SERS and Raman imaging as a new tool to monitor dyeing on textile fibres

Textile fibres containing Ag nanoparticles have been widely explored for a number of antimicrobial fabrics. Moreover, it is well‐known that textile dyeing is a critical stage in the manufacture thereof. This research shows that surface enhanced Raman scattering (SERS) and Raman imaging can be used with advantage in the monitoring of this process. Using Ag containing linen fibres stained with methylene blue (MB), it was possible to map the local distribution of the MB dye in the fibres by Raman imaging. MB was selected as the SERS molecular probe and as a model dye. Composites of linen fibres and Ag nanoparticles were prepared by distinct methods and used as SERS substrates in order to evaluate the effect of the preparative method on the Raman images. Our results demonstrate that by using Raman imaging associated to the presence of Ag nanoparticles, it is possible to distinguish the local distribution of the dye on the textile surface. This investigation allows to foreseeing the use of this technique in terms of quality control of Ag containing fabrics, which is a market in great expansion. Copyright © 2016 John Wiley & Sons, Ltd.     

Kinetic Analysis of the Decomposition of Chelates of Di-alkyldithiocarbamate of Cd(II)

The thermal decomposition kinetics of the solid complexes Cd(S₂ CNR₂ )₂ , where R =C₂ H₅ , n -C₃ H₇ , n -C₄ H₉ or iso -C₄ H₉ , was studied by using isothermal and non-isothermal thermogravimetry. The superimposed TG/DTG/DSC curves revealed that thermal decomposition reactions occur in the liquid phase. The kinetic model that best fitted the experimental isothermal TG data was the one-dimensional phase-boundary reaction-controlled process R₁ . The thermal analysis data suggested the thermal stability sequence Cd(S₂ CNBuⁿ ₂ )₂ >Cd(S₂ CNPrⁿ ₂ )₂ >Cd(S₂ CNBuⁱ ₂ )₂ >Cd(S₂ CNEt₂ )₂ , which accords with the sequence of stability of the apparent activation energies. This revised version was published online in July 2006 with corrections to the Cover Date.     

Antioxidant defenses and DNA damage induced by UV-A and UV-B radiation in the crab Chasmagnathus granulata (Decapoda, Brachyura)

The photoprotector role of pigment dispersion in the melanophores of the crab, Chasmagnathus granulata, against DNA and oxidative damages caused by UV-A and UV-B was investigated. Intact and eyestalkless crabs were used. In eyestalkless crabs, the dorsal epidermis of the cephalothorax (dispersed melanophores) and the epidermis of pereiopods (aggregated melanophores) were analyzed. Intact crabs showed only dispersed melanophores in the two epidermis. Antioxidant enzymes activity and lipoperoxidation content were analyzed after UV-A (2.5 J/cm2) or UV-B (8.6 J/cm2) irradiation. DNA damage was analyzed by single cell electrophoresis (comet) assay, after exposure to UV-B (8.6 J/cm2). UV-A radiation increased the glutatione-S-transferase activity in the pereiopods epidermis of eyestalkless crabs (P<0.05). UV-B radiation induced DNA damage in the dorsal epidermis of eyestalkless crabs (P<0.05). In pereiopod epidermis of eyestalkless crabs, there was no significant difference between control and UV-B-exposed crabs. In the pereiopods epidermis of eyestalkless, the control group showed higher scores of DNA damage and approximately 50% of cellular viability. Because in eyestalkless and irradiated crabs the cellular viability was approximately 5%, it was not possible to observe nuclei for determination of DNA damage. The findings show that melanophores can play a role in the defense against harmful effects of a momentary exposure to UV radiation.     

Preparation of nanocomposites by reversible addition‐fragmentation chain transfer polymerization from the surface of quantum dots in miniemulsion

Herein, we report the synthesis of quantum dots (QDs)/polymer nanocomposites by reversible addition‐fragmentation chain transfer (RAFT) polymerization in miniemulsions using a grafting from approach. First, the surfaces of CdS and CdSe QDs were functionalized using a chain transfer agent, a trisalkylphosphine oxide incorporating 4‐cyano‐4‐(thiobenzoylsulfanyl)pentanoic acid moieties. Using a free radical initiator (AIBN) to activate the RAFT process, a polystyrene (PS) block was grafted from the surface of the QDs. Quantum confinement effects were identified for the nanocomposite obtained, so attesting to the integrity of the QDs after the polymerization. Free PS chains were also present in the final nanocomposite, indicating that the RAFT polymerization from the surface of the QDs was accompanied by conventional free radical polymerization. After isolating the nanocomposite particles, a second poly(n‐butyl acrylate) block was tentatively grown from the initial PS block. The first results indicated a successful polymerization of the second polymer and show the potential of the current strategy to prepare block copolymers from the surface of the RAFT‐modified QDs. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5367–5377, 2009     

