Synthesis and photoelectric property of poly(3-octylthiophene)/ferric oxide complexes

Ferric oxide was prepared by the supercritical fluid drying (SCFD) method. A conducting polymer composite, poly(3-octylthiophene)/ferric oxide (POT/Fe₂O₃) was first synthesized through the chemical method. X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), and Infrared spectroscopy (IR) show that there is a chemical interaction in the composite, which indicates that Fe₂O₃ was successfully coated by poly(3-octylthiophene) molecules. The energy gap of the poly(3-octylthiophene)/ferric oxide composite is lower at 0.448 eV, which also shows that the optical performance of the new material is far superior to POT or Fe₂O₃ separately, by Ultraviolet–Visible spectra (UV–Vis) and fluorescence spectroscopy (PL). Solar cell was sensitized by POT/Fe₂O₃. A solar-to-electric energy conversion efficiency of 0.258% was attained with the system.     

Biodegradable polyester hybrid nanocomposites containing titanium dioxide network and poly(ε-caprolactone): Synthesis and characterization

In this paper, biodegradable poly(ε-caprolactone)/titanium dioxide hybrid film materials were prepared via in situ sol-gel process with tetrabutyl titanate (TBT) as inorganic precursor in the presence of poly(ε-caprolactone) and were characterized by means of Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electronic microscopy (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The hybrids displayed microphase-separated structure on the nanometer scale. The studies of crystallization and melting behaviors of the hybrid films indicate that TiO₂ inorganic components have a considerable influence on behavior of crystallization of poly(ε-caprolactone) in hybrid materials.     

Surface characteristics and photoactivity of silver-modified palygorskite clays coated with nanosized titanium dioxide particles

This paper presents the results of a study in which nanosized titanium dioxide (TiO₂) crystal particles were coated onto the surface of palygorskite fibrous clay which had been modified by silver ions using titanium tetrachloride as a precursor. Coated TiO₂ particles with the anatase structure were formed after calcining at 400 °C for 2 h in air. Various analytical techniques were used to characterize the surface properties of titanium dioxide particles on the palygorskite. Transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses showed that TiO₂ particles were supported on the surface of the palygorskite clays and their size was in the range of 3–6 nm. The titanium oxide coatings were found to be very active for the photocatalytic decomposition of methylene blue.     

One-pot polyelectrolyte assisted hydrothermal synthesis of TiO2-reduced graphene oxide nanocomposite

We demonstrated a facile and efficient strategy for the fabrication of poly(diallyldimethylammonium chloride) (PDDA)-assisted reduced graphene oxide (RGO) sheets–titanium dioxide (TiO₂) in the absence of any seeds and surfactants. PDDA is used as both a reducing agent and a stabilizer to prepare the colloidal suspension of graphene nanosheets. The incorporation of PDDA successfully turns graphene nanosheets into general platforms for in situ growth of TiO₂. The prepared TiO₂–RGO has been thoroughly characterized by spectroscopic (Fourier-transform infrared spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy) and thermogravimetric analysis. Microscopy techniques (scanning electron microscopy, atomic force microscopy and transmission electron microscopy) have been employed to probe the morphological structures as well as to investigate the exfoliation of RGO sheets. It is interesting to see that the TiO₂–RGO composites exhibited excellent photocatalytic activity to hydrogen evolution.     

Synthesis and characterization of copper ions surface-doped titanium dioxide nanotubes

Copper ions surface-doped titanium dioxide nanotubes were prepared via an assembly process based on the reactions between Cu(NH₂CH₂CH₂NH₂)₂(OH)₂ and hydroxide radicals on the surface of TiO₂ nanotubes, followed by the heat treatment in air at 723 K. The as-prepared samples were characterized with infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, and fluorescence spectroscopy (FL). The photocatalytic activity of the copper ions surface-doped titanium dioxide nanotubes was investigated by photodegradation of Rhodamine B. The results showed that copper ions were successfully introduced onto the surface of TiO₂ nanotubes. And two kinds of copper species of Cu(I) and Cu(II) were found on TiO₂ surface. Copper ions act as electron trappers facilitating the separation of electrons and holes on the surface of TiO₂ nanotubes, which allows more efficiency for the photodegradation of Rhodamine B.     

