CO optical sensing properties of nanocrystalline ZnO–Au films: Effect of doping with transition metal ions

Abstract

CO optical sensing properties of nanocrystalline ZnO-Au films: Effect of doping with transition metal ions Della Gaspera, E.; Guglielmi, M.; Perotto, G.; Agnoli, S.; Granozzi, G.; Post, M. L.; Martucci, A. Sensors and Actuators B 161 (2012) [675][676][677][678][679][680][681][682][683] Contents lists available at SciVerse ScienceDirect Keywords: Nanoparticles Nanocomposite Thin films Sensors a b s t r a c t Zinc oxide nanocrystals, pure and doped with transition metal ions, have been synthesized using colloidal techniques; after purification and concentration protocols, the ZnO solutions are mixed with monodisperse Au colloidal suspensions and used for thin film depositions. The effect of the dopant ions on the structural, morphological and optical properties of the as-synthesized colloids as well as the nanocomposite thin films has been analyzed and discussed. The dopant presence has been found to affect the CO optical sensing properties of the nanocomposite ZnO-Au films: compared to pure ZnO, an increase in sensitivity up to 80% and 55% has been detected for Co-doped and Mn-doped ZnO respectively, while Ni-doped ZnO films show only minor improvements. This observation has been ascribed to the multiple oxidation states of cobalt and manganese ions that can facilitate electron transfer between the target gas and semiconductive oxide matrix, and also to the lower surface concentration of Ni ions inside ZnO crystals, as compared to Co and Mn. A fast and reversible response after repeated CO exposures has been detected for all tested samples, and a linear response intensity with the order of magnitude of CO concentration has been observed in the 10-10,000 ppm range, with a lower detection limit of 1-2 ppm.Crown

Continuous Growth Synthesis of Zinc Oxide Nanocrystals with Tunable Size and Doping

“…6,7,8,9,10 Among these, doped metal oxides have attracted increasing interest, due to the thermal and chemical stability of metal oxides, as well as the enhanced optical, electrical and magnetic properties that may be imparted to the NCs when appropriately doped. 11,12,13,14,15 One of the main area of research for doped metal oxides is the synthesis of degenerately (aliovalently) doped wide band gap oxides, for use as transparent electrodes in optoelectronic devices including photovoltaics, light emitting diodes (LEDs) and electrochromics, but also as IR active materials for catalysis and sensing. 16,17,18,19 The colloidal synthesis of doped metal oxide NCs has been traditionally achieved using hot injection methods, which rely on the swift injection of one or more precursors into a solution containing hot solvents and/or surface ligands to trigger the nucleation of NCs.…”

CO sensing properties of Ga-doped ZnO prepared by sol–gel route

“…In addition, Gong et al synthetized Codoped ZnO thin films by co-sputtering as a CO gas sensor, obtaining sensors with the highest sensitivity towards CO at 350 °C [15]. Besides, Gaspera et al [16] considered the effects of doping transition metal ions into ZnO, resulting in a lower detection limit of 1-2 ppm CO at electrochemical deposition resulting in an economic, effective approach, suitable for largescale production [17].…”

Sol-Gel Thin Films for Plasmonic Gas Sensors

“…The beauty of this approach is the possibility to independently synthesize and tune the properties of the prepared colloids: for example, we studied the effect of the doping of ZnO with different transition metal ions, analyzing their effect on the optical sensing properties of ZnO-Au nanocrystalline films monitoring the variation in the LSPR of Au NPs. A marked increase in sensitivity to CO has been observed when ZnO is doped with Co or Mn ions ( Figure 4 a,b), validating the strategy to synthesize high quality doped colloids and then using them in a nanocrystal ink to deposit functional nanocomposite films [ 59 ]. In a similar way, Au colloids can also be dispersed within a hybrid organic/inorganic sol-gel matrix bearing specific functionalities for the recognition of target molecules.…”