Reworking nanoparticles for better composite materials
The method of nanoparticle (NP) synthesis by laser ablation in liquids enables a direct, one-step functionalisation of the NPs to be made. Critical parameters are the choice of an appropriate liquid in which the ablation takes place and the right laser ablation parameters. The method can be used to tune sizes and size distribution of the NPs by adjusting the ablation time duration. The method also avoids the use of toxic and flammable chemical precursors for the synthesis of nanomaterials and the possibility of synthesising NPs free of surface ligands. A further advantage is the overall ease of the method itself. Using this system, the EU-funded project Omalanp produced and characterised NPs of Silicon (Si) and other semiconducting materials such as Cadmium Tellurium (CdTe) and Zinc Oxide (ZnO). Colloidal solutions of these NPs were mixed directly with polymers to fabricate polymer-NP composites. The nanocomposites were deposited by spin coating as thin films on to suitable substrates, such as glass or polyethylene terepthalate (PET), commonly used in flexible organic electronic devices (OEDs). For ZnO NPs incorporated in the polymer PEDOT:PSS (poly(3,4-ethylenedioxythiophene) oxidised with poly(4-styrenesulfonate)) – a common anode electrode in OEDs – it was found that the polymer’s electrical properties could be tuned to achieve, in particular, a doubling of its electrical conductivity. The surface morphology of the composite thin films was characterised by Atomic Force Microscopy (AFM) imaging. Potentially, the work carried out in this project will have significant societal impacts. The method used is environmentally friendly which could make an important contribution towards the adoption of a 'green' technique for nanomaterial synthesis. In addition, it is an easy, fast and straightforward method for NPs synthesis, which also enables the direct, one-step functionalisation of the NP product. This in turn leads to cost and resource savings, which have important economic impact, especially for the potential use of the technology in an industrial environment.
