ZnO Nanotetrapods: Controlled Vapor‐Phase Synthesis and Application for Humidity Sensing

A systematic study on controlled synthesis of ZnO nanotetrapods by combining metal-vapor transport, oxidative nucleation/ growth, fast-flow quenching, and water-assisted cleaning is reported. The technique developed in this work makes possible the fabrication of ZnO nanotetrapods with different morphologies, with arm diameters down to 17 nm, and with arm lengths ranging from 50 nm up to a few micrometers. The octa-twin model is verified for the growth of the ZnO nanotetrapods. Photoluminescence (PL) studies indicate a higher level of surface and subsurface oxygen vacancies for smaller ZnO nanotetrapods. The ZnO nanotetrapods are first used for the fabrication of resistor-type humidity sensors, which show high sensitivity, quick response/recovery, long lifetime, and a wide range of humidity response. These favorite characteristics of the humidity sensors are ascribed to the unique morphology of the nanotetrapods, which can create a film with faceted pores and large internal surfaces.

[1]  Phaedon Avouris,et al.  Field-Effect Transistors Based on Single Semiconducting Oxide Nanobelts , 2003 .

[2]  Eicke R. Weber,et al.  Catalytic Growth of Zinc Oxide Nanowires by Vapor Transport , 2001 .

[3]  Anders Hagfeldt,et al.  Nanostructured ZnO electrodes for photovoltaic applications , 1999 .

[4]  S. Takeuchi,et al.  Inter-leg angles in tetrapod ZnO particles , 1998 .

[5]  W. K. Chan,et al.  Luminescent and structural properties of ZnO nanorods prepared under different conditions , 2003 .

[6]  W. Tai,et al.  Humidity sensitive properties of nanostructured Al-doped ZnO:TiO2 thin films , 2003 .

[7]  S. Vassilev,et al.  Lanthanum doped SnO2 and ZnO thin films sensitive to ethanol and humidity , 2000 .

[8]  A. Djurišić,et al.  Gas-sensing properties of thick film based on ZnO nano-tetrapods , 2005 .

[9]  Taihong Wang,et al.  Enhanced photocatalytic activity of ZnO nanotetrapods , 2005 .

[10]  Chenglu Lin,et al.  Fabrication and ethanol sensing characteristics of ZnO nanowire gas sensors , 2004 .

[11]  Zhong Lin Wang,et al.  Nanobelts of Semiconducting Oxides , 2001, Science.

[12]  O. Schmidt,et al.  Nanotechnology: Thin solid films roll up into nanotubes , 2001, Nature.

[13]  H. Yan,et al.  Morphogenesis of One‐Dimensional ZnO Nano‐ and Microcrystals , 2003 .

[14]  Fa-Quan He,et al.  Growth of ZnO Nanotetrapods with Hexagonal Crown , 2006 .

[15]  Heon-Jin Choi,et al.  Controlled growth of ZnO nanowires and their optical properties , 2002 .

[16]  N. Shibata,et al.  Crystal growth in c direction and crystallographic polarity in ZnO crystals , 1978 .

[17]  Jian Zhang,et al.  Humidity sensitive properties of ZnO nanotetrapods investigated by a quartz crystal microbalance , 2006 .

[18]  Enrico Traversa,et al.  Ceramic sensors for humidity detection: the state-of-the-art and future developments , 1995 .

[19]  Yong Ding,et al.  Conversion of Zinc Oxide Nanobelts into Superlattice-Structured Nanohelices , 2005, Science.

[20]  J. Nørskov,et al.  Oxygen vacancies as active sites for water dissociation on rutile TiO(2)(110). , 2001, Physical review letters.

[21]  Q. Wan,et al.  Low-field electron emission from tetrapod-like ZnO nanostructures synthesized by rapid evaporation , 2003 .

[22]  Xiangfeng Duan,et al.  General Synthesis of Compound Semiconductor Nanowires , 2000 .

[23]  Zhong Lin Wang,et al.  Large-Scale Hexagonal-Patterned Growth of Aligned ZnO Nanorods for Nano-optoelectronics and Nanosensor Arrays. , 2004, Nano letters.

[24]  Bruce E. Gnade,et al.  Mechanisms behind green photoluminescence in ZnO phosphor powders , 1996 .

[25]  P. Yang,et al.  Single Nanowire Lasers , 2001 .

[26]  S. Takeuchi,et al.  Growth model of tetrapod zinc oxide particles , 1993 .

[27]  M. Shiojiri,et al.  Structure and growth of ZnO smoke particles prepared by gas evaporation technique , 1981 .

[28]  Zhong Lin Wang,et al.  The octa-twin tetraleg ZnO nanostructures , 2003 .

[29]  Zhifeng Ren,et al.  ZnO nanobridges and nanonails , 2003 .

[30]  Junqing Hu,et al.  Two-dimensional micrometer-sized single-crystalline ZnO thin nanosheets , 2003 .

[31]  Enrico Traversa,et al.  A novel humidity-detection mechanism for ZnO dense pellets , 1995 .

[32]  Khalil Arshak,et al.  Investigation into a novel humidity sensor operating at room temperature , 2002 .

[33]  Qiang Wang,et al.  Photoelectrochemical study on charge transfer properties of TiO2-B nanowires with an application as humidity sensors. , 2006, The journal of physical chemistry. B.

[34]  L. Andrews,et al.  Reactions of laser-ablated Zn and Cd atoms with O2: Infrared spectra of ZnO, OZnO, CdO, and OCdO in solid argon , 1997 .

[35]  Dapeng Yu,et al.  Ultraviolet-emitting ZnO nanowires synthesized by a physical vapor deposition approach , 2001 .

[36]  C. M. Magdalane,et al.  Zinc(II) Oxide–Yttrium(III) Oxide Composite Humidity Sensor , 2002 .

[37]  Charles M. Lieber,et al.  Growth of nanowire superlattice structures for nanoscale photonics and electronics , 2002, Nature.

[38]  S. Takeuchi,et al.  Octahedral multiple-twin model of tetrapod ZnO crystals , 1994 .