Surface modification of polypropylene membranes by γ-ray induced graft copolymerization and their solute permeation characteristics

Porous hydrophobic polypropylene (PP) membranes were subjected to the surface modification by the γ-ray induced graft copolymerization with hydrophilic 2-hydroxyethyl methacrylate (HEMA). The structural changes and surface morphologies of the modified PP membranes were characterized by a Fourier transform infrared spectroscopy (FT-IR), elemental analysis (EA) and field emission scanning electron microscopy (FE-SEM). Peroxides produced from γ-ray irradiation were determined by a 1,1-diphenyl-2-picryl hydrazyl (DPPH) method and the surface hydrophilicities of membranes were measured by a static contact angle measurement. The contact angle of the modified membranes reduced with the degree of grafting (DG) of HEMA onto the membrane surface, and it decreased up to about half of that before modification. The permeation behaviors of all membranes were investigated by a bovine serum albumin (BSA) filtration experiment. As a result, the DG of the modified membrane increased with the reaction time. However, in the case of irradiation dosage it showed the maximum value at 20 kGy. Also, the modified membrane showed a higher solution flux, lower BSA adsorption, and the better flux recovery after cleaning than that of the unmodified membrane. Particularly, 40.6% grafted membrane showed a two-fold increase in a BSA solution flux, 62% reduction in total fouling and three-fold increase in flux recovery after chemical cleaning.     

Microporous poly(vinyl methyl ether) hydrogels prepared by γ-ray irradiation at different heating rates

We prepared thermoresponsive and microporous polymer hydrogels by γ-ray irradiation of aqueous solutions poly(vinyl methyl ether) (PVME) at different heating rates. Under all temperature programs, opaque and heterogeneous PVME gels formed, which swelled at temperatures below the lower critical solution temperature and shrank at temperatures above it. All of the samples contained porous and phase-separated structures. The shape and size of the gel pores varied depending on the temperature programs. Gels having a sponge-like continuous porous structure formed only when the radiation-induced crosslinking was carried out at an optimum heating rate, which we found to be 0.11–0.13°C min⁻¹. For temperature changes between 10°C and 40°C, gels with this structure showed rapid volume transitions on a time scale of about a minute.     

A study on feasibility of insect—control with γ-ray

Insect-control with Co-γ-ray is a method for conserving archives, books, cotton textiles, historical relics, wood structured houses and furniture, which are called irradiated objects later on. The temporary and residual effects of γ-ray on irradiated objects and the biological effects on insects are presented in this report.

Our study shows that there is no obvious harmful effect on irradiated objects when the ray is below 870 Gy, while there is obvious deterioration on the objects when the ray is above 870 Gy. On the other hand, the ray below 870 Gy is strong enough for the insects. In fact, at the dose of 43.5–130.5 Gy, the irradiated insects could be damaged on reproductive function, even sterilized, or killed.     

Radiation crosslinking of polyamide 610

In the present paper the gel formation of polyamide 610 by γ-ray irradiation in the presence of polyfunctional monomer and γ-crystal nucleating agent under vacuum or air atmosphere had been studied. It was found that the gel formation was dependent on the content of polyfunctional monomer and nucleating agent. However, there was very little difference between gel contents irradiated under vacuum and air atmosphere. The results showed that the crosslinking by γ-irradiation enhanced the mechanical properties of PA610 especially at high temperature in the presence of polyfunctional monomer and γ-crystal nucleating agent. The mechanism of radiation crosslinking and scission was discussed according to the composition and quantity of gas released from three kinds of PA during irradiation.     

KMgF3 及KMgF3∶Eu2+晶体的射线辐照效应

KMgF3∶Eu晶体中Eu3+→Eu2+的转换率在低浓度掺杂时接近100%, 完全转换的饱和掺杂摩尔分数为0.29%. 实验条件下, KMgF3晶体的X射线1 h辐照损伤可在约100 h后恢复; KMgF3∶Eu2+晶体经X射线辐照后, 360 nm锐峰发射强度略有降低. 不同剂量的γ射线辐照, KMgF3晶体热释光曲线的各个温度峰强度变化明显不同, 即使小剂量辐照, 造成的损伤也较难恢复, 如γ射线辐照剂量为103 Gy时, 辐照损伤的恢复时间约需30 d. KMgF3∶Eu2+晶体360 nm锐峰发射强度随γ射线辐照剂量增大而呈线性降低.     

