation of CS/STiO2 nanocomposite membranes for fuel cell applications. The grafting of sulfonic acid (–SO3H) groups was confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis and energy-dispersive X-ray spectroscopy. The physicochemical properties of these prepared membranes, such as water uptake, swelling ratio, thermal and mechanical stability, ion exchange capacity and proton conductivity, were determined. The proton conducting groups on the surface of nano-TiO2 can form continuous proton conducting pathways along the CS/STiO2 interface and thus improve the proton conductivity of CS/STiO2 nanocomposite membranes. The CS/STiO2 nanocomposite membrane with 5 wt% of sulfonated TiO2 showed a proton conductivity (0.035 S·cm−1) equal to that of commercial Nafion 117 membrane (0.033 S·cm−1). The thermal and mechanical stability of the nanocomposite membranes were improved because the interfacial interaction between the -SO3H group of TiO2 and the –NH2 group of CS can restrict the mobility of CS chains to enhance the thermal and mechanical stability of the nanocomposite membranes. These CS/STiO2 nanocomposite membranes have promising applications in proton exchange membrane fuel cells.

Preparation of Inorganic Filler Modified Epoxy Resin Adhesive and Study on Its Compatibility with UDMH

Epoxy resin adhesive have many advantages that other adhesives do not have, and are widely used in various fields. At the same time, it is also a thermosetting resin with high crosslinking density. Its cured product is brittle, low impact strength, and easy to crack. These shortcomings limit the further application of epoxy resin. This article takes the plugging agent of UDMH as the starting point. Epoxy resin adhesive toughened and modified with two kinds of inorganic fillers, nano-titania and micro-alumina, were prepared and study the compatibility of modified epoxy resin adhesive with UDMH. It is found that under certain conditions, the silane coupling agent KH570 can undergo a grafting reaction with the hydroxyl groups on the surface of nano-TiO2 to improve its lipophilic and hydrophobic properties, and the effect is better than KH560, KH550; Through FT-IR, SEM, TG and other characterization methods, it is found that when the content of coupling agent is 15%, the effect of surface modification is the best. In the preparation of two kinds of inorganic filler modified epoxy adhesives, it is found that when the content of nano-TiO2 is 3%, the toughening effect is the best, and the impact strength can reach 36.78 KJ/m2; When the content of micro alumina is 60%, the toughening effect is best, and the impact strength can reach 28.43 KJ/m2. In general, the toughening effect of using nano-TiO2 is significantly better than that of alumina. In the study of the compatibility of the two kinds of filler modified epoxy resin adhesives with UDMH, it is found that when nano-titanium oxide is used as the filler, the compatibility of epoxy adhesive and UDMH is improved. However, when micro-alumina is used as the filler, the compatibility of epoxy resin adhesive and UDMH becomes worse.

Fabrication and Evaluation of Nano-TiO2 Superhydrophobic Coating on Asphalt Pavement.

In order to address water damage of asphalt pavement, reduce the occurrence of water-related potholes, deformation, and other diseases, and improve the performance and service life of the pavement, a nano-TiO2 superhydrophobic coating (PSC) on asphalt pavement was prepared from waterborne polyurethane and nano-TiO2 modified by stearic acid. FT-IR measured stearic acid successfully modified low surface energy substance on the surface of nano-TiO2. The SEM image shows that the PSC has a rough surface structure. The contact angle and rolling angle of the PSC in the contact angle test are 153.5° and 4.7°, respectively. PSC has a super-hydrophobic ability, which can improve the water stability of the asphalt mixture. Although the texture depth and pendulum value have been reduced by 2.5% and 4.4%, respectively, they all comply with the standard requirements. After the abrasion resistance test, the PSC coating still has a certain hydrophobic ability. These results surface PSC coating can effectively reduce water damage on asphalt pavement, and has considerable application value.

Macroaggregation effect of TiO2 nanoparticles on the photocatalytic activity and post-reaction separation for aqueous degradation of organic compounds

Photocatalysis for the decomposition of contaminants in water is an excellent purification method. Although nano-TiO2 suspensions provide high activity, solid-liquid separation after the reaction is rather difficult. On the other hand, it has been noted that the activity of immobilized photocatalysts decreases significantly compared to powder-suspended photocatalysts. In this study, macroaggregated granular photocatalysts (MGPs) with secondary particle sizes (40–125 µm) were prepared by dehydrative condensation of OH– groups on the surface of nano-TiO2 under acidic conditions. Powder-free granules were obtained after removing remaining particles in water by sedimentation. Scanning electron microscopy was conducted and the particle size distribution was measured in water by laser diffraction. Particles less than 40 µm in diameter were almost not present in the granules. Relative diffuse reflectance and photoluminescence measurements demonstrated that Pt-loaded MGPs absorbed light more efficiently than the powdered photocatalyst and resulted in less recombination of the separated charges. Pt-loaded MGPs were tested for the decomposition of acetic acid in water under disperse conditions by varying the photocatalyst mass concentration (Cm). The activity of MGPs at Cm in the range of 3–10 g L−1 was higher than that of the photocatalyst dispersed in colloidal suspensions, resulting in a maximum CO2 production rate 1.6 times higher. The activity results of the granular and powdered catalysts, and tests with Pt-loading or no loading, indicated an effective light absorption and electron transfer to Pt via the macroaggregate structure. After the stirring stopped, MGPs completely settled within 1 min, and the recovered photocatalyst was tested again showing approximately 95% of the initial photocatalytic activity. MGPs showed excellent photocatalytic activity and facile solid-liquid separation.

