Inkjet-printed thiol self-assembled monolayer structures on gold: Quality control and microarray electrode fabrication

Abstract

Laterally structured, self-assembled monolayers (SAMs) of different thiols (HS-R-X, R = (CH2)(3-16), X = -CH3, -COOH, -NH2) on gold have been prepared by inkjet printing. The printer is a modified, low-cost desktop printer (Epson Stylus Photo R200), the ink is a 1 mM solution of the thiol in ethanol/alycerol (6:1). The quality of inkjet-printed large area SAMs obtained in this study is between that of a layer self-assembled from a thiol solution and that obtained by soft lithography, according to cyclic voltammetry, electrochemical impedance spectroscopy, scanning electrochemical microscopy (SECM), and polarization-modulated Fourier transform infrared reflection-absorption spectroscopy (PM IRRAS), For the first time, simultaneous printing of two different thiols in a single print job as an alternative to sequential printing and backfilling is demonstrated. The smallest structures consisting of conductive disks of 40 mu m diameter were analyzed as single spots by SECM and as random array electrodes with different average disk-disk distance. Conductive band electrodes with variable bandwidth (300 mu m to 1 cm) are presented, as well as a pH switchable band structure. As compared to stamping, inkjet printing allows for simultaneous multiple thiol printing in a single print job with the. resolution limited only by the droplet size and the precision of the translation stage.