In situ radical polymerization of methyl methacrylate in a solution of surface modified TiO2 and nanoparticles

Surface modified TiO₂ nanoparticles dissolved in toluene were encapsulated in PMMA by in situ radical polymerization of methyl methacrylate initiated by 2,2′-azobisisobutyronitrile. The surface modification of the TiO₂ nanoparticles (average diameter of 4.5 nm) was achieved by the formation of a charge transfer complex between TiO₂ nanoparticles and 6-palmitate ascorbic acid. The surface modified TiO₂/nanoparticles were characterized using UV−Vis and FTIR spectroscopy, while the obtained polymer nanocomposites were characterized using reflection and ¹H NMR spectroscopy, as well as gel permeation chromatography. The influence of the TiO₂ nanoparticles on the thermal properties of the PMMA matrix was investigated using thermo-gravimetric analysis and differential scanning calorimetry. The glass transition temperature of the polymer was not influenced by the presence of the nanoparticles while the thermal stability was significantly improved.     

Transparent poly(bisphenol A carbonate)-based nanocomposites with high refractive index nanoparticles

Transparent organic-inorganic nanocomposites were successfully synthesized from sulfonic acid-modified poly(bisphenol A carbonate) (SPC) and TiO₂ or ZrO₂ nanoparticles. The dispersibility of nanoparticles was significantly improved by both the surface treatment of nanoparticles with phosphoric acid 2-ethylhexyl esters (PAEH) and the introduction of a sulfonic acid moiety into the PC chain. It was found that in some cases, crystallization of the matrix caused a reduction in transparency. Efficient dispersion of nanoparticles and the absence of crystallization resulted in highly transparent nanocomposites with up to 42 wt% TiO₂ and 50 wt% ZrO₂ nanoparticles. The refractive indices of the nanocomposites based on SPC increased with the increasing amount of nanoparticles. Theoretical equation based on Maxwell-Garnett effective medium theory provided reasonably close estimation of the refractive indices to the experimentally observed values. The prepared nanocomposites had lower thermal stability than the host matrix polymers.     

Nanocomposites of poly(l-lactide) and surface-grafted TiO2 nanoparticles: Synthesis and characterization

A new method of surface modification of TiO₂ nanoparticles by surface-grafting l-lactic acid oligomer was developed. The surface-grafting reaction was evaluated by Fourier transformation infrared (FTIR) and thermal gravimetric analysis (TGA). The results showed that l-lactic acid oligomer could be easily grafted onto the TiO₂ nanoparticles surface in the presence of stannous octanoate and the highest amount of grafted polymer was about 8.5% in weight. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) results showed that grafted TiO₂ (g-TiO₂) in chloroform or PLLA matrix approximated to uniform, while unmodified TiO₂ nanoparticles tended to aggregate. The tensile strength of this material was greatly improved by the addition of g-TiO₂ nanoparticles in poly(l-lactide) (PLLA) matrix. The tensile strength of the g-TiO₂/PLLA nanocomposite containing 5 wt.% of g-TiO₂ was 72 MPa, which was 23.1% higher than that of pure PLLA. Even though the incorporation of the TiO₂ nanoparticles into PLLA led to the deterioration of its elongation at break, the g-TiO₂/PLLA nanocomposite also exhibited better ductility than that of TiO₂/PLLA nanocomposite.     

Synthesis of visible light-driven Eu, N co-doped TiO2 and the mechanism of the degradation of salicylic acid

Europium and nitrogen co-doped TiO₂ was successfully synthesized by the precipitation–peptization method. The structure and properties of the catalysts were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and UV–vis diffuse reflectance spectra. The photocatalytic efficiency was evaluated by monitoring the photocatalytic degradation of salicylic acid under visible light irradiation. It was verified that TiO₂ co-doped with nitrogen and 1% europium showed the highest photocatalytic activity. The adsorption isotherms were obtained by measuring the salicylic acid concentration before and after the dark adsorption at different original solution concentrations. The results illustrated that the doping of Eu was beneficial to the adsorption of salicylic acid. The probable degradation mechanism of salicylic acid was examined by the addition of NaF, Na₂S₂O₃, and K₂S₂O₈ as the probe molecules. It was verified that salicylic acid was first adsorbed on the surface of the catalysts, followed by the degradation by the photogenerated holes (h _vb ⁺ ).     