Rapid evaluation of oxygen vacancies-enhanced photogeneration of the superoxide radical in nano-TiO2 suspensions.

Reactive oxygen species (ROS) play an important role in the photocatalytic degradation of pollutants and are closely related to the surface defects of a semiconductor. However, the characterization of surface defects is very complex and a deeper understanding of them remains a great challenge. In this work, a series of nano-TiO2 was synthesized and their optical properties due to surface defects were studied. The results showed that the surface oxygen vacancies on nano-TiO2 can induce chemiluminescence (CL) by luminol. The greater the number of surface oxygen vacancies, the stronger the luminescence signal, and the greater the production of reactive oxygen species. Further studies revealed that the CL intensity was positively correlated with the oxygen vacancy content on the surface of nano-TiO2. Moreover, there was also a clear correlation between the oxygen vacancies and photogenerated superoxide radicals (O2˙−) on nano-TiO2 suspensions. Therefore, a simple and rapid CL method was developed for evaluating the oxygen vacancy content and their implied ability to photogenerate O2˙− on nano-TiO2 and has great potential in distinguishing surface oxygen vacancies and judging photocatalytic performance in oxides.

Synthesis and characterization of cubic Ag/TiO2 nanocomposites for the photocatalytic degradation of methyl orange in aqueous solutions

Using a hydrothermal strategy combined with photoreduction process, Ag/TiO2 nanocomposites in which ultra-small metallic Ag anchored on nano-TiO2 were synthesized. The SEM, TEM, EDS, XRD, as well as UV–Vis-NIR spectrum were used to characterize the Ag/TiO2 nanocomposites. It can be drawn the conclusion that the TiO2 exhibited irregular cube with a diameter of 20–30 nm, and metallic Ag anchored on the surface of nano-TiO2. The addition of metallic Ag successfully broaden the photoresponse range from UV region to visible light region. Photocatalytic activity of Ag/TiO2 was evaluated by degradation of methyl orange in aqueous solution. The results showed that the degradation rate of methyl orange by Ag/TiO2 reached 65.4% in 120 min, indicating a higher photocatalytic activity of Ag/TiO2 than that of pure TiO2 nanomaterials. The additional absorption of Ag/TiO2 in visible region was attributed to the plasmonic absorption of Ag. Moreover, the kinetic behavior could be described in terms of Langmuir-Hinshelwood pseudo-first-order kinetic equation.

Design and preparation of flocculant with self-degrading characteristics for dewatering of oil sand tailings

Polymer flocculation technology is widely used in the treatment of oil sand tailings pollutants. However, the most commonly used polyacrylamide flocculants have problems of secondary pollution. In this paper, under ultraviolet light, the composite was prepared by photoinitiated precipitation polymerization of acrylamide on the surface of nano TiO2, providing a facile strategy for the synthesis of organic-inorganic hybrid flocculants. A series of organic-inorganic hybrid materials with different light sources, UV irradiation times, TiO2 contents and AM contents were synthesized, and connected by covalent bonds. In addition, in order to analyze the synthesis mechanism of the composite material, the functional groups of the material were investigated by Fourier transform infrared spectroscopy (FTIR), the morphology and structure were observed by transmission electron microscopy (TEM), and thermodynamic stability was analyzed by thermogravimetry. The flocculation mechanism was studied by testing the zeta potential and GPC spectrum of the organic-inorganic composites. Moreover, the composite material increased the transmittance by 74.33% and decreased the water volume by 84% for simulated oil sand tailings. Ultimately, the degradation experiments showed that the prepared organic-inorganic composite flocculant had nice self-degradation performance, which efficiency could reach over 90% within 2 hours. In conclusion, this material can be employed to enhance the recovery of water from oil sand tailings, also with outstanding degradation characteristics.

