Preparation and characterization of low density polystyrene/TiO2 core–shell particles for electronic paper application

In order to reduce the density mismatch between TiO₂ and the low dielectric medium and improve the dispersion stability of the electrophoretic particles in the low dielectric medium for electrophoretic display application, polystyrene/titanium dioxide (PS/TiO₂) core–shell particles were prepared via in-situ sol–gel method by depositing TiO₂ on the PS particle which was positively charged with 2-(methacryloyloxy)ehyl trimethylammonium chloride (DMC). The morphology and average particle size of PS/TiO₂ core–shell particles were observed by transmission electron microscopy (TEM), scanning electron microscope (SEM) and particle size analyzer. It was found that density of PS/TiO₂ core–shell particles were reduced obviously and the particles can suspend in the low dielectric medium of low density. The PS/TiO₂ core–shell particles can endure ultrasonic treatment because of the interaction between TiO₂ and PS. Zeta potential and electrophoretic mobility of the fabricated core–shell particles in a low dielectric medium with charge control agent was measured to be −44.3 mV and −6.07 × 10⁻⁶ cm²/Vs, respectively, which presents potential in electronic paper application.     

Optimized monolayer grafting of 3-aminopropyltriethoxysilane onto amorphous,anatase and rutile TiO2

Experimental conditions were studied for optimized attachment of 3-aminopropyltriethoxysilane (APTES) onto amorphous, anatase and rutile titanium dioxide (TiO₂) surfaces. The attachment process and extent was characterized using X-ray photoelectron spectroscopy (XPS). In particular, the effect of attachment time, silane concentration, reaction temperature and the TiO₂ crystalline structure on the growth kinetics of the silane layers was studied. The measurements reveal that typically monolayers are more dense on amorphous than on crystalline TiO₂. The results show that critical experimental conditions exist where APTES attachment to the TiO₂ surface changes from a monolayer to a multilayer growth mode. The obtained results and parameters to produce optimized APTES layers are of a high practical relevance as APTES attachment often constitutes the initial step for organic modification of TiO₂ surface with biorelevant molecules such as proteins, enzymes or growth factors.     

Suppress polystyrene thin film dewetting by modifying substrate surface with aminopropyltriethoxysilane

Aminofunctional organosilanes, such as 3-aminopropyltriethoxysilane (APTES), have been widely utilized as adhesion promoters, and have also been found to have the ability to prevent dewetting of polymer thin films from substrates. The APTES molecule contains an active terminal amino group that can hydrogen bond with the multiple hydroxylated head groups in itself and hydroxyl groups on a substrate, thus forming cyclic structures and a complex loose network at ambient conditions. Upon heating, the hydrogen bond can be broken, allowing more silanol groups to condense with each other and form siloxane linkages, hence tightening the three-dimensional network. When a polymer thin film is in contact with the APTES layer during the thermal process, the polymer chains can diffuse/penetrate into the APTES network while the network is being tightened by the additional crosslinking. The penetrated and subsequently anchored chains could help to stabilize the thin film on the substrate. This hypothesis was verified by dewetting studies of thin films of polystyrene (PS), having molecular weights above and below the entanglement molecular weight (M_e), from APTES and control surfaces when the systems were subjected to various treatments. Dewetting suppression was observed for PS/APTES that was thermally treated at ∼80 °C or 120 °C prior to the annealing of the thin film at higher temperatures. Much stronger suppression was noticed for PS having a molecular weight higher than M_e. When PS thin films were deposited onto a precured APTES network, no dewetting suppression was observed.     

Synthesis of Titania-supported Copper Nanoparticles via Refined Alkoxide Sol-gel Process

Nanoparticles of titania and copper-loaded titania were synthesized by a refined sol-gel method using titanium butoxide. Unlike the conventional sol-gel procedure of adding water directly, the esterification of anhydrous butanol and glacial acetic acid provided the hydrolyzing water. In addition, acetic acid also served as a chelating ligand to stabilize the hydrolysis-condensation process and minimize the agglomeration of titania. Following the hydrolysis, Cu/TiO₂ was prepared by adding copper chloride to titania sol. The sol was dried, then calcined at 500^°C to remove organics and transformed to anatase titania which was verified by XRD. Cu/TiO₂ was further hydrogen-reduced at 300^°C. The recovery of Ti was exceeded by an average of 95% from titanium butoxide. TEM micrographs show that the Cu/TiO₂ particles are near uniform. The average crystallite sizes are 17–20 nm estimated from the peak broadening of XRD spectra. The bandgaps of TiO₂ and reduced Cu/TiO₂ range from 2.70 to 3.15 eV estimated from the diffusive reflective UV-Vis spectra. XPS analysis shows that Cu 2p_3/2 is 933.4 eV indicating primary Cu₂O form on the TiO₂ supports. The binding energy of Ti does not exhibit chemical shift suggesting negligible interaction of Cu cluster and TiO₂ support.     

