Scanning Electrochemical Microscope Observation of Defects in a Hexadecanethiol Monolayer on Gold with Shear Force-Based Tip−Substrate Positioning

Abstract

Scanning electrochemical microscopy (SECM) was used for imaging of n-hexadecanethiol-modified Au surfaces. In these studies, small defects were observed in the monolayer when a submicrometer electrode was used as an SECM tip, although a cyclic voltammogram of a Au disk electrode showed that the surface of the Au was completely covered with n-hexadecanethiol. The dependence of the SECM images on the potential of the Au electrode was also examined. A comparison of the current at the Au electrode and the tip current in the SECM images showed that direct electron transfer through the monolayer was dominant, rather than electron transfer at the defects. The size of the defects was estimated from the tip current to be 1-100 nm, under the assumption that the defects were small compared to the SECM probe.

Elektrochemische Rastermikroskopie zur direkten Abbildung von Reaktionsgeschwindigkeiten

“…[415] Alternativ kann eine UME an ein Bein eines stimmgabelförmigen Quarzresonators angebracht werden. [258,397,413,414,416,417] Das Resonanzverhalten des Systems wird in diesem Fall vor allem durch den Quarzresonator bestimmt, wodurch die Elektronik für einen engeren Frequenzbereich ausgelegt werden kann als bei der oben besprochenen Variante. Da die Masse der UME wegen der seitlichen Isolierung wesentlich größer ist als die des Quarzresonators, bestehen auch hier Empfindlichkeitsprobleme.…”

Dissolution kinetics of octadecanethiolate monolayers electro-adsorbed on Au(111)

“…The characterisation of defects of self-assembled monolayers (SAMs) has therefore received considerable attention [10][11][12][13]. Numerous techniques were used for this purpose: scanning tunnelling microscopy (STM) [11,[14][15][16][17][18][19][20][21], infrared spectroscopy, voltammetry [3,6,22], electrochemical impedance spectroscopy (EIS) [3,[23][24][25][26][27][28], X-ray diffraction [29], contact angle measurements [7], scanning electrochemical microscopy (SECM) [30,31].…”

Scanning Electrochemical Microscopy: A Multiplexing Tool for Electrochemical DNA Biosensing

“…The small size of the tip and currents minimizes problems of iR drop and allows fast mass transport to occur, which is good for monitoring fast reactions [18]. Patterned SAMs on gold have been imaged through the local inhibition of electron transfer [19][20][21]. A well-packed nonconductive SAM covers the gold substrate and behaves like an insulator.…”