Characterization and photoactivity of TiO2 sols prepared with triethylamine

Using triethylamine as a surface protective agent, a transparent and pale yellowish TiO₂ sol had been prepared at 90 °C. This method was very different from the traditional methods, which produced titanium dioxide nanoparticles with anatase crystalline structure either at high acid condition or high temperature. X-ray diffraction (XRD) and transmission electron spectroscopy (TEM) demonstrated that the as-prepared TiO₂ sol nanoparticles with anatase crystalline structure were uniformly distributed, and the average size was 3 nm. X-ray photoelectron spectroscopy (XPS) and UV-vis absorption spectra showed that triethylamine was adsorbed on TiO₂ sol particles surface. FTIR spectroscopy noted that TiO₂ sol particles had the similar spectra with Degussa P25. Photoactivity of the as-prepared TiO₂ sol was studied by investigating the photodegradation of methyl violet in hydrosol reaction system under visible light irradiation.     

Preparation of graphene–TiO2 nanocomposite and photocatalytic degradation of Rhodamine-B under solar light irradiation

GR–TiO₂ nanocomposite was prepared by simple chemical method using graphene oxide and titanium isopropoxide (Ti [OCH (CH₃)₂]₄) precursors. The crystalline nature of the composite was characterised by powder X-ray diffraction and the intercalation was explained by Raman spectroscopy. The morphology of the composite was analysed by field emission scanning electron microscopy. The elemental and quantitative measurement of the composite was determined by electron dispersive spectroscopy. The shape and size of the particle was measured by transmission electron spectroscopy and high resolution spectroscopy. The surface area and elemental composition of the composite was studied by using Brunauer–Emmett–Teller (BET) method and X-ray photoelectron spectroscopy. Photo-generated electrons were studied by photoluminescence spectra. The photocatalytic activity of nanocomposite was investigated by the degradation of Rhodamine-B (Rh-B) in an aqueous solution under solar light irradiation. The GR–TiO₂ demonstrates photocatalytic activity in the degradation with a removal rate of 98% under solar light irradiation as compared with pure TiO₂ (42%), graphite oxide (19%), and mechanical mixture GR + TiO₂ (60%) due to the increased light absorption intensity and reduction of electron–hole pair recombination with the intercalation of graphene and TiO₂. The results indicated that the GR–TiO₂ could be used as a catalyst to degrade Rh-B from coloured wastewater.     

Fabrication of carbon-core/TiO2-sheath nanofibers by carbonization of poly(vinyl alcohol)/TiO2 composite nanofibers prepared via electrospinning and an interfacial sol–gel reaction

Carbon-core/TiO₂-sheath nanofibers have been fabricated from poly(vinyl alcohol) (PVA)/TiO₂ composite nanofibers that were prepared by electrospinning an aqueous solution of PVA and introducing the thread-like droplets directly into a titanium tetraisopropoxide (TTIP)/heptane solution. The PVA/TiO₂ composite nanofibers were transformed into carbon/TiO₂ nanofibers by iodine vapor treatment at 353 K, which induced dehydration of PVA, followed by carbonization in N₂ at 873 K. The carbon/TiO₂ nanofibers had diameters of a few hundred nanometers and sheathes of tens of nanometers. The nanofibers were composed of carbon cores with a low degree of graphitization and TiO₂ sheaths with an anatase crystal structure. The electrical conductivity of the carbon/TiO₂ composite nanofibers was enhanced by 4 orders of magnitude compared with TiO₂ hollow nanofibers.     

Synthesis and conductive performance of antimony-doped tin oxide-coated TiO2 by the co-precipitation method

The synthesis of Sb–SnO₂/TiO₂ (SST) composites by assembling antimony-doped tin oxide (Sb–SnO₂) nanoparticles on the surface of titanium dioxide (TiO₂) is systematically investigated. X-ray diffraction data show that the SST composite materials with good crystallinity can be indexed as anatase TiO₂ phase and cassiterite SnO₂ phase. The scanning electron microscopy and transmission electron microscopy indicate that Sb–SnO₂ particles with average diameter of 25 nm have been successfully coated on the surface of TiO₂. In addition, the Ti–O–Sn band can be detected on the surface of TiO₂ through Fourier translation infrared spectroscopy. The influences of pH, Sn/Ti mole ratio, hydrolysis temperature and calcination temperature on the electrical resistivity of the SST powders are studied. Under the optimum experimental conditions, the electrical resistivity of the composite conductive powders is 2.546 × 10³ Ω cm. Therefore, the SST composite conductive powders are useful as conductive fillers for the application in antistatic materials.     