Threshold temperature for γ-ray detection in superheated drop detector

The γ-ray detection threshold temperatures of superheated drops of refrigerant liquid R-12 is presented here for the three γ-ray energies 59.54 keV (²⁴¹Am, 500 mCi), 662 keV (¹³⁷Cs, 32.5 mCi) and 1250 keV (⁶⁰Co, 0.45 mCi). Nucleation was detected with an active device by counting the number of drops vaporized per minute as a function of the temperature of the detector over a wide range. The results show that the threshold temperature for detection increases with the energy of the incident photons.     

Hybrid polymerization of iso-butyl vinyl ether

The radiation-induced hybrid polymerization in the presence of the N-alkoxypyridinium salt having relatively stable nonnucleophilic anion (PF₆⁻) has been investigated in the paper. Based on the analysis of experimental data and the GPC spectrum, the onium salts not only oxidize -alkoxyalkyl radicals, produced from IBVE in dichloromethane by irradiation, to the corresponding cations, but also give nonnucleophilic anions PF₆⁻ for the polymerization system. The experimental results clearly demonstrate that free radical and cationic polymerization mechanisms occurred simultaneously in IBVE/EMP⁺PF₆⁻/CH₂Cl₂ systems on irradiation with γ-ray.     

Study on the effect of spinning conditions and surface treatment on the geometry and performance of polymeric hollow-fibre membranes

Hollow-fibre membranes were prepared by the wet-dry spinning technique from polyether sulfone (PES). The effect of spinning conditions such as the flow-rate of the internal coagulant and the flow-rate, composition and temperature of the polymer solution on the geometry and performance of hollow fibres was studied. In particular, five different ratios of pore former/polymer covering the range 0.2–1.0 were investigated while the polymer content was kept constant. Since the viscosity of the spinning dope affects the morphology of the hollow-fibre membrane, hollow fibres were prepared at different temperatures of the spinning dope from 25 to 60°. By scanning electron microscopy (SEM) two layers sandwiching a finger-like cavity structure were observed. Also, the surface on the bore side of the hollow fibre was modified by grafting polyethylene glycol (PEG) with γ-ray irradiation to improve the ultrafiltration performance.     

Investigation of nylon-6 fibre structure interferometrically

Multiple-beam Fizeau fringes are used to study the changes in optical properties of Nylon-6 γ-irradiated fibres. Changes in fibre structures due to drawing have been studied using two-beam interference. Some structural parameters such as optical orientation function and electric polarizability difference (Δ/3₀) were determined. Δ/3₀ is found to be constant and depends only on the fibre structure. The generalized Lorantz-Loranz equation given by de Vries is used to determine Nylon-6 fibre structural parameters. Comparison between the results and when using Lorantz-Loranz equation are given. Refractive index profiles also can help in fibre investigations.     

A simple method for efficiency calibration of HPGe detectors in γ-spectrometric measurements

In this paper a simple, rapid and general method for γ-ray efficiency calibration of Ge detectors for environmental samples is presented. This method is based on the use of an active natural solid sample with several γ-emissions (in our case, ²²⁶Ra) as the calibrating matrix for determining the full energy peak efficiency (FEPE) _c vs γ-emission energy E_γ and the sample height h in a counting cylindrical geometry. The ²²⁶Ra activity concentration is determined by -particle spectrometry, a method that has previously been validated.     

Structural transformations of isotactic polypropylene induced by heating and UV light

Samples of commercial-grade isotactic polypropylene, both neat and nucleated with a specific β-nucleating agent (N,N′-dicyclohexylnaphthalene-2,6-dicarboxamide), were exposed to annealing and UV irradiation. Structural parameters were assessed by X-ray diffraction. Tensile mechanical characteristics were derived from stress–strain curves. The specific nucleation caused more than 70% of the crystalline phase to occur in the trigonal β-modification. The content of the β-phase introduced by the specific nucleation distinctly decreased after a certain induction period, different for annealing at 140 °C and UV exposure. At the same time, the size of the -crystallites increased while the size of the β-crystallites remained virtually unchanged. These results indicate the β →  recrystallization. On the other hand, the strain-at-break values continuously and monotonically decreased with increasing exposure time reflecting defect formation, both at the surface and in the bulk of the specimens. The differences between the effects of thermal ageing and UV degradation are discussed.     

