Development and characterization of a titanosilicate ETS-10-coated optical fiber reactor towards the photodegradation of methylene blue

An optical fiber reactor (OFR) system containing uniformly distributed quartz fibers coated with titanosilicate ETS-10 crystals was investigated. Optimum ETS-10 film thickness (～1.5 μm) and coating length (15 cm) were determined from the light propagation analysis in a single ETS-10-coated fiber. The nearly constant value of the attenuation coefficient (α ≈ 0.10 cm^?1) for films with different thickness indicated uniform fiber surface coverage with these films. The extinction coefficient, ?, decreased from ～1.6 to ～1.0 μm^?1 with ETS-10 film thickness increasing from ～0.5 to ～1.5 μm, which suggested less contact per unit film thickness between light and ETS-10 crystals inside thicker films, likely due to their lower crystal packing density. Photodegradation of methylene blue (MB) conducted in the OFR showed higher photocatalytic activity for thicker ETS-10 films. Although higher MB photodegradation rates were obtained at higher light intensity, the apparent quantum efficiency, Φ, decreased with increasing light intensity. This is consistent with the charge separation mechanism for MB photodegradation in the UV light range investigated. All ETS-10 samples investigated showed ～4–5 times higher Φ values in the OFR than in the slurry reactor, likely due to the unique light/photocatalyst/reactant contact and high fiber packing density in the OFR.     

Anti-biofouling properties of amphiphilic phosphorylcholine polymer films

Surfaces of amphiphilic phosphorylcholine polymer (PC1036) prepared by spin-coating were characterized by spectroscopic ellipsometry, water contact angle and atomic force microscopy. The antifouling properties of the PC1036 films to marine benthic diatom Nitzschia closterium MMDL533 were also investigated. The results showed that the dry PC1036 film promoted the adhesion of N. closterium MMDL533 because the hydrophobic lauryl groups were present in the film surface. The 2 h-swelled PC1036 films had excellent anti-fouling properties with extremely low attachment densities and retention densities no matter what the annealing temperature was. The thickness of the coated films lower than 147 Å had a profound effect on the film anti-fouling properties. Otherwise, when the film thickness was higher than that value, there was no more improvement of diatom cell reduction observed. The annealing temperature had only a little effect on the film resistant to diatom adhesion, which might be attributed to two factors including the PC group packing densities in the outer PC layer and the equilibrated water volume fraction in the 2 h-swelled PC1036 films.     

High-surface-area microporous carbon as the efficient photocathode of dye-sensitized solar cells

This paper reports on the application of cornstalks-derived high-surface-area microporous carbon (MC) as the efficient photocathode of dye-sensitized solar cells (DSCs). The photocathode, which contains MC active material, Vulcan XC–72 carbon black conductive agent, and TiO₂ binder, was obtained by a doctor blade method. Electronic impedance spectroscopy (EIS) of the MC film uniformly coated on fluorine doped SnO₂ (FTO) glass displayed a low charge-transfer resistance of 1.32 Ω cm². Cyclic voltammetry (CV) analysis of the as-prepared MC film exhibited excellent catalytic activity for I₃^?/I^? redox reactions. The DSCs assembled with the MC film photocathode presented a short-circuit photocurrent density (J_sc) of 14.8 mA cm^?2, an open-circuit photovoltage (V_oc) of 798 mV, and a fill factor (FF) of 62.3%, corresponding to an overall conversion efficiency of 7.36% under AM 1.5 irradiation (100 mW cm^?2), which is comparable to that of DSCs with Pt photocathode obtained by conventional thermal decomposition.     

CdS thin film: Synthesis and characterization

CdS thin films have been deposited by dip technique using succinic acid as a complexing agent. The structural characterizations of films have been studied by X-ray diffraction. X-ray diffraction pattern prove crystallinity of the deposited films that crystallize in the cubic phase of CdS. The films show high absorption and band gap value which were found to be 2.58 eV. The specific conductivity of the film was found to be in the order of 10^?7 (Ω cm)^?1.     

