Some Properties of Electron Beam-Irradiated Sheep Wool Linked to Cr(III) Sorption.

We examined the characteristics of an electron beam irradiated wool with an absorbed dose of (21-410) kGy in comparison with natural wool with respect to the determination of the isoelectric point (IEP), zero charge point (ZCP), mechanism of Cr(III) sorption from higher concentrated solutions, and the modelling of the wool-Cr(III) interaction. The data of ZPC and IEP differed between natural and irradiated samples. Increasing the dose shifted the pH of ZPC from 6.85 for natural wool to 6.20 for the highest dosed wool, while the natural wool IEP moved very little, from pH = 3.35 to 3.40 for all of the irradiated samples. The sorption experiments were performed in a pH bath set at 3.40, and the determination of the residual Cr(III) in the bath was performed by VIS spectrometry under optimized conditions. The resulting sorptivity showed a monotonically rising trend with increasing Cr(III) concentration in the bath. Lower doses, unlike higher doses, showed better sorptivity than the natural wool. FTIR data indicated the formation of complex chromite salts of carboxylates and cysteinates. Crosslinks via ligands coming from different keratin chains were predicted, preferably on the surface of the fibers, but to a degree that did not yet inhibit the diffusion of Cr(III)-cations into the fiber volume. We also present a concept of a complex octahedral structure.

Role of Post-Exposure Time in Co(II) Sorption of Higher Concentrations on Electron Irradiated Sheep Wool.

Sorption of Co(II) was investigated on natural as well as accelerated electron beam modified sheep wool involving low and high concentrations up to 200 mmol·dm-3. The sorption experiments confirmed the dependence of the sorption capacity not only on sorbate concentration and absorbed dose of energy, but also on post-exposure time. Post-exposure heating to accelerate transformation of the wool structure was of no effect on the sorption comparing with a simple storage for a period of 100 days. Under all tested conditions, the sorption maximum was measured for Co(II) concentration of 125 mmol·dm-3 and that was assigned to form a Co(II) complex with keratin. This assumption was tested on visible spectra of mixed solutions of Arginine and Co(II) to be a simplified model of Co(II) interaction with keratin. The sorption decrease is associated with generation of cross links between macro-chains through ligands of the Co-complex. The nodal points are a hindrance to diffusion of next ions into the fibers. Also, pH variations of aqueous extracts from the wool samples depending on absorbed dose and post-exposure time indicate complexity of the structural transformation being specific for each dose applied.

Why Natural or Electron Irradiated Sheep Wool Show Anomalous Sorption of Higher Concentrations of Copper(II).

Sorption of higher concentrations of Cu(II) solution onto natural sheep wool or wool irradiated by an electron beam was studied. Sorption isotherms were of unexpected character, showing extremes. The samples with lower absorbed doses adsorbed less than non-irradiated wool, while higher doses led to increased sorption varying with both concentration and dose. FTIR spectra taken from the fibre surface and bulk were different. It was concluded that there was formation of Cu(II)-complexes of carboxylic and cysteic acids with ligands coming from various keratin macromolecules. Clusters of chains crosslinked through the ligands on the surface limit diffusion of Cu(II) into the bulk of fibre, thus decreasing the sorption. After exhausting the available ligands on the surface the remaining Cu(II) cations diffuse into the keratin bulk. Here, depending on accessibility of suitable ligands, Cu(II) creates simple or complex salts giving rise to the sorption extremes. Suggestion of a mechanism for this phenomenon is presented.

Assessing the impact of synchrotron X-ray irradiation on proteinaceous specimens at macro and molecular levels.

Synchrotron radiation (SR) has become a preferred technique for the analysis of a wide range of archeological samples, artwork, and museum specimens. While SR is called a nondestructive technique, its effect on proteinaceous specimens has not been fully investigated at the molecular level. To investigate the molecular level effects of synchrotron X-ray on proteinaceous specimens, we propose a methodology where four variables are considered: (1) type of specimen: samples ranging from amino acids to proteinaceous objects such as silk, wool, parchment, and rabbit skin glue were irradiated; (2) synchrotron X-ray energy; (3) beam intensity; (4) irradiation time. Irradiated specimens were examined for both macroscopic and molecular effects. At macroscopic levels, color change, brittleness, and solubility enhancement were observed for several samples within 100 s of irradiation. At molecular levels, the method allowed one to quantify significant amino acid modifications. Aspartic acid (Asp), wool, parchment, and rabbit skin glue showed a significant increase in Asp racemization upon increasing irradiation time with rabbit skin glue showing the greatest increase in d-Asp formation. In contrast, Asp in silk, pure cystine (dimer of cysteine), and asparagine (Asn) did not show signs of racemization at the irradiation times studied; however, the latter two compounds showed significant signs of decomposition. Parchment and rabbit skin glue exhibited racemization of Asp, as well as racemization of isoleucine (Ile) and phenylalanine (Phe) after 100 s of irradiation with a focused beam. Under the experimental conditions and sample type and dimensions used here, more change was observed for focused and low energy (8 keV) beams than unfocused or higher energy (22 keV) beams. These results allow quantification of the change induced at the molecular level on proteinaceous specimens by synchrotron X-ray radiation and help to define accurate thresholds to minimize the probability of damage occurring to cultural heritage specimens. For most samples, damage was usually observed in the 1-10 s time scale, which is about an order of magnitude longer than SR studies of cultural heritage under X-ray fluorescence (XRF) mode; however, it is consistent with the duration of X-ray absorption spectroscopy (XAS) and microcomputed tomography (µCT) measurements.

