Synthesis of electrically active biopolymer–SiO 2 nanocomposite aerogel Ashutosh Tiwari a, ⁎ , A.P. Mishra b , Sanjay R. Dhakate a , Raju Khan a , S.K. Shukla c a Division of Engineering Materials, National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi, 110 012, India b Department of Science and Technology, Ministry of Science and Technology, Technology Bhawan, New Delhi, 110 016, India c USIC, University of Delhi, New Delhi, 110 007, India Received 4 January 2007; accepted 25 February 2007 Available online 12 March 2007 Abstract Silica nanoparticles encapsulated acacia gum–silica (AgSiO 2 ) composites were synthesized through sol–gel method using tetraethyl orthosilicate (TEOS) as silica precursor in basic condition. The nanocomposite gels were dried at different temperatures to form aerogels. The incorporation of nanostructured silica will influence the electronic behavior of composite. The composition of silica with acacia gum was tailored to optimize the material having good electronic properties. The resulting material was characterized by FTIR, XRD and AFM. The control curing of the composite resulted to mesoporous material with nanosize silica. At optimum composition, electrical conductivity and ion transference number of hybrid material are found to be 18.3 × 10 - 2 Scm - 1 and 4.26 × 10 2 cm 2 V - 1 s - 1 respectively. The electrical conductivity of biopolymeric hybrid is comparable to that of commercially used synthetic conducting polymers. The ion transfer number of AgSiO 2 nanocomposites attributes the superionic character for electrical conduction. © 2007 Elsevier B.V. All rights reserved. Keywords: Acacia gum; Silica; Sol–gel method; Nanocomposite; Mesoporous; Electroactive material 1. Introduction Electrically active polymers have great attention due to their wide applications in various fields such as solar materials, sensors, electronic shielding, environmental sensitive mem- branes, etc. [1–3]. The commercial electroactive polymers have limitations [4,5] in production and mechanical properties. Bio- based polymers have unique physiochemical properties and make attractive an excellent electroactive environmental friendly biocompatible material through wet chemical process [6,7]. Silica and biopolymer composites are attractive for the preparation of high performance and multifunctional materials using sol–gel method [8]. Tetraethyl orthosilicate (TEOS) has been extensively used as silica precursor for the preparation of various biopolymer–silica hybrid composites [9,10]. The bio- polymer, Acacia gum is a complex arabinogalactan polysac- charide [11,12] that exudates from an acacia tree, widely available in tropical and sub-desert regions of India. Acacia gum is light weight, biodegradable, biocompatible and possesses good flexibility with excellent ionic mobility and electrical conductivity [13–15] but poor mechanical and thermal properties. On the other hand inorganic material, silica has good mechanical properties and thermal stability but sometime too brittle. So, the homogeneous combination of inorganic and organic moieties in a single-phase may provide unique possibilities. Combination of biological, chemical and physical properties of Acacia gum is a suitable candidate of choice to demonstrate the possible extension of biomaterial for technological applications [16–19]. In the present communica- tion reported the synthesis of electrically active AgSiO 2 nanocomposite materials derived from renewable resources. 2. Experimental section 2.1. Materials Acacia gum (Merck; M w 2.34 × 10 6 ) was used after fractional precipitation, while tetraethoxysilane (Aldrich; 99%), ethanol (Merck; 99.9%) and NH 4 OH (Merck; 25%) were used. The deionized water was used for all the reactions. Materials Letters 61 (2007) 4587 – 4590 www.elsevier.com/locate/matlet ⁎ Corresponding author. Tel.: +91 11 25742609x2355; fax: +91 11 2572693852. E-mail address: ashunpl@gmail.com (A. Tiwari). 0167-577X/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2007.02.076