Impact of TiO2 nanoparticles on morphology and performance of crosslinked polyimide organic solvent nanofiltration (OSN) membranes

Chemically crosslinked polyimide organic–inorganic composite nanofiltration membranes suitable for application in harsh organic solvents were successfully prepared by phase inversion of dope solutions. TiO₂ nanoparticles were dispersed in these dope solutions, comprising polyimide (PI) in N,N-dimethylformamide/1,4-dioxane. The impact of TiO₂ on the resulting PI membranes was investigated using SEM, TGA, water contact angle, dope viscosity measurements and mechanical strength. The presence of TiO₂ nanoparticles within the membrane matrix was proved by the detection of a peak characteristic of TiO₂ in the WAXS pattern. SEM pictures of the cross-section of the PI/TiO₂ membranes showed dramatically changed morphology compared to reference membranes with no TiO₂ addition. Macrovoids present in reference membranes were suppressed by increasing loading of TiO₂ nanoparticles, and eventually disappeared completely at a TiO₂ loading above 3 wt.%. Decreasing water contact angle and an increase in ethanol flux indicated that hydrophilicity increased as nanoparticle loading increased. The effect of TiO₂ on the functional performance of the membranes was evaluated by measuring flux and rejection using cross-flow filtration. Perhaps surprisingly, the presence of TiO₂ improved the compaction resistance of the membranes, whereas rejection and steady flux were almost unaltered.     

Study on the Photodegradation of Salicylic Acid in Different Vehicles in the Absence and in the Presence of TiO2

In this work, the direct photolysis of salicylic acid, generally used as keratolytic agent in many dermatological products and as preservative in cosmetics, was investigated. The photodegradation of the acid under UVB irradiation was evaluated in different vehicles, such as water solutions at different pH, propylene glycol/water, and ethanol/water mixtures, sodium dodecyl sulphate solutions, and O/W emulsions prepared with Montanov 68 and Amphysol K as emulsifiers. The increase of pH enhanced the photodegradation of salicylic acid while the different vehicles protected the acid from the action of UVB radiations. However, the best protection was observed dissolving the acid in the lipid core of O/W emulsions, which probably removes the active from the polar environment that can promote the photolysis. The photocatalytic activity of TiO₂ on the degradation of salicylic acid also was evaluated. TiO₂ frequently is used as sunscreen in many cosmetic preparations. Salicylic acid and the pigment can be contained in the same solar formulation; hence, it can be interesting to study their interaction under UVB. TiO₂ enhanced the photodegradation of salicylic acid in all the media previously reported and its photocatalytic activity was influenced by the pH and by the components of the vehicles.     

Preparation and characterization of poly(l-lactic acid)/TiO2 nanoparticle nanocomposite films with high transparency and efficient photodegradability

Poly(l-lactic acid)-TiO₂ nanoparticle nanocomposite films were prepared by incorporating surface modified TiO₂ nanoparticles into polymer matrices. In the process of preparing the nanocomposite films, severe aggregation of TiO₂ nanoparticles could be reduced by surface modification by using carboxylic acid and long-chain alkyl amine. As a result, the nanocomposite films with high transparency, similar to pure PLA films, were obtained without depending on the amount of added TiO₂ nanoparticles. A TEM micrograph of the nanocomposite films suggests that the TiO₂ nanoparticles of 3-6 nm in diameter were uniformly dispersed in polymer matrices. Photodegradation of PLA-TiO₂ nanoparticle nanocomposite films was also investigated. The results showed that nanocomposite films could be efficiently photodegraded by UV irradiation in comparison with pure PLA.     

玻璃微珠/Ag/TiO2可见光催化剂的制备与表征

通过离子交换法将Ag纳米颗粒负载于玻璃微珠的表面及浅表层,并以钛酸四丁酯的乙醇溶液为前驱体,将TiO₂负载于包含银的玻璃微珠表面,制得一种玻璃微珠/Ag/TiO₂复合光催化剂。由于纳米银的表面等离子体吸收效应,该复合光催化剂具有一定的可见光响应特性。利用XRD、SEM对样品进行表征,可发现玻璃微珠表面形成一层均匀多孔的锐钛矿TiO₂,其粒径均在50 nm左右。由漫反射光谱可得出该催化剂具有较强的可见光吸收,并在降解甲基橙溶液的试验中表现出较好的可见光催化活性。     