Preparation and Characterization of Nano‐TiO2 Doped Polystyrene Materials by Melt Blending for Inertial Confinement Fusion

Abstract

Nano‐TiO₂ doped polystyrene (PS) materials (TiO₂‐d‐PS) used for inertial confinement fusion (ICF) targets were prepared by means of melt blending. The effect of the pretreatment process, including coupling agents and ultrasonic dispersion on nano‐TiO₂, was studied. Tensile tests were conducted to evaluate the mechanical properties of the TiO₂‐d‐PS materials. Scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS) was used to characterize the degree of dispersion of nano‐TiO₂ in the PS matrix. Transmission electron microscopy (TEM) and dynamic contact angle (DCA) measurements were introduced to demonstrate the surface state of untreated and pretreated nano‐TiO₂. The results showed that coupling agents improved the interfacial adhesion between the PS matrix and dopants; ultrasonic dispersion contributed to the increase in the tensile properties of the TiO₂‐d‐PS materials. The dispersion stability of nano‐TiO₂ powder and the stability of the TiO₂‐d‐PS materials were significantly enhanced through pretreatment, which was supported by the increase in the DCA when the nano‐TiO₂ was pretreated by the coupling agent. The results of SEM and EDS indicated that the nano‐TiO₂ dispersed homogeneously in the PS matrix. The pretreatment process is an effective way to break the aggregation of nano‐TiO₂, which was confirmed by TEM results. Melt blending is a feasible method to prepare PS doped high Z element ICF target materials.     

XPS and XRD investigation of Co/Pd/TiO2 catalysts by different preparation methods

In the article, the Co/Pd/TiO₂, Co/TiO₂ and Pd/TiO₂ catalysts prepared by the impregnation and sol–gel method are studied by using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The result shows that Co²⁺ and metal Pd may act as the active center for the direct synthesis of acetic acid from CH₄ and CO₂ by a two-step reaction sequence. When the catalysts are prepared by the sol–gel, Co²⁺ can enter the crystal lattice of the TiO₂, causing the phase transition from anatase to rutile at lower temperature, but existence of Pd²⁺ can prevent from the phase transition. When the catalysts are prepared by the impregnation, the phase transition is inhibited not only Co²⁺ but also Pd²⁺.     

Poly(vinyl chloride)-<Emphasis Type="Italic">graft</Emphasis>-poly(<Emphasis Type="Italic">N</Emphasis>-vinyl caprolactam) graft copolymer: synthesis and use as template for porous TiO<Subscript>2</Subscript> thin films in dye-sensitized solar cells

Poly(N-vinyl caprolactam) (PNVCL) side chains were grafted to a poly(vinyl chloride) (PVC) backbone via atom transfer radical polymerization. The synthesized PVC-g-PNVCL graft copolymer was templated for the preparation of porous TiO₂ thin films, which involved a sol–gel reaction and calcination process. The interaction of the carbonyl groups in the PVC-g-PNVCL with the titania was revealed by FT-IR spectroscopy. X-ray diffraction and transmission electron microscopy analysis showed the formation of porous TiO₂ thin films with the anatase phase. A series of porous TiO₂ thin films with different pore sizes and porosities was prepared by varying the solution compositions and were used as photoelectrodes in dye-sensitized solar cells (DSSC) with a polymer electrolyte. The DSSC performed best when using the TiO₂ film with higher porosity, lower interfacial resistance, and longer electron life time. The highest energy conversion efficiency, photovoltage (V _oc), photocurrent density (J _sc), and fill factor (FF) were 1.2%, 0.68 V, 3.2 mA/cm², and 0.57 at 100 mW/cm², respectively, for the quasi-solid state DSSC with a 730-nm-thick TiO₂ film.     