Sonosynthesis of nano TiO2 on wool using titanium isopropoxide or butoxide in acidic media producing multifunctional fabric.

This study presents a novel idea to prepare nanocrystalline structure of TiO2 under ambient pressure at 60-65 °C using in situ sonochemical synthesis by hydrolysis of either titanium isopropoxide or titanium butoxide in an acidic aqueous solution. The nano titanium dioxide coated wool fabrics possess significant antibacterial/antifungal activity and self-cleaning property by discoloring Methylene blue stain under sunlight irradiation. This process has no negative effect on cytotoxicity and tensile strength of the sonotreated fabric even reduces alkaline solubility and photoyellowing and improves hydrophilicity. More titanium isopropoxide or titanium butoxide as a precursor led to higher photocatalytic activities of the treated fabrics. Also introducing more ethanol improved the adsorption of TiO2 on the wool fabric surface leading to enhanced photocatalytic activity. EDS and XRD patterns, SEM images, X-ray mapping confirmed the presence of nano TiO2 particles on the fabric surface. The role of both solvent and precursor concentrations on the various properties of the fabric was investigated and the optimized conditions were obtained using response surface methodology.

Ultrasound for low temperature dyeing of wool with acid dye.

The possibility of reducing the temperature of conventional wool dyeing with an acid levelling dye using ultrasound was studied in order to reach exhaustion values comparable to those obtained with the standard procedure at 98 °C, obtaining dyed samples of good quality. The aim was to develop a laboratory method that could be transferred at industrial level, reducing both the energy consumption and fiber damage caused by the prolonged exposure to high temperature without the use of polluting auxiliary agents. Dyeings of wool fabrics were carried out in the temperature range between 60 °C and 80 °C using either mechanical or ultrasound agitation of the bath and coupling the two methods to compare the results. For each dyeing, the exhaustion curves of the dye bath were determined and the better results of dyeing kinetics were obtained with ultrasound coupled with mechanical stirring. Hence the corresponding half dyeing times, absorption rate constants according to Cegarra-Puente modified equation and ultrasonic efficiency were calculated in comparison with mechanical stirring alone. In the presence of ultrasound the absorption rate constants increased by at least 50%, at each temperature, confirming the synergic effect of sonication on the dyeing kinetics. Moreover the apparent activation energies were also evaluated and the positive effect of ultrasound was ascribed to the pre-exponential factor of the Arrhenius equation. It was also shown that the effect of ultrasound at 60 °C was just on the dye bath, practically unaffecting the wool fiber surface, as confirmed by the results of SEM analysis. Finally, fastness tests to rubbing and domestic laundering yielded good values for samples dyed in ultrasound assisted process even at the lower temperature. These results suggest the possibility, thanks to the use of ultrasound, to obtain a well equalized dyeing on wool working yet at 60°C, a temperature process strongly lower than 98°C, currently used in industry, which damages the mechanical properties of the fibers.

Photo induced silver on nano titanium dioxide as an enhanced antimicrobial agent for wool.

In this study an effective nanocomposite antimicrobial agent for wool fabric was introduced. The silver loaded nano TiO(2) as a nanocomposite was prepared through UV irradiation in an ultrasonic bath. The nanocomposite was stabilized on the wool fabric surface by using citric acid as a friendly cross-linking agent. The treated wool fabrics indicated an antimicrobial activity against both Staphylococcus aureus and Escherichia coli bacteria. Increasing the concentration of Ag/TiO(2) nanocomposite led to an improvement in antibacterial activities of the treated fabrics. Also increasing the amount of citric acid improved the adsorption of Ag/TiO(2) on the wool fabric surface leading to enhance antibacterial activity. The EDS spectrum, SEM images, and XRD patterns was studied to confirm the presence of existence of nanocomposite on the fabric surface. The role of both cross-linking agent and nanocomposite concentrations on the results was investigated using response surface methodology (RSM).