Changes induced by ultraviolet light in fluorescence of collagen in the presence of β-carotene

The influence of UV radiation (253.7 nm) on collagen fluorescence in the absence, and presence, of β-carotene was investigated. It was found that UV radiation of 253.7 nm causes irreversible destruction of tyrosyl and phenylalanyl residues. The fluorescence of collagen (excitation at 275 nm, emission at 305 nm) decreased rapidly during irradiation and a new fluorescence large band at 400–500 nm formed under UV radiation. Smaller changes in the fluorescence of collagen in the presence of β-carotene suggest that it makes collagen less sensitive to the action of UV radiation.     

A Two‐Dimensional Ruddlesden–Popper Perovskite Nanowire Laser Array based on Ultrafast Light‐Harvesting Quantum Wells

Miniaturized nanowire nanolasers of 3D perovskites feature a high gain coefficient; however, room-temperature optical gain and nanowire lasers from 2D layered perovskites have not been reported to date. A biomimetic approach is presented to construct an artificial ligh-harvesting system in mixed multiple quantum wells (QWs) of 2D-RPPs of (BA)₂(FA)_n−1Pb_nBr_3n+1, achieving room-temperature ASE and nanowire (NW) lasing. Owing to the improvement of flexible and deformable characteristics provided by organic BA cation layers, high-density large-area NW laser arrays were fabricated with high photostability. Well-controlled dimensions and uniform geometries enabled 2D-RPPs NWs functioning as high-quality Fabry–Perot (FP) lasers with almost identical optical modes, high quality (Q) factor (ca. 1800), and similarly low lasing thresholds.     

Wetting of β-casein layers adsorbed at the solid–aqueous interface

The wetting by water of the adsorbed layer of β-casein on hydrophobised silica and pure (hydrophilic) silica surface was investigated by dynamic contact angle measurements based on the Wilhelmy plate principle. The results are discussed in relation to adsorption data obtained for the protein on similar surfaces by in situ ellipsometry. β-casein adsorption on a hydrophobic surface leads to a significant decrease of the contact angle, in particular in terms of the receding contact angle, which decreased by about 70°. This indicates a strong shielding of the hydrophobic surface by the hydrophilic domain of β-casein. Adding a specific enzyme, endoproteinase Asp-N, which previously has been proposed to remove a large fraction of the hydrophilic segments, results in a significantly decreased wettability of the solid surface. The layer is now more hydrophobic and the hysterises is much smaller. The receding contact angle after the proteolysis is roughly 70°. The results are consistent with the hypothesis that β-casein adsorbs at the hydrophobic surface to form a monolayer with the hydrophobic part of the protein anchored at the surface, leaving the hydrophilic segments dangling into the solution. Less dramatic effects are observed in terms of changes of the wettability on the hydrophilic surface. The surface is still quite hydrophilic both after adsorbing β-casein and exposing the layer to endoproteinase Asp-N. These results confirm the differences in the structure of β-casein layers on the hydrophobic and hydrophilic surface.     

Comparison of γ-radiation and electron beam irradiation effects on gelatin

Gelatin is a heterogeneous mixture of water-soluble proteins of high average molecular weight derived by hydrolytic action from collagen, a protein of mammal external protective tissues. There are many characteristics of a material that can indicate its quality or performance in its intended use. The knowledge of a material's rheological characteristics is valuable to predict its pourability, its performance in a dipping or coating operation or the ease with which it may be handled, processed or used. In this work bovine powder gelatin was submitted to γ-radiation from a ⁶⁰Co source, dose rate about 7 kGy/h and to electron beam irradiation, dose rate about 11 kGy/s. The doses applied were 5, 10, 20 and 50 kGy. The radiation effects were measured following viscosity changes at 40°C of gelatin powder 10% aqueous solutions. The relationship between the decrease in viscosity of gelatin solutions and radiation dose presented close comparable values for both irradiation processes.     

