Method for Measuring the Self-Assembly of Alkanethiols on Gold at Femtomolar Concentrations
- 5 May 2007
- journal article
- Published by American Chemical Society (ACS) in Langmuir
- Vol. 23 (12), 6856-6863
- https://doi.org/10.1021/la063768r
Abstract
We describe a cantilever-based method for measuring the self-assembly of alkanethiols on a gold surface in a flow system that permits easy step changes in concentration and acquire a continuous in situ measure of the resulting chemisorption through the change in resonance frequency. A gold-coated (2.2 mm2), piezoelectric-excited, millimeter-sized cantilever (PEMC) sensor was exposed to 1-hexadecanethiol (HDT) in ethanol at concentrations ranging from 1 fM to 1 mM, sequentially and separately. A high-order flexural mode at ∼850 kHz was monitored during the self-assembly. The resonance frequency decreases as a result of increased mass as chemisorption occurs on the surface. We show for the first time that the chemisorption of HDT at 1 fM is readily measurable and gave a response of 220 ± 13 Hz (n = 4). At higher concentrations (10 and 100 fM; 1, 10, and 100 pM; 1, 10, and 100 nM; 1 μM; and 1 mM), the responses were proportionately, but nonlinearly, higher. At high concentrations (1 mM), the responses to C4, C8, C11, C16, and C18 alkanethiols were linearly proportional and were complete in ∼25 min. We report for the first time that, once the Au surface is equilibrated at 1 pM, further chemisorption at a lower HDT concentration does not take place, even though over 99% of surface adsorption sites are available. At 1 fM, the overall chemisorption rate did not increase with a 2-fold increase in the HDT flow rate, suggesting that chemisorption at 1 fM is not transport-limited. The measured overall chemisorption rate constant at 1 fM was more rapid than 0.1 min-1.Keywords
This publication has 34 references indexed in Scilit:
- Characterization of n-alkanethiol self-assembled monolayers on mercury by impedance spectroscopy and potentiometric measurementsJournal of Electroanalytical Chemistry, 2006
- Self-assembled monolayers (SAMs) of alkoxycyanobiphenyl thiols on gold—A study of electron transfer reaction using cyclic voltammetry and electrochemical impedance spectroscopyJournal of Colloid and Interface Science, 2006
- Electrochemical detection of the immobilization and hybridization of unlabeled linear and hairpin DNA on goldElectrochemistry Communications, 2005
- Deviations from 1:1 Compositions in Self-Assembled Monolayers Formed from Adsorption of Asymmetric Dialkyl Disulfides on GoldLangmuir, 1999
- Self-Assembled Monolayers of Small Aromatic Disulfide and Diselenide Molecules on Polycrystalline Gold Films: A Comparative Study of the Geometrical Constraint Using Temperature-Dependent Surface-Enhanced Raman Spectroscopy, X-ray Photoelectron Spectroscopy, and ElectrochemistryLangmuir, 1999
- Effect of Surface Wettability on the Adsorption of Proteins and DetergentsJournal of the American Chemical Society, 1998
- SPR Studies of the Nonspecific Adsorption Kinetics of Human IgG and BSA on Gold Surfaces Modified by Self-Assembled Monolayers (SAMs)Journal of Colloid and Interface Science, 1997
- X-ray Photoelectron Spectroscopy Sulfur 2p Study of Organic Thiol and Disulfide Binding Interactions with Gold SurfacesLangmuir, 1996
- Alternating current scanning tunneling spectroscopy of self-assembled monolayers on goldJournal of Vacuum Science & Technology A, 1993
- Improved charge separation and photosensitized hydrogen evolution from water with titanium dioxide particles on colloidal silica carriersJournal of the American Chemical Society, 1987