Enhanced thermal stability and structural ordering in short chain n-alkanethiol monolayers on gold probed by vibrational spectroscopy and EQCM

Subramanian, S and Sampath, S (2007) Enhanced thermal stability and structural ordering in short chain n-alkanethiol monolayers on gold probed by vibrational spectroscopy and EQCM. In: Analytical and Bioanalytical Chemistry, 388 (1). pp. 135-145.

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Abstract

Monolayers of alkanethiols with varied chain lengths, $CH_3(CH_2)_nSH$ where n=3, 5, and 7, on gold substrates have been prepared by adsorption from (1) neat thiol, (2) millimolar thiol solution in alcohol (conventional method), aand (3) potential-controlled adsorption. Reflection absorption infrared spectroscopy (RAIRS) and electrochemical quartz crystal microbalance (EQCM) have bbeen used to characterize the integrity of the monolayers. Methylene and methyl stretching modes along with C–S stretching modes have been used as benchmarks to follow the order–disorder transitions in the monolayer structure, in the temperature range from 25 to 175 °C. Monolayers adsorbed from neat thiol show superior quality in terms of stability and structural arrangement. Short chain thiols with n=3, 5, and 7 do show substantial stability. The possibility of multilayer formation is ruled out by EQCM studies comparing the frequency and mass change associated with the monolayer desorption. Self-assembled monolayers (SAMs) adsorbed under potential control behave very similarly to the monolayers adsorbed from neat thiol as far as stability and structural orientation are concerned, irrespective of the chain length. The adsorption from neat thiol gets rid of the solvent-induced defects and arrests the propagation of defects under temperature constraints.

Item Type:	Journal Article
Publication:	Analytical and Bioanalytical Chemistry
Publisher:	Springer
Additional Information:	Copyright of this article belongs to Springer.
Keywords:	RAIRS;Self-assembled monolayer; Thermal stability;EQCM; Short chain thiol
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	07 Aug 2007
Last Modified:	19 Sep 2010 04:38
URI:	http://eprints.iisc.ac.in/id/eprint/11466

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