Preparation of ZnO nanoparticles and characteristics of dye-sensitized solar cells based on nanoparticles film

ZnO nanoparticles were synthesized by hydrolization method and the effects of zinc nitrate concentration and reaction temperature on the resulted particle properties were studied. The transmission of the as-prepared and calcined films and their optical band gaps are measured and calculated respectively. Furthermore, as an application of the ZnO nanoparticles film, dye-sensitized solar cells based on it were successfully fabricated and the cell performances were characterized. The short circuit current for ZnO nanoparticles film DSSCs is 1.35 mA cm^?2, which indicates good value of the prepared film using this technique.     

Evolution of microstructure and crack pattern in NiO thin films under 200 MeV Au ion irradiation

NiO thin films grown on Si (100) substrate by electron beam evaporation method and sintered at 700 °C were irradiated with 200 MeV Au¹⁵⁺ ions. The fcc structure of the sintered films was retained up to the highest fluence (1×10¹³ ions cm^?2) of irradiation. However the microstructure of the pristine film underwent a considerable modification with increasing ion fluence. 200 MeV Au ion irradiation led to compressive stress generation in NiO medium. The diameter of the stressed region created by 200 MeV Au ions along the ion path was estimated from the variation of stress with ion fluence and found to be ～11.6 nm. The film surface started cracking when irradiated at and above the fluence of 3×10¹² ions cm^?2. Ratio of the fractal dimension of the cracked surface obtained at 200 MeV and 120 MeV (Mallick et al., 2010a) Au ions was compared with the ratio of the radii of ion tracks calculated based on Coulomb explosion and thermal spike models. This comparison indicated applicability of thermal spike model for crack formation.     

Fe-doped SnO2 transparent semi-conducting thin films deposited by spray pyrolysis technique: Thermoelectric and p-type conductivity properties

In this paper, we report structural, electrical, optical, and especially thermoelectrical characterization of iron (Fe) doped tin oxide films, which have been deposited by spray pyrolysis technique. The doping level has changed from 0 to 10 wt% in solution ([Fe]/[Sn] = 0–40 at% in solution). The thermoelectric response versus temperature difference has exhibited a nonlinear behavior, and the Seebeck coefficient has been calculated from its slope in temperature range of 300–500 K. The Hall effect and thermoelectric measurements have shown p-type conductivity in SnO₂:Fe films with [Fe]/[Sn] ≥ 7.8 at%. In doping levels lower than 7.8 at%, SnO₂:Fe films have been n-type with a negative thermoelectric coefficient. The Seebeck coefficient for SnO₂:Fe films with 7.8 at% doping level has been obtained to be as high as +1850 μV/K. The analysis of as-deposited samples with thicknesses ～350 nm by X-ray diffraction (XRD) and scanning electron microscopy (SEM) has shown polycrystalline structure with clear characteristic peak of SnO₂ cassiterite phase in all films. The optical transparency (T%) of SnO₂:Fe films in visible spectra decreases from 90% to 75% and electrical resistivity (ρ) increases from 1.2 × 10^?2 to 3 × 10³ Ω cm for Fe-doping in the range 0–40 at%.     

Raman spectroscopic study on boron-doped silicon nanoparticles

Raman analyses were performed on thin films prepared from B-doped Si nanoparticles with an average diameter of 15 nm using the spin-coating method. The resulting spectrum exhibited a broad band with a peak near 520 cm⁻¹. The band was decomposed into three bands corresponding to the crystalline, grain boundary (GB), and amorphous regions by the least-squares band-fitting method based on the three Voigt bands. The fractions of the crystalline, GB, and amorphous regions were 37%, 35%, and 28%, respectively. A spherical particle exhibited an ordered crystalline core surrounded by a disordered shell in a transmission electron microscope (TEM) image. The crystalline fraction of the 15-nm B-doped Si nanoparticle film was much lower than that of the 19-nm P-doped Si nanoparticle film. This result suggested that the B-doping mechanism was different from that of P-doping. The temperature of the sample was estimated from the ratio of the peak intensities of anti-Stokes to Stokes Raman bands (I^AS/I^S) observed near 520 cm⁻¹. The temperature of the B-doped Si nanoparticle film upon irradiation at a power density of 4.6 kW/cm² was 298 °C, whereas the temperature of the P-doped Si nanoparticle film was 92 °C. The B-doped Si nanoparticle films were capable of producing light-induced heat.     