Morphology and Crystallization in Polystyrene/polyamide 6 Blends: Influence of a Reactive Compatibilizer and Nano-TiO2

A polystyrene (PS)/polyamide 6 (PA6) (70/30, weight ratio) blend in the presence of terminal malic anhydride functionalized PS (FPS) and nano-TiO₂ were prepared using a meltmixing technique. The morphology of the blend was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The crystallization behavior of the PA6 phase in the blend was studied using DSC techniques. The results showed that by adding 7.5 phr nano-TiO₂, the size of the dispersed PA6 domains was dramatically decreased; An additional 1.5 phr FPS to the PS/PA6/TiO₂ blend, for reactive blending, caused the size of the dispersed PA6 domain to become even smaller and more uniform, and a weak, broad crystallization exotherm of PA6 was observed. However, the degree of crystallinity of PA6 in PS/PA6/TiO₂/FPS blend was sharply increased.     

The effect of surface modification with silane coupling agent on suppressing the photo-catalytic activity of fine TiO2 particles as inorganic UV filter

The effect of surface modification with 3-aminopropyltriethoxysilane (APTES) and n-propyltriethoxysilane (PTES) on photo-catalytic activity and UV-shielding ability of fine TiO₂ particles were investigated. The number of surface groups (N_R) [nm⁻²] which shows the density of modifier on TiO₂ surface was calculated from the results of elemental analysis and BET measurement. The modified samples of which N_R are different were obtained by changing the concentration of modifier. When the photo-catalytic activity and UV-shielding ability of modified samples were evaluated, it was found that APTES was more effective modifier than PTES to obtained samples with low photo-catalytic activity and high UV-shielding ability. This is probably because the adsorption mechanisms on TiO₂ surface between modifiers were different and N_R is a key factor to control the performances of fine TiO₂ particles. The result of zeta potential showed that surface character of modified samples was varied by changing N_R. It suggested from these results that N_R affected the photo-catalytic activity and UV-shielding ability because N_R changed surface character of modified samples.     

电沉积处理与染料敏化纳米薄膜太阳电池的优化

采用阳极氧化水解法对染料敏化纳米TiO₂薄膜太阳电池的光阳极进行不同方式的电沉积优化处理.借助x射线衍射仪对处理后的样品进行分析，通过超高分辨率场发射扫描电子显微镜对导电玻璃以及电沉积处理前后纳米多孔薄膜表面进行了粒径和形貌的扫描.染料敏化太阳电池实验测试结果表明，电沉积处理和修饰后可以明显提高光生电子的收集率，增大短路电流密度，提高电池效率. 关键词： 2')" href="#">纳米TiO₂ 染料敏化 电沉积 太阳电池     

Hybrid system of iron porphyrin on aminosilanized c-Si

Adsorption of iron porphyrin (Fe^IIITPPS₄) Fe(III)meso-tetra(4-sulfonatophenyl) porphine on aminosilanized surface of crystalline Si (c-Si) was investigated. Formation of nanometric structures of Fe^IIITPPS₄ on c-Si, the surface of which has been modified by various silanization procedures, was studied. Aqueous, ethanol and acetone solutions of 3-aminopropyltrietoxysilane (APTES) were prepared for deposition on c-Si by spinning or immersion techniques. Smooth homogeneous APTES films of thickness 100–500 nm were produced by multiple spin coating procedure. Thin APTES films of thickness 2.5 nm were fabricated by dipping technique followed by washing procedure. Hybrid system of Fe^IIITPPS₄/APTES/Si was prepared from a drop of Fe^IIITPPS₄ aqueous solution put on aminosilanized Si surface or by dipping the Si wafer in Fe^IIITPPS₄ aqueous solution. Nanostructures of size 50–250 nm were formed along with large rings of Ø50–100 μm which have been observed at chemisorption of highly concentrated (1 mM) Fe^IIITPPS₄ aqueous solution. Spectroscopic ellipsometry was used to characterize the APTES layer and to investigate the aggregation state of Fe^IIITPPS₄. The studies provided allowed one to presume that covalent bonds were formed between amino-groups of APTES and functional groups of sulfonic acid in porphyrin leading to immobilization of Fe^IIITPPS₄ on Si substrate.     