Investigation on the coating modification effect of nano-SiO2 particles on nano-TiO2 particles

TiO2 has received significant scientific attention as a highly operative, stable, and low-cost photocatalyst. However, the decomposition of organic matrices due to its photocatalytic action is considered to be one of the main drawbacks of TiO2 nanoparticles in its applications in inks. To overcome this problem, this study aims to coat the surface of the nano-TiO2 particles with a layer of nano-SiO2 particles through a sol-gel method. The nano-TiO2 powder was dispersed by polyvinylpyrrolidone (PVP) and 4-vinylpyridine (4VP). The effects of different concentrations of PVP and 4VP, molar ratios of silicon to titanium, and ammonia water dosage on the properties of the composite particles were investigated. Scanning electron microscopy (SEM) analysis showed that the coating effect is best when the PVP had a mass of 2 g, the 4VP had a volume of 2 ml, the ratio of titanium to silicon was 1:2, and the amount of ammonia was 5 ml. The transmission electron microscopy (TEM) images show that titania particles were successfully coated on the surface of nano-TiO2. The x-ray diffraction (XRD) patterns showed no change in the crystal structure of nano-TiO2 before and after coating with nano-SiO2. Comparing the Fourier-transform infrared (FT-IR) and x-ray photoelectron (XPS) spectra, it was found that the Ti–O–Si bond is present in the nano-TiO2/SiO2 composite particles, and the Si element is present in the TiO2 crystal in the form of Ti–O–Si. These results indicate that the nano-SiO2 was coated on the surface of the nano-TiO2 successfully, and the ultraviolet (UV) resistance of pure nano-TiO2 is effectively improved.

SURFACE MODIFICATION OF NANO TITANIUM DIOXIDE (TiO2) BY CATIONIC SURFACTANTS AND INVESTIGATION OF ITS EFFECT ON THE PROPERTIES OF NATURAL RUBBER (NR) NANOCOMPOSITES

ABSTRACT We investigate the reinforcing effects of both unmodified and surface modified nano titanium dioxide (TiO2) on the cure, mechanical, and thermal properties of natural rubber (NR) nanocomposites. The surface of nano TiO2 is modified by cationic surfactants cetyltrimethylammonium bromide (CTAB) and tetraethylammonium bromide (TEAB). The surface modification of nano TiO2 is characterized by Fourier transform infrared (FTIR) spectra and Field emission scanning electron microscopy (FESEM). The result reveals that surface modified nano TiO2 is much more efficient in improving the resulting properties of NR nanocomposites in comparison with unmodified nano TiO2. The excellent improvement in the properties of surface modified nano TiO2/NR composites is due to the better hydrophobicity and uniform dispersion of modified nano TiO2 within the NR matrix, as confirmed from morphological analysis. CTAB is much more effective than TEAB with respect to the properties of nano TiO2 based NR composites.

Effect of calcination on structure and photocatalytic property of N-TiO2/g-C3N4@diatomite hybrid photocatalyst for improving reduction of Cr(Ⅵ)

The N-TiO2/g-C3N4@diatomite (NTCD) composite has been prepared through a simple impregnation method, using titanium tetrachloride as precursor and urea as nitrogen-carbon source. Then the effects of calcination temperature on structure, surface property and photocatalytic activity of the catalysts were investigated. And XRD, TEM, XPS, FTIR and UV–vis diffuse adsorption spectroscopy were used to characterize the obtained powders. The photocatalytic activity of the NTCD was evaluated through the reduction of aqueous Cr (VI) under visible light irradiation (λ > 400 nm). The results demonstrated that the nano-TiO2 particles ranging from 15 to 30 nm in the crystal of anatase are well deposited on the surface of diatomite in the NTCD-500 which calcined at 500 °C for 2 h. Furthermore, the g-C3N4 with the lay thickness of 0.92 nm was attached to the surface of nano-TiO2. The N-doped TiO2 and g-C3N4 doped catalysts could co-enhance response in the visible light region and reduce band gap of NTCD-500 (Eg = 3.07 eV). And the NTCD-500 sample exhibited nearly 100% removal rate within 5 h for photocatalytic reduction of Cr (VI) which was higher activity than P25, crude TiO2@diatomite and g-C3N4@diatomite.

Enhanced Antibacterial Activity of Silver Doped Titanium Dioxide-Chitosan Composites under Visible Light.

Nano titanium dioxide (TiO2) with photocatalytic activity was firstly modified by diethanolamine, and it was then doped with broad spectrum antibacterial silver (Ag) by in situ method. Further, both Ag doped TiO2-chitosan (STC) and TiO2-chitosan (TC) composites were prepared by the inverse emulsion cross-linking reaction. The antibacterial activities of STC composites were studied and their antibacterial mechanisms under visible light were investigated. The results show that in situ doping and inverse emulsion method led to good dispersion of Ag and TiO2 nanoparticles on the cross-linked chitosan microsphere. The STC with regular particle size of 1–10 μm exhibited excellent antibacterial activity against E. coli, P. aeruginosa and S. aureus under visible light. It is believed that STC with particle size of 1–10 μm has large specific surface area to contact with bacterial cell wall. The increased antibacterial activity was attributed to the enhancement of both electron-hole separations at the surface of nano-TiO2 by the silver ions under the visible light, and the synergetic and sustained release of strong oxidizing hydroxyl radicals of nano-TiO2, together with silver ions against bacteria. Thus, STC composites have great potential applications as antibacterial agents in the water treatment field.