Hybrid organic-inorganic materials can self-assemble into tiny doughnut-like structures

Hybrid organic-inorganic materials can self-assemble into tiny doughnut-like structures
Credit: KAUST/Xavier Pita

Engineered nanometer- and micrometer-scale structures have a vast array of uses in electronics, sensors and biomedical applications. Because these are difficult to fabricate, KAUST researchers are trying a bottom-up philosophy, which harnesses the natural forces between atoms and molecules such that microstructures form themselves.

This , a departure from the usual top-down approach, involves the etching away of material to leave the desired sculpted structure behind; however, because this approach can be tricky, expensive and time consuming, KAUST researchers became motivated to find a new approach.

Associate Professor of Chemical Science Niveen Khashab and her team and colleagues from the Imaging and Characterization Core Lab and the Max-Planck-Institute of Colloids and Interfaces in Germany demonstrated this bottom-up approach in the self-assembly of microscale toroids (doughnut-shaped forms), made of both inorganic and organic materials1.

A number of forces can bring atoms and molecules together. These include surface tension, electrostatic attraction and repulsion, and a weak fundamental force known as van der Waals interactions. The toroids created by Khashab's team were formed via metal coordination. A metallic sodium chloride atom, an amphiphilic (both hydrophilic and lipophilic) molecule called saponin and a polymer known as chitosan were combined and formed weak chemical bonds.

"This is a result of what is known as coordination-driven self-assembly," explained Khashab. "The metal ions interact with different chemical motifs leading to the formation of novel frameworks and morphologies."

Within just a few minutes, coordination bonding between the iron atoms and the oxygen and the hydrogen in the molecules initially drives the self-assembly of star-like nanostructures. Repulsive electrostatic and hydrophobic interactions then lead to the formation of toroids.

The toroids were approximately 3.9 to 4.8 micrometers in diameter and held their shape even a month after fabrication. Disassembly of the microstructures required five hours of mechanically stirring the solution.

There are numerous naturally occurring biological structures that take a toroid shape; for example, proteins and DNA of some types of viruses and bacteria self-assemble in this way. Many of these are known to play an important role in the formation of pores in biomembranes.

This research could help to build a better understanding of how these complex biostructures are created and provide a way of mimicking them at the molecular level.

"Next, we hope to prepare a new generation of these hybrid structures with a temperature-responsive gap size," said Khashab. "These toroid structures could be used as pockets for active catalysis and separation."


Explore further

Self-assembled nanostructures hit their target

More information: Safa'a Al-Rehili et al. Anisotropic Self-Assembly of Organic–Inorganic Hybrid Microtoroids, Journal of the American Chemical Society (2016). DOI: 10.1021/jacs.6b10080
Citation: Hybrid organic-inorganic materials can self-assemble into tiny doughnut-like structures (2017, January 17) retrieved 8 December 2019 from https://phys.org/news/2017-01-hybrid-organic-inorganic-materials-self-assemble-tiny.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
7 shares

Feedback to editors

User comments