Characteristics and heterostructure of metal-doped TiO2/ZnO nanocatalysts

In this study, Ag or Al-doped TiO₂/ZnO heterostructure nanocatalysts were prepared using a sol-gel method for photocatalysis to evaluate the degradability. The photocatalytic behavior was evaluated by the degradation of methylene blue (MB) under ultraviolet (UV) light irradiation. Photocatalytic studies suggested that 1 mol% Ag-doped TiO₂/ZnO (TiO₂/ZnO = 0.75/0.25) heterostructure nanocatalysts showed higher photocatalytic activity, and that the degradation efficiency can reach 83% in 4 h, 14% higher than that for pure TiO₂. Finally, the photocatalysis mechanism for the Ag-doped TiO₂/ZnO heterostructure nanocatalysts is discussed.     

Nano TiO2 film electrode for electrocatalytic reduction of furfural in ionic liquids

Nanoporous TiO₂ having enhanced surface area was synthesized by sol–gel method. An “environmental friendly” method for production of furfuryl alcohol was presented by electrocatalytic reduction of furfural to furfuryl alcohol in ionic liquid medium at the surface of nanoporous TiO₂ film electrode. The heterogeneous catalytic redox behaviour of a nanoporous TiO₂ film electrode surface was investigated by cyclic voltammetry (CV). It was found that the catalytic reduction of furfural by Ti(IV)/Ti(III) redox system on the nanoporous TiO₂ film surface. The electrode reaction mechanism is called catalytic (EC′) mechanism, current density can reach 38 mA/cm² and yielding an overall conversion efficiency of 61.7%.     

Study on the transformation from NaCl-type Na2TiO3 to layered titanate

NaCl-type crystal structure sodium titanate (Na₂TiO₃), which exhibits a unit cell parameter of a=4.49 Å, was obtained by high temperature molten salt reaction. An intermediate phase product with layered structure was prepared by leaching the obtained Na₂TiO₃. We propose that the layered titanate structure is composed of Na₂TiO₃ and H₂O, corresponding to the host-layer and guest-substance, respectively. Furthermore, the crystal structures of layered titanate were optimized by the density functional theory (DFT). This indicates that water molecules are distributed in an orderly manner in the interlayer through the formation of hydrogen-bonded chain. Moreover, the position of the adjacent lamella translates to c/2 along the c-axis after the intercalation of water.     

Preparation and photocatalytic properties of silver nanoparticles loaded on CNTs/TiO2 composite

In this study, new nanoscale photocatalyst based on silver and CNTs/TiO₂ was successfully prepared by photoreduction method. The prepared Ag-CNTs/TiO₂ was characterized by TEM, XRD and XPS. The photocatalytic activity was also evaluated by photocatalytic degradation of Reactive Brilliant Red X-3B dye. The results indicated that the photocatalytic efficiency of CNTs/TiO₂ increased in the presence of Ag nanoparticles and the photocatalysis reaction followed a first order kinetics. The kinetic constant of Ag-CNTs/TiO₂ for dye degradation was nearly 1.2 times than that of CNTs/TiO₂, which indicated decorating Ag nanoparticles on CNTs/TiO₂ could enhance the photocatalytic ability.     

Design of europium doped SiO2–TiO2 hybrids as novel luminescent photocatalyst

SiO₂/TiO₂:Eu³⁺ composite materials were facially prepared by the sol–gel technique and all the as-derived powders exhibited europium characteristic red emissions under multiple excitation wavelengths extended to visible range (395 and 465 nm). The influence factors such as Si/Ti ratio, orders of hydrolysis, annealing temperature and doping concentration were systematically studied. The novel photocatalytic behavior for removing phenol was thoroughly investigated.     

Hydrothermal synthesis of TiO2 nanocrystals in different basic pHs and their applications in dye sensitized solar cells

In this research TiO₂ nanocrystals with sizes about 11–70 nm were grown by hydrothermal method. The process was performed in basic autoclaving pH in the range of 8.0–12.0. The synthesized anatase phase TiO₂ nanocrystals were then applied in the phtoanode of the dye sensitized solar cells. It was shown that the final average size of the nanocrystals was larger when the growth was carried out in higher autoclaving pHs. The photoanodes made of TiO₂ nanocrystals prepared in the pHs of 8.0 and 9.0 represented low amounts of dye adsorption and light scattering. The performance of the corresponding dye sensitized solar cells was also not acceptable. Nevertheless, the energy conversion efficiency was better for the state of pH of 9.0. For the photoanodes made of TiO₂ nanocrystals prepared at autoclaving pH of 10.0, the dye adsorption and light scattering were quite higher. The photovoltaic characteristics of the best cell in this state were 15.25 mA/cm², 740 mV, 0.6 and 6.8% for the short-circuit current density, open-circuit voltage, fill factor and efficiency, respectively. The photoanodes composed of TiO₂ nanocrystals prepared in autoclaving pHs of 11.0 and 12.0 demonstrated lower amount of dye adsorption and higher light scattering. This was quite considerable for the state of pH of 12.0. The energy conversion efficiencies were consequently decreased compared to that of the pH of 10.0. The optimum situation was finally discussed based on the nanocrystals size and its influence on the sensitization and light harvesting efficiency.     

