Low Temperature Sensing Properties of a Nano Hybrid Material Based on ZnO Nanotetrapods and Titanyl Phthalocyanine

ZnO nanotetrapods have recently been exploited for the realization of high-sensitivity gas sensors, but they are affected by the typical drawbacks of metal-oxides, i.e., poor selectivity and a relatively high working temperature. On the other hand, it has been also demonstrated that the combined use of nanostructured metal oxides and organic molecules can improve the gas sensing performance sensitivity or selectivity, even at lower temperatures. A gas sensor device, based on films of interconnected ZnO nanotetrapods properly functionalized by titanyl phthalocyanine (TiOPc), has been realized in order to combine the high surface to volume ratio and structural stability of the crystalline ZnO nanostructures with the enhanced sensitivity of the semiconducting TiOPc molecule, especially at low temperature. The electronic properties of the resulting nanohybrid material are different from those of each single component. The response of the hybrid nanostructure towards different gases has been compared with that of ZnO nanotetrapod without functionalization in order to highlight the peculiar properties of the hybrid interaction(s). The dynamic response in time has been studied for different gases and temperatures; in particular, an increase in the response to NO2 has been observed, even at room temperature. The formation of localized p-n heterojunctions and the possibility of exchanging charge carriers at the hybrid interface is shown to be crucial for the sensing mechanism.

[1]  Sunghoon Song,et al.  Passivation effects on ZnO nanowire field effect transistors under oxygen, ambient, and vacuum environments , 2008 .

[2]  Hildegard D. Jander,et al.  A test system for gas sensors , 1995 .

[3]  Jin Mizuguchi,et al.  Solid-State Spectra of Titanylphthalocyanine As Viewed from Molecular Distortion , 1995 .

[4]  Ya-Hsiang Tai,et al.  Bias-induced oxygen adsorption in zinc tin oxide thin film transistors under dynamic stress , 2010 .

[5]  Daoben Zhu,et al.  Organic thin-film transistors of phthalocyanines , 2008 .

[6]  A. Zappettini,et al.  Vapour‐phase growth, purification and large‐area deposition of ZnO tetrapod nanostructures , 2010 .

[7]  T. K. Starke,et al.  NO2 detection at room temperature with copper phthalocyanine thin film devices , 2000 .

[8]  L. Wang,et al.  Novel approach to tuning the physical properties of organic-inorganic hybrid semiconductors. , 2006, Physical review letters.

[9]  A. Zappettini,et al.  Low temperature thermal evaporation growth of aligned ZnO nanorods on ZnO film: a growth mechanism promoted by Zn nanoclusters on polar surfaces , 2011 .

[10]  L. Lazzarini,et al.  Large-area self-catalysed and selective growth of ZnO nanowires , 2008, Nanotechnology.

[11]  Vincenzo Guidi,et al.  ZnO gas sensors: A comparison between nanoparticles and nanotetrapods-based thick films , 2009 .

[12]  S. Iannotta,et al.  Hybrid titania–zincphthalocyanine nanostructured multilayers with novel gas sensing properties , 2008 .

[13]  Zhen Jin,et al.  Metal Oxide Nanostructures and Their Gas Sensing Properties: A Review , 2012, Sensors.

[14]  Andrea Zappettini,et al.  Growth of ZnO tetrapods for nanostructure-based gas sensors , 2010 .

[15]  Zhong Lin Wang.  Nanostructures of zinc oxide , 2004 .

[16]  J. Simon,et al.  METALLOPHTHALOCYANINES. GAS SENSORS, RESISTORS AND FIELD EFFECT TRANSISTORS , 1998 .

[17]  Andrea Zappettini,et al.  Aldehyde detection by ZnO tetrapod-based gas sensors , 2011 .

[18]  A. Pallaoro,et al.  Hybrid n-TiO2-CuPc gas sensors sensitive to reducing species, synthesized by cluster and supersonic beam deposition , 2007 .

[19]  Zhi-xuan Cheng,et al.  Fluoroalcohol and fluorinated-phenol derivatives functionalized mesoporous SBA-15 hybrids: high-performance gas sensing toward nerve agent , 2012 .