With the discovery of surface-nucleated self-assembly in the early 1980’s and the 1987 Nobel Prize to J-M Lehn for supramolecular chemistry, a new paradigm was launched that significantly impacts evolving fields:

• Precision molecular and surface engineering
• Biomimetics
• Clean, green low-tech manufacturing

Self-assembly, the spontaneous re-organization of molecules into complex, ordered supramolecular structures, is the process that nature uses to create life – molecules self-assemble in their correct places into living organisms. Expensive fab-labs or manufacturing lines are not necessary for this to happen. Every living organism does it in aqueous environments at ambient pressures and temperatures and at neutral pH.

Molecular self-assembly can be demonstrated by alkane thiol assembly on gold, which is driven by the strong attraction between the sulfur atom of the thiol chain and the gold surface in addition to the van der Waals attraction between the alkane chains. This process of self-assembly occurs quickly and results in the formation of an ordered surface only one "monolayer" thick which is referred to as self-assembled monolayer or SAM. Alkanethiol SAMs are powerful surface engineering tools because of head group chemistry, which forms the outer part of the monolayer after the sulfur end of the thiols have assembled on the gold surface. These head groups can impart the ability to attract water (hydrophilic) or reject water (hydrophobic). They can also reject proteins for medical applications (non-fouling) or capture particular chemical compounds for more advanced applications such as biological sensors.

Very pure thiol compounds are critical for many applications including molecular electronics, cell and protein studies, non-fouling surfaces, sensors and DNA binding. This is because impurities can create imperfections in the monolayer out of proportion to their concentration in the solution. These impurities can change or significantly hamper the desired function of the head group chemistry.

One of the ultimate applications of SAMs is the self-assembly of nano-electronic devices. The semiconductor industry has been doubling the semiconductor count on silicon every 24 months since 1971, a remarkable record called Moore’s Law after Intel founder, Gordon Moore. Conventional lithographic techniques will soon be unable to continue this momentum. The future is molecular self-assembly which can provide a mechanism to build computers from the ground up, molecule by molecule. The uses for self-assembled surfaces are limited only by the imagination of the researcher. The substrates for self-assembly are also becoming more varied as scientists develop chemistries that allow bonding to surfaces other than gold such as silicon, steel or someday even polymers. Nanotechnology represents the future in dozens of leading edge fields.

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