Talanta 83 (2011) 1482–1486 Contents lists available at ScienceDirect Talanta journal homepage: www.elsevier.com/locate/talanta Synthesis of polypyrrole nanoparticles and its grafting with silica gel for selective binding of chromium(VI) P. Mondal, K. Roy, S.P. Bayen, P. Chowdhury ∗ Synthetic Polymer Laboratory, Department of Chemistry, Visva-Bharati Santiniketan 731235, India article info Article history: Received 15 September 2010 Received in revised form 13 November 2010 Accepted 15 November 2010 Available online 23 November 2010 Keywords: Cr(VI) Polypyrrole nanoparticles Functionalizing Grafting Metal ion binding abstract Polypyrrole nanoparticles of desired structure have been synthesized through simple micelle technique. It is then grafted with functionalized silica gel to develop a novel organic–inorganic hybrid material. The role of dimethyl dichloro silane (coupling agent) in grafting is demonstrated. The nanoparticles are characterized by TEM, SEM and TGA. Grafting reactions are evaluated by spectral (FTIR) analysis and chemical test. The Cr(VI) binding behavior of the composite is studied in various pH of the medium. The selectivity in binding Cr(VI) is monitored. The metal ion adsorption capacity and surface area of the material are found to be 38 mg/g and 235 m 2 /g, respectively. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Inherent conducting polymers (polypyrrole, polyaniline and polythiophene) have attracted a great deal of interest owing to their remarkable properties, such as redox [1], acid–base [2], ion- exchange [3] and chemical sensing [4] in addition to its high conductivity [5]. Bulk polypyrrole is infusible, intractable and insol- uble in common solvents due to partial cross-linking [6] through hydrogen bonding. As a result the polymer has poor process abil- ity and inferior mechanical properties [7]. Various approaches [8] have been utilized to improve the process ability of polypyrrole [9–11], including (i) chemical modification of polymer backbone; (ii) copolymerization of appropriate functional co-monomers; (iii) use of polymeric or surfactant-type doping anion; and (iv) prepa- ration of stable colloidal dispersion. Formation of later through hybridization of polypyrrole with silica deserves special attention due to its composite nature. The benefit of such composite is the synergistic combination of properties of both the components. Thus one can achieve required mechanical strength of silica as well as high ion exchange properties of polypyrrole [3] in their composite (organic–inorganic hybrid material based on polypyrrole and sil- ica). The composite may be helpful in selective binding of chromate through ion exchange process [12,13]. Two types of polypyrrole ∗ Corresponding author. Tel.: +91 3463 264983; fax: +91 3463 261526. E-mail address: pranesh 02@yahoo.co.in (P. Chowdhury). silica composites (PPY–SiO 2 ) such as (a) silica rich PPY–SiO 2 nano composite [8] and (b) polypyrrole rich PPY–SiO 2 hybrid materials [7] are gaining importance now-a-days due to their various appli- cations. We have focused on the latter approach in the present study. Various authors reported on the preparation of PPY–SiO 2 com- posites. Armes and co-workers [14–17] have shown that the polymerization of pyrrole in the presence of ultra fine aqueous silica sols lead to the formation of unusual “raspberry-shaped” PPY–SiO 2 nano composite which exhibit silica-rich surfaces. Wallace et al. [18,19] used porous silica gel particles for the preparation of novel silica rich PPY–SiO 2 composite for chromatographic use. Faverolle and fellow researchers [20,21] demonstrated that polypyrrole could be deposited onto E-glass fibers with the help of silane cou- pling agent. The resulted composite leads to polypyrrole rich over layers (20–50 nm thickness). Chehimi and his group [7,22] describe the use of aminopropyl triethoxysilanes (APTS) in the preparation of polypyrrole-coated silica gel (PPY–APTS–SiO 2 ) with the aim of obtaining a polypyrrole-rich hybrid particles with surface area in the range162–184 m 2 /g. In the present work, we demonstrate the role of dimethyl dichloro silane (DDS) in the preparation of polypyrrole-grafted sil- ica gel (PPY–DDS–SiO 2 ) with a view to obtain polypyrrole-rich silica particles with surface area greater than 200 m 2 /g. The pro- cess will be compared to the method published by Chehimi et al. [7,22] and it will be different from Armes et al. [14–17]. We have synthesized polypyrrole nanoparticles for grafting onto function- alized silica gel and studied its chromium(VI) binding ability. A 0039-9140/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.talanta.2010.11.037