Colloids and Surfaces A: Physicochem. Eng. Aspects 462 (2014) 211–216 Contents lists available at ScienceDirect Colloids and Surfaces A: Physicochemical and Engineering Aspects journa l h om epage: www.elsevier.com/locate/colsurfa Characterization of the electric double layers of multi-walled carbon nanotubes, laponite and nanotube + laponite hybrids in aqueous suspensions Maryna Manilo a , Nikolai Lebovka a,b,∗ , Sandor Barany c a Institute of Biocolloidal Chemistry named after F.D. Ovcharenko, National Academy of Sciences of Ukraine, 42 Vernadsky blvd., 030142 Kyiv, Ukraine b Université de Technologie de Compiègne, TIMR, EA 4297, UTC/ESCOM, Centre de Recherche de Royallieu, B.P. 20529-60205, Compiègne Cedex, France c University of Miskolc/Hungarian Academy of Sciences “Materials Science Research Group”, and Institute of Chemistry, Hungary, The Transcarpathian II. Ferenc Rakoczi Hungarian Institute, Beregovo, Ukraine h i g h l i g h t s • Electrophoretic mobilities of carbon nanotubes (NTs), laponite and their hybrids are investigated. • Effects of electrolytes (KCl, CaCl 2 and AlCl 3 ) on electrokinetic behaviour are discussed. • Both of NTs and laponite clay disks are charged negatively. • Attraction between NTs and laponite reflects heterogeneous distribution of charged groups. • Electrophoretic mobility of NT + L hybrids decreases with increase of the laponite content. g r a p h i c a l a b s t r a c t 2 4 6 8 10 12 -3.5 -3 -2.5 -2 -1.5 0 0.2 0.4 0.6 0.8 1 -3 -2.5 -2 -1.5 -1 pH X=m L /m NT Mul-walled carbon nanotubes, 0.01 % wt C NT = 0.01 % wt Mul-walled carbon nanotubes Laponite clay disks Laponite clay disks, 2 % wt Aqueous suspensions μ, μm . cm . V -1. s -1 μ, μm . cm . V -1. s -1 a r t i c l e i n f o Article history: Received 14 June 2014 Received in revised form 29 August 2014 Accepted 4 September 2014 Available online 16 September 2014 Keywords: Carbon nanotubes Laponite clay disks Surface groups Electrophoretic mobility pH Electrolytes a b s t r a c t To characterize the electric double layers (EDLs) of multi-walled carbon nanotubes (NTs), laponite clay disks and NT + laponite hybrid particles, their electrophoretic mobility was investigated as a function of pH and concentration of electrolytes (KCl, CaCl 2 and AlCl 3 ). The electrokinetic behaviour of NTs resembles that of the lyophobic colloids. An increase in pH from 2 to 12 resulted in substantial increase of the abso- lute (negative) values of the electrophoretic mobility of NTs due to dissociation of surface hydroxyl and carbonyl groups, which was identified by infra-red (IR) spectroscopy. The observed attraction between similarly charged colloidal particles of NTs and laponite was explained by the highly heterogeneous dis- tribution of negatively charged functional groups on the surface of NTs and difference in electrophoretic mobility of NT and laponite particles. © 2014 Elsevier B.V. All rights reserved. ∗ Corresponding author at: Institute of Biocolloidal Chemistry, National Academy of Sciences of Ukraine, 42, Vernadsky av., 03142, Kyiv, Ukraine and Université de Technologie de Compiègne, TIMR, EA 4297, UTC/ESCOM, Centre de Recherche de Royallieu, B.P. 20529-60205, Compiègne Cedex, France. Tel.: +380 44 4240378; fax: +380 44 4248078. E-mail addresses: lebovka@gmail.com, Nikolai.Lebovka@utc.fr (N. Lebovka). http://dx.doi.org/10.1016/j.colsurfa.2014.09.006 0927-7757/© 2014 Elsevier B.V. All rights reserved.