Influence of sintering temperature on microstructure,critical current density and pinning potential of superconducting Bi1.6Pb0.5Sr1.8Dy0.2Ca1.1Cu2.1O8+δ ceramics

The influence of sintering temperature on the microstructure, critical current density (J_C), pinning potential values (U₀) and flux pinning properties of Bi_1.6Pb_0.5Sr_1.8Dy_0.2Ca_1.1Cu_2.1O_8+δ superconductor has been investigated. The samples are prepared by the solid-state route and sintered at temperatures ranging from 846 to 860 °C. A systematic correlation between the sintering temperature, Lotgering index, J_C, U₀ and flux pinning properties has been found. The samples sintered at lower sintering temperature (846 °C) have more grain boundaries with smaller grains while those sintered at a higher temperature (856 °C) contain larger grains with good texturing. The flux pinning force (F_P) calculated from the field dependent J_C values shows that the irreversibility lines (IL) of the Dy-doped samples shift towards higher fields to different extents depending on the sintering temperature. The maximum value of F_P = 1697 kN m^?3 is obtained for the sample sintered at 846 °C and the peak position of F_P is obtained at 0.96 T as against 616 kN m^?3 and 0.52 T for the sample sintered at 856 °C. The U₀ values calculated by Anderson's function is maximum for the sample sintered at 846 °C. But the self-field J_C value of this sample is lower than that of the samples sintered at 856 °C. The samples sintered at 856 °C show best self-field J_C due to the improved microstructure. The changes in microstructure followed by very high enhancement of self-field J_C, J_C(B) characteristics, F_P and U₀ values within a narrow temperature range, are of great scientific and technological significance and the results are explained on the basis of microstructural variation with respect to sintering temperature, hole optimization and formation of point defects due to the doping of Dy atoms in Bi_1.6Pb_0.5Sr_1.8Dy_0.2Ca_1.1Cu_2.1O_8+δ system.     

Electrical and interface state density properties of polyaniline–poly-3-methyl thiophene blend/p-Si Schottky barrier diode

We have formed conjugated polymeric aniline–thiophene organic material on p-Si substrate by adding polyaniline–poly-3-methyl thiophene blend solution in acetonitrile on top of a p-Si substrate and then evaporating the solvent. It has been seen that the forward bias current–voltage (I–V) characteristics of polyaniline–poly-3-methyl thiophene blend/p-Si/Al with a barrier height value of 0.60 eV and an ideality factor value of 3.37 showed rectifying behaviour at room temperature. The polyaniline–poly-3-methyl thiophene blend/p-Si/Al Schottky barrier diode showed non-ideal I–V behaviour with the value of ideality factor greater than unity that could be ascribed to the interfacial layer, interface states and series resistance. Furthermore, Cheung's functions and modified Norde's function were used to extract the diode parameters including ideality factor, barrier height and series resistance. It has been seen that there is a good agreement between the barrier height values from all methods. However, the values of series resistance obtained from Cheung's functions is higher than the values obtained from Norde's functions. The energy distribution of interface states density, determined from forward bias current–voltage (I–V) characteristic technique at room temperature, increases exponentially with bias from 2.81 × 10¹⁶ cm^?2 eV^?1 in (0.73–E_v) eV to 1.14 × 10¹⁷ cm^?2 eV^?1 in (0.48–E_v) eV.     

