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Partículas coloidais têm sido empregadas na síntese dirigida por molde de diversos materiais, tais como semicondutores, metais e ligas. Esse método permite um controle da espessura do material resultante através da escolha adequada da carga aplicada no sistema e é possível produzir materiais densamente depositados, sem rachaduras. Esses materiais são fidedignos à estrutura do molde e, devido às amplas áreas superficiais obtidas, são muito interessantes em aplicações eletroquímicas. Neste trabalho, a distribuição de um molde de poliestireno monodisperso foi realizada sobre substratos de ouro, platina e carbono vítreo com o intuito de exemplificar a eletrodeposição de um óxido, um polímero condutor e um material híbrido orgânico-inorgânico, com aplicações em supercapacitores e sensores. Os desempenhos dos eletrodos nanoestruturados foram comparados com os análogos massivos e os resultados obtidos são descritos.Colloidal particles have been used to template the electrosynthesis of several materials, such as semiconductors, metals and alloys. The method allows good control over the thickness of the resulting material by choosing the appropriate charge applied to the system, and it is able to produce high density deposited materials without shrinkage. These materials are a true model of the template structure and, due to the high surface areas obtained, are very promising for use in electrochemical applications. In the present work, the assembly of monodisperse polystyrene templates was conduced over gold, platinum and glassy carbon substrates in order to show the electrodeposition of an oxide, a conducting polymer and a hybrid inorganic-organic material with applications in the supercapacitor and sensor fields. The performances of the resulting nanostructured films have been compared with the analogue bulk material and the results achieved are depicted in this paper. Keywords: colloidal particle templates, polystyrene, macroporous materials, sensors, supercapacitors IntroductionThree dimensional close packed arrays of monodisperse polystyrene or silica particles have attracted attention because of their potential to template synthesis of various materials.1 These spherical colloidal particles can be either synthesized 2 or commercially acquired in a range of diameters from few nanometers up to micrometer scale.Much of the interest in applying colloidal particles to template material synthesis has come from studies in photonic crystals, 3 and the first reported electrodeposition through colloidal templates concerned the synthesis of macroporous CdS and CdSe films for photonic bandgap studies. 4 Later papers have used colloidal particles to electrodeposit ordered macroporous films of other semiconductors, 5 metals, 6,7 alloys, 8 oxides 9 and conducting polymers. [10][11][12] The template technique is able to produce high density deposited materials, since the compounds are electrodeposited inside the template voids and around the surface of the colloidal particles. When the template is removed, there is no shrinkage o...

a b s t r a c tThis work encompasses the direct electrodeposition of polypyrrole nanowires onto Au substrates using different electrochemical techniques: normal pulse voltammetry (NPV) and constant potential method with the aim in applying these films for the first time in ammonia sensing in solution. The performance of these nanowire-based sensors are compared and evaluated in terms of: film morphology (analyzed with scanning electron microscopy); their sensitivity towards ammonia; electrochemical and contact angle measurements. For nanowires prepared by NPV, the sensitivity towards ammonia increases with increasing amount of electrodeposited polypyrrole, as expected due to the role of polypyrrole as electrochemical transducer for ammonia oxidation. On the other hand, nanowires prepared potentiostatically displayed an unexpected opposite behavior, attributed to the lower conductivity of longer polypyrrole nanowires obtained through this technique. These results evidenced that the analytical and physico-chemical features of nanostructured sensors can differ greatly from those of their conventional bulky analogous.

In this work, we report the development of urea biosensors using macroporous polypyrrole as electrochemical transducer. Nanostructured polypyrrole was synthesized using monodispersed polystyrene spheres (460 nm) as template. Nanostructured urea biosensors were assembled after immobilization of urease (an enzyme that hydrolyses urea to ammonia) on macroporous polypyrrole, which was carried out using two different procedures: covalent attachment or layer-by-layer (lbl) deposition. Results show that lbl assembly of urease on macroporous polypyrrole gives rise to biosensors with improved detection kinetics (as demonstrated by higher I max values) and tunable sensitivities. Comparison with bulk urea biosensors previously described in the literature demonstrates that the use of nanostructured polypyrrole as sensing platform enhances biosensor's analytical performances, mainly due to the availability of more active sites for enzyme immobilization.