New insights into anatase crystallization behavior in ionothermal synthesis of nanostructured TiO<Subscript>2</Subscript>

The anatase crystallization behaviors in ionothermal synthesis (sol–gel method containing ionic liquid) of nanostructured TiO₂ were studied in this paper. It was found that the specific physical chemical characteristics of the water/ionic liquid mixture caused the formation path and crystallinity of anatase TiO₂ to depend on the H₂O/titanium dioxide precursor (titanium tetraisopropoxide, TIP) molar ratio. Hydroxylated titanium compound was a key intermediate for forming anatase TiO₂. It could be directly formed from hydrolysis of titanium dioxide precursor or ionic liquid-induced water dissolution of the condensation product. X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) data indicated that a higher hydroxyl group ratio content of hydroxylated titanium compound was obtained at medium H₂O/TIP molar ratio and from the system containing hydrophilic ionic liquid, such as 1-butyl-3-methylimidazolium tetrafluoroborate ([BuMIm]⁺[BF₄]⁻). The self organization ability of ionic liquid drove anatase crystallization through dehydration of the Ti–OH group of hydroxylated titanium compound in the thermal annealing process. As for the particle size of TiO₂, TEM results indicated smaller particle size of TiO₂ was obtained at medium H₂O/TIP molar ratio case.     

Photocatalytic activity of nanostructured γ-Al2O3/TiO2 composite powder formed via a polyelectrolyte-multilayer-assisted sol–gel reaction

Nanostructured, γ-Al₂O₃/TiO₂ composite powder was fabricated via an in situ, sol–gel reaction of titanium iso-propoxide in a self-assembled, polyelectrolyte multilayer (PEM) formed on the surface of high-specific-area, polycrystalline, γ-Al₂O₃ lamellas. The infiltration of the titanium precursor into the PEM, followed by the hydrolysis and condensation reactions with the water absorbed in the PEM after annealing, resulted in the formation of a nanostructured TiO₂ layer on the surface of the γ-Al₂O₃ lamellas. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) were employed to evaluate the morphology, the chemical composition and the crystallinity of the γ-Al₂O₃/TiO₂ particles of the composite powder. The as-formed, nanostructured, γ-Al₂O₃/TiO₂ composite powder exhibited a 2.7-times-higher photo-activity in the near-UV region compared to commercially available TiO₂ (Degusa P25), as monitored by the photo-decomposition of a methylene blue (MB) dye.     

Photocatalytic activity of polypyrrole/TiO<Subscript>2</Subscript> nanocomposites under visible and UV light

A series of polypyrrole (PPy)/titanium dioxide (TiO₂) nanocomposites were prepared in different polymerization conditions by ‘in situ’ chemical oxidative polymerization. The nanocomposites were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectra (FT-IR), X-ray photoelectron spectroscopy spectra (XPS), and UV–Vis diffuse reflectance spectra. The photocatalytic degradation of methyl orange (MO) was chosen as a model reaction to evaluate the photocatalytic activities of TiO₂/PPy catalysts. The results show that a strong interaction exists at the interface between TiO₂ and PPy, the deposition of PPy on TiO₂ nanoparticles can alleviate their agglomeration, PPy/TiO₂ nanocomposites show stronger absorbance than neat TiO₂ under the whole range of visible light. The obtained PPy/TiO₂ nanocomposites exhibit significantly higher photocatalytic activity than the neat TiO₂ on the degradation of MO aqueous solution under visible and UV light illumination. The reasons for improving the photocatalytic activity were also discussed.     