Radiation-induced grafting of styrene into poly(vinylidene fluoride) film by simultaneous method with two different solvents

Radiation-induced grafting of styrene into poly(vinylidene fluoride) (PVDF) films with 0.125 mm thickness at doses of 1 and 2.5 kGy in the presence of a styrene/N,N-dimethylformamide (DMF) solution (1:1, v/v) and at doses of 20, 40 and 80 kGy in presence of a styrene/toluene solution (1:1, v/v) at dose rate of 5 kGy h^?1 was carried out by the simultaneous method under nitrogen atmosphere and room temperature, using gamma rays from a Co-60. The films were characterized before and after modification by calculated grafting yield (GY %), infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetry (TG/DTG). GY results shows that grafting increases with dose, and the grafting of styrene was confirm by FT-IR due to the new characteristic peaks and by the TG and DSC attributed to changes in thermal behavior of the grafted material. Results showed that the system allows the controlled grafting of styrene into PVDF using gamma rays at doses as low as 1 kGy in DMF.     

An anion effect on the separation of AgI-containing melts using sound waves

Sound velocities in molten ((LiF + AgI)) and ((LiBr + AgI)) mixtures have been measured to investigate the relationship between the sound velocity and the temperature and the role of the anion in the (liquid + liquid) phase transition. Our results show that the ((LiBr + AgI)) system is biphasic between the melting point and T = 984 K and becomes monophasic above this temperature. We show that the upper consolute critical temperature for the AgI-containing melts increases with decreasing anion size in the series F⁻ > Cl⁻ > Br⁻. The ((LiF + AgI)) melt remains biphasic at all temperatures investigated up to T = 1218 K. The temperature coefficients for the sound velocities in the upper and lower phases of the ((LiBr + AgI)) system have opposite signs because of the superposition of the temperature and composition factors. The difference between the magnitudes of the velocities for the coexisting phases decreases exponentially with increasing temperature and is described by a critical exponent of 0.85 for the ((LiBr + AgI)) melt near the critical temperature. This value is 15% less than that found for alkali halide melts, in which long-range Coulomb forces between ions prevail. This difference may result from the fact that silver halides are intermediate between the typical ionic salts and the fully covalently bonded ones.     

Polyaniline nanotubes for impedimetric triglyceride detection

Polyaniline nanotubes (PANI-NT) based film electrophoretically deposited onto indium–tin–oxide (ITO) coated glass plate has been utilized for covalent immobilization of lipase (LIP), via glutaraldehyde (Glu), for triglyceride detection using impedimetric technique. It is shown that fatty acid molecules produced during triglyceride hydrolysis result in change in charge transfer resistance (R_CT) of PANI-NT film with varying triglyceride concentration. LIP/Glu/PANI-NT/ITO bioelectrode has linearity as 25–300 mg dL^?1, sensitivity as 2.59 × 10^?3 KΩ^?1 mg^?1 dL, response time as 20 s and regression coefficient as 0.99. A low value of apparent Michaelis–Menten constant (～0.62 mM) indicates high enzyme affinity to tributyrin. The LIP/Glu/PANI-NT/ITO bioelectrode has been utilized to estimate triglyceride in serum samples.     

On the structural and magnetoelectrical characterization of epitaxial SrRuO3 thin films grown on (001) SrTiO3 substrates

High-quality epitaxial thin films of the ferromagnetic metallic oxide SrRuO₃ (SRO) were fabricated by dc-sputtering at high oxygen pressure and their structural and magnetoelectrical properties were carefully studied. The films featured a Curie temperature T_C ～ 160 K and a magnetic moment of ～0.7 μ_B per Ru ion. The temperature dependent magnetization could be well described by the scaling relation M(T) ∝ (T_C ? T)^β with a critical exponent β = 0.53 over the entire ferromagnetic temperature range. A negative magnetoresistance, MR, on the order of a few percent was found up to room temperature. MR showed a maximum of ～4% right at T_C where a kink structure of the resistivity, ρ, at zero field was flattened out on magnetic field application. This ρ contribution could be related to scattering due to orientational disorder of the Ru magnetic moments which become aligned by an external magnetic field. In addition, an equally strong MR effect, related to localization phenomena, could be observed at lower temperature. Particularly, the second MR peak at ～35 K might be related to a Fermi-liquid to non-Fermi-liquid crossover. A scaling behavior dρ/dT ∝ |T ? T_C|^α was observed only above T_C. Here, values for the exponent α ≈ ?0.4 and α ≈ ?1.4 were obtained in zero field and in a field of 9 T, respectively. The commonly observed ρ minimum, appearing at low temperatures (～3 K in the present case), is correlated with the structural disorder of the SRO films and is believed to have its origin in quantum corrections to the conductivity (QCC).     

