Photocontrol of supramolecular architecture in azopolymers: Achiral and chiral aggregation

The absorption spectra and circular dichroism responses upon irradiation with 488 nm circularly polarized light (CPL) have been studied on polymeric films processed from two nematic copolymers containing azobenzene chromophores. Influence of the aggregation and orientation of azobenzenes on the photoinduced chiroptical properties has been analyzed. Moreover, polymeric films and 4 μm planar cells filled with the copolymers were studied by polarized optical microscopy (POM) with the aim of investigating the change of macroscopic optical properties and textures of azopolymers upon irradiation with CPL.     

Radiation induced degradation of pharmaceutical residues in water: Chloramphenicol

The γ-radiolytic degradation of chloramphenicol (CPL) was investigated in 0.1–1 mmol dm^?3 aqueous solutions at various radiation conditions. The destruction of CPL was monitored by UV–vis spectrophotometric method through the decrease in the intensity of the absorbance band at 276 nm. LC-MS/MS was used to identify the degradation products. Results indicate that ^?OH can add onto the CPL aromatic ring or can abstract H-atom from the side chain. The reductive dechlorination of CPL was also studied based on the reaction of e_aq^? with CPL. In 0.1 mmol dm^?3 solution above 2.5 kGy dose complete CPL degradation was achieved. In the presence of dissolved oxygen at relatively low dose, various oxidation products were observed. In the presence of tertiary butanol radical scavenger tertiary butanol group containing products were also detected. The toxicity increased as a function of dose to 1.0 kGy. At doses higher than 1.0 kGy the toxicity decreased continuously due to further degradation. It was also demonstrated that the O₂^??/HO₂^? pair has low reactivity in CPL solution.     

Photoinduced chirality in achiral liquid crystalline polymethacrylates containing bisazobenzene and azobenzene chromophores

One new liquid crystalline polymer containing bisazobenzene, poly[4-{(2-methacryloyloxyethyl)oxy}-4′-(4-nitrophenylazo)azobenzene] (PM2BAN), and two liquid crystalline polymers containing azobenzenes with spacers of two and six methylene units, poly[(4-(4′-nitrophenylazo)phenyloxy)x-methylene methacrylate] (PMxAN, x = 2, 6), were synthesized and characterized. The level and rate of photoinduced chirality were studied in films of the achiral polymers by irradiation with one handed circularly polarized light (CPL) at 442 nm. The results of circular dichroism (CD) suggest that left-CPL induces left helical arrangements of the polymers and right-CPL reverses the resulting arrangements into right helices. Photoinduced chirality in film of PM2BAN is increased with the increase of irradiation time. However, the level and rate of photoinduced chirality in film of PM2BAN are lower than those in films of PMxAN (x = 2, 6) at similar irradiation time. Compared with PM2AN, photoinduced CD values are higher in PM6AN. The results are discussed in terms of interactions between azobenzene chromophores and circularly polarized light.     

Preparation and photocatalytic activity of visible light-active sulfur and nitrogen co-doped SrTiO3

Nitrogen and sulfur co-doped SrTiO₃ was prepared by high energy grinding of the mixture of SrTiO₃ and thiourea. A new band gap in visible light region (522 nm) corresponding to 2.37 eV could be formed by the co-doping. The photocatalytic activity for nitrogen monoxide oxidation of SrTiO₃ in visible light region especially in the long wavelength range (λ > 510 nm) could be improved greatly. Under the irradiation of light with wavelength larger than 510 nm, the photocatalytic activity of nitrogen and sulfur co-doped SrTiO₃ was 10.9 times greater than that of pure SrTiO₃. The high visible light photocatalytic activity of this substance may be due to the formation of a new band gap that enables to absorb visible light effectively.     

