Nanowire chemical sensing

Key words metal oxide, chemical sensing, nanowires, films. 

Another important discovery that changed the field of chemical sensing was the synthesis of single crystal one-dimensional oxide nanowires. These are created by the simple evaporation of the desired commercial metal oxide powders at high temperatures and their condensation at lower temperatures on the substrates. These materials have great potential thanks to their reduced lateral dimensions and single crystal habits, both for fundamental study and for potential nanodevice applications, i.e. the third generation of metal oxide gas sensors. 

Figure 10.49 (a) Resistance response of 80-nm-wide PPY and PEDOT nanowires to analytes at 1000 ppm concentration, (b) Sensing responses from the two nanowires presented on a 2-D scatter plot. Moisture corresponds to 8% relative humidity at 23 °C. IPA stands for isopropyl alcohol. (Reprinted with permission from Advanced Materials, Precisely Defined Heterogeneous Conducting Polymer Nanowire Arrays - Fabrication and Chemical Sensing Applications by Y. Chen and Y. Luo, 21, 20, 2040-2044. Copyright (2009) Wiley-VCH)... 

Y. Cao, A.E. Kovalev, R. Xiao, J. Kim, T.S. Mayer, and T.E. MaUouk, Electrical transport and chemical sensing properties of individual conducting polymer nanowires. Nano Lett., 8, 4653 58 (2008). 

Guozhen Shen, Po-Chiang Chen, Koungmin Ryu and Chongwu Zhou. Devices and chemical sensing appfications of metal oxide nanowires, J. Mater. Chem., vol. 19, pp. 828-839,2009. 

Nanowires and nanobelts of inorganic oxides have been fashioned into chemically sensitive semiconductor devices. These include tin and zinc oxides [9], and indium oxide [30], Once again, ammonia and NO2 gases were used for initial demonstrations. Oxygen had very little effect on the sensing action. Because of the low concentrations detected and the speed of the response, it was suggested that single-molecule response could be within reach with these ultraminiaturized sensors. 

---