Recognition of Chemical Identity of Organic Adsorbates on Solid Surfaces at the Nanoscale by Molecular STM Tips

Abstract

1023 IntroductionRecent interest in functional nanomaterials, such as molecular electronics and miniaturized sensors, increasingly demands atomic-and molecular-resolution analytical tools. Scanning tunneling microscopy (STM) is one of the most suitable techniques for this purpose, because it offers a unique opportunity to directly reveal surface topography as well as electronic structure at the nanoscale. It is, however, often 2010 © The Japan Society for Analytical Chemistry This paper reviews chemically selective imaging at the single-atom/molecule level by molecular STM tips. The molecular tips enable the recognition of a particular chemical species on the basis of chemical interactions with a sample molecule, including hydrogen-bond, metal-coordination, and charge-transfer interactions. The chemical selectivity can be tailored by designing functional groups of the tip molecules. Moreover, the rational design of the molecular tip allows sophisticated chemical recognition. The discrimination of DNA bases and chiral recognition on a single molecule basis are thereby achieved. The molecular tips also revealed rectified electron transmission within an electron donor-acceptor molecular pair. Self-assembled monolayers, carboxylated carbon nanotube, and conducting polymers can be utilized for the preparation of molecular tips. This technique may be coined "intermolecular tunneling microscopy" as its principle goes, and is of general significance for novel molecular imaging of chemical identities at the membrane and solid surfaces.

Comparison of Oligo(ethylene glycol)alkanethiols versus n-Alkanethiols: Self-Assembly, Insertion, and Functionalization

“…Self-assembled monolayers (SAMs) have found widespread application to impart tailored properties to noble metal surfaces because of their simplicity, ease of use, and patterning capabilities. − In particular, n -alkanethiolate SAMs have been extensively studied because they are highly ordered, stable, and chemically versatile; a wide variety of terminal functional groups can be presented at the exposed interface, thereby determining the chemical, physical, and biological properties of these films. ,− …”

Electroanalysis and Simultaneous Determination of 6-Thioguanine in the Presence of Uric Acid and Folic Acid Using a Modified Carbon Nanotube Paste Electrode

“…35,36 In addition, the subtle electronic behavior of CNTs reveals that they have the ability to promote electron-transfer reaction and have a high electrocatalytic effect when used as electrode materials. 37 All these fascinating properties make CNTs as a suitable candidate for the modification of electrodes. 38 To the best of our knowledge, most of the previously published electrochemical studies have dealt with individual determination of 6-TG utilizing CPEs or other kinds of modified electrodes.…”

Laser-Combined STM and Related Techniques for the Analysis of Nanoparticles/Clusters

“…In addition to the high-resolution imaging of molecules (such as diether) on a surface, these CNT tips enable chemically selective observation due to electron tunneling through hydrogen-bond interactions between the atached molecule and carboxyl groups at SWNTs. The differentiation of DNA bases and chiral recognition on a single-molecule basis have also been demonstrated using molecular tips [56]. In a similar way, voltage-induced chemical contrast in an STM image was reported using chemically modified tips with hydrogen-bond donors [57].…”