Caractérisation par spectrométrie de masse MALDI–TOF de poly(isosorbide-éther)s cycliques et linéaires obtenus sous irradiation microondes

Characterisation of cyclic and linear poly(isosorbide-ether)s obtained under microwave irradiation by MALDI–TOF mass spectrometry. We studied the influence of the alkyl chain length and of the leaving group on the fraction of cyclic or linear poly(isosorbide-ether)s. A survey by MALDI–TOF MS showed that cyclic chains (C) are predominant when some short aliphatic chains are used (m = 4 or 6), whereas with longer chains (m = 8, 10 or 12), we noted that cyclic products were in a minority, whatever the leaving group (bromide or mesyl). Important non-thermal microwave effects have been demonstrated, notably a methanol-insoluble fraction of polyether considerably larger than the one obtained by conventional heating. These poly(isosorbide-ether)s have been characterized by RMN, MALDI–TOF, SEC, elementary analysis, and DSC. The survey of the thermal behaviour by DSC showed that the temperatures of fusion increase with the aliphatic chain's length (m = 12; T_f = 37 °C).     

The effects of annealing temperature on structural and optical properties of S-doped ZnO nanobelts

In this study, the effects of thermal annealing temperature on the structural and optical properties of S-doped ZnO nanobelts were investigated. The XRD pattern shows that the crystallinity of S-doped ZnO nanobelts improves with increased annealing temperature. Room temperature photoluminescence spectroscopy of the as-grown S-doped ZnO nanobelts shows no detectable ultraviolet peak with the broad peaks in the visible emission region at 480, 505, and 518 nm. A weak peak in the ultraviolet region at 383 nm appears after annealing at 400 and 600 °C. Raman spectroscopy of the sample also shows a significant change with an increase in the annealing temperature.     

The effect of gamma irradiation and particle size of CaCO3 on the properties of HDPE/EPDM blends

Mechanical blends formed of 50 wt% of high-density polyethylene (HDPE) and 50 wt% of ethylene–propylene–diene-monomer (EPDM) elastomer have been loaded with 50 wt% of three different particle size of CaCO₃, namely CaCO₃ 300, CaCO₃ 700, and CaCO₃ 2000 whereby the latter has the smallest particle size of ～311, 82 μm. Mechanical, physico-chemical and thermal properties were followed up as a function of irradiation dose for loaded and unloaded blends. The results obtained indicated that the values of tensile strength, tensile modulus at 50% elongation, gel fraction and decomposition temperature increase with increasing irradiation dose. On the other hand elongation at break, permanent set and swelling number were found to decrease with increasing irradiation dose. Moreover, the effect of particle size of CaCO₃ was observed in a limited but apparent upgrading of mechanical, physico-chemical, and thermal properties. The order of semi-reinforcing capacity of three different types of CaCO₃ is as follow: CaCO₃ 2000 > CaCO₃ 700 > CaCO₃ 300 > unloaded blend. Whereby CaCO₃ 2000 has the smallest particle size.     

Characteristics study of clear polymethylmethacrylate dosimeter,Radix W,in several kGy range

Basic characteristics of Radix W, a commercially available undyed polymethylmethacrylate (PMMA) dosimeter conventionally used by readout at 320 nm, were studied in the dose range of 0.5–8 kGy, for its wide application especially for the evaluation of the sterilization dose and the quality assurance of food irradiation. The characteristics of dose response, the effect of irradiation temperature, and its stability after irradiation were examined over candidate readout wavelengths of 270–320 nm. The dose response readout at shorter wavelength is higher than that at longer wavelength, and 280 nm is the suitable readout wavelength for measurement of dose range of 0.5–8 kGy. The post-irradiation stability of dose response for 6 kGy is less than 1% within 24 h after irradiation at an irradiation temperature of 20 °C. Dose response is higher with temperature at irradiation temperatures in the range of −40 to 20 °C.     

The absolute configuration of an inherently chiral phosphonatocavitand and its use toward the enantioselective recognition of l-adrenaline

An inherently chiral ABii diphosphonato cavitand (±)-4 bearing a single quinoxaline bridging moiety was synthesized and resolved by chiral HPLC. Its chiroptical properties were investigated and VCD experiments allowed the determination of its absolute configuration. Distinguishable diastereomeric complexes in solution with l-adrenaline were observed by ¹H and ³¹P NMR together with a noticeable enantio-discrimination at 253 K (dr ～2:1) in favor of the dextrorotatory cavitand (+)-4.     

