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.     

Fabrication of TiO2 Grating with Composites of Azobenzene Polymer and TiO2 Nanoparticles

We have used the formation of surface relief gratings (SRG) on azobenzene polymers to manipulate TiO₂ nanoparticles and to fabricate TiO₂ nanoparticle gratings. Suspensions of an azobenzene polymer (PDO3) and TiO₂ were used to spin coat thin films on glass slide substrates. By interfering coherent light from an Argon laser on the surface of the PDO3‐TiO₂ composite films, SRGs were fabricated. Atomic force microscopic images of the SRGs show TiO₂ nanoparticles dispersed throughout the sample, and in particular, at the peaks of the SRG after oxygen plasma treatment. The lateral forces acting on the azobenzene polymer during the SRG fabrication drag the TiO₂ nanoparticles. These results indicated that it is feasible to create TiO₂ nanoparticle gratings with the composites.     

Gas transport in TiO2 nanoparticle-filled poly(1-trimethylsilyl-1-propyne)

Titanium dioxide (TiO₂) nanoparticles were dispersed via solution processing in poly(1-trimethylsilyl-1-propyne) (PTMSP) to form nanocomposite films. Nanoparticle dispersion was investigated using atomic force microscopy and transmission electron microscopy. At low-particle loadings, nanoparticles were dispersed individually and in nanoscale aggregates. At high-particle loadings, some nanoparticles formed micron-sized aggregates. The gas transport and density exhibited a strong dependence on nanoparticle loading. At low-TiO₂ loadings, the composite density was similar to or slightly higher than that predicted by a two-phase additive model. However, at particle loadings exceeding approximately 7 nominal vol.%, the density was markedly lower than predicted, suggesting that the particles induced the creation of void space within the nanocomposite. For example, when the TiO₂ nominal volume fraction was 0.35, the polymer/particle composite density was 40% lower than expected based on a two-phase additive model for density. At low-nanoparticle loading, light gas permeability was lower than that of the unfilled polymer. At higher nanoparticle loadings, light gas permeability (i.e., CO₂, N₂, and CH₄) increased to more than four times higher than in unfilled PTMSP. At most, selectivity changed only slightly with particle loading.     

The release of TiO2 and SiO2 nanoparticles from nanocomposites

There is a growing interest in the development of nanocomposites consisting of organic polymers and TiO₂ or amorphous SiO₂ nanoparticles. These nanoparticles may be released from nanocomposites. There is evidence that amorphous SiO₂ and TiO₂ nanoparticles can be hazardous. Thus, in the design of nanocomposites with such nanoparticles, hazard reduction extending to the full nanocomposite life cycle would seem a matter to consider. Options for hazard reduction include: changes of nanoparticle surface, structure or composition, better fixation of nanoparticles in nanocomposites, including persistent suppression of oxidative damage to polymers by nanoparticles, and design changes leading to the release of relatively large particles.     

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.     

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.     

Electrodeposition of Zn–TiO<Subscript>2</Subscript> nanocomposite films—effect of bath composition

Zn–TiO₂ nanocomposite films were prepared by pulsed electrodeposition from acidic zinc sulphate solutions on a Ti support. The influence on the composite structural and morphological characteristics of Zn²⁺ and TiO₂ concentrations in the deposition bath has been investigated. The characterisation of the samples was made by X-ray diffraction and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDS). For all the obtained coatings, the anatase and rutile phases’ most intense diffraction lines were observed between 24° and 28° 2θ, confirming the formation of the Zn–TiO₂ nanocomposite. X-ray diffraction data show that the presence of the TiO₂ nanoparticles plays a remarkable influence on the preferred orientation of the metal matrix. For the more diluted solution, a dependence between the metallic matrix grain size and the concentration of TiO₂ in bath is observed. The grain size decreases with the increasing on the nanoparticle amounts. The SEM results for Zn and Zn–TiO₂ deposits indicate that the nanoparticles have a strong influence on the deposit surface morphology, which is caused by the changes on the deposition mechanism.     

Molecular Assembly by Sequential Ionic Adsorption of Nanocrystalline TiO2 and a Conjugated Polymer

Abstract

Cationic nanocrystalline TiO₂ particles have been synthesized for which the size and composition of the nanoparticles were analyzed by a transmission emission microscopy and energy dispersive x‐ray spectrometer (EDXS). Multilayered films have been fabricated by sequential adsorption of TiO₂ nanoparticles and poly(3‐thiophene acetic acid) (PTAA). Each layer of the nanoparticles and PTAA in the thin film has also been characterized by x‐ray photoelectron spectroscopy, atomic force microscopy, and UV‐visible spectroscopy. These types of multilayered nanocomposite films may find applications in the fabrication of efficient light harvesting photovoltaic cells.     

