Molecular conductance
Molecular Conductance (), or the
Recently, a great deal of progress has been made in the development of reliable conductance-measuring techniques. These techniques can be divided into two categories: molecular film experiments, which measure groups of tens of molecules, and single-molecule-measuring experiments.
Molecular film experiments
Molecular film experiments generally consist of the sandwiching of a thin layer of molecules between two electrodes which are used to measure the conductance through the layer. Two of the most successful implementations of this concept have been the bulk
Single-molecule-measurement
More recently, single-molecule-measurement experiments have been developed that are bringing experimenters a better look at molecular conductance. These fall under the categories of scanning probe, which involves fixed electrode, and mechanically formed junction techniques. One example of a mechanically formed junction experiment involves using a movable electrode to make contact with and then pull away from an electrode surface coated with a single layer of molecules. As the electrode is removed from the surface, the molecules that had bonded between the two electrodes begin to detach until eventually one molecule is connected. The atomic-level geometry of the tip-electrode contact has an effect on the conductance and can change from one run of the experiment to the next, so a histogram approach is required. Forming a junction in which the precise contact geometry is known has been one of the main difficulties with this approach.
Applications
An important first step toward the goal of building electronic devices on the molecular level is the ability to measure and control the electric current through an individual molecule. Based on the anticipated continuation of
Other applications focus on the insight provided by these experiments in the area of charge transport, which is a recurrent phenomenon in many chemical and biological processes. This sort of insight gives researchers the ability to read the chemical information stored in a single molecule electronically, which can then be used in a wide variety of chemical and biosensor applications.
References
- ^ Chen F, Hihath J, Huang Z, Li X, Tao NJ. 2007. Measurement of single-molecule conductance. Annu. Rev. Phys. Chem. 58:535-64