Utilization of oxidation reactions for the spectrophotometric determination of captopril using brominating agents

Three simple, accurate and sensitive methods (A–C) for the spectrophotometric assay of captopril (CPL) in bulk drug, in dosage forms and in the presence of its oxidative degradates have been described. The methods are based on the bromination of captopril with a solution of excess brominating mixture in hydrochloric acid medium. After bromination, the excess brominating mixture is followed by the estimation of surplus bromine by three different reaction schemes. In the first method (A), the determination of the residual bromine is based on its ability to bleach the indigo carmine dye and measuring the absorbance at 610 nm. Method B, involves treating the unreacted bromine with a measured excess of iron(II) and the remaining iron(II) is complexed with 1,10-phenanthroline and the increase in absorbance is measured at 510 nm. In method (C), the surplus bromine is treated with excess of iron(II) and the resulting iron(III) is complexed with thiocyanate and the absorbance is measured at 478 nm. In all the methods, the amount of bromine reacted corresponds to the drug content. The different experimental parameters affecting the development and stability of the color are carefully studied and optimized. Beer's law is valid within a concentration range of 0.4–6.0, 0.4–2.8 and 1.2–4.8 μg mL^?1 for methods A, B and C, respectively. The calculated apparent molar absorptivity was found to be 5.16 × 10⁴, 9.95 × 10⁴ and 1.74 × 10⁵ L mol^?1 cm^?1, for methods A, B and C, respectively. Sandell's sensitivity, correlation coefficients, detection and quantification limits are also reported. No interference was observed from common additives found in pharmaceutical preparations. The proposed methods are successfully applied to the determination of CPL in the tablet formulations with mean recoveries of 99.94–100.11% and the results were statistically compared with those of a reference method by applying Student's t- and F-test.     

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.     

In vitro evaluation of Radachlorin® sensitizer for photodynamic therapy

This paper reports the evaluation of a new photosensitizer, Radachlorin® in comparison with one of its well known components but used solely, Chlorin e₆. The photodynamic properties and cell uptake and localisation of the two drugs were compared. In vitro studies were conducted on human adenocarcinoma cells (HT29) and lung carcinoma cell line (A549). Both dyes showed an absorption maximum between 640 and 650 nm, but those absorption peaks are enhanced by interactions with serum, with a shifted maximum at 661 and 664 nm, and much higher absorbance. As Radachlorin® is constituted of different products and as photoreactivity is dependent on absorbed light energy, we chose to adapt concentrations so that both drugs had the same absorption at the irradiation wavelength (664 nm) for photoreactivity tests, and express concentrations in optical density at 664 nm. The capacity of the two drugs to generate Reactive Oxygen Species was identical, but on HT29 cells, Radachlorin® reaches its optimal LD50 sooner than Chlorin e₆. Radachlorin® LD50 on HT29 cells was 0.0251 OD_664nm after 2 h and 0.0672 OD_664nm for Chlorin e₆ for a 20 J cm^?2 irradiation. Radachlorin® gave very similar results on A549 cells, LD50 being 0.05 for 5 J irradiation, and 0.026 for 10 and 20 J cm^?2. Pharmacokinetics using fluorescence showed that, even if Radachlorin® quickly crossed HT29 (a human colonic cancer line) cell membrane, cellular distribution evolved from a diffuse cytoplasmic repartition 1 hour after Radachlorin® addition to a delimited localisation into organelles all around the nucleus. Radachlorin® intracellular fluorescence decreased after 4 h, whereas we did not observe a decrease of Chlorin e₆ intracellular fluorescence for times up to 24 h. In both case, a quick decline was observed as soon as the culture medium was replaced with a drug-free one. Radachlorin® appears to be an excellent photosensitizer, with similar phototoxicity to Chlorin e₆ on cell cultures, but with quicker kinetics, which could be an improvement if confirmed on further in vivo studies.     

