Modification and Patterning of Self‐Assembled Monolayers Using Electrogenerated Etchants and Homogeneous Scavenging Reactions in a Scanning Electrochemical Microscope

Abstract

Self‐assembled monolayers (SAMs) of oligoethylene glycol (OEG)‐terminated alkanethiolates on gold, which are used to control protein adsorption and cell adhesion, were patterned by reaction with Br2/HOBr electrogenerated at a microelectrode of a scanning electrochemical microscope (SECM). The spreading of the Br2 diffusion layers was limited by a homogeneous reaction with cystamine or L‐cystine as scavengers. The influence of process parameters on the patterning process was explored by simulation and combinatorial experiments. The experimental determination of pattern sizes from SECM feedback images was verified by scanning force microscopy. The simulation considered the local Br2 formation as well as Br2 consumption in the reaction with the OEG SAM, by reduction at the gold substrate, and by the homogeneous scavenging reaction. It used experimentally determined diffusion coefficients and rate constants of the scavenging reaction. and Experiments and simulation confirmed the existence of regions in the parameter space, in which the patterning process is robust against small variation of the parameters working distance, pulse time and scavenger excess.

Application of scanning electrochemical microscopy for topography imaging of supported lipid bilayers

“…21–23 Here also, the detection of nanopores is maybe possible by switching to the nanoelectrodes. Imaging the self-assembled monolayers on gold using SECM was reported earlier 24–26 but was not employed for the topography imaging of supported lipid bilayers.…”

Probing the reactive intermediate species generated during electrocatalysis by scanning electrochemical microscopy

“…Footprinting analysis (Figure 1d) is another indirect powerful methods to analyze local (electro)chemical reactions. A reactive footprint is performed by exposing a substrate modified by an organic coating [27,28] or self-assembled monolayers [29][30][31][32] to reactive intermediates, etchants, electrogenerated by a SECM tip. The reactivity between the reactive etchant and the organic layer leads most of the time to its irreversible local transformation (often destruction) producing a pattern with contrasted chemical functionalities.…”

“…The footprint can be imaged post-mortem (SECM, AFM, condensation…) or operando (during its formation) using optical monitoring [33]. This methodology allows evidencing the bulk formation of reactive species [28] and to quantitatively characterize their reactivity with the layer [30][31][32] by analyzing the footprint expansion and/or width with the local electrogeneration time. It also allows studying competing reactions of the etchant or the layers with species present in solution such as radical scavengers [32].…”

“…This methodology allows evidencing the bulk formation of reactive species [28] and to quantitatively characterize their reactivity with the layer [30][31][32] by analyzing the footprint expansion and/or width with the local electrogeneration time. It also allows studying competing reactions of the etchant or the layers with species present in solution such as radical scavengers [32]. Besides, this footprinting strategy can be exploited to develop methodologies and tools for the electrochemical micro/nanomachining of surfaces [34][35][36].…”

Investigation of Dopamine Release on Self-assembled Monolayers by Scanning Electrochemical Microscopy

“…15,16 The functionalization of a SAMs is usually achieved by utilizing the exposed functional terminal group. 17,18 Over the past decades, it has been reported that lots of physiological or biological functions have been achieved via this reliable artificial membrane. [19][20][21] For example, anti-human chorionic gonadotropin orientation was well controlled and regulated on the surface of different charged SAMs by Jiang et al 22 This work provided not only a fundamental understanding of how microenvironments affect protein behavior on surfaces but also a useful guide to design surfaces for applications.…”