Nanocomposites combining conducting and superparamagnetic components prepared via an organogel† Elena Taboada, Lise N. Feldborg, Angel P erez del Pino, Anna Roig, David B. Amabilino * and Josep Puigmart  ı-Luis * Received 1st October 2010, Accepted 15th December 2010 DOI: 10.1039/c0sm01088j A nanocomposite material combining an organic molecular gelator and oleate-coated iron oxide nanoparticles in proportions which range from one to fifty weight percent of the inorganic material has been prepared via the gel state. The proportion of nanoparticles and organic gelator in this mixed colloidal system gives very different characteristics to the final hybrid xerogel. Characterisation of the xerogels by transmission electron microscopy shows that at low loadings of the inorganic material a uniform distribution is observed, while above ten weight percent of nanoparticles a clear phase separation of the components (organic and inorganic) is revealed. Doping of the organic component of the xerogels by chemical oxidation results in the formation of conducting composites, whose electrical characteristics—probed by current sensing atomic force microscopy and spectroscopy—vary importantly with the amount of iron oxide colloid. The best conductors are found at low loadings of inorganic particles, at which an interesting alignment of the organic fibres is observed. The work shows that conducting materials incorporating magnetic particles can be prepared simply through the organogel route, and raises possibilities for the discovery of new properties that could come from the combination of these or related systems. Introduction The preparation of easily processed materials which combine electrically conducting and magnetic components is a consider- able challenge. The difficulty in this area resides in making a sufficiently conducting material with the magnetic component interspersed. The conducting pathways can be interrupted by the mere presence of another component. In crystalline materials this task is particularly difficult, although in layered systems it can be achieved. 1 Paradoxically, it is in crystalline systems that con- ducting organic materials are generally at their best. A more general area is the preparation of conducting polymers incor- porating magnetic nanoparticles, 2 yet in these systems the nature of the electrical characteristics is distinct to the metallic type conductivity observed in crystalline molecular samples. We are interested in preparing nanostructured molecular organic conducting material 3 in the form of a film that can be achieved through the gel state. 4 The conducting ‘‘wires’’ are formed, thanks to the presence of supramolecular polymers, and these can be used for making conducting systems including hybrid and composite materials. This approach allows the combination of dissimilar building blocks with pathways inter- acting and influencing upon each other in unique ways such that they can generate materials with characteristics that are distinc- tive to their components. 5 For instance, it has been proved that when superparamagnetic ferrites or semiconductor quantum dots such as CdS are immobilised they confer magnetic and/or luminescent properties to the final hybrid gel state. 6 We use the gels as a route to these materials because the fibres are ‘‘frozen’’ in the solvent matrix, which can then be evaporated, and the con- ducting material is then prepared by doping. 7 These systems are amenable to the formation of conducting hybrid nanomaterials, as we have shown for the case of gold nanoparticles containing hydrogen bonding units which help make the two components compatible. 8 Here we report a new class of self-assembled and non-covalent hybrid organogels combining conducting and super- paramagnetic components formed from an amide tetrathia- fulvalene (TTF) derivative (1) and organic soluble‡ magnetic iron oxide nanoparticles (g-Fe 2 O 3 nanoparticles, abbreviated NPs here) to fulfil the objective of reaching a conducting magnetic hybrid material. The TTF unit is the one known to form a variety of interesting nanostructures and to perform Institut de Ci encia de Materials de Barcelona (CSIC), Campus Universitari, 08193 Bellaterra, Catalonia, Spain. E-mail: amabilino@ icmab.es; jpuigma@googlemail.com; Fax: +34 93 5805729; Tel: +34 93 580 1853 † Electronic supplementary information (ESI) available: Supporting AFM images and comparitive analysis of sample conductivity and fibre alignment. See DOI: 10.1039/c0sm01088j ‡ We use the term soluble to infer that the whole of NP is homogeneously dissolved in the solvent. An alternative nomenclature from colloid chemistry would be to say that the material forms a homogeneous colloidal dispersion. This journal is ª The Royal Society of Chemistry 2011 Soft Matter , 2011, 7, 2755–2761 | 2755 Dynamic Article Links C < Soft Matter Cite this: Soft Matter , 2011, 7, 2755 www.rsc.org/softmatter PAPER Downloaded by Instituto de Ciencia de Materiales. Biblioteca Man on 28 March 2011 Published on 27 January 2011 on http://pubs.rsc.org | doi:10.1039/C0SM01088J View Online