Perfluorocarbon-Hydrocarbon Discrete Intermolecular Aggregates: An Exceptionally Short N⋯I Contact

1-Iodoperfluoroheptane ( 1a ) and tetramethylethylenediamine ( 2 , TMEDA) form the 2:1 ratio stable aggregate 3a and a similar behaviour is shown by 1-iodoperfluoroalkanes 1b-e and iodopentafluorobenzene 1f . These aggregates have been characterised in solution by 1 H/ 19 F-NMR spectroscopy and in the solid state through IR and single crystal X-ray diffraction. The determined structure of 3a (triclinic, a =6.2283(10), b =9.250(2), c =15.098(3) Å, f =81.369(5), g =81.397(5), n = 86.010(5), V =849.3(3) A m 3 , T =175(3) K, space group P-1 (No. 2), Z =1; d (calc)=2.167 g cm m 3 ; 4121 independent reflections, 3665 with I o >2( I o ); final refinement gave R1=0.0400, wR2=0.0901) showed the second shortest N > I interaction found in the crystallographic literature [2.762(3) Å] and the interdigitation of perfluorocarbon and hydrocarbon modules due to co-operative -C-H > F-C- interactions. Calculations to quantify these latter interactions have been also performed.     

CHARACTERIZATION OF POLY(VINYL ALCOHOL)-KONJAC GLUCOMANNAN BLEND FILMS

This article deals with the characterization of blend films obtained by mixing poly(vinyl alcohol) (PVA) and konjac glucomannan (KGM) in aqueous solution. The DTA curves of PVA/KGM blend films showed overlapping of the main thermal transitions characteristic of the individual polymers. The exothermic peak at 312°C, which resulted from the thermal degradation of the KGM, shifted slightly to a higher temperature at low PVA content (≤20 wt%). The weight-retention properties of the blend films indicated that thermal stability of the blend films were better than pure KGM film at PVA content below 20 wt%. The crystallinities, tensile strength, and elongation at break of the films increased with the PVA content, and reached the maximum values at 20 wt% PVA, then decreased. Changes in the carbonyl stretching band of KGM and hydroxyl stretching regions of KGM and PVA were detected by FTIR analysis. Those are attributable to the existence of a certain degree of inteaction between KGM and PVA, and resulted from intermolecular hydrogen bonds. Phase separation phenomena were observed by examining the surface of the blend films by SEM.     

Preparation and characterization of porous C-modified anatase titania films with visible light catalytic activity

Visible-light-activated C-modified anatase titania films have been synthesized from TiCl₄ and carbonic ink by using the sol–gel route. The synthesized photocatalysts were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and optical measurements. The modifying carbon not only produces homogeneous worm-like structure with uniform pores, but also extends the absorbance spectra of the as-prepared films into visible region. The results of visible-light-induced degradation of methyl orange (MO) show that the C-modified titania films exhibits much higher photocatalytic activities than that of pure titania film prepared at the same conditions.     

A model for solid-state dewetting of a fully-faceted thin film

Owing to their extremely aspect ratios, most thin films are unstable and when they are heated, they will dewet or agglomerate to form islands. This process can occur in the solid state through capillary-driven surface self-diffusion. A key feature of the dewetting process is the retraction of the edges of the film, either natural edges, patterned edges, or edges where holes have formed. Models of edge retraction have been previously developed for isotropic materials and anisotropic materials with differentiable surfaces, but the effects of faceting in highly anisotropic materials have been largely unexplored. Here, we present a two-dimensional model of edge retraction for highly anisotropic, fully-faceted thin films. This model shows generally good agreement with experimental results for edge retraction of single-crystal Ni films on MgO. In both experiments and the model, rims form as the edges retract. The effects of adjusting various physical parameters on the edge retraction rate and the evolving rim geometry were explored using the model. The film thickness, surface self-diffusivity on the top facet of the rim, the equivalent contact angle of the film on the substrate, and the absolute value of the surface energies were found to be the factors that have the greatest influence on the edge retraction rate. In isotropic models and some experimental systems, valleys form ahead of the retracting rims and deepen to contact the substrate and cause pinch-off. Our model suggests that this form of pinch-off will not occur when the rim is fully faceted and the top surface is an equilibrium facet. However, pinch-off can occur through film thinning and for films with top surfaces that do not form flat equilibrium facets.     

Critical angles for axial channeling

The critical angle for axial proton channeling has been measured as a function of temperature for a number of different crystals. The results are consistently below the values predicted from simple analytical estimates. The magnitude of this discrepancy does not seem to depend on the specific lattice structure. In point of fact, all the results are consistent with a relationship ψ_1/2 = α(p/a). ψ₁, where ψ₁ is Lindhard's characteristic angle, and α(p/a)is a function of the thermal vibrational amplitude p, measured in units of the Thomas-Fermi screening distance a. A formula for α(p/a), derived by Barrett from computer simulations, on the average predicts the magnitude of α quite well, but the observed functional dependence on p/a is considerably stronger than predicted.     

