Single-Molecule Analysis Methods Using Nanogap Electrodes and Their Application to DNA Sequencing Technologies

Abstract

Single-molecule analysis methods facilitate the investigation of the properties of single-molecule junctions (SMJs), in which single molecules are connected between a pair of nanoelectrodes that use nanogap electrodes having a spacing of less than several nanometers. Various methods have been developed to investigate numerous useful parameters for SMJs; for example, the number of molecules connected between a pair of nanoelectrodes can be determined, the types and structures of single molecules can be revealed, localized temperatures within SMJs can be evaluated, and the Seebeck coefficient and the bond strength between single molecules and electrodes can be ascertained. Single-molecule analysis methods have also been used to analyze biopolymers in solutions, and this has resulted in single-molecule sequencing technologies being developed that can determine sequences of base molecules in DNA and RNA along with sequences of amino acids in peptides. Singlemolecule analysis methods are expected to develop into digital analysis techniques that can be used to investigate the physical and chemical properties of molecules at single-molecule resolutions.

Self-assembly as a key player for materials nanoarchitectonics

“…Further to historical efforts in organic synthesis and materials' fabrication, functional optimization of materials involving structural regulation at the atomic/molecular scales and nanometre scales has been widely investigated and has been accompanied by the corresponding developments in observational techniques and instrumentation on those length scales [37][38][39]. While it is widely appreciated that nanotechnology plays a central role in materials developments involving nanoscale structures, nanotechnology also provides substantial benefits in the development of nanoscale observation and fabrication techniques including deepening our understanding of novel phenomena on the nanoscale and their guiding physical principles [40][41][42][43].…”

5 nm Nanogap Electrodes and Arrays by Super-resolution Laser Lithography

“…The LDW technique has been utilized to fabricate nanogap electrode arrays. The nanogap electrode is a vital element for wide applications in field-enhancement-based plasmonic sensors , and molecular based electronic devices. , The achievement of the sub-10 nm gap between two metallic nanostructures is of great importance to exponentially promote device performance such as via field enhancement and electrical current response. , With the developed 5 nm fabrication capability, the nanogap electrode arrays were obtained by only one round of lithography, etching, and metal deposition. Here, the metal layer (15 nm-thick gold film) was deposited on nanogap arrays without utilizing any adhesion layer by electron-beam evaporation.…”

Recent advances in techniques for fabrication and characterization of nanogap biosensors: A review

“…Therefore, it is necessary to accurately control the spacing of the nanogap electrodes to prepare nanogap devices. Even though full of obstacles, numerous effective approaches for fabricating nanogap electrodes with controlled spacing have been discovered in recent years 50 . This is achieved through several approaches where the gap is fabricated by two main processes either by size reduction or size increment using the following approaches : mechanical break junctions where the gap is buckled; electron‐beam lithography involves designing of a device layout, transfer to photomask, and subsequently transfer of the pattern; in electrochemical plating, this approach is very important especially for the device metallization, electromigration where electronic channels are created along two opposite electrode; in focused ion beam lithography, this is especially ideal for very small gap and for good surface profile; in shadow mask evaporation, this is done in buffered chemicals like oxide to selectively etch away unwanted surface; a scanning probe is usually employed with a visual‐assisted process while etching is done or pattern are transferred; atomic force microscopy lithography is mentioned earlier; on‐wire lithography is highly new and sophisticated approach to bridge the electrodes to enhance their electrical properties and to change their operational mechanism, molecular rulers among others 51 .…”