Calcification capacity of porous pHEMA–TiO2 composite hydrogels

Many investigations have been attempted to promote calcification of synthetic polymers for applications as orthopaedic and dental implants. In this study, novel titanium dioxide (TiO₂) reinforced porous poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogels were synthesized. Calcification capacity of the composite polymers was examined using light microscopy, scanning electron microscopy and Fourier transform infrared spectroscopy after incubation of the materials in a simulated body fluid up to 53 days. Mechanical strength, porosity and in vitro cytotoxicity were also investigated. Calcification capacity of porous pHEMA was significantly enhanced by the addition of TiO₂ particulates. Infiltration of calcium phosphate, up to 1000 μm, was observed. The diffusion capacity of calcium ions was affected by the porosity and the interconnectivity of pores in the hydrogel polymers which were influenced by the presence of TiO₂ and the monomer concentration. Cell viability tests indicated that porous hydrogels containing 7.5% TiO₂ were not toxic to 3T3 fibroblast cells. These results demonstrate that incorporating TiO₂ nanoparticulates can promote enhanced formation of calcium phosphate whilst maintaining the porosity and interconnectivity of the hydrogel polymers and would be very useful for the development of orthopaedic tissue engineering scaffolds.     

Controlled synthesis and characteristics of antireflection coatings of TiO2 produced from a organometallic colloid

Antireflection titanium dioxide (TiO₂) coatings have been developed on monocrystalline silicon by a sol–gel spin-coating process using titanium di-isopropoxidebis(acetylacetonate) colloidal precursor solution. The effect of titanium content in the precursor, spin rate, sintering duration and temperature have been studied and their effect on coating thickness and optical properties (i.e., refractive index and reflectivity) were investigated. The influence of post-deposition sintering temperature on the optical characteristics, composition and the microstructure of the coatings have been evaluated by UV–vis spectroscopy, ellipsometry, X-ray photoelectron spectroscopy, atomic force microscopy and X-ray diffraction techniques. Solar cells made on silicon wafers with TiO₂ as antireflection layer showed enhancement of more than 20% in short circuit current density in comparison to a cell devoid of the TiO₂ coating.     

Fabrication of TiO2/ZnO composite nanofibers by electrospinning and their photocatalytic property

TiO₂/ZnO composite nanofibers with diameters in the range of 85–200 nm were fabricated via the electrospinning technique using zinc acetate and titanium tetra-isopropoxide as precursors, cellulose acetate as the fiber template, and N,N-dimethylformamide/acetone 1:2 (v/v) mixtures as the co-solvent. After treated with 0.1 mol/L NaOH aqueous solution, TiO₂/zinc acetate/cellulose acetate composite nanofibers were transformed into TiO₂/Zn(OH)₂/cellulose composite nanofibers. TiO₂/ZnO composite nanofibers were obtained by calcinating the hydrolyzed composite fibers at 500 and 700 °C for 5 h. The structure and morphology of composite nanofibers were characterized by scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. With the blending of ZnO into TiO₂, a new crystallite ZnTiO₃ was formed in addition to the ZnO and TiO₂ crystallites, and the ultraviolet light absorption efficiency was enhanced according to the UV–vis diffuse reflectance spectroscopy. The photocatalytic activity of TiO₂/ZnO composite nanofibers toward the decomposition of Rhodamine B and phenol was investigated. Almost 100% Rhodamine B and 85% phenol were decomposed in the presence of TiO₂/ZnO composite nanofibers under mild conditions. The results demonstrated that the blending of ZnO in the TiO₂/ZnO composite nanofibers increased the photocatalytic efficiency. The optimum ZnO content in the TiO₂/ZnO composite nanofibers was 15.76 wt% to reach the most efficient photocatalytic activity. A schematic diagram of photocatalytic mechanism of TiO₂/ZnO composite nanofibers was also presented.     