Hardness anomalies on Cr 1−x Fe x (0.05<x<0.323) alloys: Mössbauer effect study

The hardness of Cr_1-xFe_x α solid solutions presents an anomalous behaviour in the range 0.10<xFe<0.30, that has been explained either by magnetic or electronic effects. In order to verify wether the anomalies were intrinsic to that phase or were induced by impurities, measurements of microhardness and isomer shift of samples of high purity Cr_1-xFe_x α solid solutions (0.05<xFe<0.323) were carried out. We found that the hardness presents a maximum and a minimum for xFe-0.19 and xFe-0.17, respectively, which are inferior to the amplitudes of the anomalies found by previous authors using lower purity alloys. Within the limit of experimental error, the isomer shift at room temperature varies linearly with the composition. These results suggest that impurities play a major role in determining the magnitude of the hardness anomalies and that electron transfer varies smoothly in the concentration range studied.     

Towards a Lanczos’ $$\tau $$-Method Toolkit for Differential Problems

The aim of this work is to build a numerical software library based on the \(\tau \)-method to solve differential problems using MATLAB. The \(\tau \)-method can be very effective in the solution of certain type of these problems, and therefore, the existence of a numerical library for its dissemination is of major importance. Furthermore, the method has been used for the solution of particular problems but has not yet been explored as a general technique. Focus will be on stability issues, namely those issued from the solution of algebraic linear systems required for the process. Additionally, preconditioners for the solution with the \(\tau \)-method will be tackled, with emphasizes on incomplete LU factorizations and (block) Jacobi preconditioners. We also propose an iterative approach, build upon an LU factorization over a moderate initial size, generating better approximations and providing a priori error estimate at each iteration. Numerical results enlightening the efficiency of the proposed methods will be presented.     

Aging mechanisms of oil-in-water emulsions based on a bioemulsifier produced by Yarrowia lipolytica

The aging mechanisms of oil-in-water emulsions prepared with Yansan, a bioemulsifier produced by a Brazilian wild strain of Yarrowia lipolytica, IMUFRJ 50682, in glucose-based fermentation medium, were studied and compared with those prepared with Gum Arabic. Oil-in-water emulsions obtained by combining three different organic phases, perfluoro-n-hexane, n-hexadecane and toluene, with two aqueous buffers of different pH, and two bioemulsifiers, were studied through the evolution of the mean droplet size. The emulsions were prepared by sonication and their droplet size distribution was followed for 60 days at 301 K using image analysis. The results indicate that the aging mechanisms of the studied emulsions depend mainly on the bioemulsifier and on the pH of the medium. It is shown that the emulsions containing Gum Arabic age by coalescence while Yansan-based emulsions change their aging mechanisms from coalescence at pH 3 to molecular diffusion at pH 7.     

Rheological behavior of thermoreversible kappa-carrageenan/nanosilica gels

The rheological behavior of silica/kappa-carrageenan nanocomposites has been investigated as a function of silica particle size and load. The addition of silica nanoparticles was observed to invariably impair the gelation process, as viewed by the reduction of gel strength and decrease of gelation and melting temperatures. This weakening effect is seen, for the lowest particle size, to become slightly more marked as silica concentration (or load) is increased and at the lowest load as particle size is increased. These results suggest that, under these conditions, the particles act as physical barriers to polysaccharide chain aggregation and, hence, gelation. However, for larger particle sizes and higher loads, gel strength does not weaken with size or concentration but, rather, becomes relatively stronger for intermediate particles sizes, or remains unchanged for the largest particles, as a function of load. This indicates that larger particles in higher number do not seem to increasingly disrupt the gel, as expected, but rather promote the formation of stable gel network of intermediate strength. The possibility of this being caused by the larger negative surface charge found for the larger particles is discussed. This may impede further approximation of neighboring particles thus leaving enough inter-particle space for gel formation, taking advantage of a high local polysaccharide concentration due to the higher total space occupied by large particles at higher loads.