Nanowire-Based Chemical Sensors

? Nanowire-Based Chemical Sensors

As compounds accessible only by high-temperature solid state syntheses, the Chevrel phases contain linear condensation oligomers (0.25 to 2.75 nm long) and polymers Mo_3nQ_3n+2 (Q=S,Se; n=2-12; lengths greater than 5 mm) based on triangular Mo₃Q₃ units. These inorganic nanowires are thermodynamically stable, electrically conducting and superconducting in high critical magnetic fields [55T at 4.2K], and they could thus be potential components of future electronic devices.

LiMo3Se3

DiSalvos group found in 1984 (J. M. Tarascon, F. J. DiSalvo, C. H. Chen, P. J. Carroll, M. Walsh, L. Rupp, J. Solid State Chem., 1984, 58, 290.), that the Li[Mo₃Se₃] polymer can be extracted into polar solvents. In dimethylsulfoxide for example, the wires occur mostly in the form of bundles of 5-15 wires, as judged from the diameter of these bundles (3-4 nm).

Our interest in LiMo₃Se₃ based nanowires concerns their potential use as as detection elements in chemical sensors. Films of chemically derivatized nanowires can sense changes in their chemical environment. When exposed to solvent vapors, the resistance of the films increases. This effect is partially due to swelling of the films, which lead to diminished electronical contact between nanowires. In order to exploit this phenomenon for the selective measurement of analytes in the solution, we are currently trying to equip the wires with molecular binding agents for the selective recognition of complementary molecules.

Resistance Measurements

In a related project we are investigating methods to use the wires as electrical connects in nanostructured materials. Towards this end, we successfully linked CdSe and Au particles to the nanowires (see below).

CdSe, Au in LiMo3Se3

	»	Metallic LiMo₃Se₃ Nanowire Film Sensors for Electrical Detection of Metal Ions in Water, Mark Allen; Erwin M. Sabio; Xiubin Qi; Bokuba Nwengela; M. Saif Islam; and Frank E. Osterloh, Langmuir, 2008, 24(13), 7031-7037. DOI: 10.1021/la8004085.

	»	The Effect of Additives on LiMo₃Se₃ Nanowire Film Chemical Sensors, Xiubin Qi, Frank E. Osterloh, J. A. Giacomo, S. Chiang, Langmuir, 2006, 22(19), 8253-8256. DOI: 10.1021/la0614278

	»	A Simple Laboratory Method to Pattern Sub-Millimeter Features of Conductive Films of Gold and Indium Tin Oxide, Amna Hawatky, Frank E. Osterloh, Instrumentation Science & Technology, 2007, 35(1), 53-58. DOI: 10.1080/10739140601000879

	»	Nanowire-Nanoparticle Crosslinking Approach to Highly Porous Electrically Conducting Solids, Nick Akl, Olga Trofymluk, Xiubin Qi, Jin Y. Kim, Frank E. Osterloh, Alexandra Navrotsky, Angew. Chem., Int. Ed. Engl., 2006, 45(22), 3653-3656. DOI: 10.1002/anie.200503950

	»	Molecular Adsorption to LiMo₃Se₃ Nanowire Film Chemiresistors, Xiubin Qi, Frank E. Osterloh, S.A. Barriga, J. A. Giacomo, S. Chiang, Anal. Chem. 2006, 78(4), 1306-1311. DOI: 10.1021/ac051701n

	»	Chemical Sensing with LiMo₃Se₃ Nanowire Films, Xiubin Qi, Frank E. Osterloh, J. Am. Chem. Soc., 2005, 127(21); 7666-7667.DOI: 10.1021/ja050960r

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.	The Osterloh Research Group is part of the University of California, Davis Department of Chemistry.

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