Inverse Opal Nanoassemblies: Novel Architectures for Gas Sensors The SnO2:Zn Case
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0915-R07-06
Inverse Opal Nanoassemblies: Novel Architectures for Gas Sensors The SnO2:Zn Case Alessandra Sutti1,2, Gianluca Calestani1, Chiara Dionigi3, Camilla Baratto4, Matteo Ferroni4, Guido Faglia4, and Giorgio Sberveglieri4 1 Dip.to di Chimica G.I.A.F., Universita' degli Studi di Parma, Parco Area delle Scienze 17/A, Parma, Italy, 43100, Italy 2 Chemical and Biomolecular Engineering, University of Melbourne, Parkville, VIC, 3010, Australia 3 ISMN, CNR, Via P. Gobetti 101, Bologna, Italy, 40129, Italy 4 Dipartimento di Chimica e Fisica per l'Ingegneria e per i Materiali, CNR - INFM - Universita' di Brescia, Via Valotti 9, Brescia, Italy, 25133, Italy
ABSTRACT A novel technique is here presented, based on inverse opal metal oxide structures for the production of high quality macro and meso-porous structures for gas sensing. Taking advantage of a sol-gel templated approach, different mixed semiconducting oxides with high surface area, commonly used in chemical sensing application, were synthesized. In this work we report the comparison between SnO2 and SnO2:Zn. As witnessed by Scanning and Transmission Electron Microscopy (SEM and TEM) analyses and by Powder x-ray Diffraction (PXRD), highly ordered meso-porous structures were formed with oxide crystalline size never exceeding 20 nm. The filled templates, in form of thick films, were bound to allumina substrate with Pt interdigitated contacts and Pt heater, through in situ calcination, in order to perform standard electrical characterization. Pollutant gases like CO and NO2 and methanol, as interfering gas, were used for the targeted electrical gas tests. All samples showed low detection limits towards both reducing and oxidizing species in low temperature measurements. Moreover, the addition of high molar percentages of Zn(II) affected the behaviour of electrical response improving the selectivity of the proposed system.
INTRODUCTION Gas sensing technologies1 are on the edge of the current environmental monitoring research, which is moving towards energy saving highly sensitive systems. The development of low cost and low power consumption gas sensors is then of main concern in miniaturizing devices towards portability. Improving surface area and sensitivity, reducing the crystalline grain size and lowering the sensor working temperature are the main goals being set in this area. The approach we present meets these requirements offering at the same time a wide range of applicability in the field of semiconducting metal oxides. Owing to their highly porous interconnected structure assuring a huge surface for interaction with gases and an ordered porosity, inverse opal (IO) structures have a great potential interest in gas sensing2, though they have been poorly considered due to the technological problems encountered in the assembly of devices. The formation of an IO can be thought as deriving from a sol-gel process performed in a confined environment, so that the preparation of IO structures can be in principle extended to all the oxides for which a preparative
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