Si-doped carbon nanostructured films by pulsed laser deposition from a liquid target

Ablation of a silicone oil, Dow Corning's DC-705 with laser pulses of sub-ps duration in high vacuum is a novel approach to fabrication of Si-doped carbon nanocomposite films. Gently focused, temporally clean 700 fs pulses @ 248 nm of a hybrid dye/excimer laser system produce power densities of the order of 10¹¹–10¹² W cm^?2 on the target surface. The evolution of the chemical structure of film material is followed by comparing Fourier Transformed Infrared and X-ray Photoelectron spectra of films deposited at temperatures between room temperature and 250 °C. Despite the low thermal budget technique, in the spectrum of films deposited at room temperature the fingerprint of the silicone oil can clearly be identified. With increasing substrate temperature the contribution of the features characteristic of the oil gradually diminishes, but does not completely disappear even at 250 °C. This result is intriguing since the chance of oil droplets to survive in their original liquid form on the hot surface should be minimal. The results of the X-ray Photoelectron Spectroscopy suggest that the chemical structure of the film material resembles that of the oil. Both reflection mode optical microscopy and low magnification Scanning Electron Microscopy reveal that the films are inhomogeneous: areas of lateral dimensions ranging from a few to tens of micrometers, characterized by different contrasts can be identified. On the other hand, surface mapping by Scanning Electron and Atomic Force Microscopy unambiguously proves that all films possess a solid surface consisting of nanoparticles of less than 100 nm dimension, without the presence of any drop of oil. Possible explanations of the puzzling results can be that the films are polymers consisting mainly of the molecules of the target material, or composites of solid C:Si nanoparticles and oil residues.     

Substrate dependent structure and in-plane dielectric properties of Ba(Sn0.15Ti0.85)O3 thin films

The structure, microstructure and in-plane dielectric properties of Barium tin titanate Ba(Sn_0.15Ti_0.85)O₃ (BTS) thin films grown on (100) LaAlO₃ (LAO) and (100) MgO single crystal substrates through sol–gel process were investigated. The films deposited on (100) LAO substrate exhibited a strong (100) preferred orientation while the film deposited on (100) MgO substrate showed polycrystalline structure. The in-plane ɛ–T measurements reveal that the films grown on (100) LAO substrate exhibited an obvious room-temperature ferroelectric state, while the film grown on MgO substrate showed paraelectric state in the temperature range of 10–130 °C. A high tunability of 52.11% was observed for the BTS films deposited on (100) LAO substrate at the frequency of 1 MHz with an applied electric field of 80 kV/cm, which is about two times larger than that of the BTS films deposited on (100) MgO substrate. The obvious differences in the dielectric properties could be attributed to the stress in the films, which come from lattice mismatch and difference in the thermal expansion coefficients between the film and substrates. This work clearly reveals the highly promising potential of BTS films for application in tunable devices.     