Association between ammonium monovanadate and β-cyclodextrin as seen by NMR and transport techniques

The interaction between vanadium (V) and the carbohydrate β-cyclodextrin (β-CD) has been studied in aqueous solutions (pH ≈ 7.5, 298.15 K) using multinuclear NMR spectroscopy, coupled with measurements of diffusion coefficients and electrical conductivity. The transport properties of vanadate ion solutions are markedly influenced by the presence of β-CD. Data from ⁵¹V, ¹H and ¹³C NMR spectroscopy show that these effects are due to strong interactions between this carbohydrate and vanadate due to formation of 2:1 (β-CD:vanadate) complexes. The formation of such 2:1 complexes is also supported by molecular mechanics calculations. Complexation is seen by conductometric and diffusion techniques to lead to a significant decrease in the molar conductivity and diffusion coefficient of vanadate solutions in the presence of β-CD. Using the above stoichiometry, it has been possible to calculate the association constant, leading to the value K = 4.3 × 10⁴ M⁻² from the analysis of the conductivity data.     

Metal ion absorption of carboxymethylcellulose gel formed by gamma-ray irradiation. For the environmental purification

Carboxymethylcellulose (CMC) is well known as a safe and biodegradable material, which is widely used as food additives, wash paste, etc., in our daily life. Aiming at the environmental purification of this eco-friendly substance, the authors have investigated Cu²⁺ absorption property of CMC gel that was crosslinked by irradiating with γ-rays without toxic crosslinker. The CMC gel has revealed to capture Cu²⁺ of which number depends on the γ-ray dose as well as the CMC concentration, indicating the chelation by carboxyl group at the end of the side chain.     

An alternative approach to amyloid fibrils morphology: CdSe/ZnS quantum dots labelled beta-amyloid peptide fragments Abeta (31-35), Abeta (1-40) and Abeta (1-42)

Aβ (31–35) peptide and control peptides as well as full length Aβ (1–40) and Aβ (1–42) peptides were labelled with luminescent CdSe/ZnS quantum dots (QDs) to observe the morphology of amyloid fibers. A comparison was made between QDs and an organic dye, namely Dansyl group, which showed that the QDs present a much better contrast for imaging than the organic dye.     

Quantum study of the active sites of the γ alumina surface (II): QM/MM (LSCF) approach to water, hydrogen disulfide and carbon monoxide adsorption

The mixed quantum mechanics/molecular mechanics (QM/MM) local self consistent field (LSCF) method is applied to study the adsorption of water, hydrogen sulfide, and carbon monoxide molecules on γ alumina surfaces. The effect of the long-range contributions included in the LSCF adsorption/dissociation energies are compared to cluster results. For the carbon monoxide, the long-range contributions do not change the adsorption energies in comparison with the cluster approach. In opposition, the long-range contributions lower the adsorption and dissociation energies of water and hydrogen disulfide. Cautions to be taken on the application of the LSCF method to γ alumina are also discussed.     

Investigation of alumina/(+)-catechin system properties. Part II: ζ-potential and surface free energy changes of alumina

The effects of (+)-catechin adsorption to the alumina surface were studied by ζ-potential and surface free energy determination. The presence of catechin causes essential changes in the alumina ζ-potential, which at the concentration slightly higher than 10⁻⁵ M reverses from the positive into negative one. At constant concentration of catechin (10⁻³ M), the effect on ζ-potential of alumina as a function of pH appears in a drastic shift of the isoelectric point, from pH 8.4 to 4.6, and the equilibrium is established practically within 2 h. This is probably due to relatively low pK_a=4.6 for catechin 3′-OH group deprotonation. At high alkaline environment (pH≥10), even in the presence of catechin in the solution, the hydroxyl OH⁻ ions play principal role in the surface charge formation for the alumina. At such pH catechin molecule is double negatively charged and hence its adsorption on highly negatively charged alumina surface is rather restricted. Nevertheless, various dimeric forms of catechin, which are formed at the alkaline pH, probably adsorb on the alumina surface. This appears in small increase in apolar surface free energy component at natural and alkaline pH. On the other hand, at acidic pH 3 small increase of the electron acceptor interaction is observed. This may result from increased number of hydroxyl groups on the alumina surface originating from the adsorbed molecules of catechin, which are mostly undissociated at this pH. The interactions of catechin with alumina surface seems to be also of some specific nature, because neither changes in the ultraviolet–visible (UV–vis) absorbance (Part I) nor in the ζ-potentials had occurred in the silica suspensions in which also catechin was present.