Aspect ratio assembly

A short oligo(L-alanine) segment was envisioned to induce self-assembly into high-aspect-ratio ID aggregates in solution via the formation of (5-sheets. 

In order to assemble gold nanorods (aspect ratio 2.4) by the click reaction, one batch of nanorods capped with 4-azidobutane-l-thiol, A, and another with hex-5-yn-l-thiol, B, were reacted in the acetonitrile-water mixture under standard conditions [12], The occurrence of the click reaction was established by infrared spectroscopy [13], The product of the reaction was investigated by electronic absorption spectroscopy and transmission electron microscopy. Fig. 1 compares the electronic absorption spectra of the gold nanorods before and after the click reaction between the A and B type nanorods. Isolated gold nanorods show transverse and longitudinal plasmon bands around 520 nm and 630 nm, respectively (see Fig. la). 

The immobilization of a large volume of liquid by a small quantity of gelator is achieved efficiently if the elementary assemblies are rodlike and have large aspect ratios. Such linear structures are determined by specific binding forces associated with the chemical constitution of the gelators. In nonaqueous liquids, the attractive forces are mainly the van der Waals type and can be supplemented by dipolar interactions, intermolecular hydrogen bonds, metal-coordination bonds, or electron transfers, etc. 

---