Low-temperature preparation of nanocrystalline anatase films through a sol-gel route

Nanocrystalline anatase (TiO₂) films were prepared at very low temperature through a sol-gel route using titanium isopropoxide and hydrogen peroxide in ethanol. Crystallization occurred after film deposition at 35°C in an atmosphere saturated with water vapor. Both thin and thick films of nanocrystalline anatase were prepared. Observed particle size in crystallized films is approximately 20–40 nm as measured with AFM. No residual organic material was apparent through FTIR after crystallization occurred. Dynamic light scattering studies performed on this system indicate that particle size measured in solution is strongly dependent on the amount of agitation samples received prior to measurement.     

Mechanical and thermal properties of irradiated films based on Tilapia (Oreochromis niloticus) proteins

Proteins are considered potential material in natural films as alternative to traditional packaging. When gamma radiation is applied to protein film forming solution it resulted in an improvement in mechanical properties of whey protein films. The objective of this work was the characterization of mechanical and thermal properties of irradiated films based on muscle proteins from Nile Tilapia (Oreochromis niloticus). The films were prepared according to a casting technique with two levels of plasticizer: 25% and 45% glycerol and irradiated in electron accelerator type Radiation Dynamics, 0.550 MeV at dose range from 0 to 200 kGy. Thermal properties and mechanical properties were determined using a differential scanning calorimeter and a texture analyzer, respectively. Radiation from electron beam caused a slightly increase on its tensile strength characteristic at 100 kGy, while elongation value at this dose had no reduction.     

Evaluation and application of Diffusive Gradients in Thin Films (DGT) technique using Chelex-100, Metsorb™ and Diphonix binding phases in uranium mining environments

A new resin- Diphonix^® in Diffusive Gradients in Thin Films (DGT) technique for the determination of uranium was investigated and compared with previously used binding phases for uranium, Chelex^®-100 and Metsorb™. The DGT gel preparation and the elution procedure were optimized for the new resin. The U uptake on Diphonix^® resin gel was 97.4 ± 1.5% (batch method; [U] = 20 μg L⁻¹; 0.01 M NaNO₃; pH = 7.0 ± 0.2). The optimal eluent was found to be 1 M 1-hydroxyethane-1, 1-diphosphonic acid (HEDPA) with an elution efficiency of 80 ± 4.2%. Laboratory DGT study on U accumulation using a DGT samplers with Diphonix^® resin showed a very good performance across a wide range of pH (3–9) and ionic strength (0.001–0.7 M NaNO₃). Diffusion coefficients of uranium at different pH were determined using both, a diffusion cell and the DGT time-series, demonstrating the necessity of the implementation of the effective diffusion coefficients into U-DGT calculations. Diphonix^® resin gel exhibits greater U capacity than Chelex^®-100 and Metsorb™ binding phase gels (a Diphonix^® gel disc is not saturated, even with loading of 10.5 μmol U). Possible interferences with Ca²⁺ (up to 1.33 × 10⁻² M), PO₄³⁻${{\text{PO}}_4}^{3\mathrm{-}}$ (up to 1.72 × 10⁻⁴ M), SO₄²⁻${{\text{SO}}_4}^{2\mathrm{-}}$ (up to 4.44 × 10⁻³ M) and −HCO₃${{\text{HCO}}_3}^{\mathrm{-}}$ (up to 8.20 × 10⁻³ M) on U-DGT uptake ([U] = 20 μg L⁻¹) were investigated. No effect or minor effect of Ca²⁺, PO₄³⁻${{\text{PO}}_4}^{3\mathrm{-}}$, SO₄²⁻${{\text{SO}}_4}^{2\mathrm{-}}$, and −HCO₃${{\text{HCO}}_3}^{\mathrm{-}}$ on the quantitative measurement of U by Diphonix^®-DGT was observed. The results of this study demonstrated the DGT technique with Diphonix^® resin is a reliable and robust method for the measurement of labile uranium species under laboratory conditions.     

Eye-protection glasses against YAG laser injury based on the band gap reflection of one-dimensional photonic crystal

Eye-protection glasses against YAG laser injury based on band gap reflection of one-dimensional photonic crystal (PC) is designed and manufactured in this paper. The laser beam (wavelength 1.06 μm) is reflected by the one-dimensional PC (with the transmission 10⁻⁷) and absorbed by the phosphatic glass substrate (with the transmission 1% for 1.06 μm), so the transmission of the device for wavelengths of1.06 μm can reach 10⁻⁹. The glasses have enough capabilities to protect the eyes from injury of ns-YAG lasers whose energy density is 1 J/cm² for all incident angles, and also to avoid a second injury to others from the reflected laser beams. The transmission of the glasses is beyond 70% for the visible lights. The testing data of the eye-protection glasses agree well with the theoretical predictions.     

拉曼光谱和红外光谱分析沉积气压对微晶硅薄膜微结构的影响

采用射频等离子体增强化学气相沉积法(RF-PECVD),在玻璃和硅衬底上以230—310Pa之间的沉积气压生长微晶硅(μc-Si:H)薄膜。利用拉曼光谱和红外光谱分析样品的微结构。结果发现样品的微结构强烈依赖于沉积气压,并且存在着最佳沉积气压250Pa,在此条件下的微晶硅薄膜晶化率为60.6%,氢含量为最小值9.1%。