Alkanethiol self-assembling on gold: Influence of high frequency ultrasound on adsorption kinetics and electrochemical blocking

Abstract

Self-assembling of undecanthiol (C11SH) on polycrystalline gold was investigated under two different conditions. The kinetics of C11SH grafting was studied without and under high frequency ultrasound irradiation. Two electrochemical experiments were extensively carried out in order to determine electrochemical surface blocking of adsorbed layers as a function of grafting time: chronoamperometry in-situ monitoring and cyclic voltammetry. Interestingly, the grafting process is highly accelerated under sonication, and C11SH modified substrates of good quality are obtained after 3h' immersion under ultrasound irradiation. This would allow elaboration of high-quality alkanethiol modified samples within much shorter times. Water contact angle measurements and X-ray Photoelectron Spectroscopy (XPS) confirmed the presence of adsorbed undecanthiol on the gold surface. A very close link between electrochemical blocking, surface hydrophobicity and species chemical grafting was established.

Effect of cavitation intensity control on self-assembling of alkanethiols on gold in room temperature ionic liquids

“…Such cavitation reorientation has been suggested by Atobe et al [18] and seems to be experimentally confirmed by our works. On the contrary, agitation generated by acoustic activity is noxious for the SAM grafting process, as showed in previous studies [11] .…”

“…Cyclic voltammetry experiments were carried out in acetonitrile with 10 mM ferrocene and 0.2 M of lithium perchlorate (supporting salt) at 100 mV/s. X-Ray Photoelectrons Spectroscopy (XPS) and Polarization-Modulation Infrared Reflection Absorption Spectroscopy (PM-IRRAS) apparatuses were described in previous work [11] .…”

“…The affinity between the reactive group and the substrate is of prime importance for ensuring efficient chemisorption on the surface. Many types of SAMs exhibiting various reactive headgroups (thiols [6] , phosphonic [7] , [8] , carboxylic [9] , [10] ) have been grafted on gold [11] , titanium [12] , copper [13] or stainless steel [14] to name just a few.…”

“…between 16 and 24 h, which renders industrial applications very difficult. In an attempt to solve this problem, some studies on the use of ultrasound to accelerate SAM grafting process have been carried out [11] , [14] , [18] , [19] , [20] . The studies by Atobe et al .…”

“…Recently, studies at high frequencies have been carried out by our group. Roy et al showed that high quality undecanethiol SAM can be grafted on gold after 1 h of modification under high frequency ultrasonic irradiation (575 kHz) compared with 19 h in silent conditions [11] . They also studied self-assembling of alkylphosphonic acids on stainless steel under high frequency ultrasonication.…”