Alternating current scanning tunneling spectroscopy of self‐assembled monolayers on gold

A meso-pyridyl porphyrin, 5-(4-(2-(4-(S-acetylthiomethyl)phenyl)ethynyl)phenyl)-10,15,20-tris(4-pyridyl) porphyrin was synthesized by coupling of 5-{4-ethynyl}phenyl-10,15,20-tris(4-pyridyl) porphyrin with 4-(S-acetylthiomethyl)-4-iodobenzene under mild palladium coupling conditions. The meso-pyridyl porphyrin was used for the preparation of self assembled monolayers on gold substrates. The gold substrates were made by the thermal evaporation of gold on oxidized Si(100) surfaces. The self-assembled monolayers (SAMs) were characterized using ground state UV absorption and X-ray photoelectron spectroscopic (XPS) techniques and also by scanning probe microscopy (SPM) techniques. The UV-absorption spectra of the porphyrin monolayer exhibited a 10 nm red shift in the Soret band compared to the porphyrin in CHCl3 solution. This indicates that the porphyrin molecules are aligned on the gold substrate in a side-by-side orientation. The typical shifts in the binding energy by XPS revealed that the chemisorption of the thiolate species of the porphyrin to the surface occurs through a strong sulfur–gold bonding mechanism. Basic hexagonal (√3×√3) R 30° well ordered self-assembled monolayers of meso-pyridyl porphyrin was observed by molecular-resolution atomic force microscopy (AFM). Room temperature current–voltage (I–V) spectra by scanning tunneling spectroscopy (STS) at varying set point current were collected to study the electronic transport properties of the monolayers on the gold surface.

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Molecular-Scale and Wide-Energy-Range Tunneling Spectroscopy on Self-Assembled Monolayers of Alkanethiol Molecules

ACS Nano ◽

10.1021/nn302405r ◽

2012 ◽

Vol 6 (10) ◽

pp. 8728-8734 ◽

Cited By ~ 32

Author(s):

Masato Nakaya ◽

Masaya Shikishima ◽

Masahiro Shibuta ◽

Naoyuki Hirata ◽

Toyoaki Eguchi ◽

...

Keyword(s):

Energy Range ◽

Tunneling Spectroscopy ◽

Self Assembled Monolayers ◽

Wide Energy Range ◽

Molecular Scale ◽

Assembled Monolayers ◽

Wide Energy ◽

Self Assembled

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Specific Immobilization of Streptavidin on Mixed Self-Assembled Monolayers as Mixing Ratio

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.121-123.495 ◽

2007 ◽

Vol 121-123 ◽

pp. 495-498 ◽

Cited By ~ 4

Author(s):

Jun Hyung Park ◽

Buyng Su Park ◽

Gu Huh ◽

Seung Hyun Lee ◽

Hyun Sook Lee ◽

...

Keyword(s):

Colorimetric Detection ◽

Gold Surface ◽

Self Assembled Monolayers ◽

Scanning Tunneling ◽

Local Domain ◽

Mixing Ratio ◽

Tunneling Microscopy ◽

Self Assembled Monolayer ◽

Assembled Monolayers ◽

Self Assembled

We report on the distribution of mixed self-assembled monolayers (SAMs) composed of biotinylated and diluent alkylthiolates for streptavidin immobilization. Two thiol derivatives, 11-mercapto-1-undecanol (MUOH) and 11-mercaptoundecanoic-(8-biotinylamido-3,6-dioxaoctyl) amide (MBDA), were employed for mixed SAM. These thiols formed self-assembled monolayer without local domain, and streptavidins were immobilized onto biotinylated gold surface without nonspecific binding. In order to find the optimized condition of immobilization of streptavidin, we controlled the mixing ratio of two kind thiols by colorimetric detection assay, and the immobilization was characterized by atomic force microscopy (AFM), scanning tunneling microscopy (STM), and ellipsometer.

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