Self-assembly of TiO2/polypyrrole nanocomposite ultrathin films and application for an NH3 gas sensor

TiO₂/polypyrrole (PPy) nanocomposite ultrathin films for NH₃ gas detection were fabricated by the in situ self-assembly technique. The films were characterized by UV–Vis absorption, FT–IR spectroscopy, and atomic force microscopy (AFM). The electrical properties of TiO₂/PPy ultrathin film NH₃ gas sensors, such as sensitivity, selectivity, reproducibility, and stability were investigated at room temperature in air as well as in N₂. The results showed that the optimum gas-sensing characteristics of TiO₂/PPy ultrathin film were obtained in the presence of 0.1?wt% colloidal TiO₂ for 20-min deposition. Compared with pure PPy thin-film sensors, the TiO₂/PPy film gas sensor has a shorter response/recovery time. It was also found that both humidity and temperature had an effect on the operation of the TiO₂/PPy film gas sensor at low NH₃ concentrations.     

High ethanol sensitivity of Palladium/TiO2 nanobelt surface heterostructures dominated by enlarged surface area and nano-Schottky junctions

TiO₂ nanobelts were prepared by the hydrothermal growth method. The surface of the nanobelts was coarsened by selective acid corrosion and functionalized with Pd catalyst particles. Three nanobelt samples (TiO₂ nanobelts, surface-coarsened TiO₂ nanobelts and Pd nanoparticle/TiO₂ nanobelt surface heterostructures) were configured as gas sensors and their sensing ability was measured. Both the surface-coarsened nanobelts and the Pd nanoparticle-decorated TiO₂ nanobelts exhibited dramatically improved sensitivity to ethanol vapor. Pd nanoparticle-decorated TiO₂ nanobelts with surface heterostructures exhibited the best sensitivity, selectivity, working temperature, response/recovery time, and reproducibility. The excellent ethanol sensing performance is attributed to the large surface area and enhancement by Schottky barrier-type junctions between the Pd nanoparticles and TiO₂ nanobelts.     

Nanocomposites of TiO 2 and Siloxane Copolymers as Environmentally Safe Flame-Retardant Materials †

Composites of titanium dioxide (TiO₂) nanoparticles and biocatalytically synthesized dimethylsiloxane copolyamides were prepared, and their thermal and flame-retardant properties were investigated. The flammability properties such as heat release capacity and total heat release were measured from microscale cumbustion calorimetry (MCC). The thermal degradation temperatures, char yields, and the heat-release capacities of these nanocomposites were significantly improved over the pure polymers. The heat-release capacities of the siloxane copolymer nanocomposites with 20wt% of TiO₂ were found to be 167 and 129 J/g K, which is a 35% less than the pure polymers (260 and 194 J/g K, respectively). The SEM/EDAX surface-analysis studies on nanocomposite films and their char revealed that nanocrystalline-TiO₂ plays an important role in forming carbonaceous silicate char on the surface as a protective layer.     

低温吸附制备Au-TiO2复合薄膜及其光电化学性质

在低温条件下将预先合成的Au溶胶吸附到TiO₂薄膜上以制备纳米Au-TiO₂复合薄膜,以超高分辨率场发射扫描电镜(FESEM)、X射线衍射(XRD)及X射线光电子能谱(XPS)表征Au-TiO₂膜,并在UV辐照下测定了Au-TiO₂薄膜电极的光电化学性质。纳米Au呈金属态,平均粒径为(4.3±1.2) nm,负载量高,均匀地沉积于TiO₂薄膜表面。光电化学测试表明,沉积纳米Au后,TiO₂电极的光生电流提高近5倍,光生电压明显向负值增大,说明纳米Au可增强光生载流子的分离效率,促进电荷在电极与溶液界面间的转移。Au-TiO₂电极的电荷传递法拉第阻抗(R_ct)是TiO₂电极的一半,说明负载的纳米Au粒抑制了光生电子-空穴的复合,提高了电极中载流子浓度。     

浸渍-分解法制备高可见光催化活性的Bi2O3/TiO2纳米管阵列

用浸渍-分解法将Bi₂O₃纳米颗粒沉积在TiO₂纳米管壁上, 制备了Bi₂O₃/TiO₂纳米管阵列. 用电感耦合等离子体发射光谱(ICP-AES)测定了Bi₂O₃/TiO₂ 纳米管阵列的化学组分, 利用X 射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)和紫外-可见(UV-Vis)吸收光谱表征了所制备的样品. 通过在可见光下(λ>400 nm)降解甲基橙(MO)水溶液来评价样品的光催化活性. 结果表明, Bi₂O₃纳米颗粒均匀地沉积在TiO₂纳米管中. Bi₂O₃/TiO₂纳米管阵列具有比纯Bi₂O₃膜和N-TiO₂纳米管阵列高得多的可见光催化活性. Bi₂O₃/TiO₂纳米管阵列活性的增强是其强可见光吸收和Bi₂O₃与TiO₂之间形成的异质结的协同作用的结果.     

