Vapor sensing

R., Gelperin, A., Katz, H. E. and Bao, Z. (2001) Organic oscillator and adaptive amplifier circuits for chemical vapor sensing./. Appl. Phys., 91, 10140. 

The contributed chapters are divided into three sections. The first section is dedicated to chemical vapor sensing. In the majority of the photonic vapor sensors described here, a layer of vapor sensitive material (polymer, ceramics, or colloidal... 

Selective Vapor Sensing Colored Self-Assembled... 

Snow, P. A. Squire, E. K. Russell, P. S. J. Canham, L. T., Vapor sensing using the optical properties of porous silicon bragg mirrors, J. Appl. Phys. 1999, 86, 1781 1784... 

Demonstration of Using the OFRR for Chemical Vapor Sensing... 

Sun, Y. Shopova, S. I. Frye Mason, G. Fan, X., Rapid chemical vapor sensing using optofluidic ring resonators, Opt. Lett. 2008, 33, 788 790... 

J. W. Grate, Hydrogen bond acidic polymers for chemical vapor sensing. Chem. Rev. 108,726 745 (2008). 

Bulk sensors certainly have a role in chemical sensing of explosives, but the subject of this book is the other basic type sensor, one that seeks molecules released from the bulk of the explosive material in an object. We will refer to these as trace chemical sensors. They are sometimes called vapor sensors, but that seems a less accurate description when they are applied to explosive molecules, which may not always be found in a vapor state. As we shall see in Chapter 5, that requires us to understand where and how to look for these molecules. It will become apparent upon a little reflection that the two types of sensors are complementary and are best used in different situations. Furthermore, even when trace sensors are used, in some situations sampling of particles of soil or vegetation or sampling from surfaces may prove to be more productive that vapor sampling. For underwater sources the term vapor sensing is also inappropriate. 

Soils with greater amounts of organic matter (agricultural or forest soils) or minerals (compared to desert sand) will sorb greater landmine signature chemicals,6 leaving less available for transfer to the air for vapor sensing. 

Soil moisture has a tremendous effect on soil-vapor sorption. Dry soils will sorb about 10,000 times more landmine signature chemicals than damp soils. This depresses the vapor levels the same amount. This process is reversible, so daily morning dew is valuable for vapor sensing, and afternoon drying is detrimental for vapor sensing. 

At the time of the studies described, and up to the present, a vapor sensing system with sensitivity adequate to routinely discover the vapor signature from buried landmines has not been fielded in quantity. Therefore, it is necessary to estimate the concentrations that may be expected, so that system developers may form realistic design goals. Jenkins and his colleagues estimated the air concentrations, for one kind of soil and two types of mines, as shown in Table 4.5 [8], The quantity Ks/a is equivalent to the K previously defined. It was calculated as the ratio of soil residue to vapor concentration in their experimental samples. 

Fisher, M., M. la Grone, and I. Sikes. Implementation of serial amplifying fluorescent polymer arrays for enhanced chemical vapor sensing of landmines, in Proceedings of UXO/Countermine Forum 2003, Orlando, Florida, September, 2003. 

Fisher, M. and J. Sikes. Minefield edge detection using a novel chemical vapor sensing technique, in R. S. Harmon, J.H. Holloway, Jr., J.T. Broach, Eds. Detection... 

Seyama, M., Iwasaki, Y, Tate, A., and Sugimoto, L, Room-temperature ionic-liquid-incorporated plasma-deposited thin films for discriminative alcohol-vapor sensing, Chem. Mater., 18, 2656-2662, 2006. 

Goubaidoulline, L, Vidrich, G., and Johannsmann, D., Organic vapor sensing with ionic liquids entrapped in alumina nanopores on quartz crystal resonators. Anal. Chem., 77,615-619,2005. 

A correlation can be made between the measured magnitude of the waveguide signals and the vapor pressures of the condensed vapors sensed. Three of the five polymer films tested showed extremely large responses to the simulant dimethyl methyl phosphonate (DUMP), and one of these films could detect DUMP vapor concentrations below the 20 ppm level. 

M. C. Lonergan, E. J. Severin, B. J. Doleman, S. A. Beaber, R. H. Grubb, and N. S. Lewis, Array-based vapor sensing using chemically sensitive, carbon black—polymer resistors , Chemistry of Materials 8, 2298 (1996). 

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