Microfluidic cell with a TiO2-modified gold electrode irradiated by an UV-LED for in situ photocatalytic decomposition of organic matter and its potentiality for voltammetric analysis of metal ions

A novel microreactor for TiO₂-assisted photocatalysis in a microfluidic electrochemical cell was designed and constructed by a technology that can be reproduced in any chemical laboratory. The cell is obtained by a two-step thermal transfer of laser printed masks onto gold CD-Rs, a subtractive one to define the electrodes, and an additive one to define the channels. The TiO₂ nanoparticles are physically embedded in a gold matrix by electrodeposition from a solution of ions of this metal also containing colloidal suspension of anatase. This modification is conducted in the assembled microfluidic cell, with minimum material and time consumption. A 100 mW UV-LED (365 nm) is focused on the modified electrode and irradiation of the sample in the thin layer microreactor is conducted under stopped flow condition. The Cu–EDTA complex served as model system to demonstrate the in situ photocatalytic digestion of organic matter followed by the voltammetric determination of the metal ion in aqueous solution. The voltammetric wave of 1.0 × 10⁻³ mol L⁻¹ Cu(II) in acetate buffer (pH 4.7) at the gold electrode is suppressed by EDTA in the −0.3 to 0.8 vs. Ag/AgCl region. Irradiation of the bare electrode at 365 nm does not recover the wave, while irradiation of the TiO₂-modified gold electrode causes the recovery of the copper wave, proving the photocatalytic destruction of the chelating agent. Diffusion transport to/from the modified electrode rapidly enrolls the whole volume of sample in the thin-layer above the electrode (about 19 nL), so that in less than four minutes the recorded voltammogram become indistinguishable from that of a copper ion solution without EDTA. This novel in situ sample pre-treatment approach is very promising, deserving further research aiming its integration in micro-TAS.     

Gamma irradiation improves the antioxidant activity of Aloe vera (Aloe barbadensis miller) extracts

Aloe has been widely used in food products, pharmaceuticals, and cosmetics because of its aromatic and therapeutic properties. In the present study, the ethanolic extracts of aloe gel were gamma-irradiated from 10 to 100 kGy. After gamma irradiation, the color of the ethanolic extracts of aloe gel changed to red; this color persisted up to 40 kGy but disappeared above 50 kGy. Liquid chromatography/mass spectrometry analysis demonstrated the production of a new, unknown compound (m/z=132) after gamma irradiation of the ethanolic extracts of aloe gel. The amount of this unknown compound increased with increasing irradiation up to 80 kGy, and it was degraded at 100 kGy. Interestingly, it was found that gamma irradiation significantly increased the antioxidant activity, as measured by the 1,1-diphenyl-2-picrylhydrazyl-radical scavenging capacity. The antioxidant activity of aloe extract was dramatically increased from 53.9% in the non-irradiated sample to 92.8% in the sample irradiated at 40 kGy. This strong antioxidant activity was retained even at 100 kGy. These results indicate that gamma irradiation of aloe extract can enhance its antioxidant activity through the formation of a new compound. Based on these results, increased antioxidant activity of aloe extracts by gamma rays can be applied to various industries, especially cosmetics, foodstuffs, and pharmaceuticals.     

Electrochemical preparation and characterisation of CoPt magnetic particles

CoPt particles of different size and modulate magnetic properties have been prepared by electrodeposition. Particles of growing size from 50 nm until continuous deposits have been obtained and their composition, crystalline structure and magnetic properties have been analyzed. The prepared CoPt particles from 50 nm to 250 nm showed ferromagnetic behaviour so did the continuous deposits. However, drastic changes in magnetism have been detected related to the size of the particles: the smallest particles presented lower coercivity which increases with increasing size, with a maximum value for particles of 150–250 nm diameter. The coercivity decreased when continuous deposits were attained due to the disordered growing and the loss of the surface anisotropy.     

Photooxidation of phenol in aqueous nanodispersion of humic acid

Photooxidation of phenol sensitized by Aldrich humic acid (AHA) has been studied in an aqueous solution at neutral and basic pH. Solutions containing phenol and AHA of various concentrations were irradiated with monochromatic light at 253.7 nm or with polychromatic light within the wavelength range of 310–420 nm. The quantum yields of phenol photodegradation under these conditions were determined. At the wavelength of 253.7 nm direct degradation of phenol was much more effective than that sensitized by AHA. With polychromatic light the photooxidation was found to be strongly dependent on pH of aqueous solution and independent on AHA concentration.     