LB技术制备SnO2-TiO2无机交替纳米薄膜

采用LB技术将SnO₂纳米粒子和TiO₂纳米粒子组装进花生酸的交替多层膜，通过热处理除去膜中的有机成分后，采用红外光谱、紫外可见光谱、X-光电子能谱、低角X-射线衍射、原子力显微镜以及扫描电子显微镜等手段对处理后的膜进行了形貌、组成和结构表征，表明制得的是SnO₂纳米粒子-TiO₂纳米粒子无机-无机交替的均匀的纳米薄膜。     

超临界流体干燥法制备纳米TiO2-SnO2-SiO2复合光催化剂及其光催化性能研究

半导体多相光催化法作为一种污染治理新技术越来越受到人们的重视,在所使用的半导体光催化剂中,TiO2以无毒,催化活性高,价廉,无污染等特点,成为最具有前途的绿色环保型催化剂之一[1],但其自身具有局限性,如禁带宽度大,需在近紫外光下才能激发产生电子空穴对,对太阳光的利用率仅     

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.     

低温静电自组装法制备贵金属修饰TiO_2纳米结构薄膜及其增强的光催化性能(英文)

以碱-水热法在金属Ti片上原位生长了TiO2纳米结构(纳米花和纳米线)薄膜,并采用低温静电自组装方法将超细贵金属(金、铂、钯)纳米颗粒均匀沉积于多孔TiO2薄膜上.负载于Ti片上的贵金属/TiO2纳米结构薄膜具有一体化结构、多孔架构和高光催化活性.超高分辨率场发射扫描电子显微镜(FESEM)直接观察表明贵金属纳米颗粒在TiO2表面分布均匀,且颗粒之间相互分离,金、铂、钯纳米颗粒的平均粒径分别约为4.0、2.0和10.0nm.俄歇电子能谱(AES)纵深成分分析表明贵金属不仅沉积于薄膜表面,且大量分布于TiO2纳米结构薄膜内部,其深度超过580 nm.X射线光电子能谱(XPS)分析表明,经300°C下在空气中热处理后,纳米金仍保持金属态,纳米铂部分被氧化成PtOabs,而钯粒子则完全被氧化成氧化钯(PdO).以低温静电自组装法沉积贵金属,贵金属负载量可通过调节组装时间与溶胶pH值来控制.光催化降解甲基橙的结果表明,沉积的纳米金和铂能显著增加TiO2纳米结构薄膜的光催化活性,说明金和铂粒子可促进光生载流子的分离;但负载的PdO对TiO2薄膜的光催化性能增强几乎无作用.     

Electrochemical preparation of PMeT/TiO<Subscript>2</Subscript> nanocomposite electrochromic electrodes with enhanced long-term stability

In this work, 3-methylthiophene (MeT) was electrochemically incorporated with nano- and mesoporous TiO₂ films to form poly(3-methylthiophene) (PMeT)/TiO₂ nanocomposite electrochromic electrodes. TiO₂ films, which were previously coated on the ITO glass sheets through a well-established technique, were introduced to enhance the adhesion of the polymers to the substrates and thus increase the long-term stability of the devices. With this effort, the nanocomposite electrodes were found to retain up to 60% of their optical response after 3,500 deep and double potential steps and retain up to 50% of their electroactivity after 10⁴ same steps, exhibiting enhanced long-term stability. Switching time and the maximum optical contrast (ΔT%) of the nanocomposite electrodes were found to be 0.6 s and 45%, respectively. Moreover, our work showed that electrochemically incorporating conductive polymers (CPs) with TiO₂ mesoporous films was an effective method to form high-quality CP/TiO₂ nanocomposite electrodes, which can be used widely in battery cathodes, photovoltaic cells, photocatalytic reaction, and photoelectrochromic cells and were supposed to enhance their performances.     

Fabrication and characterization of TiO<Subscript>2</Subscript>–SiO<Subscript>2</Subscript> composite nanoparticles and polyurethane/(TiO<Subscript>2</Subscript>–SiO<Subscript>2</Subscript>) nanocomposite films

TiO₂–SiO₂ composite nanoparticles were prepared by a sol–gel process. To obtain the assembly of TiO₂–SiO₂ composite nanoparticles, different molar ratios of Ti/Si were investigated. Polyurethane (PU)/(TiO₂–SiO₂) hybrid films were synthesized using the “grafting from” technique by incorporation of modified TiO₂–SiO₂ composite nanoparticles building blocks into PU matrix. Firstly, 3-aminopropyltriethysilane was employed to encapsulate TiO₂–SiO₂ composite nanoparticles’ surface. Secondly, the PU shell was tethered to the TiO₂–SiO₂ core surface via surface functionalized reaction. The particle size of TiO₂–SiO₂ composite sol was performed on dynamic light scattering, and the microstructure was characterized by X-ray diffraction and Fourier transform infrared. Thermogravimetric analysis and transmission electron microscopy (TEM) employed to study the hybrid films. The average particle size of the TiO₂–SiO₂ composite particles is about 38 nm when the molar ratio of Ti/Si reaches to1:1. The TEM image indicates that TiO₂–SiO₂ composite nanoparticles are well dispersed in the PU matrix.