The capacity of solids to attract and ‘hold’ substances on their surfaces (adsorption) is routinely exploited in purification and separation processes. Activated carbon is an example of a simple solid used in common consumer water filters and in masks to remove poisonous gases on the battlefield. Better control over new functionalities for adsorbing materials can increase selectivity, sensitivity, and effectiveness. With the support of the Marie Skłodowska-Curie programme, the NANODRIVE project carried out comprehensive theoretical, computational, and experimental studies of adsorption at the nanoscale. Understanding the mechanisms paves the way to the rational design of specialised nanoparticles for adsorption and release of substances in critical areas including environmental, industrial, and medical technologies.
The power in numbers
NANODRIVE focused on special macromolecules called diblock copolymers. Polymers are very large molecules made up of many smaller individual units (monomers) bonded together. When two different types of monomers cluster together and form blocks of repeating units within the large polymer, the resulting molecule is called a diblock copolymer. The dual physical or chemical functionality can be used to steer self-assembly into a pre-determined ordered or disordered phase. This is accomplished via a controlled change in parameters such as concentration, temperature, pH, or the chemical nature of the polymeric macromolecules. Project fellow Barbara Capone set her sights on designing diblock copolymers for selective adsorption of ‘cargo’ in solution. More specifically, as founder and CEO of the international NGO Sunshine4Palestine that is focused on energy and water in emergency situations, Capone targeted adsorption for large-scale water sanitation in extremely poor areas.
Written in the stars
NANODRIVE started with a simple system, silver nanoparticles and adsorption of metal ions in solution. As Capone and project coordinator Fabio Bruni explain, “Combining theoretical and experimental investigations, we were able to fully characterise the adsorption path of cobalt and nickel ions in silver nanoparticles. Further, we demonstrated that, with a few chemical or physical parameters, it is possible to completely drive both the clustering process and selective adsorption.” Scientists then turned their attention to their main focus, diblock copolymer stars in which each arm of a star consists of two parts. The inner part interacts with the cargo and the outer is used to tune and change the shape of the adsorbing macromolecule. NANODRIVE added a second functionality to the outer arms. Thermosensitivity enabled a slight change in temperature to lock the cargo for removal from the aqueous solution.
Rational design of nanoscale adsorbers meets many needs
The team is now identifying molecular interactions that will enable rational design of adsorbers for biological systems. As Capone and Bruni explain, “Starting from the adsorption properties of simple homopolymeric star polymers, we designed a set of macromolecular ‘nanobots’ able to load cargo and recognise heavy metals in a complex and crowded solution by changing either chemical composition or the geometry of the nanoparticles.” NANODRIVE’s comprehensive characterisation of nanoscale adsorption paves the way to application in a variety of fields, particularly in environmental and biomedical applications.
NANODRIVE, polymer, adsorption, star, nanoscale, nanoparticle, diblock copolymer, purification, diblock copolymer star