Enhanced photocatalytic degradation of organic dyes by ultrasonic-assisted electrospray TiO2/graphene oxide on polyacrylonitrile/β-cyclodextrin nanofibrous membranes

Polyacrylonitrile (PAN)/β-cyclodextrin (β-CD) composite nanofibrous membranes immobilized with nano-titanium dioxide (TiO₂) and graphene oxide (GO) were prepared by electrospinning and ultrasonic-assisted electrospinning. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and X-ray diffraction (XRD) confirmed that TiO₂ and GO were more evenly dispersed on the surface and inside of the nanofibers after 45 min of ultrasonic treatment. Adding TiO₂ and GO reduced the fiber diameter; the minimum fiber diameter was 84.66 ± 40.58 nm when the mass ratio of TiO₂-to-GO was 8:2 (PAN/β-CD nanofibrous membranes was 191.10 ± 45.66 nm). Using the anionic dye methyl orange (MO) and the cationic dye methylene blue (MB) as pollutant models, the photocatalytic activity of the nanofibrous membrane under natural sunlight was evaluated. It was found that PAN/β-CD/TiO₂/GO composite nanofibrous membrane with an 8:2 mass ratio of TiO₂-to-GO exhibited the best degradation efficiency for the dyes. The degradation efficiency for MB and MO were 93.52 ± 1.83% and 90.92 ± 1.52%, respectively. Meanwhile, the PAN/β-CD/TiO₂/GO composite nanofibrous membrane also displayed good antibacterial properties and the degradation efficiency for MB and MO remained above 80% after 3 cycles. In general, the PAN/β-CD/TiO₂/GO nanofibrous membrane is eco-friendly, reusable, and has great potential for the removal of dyes from industrial wastewaters.     

Preparation and photocatalytic activity of bicrystal phase TiO2 nanotubes containing TiO2-B and anatase

Bicrystal phase TiO₂ nanotubes (NTS) containing monoclinic TiO₂-B and anatase were prepared by the hydrothermal reaction of anatase nanoparticles with NaOH aqueous solution and a heat treatment. Their structure was characterized by XRD, TEM and Raman spectra. The results showed that the bicrystal phase TiO₂ NTS were formed after calcining H₂Ti₄O₉·H₂O NTS at 573 K. The bicrystal phase TiO₂ NTS exhibit significantly higher photocatalytic activity than the single phase anatase NTS and Dessuga P-25 nanoparticles in the degradation of Methyl Orange aqueous solution under ultraviolet light irradiation, which is attributed to the large surface and interface areas of the bicrystal phase TiO₂ NTS.     

Two-step annealed CdS/CdSe co-sensitizers for quantum dot-sensitized solar cells

CdS/CdSe co-sensitizers on TiO₂ films were annealed using a two-step procedure; high temperature (300 °C) annealing of TiO₂/CdS quantum dots (QDs), followed by low temperature (150 °C) annealing after the deposition of CdSe QDs on the TiO₂/CdS. For comparison, two types of films were prepared; CdS/CdSe-assembled TiO₂ films conventionally annealed at a single temperature (150 or 300 °C) and non-annealed films. The 300 °C-annealed TiO₂/CdS/CdSe showed severe coalescence of CdSe QDs, leading to the blocked pores and hindered ion transport. The QD-sensitized solar cell (QD-SSC) with the 150 °C-annealed TiO₂/CdS/CdSe exhibited better overall energy conversion efficiency than that with the non-annealed TiO₂/CdS/CdSe because the CdSe QDs annealed at a suitable temperature (150 °C) provided better light absorption over long wavelengths without the hindered ion transport. The QD-SSC using the two-step annealed TiO₂/CdS/CdSe increased the cell efficiency further, compared to the QD-SSC with the 150 °C-annealed TiO₂/CdS/CdSe. This is because the 300 °C-annealed, highly crystalline CdS in the two-step annealed TiO₂/CdS/CdSe improved electron transport through CdS, leading to a significantly hindered recombination rate.