Measurement of coefficient of thermal expansion of films using digital image correlation method

Applications of the digital image correlation method (DIC) for the determination the coefficient of thermal expansion (CTE) of films is investigated in this paper. A heating chamber was designed for applying thermal load and DIC provides the full-field thermal deformation fields of the test film sample due to temperature changes. The average normal strains in the x and y direction from the region of interest are then extracted for the determination of CTE. The influence of unavoidable small rigid body rotation is discussed and a method to eliminate it to show the pure thermal expansion of the test film is demonstrated. For validation, the CTE of a pure copper sample is determined and compared with the textbook value, confirming the effectiveness and accuracy of the proposed technique. Finally, the CTE of Polyimide (PI) composite film in the temperature range of 20–140 °C is measured. The results reveal that the DIC is a practical and effective tool for full-field thermal deformation and CTE measurement of films.     

Effect of γ-irradiation on the gauge factor of two-dimensional island platinum films

Four films (A, B, C and D) of two-dimensional island platinum films (2D-I(Pt)Fs) whose mass thicknesses (d_m) are 10, 20, 30 and 40 Å, respectively were deposited onto Corning 7059 glass substrates via the thermal evaporation technique. The increase in the film resistance with time (aging) in air is monitored until stable values are obtained. Each of the prepared films was γ-irradiated by different doses, namely, 100, 200, 300, 500 and 700 Gy; this was done using ¹³⁷Cs (0.662 MeV) radiation source of dose rate 0.5 Gy/min. For each dose the relative change in the film resistance was found at different values of strain either in the tensional or compressional mode. The gauge factor (v) of the Pt films was deduced and we found that; for particular d_m, the gauge factor decreases as the dose increases. Also, for a particular dose, v decreases as d_m increases. Qualitative interpretation for the results was offered on the ground that (i) the transfer of electrons between islands takes place by the thermally activated tunneling mechanism, (ii) the process of γ-irradiation makes the islands spread along the substrate and consequently the inter-island spacing will decrease. The micrographs taken by the Atomic Force Microscope (AFM) confirmed such spreading.     

Synthesis and physical characterization of electrically conducting polymers of polynuclear aromatic sulfonyl compounds

Potentially useful conducting polymers of sulfonyl substituted phenanthrene derivatives and non-conducting linear polymers, such as, polystyrene and poly(N-vinylcarbazole) have been synthesized and characterized using IR, thermogravimetric and dielectric measurements. The phenanthrene-based benzene, naphthalene and biphenyl copolysulfones have also been prepared and characterized through these techniques. These pendant and backbone polymer sulfones have exceptionally high thermal stability and electrical conductivity, such that dc conductivity in the range 2.80 × 10^?16 to 2.82 × 10^?7 Ω^?1 cm^?1 and ac conductivity in the range 1.69 × 10^?7 to 2.10 × 10^?6 Ω^?1 cm^?1.     

Thermally induced transformations of calcium carbonate polymorphs precipitated selectively in ethanol/water solutions

For the precipitation of calcium carbonate polymorphs in ethanol/water solutions of calcium chloride by the diffusion of the gases produced by sublimation–decomposition of solid ammonium carbonate, polymorph selection and morphology control of the precipitates were demonstrated by the effect of ethanol/water ratio in the mother liquor. The precipitated phases change systematically from gel-like aggregates of hydrated amorphous calcium carbonate in the absolute ethanol solution to well-shaped rhombohedral particles of calcite in the absolute aqueous solution via almost pure phase of vaterite with dendrite structure in 75%-ethanol/25%-aqueous and 50%-ethanol/50%-aqueous solutions. On heating the precipitated sample in flowing dry nitrogen, all the samples transformed to calcite before the thermal decomposition, where the thermal decomposition temperature shifts to higher temperatures with increasing the water content in the mother liquor due to the systematic increase in the particle size of calcite. Accordingly, the present method of controlled precipitation of calcium carbonate polymorphs is also useful to control the particle size and reactivity of calcite produced by heating the precipitates. Selecting vaterite with dendrite structure from the present series of precipitated samples, the structural phase transition to calcite was characterized as the three-dimensional growth of rhombohedral particles of calcite with the enthalpy change ΔH = ? 2.8 ± 0.1 kJ mol^?1 and the apparent activation energy E_a = 289.9 ± 5.8 kJ mol^?1.