Preparation and properties of amorphous titania-coated zinc oxide nanoparticles

Amorphous TiO₂-coated ZnO nanoparticles were prepared by the solvothermal synthesis of ZnO nanoparticles in ethanol and the followed by sol-gel coating of TiO₂ nanolayer. The analyses of X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that the resultant ZnO nanoparticles were hexagonal with a wurtzite structure and a mean diameter of about 60 nm. Also, after TiO₂ coating, the TEM images clearly indicated the darker ZnO nanoparticles being surrounded by the lighter amorphous TiO₂ layers. The zeta potential analysis revealed the pH dependence of zeta potentials for ZnO nanoparticles shifted completely to that for TiO₂ nanoparticles after TiO₂ coating, confirming the formation of core-shell structure and suggesting the coating of TiO₂ was achieved via the adhesion of the hydrolyzed species Ti-O⁻ to the positively charged surface of ZnO nanoparticles. Furthermore, the analyses of Fourier transform infrared (FTIR) and Raman spectra were also conducted to confirm that amorphous TiO₂ were indeed coated on the surface of ZnO nanoparticles. In addition, the analyses of ultraviolet-visible (UV-VIS) and photoluminescence (PL) spectra revealed that the absorbance of amorphous TiO₂-coated ZnO nanoparticles at 375 nm gradually decreased with an increase in the Ti/Zn molar ratio and the time for TiO₂ coating, and the emission intensity of ZnO cores could be significantly enhanced by the amorphous TiO₂ shell.     

Influence of surface modified TiO2 nanoparticles by gallates on the properties of PMMA/TiO2 nanocomposites

Nanocomposites based on poly(methyl methacrylate) (PMMA) and TiO₂ nanoparticles were synthesized by in situ radical polymerization of MMA in solution. The surface of TiO₂ nanoparticles was modified with four gallic acid esters (octyl, decyl, lauryl and cetyl gallate). The content of gallates present on the surface of TiO₂ was calculated from the TGA results. The influence of length of hydrophobic tail of amphiphilic alkyl gallates on dispersability of surface modified TiO₂ nanoparticles in PMMA matrix, the molecular weight and glass transition temperature of PMMA, as well as the thermal stability of the prepared PMMA/TiO₂ nanocomposites in nitrogen and air was investigated. The influence of content of TiO₂ nanoparticles on the properties of these nanocomposites was also examined. The formation of a charge transfer complex between the surface Ti atoms and the gallates was confirmed by FTIR and UV spectroscopy. TEM micrographs of the PMMA/TiO₂ nanocomposites revealed that degree of TiO₂ aggregation can be significantly lowered by increasing the length of aliphatic part of the used gallates. The molecular weight of PMMA slightly decreases with the increase of TiO₂ content, indicating that used TiO₂ nanoparticles act as radical scavengers during the polymerization of MMA. The presence of surface modified TiO₂ nanoparticles do not have an influence on the mobility of PMMA chain segments leading to the same values of glass transition temperature for all investigated samples. Thermal and thermo-oxidative stability of the PMMA matrix are improved by introducing TiO₂ nanoparticles modified with gallates.     

Au改性TiO2纳米复合物对人结肠癌细胞的光催化杀伤作用

提出了通过TiO₂表面修饰纳米Au的方法来提高纳米TiO₂光催化杀伤癌细胞的效率. 采用化学还原法合成了Au改性的TiO₂ (Au/TiO₂)纳米复合物, 并研究了不同掺杂量(1 wt%, 2 wt%, 4 wt%)的Au/TiO₂对人结肠癌LoVo细胞的光催化杀伤效应. 结果显示, Au的掺杂大大地提高了TiO₂纳米粒子光催化杀伤结肠癌LoVo细胞的效率, 而且Au掺杂量的高低影响Au/TiO₂光催化杀伤癌细胞的效率, 掺金量为2%的Au/TiO₂对结肠癌LoVo细胞具有最高的光催化杀伤效率. 在光强为1.8 mW/cm²的紫外灯(λ_max＝365 nm)下光照110 min, 50 μg/mL掺金量为2%的Au/TiO₂能够杀死所有的癌细胞, 而同样浓度的TiO₂只能杀死70%的癌细胞.     

