Ana D. Kramar

Silver incorporation on viscose and cotton fibers after air, nitrogen and oxygen DBD plasma pretreatment

Dielectric barrier discharge (DBD) pretreatments in air, nitrogen and oxygen plasma of viscose and cotton fabrics with subsequent immobilization of silver were studied. Surface activation of treated fibers was evaluated through subsequent sorption of silver from aqueous AgNO3 solution, after which changes in the surface morphology were monitored and quantity of silver deposition on fabric was measured. The plasma treatment was done in volume DBD discharge with the gap distance between electrodes of 0.5 and 2 mm. Depending on the gas used in pretreatment, significant difference in the way silver bonds to the textile surface was found. Nitrogen plasma pretreatment with gap distance of 0.5 mm led to the homogeneous fiber coating by silver nanoparticles with average size up to 300 nm estimated by SEM, while fibers treated in oxygen plasma adsorbed silver in a form of ions. The plasma pretreatment in air leads to changes that contain features of fibers treated in both nitrogen and oxygen DBD plasma. Distinct difference of used configuration of the plasma source is a use of gap distance 0.5 mm, which is in order of textile thickness. Observed results allow us to report a new way how to immobilize silver nanoparticles onto textile fibers using plasma pretreatment with subsequent sorption of silver from aqueous solution.Graphical Abstract

Study of interaction between nitrogen DBD plasma-treated viscose fibers and divalent ions Ca2+ and Cu2+

Viscose fibers were treated with atmospheric pressure dielectric barrier discharge (DBD) plasma obtained in nitrogen in order to activate the fiber surface prior to sorption of the divalent ions Ca2+ and Cu2+. Methylene blue sorption was used for estimation of carboxyl group formation on the surface after DBD plasma treatment, through the degree of fabric staining (K/S). Sorption of divalent ions was performed from solutions of each individual ion and from solutions of calcium and copper in succession onto untreated and plasma-treated viscose samples. The quantity of sorbed metal was determined from the neutralization and iodometric titration method. Scanning electron microscopy coupled with energy dispersive X-ray analysis was used for fiber morphology and surface characterization before and after plasma treatment, and after metal ions sorption. Experiments revealed copper microparticles formation on the fiber surface when sorption of copper was performed on samples with bonded calcium. Further analysis confirmed that for growth of copper particles, both calcium ions and nitrogen DBD plasma pretreatments are necessary.

Preparation and characterization of silver-loaded hemp fibers with antimicrobial activity

The objective of this research was to impart antimicrobial properties to hemp fibers by incorporation of silver ions in hemp fibers by chemisorption. Sorption properties of hemp fibers were improved by non-selective oxidation using hydrogen peroxide and potassium permanganate. The optimal conditions for silver ions sorption by hemp fibers were determined by changing sorption conditions: pH value and concentration of aqueous silver nitrate solution, as well as duration of sorption. The maximum sorption capacity of modified hemp fibers was 1.84 mmol of Ag+ ions per gram of fibers. Antimicrobial activity of silver-loaded hemp fibers against different pathogens: Staphylococcus aureus, Escherichia coli, and Candida albicans was evaluated in vitro. Obtained silver-loaded hemp fibers show antimicrobial activity against tested pathogens.

Influence of hemicelluloses and lignin content on structure and sorption properties of flax fibers (Linum usitatissimum L.)

In this work, alkali and oxidative treatments were employed to obtain flax fibers with different content of hemicelluloses and lignin, in order to study the influence of chemical composition on structure and sorption properties of flax fibers. The flax fibers were characterized using FTIR spectroscopy and FESEM microscopy, and by determination of chemical composition, carboxyl group content, electrokinetic and sorption properties. Adsorption of silver ions was used to evaluate flax fiber sorption properties, but also to obtain antimicrobial fibers whose antimicrobial activity was tested against Gram-negative bacteria Escherichia coli, Gram-positive bacteria Staphylococcus aureus and fungi Candida albicans. The progressive removal of hemicelluloses or lignin influenced the sorption properties through the increased liberation of elementary fibers and accessibility of functional surface groups of flax fibers. Removal of hemicelluloses led to increase of iodine sorption without significant change in functional groups content and electrokinetic properties. On the other hand, lignin removal led to an increase of functional groups content, namely carboxyl groups, which in turn influenced better moisture and silver ions sorption. Flax fibers with incorporated silver exhibit fair antimicrobial activity against Gram (−) E. coli, Gram (+) S. aureus and fungi C. albicans.

Electrical Resistivity of Plasma Treated Viscose and Cotton Fabrics with Incorporated Metal Ions

Cellulose fabrics (viscose and cotton) were treated with atmospheric pressure dielectric barrier discharge (DBD) in air. After DBD treatment, samples were characterized and volume electrical resistance was measured under different relative humidity conditions (φ=40-55 %). Results have shown that DBD treatment increases wettability and polar surface functional groups content, which consequently causes a decrease of volume electrical resistivity of cellulose fabrics in measured relative humidity range (φ=40-55 %). Metal ions (silver, copper, and zinc) were incorporated in untreated and plasma treated samples through sorption from aqueous solutions and incorporation of metal ions into plasma treated cellulose samples decreased electrical resistivity even further. Resistivity of cotton and viscose fabrics with incorporated metal ions followed the order Zn2+ > Cu2+ > Ag+. The most pronounced decrease, for entire order of a magnitude, was obtained by modification of cotton fabric with DBD and silver ions, where value of resistivity dropped from GΩ to a several dozens of MΩ.

Surface cleaning of raw cotton fibers with atmospheric pressure air plasma

In this work, a possibility to use atmospheric pressure plasma treatment to clean cotton fibers surface was investigated. Dielectric barrier discharge (DBD) operating in air was used as plasma source. After plasma treatment, cotton fibers were characterized using several surface techniques: SEM, XPS, ATR-FTIR and zeta potential measurement; also wettability was evaluated using capillary height measurement. Results of investigation showed that plasma treatment primarily affects cuticle and primary wall of cotton which provides cleaning of the fibers surface. This caused increase of polar groups accessibility and better wettability of cotton samples. An attempt has been made to locate influence of plasma treatment on different structural layers of cotton fibers using different surface techniques. In addition, surface charge was investigated through measuring streaming potential and a connection was established between zeta potential and plasma treatment time. Furthermore, it was shown that measuring of zeta potential could be used as an additional technique to track changes and elucidate mechanisms of plasma treatment influence on cotton fibers.

Properties of cotton yarns after oxidation of potassium permanganate in an acidic environment

The impact of nonselective cellulose oxidation (cotton fibre) by potassium permanganate in acidic environment, with or without additional treatment by sodium metabisulfite, on change of sorption (silver ions sorption), and deposition of manganese (IV) oxide were aims of this work. The standard methods and methods developed at Department of Textile Engineering of Faculty of Technology and Metallurgy Belgrade, were used for determination of introduced functional groups, sorption and mechanical properties of selected fibres. Inductively coupled plasma optical emission spectrometry ICP-OES was used for determination of manganese(IV) oxide deposited on cotton fibres. The changes of studied properties of cotton fibres were followed as a function of concentration and pH of the solution of oxidizing agent. Results obtained in this work showed that oxidized cotton fibre with improved sorption properties is appropriate as an initial raw for a wide range of textile products of special assignment.