Pentacene thin-film transistor with poly(methyl methacrylate-co-methacrylic acid)/TiO2 nanocomposite gate insulator

A poly(methyl methacrylate-co-methacrylic acid) (PMMA-co-MAA) and titanium dioxide (TiO₂) composite was fabricated to use as a gate insulator in pentacene-based organic thin-film transistors (OTFTs). The dispersion stability was confirmed by observing the sedimentation time of TiO₂ nanoparticles in the PMMA-co-MAA solution, which is essential to avoid a severe gate-leakage current in OTFTs. From the measured capacitance-frequency characteristics, a dielectric constant value of 4.5 was obtained for the composite film and 3.3 for the PMMA-co-MAA film. Consequently, we could enhance the field-induced current and reduce the threshold voltage of OTFT by adopting the composite insulator, without augmenting the gate-leakage current.     

Polymer solar cells with a TiO2:Ag layer

Photovoltaic (PV) polymer solar cells with Ag and titanium dioxide were fabricated to improve the PV performance by increasing the amount of Ag in TiO₂ (by 3, 5, 7, and 10%). Sol–gel method was used to obtain amorphous or crystalline form of titanium dioxide layers. The solar cells with poly(3-hexylthiophene) and [6,6]-phenyl-C61-butyric acid methyl ester active layer in two various positions of titanium dioxide in device were tested. Higher PV performance was received by introducing TiO₂ with 5% of Ag between ITO and PEDOT:PSS in device and by heating the layer at 130 °C. The viscosity of applied PEDOT:PSS strongly influences the values of power conversion efficiency of the constructed polymer devices with titanium dioxide.     

The influence of surfactants on the roughness of titania sol–gel films

Substrate dipping in a composite sol–gel solution was used to prepare both smooth and rough thin films of titanium dioxide (TiO₂) on commercial fiberglass. The deposition of a composite film was done in a beaker using a solution of titanium (IV) isopropoxide as the sol–gel precursor and cetyltrimethyl ammonium bromide as the surfactant. In order to establish a correlation between experimental conditions and the titanium oxide produced, as well as the film quality, the calcined samples were characterized using Raman spectroscopy, UV–vis spectrophotometry, scanning electron microscopy and atomic force microscopy. One of the most important results is that a 61-nm TiO₂ film was obtained with a short immersion of fiberglass into the sol–gel without surfactant. In other cases, the deposited film consisted of a titanium precursor gel encapsulating micelles of surfactant. The gel films were converted to only the anatase phase by calcining them at 500 °C. The resulting films were crystalline and exhibited a uniform surface topography. In the present paper, it was found that the TiO₂ films prepared from the sol–gel with a surfactant showed a granular microstructure, and are composed of irregular particles between 1.5 and 3 μm. Smooth TiO₂ films could have useful optical and corrosion-protective properties and, on other hand, roughness on the TiO₂ films can enhance the inherent photocatalytic activity.     

聚吡咯/纳米二氧化钛的制备及电化学性能

采用化学原位聚合的方法制备了聚吡咯/二氧化钛(PPy/TiO_2)复合物,其中聚吡咯和二氧化钛的质量比分别为1∶1、2∶1、3∶1、4∶1,将其作为电化学超级电容器的电极材料,采用扫描电子显微镜和X射线衍射仪研究了PPy/TiO_2的形貌和相组成,通过电化学测试研究了PPy/TiO_2的电化学性能.结果表明:TiO_2均匀地包覆在PPy基体中,PPy/TiO_2的电化学性能明显优于纯PPy;当PPy与TiO_2的质量比为3∶1时复合材料的电化学性能最佳,即在2 A/g充放电电流密度下,其比电容达到了255.68 F/g,比纯PPy提高了2倍左右;在1 A/g充放电电流密度下,循环充放电1 000圈之后PPy/TiO_2的比电容保持率为87.2%,纯PPy的比电容保持率仅为46.9%.     

Active properties of thermally excited titanium dioxide/silica composite material for the decomposition of gaseous toluene

Decomposition of gaseous toluene and oxidation of CO on thermally excited titanium dioxide (TiO₂)/silica (SiO₂) composite material were investigated using a simple flow system. TiO₂/SiO₂ composite bead was superior to TiO₂ (anatase) or TiO₂/alumina in the thermally excited activation for toluene decomposition. The composite effect of TiO₂/SiO_2, bead was recognized in our study. ESR studies showed the existence of Ti³⁺ in the material. This means that oxygen vacancy would be generated by thermally excitation of TiO₂ in the composite material.