Zeta potential of shape-controlled TiO2 nanoparticles with surfactants

Zeta potential of shape- and size-controlled TiO₂ nanoparticles obtained with the introduction of surfactants during synthesis was measured at different pH values. A unique finding is that TiO₂ nanoparticles shaped by sodium dodecyl sulfate (SDS) have double isoelectric points (IEPs), while other shape-controlled TiO₂ nanoparticles have only one IEP. The double IEPs might be due to the complex chemistry of TiO₂ nanoparticles with the presence of impurities (Na, S, C, etc.). At neutral pH, shape- and size-controlled TiO₂ nanoparticles have more negative zeta potential values and lower IEPs than TiO₂ nanoparticles obtained without the addition of surfactants during synthesis and the commercial anatase TiO₂ nanoparticles Degussa P-25. The lower IEPs could be attributed to the presence of carbonates on particle surfaces. The IEP value of TiO₂ nanoparticles increases with an increase in calcination temperature. The results suggest that the zeta potential of TiO₂ nanoparticles can be manipulated with the addition of surfactants during the synthesis process.     

Impact and mechanism of TiO2 nanoparticles on DNA synthesis in vitro

The impact of TiO₂ nanoparticles on DNA synthesis in vitro in the dark and the molecular mechanism of such impact were studied. The impact of TiO₂ nanoparticles on DNA synthesis was investigated by adding TiO₂ nanoparticles in different sizes and at various concentrations into the polymerase chain reaction (PCR) system. TiO₂ nanoparticles were premixed with the DNA polymerase, the primer or the template, respectively and then the supernatant and the precipitation of each mixture were added into the PCR system separately to observe the impact on DNA synthesis. Sequentially the interaction between TiO₂ nanoparticles and the DNA polymerase, the primer or the template was further analyzed by using UV-visible spectroscopy and polyacrylamide gel electrophoresis (PAGE). The results suggest that TiO₂ nanoparticles inhibit DNA synthesis in the PCR system in the dark more severely than microscale TiO₂ particles at the equivalent concentration and the inhibition effect of TiO₂ nanoparticles is concentration dependent. The molecular mechanism of such inhibition is that in the dark, TiO₂ nanoparticles interact with the DNA polymerase through physical adsorption while TiO₂ nanoparticles do with the primer or the template in a chemical adsorption manner. The disfunction levels of the bio-molecules under the impact of TiO₂ nanoparticles are in the following order: the primer > the template > the DNA polymerase. Supported by the National Natural Science Foundation of China (Grant Nos. 50572074 & 50673078), the Shanghai Key Fundamental Project (Grant No. 06JC14068) and the Innovation Program of Shanghai Municipal Education Commission (Grant No. 08ZZ21)     

Opportunities and Challenges in the Use of TiO2 Nanoparticles Modified with Citric Acid to Synthesize Advanced Nanocomposites Based on Poly(amide-imide) Containing N,N′-(Pyromellitoyl)-bis-L-leucine Segments

In this study, the goal was the preparation, characterization, and surface morphology of poly(amide-imide)/TiO₂-citric acid nanocomposites (PAI/TiO₂-CA NCs). Owing to the high surface energy and tendency for agglomeration, the surface of TiO₂ nanoparticles was modified with citric acid. Then poly(amide-imide) was synthesized by direct polycondensation reaction of N,N′-(pyromellitoyl)-bis-L-leucine diacid with 4,4′-diaminodiphenylmethane by triphenyl phosphite and tetra-n-butylammonium bromide as a green medium. The attained polymer and modified TiO₂ nanoparticles were used to prepare PAI/TiO₂-CA NCs through ultrasonic irradiation. The resulting PAI/TiO₂-CA NC was characterized with FT-IR spectroscopy, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis.     

Cu/Ni助催化剂对TiO2光催化制取苯酚性能的影响

以TiO₂纳米粒子为主催化剂, 采用“浸渍-还原法”构筑了铜、镍共负载的二氧化钛基光催化系统。以苯为起始原料, H₂O₂为氧化剂, 研究了Cu/Ni助催化剂对TiO₂可见光催化制取苯酚性能的影响并对Cu/Ni助催化剂的作用机制进行了探讨。结果表明, 在可见光照射下, 纯TiO₂纳米粒子对苯氧化制取苯酚反应没有催化活性。铜、镍的引入可以明显地增强TiO₂可见光催化制取苯酚的活性。当使用负载有铜、镍的TiO₂作为催化剂时, 苯酚的产率可达到18%。结果还表明Cu、Ni之间存在着很强的协同作用。在该协同作用下, Cu、Ni共负载的TiO₂纳米粒子表现出了较单一金属负载的TiO₂纳米粒子高得多的光催化活性。     