Proteomic evaluation and location of UVB-induced photo-oxidation in wool.

Photo-oxidation of proteinaceous fibres correlates directly to lowered appearance retention and performance, with particular commercial significance for wool and human hair. We here outline the first detailed proteomic evaluation of differential photo-oxidation occurring in the cuticle and cortex of wool fibres. After exposure of whole wool to UVB irradiation, physical disruption techniques designed to minimise further oxidative modification were utilised to prepare enriched cuticle and cortex fractions. This was followed by comprehensive redox proteomic analyses of photo-oxidation via the location within the fibre components of modifications to aromatic residues. An oxidative classification system was developed and applied to provide further insight into differential photo-oxidation. These results were compared with coloration changes observed within the cuticular and cortical components of the fibre. In this study, although the cuticle was observed to have a higher level of baseline oxidation, the cortex exhibited significantly higher levels of photo-oxidation under UVB irradiation. These proteomic results were supported by the observation of significantly higher photoyellowing within the cortex than within the cuticle. It has been assumed that fibre photo-oxidation was predominantly confined to the wool cuticle, and that changes within the cuticle had the greatest effect on appearance retention. These results provide new insight into the contribution of the cortex to photo-induced discoloration of proteinaceous animal fibres.

A morphology-related study on photodegradation of protein fibres.

The wool fibre has a complex morphology, consisting of an outer layer of cuticle scales surrounding an inner cortex. These two components are hard to separate effectively except by using harsh chemical treatments, making it difficult to determine the susceptibility of the different components of the fibre to photoyellowing. An approach to this problem based on mechanical fibre modification is described. To expose the inner cortex of wool to different degrees, clean wool fibres were converted into 'powders' of various fineness via mechanical chopping, air-jet milling, ball milling or their combination. Four types of powdered wool (samples A, B, C and D) were produced with reducing particle size distributions and an increasing level of surface damage as observed using SEM. Sample A contained essentially intact short fibre snippets and sample D contained a large amount of exposed cortical materials. Samples B and C contained a mixture of short fibre snippets and cortical materials. Solid wool discs were then compressed from the corresponding powder samples in a polished stainless steel die to enable colour measurement and UV irradiation studies. ATR-FTIR studies on powder discs demonstrated a small shift in the amide I band from 1644cm(-1) for disc A to 1654cm(-1) for disc D due to the different structures of the wool cuticle and cortex, in agreement with previous studies. Similarly an increase in the intensity ratio of the amide I to amide II band (1540cm(-1)) was observed for disc D, which contains a higher fraction of cortical material at the surface of the disc. Discs prepared from sample D appeared the lightest in colour before exposure and had the slowest photoyellowing rate, whereas discs made from powders A-C with a higher level of cuticle coverage were more yellow before exposure and experienced a faster rate of photoyellowing. This suggests that the yellow chromophores of wool may be more prevalent in cuticle scales, and that wool photoyellowing occurs to a greater extent in the cuticle than in the cortex. Photo-induced chemiluminescence measurements showed that sample D had a higher chemiluminescence intensity after exposure to UVA radiation and a faster decay rate than samples A and B. Thus one of the roles of the wool cuticle may be to protect the cortex by quenching of free radical oxidation during exposure to the UV wavelengths present in sunlight.

Effects of ultrasound irradiation on wet wool chlorination treatment.

In this study ultrasonic energy is applied for improving wet wool chlorination treatment one of the most well-established methods for reducing wool shrinking related to the felting. Sodium hypochlorite used for providing active chlorine in chlorination bath and samples chlorinated in the presence and absence of ultrasonic irradiation with equal processing parameters. The concentration of active chlorine during the treatment, shrinkage percentage, friction and some mechanical properties of treated samples determined and compared. Scanning Electron Microscope used for investigating the effects of different treatments on removal of wool scales. According to the results it was concluded that applying ultrasonic energy causes desirable mechanical and chemical effects in chlorination process. Cavitation phenomena causes more abrasion on wool surface especially on sharp places i.e., scales and the formation of hydrogen peroxide in ultrasonic bath managing the aggressive reaction of active chlorine on cuticle.

Properties of radicals formed by the irradiation of wool fibers.

Wool fibers of different sample conditions were irradiated in different atmospheres by (60)Co gamma-rays and were studied by electron spin resonance method (ESR). It was found that a large percentage of the alpha-carbon radicals of polymer main chain were more long-lived radicals. The ESR measurements of irradiated cortex samples of the wool fibers proved that most radicals from the cortex were long-lived ones. Low water content (as low as 27.5%) in the reaction system did not greatly affect the radical formation, but higher water contents would reduce the radical concentrations dramatically and accelerate their decaying process. The results will be of help in property modification of wool products by radiation graft copolymerization.