Thiol end-capped molecules

Thiol End-capped Molecules for Molecular Electronics Synthetic Methods, Molecular Junctions and Structure-Property Relationships... 

The fabrication of STM-based molecular junctions have relied - in most reported cases -on the deposition of thiol end-capped molecules as self-assembled monolayers on a flat gold substrate. By using an exceedingly small tip, the measurement of no more than a single or a few molecules becomes possible. A schematic illustration of an STM-based molecular junction is shown in Fig. 10.2. 

This chapter describes different synthetic approaches towards the fabrication of candidate molecules for use in molecular electronics applications with an emphasis on thiol end-capped jr-conjugated molecules, followed by a survey of the electronic transmission properties in two- and three-terminal devices. 

An early nanopore study focused on an asymmetric Au-molecule-Ti junction based on thiol end-capped biphenyl 81b molecules [45], The asymmetry of the structure led to the observation of a prominent rectifying behavior with larger current when the Ti electrode was negatively biased. Recent work by Bao and coworkers [72] has shown that vapor deposition of Ti on SAMs results in penetration of the monolayer, thus destroying it. Similar observations were made using Au and A1 deposition. However, destruction of the monolayer could in this case be prevented if SAMs of dithiols were used, since the Au or A1 would react with the free thiol end. 

Thiol end-capped oligothiophenes 105a-c were used to form the SAMs between the electrodes. A series of distinct periodic steps in the conductance was observed for all samples at low temperature (<100 K). These features were suggested to originate from vibrational modes in the molecules. A (weakly coupled) gate potential could be applied to the molecular junction, which shifted the step position in the I(V) curves but not the step widths. This observation was taken as an indication that only a single molecule was electrically active in the molecular junction. 

Simple one-pot strategy was used to prepare surface-functionalized, water-dispersible lONPs. Small organic molecules that required functional groups such as amines, carboxylics, and thiols as capping agents were injected into the reaction medium at the end of the synthesis... 

To improve the compatibility of GNPs in LC host, both of the simple n-alkyl thiol and LC/mesogen molecules are used simultaneously to form mixed mono-layer. For example, nematic cyanobiphenyl end-functionalized alkylene thiol covered GNPs and its mixing with n-alkyl thiols (n = 6, 12) in two cyanobiphenyl nematic LC hosts (5CB and 8CB) were investigated [60]. By adding small quantities of alkyl thiolate-capped GNPs there was effectively reversed nematic LC orientation which further showed opto-electronic responses [61]. Recently,... 

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