Cu/Ni助催化剂对TiO2光催化制取苯酚性能的影响

以TiO₂纳米粒子为主催化剂,采用"浸渍-还原法"构筑了铜、镍共负载的二氧化钛基光催化系统。以苯为起始原料,H₂O₂为氧化剂,研究了Cu/Ni助催化剂对TiO₂可见光催化制取苯酚性能的影响并对Cu/Ni助催化剂的作用机制进行了探讨。结果表明,在可见光照射下,纯TiO₂纳米粒子对苯氧化制取苯酚反应没有催化活性。铜、镍的引入可以明显地增强Ti₀₂可见光催化制取苯酚的活性。当使用负载有铜、镍的TiO₂作为催化剂时,苯酚的产率可达到18%。结果还表明Cu、Ni之间存在着很强的协同作用。在该协同作用下,Cu、Ni共负载的TiO₂纳米粒子表现出了较单一金属负载的TiO₂纳米粒子高得多的光催化活性。     

Photosensitized Solid-state Polymerization of Diacetylenes in Nanoporous TiO2 Structures

In situ topochemical polymerization of two diacetylene monomers within nanoporous TiO₂ thin films was carried out under visible light irradiation. One of the monomers used contains a carboxylic acid group, which could help to link the monomer onto the TiO₂ surface covalently. UV-Vis absorption and Raman studies showed that both monomers were successfully photopolymerized. These results suggest that the covalent linkage of the diacetylene to the nanoparticle through the carboxylic acid group is not needed. Since photopolymerization of diacetylene is typically induced by excitation of the monomer at λ< 300 nm, the observed red shift of the photopolymerization wavelength is attributed to the photosensitization effect of TiO₂. The morphological study of the polydiacetylene/TiO₂ nanocomposite revealed that the diacetylene monomers were polymerized in the vicinity of the TiO₂ nanoparticles. This is attributed to the fact that the electron-transfer process occurs at the interface of nanocrystalline TiO₂ (nc-TiO₂) and the diacetylene monomer and the polymerization is expected to be initiated near the nc-TiO₂ surface. Photopolymerization of the carboxylated diacetylene monomer with other oxides nanoparticles, such as ZnO and SiO₂ was also investigated.     

Chemical preparation and characterization of fibrous poly(3-methylthiophene) decorated by TiO2 nanoparticles

In this article, we report on the chemical oxidative polymerization of 3-methylthiophene (3MTh) in a concentrated TiO₂/CHCl₃ homogeneous suspension with an oxidant/monomer mole ratio of 3 at room temperature. According to the scanning electron microscopy images, in this condition, poly(3-methylthiophene) (P3MTh) was prepared with fibrous morphology decorated by nano-dimensional TiO₂ particles. P3MTh/TiO₂ was also characterized by Fourier transform infrared spectroscopy and X-ray diffraction techniques. It was found that no aggregation of nanoparticles occurred during the polymerization process. In addition, the thermal stability of P3MTh/TiO₂ nanocomposite was investigated by thermogravimetric analysis and compared with that of an analogously prepared neat P3MTh. The thermal degradation of P3MTh in the temperature range of 300–550°C decreases significantly due to the presence of the TiO₂ nanoparticles in the polymer composite.     

载有C60的TiO2纳米粒子光催化活性

以水溶性C₆₀和TiO₂粒子为前驱体,采用水热法制备了载有C₆₀的锐钛矿型TiO₂纳米粒子。应用X射线衍射、透射电子显微镜、红外光谱、紫外-可见漫反射光谱、荧光光谱对产物进行了表征。以对-硝基苯酚为模型污染物研究了产物的光催化活性,结果表明适量负载C₆₀可以提高TiO₂纳米粒子的光催化活性,C₆₀起着传输电子、促进TiO₂光生载流子分离的作用,且经7次循环使用后对-硝基苯酚的降解效率仍能达到74%。讨论了载有C₆₀的TiO₂纳米粒子光催化降解对-硝基苯酚的机理。     

Role of ammonium ions on the stability of TiO2 sol

In this paper, the role of the trace ammonium ions on the stability of TiO₂ sol prepared by peroxo titanic acid (PTA) sol was investigated. The results showed that the removal of ammonium ions in PTA sol is beneficial to reduce agglomeration and increase the negative charge on the surface of TiO₂ colloidal particles, contributing to the higher stability and longer storage time of the TiO₂ sol. It was also approved by the increase of interaction energy calculated by classical DLVO theory. In addition, the photocatalytic performance of TiO₂ sol was improved due to the decrease of aggregation of TiO₂ colloidal particles.