Colloids and Surfaces B: Biointerfaces 97 (2012) 171–174 Contents lists available at SciVerse ScienceDirect Colloids and Surfaces B: Biointerfaces jou rn al h om epage: www.elsevier.com/locate/colsurfb Short communication Plasma treatment allows water suspending of the natural hydrophobic powder (lycopodium) Edward Bormashenko ∗ , Roman Grynyov Ariel University Center of Samaria, Physics Faculty, 40700, P.O.B. 3, Ariel, Israel a r t i c l e i n f o Article history: Received 29 November 2011 Received in revised form 26 March 2012 Accepted 12 April 2012 Available online 20 April 2012 Keywords: Air and nitrogen plasma Lycopodium Water suspending Wetting properties Wetting transition a b s t r a c t Lycopodium particles which are spores of the plant Lycopodium clavatum were exposed to cold oxygen and nitrogen plasma irradiation. Wetting properties of the particles changed dramatically from hydrophobic to hydrophilic. Plasma treatment allowed obtaining stable water suspensions of lycopodium. Plasma treatment did not affect the morphology of lycopodium particles. The reported results open the way for surfactants-free manufacturing suspensions of hydrophobic particles. © 2012 Elsevier B.V. All rights reserved. 1. Introduction The plasma treatment of polymer surfaces is a widely used method to modify the physical and chemical properties of the sur- face [1–8]. The plasma treatment creates a complex mixture of surface functionalities which influence surface physical and chem- ical properties and results in a dramatic change of wetting behavior of the surface [1–8]. Not only the chemical structure but also the roughness of the surface is effected by the plasma treatment, this also could change the wettability of the surface [9]. It has been also demonstrated that wetting of biological tissue (keratin) could be modified by low temperature water vapor plasma [10,11]. It is important from the technological point of view that not only planar surfaces but also polymer powders could be successfully modified by plasma treatment. It has been shown recently that the contact angle of polyethylene powder particles could be decreased significantly with plasma treatment [12,13]. Thus, water/polymer suspensions could be produced without tensides [12,13]. Our paper reports the dramatic change in wetting prop- erties of lycopodium exposed to air and nitrogen plasma treatment. Lycopodium particles which are spores of the plant Lycopodium clavatum demonstrate pronounced hydrophobicity [14–19]. Lycopodium particles were successfully applied as sole emulsifiers of oil and water mixtures [17]. We demonstrate that ∗ Corresponding author. E-mail address: edward@ariel.ac.il (E. Bormashenko). plasma treatment of intrinsically hydrophobic lycopodium parti- cles allowed non-surfactant preparing of their water suspensions. 2. Experimental: materials and methods Lycopodium particles were supplied by Fluka. The SEM images of typical lycopodium particles are presented in Fig. 1. SEM imaging was carried out with high resolution SEM (JSM-6510 LV). Lycopodium particles were exposed to air and nitrogen plasma as depicted in Fig. 2 under the following parameters: the plasma frequency was on the order of 10 MHz, power -20 W, pressure 0.8–40 Pa. The time span of irradiation was varied from 15 s to 5 min. After exposure to plasma lycopodium particles were once more imaged by high resolution SEM. Irradiated and non-irradiated lycopodium particles were also imaged by environmental scanning electron microscopy (ESEM) carried out with a Quanta 200 FEG (field emission gun) ESEM microscope. Surfaces of irradiated and non-irradiated lycopodium particles were studied by time-of-flight secondary ion mass spectrometry (TOF-SIMS), using a TRIFT-2 mass spectrometer produced by Phys- ical Electronics Co. Non-irradiated and irradiated lycopodium particles were placed on the surface of bi-distilled water. Liquid marbles were prepared as described in detail in Ref. [18,19]. 3. Results and discussion The hydrophobicity of lycopodium particles is well-known to researchers. We demonstrate this by a simple experiment: 0927-7765/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.colsurfb.2012.04.015