Electronic and vibrational spectra of tourmaline – The impact of electron beam irradiation and heat treatment

Irradiation and heat treatment were performed on tourmalines of various colors from Antandrokomby, Madagascar. The samples were irradiated with 10 MeV electrons to fluencies of 2 ×10¹⁷ cm⁻² for 1 h and were heated at 550 °C for 3 h in air. Their electronic and vibrational spectra were investigated by UV–vis, mid-infrared, and WD-XRF spectroscopy for comparison to pristine samples. Changes in the Mn³⁺ ions after irradiation resulted in darker pink tourmalines, which had absorption peaks at 390 and 520 nm. These samples became colorless after subsequent heat treatment. After irradiation, colorless, light blue and yellow tourmalines displayed a new absorption band at 365 nm. Alteration of the stretching absorption bands and wavenumber after irradiation could be explained by the following reactions:OH⁻ + e⁻ beam irradiation → O⁻ + H°,Mn²⁺ + e⁻ beam irradiation → Mn³⁺ + e⁻ andFe²⁺ + e⁻ beam irradiation → Fe³⁺ + e⁻.Stretching vibration of the BO₃ structure occurred at 1330 cm⁻¹, while the SiO vibration absorption bands were assigned to around 1100 cm⁻¹. Colorless, green, and yellow tourmalines showed high-intensity peaks around 3608 and 3505 cm⁻¹ after irradiation. Pink and dark green tourmalines showed low-intensity peaks at 3605 and 3585 cm⁻¹, respectively. The combination modes of stretching and bending in the range of 4600–4300 cm⁻¹ were split after irradiation and heat treatment, and different color changes occurred after irradiation.     

Nutritional,physiological, physicochemical and sensory stability of gamma irradiated Kimchi (Korean fermented vegetables)

Effects of gamma irradiation on nutritional, physiological, physicochemical and sensory properties of the Korean lactic acid fermented vegetable, Kimchi, were investigated. The composition of amino acids and organic acids in Kimchi were not influenced by gamma irradiation less than 10 kGy. Angiotensine converting enzyme inhibitory, xanthin oxidase inhibitory, electron donating and antimicrobial activity of Kimchi extract were stable up to 10 kGy. There were no significant changes in pH and texture at less than 10 kGy. Color values were influenced at 10 kGy of gamma irradiation, and resulted in the increase of L*- and reduction of a*-value. About 90% of panelists identified a sensory difference between non-irradiated and 10 kGy-irradiated sample, and Kimchi irradiated at 10 kGy had lower scores in acceptability than those of the control or irradiated at 2.5 and 5 kGy.     

Systematic fabrication of chitosan nanoparticle by gamma irradiation

The present investigation is mainly focused on the systematic preparation of chitosan nanoparticle in the potential range 1–100 nm using γ-ray irradiation. The effect of irradiation conditions in terms of physical form of chitosan, i.e. flake, colloidal and acidic solution, and γ-ray dose was studied. The molecular weights of chitosan were 10, 25, and >1000 times reduced when irradiated with the γ-ray dose as high as 100 kGy in Chi-flake, Chi-colloid, and Chi-acid, respectively. The particle size reduced to 70 nm after being irradiated to only 10 kGy γ-rays and it showed a tendency to decrease when the γ-ray doses were increased. The γ-rays effectively induced the reduction of chitosan particle size to <100 nm with narrow size distribution. The effective size reduction was particularly observed in Chi-colloid. Heterogeneous chemical conjugation of deoxycholic acid onto 10 kGy irradiated Chi-colloid resulted in narrow particle size as small as 50 nm.     

Effect of gamma irradiation on physical characteristics of Jordanian durum wheat and quality of semolina and lasagna products

This study was conducted to determine the effect of using varying gamma irradiation doses on the physiochemical and rheological properties of semolina and its products. Ash, protein and water content were not influenced with gamma irradiation, while falling number and fungi counts decreased with increasing irradiation dose. Irradiation adversely affected wet gluten at 5 kGy dose. Dough stability was deteriorated vigorously with increasing irradiation dose. Sensory evaluation showed that lasagna produced from 0.25- and 1 kGy-irradiated semolina did not show any significant differences as compared with the control sample.